Tumor initiatory activity of some chloromononitrobenzenes and other compounds.

Treatment of mouse skin with pentachloronitrobenzene and each of the 3 tetrachloronitrobenzenes resulted in multiple papilloma formation during subsequent treatment with croton oil. The highest yield of papillomas was obtained with 2,3,4,5-tetrachloronitrobenzene, the only compound of the 4 that has a stable nitro group and does not give rise to appreciable mercapturic acid in the rabbit. It is suggested that the tumor initiatory ac tivity observed is due to hydroxylamine derivatives formed as intermediates in metabolic reduction of the nitro groups. Chloroacetone and /3-bromopropionic acid, but not .ZV-ethylmaleimide, also acted as tumor initiators. The chloronitrobenzenes did not affect skin carcinogenesis in the mouse by benzo[a]pyrene.