Vascular Endothelial Cell Growth Factor (VEGF) is a homodimeric protein initially purified from media conditioned by normal bovine pituitary folliculo-stellate cells and secreted by a variety of vascularized tissues. It was subsequently found to be identical to a vascular permeability factor (VPF), which was previously identified in media conditioned by tumor cell lines based upon its ability to increase the permeability of capillary blood vessels. The reported activities of VEGF include stimulation of endothelial cell growth, angiogenesis and capillary permeability. Human VEGF is a 38.2kDa homodimeric protein consisting of two 165 amino acid polypeptide chains. VEGF is expressed in many human tumor cells, including human adenocarcinoma, human pancreatic carcinoma, human hepatocellular carcinoma, renal cell carcinoma, fibrosarcoma, HL60 promyelocytic leukemia, GS-9L glioma and U937 lymphoma cells. In normal tissues, VEGF expression has been observed in activated macrophages, keratinocytes, hepatocytes, smooth muscle cells Leydig cells, embryonic fibroblasts and bronchial and choroids plexus epithelium, renal glomerular visceral epithelium and mesangial cells.