title: Angiopoietins in angiogenesis.
abstract: Tie-1 and Tie-2 tyrosine kinase receptors are expressed specifically on vascular endothelial cells and on a certain subtype of macrophages implicated in angiogenesis, thus, they have been a major focus of angiogenesis research. Tie-1 and Tie-2 are essential for vascular maturation during developmental, physiological and pathological angiogenesis. Angiopoietin 1-4 (Ang-1-4) have been identified as bona fide ligands of the Tie-2 receptor, while Tie-1 remains an orphan receptor which is able to heterodimerize with Tie-2 and to modulate Tie-2 signal transduction. The most exhaustively studied angiopoietins are Ang-1 and Ang-2. Ang-1 is a critical player in vessel maturation and it mediates migration, adhesion and survival of endothelial cells. Ang-2 disrupts the connections between the endothelium and perivascular cells and promotes cell death and vascular regression. Yet, in conjunction with VEGF, Ang-2 promotes neo-vascularization. Hence, angiopoietins exert crucial roles in the angiogenic switch during tumor progression, and increased expression of Ang-2 relative to Ang-1 in tumors correlates with poor prognosis. Its central role in the regulation of physiological and pathological angiogenesis makes the angiopoietin/Tie signaling pathway a therapeutically attractive target for the treatment of vascular disease and cancer.
authors.affiliation: Institute of Biochemistry and Genetics, Department of Biomedicine, University of Basel, Basel, Switzerland.
authors.forename: Ernesta
authors.initials: E
authors.lastname: Fagiani
authors.forename: Gerhard
authors.initials: G
authors.lastname: Christofori
mesh_terms: D042682:Angiopoietins / Q000378:metabolism*; D006801:Humans; D009369:Neoplasms / Q000098:blood supply*; D009389:Neovascularization, Pathologic; D042810:Receptor, TIE-1 / Q000378:metabolism; D042787:Receptor, TIE-2 / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology
chemical_list: D042682:Angiopoietins; D042810:Receptor, TIE-1; D042787:Receptor, TIE-2