KDR and cancer: The role of NRP1 in cancer has become of recent interest due to its ability to act as a co-receptor of important receptor tyrosine kinases (RTKs), such as VEGFR, hepatocyte growth factor receptor (MET), platelet-derived growth factor receptor (PDGFR) and transforming growth factor-beta receptor (TGF-βR), among others [10,11,12].