Effects of theaflavins on N-nitrosomethylbenzylamine-induced esophageal tumorigenesis

The purpose of this experiment was to compare the inhibitory effects of the polyphenol fraction of black tea, theaflavins (TF), the polyphenol fraction of green tea, and (-)-epigallocatechin-3-gallate (EGCG) in the rat esophageal tumor model. The tea fractions were administered in the drinking water at concentrations of 360 and 1,200 ppm for two weeks before administration of the esophageal carcinogen N-nitrosomethylbenzylamine (NMBA). NMBA was administered subcutaneously in 10% dimethyl sulfoxide three times weekly for five weeks. Additional groups of rats received only vehicle and plain drinking water or vehicle and drinking water containing 1,200 ppm of each tea fraction. Twenty-five weeks after NMBA administration began, the experiment was terminated and esophagi were excised and scored for tumors. Rats that were not dosed with NMBA had no tumors. Rats treated with NMBA only had an esophageal tumor incidence of 100% and a multiplicity of 3.3 +/- 0.4 tumors/rat. The proportion of rats developing tumors was not significantly reduced by any of the four tea fractions at the concentrations tested. However, the 1,200 ppm concentrations of each tea fraction in the drinking water produced some reduction in esophageal tumor multiplicity, although only TF significantly reduced tumor multiplicity compared with rats treated with NMBA only. The rates of esophageal tumor formation were significantly reduced at 360 and 1,200 ppm by TF and EGCG.