In lymphoid tissues ATP and STA-9090 molecular weight ADP are primarily hydrolyzed to AMP by NTPDase1/CD39, and further to adenosine by CD73. To trigger signaling cascades in the responding cells ATP and ADP bind to a series of ligand-gated (P2X) and G-protein-coupled (P2Y) receptors, whereas adenosine binds to one of the four adenosine receptors. Intriguingly, ATP and ADP generally evoke proinflammatory signals, whereas adenosine shows opposite effects by acting as an anti-inflammatory mediator.
Along with the “classical” nucleotide-inactivating chain, the counteracting adenylate kinase (AK) and nucleoside diphosphate (NDP) kinase enzymes co-exist on the cell surface. The balance between these opposing nucleotide-scavenging and ATP-regenerating pathways may represent a key element in controlling the duration and magnitude of purinergic signaling 1–3. CD73 is a glycosylphosphatidylinositol-linked surface protein expressed
on subsets of leukocytes, vascular endothelial cells and on certain epithelial cells 4–7. The preferential expression of CD73, together with NTPDase, on CD4+CD25+FoxP3+ immunosuppressive Tregs has recently drawn much attention 8–11. The enzymatic activity of CD73 modulates leukocyte–endothelial Selleckchem PLX3397 cell contacts and it improves barrier functions of the vascular lining 12–14. Altered inflammatory reactions have been reported in CD73-deficient mice in multiple find more different models, including ischemia-reperfusion injuries and autoimmune diseases 13, 15–19.
CD73 can be expressed on several cancer types such as leukemia, glioblastoma, melanoma, and ovarian, bladder, thyroid, eosophageal, gastric, colon, prostate and breast cancer 3. The ecto-nucleotidase activity on the malignant breast cancer cells is known to enhance the migration, invasion and neovascularization of these cells and to support the growth of tumors 20, 21. CD73 expression has even been suggested to serve as a prognostic marker in certain cancer types, such as breast cancer 21. Although the functions of CD73 in cancer cells have been studied to some extent, the contribution of host CD73 activity to cancer progression has not been addressed. Here, we report that CD73-deficient T cells show up-regulated NTPDase activity, and that tumor progression and intratumoral accumulation of Tregs and mannose receptor (MR)+ macrophages, which are typically considered to be type 2 macrophages 22–24, are attenuated in CD73-deficient mice. Moreover, the composition of intratumoral leukocyte populations and tumor growth can be therapeutically manipulated by targeting CD73 and NTPDase. These data indicate that suppression of the host’s CD73 activity might be a new tool to keep cancer cells under the control of anti-tumor immune responses.