Krishnamurthy et al. found that ABCG2 transcription is activated by the binding of hypoxia-inducible factor 1α (HIF1α)/ARNT heterodimer to a hypoxia response element (HRE) under low oxygen conditions [40], enhancing hypoxic cell survival, protecting hematopoietic stem cells in the bone marrow niche, and also leukemia stem cells. Here, HIF1A is linked to leukemia.