Neoplastic transformation of animal cells is accompanied with alterations of cell surfaces such as loss of contact inhibition, decrease of adhesiveness or formation of tumor specific antigens. Sphingoglycolipids have been established as components of surface membrane and showed cell-density dependent and transformation dependent changes. Some of the cell surface sphingoglycolipids are important antigenic sites and also change their organizational architecture during transformation. The objectives of the present proposal are to study: 1) Biochemical background of the chemical changes of glycolipids, i.e. the biosynthetic and biodegradative mechanism of cell contact-dependent and transformation-dependent changes of non-reducing terminal of carbohydrate chain in glycolipids, and a similar cell-contact and transformation-dependent changes of metabolic turnover rates of individual glycolipids. 2) The status of architectural organization of cell surface glycolipid haptens of known structure and its changes in relation to the function of cells as well as in transformation. This will be studied by use of univalent anti-glycolipid antibodies or their isotope labelled derivatives. 3) Relation of the chemical, biochemical and organizational changes of glycolipid to the tumor specific surface antigens. The long term goal of these studies is to determine the role of cell surface heteroglycans, which ultimately may provide clues for the control of cancer.