Endoglin (ENG, CD105) is a homodimeric cell membrane glycoprotein of 180 kDa, composed of disulphide-linked subunits of 95 kDa. Endoglin is a proliferation-associated and hypoxia-inducible protein mainly expressed on vascular endothelial cells. It acts as an accessory receptor for transforming growth factor beta (TFG-β) and is involved in vascular development and remodelling. The important role of Endoglin in angiogenesis and in tumor progression makes it an ideal target for antiangiogenic therapy and a good marker for tumor prognosis. (PMID: 1326540; 14528280; 21737653; 12773481)