ABSTRACT
BACKGROUND: Based on the cross-reactivity of the human carcinoma antigen, HCA, with epiglycanin, a mouse mammary carcinoma cell surface glycoprotein, HCA has been detected in the tissue and blood of patients with every type of epithelium-derived cancer tested. METHODS: Competitive binding assays utilized the following antiepiglycanin antibodies: a polyclonal rabbit antiserum (immunoglobulin [Ig] G and IgM) in a radioimmunoassay; mouse monoclonal antibodies (Ab-1, IgM) on immunoplates; anti-idiotypic (Ab-2) and anti-anti-idiotypic (Ab-3) monoclonal antibodies (both IgG) from spleen cells of C57BL mice immunized, respectively, with Ab-1 and Ab-2, and utilized on immunoplates. IgG and IgM antibodies were evaluated for their ability to detect HCA and to distinguish between the blood of patients with, or without, carcinomas. RESULTS: Assays with the rabbit antiserum distinguished plasmas of metastatic breast carcinoma patients from those of patients with benign breast disease with a sensitivity of approximately 93% (specificity 90%). Antiepiglycanin IgM monoclonal antibodies (i.e., AE3) showed high specificity and sensitivity (> 90%) with sera from advanced carcinoma patients when compared with normal sera. The IgG anti-anti-idiotypic (Ab-3) monoclonal antibodies (i.e., AF2), which bind the same epitope as Ab-1, appear to possess less nonspecific binding capacity, however, than the Ab-1 (IgM) antibodies. Anti-Ab-1 (i.e., C8F2) anti-idiotypic monoclonal antibodies, which bear an idiotope equivalent to the epitope present in epiglycanin and the HCA, demonstrated greater consistency as a standard calibrator and for coating wells than epiglycanin. CONCLUSIONS: The concentration of the HCA in the body fluids of patients with carcinomas may be accurately determined by competitive binding assays. It is suggested that the use of anti-idiotypic antibodies (IgG), rather than epiglycanin/HCA, and Ab-3 anti-anti-idiotypic antibodies (IgG), rather than Ab-1 (IgM), will improve the consistency, as well as the sensitivity and specificity, of the assay.
