Conjugated Linoleic Acid Suppresses Mammary Carcinogenesis and Proliferative Activity of the Mammary Gland in the Rat (original) (raw)

Conjugated linoleic acid (CLA) is a collective term which refers to a mixture of positional and geometric isomers of linoleic acid. It is naturally occurring in meat and dairy products. We have previously reported (Ip, C., Chin, S. F., Scimeca, J. A., and Pariza, M. W. Cancer Res., 5/: 6118-6124, 1991) that 1% CLA in the diet suppressed mammary carcinogenesis in rats given a high dose (10 mg) of 7,12-dimethylbenz(a)anthracene. In the present study, dietary CLA between 0.05 and 0.5% was found to produce a dose-dependent inhibition in mammary tumor yield when fed chronically to rats treated with a lower dose (5 mg) of 7,12-dimethylbenz-(a)anthracene. Short-term CLA feeding for 5 weeks, from weaning to the time of carcinogen administration at 50 days of age, also offered signifi cant protection against subsequent tumor occurrence. This period corre sponds to maturation of the mammary gland to the adult stage in the rat. The inhibitory response to short-term CLA exposure was observed with the use of 2 different carcinogens: 7,12-dimethylbenz(a)anthracene and methylnitrosourea. The fact that CLA was protective in the methylnitrosourea model suggests that it may have a direct modulating effect on susceptibility of the target organ to neoplastic transformation. The proliferative activity of the mammary epithelium was assessed by the incor poration of bromodeoxyuridine.