The effects of temperature on the incidence of skin cancer were studied in mice. Benzo(a)pyrene (50328) (BP) was applied topically at 0.1, 0.2, or 1.0 milligrams (mg) per week to male C3H/HeJ-mice that were maintained at temperatures of 16, 23, and 30 degrees-C for 36 weeks. Animals were observed for tumor development. Food intake and tissue metabolism, and oxygen uptake in the skin, muscle, and liver were determined. Food intake and tissue metabolism was highest in animals maintained at 16 degrees. BP induced skin squamous cell carcinomas. In animals given 0.1mg BP, the mean tumor appearance time (MTA) was approximately 18, 25, and 28 weeks for temperatures of 16, 23, and 30 degrees, respectively. MTA values for the animals given 0.2mg BP were approximately 17.4, 21.8, and 24.3 for temperatures of 16, 23, and 30 degrees, respectively. In animals given 1.0mg BP, MTA values were approximately 4, 6, and 8 weeks for 16, 23, and 30 degrees, respectively. No significant metastases were seen in internal organs at any temperature. The authors note that systemic metabolic changes are apparently involved in the interaction between tumorigenesis and temperature.
Division of Biomedical and Behavioral Science,NIOSH, U.S. Department of Health, Education, and Welfare, Cincinnati, Ohio