Tumor suppression in triploid trout

Triploidy was induced in rainbow trout (Oncorhynchus mykiss) by heat shock of fertilized eggs and triploid and diploid fry were treated with three car cinogens (DMBA, MNNG and aflatoxin B1) by bath exposure. The incidence of t umors was substantially lower in triploids than in diploids in the swimblad der, stomach and kidney and moderately lower in the liver. The lower tumor incidence in triploids may reflect a lower likelihood that all copies of tu mor suppressor genes would mutate during carcinogenesis in triploids. Polyp loid lower vertebrates may thus provide novel systems for investigating tum or suppressor genes in carcinogenesis. (C) 1999 Elsevier Science B.V. All r ights reserved.