Epigallocatechin-3-gallate (EGCG) is the predominant active ingredient of green tea leaves and has been shown to possess anti-tumor, anti-inflammatory, and anti-oxidant properties. EGCG confers its effects through potentially multiple mechanisms including inhibition of growth factor receptor signalling and decrease of cellular levels of anti-apoptotic proteins of the Bcl-2 family. We examined the effects of EGCG on a panel of human myeloma cell lines using EGCG concentrations ranging from 6.25–100 μM. After three days of culturing with EGCG, basal cell growth was inhibited in most of the cell lines as measured in an MTS based assay. IC50 concentrations were between 25 μM and 50 μM. IL-6 mediated growth of the IL-6 dependent INA-6 cell line was inhibited at similar doses. In these cells, stimulation with IL-6 leads to upregulation of Mcl-1 expression (

Brocke-Heidrich et al., Blood. 2004;103:242–251
). Another green tea catechin, (−)-catechin gallate, seemed to be less active when used at identical concentrations. When INA-6 cells were pretreated for two hours with EGCG, a dose-dependent inhibition of IL-6 induced STAT3 tyrosine phosphorylation was observed as revealed by Western blot analysis. In contrast, phosphorylation of p44/p42 MAPK, which is constitutively activated in INA-6 cells, was not affected. The precise mechanism by which EGCG inhibits STAT3 phosphorylation remains to be determined. In conclusion, our results suggest to further evaluate the effect of EGCG not only in B-cell chronic lymphocytic leukemia, but also in plasma cell tumors.

Topics:
green tea, interleukin-6, myeloma cells, polyphenols, signal pathway, signal transduction pathways, catechin, stat3 protein, anti-inflammatory agents, antioxidants

Disclosure: No relevant conflicts of interest to declare.

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2006, The American Society of Hematology
2006
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