ESR1 and breast cancer: To elucidate the combinatorial efficacy of the green tea polyphenol EGCG and broccoli sprouts SFN, we initiated our study to determine the optimal dose of combined EGCG and SFN treatment that will induce synergistic cellular growth inhibition in ERα-negative breast cancer MDA-MB-231 and MDA-MB-157 cells (Fig. S1).