Characterization of gastrointestinal tumor-associated carcinoembryonic antigen-related antigens defined by monoclonal antibodies.

Four major carcinoembryonic antigen-related glycopeptides (Mr 180,000, 160,000, 50,000, and 40,000) were detected in SW948 colon carcinoma cells and in colon adenocarcinoma tissue using a monoclonal antibody (C(4)20-32) generated by immunizing mice with SW1222 human colon carcinoma cells. Only the Mr 50,000 polypeptide was immunoprecipitated from normal colon mucosa by this antibody. Binding studies using other monoclonal antibodies and lectins indicated the different epitopes and carbohydrate attachment sites on each of the four polypeptides. Only monoclonal antibody C(4)20-32 recognized a common determinant on all four polypeptides which was revealed by its reactivity with each affinity-purified component.