Dietary fat in relation to hormonal induction of mammary and prostatic carcinoma in Nb rats.

Mammary carcinoma was induced in female Nb rats by implanting pellets of estrone at 25-28 days of age, and prostatic cancer was induced in male rats of the same strain by repeatedly implanting pellets of testosterone propionate. Feeding semipurified diets containing either 3% or 20% corn oil did not significantly affect the incidence or yield of mammary tumors, although tumors tended to appear somewhat earlier in animals on the high-fat diet, confirming the report of Dunning et al. published nearly 40 years ago. The yield of prostatic tumors was too low to draw any conclusions with respect to dietary fat. Hormonally induced mammary tumors appear to be less responsive to dietary fat than those induced by commonly used chemical carcinogens.