Overview of the role of purinergic signaling and insights into its role in cancer therapy.

Innovation of cancer therapy has received a dramatic acceleration over the last fifteen years thanks to the introduction of the novel immune checkpoint inhibitors (ICI). On the other hand, the conspicuous scientific knowledge accumulated in purinergic signaling since the early seventies is finally being transferred to the clinic. Several Phase I/II clinical trials are currently underway to investigate the effect of drugs interfering with purinergic signaling as stand-alone or combination therapy in cancer. This is supporting the novel concept of "purinergic immune checkpoint" (PIC) in cancer therapy. In the present review we will address a) the basic pharmacology and cell biology of the purinergic system; b) principles of its pathophysiology in human diseases; c) implications for cell death, cell proliferation and cancer; d) novel molecular tools to investigate nucleotide homeostasis in the extracellular environment; e) recent developments in the pharmacology of P1, P2 receptors and related ecto-enzymes; f) P1 and P2 ligands as novel diagnostic tools; g) current issues in PIC-based anti-cancer therapy. This review will provide an appraisal of the current status of purinergic signaling in cancer and will help identify future avenues of development.

The P2X7 Receptor is a Master Regulator of Microparticle and Mitochondria Exchange in Mouse Microglia.

Microparticles (MPs) are secreted by all cells, where they play a key role in intercellular communication, differentiation, inflammation, and cell energy transfer. P2X7 receptor (P2X7R) activation by extracellular ATP (eATP) causes a large MP release and affects their contents in a cell-specific fashion. We investigated MP release and functional impact in microglial cells from P2X7R-WT or P2X7R-KO mice, as well as mouse microglial cell lines characterized for high (N13-P2X7RHigh) or low (N13-P2X7RLow) P2X7R expression. P2X7R stimulation promoted release of a mixed MP population enriched with naked mitochondria. Released mitochondria were taken up and incorporated into the mitochondrial network of the recipient cells in a P2X7R-dependent fashion. NLRP3 and the P2X7R itself were also delivered to the recipient cells. Microparticle transfer increased the energy level of the recipient cells and conferred a pro-inflammatory phenotype. These data show that the P2X7R is a master regulator of intercellular organelle and MP trafficking in immune cells.

Regulation of GABAergic neurotransmission by purinergic receptors in brain physiology and disease.

Purinergic receptors regulate the processing of neural information in the hippocampus and cerebral cortex, structures related to cognitive functions. These receptors are activated when astrocytic and neuronal populations release adenosine triphosphate (ATP) in an autocrine and paracrine manner, following sustained patterns of neuronal activity. The modulation by these receptors of GABAergic transmission has only recently been studied. Through their ramifications, astrocytes and GABAergic interneurons reach large groups of excitatory pyramidal neurons. Their inhibitory effect establishes different synchronization patterns that determine gamma frequency rhythms, which characterize neural activities related to cognitive processes. During early life, GABAergic-mediated synchronization of excitatory signals directs the experience-driven maturation of cognitive development, and dysfunctions concerning this process have been associated with neurological and neuropsychiatric diseases. Purinergic receptors timely modulate GABAergic control over ongoing neural activity and deeply affect neural processing in the hippocampal and neocortical circuitry. Stimulation of A2 receptors increases GABA release from presynaptic terminals, leading to a considerable reduction in neuronal firing of pyramidal neurons. A1 receptors inhibit GABAergic activity but only act in the early postnatal period when GABA produces excitatory signals. P2X and P2Y receptors expressed in pyramidal neurons reduce the inhibitory tone by blocking GABAA receptors. Finally, P2Y receptor activation elicits depolarization of GABAergic neurons and increases GABA release, thus favoring the emergence of gamma oscillations. The present review provides an overall picture of purinergic influence on GABAergic transmission and its consequences on neural processing, extending the discussion to receptor subtypes and their involvement in the onset of brain disorders, including epilepsy and Alzheimer's disease.

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

Introduction: Modified Vaccinia Virus Ankara (MVA) is a safe vaccine vector inducing long- lasting and potent immune responses. MVA-mediated CD8+T cell responses are optimally induced, if both, direct- and cross-presentation of viral or recombinant antigens by dendritic cells are contributing. Methods: To improve the adaptive immune responses, we investigated the role of the purinergic receptor P2X7 (P2RX7) in MVA-infected feeder cells as a modulator of cross-presentation by non-infected dendritic cells. The infected feeder cells serve as source of antigen and provide signals that help to attract dendritic cells for antigen take up and to license these cells for cross-presentation. Results: We demonstrate that presence of an active P2RX7 in major histocompatibility complex (MHC) class I (MHCI) mismatched feeder cells significantly enhanced MVA-mediated antigen cross-presentation. This was partly regulated by P2RX7-specific processes, such as the increased availability of extracellular particles as well as the altered cellular energy metabolism by mitochondria in the feeder cells. Furthermore, functional P2RX7 in feeder cells resulted in a delayed but also prolonged antigen expression after infection. Discussion: We conclude that a combination of the above mentioned P2RX7-depending processes leads to significantly increased T cell activation via cross- presentation of MVA-derived antigens. To this day, P2RX7 has been mostly investigated in regards to neuroinflammatory diseases and cancer progression. However, we report for the first time the crucial role of P2RX7 for antigen- specific T cell immunity in a viral infection model.

The NFATc1/P2X7 receptor relationship in human intervertebral disc cells.

A comprehensive understanding of the molecules that play key roles in the physiological and pathological homeostasis of the human intervertebral disc (IVD) remains challenging, as does the development of new therapeutic treatments. We recently found a positive correlation between IVD degeneration (IDD) and P2X7 receptor (P2X7R) expression increases both in the cytoplasm and in the nucleus. Using immunocytochemistry, reverse transcription PCR (RT-PCR), overexpression, and chromatin immunoprecipitation, we found that NFATc1 and hypoxia-inducible factor-1α (HIF-1α) are critical regulators of P2X7R. Both transcription factors are recruited at the promoter of the P2RX7 gene and involved in its positive and negative regulation, respectively. Furthermore, using the proximity ligation assay, we revealed that P2X7R and NFATc1 form a molecular complex and that P2X7R is closely associated with lamin A/C, a major component of the nuclear lamina. Collectively, our study identifies, for the first time, P2X7R and NFATc1 as markers of IVD degeneration and demonstrates that both NFATc1 and lamin A/C are interaction partners of P2X7R.

Fetal bovine serum contains biologically available ATP.

ATP is a ubiquitous extracellular messenger released in a wide number of pathophysiological conditions. ATP is known to be present in minute amounts in the extracellular space in healthy tissues and in the blood, and to modulate a multiplicity of cell responses. Cell culture systems are widely used to explore purinergic signaling. We show here that currently used fetal bovine sera contain ATP in the 300-1300 pmol/L range. Serum ATP is associated with albumin as well as with microparticle/microvesicle fraction. Serum microparticles/microvesicles affect in vitro cell responses due to their content of miRNAs, growth factors, and other bioactive molecules. ATP is likely to be one of these bioactive factors found in a variable amount in sera of different commercial sources. ATP in serum supports ATP-dependent biochemical reactions such as the hexokinase-dependent phosphorylation of glucose to glucose 6-phosphate, and affects purinergic signaling. These findings show that cells growing in vitro in serum-supplemented media are exposed to varying levels of extracellular ATP, and thus to varying degrees of purinergic stimulation.

Editorial - Purinergic signalling: 50 years.

The function of almost all cells of the human and animal body is synchronized by purinergic/pyrimidinergic extracellular signalling molecules. This network activity is especially efficient in the central and peripheral nervous systems, driven by secretion of the (co)transmitter ATP (including its enzymatic degradation products ADP, AMP, and adenosine), as well as ATP/UTP (including UDP) released from the cytoplasm by either Ca2+-dependent vesicular exocytosis or by non-exocytotic pathways via a family of diverse channels. It must be pointed out that neural cells (neurons, astrocytes, and oligodendrocytes) are equal sources of nucleotides/nucleosides, as non-neural cells (e.g. the endothelium of small blood vessels). A whole plethora of purinergic receptors responding to the endogenously released purine and pyrimidine nucleotides as well as to adenosine, are instrumental in providing the structural basis for cell stimulation. The present collection of papers summarizes current knowledge and recent findings in the medicinal chemistry, electrophysiology, neuropharmacology and neurobiology of purinergic transmission. Accruing evidence supports the key role of extracellular nucleotides and nucleosides in neuroinflammation, neurodegeneration, and in neuropsychiatric diseases, thus paving the way for pharmacological intervention thanks to the development of novel brain-permeant, drug-like, purinergic ligands. We are confident that these therapies will open a new avenue for the treatment of so far uncurable diseases of the central and peripheral nervous systems.

The Concise Guide to PHARMACOLOGY 2023/24: Ion channels.

The Concise Guide to PHARMACOLOGY 2023/24 is the sixth in this series of biennial publications. The Concise Guide provides concise overviews, mostly in tabular format, of the key properties of approximately 1800 drug targets, and over 6000 interactions with about 3900 ligands. There is an emphasis on selective pharmacology (where available), plus links to the open access knowledgebase source of drug targets and their ligands (https://www.guidetopharmacology.org/), which provides more detailed views of target and ligand properties. Although the Concise Guide constitutes almost 500 pages, the material presented is substantially reduced compared to information and links presented on the website. It provides a permanent, citable, point-in-time record that will survive database updates. The full contents of this section can be found at http://onlinelibrary.wiley.com/doi/10.1111/bph.16178. Ion channels are one of the six major pharmacological targets into which the Guide is divided, with the others being: G protein-coupled receptors, nuclear hormone receptors, catalytic receptors, enzymes and transporters. These are presented with nomenclature guidance and summary information on the best available pharmacological tools, alongside key references and suggestions for further reading. The landscape format of the Concise Guide is designed to facilitate comparison of related targets from material contemporary to mid-2023, and supersedes data presented in the 2021/22, 2019/20, 2017/18, 2015/16 and 2013/14 Concise Guides and previous Guides to Receptors and Channels. It is produced in close conjunction with the Nomenclature and Standards Committee of the International Union of Basic and Clinical Pharmacology (NC-IUPHAR), therefore, providing official IUPHAR classification and nomenclature for human drug targets, where appropriate.

Macrophage Activation in Follicular Conjunctivitis during the COVID-19 Pandemic.

Among the symptoms of SARS-CoV-2, follicular conjunctivitis has become relevant. The conjunctiva acts as an open lymph node, reacting to the viral antigen that binds the epithelial cells, forming follicles of B cells with activated T cells and NK cells on its surface, which, in turn, talk to monocyte-derived inflammatory infected macrophages. Here, the NLRP3 inflammasome is a major driver in releasing pro-inflammatory factors such as IL-6 and caspase-1, leading to follicular conjunctivitis and bulbar congestion, even as isolated signs in the 'asymptomatic' patient.

Purinergic signalling in cancer therapeutic resistance: From mechanisms to targeting strategies.

Purinergic signalling, consisting of extracellular purines and purinergic receptors, modulates cell proliferation, invasion and immunological reaction during cancer progression. Here, we focus on current evidence that suggests the crucial role of purinergic signalling in mediating cancer therapeutic resistance, the major obstacle in cancer treatment. Mechanistically, purinergic signalling can modulate the tumor microenvironment (TME), epithelial-mesenchymal transition (EMT) and anti-tumor immunity, thus affecting drug sensitivity of tumor cells. Currently, some agents attempting to target purinergic signalling either in tumor cells or in tumor-associated immune cells are under preclinical or clinical investigation. Moreover, nano-based delivery technologies significantly improve the efficacy of agents targeting purinergic signalling. In this review article, we summarize the mechanisms of purinergic signalling in promoting cancer therapeutic resistance and discuss the potentials and challenges of targeting purinergic signalling in future cancer treatment.

The Coming of Age of the P2X7 Receptor in Diagnostic Medicine.

The discovery of the P2X7 receptor (P2X7R, originally named P2Z) in immune cells, its cloning, and the identification of its role in a multiplicity of immune-mediated diseases raised great hopes for the development of novel and more potent anti-inflammatory medicaments. Unfortunately, such hopes were partially deluded by the unsatisfactory results of most early clinical trials. This failure substantially reduced the interest of the pharmaceutical and biotech industries in the clinical development of P2X7R-targeted therapies. However, recent findings ushered in a second life for the P2X7R in diagnostic medicine. New P2X7R radioligands proved to be very reliable tools for the diagnosis of neuroinflammation in preclinical and clinical studies, and detection and measurement of free P2X7 receptor (or P2X7 subunit) in human blood suggested its potential use as a circulating marker of inflammation. Here we provide a brief review of these novel developments.

Unorthodox localization of P2X7 receptor in subcellular compartments of skeletal system cells.

Identifying the subcellular localization of a protein within a cell is often an essential step in understanding its function. The main objective of this report was to determine the presence of the P2X7 receptor (P2X7R) in healthy human cells of skeletal system, specifically osteoblasts (OBs), chondrocytes (Chs) and intervertebral disc (IVD) cells. This receptor is a member of the ATP-gated ion channel family, known to be a main sensor of extracellular ATP, the prototype of the danger signal released at sites of tissue damage, and a ubiquitous player in inflammation and cancer, including bone and cartilaginous tissues. Despite overwhelming data supporting a role in immune cell responses and tumor growth and progression, a complete picture of the pathophysiological functions of P2X7R, especially when expressed by non-immune cells, is lacking. Here we show that human wild-type P2X7R (P2X7A) was expressed in different samples of human osteoblasts, chondrocytes and intervertebral disc cells. By fluorescence microscopy (LM) and immunogold transmission electron microscopy we localized P2X7R not only in the canonical sites (plasma membrane and cytoplasm), but also in the nucleus of all the 3 cell types, especially IVD cells and OBs. P2X7R mitochondrial immunoreactivity was predominantly detected in OBs and IVD cells, but not in Chs. Evidence of subcellular localization of P2X7R may help to i. understand the participation of P2X7R in as yet unidentified signaling pathways in the joint and bone microenvironment, ii. identify pathologies associated with P2X7R mislocalization and iii. design specific targeted therapies.

The shed P2X7 receptor is an index of adverse clinical outcome in COVID-19 patients.

Introduction: The pathophysiology of the Corona Virus Disease 2019 (COVID-19) is incompletely known. A robust inflammatory response caused by viral replication is a main cause of the acute lung and multiorgan injury observed in critical patients. Inflammasomes are likely players in COVID-19 pathogenesis. The P2X7 receptor (P2X7R), a plasma membrane ATP-gated ion channel, is a main activator of the NLRP3 inflammasome, of the ensuing release of inflammatory cytokines and of cell death by pyroptosis. The P2X7R has been implicated in COVID-19-dependent hyperinflammation and in the associated multiorgan damage. Shed P2X7R (sP2X7R) and shed NLRP3 (sNLRP3) have been detected in plasma and other body fluids, especially during infection and inflammation. Methods: Blood samples from 96 patients with confirmed SARS-CoV-2 infection with various degrees of disease severity were tested at the time of diagnosis at hospital admission. Standard haematological parameters and IL-6, IL-10, IL-1ß, sP2X7R and sNLRP3 levels were measured, compared to reference values, statistically validated, and correlated to clinical outcome. Results: Most COVID-19 patients included in this study had lymphopenia, eosinopenia, neutrophilia, increased inflammatory and coagulation indexes, and augmented sNLRP3, IL-6 and IL-10 levels. Blood concentration of sP2X7R was also increased, and significantly positively correlated with lymphopenia, procalcitonin (PCT), IL-10, and alanine transaminase (ALT). Patients with increased sP2X7R levels at diagnosis also showed fever and respiratory symptoms, were more often transferred to Pneumology division, required mechanical ventilation, and had a higher likelihood to die during hospitalization. Conclusion: Blood sP2X7R was elevated in the early phases of COVID-19 and predicted an adverse clinical outcome. It is suggested that sP2X7R might be a useful marker of disease progression.

Extracellular ATP: A powerful inflammatory mediator in the central nervous system.

Nucleotides play a crucial role in extracellular signaling across species boundaries. All the three kingdoms of life (Bacteria, Archea and Eukariota) are responsive to extracellular ATP (eATP) and many release this and other nucleotides. Thus, eATP fulfills different functions, many related to danger-sensing or avoidance reactions. Basically all living organisms have evolved sensors for eATP and other nucleotides with very different affinity and selectivity, thus conferring a remarkable plasticity to this signaling system. Likewise, different intracellular transduction systems were associated during evolution to different receptors for eATP. In mammalian evolution, control of intracellular ATP (iATP) and eATP homeostasis has been closely intertwined with that of Ca2+, whether in the extracellular milieu or in the cytoplasm, establishing an inverse reciprocal relationship, i.e. high extracellular Ca2+ levels are associated to negligible eATP, while low intracellular Ca2+ levels are associated to high eATP concentrations. This inverse relationship is crucial for the messenger functions of both molecules. Extracellular ATP is sensed by specific plasma membrane receptors of widely different affinity named P2 receptors (P2Rs) of which 17 subtypes are known. This confers a remarkable plasticity to P2R signaling. The central nervous system (CNS) is a privileged site for purinergic signaling as all brain cell types express P2Rs. Accruing evidence suggests that eATP, in addition to participating in synaptic transmission, also plays a crucial homeostatic role by fine tuning microglia, astroglia and oligodendroglia responses. Drugs modulating the eATP concentration in the CNS are likely to be the new frontier in the therapy of neuroinflammation. This article is part of the Special Issue on 'Purinergic Signaling: 50 years'.

PML at mitochondria-associated membranes governs a trimeric complex with NLRP3 and P2X7R that modulates the tumor immune microenvironment.

Uncontrolled inflammatory response arising from the tumor microenvironment (TME) significantly contributes to cancer progression, prompting an investigation and careful evaluation of counter-regulatory mechanisms. We identified a trimeric complex at the mitochondria-associated membranes (MAMs), in which the purinergic P2X7 receptor - NLRP3 inflammasome liaison is fine-tuned by the tumor suppressor PML. PML downregulation drives an exacerbated immune response due to a loss of P2X7R-NLRP3 restraint that boosts tumor growth. PML mislocalization from MAMs elicits an uncontrolled NLRP3 activation, and consequent cytokines blast fueling cancer and worsening the tumor prognosis in different human cancers. New mechanistic insights are provided for the PML-P2X7R-NLRP3 axis to govern the TME in human carcinogenesis, fostering new targeted therapeutic approaches.

Blocking P2X7 by intracerebroventricular injection of P2X7-specific nanobodies reduces stroke lesions.

BACKGROUND: Previous studies have demonstrated that purinergic receptors could be therapeutic targets to modulate the inflammatory response in multiple models of brain diseases. However, tools for the selective and efficient targeting of these receptors are lacking. The development of new P2X7-specific nanobodies (nbs) has enabled us to effectively block the P2X7 channel. METHODS: Temporary middle cerebral artery occlusion (tMCAO) in wild-type (wt) and P2X7 transgenic (tg) mice was used to model ischemic stroke. Adenosine triphosphate (ATP) release was assessed in transgenic ATP sensor mice. Stroke size was measured after P2X7-specific nbs were injected intravenously (iv) and intracerebroventricularly (icv) directly before tMCAO surgery. In vitro cultured microglia were used to investigate calcium influx, pore formation via 4,6-diamidino-2-phenylindole (DAPI) uptake, caspase 1 activation and interleukin (IL)-1ß release after incubation with the P2X7-specific nbs. RESULTS: Transgenic ATP sensor mice showed an increase in ATP release in the ischemic hemisphere compared to the contralateral hemisphere or the sham-treated mice up to 24 h after stroke. P2X7-overexpressing mice had a significantly greater stroke size 24 h after tMCAO surgery. In vitro experiments with primary microglial cells demonstrated that P2X7-specific nbs could inhibit ATP-triggered calcium influx and the formation of membrane pores, as measured by Fluo4 fluorescence or DAPI uptake. In microglia, we found lower caspase 1 activity and subsequently lower IL-1ß release after P2X7-specific nb treatment. The intravenous injection of P2X7-specific nbs compared to isotype controls before tMCAO surgery did not result in a smaller stroke size. As demonstrated by fluorescence-activated cell sorting (FACS), after stroke, iv injected nbs bound to brain-infiltrated macrophages but not to brain resident microglia, indicating insufficient crossing of the blood-brain barrier of the nbs. Therefore, we directly icv injected the P2X7-specific nbs or the isotype nbs. After icv injection of 30 µg of P2X7 specific nbs, P2X7 specific nbs bound sufficiently to microglia and reduced stroke size. CONCLUSION: Mechanistically, we can show that there is a substantial increase of ATP locally after stroke and that blockage of the ATP receptor P2X7 by icv injected P2X7-specific nbs can reduce ischemic tissue damage.

Adenosine metabolized from extracellular ATP promotes type 2 immunity through triggering A2BAR signaling in intestinal epithelial cells.

Intestinal nematode parasites can cross the epithelial barrier, causing tissue damage and release of danger-associated molecular patterns (DAMPs) that may promote host protective type 2 immunity. We investigate whether adenosine binding to the A2B adenosine receptor (A2BAR) on intestinal epithelial cells (IECs) plays an important role. Specific blockade of IEC A2BAR inhibits the host protective memory response to the enteric helminth, Heligmosomoides polygyrus bakeri (Hpb), including disruption of granuloma development at the host-parasite interface. Memory T cell development is blocked during the primary response, and transcriptional analyses reveal profound impairment of IEC activation. Extracellular ATP is visualized 24 h after inoculation and is shown in CD39-deficient mice to be critical for the adenosine production mediating the initiation of type 2 immunity. Our studies indicate a potent adenosine-mediated IEC pathway that, along with the tuft cell circuit, is critical for the activation of type 2 immunity.

P2 Receptors: Novel Disease Markers and Metabolic Checkpoints in Immune Cells.

Extracellular ATP (eATP) and P2 receptors are novel emerging regulators of T-lymphocyte responses. Cellular ATP is released via multiple pathways and accumulates at sites of tissue damage and inflammation. P2 receptor expression and function are affected by numerous single nucleotide polymorphisms (SNPs) associated with diverse disease conditions. Stimulation by released nucleotides (purinergic signalling) modulates several T-lymphocyte functions, among which energy metabolism. Energy metabolism, whether oxidative or glycolytic, in turn deeply affects T-cell activation, differentiation and effector responses. Specific P2R subtypes, among which the P2X7 receptor (P2X7R), are either up- or down-regulated during T-cell activation and differentiation; thus, they can be considered indexes of activation/quiescence, reporters of T-cell metabolic status and, in principle, markers of immune-mediated disease conditions.

Modulation of Cell Energy Metabolism by the P2X7 Receptor.

For many years the P2X7 receptor (P2X7R) was considered the prototypic cytolytic receptor due to its ability to cause dramatic changes in plasma membrane permeability, eventually leading to cell death. However, later studies revealed that controlled P2X7R activation has beneficial effects on cell metabolism and nowadays our perception of the physiological role of this receptor has radically changed. Some of the biochemical pathways underlying the trophic effect of the P2X7R are being unveiled, thus disclosing an unanticipated role of P2X7Rs in mitochondrial and glycolytic metabolism. We provide here an update of the effects of the P2X7R on cell energy metabolism.

A2A Receptor Contributes to Tumor Progression in P2X7 Null Mice.

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-1ß), 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-ß) 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-ß 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.