Expression of P2X7R in breast cancer tissue and the induction of apoptosis by the gene-specific shRNA in MCF-7 cells

Role of the P2X7 receptor in breast cancer progression

Breast cancer is a common malignant tumor, whose incidence is increasing year by year, and it has become the malignant tumor with the highest incidence rate in women. Purine ligand-gated ion channel 7 receptor (P2X7R) is a cation channel receptor with Adenosine triphosphate ( ATP) as a ligand, which is widely distributed in cells and tissues, and is closely related to tumorigenesis and progression. P2X7R plays an important role in cancer by interacting with ATP. Studies have shown that P2X7R is up-regulated in breast cancer and can promote tumor invasion and metastasis by activating the protein kinase B (AKT) signaling pathway, promoting epithelial-mesenchymal transition (EMT), controlling the generation of extracellular vesicle (EV), and regulating the expression of the inflammatory protein cyclooxygenase 2 (COX-2). Furthermore, P2X7R was proven to play an essential role in the proliferation and apoptosis of breast cancer cells. Recently, inhibitors targeting P2X7R have been found to inhibit the progression of breast cancer. Natural P2X7R antagonists, such as rhodopsin, and the isoquinoline alkaloid berberine, have also been shown to be effective in inhibiting breast cancer progression. In this article, we review the research progress of P2X7R and breast cancer intending to provide new targets and directions for breast cancer treatment.

The role of the purinergic ligand-gated ion channel 7 receptor in common digestive system cancers

The incidence of digestive malignancies has increased in recent years, including colorectal cancer (CRC), hepatocellular carcinoma (HCC) and pancreatic cancer. Advanced stages of these cancers are prone to metastasis, which seriously reduce the standard of living of patients and lead to decline in the survival rate of patients. So far there are no good specific drugs to stop this phenomenon. It is very important and urgent to find new biomarkers and therapeutic targets. Purinergic ligand-gated ion channel 7 receptor (P2X7R) is ATP-gated and nonselective ion channel receptor involved in many inflammatory processes and cancer progression. P2X7R is present in many cancer cells and promotes or inhibits cancer development through signal transduction. Studies have presented that P2X7R plays a role in the proliferation and migration of digestive system cancers, such as CRC, HCC and pancreatic cancer. Therefore, P2X7R may serve as a biomarker or therapeutic target for digestive system cancers. This paper describes the structure and function of P2X7R, and mainly reviews the research progress on the role of P2X7R in CRC, HCC and pancreatic cancer.

Novel synthesized ionizable lipid for LNP-mediated P2X7siRNA to inhibit migration and induce apoptosis of breast cancer cells

The development of ionizable lipid (IL) was necessary to enable the effective formulation of small interfering RNA (siRNA) to inhibit P2X7 receptors (P2X7R), a key player in tumor proliferation, apoptosis, and metastasis. In this way, the synthesis and utility of IL for enhancing cellular uptake of lipid nanoparticles (LNP) improve the proper delivery of siRNA-LNPs for knockdown overexpression of P2X7R. Therefore, to evaluate the impact of P2X7 knockdown on breast cancer (BC) migration and apoptosis, a branched and synthesized ionizable lipid (SIL) was performed for efficient transfection of LNP with siRNA for targeting P2X7 receptors (siP2X7) in mouse 4T-1 cells. Following synthesis and structural analysis of SIL, excellent characterization of the LNP was achieved (Z-average 126.8 nm, zeta-potential - 12.33, PDI 0.16, and encapsulation efficiency 85.35%). Afterward, the stability of the LNP was evaluated through an analysis of the leftover composition, and toxic concentration values for SIL and siP2X7 were determined. Furthermore, siP2X7-LNP cellular uptake in the formulation was assessed via confocal microscopy. Following determining the optimal dose (45 pmol), wound healing analysis was assessed using scratch assay microscopy, and apoptosis was evaluated using flow cytometry. The use of the innovative branched SIL in the formulation of siP2X7-LNP resulted in significant inhibition of migration and induction of apoptosis in 4T-1 cells due to improved cellular uptake. Subsequently, the innovative SIL represents a critical role in efficiently delivering siRNA against murine triple-negative breast cancer cells (TNBC) using LNP formulation, resulting in significant efficacy.

P2X7 receptors: a bibliometric review from 2002 to 2023

For many years, there has been ongoing research on the P2X7 receptor (P2X7R). A comprehensive, systematic, and objective evaluation of the scientific output and status of P2X7R will be instrumental in guiding future research directions. This study aims to present the status and trends of P2X7R research from 2002 to 2023. Publications related to P2X7R were retrieved from the Web of Science Core Collection database. Quantitative analysis and visualization tools were Microsoft Excel, VOSviewer, and CiteSpace software. The analysis content included publication trends, literature co-citation, and keywords. 3282 records were included in total, with the majority of papers published within the last 10 years. Based on literature co-citation and keyword analysis, neuroinflammation, neuropathic pain, gastrointestinal diseases, tumor microenvironment, rheumatoid arthritis, age-related macular degeneration, and P2X7R antagonists were considered to be the hotspots and frontiers of P2X7R research. Researchers will get a more intuitive understanding of the status and trends of P2X7R research from this study.

P2X7 receptor promotes migration and invasion of non-small cell lung cancer A549 cells through the PI3K/Akt pathways

It has been demonstrated that the ATP-gated ion channel P2X7 receptor is involved in tumor progression and plays an important role in regulating tumor cell growth, invasion, migration and angiogenesis. However, P2X7 receptors have been relatively poorly studied in non-small cell lung cancer (NSCLC) cells. Therefore, the aim of this study was to investigate the effects of P2X7 receptor on A549 cells (NSCLC cell line) migration and invasion and to reveal the molecular mechanisms mediated by it. We detected the expression and function of P2X7 receptor in A549 cells. The effects and mechanisms of P2X7 receptor on A549 cells migration, invasion, and epithelial-mesenchymal transition were detected in vitro and in vivo. The results showed P2X7 receptor expressed by A549 cells had ion channel and macropore formation function. In addition, activation of P2X7 receptor by adenosine triphosphate (ATP) or 2'(3')-O-(4-Benzoylbenzoyl)-adenosine-5'-triphosphate (BzATP) promoted Epithelial-mesenchymal transition (EMT), migration and invasion of A549 cells, which was attenuated by treatment of cells with P2X7 receptor antagonist A438079 and Oxidized ATP. Furthermore, activation of P2X7 receptor increased phosphorylated protein kinase B (p-Akt) levels, and the phosphatidylinositol-tris-phosphate kinase 3 (PI3K)/protein kinase B (Akt) inhibitor LY294002 blocked migration and invasion of A549 cells induced by ATP or BzATP. At the same time, in vivo results showed that P2X7 receptor could also promote EMT and PI3K/Akt expression in transplanted tumors. Our study indicated that P2X7 receptor promotes A549 cells migration and invasion through the PI3K/Akt signaling pathway, suggesting that P2X7 receptor may be a potential therapeutic target for NSCLC.

Synthesis and biological evaluation of carboxamide and quinoline derivatives as P2X7R antagonists

P2X7 receptor (P2X7R) has a key role in different pathological conditions, importantly overexpressed and activated in cancers. We explored the structure activity relationship (SAR) of three novel pyrazines, quinoline-carboxamide and oxadiazole series. Their selective inhibitory potency in Ca2+ mobilization assay using h-P2X7R-MCF-7 cells improved with phenyl ring substitutions (-OCF3, -CF3, and -CH3) in carboxamide and oxadiazole derivatives, respectively. However, highly electronegative fluoro, chloro, and iodo substitutions enhanced affinity. 1e, 2f, 2e, 1d, 2 g and 3e were most potent and selective toward h-P2X7R (IC50 values 0.457, 0.566, 0.624, 0.682, 0.813 and 0.890 µM, respectively) and were inactive at h-P2X4R, h-P2X2R, r-P2Y6R, h-P2Y2R, t-P2Y1R expressed in MCF-7 and 1321N1 astrocytoma cells. Cell viability (MTT assay at 100 µM, cell line) for 3e was 62% (HEK-293T), 70% (1321N1 astrocytoma) and 85% (MCF-7). >75% cell viability was noted for 2 g and >80% for 2e and 1d in all non-transfected cell lines. Anti-proliferative effects, compared to control (Bz-ATP), of selective antagonists (10 µM) were 3e (11%) 1d, (19%) 1e, (70%, P = 0.005) and 2f, (24%), indicating involvement of P2X7R. Apoptotic cell death by flow cytometry showed 1e to be most promising, with 35% cell death (PI positive cells), followed by 2e (25%), 2f (20%), and 1d (19%), compared to control. Fluorescence microscopic analysis of apoptotic changes in P2X7R-transfected cell lines was established. 1e and 2f at 1X and 2X IC50 increased cellular shrinkage, nuclear condensation and PI/DAPI fluorescence. In-silico antagonist modeling predicted ligand receptor interactions, and all compounds obeyed Lipinski rules. These results suggest that pyrazine, quinoline-carboxamide and oxadiazole derivatives could be moderately potent P2X7R antagonists for in vivo studies and anti-cancer drug development.

Purinergic P2X7R as a potential target for pancreatic cancer

Pancreatic cancer is one of the deadliest types of cancer, with a death rate nearly equal to the incidence. The P2X7 receptor (P2X7R) is a kind of extracellular adenosine triphosphate (ATP)-gated ion channel with special permeability, which exists in most tissues of human body and mediates inflammation-related signaling pathways and immune signal transduction after activation. P2X7R is also present on the surface of several tumor cells and is involved in tumor growth and progression. P2X7R expression in pancreatic cancer has also been identified in recent studies. Activation of P2X7R in pancreatic cancer can support the proliferation of pancreatic stellate cells, participate in protein interactions, and mediate ERK1/2, IL-6/STAT3, hCAP-18/LL-37, PI3K/AKT signaling pathways to promote pancreatic cancer progression. Inhibitors targeting P2X7R can inhibit the development of pancreatic cancer and are expected to be used in clinical therapy. Therefore, P2X7R is promising as a potential therapeutic target for pancreatic cancer. This article reviews the progress of research on P2X7R in pancreatic cancer.

Purinergic signaling: Diverse effects and therapeutic potential in cancer

Regardless of improved biological insights and therapeutic advances, cancer is consuming multiple lives worldwide. Cancer is a complex disease with diverse cellular, metabolic, and physiological parameters as its hallmarks. This instigates a need to uncover the latest therapeutic targets to advance the treatment of cancer patients. Purines are building blocks of nucleic acids but also function as metabolic intermediates and messengers, as part of a signaling pathway known as purinergic signaling. Purinergic signaling comprises primarily adenosine triphosphate (ATP) and adenosine (ADO), their analogous membrane receptors, and a set of ectonucleotidases, and has both short- and long-term (trophic) effects. Cells release ATP and ADO to modulate cellular function in an autocrine or paracrine manner by activating membrane-localized purinergic receptors (purinoceptors, P1 and P2). P1 receptors are selective for ADO and have four recognized subtypes-A1, A2A, A2B, and A3. Purines and pyrimidines activate P2 receptors, and the P2X subtype is ligand-gated ion channel receptors. P2X has seven subtypes (P2X1-7) and forms homo- and heterotrimers. The P2Y subtype is a G protein-coupled receptor with eight subtypes (P2Y1/2/4/6/11/12/13/14). ATP, its derivatives, and purinoceptors are widely distributed in all cell types for cellular communication, and any imbalance compromises the homeostasis of the cell. Neurotransmission, neuromodulation, and secretion employ fast purinergic signaling, while trophic purinergic signaling regulates cell metabolism, proliferation, differentiation, survival, migration, invasion, and immune response during tumor progression. Thus, purinergic signaling is a prospective therapeutic target in cancer and therapy resistance.

Estrogen receptor β alleviates inflammatory lesions in a rat model of inflammatory bowel disease via down-regulating P2X7R expression in macrophages

Estrogen receptor beta (ERβ) agonists could inhibit inflammation in animal models of inflammatory bowel disease (IBD). However, the mechanism underlying such effect and the potential role of P2 × 7 receptor (P2X7R) remains unclear. In the present study, we examined whether the effect of ERβ activation in IBD rats was related to P2X7R. Overexpression of ERβ using a recombinant lentivirus in IBD rats improved the IBD-like symptoms, including weight loss, disease activity index (DAI) scores, and inflammatory responses. ERβ agonists DPN and ERB-041 attenuated P2X7R expression in macrophages from colitis rats and in a murine macrophage cell line (RAW264.7) in response to either lipopolysaccharide (LPS) or adenosine triphosphate (ATP). DPN and ERB-041 also blocked increased production of TNF-α, IL-6, and IL-1β in the rectocolon of colitis rats. The two ERβ agonists reversed LPS- and ATP-induced up-regulation of P2X7R and its downstream proteins, including NLRP3, ASC, caspase-1, and pro-IL-1β, in RAW264.7 cells. Also, in both the rectocolon of colitis rats and RAW264.7 cells, ERβ agonists reversed the up-regulation of extracellular regulated protein kinases (ERK), the Janus kinase 2 (JAK2), and signal transducer and activator of transcription 3 (STAT3), but not up-regulation of serine threonine kinase or cAMP-response element binding protein (CREB). Blockade of JAK2 or STAT3 phosphorylation significantly reduced the ability of DPN to down-regulate P2X7R expression and the ability of ERB-041 and DPN to inhibit IL-1β release from RAW264.7 cells. We found that ERβ and P2X7R co-localized in the macrophages of rat rectocolon and in RAW264.7 cells. Deletion of macrophages from colitis rats with clodronate abolished the inhibitory effect of DPN. These results suggest that ERβ plays an important anti-inflammatory role in IBD rats by down-regulating P2X7R expression and inhibiting IL-1β release from macrophages through the JAK2/STAT3 signaling pathway.

To inhibit or to boost the ATP/P2RX7 pathway to fight cancer-that is the question

Despite new biological insights and recent therapeutic advances, many tumors remain at baseline during treatments. Therefore, there is an urgent need to find new therapeutic strategies to improve the care of patients with solid tumors. P2RX7 receptor (P2XR7), an ATP-gated ion channel characterized by its ability to form large pore within the cell membrane, is described by most of the investigators as a "chef d'orchestre" of the antitumor immune response. The purpose of this review is to detail the recent information concerning different cellular mechanisms linking P2RX7 to hallmarks of cancer and to discuss different progresses in elucidating how activation of the ATP/P2RX7/NLRP3/IL-18 pathway is a very promising approach to fight cancer progression by increasing antitumor immune responses.

Targeting the purinergic pathway in breast cancer and its therapeutic applications

Breast cancer (BC) is the most frequent cause of death among women, representing a global public health problem. Here, we aimed to discuss the correlation between the purinergic system and BC, recognizing therapeutic targets. For this, we analyzed the interaction of extracellular nucleotides and nucleosides with the purinergic receptors P1 and P2, as well as the influence of ectonucleotidase enzymes (CD39 and CD73) on tumor progression. A comprehensive bibliographic search was carried out. The relevant articles for this review were found in the PubMed, Scielo, Lilacs, and ScienceDirect databases. It was observed that among the P1 receptors, the A1, A2A, and A2B receptors are involved in the proliferation and invasion of BC, while the A3 receptor is related to the inhibition of tumor growth. Among the P2 receptors, the P2X7 has a dual function. When activated for a short time, it promotes metastasis, but when activated for long periods, it is related to BC cell death. P2Y2 and P2Y6 receptors are related to BC proliferation and invasiveness. Also, the high expression of CD39 and CD73 in BC is strongly related to a worse prognosis. The receptors and ectonucleotidases involved with BC become possible therapeutic targets. Several purinergic pathways have been found to be involved in BC cell survival and progression. In this review, in addition to analyzing the pathways involved, we reviewed the therapeutic interventions already studied for BC related to the purinergic system, as well as to other possible therapeutic targets.

P2X7 receptor: a critical regulator and potential target for breast cancer

Breast cancer is currently the most common cancer and the leading cause of cancer death among women worldwide. Advanced breast cancer is prone to metastasis, and there is currently no drug to cure metastatic breast cancer. The purinergic ligand-gated ion channel 7 receptor is an ATP-gated nonselective cation channel receptor and is involved in signal transduction, growth regulation, cytokine secretion, and tumor cell development. Recent studies have shown that upregulation of the P2X7 receptor in breast cancer can mediate AKT signaling pathways, Ca2 þ-activated SK3 potassium channels, and EMT and regulate the secretion of small extracellular vesicles to promote breast cancer invasion and migration, which are affected by factors such as hypoxia and ATP. In addition, studies have shown that microRNAs can bind to the 3' untranslated region of the P2X7 receptor, which affects the occurrence and development of breast cancer by upregulating and downregulating P2X7 receptor expression. Studies have shown that new P2X7 receptor inhibitors, such as emodin and Uncaria tomentosa, can inhibit P2X7 receptor-mediated breast cancer invasion and are expected to be used clinically. This article reviews the research progress on the relationship between the P2X7 receptor and breast cancer to provide new ideas and a basis for clinical diagnosis and treatment.

Calcium signaling: breast cancer's approach to manipulation of cellular circuitry

Calcium is a versatile element that participates in cell signaling for a wide range of cell processes such as death, cell cycle, division, migration, invasion, metabolism, differentiation, autophagy, transcription, and others. Specificity of calcium in each of these processes is achieved through modulation of intracellular calcium concentrations by changing the characteristics (amplitude/frequency modulation) or location (spatial modulation) of the signal. Breast cancer utilizes calcium signaling as an advantage for survival and progression. This review integrates evidence showing that increases in expression of calcium channels, GPCRs, pumps, effectors, and enzymes, as well as resulting intracellular calcium signals, lead to high calcium and/or an elevated calcium- mobilizing capacity necessary for malignant functions such as migratory, invasive, proliferative, tumorigenic, or metastatic capacities.

P2X7 in Cancer: From Molecular Mechanisms to Therapeutics

P2X7 is a transmembrane receptor expressed in multiple cell types including neurons, dendritic cells, macrophages, monocytes, B and T cells where it can drive a wide range of physiological responses from pain transduction to immune response. Upon activation by its main ligand, extracellular ATP, P2X7 can form a nonselective channel for cations to enter the cell. Prolonged activation of P2X7, via high levels of extracellular ATP over an extended time period can lead to the formation of a macropore, leading to depolarization of the plasma membrane and ultimately to cell death. Thus, dependent on its activation state, P2X7 can either drive cell survival and proliferation, or induce cell death. In cancer, P2X7 has been shown to have a broad range of functions, including playing key roles in the development and spread of tumor cells. It is therefore unsurprising that P2X7 has been reported to be upregulated in several malignancies. Critically, ATP is present at high extracellular concentrations in the tumor microenvironment (TME) compared to levels observed in normal tissues. These high levels of ATP should present a survival challenge for cancer cells, potentially leading to constitutive receptor activation, prolonged macropore formation and ultimately to cell death. Therefore, to deliver the proven advantages for P2X7 in driving tumor survival and metastatic potential, the P2X7 macropore must be tightly controlled while retaining other functions. Studies have shown that commonly expressed P2X7 splice variants, distinct SNPs and post-translational receptor modifications can impair the capacity of P2X7 to open the macropore. These receptor modifications and potentially others may ultimately protect cancer cells from the negative consequences associated with constitutive activation of P2X7. Significantly, the effects of both P2X7 agonists and antagonists in preclinical tumor models of cancer demonstrate the potential for agents modifying P2X7 function, to provide innovative cancer therapies. This review summarizes recent advances in understanding of the structure and functions of P2X7 and how these impact P2X7 roles in cancer progression. We also review potential therapeutic approaches directed against P2X7.

Calcium Homeostasis: A Potential Vicious Cycle of Bone Metastasis in Breast Cancers

Cancers have been considered as one of the most severe health problems in the world. Efforts to elucidate the cancer progression reveal the importance of bone metastasis for tumor malignancy, one of the leading causes for high mortality rate. Multiple cancers develop bone metastasis, from which breast cancers exhibit the highest rate and have been well-recognized. Numerous cells and environmental factors have been believed to synergistically facilitate bone metastasis in breast cancers, from which breast cancer cells, osteoclasts, osteoblasts, and their produced cytokines have been well-recognized to form a vicious cycle that aggravates tumor malignancy. Except the cytokines or chemokines, calcium ions are another element largely released from bones during bone metastasis that leads to hypercalcemia, however, have not been well-characterized yet in modulation of bone metastasis. Calcium ions act as a type of unique second messenger that exhibits omnipotent functions in numerous cells, including tumor cells, osteoclasts, and osteoblasts. Calcium ions cannot be produced in the cells and are dynamically fluxed among extracellular calcium pools, intracellular calcium storages and cytosolic calcium signals, namely calcium homeostasis, raising a possibility that calcium ions released from bone during bone metastasis would further enhance bone metastasis and aggravate tumor progression via the vicious cycle due to abnormal calcium homeostasis in breast cancer cells, osteoclasts and osteoblasts. TRPs, VGCCs, SOCE, and P2Xs are four major calcium channels/routes mediating extracellular calcium entry and affect calcium homeostasis. Here we will summarize the overall functions of these four calcium channels in breast cancer cells, osteoclasts and osteoblasts, providing evidence of calcium homeostasis as a vicious cycle in modulation of bone metastasis in breast cancers.

Ethanol upregulates the P2X7 purinergic receptor in human macrophages

Alcohol consumption is considered to be the third leading cause of death in the United States. In addition to its direct toxicity, ethanol has two contrasting effects on the immune system: the nucleotide oligomerization domain-like receptor pyrin domain-containing-3 (NLRP3) inflammasome is inhibited by acute ethanol exposure but activated by chronic ethanol exposure. Purinergic receptors (especially the P2X7 receptor) are able to activate the NLRP3 inflammasome and are involved in many ethanol-related diseases (such as gout, pulmonary fibrosis, alcoholic steatohepatitis, and certain cancers). We hypothesized that ethanol regulates purinergic receptors and thus modulates the NLRP3 inflammasome's activity. In experiments with monocyte-derived macrophages, we found that interleukin (IL)-1β secretion was inhibited after 7 h of exposure (but not 48 h of exposure) to ethanol. The disappearance of ethanol's inhibitory effect on IL-1β secretion after 48 h was not mediated by the upregulated production of IL-1β, IL-1α, IL-6 or the inflammasome components NLRP3, apoptosis-associated speck-like protein containing a caspase recruitment domain, and caspase 1. P2X7R expression was upregulated by ethanol, whereas expression of the P2X4 and P2X1 receptors was not. Taken as a whole, our results suggest that ethanol induces NLRP3 inflammasome activation by upregulating the P2X7 receptor. This observation might have revealed a new mechanism for inflammation in ethanol-related diseases.

ATP in the tumour microenvironment drives expression of nfP2X7, a key mediator of cancer cell survival

The ATP-gated receptor P2X₇ is expressed in multiple malignant tumours including neuroblastoma, melanoma, prostate, lung and breast. P2X₇ has a significant role in mediating diverse cell responses, which upon dysregulation are associated with tumour initiation and development. The rapid, ATP-mediated activation of P2X₇ induces a fast-inward cation current in cells. However, prolonged ATP-mediated activation of P2X₇ leads to formation of a pore that increases membrane permeability and eventually causes cell death. This presents a potential paradox, as the tumour microenvironment contains extracellular ATP at levels sufficient to activate the P2X₇ pore and trigger cell death. However, P2X₇ expression is associated with enhanced cancer cell survival, proliferation and metastatic potential. At least one distinct conformational form of P2X₇, termed non-pore functional P2X₇ (nfP2X₇), has been described, which is not able to form a functional pore. We demonstrate for the first time in this study that exposure to a high ATP concentration, equivalent to those measured in the tumour microenvironment, drives nfP2X₇ expression and also that nfP2X₇ is essential for tumour cell survival. We show that monoclonal antibodies raised against a P2X₇ amino acid sequence (200–216), whose conformation is distinct from that of wild-type (WT) P2X₇, bind specifically to nfP2X₇ expressed on the surface of tumour cells. We also show that nfP2X₇ is broadly expressed in patient-derived tumour sections from a wide range of cancers. Therefore, antibodies raised against E200 provide tools that can differentiate between forms of the P2X₇ receptor that have a key role in cancer.

The P2X7 Receptor in Inflammatory Diseases: Angel or Demon?

Under physiological conditions, adenosine triphosphate (ATP) is present at low levels in the extracellular milieu, being massively released by stressed or dying cells. Once outside the cells, ATP and related nucleotides/nucleoside generated by ectonucleotidases mediate a high evolutionary conserved signaling system: the purinergic signaling, which is involved in a variety of pathological conditions, including inflammatory diseases. Extracellular ATP has been considered an endogenous adjuvant that can initiate inflammation by acting as a danger signal through the activation of purinergic type 2 receptors-P2 receptors (P2Y G-protein coupled receptors and P2X ligand-gated ion channels). Among the P2 receptors, the P2X7 receptor is the most extensively studied from an immunological perspective, being involved in both innate and adaptive immune responses. P2X7 receptor activation induces large-scale ATP release via its intrinsic ability to form a membrane pore or in association with pannexin hemichannels, boosting purinergic signaling. ATP acting via P2X7 receptor is the second signal to the inflammasome activation, inducing both maturation and release of pro-inflammatory cytokines, such as IL-1β and IL-18, and the production of reactive nitrogen and oxygen species. Furthermore, the P2X7 receptor is involved in caspases activation, as well as in apoptosis induction. During adaptive immune response, P2X7 receptor modulates the balance between the generation of T helper type 17 (Th17) and T regulatory (Treg) lymphocytes. Therefore, this receptor is involved in several inflammatory pathological conditions. In infectious diseases and cancer, P2X7 receptor can have different and contrasting effects, being an angel or a demon depending on its level of activation, cell studied, type of pathogen, and severity of infection. In neuroinflammatory and neurodegenerative diseases, P2X7 upregulation and function appears to contribute to disease progression. In this review, we deeply discuss P2X7 receptor dual function and its pharmacological modulation in the context of different pathologies, and we also highlight the P2X7 receptor as a potential target to treat inflammatory related diseases.

Involvement of P2X7 Receptor in Proliferation and Migration of Human Glioma Cells

Previous studies have demonstrated that activation of P2X₇ receptors (P2X₇R) results in the proliferation and migration of some types of tumor. Here, we asked whether and how the activated P2X₇R contribute to proliferation and migration of human glioma cells. Results showed that the number of P2X₇R positive cells was increasing with grade of tumor. In U87 and U251 human glioma cell lines, both expressed P2X₇R and the expression was enhanced by 3′-O-(4-benzoylbenzoyl) ATP (BzATP), the agonist of P2X₇R, and siRNA. Our results also showed that 10 μM BzATP was sufficient to induce the proliferation of glioma cell significantly, while the cell proliferation reached the peak with 100 μM BzATP. Also, the migration of U87 and U251 cells was significantly increased upon BzATP treatment. However, the number of apoptotic cells of U87 and U251 was not significantly changed by BzATP. In addition, the expression of ERK, p-ERK, and proliferating cell nuclear antigen (PCNA) protein was increased in BzATP-treated U87 and U251 glioma cells. PD98059, an inhibitor of the MEK/ERK pathway, blocked the increased proliferation and migration of glioma cells activated by BzATP. These results suggest that ERK pathway is involved in the proliferation and migration of glioma cells induced by P2X₇R activation.

Multifaceted Effects of Extracellular Adenosine Triphosphate and Adenosine in the Tumor-Host Interaction and Therapeutic Perspectives

Cancer is still one of the world's most pressing health-care challenges, leading to a high number of deaths worldwide. Immunotherapy is a new developing therapy that boosts patient's immune system to fight cancer by modifying tumor-immune cells interaction in the tumor microenvironment (TME). Extracellular adenosine triphosphate (eATP) and adenosine (Ado) are signaling molecules released in the TME that act as modulators of both immune and tumor cell responses. Extracellular adenosine triphosphate and Ado activate purinergic type 2 (P2) and type 1 (P1) receptors, respectively, triggering the so-called purinergic signaling. The concentration of eATP and Ado within the TME is tightly controlled by several cell-surface ectonucleotidases, such as CD39 and CD73, the major ecto-enzymes expressed in cancer cells, immune cells, stromal cells, and vasculature, being CD73 also expressed on tumor-associated fibroblasts. Once accumulated in the TME, eATP boosts antitumor immune response, while Ado attenuates or suppresses immunity against the tumor. In addition, both molecules can mediate growth stimulation or inhibition of the tumor, depending on the specific receptor activated. Therefore, purinergic signaling is able to modulate both tumor and immune cells behavior and, consequently, the tumor-host interaction and disease progression. In this review, we discuss the role of purinergic signaling in the host-tumor interaction detailing the multifaceted effects of eATP and Ado in the inflammatory TME. Moreover, we present recent findings into the application of purinergic-targeting therapy as a potential novel option to boost antitumor immune responses in cancer.

Downregulation of type 3 inositol (1,4,5)-trisphosphate receptor decreases breast cancer cell migration through an oscillatory Ca2+ signal

Breast cancer remains a research priority due to its invasive phenotype. Although the role of ion channels in cancer is now well established, the role of inositol (1,4,5)-trisphosphate (IP₃) receptors (IP₃Rs) remains enigmatic. If the three IP₃Rs subtypes expression have been identified in various cancers, little is known about their physiological role. Here, we investigated the involvement of IP₃R type 3 (IP₃R₃) in the migration processes of three human breast cancer cell lines showing different migration velocities: the low-migrating MCF-7 and the highly migrating and invasive MDA-MB-231 and MDA-MB-435S cell lines. We show that a higher IP₃R3 expression level, but not IP₃R1 nor IP₃R2, is correlated to a stronger cell line migration capacity and a sustained calcium signal. Interestingly, silencing of IP₃R3 highlights an oscillating calcium signaling profile and leads to a significant decrease of cell migration capacities of the three breast cancer cell lines. Conversely, stable overexpression of IP₃R3 in MCF-7 cells significantly increases their migration capacities. This effect is completely reversed by IP₃R3 silencing. In conclusion, we demonstrate that IP₃R3 expression level increases the migration capacity of human breast cancer cells by changing the calcium signature.

Roles of purinergic P2X7 receptor in glioma and microglia in brain tumors

This review considers evidence suggesting that activation of the ionotropic purinergic receptor P2X₇ (P2X₇R) is a contributing factor in the growth of brain tumors. Importantly, expression of P2X₇R may be upregulated in both glioma cells and in immune responding microglial cells with possible differential effects on tumor progression. The recruitment of immune cells into tumor regions may not only be involved in supporting an immunosuppressive environment aiding tumor growth but activated microglia could secrete inflammatory factors promoting neoangiogenesis in expanding tumors. The subtype P2X₇R exhibits a number of unique properties including activation of the receptor in pathological conditions associated with developing brain tumors. In particular, the tumor microenvironment includes elevated levels of ATP required for activation of P2X₇R and the sustained tumor and immune cell P2X₇R-mediated responses which in total contribute to overall tumor growth and viability. Studies on cultured rat and human glioma show marked increases in expression of P2X₇R and enhanced cell mobility relative to control. Glioma cell animal models demonstrate enhanced expression of P2X₇R in both glioma and microglia with antagonism of receptor showing differential effects on tumor growth. Overall, P2X₇R activation is associated with a complexity of modulatory actions on tumor growth in part due to ubiquitous expression of the receptor in glioma and immune responsive cells.

High expression of P2X7R is an independent postoperative indicator of poor prognosis in colorectal cancer

The purinergic P2X7 receptor (P2X7R) is a master regulator of inflammation and inflammation-related diseases. Recently, P2X7R has been reportedly involved in carcinogenesis and tumor progression. In this study, we investigated the expression pattern and prognostic merit of P2X7R in human colorectal cancer (CRC). The expression profile of P2X7R in 12 pairs of CRC and non-tumorous specimens was evaluated using Western blotting analysis. Additionally, we performed immunohistochemistry (IHC) on 116 paraffin-embedded CRC specimens, and evaluated the correlation between P2X7R expression and clinicopathological factors. P2X7R was overexpressed in CRC samples, compared with adjacent non-tumorous ones. High P2X7R expression significantly correlated with tumor size (P = .0177), Lymph node metastasis (P = .0128), and TNM stage (P = .0081). Furthermore, univariate and multivariate Cox regression analyses revealed that P2X7R expression could serve as an independent prognostic factor for poor overall survival (P = .0197). Treatment with P2X7R agonist BzATP led to the activation of Akt and NF-κB pathways. Consequently, we revealed that BzATP accelerated the proliferation of CRC cells, whereas co-incubation with PI3K/Akt inhibitor LY294002 significantly impaired BzATP-induced proliferation of CRC cells. Our findings implied that P2X7R may serve as a valuable prognostic indicator and promising therapeutic target of CRC.