Initiation, promotion and complete carcinogenesis by N-methyl-N'-nitro-N-nitrosoguanidine or ethylnitrosourea in the Sencar mouse skin tumorigenesis model.

Five doses of either N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) or ethylnitrosourea (ENU) were tested as complete carcinogens, tumor initiators and tumor promoters in the SENCAR skin tumorigenesis model. As tumor initiators, MNNG-induced papillomas at all doses tested, while ENU was active from 10-40 mumol. As complete carcinogens, MNNG from doses of 0.5-5.0 mumol and ENU from doses of 10 mumol-40 mumol were potent inducers of both papillomas and carcinomas indicating that these agents are active as both tumor initiators and tumor promoters.