ESR1 and breast cancer: There were, on average, more statistically significant interaction peaks per locus in the ER+ breast cancer cell lines (T-47D, ZR-75-1) compared to the ER− breast cancer cell lines (BT-20, MDA-MB-231, Mann–Whitney test P = 0.0008) or the control lymphoblastoid cell line (GM06990, Mann–Whitney test P = 0.002).