EFFECTS OF DIETARY N-3, N-6 AND N-9 POLYUNSATURATED FATTY-ACIDS ON BENZO(A)PYRENE-INDUCED FORESTOMACH TUMORIGENESIS IN C57BL6J MICE

The modulating effect of dietary polyunsaturated fatty acids (PUFAs) o n benzo (alpha)pyrene-induced forestomach tumorigenesis was assayed in mice fed with corn oil (GO), olein (O), Zizyphus mistol seed oil (MO) , cod liver oil (CLO), and mixed fat (Stock diet). The fatty acid comp osition of liver lipids correlated well with the fatty acid compositio n of each diet. Only mice fed the O diet showed biochemical and clinic al evidences of essential fatty acid deficiency (EFAD), Only 3 animals developed well-differentiated invading squamous cell carcinomas in th e O group. The papilloma incidence was reduced in MO and CLO with resp ect to the O group, Forestomach papillomatosis was increased in mice f ed an n-9 enriched diet in comparison to stock and CO groups, In compa rison with stock mice, the frequency of multiple epidermoidal hyperpla sia (MEH) was significantly decreased in the CLO group. Animals fed n- 3 enriched diets (MO and CLO) showed significant antipromoting effect. These findings indicate that dietary fat can modulate tumorigenesis i nitiated in mouse forestomach by benzo(alpha)pyrene. In addition, the lack of action of an n-6 fatty acid-enriched diet in our experimental model suggests that the effect of PUFAs on tumorigenesis has target-ti ssue specificity. Mistol seed oil might be of potential value as a nat ural vegetable antipromoter nutrient.