Characterization of Lewis Antigens in Normal Colon and Gastrointestinal Adenocarcinomas

The Lewis a antigen (Lea)- and Lewis b antigen (Leb)-active glycolipids and glycoproteins in normal colon mucosa, colon carcinoma tumors, and gastrointestinal tumor cell lines were studied by using monoclonal antibodies against Lewis determinants in solid-phase radioimmunoassay, chromatogram binding assay, and immunoprecipitation/PAGE. Lea-5 was a major component of the purified non-acid glycolipid fraction from normal colon mucosas from four patients examined and Lea-7 was a minor component in three of these four cases. Leain colon carcinoma of the same patients was expressed as Lea-5 in all four cases and as both Lea-5 and Lea-7 in one of the four cases. All normal colon mucosa samples expressed Leabut not Leb. Leb-6 was expressed in all tumors obtained from the same patients as normal colon mucosa (Lebnegative) samples and in the gastrointestinal tumor cell lines. These findings indicate that Lebis a colon adenocarcinoma-associated antigen and that Leaand Lebare coexpressed in tumor tissue. Evidence is presented for the coexistence of Leaand Lebcarbohydrate determinants in both glycolipid and glycoprotein forms in the same cells.