(A) Co-treatment with BTC, HP-BTC, or AcBTC significantly inhibited oxidative estrogen metabolism in E2-treated MCF-10A cells as shown by measurement of MeOE1 after 6 days. Normalization of %MeOE1 with respect to cells treated with 100%E2 alone is described fully in the text. Each data point represents an average of three independent experiments in duplicate ± SD: ** p < 0.01. (B) Classical ER/ERE signaling measured using a pERE-luciferase reporter after treatment of cells for 24 h with BTC, HP-BTC, AcBTC, or TolBTC: in MCF-7 cells to obtain data for ERα; and in MDA-MB-231:β41 cells to test for ERβ-mediated activity. Data represent an average of three independent experiments performed in duplicates ± SD.