PGF and neoplasm: The vascular endothelial growth factor (VEGF) family, including VEGF; placental growth factor (PLGF); and their receptors Flt-1, sFlt-1, and KDR (also known as VEGFR-1, sVEGFR-1, and VEGFR-2, respectively), are the most important promoters of physiological and tumor angiogenesis [37,38,39,40,41,42,43,44,45,46].