Our data showed that BTB at the concentration of 2.5, 5.0, and 10 μM could effectively suppress E2-ER transactivation in the ER-positive MCF-7 breast cancer cells, Ishikawa endometrial cancer cells, and SKOV-3 ovarian cancer cells (Figures 1(e)–1(g)). This evidence concerns the gene ESR1 and breast cancer.