Use of non-mammalian species in bioassays for carcinogenicity.

The high costs of bioassays for carcinogenicity in rodents have sparked interest in the use of non-mammalian species as possible alternatives. Invertebrate and lower vertebrate species have been used for many years in bioassays for teratogenicity, toxicity and carcinogenicity involving exposure to a range of genotoxic compounds. Carcinogenicity tests have shown that the development of neoplasia in non-mammalian species is predictable and reproducible and that the results are affected by species, age, chemical class and dose. One disadvantage of using these species in cancer bioassays is the absence of tissues of critical importance in human cancer, such as prostate, lung and breast; however, the similarities between mammals and lower species in basic cellular responses to carcinogens allow reliable correlation of many mechanisms of cancer development down the phylogenetic tree.