HIF1A and glioblastoma: However, there are noticeable areas of GBM where HIF-1α positive cells present extent malignant neovascularization, and increased VEGF positivity, accompanied by increased positivity for CD105 [62], a malignant neovascularization marker, or PDGF-C [61], which stimulates angiogenesis and revascularizes ischemic tissue.