Possible mechanisms by which pro- and prebiotics influence colon carcinogenesis and tumor growth

Oligofructose and inulin, selective fermentable chicory fructans, have been shown to stimulate the growth of bifidobacteria, which are regarded as ben eficial strains in the colon. Studies were designed to evaluate inulin (Raf tiline) and oligofructose (Raftilose) for their potential inhibitory proper ties against the development of colonic aberrant crypt foci (ACF) in rats. ACF are putative preneoplastic lesions from which adenomas and carcinomas m ay develop in the colon. The results of this study indicate that dietary ad ministration of oligofructose and inulin inhibits the development of ACF in the colon, suggesting the potential colon tumor inhibitory properties of c hicory fructans. The degree of ACF inhibition was more pronounced in animal s given inulin than in those fed oligofructose. Because these prebiotics se lectively stimulate the growth of bifidobacteria, ornithine decarboxylase ( ODC) activities, ras-p21 ontoprotein expressions and tumor inhibitory activ ity of lyophilized cultures of Bifidobacterium longum against chemically in duced colon and mammary carcinogenesis and against colonic tumor cell proli feration were examined. Dietary administration of lyophilized cultures of B . longum strongly suppressed colon and mammary tumor development and tumor burden. Inhibition of colon carcinogenesis was associated with a decrease i n colonic mucosal cell proliferation and activities of colonic mucosal and tumor ornithine decarboxylase and ras-p21. Human clinical trials are likely to broaden our insight into the importance of the pre- and probiotics in h ealth and disease.