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. Author manuscript; available in PMC: 2020 Aug 1.
Published in final edited form as: Trends Cancer. 2019 Nov 6;5(12):822–834. doi: 10.1016/j.trecan.2019.10.007

Figure 3. Adenosine signaling regulates macrophage polarization.

Figure 3.

Ectonucleoside triphosphate diphosphohydrolase 1 (CD39) expressed at the cell surface of macrophages, cancer cells, and other cells in the tumor microenvironment catalyzes the production of adenosine monophosphate (AMP). Ecto-5’-nucleotidase (CD73) further converts AMP into adenosine, which can either enter the cells through equilibrative subclass of nucleoside transporters (ENTs) or act on adenosine receptors 2A (ADORA 2A) and 2B (ADORA 2B) to induce M2 polarization of macrophages. Hypoxia-inducible factor-1 alpha (HIF-1α) further facilitates these processes by transcriptional induction of CD39/CD73 and transcriptional downregulation of ENTs.