Nectin-4 (gene name PVRL4, poliovirus receptor-like 4) is a 66 kDa type I transmembrane glycoprotein belonging to the Nectin family of Ig superfamily proteins. Nectin extracellular domains (ECDs) contain three Ig-like domains: an N-terminal V-type that mediates ligand binding, and two C2-type .Human Nectin-4 is normally expressed in the placenta, especially in endothelial cells, while in the mouse it is found in the embryo, lung, testis and brain. In humans, mutation of Nectin-4 has been correlated with ectodermal dysplasia-syndactyly syndrome,High Nectin-4/PVRL4 expression was associated with poor-prognosis in some invasive breast cancers and may be a new promising prognostic biomarker and specific therapeutic target.