Chemopreventive effect of fermented brown rice and rice bran (FBRA) on the inflammation-related colorectal carcinogenesis in Apc^Min/+mice

Abstract

Our previous study revealed that fermented brown rice and rice bran (FBRA) suppresses rat colorectal carcinogenesis induced by azoxymethane, the colon-specific carcinogen. In the present study, we examined the suppressive effect of FBRA on colon carcinogenesis in ApcMin/+mouse, a mouse model for human familial adenomatous polyposis. In contrast to previous findings with the carcinogen-induced model, administration of 5 and 10% FBRA had no effect on the tumor development in the colon of ApcMin/+mice, suggesting that the modifying effects of FBRA on colorectal carcinogenesis are different depending on rodent models for colorectal carcinogenesis. However, when FBRA is administrated in dextran sodium sulfate (DSS)-exposed ApcMin/+mouse, a mouse model for the inflammation-related colorectal carcinogenesis, FBRA significantly suppressed the multiplicity of colon tumors in comparison with control diet group. FBRA administration suppressed the cell proliferative index, which is accompanied by the significantly decreased mRNA expressions of Cox2 and iNos in colonic mucosa exposed to DSS (p<0.04 and 0.02, respectively). These findings indicate that FBRA has chemopreventive effects specifically against inflammation-related tumorigenesis in the colon. Our findings also suggest that anti-inflammatory activity is one of the underlying mechanisms by which FBRA suppresses tumorigenesis in the colon.