Numerous angiogenic factors such as vascular endothelial growth factor (VEGF) and its receptors (VEGFR-1, VEGFR-2), PDGFs, placental growth factors, transforming growth factor (TGF), basic fibroblast growth factor, Epidermal Growth Factor (EGF), hepatocyte growth factor (HGF), angiopoietins and interleukin 4 and interleukin 8 are involved in the regulation of tumor angiogenesis [27], [28], among which VEGF signaling through VEGFR-2 is the major angiogenic pathway in many cancer types. Here, FLT1 is linked to cancer.