Chemical carcinogens as specific inducers of a 60-kilodalton oncofetal protein in rats.

A 60-kd oncofetal protein which is released to circulation in vivo from tumor cells, or from normal tissues following carcinogen-treatment, has been evaluated against single dose regimens of 18 known chemical carcinogens and 13 known chemical non-carcinogens. The carcinogens included genotoxic and presumed non-genotoxic compounds and the blood plasma 21 days post-treatment of rats with the chemicals was measured. All carcinogens tested transiently induced the 60-kd factor, while none of the non-carcinogens, which included non-carcinogenic analogs or toxins, induced the factor. The results suggest that the early induction of this oncofetal protein may be an indicator of carcinogenicity. The induction of reversible phenotypic changes in normal cells by tumor promoters did not induce the 60-kd factor. Following the carcinogen-mediated transient induction, persistent production of the 60-kd factor occurred at later times if a tumor developed.