Overview: The application of immunology to the development of immunotherapeutic programs for patients with large bowel cancer

Both human and experimental large bowel carcinomas have been shown by various in vitro and in vivo techniques to possess antigens immunogenic to the original cancer host. It has been studied in the rat large bowel carcinoma model whether these antigens may induce tumor rejection. Individually unique antigens induce a strong resistance to colon carcinoma isografts, while tissue-type specific tumor-associated antigens, common to all or most colorectal carcinomas and also present in embryonic cells, induce a rather weak resistance. A stronger indication of the importance of the common tumor antigens in vivo was provided by the demonstration that primary induction of bowel carcinomas by DMH could be prevented by immunization with a colon carcinoma, but not by similar treatment with a breast tumor. It was further shown that multiparous or breeding females had a significantly reduced tumor frequency, possibly related to their immunity to embryonic antigens. Sequential sera obtained from DMH-treated rats were tested for complement-dependent cytotoxicity on cultured colon carcinoma cells. Antibody activity appeared up to 4 months prior to first tumor detection by double contrast examinations. Sera obtained after tumor detection had low activity or were negative.