Liver tumor promoters and other mouse liver carcinogens.

Mouse liver tumors are important end points for safety assessment of chemicals in rodent carcinogenicity assays. The mechanisms of induction of these tumors, whether by chemicals with significant genotoxic activities or by chemicals without such activities, remain unknown. If test mice have spontaneous tumors of high or low background incidence, the promotion of these tumors or of spontaneously initiated or susceptible cells may provide a basis for carcinogenesis induced by these compounds. Likewise, chronic toxicity and its associated target cell hyperplasia may also lead to promotion of these tumors. Experimental systems have been developed to study the mechanisms of tumor promotion in mouse liver. These models should significantly advance research into mechanisms of hepatocarcinogenesis and tumor promotion in mouse liver and may subsequently be used for human risk assessment.