FIGURE 1.

Overview of the angiogenic process in GBM. Angiogenesis is initiated by angiogenic factors released from the GBM cells in the microenvironment of a hypoxic tumor. Key angiogenic factors contributing to the GBM angiogenesis process include, FGF, VEGF, Ang-1, Ang-2, and HIF1α. These factors bind to their respective receptors on the endothelial cells and stimulate migration and proliferation of the endothelial cells. The ECM is gradually degraded and in the next phase, the endothelial cells assemble into a tube or vessel-like structure. It is notable that maturation of the blood vessel walls is accompanied by recruitment of pericytes that cover the endothelial cells from the outer surface, in order to construct a new functional blood vessel.