KDR (kinase insert domain receptor), also known as VEGFR2, is a tyrosine kinase receptor encoded on chromosome 4 that serves as the primary cell-surface receptor for VEGFA, VEGFC, and VEGFD. KDR plays an essential role in angiogenesis and vascular development by promoting endothelial cell proliferation, survival, migration, and differentiation 1. Upon ligand binding, KDR activates multiple signaling cascades including MAPK/ERK, PI3K/AKT, and PLCγ1 pathways, leading to nitric oxide production and actin cytoskeleton reorganization. Soluble KDR isoforms lacking transmembrane domains function as decoy receptors, with isoform 2 negatively regulating VEGFA-mediated lymphangiogenesis [UniProt]. During normal development, VEGF-KDR interactions coordinate ocular vascularization, including hyaloid vascular system formation and retinal vascular development 2. KDR expression also regulates biliary epithelial cell-to-hepatocyte conversion during liver repair 3. USP11-mediated deubiquitination of PRDX2 enhances KDR transcription via c-MYC, driving angiogenic responses 1. Pathologically, KDR gene amplification in glioblastoma correlates with poor prognosis 4, and KDR polymorphisms associate with diabetic nephropathy 5 and peritoneal dialysis outcomes 6. KDR silencing reduces lung cancer cell proliferation and sensitizes cells to chemotherapy 7.