The structural relationship of blood group-related oligosaccharides in human carcinoma to biological function: a perspective.

Blood group-related oligosaccharides have been isolated from a limited number of carcinomas. The carcinoma-associated oligosaccharides show chain elongation, for example due to repeating Gal 1,4 GlcNAc 1,3 sequences, or a higher degree of branching, which permit increased sialylation and fucosylation. Abnormal carbohydrate structures have been demonstrated on tumor cell membranes by immunological techniques, which suggests deletion of ABH, accumulation of 'crypt' antigens such as I and T antigens, and abnormal expression of Lewis antigens. Changes in carcinoma-associated oligosaccharides can result from altered biosynthetic processing in the Golgi apparatus or the occurrence of abnormal tumor glycosyltransferase isoenzymes. Structural alterations of oligosaccharides on the tumor cell membrane are related to the regulation of tumor growth, cell-cell interaction, cell differentiation, and metastasis. Glycoproteins secreted by tumor cells into the circulation evoke cellular and humoral immunity and cause immune suppression by binding to cytotoxic T lymphocytes and lymphocyte subsets. The relationship of oligosaccharide structures to biologic function awaits elucidation.