ESR1 and breast cancer: Our results showed that EGCG or SFN treatment alone or in combination resulted in significant ERα transcriptional activation (p < 0.001) in both ERα-negative breast cancer cells such as MDA-MB-231 cells (Fig. 2A) and MDA-MB-157 (Fig. 2B), but combination treatment induced a synergistic effect of ERα reactivation compared to the individual treatment of EGCG or SFN, especially in MDA-MB-231 cells.