METHODS OF CANCER DIAGNOSIS USING A CHIMERIC TOXIN

Abstract: The present invention relates to methods for cancer diagnosis using a chimeric toxin. In particular, the invention relates to the use of a chimeric toxin composed of gonadotropin releasing hormone (GnRH) and Pseudomonas exotoxin A (PE) to detect a tumor-associated epitope expressed by human adenocarcinomas. Mutated GnRH-PE molecules that bind but do not kill tumor cells are exemplified.

Description: METHODS OF CANCER DIAGNOSIS USING A CHIMERIC TOXIN 1. INTRODUCTION The present invention relates to methods for cancer diagnosis using a chimeric toxin. In particular, the 5 invention relates to the use of a chimeric toxin composed of gonadotropin releasing hormone (GnRH) and Pseudomonas exotoxin A (PE) to detect a tumor-associated epitope expressed by human adenocarcinomas. Mutated GnRH-PE molecules that bind but do not kill tumor cells are 0 exemplified. 2. BACKGROUND OF THE INVENTION GnRH is a decapeptide produced by hypothalamic neurons and secreted into the hypophysioportal circulation via portal vessels. It is first synthesized as a larger precursor 15 protein which is processed by proteolytic cleavage and amidation at its C-terminal glycine . GnRH stimulates gonadotroph cells in the anterior pituitary gland to release luteinizing hormone and follicle-stimulating hormone, thereby regulating the hypothalamic-pituitary gonadal control of human reproduction. 20 The involvement of GnRH has been implicated in certain carcinomas, and GnRH analogues have been used in the treatment of breast, prostatic, pancreatic, endometrial and ovarian cancers (Kadar et al . , 1988, Prostate 12:229-307). The analogues suppressed tumor cell growth in vi tro and in vivo. In addition, GnRH binding sites have been reported in 25 certain solid tumors and in established cell lines (Emons et al . , 1993, J. Clin. Endocrinol . Metab. 77:1458-1464), though- preliminary results suggest that the GnRH receptor (GnRHR) involved might differ from the previously documented receptor (Kadar et al . , 1992 , Biochem. Biophs . Res. Comm. 189:289- 30 295) . Although GnRH binding sites have been demonstrated in tumors, such tumors were derived mainly from hormone dependent tissues. Recently, Nechushtan et al . reported that certain hormone non-responsive tumors such as colon carcinomas, renal cell carcinomas and hepatocell.ular carcinomas were susceptible to killing by a chimeric toxin, GnRH-PE (J. Biol . Chem. , 1997, 272:11597). GnRH caused the chimeric toxin to bind to GnRHR-expressing tumor cells, whereas PE mediated cell killing by inhibiting protein synthesis. However, prior to the present invention, it was not known whether the observed effects were due to the expression of a natural GnRHR by- hormone non-responsive tumors or a new epitope recognized by GnRH-PE that was distinct from that bound by GnRH. 3. SUMMARY OF THE INVENTION The present invention relates to methods for detecting a tumor cell using a GnRH-PE chimeric toxin, and GnRH-PE chimeric toxins that bind but do not kill tumor cells. In particular, it relates to the use of a GnRH-PE chimeric toxin to detect an epitope expressed by adenocarcinomas. For the practice of the invention, it is preferred that the GnRH-PE is modified to reduce its cytotoxic activities without altering its binding specificity to tumor cells . Such molecules are particularly useful for the detection of tumor cells in a biological specimen and in a human subject who has cancer. The invention is based, in part, on Applicants' discovery that two mutated recombinant chimeric toxins composed of GnRH and PE, referred to as LGnRH-PE40M and LGnRH-PE66M, bind to tumor cells without killing them. Since these chimeric toxins do not bind granulosa tumor cells which express natural GnRHR recognized by GnRH, the chimeric toxins of the invention recognize a new tumor-associated epitope expressed by adenocarcinomas. 4. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1A Nucleotide sequence (SEQ ID NO:l) and and IB. amino acid sequence (SEQ ID NO: 2) of LGnRH- PE66. Amino acid residue #575 identified within a square is deleted in a mutated chimeric toxin, LGnRH-PE66M. Figure 2. Nucleotide sequence (SEQ ID NO:3) and amino acid sequence (SEQ ID NO:4) of LGnRH-PE40. Amino acid residue #336 identified within a square is deleted in a, mutated chimeric toxin, LGnRH-PE40M. Figure 3 Mutated GnRH-PE. chimeric toxins, LGι__RH-PE40.M and LGnRH-PE66M, did not exhibit ADP- ribosylation activities. Figure 4. Mutated GnRH-PE chimeric toxins, LGnRH-PE40M and LGnRH-PE66M, did not inhibit protein synthesis in 293 renal carcinoma cells, while the non-mutated chimeric toxins showed cytotoxic activities . Inhibition of protein synthesis is used as an indication of cytotoxicity. Figure 5. GnRH-PE chimeric toxins did not inhibit protein synthesis of primary cultures of granulosa tumor cells which expressed natural GnRHR. 5. DETAILED DESCRIPTION OF THE INVENTION 5.1. PRODUCTION OF GnRH-PE CHIMERIC TOXINS While the GnRH-PE chimeric toxins of the present invention may be produced by chemical synthetic methods or by chemical linkage between the two moieties, it is preferred that they are produced by fusion of a coding sequence for GnRH and a coding sequence for PE under the control of a regulatory sequence which directs the expression of the fusion polynucleotide in an appropriate host cell (Nechushtan et al . , 1997, J. Biol. Chem. 272:11597). The fusion of two coding sequences can be achieved by methods well known in the art of molecular biology. The PE coding sequence suitable for use in the present invention, includes but is not limited to, full length PE, partial fragments of PE such as domains II and/or III of PE, mutated PE in which amino acid residues in domain I have been altered to reduce non-specific cytotoxicity and mutated PE which has minimal cytotoxic 5 activities (United States Patent No. 4,892,827, Lorberboum- Galski et al . , 1990, J. Biol . Chem. 265:16311). It is preferred that a fusion polynucleotide contain only the AUG translation initiation codon at the 5 ' end of the first coding sequence without the initiation codon of the second coding sequence to avoid the production of two encoded products. In addition, a leader sequence may be placed at the 5 ' end of the polynucleotide in order to target the expressed product to a specific site or compartment within a host cell to facilitate secretion or subsequent purification after gene expression. The two coding sequences can be fused directly without any linker or by using a flexible polylinker 15 composed of the pentamer Gly-Gly-Gly-Gly-Ser (SEQ ID NO: 5) repeated 1 to 3 times. Such linker has been used in constructing single chain antibodies (scFv) by being inserted between V H and V L (Bird et al . , 1988, Science 242:423-426; Huston et al . , 1988, Proc . Natl. Acad. Sci . U.S.A. 85:5979- 20 5883) . The linker is designed to enable the correct interaction between two beta-sheets forming the variable region of the single chain antibody. Other linkers which may be used include Glu-Gly-Lys-Ser-Ser-Gly-Ser-Gly-Ser-Glu-Ser- Lys-Val-Asp (SEQ ID NO: 6) (Chaudhary et al., 1990, Proc. Natl. Acad. Sci. U.S.A. 87:1066-1070) and Lys-Glu-Ser-Gly- 25 Ser-Val-Ser-Ser-Glu-Gln-Leu-Ala-Gln-Phe-Arg-Ser-Leu-Asp (SEQ ID N0:7) (Bird et al . , 1988, Science 242:423-426). 5.2. EXPRESSION OF GnRH-PE CHIMERIC TOXINS A polynucleotide which encodes a GnRH-PE chimeric toxin, mutant polypeptides, biologically active fragments of 30 chimeric protein, or functional equivalents thereof, may be used to generate recombinant DNA molecules that direct the expression of the chimeric toxin, mutant polypeptides, peptide fragments, or a functional equivalent thereof, in appropriate host cells. Due to the inherent degeneracy of the genetic code, other DNA sequences which encode 5 substantially the same or a functionally equivalent ammo acid sequence, may be used in the practice of the invention for the cloning and expression of the chimeric toxin. Altered DNA sequences which may be used in accordance with the invention include deletions, additions or substitutions of different nucleotide residues resulting in a lu sequence that encodes the same or a functionally equivalent fusion gene product. The gene product itself may contain deletions, additions or substitutions of amino acid residues within a chimeric sequence, which result in a silent change thus producing a functionally equivalent chimeric protein. Such amino acid substitutions may be made on the basis of 15 similarity in polarity, charge, solubility, hydrophobicity, hydrophilicity, and/or the amphipathic nature of the residues involved. For example, negatively charged amino acids include aspartic acid and glutamic acid; positively charged amino acids include lysine, histidine and arginine; amino acids with uncharged polar head groups having similar 20 hydrophilicity values include the following: glycine, asparagine, glutamine, serine, threonine, tyrosine; and amino acids with nonpolar head groups include alanine, valine, isoleucine, leucine, phenylalanine, proline, methionine, tryptophan. The DNA sequences of the invention may be engi- 25 neered in order to alter a chimeric coding sequence for a variety of ends, including but not limited to, alterations which modify processing and expression of the gene product. For example, mutations may be introduced using techniques which are well known in the art, e . g. , site-directed mutagenesis, to insert new restriction sites, to reduce 30 . . . cytotoxicities , etc . In an alternate embodiment of the invention, the coding sequence of the GnRH-PE chimeric toxin could be synthesized in whole or in part, using chemical methods well known in the art. See, for example, Caruthers et al., 1980, Nuc. Acids Res . Symp . Ser. 7:215-233 ; Crea and Horn, 180, ' Nuc. Acids Res . 9 (10) :2331; Matteucci and Caruthers, 1980, Tetrahedron Letter 21 : 719 ; and Chow and Kempe, 1981, Nuc. Acids Res . 9 (12) :2807-2817. In addition, GnRH decapeptide and specific domains of PE can be synthesized by solid phase techniques, cleaved from the resin, and purified by preparative high performance liquid chromatography followed by chemical linkage to form a chimeric toxin (e.g., see Creighton, 1983, Proteins Structures And Molecular Principles, W.H. Freeman and Co., Ν.Y. pp. 50-60). The composition of the synthetic peptides may be confirmed by amino acid analysis or sequencing (e.g., the Edman degradation procedure; see Creighton, 1983, Proteins, Structures and Molecular Principles , W.H. Freeman and Co., Ν.Y. , pp. 34-49) . Alternatively, the GnRH and PE produced by synthetic or recombinant methods may be conjugated by chemical linkers according to methods well known in the art (Brinkmann and Pastan, 1994, Biochemica et Biophysica Acta 1198:27-45) . In order to express a biologically active GnRH-PE chimeric toxin, the nucleotide sequence coding for a chimeric toxin, or a functional equivalent, is inserted into an appropriate expression vector, i . e . , a vector which contains the necessary elements for the transcription and translation of the inserted coding sequence. The chimeric toxin as well- as host cells or cell lines transfected or transformed with recombinant chimeric expression vectors can be used for a variety of purposes . These include but are not limited to generating antibodies (i.e., monoclonal or polyclonal) that bind to epitopes of the proteins to facilitate their purification. Methods which are well known to those skilled in the art can be used to construct expression vectors containing the GnRH-PE chimeric toxin coding sequence and *-* * appropriate transcriptional/translational control signals. These methods include in vi tro recombinant DNA techniques, synthetic techniques and in vivo recombination/genetic recombination. See, for example, the techniques described in Sambrook et al . , 1989, Molecular Cloning A Laboratory -Manual, o Cold Spring Harbor Laboratory, N.Y. and Ausubel et al . , 1989, Current Protocols in Molecular Biology, Greene Publishing Associates and Wiley Interscience, N.Y. A variety of host-expression vector systems may be utilized to express the GnRH-PE chimeric protein coding sequence. These include but are not limited to 5 microorganisms such as bacteria transformed with recombinant bacteriophage DNA, plasmid DNA or cosmid DNA expression vectors containing the chimeric toxin coding sequence; yeast transformed with recombinant yeast expression vectors containing the chimeric toxin coding sequence; insect cell systems infected with recombinant virus expression vectors 0 (e.g. , baculovirus) containing the chimeric toxin coding sequence; plant cell systems infected with recombinant virus expression vectors (e.g. , cauliflower mosaic virus, CaMV; tobacco mosaic virus, TMV) or transformed with recombinant plasmid expression vectors (e.g. , Ti plasmid) containing the chimeric toxin coding sequence; or animal cell systems. It 5 should be noted that since PE normally kills mammalian cells, it is preferred that the chimeric toxins of the invention be expressed in prokaryotic or lower eukaryotic cells. Section~ 6 illustrates that GnRH-PE chimeric toxins can be efficiently expressed in E. coli . However, since the mutated GnRH-PE chimeric toxins in Section 6, infra, do not exhibit cytotoxic 0 activities towards human cells, they may be expressed in eukaryotic cells as well. The expression elements of each system vary in their strength and specificities. Depending on the host/vector system utilized, any of a number of suitable 5 transcription and translation elements, including constitutive and inducible promoters, may be used in the expression vector. For example, when cloning in bacterial systems, inducible promoters such as pL of bacteriophage λ, plac, ptrp, ptac (ptrp-lac hybrid promoter; cytomegalovirus promoter) and the like may be used; when cloning in insect ■ **• ■ - •■ cell systems, promoters such as the baculovirus polyhedrin promoter may be used; when cloning in plant cell systems, promoters derived from the genome of plant cells (e.g. , heat shock promoters; the promoter for the small subunit of RUBISCO; the promoter for the chlorophyll α/β binding protein) or from plant viruses (e.g. , the 35S RNA promoter of ■*■■ - ■•* CaMV; the coat protein promoter of TMV) may be used; when cloning in mammalian cell systems, promoters derived from the genome of mammalian cells (e.g. , metallothionein promoter) or from mammalian viruses (e.g.. the adenovirus late promoter; the vaccinia virus 7.5K promoter) may be used; when generating cell lines that contain multiple copies of the 20 chimeric DNA, SV40-, BPV- and EBV-based vectors may be used with an appropriate selectable marker. In bacterial systems a number of expression vectors may be advantageously selected depending upon the use intended for the chimeric toxin expressed. For example, when large quantities of chimeric toxin are to be produced, 2 5 vectors which direct the expression of high levels of protein products that are readily purified may be desirable. Such vectors include but are not limited to the pHL906 vector (Fishman et al . , 1994, Biochem. 33:6235-6243), the E. coli expression vector pUR278 (Ruther et al . , 1983, EMBO J. 2:1791), in which the chimeric protein coding sequence may be ligated into the vector in frame with the lacZ coding region so that a hybrid lacZ protein is produced; pIN vectors (Inouye & Inouye, 1985, Nucleic acids Res. 13:3101-3109; Van Heeke & Schuster, 1989, J. Biol . Chem. 264:5503-5509); and the like. An alternative expression system which could be 5 ' used to express chimeric toxin is an insect system. In one such system, Autographa californica nuclear polyhidrosis virus (AcNPV) is used as a vector to express foreign genes . The virus grows in Spodoptera frugiperda cells. The chimeric toxin coding sequence may be cloned into ήon-essentia ' l 0 regions (for example the polyhedrin gene) of the virus and placed under control of an AcNPV promoter (for example the polyhedrin promoter) . Successful insertion of the chimeric protein coding sequence will result in inactivation of the polyhedrin gene and production of non-occluded recombinant virus (i.e. , virus lacking the proteinaceous coat coded for 5 by the polyhedrin gene) . These recombinant viruses are then used to infect Spodoptera frugiperda cells in which the inserted gene is expressed. (e.g. , see Smith et al . , 1983, J. Viol. 46:584; Smith, U.S. Patent No. 4,215,051). Specific initiation signals may also be required for efficient translation of the inserted chimeric toxin u coding sequence. These signals include the ATG initiation codon and adjacent sequences. In cases where the entire chimeric gene, including its own initiation codon and adjacent sequences, is inserted into the appropriate expression vector, no additional translational control signals may be needed. However, in cases where the chimeric 5 toxin coding sequence does not include its own initiation codon, exogenous translational control signals, including the ATG initiation codon, must be provided. Furthermore, the initiation codon must be in phase with the reading frame of the chimeric protein coding sequence to ensure translation of the entire insert. These exogenous translational control ( - * signals and initiation codons can be of a variety of origins, both natural and synthetic : - The efficiency of expression may be enhanced by the inclusion of appropriate transcription enhancer elements, transcription terminators, etc. (see Bittner et al . , 1987, Methods in Enzymol . 153:516-544). In addition, a host cell strain may be chosen which modulates the expression of the inserted sequences, or modifies and processes the gene product in the specific fashion desired. Such modifications (e.g. , glycosylation) and processing (e.g.. cleavage) of protein products may be important for the function of the protein. Different host cells have characteristic and specific mechanisms for the- post-translational processing and modification of proteins. Appropriate cell lines or host systems can be chosen to ensure the correct modification and processing of the chimeric toxin. To this end, eukaryotic host cells which possess the cellular machinery for proper processing of the primary transcript, glycosylation, and phosphorylation of the chimeric protein may be used. Such mammalian host cells include but are not limited to CHO, VERO, BHK, HeLa, COS, MDCK, 293, WI38, and the like. For long-term, high-yield production of recombinant chimeric toxins, stable expression is preferred. For example, bacterial host cells or eukaryotic cell lines which stably express the chimeric toxins may be engineered. Rather than using expression vectors which contain viral origins of replication, host cells can be transformed with a chimeric coding sequence controlled by appropriate expression control elements (e.g.. promoter, enhancer, sequences, transcription terminators, polyadenylation sites, etc.), and a selectable marker. Following the introduction of foreign DNA, engineered cells may be allowed to grow for 1-2 days in an enriched media, and then are switched to a selective media. The selectable marker in the recombinant plasmid confers resistance to the selection and allows cells to stably integrate the plasmid into their chromosomes and grow to form foci which in turn can be cloned and expanded into cell lines . A number of selection systems may be used, including but not limited to the herpes simplex virus thymidine kinase (Wigler et al . , 1977, Cell 11:223), hypoxanthine-guanine phosphoribosyltransferase (Szybalska & Szybalski, 1962, Proc. Natl. Acad. Sci. USA 48:2026), and 5 ' adenine phosphoribosyltransferase (Lowy et al . , 1980, Cell 22:817) genes can be employed in tk ~ , hgprt " or aprt " cells, respectively. Also, antimetabolite resistance can be used as the basis of selection for dh.fr, which confers resistance to methotrexate (Wigler et al . , 1980, Natl. Acad. Sci. USA 10 77:3567; 0 • Hare et al . , 1981, Proc. Natl. Acad. Sci. USA 78:1527); gpt, which confers resistance to mycophenolic acid (Mulligan & Berg, 1981, Proc. Natl. Acad. Sci. USA 78:2072); neo, which confers resistance to the aminoglycoside G-418 (Colberre-Garapin et al . , 1981, J. Mol . Biol . 150:1); and 15 hygro, which confers resistance to hygromycin (Santerre et al . , 1984, Gene 30:147) genes. Additional selectable genes have been described, namely trpB, which allows cells to utilize indole in place of tryptophan; hisD, which allows cells to utilize histinol in place of histidine (Hartman & Mulligan, 1988, Proc. Natl. Acad. Sci. USA 85:8047); and ODC (ornithine decarboxylase) which confers resistance to the ornithine decarboxylase inhibitor, 2- (difluoromethyl) -DL- ornithine, DFMO (McConlogue L. , 1987, In: Current Communications in Molecular Biology, Cold Spring Harbor Laboratory ed. ) . 25 5.3. PROTEIN PURIFICATION The GnRH-PE chimeric toxins of the invention can be purified by art-known techniques such as high performance liquid chromatography, ion exchange chromatography, gel electrophoresis, affinity chromatography and the like. The 30 actual conditions used to purify each protein will depend, in part, on factors such as net charge, hydrophobicity, hydrophilicity, etc., and will be apparent to those having skill in the art. For affinity chromatography purification, any antibody which specifically binds GnRH, PE or a conformational epitope created by the fusion of GnRH and PE 5 may be used. For the production of antibodies, various host animals, including but not limited to rabbits, mice, rats, etc., may be immunized by injection with GnRH-PE chimeric toxin or a portion thereof. The protein may be attached to a suitable carrier, such as bovine serum albumin (BSA) , * by . means of a side chain functional group or linkers attached to ■ *-' • - ■ a side chain functional group. Various adjuvants may be used to increase the immunological response, depending on the host species, including but not limited to, Freund's (complete and incomplete) , mineral gels such as aluminum hydroxide, surface active substances such as lysolecithin, pluronic polyols, polyanions, peptides, oil emulsions, keyhole limpet * ■ * ■■ --' hemocyanin, dinitrophenol , and potentially useful human adjuvants such as BCG (bacilli Calmette-Guerin) and Corynebacterium par um. Monoclonal antibodies to GnRH-PE may be prepared using any technique which provides for the production of antibody molecules by continuous cell lines in culture. 20 These include but are not limited to the hybridoma technique originally described by Koehler and Milstein (1975, Nature 256 :495-497) . In addition, techniques developed for the production of "chimeric antibodies" (Morrison et al . , 1984, Proc. Natl. Acad. Sci. U.S.A. 8_1: 6851-6855 ; Neuberger et al . , 25 1984, Nature 312:604-608; Takeda et al . , 1985, Nature 314:452-454) by splicing the genes from a mouse antibody molecule of appropriate antigen specificity together with genes from a human antibody molecule of appropriate biological activity can be used. Alternatively, techniques described for the production of single chain antibodies (U.S. 30 Patent No. 4,946,778) can be adapted to produce GnRH-PE- specific single chain antibodies for protein purification and detection. 5.4. CANCER DIAGNOSIS USING GnRH-PE CHIMERIC TOXINS The GnRH-PE chimeric toxins of the invention may be used to detect human tumors in vi tro and in vivo . It is preferred that such toxins be mutated to abrogate their cytotoxic properties without affecting their binding specificity for tumor cells. Two examples of such GnRH-PE are illustrated in Section 6, infra . The GnRH-PE chimeric toxins of the invention may be used to detect an epitope expressed by a wide variety of human adenocarcinomas, including but not limited to, colon adenocarcinoma, breast adenocarcinoma, lung adenocarcinoma, ovarian adenocarcinoma, endometrial adenocarcinoma, kidney adenocarcinoma, liver adenocarcinoma, prostate adenocarcinoma, stomach adenocarcinoma, cervical adenocarcinoma, gall bladder adenocarcinoma and pancreatic adenocarcinoma. The chimeric toxins of the invention are particularly useful in differentiating adenocarcinomas from non-adenocarcinomas and normal cells that express the natural GnRHR. 5.4.1. IN VITRO DIAGNOSTIC APPLICATIONS The GnRH-PE chimeric toxins of the present invention can be used to detect cancer cells in a biological specimen such as histological and cytological specimens, and, in particular, to distinguish malignant tumors from normal tissues and non-malignant tumors for determination of surgical margin and an improved histological characterization of poorly differentiated tumors. Tissue specimens may be stained by the chimeric toxins and their binding detected by- a secondary antibody specific for a portion of the chimeric toxin. The secondary antibody is conjugated to a detectable label such as a radioisotope, an enzyme such as peroxidase and alkaline phosphatase, an ultrasonic probe, a nuclear magnetic resonance (NMR) probe, and the like. In addition, immunofluorescence techniques can use GnRH-PE to examine human tissue, cell and bodily fluid specimens. In a typical protocol, slides containing cryostat sections of frozen, unfixed tissue biopsy samples or cytological smears are air dried, formalin or acetone fixed, 5 and incubated with the GnRH-PE in a humidified chamber at room temperature. The slides are then washed and further incubated with a preparation of a secondary antibody directed against GnRH-PE. The secondary antibody is tagged with a compound such as rhodamine, phycoerythrin or fluorescein 10 isothiocyanate, that fluoresces at a particular wavelength. The staining pattern and intensities within the sample are then determined by fluorescent light microscopy and optionally photographically recorded. In another embodiment, computer enhanced fluorescence image analysis or flow cytometry can be used to ■ * ■• - ■• - examine tissue specimens or exfoliated cells, i.e., single cell preparations from aspiration biopsies of tumors using GnRH-PE. The GnRH-PE chimeric toxins of the invention are particularly useful in quantitation of live tumor cells, i.e., single cell preparations from aspiration biopsies of adenocarcinomas by computer enhanced fluorescence image 20 analyzer or with a flow cytometer. The percent GnRH-PE-bound cell population, alone or in conjunction with determination of the DNA ploidy of these cells, may, additionally, provide very useful prognostic information by providing an early indicator of disease progression. The use of GnRH-PE can be extended to the screening 25 of human biological fluids for the presence of the specific antigenic determinants recognized. In vi tro immunoserological evaluation of biological fluids withdrawn from patients thereby permits non-invasive diagnosis of cancers. By way of illustration, human bodily fluids such as whole blood, pleural effusion fluid, cerebral spinal fluid, 30 synovial fluid, prostatic fluid, seminal fluid or urine can be taken from a patient and assayed for the specific epitope, either as released antigen or membrane-bound on cells in the sample fluid, using GnRH-PE in standard radioimmunoassays or enzyme-linked immunoassays, competitive binding enzyme-linked immunoassays, dot blot or Western blot, or other assays known 5 in the art . Kits containing GnRH-PE can be prepared for in vitro diagnosis, prognosis and/or monitoring adenocarcinomas by the immunohistological, immunocytological and immunoserological methods described above . The components of * the kits can be packaged either in aqueous medium or in lyophilized form. When the GnRH-PE is used in the kits in the form of conjugates in which a label moiety is attached, such as an enzyme or a radioactive metal ion, the components of such conjugates can be supplied either in fully conjugated form, in the form of intermediates or as separate moieties to be conjugated by the user of the kit. A kit may comprise a carrier being compartmentalized to receive in close confinement therein one or more container means or series of container means such as test tubes, vials, flasks, bottles, syringes, or the like. A first of said container means or series of container means _.__ may contain GnRH-PE. A second container means or series of 20 container means may contain a label or linker-label intermediate capable of binding to GnRH-PE. 5.4.2. IN VIVO DIAGNOSTIC APPLICATIONS GnRH-PE chimeric toxins are also useful for 25 targeting adenocarcinoma cells in vivo . They can be used for tumor localization in the detection and monitoring of primary tumors as well as metastases, especially lymph nodes. Primary evaluation of the extent of tumor spread may influence the choice of therapeutic modalities. Continued monitoring of residual tumors may also contribute to better 30 surveillance and early initiation of salvage therapy. Tagged GnRH-PE may also be used intraoperatively for better debulking of a tumor, and minimizes normal tissue destruction such as lymph nodes. For these in vivo applications, it is preferred that highly purified GnRH-PE be used. For in vivo detection and/or monitoring of adenocarcinomas, the purified GnRH-PE can be covalently attached, either directly or via a linker, to a compound which serves as a reporter group to permit imaging of specific tissues or organs following administration and localization of the conjugates or complexes. A variety of different types of substances can serve as the reporter group, including such as radiopaque dyes, radioactive metal and non-metal isotopes, fluorogenic compounds, fluorescent compounds, positron emitting isotopes, non-paramagnetic metals, etc. Kits for use with such in vivo tumor localization methods containing GnRH-PE (or fragments thereof) conjugated to any of the above types of substances can be prepared. The components of the kits can be packaged either in aqueous medium or in lyophilized form. When the chimeric toxins are used in the kits in the form of conjugates in which a label is attached, the components of such conjugates can be supplied either in fully conjugated form, in the form of intermediates or as separate moieties to be conjugated by the user of the kit. 6. EXAMPLE: MUTATED GnRH-PE CHIMERIC TOXINS BOUND BUT DID NOT KILL TUMOR CELLS 6.1. MATERIALS AND METHODS 6.1.1. CONSTRUCTION OF GnRH-PE CHIMERIC TOXINS A plasmid vector carrying a full length PE gene (pJY3A1136-l,3) (Chaudhary et al . , 1990, J. Biol. Chem. 265:16306-16310; Neshushtan et al . , 1997, J. Biol. Chem. 272:11597) was cut with Ndel and Hindlll. A 36 base pair (bp) synthetic oligomer flanked by Ndel (5' end) and Hindlll (3* end) restriction sites was ligated to the vector. This oligomer insert contained a GnRH coding sequence in which the encoded amino acid at residue #6 was tryptophan instead of glycine. In addition, a sequence encoding a linker Gly-Gly- Gly-Gly-Ser (SEQ ID NO: 5) repeated twice was placed between the GnRH coding sequence and the PE coding sequence . The 5 resultant plasmid encoded a chimeric toxin, LGnRH-PE66 and it was confirmed by restriction endonuclease digestion and DNA sequence analysis (Figure 1A and IB) . In order to produce a second chimeric toxin, LGnRH- PE40, the plasmid vector encoding LGnRH-PE66 was digested with Ndel and BamHI and ligated to a Ndel-BamHI 750 bp 10 fragment obtained from the plasmid PHL-906 (Fishman et al . , 1994, Biochemistry 33:6235-6243) along with the 36 bp synthetic oligomer consisting of the GnRH coding sequence with tryptophan replacing glycine at the sixth amino acid position. A sequence encoding the above linker was again placed between the GnRH coding sequence and the PE coding 15 sequence. The resultant plasmid encoded a chimeric toxin, LGnRH-PE40, and it was confirmed by restriction endonuclease digestion and DNA sequence analysis (Figure 2) . The toxin encoded by this plasmid consisted of domains II and III of the full-length PE. 20 6.1.2. GENERATION OF MUTATED GnRH-PE CHIMERIC TOXINS In order to construct GnRH-PE chimeric toxins that were not cytotoxic to human cells, the region in the two aforementioned plasmids that encoded 122 amino acids at the 2 _ C-terminal end of PE of LGnRH-PE66 and LGnRH-PE40 was excised with BamHI and EcoRI and replaced with a corresponding fragment which contained a deletion of a single codon encoding the amino acid at position 553 of the native- PE molecule (Figures 1A, IB and 2) (Fishman et al . , 1997, Eur. J. Immunol. 27:486; Lukoc et al . , 1988, Infect. Immun. 30 56:3095) . The mutated chimeric toxins are referred to as LGnRH-PE66M and LGnRH-PE40M„ respectively. 6.1.3. EXPRESSION OF GnRH-PE CHIMERIC TOXINS The plasmids, pVMl and pVM2 , encoding the mutated GnRH-PE chimeric toxins, LGnRH-PE66M and LGnRH-PE40M, respectively, were expressed in E. coli strain BL21 (λDE3) . The plasmids that encoded LGnRH-PE40 and LGnRH-PE66 were also expressed in the same bacteria. The plasmids were transferred into E. coli and the cells were grown in medium containing ampicillin. After reaching an A 600 value of 1.5- 1.7, the cultures were induced at 37°C with 1 mM isopropyl-1- thio-β-D-galactopyranoside. The cells were collected by centrifugation and the pellet was stored at -70°C for several hours . A pellet of expressing cells was suspended in lysis buffer (50 mM Tris-HCl at pH 8.0, ImM EDTA containing 0.2 mg/ml lysosyme) , sonicated (three 30 second bursts) and centrifuged at 30,000xg for 30 min. The supernatant (soluble fraction) was removed and kept for analysis. The pellet (insoluble fraction) was denatured in extraction buffer (6 M guanidinium-HCl , 0.1 M Tris-HCl, pH 8.6, ImM EDTA, 0.05 M NaCl, and 10 mM dithiothreitol) and stirred for 30 min at 4°C. The suspension was cleared by centrifugation at 30000xg for 15 min and the pellet discarded. The supernatant was then dialyzed against 0.1 M Tris-HCl pH 8.0, ImM EDTA, 0.25mM NaCl, and 0.25mM L-arginine for 16 hours. The dialyzate was centrifuged at 15000xg for 15 min and the resulting supernatant (refolding fraction) was used as a source of the GnRH-PE chimeric toxins. Analysis of the fraction by SDS/PAGE revealed a major band corresponding to the chimeric toxin. Immunoblotting with polyclonal antibodies against PE confirmed the production of GnRH-PE chimeric toxins. 6.1.4. PURIFICATION OF RECOMBINANT GnRH-PE CHIMERIC TOXINS The refolded protein fractions were diluted with TE20 buffer (20mM Tris, pH 8.0, ImM EDTA). DEAE Sepharose (Pharmacia, Sweden) was added and stirred for half an hour at 4°C before being packed into a column. Washing of the column was done with 80mM NaCl or 50mM Nacl in TE20 buffer. Elution of protein was performed with the linear gradient of 2 x 200ml of 0.08-0.35M NaCl in TE20 (20mM Tris pH 8.0, ImM EDTA) buffer. The peak fractions were pooled, dialyzed against phosphate saline buffer and kept in aliquots at -20°C. 6.2. RESULTS A recombinant GnRH-PE chimeric toxin, LGnRH-PE66, was produced by fusion of a GnRH coding sequence and a PE coding sequence with the insertion of a linker between the two moieties. A second GnRH-PE chimeric toxin, LGnRH-PE40, was produced in a similar manner except that only domains II and III of PE was encoded by the toxin coding sequence. In addition, the coding sequences of these two chimeric toxins were mutated to result in a single amino acid deletion in the PE portion. The mutated chimeric toxins were also expressed as recombinant proteins . The four GnRH-PE chimeric toxins were purified from E. coli lysates and refolded. Since PE kills eukaryotic cells by inactivating elongation factor 2 through ADP- ribosylation during protein synthesis, the four forms of GnRH-PE chimeric toxins were tested in a cell free assay for their enzymatic activities in ADP-ribosylation (Chung and Collier, 1977, J. Infect. Immun. 16:832-841). While the two non-mutated GnRH-PE chimeric toxins, LGnRH-PE40 and LGnRH- PE66, exhibited ADP-ribosylation activities, the mutated chimeric toxins, LGnRH-PE40M and LGnRH-PE66M, were completely inactive in the same assay (Figure 3) . Thus, a single amino__ acid substitution in PE abrogated the enzymatic activities of the chimeric toxins . In addition, all four GnRH-PE chimeric toxins were tested for their ability to kill 293 renal adenocarcinoma cells . It was shown that only the non-mutated chimeric toxins showed dose-dependent inhibition of protein synthesis in the target cells (Figure 4) . However, when the chimeric toxins were incubated with the same target cells and their binding was detected by a labeled anti-PE antibody and FACS analysis, all four toxins were able to bind renal carcinoma cells with no binding to control T24A bladder carcinoma cells. Therefore, while the mutated GnRH-PE chimeric toxins were not able to kill target cells, they retained the ability to bind to tumor cells. Such non-cytotoxic chimeric toxins are particularly useful for use in cancer diagnosis in vi tro and in vivo. Primary granulosa tumor cells were obtained and shown to express GnRHR by PCR using primers corresponding to specific portions of the GnRHR. The PCR product in granulosa cells was the same size as that obtained from pituitary cells which expressed natural GnRHR. In contrast, GnRHR-negative cells such as normal human lymphocytes did not produce a detectable PCR product . Notwithstanding their expression of natural GnRHR, the granulosa cells were not susceptible to killing by any of the four GnRH-PE chimeric toxins, indicating that the chimeric toxins bind to a new epitope expressed by adenocarcinoma cells that is distinct from that bound by GnRH itself (Figure 5) . The present invention is not to be limited in scope by the exemplified embodiments which are intended as illustrations of single aspects of the invention and any sequences which are functionally equivalent are within the scope of the invention. Indeed, various modifications of the invention in addition to those shown and described herein will become apparent to those skilled in the art from the foregoing description and accompanying drawings. Such modifications are intended to fall within the scope of the appended claims . All publications cited herein are incorporated by reference in their entirety.

Claims: WHAT IS CLAIMED IS 1. A method for detecting a tumor cell in a biological specimen, comprising contacting the biological specimen with a chimeric toxin which comprises gonadotropin releasing hormone and Pseudomonas extotoxin A, and detecting chimeric toxin-bound cells in the specimen. 2. The method of Claim 1 in which biological specimen contains adenocarcinoma cells. 3. The method of Claim 2 in which the adenocarcinoma cells are selected from a group consisting of colon adenocarcinoma, breast adenocarcinoma, lung adenocarcinoma, overian adenocarcinoma, endometrial adenocarcinoma, kidney adenocarcinoma, liver adenocarcinoma, prostate adenocarcinoma, stomach adenocarcinoma, cervical adenocarcinoma, gall bladder adenocarcinoma and pancreatic adenocarcinoma . 4. The method of Claim 1 in which the Pseudomonas exotoxin is a full-length toxin. 5. The method of Claim 1 in which the Pseudomonas exotoxin contains only domains II and III of a full-length toxin. 6. The method of Claim 1 in which the chimeric toxin comprises the amino acid sequence as shown in SEQ ID NO:2. 7. The method of Claim 6 in which the chimeric toxin is encoded by a polynucleotide which comprises the nucleotide sequence as shown in SEQ ID NO:l. 8. The method of Claim 1 in which the chimeric toxin comprises the amino acid sequence of SEQ ID NO:4. 9. The method of Claim 8 in which the chimeric toxin is encoded by a polynucleotide which comprises the nucleotide sequence as shown in SEQ ID NO: 3. 10. The method of Claim 1 in which the Pseudomonas exotoxin is rendered non-cytotoxic. 11. The method of Claim 10 in which the Pseudomonas exotoxin is rendered non-cytotoxic by deleting an amino acid residue. 12. The method of Claim 1 in which the chimeric toxin comprises the amino acid sequence as shown in SEQ ID NO: 2 wherein amino acid residue #575 is deleted. 13. The method of Claim 12 in which the chimeric toxin is encoded by a polynucleotide which comprises the nucleotide sequence as shown as SEQ ID NO : 1 wherein nucleotides #1822-1824 are deleted. 14. The method of Claim 1 in which the chimeric toxin comprises the amino acid sequence as shown in SEQ ID NO: 4 wherein amino acid residue #336 is deleted. 15. The method of Claim 14 in which the chimeric toxin is encoded by a polynucleotide which comprises the nucleotide sequence as shown in SEQ ID NO: 3 wherein nucleotides #1105-1107 are deleted. 16. The method of Claim 1 in which the chimeric toxin is conjugated to a detectable label. 17. The method of Claim 16 in which the detectable label is a radioisotope, a fluorescent dye, an enzyme, an ultrasonic probe or a NMR probe. 18. The method of Claim 1 in which the biological 5 specimen is a biopsy specimen. 19. The method of Claim 1 in which the biological specimen is a bodily fluid. 20. The method of Claim 19 in which the bodily ■**■■■ - ■ fluid is whole blood. 21. The method of Claim 19 in which the bodily fluid is pleural effusion fluid. 22. The method of Claim 19 in which the bodily 15 fluid is urine. 23. A method of detecting a tumor cell in a human subject, comprising administering to the subject a chimeric toxin which comprises gonadotropin releasing hormone and Pseudomonas exotoxin A, and detecting chimeric toxin-bound 20 cells in the subject. 24. The method of Claim 23 in which the subject has adenocarcinoma. 25. The method of Claim 24 in which the 25 adenocarcinoma is selected from a group consisting of colon adenocarcinoma, breast adenocarcinoma, lung adenocarcinoma, overian adenocarcinoma, endometrial adenocarcinoma, kidney adenocarcinoma, liver adenocarcinoma, prostate adenocarcinoma, stomach adenocarcinoma, cervical adenocarcinoma, gall bladder adenocarcinoma and pancreatic 30 adenocarcinoma . 26. The method of Claim 1 in which the Pseudomonas exotoxin is rendered non-cytotoxic. 27. The method of Claim 26 in which the Pseudomonas exotoxin is rendered non-cytotoxic by deleting an amino acid residue . 28. The method of Claim 1 in which the chimeric toxin comprises the amino acid sequence as shown in SEQ ID NO: 2 wherein amino acid residue #575 is deleted. 29. The method of Claim 28 in which the chimeric toxin is encoded by a polynucleotide which comprises the nucleotide sequence as shown in SEQ ID NO : 1 wherein nucleotides #1822-1824 are deleted. 30. The method of Claim 1 in which the chimeric toxin comprises the amino acid sequence as shown in SEQ ID NO: 4 wherein amino acid residue #336 is deleted. 31. The method of Claim 30 in which the chimeric toxin is encoded by a polynucleotide which comprises the nucleotide sequence as shown in SEQ ID NO: 3 wherein nucleotides #1105-1107 are deleted. 32. The method of Claim 23 in which the chimeric toxin is conjugated to a detectable label. 33. The method of Claim 32 in which the detectable label is a radioisotope, a fluorescent dye, an enzyme, an ultrasonic probe or a NMR probe. 34. A chimeric toxin comprising gonadotropin releasing hormone and Pseudomonas exotoxin A, wherein the toxin binds but does not kill tumor cells. 35. The chimeric toxin of Claim 34 which comprises the amino acid sequence as shown in SEQ ID NO: 2 wherein the amino acid residue #575 is deleted. 36. The chimeric toxin of Claim 35 which is encoded by a polynucleotide which comprises the nucleotide sequence as shown in SEQ ID NO:l wherein nucleotides #1822- 1824 are deleted. 37. The chimeric toxin of Claim 34 which comprises the amino acid sequence as shown in SEQ ID NO: 4 wherein the amino acid residue #336 is deleted. 38. The chimeric toxin of Claim 37 which is encoded by a polynucleotide which comprises the nucleotide sequence as shown in SEQ ID NO: 3 wherein nucleotides #1105- 1107 are deleted.

Inventors: BEN-YEHUDAH AMI, LORBERBOUM-GALSKI HAYA, MARIANOVSKY IRINA, NECHUSHTAN AMOTZ, YARKONI SHAI, BEN-YEHUDAH, AMI, LORBERBOUM-GALSKI, HAYA, MARIANOVSKY, IRINA, NECHUSHTAN, AMOTZ, YARKONI, SHAI
Applicants: YISSUM RES DEV CO, YISSUM RESEARCH DEVELOPMENT COMPANY OF THE HEBREW
Application year: 1999
Main classification: C12N15
IPC codes: C07K7, C07K14, G01N33