miR-23a and miR-27a are transcribed as a part of the miR-23a ~ 27a ~ 24-2 cluster, and are elevated in various cancer cells.41,42 Using a luciferase reporter assay containing the miRNA cluster promoter, we found that HIF1α P2A OE significantly increased luciferase activity in the original promoter sequence but not in the mutated sequence with a defective hypoxia response element (HRE) (Fig. 5e), confirming that HIF1α directly binds to and transcriptionally activates the miRNA cluster promoter. The gene discussed is HIF1A; the disease is cancer.