Quantitative analysis of melanoma-associated antigen p97 in normal and neoplastic tissues

Differential responsiveness of cloned mammary carcinoma cell populations to the human recombinant leukocyte interferon enhancement of tumor antigen expression

We have previously shown that a recombinant human leukocyte interferon (IFN-alpha A)5 can mediate an increase in cell surface tumor antigen expression in human carcinoma cells but not normal cells (Greiner et al., 1984). Such a biological response modifier may prove useful in circumventing the problem of antigenic heterogeneity and could increase the effectiveness of monoclonal antibodies (MAbs) for detection and/or therapy of human carcinoma lesions. These studies also revealed that, within populations of human carcinoma cells, there exist subpopulations which are unresponsive to the antigen-enhancing properties of IFN-alpha A. Utilizing cloned cell populations from the MCF-7 human breast carcinoma cell line, we now report the differential responsiveness to the tumor antigen enhancing and antiproliferative actions of IFN-alpha A. Binding of MAb B72.3 to the 220-400 kd tumor antigen, TAG-72, is increased by IFN-alpha A treatment on the surface of the parental MCF-7 cell line and 2 cloned cell populations. A third MCF-7 clone does not express this antigen either before or after IFN-alpha A treatment, but does express a 90 kd tumor antigen and carcinoembryonic antigen which bind MAbs B6.2 and B1.1, respectively. The level of expression of these 2 surface tumor antigens remained unchanged upon interferon treatment. The growth of the parental MCF-7 cells and the 3 cloned cell lines was, however, inhibited by IFN-alpha A. These cell lines also exhibited approximately the same number of interferon receptors with similar binding affinities for IFN-alpha A. The results demonstrate a dissociation of two biological actions of IFN-alpha A-antiproliferative activity and enhancement of tumor antigen expression within a cloned human carcinoma cell line. Our studies also indicate that the differential response of cloned MCF-7 cells to tumor antigen modulation by interferon involves alterations in the transduction of signals occurring distal to receptor occupancy within the biochemical pathways responsible for the actions of this biological response modifier. In addition, the clonal cell lines we have isolated which differ in their responsiveness to interferon should prove valuable in analyzing the molecular basis of interferon actions and may provide insights into the mechanism by which this compound confers its antitumor activity.

Antigenic characterization of human hepatocellular carcinoma. Development of in vitro and in vivo immunoassays that use monoclonal antibodies

Several libraries of monoclonal antibodies have been produced by immunization of Balb/c mice with single cell suspensions of nontrypsin-treated human hepatocellular carcinoma cell (HCC) lines in order to study the antigenic properties of transformed hepatocytes. The antibodies were characterized with regards to specificity for hepatoma-associated antigens and their capability for use as reagents in radioimmunoassays (RIAs) and tumor localization in vivo. Three such antibodies namely, P215457, PM4E9917, P232524 of the IgG2a, IgG2a, and IgG1 isotypes, respectively, not only recognized separate and distinct antigenic determinants on four human hepatoma cell lines but also reacted with epitopes present on chemically induced rat hepatoma cell lines. In contrast, only 1 of 38 other human malignant and transformed cell lines demonstrated reactivity with the three antibodies; normal human tissues were also found to be unreactive. Monoclonal antibody P215457 densely stained the plasma membrane by indirect immunofluorescence, showed rapid binding activity to HCC cells in suspension, and precipitated a 50,000-mol wt cell surface protein; antibody PM4E9917 also stained the plasma membrane and precipitated a 65,000-mol wt protein, whereas P232534 recognized cytoplasmic antigenic determinants. With these antibodies "simultaneous sandwich" RIAs were established that detect soluble hepatoma-associated antigens in culture supernatants. Finally, the Fab fragment of P215457 was found to be useful in tumor localization in vivo. This antibody fragment when labeled with 131I was shown to localize by radionuclide-imaging studies in human hepatoma grown in nude mice. Thus, these investigations demonstrate that monoclonal antibodies may be produced against epitopes that reside almost exclusively on transformed hepatocytes and such antibodies may be successfully employed in the development of in vitro and in vivo immunoassays.

Review of melanoma antigens recognized by monoclonal antibodies (MAbs). Their functional significance and applications in diagnosis and treatment of melanoma

The introduction of monoclonal antibody techniques has led to a rapid advance in information concerning antigenic structures in melanoma cell membranes. These have been classified according to the extent of their expression on cells of other tissues, but it is evident that a more precise classification based on their biochemical nature is possible. Several monoclonal antibodies appear to define antigens restricted to melanoma cells and fetal tissues. Many antibodies recognize antigens shared with gliomas and nevi, whereas other groups can be defined which recognize antigens on melanocytes or other carcinomas. One of the commonly detected antigens was shown to be a high molecular weight (MW) proteoglycan which may be involved in reactions with other cells and the intercellular matrix. A second antigen was shown to be a ganglioside which may have receptor functions in cells. A third was shown to be a glycoprotein with iron transport functions. The latter antigen and the large MW proteoglycan have been a focus of attention for in vivo targeting studies in treatment and diagnosis. The ganglioside, large MW proteoglycan and a melanocarcinoma antigen may be detected in the circulation of patients and are being evaluated for monitoring of disease activity in patients with melanoma. Several monoclonals may be of value in histological evaluation of melanoma, e.g. diagnosis of preneoplastic lesions, metastatic lesions of unknown origin and identification of cell structures related to metastatic behaviour in the host. Further studies should help to define cellular structures recognized by the immune system in humans.

Immunodiagnosis of human malignancy

Definition of normal cell membrane antigens using immunologic techniques has permitted investigators to distinguish normal cells from malignant cells. Malignant cells express fetal antigens in concentrations different from normal mature cells. Mutant cells express differentiation as well as those antigens reflecting the altered cell genome. Normal cells can be transformed into malignant cells using either chemical agents or viruses. As these agents are incorporated into the genome, surface antigens are expressed that differ from normal cell isoantigens. These antigenic determinants can serve as tumor-associated or perhaps tumor-specific markers. Immunochemical methods now exist that permit isolation and purification of these antigens. Monoclonal antibodies have been generated that react with single epitopes associated with these antigens. Very sensitive and highly specific radioimmunoassays and enzyme immunosorbent assays can detect microgram quantities of these antigens in body fluids and as such permit serodiagnostic evaluation. Monoclonal antibodies can also be used for radioautography, immunofluorescent, and immunoperoxidase staining for diagnostic purposes of both cytologic and fixed tissue sections. The binding affinity and specificity of these monoclonal antibody reagents has successfully been used for in vivo tumor localization. Isotopically labeled monoclonal antibodies bind preferentially to tumor cells in the host and are useful for specific radionuclide scintigraphy. These recently developed immunodiagnostic techniques not only add specificity in terms of diagnostic accuracy but are useful for early detection of recurrent disease and in vivo localization of tumor deposits. Therapeutic implications are discussed.

In situ analysis of antigens on malignant and benign cells of the melanocyte lineage. Differential expression of two surface molecules, gp75 and p89

Monoclonal antibodies (mAb) were selected for differential binding to sections of freshly frozen biopsy material of human malignant melanomas and their precursor lesions, the melanocytic nevi. Both melanomas and normal nevi expressed human Ia-like antigens, transferrin receptor and the transferrin-related molecule p97. In contrast, only 1 nevus of 21 tested expressed both glycoprotein gp75, defined by mAb 15.75, and protein p89, defined by mAb P3.58, whereas 12 of 15 melanomas tested expressed both antigens. mAb P3.58 reacted with one additional melanoma and one nevus. The expression of these two molecules therefore appears to be correlated with the appearance of the malignant phenotype of melanocytes.

Immunopurification, characterization, and nature of membrane association of human melanoma-associated oncofetal antigen gp87 defined by monoclonal antibody 140.240

A melanoma-associated oncofetal antigen, gp87 (a p97-like molecule), defined by the monoclonal antibody (MoAb) 140.240 has been purified to homogeneity from the spent medium of cultured melanoma cells by a two-step immunoadsorbent procedure. The first immunoadsorbent step using glutaraldehyde-insolubilized MoAb 140.240 (ascites fluid) resulted in a 13-fold enrichment with 93% recovery in the bound material. In the second immunoadsorbent step constructed by the purified IgG2a of MoAb 140.240 (culture fluid) coupled to CNBr-activated Sepharose 4B the bound material from the first step was further purified resulting in a 330-fold purification with 90% recovery. SDS-polyacrylamide gel electrophoretic analysis of the final purified material revealed a single band migrating as a polypeptide with an approximate molecular weight of 87 Kd, consistent with the size of the molecule immunoprecipitated by MoAb 140.240 from lysates of radiolabelled melanoma cells. Preliminary amino acid analysis indicates a particularly high proportion of phenylalanine in gp87. We have also compared gp87 with two well defined antigens, HLA-A,B,C (integral membrane protein) and "94K" melanoma/carcinoma-associated antigen (peripheral membrane protein) with respect to antigen extractability from melanoma cells using phosphate-buffered saline, 0.1 M urea, 3 M NaCl, or nonionic detergent (NP-40). The results showed that whereas 94K antigen was extractable by each of the four different solutions, gp87, similar to HLA-A,B,C antigens, could only be extracted with NP-40, strongly suggesting that gp87 is an integral melanoma cell component.

Expression of Ia like (HLA-DR) antigens on human alveolar macrophages

The distribution of Ia like (HLA-DR) antigens on human alveolar macrophages (HAM phi) has been investigated by indirect immunofluorescence staining of viable macrophages with a panel of monoclonal antibodies (MoAb) to common determinants of these antigens. HAM phi were characterized by non-specific esterase stain, plastic adherence, phagocytosis and IgG-Fc receptor expression. Ia like antigens were expressed in approximately 45-80% of HAM phi, being localized as patchy and lineal fluorescence along the membrane. Ia like expression was higher in macrophages from non-smoker subjects (P less than 0.025). No difference in Ia like antigen expression was found between adherent and non-adherent HAM phi subsets. Ia like positive HAM phi from both smoker and non-smoker subjects consisted of a large subpopulation of phagocytic cells (60-70%) and a smaller non-phagocytic subpopulation (20-25%). These subpopulations were also present in the Ia like negative HAM phi. The percentage of Ia like positive macrophages showed variable results depending on the MoAb used, suggesting that not all anti-Ia like antibodies recognize the same antigenic determinants. Moreover, lack of staining of one macrophage subset occurred with all MoAb tested, over a large range of concentrations.

Diagnostic and therapeutic use of monoclonal antibodies to human tumor antigens

Monoclonal antibodies have been obtained to various differentiation antigens that are more strongly expressed on tumor cells than on normal cells from the adult host, some of these antigens are relatively specific for tumors of a given type, e.g. melanoma. Monoclonal anti-tumor antibodies offer strong promise for clinical use, initially for tumor diagnosis and, ultimately, also for therapy.

The localization of an anti-tumour monoclonal antibody (791T/36) in gastrointestinal tumours

Fifty-six patients with gastrointestinal cancers and four patients with benign colorectal tumours have been injected with radiolabelled anti-tumour monoclonal antibody ( 791T /36) to assess the degree of localization of the antibody by external scintiscanning and measurements on resected specimens. Twenty-nine patients with primary colorectal cancer showed increased uptake of the radiolabelled antibody in the resected tumours, with a tumour to normal tissue (T:NT) ratio of 2.5:1. All but two of fifteen patients with recurrent or metastatic tumour showed positive images of the deposits on external scintiscanning. Twelve patients with noncolonic gastrointestinal malignancy were studied and in only two patients were tumours demonstrated by external scanning. There were no positive images in four patients with benign colonic disease nor could increased uptake of radiolabelled antibody be demonstrated in the resected specimens. Immunohistology and autoradiography have shown that the antibody can be demonstrated in the pseudoacini and stroma of colon cancer. There are indications that this may represent localization to a cell surface antigen which becomes detached in the processing of the histological sections. It seems that in the gastrointestinal tract the monoclonal antibody 791T /36 is consistently taken up by colorectal cancer. Only a few noncolonic cancers and no benign colonic tumours take up the antibody. This antibody uptake may prove of value in the detection of occult metastases and in the targeting of antitumour agents.

Induction of immunity to a human tumor marker by in vivo administration of anti-idiotypic antibodies in mice

Anti-idiotypic antibodies are described that were raised against murine monoclonal antibody 8.2, an antibody specific for a human melanoma-associated cell surface marker called p97. The 8.2 idiotopes recognized by this anti-idiotypic antiserum are binding site-associated and are shared by other monoclonal anti-p97 antibodies with the same specificity as antibody 8.2. Mice immunized with the anti-idiotype demonstrate delayed-type hypersensitivity reactions when challenged with melanoma (p97-positive) tumor cells.

Monoclonal antibodies to antigens associated with transitional cell carcinoma of the human urinary bladder. II. Identification of the cellular target structures by immunoprecipitation and SDS-PAGE analysis

The cellular target structures for six monoclonal antibodies raised against cultured human bladder carcinoma cells (TCC) were investigated. The specificities of these antibodies when tested against a large panel of cells have been described in the companion paper. Radiolabeled cell lysates were precipitated with the different monoclonal antibodies bound to protein A (Staphylococcus aureus) on a matrix of Sepharose beads. The precipitates were separated by sodium dodecyl sulfate- gel electrophoresis (SDS-PAGE) and analyzed by autoradiography. The antibodies 4B5, 7E9, and 14B11 have previously been found to react in a similar way with TCC-targets and some non-TCC tumor cells, but not with normal urothelial cells or cells of hematopoietic origin. When tested with lysates of a TCC-cell line (TCCSuP) a strong 92K band and a weak 23K band were precipitated with any one of these antibodies. These polypeptides were expressed on the cell surface and were not linked by disulfide bonds. Depletion experiments confirmed that the three antibodies recognized the same antigens. Another antibody (4E8) probably directed to a differentiation antigen present on both urothelial and melanoma cells detected two high molecular polypeptides, 190K and 170K. Antibodies from the S2C6 hybridoma, which displayed a distinct dual specificity for TCC- targets and for malignant or transformed cells of B cell origin, precipitated a 50K component from extracts of either TCC- or B cell-derived cell lines. Antibodies produced by the S2A9 hybridoma were shown to bind to a framework epitope of the HLA-A, B, C heavy chain.

Radioimmunodetection and radioimmunotherapy

The development of monoclonal antibodies that recognize tumor-associated antigens has led to significantly greater practical possibilities for producing highly specific radiolabeled antibodies for diagnosis and therapy of human tumors. A number of problems remain before this technique will be ready for routine clinical application however. Achieving the high target to background ratio that are predicted on theoretical grounds is a major challenge in cancer investigation.

Localization of 131I-labeled p97-specific Fab fragments in human melanoma as a basis for radiotherapy

33 patients with advanced malignant melanoma were studied after intravenous administration of 131I-labeled Fab fragments specific for p97, an oncofetal glycoprotein of human melanoma. In all, 47 gamma camera imaging studies were performed for the purpose of localization of metastatic deposits. In addition to tumor, 131I-Fab uptake was also seen in liver and kidney. 20 of these studies included simultaneous administration of both an 131I-labeled Fab specific for p97, and an 125I-labeled Fab not specific for p97. Blood clearance of p97-specific Fab was significantly more rapid than for nonspecific Fab. Eight of these patients had biopsies of subcutaneous nodules at 48 and 72 h postinjection in order to assess whether localization of radioactivity was antigen specific. Antigen-specific localization was observed with average ratios of specific/nonspecific uptake of 3.7 (48 h) and 3.4 (72 h); uptake was strongly correlated with tumor p97 concentration (r = 0.81, P less than 0.01). Also, imaging studies of the bio-distribution of 131I-labeled anti-p97 Fab in patients selected for high p97 tumor concentration showed avid tumor uptake and more prolonged retention of labeled Fab in tumor than in normal tissues. Based on these studies, we estimated that total 131I doses of 500 mCi could be safely given to patients before dose-limiting toxicity would be observed. Accordingly, in seven selected patients, phase I radiotherapeutic trials were begun. For improved radiation safety, we developed automated methods to label Fab fragments with up to 200 mCi of 131I. So far, a total of 12 individual therapeutic doses, ranging from 34 to 197 mCi of 131I-labeled to 5 to 10 mg of Fab, have been administered with excellent tumor localization and without major target organ toxicity. Cumulative doses ranged from 132 to 529 mCi 131I. Side effects attributable to the radiation were mild, with a transient drop slightly greater than 50% in platelet and absolute neutrophil counts being observed in the two patients who received cumulative doses greater than 500 mCi. In the combined series of 47 diagnostic and 12 therapeutic studies, four acute reactions were observed: one episode each of transient chills and fever; flushing and hypotension; and two skin rashes. All of these reactions responded promptly to symptomatic therapy. After multiple administrations of 131I-(anti-p97) Fab (IgG1), isotype-specific immunity was observed in three patients. In two of these patients it was possible to successfully reinfuse after immunity had developed with 131I-(anti-p97) Fab of a different isotype (IgG2a). Dosimetry estimates were performed based on the biodistribution of (131)I-Fab in these patients,and for every 100 mCi of (131)I-Fab given, tumor receives 1,040 rads; liver. 325 rads; and bone marrow, 30 rads. Marrow would be expected to be the critical organ, if doses >500 mCi (131)I-Fab are given. These studies demonstrated that, with proper precautions, large doses (of an (131)I-labeled murine Fab fragments immunologically specific for a human melanoma-associated antigen) could be safely given to humans by using repetitive intravenous injections.

Detection of melanoma cells in bone marrow using monoclonal antibodies. A comparison of fluorescence activated cell sorting (FACS) and conventional immunofluorescence (IF)

Seven different human melanoma cell lines have been tested for the presence of melanoma associated antigen p97. The sensitivity of membrane immunofluorescence assays for the antigen was increased by using a mixture of antibodies to several epitopes of p97. Six of eight melanoma lines were strongly positive. Normal bone marrow was negative. When cultured p97-positive melanoma cells were added to normal marrow, the authors were able to detect 5% contamination, by fluorescence-activated cell sorting (FACS) and immunofluorescence (IF). No melanoma cells were found in one fresh and nine frozen bone marrow specimens of melanoma patients (including two with known positive marrow by routine histologic study) evaluated for autologous bone marrow transplantation after high-dose chemotherapy.

Immunization to a syngeneic sarcoma by a monoclonal auto-anti-idiotypic antibody

Idiotypic networks regulate the immune response to a variety of antigens. Antibodies generated against other antibodies, called anti-idiotypic antibodies, can themselves mimic antigen and elicit a specific immune response. They have been shown to induce delayed-type hypersensitivity (DTH) to model antigens in the mouse. As anti-idiotypic antibodies are thought to be involved in the response to tumour-associated antigens we tested whether injection of monoclonal antibodies derived from mice hyperimmunized to a syngeneic, chemically induced sarcoma could mimic antigen and induce DTH to the sarcoma in naive mice. One of the monoclonal antibodies, 4.72, primed BALB/c mice for DTH to the sarcoma but not for DTH to another sarcoma or to sheep erythrocytes. Antibody 4.72 did not induce DTH in mice of immunoglobulin allotype congeneic strains nor did it bind to the sarcoma cells. As antibodies specific for this sarcoma have not been detected, we do not know whether idiotype on immunoglobulin molecules is recognized by antibody 4.72. However, as the response induced by antibody 4.72 was both antigen-specific and allotype-restricted, analogous to those induced by anti-idiotypic antibodies in other systems, we propose that antibody 4.72 is an anti-idiotypic antibody.

Melanoma-associated antigen p97 continues to be expressed after prolonged exposure of cells to specific antibody

p97, a 97,000 molecular weight cell surface glycoprotein associated with human melanoma, has attracted attention as a possible target for tumor therapy. Melanoma cells were grown overnight in the presence of IgG2a or IgG1 monoclonal antibodies specific for p97, and then exposed to complement and also tested for binding of monoclonal antibodies specific for other epitopes of p97. The results indicated that melanoma cells continued to express p97 after prolonged exposure to specific antibody, a prerequisite for many therapeutic applications.

Assignment of the gene for human melanoma-associated antigen p97 to chromosome 3

p97 is a 97,000 molecular weight cell-surface glycoprotein, which is present in human melanomas but in only trace amounts in normal adult tissues. Amino acid sequence and iron binding studies have shown that p97 is structurally and functionally related to transferrin. Reports that the genes for the transferrin receptor (TR) and possibly transferrin are located on chromosome 3 prompted us to investigate the chromosomal localization of the p97 gene. Our strategy was to characterize interspecies somatic cell hybrids derived from human fibroblasts or lymphocytes for expression of p97 and presence of human chromosomes. Although fibroblasts and lymphocytes express only small amounts of p97, we were able to type the hybrids for p97 by using monoclonal antibodies in highly sensitive and specific immunoassays. Of 14 hybrids, 6 contained chromosome 3 and expressed p97, and 8 were negative for both. We conclude that the p97 gene, like the transferrin and TR genes, is located on chromosome 3.

Localization of melanoma-associated antigen p97 in cultured human melanoma, as visualized by light and electron microscopy

The expression of a human melanoma-associated antigen, p97, in cultured melanoma cells was investigated using a modification of the Sternberger peroxidase-antiperoxidase (PAP) technique. Explant cultures of two skin melanomas were found to consist of a mixture of cells, some positive and some negative, for the expression of p97. From two other melanomas two cell lines were newly established. All cells from these lines expressed detectable p97 over a period up to 18 months. With the cell lines and the explant cultures we have initiated an investigation of the expression of p97 at the ultrastructural level, using the PAP technique. Antigen expression was detected as a continuous, strongly stained band at the cell surface of the melanoma cells.

Production and characterization of monoclonal antibodies against human malignant melanoma

The specific immunoreactivities of 31 monoclonal antibodies against human malignant melanoma were analyzed on a variety of malignant and nonmalignant human cells. Seven distinct groups were defined based on reactivity in radioimmunoassay and in mixed hemadsorption assay. The Group A antibody bound to 33% of short- and long-term cultured melanomas; Group B antibodies reacted with the majority of melanomas, astrocytomas, neuroblastomas, and fetal polygonal cells; and Group C antibodies bound to melanomas, teratocarcinomas, and to melanocytes grown in the presence of tumor-promoting phorbol esters. Antibodies of Groups D-G showed a less restricted binding pattern. In all groups, antibodies of IgG2b and IgM isotypes mediated complement-dependent lysis (CDC) and antibodies of IgG1, IgG2a, and IgG2b isotypes mediated antibody-dependent cell-mediated cytotoxicity (ADCC). Biochemical analysis indicated that 16 different proteins with molecular weights ranging between 28,000 and 500,000 were detected by the monoclonal antimelanoma antibodies.

Monoclonal antibodies to different epitopes on a prostate tumor-associated antigen. Implications for immunotherapy

Mouse monoclonal antibodies alpha Pro3 and alpha Pro5 bind to different epitopes on an antigen (p54) of 54 kD reduced and 175 kD nonreduced MW. p54 antigen has been characterized previously with regard to tissue distribution using alpha Pro3 monoclonal antibody; the p54 antigen is present in substantially greater quantities in malignant prostatic tissue extracts than in benign prostatic and nonmalignant nonurogenital tissue extracts. In this report, we have established that alpha Pro5 and alpha Pro3 monoclonal antibodies exhibit same molecule-different epitope recognition. That both antibodies recognize the same molecular entity has been established by partial physiochemical characterization of the antigen recognized by the two antibodies and by sequential immunoprecipitation experiments. Different determinant recognition was established by lack of competitive surface binding between alpha Pro3 and alpha Pro5 to a prostatic carcinoma cell line. The p54 antigen can be labeled with glucosamine and immunoprecipitated from urea-solubilized membrane proteins; however, p54 cannot be detected by immunoprecipitation in a glycosylated form in spent culture medium removed from glucosamine-labeled cells. Experiments using indirect cellular immunoassays and directly radioiodinated monoclonal antibody have shown that both alpha Pro3 and alpha Pro5 form stable complexes with p54 antigen on the prostatic carcinoma cell surface. To the extent that modulation occurs upon interaction of p54 with alpha Pro3 and alpha Pro5; endocytosis of the immune complex appears to be the primary route of modulation. Furthermore, modulation by endocytosis is more intense when alpha Pro3 and alpha Pro5 are used in combination than when either monoclonal antibody is used alone. Although in vivo biologic behavior does not invariably correlate with in vitro behavior, careful in vitro analysis of monoclonal antibodies with respect to cell surface behavior, nevertheless, should precede in vivo evaluation. The data presented in this report indicate that preliminary in vitro analyses will expedite the effectiveness of in vivo immunotherapeutic trials; preliminary in vitro evaluations are absolutely essential if monoclonal-toxic agent (e.g., ricin A) conjugates, which must be internalized by the tumor cell to achieve cytotoxicity, are employed as immunotherapeutic agents.

Human hybridomas from patients with malignant disease

Lymphocytes from 180 patients with a variety of malignant diseases were collected and fused with a human myeloma-derived line, LON-LICR-HMy2/CAM1. A total of 162 hybridomas was obtained. Only B lymphocyte markers were found on the surface of the fusion products. Flow cytometric analysis revealed a stably increased DNA content in the hybridoma cells. Some hybridoma supernatants were found to contain new Ig chains. Anti-tumour binding activity was found in 12 supernatants.

Human melanoma-specific oncofetal antigen defined by a mouse monoclonal antibody

140.240, an IgG2a mouse monoclonal antibody raised against a cultured human melanoma cell line, was highly specific for melanoma cells as determined by direct and absorption analyses in a mixed hemadsorption assay. Supernatants of doubly cloned hybridomas producing antibody 140.240 reacted with all cultured and fresh melanomas tested but failed to react with a variety of carcinomas, sarcomas, lymphomas, leukemias and other tumors of neuroectodermal origin. This antibody did not react with B-lymphoid cell lines, ruling out HLA-DR specificity. Non-reactivity of antibody 140.240 with peripheral blood lymphocytes obtained from the donor of the immunizing melanoma line excluded the possibility of detecting histocompatibility antigens. Nevus cells were also non-reactive. However, antibody 140.240 did identify an antigenic determinant on tissue homogenates prepared from fetuses of 10-14 weeks' gestation. The antigen involved was shed by cultured melanoma lines and, by immunoprecipitation analysis of radiolabelled lysates, had a molecular weight of approximately 87kdal. Thus, the structure identified by monoclonal antibody 140.240 is a melanoma-specific oncofetal antigen.

Monoclonal antibodies to rat sarcomata. I. Immunization procedures and source of lymphoid cells for hybridoma production

Hybridomas secreting monoclonal antibodies with specificity for Hooded rat fibrosarcomata have been obtained by fusion of the rat myeloma Y3 Ag 1.2.3. (Galfre, Milstein & Wright, 1979) with cells taken from spleens or lymph nodes of immunized syngeneic and allogeneic donors. Two of the monoclonal antibodies, both derived from he spleens of tumour bearers, showed specificity for individual tumours one for MC24 (M10/76) and the other for HSNTC (11/160). These two antibodies had a long half-life in the blood when injected intravenously showing that they had a low affinity for normal tissue antigens. Monoclonal antibodies exhibiting broad tumour specificity or extensive cross-reactivity with normal cells were secreted by many of the hybridomas derived from both syngeneic and allogeneic rats that had been hyperimmunized with tumour cells. These results are discussed in relation to the production of monoclonal anti-tumour antibodies for use in experimental therapy.

Human melanoma cells can be killed in vitro by an immunotoxin specific for melanoma-associated antigen p97

Conjugates (immunotoxins) comprising ricin A-chain and monoclonal antibody 96.5, which is specific for human melanoma-associated antigen p97, inhibited protein synthesis and colony formation of cultured human melanoma cells that expressed more than 80,000 molecules of p97 per cell. Cells expressing fewer than 5,000 molecules of p97 were not killed. The presence of 10 mM ammonium chloride significantly increased the efficiency of the immunotoxin, tumor cells expressing high levels of p97 being killed at immunotoxin concentrations as low as 10(-10) M.

Immunohistochemical techniques in the early screening of monoclonal antibodies to human colonic epithelium

Selected monoclonal antibodies (McAbs) isolated after immunization of rats with a human colonic carcinoma membrane preparation, have been screened on frozen and paraffin sections of colonic tissue, using immunohistochemical techniques, in order to provide additional information with regard to specificity and crossreactivity with normal tissues.Of 10 McAbs previously shown to bind to a colonic carcinoma membrane preparation in a radioimmunoassay, 7 show specific staining when tested by indirect immunofluorescence on crysotat sections of colonic tissue. Three of these 7 show activity on both normal and malignant colonic epithelium, and the remaining 4 stain normal epithelium, with little or no activity on malignant tissue. In the indirect immunofluorescent and immunoperoxidase techniques on paraffin sections of the same material, only 2 McAbs retain activity; one detects an antigen in colonic mucus, and the other recognises an antigen which is sparse on normal colonic epithelium and abundant on colonic tumours.We conclude that screening of McAbs on frozen tissue sections, using indirect immunofluorescence, is a useful adjunct to conventional screening methods, e.g. binding to membrane preparations and/or cell lines in a radioimmunoassay. These techniques distinguish McAbs with similar binding values in conventional assays, identify their activity on a wide range of normal and malignant tissues, demonstrate antigens that are lost or gained in malignant transformation and finally assist in the selection of McAbs for further extensive study before possible clinical use.

Monoclonal antibodies reactive with human myeloid leukaemia cells

Hybridomas producing monoclonal antibodies that bind to determinants on myelogenous leukaemia blast cells were developed using fresh leukaemia blasts as immunogens. These monoclonal antibodies were used to quantitate the amount of a variety of antigens on both leukaemia and normal blood cells in a radioimmunoassay. The ability of these antibodies to mediate complement-dependent lysis of leukaemia cells and normal blood cells was evaluated. Significant quantitative differences in the expression of a variety of cell surface antigens were observed among different myeloid leukaemia cell samples, normal cells, and other forms of leukaemia. However, none of the monoclonal antibodies studied were found to be specific for myeloblasts. Despite the fact that these antibodies bound to both leukaemia and normal cells, several of them mediated complement-dependent cytotoxicity which was restricted to leukaemic myeloblasts (AML-1-211, AML-2-30, CML-18, CML-75, CML-115, and CML-150). None of these clones, alone or in any combination, were capable of lysing normal lymphocytes or monocytes. Others were specifically cytotoxic to leukaemia cell lines (AML-1-99), B cells and some leukaemia samples (AML-2-9), and myelomonocytic leukaemia cell samples and normal monocytes (AML-2-23). Several of the monoclonal antibodies from this panel appear to be promising for future clinical applications.

Detection of a human melanoma-associated antigen, p97, in histological sections of primary human melanomas

The unlabelled antibody technique of Sternberger was used to study the localization in histological sections of human melanoma-associated antigen p97, which is defined by a monoclonal antibody. The antigen was detected in 8 of 10 primary skin melanomas, in 6 of 7 metastatic melanomas and in 2 of 2 compound nevi. It was localized at the cell surface, the cytoplasm and the nucleus always being negative. The antigen was not seen in cells from 3 basal cell carcinomas, 1 squamous cell carcinoma, 1 leiomyosarcoma, or in samples of normal skin (including keratinocytes, connective tissue consisting of collagenous and elastic fibers, fibroblasts, sebaceous glands, blood vessels, smooth muscles, or inflammatory cells such as granulocytes, lymphocytes and macrophages), kidney or lung. There was, however, staining of some cells in the secretory segment of eccrine sweat glands from 2 patients, possibly corresponding to myoepithelial cells. Antigen expression was somewhat variable between cells from different melanomas as well as between individual cells from the same melanoma. The possible diagnostic value of this procedure for identification and classification of melanomas is discussed.

A cell-surface antigen which is present in the ganglioside fraction and shared by human melanomas

We have raised a hybridoma, 4.2, which forms an IgM antibody to an antigen expressed on cultivated cells from most human melanomas, more infrequently on cells from other human tumors, and very weakly on cultivated fibroblasts, T cells and B cells. The antigen can be detected in biopsy material of human melanoma and, in smaller amounts, in fresh samples of normal human lung and kidney. Preliminary biochemical characterization indicates that it is associated with the ganglioside fraction. We feel that the antigen (referred to as 4.2) has a sufficient degree of tumor specificity to be rated as a human melanoma-associated antigen.

Monoclonal antibodies to two mouse bladder carcinoma antigens

Carcinomas of the urinary bladder of mice were induced by 3-methyl-cholanthrene or fanft [(4-5-nitro-2-furyl)-2-thioazolyl formamide]. On transplantation in vivo, tumor lines consisting of well-differentiated transitional-cell carcinomas were established. Some tumors were also explanted in vitro. A rat was immunized with a pool of carcinomas and normal bladder tissue and its spleen cells were hybridized with NS-l mouse myeloma cells. Supernatants of hybrid cells ("hybridomas") were screened for antibody binding to antigens present in bladder carcinomas but not in normal syngeneic urinary bladder, with cell extracts as targets. Hybridomas that appeared to have the required specificity were cloned, tested further against transitional-cell bladder carcinomas, an anaplastic bladder tumor, rhabdomyosarcomas, a mammary carcinoma, myelomas and lymphomas, and normal adult urinary bladder, kidney, lung, spleen, heart, brain, thymus, and whole embryo. Antibody formed by one hybridoma, 2H5, gave significant binding to membranes from five of seven transitional-cell carcinomas but not to membranes from many other tissues. A second hybridoma, IE6, formed antibody to an antigen present in bladder carcinomas and normal liver and, in smaller amounts, in several other normal and neoplastic tissues. Fluorescence microscopy established that both antigens were present at the cell surface of transitional-cell bladder carcinomas. Immunoprecipitation and SDS-polyacrylamide gel electrophoresis were used to identify the target antigens from 125I-labelled cell membrane proteins. The antibody formed by 2H5 was found to identify a protein with a molecular weight in the range of 140 kilodaltons, which was detected in transitional-cell bladder. The molecular nature of the antigen defined by hybridoma IE6 is not known.

Monoclonal antibodies to 125 kd and 95 kd proteins on human melanoma cells: comparison with other monoclonal-defined melanoma antigens

Two monoclonal antibodies produced by hybridomas were identified by an indirect 125I-protein A binding assay that define cell surface antigens expressed on cultured human melanoma cells but not on autologous lymphoblastoid cells. The first antibody, 705F6 (an IgG2b immunoglobulin), bound to 14/14 melanoma lines, 6/9 carcinomas and sarcomas, 7/7 gliomas and neuroblastomas, 2/2 fetal cell lines, 0/8 lymphoblastoid cell lines, and weakly to 2/4 leukemia lines. The second monoclonal antibody, 436G10 (IgG1), reacted with 10/14 melanomas 5/13 carcinomas and sarcomas, 2/7 gliomas and neuroblastomas, and weakly with the fetal cells, but not with the leukemic or lymphoblastoid cell lines. Comparison of 705F6 and 436G10 with 28 other monoclonal antibodies from different laboratories identified several with similar binding patterns to a panel of tumor and nontumor cell lines. Crossblocking of 125I-labeled 436G10 was not observed by R23, I12 or L10 antibodies. However, 705F6 was completely blocked by monoclonal 376.96S, showing that these two antibodies bind to the same antigenic determinant. The 705F6 antibody immunoprecipitated a 95 kd (kilodalton) membrane protein and the 436G10 antibody bound a 125 kd protein from 125I-labeled melanoma cells. The broad distribution of these two proteins on melanomas and other solid tumors suggests that they define common oncodevelopmental antigens expressed on proliferating cells.

Workshop on monoclonal antibodies to human melanoma-associated antigens: findings of the Seattle group

The 30 workshop monoclonal antibodies identify a number of distinct cell surface antigens of human melanoma. Indirect 125I-protein A binding assays showed that virtually all of the antibodies recognized antigens at the surface of SK-MEL-28 melanoma cells. Immunoprecipitation from detergent lysates of surface-radioiodinated cells showed that 16 of the antibodies recognized cell surface proteins. Antibodies 96.5, 118.1, 133.2 and two antibodies from the Sloan-Kettering group, I12 and L10, recognized a 97,000 MW protein, p97, but none of the other antibodies did so. Many of the antigens appear to have sufficient specificity for melanoma to be of interest as potential diagnostic markers and therapeutic targets and to merit structural and functional studies.

Two human tumor-associated antigens, p155 and p210, detected by monoclonal antibodies

BALB/c mice were immunized with human melanoma cells and their spleen cells hybridized with NS-1 myeloma cells. The hybrids were screened for the production of antibodies that bound to melanoma cells. Two hybridomas of interesting specificity were identified and cloned. Hybridoma 5.1 produce an IgG1 antibody that binds to about half of the melanomas and carcinomas tested. The target is a polypeptide with an apparent molecular weight of 210 kilodaltons on sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The antigen, denoted p210, is also expressed in normal adult brain and in certain fetal tissues. Hybridoma 6.1 produces an IgM antibody that binds to about 50% of the melanomas, and 80% of the kidney carcinomas tested. The antigen defined by this antibody in melanomas has an apparent molecular weight of 155 kilodaltons and is denoted p155. It has not been observed on any normal adult or fetal tissues. The antigen present in the kidney carcinomas was not p155, but rather consisted of two proteins of approximately 60,000 and 250,000-300,000 daltons. This observation suggests the possibility that the antigenic determinant recognized by antibody 6.1 may be present on several distinct protein molecules.

Lymphocyte-dependent antibodies to antigen 3.1, a cell-surface antigen expressed by a subgroup of human melanomas

Previous work from our laboratory has led to the isolation of a monoclonal IgG2a mouse antibody, 3.2, which is specific for an antigen, 3.1, that is strongest expressed by a group of human melanomas. We have no demonstrated that this antibody can mediate antibody-dependent cellular cytotoxicity (ADCC) to human melanoma cells expressing antigen 3., and that lymphocytes from human peripheral blood can be used as the source of K cells. A monoclonal IgG1 antibody, 3.1, to the same determinant of antigen 3.1 gave only weak and inconsistent ADCC.

Analysis of normal neoplastic human tissues for the tumor-associated protein p97

We have used immunoprecipitation to test tumor biopsies and normal adult and fetal human tissues for p97, a tumor-associated protein. Five of nine melanoma biopsies contained p97 in low to very high levels. Three of seven non-melanoma tumors contained p97, but in smaller amounts. No p97 was detected in any of the normal adult tissues examined. The protein was, however, observed in samples of fetal colon and umbilical cord, and in one sample of fetal lung. One of two benign nevi contained high levels of p97, whole on benign angiofibroma was negative. We conclude that the presence of p97, in levels detectable by our method, appears to be characteristic of certain neoplastic and fetal tissues.