Tumor-associated glycolipid antigens, their metabolism and organization

A number of experimental animal tumors as well as human cancers have been characterized by dramatic changes of glycolipid composition and metabolism. This review focuses on the chemical and enzymatic basis of the appearance of tumor-associated glycolipid antigens belonging to four major structural classes, i.e., globo, ganglio, lacto type 1, and lacto type 2 series. Some antigens represent the accumulation of precursors with deletion of more complex glycolipids, and others are the result of enhanced synthesis of new structures, most of which are aberrant fucosylation or sialylation or their combination; thus, novel structures such as di- or trimeric Le chi, trifucosyl Le gamma, sialyl Le chi, sialyl dimeric Le chi and disialyl Le alpha A have been isolated and characterized. Many monoclonal antibodies are capable of recognizing antigens in high density but are not capable of reacting with the same antigen in low density. Therefore, the expression of novel structures in high densities at the cell surface is important for recognition of tumor-association antigens. Molecular models of a typical tumor-associated antigen and its organization in membranes are also presented.