-depleted cells, BCL2, CD44, CD49f, Cas9, E2, E2-, E2-inducible genes, EGFR, ER, ER+, ER+ MCF7, ER-positive cancer cells, EpCAM, HER2, KRT14, KRT19, Mammosphere, NTN4, PR, T, T-47D cell lines, UNC5A, UNC5A knockdown cells, UNC5A-depleted cells, bipotent luminal progenitor, breast cancer, breast cancers, breast tumors, cancer, cancer cells, dependence, epidermal growth factor receptor, estradiol, estrogen, estrogen receptor, estrogen receptor-positive (ER+) breast cancers, genes, histone demethylase, hormone-sensitive breast cancers, luminal progenitor, luminal/alveolar differentiation-associated ELF5, luminal/basal hybrid phenotype, phosphorylated ER, short hairpin (sh)RNA, tumor