Carcinoembryonic Antigen and Blood Group Substances1

Immunochemical studies support the view that carcinoembryonic antigens from entodermally derived adenocarcinomata are incomplete blood group substances of the ABO system. The deficient antigens have a tumor-specific activity, due to unmasking of a structural sequence that is cryptic in the normal situation. Two other serological activities of the tumor antigens are determined by ./V-acetylgalactosaminyl peptide and antigenic Complex I sequences identical to those found in blood group substances. The structural results imply that the genetic changes in oncogenesis include deletion or repression of the gene(s) controlling the transferase(s) for the terminal sequences of classical ABO-active glycoproteins. The development of specific sérodiagnostic tests for tumors of entodermal origin will probably depend on the production of sera with high activity for the tumor-specific determinant and little or no activity for the normal blood group sequences also found in carcinoembryonic antigen.