MUCIN-LIKE CARCINOMA-ASSOCIATED ANTIGEN DEFINED BY 3 MONOCLONAL-ANTIBODIES AGAINST DIFFERENT EPITOPES

  • 1 December 1988
    • journal article
    • research article
    • Vol. 48  (23) , 6799-6802
Abstract
Three monoclonal antibodies [MAb], b-8, b-12, and b-15, have previously been shown to react with mammary carcinomas and with a restricted set of cells in normal human tissues [C. Sthli et al., Experientia (Basel), 41: 1377-1381, 1985, H. R. Zenklusen et al., Virchows Arch. Abt. A Pathol. Anat., 413:3-10, 1988]. They are shown here to recognize the same high molecular weight acid soluble glycoprotein antigen. Lectin binding, biolabelling, and deglycosylation experiments demonstrate that it contains O-linked carbohydrate side chains with sialic acid and hexoses including fucose, galactose, and/or galactosamine but little if any manose. These properties, typical of mucin-like glycoproteins, agree with the antigen expression on mucin-secreting epithelial surfaces (H. R. Zenklusen et al., Virchows Arch. Abt. A Pathol. Anat., 413:3-10, 1988). The antigen is thus named mucin-like carcinoma-associated antigen (MCA). The three MAb are shown to bind to three different epitopes on MCA. Two of these epitopes (MCA-b-8 and MCA-b-15) are O-linked carbohydrates, and one (MCA-b-15) contains sialic acid. The epitope MCA-b-12 is of peptide nature. Of various two-site sandwich enzyme immunoassays composed of different combinations of the three MAb, the one with MAb b-12 in both positions is selected for a serum assay. Analyses of tumor patients'' sera demonstrate that this MCA enzyme immunoassay can be of use as a tumor patients'' sera demonstrate that this MCA enzyme immunoassay can be of use as a tumor marker assay for mammary carcinomas. The parameter MCA enzyme immunoassay is shown to differ from other parameters described in the literature.