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Proliferation of MDA-MB-231 can be suppressed by dimeric-epigallocatechin gallate through competitive inhibition of amphiregulin-epidermal growth factor receptor signaling

Triple-negative breast cancer (TNBC) is highly aggressive, with high rates of early relapse and very poor overall prognosis. Amphiregulin (AREG) is the most abundant epidermal growth factor receptor (EGFR) agonist in MDA-MB-231 TNBC cells, whose proliferation can be inhibited by (–)-epigallocatechin gallate (EGCG), a constituent of green tea that is prone to oxidative polymerization. The effect of dimeric-EGCG, a dimer of oxidized and polymerized EGCG, on MDA-MB-231 cell the proliferation warrants further exploration. In the present study, MTT, flow cytometry, migration scratch, transwell, western blotting, and surface plasmon resonance assays were used to evaluate the effect of dimeric-EGCG on MDA-MB-231 cells and explore the underlying mechanism. MDA-MB-231 cell proliferation and migration were significantly inhibited by dimeric-EGCG at concentrations as low as 10 μM. Levels of EGFR and p44/42 MAPK phosphorylation in MDA-MB-231 cells were significantly reduced by treatment with 10 μM dimeric-EGCG (P < 0.01). In addition, the levels of phosphorylation induced by exogenous AREG were also inhibited by dimeric-EGCG (P < 0.01); however, no significant effects of dimeric-EGCG were observed on epidermal growth factor or transforming growth factor-alpha signaling. Surface plasmon resonance analysis demonstrated that 10 μM dimeric-EGCG bound directly to the extracellular domain of EGFR, competitively inhibiting the binding of AREG to EGFR. These results suggest a novel mechanism underlying the inhibitory effect of dimeric-EGCG on MDA-MB-231 cells, with potential application in the development of drugs for the treatment of TNBC.