When MCF7 breast cancer cells were treated with BA, the synthesis of estrogen-responsive gene growth regulation by estrogen in breast cancer 1 (GREB1) mRNA was significantly inhibited, ERE-dependent luciferase activity was significantly suppressed, and estrogen receptor α(Erα)-mediated signaling was suppressed by inhibiting Era mRNA synthesis to suppress the ERα protein levels. This evidence concerns the gene ESR1 and breast cancer.