Sensitivity of Mice to Benzo(a)pyrene Skin Cancer following Acclimation to Cool and Warm Temperature 1

Abstract

Abstract

Skin tumorigenesis induced by benzo(a)pyrene (BaP) in male C3H/HeJ mice was accelerated in a cool (T_a = 16°) and inhibited in a warm (T_a = 32°) environment, compared to the normal T_a = 23°. For example, repetitive, topical application of 0.2 mg BaP/week in 0.08 toluene resulted in (i) the mean tumor appearance time occurring 4-5 weeks earlier in cool and 2-3 weeks later in warm compared with the 21-22 weeks average in normal T_a; (ii) the average number of tumors per mouse increasing twice as fast in cool as in warm T_a; and (iii) shortened survival in cool, lengthened in warm. There were few metastases to internal organs at any temperature. Once initiated, tumors progressed similarly in all T_a's to squamous cell carcinomas. Cool and warm T_a per se had little effect on spontaneous tumors, survival, body weight, rectal temperature, or hair growth. However, skin temperature was 1-2° lower in cool and 1-2° higher in warm T_a than the normal 32-33°. Physiological adaptation was particularly evident in the 66% average higher food intake in cool and 63% lower in warm T_a. These results may help in defining environmental risks in cancer, in increasing the efficiency of cancer screening trials, and in exploring physiological modifiers of carcinogenesis.