P2X7 protein expression and polymorphism in non-small cell lung cancer (NSCLC)

P2X7 Variants in Pathophysiology

P2X7 receptor activation by extracellular adenosine triphosphate (eATP) modulates different intracellular pathways, including pro-inflammatory and tumor-promoting cascades. ATP is released by cells and necrotic tissues during stressful conditions and accumulates mainly in the inflammatory and tumoral microenvironments. As a consequence, both the P2X7 blockade and agonism have been proposed as therapeutic strategies in phlogosis and cancer. Nevertheless, most studies have been carried out on the WT fully functional receptor variant. In recent years, the discovery of P2X7 variants derived by alternative splicing mechanisms or single-nucleotide substitutions gave rise to the investigation of these new P2X7 variants' roles in different processes and diseases. Here, we provide an overview of the literature covering the function of human P2X7 splice variants and polymorphisms in diverse pathophysiological contexts, paying particular attention to their role in oncological and neuroinflammatory conditions.

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.

P2X7 receptor antagonism by AZ10606120 significantly reduced in vitro tumour growth in human glioblastoma

Glioblastomas are highly aggressive and deadly brain tumours, with a median survival time of 14-18 months post-diagnosis. Current treatment modalities are limited and only modestly increase survival time. Effective therapeutic alternatives are urgently needed. The purinergic P2X7 receptor (P2X7R) is activated within the glioblastoma microenvironment and evidence suggests it contributes to tumour growth. Studies have implicated P2X7R involvement in a range of neoplasms, including glioblastomas, although the roles of P2X7R in the tumour milieu remain unclear. Here, we report a trophic, tumour-promoting role of P2X7R activation in both patient-derived primary glioblastoma cultures and the U251 human glioblastoma cell line, and demonstrate its inhibition reduces tumour growth in vitro. Primary glioblastoma and U251 cell cultures were treated with the specific P2X7R antagonist, AZ10606120 (AZ), for 72 h. The effects of AZ treatment were also compared to cells treated with the current first-line chemotherapeutic drug, temozolomide (TMZ), and a combination of both AZ and TMZ. P2X7R antagonism by AZ significantly depleted glioblastoma cell numbers compared to untreated cells, in both primary glioblastoma and U251 cultures. Notably, AZ treatment was more effective at tumour cell killing than TMZ. No synergistic effect between AZ and TMZ was observed. AZ treatment also significantly increased lactate dehydrogenase release in primary glioblastoma cultures, suggesting AZ-induced cellular cytotoxicity. Our results reveal a trophic role of P2X7R in glioblastoma. Importantly, these data highlight the potential for P2X7R inhibition as a novel and effective alternative therapeutic approach for patients with lethal glioblastomas.

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.

Alternatively Spliced Isoforms of the P2X7 Receptor: Structure, Function and Disease Associations

The P2X7 receptor (P2X7R) is an ATP-gated membrane ion channel that is expressed by multiple cell types. Following activation by extracellular ATP, the P2X7R mediates a broad range of cellular responses including cytokine and chemokine release, cell survival and differentiation, the activation of transcription factors, and apoptosis. The P2X7R is made up of three P2X7 subunits that contain specific domains essential for the receptor’s varied functions. Alternative splicing produces P2X7 isoforms that exclude one or more of these domains and assemble in combinations that alter P2X7R function. The modification of the structure and function of the P2X7R may adversely affect cellular responses to carcinogens and pathogens, and alternatively spliced (AS) P2X7 isoforms have been associated with several cancers. This review summarizes recent advances in understanding the structure and function of AS P2X7 isoforms and their associations with cancer and potential role in modulating the inflammatory response.

ATP-gated P2X7 receptor as a potential target for prostate cancer

Prostate cancer is the most common malignancy of the male genitourinary system and is one of the leading causes of male cancer death. The P2X7 receptor is an important member of purine receptor family. It is a gated ion channel with adenosine triphosphate (ATP) as the ligand, which exists in a variety of immune tissues and cells and can be involved in tumorigenesis and tumor progression. Studies have shown that the P2X7 receptor is abnormally expressed in prostate cancer, and is related to the level of prostate-specific antigen, P2X7 receptor may be an early biomarker of prostate cancer. The P2X7 receptor is essential in the occurrence and development of prostate cancer. The P2X7 receptor mainly affects the invasion and metastasis of prostate cancer cells through epithelial mesenchymal transition/invasion-related genes and the PI3K/AKT and ERK1/2 signaling pathways. The P2X7 receptor could be a promising therapeutic target for prostate cancer.

The role of P2X7 receptor in infection and metabolism: Based on inflammation and immunity

The P2X7 receptor (P2X7R) is a ligand-gated receptor belonging to the P2 receptor family. It is distributed in various tissues of the human body and is involved in regulating the physiological functions of tissues and cells to affect the occurrence and development of diseases. Unlike all other P2 receptors, the P2X7 receptor is mainly expressed in immune cells and can be activated not only by extracellular nucleotides but also by non-nucleotide substances which act as positive allosteric modulators. In this review, we comprehensively describe the role of the P2X7 receptor in infection and metabolism based on its role as an important regulator of inflammation and immunity, and briefly introduce the structure and general function of the P2X7 receptor. These provide a clear knowledge framework for the study of the P2X7 receptor in human health. Targeting the P2X7 receptor may be an effective method for the treatment of inflammatory and immune diseases. And its role in microbial infection and metabolism may be the main direction for in-depth research on the P2X7 receptor in the future.

Autocrine and paracrine purinergic signaling in the most lethal types of cancer

Cancer comprises a collection of diseases that occur in almost any tissue and it is characterized by an abnormal and uncontrolled cell growth that results in tumor formation and propagation to other tissues, causing tissue and organ malfunction and death. Despite the undeniable improvement in cancer diagnostics and therapy, there is an urgent need for new therapeutic and preventive strategies with improved efficacy and fewer side effects. In this context, purinergic signaling emerges as an interesting candidate as a cancer biomarker or therapeutic target. There is abundant evidence that tumor cells have significant changes in the expression of purinergic receptors, which comprise the G-protein coupled P2Y and AdoR families of receptors and the ligand-gated ion channel P2X receptors. Tumor cells also exhibit changes in the expression of nucleotidases and other enzymes involved in nucleotide metabolism, and the concentrations of extracellular nucleotides are significantly higher than those observed in normal cells. In this review, we will focus on the potential role of purinergic signaling in the ten most lethal cancers (lung, breast, colorectal, liver, stomach, prostate, cervical, esophagus, pancreas, and ovary), which together are responsible for more than 5 million annual deaths.

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.

Effect of P2X purinergic receptors in tumor progression and as a potential target for anti-tumor therapy

The development of tumors is a complex pathological process involving multiple factors, multiple steps, and multiple genes. Their prevention and treatment have always been a difficult problem at present. A large number of studies have proved that the tumor microenvironment plays an important role in the progression of tumors. The tumor microenvironment is the place where tumor cells depend for survival, and it plays an important role in regulating the growth, proliferation, apoptosis, migration, and invasion of tumor cells. P2X purinergic receptors, which depend on the ATP ion channel, can be activated by ATP in the tumor microenvironment, and by mediating tumor cells and related cells (such as immune cells) in the tumor microenvironment. They play an important regulatory role on the effects of the skeleton, membrane fluidity, and intracellular molecular metabolism of tumor cells. Therefore, here, we outlined the biological characteristics of P2X purinergic receptors, described the effect of tumor microenvironment on tumor progression, and discussed the effect of ATP on tumor. Moreover, we explored the role of P2X purinergic receptors in the development of tumors and anti-tumor therapy. These data indicate that P2X purinergic receptors may be used as another potential pharmacological target for tumor prevention and treatment.

The P2X7 purinergic receptor: a potential therapeutic target for lung cancer

PURPOSE

Purinergic P2X7 receptor (P2X7R) is a gated ion channel for which adenosine triphosphate (ATP) is a ligand. Activated P2X7R is widely expressed in a variety of immune cells and tissues and is involved in a variety of physiological and pathological processes. Studies have confirmed that P2X7R is involved in the regulation of tumor cell growth, stimulating cell proliferation or inducing apoptosis. Recent studies have found that P2X7R is abnormally expressed in lung cancer and is closely related to the carcinogenesis and development of lung cancer. In this paper, we comprehensively describe the structure, function, and genetic polymorphisms of P2X7R. In particular, the role and therapeutic potential of P2X7R in lung cancer are discussed to provide new targets and new strategies for the treatment and prognosis of clinical lung cancer.

METHODS

The relevant literature on P2X7R and lung cancer from PubMed databases is reviewed in this article.

RESULTS

P2X7R regulates the function of lung cancer cells by activating multiple intracellular signaling pathways (such as the JNK, Rho, HMGB1 and EMT pathways), thereby affecting cell survival, growth, invasion, and metastasis and patient prognosis. Targeting P2X7R with inhibitors effectively suppresses the growth and metastasis of lung cancer cells.

CONCLUSION

In summary, P2X7R is expected to become a potential target for the treatment of lung cancer, and more clinical research is needed in the future to explore the effectiveness of P2X7R antagonists as treatments.

P2RX7B is a new theranostic marker for lung adenocarcinoma patients

Rationale: The characterization of new theranostic biomarkers is crucial to improving the clinical outcome of patients with advanced lung cancer. Here, we aimed at characterizing the P2RX7 receptor, a positive modulator of the anti-tumor immune response, in patients with lung adenocarcinoma.

Methods: The expression of P2RX7 and its splice variants was analyzed by RT-qPCR using areas of tumor and non-tumor lung adenocarcinoma (LUAD) tissues on both immune and non-immune cells. The biological activity of P2RX7 was studied by flow cytometry using fluorescent dyes. Bi-molecular fluorescence complementation and confocal microscopy were used to assess the oligomerization of P2RX7. Tumor immune infiltrates were characterized by immunohistochemistry.

Results: Fifty-three patients with LUAD were evaluated. P2RX7A, and 3 alternative splice variants were expressed in LUAD tissues and expression was down regulated in tumor versus adjacent non-tumor tissues. The protein retained biological activity only in immune cells. The P2RX7B splice variant was differentially upregulated in immune cells (P < 0.001) of the tumor and strong evidence of oligomerization of P2RX7A and B was observed in the HEK expression model, which correlated with a default in the activity of P2RX7. Finally, LUAD patients with a high level of P2RX7B had non-inflamed tumors (P = 0.001).

Conclusion: Our findings identified P2RX7B as a new theranostic tool to restore functional P2RX7 activity and open alternative therapeutic opportunities to improve LUAD patient outcome.

P2X7 receptor antagonism inhibits tumour growth in human high-grade gliomas

Gliomas, the most common primary brain cancer, are highly infiltrative and extremely difficult to treat. Despite advancements, current treatment is limited, with patients surviving for a median of 14-15 months post-diagnosis. Previous research has demonstrated the upregulation of a purinergic receptor, P2X7R, in human gliomas. P2X7R is expressed on both glioma cells and microglia within the glioma microenvironment. It is hypothesized that P2X7R contributes to tumour growth and proliferation via immune-mediated mechanisms involving tumour cells and surrounding microglia. We sought to elucidate the role of P2X7R in a human glioblastoma cell line (U251) and on surgically resected human glioma samples. We treated U251 and human glioma cultures for 72 h with P2X7R antagonists, Brilliant Blue G (BBG), oxidized ATP (oATP) and AZ10606120. Cell counting via fluorescence confocal microscopy was conducted to assess tumour proliferation. We observed no significant reductions in tumour cell numbers following P2X7R antagonism with BBG (20 μM) and oATP (250 μM) in both U251 cells and human glioma samples. Interestingly, there was a significant reduction in tumour cell number in both U251 cells (p = 0.0156) and human glioma samples (p = 0.0476) treated with varying concentrations of AZ10606120. When compared with the conventional chemotherapeutic agent, temozolomide, AZ10606120 was also found to more effectively inhibit tumour proliferation in U251 cells (p < 0.0001). Our pilot results demonstrate a potential trophic role of P2X7R where its inhibition by AZ10606120, a potent antagonist, hinders glioma growth directly or through the inactivation of microglia. This sheds new light on P2X7R as a therapeutic target for human gliomas.

Genetic polymorphisms of the P2X7 gene associated with susceptibility to and prognosis of pulmonary tuberculosis

In this population-based case control study, we recruited 1601 pulmonary tuberculosis cases and 1526 healthy controls, aiming to investigate the association of genetic polymorphisms of the P2X7 gene with the susceptibility to and prognosis of pulmonary tuberculosis in a Chinese Han population. Five single-nucleotide polymorphisms (SNPs) in the P2X7 gene were genotyped. The odds ratio (OR) or relative risk (RR) together with 95% confidence interval (CI) were used to estimated the effect of genetic polymorphisms on the disease. After correction for multiple comparisons, the SNP rs1718119 remained significant. The allele A of rs1718119 was related to a reduced risk for all active tuberculosis (OR for each additional allele A: 0.81, 95% CI: 0.69-0.94) and sputum smear-positive cases (OR for each additional allele A: 0.78, 95% CI: 0.66-0.93). The effects of these genetic variations were more evident among smokers. Survival analysis showed a weak association between rs7958311 and treatment outcome, where each additional allele A of the SNP rs7958311 contributed to a 59% increase in the probability of a successful treatment outcome (adjusted RR: 1.59, 95% CI: 1.05-2.40, P=0.028); but it wasn't significant after the Bonferroni correction. We demonstrated that genetic variations of the P2X7 gene might be involved in the risk and prognosis of human tuberculosis.

Association Between P2RX7 Gene and Hepatocellular Carcinoma Susceptibility: A Case-Control Study in a Chinese Han Population

Background

Hepatocellular carcinoma (HCC) is one of the most common types of liver cancer. It is hypothesized that P2RX7 genetic polymorphisms have strong association with HCC susceptibility. Therefore, a case-control study was designed and performed to verify the association between P2RX7 gene polymorphisms and HCC susceptibility.

Material/Methods

A total of 646 subjects were recruited in our study, including 323 HCC patients and 323 healthy controls. Five gene polymorphisms, −762C>T (rs2393799), 946G>A (rs28360457), 1513A>C (rs3751143), 1068G>A (rs1718119), and 1096C>G (rs2230911), were selected. Odds ratio (ORs) and 95% confidence interval (CI) were used to quantify the association between P2RX7 gene polymorphisms and the susceptibility to HCC. All tests were performed using SPSS 20 and a 2-sided P value of less than 0.05 was considered to be statistically significant.

Results

Our results suggest that allelic frequencies of these 5 SNPs all conformed to Hardy-Weinberg equilibrium (HWE). There was no significant difference in genotype and allele distributions of −762C>T and 1096C>G between the case group and the control group. However, an increased risk of HCC was associated with 946G>A (A vs. G: OR=1.48, 95%CI=1.09–2.01, P=0.013; GA+AA vs. GG: OR=1.46, 95%CI=1.03–2.07, P=0.033). A similar increased risk was associated with 1513A>C polymorphism (C vs. A: OR=1.37, 95%CI=1.05–1.79, P=0.021; AC+CC vs. AA: OR=1.40, 95%CI=1.01–1.93, P=0.041). On the other hand, a decreased risk of HCC was associated with gene polymorphism of 1068G>A (A vs. G: OR=0.68, 95%CI=0.51–0.91, P=0.010; GA+AA vs. GG: OR=0.68, 95%CI=0.49–0.96, P=0.027; AA vs. GG: OR=0.42, 95%CI=0.18–0.99, P=0.048).

Conclusions

Our results suggest that 3 of the 5 polymorphisms of P2RX7 described above (1513A>C, 946G>A, and 1068G>A) are significantly associated with HCC susceptibility in a Chinese Han population. Studies with larger sample sizes are recommended to confirm whether our results will be applicable to different ethnic populations in China.