Detection of new cross-reacting carcinoembryonic antigen(s) on cultured tumor cells by mixed hemadsorption assay

Monoclonal antibodies to breast cancer-associated antigens as potential reagents in the management of breast cancer

Monoclonal antibodies reactive with the surface of human breast carcinoma cells have been generated and characterized. The immunogens used were membrane-enriched fractions of metastatic carcinoma lesions. The various monoclonals were shown to react with previously known as well as with novel tumor-associated antigens (TAAs). The most specific of the latter group is monoclonal B72.3, which is reactive with a 220,000 to 400,000 high-molecular-weight glycoprotein complex found in 50% of human mammary carcinomas and 80% of human colon carcinomas. Monoclonal antibody B6.2, which recognizes a 90,000-d glycoprotein, was radiolabeled and shown to efficiently localize human carcinoma transplants in athymic mice via gamma imaging without the use of second antibody or background subtraction manipulations. F(ab')2 and Fab' fragments were shown to be more efficient for tumor localization than intact immunoglobulin. Whereas the phenomenon of antigenic heterogeneity of tumor cell populations has long been known to exist, this phenomenon was also shown to manifest itself as antigenic modulation, in which specific TAAs can modulate their expression on the cell surface concurrent with different phases of the cell cycle. A phenomenon known as antigen evolution, in which a specific cloned tumor cell population can gradually drift in antigenic phenotype, has also been demonstrated. Recombinant interferon has been employed to (1) enhance the expression of specific TAAs on the surface of tumor cells already expressing the antigen; and (2) induce the expression of specific TAAs on the surface of carcinoma cells not previously expressing the antigen. The clinical implications of such phenomena in gamma scanning for the detection of tumor masses and for tumor immunotherapy are discussed. Methods for circumvention of problems inherent in the clinical use of monoclonal antibodies are also addressed.

Differential binding to human mammary and nonmammary tumors of monoclonal antibodies reactive with carcinoembryonic antigen

Splenic lymphocytes of mice immunized with membrane enriched fractions of human mammary carcinomas were fused with the NS-1 nonsecretory++ myeloma cell line. The resulting hybridomas were screened for the synthesis of immunoglobulins reactive with human mammary tumor associated antigens, and two IgG monoclonal antibodies (B1.1 and F5.5) were identified as being reactive with purified carcinoembryonic antigen (CEA). These antibodies were shown to bind to different epitopes on CEA based on their differential reactivities to five different purified CEA preparations, and their differential binding to the surface of tumor cells derived from various organ sites. Monoclonal B1.1 bound equally to the surface of human breast, colon, and melanoma cell lines. Monoclonal F5.5, on the other hand, did not react with the surface of melanoma cell lines, and showed a differential binding to breast carcinoma versus colon carcinoma cells. Monoclonals F5.5 and B1.1 were both used in immunoperoxidase studies with fixed tissue sections of a variety of histologic types of human mammary carcinomas and were shown to be reactive with 55% and 66%, respectively, of tumor masses.

Demonstration of carcinoembryonic antigen (CEA) by means of the immunoperoxidase technique in paraffin-embedded specimens of tumour tissues

The unlabelled antibody-enzyme method with the peroxidase-antiperoxidase complex (PAP-complex) was used to demonstrate carcinoembryonic antigen (CEA) or CEA-like substances in paraffin-embedded specimens of tumour tissues with an anti-CEA-antiserum of a rabbit. The anti-CEA-antiserum used in this study exhibited a high anti-CEA-activity and a low activity to an impurity. The paraffin-embedded specimens of tumour tissues were investigated at serum dilutions of 1 : 16, 1 : 64, and 1 : 256. The sections of colorectal cancer showed the highest content of CEA. In 36 of 37 cases the tumour tissue reacted to the anti-CEA-antiserum up to a dilution of 1 : 256. The stomach cancer tissues contained significantly lower CEA-levels than the colorectal cancer. The sarcomas, malignant melanomas, the tumour of testis, the prostatic cancers and basal cell carcinomas of the skin were found to contain none or very low CEA-content. In most specimens of these tumours the CEA was not demonstrable at a 1 : 16 dilution of the primary antiserum.