MOUSE-LIVER TUMOR AS AN ENDPOINT IN CARCINOGENESIS TESTS

Available carcinogenesis and mutagenesis information was reviewed for 85 chemicals that were demonstrated to increase significantly the incidence of liver tumors in mice. Sixty-one chemicals (73%) induced tumors in other tissues of mice and/or rats. For 45 of the 61 chemicals for which bacterial mutagenesis information was available, 65% were mutagenic. Of 24 chemicals inducing only mouse liver tumors, 5 of 14 tested (35%) were mutagenic. Of all 59 chemicals causing liver tumors in mice for which mutagenesis information is available, 58% were mutagenic for bacteria, primarily Salmonella typhimurium. Several classes of chemicals were represented among those inducing only mouse liver tumors or mouse liver tumors and other tumors. The findings provide evidence that the mouse liver tumor is an important endpoint in carcinogenesis tests. Limited information on the subject also suggests that certain classes of chemicals may not be mutagenic and induce only mouse liver tumors. More importantly, several nonmutagenic mouse hepatocarcinogens also induce other tumors in mice or rats. The interpretation and significance of these findings awaits further research into the mechanisms of carcinogenesis. © 1979.