A2A Receptor Contributes to Tumor Progression in P2X7 Null Mice

Abstract

ATP and adenosine are key constituents of the tumor niche where they exert opposite and complementary roles. ATP can be released in response to cell damage or actively released by tumor cells and subsequently degraded into adenosine, which accumulates within the tumor microenvironment. Notably, while ATP promotes immune eradicating responses mainly via the P2X7 receptor (P2X7R), extracellular adenosine acts as a potent immune suppressor and facilitates neovascularization thanks to the A2A receptor (A2AR). To date, studies exploring the interplay between P2X7R and A2AR in the tumor microenvironment are as yet missing. Here, we show that, in C57/bl6 P2X7 null mice inoculated with B16-F10 melanoma cells, several pro-inflammatory cytokines, including interleukin 1 beta (IL-1β), tumor necrosis factor alpha (TNF-α), interleukin 6 (IL-6), interleukin 12 (IL-12), interleukin 17 (IL-17), interferon gamma (IFN-γ) were significantly decreased, while the immune suppressant transforming growth factor beta (TGF-β) was almost three-fold increased. Interestingly, tumors growing in P2X7-null mice upregulated tumor-associated and splenic A2AR, suggesting that immunosuppression linked to lack of the P2X7R might depend upon A2AR overexpression. Immunohistochemical analysis showed that tumor cells’ A2AR expression was increased, especially around necrotic areas, and that vascular endothelial growth factor (VEGF) and the endothelial marker CD31 were upregulated. A2AR antagonist SCH58261 treatment reduced tumor growth similarly in the P2X7 wild type or null mice strain. However, SCH58261 reduced VEGF only in the P2X7 knock out mice, thus supporting the hypothesis of an A2AR-mediated increase in vascularization observed in the P2X7-null host. SCH58261 administration also significantly reduced intratumor TGF-β levels, thus supporting a key immune suppressive role of A2AR in our model. Altogether, these results indicate that in the absence of host P2X7R, the A2AR favors tumor growth via immune suppression and neovascularization. This study shows a novel direct correlation between P2X7R and A2AR in oncogenesis and paves the way for new combined therapies promoting anti-cancer immune responses and reducing tumor vascularization.

The purinergic receptor P2X7 as a modulator of viral vector-mediated antigen cross-presentation

“…We demonstrate that using MVA-OVA-infected feeder cells bearing the active P2X7 receptor led to a significantly higher CD8 + T cell activation as determined by IFNү production in B8R- specific T cells or by TNFα production in either B8R- or OVA-specific T cell lines when co-cultured with uninfected dendritic cells as cross-presenting APC ( Figure 2A ). These data are in line with the P2RX7-dependent release of these cytokines in mice ( 45 ). The frequency of cross-presenting BMDCs with SIINFEKL/H2-K b complexes on the cell surface, as well as the amount of these peptide/MHCI complexes per cell, was significantly increased ( Figure 2B left, middle).…”

The P2X7 Receptor in Oncogenesis and Metastatic Dissemination: New Insights on Vesicular Release and Adenosinergic Crosstalk

“…Hence, the impact of P2X7 on cancer growth versus tumor immune control is complicated. Indeed, we and others demonstrated that a lack of host P2X7, for example in null mice, could favor tumor growth by significantly reducing immune infiltrates and pro-inflammatory cytokines and increasing intratumoral Tregs and adenosinergic pathways related to immune suppression [ 15 , 80 , 81 , 82 , 83 , 84 ]. However, even in P2X7 null-hosts, when an implanted tumor expresses P2X7, the administration of P2X7 antagonists causes a significant reduction in neoplastic growth accompanied by a substantial increase in CD4 + infiltrates, and also a decrease in the expression of the fitness marker CD73 in Tregs [ 15 ].…”

Purine and purinergic receptors in health and disease

“…Correspondingly, the deficiency of host P2X7R leads to the decrease of CD8 and Teff cells and the increase of immunosuppressive Tregs, contributing to cancer progression 143 . In the absence of host P2X7R, the increased expression of A2AR receptors promotes tumor growth by inducing immune suppression and neovascularization 190 . Moreover, under the transient stimulation of low concentration of eATP and its analogs, P2X7R opens the channel allowing small cations to permeate, promoting tumor cell proliferation and immune response.…”