The overall objective of this project is the identification and characterization of tumor-associated antigens of human colonic tumors. This will be initially investigated by using human colonic cancer xenografts established in unconditioned golden hamsters and in continuous propagation in these hosts. Of immediate interest is the carcinoembryonic antigen (CEA) originally described by Gold and Freedman and synthesized by our human colonic cancer transplants. Immunological and chemical characterization of CEA in these tumors will be undertaken and the findings compared to similar preparations from human tumor specimens. In addition to this work with CEA, the presence of other antigenic substances in these tumors will be explored with a view toward identifying colon organ-specific, normal or neoplastic, markers. The relationship of these other antigenic markers to CEA will be investigated by immunochemical techniques.