Importantly, immunohistochemical analyses have indicated that HIF-1α and HIF-2α and their target genes, including glycolytic enzymes and VEGF are frequently overexpressed in tumour cells in hypoxic zones closest to areas of necrosis, which demarcate surrounding regions of tumour angiogenesis, during GBM development [1, 2, 127]. This evidence concerns the gene HIF1A and glioblastoma.