Identification of proangiogenic TIE2-expressing monocytes (TEMs) in human peripheral blood and cancer.
Tumor-infiltrating myeloid cells, including tumor-associated macrophages (TAMs), have been implicated in tumor progression. We recently described a lineage of mouse monocytes characterized by expression of the Tie2 angiopoietin receptor and required for the vascularization and growth of several tumor models. Here, we report that TIE2 expression in human blood identifies a subset of monocytes distinct from classical inflammatory monocytes and comprised within the less abundant "resident" population. These TIE2-expressing monocytes (TEMs) accounted for 2% to 7% of blood mononuclear cells in healthy donors and were distinct from rare circulating endothelial cells and progenitors. In human cancer patients, TEMs were observed in the blood and, intriguingly, within the tumors, where they represented the main monocyte population distinct from TAMs. Conversely, TEMs were hardly detected in nonneoplastic tissues. In vitro, TEMs migrated toward angiopoietin-2, a TIE2 ligand released by activated endothelial cells and angiogenic vessels, suggesting a homing mechanism for TEMs to tumors. Purified human TEMs, but not TEM-depleted monocytes, markedly promoted angiogenesis in xenotransplanted human tumors, suggesting a potentially critical role of TEMs in human cancer progression. Human TEMs may provide a novel, biologically relevant marker of angiogenesis and represent a previously unrecognized target of cancer therapy.
Venneri
Mary Anna
MA
San Raffaele Telethon Institute for Gene Therapy, Milan, Italy.
De Palma
Michele
M
Ponzoni
Maurilio
M
Pucci
Ferdinando
F
Scielzo
Cristina
C
Zonari
Erika
E
Mazzieri
Roberta
R
Doglioni
Claudio
C
Naldini
Luigi
L
D042501:Angiogenic Proteins / Q000032:analysis*; D042702:Angiopoietin-2; D001773:Blood Cells; D002634:Chemotaxis, Leukocyte; D006801:Humans; D009000:Monocytes / Q000737:chemistry*; D009369:Neoplasms / Q000097:blood* / Q000098:blood supply; D009389:Neovascularization, Pathologic / Q000209:etiology; D018919:Neovascularization, Physiologic; D042787:Receptor, TIE-2 / Q000032:analysis*
D042501:Angiogenic Proteins; D042702:Angiopoietin-2; D042787:Receptor, TIE-2