TitleInhibition of beta-catenin/Tcf activity by white tea, green tea, and epigallocatechin-3-gallate (EGCG): minor contribution of H(2)O(2) at physiologically relevant EGCG concentrations.
Publication TypeJournal Article
Year of Publication2002
AuthorsDashwood W-M, Orner GA, Dashwood RH
JournalBiochem Biophys Res Commun
Date Published2002 Aug 23
KeywordsAnticarcinogenic Agents, beta Catenin, Catechin, Cell Line, Cytoskeletal Proteins, Dose-Response Relationship, Drug, Humans, Hydrogen Peroxide, Kinetics, TCF Transcription Factors, Tea, Trans-Activators, Transcription Factor 7-Like 2 Protein, Transcription Factors, Transcriptional Activation

Epigallocatechin-3-gallate (EGCG) is the major polyphenol present in white tea and green tea. Recently, it was reported that the addition of EGCG and other tea polyphenols to cell culture media, minus cells, generated significant levels of H(2)O(2), with the corollary that this might represent an "artifact" in cell culture studies which seek to examine the chemopreventive mechanisms of tea. We show here that in cell growth media with and without serum, and in growth media containing human embryonic kidney 293 (HEK293) cells plus serum, physiologically relevant concentrations of EGCG (< or =25 microM) generated H(2)O(2) with a peak concentration of the order of 10-12 microM. However, addition of 20 microM H(2)O(2) directly to HEK293 cells transiently transfected with wild-type or mutant beta-catenin constructs and TCF-4 had no significant effect on beta-catenin/TCF-4 reporter activity or beta-catenin expression levels. In contrast, 2-25 microM EGCG inhibited beta-catenin/TCF-4 reporter activity in a concentration-dependent fashion and there was a concomitant reduction in beta-catenin protein levels in the cell lysates without changes in TCF-4 expression. The inhibition of reporter activity was recapitulated by white tea and green tea, each tested at a 25 microM EGCG equivalent concentration in the assay, and this was unaffected by the addition of exogenous catalase. The results indicate that physiologically relevant concentrations of tea and EGCG inhibit beta-catenin/TCF-4 reporter activity in HEK293 cells due to reduced expression of beta-catenin and that this is unlikely to be an artifact of H(2)O(2) generation under the assay conditions used here. These data are consistent with the findings from in vivo studies, showing the suppression of intestinal polyps by tea, via an apparent down-regulation of beta-catenin and Wnt target genes.

Alternate JournalBiochem. Biophys. Res. Commun.
PubMed ID12176021
Grant ListR01 CA080176-03 / CA / NCI NIH HHS / United States
CA 65525 / CA / NCI NIH HHS / United States
R01 CA065525-08 / CA / NCI NIH HHS / United States
R01 CA080176-02 / CA / NCI NIH HHS / United States
R01 CA065525-09 / CA / NCI NIH HHS / United States
R01 CA080176-05 / CA / NCI NIH HHS / United States
CA 80176 / CA / NCI NIH HHS / United States
R01 CA065525-07 / CA / NCI NIH HHS / United States
R01 CA080176-04 / CA / NCI NIH HHS / United States
R01 CA065525-06A1 / CA / NCI NIH HHS / United States