TECHNICAL FIELD

The present invention relates to the production of a novel human protein, minactivin, by recombinant DNA technology, the characterization of the DNA sequence of the gene, and the expression and purification of large quantities of biologically active minactivin from a recombinant host. It also relates to the purification of biologically active native minactivin, as well as peptides derived from minactivin and their amino acid sequences.

BACKGROUND ART

Minactivin (PAI-2) is a naturally occurring inactivator of urokinase-type plasminogen activators. This type of plasminogen activator is found in abnormally high levels in many major human carcinomas, most notably lung, colon, breast and prostate. Plasminogen activators are serine proteases which are thought to mediate the proteolytic cascade involved in cellular translocation, migration and invasion. As such, they appear to be associated with tissue destruction and remodelling, and have been implicated in tumor growth and metastasis. They may also have a role in inflammatory reactions.

Plasminogen activators are generally found to be of two types: 1 ⁾ urokinase - type and 2) tissue - type. Tissue-type plasminogen activator is mainly found in the blood and blood vessel walls and where it is responsible for activating the fibrinolytic defence system against thrombosis. Urokinase-type plasminogen activators do not appear to play a role in normal thro bolytic processes but have been implicated in those pathological events associated with invasion and tissue destruction, in particular, tumor metastasis and inflammatory reactions.

Several inhibitors specific for plasminogen activators have been described which include one isolated from placenta (Hol berg, L. Biochim. Biophys. Acta 544, 128-137 (1978)) and another (PAI-1) which is produced in cultured vascular endothelial cells (Van Mourik, J.A., Lawrence, D.A., Loskutoff, D.J., 3. Biol. Che . 259, 14914-14921 (1984)). Minactivin was found to be produced by blood monocytes and U937 cells and appears to be immunologically related to the placental inhibitor. The relationship between these various inhibitors is presently unknown.

As is the case with most other potent bic ogical1y active proteins, minactivin is produced in very small -i ounts in vivo, and as such, is difficult to purify and characterise oy conventional biochemical approaches. Therefore, as large quantities of purified minactivin are required for further evaluation of its properties and biological efficacy

in clinical applications, it is desirable to produce the protein using recombinant DNA techniques; that is, by cloning the minactivin gene into an alternate host, such as bacteria or animal cells. In order to clone minactivin it is desirable to purify to homogeneity the small amounts that can be so purified of naturally occurring minactivin in order to produce antibodies, amino acid sequences, peptide fragments and synthetic oligonucleotides derived from said purified minactivin. These reagents are of use in cloning strategies.

ABBREVIATIONS

HPLC - High pressure liquid chromatography

M - relative molecular mass

MW - molecular weight

PMA - 4-phorbol-12-myristate-13-acetate

SDS-PAGE - sodium dodecyl sulfate polyacrylamide gel electrophoresis

TFA - trifluoroacetic acid

HPA - human plasminogen activator bp - base pairs kb - kilobase pairs

PU - Ploug

DESCRIPTION OF INVENTION

In a first embodiment, the invention provides a DNA sequence comprising a first DNA sequence which acts as a coding sequence for amino acid sequences of all, part, analogues, ho ologues, derivatives or combinations thereof of minactivin, a DNA sequence which hybridizes to said first DNA sequence, a DNA sequence related by mutation, including single or multiple base substitutions, deletions, insertions and inversions, to said first DNA sequence or hybridizing sequence or a DNA sequence which on expression codes for all, part, analogues, homologues, derivatives or combinations thereof of a polypeptide which is minactivin or which displays similar immunological or biological activity to minactivin.

A preferred DNA sequence and fragments and derivatives thereof, according to the invention codes for a polypeptide displaying an immunological or biological activity of minactivin.

Such DNA sequences can be prepared _r example from mammalian cells by extracting total DNA therefrom and isc ^' -iting the sequences by standard techniques for preparation of recombinant molecules.

Also within the scope of the invention is a process for selecting a DNA sequence coding for a polypeptide displaying an immunological or

biological activity of minactivin from a group of DNA sequences, which process comprises the step of: determining which of said DNA sequences hybridises to a DNA sequence known to code for a polypeptide displaying said activity.

The selected sequence may be, for example from natural sources, synthetic DNA sequences, DNA sequences from recombinant DNA molecules and DNA sequences which are a combination thereof.

A preferred embodiment of the invention provides a process for the manufacture of a cDNA sequence which acts as a coding sequence for amino acid sequences of minactivin, which process comprises the steps of: stimulating cells to produce minactivin; obtaining RNA from said stimulated cells; isolating mRNA therefrom; and producing said cDNA from said mRNA. Preferably the cells are U937 cells.

The more preferred process for molecular cloning of the cDNA for minactivin and expression of the protein in a recombinant host includes the following methods:

1. induction of a cell line for stimulated minactivin production and expression.

2. isolation of mRNA from the appropriate cell line.

3. ύi vitro translation of the mRNA and i munoprecipitation of the minactivin translation product by complex formation with urokinase.

4. fractionation of mRNA from (2) and identification of the fraction containing minactivin translational activity.

5. construction of cDNA libraries from the mRNA from (2) and (4).

6. cloning of the cDNA libraries from (5) into suitable hosts, for example, E. coli or bacteriophage lambda.

7. identification of clones containing the minactivin gene by: a) hybrid-select translation employing (3); b) hybridization to a chemically synthesized DNA sequence probe, especially a probe comprising a synthetic oligonucleotide probe according to the invention; c) differential hybridization using labelled cDNA synthesized from induced and noninduced mRNA; d) immunological screening of cDNA expression libraries using antibodies directed agains. minactivin or other immunologically related molecules; e) screening of cDNA expression libraries for biological activity using labelled urokinase or urokinase and antibodies to urokinase.

8. extension of the cloned gene by generating cDNA libraries using oligonucleotide primers obtained from partial minactivin gene sequences, especially oligonucleotide sequences disclosed within the scope of the invention.

9. determination of the nucleotide sequence of the minactivin gene

10. expression of the minactivin gene in E. coli and refolding to obtain biologically active product.

11. expression of biologically active recombinant minactivin by cloning into alternate hosts, for example, eukaryotic cells.

12. purification of recombinant minactivin and clinical assessment of its biological properties.

In a second embodiment, the invention provides a recombinant DNA molecule which includes a first DNA sequence comprising a first DNA sequence which acts as a coding sequence for amino acid sequences of all, part, analogues, homologues, derivatives or combinations thereof of minactivin, a DNA sequence which hybridizes to said first DNA sequence, a DNA sequence related by mutation, including single or multiple base substitutions, deletions, insertions and inversions, to said first DNA sequence or hybridizing sequence or a DNA sequence which on expression codes for all, part, analogues, homologues, derivatives or combinations thereof of a polypeptide which is minactivin or which displays similar immunological or biological activity to minactivin.

Preferred recombinant DNA molecules of the invention include an expression control sequence operatively linked to a first DNA sequence comprising a first DNA sequence which acts as a coding sequence for amino acid sequences of all, part, analogues, homologues, derivatives or combinations thereof of minactivin, a DNA sequence which hybridizes to said first DNA sequence, a DNA sequence related by mutation, including single or multiple base substitutions, deletions, insertions and inversions, to said first.DNA sequence or hybridizing sequence or a DNA sequence which on expression codes for all, part, analogues, homologues, derivatives or combinations thereof of a polypeptide which is minactivin or which displays similar immunological or biological activity to minactivin.

A preferred recombinant DNA molecule of the invention is a plasmid which acts as a coding sequence ^or amino acid sequences of minactivin.

A preferred plasmid of th ³ invention has a first DNA sequence coding for a means of controlling expression of the DNA sequence of the invention linked to the DNA sequence of the invention.

The invention also provides a fused gene comprising a portable

promoter, a translation start site, and a gene coding for human minactivin.

Also within the scope of the invention is a process for the manufacture of a recombinant DNA molecule, which process comprises the step of: introducing into a cloning vehicle, a first DNA sequence comprising a first DNA sequence which acts as a coding sequence for amino acid sequences of all, part, analogues, homologues, derivatives or combinations thereof of minactivin, a DNA sequence which hybridizes to said first DNA sequence, a DNA sequence related by mutation, including single or multiple base substitutions, deletions, insertions and inversions, to said first DNA sequence or hybridizing sequence or a DNA sequence which on expression codes for all, part, analogues, homologues, derivatives or combinations thereof of a polypeptide which is minactivin or which displays similar immunological or biological activity to minactivin.

Preferably the process also includes the step of introducing an expression control sequence into the cloning vehicle.

The invention further provides a process for the manufacture of a plasmid which acts as a coding sequence for amino acid sequences of all, part, analogues, homologues, derivatives or combinations thereof of minactivin, which process comprises combining a plasmid with a DNA sequence which acts as a coding sequence for said amino acid sequences, and preferably with an expression control sequence. The DNA sequence is preferably a cDNA sequence.

In a third embodiment, the invention provides a host transformed with at least one recombinant DNA molecule which includes a first DNA sequence comprising a first DNA sequence which acts as a coding sequence for amino acid sequences of all, part, analogues, homologues, derivatives or combinations thereof of minactivin, a DNA sequence which hybridizes to said first DNA sequence, a DNA sequence related by mutation, including single or multiple base substitutions, deletions, insertions and inversions, to said first- DNA sequence or hybridizing sequence or a DNA sequence which on expression codes for all, part, analogues, homologues, derivatives or combinations thereof of a polypeptide which is minactivin or which displays similar immunological or biological activity to minactivin.

Suitable hosts include bacteria, yeasts, other fungi, mice or other animal hosts, plant hosts, insect hosts and other eukaryotic hosts e.g. mammalian, including human tissue cells. Suitable bacteria include E. coli , Pseudomonas species, and Bacillus species.

Especially preferred is a microorganism with the genetic information for the biosynthesis of minactivin.

Also included within the invention is a process for transforming a host, which process comprises the step of: introducing into a host a recombinant DNA molecule which includes a first DNA sequence comprising a first DNA sequence which acts as a coding sequence for amino acid sequences of all, part, analogues, homologues, derivatives or combinations thereof of minactivin, a DNA sequence which hybridizes to said first DNA sequence, a DNA sequence related by mutation, including single or multiple base substitutions, deletions, insertions and inversions, to said first DNA sequence or hybridizing sequence or a DNA sequence which on expression codes for all, part, analogues, homologues, derivatives or combinations thereof of a polypeptide which is minactivin or which displays similar immunological or biological activity to minactivin.

The invention also provides a process for the manufacture of a microorganism with the genetic information for the biosynthesis of all, part, analogues, homologues, derivatives or combinations thereof of minactivin, which process comprises transforming a microorganism with a plasmid or other vector which acts as a coding sequence for amino acid sequences of all, part analogues homologues, derivatives or combinations thereof minactivin.

In a fourth embodiment, the invention provides a process for the preparation of peptides derived from purified minactivin which process comprises purifying minactivin to homogeneity then obtaining amino acid sequences unique to minactivin.

A preferred embodiment of this process comprises: a) Culturing a cell line capable of expressing minactivin; b) harvesting the supernatant; c) concentrating the supernatant; d) dialysing the supernatant, then centrifuging said culture supernatant to remove residual cell debris and

•protein which may have precipitated during dialysis; e) fractionating the culture supernatant chro atographicall and electrophoretically; f ⁾ concentrating the fraction containing minactivin activity; g ⁾ analysing the fraction containing minactivin activity to demonstrate purity; h ⁾ obtaining aminc acid sequences unique to minactivin. In a preferred rorm the process comprises: a ⁾ culturing a minactivin producing culture or cell line; b ⁾ harvesting the culture supernatant and concentrating said culture

supernatant; c) dialysing the culture supernatant, then centrifuging said culture supernatant to remove residual cell debris and protein which may have precipitated during dialysis; d) fractionating the culture supernatant by ion exchange chromatography; e) pooling and concentrating the eluates of highest minactivin specific activity; f) fractionating the pooled, concentrated eluates by gel filtration chromatography; g) concentrating the eluate then isoelectrofocussing said eluate; h) probing fractions isolated from the isoelectrofocussing gel with antibodies reactive with minactivin, to locate the minactivin band; i) concentrating the fraction containing minactivin activity; j) further fractionating the fraction containing minactivin activity by partition chromatography then analysing the purified fraction containing minactivin activity by gel electrophoresis; k) digesting the purified minactivin and separating the resulting peptides by parti ion chromatography.

In a more preferred form the culture is of the human macrophage cell line U937. Preferred culture conditions include culturing in the absence of serum and/or in the presence of a sufficient amount of a substance or substances which will inhibit urokinase production or induce constitutive production of minactivin. A suitable substance for this purpose is dexamethasone which is preferably used at a concentration of IμM. The culture may also be grown in the presence of PMA. A preferred concentration range of PMA in the culture is l-300ng/ml, more preferably 10-30ng/ml .

A preferred volume of harvested culture supernatant is 4-5 litres. The initial concentration step is preferably a 10-fold concentration step. A suitable apparatus for this concentration is an Amicon DC2 Hollow Fibre Dialysis/Concentration unit equipped with a 30000M cut off cartridge.

The dialysis according to step c) is preferably with a dialysate such as 50mM glycine, pH7.8. More preferably the 50mM glycine pH7.8 dialysate should be used at at least equal volume to the volume of the sample being dialysed against said dialysate.

The ion e>:~ ange chromatography according to step d) is preferably performed on a pπenyl-sepharose column, the elution being preferably a step pH elution. More preferably, for the pH step elution, the ionic strength of the supernatant should be adjusted to 2M, especially this may be by the

addition of solid NaCl , then the pH should be adjusted to 5.5 preferably with citric acid. A preferred equilibrant for the phenyl-sepharose column is a solution of 50mM Na citrate pH5.5, 2M NaCl and lmM EDTA. The column may be eluted initially with equilibration buffer, then with 50mM Na citrate pH5.5 containing 0.5M NaCl and lmM EDTA and finally with 50mM glycine pH9.0.

The concentration of the sample according to step g) is preferably performed on an Amicon YM10 membrane, with a final concentrate volume of 3ml. The isoelectrofocussing step is preferably performed on a preparative flatbed gel of Ultrodex containing Ampholines in the pH range 4.5 to 6.0. More preferably the gel is electrofocussed at 10°C for 23 hours, on an LKB Multiphor isoelectrofocussing apparatus. A preferred elutant for proteins from the electrofocussing gel is IM glycine containing lmM EDIA pH9.0, more preferably in a 10ml volume. Suitable antibodies according to step h) include goat anti-placental inhibitor antibodies.

The concentration according to step i) may be performed on an Amicon YM10 membrane.

The partition chromatography according to step j) is preferably HPLC, more preferably performed on a Vydac C-4 reverse phase column using a Waters high pressure liquid chro atograph. The elution gradient is preferably acetonitrile in 0.1% TFA. Gel electrophoresis according to step j) is preferably SDS-PAGE.

Digestion of the purified minactivin, according to step k) is preferably with endoproteinase LysC. Suitable digestion conditions include 3-5μg minactivin with 0.1μg endoproteinase LysC in 20mM Tris-Cl pH8.5, 5M urea, at a volume of 50μl and 22°C for δhours. A suitable form of partition chromatography is reverse phase HPLC, particularly employing a Synchropak RP-P(C-8) column with a gradient of acetonitrile in 0.1% TFA.

In a fifth embodiment the invention provides minactivin in substantially pure form. Preferably said minactivin is purified to homogeneity.

In a sixth embodiment the invention provides purified minactivin when prepared by a process according to the invention.

In a seventh embodiment the invention provides peptides derived from purified mi ⁿ activin and peptides displaying similar immunological or biological ^a ctivity to said peptides.

Preferred peptides according to the invention include peptides of the following sequences:

AQILELPY-GDV-MFLLLP-E... GRANFSGMSE-NDLF... MAE-EVEVYIPQFKLEE-Y... LNIGYIEDLK IPNLLPEG-V

The invention also provides peptides according to the invention when prepared by a process according to the invention.

In an eighth embodiment, the invention provides a microbiologically prepared peptide, all or part of which contains the amino acid sequence of all, part, analogues, homologues, derivatives or combinations thereof minactivin.

A peptide and fragments and derivatives thereof which display an immunological or biological activity of minactivin are also within the scope of the present invention.

The preferred peptide or fragments or derivatives thereof are coded for by a DNA sequence which hybridises to a DNA sequence which acts as a coding sequence for amino acid sequences of minactivin and displays the biological or immunological activity of minactivin, which activity is destroyed by antisera to minactivin.

The invention also provides a process for the manufacture of all, part, analogues, homologues, derivatives or combinations thereof of unglycosylated minactivin, which process comprises the steps of: obtaining the genetic information for the biosynthesis of minactivin using mRNA from cells of monocytic lineage; incorporating the resulting gene into a microorganism; selecting and culturing said microorganism to produce said minactivin; and collecting said minactivin.

The invention further provides a process for the manufacture of a peptide displaying an immunological or biological activity of minactivin, which process comprises the steps of: culturing a host which has been transformed with a recombinant DNA molecule which includes a first DNA sequence comprising a first DNA sequence which acts as a coding sequence for amino acid sequences of all, part, analogues, homologues, derivatives or combinations thereof of minactivin, a DNA sequence which hybridizes to -said first DNA sequence, a DNA sequence related by mutation, including single or multiple base substitutions, deletions, insertions and inver:*ons, to said first DNA sequence or hybridizing sequence or a DNA sequence which on expression codes for all, part, analogues, homologues, derivatives or combinations thereof of a polypeptide which is minactivin or which displays similar immunological or. biological activity to minactivin.

The invention also provides a reagent for locating and defining the boundaries of tumours in histological specimens or vn vivo which reagent comprises suitably labelled minactivin, especially recombinant DNA derived minactivin, or fragments of minactivin and the associated method of locating and defining the boundaries of tumours in histological specimens or j_n vivo which comprises applying or administering suitably labelled minactivin or fragments thereof and subsequently imaging to determine the site of concentration of the label.

The invention further provides a method of inhibiting tumour invasion and treating tumours comprising administering to a patient requiring such treatment a therapeutically effective amount of minactivin, suitably labelled minactivin, fragments of minactivin or labelled fragments of minactivin; a method of treatment of chronic inflammation such as rheumatoid arthritis comprising administering to a patient requiring such treatment a therapeutically effective amount of minactivin or fragments of minactivin; and a method of monitoring chronic inflammation comprising the detection of minactivin in samples of body fluids and tissues using antibodies prepared against minactivin or fragments of minactivin.

Also included within the invention are antibody preparations prepared against minactivin including recombinant minactivin, purified natural minactivin and fragments thereof. The invention also provides therapeutic, diagnostic or prophylactic compositions which comprise minactivin, especially recombinant DNA derived minactivin, fragments of minactivin or antibodies to minactivin or fragments of minactivin and a pharmaceutically acceptable non-toxic carrier or diluent therefor.

The invention further provides synthetic oligonucleotide probes, the sequence of said probes comprising a first nucleotide sequence which on expression codes for the amino acid sequence of a peptide according to the invention, a nucleotide sequence sufficiently related to said first nucleotide sequence to hybridize to said first nucleotide sequence or a DNA sequence related by mutation including single or multiple base insertions, inversions deletions or substitutions to said first nucleotide sequence.

Included within the scope of the invention is a process for the production of said synthetic oligonucleotide probes which process comprises d ^e termining the amino acid sequence of peptide fragments derived from "rified minactivin and synthesizing corresponding oligonucleotides. In a preferred form said synthesis is performed on an Applied Biosystems 380A DNA synthesizer.

The invention provides formulations comprising synthetic

oligonucleotide probes according to the invention.

Preferably said formulations are diagnostic reagents.

The invention also provides a method for the detection of human carcinomas and inflammatory conditions and susceptibility thereto which method comprises using a formulation comprising said synthetic oligonucleotide probe in an assay designed for the detection of DNA coding for minactivin. Deficiency in ability of tissues to produce minactivin may be related to susceptibility to carcinomas and inflammatory conditions. Detected deficiencies may be treated by administration of purified minactivin to the patient, and may also serve as a marker for tissues affected by carcinomas and inflammation.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a plot of minactivin activity illustrating the effect of PMA on minactivin secretion.

Fig. 2 is a gel analysis of a size fractionated minactivin mRNA preparation.

Fig. 3 is an autoradiograph of the immunoprecipitation products following j_n vitro translation of size fractionated mRNA showing minactivin mRNA in the fractions centred around 18S rRNA standard.

Fig. 4 is an autoradiograph of i munoprecipitated translation products showing the specificity of complex formation with urokinase using anti urokinase antibodies.

Fig. 5 is an autoradiograph of immunoprecipitated translation products showing the specificity of complex formation with urokinase using anti placental inhibitor antibodies, (autoradiograph showing identity of results using anti placental inhibitor antibodies with results using anti urokinase antibodies).

Fig. 6 is an autoradiograph showing identification of the minactivin translation product by comparison of immunoprecipitation products in the presence and absence of urokinase under reducing conditions.

Fig. 7 is a representation of a gel showing differentation of urokinase species using the fibrin overlay technique.

Fig. 8 is a Sephacryl S-200 chromatogram showing elution of enriched minactivin activity relative to total protein elution.

Fig. 9 is a plot showing differential elution of minactivin activity from phenyl-boronate agarose under varied elution conditions.

Fig. 10 is a chromatograph showing elution of minactivin activity relative to total protein eluted from a chromofocussing column as a function of pH of elution.

Fig. 11 is a superi position showing minactivin activity over a gel of the protein fractions isolated from an isoelectrofocussing gel to demonstrate protein content versus minactivin activity.

Fig. 12a is an elution profile of an immunoaffinity column showing elution of minactivin activity.

Fig. 12b is a representation of an SDS-PAGE gel of minactivin eluted from the i munoaffinity column and a Western blot of this gel.

Fig. 13 is an autoradiograph of I ¹²⁵ -labelled urokinase on SDS-PAGE showing high and low molecular weight forms and dissociation of high molecular weight form under reducing conditions.

Fig. 14 shows the elution profile of minactivin activity and protein from the step pH elution of the phenyl-sepharose column.

A:elution with 50mM sodium citrate, pH5.5, ImMEDTA, 0.5M sodium chloride.

B:elution with 50mM glycine, pH9.0.

Fig. 15 is a superimposition of minactivin activity over an SDS-PAGE gel of the protein fractions isolated from an isoelectric focussing gel to demonstrate protein content versus minactivin activity.

Fig. 16 is a representation of the fractions from the isoelectric focussing experiment shown in Fig. 15 after Western transfer of the protein onto nitrocellulose and immunological detection of the proteins with anti-placental inhibitor antibodies.

Fig. 17 shows an elution profile of the highly purified minactivin preparation from a Vydac C-4 reverse phase high pressure liquid chromatography run.

Fig. 18 is a representation of an SDS-PAGE showing homogeneous minactivin obtained from peak 5 of the HPLC run shown in Fig. 17.

Fig. 19 shows the elution profile of peptides of minactivin eluted form a Synchropak RP-P (C-8) column high pressure liquid chromatography run.

.Fig. 20 depicts the endonuclease restriction map and DNA sequencing strategy of the clones containing segments of the minactivin gene.

Fig. 21 shows hybrid select translation of minactivin mRNA.

Fig. 22 shows the construction of the plasmid pBTA438 containing the contiguous minactivin gene.

Fig. 23 shows the complete cDNA of the minactivin gene and the deduced amino acid sequence of the minactivin protein. The 5 peptides obtained from the amino acid sequence analysis are underlined.

Fig. 24 shows the construction of minactivin expression vectors pBTA444 and pBTA447.

Fig. 25 shows the SDS polyacryl amide gel electrophoresi s , Western

~c analysis and S pulse labelled protein analysis of minactivin expressed from pBTA444, and pBTA447.

Fig. 26 shows the construction of hybrid protein expression vectors a)pBTA440 and b)pBTA586.

Fig. 27 shows the SDS polyacrylamide gel electrophoresis Western

35 analysis and S pulsed labelled protein analysis of hybrid minactivin proteins expressed from pBTA440 and pBTA586.

Fig. 28 shows the construction of mammalian cloning vectors pBTA587, PBTA588 and pBTA590 containing the minactivin gene.

Fig. 29 is an autoradiograph showing expression of minactivin in mammalian cells following immunoprecipitation in the presence and absence of urokinase.

BEST MODE OF CARRYING OUT THE INVENTION Induction of U937 cell line for enhanced minactivin synthesis.

Minactivin has been found to be produced by induced human monocytes, certain macrophages, and transformed cells of monocytic lineage (refer to international patent application W086/01212). The transformed cell line U937 (ATCC CRL 1593) was found to produce minactivin constitutively in the presence of dexamethasone. The level of minactivin secreted by these cells under serum free conditions was found to be only about 0.06% of the total protein secreted by these cells. It was found that this level could be enhanced by approximately an order of magnitude to 0.4% with the addition of 4-phorbol-12-myristate-13-acetate (PMA). The effect of PMA on minactivin secretion with time followed a biphasic course with an initial lag period of 6 hours, followed by a linear increase in minactivin activity up to 60 hours (Figure 1). No differences were observed by increasing the PMA concentration from lOng/ml to 30ng/ml . Furthermore, it was determined that the phorbol esters were tightly associated with the cells, as radiolabelled PMA could be detected only in small amounts (less than 10%) in the culture supernatants even after 17 hours.

The following examples illustrate preferred embodiments of the invention. They should not be construed as limiting on the scope of the invention. Unless otherwise stated, all parts and percentages are by weight.

EXAMPLE 1 Cell Culture

The human macrophage cell line, U937, was cultured in RPMI 1640 containing 10% foetal calf serum and IμM dexamethasone, either in T175

culture flasks or in a 10 litre Braun fermenter. The cells were maintained at densities of 1-3 x 10 cells/ml. Although minactivin was secreted by the cells during this growth phase, the cells were transferred to serum-free medium to obtain supernatants for minactivin purification. The cells were pelleted, washed once, resuspended in RPMI 1640, containing IμM dexamethasone, and cultured for a period of three days. The level of minactivin secreted by these cells under serum free conditions could be enhanced by approximately an order of magnitude to 0.4% with the addition of PMA.

The cells were then harvested and the supernatants used in the purification scheme which follows.

EXAMPLE 2 Purification of Homogeneous Minactivin a) Concentration of Serum Free Minactivin Supernatants Typically, 4 to 5 litres of culture supernatant was concentrated

10-fold using an Amicon DC2 Hollow Fiber Dialysis/Concentration unit equipped with a 30000 MW cut-off cartridge The concentrate was then dialysed against at least an equal volume of 50mM glycine, pH7.8, to remove all traces of dye. b) Ceπtrifugation of Minactivin Concentrate

The dialysed concentrate was centrifuged in a JA10 rotor at 8000rpm for 30 min at 4°C to pellet residual cell debris and protein that may have precipitated during dialysis. The clarified supernatant is then aliquoted and frozen at -20°C until required for subsequent purification. c ⁾ Pheπyl-Sepharose Chromatography using a Step pH Elution Minactivin was further purified from ten-times concentrated culture supernatant obtained from cells cultured in the absence of PMA by step pH elution using phenyl-sepharose as follows.

The ionic strength of the supernatant (200ml; 12000 units; specific activi.ty 102 units/mg) was adjusted to 2M by the addition of solid NaCl and the pH adjusted to 5.5 with citric acid. This solution was applied to a phenyl-sepharose column (4.4cm x 5.0cm) equilibrated in 50mM Na citrate, pH5.5, 2M NaCl and lmM EDTA and eluted with the same buffer until the baseline absorbance at 280nm (A280) returned to baseline. The column was then eluted with 50mM sodium citrate, pH5.5 containing 0.5M NaCl and lmM EDTA and again the A280 monitored until the absorbance returned to baseline. The minactivin was then eluted from the column with 50mM glycine, pH9.0. Figure 14 shows the elution profile.

The recovery of minactivin by this method was 9553 units which

represents 80% of the units applied to the column. The material of highest specific activity was pooled (6700 units; specific activity 1343 units/mg ⁾ and concentrated to 3ml on an Amicon YM10 membrane. d) Sephacryl S-200 Gel Permeation Chromatography

The pooled, concentrated minactivin was applied to a 2.2cm x 78cm column of Sephacryl S-200 equilibrated with 0.IM sodium borate, pH9.0. Fractions of 5.0ml were collected at a flow rate of 0.46m1/min. Figure 8 shows that minactivin was eluted at the tailing edge of the major protein peak. The fractions containing minactivin activity were pooled (4480 units; specific activity 1355 units/mg) and concentrated to 3ml using a YM10 membrane. Calibration of this column with known M standards indicated that minactivin had an M of 45-48kD. e) Isoelectric Focussing

The concentrated minactivin solution was applied to a preparative flat bed gel of Ultrodex containing Ampholines in the pH range 4.5-6.0 and electrofocussed for 23hrs at 10°C on an LKB Multiphor isoelectric focussing apparatus. Following completion of the run, 30 zones across the length of the gel were scraped out and the protein eluted from each with 10ml of IM glycine containing lmM EDTA, pH9.0. Aliquots of each fraction were assayed for minactivin activity and electrophoresed on 15% SDS-polyacrylamide gels to locate protein. Figure 15 illustrates that a significant amount of protein has been removed from the fractions containing the minactivin activity. Under these conditions minactivin focusses between pH5 and pH5.2 and within this region of the gel 15% of the total activity applied to the gel was recovered.

In fact, in the region of the isoelectric focussing gel containing minactivin activity, only two protein bands are visible (Figure 15). To determine which of these bands is minactivin the protein on an equivalent polyacrylamide gel was transferred onto nitrocellulose and probed with antibodies made in goat to placental inhibitor. Due to similar biological properties it was considered likely that the two proteins would be immunologically related. As shown in Figure 16 the protein band of = 45-48kD specifically cross reacts with the anti-placental inhibitor antibodies suggesting that this protein band is minactivin. Furthermore, this observation is consistent with the M of 45-48kD determined for native minactivin on gel permeation chromatography. f) High Pressure Liquid Chromatography

The fractions from the isoelectric focussing above which contained minactivin activity were concentrated 10-fold on an Amicon YM10

ultrafiltration membrane and further fractionated on a Vydac C-4 reverse phase column using a Waters high pressure liquid chromatograph. The proteins were eluted from the reverse phase column using a gradient of acetonitrile in 0.1% TFA as shown in Figure 17. Each of the absorbance peaks was examined by SDS-PAGE and peak 5 was found to contain pure minactivin (Figure 18).

EXAMPLE 2A

(a) Gel Filtration

Cell free supernatants were processed through steps (a) and (b ⁾ as described in Purification Example 2 of W086/01212, and then through Phenyl-Sepharose using a step pH elution as described in Purification Example 1 of W086/01212. The fractions containing minactivin activity were pooled, concentrated by precipitation with 85% saturated ammonium sulphate and applied to a 2.2cm x 80cm column of Sephacryl S-200 equilibrated in 0.1M sodium borate, pH9.0. Fractions of 3.5 ml were collected at a flow rate of 0.46ml/min. Figure 8 shows that minactivin was eluted at the tailing edge of the major protein peak and had a peak specific activity of 2206 Units/mg representing an overall increase in specific activity of 31 fold. Under these conditions the minactivin behaves as a molecule with a Stokes radius similar to ovalbumin, suggesting a molecular size of 45-49x10 ³ daltons.

(b) Phenyl-Boronate Agarose Chromatography

Cell free supernatants were processed through steps (a) and (b) as described in Purification Example 2 of W086/01212. One ml of the supernatant was made to lO M in MgCl- and the pH then adjusted to pH8.5 with sodium hydroxide. This solution was applied to a column of phenyl-boronate agarose -30 (PBA 30) (0.8cm x 2.5cm) equilibrated in 50mM glycine, pH8.5 containing 10mM MgCl- at 4°C. The column was then washed with 9ml of the above buffer and then serially as follows: a) -TOml of 50mM glycine, pH8.5 containing lOmM EDTA b) 10ml of 50mM glycine, pH8.5 containing lOOmM sorbitol c) 10ml of lOOmM Tris-HCl, pH8.5 d) 10ml of 50mM sodium acetate, pH5.0.

Fractions of 5ml were collected and dialysed against 50mM glycine, pH7.8 overnight at 4°C prior to minactivin activity and protein determinations. The results shown in Figure 9 illustrate that two distinct peaks of activity elute from the column under different conditions. The first peak, eluted with EDTA, contains 35% of the total activity loaded onto the column with an increase in specific activity of 14 fold. The

second peak represents 32% of the i ni tial acti vi ty wi th a 4.4 fol d i ncrease i n specifi c activi ty.

(c) Chromofocussing

Cell free supernatants were processed through steps ⁽ a ⁾ and ⁽ b ⁾ as described in Purification Example 2 of W086/01212. Four ml of this supernatant was dialysed against 25mM imidazole-HCl buffer, pH7.4 and then applied to a PBE 94 chromofocussing column (1cm x 27cm) equilibrated in the above buffer. A linear pH gradient was then established by applying 200ml of polybuffer pH4.0 and 4ml fractions were collected into 4ml aliquots of IM Tris.HCl, pH7.5. Every 10 fractions were pooled, concentrated and washed on a centricon 30 and assayed for minactivin activity and protein concentration. Figure 10 shows that the majority of the activity eluted near pH5. The overall recovery of activity was 82% and there was a 2 fold increase in specific activity.

(d) Isoelectric focussing

Cell free supernatants were processed through steps (a ⁾ and ⁽ b ⁾ as described in Purification Example 2 of WO86/01212, and then through phenyl Sepharose using a step pH elution as described in Purification Example 1 of WO86/01212. The fractions containing minactivin activity were pooled, concentrated by precipitation with 85% saturated ammonium sulphate and dialysed overnight against 50mM glycine pH9.0. This solution was applied to a preparative flat bed gel of Ultrodex containing Ampholines in the pH range 4.5-6.0 and electrofocussed for 23hrs at 10°C on an LKB Multiphor isoelectric focussing apparatus. Following completion of the run, 30 zones across the length of the gel were scraped out and the protein eluted from each with 10ml of IM ^" gϊ c ne ^~ containing lmM EDTA, pH9.0. Aliquots of each fraction were assayed for minactivin activity and electrophoresed on 15% SDS-polyacrylamide gels to locate protein. Figure 11 illustrates that a significant amount of protein has been removed from the fractions contain-ing the minactivin activity. Under these conditions minactivin focusses between pH5 and pH5.2 and within this region of the gel 39% of the total activity applied to the gel was recovered.

(e ⁾ Immunoaffinity Chromatography

Cell free supernatants were processed as through Purification Example 1. A 4.6ml aliquot of this minactivin preparation (2300 Units, 2.25mg, specific activity 1020U/mg) was made 0.05M in sodium phosphate, 0.5 in NaCl, 0.01% in TritonX-100, 0.1% in sodium azide, lmM in EDTA and the pH adjusted to 7.5. This solution was diluted to 15ml with the above buffer and added to 15ml of Sepharose 4B to which lO g of anti-placental inhibitor

antibody had been chemically coupled. The slurry was shaken overnight at

4°C and then poured into 2.5cm x 3.1cm column. Unbound protein was drained from the column and the column washed with buffer until the absorbance at 280nm returned to baseline. The column was then eluted with

3M KSCN containing lOmM Tris. HCl, pH8.0. The elution profile is shown in

Figure 12. The fractions eluted by the KSCN were concentrated 8.5 fold on a Centricon 10, washed with 40mM glycine, pH7.8 and analysed for minactivin activity and by SDS-PAGE. The majority of the minactivin activity did not bind to the antibody column. However, a small amount of minactivin activity (8.5 units) is bound specifically and is eluted with 3M KSCN.

This indicates that under these conditions the antibody column has been overloaded with minactivin. Furthermore, minactivin loses over 90% of its activity in the presence of KSCN over a comparable period of time suggesting that the low recovery of minactivin activity may be due to inactivation of the molecules in KSCN. The SDS-PAGE results show that the vast majority of the protein elutes unretarded from the column. The KSCN eluate however contains a major protein band of molecular weight ca 45 000, similar to the molecular size of minactivin on gel filtration (see Example

2A(a)) (Figure 12a). Western analysis of this minactivin preparation showed a single immunologically cross reactive species migrating identically with the protein band observed following SDS-PAGE (Figure 12b).

Under certain conditions, minactivin has been observed to have a molecular size of approximately 60-70,000 (as detailed in PCT191-85). This discrepancy may be due to altered mobility due to the degree of glycosylation of minactivin.

_EχAMpLE -

Isolation and Sequence of Peptide Fragments from Minactivin

Minactivin was purified from PMA induced U937 cells as described in Example 2 above. The minactivin (3-5μg) was then digested with endoproteinase Lys C (O.lμg) in 20mM Tris-HCl, pH 8.5 containing 5M Urea in a final volume of 50μl for 8h at 22°C. The resultant peptides were separated by reverse phase high pressure liquid chromatography on a Synchropak RP-P (C-8) column using a gradient of acetonitrile in 0.1% TFA ⁽ Figure 19 ⁾ . The peptides indicated by the asterisks were sequenced on an Applied Biosystems 470A gas phase sequencer and the sequences are as follows:

Pepti de 13 AQILELPY-GDV-MFLLLP-E . . . Pepti de 1 1 GRANFSGMSE-NDLF . . . Pepti de 10 MAE-EVEVYIPQFKLEE-Y . . . Pepti de 6 LNIGYIEDLK Pepti de 9 IPNLLPEG-V

EXAMPLE 4

Molecular Cloning of Minactivin a) Isolation of mRNA

From Figure 1, the optimal time of transcription for PMA induced U937 cells could be estimated to be between 15 and 25 hours. Therefore, a four litre serum-free culture of U937 cells at a cell density of 1.2 x 10 cells/ml was incubated for 19 hours in the presence of PMA, the cells harvested, and quick frozen in liquid nitrogen until further use. Non-PMA stimulated U937 cells from three day serum-free cultures were also retained for mRNA isolation. Human blood monocytes prepared as described in international patent application W086/01212, and cultured for 3 days i_n vitro were also used as a source of mRNA.

Total RNA from each of the above sources was extracted by a modification of the Guanidine-HCL method. The cell pellet was homogenized in 20 volumes (per gram weight) of buffer containing 4M guanidine isothiocyanate, 50mM Tris HCl, pH7.5, lOmM EDTA, 0.5% Sarkosyl , 0.1M 2-mercaptoethanol in a blender at low speed for three minutes at 4°C. The suspension was then centrifuged for 10 minutes to remove debris. Nucleic acids were precipitated from the supernatant by the addition of acetic acid to 25mM and 0.75 volumes of cold ethanol, and incubated overnight at -20°C. The suspension was centrifuged again for 30 minutes at -10°C, and the pellet dissolved in buffer containing 7.5M guanidine HCl, 20mM sodium acetate pH5.0, lmM dithiothreitol at 20% of the original volume. After centrifuging to remove any undissolved material, the RNA was repreci-pitated with 0.55 volumes of cold ethanol at -20°C for 1-3 hours. The RNA was recovered by centrifugation, redissolved in the guanidine HCl buffer, and reprecipitated. The last step was repeated 3 times. Following the last precipitation, the pellet was dissolved in 20mM EDTA, pH7.0 and extracted with an equal volume of chloroform: butanol (4:1). RNA was then precipitated from the aqueous phase by the addition of sodium acetate, pH5.0 to 0.3M and two volumes of cold ethanol at -20°C overnight. The RNA was recovered by centrifugation and treated with lOOmg/ml proteinase K in 20mM HEPES, pH7.4, 0.5% sodium dodecyl sulfate for 4 hours at 50°C to remove any residual protein. The RNA was then recovered by precipitation

in the presence of 0.2M sodium acetate, pH5.0 and two volumes of ethanol at -20°C. Following recovery by centrifugation, any residual DNA was removed by precipitation of the RNA in the presence of 3M sodium acetate, pH6.0, overnight at 4°C. The RNA was recovered by centrifugation and precipitated in the presence of 0.25N sodium chloride and two volumes of ethanol. The RNA was again recovered by centrifugation. Poly A ⁺ mRNA was then isolated by two cycles of adsorption and elution from oligo (dT)-cellulose.

The poly A ⁺ mRNA was enriched 10 to 20 fold for minactivin mRNA by sucrose density gradient centrifugation. The sample was layered on a 15 to 34% (w/w) sucrose gradient and centrifuged in a Beckman SW41 rotor at 33 OOOrpm for 16hours at 4°C. Figure 2 shows a gel analysis under denaturing conditions of the size fractionated mRNA preparation. Minactivin mRNA was detected in those fractions (Fractions 16 and 17) centered around the 18S ribosomal RNA standard as determined by in vitro translation and immunoprecipitation (method described below) as shown in Figure 3. b) Identification of the Minactivin Translation Product

Minactivin mRNA was identified by j_n vitro translation in a cell free reticulocyte lysate system followed by immunoprecipitation of the minactivin translation product utilizing its natural substrate, urokinase.

Rabbit reticulocyte lysate commercially available from Amersha , was used primarily according to the manufacturer's instructions with the addition of calf liver tRNA (Boehringer Mannheim) at a concentration of

35 lOOng/ml. S-methionine (Amersham) was added at a concentration of

2mCi/ml to allow detection of the translation products by autoradiography.

Poly A ⁺ mRNA prepared as described above was translated at a concentration of 50mg/ml for 90 minutes at 30°C. Twenty-five microliters of the translation mixture was used for each immunoprecipitation. Following incubation and removal of a washed suspension of whole Staphylococcus aureus-cells (Pansorbin, Calbiochem) to minimize nonspecific binding, the sample was incubated with 50mPU of urokinase (Calbiochem) for 90 minutes at room temperature. This step allows complex formation between the minactivin translation product and urokinase. The complex was removed from the solution by the addition of l-2μl anti-urokinase antiserum (Green

Cross Corp.), or antibodies against placental inhibitor and incubated at room temperature for 30 minutes and overnight at 4°C, and then precipitated by the addition of

25μl of washed Pansorbin. After centrifugation the minactivin-urokinase-antibody-Pansorbin pellet was. ashed, disrupted by

boiling in the presence of 2% SDS, and 2-mercaptoethanol , and the products analysed by gel electrophoresis followed by autoradiography.

35 Immunoprecipitation of the S-labelled translation products with antibodies against urokinase yielded urokinase specific translation products having s of 69000 and 79000. These protein bands represent specific complexes of minactivin with urokinase as:

1) they are not present in the absence of urokinase or mRNA;

2) they do not precipitate in the absence of antibody, and;

3) they compete with unlabelled purified minactivin and placental inhibitor (Calbiochem) preparations for urokinase binding (Figure 4 ⁾ . The immunoprecipitated product was found to represent 0.05% of the total protein synthesized from mRNA obtained from PMA induced U937 cells. No immunoprecipitation products could be detected from mRNA obtained from non-induced U937 cells, presumably due to the decreased levels of minactivin mRNA in this preparation.

Immunoprecipitation of the urokinase - minactivin translation products using antibodies to placental inhibitor yielded identical results. Several anti-placental inhibitor antibody preparations precipitated the distinctive urokinase-minactivin translation product complexes at 69000 and 79000 MW (Figure 5).

A comparison of the immunoprecipitation products obtained in the presence and absence of urokinase allows direct identification of the minactivin translation product as shown in Figure 6. It is present as a distinct band at a M of 43000. This molecular weight appears to be slightly less than that observed for the native protein possibly due to glycosylation. In the presence of urokinase, this band disappears and the characteristic urokinase-minactivin translation product is detected at 69000 M _f . The additional protein band at 79 to 80000 M _f observed previously appears to represent a non-reduced form of the complex as the samples were analyzed under partially reduced conditions.

Furthermore, it was found that complex formation with the minactivin translation product was dependent on the presence of the low molecular weight form of urokinase (HPA 33). Pure preparations of HPA 52 and HPA 33 were obtained ⁽ Calbiochem) and verified to be predominantly one species or the other by fibrin overlay (Figure 7). In addition, plasminogen/plas-in was added to HPA 33 to convert any residual traces of HPA 52 in the preparation to the low molecular weight form. The distinctive urokinase-minactivin translation product complex at 69000 MW appeared only when the urokinase preparations used contained HPA 33. The explanation for

this result is unknown. Addition of trasylol to the lysate mixture to inhibit possible proteolysis had no effect on this result.

In summary, i_n vitro translation of mRNA from U937 cells clearly yields a biologically active minactivin translation product of M approximately 43000 which can be easily identified by the formation of its complex with urokinase giving a characteristic M of 69000. c) Construction of Complementary DNA Libraries cDNA libraries were constructed from total poly A+ mRNA or sucrose density gradient fractionated mRNA using a variety of established methods. By way of example, the first strand complementary DNA was generally synthesized from the mRNA using primer initiated reverse transcriptase. Second strand was then synthesized, for example, by (1) conventional hairpin-loop primed DNA synthesis using DNA polymerase or reverse transcriptase; (2) RNase H-DNA polymerase I - mediated second strand synthesis or (3) 5 ¹ -tailed priming method. After treatment with SI nuclease (if required), the DNA is methylated and blunt ends generated using standard methods of filling-in, e.g. DNA polymerase, the Klenow fragment, or T4-polymerase. Subsequently, the cDNA's can be cloned by joining them to suitable plasmid (e.g. pBR322, pUC or pUR systems) or bacteriophage (e.g. lambda gt 11) vectors through complementary homopolymeric tails or cohesive ends created with synthetic linker segments containing appropriate restriction sites using standard procedures, and then transforming a suitable host.

EXAMPLE 5

A preferred method of constructing the cDNA libraries is as follows. cDNA was synthesized from 6μg of total poly A+ mRNA using Moloney murine leukemia virus reverse transcriptase (BRL,200U/μg mRNA) in the presence of 50mM Tris HCl, 75mM KC1 , lOmM DTT, 3mM MgCl , lmM each of dATP, dCTP, dGTP, and dTTP, lOμg/ml 01igo(dT) ₁₂ _- ₈ and lOOμg/ml BSA. A 200μl reaction volume was incubated at 37°C for 40 minutes. Second strand was synthesized by hairpin loop primed synthesis using the Klenow fragment of DNA polymerase I. The reaction was heated at 70°C for 10 minutes to separate DNA/RNA duplexes, diluted to twice the volume and Klenow added to 325U/ml in the presence of lOμCi of dATP (1800 Ci/mmole). The reaction was allowed to incubate for 1 hour at 15°C. Following phenol :chloroform ⁽ 1:1 ⁾ extraction and ethanol precipitation, the DNA was dissolved and the hairpin loop was removed by treatment with 80 units of SI Nuclease (P/L Biochemicals) in the presence of 0.2M NaCl, 50mM sodium acetate pH 4.5, lmM ZnS0 ₄ and 0.5% glycerol and precipitated as described previously.

The double stranded cDNA was then methylated using 20 Units of EcoRl Methylase (Biolabs) in the presence of lOOmM Tris-HCl pH 8.0, 10mM EDTA and 80μM S-adenosyl methionine. The DNA was repaired by the addition of 2.5U of T4 DNA Polymerase in the presence of 33mM Tris acetate pH8.0, 66mM potassium acetate, lOmM magnesium acetate, 0.5mM dithiothreitol , O.lmg/ml BSA and 0.5mM each of dATP, dCTP, dGTP, and dTTP for 1 hour at 37 ^β C, followed by the addition of T4 polynucleotide kinase (20U) and O.l M ATP. Following phenol :chloroform (1:1) extraction and ethanol precipitation, Eco Rl linkers were added to the redissolved DNA (2μg linkers/lug cDNA ⁾ using T4 DNA ligase (IBI; 1.2U/μg, DNA). The reaction was carried out on a concentrated cDNA solution (167μg/ml) at 26°C for 4 hours. After treatment with EcoRl, the free linkers were separated from the cDNA by chromatography on Biogel A150M. Fractions containing cDNA of average length greater than 1 000b.p. were pooled and the cDNA concentrated and precipitated by the addition of two volumes of ethanol. The yield of cDNA was 2.5μg. cDNA libraries were prepared in both lambda gt 11 and gt 10. cDNA (lOOng) was ligated to EcoRl- cleaved, phosphatased lambda gt 11 lμg), at a DNA concentration of 220μg/ml at 4°C for 16 hours. The DNA was packaged using prepared packaging preparations from Vector Cloning Systems. Phages were amplified by adsorption to E.coli strain Y1088 and screened in Y1090. The lambda gt 11 library contained approximately 8x10 recombinants per μg cDNA (94% of total phages). The proportion of recombinants that contained cDNA molecules was determined by screening

32 the library with cDNA synthesized in the presence of α[ P_- dATP. Around 90% of white plaques hybridized with this probe.

For the library prepared in lambda gt 10, cDNA (200ng) was ligated to EcoRl cleaved, phosphatased lambda gt 10 (Iμg), at a DNA concentration of 240μg/ml at 25°C for 4 hours. The DNA was packaged as above using E.coli strain- C600 hf1.

The lambda gt 10 library contained approximately 7.5x10 recombinants per μg cDNA. The proportion of recombinants that contained cDNA molecules was determined by screening the library with radiolabellad cDNA. Greater than 90% of plaques hybridized with this probe.

EXAMPLE 6

Identification of Clones containing the Minactivin Gene

The clone(s) containing the gene encoding minactivin may be identified with the probes described in the following examples using established techniques.

EXAMPLE 6a

Hybrid - Select Translation cDNA clones containing sequences complementary to minactivin mRNA may be identified by hybridization selection. The cloned DNA is denatured, immobilized to a solid matrix such as nitrocellulose, and hybridized to preparations of total mRNA. The RNA/DNA duplex is heated to release the mRNA which is then translated in the j_n vitro rabbit reticulocyte lysate cell free system as described above. The translation product may then be identified as described in Example 4b.

EXAMPLE 6b

DNA Probes Complementary to the Minactivin Gene Sequence

Using the amino acid sequence obtained for peptides of minactivin as described in Example 3, oligonucleotide sequences which would code for the amino acid sequence can then be predicted and oligonucleotide probes synthesised using conventional established technology.

Using this sequence data, a number of oligonucleotide probes were synthesized using an Applied Biosystems 380A DNA synthesizer. The sequences of these oligonucleotides are:

(C) (A) (T) (G) (A)

1. TT(G) AA(C) TG(A) ACI AT(G) TA

(T)

(A) (A)

(G) (T) (G) (C)

2. TA(T) AC(C) TC(T) AC(T) TC

(C) (C)

(A) (A) (G) (A) (T) (G)

3. TC(T) A(G)I AT(C) TG(C) GC

(C) (T)

(T) (T) (T)

4. TTG AA ⁽ C) TGI ACI ATG TAI AC(C) TCI AC(C) TC

(T)

5. (T) (A) (C) (A) TC ⁽ C ⁾ TCI AT(G) TA(A) CCI AT(G) TT

(G)

(T) (T) ⁽ C) (G)(C)

6. AAI TT(A) GCI C(T)(A) CC

⁽ G) (G)

7. ATA TGT TTC CTC GAG CTT GAA CTG AGG GAT GTA CAC CTC GAC TTC GCT CTC TGC CAT

8. TTC ATC AGG CAA CAG GAG GAA CAT GCT CAC ATC TCC GGC GTA AGG GAG TTC CAG GAT CTT CAT TTT

9. CTC CTC CAG CTT GAA CTG GGG GAT GTA GAC CTC CAC CTC

(A) (G) (C)

10. CTT GAA CTG (G)GG (A)AT GTA (G)AC CTC CAC CTC

The specific oligonucleotide probe may be radiolabelled and then used to screen cDNA libraries by in situ hybridization of bacterial colonies or bacteriophage plaques using standard techniques to identify clones containing all or part of the minactivin gene.

EXAMPLE 6c Immunological Screening

The clones may be screened using standard procedures with antibodies which cross-react with the native minactivin protein.

Antibodies to minactivin are prepared by standard methods, for example, each rabbit is immunized with 10 to lOOμg of purified minactivin in the presence of a suitable adjuvant, such as Freunds complete or montanide. Following a boost of an equivalent amount approximately four weeks later, rabbit serum may be obtained which can be assayed for antibodies to minactivin.

EXAMPLE 6d Screening for biological activity

Clones containing the minactivin gene may be tested or screened for minactivin activity using either radiolabelled urokinase or urokinase and antibodies to urokinase. This would be accomplished using standard techniques of immunological screening. Urokinase and antibodies to urokinase may be obtained commercially. Radiolabelled urokinase may be prepared as described below.

Commercially obtained urokinase (Calbiochem) was affinity purified by chromatography on p-aminobenzamidine sepharose according to published protocols [Hol berg, L., Bladh, B., Astedt, B. Biochim. Biophys. Acta 445, 215-222 ⁽ 1976 ⁾ , and Goldfarb, R.H., Quigley, J.P. Biochemistry 19, 5463-5471 ⁽ 1980 ⁾ ]. Seventy-five Ploug units of the purified urokinase was iodinated by conjugation with N-succinimidyl 3-(4-hydroxy, 5- [I ¹²⁵ ] iodophenyl ⁾ proprionate according to the Bolton Hunter procedure. The

125 I -labelled urokinase was separated from the fre-s label by chromatography on Sephadex G-25M equilibrated in IM sodium phosphate, pH 7.0, 0.4M sodium chloride, 0.1% Triton XlOO and 1% carrier bovine serum albumin.

1 5 Analysis of the I -labelled urokinase preparation by SDS - polyacrylamide gel electrophoresis under non-reducing conditions showed the presence of the characteristic high (M _f 55000) and low (M 33000 ⁾ molecular weight forms of urokinase (Figure 13). Under reducing conditions, the high molecular weight form is dissociated into its characteristic 33000 and 22000 M _r subunits. Iodination of the urokinase preparation resulted in a loss of 10 to 15% plasminogen activator activity as measured by the assay of Coleman and Green [Ann. N.Y. Acad.

Sci . 370, 617 (1981)], but had no effect on minactivin inhibition of the enzyme. Dot blot assays in which various dilutions of minactivin were spotted on nitrocellulose paper, incubated overnight with radiolabelled urokinase, washed, dried, and autoradiographed, showed that the radiolabelled urokinase could detect minactivin bound to a solid phase at a sensitivity of lOmU or approximately O.lng minactivin.

EXAMPLE 7

Identification of the Minactivin Gene

The preferred method of identifying the minactivin gene is as follows. Following synthesis, the oligonucleotide probes 7 - 10 described in Example 6b were purified by polyacrylamide gel electrophoresis, and labelled with polynucleotide kinase (IBI, lU/p ole DNA) and

32 gamma- P-ATP and purified by ion exchange chromatography using standard procedures.

The lambda gtlO library as described in Example 5 was screened by in situ hybridization according to standard experimental procedures. Hybridization conditions were adjusted to allow specific binding with minimum background and were determined to be as follows:

Probes 7 and 8: 3 hours at 50°C in 6xSSC, SxDenhardt's, 0.1% SDS, 20μg/ml tRNA, following prehybridization for 1 hour at 42°C in 6xSSC, 5xDenhardt's 0.5% SDS, 0.2mg/ml sheared calf thymus DNA.

^' Probes 9 and 10: 16 hours at 37 ^β C in lOx Denhardt's, 5xSSC, 0.05% sodium pyrophosphate.

32 P-labelled oligonucleotide probes of specific activity greater

Q than 10 cpm/μg were used at approximately 0.5 pmole/ml. The filters were washed in 0.5X or 2xSSC containing 0.1% SDS at increasing temperatures to raise the stringency for selection of positive clones.

Plaques giving positive signals were pi ^c ked, rescreened, and the phage DNA purified using standard procedures vsee for example Maniatis et aj_. Molecular Cloning 1982).

Two recombinant bacteriophage clones MINID and MIN611, containing

sequences which cross-hybridized to each other were obtained, with EcoRI-linkered cDNA inserts of 2100 and 1060 base pairs respectively. These inserts were subcloned into plasmid pUC18 to create plas ids pBTA440 and pBTA441 respectively and mapped by restriction enzyme analysis as shown in Figure 20. Southern blot analysis of clone MIN1D located the binding region of oligonucleotide probes 7 and 8 within a 320 base pair Xbal-Ncol restriction fragment as illustrated in Figure 20.

That these clones contained genes which code for minactivin was verified by hybrid-select translation and DNA sequence analysis.

Hybrid Select Translation

Purified pBTA440 was immobilized on nitrocellulose filters at a concentration of 20μg per 3mm x 3mm filter according to the procedure described by Maniatis et a (Molecular Cloning 1982). After washing, each filter was incubated with 50μg of total mRNA and hybridized for 3 hours at 50°C. After thorough washing, the specifically hybridized mRNA was eluted by boiling and then translated in vitro using a commercial rabbit reticulocyte lysate preparation (Amersham).

As illustrated in Figure 21, the hybridized mRNA was shown to specifically code for a translation product of M _f 43 000 by gel electrophoresis, characteristic of the minactivin translation product described in Example 4b. Furthermore in the presence of urokinase, this band disappeared and the characteristic urokinase-minactivin complex was detected at 69000M _r .

DNA sequence analysis

Restriction fragments of pBTA440 were subcloned into the single stranded phage vectors M13mp9, M13mpl8 and M13mpl9 and the DNA sequence of the 2 100 bp inserted was determined using the Sanger chain termination method. Examination of the DNA sequence indicated that the 2100bp insert did not contain the entire coding sequence of the minactivin gene.

Primer extension

To obtain the remainder of the DNA sequence encoding the N-terminal region of minactivin a second cDNA library was constructed using primer extension. The library was prepared by priming 5 icrograms of polyA ⁺ mRNA with the oligonucleotide 5' TTC CAG TAA ATA ATT CCC TGT GGA TGC ATT 3' being complementary to the previously se uenced nucleotides 391 to 420. EcoRI-linkered cDNA inserts were subseq ^e ntly cloned in lambda gtlO using standard techniques.

Approximately 5.3 x 10 of the 7.2 x 10 clones obtained were screened with a second oligonucleotide 5' GCC TGC AAA ATC GCA TCA GGA TAA

CTA CC 3' (complementary to nucleotides 310-335). Of the 100 positive clones obtained, 15 were purified and the clone (clone 13) with the largest cDNA insert (430bp) was subcloned into plasmid pUC18 to create plasmid pBTA442. The DNA sequence of pBTA442 was determined as described above (see also Fig. 20).

The coding sequence of the minactivin gene, contained in pBTA440 and pBTA443, a plasmid containing the 430bp 5' minactivin sequence in pUC18 in opposite orientation to pBTA442, was made contiguous by recombining certain DNA restriction fragments to create pBTA438 as shown in Figure 22. E. coli K-12, strain JM109 containing pBTA438 has been deposited with the American Type culture collection, 12301 Parklawn Drive, Rockville, Maryland 20852, United States of America on 11 February 1987 under accession number ATCC 53585.

The complete cDNA sequence of the minactivin gene and the deduced amino acid sequence of the minactivin protein are given in Figure 23. The complete translation product consists of 415 amino acids (M _r 46 543 ⁾ . The gene encodes the 5 peptides obtained from the amino acid sequence analysis of native minactivin as illustrated in Figure 23.

The DNA sequence analysis reveals that minactivin is a member of the serine protease inhibitor superfamily, (known as serpins) albeit specific for urokinase type plasminogen activators.

EXAMPLE 8 Expression of Biologically Active Minactivin

High-level expression of the biologically active molecule is obtained, for example, by integration of the full-length cDNA present in pBTA438 into various vectors which can direct the synthesis of the protein in a variety of hosts such as bacteria or eukaryotic cells (such as mammalian cells transfected or transformed with the vector). The vector preferably contains a nucleotide sequence capable of controlling expression of the ^" nucleotide sequence coding for minactivin. This second nucleotide sequence may include, by way of example, a promoter sequence, polyadenylation sequences, or nucleotide sequences which allow the protein to be expressed as a hybrid molecule fused with another protein.

EXAMPLE 9 Bacterial expr ^e ssion of minactivin

The general approach is the p ^r eparation of an expression vector or cloning vehicle replicable in E . con , which contains a DNA sequence which codes for the expression of minactivin.

Minactivin may be expressed in its native form or as a hybrid

molecule fused to another protein. These constructions are shown in Figures 24 and 26.

One series of plasmid constructs used the lambda P. expression vectors pLK57, and pLK58 (Botterman et a_h Gene 37; 229-239, 1985, to express native or near-native (N-terminal amino acid modified) minactivin.

As shown in Figure 24, the plasmid pBTA438 was digested with EcoRl and Dral and a 1610bp EcoRI-Dral restriction fragment was isolated from an agarose gel. This fragment was ligated with T4 llgase to vector pLK57 which had been digested with EcoRl and EcoRV. The derivative plasmid PBTA444 contains the lambda P, promoter controlling the expression of native minactivin.

The expression vector pBTA444 was used to transform E. coli K-12 strain N4830 (Joyce et al_. PNAS 80, 1830-1834, 1983) which contains the thermolabile cl repressor of lambda. Cells transformed with pBTA444 were grown overnight in in MEB medium (Mott et ai PNAS 82, 88-92, 1985)) with lOOμg/ml ampicillin at 28°C. Cells were diluted in MEB medium, grown at 28°C to an ODg-- of 1.0 when prewarmed (65°) MEB medium was added in equal volume to equilibrate the temperature to 42°. Following 4 hours of growth at 42°C the cells were harvested and membrane and soluble protein fractions prepared by resuspending washed cells (after -70°C freezing and thawing) in 200μ of 20% sucrose 30mM Tris-HCl pH8.1. and mg/rnl lysozyme solution followed by the addition of 3m1s of 3M EDTA pH7.3. The cell extract was clarified by brief sonification and membrane and insoluble proteins pelleted by centifugation (27,000xg), 60 mins). The soluble proteins were precipitated by the addition of trichloroacetic acid ⁽ 105% /v) to the supernatant and the pellet dissolved in water. The pelleted membranes wee also dissolved in water. Samples of these fractions for both uninduced (28 ^β C) and induced (42°C) cells were analysed by SDS-polyacrylamide gel electroploresis and immunological detection of minactivin by western transfer using antiserum against human placental inhibitor. As shown in Fig. 25 a minactivin protein band (Mr 40-50K) , visualized by western transfer using antibodies to human placental inhibitor and rabbit anti-goat IgG coupled to alkaline phosphatase (Sigma) is present in both the induced (42°C) soluble and membrane fractions.

An alternative method for producing native minactivin is also shown in Figure 24. The plasmid pBTA442 was digested with XhoII and a 243bp XhoII restriction fragment was purified from an agarose gel. This fragment was ligated with T4 ligase to vector pLK58 digested with Bglll. The derivative plasmid pBTA445 was digested with PvuII and S al and a 2800bp

fragment purified and ligated with T4 ligase to a purified 1320bp PvuII-Dral restriction fragment from pBTA438. The derivative plasmid pBTA446 was linearized with Bglll and ligated to a synthetic double stranded 26 mer oligonucleotide containing a bacterial ribosome binding site and the initial nucleotides of the native minactivin gene, creating plasmid pBTA447. When pBTA447 is transformed into an appropriate host, such as N4830, induced and analysed as described above, minactivin is again produced as shown in Fig. 25. In both cases, for pBTA444 and pBTA447 containing cells, minactivin was present in both the induced (42°C) soluble and membrane fractions.

To assess the biological activity of minactivin produced in E.coli N4830, soluble and membrane fractions were incubated for 90 mins with high and low molecular weight forms of urokinase as described in example 4. Samples were then precipitated with acetone, resuspended in water, and run on a reducing SDS-polyacryl mide gel. Minactivin and minactivin-urokinase complexes were visualized by western transfer as described above. As shown in Fig. 25 minactivin in the soluble fraction from induced E.coli N4830 containing pBTA447 complexes with urokinase under standard assay conditions. This indicates that minactivin produced from these bacterial cells retains biological activity.

Two examples of a method for producing a protein that is the fusion of all or part of one protein coding sequence and all or part of the minactivin coding sequence follows. As shown in Figure 26, the plasmid pBTA440 was digested with Sspl and Dral and a IllObp fragment was isolated from an agarose gel. This fragment was ligated to the vector pBTA449 digested with EcoRV creating pBTA450. pBTA450 was then digested with Aval and a purified 2800 bp fragment ligated to the plasmid pLK57 digested with Aval to create plasmid pBTA586. This places part of the minactivin coding sequence under the control of the lambda P, promoter and fused to the coding ^" sequence of the first 80 amino acids of traT gene, the first 20 of which constitutes a signal sequence that results in the fusion appearing in the outer membrane of E. coli . This signal sequence is cleaved off during transport to the outer membrane, which is the normal location of the traT protein.

When plasmid pBTA585 is transformed into an appropriate host, such as N4830, and induced with t ^e mperature shift as above, the TraT-Minactivin fusion protein appears in the outer membrane, as shown in Figure 27.

A second example of a method for producing a fusion is shown in Figure 26. In plasmid pBTA440, the minactivin coding sequence is fused in

frame with a portion of the β-galactosidase gene present on plasmid pUC18.

When plasmid pBTA440 is transformed into an appropriate host, such as JM101, or any E. col 1 strain which contains the lad ⁰¹ gene, and induced by addition of isopropyl-thio-β-D-galactopyranoside (final concentration lmM), minactivin production can be detected as described above (Figure 27 ⁾ .

EXAMPLE 10 Expression of Recombinant Minactivin in Eukaryotic Cells

A fragment of pBTA438 containing the entire coding region of minactivin was inserted into a series of vectors capable of stable integration and expression of eukaryotic genes in mammalian cells. These included 1) pKC3 (derived from pKO-neo, Van Doren, Hanahan, D., Gluzman, Y., J. Virol. 50 606-614 (1984)) wherein the minactivin cDNA sequence is placed under the control of the SV40 early promoter; 2) pZlpNeoSV(X)! (Cepko, C.L., Roberts, B.E., Mulligan, R.C., Cell 37 1053-1062 (1984 ⁾⁾ , a Molony Murine Leukemia virus-derived retroviral shuttle system in which the minactivin gene is placed downstream from the retroviral LTR promoter and selection is based on the neo gene which confers kanamycin resistance in prokaryotes and G418 resistance in eukaryotes; and 3) pMSG (commercially available from Pharmacia), wherein regulated expression of minactivin is achieved by utilizing a dexamethasone inducible promoter contained within the Mouse Mammary Tumor-Virus (MMTV) 5' - LTR.

The construction of these three vectors is shown in Figure 28 and the details are as follows. The coding region of the minactivin gene was isolated from pBTA438 as a 1610 bp EcoRI-Dral fragment and inserted into the following vectors as described below.

The 1610bp EcoRI-Dral fragment was ligated into pKC3 which had been digested with EcoRl and Smal, and then transformed into E. coll C600γ. The resultant plasmid was designated pBTA587.

In the second construction, the 1610bp EcoRI-Dral fragment was rendered flush-ended using the Klenow fragment of DNA polymerase I, ligated into the Smal site of pMSG, and transformed into a suitable E. col1 K-12 host. Colonies containing the minactivin gene in pMSG were detected by

32 colony hybridization using the P-labelled oligonucleotide (29 mer) previously described in Example 7 (complementary to nucleotides 310-335).

The resultant plasmii was designated pBTA588.

In the third construction, the flush-ended EcoRI/Dral fragment described above was πgated into pUC7 which had been digested with Hindi giving the construction designated pBTA589. As the Hindi site in pUC7 is flanked by BamHI sites, this allowed the minactivin gene to be isolated

following BamHI digestion and ligated into the BamHI site of pZIPNeo SV ⁽ X ⁾ 1. Following transformation into a suitable E. coli K-12 host, colonies containing the minactivin gene were detected by colony hybridization as described above. The resultant plasmid was designated pBTA590.

Transfection of Eukaryotic Cells

All plasmids were transfected into eukaryotic cells by the calcium phosphate method. Approximately 1-2 x 10 cells were seeded into a T25 flask in 5ml of Dulbecco modified Eagle medium supplemented with 10% ⁽ v/v ⁾ foetal calf serum, 3.6 mM glutamine 200 M, 45IU/ml penicillin and 45mg/ml streptomycin (complete medium). Approximately 1 to 5μg of CsCI gradient purified DNA was precipitated with calcium phosphate and added to the cells. After 4 hours, the cells were treated to a glycerol shock, and cultured in complete medium for 3 days. The culture supernatant was then removed for measurement of transient expression. The cells were then trypsinized and split 1/3 into T75 flasks with complete medium containing the appropriate antibiotic selection (see below). The cells were washed every 6 to 7 days with the same medium and transfectants picked at 14 to 28 days and cultured individually until confluent growth was achieved.

The conditions of transfection for each of pBTA587, pBTA588 and pBTA590 were as follows:

PBTA587. As pKC3 does not contain a selectable marker, pBTA587 was cotransfected with pZIPNeo SV(X)1 at a molar ratio of 7.5:1, pBTA587: pZIPNeo SV(X)I. Transfectants were selected with complete medium containing 0.4mg/ml G418. Transfections were carried out in COS cells.

PBTA588. As pMSG contains the E. coli xanthine-guanine phosphoribosyltransferase (gpt) gene expressed from the SV40 early promotors, stably transfected cells were selected in HAT medium containing hypoxanthine, aminopterin and mycophenolic acid. Transfections were carried out using NIH3T3 cells.

.PBTA590. Transfectants were selected using complete medium containing 0.4mg/ml G418. Transfections were carried out in NIH3T3 cells. Analysis of Expression of Recombinant Minactivin in Eukaryotic Cells

Following transfection, transient expression of recombinant minactivin is detected by culturing the cells in the presence of

35 S-methionine and specific immunoprecipitation of the recombinant radiolabelled rr.'nactivin using antibodies to placental inhibitor essentially according to the method described in Example 4b. For example, forty-eight hours after transfection of pBTA5.87 into COS cells, the supernatant was removed and the cells cultured in the presence of 1ml

35 methionine-free EMEM (Flow), supplemented with S-methionine

(Amersham). Following immunoprecipitation with 50μg goat anti-placental inhibitor antibodies and 200μl washed Pansorbin, the complexes were analysed by SDS-polyacrylamide gel electrophoresis (reducing conditions) and visualized by autoradiography as shown in Figure 29. Recombinant minactivin is detected as a band of Mr 45-48,000, which is not observed in the corresponding control transfection containing the vector (pKC3) alone.

When urokinase (15 Plough units, Calbiochem) is added to the supernatant prior to immunoprecipitation, this band disappears which is characteristic of biologically active minactivin. A band is observed at M 69,000 which is indicative of the minactivin urokinase complex, but is somewhat obscured by a nonspecific protein band at the same position. Some of the recombinant minactivin also appears to have been proteolytically nicked following the addition of the urokinase preparation, as evidenced by the

M _r 35-37,000 band detected.

That the recombinant minactivin produced was biologically active was determined by culturing the cells in the absence of serum for 4 hours and quantitating the inhibition of urokinase activity by the colorimetric assay essentially as described in Example 1. A level of inhibition was detected which corresponded to approximately 1 unit/ml minactivin activity above background.

EXAMPLE 11 Purification and Recovery of Biologically Active Protein

Following the establishment of conditions for the expression of minactivin in E.coli at high levels the cells harbouring the plasmid encloding the minactivin gene are harvested at late log phase. One volume of packed cells are suspended in two volumes of lysis buffer (0.1M sodium phosphate, pH7.0 containing lmM EDTA and lmM phenyl methyl sulphonyl fluoride ⁾ and lysed by three passages through a French Press at 15,000 psi. -The suspension is centrifuged at 23,000xg for 20 minutes and the pellet resuspended in two volumes of lysis buffer containing 5% Triton X-100. The suspension is again centrifuged at 23,000xg for 20 minutes and the pellet suspended in three volumes of 0.1M Tris-Cl, pH8.0 containing 8M urea and 0.1M DTT. The solution is flushed with nitrogen and incubated in a sealed t__e at 37°C for 2 hours. Following incubation the pH of the solution ', -- lowered to approximately pH3.5 by the addition of 50μl of glacial acetic acid for every ml of solution. The suspension is clarified by centrifuging as above and the supernatant applied to a Sephadex G-75 column (3.2cm x 90cm) equlibrated in 0.1M acetic acid. The fractions

containing the minactivin are located by SDS-PAGE. The fractions containing the minactivin are pooled and dialysed against lOmM Tris-Cl, pH8.0 containing 8M Urea and O.l M DTT at room temperature for 16 hours. The analysed solution is then applied to a DEAE- Sephadex column ⁽ 2.2cm x 25cm) equilibrated in the above buffer and the column washed to elute unbound material. The minactivin is then eluted from the column using a linear gradient of sodium chloride from 0 to 0.5M in the same buffer. The fractions containing the minactivin are indentified by SDS-PAGE and dialysed extensively against distilled water. The protein, which precipitates during this procedure, is recovered by lyophilization. The lyophilized protein is redissolved in 0.1% trifluoroacetic acid and applied to a Vydac C-4 reverse phase column attached -to a Waters high pressure liquid chromatograph. The pure minactivin is eluted from the column using a linear gradient of acetonitrile from 0 to 80% in 0.1% trifluoroacetic acid. The A- ₂₀ peak corresponding to minactivin is identified by SDS-PAGE, the fractions pooled and lyoplilized.

The lyophilized, purified minactivin is dissolved in 0.1M Tris-Cl, pH8.0 containing 8M urea at a concentration of lOmg/ l and diluted to lOμgm/ml into 0.1M Tris C1 , pH8.0 containing lmM reduced glutathione and O.l M oxidized glutathione. The refolding reaction is allowed to proceed at room-temperature for 24 hrs and then the solution concentrated and diafiltered against 0.IM sodium phospate pH7.0 on an Amicon stirred cell using a YM10 membrane. The resultant solution containing active minactivin is assayed using the assay described above (Example 1).

The recovery of biologically active minactivin secreted at high levels from mammalian cells employs the same procedures as described in Example 2 for the purification of the native minactivin from U937 cells. This involves initially a ten fold concentration of the cell free supernatant using an Amicon DC-2 hollow fibre concentrator equipped with a 30,000 dalton cut-off cartridge. The concentrate is then dialysed against at least an equal volume of 50mM glycine, pH7'8, to remove all traces of dye. The dialysed concentrate is centrifuged in a JA10 rotor at 8000rpm for 30 min at 4°C to pellet residual cell debris and protein that may have precipitated during dialysis. The clarified supernatant is then aliquoted and frozen at -20°C until required for subsequent purification.

Minactivin is further purified from ten-time concentrated culture supernatant by step pH elution using Phenyl-Sepharose as follows.

The ionic strength of the supernatant is adjusted to 2M by the addition of solid NaCl and the pH adjusted to 5.5 with citric acid. This

solution is applied to a Phenyl-Sepharose column (4.4cm x 5.0cm ⁾ equilibrated in 50mM Na citrate, pH5.5, 2M Nacl and lmM EDTA and eluted with the same buffer until the baseline absorbance at 280nm (A280) returned to baseline. The minactivin is then eluted from the column with 50mM glycine, pH9.0. Fractions containing the highest specific activity minactivin are pooled and concentrated on an Amicon YM10 membrane.

The pooled, concentrated minactivin is then applied to a 2.2cm X 78cm column of Sephacryl S-200 equilibrated with 0.1M sodium borate, pH9.0. Fractions of 5.0ml are collected at a flow rate of 0.46ml/min. The fractions containing minactivin activity were pooled and concentrated to 3ml using a YM10 membrane. Calibration of this column with known M standards indicates that minactivin has a M of 45-48kD.

The concentrated minactivin solution is applied to a preparative flat bed gel of Ultrodex containing Ampholines in the pH range 4.5-6.0 and electrofocussed for 23 hrs at 10°C on an LKB Multiphor isoelectric-focussing apparatus. Following completion of the run, 30 zones across the length of the gel are scraped out and the protein eluted from each with 10ml of IM glycine containing lmM EDYA, pH9.0. Aliquots of each frction are assayed for minactivin activity and electrophoresed on 15% SDS-polyacryl mide gels to locate protein. Under these conditions minactivin focusses between pH5 and pH5.2 and is highly purified. This material is again concentrated on an Amicon YM10 membrane and stored at -20°C in 50mM glycine, pH9.0, containing lmM EDTA and 50% glycerol.

INDUSTRIAL APPLICATION

As a specific inactivator of urokinase-type plasminogen activators, minactivin has a range of potential industrial applications as a clinical reagent for the diagnosis and possible treatment of various human carcinomas and inflammatory conditions.

Studies of cell transformation in vitro by tumor viruses ⁽ Ossowski ,1et al . J. Exp. Med. 137, 112, 1973) and by chemical carcinogens (Sisskin, et al . Int. J. Cancer, 2j5, 331, 1980) both show that plasminogen activator secretion is the most consistent early biochemical event associated with transformation. Furthermore, the ability of cell lines to metastasize i_n ivo has been found to correlate with their ability to express plasminogen '.tivator ⁽ Wang et al . Cancer Research 40,288, 1980). It is also well established that tumor cells of several of the most prevalent human cancers, _ e.. carcinoma of the lung, breast, prostate and colon, produce high levels of urokinase-type plasminogen activator (Duffy, M.J., O'Grady,

P.Eur.J. Clin. Oncol. 20(5)577-582, 1984).

Our previous studies (Stephens, R.S. et al . Blood 66, 333-337, 1985 ⁾ on malignancy in colon ucosa and conditions which predispose to malignancy, . adenomatous polyps, polyposis coli and inflammatory conditions of the colon such as Crohn's disease and ulcerative colitis, have demonstrated that human colon cancers produce significantly greater amount of urokinase-type plasminogen activator than that occurring in adjacent noninvolved tissue. Minactivin was found to be capable of binding to and inhibiting this tumor associated plasminogen activator (Stephens et al- Blood 66, 333-337, 1985). Thus, it follows that minactivin has industrial application as a reagent for identifying and defining tumors both in vivo and in histological specimens. For imaging tumors in vivo, minactivin may be labelled with an appropriate isotope, such as Technetium-99m (Richardson, V.J. Brit.J. Cancer 40, 35, 1979) or Iodine-131 (Begent, R.H.J. Lancet, Oct 2, 1982). Following administration of the minactivin preparation, the location and boundaries of the tumor may be determined by known radioisotopic methods, such as gamma-camera imaging. Thus, minactivin offers a sensitive method for enabling the identification of small metastatic cancers particularly those arising after surgical intervention. In the analysis of histochemical specimens, minactivin or

131 its antibody, may be labelled with an isotope such a I , or conjugated to an appropriate enzyme or other chemical reagent. On contact with a histological specimen, such as a biopsy section, minactivin will bind to the tumor type plasminogen activator at its place of secretion, thereby identifying the tumor boundaries and potentially the metastatic state of the tumor. In addition to its diagnostic applications, minactivin is also indicated for use in the direct treatment of tumors. As a specific inhibitor of the enzyme implicated in the process by which tumors invade surrounding tissues (Dano, K. et al . , Adv. in Cancer Res. 44, 139, 1985), regulation and, in particular, inhibition of tumor growth and metastases can be achieved. Furthermore, minactivin can be used as a drug delivery system to deliver lectins or toxins directly to growing tumors. It will be appreciated that this system could offer many advantages in terms of specificily and extremely potent tumoricidal capability.

Other biological processes in which urokinase-type plasminogen activators have been implicated involve those physiological events associated with invasion and tissue destruction, such as chronic inflammatory conditions including rheumatoid arthritis. As minactivin is part of the natural host response to tissue degradation, it will prove a

useful marker for monitoring the status of the disease particularly during prescribed courses of treatment. Labelled antibodies or DNA probes derived from minactivin have Industrial application as diagnostic reagents for monitoring minactivin levels in blood plasma, in macrophages of tissue biopsies and in synovial fluid for correlations with diseased states. Similarly, minactivin itself is also indicated to have a therapeutic effect when administered in vi o in ameliorating such conditions.