These results indicated that the combination of EGCG and TSA can induce functional ERα re-expression and re-sensitize ERα-negative breast cancer cells to E2 activator and tamoxifen antagonist, which could provide an extremely important clinical implication in potential application of green tea EGCG with HDACs inhibitors in future therapeutic strategies for hormone-resistant breast cancer. The gene discussed is ESR1; the disease is breast cancer.