TUMOR-PROMOTING AND TUMOR-PROTECTIVE EFFECTS OF HIGH-FAT DIETS ON CHEMICALLY-INDUCED MAMMARY-CANCER IN RATS

We studied the effects of different dietary fats on experimental rat m ammary lumorigenesis induced by 9,10-dimethyl-1,2-benzanthracene (DMBA ). Rats were randomly placed into four groups fed different diets: A c how diet, and high-fat (15%) diets derived from avocado, soybean or ol ive oils. The rats were killed 12 weeks afjer treatment with DMBA (a s ingle dvse of 10 mg/rat) and maintenance on these diets. The olive die t was associated with a significant reduction in the tumorigenic effec t of DMBA: tumor incidence decreased to 30%, as compared to 44% - 55% in the other dietary groups studied (p < 0.05). The protective antitum or effect of the olive diet was found to be connected to its dietary c ontent of monounsaturated fatty acids such as oleic and palmitic acids and with serum concentrations of stearic acid. The promotive tumorige nic effects of the other high-fat diets were associated with their hig h levels of some polyunsaturated fatty acids (linoleic and a-linoleini c). Malignant mammary tissue exhibited higher values than benign tissu e for all the argyrophilic-nucleolar-organizer region parameters measu red. The tumor-associated protein p53 was accumulated to high levels i n the blood of tumor-bearing rats, but not in that of the non tumor-be aring rats.