Furthermore, we also investigated the stimulatory effects of CoCl2 exposure on the BCSC sphere formation (Supplementary Figure 5A), the size of the CD44+/CD24– subpopulation (Supplementary Figure 5B), and the expression of HIF1α and HIF2α (Supplementary Figure 5C) with or without HIF2α inhibitor 76 treatment in other liable human breast cancer cell lines such as MDA-MB-231. Here, HIF1A is linked to breast cancer.