The Implications of Embryonic Gene Expression in Neoplasia

The discovery that human as well as animal tumors generally expressed oncofetal antigens (OFAs) and that these antigens generate a variety of immune responses in the tumor-bearing host is of potential major significance in tumor biology. The concept of the reexpression of embryonic or fetal antigens (EAs) encoded by DNA, which is silent in adults but is essential in metazoan development, may mesh with the exciting concept of cancer causation. While this scenario is still only speculative, it provides an interesting forum for reviewing the current data concerning the role of OFAs in cancer processes. The literature describing OFAs and their embryonic counterparts, the EAs, in modern tumor and fetal immunobiology has become extensive and, unfortunately, is quite scattered. This article seeks to synthesize this complicated data base into a cogent presentation focusing on the immunological role of EAs and OFAs in fetal survival in utero and in tumor progression and regression, respectively. The immunogenicity and characteristics of the immune responses to EAs and OFAs will be presented and placed in perspective to the rapidly unraveling story of protooncogenes and oncogenes in tumor induction.