The effect of various dietary fats on skin tumor initiation.

The type of dietary fat has been shown to modulate the initiation stage of mammary tumorigenesis, with saturated fat fed before and/or during carcinogen treatment resulting in increased tumor incidence. This study was designed to determine whether different types of dietary fat alter the initiation stage of skin carcinogenesis by use of the initiation-promotion mouse skin carcinogenesis model. Sencar mice were divided into three groups and maintained on one of the experimental diets. The AIN-76-based diets consisted of 10% total fat with various types of fat: 8.5% menhaden oil plus 1.5% corn oil, 8.5% coconut oil plus 1.5% corn oil, and 10% corn oil. After three weeks mice were initiated with 10 nmol dimethylbenz[a]anthracene (DMBA). Two weeks later, all mice were switched to a diet containing 5% corn oil. Promotion began four weeks after initiation with twice-weekly application of 1 microgram 12-O-tetradecanoylphorbol-13-acetate and continued for 12 weeks. No statistically significant differences in kilocalories of food consumed or body weights were observed between diet groups during the study. The final papilloma incidence, yield, and size were not significantly different among the diet groups. In a parallel study, [3H]DMBA binding to epidermal DNA showed no dietary differences. Unlike the mammary carcinogenesis model, these data suggest that the type of fat fed during DMBA initiation had minimal effects on this stage of skin carcinogenesis.