N6-methyladenosine-associated prognostic pseudogenes contribute to predicting immunotherapy benefits and therapeutic agents in head and neck squamous cell carcinoma.

Rationale: N6-methyladenosine (m6A) is involved in critical cancerous processes. Pseudogenes play various roles in carcinogenesis and progression. However, the functional roles of m6A-associated pseudogenes in head and neck squamous cell carcinoma (HNSCC) are largely unknown. Methods: We systematically analyzed the mRNA profile of 24 m6A regulators and 13931 pseudogenes from The Cancer Genome Atlas HNSCC dataset and ultimately identified 10 m6A-associated prognostic pseudogenes, which were validated in the Gene Expression Omnibus and our hospital datasets. Based on the risk score of m6A-associated pseudogenes, comprehensive analytical frameworks and experimental validation were implemented among pseudogene-defined low-/high-risk subtypes. Results: Here, we found expression pattern of m6A-associated pseudogenes was significantly associated with infiltrating immune cell compositions, and the expression of antitumor immune response markers, including T cell exhaustion, antigen presentation, interferon, and kinase genes. The m6A-associated pseudogenes, which had dramatic m6A peaks and higher m6A levels, could regulate the expression of targeted immune-involved genes through miRNAs. We experimentally validate the oncogene PDIA3P1, and tumor-suppressor RRN3P3, which promote the RNA and protein expression of their targeted immune-involved genes AKT1 and EZH2 via miR-34a-5p and miR-26b-5p, respectively. Moreover, HNSCC patients in the high-risk subtype could benefit more from immune checkpoint inhibitors therapy. Furthermore, doxorubicin and topotecan were considered to hold the most promising therapeutic potential robustly in silico evidence and in vitro experiments for HNSCC patients in the high-risk subtype. Conclusions: Our discovery revealed that the 10 m6A-associated prognostic pseudogenes significantly contribute to predicting immunotherapy benefits and therapeutic agents, which might bring some potential implications for both immunotherapy and chemotherapy in HNSCC.

The adenosinergic signaling in the pathogenesis and treatment of multiple sclerosis.

Multiple sclerosis (MS) is a highly disabling, progressive neurodegenerative disease with no curative treatment available. Although significant progress has been made in understanding how MS develops, there remain aspects of disease pathogenesis that are yet to be fully elucidated. In this regard, studies have shown that dysfunctional adenosinergic signaling plays a pivotal role, as patients with MS have altered levels adenosine (ADO), adenosine receptors and proteins involved in the generation and termination of ADO signaling, such as CD39 and adenosine deaminase (ADA). We have therefore performed a literature review regarding the involvement of the adenosinergic system in the development of MS and propose mechanisms by which the modulation of this system can support drug development and repurposing.

Immune Infiltration of Ulcerative Colitis and Detection of the m6A Subtype.

Ulcerative colitis (UC) is an inflammatory bowel disease characterized by persistent colon inflammation. N6-methyladenosine (m6A) methylation is one of the most prevalent RNA modifications with key roles in both normal and illness, but m6A methylation in ulcerative colitis is unknown. This research investigated m6A methylation in UC. We examined the expression of known m6A RNA methylation regulators in UC using the Gene Expression Omnibus database (GEO database). First, we used m6A regulators to examine m6A change in UC samples. These two patient groups were created by clustering three m6A gene expression datasets. These genes were then utilized to build an m6A gene network using WGCNA and PPI. These networks were built using differentially expressed genes. The 12 m6A regulators were found to be dispersed throughout the chromosome. The study's data were then connected, revealing positive or negative relationships between genes or signaling pathways. Then, PCA of the 12 m6A-regulated genes indicated that the two patient groups could be discriminated in both PC1 and PC2 dimensions. The ssGSEA algorithm found that immune invading cells could be easily distinguished across diverse patient groups. Both groups had varied levels of popular cytokines. The differential gene analysis of the two samples yielded 517 genes like FTO and RFX7. It found 9 hub genes among 121 genes in the blue module, compared their expression in two groups of samples, and found that the differences in expression of these 9 genes were highly significant. The identification of 9 possible m6A methylation-dependent gene regulatory networks suggests that m6A methylation is involved in UC pathogenesis. Nine candidate genes have been identified as possible markers for assessing UC severity and developing innovative UC targeted therapeutic approaches.

Decreased Expression of Programmed Death Ligand-L1 by Seven in Absentia Homolog 2 in Cholangiocarcinoma Enhances T-Cell-Mediated Antitumor Activity.

N6-methyladenosine (m6A) has been reported as an important mechanism of post-transcriptional regulation. Programmed death ligand 1 (PD-L1) is a primary immune inhibitory molecule expressed on tumor cells that promotes immune evasion. In addition, seven in absentia homolog 2 (Siah2), a RING E3 ubiquitin ligase, has been involved in tumorigenesis and cancer progression. However, the role of m6A-METTL14-Siah2-PD-L1 axis in immunotherapy remains to be elucidated. In this study, we showed that METTL14, a component of the m6A methyltransferase complex, induced Siah2 expression in cholangiocarcinoma (CCA). METTL14 was shown to enrich m6A modifications in the 3'UTR region of the Siah2 mRNA, thereby promoting its degradation in an YTHDF2-dependent manner. Furthermore, co-immunoprecipitation experiments demonstrated that Siah2 interacted with PD-L1 by promoting its K63-linked ubiquitination. We also observed that in vitro and in vivo Siah2 knockdown inhibited T cells expansion and cytotoxicity by sustaining tumor cell PD-L1 expression. The METTL14-Siah2-PD-L1-regulating axis was further confirmed in human CCA specimens. Analysis of specimens from patients receiving anti-PD1 immunotherapy suggested that tumors with low Siah2 levels were more sensitive to anti-PD1 immunotherapy. Taken together, our results evidenced a new regulatory mechanism of Siah2 by METTL14-induced mRNA epigenetic modification and the potential role of Siah2 in cancer immunotherapy.

Fighting in a wasteland: deleterious metabolites and antitumor immunity.

As cancers progress, they produce a local environment that acts to redirect, paralyze, exhaust, or otherwise evade immune detection and destruction. The tumor microenvironment (TME) has long been characterized as a metabolic desert, depleted of essential nutrients such as glucose, oxygen, and amino acids, that starves infiltrating immune cells and renders them dysfunctional. While not incorrect, this perspective is only half the picture. The TME is not a metabolic vacuum, only consuming essential nutrients and never producing by-products. Rather, the by-products of depleted nutrients, "toxic" metabolites in the TME such as lactic acid, kynurenine, ROS, and adenosine, play an important role in shaping immune cell function and cannot be overlooked in cancer immunotherapy. Moreover, while the metabolic landscape is distinct, it is not unique, as these toxic metabolites are encountered in non-tumor tissues, where they evolutionarily shape immune cells and their response. In this Review, we discuss how depletion of essential nutrients and production of toxic metabolites shape the immune response within the TME and how toxic metabolites can be targeted to improve current cancer immunotherapies.

Comprehensive Analysis of m6A RNA Methylation Regulators and the Immune Microenvironment to Aid Immunotherapy in Pancreatic Cancer.

Pancreatic cancer (PAAD) is one of the most malignant cancers and immune microenvironment has been proved to be involved in pathogenesis of PAAD. m6A modification, related to the expression of m6A regulators, participates in the development of multiple cancers. However, the correlation between m6A regulators and immune microenvironment was largely unknown in PAAD. And because of the small sample size of pancreatic cancer in the TCGA database, it is not enough to draw a convincing conclusion. In the present study, we downloaded seven pancreatic cancer datasets with survival data and removed batch effects among these datasets to be used as the PAAD cohort to analyze the immune landscape of PAAD and the expression pattern of m6A regulators and divided the integrated dataset into cluster 1 and cluster 2 by consensus clustering for m6A regulators. Lower m6A regulators were found to be related to higher immune cell infiltration and a better survival. Moreover, we identified six m6A regulators and constructed the prognostic signature of m6A regulators. Patients with low-risk score had a higher response to immune checkpoint inhibitor and a longer overall survival. To figure out the underlying mechanism, we analyzed the cancer immunity cycle, most altered genes, gene set enrichment analysis (GSEA) and gene set variation analysis (GSVA) in risk subtypes. In summary, the present study proved m6A regulators modulated the PAAD immune microenvironment. And risk scores served as predictive indicator for immunotherapy and played a prognostic role for PAAD patients. Our study provided novel therapeutic targets to improve immunotherapy efficacy.

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.

Expression of N6-methyladenosine (m6A) regulators correlates with immune microenvironment characteristics and predicts prognosis in diffuse large cell lymphoma (DLBCL).

This study conducted a comprehensive analysis of the clinical significance of N6-methyladenosine (m6A) regulators and their relationship with immune microenvironment characteristics in diffuse large cell lymphoma (DLBCL). Consensus clustering was performed to molecularly discriminate DLBCL subtypesbased on m6A regulators' expression. Using the Cox and Lasso regression algorithm, survival-associated m6A regulators were identified, and a m6A-based prognostic signature was established. The influence of m6A risk on immune cell infiltration, immune checkpoint genes, cancer immunity cycle, and immunotherapeutic response was evaluated. Potential molecular pathways related to m6A risk were investigated using gene set enrichment analysis. The m6A regulators showed satisfactory performance in distinguishing DLBCL subgroups with distinct clinical traits and outcomes. A six m6A regulator-based prognostic signature was established and validated as an independent predictor, which separated patients into low- and high-risk groups. High-risk m6A indicated worse survival. The B cells naïve, T cells gamma delta, and NK cells resting were the three most affected immune cells by m6A risk. Up-regulated (PDCD1 and KIR3DL1) and down-regulated (TIGIT, IDO1, and BTLA) immune checkpoint genes in the high-risk group were identified. The m6A risk was found to influence several steps in the cancer immunity cycle. Patients with high-risk m6A were more likely to benefit from immunotherapy. Biological function enrichment analysis revealed that high-risk m6A to be tended related to malignant tumor characteristics, while low-risk m6A showed trend to be related to defensive response processes. Collectively, the m6A-based prognostic signature could be a practical prognostic predictor for DLBCL and immune microenvironment characteristics affected by m6A may be part of the mechanism.

N6-Methyladenosine in Cancer Immunotherapy: An Undervalued Therapeutic Target.

N6-methylation of adenosine (m6A), a post-transcriptional regulatory mechanism, is the most abundant nucleotide modification in almost all types of RNAs. The biological function of m6A in regulating the expression of oncogenes or tumor suppressor genes has been widely investigated in various cancers. However, recent studies have addressed a new role of m6A modification in the anti-tumor immune response. By modulating the fate of targeted RNA, m6A affects tumor-associated immune cell activation and infiltration in the tumor microenvironment (TME). In addition, m6A-targeting is found to affect the efficacy of classical immunotherapy, which makes m6A a potential target for immunotherapy. Although m6A modification together with its regulators may play the exact opposite role in different tumor types, targeting m6A regulators has been shown to have wide implications in several cancers. In this review, we discussed the link between m6A modification and tumor with an emphasis on the importance of m6A in anti-tumor immune response and immunotherapy.

RNA N6 -methyladenosine modification in the lethal teamwork of cancer stem cells and the tumor immune microenvironment: Current landscape and therapeutic potential.

N6 -methyladenosine (m6 A), the newest and most prevalent layer of internal epigenetic modification in eukaryotic mRNA, has been demonstrated to play a critical role in cancer biology. Increasing evidence has highlighted that the interaction between cancer stem cells (CSCs) and the tumor immune microenvironment (TIME) is the root cause of tumorigenesis, metastasis, therapy resistance, and recurrence. In recent studies, the m6 A modification has been tightly linked to this CSC-TIME interplay, participating in the regulation of CSCs and TIME remolding. Interestingly, the m6 A modification has also been identified as a novel decisive factor in the efficacy of immunotherapies-particularly anti-PD-1/PD-L1 monotherapies-by changing the plasticity of the TIME. Given the functional importance of the m6 A modification in the crosstalk between CSCs and the TIME, targeting m6 A regulators will open new avenues to overcome therapeutic resistance, especially for immune checkpoint-based immunotherapy. In the present review, we summarize the current landscape of m6 A modifications in CSCs and the TIME, and also prospect the underling role of m6 A modifications at the crossroads of CSCs and the TIME for the first time. Additionally, to provide the possibility of modulating m6 A modifications as an emerging therapeutic strategy, we also explore the burgeoning inhibitors and technologies targeting m6 A regulators. Lastly, considering recent advances in m6 A-seq technologies and cancer drug development, we propose the future directions of m6 A modification in clinical applications, which may not only help to improve individualized monitoring and therapy but also provide enhanced and durable responses in patients with insensitive tumors.

Sepsis expands a CD39+ plasmablast population that promotes immunosuppression via adenosine-mediated inhibition of macrophage antimicrobial activity.

Sepsis results in elevated adenosine in circulation. Extracellular adenosine triggers immunosuppressive signaling via the A2a receptor (A2aR). Sepsis survivors develop persistent immunosuppression with increased risk of recurrent infections. We utilized the cecal ligation and puncture (CLP) model of sepsis and subsequent infection to assess the role of adenosine in post-sepsis immune suppression. A2aR-deficient mice showed improved resistance to post-sepsis infections. Sepsis expanded a subset of CD39hi B cells and elevated extracellular adenosine, which was absent in mice lacking CD39-expressing B cells. Sepsis-surviving B cell-deficient mice were more resistant to secondary infections. Mechanistically, metabolic reprogramming of septic B cells increased production of ATP, which was converted into adenosine by CD39 on plasmablasts. Adenosine signaling via A2aR impaired macrophage bactericidal activity and enhanced interleukin-10 production. Septic individuals exhibited expanded CD39hi plasmablasts and adenosine accumulation. Our study reveals CD39hi plasmablasts and adenosine as important drivers of sepsis-induced immunosuppression with relevance in human disease.

Adenosine: The common target between cancer immunotherapy and glaucoma in the eye.

Adenosine, an endogenous purine nucleoside, is a well-known actor of the immune system and the inflammatory response both in physiologic and pathologic conditions. By acting upon particular, G-protein coupled adenosine receptors, i.e., A1, A2- a & b, and A3 receptors mediate a variety of intracellular and immunomodulatory actions. Several studies have elucidated Adenosine's effect and its up-and downstream molecules and enzymes on the anti-tumor response against several types of cancers. We have also targeted a couple of molecules to manipulate this pathway and get the immune system's desired response in our previous experiences. Besides, the outgrowth of the studies on ocular Adenosine in recent years has significantly enhanced the knowledge about Adenosine and its role in ocular immunology and the inflammatory response of the eye. Glaucoma is the second leading cause of blindness globally, and the recent application of Adenosine and its derivatives has shown the critical role of the adenosine pathway in its pathophysiology. However, despite a very promising background, the phase III clinical trial of Trabodenoson failed to achieve the non-inferiority goals of the study. In this review, we discuss different aspects of the abovementioned pathway in ophthalmology and ocular immunology; following a brief evaluation of the current immunotherapeutic strategies, we try to elucidate the links between cancer immunotherapy and glaucoma in order to introduce novel therapeutic targets for glaucoma.

End-labeling-based electrochemical strategy for detection of adenine methylation in nucleic acid by differential pulse voltammetry.

A promising electrochemical strategy for assay of N6-methyladenosine (m6A)/N6-methyladenine (6mA) in RNA/DNA is proposed. The key of this strategy is the end-labeling of nucleic acid, which makes it possible to detect methylation level in unknown sequence. Firstly, the end of m6A-RNA or 6mA-DNA was labeled with sulfhydryl group through T4 polynucleotide kinase (T4 PNK) and then directly assembled on a gold nanoparticle-modified glassy carbon electrode (AuNPs/GCE). Secondly, methylation sites in RNA/DNA were specifically recognized by anti-m6A-antibody, and then, horseradish peroxidase-labeled goat anti-rabbit IgG (HRP-IgG) was further conjugated on the antibody. Thirdly, HRP-IgG catalyzed the hydroquinone oxidation reaction to generate amplified current signal which correlates with the amount of m6A/6mA in nucleic acid. This method showed a wide linear range from 0.0001 to 10 nM for m6A-RNA, 0.001 to 100 nM for 6mA-dsDNA, and 0.0001 to 10 nM for 6mA-ssDNA. The method was successfully applied to detection of m6A/6mA in RNA/DNA from HeLa cells and E. coli cells and validation of the decrease of m6A-RNA in HeLa cells after treatment with FTO protein.

The m6A reader IMP2 directs autoimmune inflammation through an IL-17- and TNFα-dependent C/EBP transcription factor axis.

Excessive cytokine activity underlies many autoimmune conditions, particularly through the interleukin-17 (IL-17) and tumor necrosis factor-α (TNFα) signaling axis. Both cytokines activate nuclear factor κB, but appropriate induction of downstream effector genes requires coordinated activation of other transcription factors, notably, CCAAT/enhancer binding proteins (C/EBPs). Here, we demonstrate the unexpected involvement of a posttranscriptional "epitranscriptomic" mRNA modification [N6-methyladenosine (m6A)] in regulating C/EBPß and C/EBPδ in response to IL-17A, as well as IL-17F and TNFα. Prompted by the observation that C/EBPß/δ-encoding transcripts contain m6A consensus sites, we show that Cebpd and Cebpb mRNAs are subject to m6A modification. Induction of C/EBPs is enhanced by an m6A methylase "writer" and suppressed by a demethylase "eraser." The only m6A "reader" found to be involved in this pathway was IGF2BP2 (IMP2), and IMP2 occupancy of Cebpd and Cebpb mRNA was enhanced by m6A modification. IMP2 facilitated IL-17-mediated Cebpd mRNA stabilization and promoted translation of C/EBPß/δ in response to IL-17A, IL-17F, and TNFα. RNA sequencing revealed transcriptome-wide IL-17-induced transcripts that are IMP2 influenced, and RNA immunoprecipitation sequencing identified the subset of mRNAs that are directly occupied by IMP2, which included Cebpb and Cebpd Lipocalin-2 (Lcn2), a hallmark of autoimmune kidney injury, was strongly dependent on IL-17, IMP2, and C/EBPß/δ. Imp2-/- mice were resistant to autoantibody-induced glomerulonephritis (AGN), showing impaired renal expression of C/EBPs and Lcn2 Moreover, IMP2 deletion initiated only after AGN onset ameliorated disease. Thus, posttranscriptional regulation of C/EBPs through m6A/IMP2 represents a previously unidentified paradigm of cytokine-driven autoimmune inflammation.

Adenosine and Inflammation: Here, There and Everywhere.

Adenosine is a ubiquitous endogenous modulator with the main function of maintaining cellular and tissue homeostasis in pathological and stress conditions. It exerts its effect through the interaction with four G protein-coupled receptor (GPCR) subtypes referred as A1, A2A, A2B, and A3 adenosine receptors (ARs), each of which has a unique pharmacological profile and tissue distribution. Adenosine is a potent modulator of inflammation, and for this reason the adenosinergic system represents an excellent pharmacological target for the myriad of diseases in which inflammation represents a cause, a pathogenetic mechanism, a consequence, a manifestation, or a protective factor. The omnipresence of ARs in every cell of the immune system as well as in almost all cells in the body represents both an opportunity and an obstacle to the clinical use of AR ligands. This review offers an overview of the cardinal role of adenosine in the modulation of inflammation, showing how the stimulation or blocking of its receptors or agents capable of regulating its extracellular concentration can represent promising therapeutic strategies for the treatment of chronic inflammatory pathologies, neurodegenerative diseases, and cancer.

Timing Effect of Adenosine-Directed Immunomodulation on Mouse Experimental Autoimmune Uveitis.

Adenosine is an important regulatory molecule of the immune response. We have previously reported that treatment of experimental autoimmune uveitis (EAU)-prone mice with an adenosine-degrading enzyme (adenosine deaminase) prohibited EAU development by inhibiting Th17 pathogenic T cell responses. To further validate that the targeting of adenosine or adenosine receptors effectively modulates Th17 responses, we investigated the effect of adenosine receptor antagonists. In this study, we show that the A2AR antagonist SCH 58261 (SCH) effectively modulates aberrant Th17 responses in induced EAU. However, timing of the treatment is important. Whereas SCH inhibits EAU when administered during the active disease stage, it did not do so if administered during quiescent disease stages, thus implying that the existing immune status influences the therapeutic effect. Mechanistic studies showed that inhibition of γδ T cell activation is crucially involved in adenosine-based treatment. Adenosine is an important costimulator of γδ T cell activation, which is essential for promoting Th17 responses. During ongoing disease stages, adenosine synergizes with existing high levels of cytokines, leading to augmented γδ T cell activation and Th17 responses, but in quiescent disease stages, when existing cytokine levels are low, adenosine does not enhance γδ T cell activation. Our results demonstrated that blockade of the synergistic effect between adenosine and inflammatory cytokines at active disease stages can ameliorate high-degree γδ T cell activation and, thus, suppress Th17 pathogenic T cell responses.

Signatures and Prognostic Values of N6-methyladenosine (m6A) - related Immune Genes in Bladder Cancer.

In recent years, genes associated with N6-methyladenosine (m6A) modification were found to participate in modulation of multiple tumor biological processes. Concomitantly, the significantly complicated dual effects of tumor microenvironment have been observed on cancer progression. The present study aims to investigate m6A-related immune genes (m6AIGs) for their signatures and prognostic values in bladder cancer (BC). Out of 2856 differentially expressed genes (DEGs) of BC, a total of 85 genes were obtained following intersection of DEGs, immune genes and m6A-related genes. The results of multivariate Cox regression analysis illustrated four genes (BGN, GRK5, IL32, and SREBF1) were significantly associated with the prognosis of BC patients. The BC samples were divided into two types based on the consensus clustering, and the principal component analysis demonstrated a separation between them. It was found that high expression of BGN and GRK5 were linked with advanced T and N stage, and the expression of SREBF1 in early T stage was higher than that in advanced T stage. Subsequently, the nomogram to predict 3- and 5-year survival probability of BC patients was developed and calibrated. GSEA analysis for risk subgroups showed WNT and TGF-beta signaling pathways were involved in regulation of BC progression in high risk level group. In the low risk level group, cytosolic DNA-Sensing cGAS-STING and RIG-I-like receptors signaling pathways were found to be correlated with BC development. These findings provide a novel insight on studies for BC progression.

Methyltransferase-Like Protein 14 Attenuates Mitochondrial Antiviral Signaling Protein Expression to Negatively Regulate Antiviral Immunity via N6 -methyladenosine Modification.

Mitochondrial antiviral signaling (MAVS) protein is the core signaling adaptor in the RNA signaling pathway. Thus, appropriate regulation of MAVS expression is essential for antiviral immunity against RNA virus infection. However, the regulation of MAVS expression at the mRNA level especially at the post transcriptional level is not well-defined. Here, it is reported that the MAVS mRNA undergoes N6 -methyladenosine (m6 A) modification through methyltransferase-like protein 14 (METTL14), which leads to a fast turnover of MAVS mRNA. Knockdown or deficiency of METTL14 increases MAVS mRNA stability, and downstream phosphorylation of TBK1/IRF3 and interferon-ß production in response to RNA viruses. Compared to wild-type mice, heterozygotes Mettl14+/- mice better tolerate RNA virus infection. The authors' findings unveil a novel mechanism to regulate the stability of MAVS transcripts post-transcriptionally through m6 A modification.

Release of adenosine-induced immunosuppression: Comprehensive characterization of dual A2A/A2B receptor antagonist.

Immunosuppression is one of the main mechanisms facilitating tumor expansion. It may be driven by immune checkpoint protein expression, anti-inflammatory cytokine secretion or enhanced metabolic enzyme production, leading to the subsequent build-up of metabolites such as adenosine. Under physiological conditions, adenosine prevents the development of tissue damage resulting from a prolonged immune response; the same mechanism might be employed by tumor tissue to promote immunosuppression. Immune cells expressing A2A and A2B adenosine receptors present in an adenosine-rich environment have suppressed effector functions, such as cytotoxicity, proinflammatory cytokine release, antigen presentation and others, making them inert to cancer cells. This study was designed to investigate the dual antagonist potential of SEL330-639 to abolish adenosine-driven immunosuppression. SEL330-639 has slow dissociation kinetics. It inhibits cAMP production in human CD4+ cells, CD8+ cells and moDCs, which leads to diminished CREB phosphorylation and restoration of antitumor cytokine production (IL-2, TNFα, IL-12) in multiple primary human immune cells. The aforementioned results were additionally validated by gene expression analysis and functional assays in which NK cell line cytotoxicity was recovered by SEL330-639. Adenosine-driven immunosuppression is believed to preclude the effectiveness of immune checkpoint inhibitor therapies. Hence, there is an urgent need to develop new immuno-oncological strategies. Here, we comprehensively characterize SEL330-639, a novel dual A2A/A2B receptor antagonist effective in both lymphoid and myeloid cell populations with nanomolar potency. Due to its tight binding to the A2A and A2B receptors, this binding is sustained even at high adenosine concentrations mimicking the upper limit of the range of adenosine levels observed in the tumor microenvironment.

Emerging role of RNA modification N6-methyladenosine in immune evasion.

The innate and adaptive immune cells have complex signaling pathways for sensing and initiating immune responses against disease. These pathways are interrupted at different levels to occur immune evasion, including by N6-methyladenosine (m6A) modification. In this review, we discuss studies revealing the immune evasion mechanism by m6A modification, which underlies the retouching of these signaling networks and the rapid tolerance of innate and adaptive immune molecules during disease. We also focus on the functions of m6A in main chemokines regulation, and their roles in promotive and suppressive immune cell recruitment. We then discuss some of the current challenges in the field and describe future directions for the immunological mechanisms of m6A modification.