In the context of GBM, HIF-1a plays a role in regulating tumor metabolism and increases GBM aggressiveness by promoting angiogenesis via upregulation of vascular endothelial growth factor (VEGF), erythropoietin (EPO), and platelet-derived growth factor (PDGF) family proteins [115,116,117] (Figure 1C). Here, EPO is linked to neoplasm.