ESR2 and neoplasm: We observed the enrichment of both Mesenchymal BCSC (m-BCSC) as well as epithelial BCSC (e-BCSC) subpopulations, characterized by Vimentin and ALDH1, respectively, in MDA-MB-231, HCC1806, and BT549 when the TNBC cell lines were treated with ERβ antagonist treatment, also confirming the tumor suppressor role of ERβ1 in mammary epithelial cells, reported by many researchers [55].