Hypoxia is a crucial characteristic of tumor microenvironment, and HIF-1 is a key transcription factor that is induced by hypoxia, which regulates the expression of genes that lead to angiogenesis, metabolic reprogramming, extracellular matrix remodeling, epithelial-mesenchymal transition, motility, invasion, metastasis, cancer stem cell maintenance, immune evasion, and resistance to chemotherapy and radiation therapy (Carmeliet et al., 1998; Hanahan and Weinberg, 2000; Harris, 2002; Schito and Semenza, 2016). The gene discussed is HIF1A; the disease is neoplasm.