Using knockdown and rescue experiments in MDA-MB-231 cells, Jardin et al. [21] showed that Orai1 is crucial for spheroid formation and self-renewal in human epidermal growth factor receptor 2-positive (HER2+) and triple-negative breast cancer stem cells (BCSCs), but not in estrogen receptor-positive (ER+) BCSCs or BSCs [21]. Here, ESR1 is linked to triple-negative breast carcinoma.