Marine phosphatidylcholine suppresses 1,2-dimethylhydrazine-induced colon carcinogenesis in rats by inducing apoptosis

Abstract

In vitro and animal studies indicate that n-3 polyunsaturated fatty acids (PUFAs) suppress carcinogenesis. This study presents a new insight on effectiveness of marine phospholipids for suppression of colon carcinogenesis. The purpose of this study was to investigate growth inhibition and apoptosis inducing effects of n-3 PUFA in the form of marine phosphatidylcholine (PC) on chemically induced (1,2-dimethylhydrazine) colon cancer in rats. Growth inhibition of Caco-2 cells was determined by colorimetric sodium 2-(4-iodophenyl)-3-(4-nitrophenyl)-5-(2,4-disulfophenyl)-2H-tetrazolium (WST-1) dye reduction assay. For animal studies, the rats were fed 5 different diets containing docosahexaenoic acid (DHA)-ethyl ester, eicosapentaenoic acid (EPA)-ethyl ester, squid meal PC (rich in DHA), starfish PC (rich in EPA), and corn oil. The 1,2-dimethylhydrazine (30 mg/kg) or saline was injected 48 hours before the experiment. Rats were anesthetized, and apoptotic as well as mitotic cells in crypt were counted based on morphological criteria in isolated crypts. Squid meal and starfish PC potently inhibited the growth of Caco-2 cells. The experimental diets containing n-3 PUFA suppressed colon cancer in rats. Rats that consumed diets containing DHA-ethyl ester, EPA-ethyl ester, squid meal PC, and starfish PC showed increased apoptosis (P < .01) and suppressed proliferation. These results suggest that marine PC-containing diets might be an effective dietary protective factor against colon cancer.