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 3

CD73 deficiency causes increased paracellular permeability of ruthenium red in vivo.

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CD73 deficiency causes increased paracellular permeability of ruthenium ...
Ten- to fourteen-week-old proestrus-staged C57BL/6 and CD73-deficient (Cd73–/–) mice were exposed to hypoxia (7% O2) or room air for 4 hours. Uterine horns were perfusion fixed in vivo with 0.2% ruthenium red and 2% glutaraldehyde. Ruthenium red paracellular permeability was quantified by assessing approximately 200 consecutive paracellular spaces per uterine section by transmission electron microscopy. The percentage of permeability is the ratio of paracellular spaces containing ruthenium red to the total number of paracellular spaces assessed. (A) Electron photomicrograph shows the presence (black arrows) and absence (white arrow) of electron-dense ruthenium red (black deposit) in the paracellular space of a uterine section. (B) Percentage of ruthenium red paracellular permeability for uterine sections (n = 6 mice). (C) Representative electron photomicrographs of uterine sections from C57BL/6 and Cd73–/– mice exposed to hypoxia (7% O2) for 4 hours. Black arrow (bottom panel) indicates the paracellular space with ruthenium red; white arrow (top panel) indicates the paracellular space showing no ruthenium red. M, microvilli. (D) Cd73–/– mice were i.p. injected with 0.1 mg/kg NECA or DMSO prior to hypoxia exposure (7% O2) for 4 hours. Data represent the mean ± SEM. (B) **P < 0.005 compared with hypoxic C57BL/6 mice; #P < 0.005 compared with normoxic Cd73–/– mice; 1-way ANOVA with Tukey’s post test. (D) *P = 0.019; unpaired, 2-tailed t test. Scale bars and original magnification: (A) 500 nm, ×25,000; (C and D) 500 nm, ×50,000.