Protection Against Azoxymethane-Induced Mouse Colon Tumorigenesis by Wheat Bran and Black Tea

Black tea (BT) and wheat bran (WB) were evaluated for their ability to modulate azoxymethane (AOM) - induced colon tumors in SWA mice. Female SWA mice, 6 weeks of age, were allocated in two separate experiments. Two dose levels of BT (4 and 8 mg tea solids/ml in drinking fluid) and WB (10 and 20% in basal diet) were administered during either the initiation and postinitiation (experiment 1) or postinitiation (experiment 2) stages of colon carcinogenesis. In experiment 1, the oral administration of 4mg BT insignificantly reduced the incidence and multiplicity of colon adenomas and adenocarcinomas ; whereas, 8mg BT significantly reduced the incidence and multiplicity of colon adenomas. Supplementing the diet with 10 or 20% WB significantly (P< 0.05) reduced, in a dose-dependent manner, the incidence, multiplicity and volume of adenomas and adenocarcinomas as compared to AOM alone group. Administration of 4 or 8 mg BT inhibited the number of colon adenomas per mouse by 8 and 28% and the number of colon carcinomas per mouse by 10 or 19%, respectively. Oral administration of 10 or 20% WB significantly inhibited the number of adenomas per mouse by 67 and 71% and the number of carcinomas per mouse by 48 and 56%, respectively (experiment 1). Administration of 4 or 8mg BT during the postinitiation phase (experiment 2) did not significantly alter the incidence and multiplicity of colon tumors (adenomas or adenocarcinomas). On the other hand, supplementing diet with 10 or 20 % WB significantly (P> 0.05) reduced the incidence, multiplicity and volume of tumors/mouse. Low and high doses of BT insignificantly inhibited the number of adenomas per mouse by 8 and 10 % and the number of adenocarcinomas per mouse by 8 and 12%, respectively. In contrast, 10 or 20 % WB markedly inhibited the number of adenomas per mouse by 32 and 49 % and the number of carcinomas per mouse by 27 and 39 %, respectively. In this protocol, supplementing diets with WB provided a significant protection against AOM-induced colon tumors when applied during either the initiation and postinitiation or the postinitiation stages, whereas, BT was slightly effective in modulating colon carcinogenesis under the same experimental conditions.