VEGFA and neoplasm: Under hypoxic (1–2% O2) conditions, hypoxia inducible factor-1α (HIF-1α) is upregulated and binds to and activates hypoxia response elements (HREs) present on the promoters of genes implicated in angiogenesis, such as VEGF-A [75], which is itself upregulated in tumor as well as stromal cells in GBM [76].