COMPOSITIONS AND METHODS FOR INHIBITING TUMOR PROGRESSION

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No. 60/988,874, filed November 19, 2007, the disclosure of which is incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to genes and polypeptides involved in tumor progression and other cellular processes.

BACKGROUND

EMT

During tumorigenesis, carcinoma cells lose many of their normal epithelial characteristics and acquire mesenchymal properties through a process called the "epithelial-mesenchymal transition," or EMT. EMT is associated with changes in cell adhesion and motility that promote both local invasion and metastasis to distant sites. Some genes capable of inducing EMT in model systems, such as MMPl 1 and TGFBl, have been described. For review, see, e.g., Huber et al, Curr. Opin. Cell Biol. 17:548-558, 2005; Lee et al, J. Cell Biol. 172:973-981, 2006; Theiry et al., Nat. Rev. MoI. Cell Biol. 7: 131-142, 2006. However, there is a need in the art to identify further genes involved with induction of EMT in tumor cells. Such genes and their encoded proteins are useful targets, e.g., in the treatment of cancer. The invention described herein meets this need and provides other benefits.

U β2, which is encoded by the SCN2B gene, is a single-pass transmembrane protein with an extracellular domain containing an immunoglobulin fold similar to those found in cell adhesion

proteins (Eubanks et al, Neuroreport 8:2775-2779, 1997; Isom et al, Cell 83:433-442, 1995). Originally characterized as a modulator of sodium channel properties and membrane surface area (Eubanks et al., supra), β2, along with the βl subunit, is also capable of acting independently of the sodium channel as a cell adhesion molecule. In Drosophila S2 cells, the β 1 and β2 subunits can bind in a trans-homophilic fashion, and with matrix proteins Tenascin C and Tenascin R via their EGF repeat motif, resulting in changes to the cytoskeleton, as well as alterations in cell adhesion and aggregation properties (Malhotra et al., J. Biol. Chem. 275:11383-11388, 2000; Xiao et al., J. Biol. Chem. 274:26511-26517, 1999). In addition, β2 has been characterized as a gamma-secretase target that induces migration in Chinese Hamster Ovary (CHO) cells (Kim et al., J. Biol. Chem. 280:23251-23261, 2005). These studies have also suggested that β2 undergoes ectodomain shedding mediated by an α-secretase-like protease(s). Kim et al., supra. Notch

The Notch receptor family is a class of evolutionarily conserved transmembrane receptors that transmit signals affecting development in organisms as diverse as sea urchins and humans. Both Notch receptors and its family of ligands Delta and Serrate (the latter known as Jagged in mammals) are transmembrane proteins with large extracellular domains that contain epidermal growth factor (EGF)-like repeats. The number of Notch paralogies differs between species. For example, there are four Notch receptors in mammals (Notch 1-Notch4), two in Caenorhabditis elegans (LIN- 12 and GLP-I) and one in Drosophila melanogaster (Notch). Notch receptors are proteolytically processed during transport to the cell surface by a furin-like protease at a site S 1 external to the transmembrane domain, producing an extracellular Notch (ECN) subunit and a Notch transmembrane subunit (NTM). These two subunits remain non-covalently associated and constitute the mature heterodimeric cell-surface receptor. Notch 1 ECN subunits contains 36 N- terminal EGF-like repeats followed by three tandemly repeated Lin 12/Notch Repeat (LNR) modules that precede the Sl site. Each LNR module contains three disulfide bonds and a group of conserved acidic and polar residues predicted to coordinate a calcium ion. Within the EGF repeat region lie binding sites for the activating ligands. The LNR modules, which comprise a unique domain of Notch receptors, participate in maintaining Notch in a resting conformation before ligand-induced activation. The Notch 1 NTM comprises an extracellular region (which

harbors the S2 cleavage site), a transmembrane segment (which harbors the S3 cleavage site), and a large intracellular part that includes a RAM domain, ankyrin repeats, a transactivation domain and a carboxy-teminal PEST sequence. Stable association of the ECN and NTM subunits is dependent on a heterodimerization domain (HD) comprising the carboxy-terminal end of the ECN (termed HD-C) and the extracellular amino-terminal end of NTM (termed HD-N). Binding of a Notch ligand to the ECN subunit initiates two successive proteolytic cleavages that occur through regulated intramembrane proteolysis. The first cleavage by a metalloprotease at site S2 renders the Notch transmembrane subunit susceptible to the second cleavage at site S3 close to the inner leaflet of the plasma membrane. Site S3 cleavage, which is catalyzed by a multiprotein complex containing presenilin and nicastrin, liberates the intracellular portion of the Notch transmembrane subunit, allowing it to translocate to the nucleus and activate transcription of target genes.

Five Notch ligands of the Jagged and Delta- like classes have been identified in humans (Jaggedl (also termed Serratel), Jagged2 (also termed Serrate2), Delta-likel (also termed DLLl), Delta-like3 (also termed DLL3), and Delta-like4 (also termed DLL4)). Each of the ligands is a single-pass transmembrane protein with a conserved N-terminal Delta, Serrate, LAG-2 (DSL) motif essential for binding Notch. A series of EGF-like modules C-terminal to the DSL motif precede the membrane-spanning segment. Unlike the Notch receptors, the ligands have short cytoplasmic tails of 70-215 amino acids at the C-terminus. In addition, other types of ligands have been reported (e.g., DNER, NB3, and F3/Contactin).

The Notch pathway functions during diverse developmental and physiological processes including those affecting neurogenesis in flies and vertebrates. In general, Notch signaling is involved in lateral inhibition, lineage decisions, and the establishment of boundaries between groups of cells (see, e.g., Bray, Molecular Cell Biology 7:678-679, 2006). A variety of human diseases, including cancers and neurodegenerative disorders, have been shown to result from mutations in genes encoding Notch receptors or their ligands (see, e.g., Nam et al., Curr. Opin. Chem. Biol. 6:501-509, 2002). The connection between unrestrained Notch signaling and malignancy was first recognized when a recurrent t(7;9)(q34;q34.3) chromosomal translocation, which creates a truncated, constitutively active variant of human Notchl, was identified in a

subset of human acute lymphoblastic leukemias (T-ALL). In mouse models, Notchl signaling has been shown to be essential for T cell development and that Notchl -mediated signals promote T cell development at the expense of B cell development. Also, in mouse models, excess Notch signaling during development leads to T cell neoplasia. Moreover, Notch receptors are expressed in a wide-range of human cancers and tumor- derived cell lines and promote neural fates in human embryonic stem cells. For instance, Notch is highly expressed in neoplastic lesions in the human cervix and in human renal cell carcinoma cells. Given the involvement of Notch signaling in a wide variety of human disease it is clear that there continues to be a need for agents that regulate Notch signaling and that have clinical attributes that are optimal for development as therapeutic agents. The invention described herein meets this need and provides other benefits. REST

REST (also called NRSF) is a transcriptional repressor of neuronal gene expression in non-neuronal tissues (Westbrook et al, Cell: 121:837-848, 2005). REST has been characterized as a tumor suppressor. The REST gene was identified as a frequent target of deletion in colorectal cancer. Further, a dominant negative form of REST has been identified which is capable of transforming epithelial cells. There is a need in the art to identify genes involved with REST tumor suppression. Such genes and their encoded proteins are useful targets, e.g., in the treatment of cancer. The invention described herein meets this need and provides other benefits.

SUMMARY

The invention is based, in part, on the discovery that loss of the transcriptional repressor REST leads to expression of β2, which in turn activates Notch signaling in tumors. The invention is further based, in part, on the identification of β2 as a novel ligand of Notch, whereby β2 induces EMT by binding to Notch and activating Notch signaling. These discoveries indicate that the REST/β2/Notch pathway promotes tumor progression and/or metastasis.

In one aspect, compositions and methods are provided for the classification, diagnosis, treatment, and prevention of tumors characterized by loss of REST function, expression of β2, and/or activation of Notch.

In another aspect, a monoclonal antibody that binds to β2 and blocks binding of β2 to Notch is provided. In one embodiment, the monoclonal antibody (a) is produced by a hybridoma selected from ATCC Accession Number PTA-8404, PTA-8405 and PTA-8406; (b) is a humanized form of the antibody of (a); (c) binds to the same epitope as the antibody of (a); or (d) competes with the antibody of (a) for binding to β2.

In another aspect, an isolated soluble polypeptide is provided, wherein the polypeptide comprises a fragment of Notch that specifically binds to β2.

In another aspect, a method of inhibiting tumor progression is provided, the method comprising exposing a tumor to an antagonist of β2. In one embodiment, the antagonist of β2 is an antisense nucleic acid specific for SCN2B. In one such embodiment, the antisense nucleic acid is a regulatory RNA capable of RNAi. In another embodiment, the antagonist of β2 is an antibody that binds to β2 and blocks binding of β2 to Notch. In one such embodiment, the antibody (a) is produced by a hybridoma selected from ATCC Accession Number PTA-8404, PTA-8405 and PTA-8406; (b) is a humanized form of the antibody of (a); (c) binds to the same epitope as the antibody of (a); or (d) competes with the antibody of (a) for binding to β2. In another embodiment, the antagonist of β2 is an antibody that binds to Notch and blocks binding of Notch to β2. In one such embodiment, the antibody binds within a region of Notch 1 comprising EGF repeats 10-21. In another embodiment, the antagonist of β2 comprises a soluble polypeptide comprising a fragment of Notch that specifically binds to β2. In another embodiment, the tumor is metastatic. In another embodiment, the tumor is resistant to chemotherapy. In another embodiment, the tumor is a colon tumor. In another embodiment, the tumor has decreased REST activity or increased β2 activity.

In another aspect, a method of inhibiting EMT in a cell is provided, the method comprising exposing the cell to an antagonist of β2. In one embodiment, the antagonist of β2 is an antisense nucleic acid specific for SCN2B. In one such embodiment, the antisense nucleic acid is a regulatory RNA capable of RNAi. In another embodiment, the antagonist of β2 is an antibody that binds to β2 and blocks binding of β2 to Notch. In one such embodiment, the antibody (a) is produced by a hybridoma selected from ATCC Accession Number PTA-8404, PTA-8405 and PTA-8406; (b) is a humanized form of the antibody of (a); (c) binds to the same

epitope as the antibody of (a); or (d) competes with the antibody of (a) for binding to β2. In another embodiment, the antagonist of β2 is an antibody that binds to Notch and blocks binding of Notch to β2. In one such embodiment, the antibody binds within a region of Notch 1 comprising EGF repeats 10-21. In another embodiment, the antagonist of β2 comprises a soluble polypeptide comprising a fragment of Notch that specifically binds to β2. In another embodiment, the cell is a tumor cell. In another embodiment, the tumor cell is derived from a metastatic tumor. In another embodiment, the tumor cell is derived from a tumor that is resistant to chemotherapy. In another embodiment, the tumor cell is a colon tumor cell. In another embodiment, the cell is in vitro. In another embodiment, the cell is in vivo. In another aspect, a method of determining whether a tumor will respond to an antagonist of β2 or an antagonist of Notch is provided, the method comprising detecting decreased REST activity or increased β2 activity in the tumor, wherein decreased REST activity or increased β2 activity in the tumor indicates that the tumor will respond to an antagonist of β2 or an antagonist of Notch. In one embodiment, the method comprises detecting decreased REST activity. In another embodiment, the method comprises detecting increased β2 activity. In another embodiment, the tumor is metastatic. In another embodiment, the tumor is resistant to chemotherapy. In another embodiment, the tumor is a colon tumor.

The above embodiments and further embodiments are provided in the description below.

BRIEF DESCRIPTION OF THE FIGURES

Figure IA

SCN2B expression in normal colon epithelium (lanes 1 - 5) and colon tumor epithelium (lanes 6 - 13). RNA was isolated following laser capture microdissection, and SCN2B expression was measured by microarray analysis. Values represent relative expression levels as a ratio of SCN2B transcript to a universal reference RNA (derived from a pool of tumor cell lines). The value of 33 for the sample in lane 7 is truncated, indicated by bars.

Figure IB

Examples of β2 protein expression in colon tumors and normal colon using an α-β2 monoclonal antibody (3Dl).

Figure 2A

Visualization of the actin cytoskeleton of cell lines (names on left) treated with control conditioned media (C-CM) or β2 ECD in conditioned media (β2-CM) or transfected with full length β2 (FL: β2). Images for experimental groups were collected using the same settings. The actin cytoskeleton was stained with phalloidin and nuclei with DAPI. 15 μm scale bars are indicated in lower left corner.

Figure 2B

Antibody blocking of β2-induced phenotypic change in β2-transfectected CHO (upper 2 panels) or β2-transfectected SW620 (lower 2 panels) cells treated with antibodies against Ragweed (RW, left panels) or β2 (right panels). The actin cytoskeleton was stained with phalloidin and nuclei with DAPI. All images for experimental groups were collected using the same settings. Scale bar: 15 μm.

Figure 2C β2 ECD depletion assay: NCI-H226 cells were treated with control (C-CM) or β2 conditioned media (β2-CM) subjected to mock β2 depletion or partial or complete β2 depletion. The corresponding protein recovery is indicated by lane on the α-β2 immunoblot. Lane 1 contains β2 isolated from conditioned media as a positive control. The actin cytoskeleton was stained with phalloidin and nuclei with DAPI. All images were collected using the same settings. Scale bar: 15 μm. Figure 3A

Migration of vector-transfected (Vec) SW620 control cells or β2-transfected SW620 (FL: β2) cells, or SW620 cells treated with control conditioned medium (C-CM) or β2 ECD in conditioned medium (β2-CM), in 0.1% fetal bovine serum (FBS). No migration was observed in the absence of serum (0% FBS). Fluorescence intensity is of migrated cells stained with YO- PRO-I . Error bars represent standard deviation of mean values, derived from triplicates. A statistically significant increase in migration was observed for both β2-transfected or β2-ECD treated SW620 cells (p = 0.03 and p = 0.0009, respectively).

Figure 3B

Migration of SW480 cells treated with an α-Ragweed (RW) antibody or 2 different α-β2 antibodies (3Dl or 12A9). Fluorescence intensity is of migrated cells stained with YO-PRO-I. Error bars represent standard deviation of mean values, derived from triplicates. A statically significant decrease in migration was observed in the presence of both α-β2 antibodies (p = 0.001 for each).

Figure 3 C

Starvation assay: cell death of vector-transfected (Vec) SW620 control cells or β2- transfected SW620 (FL: β2) cells as a percentage of total cells after starvation. Experiments were performed in triplicate, error bars represent standard deviation of mean values. A statically significant decrease in cell death was observed for SW620 cells transfeced with β2 (p = 0.002).

Figure 3D

Doxorubicin resistance in SW620 cells: cell viability (Y axis) in the presence of doxorubicin (μg/ml, X-axis) for cells transfected with vector only (Vec) or full length β2 (FL: β2). Experimental points were performed in triplicate, error bars represent standard deviation of mean values.

Figure 3 E

Methotrexate resistance in CHO cells: cell death of cells treated with control conditioned medium (C-CM) or β2 ECD in conditioned medium (β2-CM), as a percentage of total. Experiments performed in triplicate, error bars represent standard deviation of mean values. A statically significant decrease in cell death was observed for CHO cells treated with β2 ECD (p = 0.01).

Figure 4A

E-cadherin staining of SW620 control-treated cells (C-CM) or cells transfected with β2 protein (FL: β2) or treated with β2 ECD in conditioned media (β2-CM). Nuclei were stained with DAPI. All images were collected using the same settings. Scale bar: 15 μm.

Figure 4B

FACS analysis of E-cadherin staining of SW620 in (i) cells transfected with vector (Vec) or full length β2 (FL: β2), or (ii) cells treated with control conditioned medium (C-CM) or β2 ECD in conditioned medium (β2-CM). Median ratio values were plotted and error bars represent the standard deviation of duplicates.

Figure 4C

Vimentin staining of SW620 control-treated cells (C-CM) or cells transfected with β2 protein (FL: β2) or treated with β2 ECD in conditioned media (β2-CM). Nuclei were stained with DAPI. All images were collected using the same settings. Scale bar: 15 μm. Figure 4D

Twistl depletion: actin cytoskeleton (phalloidin, upper panel) and E-cadherin (lower panel) staining of SW620 cells treated with β2 ECD in conditioned media (β2-CM) after siRNA knockdown using a non-targeting control sequence (siNT) or a siRNA targeting Twistl (siTwistl). No change in phenotype or E-cadherin staining was detected in siNT or siTwistl cells treated with control conditioned medium (C-CM). Images for experimental groups were collected using the same settings. Nuclei were stained with DAPI. Scale bar: 15 μm.

Figure 4E

E-cadherin levels: quantitative analysis of E-cadherin staining in Twistl depletion experiments for SW620 cells treated with control conditioned media (C-CM) or β2 conditioned media (β2-CM). Statistical analyses indicated that E-cadherin levels for β2-ECD treated cells depleted for Twistl (siTwistl and siTwistl (3)) were significantly different compared to β2-ECD treated cells transfected with a non-targeting control (siNT) (p = 0.001 and 0.009). The last set of columns, siTwistl(3), represent a combined analysis of the data for 3 additional independent siRNA sequences targeting Twistl. At least 5 independent fields of cells were used for quantitative analysis using Metamorph as described. Error bars represent the standard error.

Figure 5A β2 (left column) and REST (right column) staining of SW620 and SW480 cells (top 2 panels) and in colon tumor and normal colon (bottom 2 panels). All images for an experimental group were collected using the same settings. Scale bar: 15 μm Figure 5B

Immunoblot analysis of REST (upper panel) and β2 (lower panel) in SW620 following siRNA knockdown of REST (siREST) as compared to a non-targeting control (siNT). Molecular weight (KDa) is indicated on the left. The blot was also probed for β-tubulin (middle panel) as a loading control. Figure 5C

Relative decrease in REST protein (REST) and increase in β2 (β2) after REST knockdown using siRNA, normalized with respect to the non-targeting siRNA control (siNT, set tolOO%). Values determined from Licor intensity readings of the immunoblot in 5B, background- subtracted and normalized to β-tubulin. Figure 5D

REST depletion: actin cytoskeleton (phalloidin, upper panel), E-cadherin (middle panel) and vimentin (lower panel) staining of SW620 cells after knockdown of REST using siRNA (siREST) or a non-targeting control (siNT), and in the presence of α-Ragweed (siREST, α-RW) or α-β2 (siREST, α-β2) antibodies. Images for all experimental groups were collected using the same settings. Nuclei were stained with DAPI. Scale bar: 15 μm

Figure 5 E

E-cadherin levels: quantitative analysis of E-cadherin staining in siREST depletion for SW620 cell experimental groupings in Figure 5D. E-cadherin levels for cells transfected with REST-specifϊc siRNA (siREST) were significantly decreased compared to the levels detected in cells transfected with the non-targeting control (siNT; p = 0.001). REST depletion in the presence of α-β2 antibodies 3Dl (siREST:3Dl) and 2E3 (siREST:2E3) resulted in wild-type levels of E-cadherin staining that were significantly increased compared to REST-depleted cells

(siREST) or REST-depleted cells treated with an α-Ragweed (siREST: α-RW) antibody (p = 0.02 and p = 0.01). At least 5 independent fields of cells were used for quantitative analysis using Metamorph as described. Error bars represent the standard error.

Figure 6A Notchl depletion: actin cytoskeleton (phalloidin, upper panel) and E-cadherin (lower panel) staining of SW620 cells treated with β2 ECD in conditioned media (β2-CM) after siRNA knockdown using a non-targeting control sequence (siNT) or a siRNA targeting Notchl (siNotchl). No change in phenotype or E-cadherin staining was detected in siNT or siNotchl cells treated with control conditioned medium (C-CM). Images for experimental groups were collected using the same settings. Nuclei were stained with DAPI. Scale bar: 15 μm.

Figure 6B

Chemical inhibition of Notch signaling: E-cadherin staining of SW620 cells treated with β2 ECD in conditioned media (β2-CM) after addition of DMSO or DAPT in DMSO (DAPT). No change in E-cadherin staining was detected in cells treated with control conditioned medium (C-CM) in DMSO. Images for experimental groups were collected using the same settings. Nuclei were stained with DAPI. Scale bar: 15 μm.

Figure 6C

E-cadherin levels: quantitative analysis of E-cadherin staining in siNotchl depleted and DAPT-treated SW620 cells treated with control conditioned media (C-CM) or β2 conditioned media (β2-CM). Statistical analyses indicated that E-cadherin levels for β2-ECD treated cells depleted for Notchl (siNotchl and siNotchl (3)) were significantly different compared to β2- ECD treated cells transfected with a non targeting control (siNT) (p = 0.03 and 0.03). Columns labeled siNotchl (3) represent a combined analysis of the data for 3 additional independent siRNA sequences targeting Notchl. E-cadherin levels were also significantly different for DAPT-treated cells (DAPT) treated with β2-ECD (β2-CM) compared to β2-ECD treated cells in DMSO (DMSO) (p = 0.00001) At least 5 independent fields of cells were used for quantitative analysis using Metamorph as described. Error bars represent the standard error.

Figure 7A

Co-immunoprecipitation of endogenous Notchl in SW620 cells using α-β2 antibodies (β2: lanes 2, 3, 5, 6) or an α-Ragweed antibody (RW: lanes 1, 4) in SW620 cells transfected with vector only (Vec: lanes 1 - 3) or with β2 (FL: β2: lanes 4 - 6). The immunoblot was probed with a Notchl polyclonal antibody (G20) and bands were detected at the expected size for this antibody (-120 kDa, indicated on the left). The level and doublet band pattern of endogenous Notchl is shown in Lane 7, which contains an SW620 cell lysate (25 μg total protein).

Figure 7B

Binding of Notchl and β2 ECDs. Lanes 1 and 3 contain β2 conditioned media from CHO cells (containing His(8) tagged β2 ECD) and lanes 2 and 4 control conditioned media from CHO cells containing an irrelevant His(8) tagged protein (GIi-I). Flag-tagged Notchl ECD protein was added to lanes 1 - 4 as described. Lane 5 contains 100 ng purified Notchl ECD, Lane 6 contains 50 ng β2 ECD (expressed and purified from E. coli). The blot was probed for Notchl using an α- Flag antibody (labeled Notchl, upper section of immunoblot) then stripped and re-probed for β2 using an α-β2 monoclonal antibody (3Dl, labeled β2 lower section of immunoblot). Molecular weight (KDa) is indicated on the left.

Figure 7C

Binding of Notchl ECD fragment containing EGF repeat region 10-21 and β2 ECD. Lanes 1 and 3 contain β2 conditioned media from CHO cells (containing His(8) tagged β2 ECD) and lanes 2 and 4 control conditioned media from CHO cells containing an irrelevant His(8) tagged protein. Flag-tagged Notchl ECD EGF repeat regions were added to lanes 1 and 2 (EGF 10-21) and lanes 3 and 4 (EGF 22-33). Lanes 5 and 6 contain 75 ng purified Notchl ECD, EGF 10-21 or EGF22-33, respectively. The blot was probed for Notch ECD using an α-Flag antibody. Molecular weight (KDa) is indicated on the left. Figure 7D

Translocation of Notchl NICD to nucleus in response to β2. Notchl NICD staining in SW620 cells transfected with vector only (Vec) or full length β2 protein (FL: β2) is shown in the left 2 panels, and NICD staining for SW620 cells treated with control conditioned medium (C-

CM) or β2 ECD in conditioned medium (β2-CM) is shown in the right 2 panels. Nuclei were stained with DAPI. Scale bar: 15 μm. The lower series of panels contain enlarged regions from the images in the upper panels.

Figure 8 Overview of proposed pathway for induction of EMT resulting from loss of REST, expression of β2, and activation of Notch pathway signaling. CDHl = E-cadherin.

Figure 9

Anti-correlation of REST and β2 in tumor cell lines: summary of immunofluoresence analysis of tumor cell lines for REST and β2 expression. Semi-quantitative evaluation of staining indicated by +.

Figure IQA

LCM strategy from fresh-frozen colon tumor sections with examples of a well differentiated primary colon tumor (HF3766, upper panel) and a poorly differentiated invasive primary colon tumor (HF3546, lower panel). Captured cells are outlined in the left panels. Figure IQB

RT-PCR analysis of β2 transcript expression in sections from samples used for LCM and microarray analysis, normalized to β-actin expression.

Figure IQC

Non-isotopic in situ hybridization (ISH) for β2 transcript on colon tumor sections matching those used for LCM (fresh-frozen sections). Sense controls were run on matching sections and are shown for each image in the lower panel.

Figure IQD

Detection of β2 protein on an immunoblot using an α-β2 monoclonal antibody (3Dl) in SW620 transfected with vector only (VEC: lane 2) a or with full-length β2 (β2: lane 3). 25 μg of total cell protein was loaded in lanes 2 and 3. Purified β2 ECD (4 ng) was loaded in lane 1 (labeled ECD). Molecular weight (KDa) is indicated on the right.

Figure IQE β2 detection across human tumors by immunoblot analysis using an α-β2 monoclonal antibody (3Dl, upper panel). All samples are tumor samples and the tissue of origin is listed across the top. The blot was also probed with β-tubulin as a loading control (lower panel). Molecular weight (KDa) is indicated on the left.

Figure HA

Staining of the actin cytoskeleton (phalloidin) for a variety of cell lines treated with β2 ECD in conditioned medium (β2-CM, right panels) or with control conditioned medium (C-CM, left panels). Cell lines (names are listed on the left): SW480, PC3, HUVEC, MDCK, HEK293. Nuclei were stained with DAPI.

Figure HB

Notchl transcript expression in β2-responsive tumor cell lines SW620, SW480, NCI- H226, PC-3, and endothelial cell line HUVEC. From Affymetrix microarray data, MAS5 intensity values are plotted on the Y-axis. Figure HC

Notch2 transcript expression in β2-responsive tumor cell lines SW620, SW480, NCI- H226, PC-3, and endothelial cell line HUVEC. From Affymetrix microarray data, MAS5 intensity values are plotted on the Y-axis.

Figure HP Expression of other Notch ligands and receptors in SW620: Jagged 1 (JAGl), Jagged2

(JAG2), Notch3, Notch4. From Affymetrix microarray data, MAS5 intensity values are plotted on the Y-axis.

Figure 12A

HESl and Twistl transcript expression from 0 - 72 hours in SW620 cells treated β2 ECD in conditioned medium. RNA was extracted from cells at 0, 6, 18, 24, 48, and 72 hour timepoints and microarray analysis performed on Agilent Whole Human Genome microarrays versus a

universal reference RNA. Log ratio (Y-axis) is plotted against time in hours (X-axis). Transcript data for 2 independent HESl oligonucleotide probe sequences and for Twistl are shown.

Figure 12B

RT-PCR analysis of Twistl transcript expression at 0, 6, and 18 hr timepoints in SW620 cells treated with β2 ECD. Twistl expression was normalized to housekeeping gene RPL 19.

Figure 13A

REST depletion: RT-PCR analysis of REST (i) and β2 (ii) transcript expression in SW620 cells transfected with an siRNA specific to REST (siREST) or a non-targeting control (siNT). Transcript levels were normalized to housekeeping gene RPL 19. Figure 13B

REST depletion: Immunofluorescence analysis of REST (upper panel) and β2 (lower panels) in SW620 cells transfected with an siRNA specific to REST (siREST: right panels) or a non-targeting control (siNT: left panels). Nuclei were stained with DAPI. All experimental groups were imaged using the same settings. Scale bar: 15 μm Figure 13C

Notchl depletion: RT-PCR analysis Notchl transcript expression in SW620 cells transfected with an siRNA specific to Notchl (siNotchl) or a non-targeting control (siNT). Transcript levels were normalized to housekeeping gene RPLl 9.

Figure 14 Antibody blocking experiments. Five different anti-β2 antibodies were subject to competitive binding assays.

DETAILED DESCRIPTION OF EMBODIMENTS

The invention is based, in part, on the identification of β2 as a novel ligand of Notch that links loss of REST with activation of Notch signaling, thereby defining a role for β2, REST and Notch in tumor progression and metastasis.

I. DEFINITIONS

The term "β2" refers to any native sodium channel beta 2 subunit from any vertebrate source, including mammals such as primates (e.g. humans) and rodents (e.g., mice and rats), unless otherwise indicated. The term encompasses "full-length," unprocessed β2 as well as any form of β2 that results from processing in the cell. The term also encompasses naturally occurring variants of β2, e.g., splice variants or allelic variants.

The term "Notch" or "Notch receptor," as used herein, refers to any protein that belongs to the Notch family of single-pass heterodimeric transmembrane receptors. The term encompasses native Notch from any vertebrate source, including mammals such as primates (e.g. humans) and rodents (e.g., mice and rats), unless otherwise indicated. The term encompasses the mammalian Notch receptors (Notchl , Notch2, Notch3, and Notch4). The term encompasses "full-length," unprocessed Notch as well as any form of Notch that results from processing in the cell. The term also encompasses naturally occurring variants of Notch, e.g., splice variants or allelic variants. The term "Jagged," as used herein, refers to any protein that that belongs to the Jagged (or

"Serrate") family of ligands for Notch. The term encompasses native Jagged from any vertebrate source, including mammals such as primates (e.g. humans) and rodents (e.g., mice and rats), unless otherwise indicated. The term encompasses the mammalian Jagged family members termed Jagged 1 (also called Serratel) and Jagged 2 (also called Serrate 2). The term encompasses "full-length," unprocessed Jagged as well as any form of Jagged that results from processing in the cell. The term also encompasses naturally occurring variants of Jagged, e.g., splice variants or allelic variants.

The term "DLL," as used herein, refers to any protein that that belongs to the Delta-like family of ligands for Notch. The term encompasses native DLL from any vertebrate source, including mammals such as primates (e.g. humans) and rodents (e.g., mice and rats), unless otherwise indicated. The term encompasses the mammalian DLL family members termed Delta- like 1 (DLLl), Delta-like3 (DLL3), and Delta-like4 (DLL4). The term encompasses "full- length," unprocessed DLL as well as any form of DLL that results from processing in the cell.

The term also encompasses naturally occurring variants of DLL, e.g., splice variants or allelic variants.

The term "REST," as used herein, refers to any native repressor element 1 silencing transcription (REST) factor from any vertebrate source, including mammals such as primates (e.g. humans) and rodents (e.g., mice and rats), unless otherwise indicated. The term encompasses "full-length," unprocessed REST as well as any form of REST that results from processing in the cell. The term also encompasses naturally occurring variants of REST, e.g., splice variants or allelic variants.

The term "PRO" refers generally to any protein described herein, including but not limited to any of β2 , Notch, Jagged, DLL, and REST.

An "antagonist of β2" refers to an agent that inhibits production of β2 or nucleic acid encoding β2 (e.g., SCN2B nucleic acid); that inhibits processing of β2 (e.g., release of the ECD from β2); or that interacts directly with β2 or with Notch to inhibit binding of β2 to Notch.

A "disorder" is any condition or disease that would benefit from treatment with a composition or method of the invention. This includes chronic and acute disorders including those pathological conditions which predispose the mammal to the disorder in question. Non- limiting examples of disorders to be treated herein include conditions such as cancer (e.g., colon cancer) including refractory or metastatic cancers.

As used herein, "treatment" (and variations such as "treat" or "treating") refers to clinical intervention in an attempt to alter the natural course of the individual or cell being treated, and can be performed either for prophylaxis or during the course of clinical pathology. Desirable effects of treatment include preventing occurrence or recurrence of disease, alleviation of symptoms, diminishment of any direct or indirect pathological consequences of the disease, preventing metastasis, decreasing the rate of disease progression, amelioration or palliation of the disease state, and remission or improved prognosis. In some embodiments, antibodies of the invention are used to delay development of a disease or disorder or to slow the progression of a disease or disorder.

An "individual," "subject," or "patient" is a vertebrate. In certain embodiments, the vertebrate is a mammal. Mammals include, but are not limited to, farm animals (such as cows),

sport animals, pets (such as cats, dogs, and horses), primates, mice and rats. In certain embodiments, a mammal is a human.

The term "pharmaceutical formulation" refers to a preparation which is in such form as to permit the biological activity of the active ingredient to be effective, and which contains no additional components which are unacceptably toxic to a subject to which the formulation would be administered. Such formulations may be sterile.

An "effective amount" refers to an amount effective, at dosages and for periods of time necessary, to achieve the desired therapeutic or prophylactic result.

A "therapeutically effective amount" of a substance/molecule of the invention may vary according to factors such as the disease state, age, sex, and weight of the individual, and the ability of the substance/molecule, to elicit a desired response in the individual. A therapeutically effective amount encompasses an amount in which any toxic or detrimental effects of the substance/molecule are outweighed by the therapeutically beneficial effects. A "prophylactically effective amount" refers to an amount effective, at dosages and for periods of time necessary, to achieve the desired prophylactic result. Typically, but not necessarily, since a prophylactic dose is used in subjects prior to or at an earlier stage of disease, the prophylactically effective amount would be less than the therapeutically effective amount.

The term "cytotoxic agent" as used herein refers to a substance that inhibits or prevents a cellular function and/or causes cell death or destruction. The term is intended to include rad _J i-oac ₄ t _. i-ve i■so ₄ t _. opes ( _f e.g., A _A t.211 , _T 1131 , _T 1125 , _λ Y ₇ 90 , _π Re186 , _π Re188 , _c Sm153 , „Bi.212 , „ P32 , ^ P,b212 and,

radioactive isotopes of Lu), chemotherapeutic agents (e.g., methotrexate, adriamicin, vinca alkaloids (vincristine, vinblastine, etoposide), doxorubicin, melphalan, mitomycin C, chlorambucil, daunorubicin or other intercalating agents, enzymes and fragments thereof such as nucleolytic enzymes, antibiotics, and toxins such as small molecule toxins or enzymatically active toxins of bacterial, fungal, plant or animal origin, including fragments and/or variants thereof, and the various antitumor or anticancer agents disclosed below. Other cytotoxic agents are described below. A tumoricidal agent causes destruction of tumor cells.

A "toxin" is any substance capable of having a detrimental effect on the growth or proliferation of a cell.

A "chemotherapeutic agent" is a chemical compound useful in the treatment of cancer. Examples of chemotherapeutic agents include alkylating agents such as thiotepa and cyclosphosphamide (CYTOXAN®); alkyl sulfonates such as busulfan, improsulfan and piposulfan; aziridines such as benzodopa, carboquone, meturedopa, and uredopa; ethylenimines and methylamelamines including altretamine, triethylenemelamine, triethylenephosphoramide, triethylenethiophosphoramide and trimethylomelamine; acetogenins (especially bullatacin and bullatacinone); delta-9-tetrahydrocannabinol (dronabinol, MARINOL®); beta-lapachone; lapachol; colchicines; betulinic acid; a camptothecin (including the synthetic analogue topotecan (HYCAMTIN®), CPT-I l (irinotecan, CAMPTOS AR®), acetylcamptothecin, scopolectin, and 9-aminocamptothecin); bryostatin; callystatin; CC- 1065 (including its adozelesin, carzelesin and bizelesin synthetic analogues); podophyllotoxin; podophyllinic acid; teniposide; cryptophycins (particularly cryptophycin 1 and cryptophycin 8); dolastatin; duocarmycin (including the synthetic analogues, KW-2189 and CBl-TMl); eleutherobin; pancratistatin; a sarcodictyin; spongistatin; nitrogen mustards such as chlorambucil, chlornaphazine, chlorophosphamide, estramustine, ifosfamide, mechlorethamine, mechlorethamine oxide hydrochloride, melphalan, novembichin, phenesterine, prednimustine, trofosfamide, uracil mustard; nitrosoureas such as carmustine, chlorozotocin, fotemustine, lomustine, nimustine, and ranimnustine; antibiotics such as the enediyne antibiotics (e. g., calicheamicin, especially calicheamicin gammall and calicheamicin omegall (see, e.g., Nicolaou et ah, Angew. Chem Intl. Ed. Engl, 33: 183-186 (1994)); CDP323, an oral alpha-4 integrin inhibitor; dynemicin, including dynemicin A; an esperamicin; as well as neocarzinostatin chromophore and related chromoprotein enediyne antibiotic chromophores), aclacinomysins, actinomycin, authramycin, azaserine, bleomycins, cactinomycin, carabicin, carminomycin, carzinophilin, chromomycins, dactinomycin, daunorubicin, detorubicin, 6-diazo-5-oxo-L-norleucine, doxorubicin (including ADRIAMYCIN®, morpholino-doxorubicin, cyanomorpholino-doxorubicin, 2-pyrrolino-doxorubicin, doxorubicin HCl liposome injection (DOXIL®), liposomal doxorubicin TLC D-99 (MYOCET®), peglylated liposomal doxorubicin (CAELYX®), and deoxydoxorubicin), epirubicin, esorubicin, idarubicin, marcellomycin, mitomycins such as mitomycin C, mycophenolic acid, nogalamycin, olivomycins, peplomycin, porfiromycin, puromycin, quelamycin, rodorubicin, streptonigrin,

streptozocin, tubercidin, ubenimex, zinostatin, zorubicin; anti-metabolites such as methotrexate, gemcitabine (GEMZAR®), tegafur (UFTORAL®), capecitabine (XELOD A®), an epothilone, and 5-fluorouracil (5-FU); folic acid analogues such as denopterin, methotrexate, pteropterin, trimetrexate; purine analogs such as fludarabine, 6-mercaptopurine, thiamiprine, thioguanine; pyrimidine analogs such as ancitabine, azacitidine, 6-azauridine, carmofur, cytarabine, dideoxyuridine, doxifluridine, enocitabine, floxuridine; androgens such as calusterone, dromostanolone propionate, epitiostanol, mepitiostane, testolactone; anti-adrenals such as aminoglutethimide, mitotane, trilostane; folic acid replenisher such as frolinic acid; aceglatone; aldophosphamide glycoside; aminolevulinic acid; eniluracil; amsacrine; bestrabucil; bisantrene; edatraxate; defo famine; demecolcine; diaziquone; elfornithine; elliptinium acetate; an epothilone; etoglucid; gallium nitrate; hydroxyurea; lentinan; lonidainine; maytansinoids such as maytansine and ansamitocins; mitoguazone; mitoxantrone; mopidanmol; nitraerine; pentostatin; phenamet; pirarubicin; losoxantrone; 2-ethylhydrazide; procarbazine; PSK® polysaccharide complex (JHS Natural Products, Eugene, OR); razoxane; rhizoxin; sizofϊran; spirogermanium; tenuazonic acid; triaziquone; 2,2',2'-trichlorotriethylamine; trichothecenes (especially T-2 toxin, verracurin A, roridin A and anguidine); urethan; vindesine (ELDISINE®, FILDESIN®); dacarbazine; mannomustine; mitobronitol; mitolactol; pipobroman; gacytosine; arabinoside ("Ara-C"); thiotepa; taxoid, e.g., paclitaxel (TAXOL®), albumin-engineered nanoparticle formulation of paclitaxel (ABRAXANE™), and docetaxel (TAXOTERE®); chloranbucil; 6- thioguanine; mercaptopurine; methotrexate; platinum agents such as cisplatin, oxaliplatin (e.g., ELOXATIN®), and carboplatin; vincas, which prevent tubulin polymerization from forming microtubules, including vinblastine (VELBAN®), vincristine (ONCOVIN®), vindesine (ELDISINE®, FILDESIN®), and vinorelbine (NAVELBINE®); etoposide (VP- 16); ifosfamide; mitoxantrone; leucovorin; novantrone; edatrexate; daunomycin; aminopterin; ibandronate; topoisomerase inhibitor RFS 2000; difluoromethylornithine (DMFO); retinoids such as retinoic acid, including bexarotene (TARGRETIN®); bisphosphonates such as clodronate (for example, BONEFOS® or OSTAC®), etidronate (DIDROC AL®), NE-58095, zoledronic acid/zoledronate (ZOMETA®), alendronate (FOSAMAX®), pamidronate (AREDIA®), tiludronate (SKELID®), or risedronate (ACTONEL®); troxacitabine (a 1,3-dioxolane nucleoside cytosine analog);

antisense oligonucleotides, particularly those that inhibit expression of genes in signaling pathways implicated in aberrant cell proliferation, such as, for example, PKC-alpha, Raf, H-Ras, and epidermal growth factor receptor (EGF-R); vaccines such as THERATOPE® vaccine and gene therapy vaccines, for example, ALLOVECTIN® vaccine, LEUVECTIN® vaccine, and VAXID® vaccine; topoisomerase 1 inhibitor (e.g., LURTOTECAN®); rmRH (e.g.,

ABARELIX®); BAY439006 (sorafenib; Bayer); SU-11248 (sunitinib, SUTENT®, Pfizer); perifosine, COX-2 inhibitor (e.g. celecoxib or etoricoxib), proteosome inhibitor (e.g. PS341); bortezomib (VELC ADE®); CCI-779; tipifarnib (Rl 1577); orafenib, ABT510; Bcl-2 inhibitor such as oblimersen sodium (GENASENSE®); pixantrone; EGFR inhibitors (see definition below); tyrosine kinase inhibitors (see definition below); serine-threonine kinase inhibitors such as rapamycin (sirolimus, RAPAMUNE®); farnesyltransferase inhibitors such as lonafarnib (SCH 6636, SARASAR™); and pharmaceutically acceptable salts, acids or derivatives of any of the above; as well as combinations of two or more of the above such as CHOP, an abbreviation for a combined therapy of cyclophosphamide, doxorubicin, vincristine, and prednisolone; and FOLFOX, an abbreviation for a treatment regimen with oxaliplatin (ELOXATIN™) combined with 5 -FU and leucovorin.

Chemotherapeutic agents as defined herein include "anti-hormonal agents" or "endocrine therapeutics" which act to regulate, reduce, block, or inhibit the effects of hormones that can promote the growth of cancer. They may be hormones themselves, including, but not limited to: anti-estrogens with mixed agonist/antagonist profile, including, tamoxifen (NOLVADEX®), 4- hydroxytamoxifen, toremifene (FARESTON®), idoxifene, droloxifene, raloxifene (EVISTA®), trioxifene, keoxifene, and selective estrogen receptor modulators (SERMs) such as SERM3; pure anti-estrogens without agonist properties, such as fulvestrant (FASLODEX®), and EM800 (such agents may block estrogen receptor (ER) dimerization, inhibit DNA binding, increase ER turnover, and/or suppress ER levels); aromatase inhibitors, including steroidal aromatase inhibitors such as formestane and exemestane (AROMASIN®), and nonsteroidal aromatase inhibitors such as anastrazole (ARIMIDEX®), letrozole (FEMARA®) and aminoglutethimide, and other aromatase inhibitors include vorozole (RIVISOR®), megestrol acetate (MEGASE®), fadrozole, and 4(5)-imidazoles; lutenizing hormone-releaseing hormone agonists, including

leuprolide (LUPRON® and ELIGARD®), goserelin, buserelin, and tripterelin; sex steroids, including progestines such as megestrol acetate and medroxyprogesterone acetate, estrogens such as diethylstilbestrol and premarin, and androgens/retinoids such as fluoxymesterone, all transretionic acid and fenretinide; onapristone; anti-progesterones; estrogen receptor down- regulators (ERDs); anti-androgens such as flutamide, nilutamide and bicalutamide; and pharmaceutically acceptable salts, acids or derivatives of any of the above; as well as combinations of two or more of the above.

A "growth inhibitory agent" when used herein refers to a compound or composition which inhibits growth of a cell either in vitro or in vivo. Thus, the growth inhibitory agent may be one which significantly reduces the percentage of cells in S phase. Examples of growth inhibitory agents include agents that block cell cycle progression (at a place other than S phase), such as agents that induce Gl arrest and M-phase arrest. Classical M-phase blockers include the vincas (vincristine and vinblastine), taxanes, and topoisomerase II inhibitors such as doxorubicin, epirubicin, daunorubicin, etoposide, and bleomycin. Those agents that arrest Gl also spill over into S-phase arrest, for example, DNA alkylating agents such as tamoxifen, prednisone, dacarbazine, mechlorethamine, cisplatin, methotrexate, 5-fluorouracil, and ara-C. Further information can be found in Mendelsohn and Israel, eds., The Molecular Basis of Cancer, Chapter 1, entitled "Cell cycle regulation, oncogenes, and antineoplastic drugs" by Murakami et al. (W.B. Saunders, Philadelphia, 1995), e.g., p. 13. The taxanes (paclitaxel and docetaxel) are anticancer drugs both derived from the yew tree. Docetaxel (TAXOTERE®, Rhone-Poulenc Rorer), derived from the European yew, is a semisynthetic analogue of paclitaxel (TAXOL®, Bristol-Myers Squibb). Paclitaxel and docetaxel promote the assembly of microtubules from tubulin dimers and stabilize microtubules by preventing depolymerization, which results in the inhibition of mitosis in cells. The terms "cancer" and "cancerous" refer to or describe the physiological condition in mammals that is typically characterized by unregulated cell growth/proliferation. Examples of cancer include, but are not limited to, carcinoma, lymphoma (e.g., Hodgkin's and non-Hodgkin's lymphoma), blastoma, sarcoma, and leukemia. More particular examples of such cancers include squamous cell cancer, small-cell lung cancer, non-small cell lung cancer, adenocarcinoma of the

lung, squamous carcinoma of the lung, cancer of the peritoneum, hepatocellular cancer, gastrointestinal cancer, pancreatic cancer, glioma, cervical cancer, ovarian cancer, liver cancer, bladder cancer, hepatoma, breast cancer, colon cancer, colorectal cancer, endometrial or uterine carcinoma, salivary gland carcinoma, kidney cancer, liver cancer, prostate cancer, vulval cancer, thyroid cancer, hepatic carcinoma, leukemia and other lymphoproliferative disorders, and various types of head and neck cancer.

The terms "cell proliferative disorder" and "proliferative disorder" refer to disorders that are associated with some degree of abnormal cell proliferation. In one embodiment, the cell proliferative disorder is cancer. "Inhibiting cell growth or proliferation" means decreasing a cell's growth or proliferation by at least 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, or 100%, and includes inducing cell death.

"Tumor," as used herein, refers to all neoplastic cell growth and proliferation, whether malignant or benign, and all pre-cancerous and cancerous cells and tissues. The terms "cancer," "cancerous," "cell proliferative disorder," "proliferative disorder" and "tumor" are not mutually exclusive as referred to herein.

The term "colorectal tumor" or "colorectal cancer" refers to any tumor or cancer of the large bowel, which includes the colon (the large intestine from the cecum to the rectum) and the rectum. A "colorectal cancer cell" refers to a colon cancer cell or a rectal cancer cell, either in vivo or in vitro, and encompasses cell lines derived from colorectal cancer cells.

The term "colon tumor" or "colon cancer" refers to any tumor or cancer of the colon.

A "colon cancer cell" refers to a colon cancer cell, either in vivo or in vitro, and encompasses cell lines derived from colon cancer cells. The term "neoplasm" or "neoplastic cell" refers to an abnormal tissue or cell that proliferates more rapidly than corresponding normal tissues or cells and continues to grow after removal of the stimulus that initiated the growth.

The term "epithelial-mesenchymal transition" or "EMT" refers to the process by which a cell loses epithelial properties and acquires mesenchymal properties, including but not limited to

loss of cell adhesion and increased migration, that in the case of tumor cells, promote local invasion and/or metastasis.

The term "tumor progression" refers to all stages of a tumor, including tumorigenesis, tumor growth and proliferation, invasion, and metastasis. The term "inhibiting tumor progression" means inhibiting the development, growth, proliferation, or spreading of a tumor, including without limitation the following effects: (1) inhibition, to some extent, of tumor growth, including slowing down or complete growth arrest; (2) reduction in the number of tumor cells; (3) reduction in tumor size; (4) inhibition (i.e., reduction, slowing down or complete stopping) of tumor cell infiltration into adjacent peripheral organs and/or tissues; (5) inhibition (i.e. reduction, slowing down or complete stopping) of metastasis; (6) increase in the length of survival of a patient or patient population following treatment for a tumor; and/or (7) decreased mortality of a patient or patient population at a given timepoint following treatment for a tumor.

A tumor "responds" to a particular agent if tumor progression is inhibited as defined above.

The term "antisense nucleic acid" refers to a nucleic acid that reduces expression of a target polynucleotide to which it is partially or fully complementary. An antisense nucleic acid is "specific" for a target polynucleotide if it (a) selectively binds to the target polynucleotide or its encoded mRNA and (b) reduces expression of the target polynucleotide by at least about 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99%.

The term "RNAi" or RNA interference" refers to partial or complete inhibition of gene expression by an RNA-mediated mechanism, e.g., by a double-stranded RNA-mediated mechanism. The term "knock down" refers to such partial or complete inhibition of gene expression.

The term "regulatory RNA" or "regulatory RNA molecule" refers to an RNA capable of regulating expression of a gene, e.g., by regulating expression of the corresponding mRNA. Such regulatory RNAs include, but are not limited to, RNA capable of RNAi. A regulatory RNA is "specific" for a target polynucleotide if it (a) selectively binds to the target polynucleotide or its

encoded mRNA and (b) reduces expression of the target polynucleotide by at least about 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% when the regulatory RNA is expressed in a cell that expresses the target polynucleotide.

The term "siRNA" or "short interfering RNA" refers to a double stranded RNA that has the ability to reduce expression of a target polynucleotide when the siRNA is expressed in the same cell as the target polynucleotide. The complementary strands of an siRNA that form the double stranded RNA typically have substantial or complete identity. In one embodiment, an siRNA refers to a double-stranded RNA, one strand of which (also referred to as the "antisense" strand) has substantial or complete identity to at least a portion of a target mRNA. In certain embodiments, an siRNA is about 15-50 nucleotides in length, about 20-30 nucleotides in length, about 20-25 nucleotides in length, or 24-29 nucleotides in length, including any length that is an integer within the above-stated ranges. See also PCT/US03/07237, published as WO03076592, herein incorporated by reference in its entirety. An siRNA molecule is "specific" for a target polynucleotide if it (a) selectively binds to the target polynucleotide or its encoded mRNA and (b) reduces expression of the target polynucleotide by at least about 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% when the siRNA is expressed in a cell that expresses the target polynucleotide.

The term "siRNA" encompasses RNA capable of forming a hairpin structure, e.g., microRNA precursors (pre-miRNA) and short hairpin RNA (shRNA). See, e.g., Brummelkamp et al. (2002) Science 550-553. A pre-miRNA or an shRNA is a self-complementary RNA molecule having a sense region, an antisense region, and a loop region, and which is capable of forming a hairpin structure. In certain embodiments, the sense and antisense regions are each about 15-50 nucleotides in length, about 20-30 nucleotides in length, about 20-25 nucleotides in length, or about 24-29 nucleotides in length, including any length that is an integer within the foregoing ranges; and the loop portion is about 2-15 nucleotides in length or about 6-9 nucleotides in length, including any length that is an integer within the foregoing ranges.

The term "extracellular domain" or "ECD" refers to a region of a transmembrane protein that excludes essentially all of the transmembrane and cytoplasmic domains.

The term "soluble polypeptide" refers to a polypeptide that is not membrane-bound.

A "refractory" tumor refers to a tumor that a clinician skilled in the relevant art would conclude is significantly resistant to and/or is (or is expected to be) significantly non-responsive to a therapeutic treatment (e.g., there is increased tumor volume, number of cancerous cells, and/or spreading of the cancer even though a therapeutic treatment is given). In this context, such therapeutic treatment includes, but is not limited to, chemotherapy, radiation, stem cell transplantation, and surgical treatment, excluding treatment with agonists of REST, antagonists of β2, or antagonists of Notch. The phrase "resistant to chemotherapy" refers to a tumor that a clinician skilled in the relevant art would conclude is significantly resistant to and/or is (or is expected to be) significantly non-responsive to chemotherapy, excluding chemotherapy with agonists of REST, antagonists of β2, or antagonists of Notch.

"Relapsed" refers to the regression of a patient's illness substantially back to its former diseased state following a therapeutic treatment, especially the return of symptoms (e.g., cancer cells) following an apparent recovery or partial recovery (e.g., remission) in response to the therapeutic treatment. In this context, such therapeutic treatment includes, but is not limited to, chemotherapy, radiation, stem cell transplantation, and surgical treatment, excluding treatment with agonists of REST, antagonists of β2, or antagonists of Notch.

The term "antibody" herein is used in the broadest sense and specifically covers monoclonal antibodies, polyclonal antibodies, multispecific antibodies (e.g. bispecifϊc antibodies) formed from at least two intact antibodies, and antibody fragments so long as they exhibit the desired biological activity.

An "isolated" antibody is one which has been identified and separated and/or recovered from a component of its natural environment. Contaminant components of its natural environment are materials which would interfere with research, diagnostic or therapeutic uses for the antibody, and may include enzymes, hormones, and other proteinaceous or nonproteinaceous solutes. In some embodiments, an antibody is purified (1) to greater than 95% by weight of antibody as determined by, for example, the Lowry method, and in some embodiments, to greater than 99% by weight; (2) to a degree sufficient to obtain at least 15 residues of N-terminal or internal amino acid sequence by use of, for example, a spinning cup sequenator, or (3) to homogeneity by SDS-PAGE under reducing or nonreducing conditions using, for example,

Coomassie blue or silver stain. Isolated antibody includes the antibody in situ within recombinant cells since at least one component of the antibody's natural environment will not be present. Ordinarily, however, isolated antibody will be prepared by at least one purification step. "Native antibodies" are usually heterotetrameric glycoproteins of about 150,000 daltons, composed of two identical light (L) chains and two identical heavy (H) chains. Each light chain is linked to a heavy chain by one covalent disulfide bond, while the number of disulfide linkages varies among the heavy chains of different immunoglobulin isotypes. Each heavy and light chain also has regularly spaced intrachain disulfide bridges. Each heavy chain has at one end a variable domain (V _R ) followed by a number of constant domains. Each light chain has a variable domain at one end (V _L ) and a constant domain at its other end; the constant domain of the light chain is aligned with the first constant domain of the heavy chain, and the light chain variable domain is aligned with the variable domain of the heavy chain. Particular amino acid residues are believed to form an interface between the light chain and heavy chain variable domains.

The term "anti-PRO antibody" or "an antibody that binds to PRO" refers to an antibody that is capable of binding PRO with sufficient affinity such that the antibody is useful as a diagnostic and/or therapeutic agent in targeting PRO. Preferably, the extent of binding of an anti-PRO antibody to an unrelated, non-PRO protein is less than about 10% of the binding of the antibody to PRO as measured, e.g., by a radioimmunoassay (RIA). In certain embodiments, an antibody that binds to PRO has a dissociation constant (Kd) of < lμM, < 100 nM, < 10 nM, < 1 nM, or < 0.1 nM. In certain embodiments, an anti-PRO antibody binds to an epitope of PRO that is conserved among PRO from different species.

The "variable region" or "variable domain" of an antibody refers to the amino-terminal domains of the heavy or light chain of the antibody. The variable domain of the heavy chain may be referred to as "VH." The variable domain of the light chain may be referred to as "VL." These domains are generally the most variable parts of an antibody and contain the antigen- binding sites.

The term "variable" refers to the fact that certain portions of the variable domains differ extensively in sequence among antibodies and are used in the binding and specificity of each particular antibody for its particular antigen. However, the variability is not evenly distributed

throughout the variable domains of antibodies. It is concentrated in three segments called hypervariable regions (HVRs) both in the light-chain and the heavy-chain variable domains. The more highly conserved portions of variable domains are called the framework regions (FR). The variable domains of native heavy and light chains each comprise four FR regions, largely adopting a beta-sheet configuration, connected by three HVRs, which form loops connecting, and in some cases forming part of, the beta-sheet structure. The HVRs in each chain are held together in close proximity by the FR regions and, with the HVRs from the other chain, contribute to the formation of the antigen-binding site of antibodies (see Kabat et al., Sequences of Proteins of Immunological Interest, Fifth Edition, National Institute of Health, Bethesda, MD (1991)). The constant domains are not involved directly in the binding of an antibody to an antigen, but exhibit various effector functions, such as participation of the antibody in antibody- dependent cellular toxicity.

The "light chains" of antibodies (immunoglobulins) from any vertebrate species can be assigned to one of two distinct types, called kappa (K) and lambda (λ), based on the amino acid sequences of their constant domains.

Depending on the amino acid sequences of the constant domains of their heavy chains, antibodies (immunoglobulins) can be assigned to different classes. There are five major classes of immunoglobulins: IgA, IgD, IgE, IgG, and IgM, and several of these may be further divided into subclasses (isotypes), e.g., IgG ₁ , IgG ₂ , IgG ₃ , IgG ₄ , IgA ₁ , and IgA ₂ . The heavy chain constant domains that correspond to the different classes of immunoglobulins are called α, δ, ε, γ, and μ, respectively. The subunit structures and three-dimensional configurations of different classes of immunoglobulins are well known and described generally in, for example, Abbas et al. Cellular and MoI. Immunology, 4th ed. (W.B. Saunders, Co., 2000). An antibody may be part of a larger fusion molecule, formed by covalent or non-covalent association of the antibody with one or more other proteins or peptides.

The terms "full length antibody," "intact antibody" and "whole antibody" are used herein interchangeably to refer to an antibody in its substantially intact form, not antibody fragments as defined below. The terms particularly refer to an antibody with heavy chains that contain an Fc region.

A "naked antibody" for the purposes herein is an antibody that is not conjugated to a cytotoxic moiety or radiolabel.

"Antibody fragments" comprise a portion of an intact antibody, preferably comprising the antigen binding region thereof. Examples of antibody fragments include Fab, Fab', F(ab') ₂ , and Fv fragments; diabodies; linear antibodies; single-chain antibody molecules; and multispecifϊc antibodies formed from antibody fragments.

Papain digestion of antibodies produces two identical antigen-binding fragments, called "Fab" fragments, each with a single antigen-binding site, and a residual "Fc" fragment, whose name reflects its ability to crystallize readily. Pepsin treatment yields an F(ab') ₂ fragment that has two antigen-combining sites and is still capable of cross-linking antigen.

"Fv" is the minimum antibody fragment which contains a complete antigen-binding site. In one embodiment, a two-chain Fv species consists of a dimer of one heavy- and one light-chain variable domain in tight, non-covalent association. In a single-chain Fv (scFv) species, one heavy- and one light-chain variable domain can be covalently linked by a flexible peptide linker such that the light and heavy chains can associate in a "dimeric" structure analogous to that in a two-chain Fv species. It is in this configuration that the three HVRs of each variable domain interact to define an antigen-binding site on the surface of the VH-VL dimer. Collectively, the six HVRs confer antigen-binding specificity to the antibody. However, even a single variable domain (or half of an Fv comprising only three HVRs specific for an antigen) has the ability to recognize and bind antigen, although at a lower affinity than the entire binding site.

The Fab fragment contains the heavy- and light-chain variable domains and also contains the constant domain of the light chain and the first constant domain (CHl) of the heavy chain. Fab' fragments differ from Fab fragments by the addition of a few residues at the carboxy terminus of the heavy chain CHl domain including one or more cysteines from the antibody hinge region. Fab'-SH is the designation herein for Fab' in which the cysteine residue(s) of the constant domains bear a free thiol group. F(ab') ₂ antibody fragments originally were produced as pairs of Fab' fragments which have hinge cysteines between them. Other chemical couplings of antibody fragments are also known.

"Single-chain Fv" or "scFv" antibody fragments comprise the VH and VL domains of antibody, wherein these domains are present in a single polypeptide chain. Generally, the scFv polypeptide further comprises a polypeptide linker between the VH and VL domains which enables the scFv to form the desired structure for antigen binding. For a review of scFv, see, e.g., Pluckthϋn, in The Pharmacology of Monoclonal Antibodies, vol. 113, Rosenburg and Moore eds., (Springer-Verlag, New York, 1994), pp. 269-315.

The term "diabodies" refers to antibody fragments with two antigen-binding sites, which fragments comprise a heavy-chain variable domain (VH) connected to a light-chain variable domain (VL) in the same polypeptide chain (VH-VL). By using a linker that is too short to allow pairing between the two domains on the same chain, the domains are forced to pair with the complementary domains of another chain and create two antigen-binding sites. Diabodies may be bivalent or bispecifϊc. Diabodies are described more fully in, for example, EP 404,097; WO 1993/01161; Hudson et al, Nat. Med. 9: 129-134 (2003); and Hollinger et al, Proc. Natl. Acad. Sci. USA 90: 6444-6448 (1993). Triabodies and tetrabodies are also described in Hudson et al., Nat. Med. 9:129-134 (2003).

The term "monoclonal antibody" as used herein refers to an antibody obtained from a population of substantially homogeneous antibodies, i.e., the individual antibodies comprising the population are identical except for possible mutations, e.g., naturally occurring mutations, that may be present in minor amounts. Thus, the modifier "monoclonal" indicates the character of the antibody as not being a mixture of discrete antibodies. In certain embodiments, such a monoclonal antibody typically includes an antibody comprising a polypeptide sequence that binds a target, wherein the target-binding polypeptide sequence was obtained by a process that includes the selection of a single target binding polypeptide sequence from a plurality of polypeptide sequences. For example, the selection process can be the selection of a unique clone from a plurality of clones, such as a pool of hybridoma clones, phage clones, or recombinant DNA clones. It should be understood that a selected target binding sequence can be further altered, for example, to improve affinity for the target, to humanize the target binding sequence, to improve its production in cell culture, to reduce its immunogenicity in vivo, to create a multispecifϊc antibody, etc., and that an antibody comprising the altered target binding sequence

is also a monoclonal antibody of this invention. In contrast to polyclonal antibody preparations, which typically include different antibodies directed against different determinants (epitopes), each monoclonal antibody of a monoclonal antibody preparation is directed against a single determinant on an antigen. In addition to their specificity, monoclonal antibody preparations are advantageous in that they are typically uncontaminated by other immunoglobulins.

The modifier "monoclonal" indicates the character of the antibody as being obtained from a substantially homogeneous population of antibodies, and is not to be construed as requiring production of the antibody by any particular method. For example, the monoclonal antibodies to be used in accordance with the present invention may be made by a variety of techniques, including, for example, the hybridoma method (e.g., Kohler and Milstein, Nature, 256:495-97 (1975); Hongo et al, Hybridoma, 14 (3): 253-260 (1995), Harlow et al, Antibodies: A Laboratory Manual, (Cold Spring Harbor Laboratory Press, 2nd ed. 1988); Hammerling et al., in: Monoclonal Antibodies and T-CeIl Hybridomas 563-681 (Elsevier, N.Y., 1981)), recombinant DNA methods (see, e.g., U.S. Patent No. 4,816,567), phage-display technologies (see, e.g., Clackson et al., Nature, 352: 624-628 (1991); Marks et al., J. MoI. Biol. 222: 581-597 (1992); Sidhu et al., J. MoI. Biol. 338(2): 299-310 (2004); Lee et al., J. MoI. Biol. 340(5): 1073-1093 (2004); Fellouse, Proc. Natl. Acad. Sci. USA 101(34): 12467-12472 (2004); and Lee et al., J. Immunol. Methods 284(1-2): 119-132(2004), and technologies for producing human or humanlike antibodies in animals that have parts or all of the human immunoglobulin loci or genes encoding human immunoglobulin sequences (see, e.g., WO 1998/24893; WO 1996/34096; WO 1996/33735; WO 1991/10741; Jakobovits et al., Proc. Natl. Acad. Sci. USA 90: 2551 (1993); Jakobovits et al., Nature 362: 255-258 (1993); Bruggemann et al., Year in Immunol. 7:33 (1993); U.S. Patent Nos. 5,545,807; 5,545,806; 5,569,825; 5,625,126; 5,633,425; and 5,661,016; Marks et al., Bio/Technology 10: 779-783 (1992); Lonberg et al., Nature 368: 856-859 (1994); Morrison, Nature 368: 812-813 (1994); Fishwild et al., Nature Biotechnol. 14: 845-851 (1996); Neuberger, Nature Biotechnol. 14: 826 (1996); and Lonberg and Huszar, Intern. Rev. Immunol. 13: 65-93 (1995).

The monoclonal antibodies herein specifically include "chimeric" antibodies in which a portion of the heavy and/or light chain is identical with or homologous to corresponding

sequences in antibodies derived from a particular species or belonging to a particular antibody class or subclass, while the remainder of the chain(s) is identical with or homologous to corresponding sequences in antibodies derived from another species or belonging to another antibody class or subclass, as well as fragments of such antibodies, so long as they exhibit the desired biological activity (see, e.g.,XJ.S. Patent No. 4,816,567; and Morrison et al., Proc. Natl. Acad. Sci. USA 81 :6851-6855 (1984)). Chimeric antibodies include PRIMATIZED® antibodies wherein the antigen-binding region of the antibody is derived from an antibody produced by, e.g., immunizing macaque monkeys with the antigen of interest.

"Humanized" forms of non-human (e.g., murine) antibodies are chimeric antibodies that contain minimal sequence derived from non-human immunoglobulin. In one embodiment, a humanized antibody is a human immunoglobulin (recipient antibody) in which residues from a HVR of the recipient are replaced by residues from a HVR of a non-human species (donor antibody) such as mouse, rat, rabbit, or nonhuman primate having the desired specificity, affinity, and/or capacity. In some instances, FR residues of the human immunoglobulin are replaced by corresponding non-human residues. Furthermore, humanized antibodies may comprise residues that are not found in the recipient antibody or in the donor antibody. These modifications may be made to further refine antibody performance. In general, a humanized antibody will comprise substantially all of at least one, and typically two, variable domains, in which all or substantially all of the hypervariable loops correspond to those of a non-human immunoglobulin, and all or substantially all of the FRs are those of a human immunoglobulin sequence. The humanized antibody optionally will also comprise at least a portion of an immunoglobulin constant region (Fc), typically that of a human immunoglobulin. For further details, see, e.g., Jones et al., Nature 321 :522-525 (1986); Riechmann et al, Nature 332:323-329 (1988); and Presta, Curr. Op. Struct. Biol. 2:593-596 (1992). See also, e.g., Vaswani and Hamilton, Ann. Allergy, Asthma & Immunol. 1 :105-115 (1998); Harris, Biochem. Soc. Transactions 23:1035-1038 (1995); Hurle and Gross, Curr. Op. Biotech. 5:428-433 (1994); and U.S. Pat. Nos. 6,982,321 and 7,087,409.

A "human antibody" is one which possesses an amino acid sequence which corresponds to that of an antibody produced by a human and/or has been made using any of the techniques for making human antibodies as disclosed herein. This definition of a human antibody specifically

excludes a humanized antibody comprising non-human antigen-binding residues. Human antibodies can be produced using various techniques known in the art, including phage-display libraries. Hoogenboom and Winter, J. MoI Biol, 227:381 (1991); Marks et al, J. MoI. Biol, 222:581 (1991). Also available for the preparation of human monoclonal antibodies are methods described in Cole et al, Monoclonal Antibodies and Cancer Therapy, Alan R. Liss, p. 77 (1985); Boerner et al, J. Immunol, 147(l):86-95 (1991). See also van Dijk and van de Winkel, Curr. Opin. Pharmacol, 5: 368-74 (2001). Human antibodies can be prepared by administering the antigen Xo a transgenic animal that has. been modified to produce such antibodies in response to antigenic challenge, but whose endogenous loci have been disabled, e.g,, immunized κenomiee kee, e.g., U.S. Pat. Nos. ^,075, 181 and 6,150,5X4 regarding XENOMOUSE™ technology). Sec also, for example, I i et al, Proc. Nail Acad, Sd. USA, 103:3557-35^2 (2006) regarding human antibodies generated via a human B-ecll hybridoma technology.

The term "hypervariable region," "HVR," or "HV," when used herein refers to the regions of an antibody variable domain which are hypervariable in sequence and/or form structurally defined loops. Generally, antibodies comprise six HVRs; three in the VH (Hl, H2, H3), and three in the VL (Ll, L2, L3). In native antibodies, H3 and L3 display the most diversity of the six HVRs, and H3 in particular is believed to play a unique role in conferring fine specificity to antibodies. See, e.g., Xu et al., Immunity 13:37-45 (2000); Johnson and Wu, in Methods in Molecular Biology 248:1-25 (Lo, ed., Human Press, Totowa, NJ, 2003). Indeed, naturally occurring camelid antibodies consisting of a heavy chain only are functional and stable in the absence of light chain. See, e.g., Hamers-Casterman et al., Nature 363:446-448 (1993); Sheriff et al., Nature Struct. Biol. 3:733-736 (1996).

"Framework" or "FR" residues are those variable domain residues other than the HVR residues. An "affinity matured" antibody is one with one or more alterations in one or more HVRs thereof which result in an improvement in the affinity of the antibody for antigen, compared to a parent antibody which does not possess those alteration(s). In one embodiment, an affinity matured antibody has nanomolar or even picomolar affinities for the target antigen. Affinity matured antibodies may be produced using certain procedures known in the art. For example,

Marks et al. Bio/Technology 10:779-783 (1992) describes affinity maturation by VH and VL domain shuffling. Random mutagenesis of HVR and/or framework residues is described by, for example, Barbas et al. Proc Nat. Acad. Sci. USA 91 :3809-3813 (1994); Schier et al. Gene 169:147-155 (1995); Yelton et al. J. Immunol. 155:1994-2004 (1995); Jackson et al, J. Immunol. 154(7):3310-9 (1995); and Hawkins et al, J. MoI. Biol. 226:889-896 (1992).

A "blocking" antibody or an "antagonist" antibody is one which inhibits a biological activity of the antigen it binds. Blocking antibodies or antagonist antibodies may substantially or completely inhibit the biological activity of the antigen.

An "agonist antibody," as used herein, is an antibody which partially or fully mimics at least one of the functional activities of a polypeptide of interest.

"Growth inhibitory" antibodies are those that prevent or reduce proliferation of a cell expressing an antigen to which the antibody binds. For example, the antibody may prevent or reduce proliferation of cancer cells in vitro and/or in vivo.

Antibody "effector functions" refer to those biological activities attributable to the Fc region (a native sequence Fc region or amino acid sequence variant Fc region) of an antibody, and vary with the antibody isotype. Examples of antibody effector functions include: CIq binding and complement dependent cytotoxicity (CDC); Fc receptor binding; antibody-dependent cell-mediated cytotoxicity (ADCC); phagocytosis; down regulation of cell surface receptors (e.g. B cell receptor); and B cell activation. The term "Fc region" herein is used to define a C-terminal region of an immunoglobulin heavy chain, including native sequence Fc regions and variant Fc regions. Although the boundaries of the Fc region of an immunoglobulin heavy chain might vary, the human IgG heavy chain Fc region is usually defined to stretch from an amino acid residue at position Cys226, or from Pro230, to the carboxyl- terminus thereof. The C-terminal lysine (residue 447 according to the EU numbering system) of the Fc region may be removed, for example, during production or purification of the antibody, or by recombinantly engineering the nucleic acid encoding a heavy chain of the antibody. Accordingly, a composition of intact antibodies may comprise antibody populations with all K447 residues removed, antibody populations with no K447 residues removed, and antibody populations having a mixture of antibodies with and without the K447 residue.

A "functional Fc region" possesses an "effector function" of a native sequence Fc region. Exemplary "effector functions" include CIq binding; CDC; Fc receptor binding; ADCC; phagocytosis; down regulation of cell surface receptors (e.g. B cell receptor; BCR), etc. Such effector functions generally require the Fc region to be combined with a binding domain (e.g., an antibody variable domain) and can be assessed using various assays as disclosed, for example, in definitions herein.

A "native sequence Fc region" comprises an amino acid sequence identical to the amino acid sequence of an Fc region found in nature. Native sequence human Fc regions include a native sequence human IgGl Fc region (non-A and A allotypes); native sequence human IgG2 Fc region; native sequence human IgG3 Fc region; and native sequence human IgG4 Fc region as well as naturally occurring variants thereof.

A "variant Fc region" comprises an amino acid sequence which differs from that of a native sequence Fc region by virtue of at least one amino acid modification, preferably one or more amino acid substitution(s). Preferably, the variant Fc region has at least one amino acid substitution compared to a native sequence Fc region or to the Fc region of a parent polypeptide, e.g. from about one to about ten amino acid substitutions, and preferably from about one to about five amino acid substitutions in a native sequence Fc region or in the Fc region of the parent polypeptide. The variant Fc region herein will preferably possess at least about 80% homology with a native sequence Fc region and/or with an Fc region of a parent polypeptide, and most preferably at least about 90% homology therewith, more preferably at least about 95% homology therewith.

"Fc receptor" or "FcR" describes a receptor that binds to the Fc region of an antibody. In some embodiments, an FcR is a native human FcR. In some embodiments, an FcR is one which binds an IgG antibody (a gamma receptor) and includes receptors of the FcγRI, FcγRII, and FcγRIII subclasses, including allelic variants and alternatively spliced forms of those receptors. FcγRII receptors include FcγRIIA (an "activating receptor") and FcγRIIB (an "inhibiting receptor"), which have similar amino acid sequences that differ primarily in the cytoplasmic domains thereof. Activating receptor FcγRIIA contains an immunoreceptor tyrosine-based activation motif (ITAM) in its cytoplasmic domain. Inhibiting receptor FcγRIIB contains an immunoreceptor tyrosine-based inhibition motif (ITIM) in its cytoplasmic domain, (see, e.g., Daeron, Annu. Rev. Immunol. 15:203-234 (1997)). FcRs are reviewed, for example, in Ravetch

and Kinet, Annu. Rev. Immunol 9:457-92 (1991); Capel et al, Immunomethods 4:25-34 (1994); and de Haas et al, J. Lab. Clin. Med. 126:330-41 (1995). Other FcRs, including those to be identified in the future, are encompassed by the term "FcR" herein.

The term "Fc receptor" or "FcR" also includes the neonatal receptor, FcRn, which is responsible for the transfer of maternal IgGs to the fetus (Guyer et al, J. Immunol. 117:587 (1976) and Kim et al., J. Immunol. 24:249 (1994)) and regulation of homeostasis of immunoglobulins. Methods of measuring binding to FcRn are known (see, e.g., Ghetie and Ward., Immunol. Today 18(12):592-598 (1997); Ghetie et al., Nature Biotechnology, 15(7):637- 640 (1997); Hinton et al., J. Biol. Chem. 279(8):6213-6216 (2004); WO 2004/92219 (Hinton et al.).

Binding to human FcRn in vivo and serum half life of human FcRn high affinity binding polypeptides can be assayed, e.g., in transgenic mice or transfected human cell lines expressing human FcRn, or in primates to which the polypeptides with a variant Fc region are administered. WO 2000/42072 (Presta) describes antibody variants with improved or diminished binding to FcRs. See also, e.g., Shields et al. J. Biol. Chem. 9(2):6591-6604 (2001).

"Human effector cells" are leukocytes which express one or more FcRs and perform effector functions. In certain embodiments, the cells express at least FcγRIII and perform ADCC effector function(s). Examples of human leukocytes which mediate ADCC include peripheral blood mononuclear cells (PBMC), natural killer (NK) cells, monocytes, cytotoxic T cells, and neutrophils. The effector cells may be isolated from a native source, e.g., from blood.

"Antibody-dependent cell-mediated cytotoxicity" or "ADCC" refers to a form of cytotoxicity in which secreted Ig bound onto Fc receptors (FcRs) present on certain cytotoxic cells (e.g. NK cells, neutrophils, and macrophages) enable these cytotoxic effector cells to bind specifically to an antigen-bearing target cell and subsequently kill the target cell with cytotoxins. The primary cells for mediating ADCC, NK cells, express FcγRIII only, whereas monocytes express FcγRI, FcγRII, and FcγRIII. FcR expression on hematopoietic cells is summarized in Table 3 on page 464 of Ravetch and Kinet, Annu. Rev. Immunol 9:457-92 (1991). To assess ADCC activity of a molecule of interest, an in vitro ADCC assay, such as that described in US Patent No. 5,500,362 or 5,821,337 or U.S. Patent No. 6,737,056 (Presta), may be performed.

Useful effector cells for such assays include PBMC and NK cells. Alternatively, or additionally, ADCC activity of the molecule of interest may be assessed in vivo, e.g., in an animal model such as that disclosed in Clynes et al. PNAS (USA) 95:652-656 (1998).

"Complement dependent cytotoxicity" or "CDC" refers to the lysis of a target cell in the presence of complement. Activation of the classical complement pathway is initiated by the binding of the first component of the complement system (CIq) to antibodies (of the appropriate subclass), which are bound to their cognate antigen. To assess complement activation, a CDC assay, e.g., as described in Gazzano-Santoro et al., J. Immunol. Methods 202:163 (1996), may be performed. Polypeptide variants with altered Fc region amino acid sequences (polypeptides with a variant Fc region) and increased or decreased CIq binding capability are described, e.g., in US Patent No. 6,194,551 Bl and WO 1999/51642. See also, e.g., Idusogie et al. J. Immunol. 164: 4178-4184 (2000).

The term "Fc region-comprising antibody" refers to an antibody that comprises an Fc region. The C-terminal lysine (residue 447 according to the EU numbering system) of the Fc region may be removed, for example, during purification of the antibody or by recombinant engineering of the nucleic acid encoding the antibody. Accordingly, a composition comprising an antibody having an Fc region according to this invention can comprise an antibody with K447, with all K447 removed, or a mixture of antibodies with and without the K447 residue.

"Binding affinity" generally refers to the strength of the sum total of noncovalent interactions between a single binding site of a molecule {e.g., an antibody) and its binding partner {e.g., an antigen). Unless indicated otherwise, as used herein, "binding affinity" refers to intrinsic binding affinity which reflects a 1 : 1 interaction between members of a binding pair {e.g. , antibody and antigen). The affinity of a molecule X for its partner Y can generally be represented by the dissociation constant (Kd). Affinity can be measured by common methods known in the art, including those described herein. Low-affinity antibodies generally bind antigen slowly and tend to dissociate readily, whereas high-affinity antibodies generally bind antigen faster and tend to remain bound longer. A variety of methods of measuring binding affinity are known in the art, any of which can be used for purposes of the present invention.

Specific illustrative and exemplary embodiments for measuring binding affinity are described in the following.

In one embodiment, the "Kd" or "Kd value" according to this invention is measured by a radiolabeled antigen binding assay (RIA) performed with the Fab version of an antibody of interest and its antigen as described by the following assay. Solution binding affinity of Fabs for antigen is measured by equilibrating Fab with a minimal concentration of ( ¹²⁵ I)-labeled antigen in the presence of a titration series of unlabeled antigen, then capturing bound antigen with an anti- Fab antibody-coated plate (see, e.g., Chen, et al, J. MoI. Biol. 293:865-881(1999)). To establish conditions for the assay, MICROTITER ^R multi-well plates (Thermo Scientific) are coated overnight with 5 μg/ml of a capturing anti-Fab antibody (Cappel Labs) in 50 mM sodium carbonate (pH 9.6), and subsequently blocked with 2% (w/v) bovine serum albumin in PBS for two to five hours at room temperature (approximately 23°C). In a non-adsorbent plate (Nunc #269620), 100 pM or 26 pM [ I]-antigen are mixed with serial dilutions of a Fab of interest (e.g., consistent with assessment of the anti-VEGF antibody, Fab- 12, in Presta et al., Cancer Res. 57:4593-4599 (1997)). The Fab of interest is then incubated overnight; however, the incubation may continue for a longer period (e.g., about 65 hours) to ensure that equilibrium is reached. Thereafter, the mixtures are transferred to the capture plate for incubation at room temperature (e.g., for one hour). The solution is then removed and the plate washed eight times with 0.1% TWEEN-20™ in PBS. When the plates have dried, 150 μl/well of scintillant (MICROSCINT-20 ™; Packard) is added, and the plates are counted on a TOPCOUNT ™ gamma counter (Packard) for ten minutes. Concentrations of each Fab that give less than or equal to 20% of maximal binding are chosen for use in competitive binding assays.

According to another embodiment, the Kd or Kd value is measured by using surface plasmon resonance assays using a BIACORE ^® -2000 or a BIACORE ^® -3000 (BIAcore, Inc., Piscataway, NJ) at 25°C with immobilized antigen CM5 chips at ~10 response units (RU).

Briefly, carboxymethylated dextran biosensor chips (CM5, BIACORE, Inc.) are activated with N- ethyl-N'- (3-dimethylaminopropyl)-carbodiimide hydrochloride (EDC) and N- hydroxysuccinimide (NHS) according to the supplier's instructions. Antigen is diluted with 10 mM sodium acetate, pH 4.8, to 5 μg/ml (~0.2 μM) before injection at a flow rate of 5 μl/minute

to achieve approximately 10 response units (RU) of coupled protein. Following the injection of antigen, 1 M ethanolamine is injected to block unreacted groups. For kinetics measurements, two-fold serial dilutions of Fab (0.78 nM to 500 nM) are injected in PBS with 0.05% TWEEN- 20™ surfactant (PBST) at 25°C at a flow rate of approximately 25 μl/min. Association rates (k _on ) and dissociation rates (k _o ff) are calculated using a simple one-to-one Langmuir binding model (BIACORE Evaluation Software version 3.2) by simultaneously fitting the association and dissociation sensorgrams. The equilibrium dissociation constant (Kd) is calculated as the ratio k _o ff/k _on See, e.g., Chen et al, J. MoI. Biol. 293:865-881 (1999). If the on-rate exceeds Iθ6 M'l s ^~ l by the surface plasmon resonance assay above, then the on-rate can be determined by using a fluorescent quenching technique that measures the increase or decrease in fluorescence emission intensity (excitation = 295 nm; emission = 340 nm, 16 nm band-pass) at 25 ⁰ C of a 20 nM anti-antigen antibody (Fab form) in PBS, pH 7.2, in the presence of increasing concentrations of antigen as measured in a spectrometer, such as a stop-flow equipped spectrophometer (Aviv Instruments) or a 8000-series SLM-AMINCO ™ spectrophotometer (ThermoSpectronic) with a stirred cuvette.

An "on-rate," "rate of association," "association rate," or "k _on " according to this invention can also be determined as described above using a BIACORE ^R -2000 or a BIACORE ^R -3000 system (BIAcore, Inc., Piscataway, NJ).

The term "substantially similar" or "substantially the same," as used herein, denotes a sufficiently high degree of similarity between two numeric values (for example, one associated with an antibody of the invention and the other associated with a reference/comparator antibody), such that one of skill in the art would consider the difference between the two values to be of little or no biological and/or statistical significance within the context of the biological characteristic measured by said values (e.g., Kd values). The difference between said two values is, for example, less than about 50%, less than about 40%, less than about 30%, less than about 20%, and/or less than about 10% as a function of the reference/comparator value.

The phrase "substantially different," as used herein, denotes a sufficiently high degree of difference between two numeric values (generally one associated with a molecule and the other associated with a reference/comparator molecule) such that one of skill in the art would consider

the difference between the two values to be of statistical significance within the context of the biological characteristic measured by said values (e.g., Kd values). The difference between said two values is, for example, greater than about 10%, greater than about 20%, greater than about 30%, greater than about 40%, and/or greater than about 50% as a function of the value for the reference/comparator molecule.

"Purified" means that a molecule is present in a sample at a concentration of at least 95% by weight, or at least 98% by weight of the sample in which it is contained.

An "isolated" nucleic acid molecule is a nucleic acid molecule that is separated from at least one other nucleic acid molecule with which it is ordinarily associated, for example, in its natural environment. An isolated nucleic acid molecule further includes a nucleic acid molecule contained in cells that ordinarily express the nucleic acid molecule, but the nucleic acid molecule is present extrachromosomally or at a chromosomal location that is different from its natural chromosomal location.

The term "vector," as used herein, is intended to refer to a nucleic acid molecule capable of transporting another nucleic acid to which it has been linked. One type of vector is a

"plasmid," which refers to a circular double stranded DNA into which additional DNA segments may be ligated. Another type of vector is a phage vector. Another type of vector is a viral vector, wherein additional DNA segments may be ligated into the viral genome. Certain vectors are capable of autonomous replication in a host cell into which they are introduced (e.g., bacterial vectors having a bacterial origin of replication and episomal mammalian vectors). Other vectors (e.g., non-episomal mammalian vectors) can be integrated into the genome of a host cell upon introduction into the host cell, and thereby are replicated along with the host genome. Moreover, certain vectors are capable of directing the expression of genes to which they are operatively linked. Such vectors are referred to herein as "recombinant expression vectors," or simply, "expression vectors." In general, expression vectors of utility in recombinant DNA techniques are often in the form of plasmids. In the present specification, "plasmid" and "vector" may be used interchangeably as the plasmid is the most commonly used form of vector.

"Polynucleotide," or "nucleic acid," as used interchangeably herein, refer to polymers of nucleotides of any length, and include DNA and RNA. The nucleotides can be

deoxyribonucleotides, ribonucleotides, modified nucleotides or bases, and/or their analogs, or any substrate that can be incorporated into a polymer by DNA or RNA polymerase or by a synthetic reaction. A polynucleotide may comprise modified nucleotides, such as methylated nucleotides and their analogs. If present, modification to the nucleotide structure may be imparted before or after assembly of the polymer. The sequence of nucleotides may be interrupted by non-nucleotide components. A polynucleotide may comprise modification(s) made after synthesis, such as conjugation to a label. Other types of modifications include, for example, "caps," substitution of one or more of the naturally occurring nucleotides with an analog, internucleotide modifications such as, for example, those with uncharged linkages (e.g., methyl phosphonates, phosphotriesters, phosphoamidates, carbamates, etc.) and with charged linkages (e.g., phosphorothioates, phosphorodithioates, etc.), those containing pendant moieties, such as, for example, proteins (e.g., nucleases, toxins, antibodies, signal peptides, ply-L-lysine, etc.), those with intercalators (e.g., acridine, psoralen, etc.), those containing chelators (e.g., metals, radioactive metals, boron, oxidative metals, etc.), those containing alkylators, those with modified linkages (e.g., alpha anomeric nucleic acids, etc.), as well as unmodified forms of the polynucleotides(s). Further, any of the hydroxyl groups ordinarily present in the sugars may be replaced, for example, by phosphonate groups, phosphate groups, protected by standard protecting groups, or activated to prepare additional linkages to additional nucleotides, or may be conjugated to solid or semi-solid supports. The 5' and 3' terminal OH can be phosphorylated or substituted with amines or organic capping group moieties of from 1 to 20 carbon atoms. Other hydroxyls may also be derivatized to standard protecting groups. Polynucleotides can also contain analogous forms of ribose or deoxyribose sugars that are generally known in the art, including, for example, 2'-O-methyl-, 2'-O-allyl-, 2'-fluoro- or 2'-azido-ribose, carbocyclic sugar analogs, α-anomeric sugars, epimeric sugars such as arabinose, xyloses or lyxoses, pyranose sugars, furanose sugars, sedoheptuloses, acyclic analogs, and basic nucleoside analogs such as methyl riboside. One or more phosphodiester linkages may be replaced by alternative linking groups. These alternative linking groups include, but are not limited to, embodiments wherein phosphate is replaced by P(O)S ("thioate"), P(S)S ("dithioate"), (O)NR ₂ ("amidate"), P(O)R, P(O)OR', CO, or CH2 ("formacetal"), in which each R or R' is independently H or substituted or

unsubstituted alkyl (1-20 C) optionally containing an ether (-O-) linkage, aryl, alkenyl, cycloalkyl, cycloalkenyl or araldyl. Not all linkages in a polynucleotide need be identical. The preceding description applies to all polynucleotides referred to herein, including RNA and DNA.

"Oligonucleotide," as used herein, generally refers to short, generally single-stranded, generally synthetic polynucleotides that are generally, but not necessarily, less than about 200 nucleotides in length. The terms "oligonucleotide" and "polynucleotide" are not mutually exclusive. The description above for polynucleotides is equally and fully applicable to oligonucleotides.

II. EMBODIMENTS OF THE INVENTION

In various embodiments, compositions and methods are provided for the classification, diagnosis, treatment, and prevention of tumors characterized by loss of REST function, expression of β2, and/or activation of Notch. In further embodiments, compositions and methods are provided for modulation of cellular processes such as EMT, cell migration, and apoptosis. These and further embodiments of the invention are based on the discovery that loss of the transcriptional repressor REST leads to expression of β2, which in turn binds to and activates Notch signaling in tumors.

A. Compositions

Compositions are provided for the treatment or prevention of tumors, including refractory tumors. Such compositions may comprise REST agonists, β2 antagonists, and Notch antagonists, either singly or in combination.

In one aspect, a β2 antagonist is a blocking antibody that binds to β2. In one embodiment, such an antibody blocks (either partially or completely) binding of β2 to Notch. In one embodiment, a blocking antibody binds to the ECD of β2. Certain antibodies that bind to β2 are described herein and are designated 3D1.4.1 ("3Dl"), 12A9.22.1 ("12A9"), 2E3.1.1 ("2E3"), 12E3, or 3G5. Also provided herein are antibodies that bind to the same epitope as do any of 3Dl, 12A9, 2E3, 12E3, or 3G5, as well as antibodies that compete with any of 3Dl, 12A9, 2E3, 12E3, or 3G5 for binding to β2. In one embodiment, a blocking antibody is selected from 3Dl, 12A9, 2E3, or 3G5. In one embodiment, a blocking antibody binds to the same epitope as does

3Dl, 12A9, 2E3, or 3G5. In one embodiment, a blocking antibody competes with any of 3Dl, 12A9, 2E3, or 3G5 for binding to β2.

In certain embodiments, an antibody provided herein is a monoclonal antibody. In certain embodiments, an antibody is an antibody fragment, e.g., a Fab, Fab'-SH, Fv, scFv, or (Fab') ₂ fragment, or a single domain antibody (Domantis, Inc., Waltham, MA; see, e.g., US Pat. No. 6,248,516 Bl). In certain embodiments, an antibody is a bispecifϊc antibody (see, e.g., WO94/04690 and Suresh et al. (1986) Methods in Enzymology 121 :210). In certain embodiments, an antibody is a chimeric, humanized, or human antibody. For example, humanized forms of any of 3Dl, 12A9, 2E3, 12E3, or 3G5 are provided herein. In another aspect, a β2 antagonist is a nucleic acid that decreases SCN2B expression. In one embodiment, the nucleic acid is an antisense nucleic acid specific for SCN2B. In one such embodiment, the nucleic acid is a regulatory RNA. In one such embodiment, the nucleic acid reduces SCN2B expression by RNAi. In one such embodiment, the nucleic acid is an siRNA. Certain SCN2B-specifϊc siRNAs are known in the art. For example, certain SCN2B-specifϊc shRNAs are commercially available (e.g., from Sigma-Aldrich, St. Louis, MO). Certain other β2 antagonists may be found in the art. For example, TAPI-I, a small molecule inhibitor of α- secretase, can be used to inhibit ectodomain shedding from β2. (See Kim et al., J. Biol. Chem. 280:23251-23261, 2005.)

In another aspect, a β2 antagonist is an isolated polypeptide, preferably a soluble polypeptide, that comprises a fragment of Notch that binds to β2. A fragment of Notch that binds to β2 would be expected to compete with endogenous Notch for binding to β2. In certain embodiments, such a fragment is substantially incapable of effecting Notch signaling. In one embodiment, a polypeptide comprises a fragment of mammalian Notch 1 comprising EGF repeats 10-21 or 14-21, or a functionally equivalent fragment of a member of the Notch family, e.g., Notch2, Notch3, or Notch4. Such a functionally equivalent fragment may be routinely ascertained, e.g., by aligning the amino acid sequence of Notchl with the polypeptide sequence of a second Notch family member to identify a corresponding fragment in the latter, and optionally, testing the fragment thus identified for β2 binding. The amino acid sequence of a

human Notch is shown in SEQ ID NO: 1. EGF repeats 10-21 are located in SEQ ID NO: 1 at approximately the following positions:

In another embodiment, an isolated polypeptide comprises a fragment of Notch that specifically binds to β2, wherein "specifically binds," in this context, means that the fragment does not substantially bind to any other Notch ligand. In another embodiment, an isolated polypeptide comprises a fragment of Notch that binds to β2 but does not bind to Jagged and/or DLL. In another embodiment, an isolated polypeptide comprises a fragment of Notch that binds to β2 and is less than or equal to 500, 450, 400, 350, 300, 250, 200, 150, or 100 amino acids in length. In another aspect, a β2 antagonist is an antibody that binds to a region of Notch that binds to β2. In one embodiment, the region is a region of mammalian Notch 1 comprising EGF repeats 10-21 or 14-21, or a functionally equivalent region of a member of the Notch family, e.g., Notch2, Notch3, or Notch4. Such a functionally equivalent region may be routinely ascertained, e.g., by aligning the polypeptide sequence of Notchl with the polypeptide sequence of a second Notch family member to identify a corresponding region in the latter, and optionally, testing the region thus identified for β2 binding. In certain embodiments, an antibody that binds to a region

of Notch that binds to β2 specifically blocks binding of β2 to Notch, wherein "specifically blocks," in this context, means that the antibody does not block binding of any other Notch ligand to Notch. In certain embodiments, an antibody that binds to a region of Notch that binds to β2 does not block binding of Jagged and/or DLL. In another aspect, a composition comprises a REST agonist. In one embodiment, a REST agonist is REST, including fragments or variants of full-length REST that retain a biological activity of REST (e.g., tumor suppressor activity). In another embodiment, a REST agonist is a nucleic acid encoding any of the foregoing.

In another aspect, a composition comprises a Notch antagonist. Notch activity may be antagonized by a variety of selective approaches (e.g., antisense, monoclonal antibodies, and RNAi) and non-selective approaches (e.g., soluble forms of Notch or Notch decoys, γ-secretase inhibitors, intracellular MAMLl decoys, and Ras signaling inhibitors), and various Notch antagonists are known in the art. For example, various γ-secretase inhibitors are known to inhibit Notch signaling activity. See Zayzafoon et al, J. Biol. Chem. 279:3662-3670, 2004 (describing the Notch-inhibiting effects of the peptidomimetic L-685,458); and Curry et al.,

Oncogene 24:6333-6344, 2005 (describing the Notch-inhibiting effects of a tripeptide aldehyde inhibitor and a peptidomimetic inhibitor (LY-411,575) of γ-secretase). MK-0752, a small molecule inhibitor of γ-secretase and an inhibitor of Notch signaling activity, is currently being tested in clinical trials. See J. CHn. Oncol, 2006 ASCO Annual Meeting Proceedings Part I. VoI 24, No. 18S (June 20 Supplement), 2006: 6585.

Compositions are also provided herein for promoting EMT, cell migration, and/or resistance to apoptosis. Such compositions would be useful in a therapeutic setting, e.g., where increased cell viability and/or cell migration is desired (e.g., in wound healing). Such compositions would also be useful in a research setting. Such compositions may comprise β2 agonists, REST antagonists, or Notch agonists, either singly or in combination.

In one aspect, exemplary β2 agonists comprise β2, including fragments or variants of full- length β2 that retain a biological activity of β2 (e.g., the ability to bind Notch and/or activate Notch signaling). A β2 agonist may comprise, e.g., the ECD of β2 or a fragment or variant thereof that retains the ability to bind Notch and/or activate Notch signaling. In another

embodiment, a β2 agonist is a nucleic acid encoding any of the foregoing. The amino acid sequence of a human β2 is shown in SEQ ID NO:2. The approximate locations of the following features are provided: signal peptide from amino acids 1-29; ECD from amino acids 30-159; transmembrane domain from amino acids 160-180; cytoplasmic domain from amino acids 181- 215, and Ig-like domain from amino acids 32-154.

In another aspect, exemplary Notch agonists comprise Notch, including fragments or variants of full-length Notch that retain a biological activity of Notch (e.g., the ability to activate expression of target genes). For example, Notch receptors lacking extracellular subunits are constitutively activated and have transforming activity in vitro and in animal models. See Nickoloff et al., Oncogene 22:6598-6608. In another embodiment, a Notch agonist is an agonist antibody that binds to Notch.

In another aspect, exemplary REST antagonists include deletion mutants and other mutant forms of REST that have decreased REST activity (e.g., decreased tumor suppressor activity). See, e.g., Westbrook et al., Cell 121 :837-848, 2005.

B. Methods

In one aspect, methods are provided herein for the treatment or prevention of tumor progression, including the progression of refractory tumors. In certain embodiments, a method for inhibiting tumor progression is provided, the method comprising exposing the tumor to one or more agents selected from an antagonist of β2, an antagonist of Notch, and an agonist of REST. Certain antagonists of β2, antagonists of Notch, and agonists of REST are discussed above and can be used in the methods described herein. In one embodiment, the agent is an antagonist of β2.

In another embodiment, the tumor has decreased REST activity. "Decreased REST activity" refers to a significant decrease in the level of REST or a significant loss of REST function (either complete or partial loss of REST function) due to, e.g., mutation in the REST gene, including but not limited to deletion of all or a portion of the REST gene, or any other event that leads to a decrease in a biological activity of REST (e.g., transcriptional repressor activity and/or tumor suppressor activity). Decreased REST activity in a tumor may be detected,

e.g., by comparing the level or activity of REST in the tumor as compared to the level or activity of REST in normal tissue of the same tissue type as the tumor.

In another embodiment, the tumor has increased β2 activity. "Increased β2 activity" refers to a significant increase in the level or activity of β2 (e.g., ability to bind Notch; ability to induce EMT; ability to induce cell migration; or ability to block apoptosis). Increased β2 activity may be detected, e.g., by comparing the level or activity of β2 in a tumor as compared to the level or activity of β2 in normal tissue of the same tissue type as the tumor.

In another embodiment, the tumor has increased Notch activity. "Increased Notch activity" refers to a significant increase in the level or activity of Notch (e.g., ability to increase expression of one or more target genes, e.g., HES family genes, cell cycle regulation genes (e.g., p21 ^cipl/wafl , cyclin Dl), NF-κB family genes, or PPAR family genes). Increased Notch activity may be detected, e.g., by comparing the level or activity of Notch in a tumor as compared to the level or activity of Notch in normal tissue of the same tissue type as the tumor.

In another embodiment, the tumor is a refractory tumor. In one such embodiment, the tumor is resistant to chemotherapy. In another embodiment, the tumor is metastatic. In another embodiment, the tumor is a colon tumor or a tumor selected from the tumor types shown in Figure 1OE. In another embodiment, the tumor occurs in a relapsed patient.

In another aspect, a method of inhibiting EMT in a cell is provided, the method comprising exposing the cell to one or more agents selected from an antagonist of β2, an agonist of REST, and an antagonist of Notch. Certain antagonists of β2, antagonists of Notch, and agonists of REST are discussed above and can be used in the methods described herein. In one embodiment, the agent is an antagonist of β2. In another embodiment, the cell has decreased REST activity, as defined above. In another embodiment, the cell has increased β2 activity, as defined above. In another embodiment, the cell has increased Notch activity, as defined above. In another embodiment, the cell is in vitro. In another embodiment, the cell is in vivo. In another embodiment, the cell is a tumor cell. In one such embodiment, the tumor cell is derived from a refractory tumor. In one such embodiment, the tumor is resistant to chemotherapy. In another embodiment, the tumor cell is derived from a metastatic tumor. In another embodiment,

the tumor cell is a colon tumor cell or a tumor cell type selected from Figure 1OE. In another embodiment, the tumor cell is derived from a relapsed patient.

In another aspect, a method of inhibiting migration of a cell is provided, the method comprising exposing the cell to one or more agents selected from an antagonist of β2, an agonist of REST, and an antagonist of Notch. Certain antagonists of β2, antagonists of Notch, and agonists of REST are discussed above and can be used in the methods described herein. In one embodiment, the agent is an antagonist of β2. In another embodiment, the cell has decreased REST activity, as defined above. In another embodiment, the cell has increased β2 activity, as defined above. In another embodiment, the cell has increased Notch activity, as defined above. In another embodiment, the cell is in vitro. In another embodiment, the cell is in vivo. In another embodiment, the cell is a tumor cell. In one such embodiment, the tumor cell is derived from a refractory tumor. In one such embodiment, the tumor is resistant to chemotherapy. In another embodiment, the tumor cell is derived from a metastatic tumor. In another embodiment, the tumor cell is a colon tumor cell or a tumor cell type selected from Figure 1OE. In another embodiment, the tumor cell is derived from a relapsed patient.

In another aspect, a method of promoting apoptosis in a cell is provided, the method comprising exposing the cell to one or more agents selected from an antagonist of β2, an agonist of REST, and an antagonist of Notch. Certain antagonists of β2, antagonists of Notch, and agonists of REST are discussed above and can be used in the methods described herein. In one embodiment, the agent is an antagonist of β2. In another embodiment, the cell has decreased REST activity, as defined above. In another embodiment, the cell has increased β2 activity, as defined above. In another embodiment, the cell has increased Notch activity, as defined above. In another embodiment, the cell is in vitro. In another embodiment, the cell is in vivo. In another embodiment, the cell is a tumor cell. In one such embodiment, the tumor cell is derived from a refractory tumor. In one such embodiment, the tumor is resistant to chemotherapy. In another embodiment, the tumor cell is derived from a metastatic tumor. In another embodiment, the tumor cell is a colon tumor cell or a tumor cell type selected from Figure 1OE. In another embodiment, the tumor cell is derived from a relapsed patient.

In another aspect, a method of promoting EMT in a cell is provided, the method comprising exposing the cell to one or more agents selected from an agonist of β2, an antagonist of REST, and an agonist of Notch. Certain agonists of β2, agonists of Notch, and antagonists of REST are discussed above and can be used in the methods described herein. In one embodiment, the agent is an agonist of β2. In another embodiment, the cell is in vitro. In another embodiment, the cell is in vivo.

In another aspect, a method of promoting cell migration is provided, the method comprising exposing the cell to one or more agents selected from an agonist of β2, an antagonist of REST, and an agonist of Notch. Certain agonists of β2, agonists of Notch, and antagonists of REST are discussed above and can be used in the methods described herein. In one embodiment, the agent is an agonist of β2. In another embodiment, the cell is in vitro. In another embodiment, the cell is in vivo.

In another aspect, a method of blocking apoptosis is provided, the method comprising exposing the cell to one or more agents selected from an agonist of β2, an antagonist of REST, and an agonist of Notch. Certain agonists of β2, agonists of Notch, and antagonists of REST are discussed above and can be used in the methods described herein. In one embodiment, the agent is an agonist of β2. In another embodiment, the cell is in vitro. In another embodiment, the cell is in vivo.

In another aspect, a method of determining whether a tumor will respond to an antagonist of β2 or an antagonist of Notch is provided, the method comprising detecting decreased REST activity or increased β2 activity in the tumor, wherein decreased REST activity or increased β2 activity in the tumor indicates that the tumor will respond to an antagonist of β2 or an antagonist of Notch. In one embodiment, the method comprises detecting decreased REST activity in the tumor. In one such embodiment, the method comprises detecting a mutation in the REST gene that results in decreased REST activity. In one such embodiment, the method comprises detecting a deletion in the REST gene. In another embodiment, the method comprises detecting increased β2 activity in the tumor. In one such embodiment, the method comprises detecting increased levels of SCN2B mRNA. In another such embodiment, the method comprises detecting increased levels of β2 protein. In one such embodiment, the method comprises

detecting increased levels of β2 ECD in the extracellular environment. In another embodiment, the tumor is a refractory tumor. In one such embodiment, the tumor is resistant to chemotherapy. In another embodiment, the tumor is metastatic. In another embodiment, the tumor is a colon tumor or a tumor selected from the tumor types shown in Figure 1OE. In another embodiment, the tumor is from a relapsed patient.

In another aspect, a method of assessing the prognosis of a tumor is provided, the method comprising detecting decreased REST activity or increased β2 activity in the tumor, wherein decreased REST activity or increased β2 activity indicates that the tumor has a poor prognosis. "Poor prognosis" means that there is a substantial likelihood (>50% chance) that the tumor is or will be refractory and/or metastatic. In one embodiment, the method comprises detecting decreased REST activity in the tumor. In one such embodiment, the method comprises detecting a mutation in the REST gene that results in decreased REST activity. In one such embodiment, the method comprises detecting a deletion in the REST gene. In another embodiment, the method comprises detecting increased β2 activity in the tumor. In one such embodiment, the method comprises detecting increased levels of SCNB2 mRNA. In another such embodiment, the method comprises detecting increased levels of β2 protein. In one such embodiment, the method comprises detecting increased levels of β2 ECD in the extracellular environment. In another embodiment, the tumor is a colon tumor or a tumor selected from the tumor types shown in Figure 1OE. In another aspect, a method of classifying a tumor as one in which Notch signaling is activated, the method comprising detecting decreased REST activity or increased β2 activity in the tumor, wherein decreased REST activity or increased β2 activity indicates that the tumor is one in which Notch signaling is activated. In one embodiment, the method comprises detecting decreased REST activity in the tumor. In one such embodiment, the method comprises detecting a mutation in the REST gene that results in decreased REST activity. In one such embodiment, the method comprises detecting a deletion in the REST gene. In another embodiment, the method comprises detecting increased β2 activity in the tumor. In one such embodiment, the method comprises detecting increased levels of SCNB2 mRNA. In another such embodiment, the method comprises detecting increased levels of β2 protein. In one such embodiment, the

method comprises detecting increased levels of β2 ECD in the extracellular environment. In another embodiment, the tumor is a colon tumor or a tumor selected from the tumor types shown in Figure 1OE. In another embodiment, the tumor is a refractory tumor. In one such embodiment, the tumor is resistant to chemotherapy. In another embodiment, the tumor is metastatic. In another embodiment, the tumor is from a relapsed patient. C. Pharmaceutical Formulations and Administration

Pharmaceutical formulations comprising an agent, e.g., an antibody, protein or nucleic acid provided above in Section ILA., may be prepared according to methods generally known in the art. Such formulations may be prepared for storage by mixing the agent having the desired degree of purity with optional physiologically acceptable carriers, excipients or stabilizers

{Remington's Pharmaceutical Sciences 16th edition, Osol, A. Ed. (1980)) in the form of aqueous solutions or lyophilized or other dried formulations. Acceptable carriers, excipients, or stabilizers are generally of low toxicity to recipients at the dosages and concentrations employed, and include buffers such as phosphate, citrate, histidine and other organic acids; antioxidants including ascorbic acid and methionine; preservatives (such as octadecyldimethylbenzyl ammonium chloride; hexamethonium chloride; benzalkonium chloride, benzethonium chloride); phenol, butyl or benzyl alcohol; alkyl parabens such as methyl or propyl paraben; catechol; resorcinol; cyclohexanol; 3-pentanol; and m-cresol); low molecular weight (less than about 10 residues) polypeptides; proteins, such as serum albumin, gelatin, or immunoglobulins; hydrophilic polymers such as polyvinylpyrrolidone; amino acids such as glycine, glutamine, asparagine, histidine, arginine, or lysine; monosaccharides, disaccharides, and other carbohydrates including glucose, mannose, or dextrins; chelating agents such as EDTA; sugars such as sucrose, mannitol, trehalose or sorbitol; salt-forming counter-ions such as sodium; metal complexes {e.g., Zn-protein complexes); and/or non-ionic surfactants such as TWEEN™, PLURONICS™ or polyethylene glycol (PEG). Pharmaceutical formulations to be used for in vivo administration are generally sterile. This is readily accomplished, e.g., by filtration through sterile filtration membranes.

An agent may also be entrapped in microcapsule prepared, for example, by coacervation techniques or by interfacial polymerization, for example, hydroxymethylcellulose or gelatin-

microcapsule and poly-(methylmethacylate) microcapsule, respectively, in colloidal drug delivery systems (for example, liposomes, albumin microspheres, microemulsions, nano-particles and nanocapsules) or in macroemulsions. Such techniques are disclosed in Remington's Pharmaceutical Sciences 16th edition, Osol, A. Ed. (1980). Sustained-release preparations may be prepared. Suitable examples of sustained-release preparations include semipermeable matrices of solid hydrophobic polymers containing the active agent, which matrices are in the form of shaped articles, e.g., films, or microcapsule. Examples of sustained-release matrices include polyesters, hydrogels (for example, poly(2- hydroxyethyl-methacrylate), or poly(vinylalcohol)), polylactides (U.S. Pat. No. 3,773,919), copolymers of L-glutamic acid and γ ethyl-L-glutamate, non-degradable ethylene-vinyl acetate, degradable lactic acid-glycolic acid copolymers such as the LUPRON DEPOT™ (injectable microspheres composed of lactic acid-glycolic acid copolymer and leuprolide acetate), and poly- D-(-)-3-hydroxybutyric acid. While polymers such as ethylene-vinyl acetate and lactic acid- glycolic acid enable release of molecules for over 100 days, certain hydrogels release proteins for shorter time periods. When encapsulated agents remain in the body for a long time, they may denature or aggregate as a result of exposure to moisture at 37 ⁰ C, resulting in a loss of biological activity and, for antibodies, possible changes in immunogenicity. Rational strategies can be devised for stabilization depending on the mechanism involved. For example, if the aggregation mechanism is discovered to be intermolecular S-S bond formation through thio-disulfide interchange, stabilization may be achieved by modifying sulfhydryl residues, lyophilizing from acidic solutions, controlling moisture content, using appropriate additives, and developing specific polymer matrix compositions.

In another aspect, methods are provided for administering an agent, e.g., an antibody, protein or nucleic acid as provided in Section ILA., above, for treatment or prophylaxis. In certain embodiments, the agent is administered in combination with at least one additional therapeutic agent and/or adjuvant. In certain embodiments, an additional therapeutic agent is a cytotoxic agent, a chemotherapeutic agent, or a growth inhibitory agent. In one of such embodiments, a chemotherapeutic agent is an agent or a combination of agents used in the treatment of colon cancer. Such agents include, but are not limited to, fluorouracil (5FU) alone

or in combination with leucovorin or levamisole; edrocolomab; irinotecan; oxaliplatin; raltitrexed; and fluoropyrimidines.

Such combination therapies noted above encompass combined administration (where two or more therapeutic agents are included in the same or separate formulations), and separate administration, in which case, administration of the agent can occur prior to, simultaneously, and/or following, administration of the additional therapeutic agent and/or adjuvant. The agent can also be used in combination with radiation therapy.

An agent (and any additional therapeutic agent or adjuvant) can be administered by any suitable means, including parenteral, subcutaneous, intraperitoneal, intrapulmonary, and intranasal, and, if desired for local treatment, intralesional administration. Parenteral infusions include intramuscular, intravenous, intraarterial, intraperitoneal, or subcutaneous administration. In addition, an agent may be administered by pulse infusion, particularly with declining doses of the agent. Dosing can be by any suitable route, e.g. by injections, such as intravenous or subcutaneous injections, depending in part on whether the administration is brief or chronic. Gene therapy methods may be used, e.g., to deliver any of the nucleic acids described herein to cells in vivo. According to one embodiment, a targeting agent is used to direct the vehicle containing the nucleic acid to a desired tissue.

Presently, there are generally two major approaches to getting a nucleic acid (optionally contained in a vector) into a mammal's cells: in vivo and ex vivo. For in vivo delivery the nucleic acid is injected directly into a mammal, usually at the sites where the nucleic acid and, if applicable, the encoded polypeptide, are desired. For ex vivo treatment, the mammal's cells are removed, the nucleic acid is introduced into these isolated cells, and the modified cells are administered to the mammal either directly or, for example, encapsulated within porous membranes that are implanted into the mammal {see, e.g., U.S. Pat. Nos. 4,892,538 and 5,283,187).

There are a variety of techniques available for introducing nucleic acids into viable cells. The techniques vary depending upon whether the nucleic acid is transferred into cultured cells in vitro, or transferred in vivo in the cells of the intended host. Techniques suitable for the transfer of nucleic acid into mammalian cells in vitro include the use of liposomes, electroporation,

microinjection, transduction, cell fusion, DEAE-dextran, the calcium phosphate precipitation method, etc. Transduction involves the association of a replication-defective, recombinant viral (including, but not limited to, retroviral) particle with a cellular receptor, followed by introduction of the nucleic acids contained in the particle into the cell. A commonly used vector for ex vivo delivery of a nucleic acid is a retrovirus.

Commonly used in vivo nucleic acid transfer techniques include transfection with viral or non-viral vectors (such as adenovirus, lentivirus, Herpes simplex I virus, or adeno-associated virus (AAV)) and lipid-based systems (useful lipids for lipid-mediated transfer of a nucleic acid are, for example, DOTMA, DOPE, and DC-Choi; see, e.g., Tonkinson et al, Cancer Investigation, 14(1): 54-65 (1996)). Such vectors are used to synthesize virus that can be used as vehicles for delivering agents, such as antagonists and nucleic acid molecules of this invention. The most commonly used vectors for use in gene therapy are viruses, e.g., adenoviruses, AAV, lentiviruses, or retroviruses. In one embodiment, a viral vector such as a retroviral vector includes at least one transcriptional promoter/enhancer or locus-defining element(s), or other elements that control gene expression by other means such as alternate splicing, nuclear RNA export, or post-translational modification of messenger. In addition, a viral vector such as a retroviral vector may include a nucleic acid molecule that is operably linked to a nucleic acid of interest and acts as a translation initiation sequence. Such vector constructs may also include a packaging signal, long terminal repeats (LTRs) or portions thereof, and positive and negative strand primer binding sites appropriate to the virus used (if these are not already present in the viral vector). In addition, such vector constructs may include a signal sequence for secretion of the encoded polypeptide from a host cell in which it is placed. Optionally, the vector construct can also include a signal that directs polyadenylation, as well as one or more restriction sites and a translation termination sequence. By way of example, vectors will typically include a 5' LTR, a tRNA binding site, a packaging signal, an origin of second-strand DNA synthesis, and a 3' LTR or a portion thereof. Other vectors that can be used are non-viral, such as cationic lipids, polylysine, and dendrimers.

In some situations, the vehicle used for delivery of a nucleic acid or other molecule is associated with a targeting agent that targets the vehicle to specific cell populations. In one

embodiment, the targeting agent is an antibody specific for a cell-surface membrane protein on the target cell, a ligand for a receptor on the target cell, etc. Where liposomes are employed, proteins that bind to a cell-surface membrane protein associated with endocytosis can be used for targeting and/or to facilitate uptake. The technique of receptor-mediated endocytosis is described, for example, by Wu et al, J. Biol. Chem., 262: 4429-4432 (1987); and Wagner et al, Proc. Natl. Acad. Sci. USA, 87: 3410-3414 (1990).

For a review of the currently known gene marking and gene therapy protocols, see, Anderson et al., Science, 256: 808-813 (1992). See also WO 93/25673 and the references cited therein. Suitable gene therapy and methods for making retroviral particles and structural proteins can be found in, e.g., U.S. Pat. No. 5,681,746.

Antibodies of the invention would be formulated, dosed, and administered in a fashion consistent with good medical practice. Factors for consideration in this context include the particular disorder being treated, the particular mammal being treated, the clinical condition of the individual patient, the cause of the disorder, the site of delivery of the agent, the method of administration, the scheduling of administration, and other factors known to medical practitioners. The antibody need not be, but is optionally formulated with one or more agents currently used to prevent or treat the disorder in question. The effective amount of such other agents depends on the amount of antibody present in the formulation, the type of disorder or treatment, and other factors discussed above. These are generally used in the same dosages and with administration routes as described herein, or about from 1 to 99% of the dosages described herein, or in any dosage and by any route that is empirically/clinically determined to be appropriate.

For the prevention or treatment of disease, the appropriate dosage of an antibody of the invention (when used alone or in combination with one or more other additional therapeutic agents) will depend on the type of disease to be treated, the type of antibody, the severity and course of the disease, whether the antibody is administered for preventive or therapeutic purposes, previous therapy, the patient's clinical history and response to the antibody, and the discretion of the attending physician. The antibody is suitably administered to the patient at one time or over a series of treatments. Depending on the type and severity of the disease, about 1

μg/kg to 15 mg/kg (e.g. O.lmg/kg-lOmg/kg) of antibody can be an initial candidate dosage for administration to the patient, whether, for example, by one or more separate administrations, or by continuous infusion. One typical daily dosage might range from about 1 μg/kg to 100 mg/kg or more, depending on the factors mentioned above. For repeated administrations over several days or longer, depending on the condition, the treatment would generally be sustained until a desired suppression of disease symptoms occurs. One exemplary dosage of the antibody would be in the range from about 0.05 mg/kg to about 10 mg/kg. Thus, one or more doses of about 0.5 mg/kg, 2.0 mg/kg, 4.0 mg/kg or 10 mg/kg (or any combination thereof) maybe administered to the patient. Such doses may be administered intermittently, e.g. every week or every three weeks (e.g. such that the patient receives from about two to about twenty, or e.g. about six doses of the antibody). An initial higher loading dose, followed by one or more lower doses may be administered. An exemplary dosing regimen comprises administering an initial loading dose of about 4 mg/kg, followed by a weekly maintenance dose of about 2 mg/kg of the antibody. However, other dosage regimens may be useful. The progress of this therapy is easily monitored by conventional techniques and assays.

III. EXAMPLES

A. Materials and Methods

1. Detection of β2 in tumor tissues Fresh frozen colon tumor tissues were sectioned at 5 - 10 mm on glass slides. LCM was performed using Arcturus PixCell System. Tumor cells or normal epithelia were dissected from H&E stained sections using 15 or 30 mm laser pixel size; 100 - 3000 cell equivalents were collected per sample. RNA was isolated and probes generated and hybridized on cDNA microarrays. Immunohistochemistry (IHC) was performed using MACH 3 Rabbit-Probe HRP polymer kit or MACH 3 Mouse-Probe HRP polymer kit from Biocare Medical (Concord, CA) following the manufacturer's directions. α-REST polyclonal antibody (Upstate, Lake Placid, NY) or α-β2 monoclonal antibody (3Dl, Genentech, Inc.) were used with human colon

adenocarcinoma (grade III) and colon metastatic carcinoma tissue arrays (Cybrdi, Gaithersburg,MD).

2. SCN2B (β2) plasmid constructions and transfection

SCN2B.ECD.HIS construct: nucleic acid encoding the C-terminal polyhistidine-tagged (HIS8) ECD of SCN2B was cloned into the pSVI7 vector (DHFR) and transfected into DP12 CHO cells using Fugene 6 (Roche Diagnostics, Indianapolis, IN). Clones were selected in medium containing 20OnM methotrexate. β2 protein was purified from the transfected DP 12 cell culture media using Ni-NTA beads (Qiagen, Valencia, CA) for phenotype studies, generation of monoclonal antibodies, and Notchl binding studies. SCN2B.FL.GFP: Full-length SCN2B constructs were cloned into a pSVIPD.IRES.GFP vector (puromycin resistance marker) and transfected into CHO or SW620 cells for antibody screening and phenotype assays.

3. Cell Culture

Human tumor cell lines were maintained in RPMI1640 or F12:DMEM50:50 medium supplemented with 10%FBS, L-glutamine and Penicillin-streptomycin. CHO cells were maintained in F12:DMEM50:50 medium supplemented with 10%FBS, GHT, L-glutamine and penicillin-streptomycin. HUVEC cells were maintained in EBM-2 medium supplemented with EGM-2 (Cambrex, Valkersville, MD).

4. Immunoblot Analysis

Cells were lysed in lysis buffer (10OmM NaH2PO4, 1OmM Tris-HCL, 8M Urea and 0.05% tween-20, pH 8.0) with sonication and the lysate (typically 25 μg total protein) was loaded onto 4-12% Tris-Glycine gel (Invitrogen). Proteins were transferred onto PVDF membrane (Invitrogen, Carlsbad, CA) or Nictrocellulose membranes (Invitrogen). Immunoblots were blocked overnight at 4°C in 2% BSA, 5% dry milk in PBS. The following antibodies were used: mouse α-β2 monoclonal or rabbit α-β2 polyclonal (Genentech, Inc.), α-REST polyclonal antibody (Upstate, Lake Placid, NY), α-Notchl (G20) polyclonal antibody (Santa Cruz

Biotechnology, Santa Cruz, CA), α-FLAG antibody (Sigma). Secondary detection was performed using IRDye680-conjugated goat α-mouse IgG or IRDye680-conjugated donkey α-rabbit IgG (Rockland Inc., Gilbertsville, PA). Imunoreactive bands were detected and analyzed by

scanning the blot with Odyssey Infrared Imaging System (LI-COR Biosciences, Lincoln, NE). Alternatively, secondary detection was performed using ECL α-mouse IgG HRP (Amersham) and detected using Chemiglow West (Alpha Innotech). 5. Generation ofβ2 antibodies Five Balb/c mice (Charles River Laboratories, Hollister, CA) were hyperimmunized with recombinant polyhistidine-tagged (HIS8) human β2 ECD from CHO cells (Genentech, Inc., South San Francisco, CA) in Ribi adjuvant (Ribi Immunochem Research, Inc., Hamilton, MO). B-cells from these mice, all of which demonstrated high α-β2 antibody titers by direct ELISA and specific binding to β2 expressed on CHO cells by FACS, were fused with mouse myeloma cells (X63.Ag8.653; American Type Culture Collection, Rockville, MD) using a modified protocol analogous to one previously described (Kohler and Milstein, Nature 256:495-497, 1975; Hongo et al., Hybridoma 14:253-260, 1995). After 10-12 days, the supernatants were harvested and screened for antibody production by direct ELISA and FACS. Clones showing the highest immunobinding after the second round of subcloning were expanded and cultured. The supernatants harvested from each hybridoma lineage were purified by affinity chromatography (Pharmacia fast protein liquid chromatography [FPLC]; Pharmacia, Uppsala, Sweden) using a modified protocol analogous to one previously described (Hongo et al., supra). The purified antibody preparations were then sterile filtered (0.2-μm pore size; Nalgene, Rochester NY) and stored at 4°C in phosphate buffered saline (PBS). 6. Immunofluoresence

Vimentin and actin cytoskeleton (rhodamine-phalloidin): cells were fixed in 4% paraformaldehyde for 20 minutes at room temperature and permeabilzed with 0.05% saponin for 5 minutes at room temperature. For β2, REST, cleaved-Notchl NICD and E-cadherin staining: cells were fixed in methanol at 4°C for 2 minutes. Primary antibody incubation was at room temperature for 1 hour (for vimentin staining), or for 15 minutes (for rhodamine-phalloidin staining) or at 37°C for 1 hour (for β2, REST, cleaved-Notchl NICD and E-cadherin staining). Secondary antibody incubation was at room temperature for 30 minutes. Antibodies used were as following: α-ankyrin monoclonal antibody (Chemincon International, Temecula, CA); α-

vimentin monoclonal antibody (Sigma- Aldrich, St. Louis, MO); rhodamine-phalloidin (Molecular Probes, Eugene, OR), α-REST polyclonal antibody (Upstate, Lake Placid, NY) , α-E- cadherin monoclonal antibody (Invitrogen, Carlsbad, CA), α-Notchl (Vall744 peptide, detects both intact and cleaved Notchl NICD) (Cell Signaling, Danvers, MA) or α-β2 monoclonal antibody (Genentech, Inc.). Secondary antibodies were as follows: Cy3 -conjugated rabbit α- mouse IgG or Cy3 -conjugated donkey α-rabbit IgG (Jackson Lab, Bar Harbor, Maine). Slides were mounted with Vectashield mounting media with DAPI (4',6-diamidino-2-phenylindole) (Vector Lab, Burlingame, CA). Images were acquired using 6OX magnification on a microscope equipped with a camera. Images overlays were generated using Adobe Photoshop software. For intact or cleaved Notchl NICD staining, after the secondary antibody incubation, slides were incubated with Hoechst 44257 to stain nuclei at room temperature for 20 minutes, and mounted with Prolong Gold anti-fade reagent (Invitrogen, Carlsbad, CA). Images were acquired using a LSM510 laser scanning confocal microscope (Carl Zeiss Micro Imaging, Inc., Thornwood, NY). Two-photon excitation by a Chameleon laser (Coherent, Santa Clara, CA) was used for DAPI visualization, with a fully open pinhole. A HeNe (543 nm) laser was used for the fluorochrome excitation, with the pinhole set to one Airy unit. Images were saved in TIFF format and assembled in Photoshop.

7. β2 and β2-ECD Induced Phenotype Assays

CHO cells expressing β2 ECD were grown to 80% confluence and media was collected and centrifuged to remove any cell debris. This conditioned media was used to treat cell lines for the described analyses. Media collected from vector-transfected CHO cells was used as a control. For phalloidin, vimentin and E-cadherin staining, condition media treated cells were stained with antibodies at 48 or 72 hours.

8. Antibody Blocking Assay SCN2B and vector transfected CHO cells and SW620 cells were seeded onto 1-well chamber glass slides (Nalge Nunc International, Rochester, New York) at 25% confluence. α-β2 monoclonal antibody was added to the cell culture media at 100 ng/ml. After 72 hours, cells were stained with rhodamine phallodin.

9. β2 Depletion Assay α-β2 monoclonal antibody-coupled gel was made using Seize Primary Immunoprecipitation Kits (Pierce, Rockford, IL) following manufacturer's instructions. Cell culture media collected from DP12/SCN2B.ECD.HIS cells was incubated with α-β2 monoclonal antibody-coupled gel for 2 hours to remove β2. The flow through was added to cells for phenotype analysis. A mock depletion of β2 was done with PBS-coupled gel using the same procedure. β2 was also depleted using Ni-NTA beads (Qiagen).

10. Migration Assay

Migration assays were performed using the HTS FluoroBlock Multiwell insert system with 8 mm pore size (BD Biosciences, Bedford, MA). 10 ⁵ cells/well were seeded into the upper wells and FBS was added to the bottom wells. After 18hr, cells that migrated to the other side of the trans-well membrane were stained in 10 um YO-PRO-I iodide (Invitrogen, Eugene, OR) and quantitated using the fluorescence plate reader Spectra Max GeminiEM (Molecular Devices, Sunnyvale, CA). 11. Cell Death and Drug Resistance:

Resistance to starvation: SW620 cells were seeded into 6 well plates at 25% confluence in complete media overnight. This media was replaced the next morning with media lacking FBS. For the assay, cells were detached using trypsin, washed, and stained in 0.4% Trypan Blue (Invitrogen, Carlsbad, CA). Total cells and dead cells were counted using a hemocytometer. Assays were performed in triplicate. Doxorubicin resistance: 2x10 ⁴ SW620 cells were seeded in 96 well clear bottom black plates (Corning Inc., Corning, NY) with serial dilutions of doxorubicin hydrochloride (Sigma-Aldrich, St. Louis, MO) and incubated for 5 days. Cell viability was measured by using Cell Titer GIo Luminescent Cell Viability Kit (Promega, Madison, WI). Luminescence was quantified using an Envision 2103 multilabel reader (PerkinElmer, Finland). Methotrexate resistance: 5xlO ⁵ CHO cells were seeded in 6-well plates with β2 ECD in conditioned medium or control conditioned medium containing 200nm methotrexate (Genentech Inc.). Cells were detached from the plate and stained with Trypan Blue 0.4% (Invitrogen, Carlsbad, CA) as described.

12. siRNA knock down siRNA knock down of REST, Twistl or Notchl in SW620 cells was performed using 60nm of siRNA with DharmaFECT 2 as the transfectant. A non-targeting siRNA sequence (Dharmacon, Lafayette, CO) was used as a negative control. Immunofluoresence staining and RT-PCR analysis were performed 4 days after siREST transfection. For Twistl and Notchl knock downs, cells were treated with β2 ECD in conditioned media 24-48 hours after transfection, followed by immunofluoresence staining or RT-PCR analysis after an additional 24- 48 hours of incubation. For siREST experiments, α-β2 antibodies were added after 12 hours after transfection. The siRNA duplexes were designed and synthesized by Dharmacon (Lafayette, CO). The primary target sequences are as follows: siREST: 5'-CAACGAAUCUACCCAUAUUUU-S ' (SEQ ID NO:3). siTwistl : 5 '-GCGACGAGCUGGACUCCAAUU-S ' (SEQ ID NO:4). siNotchl : 5 '-GCGACAAGGUGUUGACGUUUU-S ' (SEQ ID NO:5).

Additional siRNA sequences: siTWISTl : 5 '-CUGCAGACGCAGCGGGUCAUU-S ' (SEQ ID NO:6),

5'-GGAGUCCGCAGUCUUACGAUU-S' (SEQ ID NO:7), 5'-GAGCAAGAUUCAGACCCUCUU-S' (SEQ ID NO:8); SiNOTCHl: 5'-GAUGCGAGAUCGACGUCAAUU-S' (SEQ IDN0:9), 5'-GAACGGGGCUAACAAAGAUUU-S' (SEQ ID NO:10), 5'-GCAAGGACCACUUCAGCGAUU-S' (SEQ ID NO:11).

13. Image processing for E-cadherin intensity calculations

Images were converted from Photoshop format to Tif in Photoshop CS2 (version 9.0.2, Adobe; San Jose, CA). Images were opened in Metamorph (version 7.0r4, Molecular Devices; Sunnyvale, CA) and subjected to an automated analysis routine. Briefly, a threshold value was applied for each set of images (approx. 10-15% of maximum pixel value) to remove background. A standard erode function was used to further reduce background and smoothen the edges of the remaining regions. Area and intensity measurements for each individual region were output directly to Excel (Microsoft, Redmond, WA). A small subset of images had specific staining that was above background, but below the threshold value. For this subset, regions of interest were

created manually in order to obtain area and intensity measurements. Typically, 5 independent regions were analyzed and combined for each analysis. 14. Statistical analysis

Analyses were performed in triplicate (or greater) and analyzed using a Student's T-test (equal variance, 1 tailed distribution) in Microsoft Excel. 75. Binding Assays

Immunoprecipitation: cells were removed from culture plates using 5mm EDTA and lysed in TBS buffer containing 0.5% NP-40, EDTA-free protease inhibitor (Roche Diagnostics, Indianapolis, IN) and lmm PMSF. The cell lysate was incubated with pre-saturated protein G- agarose (Roche Diagnostics, Indianapolis, IN) at 4°C for 1.5 hour followed by incubation with α- β2 monoclonal antibody at 4°C for 2 hours. This cell lysate and antibody mixture was then incubated with pre-saturated protein G-agarose at 4°C overnight. The agarose was collected and proteins were eluted in Tris-Glycine gel loading buffer (Invitrogen, Carlsbad, CA) for immunoblot analysis. Direct binding: conditioned media was collected as described above, incubated with FLAG-tagged Notch 1 ECD: 6-36 (5 μg) in 15 ml for 2 hours at room temperature with shaking. 50 μl of Ni-NTA agarose bead slurry (Qiagen) was added with incubation for 2 hours at room temperature with shaking. Ni-NTA beads were collected by centrifugation and washed 3 times with PBS. Alternatively, conditioned media was treated with Ni-NTA beads to enrich for β2 and the resulting slurry incubated with Notchl ECD:6-36 (5 μg) in 1 ml PBS and incubated and washed as described. Samples were eluted into 2X loading buffer. 16. Microarray Analysis

Microarrays representing 9031 genes were generated by printing PCR products derived from cDNA clones (Invitrogen, Carlsbad, California and Genentech, Inc.) on glass slides coated with 3-aminopropyltriethoxysilane(Aldrich, Milwaukee WI) and 1 ,4-phenylenediisothiocyanate (Aldrich, Milwaukee, WI) using a robotic arrayer (Norgren Systems, Mountain View, California). RNA isolation from LCM material was accomplished by CsCl step gradient (Kingston RE, in Current Protocols in Molecular Biology, Vol. 1 (ed. Ausubel FM, et al.) 4.2.5- 4.2.6 (John Wiley and Sons, Inc., USA, 1998)). Probes for array analysis were generated by

conservative amplification and subsequent labelling as follows: double-stranded DNA generated from oligo dT priming of total RNA (Invitrogen, Carlsbad, CA) was amplified using a single round of a modified in vitro transcription protocol (MEGASCript T7 from Ambion, Austin, Texas). The resulting cRNA was used as a template to generate a sense DNA probe using random primers (9mers, 0.15 mg/ml), Alexa 488 dUTP or Alexa 546 dUTP (40 μM and 6 μM, respectively, Molecular Probes, Eugene, Oregon) using MMLV-derived reverse transcriptase (Invitrogen, Carlsbad, CA). A reference probe to reflect general epithelial cell expression was generated from 0.1 μg of total RNA from a universal reference RNA (Strategene, La Jolla, CA). Probes were hybridized to arrays overnight in 50% formamide / 5XSSC at 37 ⁰ C and washed the next day in 2XSSC, 0.2% SDS followed by 0.2XSSC, 0.2% SDS. Array images were collected using a CCD-camera based imaging system (Norgren Systems, Mountain View, California) equipped with a Xenon light source and optical filters appropriate for each dye. Full dynamic- range images were collected (Autograb, Genentech Inc) and intensities and ratios extracted using automated gridding and data extraction software (glmage, Genentech, Inc.) built on a Matlab (the Math Works, Natick, Massachusetts) platform. 17. Microarray Data Analysis

Ratio values were normalized for experimental scatter at different intensity values within each experiment by plotting log ratio versus N intensity and by fitting a normal distribution at each intensity level. A measure of standard deviation (Z score) around a mean of zero was derived for each transcript in each experiment and this value was used in data mining.

Specifically, for each microarray, we normalized the data by computing Z-scores, which were obtained from a scatterplot of the logarithm of the ratio of the test and reference data versus the logarithm of the minimum of the test and reference data. We estimated the median of the ratio as a function of intensity by applying the loess algorithm to the scatterplot. We estimated the standard error by applying loess to the square root of the absolute residuals, and squaring the result to obtain the median absolute deviation (MAD), and making a multiplicative correction to convert from MAD to a standard error. The Z scores were determined for each ratio by dividing its vertical distance from the median loess curve by the standard error at that intensity. Genes that

were differentially expressed between tumor and normal epithelium were identified using a statistical test (Student's T test, equal variance, two-tailed distribution) in Rosetta Resolver. B. Results

1. β2 is expressed in tumors We discovered β2 expression in colon tumor cells through microarray expression profiling of laser capture microdissected material, a technique with demonstrated utility in isolating discrete cell populations from complex tissues and disease states such as tumors, allowing identification of gene expression not previously associated with these cells (Buckanovich et al., Cancer Biol. Ther. 5:635-642, 2006; Espina et al., Methods MoI. Biol. 319:213-229, 2006)

Laser capture microdissection (LCM) and transcript profiling were performed on fresh- frozen colon tumor sections. Sample collection was biased toward tumor cells near the tumor- stroma boundary. Five sets of normal colon epithelium were also isolated using LCM. β2 transcript was identified as overexpressed in tumor epithelium as compared to normal epithelium in a Student's T test comparing the sample populations (p value = 0.0014, Figure IA; Figure

10A). Detection of β2 transcript was validated using RT-PCR on RNA isolated from a subset of adjacent tumor sections (Figure 10B). As an additional validation, non-isotopic in situ hybridization was performed on some adjacent tumor sections (Figure 10C), confirming tumor cell expression. More extensive analysis of β2 expression in colon tumors by immunohistochemistry using an α-β2 monoclonal antibody and tissue microarrays revealed expression in tumor cells in grade III primary tumors and metastatic tumors (typically lymph node) from 22 of 41 patients (54%), and in 5 of 62 normal colon samples (8%). The tumor staining was heterogeneous and often punctate in nature, showing variation in intensity and distribution across the tumor epithelium (Figure IB). While the LCM analysis was biased toward the tumor-stroma boundary, this does not preclude expression elsewhere, and β2 was detected at the tumor edge as well as other regions of tumor epithelia not obviously bounded by stroma. The staining observed in the 5 β2-positive normal colons was weak to moderate, and present only in surrounding cells, not in

the epithelial crypt cells. Overall, these data indicate that both the β2 transcript and protein are expressed in over 50% of colon tumors, contrasting with very limited expression in normal colon epithelium. Immunoblot analysis of protein isolated from tumor tissues indicated that β2 was also expressed in other tumor types, as well (Figure 10E). 2. β2 induces morphological transformation of cells

EMT is a transdifferentiation process in which epithelial cells acquire many attributes of more motile, invasive cells, including development of a more spindle-like, fibroblastic morphology. Expression of either β2 full-length protein or treatment of cells with conditioned media containing β2 extracellular domain (ECD) alone induced significant elongation and enlargement of cells as well as remodeling of the actin cytoskeleton (Figure 2A). These changes were observed in numerous cell lines, including tumor cell lines such as NCI-H226 and SW620, as well as CHO cells (Chinese Hamster Ovary; Figure 2A). Confirming that these changes resulted from expression of β2 protein, these effects could be blocked using a monoclonal antibody specific to the ECD of β2 (Figure 2B): many newly divided cells were restored to a more normal, rounded appearance. Cells treated with an irrelevant control antibody (α-Ragweed) retained the β2-induced morphological change. β2 contains a predicted mature ECD of- 129 amino acids, consisting largely of an Ig domain, along with a transmembrane region and a short (~ 35 amino acid) intracellular domain. We investigated whether the ECD alone could induce morphological change, by expressing a C- terminal his(8)-tagged ECD construct that was designed to be secreted from CHO cells.

Conditioned media containing β2 ECD was capable of inducing phenotypic changes similar to those described above after 48 - 72 hours when placed on a variety of distinct cell types (naϊve CHO cells, MDCK cells, HUVEC (endothelial), or tumor cell lines NCI-H226, SW620, SW480, and PC-3; Figure 2A, Figure 1 IA). To confirm that these effects were due to the presence of the β2 ECD, the β2 protein was depleted from the media, which was then added to naϊve NCI-H226 cells. Changes in the actin cytoskeleton were assessed using rhodamine-phalloidin staining, and each sample was also analyzed by immunoblotting for β2 protein (Figure 2C). Mock-depleted conditioned media contained β2 protein and induced complete phenotypic change. Conditioned

media from which β2 was substantially depleted (> 90%) yielded no detectable phenotypic changes, whereas conditioned media from which β2 was partially-depleted produced an intermediate phenotype, in which cells were enlarged and elongated but to a lesser degree than mock-treated cells. These data indicate that the phenotypic changes observed in β2 ECD conditioned media are dependent on the β2 ECD and reflect the level of β2 protein. 3. β2 promotes migration and confers protection against cell death

A physical property closely associated with cells undergoing EMT is increased motility. The effect of β2 on tumor cell migration was investigated by comparing the ability of β2 transfected and vector-transfected SW620 cells, or β2 ECD treated cells, to migrate across a transwell membrane to media containing fetal bovine serum (0.1%). Transfection efficiency was ~ 75%, with ~ 40% of cells in the SCN2B transfected pool displaying typical β2-induced phenotypic changes. After 18 hours, a significant increase in migration was observed for both β2 transfected cells and cells treated with β2 ECD in conditioned media (Figure 3A; p = 0.03 and 0.0009, respectively). Conversely, treating SW480 cells, which express β2 endogenously (see Figure 5A), with 2 independent α-β2 antibodies resulted in a decrease in migration (Figure 3B, p = 0.001 for each antibody), further supporting a role for β2 in promoting cellular migration. Another hallmark of EMT is increased resistance to cell death (Lee et al., 2006). The ability of β2 to influence this property was investigated in SW620 cells, which were subjected both to starvation and to treatment with chemotherapeutic drugs. β2-transfected or vector transfected control cells were subjected to starvation for a period of 2 weeks in media lacking serum and cell viability was compared to vector-transfected control cells using a trypan blue exclusion assay. β2 significantly increased cell viability, with less than 10% cell death as compared to 35% of vector-transfected control cells (p = 0.002, Figure 3C). β2 also promoted resistance to cell death upon exposure to the chemotherapeutic drug, doxorubicin (Figure 3D). SW620 cells transfected with β2 exhibited significantly increased viability compared to vector- transfected control cells, over a 10-fold range of drug concentration, as determined by a quantitative cell viability assay (Cell Titer GIo, Promega, Madison, WI). Finally, we observed that expression of β2 by CHO cells increased their resistance to the chemotherapeutic drug,

methotrexate, which was used as a selection for full-length β2 transfected CHO cells. To assess this independently, conditioned media from CHO cells expressing the β2 ECD only was added to naϊve CHO cells and compared to control conditioned media-treated cells. In the presence of 200 nM methotrexate for 48 hours, 60% of control-treated cells died whereas the majority of β2-ECD treated cells remained viable (Figure 3E, p = 0.01), with only 10% cell death. These data indicate that the β2 ECD alone confers resistance to chemotherapeutic drugs.

4. β2 induces loss of E-cadherin and gain ofvimentin and this process is dependent on the EMT-associated transcription factor Twistl

E-cadherin serves as one of the caretakers of epithelial phenotype and its loss is associated with both initiation and progression of tumors (Thiery and Sleeman, Nat. Rev. MoI. Cell Biol. 7: 131-142, 2006). Loss of E-cadherin is also strongly associated with cells undergoing EMT. SW620 cells express E-cadherin (Figure 4A) and transfection with β2 or treatment with β2 ECD in conditioned media for 48 hours greatly reduced E-cadherin protein levels, as evident by both immunofluoresence (Figure 4A) and FACS analysis (Figure 4B). Induced expression of the mesenchymal intermediate filament protein vimentin is another hallmark of epithelial cells undergoing EMT (Huber et al, Curr. Opin. Cell Biol. 17:548-558, 2005; Lee et al., J. Cell Biol. 172:973-981, 2006; Thiery and Sleeman, supra). Immunofluorescent staining of SW620 cells expressing either full length β2 or treated with β2 ECD in conditioned media, with α-vimentin antibodies, revealed a substantial increase in vimentin protein expression from otherwise undetectable levels (Figure 4C).

Given the ability of both full length β2 and β2 ECD to induce loss of E-cadherin and morphological transformation, the expression of transcription factors capable of mediating EMT was investigated. To facilitate detection of transcripts that might exhibit transitory expression or be subject to feedback regulation, SW620 cells were treated with β2 ECD in conditioned media and RNA was isolated at different time-points. Microarray analysis revealed induction of Twistl transcript 6 hours after treatment with β2 ECD with an oscillating pattern of expression at subsequent timepoints (Figure 12A). RT-PCR analysis confirmed expression of Twistl (Figure 12B) and no significant or robust evidence of induction of transcripts for other characterized EMT transcription factors such as Snail and Slug/Snail2 (not shown). An oscillating pattern of

regulation has been reported for transcription factors such as HESl, which mediate their own negative regulation (Hirata et al., Science 298:840-843, 2002) and our observations for Twistl suggest the possibility that it is similarly regulated, or induced by a transcription factor that oscillates in this manner. As Twistl is a transcriptional repressor that acts upon E-box sequences in the promoter of E-cadherin, and is capable of inducing EMT in epithelial cells (Batlle et al., Nat. Cell Biol. 2:84-89, 2000; Bolos et al., J. CeIl Sd. 116:499-511, 2003; Cano et al., λtø. Cell Biol. 2:76-83, 2000; Conacci-Sorrell et al., J. Cell Biol. 163:847-857, 2003; Yang et al., Cell 117:927-939, 2004), these data suggest that induction of Twistl expression after exposure to β2 may play a significant role in the morphological transformation observed. To further investigate the role of Twistl in the EMT-like morphological transformation induced by β2, Twistl was depleted from SW620 cells using siRNA knockdown. The cells were then treated with β2 ECD in conditioned media (Figure 4D), and the actin cytoskeleton and E- cadherin staining assessed. In control cells treated with a non-targeting siRNA, treatment with β2 induced remodeling of the actin cytoskeleton and loss of E-cadherin, whereas control conditioned media had no effect on cells. However, in the presence of siRNAs specific to Twistl, β2 was no longer capable of inducing EMT: E-cadherin staining remained positive and cellular morphology was normal (Figure 4D). Quantitative analysis of E-cadherin staining from multiple independent fields of cells revealed a statistically significant difference for β2 ECD-treated cells depleted for Twistl as compared to control cells (Figure 4E, p = 0.001 and 0.009). These data indicate that the EMT induced by β2 in SW620 is dependent upon the presence of Twistl . Crosstalk and cooperation between EMT-associated transcription factors in development has been described (Aybar et al., Development 130:483-494, 2003; Ganguly et al., Development 132:3419-3429, 2005), and while their transcripts were not robustly detected in this study, it is possible that transcription factors such as Snail and Slug could also play a role in β2 induced EMT, either in these cells or in different cell types. Overall, given both the induction of Twistl on treatment with β2 ECD and the dependence of the β2-induced morphological transformation on Twistl, a characterized EMT-inducing transcription factor, these results strongly support our phenotypic data findings that β2 does indeed induce EMT.

5. Knockdown of REST in tumor cells results in EMT-like morphological transformation that is mediated by β2

REST, a negative transcriptional regulator that restricts expression of neuronal genes in non-neural tissues, was more recently characterized as a tumor suppressor in colon and possibly other cancers (Westbrook et al., Cell 121 :837-848, 2005). The type II voltage-dependent sodium channel and associated proteins are neuronally and developmentally expressed, and SCN2A was one of the first REST-regulated genes identified. Analysis of the SCN2B genomic region (encoding β2) revealed a cluster of 4 consensus REST binding sites in the first intron, suggesting that REST might regulate β2 expression. We further investigated a possible connection between the expression of β2 in tumor cells and REST deregulation using colon tumor cell lines. Staining of cell lines for REST and β2 proteins revealed reciprocal expression: colon cell lines SW480, SW1417, described as REST negative (Westbrook et al., supra), along with SWl 116, were β2 positive whereas β2 was not detected in REST positive line SW620 (Figure 9, Figure 5A). DLD- 1 expresses a mutant REST protein lacking a repressor domain (Westbrook et al., supra) and stained positive for β2 (Figure 9). These data are consistent with β2 being transcriptionally repressed by REST, either directly or indirectly. Analysis of REST and β2 protein expression in colon tumors by immunohistochemistry revealed that this relationship persists: we found a reciprocal pattern of staining for REST and β in the grade III adenocarcinoma and metastatic colon tumor samples described earlier. Punctate REST staining was observed in tumors from 18 of 41 patients (44%; Figure 5A) and in only one tumor was there overlap in staining between

REST and β2 (for which expression was detected in 22 of 41 cases). REST staining was detected in 40 of 62 normal colon samples (65%), none of which were β2 positive. These results indicate that the anti-correlation in expression is not just a cell line phenomenon but is also true for tumor tissues, and supports the hypothesis that loss of REST in human tumor cells could contribute to the expression of β2.

We further investigated the possibility of a biologically-relevant functional relationship between the REST tumor suppressor and β2. To determine whether loss of REST might result in expression of β2 and induction of EMT in a tumor cell context, REST was depleted in SW620

using RNAi. SW620 shows a pattern of REST and β2 staining opposite to that of SW480 (Figure 5A), but is derived from tumors from the same individual. Five days after transfection with REST-specifϊc siRNA, immunoblot analysis confirmed a substantial decrease in REST and a significant increase in β2 protein as compared to cells transfected with a non-targeting control siRNA (Figure 5B, C; Figure 13 A, B). Changes in cell morphology consistent with the β2- induced EMT as visualized using rhodamine-phalloidin staining of the actin cytoskeleton, substantial reduction of E-cadherin, and induction of vimentin were also apparent in the REST knockdown cells (Figure 5D). Quantitative analysis of E-cadherin staining from multiple independent fields of cells revealed a statistically significant decrease for cells transfected with REST-specific siRNA as compared to cells transfected with a non-targeting control siRNA

(Figure 5E; p = 0.001). Overall, these data indicate that, in a tumor-cell context, one consequence of loss of REST is expression of β2 and induction of morphological changes consistent with EMT.

Having demonstrated that knockdown of REST induced changes in morphology and marker expression consistent with EMT, we used functionally-blocking β2 monoclonal antibodies to determine if the induction of EMT resulting from loss of REST is primarily mediated by expression of β2. REST was depleted in SW620 cells using siRNA, and cells were allowed to grow for 4 days in the presence of antibodies directed against either β2 or an irrelevant target (Ragweed). Cells were then stained with phalloidin to visualize the actin cytosekeleton or with an α-E-cadherin or α -vimentin antibody. α-Ragweed antibody treated cells underwent morphological change and loss of E-cadherin typical of the β2-induced EMT and REST knockdown. However, REST-depleted cells treated with β2-specific blocking monoclonal antibodies 3Dl and 2E3 had normal morphology, strong E-cadherin expression, and little or no expression of vimentin, similar to that observed with the non-targeting siRNA control (Figure 5D). Quantitative analysis of E-cadherin staining from multiple independent fields of cells revealed a statistically significant increase in E-cadherin levels in siREST cells treated with each of the independent β2 functionally-blocking antibodies 3Dl and 2E3 compared to the untreated siREST or α-Ragweed treated siREST cells (Figure 5E, p = 0.02 and 0.01, respectively). These

results are consistent with the EMT-lik morphological transformation induced by loss of REST being mediated by β2, and indeed requiring extracellular expression of β2.

6. Induction ofEMT-like morphological transformation by β2 is dependent upon Notchl Notch signaling is an ancient and conserved system that regulates cell fate in development and in adult self-renewing cells (Artavanis-Tsakonas et al., Science 284:770-776, 1999). HESl is a characterized target of Notch pathway signaling (Jarriault et al., Nature 377:355-358, 1995) which undergoes an oscillating cycle of transcript expression, due to self- mediated negative regulation (Hirata et al., Science 298:840-843, 2002). Oscillating HESl expression at early timepoints (6 - 24 hrs) in transcript expression data derived from SW620 cells treated with β2 ECD (Figure 12A) suggested a role for Notch signaling in the EMT induced by β2. Transcript analysis indicated that Notchl was the only Notch family receptor expressed at significant levels on SW620 cells (Figures 1 IB, C, D). To determine whether Notchl was required for the β2 ECD to induce EMT in SW620 cells, cells were transfected with siRNAs specific for Notchl or a non-targeting control siRNA, treated with β2 ECD in conditioned media, and analyzed for loss of E-cadherin, as a primary marker of Twist 1 activity and EMT. Cells transfected with a non-targeting siRNA and treated with β2 ECD demonstrated loss of E- cadherin staining as compared to control-media treated cells, but depletion of Notchl blocked this morphologic transformation and resulted in cells with a normal actin cytoskeleton which were positive for E-cadherin (Figure 6 A, C). These data indicate that Notchl is necessary for the induction of the EMT-like morphological transformation by β2.

Activation of Notch signaling requires cleavage of the receptor by both an ADAM protease and gamma-secretase to release the Notch intracellular domain (NICD). We thus asked whether a gamma-secretase inhibitor, which prevents Notch signaling (De Strooper et al., Nature 398:518-522, 1999) would also inhibit β2-induced EMT. SW620 cells were mixed with DMSO (vehicle control) or the specific gamma-secretase inhibitor DAPT (N-[N-(3,5- difluorophenylacetyl-L-alanine)]-S-phenylglycine t-butylester) at 500 nM in DMSO, treated with β2 ECD in conditioned media, and analyzed for loss of E-cadherin. Unlike full-length β2, the β2 ECD construct does not contain the characterized gamma-secretase cleavage site (Kim et al., J.

Biol. Chem. 280:23251-23261, 2005) and thus is not a target for inhibition of processing by DAPT. Cells treated with β2 ECD in the presence of DMSO showed the typical loss of E- cadherin, as compared to cells treated with control conditioned media. However, cells treated with β2 ECD in the presence of DAPT remained E-cadherin positive, suggesting that Notchl signaling is required for the induction of EMT by β2 (Figure 6B, C). Quantitative analysis of E- cadherin in both siRNA knockdown and gamma-secretase inhibition experiments confirmed a statistically significant difference in E-cadherin levels in cells treated with β2 ECD in which Notchl was depleted or Notchl signaling was inhibited (Figure 6C).

SW620 cells express the Notch ligands Jagged 1 and Jagged2 (Figure 1 ID), yet are not undergoing EMT. Given the apparent role of Notch signaling in the EMT induced by β2, we investigated whether Notch ligands from the Jagged or Delta-like families could induce EMT. Cells were stimulated by exogenous addition of the ligands Jagged 1 or DLLl in various formats, including in trans by co-culture with ligand-expressing cells or using plate-bound ligand, but no evidence of EMT was observed under any of the conditions used (data not shown). As a positive control, co-culture of Notch ligand-expressing cells with 3T3 cells transfected with Notchl produced evidence of Notch pathway signaling as determined by a luciferase reporter assay from a CSL-binding promoter construct (data not shown). However, treatment of SW620 in similar co-culture assays with Jagged 1 -expressing or DLLl -expressing cells failed to induce either EMT-like morphological change or significant activity by the reporter construct (data not shown). It is possible that the reporter construct was insufficiently sensitive to detect endogenous Notch signaling in SW620, but this consideration notwithstanding, there was no evidence of induction of EMT or related morphological change by either Jagged 1 or DLLl, suggesting that expression and presentation of these characterized Notch ligands in trans was not sufficient to induce EMT in these cells. 7. β2 binds Notchl and induces nuclear localization of the Notch intracellular domain (NICD)

Treatment of cells with the β2 ECD induced phenotypic changes in cells that do not endogenously express β2 (eg. SW620), indicating that the receptor through which β2 acts is not β2 itself. Having established that the EMT induced by β2 was dependent upon Notchl and Notch

pathway signaling, and having observed induction of HESl transcript at a 6 hour timepoint (Figure 12A), well prior to the appearance of phenotypic changes (24 - 72 hours), we investigated the possibility that β2 might be a ligand or binding partner of Notch 1. β2, an Ig domain protein, does not share the sequence properties of classical Notch ligands such as Jagged- 1 or 2 and DLLl . However, two other Ig domain proteins, contactin/F3 and NB3, have been described as novel Notch ligands that contribute to the determination of cell fate in neuronal precursors (Cui et al, J. Biol. Chem. 279:25858-25865, 2004; Hu et al, Cell 115:163-175, 2003). In considering Notchl as a candidate receptor for β2, Notchl (or possibly Notch2) expression would be expected in cells that undergo morphological change in response to the β2 ECD. Transcript analysis revealed that β2-responsive tumor cell lines expressed Notchl (and frequently, also Notch2; examples in Figures 1 IB, C). Endothelial HUVEC cells expressed Notchl and also responded to β2, whereas HEK293 cells, which showed no phenotypic change in response to β2 (Figure 1 IA), do not express Notchl (Hicks et al., Nat. Cell Biol. 2:515-520, 2000; Ray et al., J. Biol. Chem. 274:36801-36807, 1999). These observations are consistent with Notchl being an effector or receptor for β2.

To determine whether Notchl and β2 can physically associate, we performed a co- immunoprecipitation and immunoblot analysis of full-length β2-transfected SW620 cells, using α-β2 monoclonal antibodies or an irrelevant control antibody (α -Ragweed) in the immunoprecipitation. Immunob lotting with a Notchl -specific monoclonal antibody revealed that α-β2 antibodies co-precipitated endogenous Notchl from β2-transfected cell lysates. This co- precipitation appeared specific as we did not observe Notchl precipitation using the control antibody or using the α-β2 antibody with control lysates from cells not expressing β2 (Figure 7A).

The possibility that β2 can bind Notchl directly was investigated using C-terminal histidine -tagged β2 ECD and a purified Notchl ECD region containing the majority of the EGF repeat region (repeats 6 - 36) with a C-terminal FLAG tag. Notchl ECD (0.33 μg/ml) was incubated with β2 ECD in conditioned media (β2 estimated at 0.4 μg/ml) and β2 protein was then collected using Ni-NTA beads. Alternatively, β2 was enriched from conditioned media

using Ni-NTA beads and subsequently incubated with tagged Notchl ECD (at 3.3 μg/ml) in PBS. Both approaches yielded recovery of tagged Notchl by β2, as compared to control conditioned media containing an irrelevant histidine-tagged protein (Figure 7B). Notably, the β2 - Notchl binding occurred even at low concentrations of both proteins (approximately 1 nM Notchl ECD and 20 nM β2 ECD, Figure 7B lane 1) and in the presence of serum, other CHO- produced proteins and degradative enzymes present in the conditioned media. Purified Notchl ECD migrated as a doublet band, possibly due to glycosylation or other modification (Figure 7B). However, binding to β2 resulted in a single well-defined band for the tagged Notchl ECD, suggesting specificity, or possible modification, associated with binding. Overall, these results support a role for β2 as a binding partner of Notchl . Similar to other Notch ligands, we anticipate that β2 would also bind close homolog Notch2, which is highly expressed on some β2 responsive cell lines.

To further characterize the binding of β2 and Notchl, conditioned media containing tagged β2 ECD were incubated as described above with purified fragments of the Notchl ECD, containing either EGF repeats 10-21 or 22-33. (Jagged- 1 binds EGF repeats 11-13 of Notchl, and Drosophila Delta and Serrate bind EGF repeats 11-12 of Notch.) Each of these Notchl ECD fragments contained a C-terminal FLAG tag to allow detection on an immunoblot with α-FLAG antibody. The β2 ECD specifically bound the Notchl ECD fragment containing EGF repeats 10- 21, with no detectable binding of the ECD fragment containing EGF repeats 22-33 (Figure 7C). These data indicate that the binding of β2 and Notchl is specific, rather than a non-specific association through EGF repeat structures.

Activation of Notchl by ligands results in cleavage to release the NICD, which translocates to the nucleus, and in concert with other proteins, directly regulates Notch target gene transcription. We analyzed whether nuclear NICD could be detected in cells in response to β2. As the NICD has been historically difficult to detect, we grew cells in the presence of a proteasome inhibitor (100 um Lactacystin) to assist in protein stabilization, and used high- resolution confocal microscopy for imaging. Nuclear NICD was detected in the majority of cells transfected with β2 compared to the vector-transfected control, in which, with the exception of 1

cell, cytoplasmic or membraneous staining only was observed (Figure 7D). Similarly, nuclear NICD was detected in SW620 cells 6 hours after treatment with β2 ECD in conditioned media (Figure 7D), consistent with the elevated HESl transcript observed in these cells at 6 hours. These data indicate that β2 induces activation of the Notch signaling pathway. Taken together, our data indicate that, beyond a role as an accessory protein or adhesion molecule, β2 can induce morphological transformation consistent with EMT. Expression of this neuronal protein in tumors can result from the loss of REST, a transcriptional repressor of neuronal gene expression in non-neuronal tissues. Furthermore, the morphological transformation induced by β2 depends on Notch, an evolutionarily conserved master regulator of development, differentiation and cell fate (Artavanis-Tsakonas et al., Science 284:770-776, 1999). In linking loss of REST and the Notch pathway signaling via a novel Notch binding partner β2, we describe a role for all three in tumor progression and metastasis.

8. Antibody cross-blocking experiments suggest three distinct epitopes

Antibody cross-blocking experiments were performed to determine whether the following α-β2 monoclonal antibodies bind to the same or different epitopes: 3Dl, 12A9, 12E3, 2E3, and 3G5. In those experiments, the binding of biotinylated antibody to β2 antigen was assessed in the presence of an unlabeled "competitor" antibody, as depicted in Figure 14. The results indicated that antibodies 3Dl and 12A9 bound to a first epitope ("Epitope A"); antibody 12E3 bound to a second epitope ("Epitope B"); and antibodies 2E3 and 3G5 bound to a third epitope ("Epitope C").

9. ATCC Deposits

The following hybridoma cell lines have been deposited with the American Type Culture Collection, 10801 University Blvd., Manassas, VA 20110-2209 USA (ATCC):

Hybridoma/ Antibody Designation ATCC No. Deposit Date 12A9.22.1 (12A9) PTA-8404 May 2, 2007

3D1.4.1 (3Dl) PTA-8405 May 2, 2007

2E3.1.1 (2E1) PTA-8406 May 2, 2007

These deposits were made under the provisions of the Budapest Treaty on the International Recognition of the Deposit of Microorganisms for the Purpose of Patent Procedure

and the Regulations thereunder (Budapest Treaty). This assures the maintenance of a viable culture of the deposit for 30 years from the date of deposit and for at least five (5) years after the most recent request for furnishing of a sample of the deposit. The deposit will be made available by the ATCC under the terms of the Budapest Treaty, and subject to an agreement between Genentech, Inc., and the ATCC, which assures that all restrictions imposed by the depositor on the availability to the public of the deposited material will be irrevocably removed upon the granting of the pertinent U.S. patent; assures permanent and unrestricted availability of the progeny of the culture of the deposit to the public upon issuance of the pertinent U.S. patent or upon laying open to the public of any U.S. or foreign patent application, whichever comes first; and assures availability of the progeny to one determined by the U.S. Commissioner of Patents and Trademarks to be entitled thereto according to 35 U.S. C. § 122 and the Commissioner's rules pursuant thereto (including 37 C.F.R. § 1.14 with particular reference to 886 OG 638).

The assignee of the present application has agreed that if the culture on deposit should die or be lost or destroyed when cultivated under suitable conditions, it will be promptly replaced on notification with a viable specimen of the same culture. Availability of the deposited cell line is not to be construed as a license to practice the invention in contravention of the rights granted under the authority of any government in accordance with its patent laws.

Although the foregoing invention has been described in some detail by way of illustration and example for purposes of clarity of understanding, the descriptions and examples should not be construed as limiting the scope of the invention. The disclosures of all patent and scientific literatures cited herein are expressly incorporated in their entirety by reference.