The skin
tumor-initiating activities of the 12 isomeric
phenols of
benzo(a)pyrene (BP) were determined in mice by use of a two-stage system of
tumorigenesis. 11-Hydroxybenzo(a)pyrene was moderately active, whereas
2-hydroxybenzo(a)pyrene and BP were strong
tumor initiators when applied topically to CD-1 mice and followed by twice-weekly applications of the promoter 12-O-tetradecanoylphorbol-13-acetate. 1-, 3-, 4-, 5-, 6-, 7-, 8-, 9-, 10-, and 12-hydroxybenzo(a)pyrene had less than 5% of the
tumor-initiating activity of BP when the data were expressed as
papillomas per mouse. After 30 weeks of promotion, the number of
papillomas per mouse was 8.4, 8.5, and 2.8, respectively, for the animals treated with BP,
2-hydroxybenzo(a)pyrene, and 11-hydroxybenzo(a)pyrene. A 5-week latency period before the appearance of the first
tumor was observed after the application of either
2-hydroxybenzo(a)pyrene or BP, whereas a slightly longer latency period of 7 weeks was observed following application of 11-hydroxybenzo(a)pyrene. The time required for 50% of the animals to develop
tumors was 13 weeks for animals treated with BP and 15 weeks for animals treated with 2- or 11-hydroxybenzo(a)pyrene.