Role of the extracellular ATP/adenosine pathway in neutrophil-mediated T cell suppression in ovarian cancer microenvironment

Abstract

Abstract The extracellular ATP (eATP)/adenosine (ADO) pathway is a key modulator of innate and adaptive immunity and is a target for immunotherapy for cancer. In the tumor microenvironment (TME) and conditions of chronic injury, ATP is released by dying cells and is hydrolyzed by the ecto-nucleotidase CD39 to AMP, and further to ADO by CD73. We previously observed that normal neutrophils (PMN) acquire a T cell suppressor phenotype mimicking PMN-MDSCs when exposed to the TME. Using a coculture system consisting of ascites supernatants (ASC) from patients with ovarian cancer (OC) as an authentic component of the TME and concentrations of healthy donor PMN and T cells that mimic those in OC ascites, we found that ASC-primed PMNs inhibit stimulated T cell proliferation, activation and metabolic responses. This suppressor activity was dependent on several PMN pathways, including complement signaling and NADPH oxidase. Since PMNs regulate and respond to signaling from the eATP/ADO pathway, we asked whether eATP/ADO mediates PMN suppressor function. PMNs had high constitutive expression of CD39 that was unaffected by ASC exposure, and inhibition of CD39 by POM-1 abrogated PMN suppressor function. CD73 inhibitor Adenosine 5′-(α,β-methylene) diphosphate also abrogated PMN suppressor function while using a different inhibitor (AB-680) had no effect. Neither ADO receptor inhibitors nor the addition of adenosine deaminase to deplete ADO affected PMN suppressor function. Together, these studies point to eATP as a modulator of PMN suppressor function in the TME and the potential to abrogate suppression by targeting CD39. Future studies will address the specific signaling functions of eATP on PMN in the TME that drive suppressor function. Supported by grant from NIH (5R01CA188900)