Tie2-expressing monocytes and tumor angiogenesis: regulation by hypoxia and angiopoietin-2.
Recent findings indicate that tumor-associated macrophages are important drivers of tumor angiogenesis. Here, we review the essential role played by Tie2-expressing monocytes (TEM) in this phenomenon. TEMs are present in human blood and tumors and their elimination in various tumor models suppresses tumor angiogenesis. A ligand for Tie2, angiopoietin-2 (Ang-2), is produced by angiogenic tumor vessels and is a chemoattractant for TEMs. Hypoxia up-regulates Tie2 expression on TEMs and, together with Ang-2, down-regulates their antitumor functions. Learning more about the regulation of TEMs by the tumor microenvironment may yield new strategies to ablate the tumor vasculature.
Lewis
Claire E
CE
Tumor Targeting Group, Academic Unit of Pathology, The Sir Henry Wellcome Laboratories for Medical Research, University of Sheffield Medical School, Sheffield, United Kingdom. claire.lewis@sheffield.ac.uk
De Palma
Michele
M
Naldini
Luigi
L
D042702:Angiopoietin-2 / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D015687:Cell Hypoxia; D006801:Humans; D009000:Monocytes / Q000201:enzymology*; D009369:Neoplasms / Q000097:blood / Q000098:blood supply* / Q000201:enzymology* / Q000235:genetics; D009389:Neovascularization, Pathologic / Q000097:blood / Q000201:enzymology; D042787:Receptor, TIE-2 / Q000096:biosynthesis* / Q000235:genetics; D015854:Up-Regulation
D042702:Angiopoietin-2; D042787:Receptor, TIE-2