Carbohydrate Antigens in Human Colonic and Gastric Cancers Mosaicism in the Expression of Tumor-associated

Serial sequential sections from a single tumor were examined by immunohistological staining with several monoclonal antibodies directed, respectively, to different tumor-associated carbohydrate epitopes. Stain ing patterns were compared with those of conventional staining with hematoxylin-eosin or periodate/Schiffs reagent. Each tumor showed different areas of staining with different antibodies, and the combined staining map shows a clear mosaicism of antigen expression within the same tumor. For example, some areas of a given tumor were stained by FH4 (defining dimeric Lex), while other complementary areas were strongly stained, in a mutually exclusive manner, by SHI (defining Le"), AH6 (defining Le>), FH6 (defining sialosyl dimeric Ir1), or TKH2 (defining sialosyl-Tn). Some areas were stained by two or three of these antibodies. Comparisons of the mosaic-staining patterns with cytohistological properties of tumor cells within specific areas suggested that the pattern of antigen expression is correlated with degree of differentiation; e.g., poorly-differentiated cells with severe dysplasia did not express high levels of If or Le' but did express sialyl-Le* or dimeric Le*; on the other hand, moderately or well-differentiated tumor cells in some areas expressed high levels of Lex or Le' but lower levels of sialyl-Le". Areas showing strong expression of sialyl-Tn in their secretions were consist ently correlated with presence of well-differentiated tumor cells, whereas secretions from normal mucosae were consistently characterized by lack of sialyl-Tn expression. It is postulated that the original in situ tumors (which had homogeneous glycosylation patterns) evolved into several spatially discrete cell populations displaying different degrees of glyco sylation, reflecting stages of tumor cell differentiation and progression.