KDR and cancer: The mechanism of action of this class of drugs is based on the block of several key tyrosine kinase pathways in human cancers, including the vascular endothelial growth factor receptor (VEGFR), epidermal growth factor receptor (EGFR), human epidermal growth factor receptor 2 (HER2), and platelet-derived growth factor receptor (PDGFR) [4–6].