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Title:
PHOTOACTIVATABLE CAGED TAMOXIFEN AND TAMOXIFEN DERIVATIVE MOLECULES AND METHODS OF USE THEREOF
Document Type and Number:
WIPO Patent Application WO/2013/158268
Kind Code:
A1
Abstract:
Provided herein are compositions containing photoactivatable caged tamoxifen and tamoxifen derivative molecules. Also provided are kits containing one of these compositions and a light source. Also provided are methods of optically inducing nuclear translocation of a fusion protein containing a mammalian estrogen receptor ligand binding domain in a eukaryotic cell and methods of optically inducing recombination in a eukaryotic cell that include contacting a eukaryotic cell with at least one of these compositions. Also provided are methods of treating breast cancer in a subject that include administering a photoactivatable caged tamoxifen or tamoxifen derivative molecule to a subject having breast cancer.

Inventors:
LU XIN (US)
AGASTI SARIT S (US)
DEPINHO RONALD A (US)
WEISSLEDER RALPH (US)
Application Number:
PCT/US2013/031165
Publication Date:
October 24, 2013
Filing Date:
March 14, 2013
Export Citation:
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Assignee:
LU XIN (US)
AGASTI SARIT S (US)
DEPINHO RONALD A (US)
WEISSLEDER RALPH (US)
International Classes:
C12N15/63
Foreign References:
US20080120731A12008-05-22
US7883846B22011-02-08
Other References:
OUYANG ET AL.: "Synthetic strategies for studying embryonic development.", CHEM BIOL., vol. 17, no. 6, 25 June 2010 (2010-06-25), pages 590 - 606
SINHA ET AL.: "Photocontrol of Protein Activity in Cultured Cells and Zebrafish with One- and Two-Photon Illumination.", CHEMBIOCHEM, vol. 11, 2010, pages 653 - 663
PICARD.: "Regulation of protein function through expression of chimaeric proteins.", CURRENT OPINION IN BIOTECHNOLOGY, vol. 5, 1994, pages 511 - 515
Attorney, Agent or Firm:
REITER, Tiffany (P.O. Box 1022Minneapolis, Minnesota, US)
Download PDF:
Claims:
Claims

1. A composition compris

acceptable salt thereof.

2. The composition of claim 1, further comprising a physiologically acceptable excipient or buffer.

3. The composition of claim 2, wherein the composition is formulated as a liquid.

4. The composition of claim 3, wherein the composition is formulated for intravenous, intaarterial, transdermal, intramuscular, intraperitoneal, subcutaneous, intrathecal, interductal, periductal, or ocular administration.

5. The composition of claim 1, wherein the composition is formulated as a solid.

6. The composition of claim 5, wherein the composition is formulated as a gel.

7. The composition of clam 5, wherein the composition is formulated for oral administration.

8. The composition of claim 1, wherein the composition contains at least 80% by weight of

or a pharmaceutically acceptable salt thereof.

9. A kit comprising:

one or more doses of the composition of claim 1 ; and

a light source that emits light of a wavelength of between 350 nm to 410 nm.

10. A method of inducing nuclear translocation of a fusion protein compris human estrogen receptor ligand binding domain in a eukaryotic cell, the method comprising: providing a eukaryotic cell that contains a fusion protein comprising a human estrogen receptor ligand binding domain,

contacting the eukaryotic cell with the composition of claim 1 ; and

irradiating the eukaryotic cell with a wavelength of light between 350 nm to 410 nm for a period of time sufficient to release 4-hydroxycyclofen from the composition,

wherein the released 4-hydroxycyclofen induces the nuclear translocation of the fusion protein.

11. The method of claim 10, wherein the eukaryotic cell is in vitro.

12. The method of claim 11, further comprising administering the irradiated eukaryotic cell to a mammal.

13. The method of claim 10, wherein the eukaryotic cell is in a mammal.

14. The method of claim 13, wherein the mammal is a mouse or rat.

15. The method of claim 13, wherein the eukaryotic cell is present in the mammary gland or the skin.

16. The method of claim 13, wherein the composition is locally administered to a target tissue in the mammal that contains the eukaryotic cell.

17. The method of claim 13, wherein the composition is administered to the mammal via oral, intravenous, intaarterial, transdermal, intramuscular, intraperitoneal, subcutaneous, intrathecal, interductal, periductal, nasal, or ocular administration.

18. The method of claim 10, wherein the eukaryotic cell comprises a nucleic acid encoding the fusion protein, and the nucleic acid is stably integrated into a chromosome of the cell.

19. The method of claim 18, wherein the nucleic acid encoding the fusion protein is operably linked to a tissue-specific promoter sequence. 20. The method of claim 18, wherein the nucleic acid encoding the fusion protein is operably linked to a ubiquitous promoter.

21. The method of claim 18, wherein the nucleic acid encoding the fusion protein is operably linked to an inducible promoter sequence, and the eukaryotic cell is further contacted with a chemical inducing agent.

22. The method of claim 10, wherein the fusion protein comprises a sequence of a recombinase, and the fusion protein has recombinase enzymatic activity.

23. The method of claim 22, wherein the recombinase is Cre recombinase.

24. The method of claim 10, wherein the fusion protein comprises a sequence of a transcription factor, and the fusion protein is capable of promoting gene transcription in the nucleus of the eukaryotic cell.

25. The method of claim 24, wherein the fusion protein promotes gene transcription of a gene that is present in a recombinant gene construct that is integrated into a chromosome of the eukaryotic cell.

26. The method of claim 10, wherein the fusion protein comprises a sequence of a transcription repressor, and the fusion protein is capable of repressing transcription of a gene in the nucleus of the eukaryotic cell.

27. The method of claim 26, wherein the fusion protein represses the transcription of a gene that is present in a recombinant gene construct that is integrated into a chromosome of the eukaryotic cell.

28. The method of claim 10, wherein the fusion protein comprises a sequence of a histone deacetylase, a histone acetyltransferase, or an O-6-methylguanine-DNA

methyltransferase, and the fusion protein has histone deacetylase, histone acetyltransferase, or O-6-methylguanine-DNA methyltransferase activity, respectively.

29. The method of claim 10, wherein the fusion protein comprises a sequence of a telomerase, and the fusion protein has telomerase activity.

30. The method of claim 10, wherein the fusion protein comprises a sequence of an oncogene.

31. The method of claim 10, wherein the eukaryotic cell is an epithelial cell, an endothelial cell, a muscle cell, an adipose cell, a bone cell, a cartilage cell, or a neuron.

32. The method of claim 10, wherein the eukaryotic cell is an undifferentiated cell, and the fusion protein comprises a sequence of a transcription factor or transcription repressor that induces cellular differentiation. 33. The method of claim 10, wherein the irradiating is performed for less than a total of 15 minutes.

34. The method of claim 10, wherein the contacting and irradiating occur within 24 hours of each other.

35. The method of claim 34, wherein the contacting and irradiating occur within 6 hours of each other.

36. The method of claim 35, wherein the contacting and irradiating occur within 1 hour of each other.

37. A method of inducing recombination in a eukaryotic cell, the method comprising: providing a eukaryotic cell that comprises (i) a nucleic acid encoding a fusion protein comprising a sequence of a recombinase and a sequence of a human estrogen receptor ligand binding domain, wherein the fusion protein has recombinase activity, and (ii) a recombinase recognition sequence that is specifically recognized by the fusion protein, wherein both the nucleic acid encoding the fusion protein and the recombinase recognition sequence are integrated into a chromosome within the nucleus of the eukaryotic cell;

contacting the eukaryotic cell with a composition of claim 1 ; and

irradiating the eukaryotic cell with a wavelength of light between 350 nm to 410 nm for a period of time sufficient to release 4-hydroxycyclofen from the composition,

wherein the 4-hydroxycyclofen stimulates the nuclear importation of the fusion protein and the fusion protein stimulates recombination at the recombinase recognition sequence.

38. The method of claim 37, wherein the eukaryotic cell is in vitro.

39. The method of claim 37, wherein the eukaryotic cell is in a mammal.

40. The method of claim 39, wherein the mammal is a mouse or rat.

41. The method of claim 39, wherein the eukaryotic cell is present in the mammary gland or the skin.

42. The method of claim 39, wherein the composition is locally administered to a target tissue in the mammal that contains the eukaryotic cell.

43. The method of claim 39, wherein the composition is administered to the mammal via oral, intravenous, intaarterial, transdermal, intramuscular, intraperitoneal, subcutaneous, intrathecal, interductal, periductal, nasal, or ocular administration.

44. The method of claim 37, wherein the recombinase is Cre recombinase.

45. The method claim 37, wherein the recombination results in a decrease in the expression of a transgene located between two recombinase recognition sequences in the chromosome.

46. The method of claim 37, wherein the recombination results in the replacement of a sequence between two recombinase recognition sequences with a new transgenic sequence.

47. The method of claim 37, wherein the recombination results in the increase in the proximity of a promoter or enhancer sequence to a transgene, wherein the recombination results in increased expression of the transgene.

48. The method of claim 37, wherein the nucleic acid encoding the fusion protein is operably linked to tissue specific promoter sequence in the chromosome of the eukaryotic cell.

49. The method of claim 37, wherein the nucleic acid encoding the fusion protein is operably linked to an inducible promoter in the chromosome of the eukaryotic cell, and the eukaryotic cell is further contacted with a chemical inducing agent.

50. The method of claim 37, wherein the nucleic acid encoding the fusion protein is operably linked to a ubiquitous promoter in the chromosome of the eukaryotic cell.

51. The method of claim 39, wherein the composition is administered to the animal by systemic administration and a specific tissue of the mammal is irradiated.

52. The method of claim 37, wherein the contacting and irradiating occur within 24 hours of each other.

53. The method of claim 52, wherein the contacting and irradiating occur within 6 hours of each other.

54. The method of claim 53, wherein the contacting and irradiating occur within 1 hour of each other.

55. The method of claim 39, wherein the irradiating is performed using an endoscopic light source.

56. A composition comprising:

pharmaceutically acceptable salt thereof.

57. The composition of claim 56, wherein the composition further comprises at least one additional breast cancer therapeutic.

58. The composition of claim 56, further comprising a physiologically acceptable excipient or buffer.

59. The composition of claim 58, wherein the composition is formulated as a liquid.

60. The composition of claim 59, wherein the composition is formulated for intravenous, intaarterial, transdermal, intramuscular, intraperitoneal, subcutaneous, intrathecal, interductal, periductal, or ocular administration.

61. The composition of claim 56, wherein the composition is formulated as a solid.

62. The composition of claim 61, wherein the composition is formulated as a gel.

63. The composition of clam 61, wherein the composition is formulated for oral administration.

64. A method of treating breast cancer in a subject, the method comprising:

administering to the subject an amount of the composition of claim 56 sufficient to treat breast cancer in a subject, and

irradiating the mammary tissue of the subject with light between 350 nm and 410 nm, wherein the irradiating mediates the release of 4-hydroxytamoxifen in the irradiated mammary tissue.

65. The method of claim 64, wherein the subject is diagnosed as having breast cancer.

66. The method of claim 64, wherein the composition is locally administered to the mammary tissue of the subject.

67. The method of claim 64, wherein the composition is systemically administered to the subject.

68. The method of claim 67, wherein the composition is administered to the mammal via oral, intravenous, intaarterial, transdermal, intramuscular, intraperitoneal, subcutaneous, intrathecal, interductal, periductal, nasal, or ocular administration.

69. The method of claim 64, wherein the contacting and irradiating occur within 24 hours of each other.

70. The method of claim 69, wherein the contacting and irradiating occur within 6 hours of each other.

71. The method of claim 70, wherein the contacting and irradiating occur within 1 hour of each other. 72. The method of claim 64, further comprising administering to the subject one or more additional breast cancer therapeutics.

73. A kit containing:

one or more doses of the composition of claim 56; and

a light source that emits light of a wavelength of between 200 nm to 900 nm.

74. A kit containing:

one or more doses of the composition of claim 57; and

a light source that emits light of a wavelength of between 200 nm to 900 nm.

Description:
PHOTOACTIVA TABLE CAGED TAMOXIFEN AND TAMOXIFEN DERIVATIVE MOLECULES AND METHODS OF USE THEREOF

Cross-Reference to Related Applications

This application claims priority to U.S. Provisional Patent Application Serial No. 61/635,068, filed April 18, 2012, the entire contents of which are incorporated by reference herein.

Federally Sponsored Research

This invention was made with Government support under grant number

U01CA141508 awarded by the National Cancer Institute and grant numbers

HHSN2682010004C, P50-CA86355, and U24CA092782 awarded by the National Institutes of Health. The Government has certain rights in the invention.

Background of the Invention

Spatial and temporal genetic control is necessary to better dissect the role of specific genes and cell populations in development, disease, and therapy. Site-specific recombination mediated by Cre recombinase is a powerful genetic tool to manipulate genetic elements in model organisms (Nagy, Genesis 26:99, 2000). When placed under the control of a tissue- specific promoter, Cre/LoxP-mediated recombination allows tissue-specific investigation of gene functions (Nagy, Genesis 26:99, 2000). Fusing Cre with a mutant form of the estrogen receptor (ER) ligand binding domain further enables temporal control of recombination (Nagy, Genesis 26:99, 2000). While this conditional CreER system allows for temporal control, the spatial control through tissue-specific promoters is limited by relatively broad activation in all target cells, non-specificity of many of such cell type-'specific' promoters, and/or the lack of validated promoters in certain cell types.

Summary of the Invention

The invention is based, in part, on the discovery that conjugation of tamoxifen or tamoxifen derivatives to photoactivatable caged molecules (e.g., l-(4,5-dimethoxy-2- nitrophenyl)ethyl (DMNPE)) results in a sensitive and specific optical release of tamoxifen or tamoxifen derivatives to eukaryotic (e.g., mammalian, plant, yeast, nematode, parasite, or reptile) cells following irradiation. In view of this discovery, provided herein are compositions containing photoactivatable caged tamoxifen and caged tamoxifen derivative molecules, and methods of optically inducing nuclear translocation of a fusion protein containing a mammalian estrogen receptor ligand binding domain in a eukaryotic (e.g., mammalian, plant, yeast, nematode, parasite, or reptile) cell and methods of optically inducing recombination in a eukaryotic (e.g., mammalian, plant, yeast, nematode, parasite, or reptile) cell that include contacting a eukaryotic cell with at least one of these compositions. Also provided are methods of treating breast cancer in a subject that include administering a photoactivatable caged tamoxifen or caged tamoxifen derivative molecule to a subject having breast cancer.

Provided herein are compositions containing:

 or a pharmaceutically acceptable salt thereof.

In some embodiments, the composition further contains a physiologically acceptable excipient or buffer. In some embodiments, the composition is formulated as a liquid.

In some embodiments, the composition is formulated for intravenous, intaarterial, transdermal, intramuscular, intraperitoneal, subcutaneous, intrathecal, interductal, periductal, or ocular administration. In some embodiments, the composition is formulated as a solid. In some embodiments, the composition is formulated as a gel. In some embodiments, the composition is formulated for oral administration.

In some embodiments, the composition contains at least 80% by weight of

or a pharmaceutically acceptable salt thereof.

Also provided are kits containing one or more doses of any of the compositions described herein; and a light source that emits light of a wavelength of between 350 nm to 410 nm.

Also provided are methods of inducing nuclear translocation of a fusion protein containing a human estrogen receptor ligand binding domain in a eukaryotic cell that include providing a eukaryotic cell that contains a fusion protein containing a human estrogen receptor ligand binding domain, contacting the eukaryotic cell with any of the compositions described herein; and irradiating the eukaryotic cell with a wavelength of light between 350 nm to 410 nm for a period of time sufficient to release 4-hydroxycyclofen from the composition, where the released 4-hydroxycyclofen induces the nuclear translocation of the fusion protein. In some embodiments, the eukaryotic cell is in vitro. Some embodiments further include administering the irradiated eurkaryotic cell to a mammal. In some embodiments, the eukaryotic cell is in a mammal (e.g., a mouse or rat). In some

embodiments, the eukaryotic cell is present in the mammary gland or the skin. In some embodiments, the composition is locally administered to a target tissue in the mammal that contains the eukaryotic cell. In some embodiments, the composition is administered to the mammal via oral, intravenous, intaarterial, transdermal, intramuscular, intraperitoneal, subcutaneous, intrathecal, interductal, periductal, nasal, or ocular administration.

In some embodiments, the eukaryotic cell contains a nucleic acid encoding the fusion protein, and the nucleic acid is stably integrated into a chromosome of the cell. In some embodiments, the nucleic acid encoding the fusion protein is operably linked to a tissue- specific promoter sequence. In some embodiments, the nucleic acid encoding the fusion protein is operably linked to a ubiquitous promoter. In some embodiments, the nucleic acid encoding the fusion protein is operably linked to an inducible promoter sequence, and the eukaryotic cell is further contacted with a chemical inducing agent.

In some embodiments, the fusion protein contains a sequence of a recombinase, and the fusion protein has recombinase enzymatic activity. In some embodiments, the recombinase is Cre recombinase. In some embodiments, the fusion protein contains a sequence of a transcription factor, and the fusion protein is capable of promoting gene transcription in the nucleus of the eukaryotic cell. In some embodiments, the fusion protein promotes gene transcription of a gene that is present in a recombinant gene construct that is integrated into a chromosome of the eukaryotic cell. In some embodiments, the fusion protein contains a sequence of a transcription repressor, and the fusion protein is capable of repressing transcription of a gene in the nucleus of the eurkaryotic cell. In some

embodiments, the fusion protein represses the transcription of a gene that is present in a recombinant gene construct that is integrated into a chromosome of the eukaryotic cell.

In some embodiments, the fusion protein contains a sequence of a histone deacetylase, a histone acetyltransferase, or an O-6-methylguanine-DNA methyltransferase, and the fusion protein has histone deacetylase, histone acetyltransferase, or O-6-methylguanine-DNA methyltransferase activity, respectively. In some embodiments, the fusion protein contains a sequence of a telomerase, and the fusion protein has telomerase activity. In some

embodimennts, the fusion protein contains a sequence of an oncogene.

In some embodiments, the eukaryotic cell is an epithelial cell, an endothelial cell, a muscle cell, an adipose cell, a bone cell, a cartilage cell, or a neuron. In some embodiments, the eukaryotic cell is an undifferentiated cell, and the fusion protein comprises a sequence of a transcription factor or transcription repressor that induces cellular differentiation. In some embodiments, the irradiating is performed for less than a total of 15 minutes. In some embodiments, the contacting and irradiating occur within 24 hours of each other. In some embodiments, the contacting and irradiating occur within 6 hours of each other. In some embodiments, the contacting and irradiating occur within 1 hour of each other.

Also provided are methods of inducing recombination in a eukaryotic cell that include: providing a eukaryotic cell that contains (i) a nucleic acid encoding a fusion protein containing a sequence of a recombinase and a sequence of a human estrogen receptor ligand binding domain, where the fusion protein has recombinase activity, and (ii) a recombinase recognition sequence that is specifically recognized by the fusion protein, where both the nucleic acid encoding the fusion protein and the recombinase recognition sequence are integrated into a chromosome within the nucleus of the eukaryotic cell; contacting the eukaryotic cell any of the compositions described herein; and irradiating the eukaryotic cell with a wavelength of light between 350 nm to 410 nm for a period of time sufficient to release 4-hydroxycyclofen from the composition, where the 4-hydroxycyclofen stimulates the nuclear importation of the fusion protein and the fusion protein stimulates recombination at the recombinase recognition sequence. In some embodiments, the eukaryotic cell is in vitro. In some embodiments, the eukaryotic cell is in a mammal. In some embodiments, the mammal is a mouse or rat. In some embodiments, the eukaryotic cell is present in the mammary gland or the skin. In some embodiments, the composition is locally administered to a target tissue in the mammal that contains the eukaryotic cell. In some embodiments, the composition is administered to the mammal via oral, intravenous, intaarterial, transdermal, intramuscular, intraperitoneal, subcutaneous, intrathecal, interductal, periductal, nasal, or ocular administration.

In some embodiments, the recombinase is Cre recombinase. In some embodiments, the recombination results in a decrease in the expression of a transgene located between two recombinase recognition sequences in the chromosome. In some embodiments, the recombination results in the replacement of a sequence between two recombinase recognition sequences with a new transgenic sequence. In some embodiments, the recombination results in the increase in the proximity of a promoter or enhancer sequence to a transgene, wherein the recombination results in increased expression of the transgene.

In some embodiments, the nucleic acid encoding the fusion protein is operably linked to tissue specific promoter sequence in the chromosome of the eukaryotic cell. In some embodiments, the nucleic acid encoding the fusion protein is operably linked to an inducible promoter in the chromosome of the eukaryotic cell, and the eukaryotic cell is further contacted with a chemical inducing agent. In some embodiments, the nucleic acid encoding the fusion protein is operably linked to a ubiquitous promoter in the chromosome of the eukaryotic cell.

In some embodiments, the composition is administered to the animal by systemic administration and a specific tissue of the mammal is irradiated. In some embodiments, the contacting and irradiating occur within 24 hours of each other. In some embodiments, the contacting and irradiating occur within 6 hours of each other. In some embodiments, the contacting and irradiating occur within 1 hour of each other. In some embodiments, the irradiating is performed using an endoscopic light source.

Also provided are compositions that contain:

pharmaceutically acceptable salt thereof.

In some embodiments, the composition further comprises at least one additional breast cancer therapeutic. In some embodiments, the composition further contains a physiologically acceptable excipient or buffer. In some embodiments, the composition is formulated as a liquid. In some embodiments, the composition is formulated for intravenous, intaarterial, transdermal, intramuscular, intraperitoneal, subcutaneous, intrathecal, interductal, periductal, or ocular administration. In some embodiments, the composition is formulated as a solid. In some embodiments, the composition is formulated as a gel. In some

embodiments, the composition is formulated for oral administration.

Also provided are methods of treating breast cancer in a subject that include:

administering to the subject an amount of any of the compositions described herein sufficient to treat breast cancer in a subject; and irradiating the mammary tissue of the subject with light between 200 nm and 900 nm, wherein the irradiating mediates the release of 4- hydroxytamoxifen in the irradiated mammary tissue. In some embodiments, the subject is diagnosed as having breast cancer. In some embodiments, the composition is locally administered to the mammary tissue of the subject. In some embodiments, the composition is systemically administered to the subject. In some embodiments, the composition is administered to the mammal via oral, intravenous, intaarterial, transdermal, intramuscular, intraperitoneal, subcutaneous, intrathecal, interductal, periductal, nasal, or ocular

administration. In some embodiments, the contacting and irradiating occur within 24 hours of each other. In some embodiments, the contacting and irradiating occur within 6 hours of each other. In some embodiments, the contacting and irradiating occur within 1 hour of each other. Some embodiments further include administering to the subject one or more additional breast cancer therapeutics.

Also provided are kits containing one or more doses of any of the compositsions described herein; and a light source that emits light of a wavelength of between 200 nm to 900 nm.

By the term "mammalian estrogen receptor ligand binding domain" is meant a contiguous sequence of amino acids that is at least 80% (e.g., at least 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100%) identical to the sequence of the ligand binding domain of a mammalian (e.g., human, mouse, or rat) estrogen receptor that has the ability to bind to tamoxifen or a tamoxifen derivative (e.g., 4-hydroxycyclofen). Non-limiting exemplary mammalian receptor ligand binding domains are described herein. Methods for determining the ability of a mammalian estrogen receptor ligand binding domain to bind tamoxifen or a tamoxifen derivative are described herein.

By the term "human estrogen receptor ligand binding domain" is meant a contiguous sequence of amino acids that is at least 80% (e.g., at least 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100%) identical to the sequence of the ligand binding domain of a human estrogen receptor that has the ability to bind to tamoxifen or a tamoxifen derivative (e.g., 4- hydroxycyclofen). Non-limiting examples of human estrogen receptor ligand binding domains are described herein. Additional examples of human estrogen receptor ligand binding domains are known in the art. In some embodiments, the human estrogen receptor ligand binding domain contains a sequence at least 80% (e.g., at least 85%, 90%, 96%, 97%, 98%, 99%, or 100%) identical to amino acids 310 to 547 of SEQ ID NO: 1. Methods for determining the ability of a human estrogen receptor ligand binding domain to bind tamoxifen or a tamoxifen derivative are described herein.

By the term "estrogen receptor fusion protein," "ER fusion protein," or "fusion protein containing an ER ligand binding domain" is meant a polypeptide sequence containing a mammalian estrogen receptor ligand binding domain (e.g., a human estrogen receptor ligand binding domain) and at least one additional polypeptide sequence (a fusion partner polypeptide). Non-limiting examples of fusion partner polypeptides are described herein. Additional examples of fusion partner polypeptides are known in the art. In some embodiments, the fusion partner polypeptide can be derived from a mammal (e.g., the same or a different mammal), a bacterium, a virus, or a parasite. In some embodiments, the mammalian estrogen receptor ligand binding domain can be located at the N-terminus of the ER fusion protein or can be located N-terminal to the fusion partner polypeptide. In some embodiments, the mammalian estrogen receptor ligand binding domain can be located at the C-terminus of the ER fusion protein or can be located C-terminal to the fusion partner polypeptide. In some embodiments, there can be an intervening amino acid sequence between the mammalian estrogen receptor ligand binding domain and the fusion partner polypeptide.

By the term "caged tamoxifen molecule" is meant a molecule containing tamoxifen conjugated to a photoactivatable caging molecule (e.g., l-(4,5-dimethoxy-2-nitrophenyl) ethanol (DMNPE)) that releases tamoxifen upon exposure to light. Additional examples of photoactivatable caging molecules that can be present in caged tamoxifen molecules are described herein. In some embodiments, there is a linking group present between the tamoxifen and the photoactivatable caging molecule. In some embodiments, the tamoxifen and the photoactivatable caging molecule are joined by an ester, an ether, an amido group, a carbonate, a carbamate, or an acetal.

By the term "caged tamoxifen derivative molecule" is meant a molecule containing tamoxifen derivative (e.g., 4-hydroxy tamoxifen or 4-hydroxycyclofen) conjugated to a photoactivatable caging molecule (e.g., l-(4,5-dimethoxy-2-nitrophenyl) ethanol (DMNPE)) that releases the tamoxifen derivative upon exposure to light. Additional examples of photoactivatable caging molecules that can be present in caged tamoxifen derivative molecules are described herein. In some embodiments, there is a linking group present between the tamoxifen derivative and the photoactivatable caging molecule. In some embodiments, the tamoxifen derivative and the photoactivatable caging molecule are joined by an ester, an ether, an amido group, a carbonate, a carbamate, or an acetal.

By the term "tissue-specific promoter sequence" is meant a nucleic acid sequence that is bound by a transcription factor and promotes the transcription of an operably linked gene within a specific tissue in a mammal. Non-limiting examples of tissue-specific promoter sequences are described herein. Additional examples of tissue-specific promoter sequences are known in the art.

By the term "inducible promoter sequence" is meant a nucleic acid sequence that is bound by a transcription factor and promotes the transcription of an operably linked gene when the transcription factor is contacted with a chemical inducing agent (e.g., tetracycline). Non-limiting examples of inducible promoters and chemical inducing agents are described herein. Additional examples of inducible promoters and chemical inducing agents are known in the art.

By the term "ubiquitous promoter" is meant a nucleic acid sequence that is bound by a transcription factor and promotes transcription of an operably linked gene in a majority of the tissues present within a mammal (e.g., β-actin promoter). Non-limiting examples of ubiquitous promoters are described herein. Additional examples of ubiquitous promoters are known in the art.

By the term "recombinase" is meant an enzyme that recognizes a recombinase recognition sequence present within a double stranded DNA, cleaves the double stranded DNA within or near the recombinase recognition sequence, and ligates at least one of the severed ends of the double-stranded DNA to form a contiguous piece of DNA. In some embodiments, the activity of a recombinase results in the deletion of a nucleic acid sequence located between two different recombinase recognition sequences. In some embodiments, the activity of a recombinase results in the replacement of the sequence between two different recombinase recognition sequences with a different nucleic acid sequence (a different nucleic acid sequence that has a recombinase recognition sequence located at its 5' and 3 ' ends). Non-limiting examples of recombinases and recombinase recognition sequences are described herein. Additional examples of recombinases and recombinase recognition sequences are known in the art.

By the term "recombinant gene construct" is meant a heterologous artificial gene construct that is stably introduced into a chromosome of a eukaryotic (e.g., mammalian, plant, yeast, nematode, parasite, or reptile) cell. In some embodiments, the recombinant gene construct contains a sequence encoding an ER fusion protein (e.g., any of the ER fusion proteins described herein). In some embodiments, the recombinant gene construct contains a sequence encoding an ER fusion protein operatively linked to one or more promoter or enhancer sequences (e.g., an inducible, tissue-specific, or ubiquitous promoter). In some embodiments, the recombinant gene construct contains a nucleic acid sequence that contains at least one recombinase recognition sequence (e.g., any of the recombinase recognition sequences described herein or known in the art).

As is used throughout, the term "transgenic" refers to a eukaryotic (e.g., mammalian, plant, yeast, nematode, parasite, or reptile) cell in vitro or a non-human eukaryote (e.g., mammal) that contains at least one recombinant gene construct.

By the term "transcription repressor" is meant a protein that binds to a promoter sequence in DNA and mediates a decrease in the transcription of a nucleic acid sequence operatively linked to the promoter sequence.

By the term "transcription factor" or "transcription activator" is meant a protein that binds to a promoter sequence in DNA and mediates an increase in the transcription of a nucleic acid sequence operatively linked to the promoter sequence.

By the term "oncogene" is meant a polypeptide that contributes to the development of cancer in a mammal. In some embodiments, the oncogene results in a decreased function in an apoptotic signaling pathway in a mammalian cell. In some embodiments, the oncogene results in the deregulation of the cell cycle in a mammalian cell. A variety of different oncogenes are known in the art.

Other definitions appear in context throughout this disclosure. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Methods and materials are described herein for use in the present invention; other, suitable methods and materials known in the art can also be used. The materials, methods, and examples are illustrative only and not intended to be limiting. All publications, patent applications, patents, sequences, database entries, and other references mentioned herein are incorporated by reference in their entirety. In case of conflict, the present specification, including definitions, will control.

Other features and advantages of the invention will be apparent from the following detailed description and figures, and from the claims.

Brief Description of the Drawings

Figure 1 is a schematic showing the photoactivation-dependent CreER/loxP system in the Rosa26CreER ; mT/mG reporter mice.

Figure 2 is a schematic showing the synthesis of caged 4-OHC using Mitsonobu reaction conditions. Figure 3 is a schematic showing the photocleavage reaction of caged 4-OHC using 365 nm UV light.

Figure 4 is a set of absorbance spectra that show the changes in UV-Vis absorbance that occur during the photocleavage of caged 4-OHC in water: acetonitrile (1 : 1 v/v).

Figure 5 is a graph showing the change in absorbance of caged 4-OHC at 375 nm over

UV irradiation time.

Figure 6 is a set of three HPLC-MS chromatograms showing the quantitative release of 4-OHC from caged 4-OHC upon UV irradiation. The three chromatograms represent a UV exposure of 0 minute, 1 minute, and 10 minutes. The peaks corresponding to caged 4- OHC (*) and released 4-OHC (**) are indicated.

Figure 7 is a set of eight fluorescent micrographs of mouse embryonic fibroblasts (MEFs) isolated from Rosa26CreER ; mT/mG mice following treatment with vehicle alone (two left panels), 4-OHC (two left center panels), caged 4-OHC (two right center panels), and caged 4-OHC with light exposure (two right panels).

Figure 8 is a graph showing the percentage of enhanced green fluorescent protein

(EGFP)-positive MEFs (normalized to 4-OHC-treated MEF controls) in MEFs treated with 4- OHC or caged 4-OHC following different durations of UV activation. The "intracellular + medium" group represents cell samples without PBS wash before UV irradiation. The "intracellular only" group represents cell samples washed twice with PBS before UV irradiation.

Figure 9 is a schematic of the photoactivati on-dependent CreER/loxP system in the Rosa26CreER ;R26R reporter mice. Photoactivated release of lacZ gene expression occurs in illuminated and caged 4-OHC-treated cells.

Figure 10 is a set of four micrographs of X-gal stained MEFs from

Rosa26CreER ;R26R mice embryos following treatment with vehicle alone (upper left panel), 4-OHC (upper right panel), caged 4-OHC (bottom left panel), and caged 4-OHC with 365 nm light exposure (bottom right panel).

Figure 1 1 is a set of four photomicrographs showing the EGFP expression induced by 365 nm UV activation of caged 4-OHC in mammary epithelial cells isolated from

Rosa26CreER ; mT/mG female mice and cultured to form acini on Matrigel. The images shown are projections of the Z-stack confocal images.

Figure 12 is a graphic showing the culturing of mammary epithelial cell acini from Rosa26CreER ; mT/mG female mice and two fluorescent micrographs of individual acini. The acini were illuminated with the 60X objective of an inverted epifluorescent microscope equipped with a standard DAPI filter set for 1 minute after treatment with 5 μΜ caged 4- OHC and brief PBS wash. The fluorescent micrographs were collected four days later from the live acini using a laser scanning confocal microscope. The left panel is a micrograph of an acini treated with caged 4-OHC and exposed to light, and the right panel is a micrograph of an acini treated with caged 4-OHC and not exposed to light.

Figure 13 is a set of six images showing the expression of EGFP in Rosa26CreER ; mT/mG mice following treatment with 4-OHC. EGFP expression was detected using an OV- 110 epifluorescent imager. Mice treated with vehicle control and irradiated with 365 nm UV light are shown in the left panels. Mice treated with 4-OHC are shown in the right panels.

Figure 14 is a set of two images showing the EGFP expression in the ventral skin of Rosa26CreER ; mT/mG reporter mice following treatment with caged 4-OHC and no light treatment (left panel) or caged 4-OHC with 365 nm light treatment. An increase in EGFP signal is followed by a decrease in tdTomato signal; low values of EGFP/tdTomato ratio correspond to low EGFP and high tdTomato, while high values of ratios correspond to high EGFP and low tdTomato.

Figure 15 is a schematic of the experimental design for intraperitoneal injection of vehicle or caged 4-OHC into the Rosa26CreER ; mT/mG female mice and subsequent 365 nm illumination on the right inguinal (#4) mammary fat pad.

Figure 16 is a set of four images of ex vivo mammary tissue from Rosa26CreER ; mT/mG female mice intraperitoneally injected with vehicle and exposed (right panels) or unexposed (left panels) to 365 nm light. The mammary tissue was imaged with an IV-110 epifluorescent imager.

Figure 17 is a set of four images of ex vivo mammary tissue from Rosa26CreER ; mT/mG female mice intraperitoneally injected with caged 4-OHC and exposed (right panels) or unexposed (left panels) to 365 nm light. The mammary tissue was imaged with an IV-110 epifluorescent imager. The illuminated mammary gland tissues injected with caged 4-OHC expressed EGFP.

Figure 18 is a set of eight photomicrographs showing the X-gal stained mouse embryonic fibroblasts from Rosa26-CreERT2; Lox-STOP-Lox-lacZ embryos following no treatment (upper left panel), treatment with 5 μΜ 4-OHC (positive control; lower left panel), treatment with Caged Molecule I ("Compound I") with or without 365 nm UV light exposure (top right and top center panels, respectively), treatment with Caged Molecule II ("Compound II") with or without 365 nm UV light exposure (middle right and middle center panels, respectively), or treatment with Caged Molecule III ("Compound III") with or without 365 UV light exposure (bottom right and bottom left panels, respectively). Detailed Description of the Invention

The invention is based, in part, on the discovery that photoactivatable caged tamoxifen and caged tamoxifen derivative molecules can be used to selectively and sensitively deliver tamoxifen or tamoxifen derivatives to cells following irradiation. Thus, provided herein are compositions containing these caged tamoxifen and caged tamoxifen derivative molecules, and methods of inducing nuclear translocation of an ER fusion protein in a eukaryotic (e.g., mammalian, plant, yeast, nematode, parasite, or reptile) cell and methods of inducing recombination in a eukaryotic (e.g., mammalian, plant, yeast, nematode, parasite, or reptile) cell that include contacting a eukaryotic cell with one of the caged tamoxifen or caged tamoxifen derivative molecules and irradiating the eukaryotic cell. Also provided are methods of treating breast cancer in a subject that include administering a photoactivatable caged tamoxifen or caged tamoxifen derivative molecule to a subject having breast cancer. Various, non-limiting features of each aspect of the invention are described below. Compounds

Provided herein are caged tamoxifen and caged tamoxifen derivative molecules that are sensitive to light- induced degradation. Light exposure of the caged tamoxifen or caged tamoxifen derivative molecules triggers the release of the tamoxifen or tamoxifen derivative. Any of the caged tamoxifen or caged tamoxifen derivative molecules described herein can be used in any of the methods described herein.

A prior version of caged tamoxifen (4-hydrocyclofen conjugated with the

photoactivatable 4,5-demethoxy-2-nitrophenl methanol (DM PM) group demonstrated spontaneous breakdown in the absence of appropriate light exposure. These results indicated that the DMNPM caging group or the DMNPM caged 4-hydroxycyclofen can be unstable in the absence of appropriate light exposure. In addition, the photocleavage of the DMNPM caged 4-hydroxycyclofen results in the generation of a reactive aldehyde group (shown in Schematic #1 below). This reactive aldehyde product may trigger unwanted side reactions with amine containing biomolecules in the cell. This process can lead to unwanted, detrimental chemical side reactions in the cell.

Provided herein are caged tamoxifen or caged tamoxifen derivative molecules that have improved stability in the absence of appropriate light exposure. In some embodiments, the caged tamoxifen or caged tamoxifen derivative molecules contain tamoxifen or a tamoxifen derivative (e.g., 4-hydroxycyclofen) conjugated to l-(4,5-dimethoxy-2- nitrophenyl) ethanol (DMNPE). In some embodiments, the caged tamoxifen or caged tamoxifen derivative is conjugated to photoactivatable caging group selected from the group of: carboxy-2-nitrobenzyl (CNB); 4,5-dimethoxy-2-nitrobenzyl (DMNB); 2,2'- dinitrobenzhydryl (DNBH); 1 -(2-nitrophenyl)ethyl (NPE); (4,4'-bis- {8-[4-nitro-3-(2-propyl)- styryl]}-3,3 '-dimethoxybiphenyl (BNSMB); (2,7-bis- {4-nitro-8-[3-(2-propyl)-styryl]}-9,9- bis-[l-(3,6-dioxaheptyl)]-fluorene (BNSF); 4-carboxymethoxy-5,7-dinitroindolinyl (CDNI); 2-nitrobenzyl and 7-nitroindoline derivatives; coumarin-4-ylmethyl; 8-bromo-7- hydroxyquinoline derivatives; p-hydroxyphenacyl; and heavy metal. In some embodiments, the photoactivatable caging molecule is connected to the tamoxifen or tamoxifen derivative by an ester, an ether, an amido group, a carbonate, a carbamate, or an acetal.

In some embodiments, the tamoxifen derivative contains a modification to the triphenyl ethylene skeleton. Non-limiting examples of tamoxifen derivatives include 4- hydroxycyclofen and 4-hydroxytamoxifen. Additional non-limiting examples of tamoxifen derivatives are shown below (Schematic #2). Schematic #2. Exemplary Tamoxifen Derivatives

In some embodiments, the caged tamoxifen derivative molecule is l-(4,5-dimethoxy- 2-nitrophenyl) ethanol (DMNPE) caged 4-hydroxycyclofen (DMNPE-4-OHC). DMNPE-4- OHC did not appear to show any sign of breakdown prior to illumination (essentially inert in the dark). DMNPE-4-OHC can be decaged using a wavelength of light between 350 nm and 405 nm (see Example). The light-induced breakdown of DMNPE-4-OHC generates a ketone product (shown in Schematic #3 below), rather than a reactive aldehyde-containing product. The production of a ketone product reduces the possibility of any detrimental side reactions within a cell.

Schematic #3. Breakdown of DMNPE-4-OHC to Release 4-OHC

In some embodiments, the caged tamoxifen derivative is one of the structures shown in Schematic #4 below. Schmetic #4. Additional Exemplary DMNPE-Tamoxifen Derivatives

Caged Molecule A Caged Molecule B

Caged Molecule C Caged Molecule D

Caged Molecule E Caged Molecule F

Caged Molecule G Caged Molecule H

In some embodiments, the caged tamoxifen derivative is one of the three structures shown in Schematic #5 below. S

Caged Molecule I Caged Molecule II Caged Molecule III Caged Molecules I, II, and III (shown in Schematic #5) were tested in cell culture experiments and were able to induce nuclear translocation of an ER fusion protein in vitro (see, Figure 17). Caged Molecule III (shown in Schematic #5) is a two-photon activatable caged tamoxifen derivative. Activation using a two-photon light source is particularly beneficial for in vivo study due to its ability to allow deep tissue penetration and low tissue damaging effect. A two-photon light source emits wavelengths that are greater than 600 nm (e.g., emits a wavelength that is between 700 nm and 800 nm, between 700 nm and 900 nm, between 650 nm and 850 nm, between 500 nm and 800 nm, or between 600 nm and 900 nm). In some embodiments where the nuclear translocation of an ER fusion protein within an internal organ is desired, a mammal is administered a composition containing Caged

Molecule III (shown in Schematic #5 above).

In some embodiments, the caged tamoxifen derivative is DMNPE-conjugated 4- hydroxy tamoxifen (shown in Schematic #6 below). 4-hydroxy tamoxifen is the active metabolite form of tamoxifen. As described below, the DMNPE-conjugated 4-hydroxy tamoxifen can be used as a prodrug for light- induced localized treatment of breast cancer in a subject.

Schematic #6. DMNPE-conjugated 4-hydroxy tamoxifen

Synthetic methods for conjugating tamoxifen or a tamoxifen derivative (e.g., any of the tamoxifen derivatives described herein) to a photoactivatable caging molecule (e.g., any of the caging molecules described herein) are known in the art. For example, DMNPE can be conjugated to a tamoxifen derivative (e.g., 4-hydroxycyclofen) using Mitsonobu coupling conditions (see, e.g., the method described in the Example). In some embodiments, the tamoxifen or tamoxifen derivative can be conjugated to a bromo derivative of the photoactivatable-caged molecule (e.g., DMNPE) via a nucleaophilic substitution reaction. After the synthesis, the caged tamoxifen or caged tamoxifen derivative molecule can be purified, e.g., using a S1O2 (see, e.g., the method described in the Example). In some embodiments, the caged tamoxifen or caged tamoxifen derivative molecule can be at least 80% (e.g., at least 85%, 90%, 95%, or 99%) pure by weight.

Compositions and Kits

Provided herein are compositions containing at least one of any of the caged tamoxifen molecules or caged tamoxifen derivative molecules described herein. In some embodiments, the composition contains at least 80% (e.g., at least 85%, 90%, 95%, or 99%) of the caged tamoxifen or the caged tamoxifen derivative molecule by weight. In some embodiments, the composition contains a pharmaceutically acceptable excipient or buffer (e.g., saline, DMSO, PEG400, an acetate buffer, VitE-TPGS, ethanol, Solutol, cremophor, Tween, and mixtures thereof). In some embodiments, the compositions are formulated using a combination of ethanol, a polyethylene glycol, Tween, and Solutol. In some embodiments, the compositions are formulated in 10% Ν,Ν-dimethylacetamide (DMAC) and 10% Solutol in saline.

In some embodiments, the compositions are formulated as a liquid for systemic administration. In some embodiments, the compositions are formulated for intraarterial, intravenous, intraperitoneal, intrathecal, ocular, nasal, intramuscular, intraductal, or subcutaneous administration.

In some embodiments, the compositions are formulated as a solid. In some embodiments, the compositions are formulated for oral or topical (e.g., transdermal) administration. In some embodiments, the compositions are formulated as a suppository.

In some embodiments, the compositions are encapsulated in nanomaterials for targeted delivery (e.g., encapsulated in a nanomaterial having one or more tissue- or cell- targeting molecules on its surface). In some embodiments, the compositions are formulated as an emulsion or as a liposome-containing composition. In some embodiments, the compositions can contain dimers, multimers, or polymers of any of the caged tamoxifen or caged tamoxifen derivative molecules described herein. In some embodiments, the caged tamoxifen or caged tamoxifen derivative molecules are formulated for sustained release (e.g., formulated in a biodegradable polymers or in nanoparticles). In some embodiments, the compositions are formulated in an implantable device that allows for sustained release of the caged tamoxifen or caged tamoxifen derivative molecules.

Pharmaceutical compositions are formulated to be compatible with their intended route of administration or the intended target tissue or cell, e.g., systemic or local administration. In some embodiments, the compositions are formulated for oral, intravenous, intradermal, subcutaneous, transmucosal (e.g., nasal sprays are formulated for inhalation), or transdermal (e.g., topical ointments, salves, gels, patches, or creams as generally known in the art) administration. The compositions can include a sterile diluent (e.g., sterile water or saline), a fixed oil, polyethylene glycol, glycerine, propylene glycol, or other synthetic solvents; antibacterial or antifungal agents, such as benzyl alcohol or methyl parabens, chlorobutanol, phenol, ascorbic acid, thimerosal, and the like; antioxidants, such as ascorbic acid or sodium bisulfite; chelating agents, such as ethylenediaminetetraacetic acid; buffers such as acetates, citrates, or phosphates; and isotonic agents, such as sugars (e.g., dextrose), polyalcohols (e.g., manitol or sorbitol), or salts (e.g., sodium chloride). Liposomal suspensions can also be used as pharmaceutically acceptable carriers (see, e.g., U.S. Patent No. 4,522,811 ; herein incorporated by reference). Preparations of the compositions can be formulated and enclosed in ampules, disposable syringes, or multiple dose vials that prevent exposure of the caged tamoxifen or caged tamoxifen derivative molecules to light. Where required (as in, for example, injectable formulations), proper fluidity can be maintained by, for example, the use of a coating such as lecithin, or a surfactant. Absorption of the caged tamoxifen or caged tamoxifen derivative molecules can be prolonged by including an agent that delays absorption (e.g., aluminum monostearate and gelatin). Alternatively, controlled release can be achieved by implants and microencapsulated delivery systems, which can include biodegradable, biocompatible polymers (e.g., ethylene vinyl acetate, polyanhydrides, polyglycolic acid, collagen, polyorthoesters, and polylactic acid; Alza Corporation and Nova Pharmaceutical, Inc.).

Where oral administration is intended, the agent can be included in pills, capsules, troches and the like, and can contain any of the following ingredients, or compounds of a similar nature: a binder, such as microcrystalline cellulose, gum tragacanth, or gelatin; an excipient, such as starch or lactose; a disintegrating agent, such as alginic acid, Primogel, or corn starch; a lubricant, such as magnesium stearate; a glidant, such as colloidal silicon dioxide; a sweetening agent, such as sucrose or saccharin; or a flavoring agent, such as peppermint, methyl salicylate, or orange flavoring.

The compositions described herein can be formulated for ocular or parenteral (e.g., oral) administration in dosage unit form (i.e., physically discrete units containing a predetermined quantity of active compound for ease of administration and uniformity of dosage). Toxicity and therapeutic efficacy of compounds can be determined by standard pharmaceutical procedures in cell cultures or experimental animals. One can, for example, determine the LD50 (the dose lethal to 50% of the population) and the ED50 (the dose therapeutically effective in 50% of the population), the therapeutic index being the ratio of LD50:ED50. Agents that exhibit high therapeutic indices are preferred. Where an agent exhibits an undesirable side effect, care should be taken to target that agent to the site of the affected or targeted tissue (the aim being to minimize potential damage to unaffected cells and, thereby, reduce side effects). Toxicity and therapeutic efficacy can be determined by other standard pharmaceutical procedures.

In some embodiments, the composition containing a caged tamoxifen or caged tamoxifen derivative molecule is formulated in a single dosage form (e.g., a single dosage form containing between 1 mg to 500 mg, between 1 mg and 400 mg, between 1 mg and 300 mg, between 1 mg and 250 mg, between 1 mg and 200 mg, between 1 mg and 100 mg, and between 1 mg and 50 mg of the caged tamoxifen or caged tamoxifen derivative molecule).

In some embodiments, the compositions contain at least one caged tamoxifen molecule or at least one caged tamoxifen derivative molecule and one or more additional breast cancer therapeutics (e.g., any of the breast cancer therapeutics described herein).

Also provided herein are kits that contain at least one dose of any of the compositions described herein. In some embodiments, the kits can further include an item for use in administering a composition (e.g., any of the compositions described herein) to the subject (e.g., a syringe, e.g., a pre-filled syringe). In some embodiments, the kits contain one or more doses (e.g., at least two, three, four, five, six, seven, eight, nine, ten, eleven, twelve, thirteen, fourteen, twenty, thirty, or fourty doses) (e.g., oral doses) of any of the compositions described herein. In some embodiments, the kit further contains instructions for

administering the composition (or a dose of the composition) to a mammal (e.g., a non- human transgenic mammal or a human having breast cancer). In some embodiments, the kits contain a composition containing at least one of the caged tamoxifen molecules or at least one of the caged tamoxifen derivative molecules, and a composition containing at least one additional breast cancer therapeutic (e.g., any of the additional breast cancer therapeutics described herein). In some embodiments, the kit further contains instructions for performing any of the methods described herein

In some embodiments, the kits can further contain a light source (e.g., any of the light sources described herein, e.g., a hand-held light source or a light source that can be used in an endoscopic or orthroscopic procedure). In some embodiments, the kits contain a two-photon light source (e.g., a hand-held two photon light source). In some embodiments, a light source emits a wavelength of light that is between 700 nm and 800 nm, between 700 nm and 900 nm, between 650 nm and 850 nm, between 500 nm and 800 nm, or between 600 nm and 900 nm. In some embodiments, the light source emits light at a wavelength of approximately 730 nm.

Light Sources

Light sources that emit light between 200 nm and 900 nm (e.g., between 300 nm and 700 nm, between 300 nm and 600 nm, between 300 nm and 500 nm, between 350 nm and 410 nm, between 200 nm and 700 nm, and between 700 nm and 900 nm) that can be used to breakdown the caged tamoxifen or caged tamoxifen derivative molecules (e.g., any of the caged tamoxifen or caged tamoxifen derivative molecules described herein). In some embodiments, the light source emits a wavelength of between 700 nm and 800 nm, between 700 nm and 900 nm, between 650 nm and 850 nm, between 500 nm and 800 nm, or between 600 nm and 900 nm. In some embodiments, a light source that emits light of 350 nm to 410 nm is used to breakdown DMNPE-caged 4-hydroxycyclofen.

In some embodiments, the light source can be directed to a particular tissue or cell that is expressing the ER fusion protein (e.g., any of the ER fusion proteins described herein) and that has been contacted with any of the caged tamoxifen or caged tamoxifen derivative molecules described herein. In some embodiments, the light source is used to irradiate an animal containing a cell containing the ER fusion protein that has been contacted with any of the caged tamoxifen or caged tamoxifen derivative molecules described herein. In some embodiments, the light source is a hand-held device. In some embodiments, the light source is placed at the end of an endoscope or orthoscopic device. In some embodiments, the light source is inserted into a tissue in the body through the use of a catheter. In some

embodiments, the light source is a two-photon light source.

ER Fusion Proteins

Estrogen receptor (ER)-fusion proteins as described herein are proteins that contain a mammalian estrogen receptor ligand binding domain and an additional polypeptide sequence (a fusion partner polypeptide). In some embodiments, the ER- fusion protein contains a human estrogen receptor ligand binding domain. In some embodiments, the mammalian (e.g., human) estrogen receptor ligand binding domain is located at the N-terminus of the ER- fusion protein or is located N-terminal to the additional polypeptide sequence (fusion partner polypeptide). In some embodiments, the mammalian (e.g., human) estrogen receptor ligand binding domain is located at the C-terminus of the ER fusion protein or is located C-terminal to the additional polypeptide sequence (fusion partner polypeptide). Mammalian Estrogen Receptor Ligand Binding Domains

In some embodiments, the mammalian estrogen receptor ligand binding domain contains a contiguous sequence that is at least 80% (e.g., at least 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100%) identical to a contiguous sequence present in a human estrogen ligand binding domain, and has the ability to bind to tamoxifen or a tamoxifen derivative (e.g., any of the tamoxifen derivatives described herein). In some embodiments, the mammalian estrogen receptor ligand binding domain contains a sequence that is at least 80% (e.g., at least 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100%) identical to a contiguous sequence present between amino acids 310 to 547 of SEQ ID NO: 1 (underlined below). In some

embodiments, amino acids 346, 351, 353, 387, 394, 521, 524 of SEQ ID NO: 1 are conserved (underlined and in bold below).

Human Estrogen Receptor Protein (SEQ ID NO: 1)

1 mtmtlhtkas gmallhqiqg neleplnrpq lkiplerplg evyldsskpa vynypegaay

61 efnaaaaana qvygqtglpy gpgseaaafg snglggfppl nsvspsplml lhpppqlspf 121 lqphgqqvpy ylenepsgyt vreagppafy rpnsdnrrqg grerlastnd kgsmamesak

181 etrycavcnd yasgyhygvw scegckaffk rsiqghndym cpatnqctid knrrkscqac

241 rlrkcyevgm mkggirkdrr ggrmlkhkrq rddgegrgev gsagdmraan lwpsplmikr

301 skknslalsl tadqmvsall daeppilyse ydptrpfsea smmglltnla drelvhminw akrvpgfvdl tlhdqvhlle cawleilmig Ivwrsmehpg kllfapnlll drnqgkcveg mveifdmlla tssrfrmmnl qgeefvclks iillnsgvyt flsstlksle ekdhihrvld kitdtlihlm akagltlqqq hqrlaqllli lshirhmsnk gmehlysmkc knvvplydll lemldahrlh aptsrggasv eetdqshlat agstsshslq kyyitgeaeg fpatv

An exemplary cDNA encoding a human estrogen receptor protein is SEQ ID NO: 2.

Additional examples of human estrogen receptor ligand binding domains that can be used in the fusion proteins are described in Pfannkuche et al, Biotechniques 48: 113-120, 2010; Andersson et al, Transgenic Res. 19:715-725, 2010; Maeda et al, Bone 46:472-478, 2010; Tumurbaatar et al, J. Virol. Methods 146:5-13, 2007; Dworniczak et al, Nephron Exp. Nephrol. 106:el l-e20, 2007; Weber et al, Biol. Reprod. 68:553-539, 2003; Hayashi et al, Dev. Biol. 244:305-318, 2002; Vallier et al, Proc. Natl. Acad. Sci. U.S.A. 98:2467-2472, 2001; Fuhrmann-Benzakein et al, Nucleic Acids Res. 28:E99, 2000; Indra et al, Nucleic Acids Res. 27:4324-4327, 1999; and Metzger et al, Proc. Natl. Acad. Sci. U.S.A. 92:6991- 6995, 1995. These references describe Cre recombinase-human estrogen receptor ligand binding domain fusion proteins. Sequences encoding the human estrogen receptor ligand binding domain are described in these references, and these sequences can be isolated and used to form any of the ER fusion proteins described herein using molecular biology methods known in the art.

In some embodiments, the mammalian estrogen receptor ligand binding domain contains a contiguous sequence that is at least 80% (e.g., at least 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100%) identical to a contiguous sequence present in a mouse estrogen receptor ligand binding domain. In some embodiments, the mammalian estrogen receptor ligand binding domain contains a sequence that is at least 80% (e.g., at least 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100%) identical to a contiguous sequence present between amino acids 314 to 551 of SEQ ID NO: 3 (underlined below). In some embodiments, amino acids 350, 355, 357, 391, 398, 525, and 528 of SEQ ID NO: 3 are conserved (underlined and in bold below).

Mouse Estrogen Receptor Protein (SEQ ID NO: 3)

1 mtmtlhtkas gmallhqiqg neleplnrpq lkmpmeralg evyvdnskpt vfnypegaay 61 efnaaaaaaa aasapvygqs giaygpgsea aafsanslga fpqlnsvsps plmllhpppq 121 lspflhphgq qvpyylenep sayavrdtgp pafyrsnsdn rrqngrerls ssnekgnmim 181 esaketryca vcndyasgyh ygvwscegck affkrsiqgh ndymcpatnq ctidknrrks

241 cqacrlrkcy evgmmkggir kdrrggrmlk hkrqrddleg rnemgasgdm raanlwpspl

301 vikhtkknsp alsltadqmv salldaeppm iyseydpsrp fseasmmgll tnladrelvh

361 minwakrvpg fgdlnlhdqv hllecawlei lmiglvwrsm ehpgkllfap nllldrnqgk cvegmveifd mllatssrfr mmnlqgeefv clksiillns gvytflsstl ksleekdhih rvldkitdtl ihlmakaglt lqqqhrrlaq lllilshirh msnkgmehly nmkcknvvpl ydlllemlda hrlhapasrm gvppeepsqt qlattsstsa hslqtyyipp eaegfpnti

An exemplary cDNA encoding a mouse estrogen receptor protein is SEQ ID NO: 4.

In some embodiments, the mammalian estrogen receptor ligand binding domain contains a contiguous sequence that is at least 80% (e.g., at least 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100%) identical to a contiguous sequence present in a rat estrogen receptor ligand binding domain. In some embodiments, the mammalian estrogen receptor ligand binding domain contains a sequence that is at least 80% (e.g., at least 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100%) identical to a contiguous sequence present between amino acids 315 to 552 of SEQ ID NO: 5 (underlined below). In some embodiments, amino acids 351, 356, 358, 392, 399, 526, and 529 of SEQ ID NO: 5 are conserved (underlined and in bold below).

Rat Estrogen Receptor Protein (SEQ ID NO: 5)

1 mtmtlhtkas gmallhqiqg neleplnrpq lkmpmeralg evyvdnskpa vfnypegaay 61 efnaaaaaaa agasapvygq ssitygpgse aaafganslg afpqlnsvsp splmllhppp 121 hvspflhphg hqvpyylene psayavrdtg ppafyrsnsd nrrqngrerl ssssekgnmi 181 mesaketryc avcndyasgy hygvwscegc kaffkrsiqg hndymcpatn qctidknrrk 241 scqacrlrkc yevgmmkggi rkdrrggrml khkrqrddle grnemgtsgd mraanlwpsp 301 lvikhtkkns palsltadqm vsalldaepp liyseydpsr pfseasmmgl ltnladrelv 361 hminwakrvp gfgdlnlhdq vhllecawle ilmiglvwrs mehpgkllfa pnllldrnqg kcvegmveif dmllatssrf rmmnlqgeef vclksiilln sgvytflsst lksleekdhi hrvldkindt lihlmakagl tlqqqhrrla qlllilshir hmsnkgmehl ynmkcknvvp lydlllemld ahrlhapasr mgvppeepsq sqltttssts ahslqtyyip peaegfpnti

An exemplary cDNA encoding a rat estrogen receptor protein is SEQ ID NO: 6. The ability of an ER fusion protein to bind to tamoxifen or a tamoxifen derivative can be assessed directly using high performance liquid chromatograph-mass spectrometry (HPLC-MS) or circular dichroism (see, e.g., Nair et al, J. Mol. Endocrinol. 35:21 1-223, 2005). The ability of an ER fusion protein to bind tamoxifen or a tamoxifen derivative can also be assessed indirectly by the detection of the nuclear translocation of an ER fusion protein (e.g., detected by immunofluorescent microscopy or induced expression of a reporter trans gene integrated within a chromosome of the cell) or the detection of an activity of the ER fusion protein within the nucleus of the cell. Exemplary methods for detecting tamoxifen- or tamoxifen derivative-induced nuclear translocation are described in the Examples. Methods for detecting the activity of an ER fusion protein within the nucleus of the cell depend on the specific activity of the ER fusion protein. Methods to detect the activity of an ER fusion protein within the nucleus of the cell are also known in the art.

Fusion Partner Polypeptides

ER fusion proteins can contain a fusion partner polypeptide from any source (e.g., a human, mouse, rat, bacterial, viral, or parasitic polypeptide sequence). In some

embodiments, the fusion partner polypeptide contains a polypeptide sequence of a recombinase (e.g., a Cre recombinase from P I phage, FLP from S. cerevisiae, λ integrase from lambda phage, gamma-delta resolvase from TnlOOO transposon, Tn3 resolvase from the Tn3 transposon, and (pC31 integrase from (pC31 phage) and the fusion protein has recombinase activity in a cell treated with tamoxifen or a tamoxifen derivative. Non-limiting exemplary sequences of Cre recombinase polypeptides that can be included in the ER fusion proteins, as well as exemplary ER fusion proteins containing a Cre recombinase polypeptide are described in Pfannkuche et al, Biotechniques 48: 113-120, 2010; Andersson et al, Transgenic Res. 19:715-725, 2010; Maeda et al, Bone 46:472-478, 2010; Tumurbaatar et al, J. Virol. Methods 146:5-13, 2007; Dworniczak et al, Nephron Exp. Nephrol. 106:el l-e20, 2007; Weber et al, Biol. Reprod. 68:553-539, 2003; Hayashi et al, Dev. Biol. 244:305-318, 2002; Vallier et al, Proc. Natl. Acad. Sci. U.S.A. 98:2467-2472, 2001 ; Fuhrmann-Benzakein et al, Nucleic Acids Res. 28:E99, 2000; Indra et al, Nucleic Acids Res. 27:4324-4327, 1999; and Metzger et al, Proc. Natl. Acad. Sci. U.S.A. 92:6991-6995, 1995. Additional non- limiting polypeptide sequences of fusion partner polypeptides are listed in Table 1 below. Methods for detecting recombinase activity of a fusion protein in a cell treated with tamoxifen or a tamoxifen derivative are known in the art. Non-limiting exemplary methods for detecting recombinase activity of a fusion protein in a cell treated with tamoxifen or a tamoxifen derivative are described in the Example.

Table 1. Exemplary Recombinase Fusion Partner Polypeptide Sequences

In some embodiments, the fusion partner polypeptide contains a polypeptide sequence of a transcription factor (e.g., a transcription factor that plays a role in cellular differentiation) and the fusion protein is capable of inducing gene transcription in a cell treated with tamoxifen or a tamoxifen derivative. In some embodiments, the fusion partner polypeptide contains a polypeptide sequence of a transcription repressor (e.g., a transcription repressor that plays a role in cellular differentiation) and the fusion protein is capable of inhibiting gene transcription in a cell treated with tamoxifen or a tamoxifen derivative. In some

embodiments, the fusion partner polypeptide contains a polypeptide sequence of a histone deacetylase and the fusion protein has histone deacetylase activity in a cell treated with tamoxifen or a tamoxifen derivative. In some embodiments, the fusion partner polypeptide contains a polypeptide sequence of an O-6-methylguanine-DNA methyltransferase and the fusion protein has O-6-methylguanine-DNA methyltransferase activity in a cell treated with tamoxifen or a tamoxifen derivative. In some embodiments, the fusion partner polypeptide contains a polypeptide sequence of a telomerase and the fusion protein has telomerase activity in a cell treated with tamoxifen or a tamoxifen derivative. Non-limiting exemplary sequences of histone acetyltransferase, histone deactyltransferase, O-6-methylguanine-DNA methyltransferase, and telomerase that can be present in an ER fusion protein are listed in Table 2 below. Methods for detecting gene transcription, histone deacetylase activity, histone acetyltransferase activity, O-6-methylguanine-DNA methyltransferase activity, and telomerase activity are known in the art. Table 2. Exemplary Fusion Partner Polypeptides

In some embodiments, the fusion partner polypeptide contains a polypeptide sequence of a viral protein (e.g., an adenoviral, lentiviral, or a retroviral protein). In some

embodiments, the fusion partner polypeptide contains a polypeptide sequence from a pathogenic bacterium or a parasite. In some embodiments, the fusion partner polypeptide contains a polypeptide sequence of an oncogene (e.g., a human, mouse, rat, or monkey oncogene). Additional sequences of fusion partner polypeptides are described in the examples and are known in the art.

In some embodiments, the ER fusion proteins can contain a polypeptide sequence of an additional reporter protein (e.g., a fluorescent protein such as green fluorescent protein or yellow fluorescent protein, or an enzyme capable of producing a colored product (e.g., β- galactosidase) or an additional epitope (e.g., a His-tag).

Promoters

In some embodiments, a nucleic acid encoding the ER fusion protein (e.g., any of the ER fusion proteins described herein) is stably integrated into a chromosome in the nucleus of a eukaryotic (e.g., mammalian, plant, yeast, nematode, parasite, or reptile) cell. In some embodiments, a nucleic acid encoding the ER fusion protein is introduced into a chromosome of the eukaryotic (e.g., mammalian, plant, yeast, nematode, parasite, or reptile) cell using a recombinant virus (e.g., a recombinant adenovirus, lentivirus, or retrovirus). In some embodiments, a nucleic acid encoding the ER fusion protein is introduced into an embryo or blastocyst of non-human mammal to produce a transgenic mammal.

In some embodiments, a nucleic acid encoding the ER fusion protein (e.g., any of the

ER fusion proteins described herein) is located in an expression plasmid or an artificial mammalian chromosome (e.g., a human artificial chromosome), and the expression plasmid or artificial mammalian chromosome is introduced into a mammalian cell (e.g., a mammalian embryo or blastocyst). In some embodiments, the eukaryotic cell is a yeast cell and a yeast artificial chromosome is introduced into the yeast cell. In some embodiments, the expression plasmid is introduced into the eukaryotic cell by electroporation or lipofection. In some embodiments, the artificial chromosome is introduced into the eukaryotic cell by

microinjection or cell fusion (e.g., fusion of a target cell (e.g., an embryo) with a cell (e.g., a fetal fibroblast) containing a mammalian artificial chromosome). A variety of different eukaryotic (e.g., mammalian) expression plasmids and mammalian artificial chromosomes are known in the art. A variety of different molecular biology methods for introducing an expression plasmid or a mammalian artificial chromosome into a eukaryotic cell are also known in the art.

In some embodiments, one or more promoter or enhancer sequences can be operatively linked (e.g., upstream) to the sequence encoding the ER fusion protein. In some embodiments, the one or more promoter sequences can be a tissue-specific promoter, an inducible e promoter, or a ubiquitous (e.g., strong ubiquitous) promoter. Non-limiting examples of tissue-specific promoters include B29 promoter (B-cell expression), CD 14 promoter (monocyte expression), CD43 promoter (leukocyte and platelet expression), CD45 promoter (haematopoietic cell expression), CD68 promoter (macrophage expression), desmin promoter (muscle cell expression), elastase-1 promoter (pancreatic acinar cell expression), endoglin promoter (endothelial cell expression), fibronectin promoter (differentiating cell expression), Flt-1 promoter (endothelial cell expression), GFAP promoter (astrocyte expression), GPIIB promoter (megakaryocyte expression), ICAM-2 promoter (endothelial cell expression), INF-β promoter (hematopoietic cell expression), Mb promoter (muscle cell expression), Nphsl promoter (podocyte expression), OG-2 promoter (osteoblast expression), SP-B promoter (lung cell expression), SY l promoter (neuron expression), WASP promoter (hematopoietic cell expression), SV40/bAlb promoter (liver cell expression), and NSE/Ru5' promoter (mature neuron expression) (these promoter sequences are available in

commercially available vectors, e.g., expression vectors available from InvivoGen). In some embodiments, an aromatase promoter is used to drive expression of the ER fusion protein in breast tissue (see, e.g., Khan et al, Reprod. Biol. Endocrinol. 9:91, 201 1). In some embodiments, a carbonic anhydrase I promoter/enhancer is used to express the ER fusion protein in colon tissue (see, e.g., Xue et al, Mol. Cancer Res. 8: 1095, 2010). In some embodiments, a keratin 14 promoter is used to express the ER fusion protein in skin tissue

(see, e.g., Vandermeulen et al., Vaccine 27:4272-4277, 2009). Additional examples of tissue- specific promoter sequences are known in the art. In some embodiments, the nucleic acid encoding the ER fusion protein is operatively linked (e.g., upstream) to an inducible promoter sequence and the cell is further contacted with a chemical inducing agent. Non-limiting examples of inducible promoter sequences include tetracycline-regulated promoters (see, e.g., the T-Rex™ system from Life

Technologies), doxycycline-inducible promoters (see, e.g., Qin et al, PLoS ONE 5:el0611, 2010), RU486-inducible promoters (see, e.g., U.S. Patent Application Publication No.

2009/0293139), and polyinosinic:polycytidylic acid (Poly(I:C))-inducible promoters (Tomita et al, Mol. Endocrinol. 14: 1674-1681, 2000). Additional inducible promoter sequences and chemical inducing agents are known in the art.

In some embodiments, the nucleic acid encoding the ER fusion protein is operatively linked (e.g., upstream) to a ubiquitous (e.g., a strong ubiquitous) promoter sequence. Non- limiting examples of ubiquitous promoters include β-actin promoter, CMV promoter, SV40 promoter, UBC promoter, EF1A promoter, PGK promoter, and CAGG promoter (see, e.g., Qin et al., PLoS One 5:el0611, 2010). One or more of the promoter sequences described herein can be operatively linked to a nucleic acid encoding an ER fusion protein using molecular biology methods known in the art.

Methods of Inducing Nuclear Translocation

Provided herein are methods of optically inducing nuclear translocation of a fusion protein containing a mammalian estrogen receptor ligand binding domain (e.g., a human estrogen receptor ligand binding domain) in a eukaryotic (e.g., mammalian, plant, yeast, nematode, parasite, or reptile) cell. These methods include providing a eukaryotic ((e.g., mammalian, plant, yeast, nematode, parasite, or reptile) cell that contains a fusion protein containing a mammalian (e.g., human) estrogen receptor ligand binding domain, contacting the cell with any of the compositions described herein; and irradiating the cell with a wavelength of light between of between 200 nm and 900 nm (e.g., between 350 nm to 410 nm, between 200 nm and 700 nm, and between 700 nm and 900 nm) for a period of time sufficient to stimulate release of tamoxifen or a tamoxifen derivative from the composition, where the released tamoxifen or tamoxifen derivative induces the nuclear translocation of the fusion protein. In some embodiments, the fusion protein is any of the fusion proteins (ER fusion proteins) described herein.

The nuclear translocation of a fusion protein can be detected using

immunofluorescence using antibodies that bind specifically to either the mammalian estrogen receptor ligand binding domain or the fusion partner polypeptide. The nuclear translocation of the fusion protein can also be assessed by detecting the activity of the fusion protein in the nucleus of the cell (e.g., transcription factor activity, transcription repressor activity, telomerase activity, oncogene activity, histone deacetylase activity, histone acetyltransferase activity, or O-6-methylguanine DNA methyltransferase activity in the nucleus of the cell). In some embodiments, the fusion protein can further contain a detectable reporter protein (e.g., a green fluorescent protein or yellow fluorescent protein) that can be used to detect the presence of the fusion protein in the nucleus of the cell.

In some embodiments, the eukaryotic (e.g., mammalian, plant, yeast, nematode, parasite, or reptile) cell contains a nucleic acid encoding the fusion protein. In some embodiments, the nucleic acid encoding the fusion protein is stably integrated in a chromosome within the nucleus of the eukaryoatic (e.g., mammalian, plant, yeast, nematode, parasite, or reptile) cell. In some embodiments, the nucleic acid encoding the fusion protein is located in an expression plasmid or a mammalian artificial chromosome (e.g., a human artificial chromosome). In some embodiments, the nucleic acid encoding the fusion protein is operably linked to one or more promoter or enhancer sequences. In some embodiments, the nucleic acid is operatively linked to a inducible promoter (e.g., any of the inducible promoters described herein or known in the art) and the cell is further contacted with a chemical inducing agent (e.g., any of the chemical inducing agents described herein or known in the art) (e.g., prior to contacting with the caged tamoxifen or caged tamoxifen derivative molecule, prior to contacting with the caged tamoxifen or caged tamoxifen derivative molecule and prior to irradiation, or after contacting with the caged tamoxifen or caged tamoxifen derivative molecule and after irradiation). In some embodiments, the nucleic acid encoding the fusion protein is operatively linked to a tissue-specific promoter (e.g., any of the tissue-specific promoters described herein or known in the art). In some embodiments, the nucleic acid encoding the fusion protein is operatively linked to a ubiquitous promoter (e.g., any of the ubiquitous promoters described herein or known in the art).

In some embodiments, the eukaryotic (e.g., mammalian, plant, yeast, nematode, parasite, or reptile) cell is present in vitro or ex vivo. In some embodiments, the eukaryotic (e.g., mammalian) cell is an epithelial cell, a lung cell, a kidney cell, an endothelial cell, a muscle cell, an adipose cell, a bone cell, a cartilage cell, or a neuron. In some embodiments, the eukaryotic (e.g., mammalian) cell is an undifferentiated cell or a stem cell (e.g., an embryonic stem cell) and the fusion protein contains a sequence of a transcription factor or a transcription repressor that induces cellular differentiation. In some embodiments, the eukaryotic (e.g., mammalian) cell is implanted into a mammal following the contacting with the caged tamoxifen or caged tamoxifen derivative molecule and irradiation.

In some embodiments, the cell is present in a mammal (e.g., a mouse or rat). In some embodiments, the cell is present in the breast tissue, skin, kidney, lung, colon, liver, pancreas, stomach, intestine, colon, muscle, mammary gland, ovary, testes, prostate, brain, spinal cord, peripheral nerve, and heart of the mammal. In some embodiments, the mammal is a child. In some embodiments, the mammal is an adult. In some embodiments, the mammal is an embryo or blastocyst.

In some embodiments, the composition is locally administered to a tissue containing the cell. In some embodiments, the composition is systemically administered (e.g., intravenous, intaarterial, intramuscular, intraperitoneal, subcutaneous, oral, transdermal, ocular, nasal, or intrathecal administration). In some embodiments, more than one dose of the composition is administered to the mammal before the cell is irradiated. In some embodiments, the cell can be contacted with a dose of the composition and then irradiated several times (e.g., one or more (e.g., at least two, three, four, or five) rounds of contacting and irradiating can be performed).

In some embodiments, a mammal is administered a dose of between 1 mg to 500 mg of the composition (e.g., between 1 mg to 400 mg, between 1 mg to 300 mg, between 1 mg and 250 mg, between 1 mg and 200 mg, between 1 mg and 150 mg, between 1 mg and 100 mg, between 1 mg and 50 mg, between 5 mg and 50 mg, and between 5 mg and 40 mg).

In some embodiments, the fusion protein contains a sequence of a recombinase (e.g., any of the recombinases described herein or known in the art), and the fusion protein has recombinase activity. In some embodiments, the fusion protein contains a sequence of a transcription factor, and the transcription factor is capable of promoting gene transcription in the nucleus of the cell. In some embodiments, the fusion protein promotes gene transcription of a gene that is present in a recombinant gene construct that is stably integrated in a chromosome present in the nucleus of the cell. In some embodiments, the fusion protein promotes transcription of an endogenous gene. Methods of determining the ability of a fusion protein to promote gene transcription are known in the art (e.g., reverse-transcriptase real-time polymerase chain reaction (PCR)).

In some embodiments, the fusion protein contains a sequence of a transcription repressor, and the fusion protein is capable of repressing gene transcription in the nucleus of the cell. In some embodiments, the fusion protein represses gene transcription of a gene that is present in a recombinant gene construct that is stably integrated in a chromosome present in the nucleus of the cell. In some embodiments, the fusion protein represses gene transcription of an endogenous gene. Methods of determining the ability of a fusion protein to repress gene transcription are known in the art (e.g., reverse transcriptase real-time PCR).

In some embodiments, the fusion protein contains a sequence of a histone deacetylase, a histone acetyltransferase, or an O-6-methylguanine DNA methyltransferase, and the fusion protein has histone deacetylase, histone acetyltransferase, or O-6-methylguanine DNA methyltransferase activity, respectively. In some embodiments, the fusion protein contains a sequence of a telomerase, and the fusion protein has telomerase activity. Methods for determining the histone deacetylase, histone acetyltransferase, O-6-methylguanine DNA methyltransferase, or telomerase activity are known in the art.

In some embodiments, the fusion protein contains a sequence of an oncogene.

In some embodiments, the cell is irradiated for a period of at least 1 minute (e.g., at least 5, 10, 15, 20, 30, 40, 50, or 60 minutes). In some embodiments, the cell is illuminated for a maximum of 15, 20, 25, 30, 35, 40, 45, 50, 55, or 60 minutes. In some embodiments, the cell is illuminated using any of the light sources described herein (e.g., a hand-held light source). In some embodiments, the contacting and the irradiating occur within 24 hours of each other (e.g., within 20, 16, 12, 10, 8, 6, 4, 3, 2, or 1 hour of each other).

In some embodiments of all of these methods, the composition contains DMNPE- conjugated 4-hydroxycyclofen and the cell is irradiated with 350 nm to 410 nm light.

In some embodiments of all of these methods, the cell is irradiated with light of between 700 nm and 800 nm, between 700 nm and 900 nm, between 650 nm and 850 nm, between 500 nm and 800 nm, or between 600 nm and 900 nm.

Methods of Inducing Recombination

Also provided are methods of optically inducing recombination in a eukaryotic (e.g., mammalian, plant, yeast, nematode, parasite, or reptile) cell. These methods include:

providing a eukatyotic (e.g., mammalian, plant, yeast, nematode, parasite, or reptile) cell that contains (i) a nucleic acid encoding a fusion protein containing a sequence of a recombinase and a sequence of a human estrogen receptor ligand binding domain, where the fusion protein has recombinase activity, and (ii) a recombinase recognition sequence that is specifically recognized by the fusion protein, where both the nucleic acid encoding the fusion protein and the recombinase recognition sequence are integrated into a chromosome within the nucleus of the cell; contacting the cell with any of the compositions described herein; and irradiating the cell with a wavelength of light between 200 nm to 900 nm (e.g., between 350 nm to 410 nm, between 200 nm and 700 nm, and between 700 nm and 900 nm) for a period of time sufficient to stimulate release of tamoxifen or a tamoxifen derivative from the composition, where the tamoxifen or tamoxifen derivative stimulates the nuclear translocation of the fusion protein and the fusion protein stimulates recombination at the recombinase recognition sequence. In some embodiments, the cell is irradiated with light between 700 nm and 800 nm, between 700 nm and 900 nm, between 650 nm and 850 nm, between 500 nm and 800 nm, or between 600 nm and 900 nm.

In some embodiments, the nucleic acid encodes a fusion protein containing a sequence of any of the recombinases described herein (e.g., a Cre recombinase). As is known in the art, each recombinase recognizes a unique recombinase recognition sequence. For example, Cre recombinase recognizes a 34-base pair loxP recombinase recognition sequence.

In some embodiments, the nucleic acid encoding the fusion protein is operably linked to one or more promoter or enhancer sequences. In some embodiments, the nucleic acid is operatively linked to a inducible promoter (e.g., any of the inducible promoters described herein or known in the art) and the cell is further contacted with a chemical inducing agent (e.g., any of the chemical inducing agents described herein or known in the art) (e.g., prior to contacting with the caged tamoxifen or caged tamoxifen derivative, prior to contacting with the caged tamoxifen or caged tamoxifen derivative and prior to irradiation, or after contacting with the caged tamoxifen or caged tamoxifen derivative and after irradiation). In some embodiments, the nucleic acid encoding the fusion protein is operatively linked to a tissue- specific promoter (e.g., any of the tissue-specific promoters described herein or known in the art). In some embodiments, the nucleic acid encoding the fusion protein is operatively linked to a ubiquitous promoter (e.g., any of the ubiquitous promoters described herein or known in the art).

In some embodiments, the nucleic acid encoding the fusion protein and the recombinase recognition sequence are located on different chromosomes in the nucleus of the cell. In some embodiments, the recombination results in a decrease in the expression of a transgene located between two recombinase recognition sequences in the chromosome. In some embodiments, the recombination results in the replacement of a sequence between two recombinase recognition sequences with a new transgenic sequence. In some embodiments, the recombination results in the increase in the proximity of a promoter or enhancer sequence to a transgene, wherein the recombination results in increased expression of the transgene. In some embodiments, the recombination results in the increase in the proximity of a repressor sequence or heterochromatin to a transgene, wherein the recombination results in decreased expression of the transgene.

In some embodiments, the removal of a sequence present between two recombinase recognition sequences results in an increase in the expression of a proximal transgene or proximal homologous gene. In some embodiments, removal of a sequence between two recombinase recognition sequences results in a decrease in the expression of a proximal transgene or a proximal homologous gene.

In some embodiments, the eukaryotic (e.g., mammalian, plant, yeast, nematode, parasite, or reptile) cell is present in vitro or ex vivo. In some embodiments, the eukaryotic (e.g., mammalian) cell is an epithelial cell, a lung cell, a kidney cell, an endothelial cell, a muscle cell, an adipose cell, a bone cell, a cartilage cell, or a neuron. In some embodiments, the eukaryotic (e.g., mammalian) cell is an undifferentiated cell or a stem cell (e.g., an embryonic stem cell). In some embodiments, the cell is implanted into a mammal following the contacting with the caged tamoxifen or caged tamoxifen derivative molecule and irradiation.

In some embodiments, the cell is present in a mammal (e.g., a mouse or rat). In some embodiments, the cell is present in the breast tissue, skin, kidney, lung, colon, liver, pancreas, stomach, intestine, colon, muscle, mammary gland, ovary, testes, prostate, brain, spinal cord, peripheral nerve, and heart. In some embodiments, the mammal is a child. In some embodiments, the mammal is an adult. In some embodiments, the mammal is a female. In some embodiments, the mammal is a male. In some embodiments, the mammal is an embryo or blastocyst.

In some embodiments, the composition is locally administered to a tissue containing the cell. In some embodiments, the composition is systemically administered (e.g., intravenous, intaarterial, intramuscular, intraperitoneal, subcutaneous, oral, transdermal, ocular, nasal, or intrathecal administration). In some embodiments, more than one dose of the composition is administered to the mammal before the cell is irradiated. In some embodiments, the composition is systemically administered and a specific target tissue is irradiated. In some embodiments, the composition is locally administered to a target tissue and the target tissue is irradiated. In some embodiments, a mammal is administered a dose of between 1 mg to 500 mg of the composition (e.g., between 1 mg to 400 mg, between 1 mg to 300 mg, between 1 mg and 250 mg, between 1 mg and 200 mg, between 1 mg and 150 mg, between 1 mg and 100 mg, between 1 mg and 50 mg, between 5 mg and 50 mg, and between 5 mg and 40 mg).

In some embodiments, the cell is irradiated for a period of at least 1 minute (e.g., at least 5, 10, 15, 20, 30, 40, 50, or 60 minutes). In some embodiments, the cell is irradiated for a maximum of 15, 20, 25, 30, 35, 40, 45, 50, 55, or 60 minutes. In some embodiments, the cell is irradiated using any of the light sources described herein (e.g., a hand-held light source). In some embodiments, the cell is irradiated using an endoscopic or orthoscopic procedure. In some embodiments, the cell is irradiated using a two-photon light source. In some embodiments, the contacting and the irradiating occur within 24 hours of each other (e.g., within 20, 16, 12, 10, 8, 6, 4, 3, 2, or 1 hour of each other).

Methods of Treatment of Breast Cancer

Also provided are methods of treating a breast cancer in a mammal (e.g., human) that include administering a therapeutically effective amount of a composition containing a caged tamoxifen or a caged tamoxifen derivative (e.g., any of the caged tamoxifen or caged tamoxifen derivative molecules described herein), and irradiating a mammary tissue with light of between 200 nm to 900 nm (e.g., between 350 nm to 410 nm, between 200 nm and 700 nm, and between 700 nm and 900 nm), wherein the irradiating results in the release of tamoxifen or a tamoxifen derivative in the mammary tissue of the subject.

In some embodiments the composition contains

In some embodiments, the composition is formulated for sustained-release (e.g., formulated in a biodegradable polymer or a nanoparticle). In some embodiments, the composition is administered locally to the mammary tissue of the subject (e.g., local intraglandular, periglandular, subcutaneous, interductal, transdermal, or intramuscular administration). In some embodiments, the composition is administered systemically (e.g., oral, intravenous, intaarterial, intraperitoneal, intramuscular, or subcutaneous administration). In some embodiments, the composition is formulated for oral, intraglandular, periglandular, subcutaneous, interductal, intramuscular, intraperitoneal, intramuscular, intraarterial, transdermal, or intravenous administration).

In some embodiments, the subject is a female. In some embodiments, the subject is a male. In some embodiments, the subject is a child. In some embodiments, the subject is an adult (e.g., at least 18, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100 years old). In some embodiments, the subject has been diagnosed as having breast cancer. In some embodiments, the subject has been resistant to other breast cancer therapeutics.

A subject can be identified as having breast cancer by the detection or observation of one of more the following symptoms in a subject: breast lump or thickening, bloody discharge from a nipple, change in the size or shape of breast, changes to the skin over the breast, inverted nipple, peeling, flaking, or scaling of a nipple or breast skin, redness or pitting of the skin over the breast, mutations in the Her2/neu receptor, and mutations in BRCA1 or BRCA2. A subject can be diagnosed as having breast cancer by a medical professional (e.g., a physician, a nurse, a nurse's assistant, a physician's assistant, or a laboratory technician). The efficacy of a treatment of a breast cancer can be detected by a decrease in the size of a breast cancer tumor, a decrease in the spread of the breast cancer in the mammary tissue of the subject, a decrease in the rate of metastasis of breast cancer in the subject (e.g., as compared to a subject not receiving a treatment or receiving a different treatment for breast cancer), a decrease in the rate of growth of a breast cancer tumor in a subject, and a decrease in one or more physical symptoms of breast cancer (e.g., a decrease in one or more of the physical symptoms listed above).

In some embodiments, the subject is administered a dose of between 1 mg to 500 mg of any of the compositions described herein (e.g., between 1 mg to 400 mg, between 1 mg to 300 mg, between 1 mg and 250 mg, between 1 mg and 200 mg, between 1 mg and 150 mg, between 1 mg and 100 mg, between 1 mg and 50 mg, between 5 mg and 50 mg, and between 5 mg and 40 mg). The amount of the composition administered will depend on whether the composition is administered locally or systemically. A skilled artisan can further determine the appropriate dosage depending, for example, on the following factors: whether the administration is local or systemic, the age of the subject, the severity or stage of the disease, the other therapies administered to the subject, the subject's mass, the subject's sex, and the subject's responsiveness to other breast cancer therapeutics. In some embodiments, the subject is administered more than one dose of the composition. In some embodiments, the subject is administered a dose of the composition at least once a month (e.g., at least twice a month, at least three times a month, at least four times a month, at least once a week, at least twice a week, three times a week, once a day, or twice a day). In some embodiments, the mammary tissue of the subject is irradiated within 24 hours (e.g., within 20, 16, 12, 10, 8, 6, 4, 2, or 1 hour) of the administration of the composition. In some embodiments, the mammary tissue of the subject is irradiated within 30 minutes (e.g., within 20 minutes, 15 minutes, 10 minutes, or 5 minutes) of the

administration of the composition.

In some embodiments, the mammary tissue is irradiated for a period of at least 1 minute (e.g., at least 5, 10, 15, 20, 30, 40, 50, or 60 minutes). In some embodiments, the mammary tissue is irradiated for a maximum of 15, 20, 25, 30, 35, 40, 45, 50, 55, or 60 minutes. In some embodiments, the mammary tissue is irradiated using any of the light sources described herein (e.g., a hand-held light source). In some embodiments, the mammary tissue is irradiated using two-photon light source.

In some embodiments, serial rounds of contacting and irradiating can be performed in the subject (e.g., at least two rounds of contacting/irradiating). In some embodiments, the rounds of contacting/irradiating can be performed periodically (e.g., at least once a week, at least a month, at least once every two months, at least once every three months) in the subject over an extended period of time (e.g., a period of at least 2 weeks, at least one month, at least two months, at least six months, at least one year, and at least two years).

In some embodiments, the administering and irradiating are performed by a health care professional (e.g., a nurse, a nurse's assistant, a physician, a physician's assistant, or a laboratory technician). In some embodiments, the administering and irradiating are performed by the subject.

In some embodiments, the subject is administered one or more additional breast cancer therapeutics. In some embodiments, the one or more additional breast cancer therapeutics are selected from the group consisting of: cyclophosphamide, methotrexate, 5- fluorouracil, doxorubicin, paclitaxel, doxorubicin, epirubicin, trastuzumab, lapatinib, bevacizumab, abraxane, pamidronate, anastrozole, exemastane, fulvestrant, letrozole, gemcitabine, pegfilgrastim, filgrastin, doxetaxel, capecitabine, goserelin, zoledronic acid, and ixabepilone. In some embodiments, the compositions contain a caged tamoxifen or caged tamoxifen derivative molecule (e.g., any of the caged tamoxifen or caged tamoxifen derivative molecules described herein) and one or more additional breast cancer therapeutics (e.g., any of the additional breast cancer therapeutics described herein).

The invention is further described in the following example, which does not limit the scope of the invention described in the claims.

EXAMPLE

Example 1. Sythesis and Use of Caged 4-OHC to Achieve Precise Genetic Engineering Control in Mice

In order to achieve cell-specific gene activation, a caged tamoxifen derivative molecule was synthesized and tested in a series of in vitro and in vivo photoactivation experiments to determine whether it could reliably induce efficient light-dependent Cre- mediated recombination in mice. The methods and materials used in these experiments are described below.

Materials and Methods

Reagents and Instrument

Unless otherwise stated, all the reagents for the synthesis of caged 4-OHC were obtained from Sigma-Aldrich (St. Louis, Missouri, USA) and used as received. l H NMR spectra were recorded on a Varian 400 MHz spectrometer. High performance liquid chromatography-mass spectrometry (HPLC-MS) analysis was performed on a Waters (Milford, MA) LC-MS system. In the LC-MS system, electrospray ionization (ESI) was used to obtain mass spectrometry. A Waters XTerra C18 5-μιη column was used for HPLC-MS analysis (eluents: 0.1% trifluoroacetic acid (v/v) in water and acetonitrile; gradient: 0-9.5 min, 5-100% B; 9.5-10.0 min 100% B). The chromatograms were processed using

MassLynx software (from Waters). UV-Vis spectra were recorded in a TECAN microplate reader. A 6W hand-held UV lamp (UVP, LLC) was used for uncaging the caged 4-OHC both in vitro and in vivo. Mice

Homozygous Rosa26CreER (Ventura et al, Nature 445:661-665, 2007), mT/mG (Muzumdar et al, Genesis 45:593-605, 2007), and R26R (Soriano et al, Nat. Genetics 21 :70- 71, 1999) mice in C57BL/6 background were obtained from The Jackson Laboratory (Stock Numbers: 8463, 7676 and 3474, respectively). Heterozygous Rosa26CreER ;mT/mG and Rosa26CreER T2 ;R26R mice were generated by crossing the homozygous mice.

Synthesis of Caged 4-OHC

The DMNPE photoactivatable caging group and 4-OHC were synthesized as described (Sinha et al, Chembiochem 11 :653-663, 2010; Dyer et al., J. Org. Chem. 64:7988- 7995, 1999). DMNPE was conjugated to 4-OHC under Mitsonobu coupling conditions. Briefly, in a 25-mL round bottom flask, DMNPE (0.014 g, 0.063 mmol), 4-OHC (0.020 g, 0.057 mmol), and triphenyl phosphine (PPh 3 , 0.016 g, 0.063 mmol) were mixed together in 0.5 mL of tetrahydrofuran (THF) under an argon atmosphere. After stirring the solution at room temperature ( T) for -5 min, diisopropyl azodicarboxylate (DIAD, 0.012 ml, 0.063 mmol) was added drop-wise to the reaction mixture. The reaction mixture was allowed to stir at RT for ~ 2.5 h. The crude product was directly charged to a S1O2 column for purification (eluent: 100% dichloromethane to 10% methanol in dichloromethane v/v). Caged 4-OHC was isolated as a yellow solid. Yield = 31%. ¾ NMR (400 MHz, CDC1 3 ): 7.65 (s, 1H), 7.20 (s, 1H), 6.93 (m, 4H), 6.79 (d, 2 J= 8.8 Hz, 2H), 6.67 (d, 2 J= 8.8 Hz, 2H), 6.10 (q, 4 J= 6.13 Hz, 1H), 4.03 (t, 3 J= 5.8 Hz, 2H), 3.94 (s, 3H), 3.89 (s, 3H), 2.72 (t, 3 J= 5.8 Hz, 2H), 2.35 (s, 6H), 2.18 (m, 4H), 1.67 (d, 2 J= 6 Hz, 3H), 1.56 (m, 6H). MS (electrospray ionization mass spectrometry: ESI-MS) calculated: 560.29, found: 561.40 [M+H] + .

UV-Vis and HPLC-MS Characterization of the Photocleavage of Caged 4-OHC A 0.25 mM solution of caged 4-OHC in 1 : 1 (v/v) water: acetonitrile was used for the UV-Vis spectroscopic characterization of the photocleavage reaction. The solution of the caged 4-OHC was placed in a 96-well black clear bottom microplate. The solution was then irradiated at -365 nm using a hand-held UV lamp. After light exposure, UV-Vis spectra of the solution was recorded in a TECAN microplate reader. A time course of the

photocleavage reaction was monitored by exposing the caged 4-OHC solution to light for different durations, and subsequently recording the UV-Vis spectra of the solution.

A 2.0 mM solution of caged 4-OHC in 1 : 1 (v/v) water: acetonitrile was used for the HPLC-MS study. The solution of the caged 4-OHC was placed in a glass vial and irradiated at -365 nm using a hand-held UV lamp. Aliquots were taken at different time intervals and injected to the HPLC-MS machine for analysis. Prism 5 (GraphPad, La Jolla, CA) for Mac was used to plot the data. MEF Isolation and Photoactivation Procedure

Mouse embryonic fibroblasts (MEFs) were isolated as described (Sharpless et al, Mol Cell 8: 1187-1 196, 2001) and grown in DMEM with 10% FBS. To shed UV light on the cells, the cells were first grown in 60-mm dish overnight to become nearly confluent. The next day, the medium was replaced with medium containing caged 4-OHC at 5 μΜ and incubated for 30 minutes. The cells were washed twice quickly with warm PBS and covered with fresh medium. The dish was placed on the UV emission surface of a handheld 6W long- wavelength UV lamp (UVP, LLC), and UV light was kept on for a designated period of time. The cells were put back into the incubator to culture for 48-72 h before live imaging or flow cytometric analysis.

Mammary 3D Culture and Photoactivation Procedure.

Mouse mammary epithelial cells (MEFs) were isolated from 6-8 week old female Rosa26CreER T2 ;mT/mG mice as previously described (Tiede et al, PLoS One 4:e8035, 2009). Briefly, mammary glands were excised, minced using scalpels, and digested for 1 hour in 300 U/mL type 1A collagenase (Sigma) and lOOU/mL hyaluronidase (Sigma). The cells were then treated with 0.25% trypsin/EDTA, dispase (Invitrogen)/DNase (Sigma), and ACK lysing buffer (Invitrogen) in succession. Between each treatment, cells were rinsed in MEGM (1 : 1 DMEM:F12 Ham supplemented with 5 mg/mL insulin, 500 ng/niL

hydrocortisone, 10 ng/niL EGF, 20 ng/mL cholera toxin, 5% bovine calf serum, and IX penicillin/streptomycin). Afterwards, cells were filtered twice through 40-mm nylon cell strainers and seeded in 35 -mm dishes that contained a layer of Growth Factor Reduced Matrigel (BD Biosciences) measuring approximately 1-2 mm thickness. Acini usually formed in 4-8 days. During photoactivation, the acini were incubated with MEGM containing 5 μΜ caged 4-OHC for 1 hour. The cells were washed twice quickly with warm PBS and covered with fresh medium. The dish was placed on the UV emission surface of a hand-held 6W long-wavelength UV lamp (UVP, LLC, exposure time: 1 minute) or above the 60X objective of an inverted epifluorescent microscope equipped with a standard DAPI filter set. The cells were returned to the incubator to culture for >48h before live-cell imaging using an upright Zeiss 710 laser scanning confocal microscope equipped with 20x and 40x water immersion objectives. Photoactivation Procedure in Mice

Female mice of 6-8 weeks old were clean shaven on the dorsal and ventral sides. The caged 4-OHC was dissolved in 20% Solutol for in vivo delivery. The vehicle or 1 mg caged 4-OHC in vehicle was injected intraperitoneally. One hour later, the mice were anesthetized with isoflurane and exposed to UV light from the hand-held 6W long-wavelength UV lamp (UVP, LLC) for 15 minutes. Alternatively, for mammary tissue illumination, the right inguinal (#4) mammary fat pad was exposed by creating a small skin flap and illumination with UV light for 15 minutes. For enhanced photoconversion, this procedure was repeated four times. On the seventh day, the mice were imaged with Olympus OV-110

epifluorescence imager (Thurber et al, PLoS One 4:e8053, 2009) to detect fluorescent signals emitted from the skin on the dorsal and ventral sides. Alternatively, the left and right mammary glands were dissected and immediately imaged using the intravital laser scanning microscope IV- 110 (Kelly et al, PLoS Med. 5:e85, 2008). Results

A recently developed double-fluorescent Cre reporter mouse, the mT/mG strain (Muzumdar, Genesis 45:593, 2007) was used to design a biological system that can faithfully report on the induced activity of CreER. This mouse model expresses tdTomato prior to and EGFP following Cre-mediated recombination ubiquitously in tissues. The homozygous mT/mG mouse was crossed to the homozygous Rosa26CreER strain (Ventura et al, Nature 445:661, 2007), and the progeny, Rosa26CreER n ;mT/mG, were heterozygous for both alleles. The photoinduced activity of caged tamoxifen and caged tamoxifen derivative molecules can be assessed by illuminating the cells and tissues from these mice and looking for EGFP-expressed cells (Figure 1).

In these experiments, a 4-hydroxytamoxifen (4-OHT) analogue, 4-hydroxycyclofen (4-

OHC), was used as a small molecule agonist of the ER component of the fusion protein. Although 4-OHT and 4-OHC have similar binding affinity to the ER, 4-OHC is preferred over 4-OHT in view of its synthetic accessibility and better photostability (Zinha et al, Zebrafish 7: 199, 2010). As shown in Figure 2, 4-OHC was caged by attaching a photolabile l-(4,5-dimethoxy-2-nitrophenyl)ethyl (DMNPE) moiety to the free hydroxy group of 4-OHC using the Mitsonobu reaction (Zinha et al, Zebrafish 7: 199, 2010). Under ambient light, the DMNPE caging group is stable in physiological conditions. However, exposure to long wavelength UV irradiation (~ 350-410 nm with a peak at 365 nm) leads to photo lytic cleavage, releasing 4-OHC (Figure 3). The photocleavage reaction of the caged 4-OHC was monitored by UV-Vis spectroscopy. A change in the UV-Vis absorption spectrum was observed when a solution of caged 4-OHC was exposed to a hand-held 365 nm UV lamp. This change was typical of the breakage of the DMNPE caging group (Figure 4). The photochemical reaction was complete within 10 min of exposure (Figure 5). High performance liquid chromatography-mass spectrometry (HPLC-MS) verified the chemical identity of the photoreleased products and also confirmed quantitative, unidirectional conversion to 4-OHC (Figure 6). Overall, these characterizations indicate that the caged 4- OHC undergoes efficient photocleavage at 365 nm UV light and releases 4-OHC.

Mouse embryonic fibroblasts (MEFs) isolated from the Rosa26CreER ;mT/mG mice in cell culture were used to test the caged 4-OHC activity. The Rosa26CreER ;mT/mG MEFs were treated with either 4-OHC or caged 4-OHC and illuminated at 365 nm. As expected, photocleavage of the caged 4-OHC induced EGFP expression in a stringent fashion (Figures 7 and 8). To further test the caged 4-OHC, another reporter mouse was generated

T2 T2

(Rosa26CreER ;R26R mice). The Rosa26CreER ;R26R mice were generated by crossing homozygous Rosa26CreER mice with homozygous Rosa26-loxP-STOP-loxP-lacZ mice (experimental system shown in Figure 9). Similar results were observed in the

Rosa26CreER ;R26R MEFs (Figure 10). No significant phototoxicity or cell viability changes due to the UV irradiation was observed in these experiments (energy density 1.6 mW/cm 2 , photon energy 3.4 eV, number of photons per second per cm 2 2xl0 15 , up to 3 min exposure time), consistent with other reports (Young et al, Org. Biomol. Chem. 5:999, 2007).

While a convenient system, 2D-cell culture cannot manifest all the biological responses of cells to external perturbations in a 3D-environment. Additional tests were performed in mammary acinus culture to determine whether caged 4-OHC would enable light-dependent Cre recombination in this well-established organoid model. Mammary epithelial cells from Rosa26CreER ;mT/mG mice were isolated and overlaid on a basement membrane to allow polarized acinar structure development. The formed acini were subjected to caged 4-OHC treatment with or without subsequent brief UV illumination by the UV lamp (energy density 1.6 mW/cm 2 , photon energy 3.4 eV, number of photons per second per cm 2 2xl0 15 , 1 min exposure time) (Figure 1 1) or the 60X objective of an inverted fluorescent microscope equipped with a standard DAPI filter set (Figure 12). Similar to the 2D-culture results, the caged 4-OHC allowed very tight control of EGFP expression in response to photoactivation in the mammary acini experimental model. Additional experiments were performed to determine whether caged 4-OHC is able to induce gene activation in vivo in mice upon photoactivation. These experiments focused on two organs: skin and mammary glands. A custom-built broad illumination method was used to perform this in vivo testing. In a first set of experiments, EGFP/tdTomato expression at the whole mouse level was assessed using the Olympus OV-110 epifluorescence imager. Very low green autofluorescence was detected in Rosa26CreER T2 ;mT/mG mice when treated with vehicle control and irradiated with 365 nm UV, and strong EGFP signal was detected when treated with 4-OHC (Figure 13). In a second experiment, Rosa26CreER ;mT/mG mice were injected intraperitoneally with caged 4-OHC and subjected to UV illumination only on the ventral (but not dorsal) skin. Resultant EGFP signal was observed on the ventral skin but not on the dorsal skin (Figure 14) with an average 2.5-fold increase in fluorescence intensity. Because the increase of the EGFP signal was concomitant with the decrease of the tdTomato signal, EGFP/tdTomato ratios were also calculated in Figure 14 for both ventral and dorsal skin.

A set of additional experiments was performed to determine whether caged 4-OHC could be used to induce CreER activity in the mammary glands of the female

Rosa26CreER ;mT/mG mice following light exposure. The mice were injected with vehicle or caged 4-OHC, and only the right mammary gland was exposed to the 365 nm light, whereas the left was not (Figure 15). Seven days later, the right and left mammary glands were resected for ex vivo imaging at a high spatial resolution using the Olympus Intravital Laser Scanning Microscope IV- 110. The data show that 365 nm UV illumination of the mammary gland alone did not cause noticeable green autofluorescence increase or tissue morphological changes (Figure 16). However, when caged 4-OHC was injected, the right, but not the left, mammary gland showed strong EGFP induction (Figure 17). Taken together, the skin and mammary gland data clearly establish that the caged 4-OHC displayed superior in vivo inducibility by light and limited diffusion after uncaging to affect other organs.

An additional set of experiments were performed to test the ability of Caged

Molecules I, II, and III (shown in Schematic #5) to induce nuclear translocation of a ER fusion protein in a cell following light exposure. Mouse embryonic fibroblasts from Rosa26- CreER n ; Lox-STOP-Lox-lacZ embryos were treated with 5 μΜ 4-OHC (positive control; lower left panel), treat Caged Molecule I ("Compound I") with or without 365 nm UV light exposure (top right and top center panels, respectively), Caged Molecule II ("Compound II") with or without 365 nm UV light exposure (middle right and middle center panels, respectively), or Caged Molecule III ("Compound III") with or without 365 UV light exposure (bottom right and bottom left panels, respectively). The data show that irradiation of Caged Molecules I, II, and III resulted in an increase in the nuclear transport of the ER fusion protein (a CreER fusion protein) in the cells (Figure 18).

In sum, the data show that the presently provided caged tamoxifen derivative molecules can efficiently regulate CreER-mediated recombination in a light-dependent manner in mice. One major advantage of using caged tamoxifen and caged tamoxifen derivative molecules over other methods of making Cre activity photo-regulatable is that one can seamlessly integrate the light into numerous existing CreER models to achieve an additional level of stringent control, i.e., regional- and cell-specific control of gene expression. For example, the villin-CreER T2 mouse allows efficient target gene

recombination throughout the entire digestive epithelium in response to systemic tamoxifen treatment (El Marjou et al, Genesis 39: 186-193, 2004), and by restricting light activation of caged tamoxifen or caged tamoxifen derivative molecules to the colon, this mouse strain may become an excellent driver for spatiotemporal modeling of colorectal cancer in mice.

Moreover, the application of this optochemogenetic (OCG) switch is not confined to CreER; as described further herein, it can provide photoregulation of a spectrum of ER- fusion proteins. These ER fusion proteins would be subject to tamoxifen- or tamoxifen derivative- dependent control of nuclear localization and protein activity in the nucleus. For example, such a fusion protein can be a telomerase-ER fusion protein (Jaskelioff et al., Nature 469: 102-106, 201 1). The OCG switch approach can use used in broad applications, especially in tumor and developmental biology, where localized and pattern-specific gene manipulation is of central importance to address many outstanding questions. OTHER EMBODIMENTS

It is to be understood that while the invention has been described in conjunction with the detailed description thereof, the foregoing description is intended to illustrate and not limit the scope of the invention, which is defined by the scope of the appended claims. Other aspects, advantages, and modifications are within the scope of the following claims.