EFFECT OF TEA EXTRACTS, POLYPHENOLS, AND EPIGALLOCATECHIN GALLATE ON AZOXYMETHANE-INDUCED COLON-CANCER

Studies were conducted to determine the chemopreventive efficacy of se veral types of tea extracts on azoxymethane-induced colon cancer in ma le F344 rats, After determining the maximally tolerated dosage of the tea products, their effect in a colon cancer model was investigated, G roups of 36 male F344 rats received 2 subcutaneous doses of 15 mg/kg a zoxymethane (AOM) at Weeks 6 and 7, Experimental groups also received as drinking fluids 3600 ppm of black or green tea extracts, 1800 ppm o f EGCG, or 1800 ppm of black or green tea polyphenols beginning at 5 w eeks of age, Additional groups drank a lower dose of 360 ppm of the fi ve tea products. The experiments were terminated 43 weeks after the fi rst tea exposure, No evidence of toxicity was observed since the body weight gain of all groups was similar, The rats given AOM had carcinom a of the small intestine and of the colon, classified histologically a s in situ carcinoma, exophytic, invasive, and Peyer's patch carcinoma, In the small intestine, most of the neoplasms were classified as inva sive, but in the colon, most were exophytic. The various tea products failed to produce a significant difference in the incidence of the sev eral types of colon and small intestine carcinoma. The multiplicity of colon cancers ranged from 1.2-2.8 in all groups, The group on 3600 pp m of green tea had a significantly higher tumor multiplicity than the control group on AOM and water, Also, the group on 3600 ppm of green t ea had a significantly higher tumor multiplicity than the group on 360 ppm, The tea products did not affect the development aspects of the t umors in most groups. The mechanisms underlying these findings rest on the fact that azoxymethane is metabolized mainly by cytochrome P450 2 E1, and this enzyme system is not affected by tea.