The binding of VEGF ligands to VEGFR receptors in the cell membrane induces dimerization and activation of the latter, initiating intracellular signaling cascades that result in proliferation, survival, migration and increased permeability of vascular endothelial cells (Matsumoto and Mugishima, 2006). The receptors predominantly form homodimers but heterodimers between VEGFR-1 and -2 have been observed. Although both VEGFR-1 and -2 are expressed in the vascular endothelium, the angiogenic activities of VEGFs are transduced mainly through VEGFR-2 in vivo.
