VEGF is characterized by its highly specific mitogenic activity in endothelial cells and its angiogenic effect observed in vitro and in vivo. The VEGF family consists of four isoforms (A-D). VEGF-A is considered the most important of these with respect to tumor angiogenesis. and the splice variant isoforms VEGF121 and VEGF165 were found to be secreted by a wide spectrum of cell types, including smooth muscle cells, fibroblasts, epithelial cells, keratinocytes, macrophages, cardiac myocytes and various tumor cells. Inhibition of VEGF with a specific monoclonal antibody can suppress tumor growth in vivo.