ESR1 and breast carcinoma: However, studies have demonstrated that BPA sulfation promotes unconjugated BPA uptake into MCF‐7 cells expressing estrogen sulfatases, a group of enzymes responsible for desulfation, and results in stimulated growth of human breast cells.123 Of note, a study by LaPensee and colleagues revealed that BPA could antagonize the cytotoxic effects of several chemotherapy agents in both ER‐positive and ER‐negative human breast cancer cell lines at low concentrations, indicating that BPA may reduce the efficacy of treatment with some anticancer drugs.124