Dramatic changes in glycolipid metabolism associated with oncogenic transformation implicate a specific role for membrane glycolipids in regulation of cell growth and cellular interaction. These changes give rise to tumor specific membrane antigens which are useful diagnostically and as potential targets for immunotherapy. Although many examples of these tumor antigens have been documented, not much information is available relating to regulation of the biosynthetic mechanism which prevents expression of these antigens in normal cells and tissues and is activated to produce them in association with oncogenesis. This application proposes to study the regulation of synthesis of the X determinant antigen, important in many human adenocarcinomas, by detailed study of the glycosyltransferase enzymes associated with its biosynthesis and their differences in expression in normal tissues and tumors. A bl-4galactosyltransferase involved in the synthesis of type 2 glycolipid carbohydrate chain precursors and an al-3fucosyltransferase which utilizes type 2 chain structures as precursors for X determinant biosynthesis will be purified to homogeneity by affinity chromatographic procedures and their properties characterized. Antibodies specific for these enzymes will be prepared and used to study the tissue specificity of these enzymes in normal tissues and tumors. Glycolipids isolated from normal human colonic mucosa, colonic adenocarcinomas, and tumor cell lines will be characterized by thin layer chromatographic immunostain analysis for the presence of X determinant carrying structures and their precursors. These results will be correlated with the presence or absence of specific glycosyltransferase activities relating to synthesis of these antigens in order to determine the nature of the enzymatic block preventing expression in normal tissues. The nature of the regulatory properties of these transferase activities will be investigated with respect to other processes which may modulate their activity and be associated with alterations in the expression of X antigen. These studies will provide information relating to the biochemical changes occurring in association with oncogenesis which gives rise to an important and potentially immunologically useful human tumor associated antigen, the X determinant structure.
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