ESR2 and breast cancer: BPF functions as a stimulator of ERβ1 (and ERα) transiently expressed in MDA-MB-231 and SK-BR-3 breast cancer cells (EC50 values for ERβ: 6.87 and 2.58 nM, respectively, and EC50 values for ERα: 24.7 and 181 nM, respectively) (58).