Synergistically cytotoxic to MDA-MB-231 estrogen receptor α (ERα) human breast cancer cells in vitro when compared to effects of the individual polyphenols.EGCG + curcumin also synergistically inhibited tumor growth within female athymic nude mice implanted with MDA-MB-231 estrogen receptor (ERα) human breast cancer cells compared to individual polyphenols. Proposed mechanism of action: Cell cycle arrest and decrease in the expression of vascular endothelial growth factor receptor in tumor may play a role. The gene discussed is ESR1; the disease is breast cancer.