Cell surface antigens of human ovarian and endometrial carcinoma defined by mouse monoclonal antibodies

Atlas of Lobular Breast Cancer Models: Challenges and Strategic Directions

Invasive lobular carcinoma (ILC) accounts for up to 15% of all breast cancer (BC) cases and responds well to endocrine treatment when estrogen receptor α-positive (ER+) yet differs in many biological aspects from other ER+ BC subtypes. Up to 30% of patients with ILC will develop late-onset metastatic disease up to ten years after initial tumor diagnosis and may experience failure of systemic therapy. Unfortunately, preclinical models to study ILC progression and predict the efficacy of novel therapeutics are scarce. Here, we review the current advances in ILC modeling, including cell lines and organotypic models, genetically engineered mouse models, and patient-derived xenografts. We also underscore four critical challenges that can be addressed using ILC models: drug resistance, lobular tumor microenvironment, tumor dormancy, and metastasis. Finally, we highlight the advantages of shared experimental ILC resources and provide essential considerations from the perspective of the European Lobular Breast Cancer Consortium (ELBCC), which is devoted to better understanding and translating the molecular cues that underpin ILC to clinical diagnosis and intervention. This review will guide investigators who are considering the implementation of ILC models in their research programs.

Immunohistochemical Reactivity of a Monoclonal Antibody Prepared against Human Ovarian Carcinoma on Normal and Pathological Female Genital Tissues

The reactivity profile of the monoclonal antibody (MAb) MOv18, raised against a poorly differentiated ovarian carcinoma specimen, was studied on normal tissues and tumors from the female reproductive system and on the kidney, which like the oviducts, vagina and uterus, also derives from the intermediate mesoderm. The obtained results indicate that MOv18 recognizes an epitope present on the normal epithelium of the oviducts, on 14-week old fetal kidney and, focally, on proximal and distal tubules of normal adult kidney. A strong reactivity was found on ovarian carcinomas, on invasive squamous carcinomas of the cervix and on endometrial carcinomas and hyperplasias. The antigen recognized by MOv18 (CaMOv18) therefore seems to be an epithelial cell marker associated with intermediate mesoderm differentiation, which can be derepressed during the neoplastic transformation of the ovary and the uterus.

Small antibody mimetics comprising two complementarity-determining regions and a framework region for tumor targeting

Here we show that fusion of two complementarity-determining regions (CDRs), VHCDR1 and VLCDR3, through a cognate framework region (VHFR2) yields mimetics that retain the antigen recognition of their parent molecules, but have a superior capacity to penetrate tumors. The antigen-recognition abilities of these approximately 3 kDa mimetics surpass those of comparable fragments lacking the framework region. In vivo activities of the mimetics suggests that the structural orientation of their CDRs approximates the conformation of the CDRs in the complex of the parent antibody with antigen. We linked the antibody mimetics to the bacterial toxin colicin Ia to create fusion proteins called "pheromonicins," which enable targeted inhibition of tumor growth. In mice bearing human malignant tumors, pheromonicins directed against tumor-specific surface markers show greater capacity to target and penetrate tumors than their parent antibodies. Rational recombination of selected VH/VL binding sites and their framework regions might provide useful targeting moieties for cytotoxic cancer therapies.

Initial immunochemical characterization of MX35 ovarian cancer antigen

Monoclonal antibody (mAb) MX35 reacts with approximately 90% of ovarian epithelial cancers and has been studied in localization and biodistribution trials in ovarian cancer patients. This study shows that mAb MX35 recognizes a cell surface antigen of about 95,000 D on OVCAR-3 ovarian cancer cells. The antigen could be immunoprecipitated from lysates of cells metabolically labeled with [3H]glucosamine and it bound to concanavalin A and wheat germ agglutinin lectins, showing that it is a glycoprotein. MX35 antigen can also be detected in detergent lysates of OVCAR-3 cells by Western blotting. Using this technique the MX35 epitope(s) was shown to be heat stable but susceptible to reduction by 2-mercaptoethanol. Protease digestion of the antigen resulted in smaller fragments (42-52 kDa) that still reacted with antibody. We conclude that MX35 antigen is a 95 kDa glycoprotein, stabilized by disulfide bonds, with a large protease-resistant region that carries the MX35 epitopes.

Detection of ovarian cancer by 198Au-labeled human monoclonal antibody

BACKGROUND

There is no reliable method for the early diagnosis of ovarian cancer. Radiolabeled monoclonal antibodies have potential to assist in early diagnosis, but they are limited by problems that include antibody specificity, stability, and immunoreactivity, as well as patient reactions to the antibodies used.

METHODS

Methods were developed to 198Au-label a human monoclonal antibody (TC5 antibody), developed against an ovarian cancer cell surface antigen. Antigen binding sites on the TC5 antibody were protected with sepharose 4B affinity chromatography before 198Au-labeling. The 198Au-labeled TC5 antibody was evaluated with biopsy specimens in a blind study. The immunoreactivity of radiolabeled TC5 antibody also was evaluated in slot-blot experiments with extracts of the biopsy specimens.

RESULTS

The 198Au-labeled TC5 antibody had high binding reaction to all biopsy specimens (six of six) pathologically diagnosed as ovarian cancer (serous and endometrioid adenocarcinoma). The radiolabeled TC5 antibody did not bind to any normal (non-neoplastic) specimens (zero in ten), with one exception. One "normal" ovary specimen had high binding of radiolabeled TC5 antibody, and metastatic ovarian cancer was diagnosed 4 months later. The TC5 antibody labeled with 198Au, without protecting antigen-binding sites, did not bind to any biopsy specimens.

CONCLUSIONS

The affinity-labeling method was necessary to protect antigen-binding sites and preserve the immunoreactivity of the TC5 antibody. The 198Au-labeling method may be an ideal technique to evaluate monoclonal antibodies in vitro. The TC5 antibody had high sensitivity and specificity for detecting ovarian cancer.

In vivo targeting of integrin receptors in human skin xenografts by intravenously applied antibodies

We examined whether systemically injected monoclonal antibodies (mAbs) directed to cell-surface glycoproteins of human keratinocytes reach their target antigens in xenograft transplants of normal human skin on SCID mice. The integrins alpha 6 beta 4, expressed in the basal cell layer of human epidermis, and glycoprotein T16 (gp 40/50), expressed in terminally differentiating keratinocytes of the stratum spinosum, were selected as targets. It was found that all injected mAbs selectively localized to their antigens and bound and saturated their targets even in the uppermost layers of the stratum malpighii. This could easily be monitored by direct immunofluorescence staining since SCID mice lack endogenous production of significant amounts of immunoglobulins. After a single injection, mAbs could still be detected at the target site after 14 days. Our results proved that heterologous immunoglobulins pass systemic capillary filters in this xenograft model and specifically bind to their target molecules. Thus, xenografted SCID mice provide a versatile model for studying cell-surface glycoprotein-mediated interactions by the use of functionally interfering antibodies under in vivo conditions in human skin.

Trophoblast and ovarian cancer antigen LK26. Sensitivity and specificity in immunopathology and molecular identification as a folate-binding protein

The LK26 antigen is a cell surface glycoprotein (M(r)35,000 to 40,000) of normal placenta and gestational choriocarcinomas that shows highly restricted distribution in normal tissues, being expressed primarily in a subset of simple epithelia. In this study, immunohistochemical methods were used to examine LK26 expression in 78 ovarian tumors and > 400 tumors of other histological types. Ovarian carcinomas derived from coelomic epithelium showed the most consistent and strongest immunostaining for LK26, with 52 of 56 cases being LK26+. Ovarian tumors of sex cord, germ cell, and stromal origin were generally LK26-. LK26 was not found in normal fetal or adult ovary; however, it was present in the lining epithelia of some benign ovarian cysts. Mesotheliomas, which share a common mesothelial origin with LK26+ ovarian tumors, expressed no or only low levels of LK26. Other epithelial cancers expressed LK26 in subsets of cases and generally showed heterogeneous or weak immunostaining; this group of LK26+ tumors includes endometrial (10 of 11 cases tested), colorectal (six of 27), breast (11 of 53), lung (six of 18), and renal cell (nine of 18) carcinomas. Four of five brain metastases derived from epithelial cancers and three of 21 neuroendocrine carcinomas showed prominent LK26 immunoreactivity. Only rare neuroectodermal tumors (two of 70) and none of the sarcomas (none of 58) or lymphomas tested (none of 21) were LK26+. Tests with cultured cells showed that the LK26 proteins expressed in choriocarcinoma and ovarian cancer cells are biochemically similar, and transfection experiments identified LK26 as an adult-type, high-affinity folate-binding protein. The present study provides the first detailed specificity and sensitivity analysis for folate-binding protein/LK26 in human tumors and defines a role for folate-binding protein/LK26 in immunobiological studies of ovarian cancers and other LK26+ neoplasms.

Human monoclonal antibody recognizing an antigen associatedwith ovarian and other adenocarcinomas

MS2B6, a human monoclonal antibody derived from a patient with advanced ovarian cancer, has been used to study the distribution and characteristics of its target antigen. The MS2B6 antigen was detected by immunoperoxidase studies in 41 of 41 epithelial ovarian cancers and in the majority of nonovarian adenocarcinomas. Among normal tissues the MS2B6 antigen was found in the adult epithelia of the fallopian tube, endometrium, endocervix, colon, bronchus, breast, sweat duct, and large renal ducts. No detectable antigen was found in peritoneal epithelia, tissue stromal cells, spleen, thymus, or blood-borne cells. Immunoblotting analysis showed that the MS2B6 epitope resides on polypeptides of 38, 44, and 60 kd. The cellular location of the MS2B6 antigen was studied with immunoperoxidase and immunofluorescent staining and immunoelectronmicroscopy of ovarian cancer ascites tumor cells. The results suggest that in ascites tumor cells the MS2B6 antigen is located in a layer of the peripheral cytoplasm beginning just below the cell membrane. MS2B6 may be useful as an imaging or therapeutic agent.

Isolation and characterization of a monoclonal antibody, K1, reactive with ovarian cancers and normal mesothelium

We have isolated a new monoclonal antibody (MAb), K1, that reacts with an epitope on the surface of human ovarian carcinoma cells. This antibody was generated by immunization of mice with periodate-treated human ovarian carcinoma (OVCAR-3) cells. These mice had been previously made tolerant with normal human kidney membranes. Spleen lymphocytes from these mice were selected prior to fusion using a panning purification method on living OVCAR-3 cells. Initial screening of surface-reactive clones was performed in a single day using immunofluorescence on living OVCAR-3 cells, and secondary screening was performed using immunoperoxidase histochemistry on cryostat sections of normal human tissues and human tumors. The K1 clone was subcloned and identified as an IgM isotype, but was subsequently isotype-switched to IgG1K using a panning selection method. When evaluated by immunohistochemistry, the antigen reactive with K1 was found in many ovarian non-mucinous tumors, as well as in squamous tumors of the esophagus, and cervical cancer. The only normal adult human tissues showing uniform reactivity with K1 were the mesothelia of the peritoneal, pleural and pericardial cavities. There was also limited reactivity with epithelia of the trachea, tonsil and Fallopian tube. A similar tissue reactivity for K1 was found in tissues from cynomolgus monkeys. K1 reacted with many of the same tissues and tumors as the previously identified antibody OC125, but several lines of evidence indicate that K1 reacts with a different epitope and probably a different molecule, when compared to OC125. This evidence included assays employing immunofluorescence competition, double-label immunofluorescence, and solid-phase and live-cell radioimmunoassays. Since our data indicate that the antigen reactive with the K1 antibody is a new molecular species, we have named the antigen CAK1. Unlike the shed antigen CA125, CAK1 was only cell-associated and was not found in the supernatant of cultured OVCAR-3 cells or in the blood of ovarian cancer patients. The K1 antibody may be useful as a targeting agent for therapy and in the diagnosis of ovarian carcinoma, as well as some other human cancers.

Normal tissue reactivity of four anti-tumor monoclonal antibodies of clinical interest

Normal tissue reactivity on frozen sections was examined with 4 monoclonal antibodies (MAbs) that were reported previously to be negative or weakly reactive with normal tissues, and strongly reactive with some types of carcinoma. All 4 antibodies reacted strongly with certain normal epithelial cells. The antibodies tested include 2 antibodies to ovarian cancer, MOv18 and MOv19, one antibody to breast cancer, H23, and one antibody reactive with a range of carcinomas, B72.3. MOv18, MOv19 and H23 reacted with many normal glandular and ductal epithelial cells, while B72.3 reacted most strongly with secretions of the small intestine epithelium and the suprabasal squamous epithelial cells of the esophagus. Since the tissue distribution of MOv19 was very similar to that of another antibody described previously, MW207, these two antibodies were compared by competitive binding inhibition, and found to recognize the same epitope. Our data emphasize the importance of repeated, independent tests of antibody specificity.

Integrins of normal human epidermis: differential expression, synthesis and molecular structure

The expression of integrin cell surface receptors in normal skin and their synthesis and molecular structure in keratinocyte cultures was investigated. The reactivity of four different polypeptides of the integrin family (alpha 2-, alpha 3-, alpha 6- and beta 1-chains) was demonstrated in the basal cell layer of normal epidermis. Studies of labelled keratinocyte cell lines showed that the polypeptides were expressed as alpha 2 beta 1, alpha 3 beta 1 and alpha 6 beta 4 integrins. Only the alpha 6 beta 4 integrin showed polarization towards the basement membrane attachment site of basal layer keratinocytes, and was preferentially expressed at microvillous projections. In contrast, alpha 2 beta 1 and alpha 3 beta 1 integrins were equally expressed throughout the basal cell plasma membrane.

Expression of 38-kD cell-surface glycoprotein in transformed human keratinocyte cell lines, basal cell carcinomas, and epithelial germs

In this study, we attempted to identify and characterize transformation-induced cell-surface glycoproteins of human keratinocytes. Therefore, we first searched for glycoproteins which are significantly elevated in human keratinocytes after transformation and immortalization by SV40 virus and which are also found at high levels in keratinocytic cell lines derived from squamous cell carcinomas of the skin. Out of at least 80 different cell-surface antigenic systems of human tumor cells, only three glycoproteins showed elevated expression in transformed keratinocytes. Among these, a 38-kD glycoprotein (gp 38) was highly increased in all transformed keratinocyte cell lines tested, but was not elevated in transformed fibroblasts. The expression of gp 38 was further characterized in normal epidermis and in its benign and malignant hyperproliferative disorders: gp 38 was generally not expressed in normal epidermis and in benign hyperproliferative disorders. In contrast, strong and homogeneous reactivity was found in solid and fibrosing basal cell carcinomas whereas no or low reactivity was detected in squamous cell carcinomas and in those parts of BCC revealing keratotic differentiation. Interestingly, high expression of gp 38 was also found in primary epithelial germs of fetal skin, secondary germ cells of the telogenic hair follicle and secretory tubules of sweat glands. The immunohistologic data suggest that gp 38 is preferentially expressed by epidermal cells which lack squamous and pilosebaceous differentiation.

Six new monoclonal antibodies to serous, mucinous, and poorly differentiated ovarian adenocarcinomas

Six monoclonal antibodies directed against ovarian adenocarcinoma were generated by use of 100,000 x g supernatants of Triton-X-100 solubilized extracts of ovarian serous adenocarcinoma as the antigen source. Immunoperoxidase preparation of frozen-sections and routinely processed paraffin section specimens revealed a highly restricted reactivity of these antibodies when tested with adult (n = 2) and fetal (n = 3) tissue types. Coreactivities were occasionally observed with epithelia of the kidney, mammary gland, and pancreas. One monoclonal antibody, Ki-OC I-6-2, cross-reacted only with epididymal epithelia. No coreaction occurred with normal tissue of the ovary, Fallopian tube, or uterus. All antibodies were additionally tested on 74 cases of nonovarian malignancies, 15 cases of ovarian metastases of nonovarian carcinomas, and 114 specimens of ovarian neoplasms other than carcinomas. Ki-OC I-6-2 had no cross-reactivity with these tumors except for one case of renal cell carcinoma. This monoclonal antibody recognized serous, mucinous, and poorly differentiated adenocarcinoma cell types. None of the six antibodies reacted with clear cell or endometrioid carcinoma. All were found to be of the IgG-1 subclass. The tumor antigen to which Ki-OC I-6-2 immunoreacted was estimated to have a molecular weight of 80 kilodaltons (KD).

Serum levels and biochemical characteristics of human ovarian carcinoma-associated antigen defined by murine monoclonal antibody, CF511

The murine monoclonal antibody (Mab) against human common epithelial ovarian carcinoma, CF511, was generated by immunising mice with human fetal tissue extract from early first trimester, followed by booster injection of an ovarian cancer cell line. Mab CF511 recognised the 600 kDa sialylated glycoprotein as different from previously known tumour associated-marker antigens. Distribution of the Mab CF511-recognised antigen (CF511 antigen) in various tissues and sera was investigated. In immunohistochemical analysis, Mab CF511 reacted strongly with tumour cells of ovarian serous, clear cell, endometrioid and undifferentiated carcinoma and partially with those of mucinous carcinoma. Mab CF511 also reacted with breast carcinoma as well as lung carcinoma. In normal tissues, Mab CF511 cross-reacted with only five tissues, namely lung, breast, thyroid gland, fallopian tube and uterus. Serum levels of CF511 antigen were tested by ELISA inhibition using Mab CF511. This assay showed the circulating CF511 antigen levels to be elevated in 25 of 36 sera from patients with various clinical stages of common epithelial ovarian carcinoma compared to three of 47 and three of 111 sera from patients with other benign gynaecological diseases, including ovarian cysts, uterine fibroids with or without endometriosis and normal healthy subjects, respectively. For the relation between antigen levels and clinical stages of common epithelial ovarian carcinoma, greater than 34.0% ELISA inhibition was detected in 100% of patients with advanced stages (FIGO III and IV) compared with in 35.3% with early stages (FIGO I and II) patients. While patients with breast carcinoma (100%) and lung carcinoma (100%) also had elevated circulating CF511 antigen levels, patients with hepatoma, colorectal carcinoma and gastric carcinoma had no detectable elevation of antigen. Although the test showed a high degree of specificity, the detection of an elevated CF511 antigen level would not be so helpful in distinguishing patients with ovarian carcinoma from those with either breast carcinoma or lung carcinoma. These data suggest that CF511 antigen is a useful new ovarian tumour marker for diagnosis and management of the disease.

Cancer antigens are expressed in a carcinogen-transformed Bloom syndrome B-lymphoblastoid cell line

We have cloned malignant cells carrying specific antigens associated with ovarian cancer (OVC) and malignant lymphoma (ML) from BS-SHI-4M cells, a line derived from a 1-methyl-3-nitro-1-nitrosoguanidine-treated B-lymphoblastoid cell line isolated from a patient with Bloom syndrome. Since BS-SHI-4M cells react with sera from various individual cancer patients at relatively low frequencies (2-9%), as detected by an indirect immunofluorescence technique, cell clones that specifically react with sera from patients with OVC and ML were separated by the "panning" method in which polystyrene dishes were coated with sera from OVC and ML patients and cells with the corresponding antigens bound to the dishes. Subsequent cloning by limiting dilution provided cell clones highly enriched for OVC- and ML-associated antigens. Karyotype analyses revealed that cell clones with OVC and ML antigens had common marker chromosomes, der(14)t(14;14) (p11;q11),t(6;?)(p25;?) and t(9;?)(q34;?), besides t(17;?) (q25;?) found in the OVC-antigen-positive clones and t(5;?) (p13;?),t(7;?)(q36;?) found in the ML-antigen-positive clones. Interestingly, in cell clones with a strong OVC antigen response, the distal part of the Y chromosome (Yq11) was missing in 100% of the cells. Therefore the cell line BS-SHI-4M appears to be a reservoir of cell clones each of which carries a specific tumor antigen and thus provides a potential tool for rapid serological diagnosis of cancer.

Clinical applications of monoclonal antibodies against ovarian cancer-associated antigens

Monoclonal antibodies (McAbs), reactive with tumour-associated antigens (TAAs) present on tumour cells, appear to offer new possibilities in the diagnosis and treatment of cancer (Table I). In addition to these prospects for clinical application, monoclonal antibodies also serve as useful instruments in basic cancer research. The hybridoma technology initiated by Köhler and Milstein in 1975, underwent a very rapid development and has now shown its potential in the field of oncology. This technique made it possible to produce very large quantities of homogeneous antibodies of a stable quality. These McAbs often recognize only one antigenic determinant, or epitope, of cell surface and other molecules. This high specificity is essential for in vivo applications, especially in therapeutic immunotargeting. A central question is whether the antibodies can reach and identify those antigens on ovarian tumour cells that are not shared with normal tissues. Various antibodies have been described in the field of gynaecological oncology, which are assumed to be capable of recognizing such ovarian tumour-related antigens. These McAbs, single or in combination, are capable of showing, unambiguously, the presence of various tumour-associated antigens on ovarian carcinoma cells either in tissue or, when antigen shedding occurs, in blood. However, these McAbs may also react with tumour-associated antigens present on endometrial, cervical, colorectal, breast or other carcinoma cells. The original immunogens used to generate these McAbs differ as to their origin: ovarian cancer cells, breast cancer cells, human milk-fat preparations, trophoblastic cells, endometrial cancer cells have been used as well as osteogenic sarcoma cells, epidermoid carcinoma cells and small-cell lung cancer, colorectal, pancreatic and laryngeal carcinoma cells. The histological distribution patterns of the antigens recognized by these McAbs vary widely: cross-reactions with normal tissue and with carcinomas different from those used as immunogen are frequently seen.

A transformation-associated 130-kD cell surface glycoprotein is growth controlled in normal human cells

Two characteristics of cell surface molecules involved in the regulation of cell proliferation are altered expression in relation to growth phase in normal cells and overexpression in transformed cells. Here, we describe a similar pattern of expression for a 130-kD cell surface glycoprotein (gp 130) in human cells. Synthesis and cell surface expression of gp130 were greatly increased in both virally and chemically transformed fibroblasts, fibrosarcomas, a squamous cell carcinoma of the skin, and T cell leukemia lines. Furthermore, gp130 expression was induced in serum-starved fetal fibroblasts by serum stimulation, and in fresh T cells by various activating agents. Expression in response to serum stimulation was associated primarily with the transition from a quiescent state (G0) into the cell cycle (G1).

Human ovarian carcinoma lysis by cytotoxic T cells targeted by bispecific monoclonal antibodies: analysis of the antibody components

In the perspective of in vivo therapeutic applications, the monoclonal antibody (MAb) MOv18 was selected for its restricted reactivity with human ovarian carcinoma. Using the pH 2.8 desorption assay, we found that the antigen recognized by MOv18 had a high stability on the cell membrane and poor internalization. Therefore, a therapeutic approach which does not require internalization, i.e., the re-targeting of cytotoxic T lymphocytes (CTL) by bispecific MAbs, was investigated. MOv18 and anti-CD3 MAbs were used to produce bispecific reagents, obtained either by chemical cross-linkage (hetero-conjugates) or by somatic hybridization techniques (hybrid MAbs). The maintenance of the binding reactivity and specificity of the bispecific MAbs was analyzed by solid-phase radioimmunoassay, immunofluorescence and cross-competition tests on the relevant target cells (ovarian carcinoma cell line OVCA 432 for MOv18 and PHA-stimulated peripheral blood mononuclear cells for anti-CD3 MAbs), and on 2 irrelevant tumor cell lines. Bv a 51Cr-release assay the bispecific MAbs were found to efficiently promote, at picomolar concentration, cell lysis by CTL clones, but the specificity pattern was wider than that predicted by the binding studies. The F(ab')2 fragment of one hybrid MAb mediated a lysis which was just as efficient as the entire MAb on the relevant target cells and allowed specific lysis to be distinguished from Fc-receptor-mediated lysis. Human immunoglobulins were unable to compete with the Fc receptor binding of the hybrid MAbs and therefore, in the perspective of in vivo applications, Fc fragment removal seems to be an essential step. Analysis of the bispecific reagents indicated that hybrid MAbs are superior to the heteroconjugate as far as storage stability is concerned.

The use of monoclonal antibody B72.3 in the management of gynecologic malignancies

Monoclonal antibodies are currently used in the diagnosis of gynecologic malignancies by way of immunohistochemical assays, serum assays, and in situ radiolocalization of carcinoma lesions. Among them is MAb B72.3, generated against a human tumor-associated antigen (TAG-72). Using immunohistochemical techniques, MAb B72.3 has shown reactivity with 100 percent of common epithelial ovarian carcinomas and endometrial carcinomas and non-reactivity with normal adult tissues, with the exception of normal secretory endometrium. B72.3 appears to be a valuable immunocytologic adjunct, with greater than 90 percent of effusions and fine-needle aspiration biopsies from gynecologic carcinomas showing reactivity. Using a serum assay developed to detect the presence of the TAG-72 antigen, 48 percent of patients with ovarian carcinoma demonstrated TAG-72-positive sera versus 1 percent of control sera. 131I-labeled MAb B72.3 IgG and gamma scanning have been used for the in situ detection of metastatic carcinoma. Twelve of 15 patients with ovarian carcinoma showed positive gamma scans, and approximately 80 percent of the lesions demonstrated specific localization of the antibody. These studies indicate the potential utility of MAb B72.3 in the diagnosis of gynecologic carcinoma.

Changes in cell surface glycoprotein expression during differentiation of human keratinocytes

Six cell surface glycoproteins defined by monoclonal antibodies were selected for study on human epidermal cells. In tests on tissue sections, three of the glycoproteins [J143 (gp140/30); T43 (gp85/36); H99 (gp38)] were expressed in the basal cell layer of the epidermis, whereas the other three glycoproteins [T179 (gp140/95); T16 (gp40/50); BT15 (gp80)] were preferentially expressed in maturing keratinocytes above the basal layer. We compared synthesis of these glycoproteins in fresh epidermis and in primary epidermal short term cultures using [35S]methionine for metabolic labeling. Synthesis of J143 was 8- to 20-fold higher and synthesis of T43 was 4- to 10-fold lower in cultured cells compared with fresh epidermis. BT15, an antigen strongly expressed on terminally differentiating keratinocytes, was synthesized at 5- to 15-fold higher levels in fresh epidermis than in cultured cells. Biosynthesis levels of H99, T179, and T16 did not change in cultured epidermal cells. Based on our findings, we propose a model of surface antigenic changes that occur during keratinocyte differentiation in vivo.

Pros and cons of gynecologic tumor markers

The use of a tumor marker not only depends upon its sensitivity and specificity, but also upon its ability to influence decisions between alternative plans for patient management. Use of beta human chorionic gonadotropin (hCG) for monitoring gestational trophoblastic neoplasia has set the standard to which other assays must be compared. Beta hCG and alphafetoprotein have provided useful markers for ovarian germ cell tumors. Recently, a monoclonal antibody-based immunoassay for CA 125 antigen has been used to monitor the treatment of epithelial ovarian carcinomas. Persistent elevation of CA 125 in serum has generally reflected persistence of disease at second look surveillance procedures. CA 125 levels can, however, return to within normal limits and residual disease can be found at laparoscopy or laparotomy. CA 125 shows promise for distinguishing benign from malignant pelvic masses. Trials are currently underway to evaluate the potential of CA 125 in combination with other markers to facilitate earlier detection of occult ovarian cancer.

Clinical applications of monoclonal antibodies in gynecologic oncology

The advances of both murine and human monoclonal antibody (MoAb) technology have allowed the development of several antibodies against gynecologic tumors. The goals are to produce effective and specific reagents for both immunodiagnosis and therapy. However, despite an extensive research effort, a clear demonstration of specific cancer-associated antigens in gynecologic malignancies, or of specific immune responses to such antigens has been elusive. Currently, most antibodies found are cross reactive with either oncofetal antigens or some normal adult tissues. Clinical usefulness of these MoAbs as a screening test in radioimaging or in immunotherapy remains to be proven. However, the use of MoAb technology in defined antigens/tumor markers such as beta-human chorionic gonadotropin, and alpha fetal proteins has provided convenient, reproducible and highly specific reagents. More recently, promising antibodies have been shown to detect tumor antigens in serum of patients with ovarian cancer.

Monoclonal antibody to an intracellular antigen images human melanoma transplants in nu/nu mice

Mouse monoclonal antibody TA99 detects a 70-kDa pigmentation-associated glycoprotein in human melanoma cell lines. The antigen cannot be detected on the cell surface by sensitive rosetting techniques or absorption studies, nor can it be detected as a secreted product in culture fluids. Contrary to expectation, 125I-labeled TA99 specifically localized to pigmented human melanoma transplants in nu/nu mice; no localization to nonpigmented melanoma or control tumors was found. Tumor imaging was initially obscured by circulating 125I-labeled TA99 during the first 6 days after antibody injection. With clearance of 125I-labeled TA99 from the blood (half-life, 4-7 days), specific tumor images could be clearly defined by day 13. Due to the persistence of 125I-labeled TA99 at the tumor site (8.9% of the injected dose at 1 week and 4.6% at 8-10 weeks), images were obtainable for up to 10 weeks. At 8-10 weeks, the tumor/blood ratio was 10(4)-10(5), and the tumor/normal tissue ratio ranged from 10(2) to 10(5). In view of these findings, antibodies detecting intracellular antigens may have a role in tumor imaging and therapy.

Characterization of human ovarian carcinoma-associated antigens defined by novel monoclonal antibodies with tumor-restricted specificity

Three new monoclonal antibodies (MAbs) (MOv16, MOv18 and MOv19) were raised against human ovarian carcinoma. To obtain more specific reagents than those produced so far, we adopted the following experimental approach which consisted of: the selection of a poorly differentiated ovarian carcinoma which was unreactive with all the MAb previously selected in our laboratory; and the application of a particular immunization protocol. The reactivity of the selected MAbs was studied by solid-phase RIA on live and fixed cells from tumor cell lines and by immunofluorescence on frozen sections from surgical specimens. The MAb MOv16 reacted with 60% of ovarian carcinomas as well as with a high percentage of other carcinomas and with some normal tissues. In contrast, MOv18 and MOv19 appeared to have restricted specificities for ovarian carcinomas and cystadenomas. Reactivity on other carcinomas was only observed in a few cases and no reactivity was found on non-epithelial tumors or normal tissues. Immunoprecipitation experiments indicated that MOv16 recognizes a 48-50-kDA protein, whereas MOv18 and MOv19 both identify a 38-40 kDA glycoprotein band. Cross-competition experiments, together with a double-determinant immunoradiometric assay which uses MOv18 as catcher and MOv19 as tracer, suggested that they recognize different epitopes carried by the same molecule. The affinity constants of MOv18 and MOv19 were estimated to be in the range of 10(8)-10(9) M-1. Taken together, the properties of these antibodies, their restricted ovarian tumor specificities and relative high affinity constants, suggest that they could represent promising tools for in vivo applications.

Human carcinoma cell lines xenografted in athymic mice: biological and antigenic characteristics of an intraabdominal model

In order to investigate in vivo clinical applications of murine monoclonal antibodies directed against human ovarian carcinoma a preclinical in vivo model was developed using BALB/c athymic mice. Three human carcinoma cell lines (MCF7, HT29, and SW626) were injected into the peritoneal cavity of pristane-primed animals and the biological and antigenic characteristics of the i.p. grown tumors were studied. The animals were killed when moribund or 6-8 weeks after tumor injection. At autopsy tumor take was observed in 85% of the injected animals, whereas palpable nodules were evident in only 83%. Examination of the peritoneal cavity revealed intraabdominal carcinomatosis with tumor masses varying in size between 0.2 and 0.5 cm in diameter and tumor sheets. The most frequently affected organs were the diaphragm, the liver, and the reproductive system. Ascitic fluid formation was rare and no animal developed tumors outside the peritoneal cavity. To determine whether the in vivo tumors retained the same antigenic characteristics as the in vitro cell lines, four monoclonal antibodies (MBr1, MOv2, MOv8, and MOv15) directed against ovarian carcinoma-associated antigens and two different experimental approaches (immunofluorescence and immunoblotting) were used. Variations at either a quantitative or a qualitative level were observed for some antigens, whereas no evident changes were apparent for others. In particular, the antigens detected by MBr1 and MOv15 on the MCF7 line both maintained high levels of expression and immunoblotting staining pattern, whereas the antigens detected by MOv2 on the HT29 and SW626 lines, although present at a high level, clearly changed their staining pattern. As regards the antigens recognized by MOv8 and MOv15 on the HT29 and SW626 lines, we observed a drastic decrease in the level of their expression and in many cases a drop below the threshold of detectability of the test. The intraabdominal carcinomatosis described partially mimics the growth characteristics of human ovarian cancer and maintains the expression of some antigenic markers associated with epithelial tumors of the ovary and may therefore be useful in devising immunodiagnostic and/or immunotherapeutic strategies for ovarian carcinoma.

Monoclonal antibodies against antigens expressed on human hepatocellular carcinoma cells

Monoclonal antibodies with selectivity for human hepatoma cell lines were produced by immunizing BALB/c mice with human hepatoma cell lines, HA22T/VGH or Hep 3B, and fusing sensitized mouse spleen cells with mouse myeloma cells. Two monoclonal antibodies recognizing antigens present only on human hepatoma cell lines were investigated. The monoclonal antibody IB1 was found to react with 3 of 9 hepatoma cell lines. Monoclonal antibody 9B2 reacted with all nine hepatoma cell lines. None of the other 20 cell lines tested was bound by IB1 and 9B2. The immunoperoxidase staining of monoclonal antibodies on frozen sections of paired hepatoma and normal liver tissues from the same individuals were studied. Antibody IB1 reacted with 3 of 13 hepatoma tissues, but with none of the normal liver and other tissues, and antibody 9B2 was reactive with antigens appearing on the bile canalicular domain of hepatoma and normal liver tissues. The antibody 9B2 stained no normal tissues with the exception of proximal tubules of kidney. Radioimmunoprecipitation tests identified two antigens reacting with 9B2. The major antigen had an apparent molecular weight of 140,000 and a minor one of 130,000. Therefore, antibody IB1 seems to be specific for antigens present on a group of human hepatoma cells and may be useful for classification and diagnosis of human hepatomas. Antibody 9B2 is quite specific to human liver cells and may be used to provide clues for the characterization of tumor cell lines, identification of metastatic tumors with hepatocytic origin, and study of the structure and function of bile canaliculi.

Assignment of human nerve growth factor receptor gene to chromosome 17 and regulation of receptor expression in somatic cell hybrids

Nerve growth factor (NGF) is a polypeptide hormone which plays a central role in the development and growth of sympathetic and sensory neurons. The effects of NGF on target cells are mediated by a specific cell surface structure, nerve growth factor receptor (NGFr), which has been identified in human cells as a 75,000-mol-wt glycoprotein. We have used a monoclonal antibody to human NGFr to study cell-surface expression of the receptor on a panel of mouse-human neuroblastoma hybrids, and the serological typing results permit assignment of the gene coding for NGFr (NGFR) to chromosome 17q21-qter. In addition to mouse-human neuroblastoma hybrids, human NGFr was also detected on hybrids derived from fusions between mouse L-cell fibroblasts and human neuroblastoma and melanoma cells. Furthermore, induction of human NGFr expression was observed in hybrids derived from NGFr- human kidney epithelial cells and mouse L cells, but not in hybrids derived from human kidney epithelial cells and mouse RAG kidney carcinoma cells. These results suggest that cell-surface expression of human NGFr is controlled by trans-acting regulatory signals.

Production of murine monoclonal antibodies against cell-surface antigens of human ovarian carcinoma

Splenic lymphocytes of BALB/c mice immunized with human ovarian carcinoma cells were fused with the mouse myeloma cell line, NS-1 in the presence of polyethylene glycol, MW 1500. The hybrid cultures were screened by a viable cell-binding radioimmunoassay (RIA) for the production of relevant antibodies. Hybrids that produced antibodies that bound to the surface of the immunizing cell line and other ovarian carcinoma cell lines, but not to human fibroblast cell lines or erythrocytes and leucocytes isolated from peripheral blood, were cloned twice by the limiting dilution method. Two such clones designated 8C3, of the IgG2a isotype, and 10D6, of the IgG1 isotype, were checked for specificity by a solid-phase membrane RIA. The monoclonal antibodies (MoAbs) recognized an antigenic determinant present on different human adenocarcinomas such as ovary, breast, endometrium, colon, and stomach. The normal counterpart tissues of these histiotypes showed negligible binding to the MoAbs. The relative specificity of these MoAbs encourage further studies towards their characterization and evaluation as possible diagnostic and therapeutic agents in human cancer.

A monoclonal antibody against basal cells of human epidermis. Potential use in the diagnosis of cervical neoplasia

A murine monoclonal antibody was generated against human skin cells obtained from psoriatic plaques. The antibody, called VM-2, recognizes an epitope expressed on the basal cell layer of human skin and other epithelia. VM-2 also binds to cultured cells from a variety of human carcinomas including HeLa cervical carcinoma, A-431 vulvar carcinoma, A-549 lung alveolar carcinoma, and SCL-1 skin squamous cell carcinoma cells. In several primary human cell lines, including fibroblasts, endothelial cells, and cells from the hematopoietic lineage, the antigenic site recognized by VM-2 could not be detected. The cellular antigen when immunoprecipitated by VM-2 from both normal and transformed cells appears to be proteins of approximately 100,000 and 120,000 mol weight. In frozen sections from human tumor-containing tissues, VM-2 labels skin, cervical, and lung squamous carcinoma cells, as well as skin basal carcinoma cells. Malignant cells present in exfoliative smears from epidermoid invasive neoplasias of the cervix are also selectively recognized by VM-2 in distinction to normal squamous cervical cells. VM-2 is thus directed against an antigen associated with neoplastic cells when applied in selected sites of exfoliative cytology. This monoclonal antibody represents a new reagent that should prove useful in the diagnosis of cervical neoplasia.

Cell surface antigens of human trophoblast and choriocarcinoma defined by monoclonal antibodies

Six distinct cell surface antigens of human trophoblast and choriocarcinoma were defined with MAbs. The distribution of the antigens was determined by MHA assays on 150 tumor cell lines and normal cell cultures and by immunofluorescence tests with a wide range of normal adult and fetal tissues and a tumor panel. Antigen LK26 is expressed on all cultured choriocarcinoma, teratocarcinoma and renal cancer lines but is absent from most cell lines derived from other tumor types and from cultures of normal kidney epithelium and fibroblasts. LK26 expression in normal tissues is restricted to the trophoblast. No other adult or fetal tissue was found to express the antigen, but choriocarcinoma and teratocarcinoma tissues were LK26+. SV19 is expressed on cultured choriocarcinomas and teratocarcinomas and on subsets of breast and colon cancer lines, but not on 120 additional cultures tested. In tissues, SV19 is detected in normal placenta, mammary gland and colon epithelium as well as in tumors of breast, colon and lung. Two antibodies, AbSV63 and AbK8, react with PLAP and AbSV63 also reacts with the intestinal form of the enzyme. AbLK24 defines a heat-stable determinant present on choriocarcinoma and breast cancer cell lines but absent from most other cultured cells. It is expressed on a small range of normal and malignant epithelial tissues, including normal trophoblast, normal breast epithelium and urothelium and tumors derived from these tissues. One antigen, K66, showed a wide distribution on cultured epithelial cells but was not found in any normal or malignant tissue. Finally, S4, a previously described marker of normal and malignant kidney epithelial cells, was also expressed on the choriocarcinoma cell lines. Four of the antigens are glycoproteins that could be immunoprecipitated from radiolabelled extracts of choriocarcinoma cells: LK26 (Mr 35,000), SV19 (Mr 40,000), PLAP (Mr 68,000) and S4 (Mr 160,000). The highly restricted distribution of LK26, SV19, S4, and PLAP in normal tissues and their expression in tumors make these antigens potential diagnostic markers of gestational choriocarcinoma and germ-cell tumors and, possibly, targets for immunotherapy.

Genes controlling gp25/30 cell-surface molecules map to chromosomes X and Y and escape X-inactivation

The monoclonal antibody AbO13 defines a cell-surface antigen that is expressed on most cultured human cells, but not on rodent cells. AbO13 precipitates glycoproteins of 25,000 and 30,000 mol. wt. from lysates of [3H]glucosamine-labeled human cells. Results of the serological typing of a panel of 25 rodent-human somatic cell hybrid clones show that reactivity with AbO13 segregates with the human X and Y chromosomes. The presence of either of these chromosomes is sufficient for O13 expression on the hybrid cell surface. Analysis of hybrid clones containing human X chromosomes with karyotypically defined deletions permitted the regional assignment of the X-linked gene locus controlling the expression of O13 to Xp22-pter. In addition, AbO13 is reactive with Chinese hamster-human hybrids derived from fibroblasts of a 49,XXXXX individual that contained only inactivated copies of the human X chromosome. These results suggest that the X-linked locus determining the expression of O13 is not subject to X-inactivation.

Recent progress in the immunological monitoring of carcinomas using monoclonal antibodies

In efforts to improve the specificity and sensitivity of tests to monitor patients with carcinoma, monoclonal antibody technology has been widely embraced by the scientific community. Results clearly indicate that novel antigen determinants have been identified and that significant improvements have been realized for the study of "classical" tumor antigens previously detected with polyclonal reagents. The concept of tumor specificity has also been amenable to an increased level of objectivity as based upon the probelike characteristic of monoclonal antibodies. It is apparent from this work that an antigen does not have to be tumor specific to be useful as a marker.

Biochemical characterization of human carcinoma surface antigen associated with protein kinase activity

MAb 50H.19 immunoprecipitates two proteins from lysates of human carcinoma cell lines, and embryonic fibroblasts intrinsically labelled with 3H-leucine, 35S-methionine, or a 3H-amino acid mixture; a major component of Mr = 22,000 (22 kd component) and a minor component of Mr = 24,000 (24 kd component). Oligomeric forms of the proteins are not observed under reducing or non-reducing conditions. Both proteins are expressed on the plasma membrane, and are glycoproteins. We investigated the relationship between the proteins in terms of their glycosylation and derivation from precursors. The 22 kd component is O-glycosylated as demonstrated by 3H-galactose incorporation, insensitivity to tunicamycin (TM), and its stepwise generation from a 20.5 kd precursor. The 24 kd protein is N-glycosylated, as shown by 3H-mannose incorporation, and by the total inhibition of its synthesis in the presence of TM. Further evidence for its N-glycosylation is provided by the appearance of a 23 kd precursor in lysates from the osteogenic sarcoma cell line SKOSC pulse-labelled for 5 min, a time preceding O-glycosylation of the 20.5 kd protein. Furthermore, mild alkali treatment of the immune complex leads to a loss of approximately 1,000 daltons in each glycoprotein confirming the O-glycosylated nature of the 22 kd component, and suggesting that the 24 kd component is additionally O-glycosylated. Both glycoproteins undergo an apparent increase of molecular weight of about 500 daltons when run in the non-reduced form on SDS polyacrylamide gels under standard electrophoretic conditions, suggesting they contain a similar degree of intra-chain disulphide bonding. Confirmatory evidence that the two components share a common polypeptide backbone is provided by the appearance of only the 20.5 kd component in lysates from SKOSC cells pulse-labelled for 5 min in the presence of TM.

Three human cell surface antigen systems determined by genes on chromosome 12

The mouse monoclonal antibodies AbA123, AbA127, AbK152, AbM68, and AbV1 were derived after immunization with cultured human tumor cells or melanocytes. Antibodies AbA123, AbA127, and AbK152 recognize human cell surface antigens expressed on most cultured human cells and show an identical pattern when tested on a panel of 47 human cell lines. They recognize at least two different epitopes on the same glycoprotein complex, designated A123/A127, which consists of 30,000-and 40,000-mol-wt glycopeptides. Antigens M68 and V1 are also expressed on most cultured human cell types but show distinct patterns of distribution on the cell line panel. The antigens defined by AbM68 and AbV1 have the characteristics of glycolipids. They are heat stable, and immunoprecipitation of metabolically labeled cell lysates did not yield any detectable components when analyzed by SDS-polyacrylamide gel electrophoresis. Serological typing of a panel of 23 independently derived mouse-human and Chinese hamster-human somatic cell hybrids showed unequivocally that the expression of cell surface antigens A123/A127, M68, and V1 segregates with human chromosome 12. The analysis of hybrids containing karyotypically defined deletions of chromosome 12 permitted the assignment of the loci determining the expression of antigens. A123/A127 and V1 to region 12cen-qter, and the locus determining the expression of antigen M68 to region 12cen-pter. These antigens can be distinguished from the cell surface molecules previously assigned to chromosome 12 and thus represent new assignments to this chromosome.

Immunohistological characterization of a monoclonal antibody (OV632) against epithelial ovarian carcinomas

A hybridoma cell line (OV632) producing monoclonal antibody against ovarian carcinomas was developed from the spleen cells of a mouse immunized with cystic fluid from a serous cystadenocarcinoma. Immunohistological studies in frozen sections showed that 22 out of 28 nonmucinous ovarian carcinomas, which included serous, endometrioid, clear cell, and undifferentiated tumours, reacted with this antibody. Three out of 7 mucinous ovarian carcinomas were positive, whereas only 7 out of 122 extra-genital malignant lesions, predominantly adenocarcinomas, were positive. The negative cases included 38 breast carcinomas and 24 colon carcinomas, tumours which are responsible for most of metastatic disease in the ovary. On the basis of these findings, the antibody OV632 is considered appropriate for histodiagnostic purposes as an aid in the distinction between primary and secondary ovarian cancer.