Carcinogenesis, Vol 19, 229-232, Copyright © 1998 by Oxford University Press
JH Weisburger, A Rivenson, J Reinhardt, C Aliaga, J Braley, B Pittman and E Zang
Two sets of experiments on the role of tea in azoxymethane (AOM) induced
colon cancer were performed. The first test involved male F344 rats given
1.25% solutions of black tea beginning at 5 weeks of age and ending at 51
days of age. At 6 and 7 weeks of age, they received 15 mg/kg AOM and were
held for 50 weeks. Another group received the AOM dosage at 6 and 7 weeks
and were placed on the tea solutions 2 days after the last AOM dosage, at
51 days of age, and held for the 50-week period. The end point was the
occurrence and multiplicity of colon cancer, classified as in situ,
exophytic, invasive and Peyer's patch carcinomas. Tea failed to affect the
incidence and multiplicity of colon cancers when given during or after the
AOM administration, but tea after AOM increased the multiplicity of
exophytic carcinomas. In a second series of tests, solutions of 0.6, 1.25,
1.75 or 2.5% tea were given, beginning 1 week prior to the two AOM doses
and extending for 42 weeks. Also, one group received 1.25% tea and 1.85%
whole milk. The incidence of exophytic or invasive colon cancer and tumor
multiplicity were similar in all treatment groups, although the incidence
of exophytic neoplasms was higher with 2.5% tea. Thus, chronic
administration failed to significantly change the incidence and
multiplicity of the AOM-induced colon cancers. These findings are accounted
for by the underlying mechanism, namely the fact that tea solutions do not
alter the amount of cytochrome P-4502E1 required for the metabolic
activation of AOM.
ARTICLES
Effect of black tea on azoxymethane-induced colon cancer
Naylor Dana Institute, American Health Foundation, Valhalla, New York 10595-1599, USA. John_Weisburger@NYMC.Edu
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