The A2B Adenosine Receptor Modulates the Epithelial- Mesenchymal Transition through the Balance of cAMP/PKA and MAPK/ERK Pathway Activation in Human Epithelial Lung Cells

Altered purinergic P2X7 and A2B receptors signaling limits macrophage-mediated host defense in schistosomiasis

BACKGROUND

The occurrence of co-infections during schistosomiasis, a neglected tropical disease, with other parasites have been reported suggesting an impaired host immune defense. Macrophage purinergic P2X7 receptor (P2X7R) plays an important role against intracellular pathogens. Therefore, we investigated the P2X7R-mediated phagocytosis and killing capacity of Leishmania amazonensis by macrophages during schistosomiasis in vitro and in vivo.

METHODS

Swiss and C57BL/6 (Wild type) and P2X7R-/- were randomized in two groups: control (uninfected) and Schistosoma mansoni-infected. Alternatively, control Swiss and S. mansoni-infected mice were also infected with L. amazonensis.

RESULTS

The pre-treatment of control macrophages with the P2X7R antagonist (A74003) or TGF-β reduced the phagocytosis index, mimicking the phenotype of cells from S. mansoni-infected mice and P2X7R-/- mice. Apyrase also reduced the phagocytosis index in the control group corroborating the role of ATP to macrophage activation. Moreover, l-arginine-nitric oxide pathway was compromised during schistosomiasis, which could explain the reduced killing capacity in response to ATP in vitro and in vivo. We found an increased extracellular nucleotide (ATP, ADP and AMP) hydrolysis along with an increased frequency of F4/80+ CD39+ macrophages from the S. mansoni-infected group. Moreover, the content of adenosine in the cell supernatant was higher in the S. mansoni-infected group in relation to controls. Schistosomiasis also increased the expression of macrophage adenosine A2BR. In good accordance, both ADA and the selective A2BR antagonist restored the phagocytosis index of macrophages from S. mansoni-infected group.

CONCLUSIONS

Altogether, the altered P2X7R and A2BR signaling limits the role of macrophages to host defense against L. amazonensis during schistosomiasis, potentially contributing to the pathophysiology and clinically relevant co-infections.

Extracellular adenosine oppositely regulates the purinome machinery in glioblastoma and mesenchymal stem cells

Glioblastoma (GB) is a lethal brain tumor that rapidly adapts to the dynamic changes of the tumor microenvironment (TME). Mesenchymal stem/stromal cells (MSCs) are one of the stromal components of the TME playing multiple roles in tumor progression. GB progression is prompted by the immunosuppressive microenvironment characterized by high concentrations of the nucleoside adenosine (ADO). ADO acts as a signaling molecule through adenosine receptors (ARs) but also as a genetic and metabolic regulator. Herein, the effects of high extracellular ADO concentrations were investigated in a human glioblastoma cellular model (U343MG) and MSCs. The modulation of the purinome machinery, i.e., the ADO production (CD39, CD73, and adenosine kinase [ADK]), transport (equilibrative nucleoside transporters 1 (ENT1) and 2 (ENT2)), and degradation (adenosine deaminase [ADA]) were investigated in both cell lines to evaluate if ADO could affect its cell management in a positive or negative feed-back loop. Results evidenced a different behavior of GB and MSC cells upon exposure to high extracellular ADO levels: U343MG were less sensitive to the ADO concentration and only a slight increase in ADK and ENT1 was evidenced. Conversely, in MSCs, the high extracellular ADO levels reduced the ADK, ENT1, and ENT2 expression, which further sustained the increase of extracellular ADO. Of note, MSCs primed with the GB-conditioned medium or co-cultured with U343MG cells were not affected by the increase of extracellular ADO. These results evidenced how long exposure to ADO could produce different effects on cancer cells with respect to MSCs, revealing a negative feedback loop that can support the GB immunosuppressive microenvironment. These results improve the knowledge of the ADO role in the maintenance of TME, which should be considered in the development of therapeutic strategies targeting adenosine pathways as well as cell-based strategies using MSCs.

CD38 symmetric dimethyl site R58 promotes malignant tumor cell immune escape by regulating the cAMP-GSK3β-PD-L1 axis

In recent years, immunotherapy has emerged as an effective approach for treating tumors, with programmed cell death ligand 1 (PD-L1)/programmed cell death protein-1 (PD-1) immune checkpoint blockade (ICB) being a promising strategy. However, suboptimal therapeutic efficacy limits its clinical benefit. Understanding the regulation mechanism of PD-L1 expression is crucial for improving anti-PD-L1/PD-1 therapy and developing more effective tumor immunotherapy. Previous studies have revealed that resistance to PD-L1/PD-1 blockade therapy arises from the upregulation of CD38 on tumor cells induced by ATRA and IFN-β, which mediates the inhibition of CD8+ T cell function through adenosine receptor signaling, thereby promoting immune evasion.Yet, the precise role of CD38 in regulating PD-L1 on malignant tumor cells and its impact on CD8+ T cells through PD-L1 remain unclear. Here, we demonstrate that CD38 is highly expressed in malignant tumors (lung cancer, nasopharyngeal carcinoma, cervical cancer) and upregulates PD-L1 protein expression, impairing CD8+ T cell function. Mechanistically, CD38 phosphorylates GSK3β via the adenosine-activated cAMP-PKA signaling pathway, leading to GSK3β inactivation and enhanced PD-L1 stability and expression, facilitating tumor immune escape. Furthermore, we identify PRMT5 as a novel CD38-interacting molecule that symmetrically dimethylates CD38 arginine position 58, augmenting PD-L1 stability and expression through the ADO-cAMP-GSK3β signaling axis. This inhibits CD8+ T cell-mediated tumor cell killing, enabling tumor cells to evade immune surveillance. Our findings suggest that targeting the CD38 R58 site offers a new avenue for enhancing anti-PD-L1/PD-1 therapy efficacy in tumor treatment.

1-palmitoyl-2-linoleoyl-3-acetyl-rac-glycerol treatment inhibits abnormal tumor growth by regulating neutrophil infiltration in a non-small cell lung carcinoma mouse model

Excessive neutrophil infiltration into the tumor microenvironment (TME) is an important factor that contributes to tumor overgrowth and limited immunotherapy efficacy. Neutrophils activate various receptors involved in tumor progression, while suppressing the infiltration and activity of cytotoxic T cells and creating optimal conditions for tumor growth. Therefore, the appropriate control of neutrophil infiltration is an effective strategy for tumor treatment. In the present study, 1-palmitoyl-2-linoleoyl-3-acetyl-rac-glycerol (PLAG) inhibited tumor overgrowth by suppressing excessive neutrophil infiltration, resulting in >74.97 % reduction in tumor size in a Lewis lung carcinoma (LLC-1) mouse model. All subjects in the positive control group died during the 90-day survival period, whereas only four subjects in the PLAG treatment group survived. PLAG had a significantly higher tumor growth inhibitory effect and survival rate than other neutrophil infiltration-targeting inhibitors (e.g., Navarixin, lymphocyte antigen 6 complex locus G6D antibody [aLy6G]). The ability of PLAG to regulate neutrophil infiltration and inhibit tumor growth depends on thioredoxin-interacting protein (TXNIP). In tumors lacking TXNIP expression, PLAG failed to control neutrophil infiltration and infiltration-related factor release, and the inhibitory effect of PLAG on tumor growth was reduced. PLAG-mediated inhibition of neutrophil infiltration enhances the efficacy of immune checkpoint inhibitors (ICIs), increasing the antitumor efficacy and survival rate by 30 %. In conclusion, PLAG could be a novel alternative to anti-tumor drugs that effectively targets excessive neutrophil infiltration into cancer tissues.

Regulation of CD73 on NAD metabolism: Unravelling the interplay between tumour immunity and tumour metabolism

CD73, a cell surface-bound nucleotidase, serves as a crucial metabolic and immune checkpoint. Several studies have shown that CD73 is widely expressed on immune cells and plays a critical role in immune escape, cell adhesion and migration as a costimulatory molecule for T cells and a factor in adenosine production. However, recent studies have revealed that the protumour effects of CD73 are not limited to merely inhibiting the antitumour immune response. Nicotinamide adenine dinucleotide (NAD+) is a vital bioactive molecule in organisms that plays essential regulatory roles in diverse biological processes within tumours. Accumulating evidence has demonstrated that CD73 is involved in the transport and metabolism of NAD, thereby regulating tumour biological processes to promote growth and proliferation. This review provides a holistic view of CD73-regulated NAD + metabolism as a complex network and further highlights the emerging roles of CD73 as a novel target for cancer therapies.

Unlocking the adenosine receptor mechanism of the tumour immune microenvironment

The suppressive tumour microenvironment significantly hinders the efficacy of immunotherapy in treating solid tumors. In this context, stromal cells, such as tumour-associated fibroblasts, undergo changes that include an increase in the number and function of immunosuppressive cells. Adenosine, a factor that promotes tumour growth, is produced from ATP breakdown and is markedly elevated in the tumour microenvironment. It acts through specific binding to adenosine receptors, with A2A and A2B adenosine receptor being primary drivers of immunosuppression. This paper presents the roles of various adenosine receptors in different tumour microenvironments. This review focus on the function of adenosine receptors in the stromal cells and non-cellular components of the tumour microenvironment. Additionally, we summarize and discuss recent advances and potential trends in using adenosine receptor antagonists combined with immunotherapy.

Formoterol Exerts Anti-Cancer Effects Modulating Oxidative Stress and Epithelial-Mesenchymal Transition Processes in Cigarette Smoke Extract Exposed Lung Adenocarcinoma Cells

Lung cancer frequently affects patients with Chronic Obstructive Pulmonary Disease (COPD). Cigarette smoke (CS) fosters cancer progression by increasing oxidative stress and by modulating epithelial-mesenchymal transition (EMT) processes in cancer cells. Formoterol (FO), a long-acting β2-agonist widely used for the treatment of COPD, exerts antioxidant activities. This study explored in a lung adenocarcinoma cell line (A549) whether FO counteracted the effects of cigarette smoke extract (CSE) relative to oxidative stress, inflammation, EMT processes, and cell migration and proliferation. A549 was stimulated with CSE and FO, ROS were evaluated by flow-cytometry and by nanostructured electrochemical sensor, EMT markers were evaluated by flow-cytometry and Real-Time PCR, IL-8 was evaluated by ELISA, cell migration was assessed by scratch and phalloidin test, and cell proliferation was assessed by clonogenic assay. CSE significantly increased the production of ROS, IL-8 release, cell migration and proliferation, and SNAIL1 expression but significantly decreased E-cadherin expression. FO reverted all these phenomena in CSE-stimulated A549 cells. The present study provides intriguing evidence that FO may exert anti-cancer effects by reverting oxidative stress, inflammation, and EMT markers induced by CS. These findings must be validated in future clinical studies to support FO as a valuable add-on treatment for lung cancer management.

Adenosine receptor signalling as a driver of pulmonary fibrosis

Pulmonary fibrosis is a debilitating and life-limiting lung condition in which the damage- response mechanisms of mixed-population cells within the lungs go awry. The tissue microenvironment is drastically remodelled by aberrantly activated fibroblasts which deposit ECM components into the surrounding lung tissue, detrimentally affecting lung function and capacity for gas exchange. Growing evidence suggests a role for adenosine signalling in the pathology of tissue fibrosis in a variety of organs, including the lung, but the molecular pathways through which this occurs remain largely unknown. This review explores the role of adenosine in fibrosis and evaluates the contribution of the different adenosine receptors to fibrogenesis. Therapeutic targeting of the adenosine receptors is also considered, along with clinical observations pointing towards a role for adenosine in fibrosis. In addition, the interaction between adenosine signalling and other profibrotic signalling pathways, such as TGFβ1 signalling, is discussed.

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.

Dexmedetomidine alleviates pulmonary fibrosis through the ADORA2B-Mediated MAPK signaling pathway

BACKGROUND

Idiopathic pulmonary fibrosis (IPF) is a chronically progressive fibrotic pulmonary disease characterized by an uncertain etiology, a poor prognosis, and a paucity of efficacious treatment options. Dexmedetomidine (Dex), an anesthetic-sparing alpha-2 adrenoceptor (α2AR) agonist, plays a crucial role in organ injury and fibrosis. However, the underlying mechanisms of IPF remain unknown.

METHODS

In our study, the role of Dex in murine pulmonary fibrosis models was determined by Dex injection intraperitoneally in vivo. Fibroblast activation and myofibroblast differentiation were assessed after Dex treatment in vitro. The activation of MAPK pathway and the expression of Adenosine A2B receptor (ADORA2B) were examined in lung myofibroblasts. Moreover, the role of ADORA2B in Dex suppressing myofibroblast differentiation and pulmonary fibrosis was determined using the ADORA2B agonist BAY60-6583.

RESULTS

The results revealed that Dex could inhibit Bleo-induced pulmonary fibrosis in mice. In vitro studies revealed that Dex suppressed TGF-β-mediated MAPK pathway activation and myofibroblast differentiation. Furthermore, Dex inhibits myofibroblast differentiation and pulmonary fibrosis via downregulating ADORA2B expression.

CONCLUSIONS

Our findings suggest Dex as a potential therapeutic agent for pulmonary fibrosis. Dex may alleviate lung fibrosis and myofibroblast differentiation through the ADORA2B-mediated MAPK signaling pathway.

The interplay between the DNA damage response and ectonucleotidases modulates tumor response to therapy

The extracellular nucleoside adenosine reduces tissue inflammation and is generated by irreversible dephosphorylation of adenosine monophosphate (AMP) mediated by the ectonucleotidase CD73. The pro-inflammatory nucleotides adenosine triphosphate, nicotinamide adenine dinucleotide, and cyclic guanosine -monophosphate-AMP (cGAMP), which are produced in the tumor microenvironment (TME) during therapy-induced immunogenic cell death and activation of innate immune signaling, can be converted into AMP by ectonucleotidases CD39, CD38, and CD203a/ENPP1. Thus, ectonucleotidases shape the TME by converting immune-activating signals into an immunosuppressive one. Ectonucleotidases also hinder the ability of therapies including radiation therapy, which enhance the release of pro-inflammatory nucleotides in the extracellular milieu, to induce immune-mediated tumor rejection. Here, we review the immunosuppressive effects of adenosine and the role of different ectonucleotidases in modulating antitumor immune responses. We discuss emerging opportunities to target adenosine generation and/or its ability to signal via adenosine receptors expressed by immune and cancer cells in the context of combination immunotherapy and radiotherapy.

A2b and A3 adenosine receptors may act as promotive and prognostic factors in oral squamous cell carcinoma

This study aimed to examine the expression and potential effects of adenosine receptors in oral squamous cell carcinoma (OSCC). Data on mRNA expression of adenosine receptors in OSCC samples were collected from The Cancer Genome Atlas database. Adenosine-regulated signaling pathways and biological processes were investigated via immune cell infiltration analysis, bioinformatics analysis, and immunohistochemistry. Overexpression of A2bR and A3R was significantly correlated with the prognosis of OSCC (P < 0.05). A3R expression in OSCC patients was significantly and positively correlated with the infiltration of six types of immune cells: B cells, CD4+ T cells, CD8+ T cells, neutrophils, macrophages, and myeloid dendritic cells. A2bR expression weakly and negatively correlated with B-cell infiltration only. The expression of A2bR in OSCC was positively correlated with E-cadherin and PCNA, while the expression of A3R was positively correlated with that of cleaved caspase-3. Within the limitations of the study it seems that the overexpression of A2bR and A3R results in the poor prognosis of OSCC, suggesting that A2bR promotes cell proliferation in OSCC, while A3R may be involved in OSCC progression by regulating tumor cell apoptosis and immune microenvironment.

FFAR2 antagonizes TLR2- and TLR3-induced lung cancer progression via the inhibition of AMPK-TAK1 signaling axis for the activation of NF-κB

BACKGROUND

Free fatty acid receptors (FFARs) and toll-like receptors (TLRs) recognize microbial metabolites and conserved microbial products, respectively, and are functionally implicated in inflammation and cancer. However, whether the crosstalk between FFARs and TLRs affects lung cancer progression has never been addressed.

METHODS

We analyzed the association between FFARs and TLRs using The Cancer Genome Atlas (TCGA) lung cancer data and our cohort of non-small cell lung cancer (NSCLC) patient data (n = 42), and gene set enrichment analysis (GSEA) was performed. For the functional analysis, we generated FFAR2-knockout (FFAR2KO) A549 and FFAR2KO H1299 human lung cancer cells and performed biochemical mechanistic studies and cancer progression assays, including migration, invasion, and colony-formation assays, in response to TLR stimulation.

RESULTS

The clinical TCGA data showed a significant down-regulation of FFAR2, but not FFAR1, FFAR3, and FFAR4, in lung cancer, and a negative correlation with TLR2 and TLR3. Notably, GSEA showed significant enrichment in gene sets related to the cancer module, the innate signaling pathway, and the cytokine-chemokine signaling pathway in FFAR2^DownTLR2^UpTLR3^Up lung tumor tissues (LTTs) vs. FFAR2^upTLR2^DownTLR3^Down LTTs. Functionally, treatment with propionate (an agonist of FFAR2) significantly inhibited human A549 or H1299 lung cancer migration, invasion, and colony formation induced by TLR2 or TLR3 through the attenuation of the cAMP-AMPK-TAK1 signaling axis for the activation of NF-κB. Moreover, FFAR2KO A549 and FFAR2KO H1299 human lung cancer cells showed marked increases in cell migration, invasion, and colony formation in response to TLR2 or TLR3 stimulation, accompanied by elevations in NF-κB activation, cAMP levels, and the production of C-C motif chemokine ligand (CCL)2, interleukin (IL)-6, and matrix metalloproteinase (MMP) 2 cytokines.

CONCLUSION

Our results suggest that FFAR2 signaling antagonized TLR2- and TLR3-induced lung cancer progression via the suppression of the cAMP-AMPK-TAK1 signaling axis for the activation of NF-κB, and its agonist might be a potential therapeutic agent for the treatment of lung cancer.

Forskolin affects proliferation, migration and Paclitaxel-mediated cytotoxicity in non-small-cell lung cancer cell lines via adenylyl cyclase/cAMP axis

Non-Small-Cell Lung Cancer (NSCLC) is considered one of the most frequently diagnosed cancers and the leading cause of cancer-related deaths worldwide. Despite the undoubted therapeutic advances that have occurred in clinical practice over time, due to its high degree in both heterogeneity and resistance, NSCLC remains largely incurable. As a natural cAMP elevating agent, Forskolin has shown anti-cancer properties in different tumor types, thus supposing its possible usage in treating malignancies. In this study, we investigated the Forskolin outcome in H1299 and A549 NSCLC cell lines, either alone or in combination with Paclitaxel. We proved that Forskolin impairs cell growth and migration ability of these cells, concurrently. Albeit with a different extent between H1299 and A549, changes in cell-cycle progression and epithelial-mesenchymal markers were observed in response to Forskolin administration. Interestingly, comparable cell growth impairment was also obtained with the cAMP phosphodiesterase inhibitor IBMX, while the employment of adenylyl cyclase inhibitor SQ22536 counteracted, at least in part, the Forskolin-mediated anticancer effects. Besides as a single agent, we also demonstrated that Forskolin strongly enhances Paclitaxel-induced cytotoxicity, affecting cell death mainly via apoptosis induction. Notably, H89-mediated protein kinase A (PKA) inhibition further deteriorated the combination outcome. Altogether, our data designate Forskolin as a possible anticancer molecule in NSCLC, and recognize the adenylyl cyclase/cAMP axis as one of the pathways involved in. Although achieved at preclinical stage, our findings encourage the design of future studies aimed at further exploring the Forskolin employment in NSCLC treatment.

Istradefylline induces A2A/P2X7 crosstalk expression inducing pro-inflammatory signal, and reduces AKT/mTOR signaling in melanoma-bearing mice

ATP and adenosine (ADO) are critical players in the context of cancer. In the tumor microenvironment, the signaling dependent on these molecules, and immune cells, is regulated by an enzymatic chain and purinergic receptors called purinome. Primarily, the A2A receptor (A2AR) has a pro-tumor action since it reduces the immune response and favors the growth of malignant melanoma. Therefore, this study aimed to verify the effects of A2AR antagonism with Istradefylline (IST) on the purinergic signaling profile of the melanoma tumor and immunological compartments. We observed reduced tumor growth of melanoma in IST-treated animals. IST inhibited AKT/mTOR pathway, which is involved with tumor growth. In the tumor, spleen, and thymus, the modulation of purinergic enzymes (CD39, CD73, and E-ADA) characterized a pro-inflammatory profile since it favored increased extracellular concentrations of ATP to the detriment of ADO. A2AR inhibition generated a compensatory feedback process with increased A2AR expression at the tumor level. However, there was also an increase in the expression of the P2X7 receptor (P2X7R), which culminated in an increase in pro-inflammatory pathways with the release of IL-1β and pro-inflammatory cytokines such as IFN-γ and TNF-α. Our data evidence the cross-involvement between expression and action of the A2AR and P2X7R. We suggest that IST is a promising drug for off-label use in cancer since it promotes an anti-tumoral response by producing pro-inflammatory cytokines and blocking of AKT/mTOR tumor growth pathway.

A2B Adenosine Receptor in Idiopathic Pulmonary Fibrosis: Pursuing Proper Pit Stop to Interfere with Disease Progression

Purine nucleotides and nucleosides are involved in various human physiological and pathological mechanisms. The pathological deregulation of purinergic signaling contributes to various chronic respiratory diseases. Among the adenosine receptors, A2B has the lowest affinity such that it was long considered to have little pathophysiological significance. Many studies suggest that A2BAR plays protective roles during the early stage of acute inflammation. However, increased adenosine levels during chronic epithelial injury and inflammation might activate A2BAR, resulting in cellular effects relevant to the progression of pulmonary fibrosis.

The early and late intervention effects of collagen-binding FGF2 on elastase-induced lung injury

INTRODUCTION

Chronic obstructive pulmonary disease (COPD) has high morbidity and mortality, with no effective treatment at present. Emphysema, a major component of COPD, is a leading cause of human death worldwide. Fibroblast growth factor 2 (FGF2) is implicated in the pathogenesis of pulmonary emphysema and may play an important role in the lung repair process after injury, but concerns remain with respect to its effectiveness.

OBJECTIVE

In the present work, we sought to determine how the timing (early and late intervention) of sustained-release FGF2 system administration impacted its effectiveness on a porcine pancreatic elastase (PPE)-induced lung injury mouse model.

METHODS

To examine the early intervention efficiency of collagen-binding FGF2 (CBD-FGF2), mice received intratracheally nebulized CBD-FGF2 with concurrent intratracheal injection of PPE. To explore the late intervention effect, CBD-FGF2 was intratracheally aerosolized after PPE administration, and lungs were collected after CBD-FGF2 treatment for subsequent analysis.

RESULT

In response to PPE, mice had significantly increased alveolar diameter, collagen deposition and expression of inflammatory factors and decreased lung function indices and expression of alveolar epithelium markers. Our results indicate that CBD-FGF2 administration was able to prevent and repair elastase-induced lung injury partly through the suppression of the inflammatory response and recovery of the alveolar epithelium. The early use of CBD-FGF2 for the prevention of PPE-induced emphysema showed better results than late therapeutic administration against established emphysema.

CONCLUSION

These data provide insight regarding the prospective role of a drug-based option (CBD-FGF2) for preventing and curing emphysema.

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.

Elevation of Anticancer Drug Toxicity by Caffeine in Spheroid Model of Human Lung Adenocarcinoma A549 Cells Mediated by Reduction in Claudin-2 and Nrf2 Expression

Claudin-2 (CLDN2), a component of tight junctions, is abnormally expressed in human lung adenocarcinoma tissue. CLDN2 contributes to chemoresistance in human lung adenocarcinoma-derived A549 cells, and it may be a target for cancer therapy. Here, we found that coffee ingredients, namely caffeine and theobromine, decreased the protein level of CLDN2 in human lung adenocarcinoma-derived A549 cells. In contrast, other components, such as theophylline and chlorogenic acid, had no effect. These results indicate that the 7-methyl group in methylxanthines may play a key role in the reduction in CLDN2 expression. The caffeine-induced reduction in the CLDN2 protein was inhibited by chloroquine, a lysosome inhibitor. In a protein-stability assay using cycloheximide, CLDN2 protein levels decreased faster in caffeine-treated cells than in vehicle-treated cells. These results suggest that caffeine accelerates the lysosomal degradation of CLDN2. The accumulation and cytotoxicity of doxorubicin were dose-dependently increased, which was exaggerated by caffeine but not by theophylline in spheroids. Caffeine decreased nuclear factor-erythroid 2-related factor 2 (Nrf2) levels without affecting hypoxia-inducible factor-1α levels. Furthermore, caffeine decreased the expression of Nrf2-targeted genes. The effects of caffeine on CLDN2 expression and anticancer-drug-induced toxicity were also observed in lung adenocarcinoma RERF-LC-MS cells. We suggest that caffeine enhances doxorubicin-induced toxicity in A549 spheroids mediated by the reduction in CLDN2 and Nrf2 expression.

Cupping alleviates lung injury through the adenosine/A2BAR pathway

BACKGROUND

Acute lung injury (ALI) is a serious condition. Inflammation plays a crucial role in the pathogenesis of ALI. Cupping, as a part of traditional Chinese medicine, is still a popular complementary and alternative therapy for a variety of ailments including respiratory diseases. However, reliable scientific data about cupping therapy are scarce. Adenosine, a purine nucleoside produced under metabolic stress by the action of extracellular ectonucleotidases (i.e. CD39 and CD73), can attenuate ALI through the A2BAR receptor. The aim of this study was to investigate the protective effect of cupping in a rat model of ALI and the role of adenosine in it.

METHODS

Male adult rats were subjected to ALI by intratracheal LPS instillation (0.3 mg/kg). Immediately after intratracheal LPS instillation, vacuum pressure was applied to a sanitized plastic bell cup on the back of the rat by suction for 10 min. Pulmonary injury and inflammation were assessed at 4 h after LPS challenge. The role of adenosine and A2BAR in cupping's protection after LPS instillation were evaluated.

RESULTS

Cupping alleviated LPS-induced lung injury, reduced inflammation and inhibited NF-kB activation in rats. Cupping upregulated CD39 and CD73 mRNA expression of the skin tissue at the cupping site and increased circulating levels of adenosine. Administration of PSB1115, a specific adenosine A2BAR receptor antagonist, abolished cupping's beneficial effects in LPS-induced ALI.

CONCLUSIONS

Cupping attenuates lung inflammation and injury through the adenosine/A2BAR pathway. The current study provides evidence-based information about cupping therapy in ALI.

Effects of Para-Toluenesulfonamide on Canine Melanoma Xenotransplants in a BALB/c Nude Mouse Model

The pharmacological pathway of para-toluenesulfonamide (PTS) restricts the kinase activity of the mammalian target of rapamycin, potentially leading to reductions in cell division, cell growth, cell proliferation, and inflammation. These pathways have a critical effect on tumorigenesis. We aimed to examine the antitumor effect of PTS or PTS combined with cisplatin on canine melanoma implanted in BALB/c nude mice by estimating tumor growth, apoptosis expression, inflammation, and metastasis. The mice were randomly divided into four groups: control, cisplatin, PTS, and PTS combined with cisplatin. Mice treated with PTS or PTS combined with cisplatin had retarded tumor growth and increased tumor apoptosis through the enhanced expression of cleaved caspase 3 and extracellular signal-regulated kinase phosphorylation, decreased inflammatory cytokine levels, reduced inflammation-related factors, enhanced anti-inflammation-related factors, and inhibition of metastasis-related factors. Mice treated with PTS combined with cisplatin exhibited significantly retarded tumor growth, reduced tumor size, and increased tumor inhibition compared with those treated with cisplatin or PTS alone. PTS or PTS combined with cisplatin could retard canine melanoma growth and inhibit tumorigenesis. PTS and cisplatin were found to have an obvious synergistic tumor-inhibiting effect on canine melanoma. PTS alone and PTS combined with cisplatin may be antitumor agents for canine melanoma treatment.

The low affinity A2B adenosine receptor enhances migratory and invasive capacity in vitro and angiogenesis in vivo of glioblastoma stem-like cells

Glioblastoma (GBM) is the most common and deadly malignant brain tumor, with a median survival of 15 to 17 months for a patient. GBM contains a cellular subpopulation known as GBM stem-like cells (GSCs) that persist in hypoxic niches and are capable of infiltrating into healthy brain tissue. For this reason, GSCs are considered one of the main culprits for GBM recurrence. A hypoxic microenvironment increases extracellular adenosine levels, activating the low affinity A2B adenosine receptor (A_2BAR). Adenosine, through A_2BAR, is capable of modulating invasiveness. However, its role in the invasion/migration of hypoxic-GSCs is still unknown. This study aims to understand the importance of A_2BAR in modulating the migratory/invasive capacity of GSCs under hypoxia. Data analysis from The Cancer Genome Atlas (TCGA) program correlates A_2BAR expression with high-grade glioma and hypoxic necrotic areas. U87MG and primary culture-derived GSCs under hypoxic conditions (0.5% O₂) increased A_2BAR mRNA and protein levels. As expected, the migratory and invasive capacity of GSCs increased under hypoxia, which was counteracted by blocking A_2BAR, through the downregulation of MMP9 activity and epithelial–mesenchymal transition marker expression. Finally, in a xenograft mouse model, we demonstrate that treatment with MRS1754 did not affect the tumor volume but could decrease blood vessel formation and VEGF expression. Our results suggest that extracellular adenosine, through the activation of A_2BAR, enhances the migratory and invasive capacity of GSCs in vitro under hypoxic conditions. Targeting A_2BAR can be an effective therapy for GBM recurrence.

The crossroads of adenosinergic pathway and epithelial-mesenchymal plasticity in cancer

Epithelial-mesenchymal transition (EMT) is a key mechanism related to tumor progression, invasion, metastasis, resistance to therapy and poor prognosis in several types of cancer. However, targeting EMT or partial-EMT, as well as the molecules involved in this process, has remained a challenge. Recently, the CD73 enzyme, which hydrolyzes AMP to produce adenosine (ADO), has been linked to the EMT process. This relationship is not only due to the production of the immunosuppressant ADO but also to its role as a receptor for extracellular matrix proteins, being involved in cell adhesion and migration. This article reviews the crosstalk between the adenosinergic pathway and the EMT program and the impact of this interrelation on cancer development and progression. An in silico analysis of RNAseq datasets showed that several tumor types have a significant correlation between an EMT score and NT5E (CD73) and ENTPD1 (CD39) expressions, with the strongest correlations in prostate adenocarcinoma. Furthermore, it is evident that the cooperation between EMT and adenosinergic pathway in tumor progression is context and tumor-dependent. The increased knowledge about this topic will help broaden the view to explore new treatments and therapies for different types of cancer.

Synergistic effects of BAY606583 on docetaxel in esophageal cancer through modulation of ERK1/2

Docetaxel (DTX) is a taxane chemotherapy agent used to treat many types of cancers, including esophageal squamous cell carcinoma. Adenosine is a purinergic signaling molecule that contributes to cancer cell proliferation via A2B adenosine receptor (A2BAR) activation. Extracellular signal-regulated protein kinase (ERK) plays a crucial role in cell proliferation in various types of cancers. Stimulation of A2BAR involves a regulated ERK signaling pathway, and might provide a fascinating approach for treatment, leading to decreased proliferation in certain tumors that express A2BAR. Recent studies demonstrated that DTX and A2BAR have anticancer effects. The current study was designed to investigate the synergistic effect of the A2BAR agonist (BAY606583) on DTX in inducing antiproliferation effects on esophageal squamous cells carcinoma (ESCCs). The cell viability was assessed using the MTT assay in KYSE-30 and Ym-1 cells. In addition, the synergistic effect of DTX on the A2BAR agonist was evaluated. Subsequently, apoptosis was assessed by Annexin-V and propidium iodide staining, and Bcl-2, Bax, and ERK1/2 protein-level expressions were evaluated by Western blot. Use of BAY606583 and cotreatment of DTX and BAY606583 significantly decreased cell proliferation in KYSE-30 and Ym-1 cell lines. The use of BAY606583 and cotreatment of DTX with the A2BAR agonist induced apoptosis in KYSE-30 and Ym-1 cells. Western blot analysis revealed that the use of the A2BAR agonist and cotreatment of DTX with the A2BAR agonist inhibited the expression of apoptotic regulatory proteins as well as the expression of ERK1/2 proteins. Our findings suggested that use of BAY606583 and cotreatment of BAY606583/DTX have an antiproliferative effect on ESCC cell lines through ERK signaling pathway inhibition. BAY606583 has a synergistic effect on DTX, which could be used as an adjuvant for esophageal cancer therapy.

Suppression of tumor progression by thioredoxin-interacting protein-dependent adenosine 2B receptor degradation in a PLAG-treated Lewis lung carcinoma-1 model of non-small cell lung cancer

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PLAG effectively inhibited excessive growth of LLC1 cells in an NSCLC model.

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PLAG inhibited tumor growth by inducing adenosine 2B receptor (A2BR) degradation.

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Unlike antagonists, PLAG terminates rather than suppresses signaling pathways.

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A2BR degradation by PLAG occurs through expression and re-localization of TXNIP.

Extracellular adenosine in the tumor microenvironment plays a vital role in cancer development. Specifically, activation of adenosine receptors affects tumor cell growth and adenosine release.

We examined the anti-tumor efficacy of 1-palmitoyl-2-linoleoyl-3-acetyl-rac-glycerol (PLAG) in animal models, revealing the role of PLAG in inhibiting tumor progression by promoting the degradation of adenosine 2B receptors (A2BRs) in tumors. PLAG induced the expression of thioredoxin-interacting protein (TXNIP), a type of α-arrestin that accelerates A2BR internalization by interacting with A2BR complexes containing β-arrestin. Engulfed receptors bound to TXNIP were rapidly degraded after E3 ligase recruitment and ubiquitination, resulting in early termination of intracellular signals that promote tumor overgrowth. However, in control cancer cells, A2BRs bound to protein phosphatase 2A and were returned to the cell membrane instead of being degraded, resulting in continuous receptor-mediated signaling by pathways including the Raf-Erk axis, which promotes tumor proliferation. A TXNIP-silenced cell-implanted mouse model and TXNIP knockout (KO) mice were used to verify that PLAG-mediated suppression of tumor progression is dependent on TXNIP expression. Increased tumor growth was observed in TXNIP-silenced cell-implanted mice, and the anti-tumor effects of PLAG, including delayed tumor overgrowth, were greatly reduced. However, the anti-tumor effects of PLAG were observed in cancer cell-implanted TXNIP-KO mice, which indicates that PLAG produces anti-tumor effects by enhancing TXNIP expression in tumor cells.

These essential functions of PLAG, including delaying tumor growth via A2BR degradation, suggest innovative directions for anticancer drug development.

Adenosine Receptor A2B Negatively Regulates Cell Migration in Ovarian Carcinoma Cells

The purinergic system is fundamental in the tumor microenvironment, since it regulates tumor cell interactions with the immune system, as well as growth and differentiation in autocrine-paracrine responses. Here, we investigated the role of the adenosine A2B receptor (A2BR) in ovarian carcinoma-derived cells’ (OCDC) properties. From public databases, we documented that high A2BR expression is associated with a better prognostic outcome in ovarian cancer patients. In vitro experiments were performed on SKOV-3 cell line to understand how A2BR regulates the carcinoma cell phenotype associated with cell migration. RT-PCR and Western blotting revealed that the ADORA2B transcript (coding for A2BR) and A2BR were expressed in SKOV-3 cells. Stimulation with BAY-606583, an A2BR agonist, induced ERK1/2 phosphorylation, which was abolished by the antagonist PSB-603. Pharmacological activation of A2BR reduced cell migration and actin stress fibers; in agreement, A2BR knockdown increased migration and enhanced actin stress fiber expression. Furthermore, the expression of E-cadherin, an epithelial marker, increased in BAY-606583-treated cells. Finally, cDNA microarrays revealed the pathways mediating the effects of A2BR activation on SKOV-3 cells. Our results showed that A2BR contributed to maintaining an epithelial-like phenotype in OCDC and highlighted this purinergic receptor as a potential biomarker.

Extracellular ATP and adenosine in tumor microenvironment: Roles in epithelial-mesenchymal transition, cell migration, and invasion

Under nonpathological conditions, the extracellular nucleotide concentration remains constant and low (nM range) because of a close balance between ATP release and ATP consumption. This balance is completely altered in cancer disease. Adenine and uridine nucleotides are found in the extracellular space of tumors in high millimolar (mM) concentrations acting as extracellular signaling molecules. In general, although uridine nucleotides may be involved in different tumor cell responses, purinergic signaling in cancer is preferentially focused on adenine nucleotides and nucleosides. Extracellular ATP can bind to specific receptors (P receptors) triggering different responses, or it can be hydrolyzed by ectoenzymes bound to cell membranes to render the final product adenosine. The latter pathway plays an important role in the increase of adenosine in tumor microenvironment. In this study, we will focus on extracellular ATP and adenosine, their effects acting as ligands of specific receptors, activating ectoenzymes, and promoting epithelial-mesenchymal transition, migration, and invasion in cancer cells. Finding the roles that these nucleotides play in tumor microenvironment may be important to design new intervention strategies in cancer therapies.

Current Adenosinergic Therapies: What Do Cancer Cells Stand to Gain and Lose?

A key objective in immuno-oncology is to reactivate the dormant immune system and increase tumour immunogenicity. Adenosine is an omnipresent purine that is formed in response to stress stimuli in order to restore physiological balance, mainly via anti-inflammatory, tissue-protective, and anti-nociceptive mechanisms. Adenosine overproduction occurs in all stages of tumorigenesis, from the initial inflammation/local tissue damage to the precancerous niche and the developed tumour, making the adenosinergic pathway an attractive but challenging therapeutic target. Many current efforts in immuno-oncology are focused on restoring immunosurveillance, largely by blocking adenosine-producing enzymes in the tumour microenvironment (TME) and adenosine receptors on immune cells either alone or combined with chemotherapy and/or immunotherapy. However, the effects of adenosinergic immunotherapy are not restricted to immune cells; other cells in the TME including cancer and stromal cells are also affected. Here we summarise recent advancements in the understanding of the tumour adenosinergic system and highlight the impact of current and prospective immunomodulatory therapies on other cell types within the TME, focusing on adenosine receptors in tumour cells. In addition, we evaluate the structure- and context-related limitations of targeting this pathway and highlight avenues that could possibly be exploited in future adenosinergic therapies.

Pulmonary fibrosis from molecular mechanisms to therapeutic interventions: lessons from post-COVID-19 patients

Pulmonary fibrosis (PF) is characterised by several grades of chronic inflammation and collagen deposition in the interalveolar space and is a hallmark of interstitial lung diseases (ILDs). Recently, infectious agents have emerged as driving causes for PF development; however, the role of viral/bacterial infections in the initiation and propagation of PF is still debated. In this context, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus responsible for the current coronavirus disease 2019 (COVID-19) pandemic, has been associated with acute respiratory distress syndrome (ARDS) and PF development. Although the infection by SARS-CoV-2 can be eradicated in most cases, the development of fibrotic lesions cannot be precluded; furthermore, whether these lesions are stable or progressive fibrotic events is still unknown. Herein, an overview of the main molecular mechanisms driving the fibrotic process together with the currently approved and newly proposed therapeutic solutions was given. Then, the most recent data that emerged from post-COVID-19 patients was discussed, in order to compare PF and COVID-19-dependent PF, highlighting shared and specific mechanisms. A better understanding of PF aetiology is certainly needed, also to develop effective therapeutic strategies and COVID-19 pathology is offering one more chance to do it. Overall, the work reported here could help to define new approaches for therapeutic intervention in the diversity of the ILD spectrum.

Inhaled β2 Adrenergic Agonists and Other cAMP-Elevating Agents: Therapeutics for Alveolar Injury and Acute Respiratory Disease Syndrome?

Inhaled long-acting β-adrenergic agonists (LABAs) and short-acting β-adrenergic agonists are approved for the treatment of obstructive lung disease via actions mediated by β2 adrenergic receptors (β2-ARs) that increase cellular cAMP synthesis. This review discusses the potential of β2-AR agonists, in particular LABAs, for the treatment of acute respiratory distress syndrome (ARDS). We emphasize ARDS induced by pneumonia and focus on the pathobiology of ARDS and actions of LABAs and cAMP on pulmonary and immune cell types. β2-AR agonists/cAMP have beneficial actions that include protection of epithelial and endothelial cells from injury, restoration of alveolar fluid clearance, and reduction of fibrotic remodeling. β2-AR agonists/cAMP also exert anti-inflammatory effects on the immune system by actions on several types of immune cells. Early administration is likely critical for optimizing efficacy of LABAs or other cAMP-elevating agents, such as agonists of other Gs-coupled G protein-coupled receptors or cyclic nucleotide phosphodiesterase inhibitors. Clinical studies that target lung injury early, prior to development of ARDS, are thus needed to further assess the use of inhaled LABAs, perhaps combined with inhaled corticosteroids and/or long-acting muscarinic cholinergic antagonists. Such agents may provide a multipronged, repurposing, and efficacious therapeutic approach while minimizing systemic toxicity. SIGNIFICANCE STATEMENT: Acute respiratory distress syndrome (ARDS) after pulmonary alveolar injury (e.g., certain viral infections) is associated with ∼40% mortality and in need of new therapeutic approaches. This review summarizes the pathobiology of ARDS, focusing on contributions of pulmonary and immune cell types and potentially beneficial actions of β2 adrenergic receptors and cAMP. Early administration of inhaled β2 adrenergic agonists and perhaps other cAMP-elevating agents after alveolar injury may be a prophylactic approach to prevent development of ARDS.

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.

Novel positive allosteric modulators of A2B adenosine receptor acting as bone mineralisation promoters

Small-molecules acting as positive allosteric modulators (PAMs) of the A_2B adenosine receptor (A_2B AR) could potentially represent a novel therapeutic strategy for pathological conditions characterised by altered bone homeostasis, including osteoporosis. We investigated a library of compounds (4-13) exhibiting different degrees of chemical similarity with three indole derivatives (1-3), which have been recently identified by us as PAMs of the A_2B AR able to promote mesenchymal stem cell differentiation and bone formation. Evaluation of mineralisation activity of 4-13 in the presence and in the absence of the agonist BAY60-6583 allowed the identification of lead compounds with therapeutic potential as anti-osteoporosis agents. Further biological characterisation of one of the most performing compounds, the benzofurane derivative 9, confirmed that such a molecule behaves as PAM of the A_2B AR.

Proteome Characterization of BALF Extracellular Vesicles in Idiopathic Pulmonary Fibrosis: Unveiling Undercover Molecular Pathways

In the longtime challenge of identifying specific, easily detectable and reliable biomarkers of IPF, BALF proteomics is providing interesting new insights into its pathogenesis. To the best of our knowledge, the present study is the first shotgun proteomic investigation of EVs isolated from BALF of IPF patients. Our main aim was to characterize the proteome of the vesicular component of BALF and to explore its individual impact on the pathogenesis of IPF. To this purpose, ultracentrifugation was chosen as the EVs isolation technique, and their purification was assessed by TEM, 2DE and LC-MS/MS. Our 2DE data and scatter plots showed considerable differences between the proteome of EVs and that of whole BALF and of its fluid component. Analysis of protein content and protein functions evidenced that EV proteins are predominantly involved in cytoskeleton remodeling, adenosine signaling, adrenergic signaling, C-peptide signaling and lipid metabolism. Our findings may suggest a wider system involvement in the disease pathogenesis and support the importance of pre-fractioning of complex samples, such as BALF, in order to let low-abundant proteins-mediated pathways emerge.

Altered Expression of Candidate Genes in Mayer-Rokitansky-Küster-Hauser Syndrome May Influence Vaginal Keratinocytes Biology: A Focus on Protein Kinase X

Mayer-Rokitansky-Küster-Hauser (MRKH) syndrome is a rare and complex disease defined by congenital aplasia of the vagina and uterus in 46,XX women, often associated with kidney and urinary tract anomalies. The aetiopathogenesis of MRKH syndrome is still largely unknown. Herein, we investigated the role of selected candidate genes in the aetiopathogenesis of MRKH syndrome, with a focus on PRKX, which encodes for protein kinase X. Through RT-qPCR analyses performed on vaginal dimple samples from patients, and principal component analysis (PCA), we highlighted a phenotype-related expression pattern of PRKX, MUC1, HOXC8 and GREB1L in MRKH patients. By using an in vitro approach, we proved that PRKX ectopic overexpression in a cell model of vaginal keratinocytes promotes cell motility through epithelial-to-mesenchymal transition (EMT) activation, a fundamental process in urogenital tract morphogenesis. Moreover, our findings showed that PRKX upregulation in vaginal keratinocytes is able to affect transcriptional levels of HOX genes, implicated in urinary and genital tract development. Our study identified the dysregulation of PRKX expression as a possible molecular cause for MRKH syndrome. Moreover, we propose the specific role of PRKX in vaginal keratinocyte biology as one of the possible mechanisms underlying this complex disease.

The Anti-Cancer Effects of a Zotarolimus and 5-Fluorouracil Combination Treatment on A549 Cell-Derived Tumors in BALB/c Nude Mice

Zotarolimus is a semi-synthetic derivative of rapamycin and a novel immunosuppressive agent used to prevent graft rejection. The pharmacological pathway of zotarolimus restricts the kinase activity of the mammalian target of rapamycin (mTOR), which potentially leads to reductions in cell division, cell growth, cell proliferation, and inflammation. These pathways have a critical influence on tumorigenesis. This study aims to examine the anti-tumor effect of zotarolimus or zotarolimus combined with 5-fluorouracil (5-FU) on A549 human lung adenocarcinoma cell line implanted in BALB/c nude mice by estimating tumor growth, apoptosis expression, inflammation, and metastasis. We established A549 xenografts in nude mice, following which we randomly divided the mice into four groups: control, 5-FU (100 mg/kg/week), zotarolimus (2 mg/kg/day), and zotarolimus combined with 5-FU. Compared the results with those for control mice, we found that mice treated with zotarolimus or zotarolimus combined with 5-FU retarded tumor growth; increased tumor apoptosis through the enhanced expression of cleaved caspase 3 and extracellular signal-regulated kinase (ERK) phosphorylation; decreased inflammation cytokines levels (e.g., IL-1β, TNF-α, and IL-6); reduced inflammation-related factors such as cyclooxygenase-2 (COX-2) protein and nuclear factor-κB (NF-κB) mRNA; enhanced anti-inflammation-related factors including IL-10 and inhibitor of NF-κB kinase α (IκBα) mRNA; and inhibited metastasis-related factors such as transforming growth factor β (TGF-β), CD44, epidermal growth factor receptor (EGFR), and vascular endothelial growth factor (VEGF). Notably, mice treated with zotarolimus combined with 5-FU had significantly retarded tumor growth, reduced tumor size, and increased tumor inhibition compared with the groups of mice treated with 5-FU or zotarolimus alone. The in vivo study confirmed that zotarolimus or zotarolimus combined with 5-FU could retard lung adenocarcinoma growth and inhibit tumorigenesis. Zotarolimus and 5-FU were found to have an obvious synergistic tumor-inhibiting effect on lung adenocarcinoma. Therefore, both zotarolimus alone and zotarolimus combined with 5-FU may be potential anti-tumor agents for treatment of human lung adenocarcinoma.

Allosterism vs. Orthosterism: Recent Findings and Future Perspectives on A2B AR Physio-Pathological Implications

The development of GPCR (G-coupled protein receptor) allosteric modulators has attracted increasing interest in the last decades. The use of allosteric modulators in therapy offers several advantages with respect to orthosteric ones, as they can fine-tune the tissue responses to the endogenous agonist. Since the discovery of the first A₁ adenosine receptor (AR) allosteric modulator in 1990, several efforts have been made to develop more potent molecules as well as allosteric modulators for all adenosine receptor subtypes. There are four subtypes of AR: A₁, A_2A, A_2B, and A₃. Positive allosteric modulators of the A₁ AR have been proposed for the cure of pain. A₃ positive allosteric modulators are thought to be beneficial during inflammatory processes. More recently, A_2A and A_2B AR allosteric modulators have also been disclosed. The A_2B AR displays the lowest affinity for its endogenous ligand adenosine and is mainly activated as a consequence of tissue damage. The A_2B AR activation has been found to play a crucial role in chronic obstructive pulmonary disease, in the protection of the heart from ischemic injury, and in the process of bone formation. In this context, allosteric modulators of the A_2B AR may represent pharmacological tools useful to develop new therapeutic agents. Herein, we provide an up-to-date highlight of the recent findings and future perspectives in the field of orthosteric and allosteric A_2B AR ligands. Furthermore, we compare the use of orthosteric ligands with positive and negative allosteric modulators for the management of different pathological conditions.

LncRNA CHRF promotes TGF-β1 induced EMT in alveolar epithelial cells by inhibiting miR-146a up-regulating L1CAM expression

PURPOSE

Idiopathic pulmonary fibrosis (IPF) is a type of progressive lung fibrosis disease. The survival time of diagnosed IPF patients is often only 2 years. Currently much evidence showed that the epithelial-mesenchymal transition (EMT) process is the main cause of the occurrence and development of IPF. LncRNA cardiac hypertrophy related factor (CHRF) was reported to be related with IPF development. Here we explored the functions and regulatory mechanisms of CHRF on EMT in IPF.

MATERIALS AND METHODS

A549 cells were treated with transforming growth factor-β1 (TGF-β1) for 48 h to construct IPF cell model. CHRF and miR-146a expression were quantified using qPCR. The expression of L1 cell adhesion molecule (L1CAM) and EMT related indicators (E-cadherin, Vimentin, Slug and N-cadherin) were detected by qPCR and western blot. Dual luciferase reporter experiment was conducted to prove the molecular interaction of miR-146a and L1CAM, as well as CHRF and miR-146a.

RESULTS

CHRF and L1CAM expression were significantly upregulated and promoted the EMT process in A549 after treatment of TGF-β1. MiR-146a was obviously down-regulated, and knockdown of CHRF inhibited the EMT process by up-regulating miR-146a, in A549 after treatment of TGF-β1. Meanwhile, overexpression of miR-146a inhibited EMT process via targeting L1CAM. In addition, L1CAM overexpression eliminated the inhibitory effect of sh-CHRF on the EMT process.

CONCLUSIONS

These results provided evidence that CHRF promoted EMT process in A549 after treatment of TGF-β1, which proposed a new insight for depth understanding the pathological mechanisms of IPF.

Platelet-derived growth factor-B signalling might promote epithelial-mesenchymal transition in gastric carcinoma cells through activation of the MAPK/ERK pathway

Introduction

Epithelial-mesenchymal transition (EMT) is important in the metastasis of tumours and is triggered by several key growth factors, including platelet-derived growth factor-B (PDGF-B). But, whether PDGF-B signalling promotes EMT in gastric carcinoma cells is still unknown.

Material and methods

We established 2 gastric carcinoma cell lines (MKN28 and MKN45) to stably overexpress PDGF-B by lentiviral vectors, and expression of E-cadherin, N-cadherin, and ERK-1 were detected by western blot assay. Then, PDGF-B overexpression and normal MKN28 and MKN45 cells were cocultured with PDGFR-b positive fibroblast (hs738) and MAPK inhibitors were added; also, the expressions of ERK-1, E-cadherin, and N-cadherin were detected by western blot assay.

Results

After being cocultured with hs738 cells, expressions of ERK-1 and N-cadherin protein in PDGF-B overexpression MKN28 and MKN45 cells were much higher than normal MKN28 and MKN45 cells (p < 0.05), and those could be decreased by MAPK inhibitor. Also, expressions of E-cadherin protein in PDGF-B overexpression MKN28 and MKN45 cells were much lower than normal MKN28 and MKN45 cells (p < 0.05), and they could be increased by MAPK inhibitor.

Conclusions

Our data indicate that PDGF-B signalling can induce EMT in gastric carcinoma cells. Thr tumour microenvironment is imperative in the process of PDGF-B signalling inducing EMT in gastric carcinoma cells. Also, activation of MAPK/ERK pathway, which is a downstream pathway of PDGF-B signalling, might participate in this process.

CD73 facilitates EMT progression and promotes lung metastases in triple-negative breast cancer

CD73 is a cell surface ecto-5′-nucleotidase, which converts extracellular adenosine monophosphate to adenosine. High tumor CD73 expression is associated with poor outcome among triple-negative breast cancer (TNBC) patients. Here we investigated the mechanisms by which CD73 might contribute to TNBC progression. This was done by inhibiting CD73 with adenosine 5′-(α, β-methylene) diphosphate (APCP) in MDA-MB-231 or 4T1 TNBC cells or through shRNA-silencing (sh-CD73). Effects of such inhibition on cell behavior was then studied in normoxia and hypoxia in vitro and in an orthotopic mouse model in vivo. CD73 inhibition, through shRNA or APCP significantly decreased cellular viability and migration in normoxia. Inhibition of CD73 also resulted in suppression of hypoxia-induced increase in viability and prevented cell protrusion elongation in both normoxia and hypoxia in cancer cells. Sh-CD73 4T1 cells formed significantly smaller and less invasive 3D organoids in vitro, and significantly smaller orthotopic tumors and less lung metastases than control shRNA cells in vivo. CD73 suppression increased E-cadherin and decreased vimentin expression in vitro and in vivo, proposing maintenance of a more epithelial phenotype. In conclusion, our results suggest that CD73 may promote early steps of tumor progression, possibly through facilitating epithelial–mesenchymal transition.

Tackling Immune Targets for Breast Cancer: Beyond PD-1/PD-L1 Axis

The burden of breast cancer is imposing a huge global problem. Drug discovery research and novel approaches to treat breast cancer have been carried out extensively over the last decades. Although immune checkpoint inhibitors are showing promising preclinical and clinical results in treating breast cancer, they are facing multiple limitations. From an immunological perspective, a recent report highlighted breast cancer as an "inflamed tumor" with an immunosuppressive microenvironment. Consequently, researchers have been focusing on identifying novel immunological targets that can tune up the tumor immune microenvironment. In this context, several novel non-classical immune targets have been targeted to determine their ability to uncouple immunoregulatory pathways at play in the tumor microenvironment. This article will highlight strategies designed to increase the immunogenicity of the breast tumor microenvironment. It also addresses the latest studies on targets which can enhance immune responses to breast cancer and discusses examples of preclinical and clinical trial landscapes that utilize these targets.

Co-inhibition of CD73 and ADORA2B Improves Long-Term Cigarette Smoke Induced Lung Injury

Adenosine (ADO) involvement in lung injury depends on the activation of its receptors. The ADO A_2A receptor (ADORA2A) and A_2B receptor (ADORA2B) are best described to have both tissue-protective and tissue-destructive processes. However, no approach has been effective in delineating the mechanism(s) involved with ADO shifting from its tissue-protective to tissue-destructive properties in chronic airway injury. Using cigarette smoke (CS) as our model of injury, we chronically exposed Nuli-1 cells to 5% CS extract (CSE) for 3 years establishing a long-term CSE exposure model (LTC). We found significant morphological changes, decreased proliferation, and migration resulting in impaired airway wound closure in LTC. Further investigations showed that long-term CSE exposure upregulates CD73 and ADORA2B expression, increases ADO production, inhibits PKC alpha activity and p-ERK signaling pathway. Knocking down ADORA2B and/or CD73 in LTC activates PKC alpha and increases p-ERK signaling. Knocking down both showed better improvement in wound repair than either alone. In vivo experiments also showed that double knockout CD73 and ADORA2B remarkably improved CS-induced lung injury by activating PKC alpha, reducing the inflammatory cell number in bronchoalveolar lavage fluid and the production of inflammatory mediator IL-6, inhibiting the fibrosis-like lesions and decreasing collagen deposition surrounding bronchioles. Collectively, long-term CSE exposure upregulates CD73 expression and increases ADO production, which promotes low affinity ADORA2B activation and subsequent diminution of PKC alpha activity and ERK signaling pathway, and inhibition of airway wound repair. Moreover, the data suggesting ADORA2B and CD73 as potential therapeutic targets may be more efficacious in improving chronic CS lung diseases and impaired wound repair.

Role of β2-adrenergic receptors in chronic obstructive pulmonary disease

Beta-2 adrenergic receptors (β2-ARs) have important roles in the pathogenesis and treatment of chronic obstructive pulmonary disease (COPD). In recent years, progress has been made in the study of β2-ARs. Here, we introduce the basic concepts of β2-ARs, related pathways, as well as application of blockers/agonists of β2-ARs, and β2-AR autoantibodies in COPD. Drugs targeting the β2-AR are being developed rapidly, and we expect them to improve the symptoms and prognosis of COPD patients in the future.

Enzymatic Activity of CD73 Modulates Invasion of Gliomas via Epithelial-Mesenchymal Transition-Like Reprogramming

Glioblastoma (GBM) is the most aggressive malignant primary brain tumour in adulthood. Despite strong research efforts current treatment options have a limited impact on glioma stem-like cells (GSCs) which contribute to GBM formation, progression and chemoresistance. Invasive growth of GSCs is in part associated with epithelial-mesenchymal-like transition (EMT), a mechanism associated with CD73 in several cancers. Here, we show that CD73 regulates the EMT activator SNAIL1 and further investigate the role of enzymatic and non-enzymatic CD73 activity in GBM progression. Reduction of CD73 protein resulted in significant suppression of GSC viability, proliferation and clonogenicity, whereas CD73 enzymatic activity exhibited negative effects only on GSC invasion involving impaired downstream adenosine (ADO) signalling. Furthermore, application of phosphodiesterase inhibitor pentoxifylline, a potent immunomodulator, effectively inhibited ZEB1 and CD73 expression and significantly decreased viability, clonogenicity, and invasion of GSC in vitro cultures. Given the involvement of adenosine and A3 adenosine receptor in GSC invasion, we investigated the effect of the pharmacological inhibition of A3AR on GSC maintenance. Direct A3AR inhibition promoted apoptotic cell death and impaired the clonogenicity of GSC cultures. Taken together, our data indicate that CD73 is an exciting novel target in GBM therapy. Moreover, pharmacological interference, resulting in disturbed ADO signalling, provides new opportunities to innovate GBM therapy.

MiR-503 suppresses fibroblast activation and myofibroblast differentiation by targeting VEGFA and FGFR1 in silica-induced pulmonary fibrosis

Inhalation and deposition of crystalline silica particles in the lung can cause pulmonary fibrosis, then leading to silicosis. Given the paucity of effective drugs for silicosis, new insights for understanding the mechanisms of silicosis, including lung fibroblast activation and myofibroblast differentiation, are essential to explore therapeutic strategies. Our previous research showed that the up-regulation of miR-503 alleviated silica-induced pulmonary fibrosis in mice. In this study, we investigated whether miR-503 can regulate the TGF-β1-induced effects in lung fibroblasts. Mimic-based strategies aiming at up-regulating miR-503 were used to discuss the function of miR-503 in vivo and in vitro. We found that the expression level of miR-503 was decreased in fibroblasts stimulated by TGF-β1, and the up-regulation of miR-503 reduced the release of fibrotic factors and inhibited the migration and invasion abilities of fibroblasts. Combined with the up-regulation of miR-503 in a mouse model of silica-induced pulmonary fibrosis, we revealed that miR-503 mitigated the TGF-β1-induced effects in fibroblasts by regulating VEGFA and FGFR1 and then affecting the MAPK/ERK signalling pathway. In conclusion, miR-503 exerted protective roles in silica-induced pulmonary fibrosis and may represent a novel and potent candidate for therapeutic strategies in silicosis.

High Adenosine Extracellular Levels Induce Glioblastoma Aggressive Traits Modulating the Mesenchymal Stromal Cell Secretome

Glioblastoma is an aggressive, fast-growing brain tumor influenced by the composition of the tumor microenvironment (TME) in which mesenchymal stromal cell (MSCs) play a pivotal role. Adenosine (ADO), a purinergic signal molecule, can reach up to high micromolar concentrations in TME. The activity of specific adenosine receptor subtypes on glioma cells has been widely explored, as have the effects of MSCs on tumor progression. However, the effects of high levels of ADO on glioma aggressive traits are still unclear as is its role in cancer cells-MSC cross-talk. Herein, we first studied the role of extracellular Adenosine (ADO) on isolated human U343MG cells as a glioblastoma cellular model, finding that at high concentrations it was able to prompt the gene expression of Snail and ZEB1, which regulate the epithelial-mesenchymal transition (EMT) process, even if a complete transition was not reached. These effects were mediated by the induction of ERK1/2 phosphorylation. Additionally, ADO affected isolated bone marrow derived MSCs (BM-MSCs) by modifying the pattern of secreted inflammatory cytokines. Then, the conditioned medium (CM) of BM-MSCs stimulated with ADO and a co-culture system were used to investigate the role of extracellular ADO in GBM-MSC cross-talk. The CM promoted the increase of glioma motility and induced a partial phenotypic change of glioblastoma cells. These effects were maintained when U343MG cells and BM-MSCs were co-cultured. In conclusion, ADO may affect glioma biology directly and through the modulation of the paracrine factors released by MSCs overall promoting a more aggressive phenotype. These results point out the importance to deeply investigate the role of extracellular soluble factors in the glioma cross-talk with other cell types of the TME to better understand its pathological mechanisms.

Cryptochrome 1 Alleviates the Antiproliferative Effect of Isoproterenol on Human Gastric Cancer Cells

Background:

Cryptochrome 1 (CRY1) is a key protein that regulates the feedback loop of circadian clock. The abnormal expression of CRY1 was reported in numerous cancers, and contributed to tumorigenesis and progression. But the underlying mechanism remains undefined.

Methods:

CRY1 overexpression was constructed by lentivirus vector. Gene and protein expression was detected by reverse transcription quantitative polymerase chain reaction and Western blot. Cell proliferation was analyzed by CCK-8 assay. Cell migration ability was analyzed by scratch assay and transwell migration assay. The cAMP concentration was measured by intracellular cAMP assay.

Results:

Overexpression of CRY1 showed slightly effect on the proliferation and migration of HGC-27 cells. Upon exposure to isoproterenol (ISO), a β-adrenergic receptor agonist, cell proliferation, and migration were inhibited while the cAMP/PKA pathway was activated and ERK1/2 phosphorylation was suppressed. CRY1 overexpression reduced cAMP accumulation, retained ERK1/2 phosphorylation level and alleviated the antiproliferative effect upon exposure to ISO. However, CRY1 overexpression was inoperative on the antiproliferative effect of forskolin (FSK), a direct activator of adenyl cyclase (AC), or 3-isobutyl-1-methylxanthine (IBMX), a phosphodiesterase (PDE) inhibitor.

Conclusions:

Our results suggest CRY1 overexpression may protect cells from the antiproliferative effects via activation of the cAMP/PKA pathway through interrupting signal transduction from G protein-coupled receptors to AC.

Using Cytometry for Investigation of Purinergic Signaling in Tumor-Associated Macrophages

Tumor-associated macrophages are widely recognized for their importance in guiding pro-tumoral or antitumoral responses. Mediating inflammation or immunosuppression, these cells support many key events in cancer progression: cell growth, chemotaxis, invasiveness, angiogenesis and cell death. The communication between cells in the tumor microenvironment strongly relies on the secretion and recognition of several molecules, including damage-associated molecular patterns (DAMPs), such as adenosine triphosphate (ATP). Extracellular ATP (eATP) and its degradation products act as signaling molecules and have extensively described roles in immune response and inflammation, as well as in cancer biology. These multiple functions highlight the purinergic system as a promising target to investigate the interplay between macrophages and cancer cells. Here, we reviewed purinergic signaling pathways connecting cancer cells and macrophages, a yet poorly investigated field. Finally, we present a new tool for the characterization of macrophage phenotype within the tumor. Image cytometry emerges as a cutting-edge tool, capable of providing a broad set of information on cell morphology, expression of specific markers, and its cellular or subcellular localization, preserving cell-cell interactions within the tumor section and providing high statistical strength in small-sized experiments. Thus, image cytometry allows deeper investigation of tumor heterogeneity and interactions between these cells. © 2020 International Society for Advancement of Cytometry.

Purinergic Signaling in the Hallmarks of Cancer

Cancer is a complex expression of an altered state of cellular differentiation associated with severe clinical repercussions. The effort to characterize this pathological entity to understand its underlying mechanisms and visualize potential therapeutic strategies has been constant. In this context, some cellular (enhanced duplication, immunological evasion), metabolic (aerobic glycolysis, failure in DNA repair mechanisms) and physiological (circadian disruption) parameters have been considered as cancer hallmarks. The list of these hallmarks has been growing in recent years, since it has been demonstrated that various physiological systems misfunction in well-characterized ways upon the onset and establishment of the carcinogenic process. This is the case with the purinergic system, a signaling pathway formed by nucleotides/nucleosides (mainly adenosine triphosphate (ATP), adenosine (ADO) and uridine triphosphate (UTP)) with their corresponding membrane receptors and defined transduction mechanisms. The dynamic equilibrium between ATP and ADO, which is accomplished by the presence and regulation of a set of ectonucleotidases, defines the pro-carcinogenic or anti-cancerous final outline in tumors and cancer cell lines. So far, the purinergic system has been recognized as a potential therapeutic target in cancerous and tumoral ailments.

Kinase inhibitors in the treatment of obstructive pulmonary diseases

Chronic pulmonary diseases, including chronic obstructive pulmonary disease (COPD) and asthma, are major causes of death and reduced quality of life. Characteristic of chronic pulmonary disease is excessive lung inflammation that occurs in response to exposure to inhaled irritants, chemicals, and allergens. Chronic inflammation leads to remodeling of the airways that includes excess mucus secretion, proliferation of smooth muscle cells, increased deposition of extracellular matrix proteins and fibrosis. Protein kinases have been implicated in mediating inflammatory signals and airway remodeling associated with reduced lung function in chronic pulmonary disease. This review will highlight the role of protein kinases in the lung during chronic inflammation and examine opportunities to use protein kinase inhibitors for the treatment of chronic pulmonary diseases.