VEGF-R1 is one of the three main subtypes of VEGFR. The ligands for VEGF-R1 are VEGF-B and VEGF-A. Vascular endothelial growth factor (VEGF) is a 27KDa signaling protein produced by cells that stimulates vasculogenesis and angiogenesis. VEGF is a heparin binding protein and exists as a disulfide linked homo-dimer. It has at least 6 isoforms produced by alternative splicing. VEGF induces endothelial cell proliferation, promotes cell migration, inhibits apoptosis, and induces permeabilization of blood vessels.