Hormones and dietary fat as promoters in mammary carcinogenesis.

Hormones, particularly ovarian steroids and pituitary prolactin, promote mammary carcinogenesis in rats treated with a carcinogen. Hormones also play a critical role during the initiation process as demonstrated by mammary carcinogenesis in ovariectomized rats. A diet high in fat content, especially polyunsaturated fat, promotes mammary tumorigenesis when it is fed to carcinogen-treated rats for a prolonged period of time. Although a high fat diet is not essential for neoplastic transformation of the mammary cells, its effect on initiation is demonstrated when it is fed to rats for a long duration. Thus, both hormones and high dietary fat play a dual function in mammary carcinogenesis. There are indications that dietary fat may modulate endocrine activities, but a relationship between dietary fat and endocrine function remains to be conclusively demonstrated.