Under hypoxic conditions, HIF-1α forms a heterodimer with HIF-1ß, and binds to the hypoxia-responsive elements of the promoters to activate downstream hypoxia-responsive genes, including vascular endothelial growth factor (VEGF), to increase angiogenesis and tumor metastasis or to promote cancer cell proliferation and migration [17]. The gene discussed is HIF1A; the disease is cancer.