Loss of CD73-mediated actin polymerization promotes endometrial tumor progression
Jessica L. Bowser, … , Kenneth Dunner Jr., Russell R. Broaddus
Jessica L. Bowser, … , Kenneth Dunner Jr., Russell R. Broaddus
Published December 7, 2015
Citation Information: J Clin Invest. 2016;126(1):220-238. https://doi.org/10.1172/JCI79380.
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Research Article Oncology

Loss of CD73-mediated actin polymerization promotes endometrial tumor progression

Abstract

Ecto-5′-nucleotidase (CD73) is central to the generation of extracellular adenosine. Previous studies have highlighted a detrimental role for extracellular adenosine in cancer, as it dampens T cell–mediated immune responses. Here, we determined that, in contrast to other cancers, CD73 is markedly downregulated in poorly differentiated and advanced-stage endometrial carcinoma compared with levels in normal endometrium and low-grade tumors. In murine models, CD73 deficiency led to a loss of endometrial epithelial barrier function, and pharmacological CD73 inhibition increased in vitro migration and invasion of endometrial carcinoma cells. Given that CD73-generated adenosine is central to regulating tissue protection and physiology in normal tissues, we hypothesized that CD73-generated adenosine in endometrial carcinoma induces an innate reflex to protect epithelial integrity. CD73 associated with cell-cell contacts, filopodia, and membrane zippers, indicative of involvement in cell-cell adhesion and actin polymerization–dependent processes. We determined that CD73-generated adenosine induces cortical actin polymerization via adenosine A1 receptor (A1R) induction of a Rho GTPase CDC42–dependent conformational change of the actin-related proteins 2 and 3 (ARP2/3) actin polymerization complex member N-WASP. Cortical F-actin elevation increased membrane E-cadherin, β-catenin, and Na+K+ ATPase. Together, these findings reveal that CD73-generated adenosine promotes epithelial integrity and suggest why loss of CD73 in endometrial cancer allows for tumor progression. Moreover, our data indicate that the role of CD73 in cancer is more complex than previously described.

Authors

Jessica L. Bowser, Michael R. Blackburn, Gregory L. Shipley, Jose G. Molina, Kenneth Dunner Jr., Russell R. Broaddus

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Figure 4

CD73 localizes to membrane areas of cell-cell contacts and filopodia.

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CD73 localizes to membrane areas of cell-cell contacts and filopodia. (A...
(A) CD73 immunofluorescence and ecto-AMPase activity (brown deposit), in the presence of 5 mM levamisole, in HEC-1-A cells. Asterisks indicate membrane areas absent of cell-cell contact; arrows indicate membrane areas of cell-cell contact. (B) Ecto-AMPase intensity by regions of interest (ROIs) placed at membrane areas of cell-cell contact, membrane areas absent of cell-to-cell contact, and in the cytoplasm (ImageJ software; NIH). ROI intensity was corrected by inverting the mean (1/ROI mean intensity). ROIs were assessed in 10 images at ×40 original magnification for 10 to 25 cells per image. Total ROIs are indicated as (n =). Data are expressed as the mean ± SEM. **P < 0.001; 1-way ANOVA with Tukey’s post test. C-C, cell-to-cell contact. (C) Electron photomicrographs of ecto-AMPase activity (black deposit) in HEC-1-A cells. Left panel: low-magnification image of cell-cell contacts showing ecto-AMPase activity. Right panel: high-magnification image of a cell-cell contact with ecto-AMPase activity and filopodia (arrows). Scale bars and original magnification: 20 μm (A), 10 μm, ×2,500 (C, left panel); 500 nm, ×50,000 (C, right panel).