ABSTRACT
Objective To study the effect and mechanism of epigallocatechol gallate (EGCG) combined with trastuzu-mab on the proliferation of human epidermal growth factor receptor 2 (HER2) overexpressing breast cancer cells. Methods Trastuzumab was expressed and purified. The cell proliferation of HER2 overexpressing breast cancer cells BT474 and SK-BR-3 treated with trastuzumab, EGCG, or trastuzumab plus EGCG was evaluated by CCK8 assay. The effects of EGCG and trastuzumab on the expression of HER2, epidermal growth factor receptor (EGFR), mitogen-activated protein kinase (MAPK), protein kinase B (Akt), and their phosphorylated proteins in BT474 breast cancer cells were detected by Western blot. Results The results of cell proliferation assay indicated that EGCG and trastuzumab, alone or in combination, effectively inhibited the proliferation of BT-474 and SK-BR-3 cells. And within a certain concentration range, EGCG and trastuzumab showed a synergistic proliferation inhibitory effect on HER2 overexpressing breast cancer cells. Consistent with these results, Western blot results showed that trastuzumab and EGCG, alone or in combination significantly reduced the phosphorylation levels of Akt, MAPK, EGFR, and HER2 in BT474 cells. Moreover, the inhibition effect of EGCG plus trastuzumab was significantly more potent than either EGCG or trastuzumab. Conclusion EGCG and trastuzumab could synergistically inhibit the proliferation of HER2 overexpressing breast cancer cells, which may be related to the regulation of Akt and MAPK signaling pathways.