Reduction of N-methyl-N-nitrosourea-induced colon tumors in the rat by cholesterol.

Patient populations with a propensity to develop colon cancer have increased amounts of fecal cholesterol (and/or cholesterol metabolites). In this study, we report the effect of increased colonic concentrations of cholesterol and its metabolites on colon tumor promotion. The chemical carcinogen N-methyl-N-nitrosourea was instilled intrarectally into rats to initiate colon tumor formation. Following initiation, a cholesterol-supplemented diet was given. Despite a 2-fold elevation of fecal cholesterol, the number of colon tumors found was significantly reduced. These studies suggest that under certain conditions cholesterol may inhibit colon carcinogenesis.