Figure 2.

Five mechanisms of vascularization in glioblastoma. Angiogenesis: mainly attributed to interplay between GSCs and endothelial cells via VEGFR, Notch, DLL-4, and NO signals; vasculogenesis: bone marrow-derived endothelial progenitor cell (EPC) is recruited via SDF-1/CXCR-4 axis; vascular mimicry: tumor cells constitute vascular channels which have no endothelial cells but are still capable of transporting erythrocytes; vessel co-option: initiates proliferation of GBMs and is followed by angiogenesis; Intussusception: a blood vessel divides into two.