Cancer chemopreventive effects of polyunsaturated fatty acids

The inhibitory effects on Epstein-Barr virus early antigen (EBV-EA) activation induced by the tumor promoter, 12-O-tetradecanoylphorbol-13-acetate (TPA), in Raji cells as a primary screening test for anti-tumor promoters, for 22 fatty acids (as free and esterified forms), including 10 di- and polyunsaturated acids, and the inhibitory effects on activation of (±)-(E)-methtyl-2-[(E)-hydroxy-imino]-5-nitro-6-methoxy-3-hexemide (NOR 1), a nitric oxide (NO) donor, as a primary screening test for anti-tumor initiators, for 17 fatty acids (as methyl ester forms), were evaluated. Among the fatty acids tested, three n-3 polyunsaturated acids, eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA), and docosahexaenoic acid (DHA), exhibited potent inhibitory effects both on EBV-EA and NOR 1 activation. Furthermore, DHA methyl ester exhibited remarkable anti-tumor-promoting activity on an in vivo two-stage carcinogenesis test of mouse tumor using 7,12-dimethylbenz[a]anthracene (DMBA) as an initiator and TPA as a promoter.