Mosaicism in the expression of tumor-associated carbohydrate antigens in human colonic and gastric cancers.

Serial sequential sections from a single tumor were examined by immunohistological staining with several monoclonal antibodies directed, respectively, to different tumor-associated carbohydrate epitopes. Staining patterns were compared with those of conventional staining with hematoxylin-eosin or periodate/Schiff's 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 Le(x)), while other complementary areas were strongly stained, in a mutually exclusive manner, by SH1 (defining Le(x)), AH6 (defining Le(y)), FH6 (defining sialosyl dimeric (Le(x)), 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 Le(x) or Le(y) but did express sialyl-Le(x) or dimeric Le(x); on the other hand, moderately or well-differentiated tumor cells in some areas expressed high levels of Le(x) or Le(y) but lower levels of sialyl-Le(x). Areas showing strong expression of sialyl-Tn in their secretions were consistently 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 glycosylation, reflecting stages of tumor cell differentiation and progression.