ESR1 and breast cancer: We performed scRNA-seq on cells derived from MS of two ER+ breast cancer cell lines, MCF-7 and T47D, and then assessed BCSC properties using several widely recognized characteristics of stem cells: i) expression of classical stem cells markers and an enrichment for stem cell-associated gene signatures (Fig. 1), ii) proliferation status (Fig. 2 and Additional file 1: S. Fig 1), and (iii) enrichment in MS vs 2D-cultured cells (Fig. 3).