HIF1A and neoplasm: HIF-1α/1β heterodimer activates the HIF target gene and promotes HIF expression by combining the HIF-1α/1β heterodimer with p300/CBP and hypoxia response element (HRE), thus regulating various biological processes of tumor cells, including metabolic reprogramming, immunoregulation, angiogenesis, tumor cell invasion, and drug resistance (74, 75).