DIETARY CONJUGATED LINOLEIC-ACID MODULATION OF PHORBOL ESTER SKIN TUMOR PROMOTION

The fatty acid derivative conjugated dienoic linoleate (CLA) has been shown to inhibit initiation and postinitiation stages of carcinogenesi s in several experimental animal models. The goal of the present study was to determine the role of increasing levels of dietary CLA in mous e skin tumor promotion elicited by 12-O-tetradecanoylphorbol-13-acetat e (TPA). Mice were fed control (no CLA) diet during initiation, then s witched to diets containing 0.0%, 0.5%, 1.0%, or 1.5% (wt/wt) CLA duri ng skin tumor promotion by TPA. Body weights of mice fed 0.5%, 1.0%, o r 1.5% CLA were similar to each other but were significantly lower (p < 0.05) than weights of mice fed no CLA (0.0%) throughout promotion. A reduction in papilloma incidence was observed in mice fed 1.5% CLA fr om Weeks 8 to 24 compared with mice fed diets containing 0.0-1.0% CLA (p < 0.05). Twenty-four weeks after tumor promotion was begun, diets c ontaining 1.0% and 1.5% CLA inhibited tumor yield (4.94 and 4.35 tumor s/mouse, respectively) compared with diets without CLA (0.0% CLA, 6.65 tumors/mouse, p < 0.05) or 0.5% CLA (5.92 tumors/mouse, p < 0.05). Th ese data indicate that CLA inhibits tumor promotion in a manner that i s independent of its anti-initiator activity. Further studies are warr anted in identifying cellular mechanisms that are likely to be involve d with the antipromoter effects of CLA.