ESR1 and breast cancer: We also evaluated the impact of SER137, SER142, SER167, SER195, SER196, SER198, SER79, SER177, SER31, SER68 on BC cell lines with different molecular features: SKBR3 (ER−, PR+, HER2+) and MDA-MB231 (ER−, PR−, HER2−).