Natural antibodies directed against murine lymphosarcoma cells.

Natural antibodies reacting in a test of complement-dependent cytotoxicity with untreated murine lymphosarcoma cells of thymic origin were found in murine sera. Normal thymus cells were unaffected and unable to absorb the serum activity. The natural antibodies were IgM-like and stable at 56 degrees C. They were not uniformly distributed in the studied strains, and high (C3H/He and C3Hf), intermediate (AKR and CBA/J), and low level strains (BALB/c, DBA/2, C57BL, and C57BL/6J) were found. Hybrids between a high (C3Hf) and a low level strain (C57BL) had the same response as the parental C3Hf mice. An inverse relationship was demonstrated between cytotoxicity of, and susceptibility to, serum of lymphoma cells in a given strain, which suggested that an immunologic modulation was at work. Embryonic cells absorbed the cytotoxic activity of the normal serum.

Embryonic antigens shared between chemically induced lymphosarcomas and fibrosarcomas of the mouse.

An antiserum obtained by the immunization of C57BL/HeDp mice with a pool of C3HF/Dp 7,12-dimethylbenz[alpha]anthracene (DMBA)-induced fibrosarcomas exerted a specific cytotoxic activity in vitro on C57BL/HeDp chemically induced lymphosarcomas. Conversely, C57BL/HeDp spleen cells sensitized against C3Hf/Dp chemically induced lymphosarcomas or embryo cells were cytotoxic for plated cells of syngeneic DMBA-induced fibrosarcomas. Absorption studies with antiembryo and antilymphoma antisera showed that embryonic antigens were shared between lymphosarcomas and fibrosarcomas and that all serologically defined antigens present on lymphoma cells, including virus-related antigens, were also on fibrosarcoma cells.

Human renal antigen defined by a murine monoclonal antibody.

Fusion of spleen cells from a mouse immunized with a surgical specimen of a human renal carcinoma with murine P3 myeloma cells resulted in the establishment of a hybridoma cell line that secreted a monoclonal antibody (MKi-1), of IgG1 subclass, which preferentially reacted on kidney crude membrane (CM) preparations. This monoclonal antibody was tested by solid-phase radioimmunometric assay and immunofluorescence (IF) on a panel of tumor cell lines and on CM preparations and cell suspensions from surgical specimens of normal and neoplastic tissues. In addition, cryosections of normal and cancer tissues of various histologic types were tested by IF. The expression of the MKi-1 antigen was limited to normal kidney epithelium, renal cancers, some areas in the pancreas, the apical region of some breast ducts, and a proportion (5-50%) of activated lymphocytes. Electron microscopic study by the immunoperoxidase technique on fixed sections from normal kidney showed that MKi-1 stained the brush border of almost all proximal tubules. The molecule recognized by MKi-1 was a single polypeptide chain with a molecular weight of 140,000.

Ricin A chain conjugated with monoclonal antibodies selectively killing human carcinoma cells in vitro.

Ricin A chain was coupled to murine monoclonal antibodies MBr1 and MOv2 respectively raised against human breast and ovarian carcinomas. Inhibition of protein synthesis only occurred in those cultured human tumor cells bearing the appropriate target antigens, demonstrating that both components of the conjugate were unchanged in regards to specificity and toxicity. Conjugates were 125-200 times more efficient in inhibiting [3H]proline incorporation than the uncoupled ricin A chain. They were however unable to kill the entire population of the appropriate cells even after repeated treatment. Although the two monoclonal antibodies had similar binding kinetics, the conjugates differed in their cytotoxicity kinetics. The MBr1-ricin A chain conjugate had slow kinetics, and about 20 hours were needed to obtain a protein synthesis inhibition above 50% on the appropriate line (mammary carcinoma MCF-7). In contrast, the MOv2-ricin A chain conjugate showed very fast kinetics, reaching 50% inhibition after only 30 minutes of treatment on both appropriate cell lines SW626 and HT-29 from ovarian and colon carcinomas, respectively. Growth conditions of cell lines, i.e., adherent cells versus suspended cells, and plating time were found to greatly influence the conjugates' killing efficiencies. These studies confirm the possibility of preparing ricin A chain-antibody conjugates, which retain specific cytotoxicity against tumor cells; but they also underline the need for further in vitro studies of various parameters before one considers a therapeutic use of such conjugates.

Prognostic significance of the 67-kilodalton laminin receptor expression in human breast carcinomas.

BACKGROUND: The 67-kd laminin receptor is a cell-surface protein that binds laminin with high affinity. In vitro studies suggest that this protein is involved in the progression of human tumors to invasive cancers (metastasis), but there have been few in vivo studies. Identification of such proteins would allow development of therapies aimed at interfering with their mechanisms of action. PURPOSE: This large retrospective study was designed to investigate the association of expression of this laminin receptor molecule with established prognostic factors and overall survival in breast carcinoma patients. METHODS: We immunohistochemically stained archival paraffin-embedded sections of 1160 primary breast carcinomas, using an immunoperoxidase technique and the MLuC5 monoclonal antibody, which is specific for the 67-kd laminin receptor. Specimens were obtained from consecutive surgeries performed from January 1968 through December 1971. Patients with negative lymph nodes or involved regional nodes had been treated with surgery alone; those with positive axillary nodes had received surgery and radiotherapy. No chemotherapy had been administered until disease recurrence. The statistical analysis was carried out using the logrank method for the survival curves and the actuarial life table to calculate survival rates according to the different prognostic variables. RESULTS: We found statistically significant associations between laminin receptor expression and young age (P < .001), premenopausal status (P = .001), positive axillary lymph nodes (P = .01), peritumoral lymphatic invasion (P = .02), and the diameter of the tumor (P = .05). Moreover, the association of expression of the receptor protein with poor prognosis, as indicated by survival curves, was statistically significant (P < .01). For patients with receptor-negative tumors, the survival rate was 50% at 20 years; for those with receptor-positive tumors, the survival rate was 50% at 13 years. Multivariate analysis showed the laminin receptor to be an independent prognostic factor (P = .005), indicating its predictive value in relation to overall survival. CONCLUSIONS: Our data suggest that the 67-kd laminin receptor is associated with the metastatic process. IMPLICATIONS: These preliminary findings also suggest that hormones may have a regulatory role in the in vivo expression of the 67-kd laminin receptor, which supports the hypothesis that hormone therapy might inhibit expression of the receptor. Studies of expression of this receptor in tumors of patients with extremely different sex hormone levels (e.g., men and pregnant women) are in progress.

Regression of advanced ovarian carcinoma by intraperitoneal treatment with autologous T lymphocytes retargeted by a bispecific monoclonal antibody.

BACKGROUND: The high frequency of relapse after induction chemotherapy of advanced ovarian carcinoma calls for new therapeutic approaches. Lysis of ovarian carcinoma cells can be achieved by retargeting of T lymphocytes using F(ab')2 fragments of the bispecific monoclonal antibody (MAb) OC/TR, which is directed to the CD3 molecule on T lymphocytes and to the folate receptor on ovarian carcinoma cells. PURPOSE: Our purpose was to assess in ovarian carcinoma patients the antitumor activity of in vitro-activated autologous peripheral blood T lymphocytes retargeted with OC/TR. METHODS: Patients with epithelial ovarian cancer (International Federation of Gynecology and Obstetrics stages III and IV) meeting specific criteria were eligible to enter a phase II immunotherapy trial. Before immunotherapy, the 28 patients who entered the trial underwent laparotomy to reduce their tumor load and to allow measurement of all indicator lesions. They then received two cycles of five daily intraperitoneal infusions of autologous in vitro activated peripheral blood T lymphocytes retargeted with OC/TR plus recombinant interleukin 2 (IL-2) with (n = 11) or without (n = 17) a second daily infusion of OC/TR F(ab')2 and IL-2. Response to treatment could be assessed in 26 patients following explorative laparotomy; time to progression could be assessed in 27 patients. RESULTS: Seven patients had clinical evidence of progressive disease after treatment and therefore did not undergo laparotomy. Of the 19 patients evaluated by surgery and histology, three showed complete response, one showed complete intraperitoneal response with progressive disease in retroperitoneal lymph nodes, three showed partial response, seven had stable disease, and five had progressive disease. The overall intraperitoneal response rate was 27% (95% confidence interval [CI] = 10%-44%). The complete responses seen in three patients lasted 26 months in one patient, 23 months in the second, and 18 months in the third. Two patients were not assessable for response. One of these patients had bowel perforation during catheter removal, which precluded further evaluation. The second patient was positive only by cytologic examination before immunotherapy, was tumor free at laparotomy after immunotherapy, and remained so for the entire 21 months of follow-up, as determined by cytologic examination of random biopsy specimens. The median time to disease progression in the 15 assessable patients plus those who had stable disease was 11 months (95% CI = 6-18 months). Immunotherapy-related toxic effects included mild to moderate fever, nausea, emesis, and fatigue. Anti-mouse antibodies were detectable by the end of the treatment in 21 of 25 patients tested. CONCLUSIONS: Locoregional immunotherapy of ovarian cancer with bispecific MAb-retargeted T lymphocytes can result in tumor regression. Toxicity was mild to moderate and only transient. IMPLICATIONS: Improvement in systemic antitumor responses is needed before this approach can prove useful as adjunctive treatment following induction chemotherapy in patients with minimal residual disease.

Oral administration of anti-doxorubicin monoclonal antibody prevents chemotherapy-induced gastrointestinal toxicity in mice.

Gastrointestinal mucositis is a common and painful condition that afflicts a proportion of cancer patients receiving chemotherapeutic drugs including anthracyclines, and it has become the dose-limiting toxicity for a number of chemotherapeutic regimens. The murine monoclonal antibody MAD11 recognizes the anthracycline doxorubicin, and systemic administration of this antibody in mice treated with doxorubicin was found previously to prevent the toxic effects of the drug. The purpose of this study was to determine whether gastrointestinal toxicity associated with doxorubicin can be reduced by oral administration of anti-doxorubicin MAD11 in mice. Our experiments show that orally administered MAD11 antibodies: (a) are essentially not absorbed in the blood circulation since less than 0.5% of protein-associated radioactivity was recovered from blood samples; (b) reduce the extent of doxorubicin-induced apoptosis in murine intestinal crypts, as determined by labeling strand breaks with modified nucleotides in an enzymatic reaction; and (c) reduce the body weight loss in mice treated with 12 mg/kg body weight of doxorubicin and decrease the early mortality in mice treated with 16 mg/kg body weight. This type of treatment may be useful in preventing anthracycline-induced gastrointestinal mucositis in cancer patients.

Antibody response against the c-erbB-2 oncoprotein in breast carcinoma patients.

Indirect immunofluorescence analysis of sera from breast carcinoma patients whose tumors were characterized for overexpression of the c-erbB-2 oncoprotein (p185HER2) and for lympho-plasma cell infiltration, revealed no circulating antibodies specifically directed against the p185HER2 molecule in the 20 samples tested, whereas supernatants of B-cell clones, derived from Epstein-Barr virus-transformed peripheral blood lymphocytes from 10 of these patients, contained such antibodies in 6 of the 7 c-erbB-2- and lympho-plasma cell infiltration-positive cases. The antibodies contained in two of the positive supernatants immunoprecipitated a M(r) 185,000 molecule from oncoprotein-positive cell extracts that was identified as the oncoprotein in sequential immunoprecipitation experiments with anti-p185HER2 monoclonal antibodies. No cells producing antibodies with a similar reactivity were obtained from Epstein-Barr virus-transformed peripheral blood lymphocytes from breast carcinoma patients with p185HER2-negative tumors or from healthy donors. These data prove the existence of an antibody response specifically directed against the p185HER2 oncoprotein in breast carcinoma patients that may represent an important effector mechanism in the control of c-erbB-2-overexpressing tumors.

Generation of monoclonal antibodies reacting with normal and cancer cells of human breast.

From the fusion of the murine myeloma P3- X63-Ag8-U1 with spleen cells from a mouse immunized with the human breast cancer cell line MCF-7, 88 hybridomas producing antibodies reacting with the immunizing cells were obtained. After a first screening on human leukocytes, red blood cells, and platelets and on human and fetal calf serum, three monoclonal antibodies, MBr1, MBr2, and MBr3, with specificity for the immunizing cells were isolated and further characterized. The three monoclonals were tested by isotopic antiglobulin assay and immunofluorescence on a panel of normal cells or cell membrane preparations, including milk epithelial and foam cells; on plasma and milk proteins; on cells or cell membrane preparations from fresh surgical specimens of breast, kidney, and ovarian carcinomas; and on various tumor cell lines. MBr1 and MBr2 had a superimposable reactivity and showed specificity for a structure which seems to characterize both normal and neoplastic mammary gland epithelial cells.

Immunochemical analysis of the determinant recognized by a monoclonal antibody (MBr1) which specifically binds to human mammary epithelial cells.

A monoclonal antibody (MBr1) raised against a membrane preparation (CM) of a human breast cancer line (MCF-7) and characterized as mammary gland epithelium associated (S. Mènard, E. Tagliabue, S. Canevari, G. Fossati, and M. I. Colnaghi. Generation of monoclonal antibodies reacting with normal and cancer cells of human breast. Cancer Res., 43:1295-1300, 1983), was used to biochemically define and partially purify its target antigen. The antigenic activity recognized by MBr1 was unaffected by treatment of MCF-7 cells with trypsin, protease K, or Vibrio cholerae neuraminidase and by heating at 100 degrees but was abolished by treatment with methanol. Since this behavior suggested a glycolipid nature of the MBr1-defined antigen, total lipids were obtained by chloroform:methanol or tetrahydrofuran:phosphate buffer extractions from crude membrane preparations of MCF-7 cells and of breast cancer surgical specimens. Total absorption of MBr1 activity was found by breast cancer lipid extracts, whereas no absorbing capability was detected with a series of highly purified acid and neutral glycolipids or with normal and neuraminidase-treated red blood cells of human, ox, and sheep species. The same pattern of inhibition of MBr1-binding activity was obtained with total lipid extract and both phases after diethyl ether partition. However, when the three extracts were chromatographed on diethylaminoethyl-Sepharose, the antigenic activity was recovered only in the neutral glycolipid fractions. Periodate oxidation of MCF-7 crude membrane preparation abolished MBr1-binding activity, suggesting that the carbohydrate portion of the molecule may constitute the antigenic determinant.

Cooperative effects of Mycobacterium tuberculosis Ag38 gene transduction and interleukin 12 in vaccination against spontaneous tumor development in proto-neu transgenic mice.

An approach to stimulating an immune response against tumors is to transduce tumor cells with bacterial genes, which represent a "danger signal" and can induce a wide immune response. Mycobacterium tuberculosis genes and their encoded proteins play a pivotal role in linking innate and cell-mediated adaptive immunity and represent ideal candidates as immune adjuvants for tumor vaccines. The efficacy of a cancer vaccine, obtained by transduction of a mammary tumor cell line with the M. tuberculosis Ag38 gene, was investigated in female mice transgenically expressing the rat HER-2/neu proto-oncogene. These mice spontaneously develop stochastic mammary tumors after a long latency period. The onset of spontaneous mammary tumors was significantly delayed in mice vaccinated with Ag38-transduced cells but not in mice vaccinated with nontransduced cells as compared with untreated mice. Protection from spontaneous tumor development was increased when mice were vaccinated with the mycobacterium gene-transduced vaccine plus a systemic administration of interleukin 12 (IL-12) at a low dose. Mice vaccinated with nontransduced cells plus IL-12 developed tumors, with only a slight delay in tumor appearance as compared with the control group. Lymphocytes obtained from lymph nodes of mice vaccinated with transduced cells secreted high levels of IFN-gamma. CD3+CD8+ spleen cells derived from these mice responded to the tumor with IFN-gamma production. These data indicate the efficacy of a short-term protocol of vaccinations exploiting the adjuvant potency of a M. tuberculosis gene and low doses of IL-12 in a model of stochastic development of mammary tumors. This adjuvant approach may represent a promising immunotherapeutic strategy for cancer immunization.

Gene transfection and expression of the ovarian carcinoma marker folate binding protein on NIH/3T3 cells increases cell growth in vitro and in vivo.

The glycoprotein gp38 is overexpressed in 90% of ovarian carcinomas and recognized by monoclonal antibodies MOv18 and MOv19. This molecule is a high affinity folate binding protein (FBP) and a potential marker for ovarian carcinoma. We have developed a model to investigate the biochemical and biological properties of this folate receptor by transfecting NIH/3T3 cells, which do not endogenously express FBP, with a vector containing the complementary DNA for the gp38 cloned from the ovarian carcinoma cell line IGROV1. The FBP expressed shows features identical to those of the protein produced by IGROV1 cell. The FBP is expressed on the cell membrane in a glycosylphosphatidylinositol-linked form, since it is released by treatment with phosphatidylinositol-specific phospholipase C, and is shed into the culture medium of the NIH/3T3 transfectants. Immunoblot analysis with MAbs MOv18 and MOv19 showed that both the glycosylphosphatidylinositol-linked and the soluble FBP migrate at the same apparent molecular weight as the respective IGROV1 proteins. The FBP-transfected NIH/3T3 cells bound folic acid and internalized about 30-fold more folic acid than mock-transfected cells. Growth analysis revealed that FBP-transfected NIH/3T3 cells like IGROV1 maintained their growth rate after 10 days of culture in medium containing physiological or low folate concentration, and tumors arising after transplanting FBP-tNIH/3T3 cells in nude mice were 3-fold heavier than those arising after transplantation of non-FBP-expressing NIH/3T3 cells. These results suggest a correlation between human ovarian carcinoma growth and FBP overexpression.

CD3-CD28 costimulation as a means to avoiding T cell preactivation in bispecific monoclonal antibody-based treatment of ovarian carcinoma.

One of the major limitations to the immunotherapy of ovarian carcinoma based on the use of anti-CD3/antitumor bispecific monoclonal antibodies (bi-mAb) is the need for preactivation of effector cells ex vivo, because cross-linking of the T cell receptor-CD3 complex per se may lead to T-cell unresponsiveness or even apoptosis. The bi-mAb OC/TR, which recognizes the folate-binding protein (FBP) overexpressed in 90% of ovarian carcinomas and the CD3 molecule on T cells, has demonstrated efficacy in a clinical setting. Here we investigated the possibility of delivering accessory signals to OC/TR-retargeted peripheral blood mononuclear cells (PBMCs) via an anti-CD28 mAb or an anti-FBP/anti-CD28 bi-mAb. Coculture of resting PBMCs from healthy donors with OC/TR, anti-FBP/anti-CD28 bi-mAb, and FBP+ tumor cell lines resulted in a highly activated phenotype of effector cells and in a dramatic in vitro growth inhibition of the target cells without an increase in OC/TR-redirected lysis. Whereas both the CD4 and CD8 T cell subsets were involved in the growth inhibition, only the CD8 subpopulation accounted for the cytotoxic activity. The in vitro tumor growth inhibition was mediated mainly by soluble factors, which were active on both FBP+ and FBP- ("bystander effect") cell lines. Activation and antitumor activity were also observed, albeit to a lesser extent, using OC/TR and monospecific bivalent anti-CD28 mAb. In vitro analysis demonstrated that cross-linking between tumor and effector cells for at least 24 h was needed to achieve T-cell activation and development of antitumor activities. Thus, ex vivo CD3-CD28 costimulation on resting PBMCs might be of therapeutic utility for local treatment of minimal residual disease.

Tamoxifen chemoprevention of a hormone-independent tumor in the proto-neu transgenic mice model.

We evaluated the effect of tamoxifen (TAM) on tumor development in proto-neu transgenic mice that spontaneously develop mammary carcinomas overexpressing the neu protein. These mammary carcinomas are hormone independent because superimposable growth of transplants was observed in females and males. Virgin transgenic mice treated with TAM from 24 weeks of age, ie., when subclinical mammary tumors are already present, showed a slightly accelerated tumor development. In contrast, transgenic mice treated with TAM starting at 12 weeks of age, when subclinical tumors are not yet present, showed a 50% reduction of tumor incidence. Light microscopy analysis of the mammary gland of these mice revealed an apparently normal ductal branching but a complete regression of the acini. In conclusion, TAM can prevent the occurrence of hormone-independent breast carcinoma if given early enough to inhibit normal cells.

Chimeric murine-human antibodies directed against folate binding receptor are efficient mediators of ovarian carcinoma cell killing.

The MOv18 (gamma 1, kappa) and MOv19 (gamma 2a, kappa) murine monoclonal antibodies (MAbs) recognize different epitopes on the human folate binding receptor which is overexpressed on 90% of nonmucinous epithelial ovarian tumors. A chimeric murine-human (human gamma 1, kappa) version of both antibodies was constructed and expressed. The genes encoding the murine heavy and light chain variable regions of the MOv18 and MOv19 MAbs were cloned from the parental hybridomas, fused with genes encoding the human heavy (gamma 1) and light (kappa) chain constant regions, respectively, and expressed in the SP2/0 murine myeloma cell line. Using human peripheral blood mononuclear cells as effector cells and conditions that provide for maximum lysis (effector target = 50:1, saturating antibody concentration), the murine MOv18 MAb (IgG1) mediated variable levels of specific cytolysis of the target ovarian cancer cell line IGROV1. In contrast, the chimeric MOv18 MAb mediated higher and more consistent lysis even at a 10-100-fold lower antibody concentration. The murine MOv19 MAb (IgG2a) mediated specific lysis of IGROV1 cells, and the chimeric version of this antibody mediated an amount of lysis at least equal to that mediated by its murine counterpart. A comparison of the ED50 values obtained for the murine MOv19 and chimeric MOv19 antibodies indicates that the chimeric MOv19 MAb was 3 to 10 times more potent than the murine MOv19 antibody. In addition, the ED50 values obtained for the chimeric MOv18 and chimeric MOv19 MAbs were similar, indicating that these MAbs are equally potent. The level of maximal lysis obtained was dependent on the number of target molecules/cell; the same high level of lysis mediated by cMOv18, MOv19, and cMOv19 was observed with both IGROV1 and OvCA432 target cells. However, only low levels of lysis were obtained when the SW626 cell line, which expresses 1 x 10(4) folate binding protein sites/cell, was used as a target. An equimolar mixture of the chimeric MOv18 and MOv19 MAbs was no more effective in the mediation of lysis than an equivalent amount of either chimeric MAb alone. These data suggest that the folate binding receptor is expressed on IGROV1 cells at a density sufficient to provide for optimal levels of antibody-mediated lysis using a single chimeric antibody directed at the folate binding receptor.

Biochemical analysis of human ovarian cancer-associated antigens defined by murine monoclonal antibodies.

Two monoclonal antibodies (MOv1 and MOv2) raised against a membrane preparation of a human surgical specimen from a mucinous ovarian cystoadenocarcinoma were used to biochemically define their target antigens. The heating of peritumoral mucus-soluble extracts and the sialidase treatment of crude membrane preparations did not affect the binding capacity of MOv1 and MOv2, which, on the contrary, was significantly reduced by periodate oxidation of the same materials. Pronase digestion completely solubilized MOv1-defined antigens, whereas MOv2-defined antigens were only partially solubilized. This, however, did not affect antibody binding with digested products. These data suggest that carbohydrate residues of recognized molecules constitute the antigenic determinants and that sialic acid residues are not involved. Gel filtration on Sepharose 4B of the peritumoral mucus, solubilized either by 200 mM NaCl or Pronase, revealed that most of the antigenic activity eluted in the void-volume fractions with a high carbohydrate content and in the included fractions before the elution volume of the ferritin standard protein. When CsCl gradient equilibrium ultracentrifugation of the solubilized mucus was used, MOv1-recognized antigens sedimented with a density of 1.45 g/ml, while the MOv2-defined epitope was carried by molecules with a density of 1.52 g/ml as well as by molecules with a lower density. Using thin-layer chromatography of organic solvent extracts obtained from mucus and crude membrane preparations, only MOv2-positive molecules could be resolved as a single band of glycolipid. Altogether, these data suggest that the antigens detected by MOv1 are mainly mucins whereas the determinant recognized by MOv2 is carried by both mucins and a glycolipid. To analyze the diagnostic potential of MOv1- and MOv2-recognized molecules, we tested their presence, as soluble products, in supernatants of tumor cell lines and in peritoneal effusions from cancer patients. To this aim, we developed an immunoradiometric assay using the same monoclonal antibody in insolubilized and soluble form. Whereas MOv1-immunoradiometric assay was always negative, by MOv2-immunoradiometric assay it was possible to detect the relevant antigen in 8 of the 10 effusions from patients with well-differentiated ovarian tumors and in 5 of the 11 effusions from patients with poorly differentiated ovarian tumors, whereas the 10 control effusions from patients with various diseases were negative.

Panning phage antibody libraries on cells: isolation of human Fab fragments against ovarian carcinoma using guided selection.

The display of repertoires of human antibody (Ab) fragments on filamentous phages and selection by binding of the phage to antigen (Ag) have provided a ready means of deriving human Ab against purified Ag. However, it has been more difficult to obtain phage Ab against an individual Ag of a complex mixture, such as cell surface Ag. Using the technique of "guided selection," we generated human Ab against the high-affinity folate-binding protein (FBP), a cell surface Ag that is overexpressed in many human ovarian carcinomas. The guiding Ab template was provided by the light chain of mouse monoclonal Ab Mov19 (K[aff], 10[8] M[-1]) directed against FBP; this was paired with repertoires of human heavy chains displayed on phages, and the hybrid Ab fragments were selected by binding to an ovarian carcinoma cell line (OVCAR3). The selected human heavy chains were then paired with repertoires of human light chains. Further panning led to the isolation of a human Fab fragment, C4, with a binding affinity of 0.2 x 10(8) M(-1). This was highly specific for FBP, as demonstrated by ELISA and flow cytometry data and by immunoprecipitation of the relevant molecule from the cell surface of ovarian carcinoma cells. Moreover, C4 targeted the same or a closely related epitope of the Ag, as did the template rodent monoclonal Ab Mov19. These results suggest the usefulness of guided selection as a simple means to deriving human Ab against cell surface Ag for which a rodent Ab is available.

Generation of monoclonal antibodies reacting with human epithelial ovarian cancer.

Fusion of the murine myeloma line P3-X63-Ag8-U1 with spleen cells from a mouse immunized with a membrane preparations (CM) of a mucinous ovarian cystoadenocarcinoma yielded two monoclonal antibodies, MOv1 and MOv2, which reacted by solid-phase radioimmunoassay with immunizing tumor CM but were unreactive with normal kidney CM as well as with plasma proteins and peripheral blood cells from the immunizing carcinoma patient. MOv1 and MOv2 were further tested by solid-phase radioimunoassay on a panel of different CM from fresh surgical specimens of ovarian and nonovarian carcinomas, benign ovarian tumors, normal ovary and kidney tissues, and on various tumor cell lines. In addition, the antibodies were characterized by immunofluorescence on live cells from cell lines and surgical specimens, and on frozen sections of benign and malignant ovarian tumors, of nonovarian tumors, and of normal tissues. The results obtained indicate that MOv1 and MOv2 recognize two different epitopes on molecules present on malignant and benign ovarian mucinous tumors and colonic glands. In addition, the antigen recognized by MOv2 was also detected in carcinmas of lung, colon, stomach, and breast; in gastrointestinal glands; and in the glandular lumina of normal lactating breast.

Cloning of a tumor-associated antigen: MOv18 and MOv19 antibodies recognize a folate-binding protein.

Monoclonal antibodies MOv18 and MOv19, raised against a membrane preparation of an ovarian carcinoma surgical specimen, react with a surface antigen present on the majority of nonmucinous ovarian malignant tumors tested but not with normal adult tissue (S. Miotti, S. Canevari, S. Ménard, D. Mezzanzanica, G. Porro, S. M. Pupa, M. Regazzoni, E. Tagliabue, and M. I. Colnaghi, Int. J. Cancer, 39: 297-303, 1987). This surface antigen was purified as a soluble glycoprotein (molecular mass, 36-38 kDa) released from the cell surface of an ovarian carcinoma cell line (IGROV1) by digestion with Bacillus thuringiensis phospholipase C. Immunoblotting demonstrated that the purified protein reacted with MOv18 and MOv19 and that treatment of the purified preparation with N-glycanase resulted in a protein with a molecular mass of 27 kDa. The NH3-terminal amino acid sequence of the purified antigen was determined. This sequence is highly homologous to an internal stretch of 27 amino acids located near the NH3 terminus of human folate-binding protein. An oligonucleotide probe was synthesized and used to screen an IGROV1 ovarian carcinoma, lambda gt11 complementary DNA library to obtain three complementary DNA clones. The complete nucleotide sequence of one of these complementary DNA clones was determined. This sequence is nearly identical to that of a folate-binding protein clone obtained from the Caco-2 human carcinoma cell line. In addition, the nucleotide sequence of the 5'-untranslated region of the other two clones was determined. This region of all three clones was different. The product of the Caco-2 folate-binding protein clone expressed in Chinese hamster ovary cells was recognized by the MOv18 and MOv19 antibodies, confirming that the antigen and folate-binding protein are one and the same. Furthermore, a cell line that binds the MOv18 and MOv19 antibodies expressed increased levels of folate-binding protein mRNA compared with a cell line that does not bind these antibodies. These results indicate that the MOv18 and MOv19 monoclonal antibodies bind to at least one form of folate-binding protein and that this protein, which is evidently overexpressed in certain malignant tumors, may provide a suitable target for immunotherapy with these antibodies.

A comparative study of p53 gene mutations, protein accumulation, and response to cisplatin-based chemotherapy in advanced ovarian carcinoma.

The p53 protein is a multifunctional transcriptional regulator involved in cellular response to DNA damage and has been implicated as a putative determinant of sensitivity of tumor cells to cytotoxic agents. Since the p53 gene becomes inactivated in over one-half of advanced ovarian carcinoma, in this study we have examined the relationships between p53 gene alterations, p53 immunoreactivity, and response to cisplatin-based chemotherapy in ovarian cancer patients. All patients had advanced (FIGO stage III or IV) ovarian carcinoma and, with one exception, were untreated at the time of collection of tumor specimens. After initial debulking surgery, patients received high-dose cisplatin therapy. Tumor samples were analyzed for p53 gene mutations and for p53 protein accumulation, and the findings were correlated with tumor responsiveness. Of the 33 tumors examined, p53 gene mutations were found in 20 cases, including 15 missense mutations, 2 deletions, 2 nonsense mutations, and a base substitution at splice site. Twenty tumors showed positive immunostaining for p53. Only missense mutations were associated with positive immunostaining. In addition, p53 overexpression was detected in five tumors in the absence of mutations. Most (12 of 14) of the missense mutations associated with p53 protein stabilization were found refractory to therapy, as well as tumors overexpressing wild-type p53 (4 of 5). A significant correlation has been found between p53 accumulation, type of mutation (i.e., missense mutations), and pathological response to cisplatin-based therapy. In conclusion, the present results are consistent with a role of p53 as a determinant of chemosensitivity of ovarian carcinoma.