Discrimination of initiating and promoting carcinogens in fish.
Genetic molecular and biochemical principles of the development of fish strains that can discriminate between melanoma-initiating and melanoma-promoting activities of agents of unknown carcinogenic potential are described. These strains are certain backcrosses of Xiphophorus maculatus (platyfish) with X. helleri (swordtail). Trenbolone and several steroid hormones did not induce melanoma, but were strong promoters of melanoma. The principles presented are valid for other types of neoplasms.