Adenosine-Metabolizing Enzymes, Adenosine Kinase and Adenosine Deaminase, in Cancer

Novel homozygous ADK out-of-frame deletion causes adenosine kinase deficiency with rare phenotypes of sepsis, metabolites disruption and neutrophil dysfunction

Adenosine kinase deficiency (OMIM #614300) is a type of inborn errors of metabolism with multiorgan symptoms primarily neurological disorders, hepatic impairment, global developmental delay, and mild dysmorphism. The genetic causes of adenosine kinase deficiency are homozygous or compound heterozygous loss-of-function variants of ADK. To date, fewer than 25 cases of adenosine kinase deficiency have been reported worldwide and none have been reported in China. In this research, trio whole-exome sequencing (Trio-WES) identified a novel homozygous ADK (NM_001123.4) out-of-frame deletion, c.518_519delCA (p.Thr173Serfs*15), in a Chinese patient with rare phenotypes of sepsis, metabolites disruption and neutrophil dysfunction. This variant was dysfunctional, with marked reduction of ADK level in both the patient's peripheral blood and cells transfected with the corresponding variant. Additionally, metabolomics detected by high-throughput mass spectrometry showed disturbances in the methionine (Met) and energy pathway. RNA sequencing (RNA-seq) of the patient's peripheral blood suggested a defective anti-inflammatory response characterized by impaired neutrophil activation, migration, and degranulation, which might be the primary cause for the sepsis. To our knowledge, we identified the first Chinese patient of adenosine kinase deficiency with a novel homozygous out-of-frame deletion in ADK causing multiorgan disorders, metabolites disruption, rare phenotypes of sepsis, and neutrophil dysfunction. Our findings broaden the genetic spectrum and pathogenic mechanisms of adenosine kinase deficiency.

Nanoparticles targeting the adenosine pathway for cancer immunotherapy

Cancer immunotherapy, as an emerging approach to cancer treatment, has tremendous potential for application. Compared to traditional methods such as surgery, chemotherapy, and radiation therapy, it has the ability to restore the patient's immune system, leading to long-term immune memory with less damage to normal tissues. However, immunotherapy has its limitations, including limited therapeutic efficacy, restricted patient populations, and inconsistent treatment responses. Finding effective immunotherapeutic approaches has become a key focus of its clinical application. The adenosine pathway is a recently discovered tumor immune regulatory signaling pathway. It can influence the metabolism and growth of tumor cells by acting through key enzymes in the adenosine pathway, thereby affecting the development of tumors. Therefore, inhibiting the adenosine pathway is an effective cancer immunotherapy. Common adenosine pathway inhibitors include small molecules and antibody proteins, and extensive preclinical trials have demonstrated their effectiveness in inhibiting tumor growth. The short half-life, low bioavailability, and single administration route of adenosine pathway inhibitors limit their clinical application. With the advent of nanotechnology, nano-delivery of adenosine pathway inhibitors has addressed these issues. Compared to traditional drugs, nano-drugs extend the drug's circulation time and improve its distribution within the body. They also offer targeting capabilities and have low toxic side effects, making them very promising for future applications. In this review, we discuss the mechanism of the adenosine pathway in tumor immune suppression, the clinical applications of adenosine pathway inhibitors, and nano-delivery based on adenosine pathway inhibitors. In the final part of this article, we also briefly discuss the technical issues and challenges currently present in nano-delivery of adenosine pathway inhibitors, with the hope of advancing the progress of adenosine inhibitor nano-drugs in clinical treatment.

Proteomic Identification of Small Extracellular Vesicle Proteins LAMB1 and Histone H4 for Prostate Cancer Diagnosis and Risk Stratification

Diagnosis and stratification of prostate cancer (PCa) patients using the prostate-specific antigen (PSA) test is challenging. Extracellular vesicles (EVs), as a new star of liquid biopsy, has attracted interest to complement inaccurate PSA screening and invasiveness of tissue biopsy. In this study, a panel of potential small EV (sEV) protein biomarkers is identified from PCa cell lines using label-free LC-MS/MS proteomics. These biomarkers underwent further validation with plasma and urine samples from different PCa stages through parallel reaction monitoring-based targeted proteomics, western blotting, and ELISA. Additionally, a tissue microarray containing cancerous and noncancerous tissues is screened to provide additional evidence of selected sEV proteins associated with cancer origin. Results indicate that sEV protein LAMB1 is highly expressed in human plasma of metastatic PCa patients compared with localised PCa patients and control subjects, while sEV protein Histone H4 is highly expressed in human urine of high-risk PCa patients compared to low-risk PCa patients and control subjects. These two sEV proteins demonstrate higher specificity and sensitivity than the PSA test and show promise for metastatic PCa diagnosis, progression monitoring, and risk stratification.

Selective refueling of CAR T cells using ADA1 and CD26 boosts antitumor immunity

Chimeric antigen receptor (CAR) T cell therapy is hindered in solid tumor treatment due to the immunosuppressive tumor microenvironment and suboptimal T cell persistence. Current strategies do not address nutrient competition in the microenvironment. Hence, we present a metabolic refueling approach using inosine as an alternative fuel. CAR T cells were engineered to express membrane-bound CD26 and cytoplasmic adenosine deaminase 1 (ADA1), converting adenosine to inosine. Autocrine secretion of ADA1 upon CD3/CD26 stimulation activates CAR T cells, improving migration and resistance to transforming growth factor β1 suppression. Fusion of ADA1 with anti-CD3 scFv further boosts inosine production and minimizes tumor cell feeding. In mouse models of hepatocellular carcinoma and non-small cell lung cancer, metabolically refueled CAR T cells exhibit superior tumor reduction compared to unmodified CAR T cells. Overall, our study highlights the potential of selective inosine refueling to enhance CAR T therapy efficacy against solid tumors.

Genomic and Transcriptome Analysis Reveals the Biosynthesis Network of Cordycepin in Cordyceps militaris

Cordycepin is the primary active compound of Cordyceps militaris. However, the definitive genetic mechanism governing cordycepin synthesis in fruiting body growth and development remains elusive, necessitating further investigation. This study consists of 64 C. militaris strains collected from northeast China. The high-yielding cordycepin strain CMS19 was selected for the analysis of cordycepin production and the genetic basis of cordycepin anabolism. First, the whole-genome sequencing of CMS19 yielded a final size of 30.96 Mb with 8 contigs and 9781 protein-coding genes. The genome component revealed the presence of four additional secondary metabolite gene clusters compared with other published genomes, suggesting the potential for the production of new natural products. The analyses of evolutionary and genetic differentiation revealed a close relationship between C. militaris and Beauveria bassiana. The population of strains distributed in northeast China exhibited the significant genetic variation. Finally, functional genes associated with cordycepin synthesis were identified using a combination of genomic and transcriptomic analyses. A large number of functional genes associated with energy and purine metabolism were significantly enriched, facilitating the reconstruction of a hypothetical cordycepin metabolic pathway. Therefore, our speculation of the cordycepin metabolism pathway involved 24 genes initiating from the glycolysis and pentose phosphate pathways, progressing through purine metabolism, and culminating in the core region of cordycepin synthesis. These findings could offer fundamental support for scientific utilizations of C. militaris germplasm resources and standardized cultivation for cordycepin production.

The Interaction between ADK and SCG10 Regulate the Repair of Nerve Damage

The cytoskeleton must be remodeled during neurite outgrowth, and Superior Cervical Ganglion 10 (SCG10) plays a critical role in this process by depolymerizing Microtubules (MTs), conferring highly dynamic properties to the MTs. However, the precise mechanism of action of SCG10 in the repair of injured neurons remains largely uncertain. Using transcriptomic identification, we discovered that SCG10 expression was downregulated in neurons after Spinal Cord Injury (SCI). Additionally, through mass spectrometry identification, immunoprecipitation, and pull-down assays, we established that SCG10 could interact with Adenosine Kinase (ADK). Furthermore, we developed an excitotoxicity-induced neural injury model and discovered that ADK suppressed injured neurite re-growth, whereas, through overexpression and small molecule interference experiments, SCG10 enhanced it. Moreover, we discovered ADK to be the upstream of SCG10. More importantly, the application of the ADK inhibitor called 5-Iodotubercidin (5-ITu) was found to significantly enhance the recovery of motor function in mice with SCI. Consequently, our findings suggest that ADK plays a negative regulatory role in the repair of injured neurons. Herein, we propose a molecular interaction model of the SCG10-ADK axis to regulate neuronal recovery.

A signature based on circadian rhythm-associated genes for the evaluation of prognosis and the tumour microenvironment in HNSCC

The morbidity and mortality rates of head and neck squamous cell carcinoma (HNSCC) remain high worldwide. Therefore, there is an urgent need to identify a new prognostic biomarker to guide the personalized treatment of HNSCC patients. Increasing evidence suggests that circadian rhythm genes play an important role in the development and progression of cancer. We aimed to explore the value of circadian rhythm genes in predicting prognosis and guiding the treatment of HNSCC. We first obtained a list of circadian rhythm genes from previous research. The sequencing data were retrieved from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases. Finally, univariate Cox proportional hazard analysis, least absolute shrinkage and selection operator (LASSO) regression, and multivariate Cox proportional hazard analysis were performed to develop a prognostic signature (Circadian Rhythm-Related Gene Prognostic Index, CRRGPI) consisting of nine circadian rhythm genes. The signature exhibited good performance in predicting overall survival. Patients with low CRRGPI scores had lower metabolic activities and an active antitumour immunity ability. Additionally, a clinical cohort was used to further evaluate the ability of the CRRGPI to predict the efficacy of immune checkpoint inhibitors. In conclusion, the novel circadian rhythm-related gene signature can provide a precise prognostic evaluation with the potential capacity to guide individualized treatment regimens for HNSCC patients.

Adenosine Deaminase as a Potential Diagnostic and Prognostic Biomarker for Severe Fever with Thrombocytopenia Syndrome

BACKGROUND

Severe fever with thrombocytopenia syndrome (SFTS) is a serious infectious disease caused by the Dabie bandavirus, with a high mortality rate. Currently, there are no effective vaccines or specific treatments for SFTS. Early diagnosis and accurate severity assessment are crucial.

METHODS

This study included 171 cases of SFTS, COVID-19, and hepatitis B virus (HBV) patients and healthy controls. We compared the serum adenosine deaminase (ADA) activity across these groups. The diagnostic and prognostic efficiency of serum ADA for SFTS was evaluated by using receiver operating characteristic (ROC) curve analysis. We also examined the correlation between serum ADA in SFTS patients and clinical lab parameters as well as serum cytokines.

RESULTS

SFTS patients had significantly higher serum ADA activity than those of COVID-19, HBV patients, and healthy controls. Nonsurvivor SFTS patients had notably higher ADA than survivors. ROC analysis indicated ADA as an effective SFTS diagnostic and prognostic biomarker. ADA correlated with prognosis, viral load, APTT, PT, AST, ferritin, negatively with HDL-c and LDL-c, and positively with cytokines like IL-6, TNF-α, and IL-1β. Multiorgan failure patients showed significant ADA increase.

CONCLUSION

Elevated serum ADA activity in SFTS patients is linked with disease severity and prognosis, showing potential as a diagnostic and prognostic biomarker for SFTS.

Mechanistic role of quercetin as inhibitor for adenosine deaminase enzyme in rheumatoid arthritis: systematic review

Rheumatoid arthritis (RA) is an autoimmune disease involving T and B lymphocytes. Autoantibodies contribute to joint deterioration and worsening symptoms. Adenosine deaminase (ADA), an enzyme in purine metabolism, influences adenosine levels and joint inflammation. Inhibiting ADA could impact RA progression. Intracellular ATP breakdown generates adenosine, which increases in hypoxic and inflammatory conditions. Lymphocytes with ADA play a role in RA. Inhibiting lymphocytic ADA activity has an immune-regulatory effect. Synovial fluid levels of ADA are closely associated with the disease's systemic activity, making it a useful parameter for evaluating joint inflammation. Flavonoids, such as quercetin (QUE), are natural substances that can inhibit ADA activity. QUE demonstrates immune-regulatory effects and restores T-cell homeostasis, making it a promising candidate for RA therapy. In this review, we will explore the impact of QUE in suppressing ADA and reducing produced the inflammation in RA, including preclinical investigations and clinical trials.

Adenosinergic metabolism pathway: an emerging target for improving outcomes of solid organ transplantation

Extracellular nucleotides are widely recognized as crucial modulators of immune responses in peripheral tissues. Adenosine triphosphate (ATP) and adenosine are key components of extracellular nucleotides, the balance of which contributes to immune homeostasis. Under tissue injury, ATP exerts its pro-inflammatory function, while the adenosinergic pathway rapidly degrades ATP to immunosuppressive adenosine, thus inhibiting excessive and uncontrolled inflammatory responses. Previous reviews have explored the immunoregulatory role of extracellular adenosine in various pathological conditions, especially inflammation and malignancy. However, current knowledge regarding adenosine and adenosinergic metabolism in the context of solid organ transplantation remains fragmented. In this review, we summarize the latest information on adenosine metabolism and the mechanisms by which it suppresses the effector function of immune cells, as well as highlight the protective role of adenosine in all stages of solid organ transplantation, including reducing ischemia reperfusion injury during organ procurement, alleviating rejection, and promoting graft regeneration after transplantation. Finally, we discuss the potential for future clinical translation of adenosinergic pathway in solid organ transplantation.

Expression of ADK-S and ADK-L Isoforms and Their Association with CD39/CD73/A2aR in Colorectal Cancer

The level of mRNA of the long (L) and short (S) isoforms of adenosine kinase (ADK) was analyzed in patients with colorectal cancer (CRC). ADK is required to convert adenosine (ADO) to AMP. It was shown that tumor and normal colon tissues (n=13) do not differ in the level of ADK-S and ADK-L mRNA. At the same time, the level of ADK-S mRNA (tumor: p=0.0214, normal: p=0.005) in the colon tissue was lower than in the blood of CRC patients (n=20), and the level of ADK-L mRNA (tumor: p=0.007, normal: p=0.024), on the contrary, was higher. A negative correlation was found between the level of ADK-S mRNA and the level of A2aR mRNA in both tumor and normal tissues (p=0.018 and p=0.0014, respectively). In the tumor tissue, a positive correlation was shown between ADK-L and CD73 mRNA levels (p=0.017). The obtained data indicate the association ADK with the expression of CD39/CD73/A2aR in CRC patients. In this regard, the effect of recombinant ADK on the expression of CD39 and CD73 ectonucleotidase by T cells in vitro was analyzed. In a culture of peripheral blood mononuclear cells isolated from the blood of 5 healthy donors, ADK did not abolish the inhibitory effect on the expression of CD39 and CD73 by CD8+T cells in the presence of a high concentration of ATP (a source for ADO). Effects on CD39+CD4+, CD73+CD4+T cells and CD39+ Treg cells were also not found.

A Nucleotide Metabolism-Related Gene Signature for Risk Stratification and Prognosis Prediction in Hepatocellular Carcinoma Based on an Integrated Transcriptomics and Metabolomics Approach

Hepatocellular carcinoma (HCC) is a leading cause of cancer-related mortality worldwide. The in-depth study of genes and metabolites related to nucleotide metabolism will provide new ideas for predicting the prognosis of HCC patients. This study integrated the transcriptome data of different cancer types to explore the characteristics and significance of nucleotide metabolism-related genes (NMGRs) in different cancer types. Then, we constructed a new HCC classifier and prognosis model based on HCC samples from TCGA and GEO, and detected the gene expression level in the model through molecular biology experiments. Finally, nucleotide metabolism-related products in serum of HCC patients were examined using untargeted metabolomics. A total of 97 NMRGs were obtained based on bioinformatics techniques. In addition, a clinical model that could accurately predict the prognostic outcome of HCC was constructed, which contained 11 NMRGs. The results of PCR experiments showed that the expression levels of these genes were basically consistent with the predicted trends. Meanwhile, the results of untargeted metabolomics also proved that there was a significant nucleotide metabolism disorder in the development of HCC. Our results provide a promising insight into nucleotide metabolism in HCC, as well as a tailored prognostic and chemotherapy sensitivity prediction tool for patients.

The Immune Regulatory Role of Adenosine in the Tumor Microenvironment

Adenosine, an immunosuppressive metabolite, is produced by adenosine triphosphate (ATP) released from dying or stressed cells and is found at high levels in the tumor microenvironment of most solid tumors. It mediates pro-tumor activities by inducing tumor cell proliferation, migration or invasion, tumor tissue angiogenesis, and chemoresistance. In addition, adenosine plays an important role in regulating anti-tumor immune responses and facilitating tumor immune escape. Adenosine receptors are broadly expressed by tumor-infiltrated immune cells, including suppressive tumor-associated macrophages and CD4+ regulatory T cells, as well as effector CD4+ T cells and CD8+ cytotoxic T lymphocytes. Therefore, adenosine is indispensable in down-regulating anti-tumor immune responses in the tumor microenvironment and contributes to tumor progression. This review describes the current progress on the role of adenosine/adenosine receptor pathway in regulating the tumor-infiltrating immune cells that contribute to tumor immune evasion and aims to provide insights into adenosine-targeted tumor immunotherapy.

Drugs targeting adenosine signaling pathways: A current view

Adenosine is an endogenous nucleoside that regulates many physiological and pathological processes. It is derived from either the intracellular or extracellular dephosphorylation of adenosine triphosphate and interacts with cell-surface G-protein-coupled receptors. Adenosine plays a substantial role in protecting against cell damage in areas of increased tissue metabolism and preventing organ dysfunction in pathological states. Targeting adenosine metabolism and receptor signaling may be an effective therapeutic approach for human diseases, including cardiovascular and central nervous system disorders, rheumatoid arthritis, asthma, renal diseases, and cancer. Several lines of evidence have shown that many drugs exert their beneficial effects by modulating adenosine signaling pathways but this knowledge urgently needs to be summarized, and most importantly, actualized. The present review collects pharmaceuticals and pharmacological or diagnostic tools that target adenosine signaling in their primary or secondary mode of action. We overviewed FDA-approved drugs as well as those currently being studied in clinical trials. Among them are already used in clinic A2A adenosine receptor modulators like istradefylline or regadenoson, but also plenty of anti-platelet, anti-inflammatory, or immunosuppressive, and anti-cancer drugs. On the other hand, we investigated dozens of specific adenosine pathway regulators that are tested in clinical trials to treat human infectious and noninfectious diseases. In conclusion, targeting purinergic signaling represents a great therapeutic challenge. The actual knowledge of the involvement of adenosinergic signaling as part of the mechanism of action of old drugs has open a path not only for drug-repurposing but also for new therapeutic strategies.

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.

Cordycepin: A review of strategies to improve the bioavailability and efficacy

Cordycepin is a bioactive compound extracted from Cordyceps militaris. As a natural antibiotic, cordycepin has a wide variety of pharmacological effects. Unfortunately, this highly effective natural antibiotic is proved to undergo rapid deamination by adenosine deaminase (ADA) in vivo and, as a consequence, its half-life is shortened and bioavailability is decreased. Therefore, it is of critical importance to work out ways to slow down the deamination so as to increase its bioavailability and efficacy. This study reviews recent researches on a series of aspects of cordycepin such as the bioactive molecule's pharmacological action, metabolism and transformation as well as the underlying mechanism, pharmacokinetics and, particularly, the methods for reducing the degradation to improve the bioavailability and efficacy. It is drawn that there are three methods that can be applied to improve the bioavailability and efficacy: to co-administrate an ADA inhibitor and cordycepin, to develop more effective derivatives via structural modification, and to apply new drug delivery systems. The new knowledge can help optimize the application of the highly potent natural antibiotic-cordycepin and develop novel therapeutic strategies.

Changes in Adenosine Deaminase Activity and Endothelial Dysfunction after Mild Coronavirus Disease-2019

Endothelial cells are a preferential target for SARS-CoV-2 infection. Previously, we have reported that vascular adenosine deaminase 1 (ADA1) may serve as a biomarker of endothelial activation and vascular inflammation, while ADA2 plays a critical role in monocyte and macrophage function. In this study, we investigated the activities of circulating ADA isoenzymes in patients 8 weeks after mild COVID-19 and related them to the parameters of inflammation and microvascular/endothelial function. Post-COVID patients revealed microvascular dysfunction associated with the changes in circulating parameters of endothelial dysfunction and inflammatory activation. Interestingly, serum total ADA and ADA2 activities were diminished in post-COVID patients, while ADA1 remained unchanged in comparison to healthy controls without a prior diagnosis of SARS-CoV-2 infection. While serum ADA1 activity tended to positively correspond with the parameters of endothelial activation and inflammation, sICAM-1 and TNFα, serum ADA2 activity correlated with IL-10. Simultaneously, post-COVID patients had lower circulating levels of ADA1-anchoring protein, CD26, that may serve as an alternative receptor for virus binding. This suggests that after the infection CD26 is rather maintained in cell-attached form, enabling ADA1 complexing. This study points to the possible role of ADA isoenzymes in cardiovascular complications after mild COVID-19.

EGFR alterations in glioblastoma play a role in antitumor immunity regulation

The epidermal growth factor receptor (EGFR) is the most frequently altered gene in glioblastoma (GBM), which plays an important role in tumor development and anti-tumor immune response. While current molecular targeted therapies against the EGFR signaling pathway and its downstream key molecules have not demonstrated favorable clinical outcomes in GBM. Whereas tumor immunotherapies, especially immune checkpoint inhibitors, have shown durable antitumor responses in many cancers. However, the clinical efficacy is limited in patients carrying EGFR alterations, indicating that EGFR signaling may involve tumor immune response. Recent studies reveal that EGFR alterations not only promote GBM cell proliferation but also influence immune components in the tumor microenvironment (TME), leading to the recruitment of immunosuppressive cells (e.g., M2-like TAMs, MDSCs, and Tregs), and inhibition of T and NK cell activation. Moreover, EGFR alterations upregulate the expression of immunosuppressive molecules or cytokines (such as PD-L1, CD73, TGF-β). This review explores the role of EGFR alterations in establishing an immunosuppressive TME and hopes to provide a theoretical basis for combining targeted EGFR inhibitors with immunotherapy for GBM.

The recent progress of myeloid-derived suppressor cell and its targeted therapies in cancers

Myeloid-derived suppressor cells (MDSCs) are an immature group of myeloid-derived cells generated from myeloid cell precursors in the bone marrow. MDSCs appear almost exclusively in pathological conditions, such as tumor progression and various inflammatory diseases. The leading function of MDSCs is their immunosuppressive ability, which plays a crucial role in tumor progression and metastasis through their immunosuppressive effects. Since MDSCs have specific molecular features, and only a tiny amount exists in physiological conditions, MDSC-targeted therapy has become a promising research direction for tumor treatment with minimal side effects. In this review, we briefly introduce the classification, generation and maturation process, and features of MDSCs, and detail their functions under various circumstances. The present review specifically demonstrates the environmental specificity of MDSCs, highlighting the differences between MDSCs from cancer and healthy individuals, as well as tumor-infiltrating MDSCs and circulating MDSCs. Then, we further describe recent advances in MDSC-targeted therapies. The existing and potential targeted drugs are divided into three categories, monoclonal antibodies, small-molecular inhibitors, and peptides. Their targeting mechanisms and characteristics have been summarized respectively. We believe that a comprehensive in-depth understanding of MDSC-targeted therapy could provide more possibilities for the treatment of cancer.

Could Oxidative Stress Play a Role in the Development and Clinical Management of Differentiated Thyroid Cancer?

Increased oxidative stress (OS) has been implicated as a relevant risk factor for cancer progression. Furthermore, patients diagnosed with differentiated thyroid cancer (DTC) have been characterized by an increased OS status. Therefore, assessing OS status could potentially be considered a useful tool in DTC clinical management. This measurement could be particularly valuable in personalizing treatment protocols and determining new potential medical targets to improve commonly used therapies. A literature review was conducted to gather new information on DTC clinical management, with a particular focus on evaluating the clinical utility of OS. These meta-analyses concentrate on novel approaches that employ the measurement of oxidative-antioxidant status, which could represent the most promising area for implementing clinical management.

Review immune response of targeting CD39 in cancer

The ATP-adenosine pathway has emerged as a promising target for cancer therapy, but challenges remain in achieving effective tumor control. Early research focused on blocking the adenosine generating enzyme CD73 and the adenosine receptors A2AR or A2BR in cancer. However, recent studies have shown that targeting CD39, the rate-limiting ecto-enzyme of the ATP-adenosine pathway, can provide more profound anti-tumor efficacy by reducing immune-suppressive adenosine accumulation and increasing pro-inflammatory ATP levels. In addition, combining CD39 blocking antibody with PD-1 immune checkpoint therapy may have synergistic anti-tumor effects and improve patient survival. This review will discuss the immune components that respond to CD39 targeting in the tumor microenvironment. Targeting CD39 in cancer has been shown to not only decrease adenosine levels in the tumor microenvironment (TME), but also increase ATP levels. Additionally, targeting CD39 can limit the function of Treg cells, which are known to express high levels of CD39. With phase I clinical trials of CD39 targeting currently underway, further understanding and rational design of this approach for cancer therapy are expected.

New paradigms in purinergic receptor ligand discovery

The discovery and clinical implementation of modulators of adenosine, P2Y and P2X receptors (comprising nineteen subtypes) have progressed dramatically in ∼50 years since Burnstock's definition of purinergic signaling. Although most clinical trials of selective ligands (agonists and antagonists) of certain purinergic receptors failed, there is a renewed impetus to redirect efforts to new disease conditions and the discovery of more selective or targeted compounds with potentially reduced side effects, such as biased GPCR agonists. The elucidation of new receptor and enzyme structures is steering rational design of potent and selective agonists, antagonists, allosteric modulators and inhibitors. A2A adenosine receptor (AR) antagonists are being applied to neurodegenerative conditions and cancer immunotherapy. A3AR agonists have potential for treating chronic inflammation (e.g. psoriasis), stroke and pain, as well as cancer. P2YR modulators are being considered for treating inflammation, metabolic disorders, acute kidney injury, cancer, pain and other conditions, often with an immune mechanism. ADP-activated P2Y12R antagonists are widely used as antithrombotic drugs, while their repurposing toward neuroinflammation is considered. P2X3 antagonists have been in clinical trials for chronic cough. P2X7 antagonists have been in clinical trials for inflammatory diseases and depression (compounds that penetrate the blood-brain barrier). Thus, purinergic signaling is now recognized as an immense regulatory system in the body for rebalancing tissues and organs under stress, which can be adjusted by drug intervention for therapeutic purposes. The lack of success of many previous clinical trials can be overcome given more advanced pharmacokinetic and pharmacodynamic approaches, including structure-based drug design, prodrugs and biased signaling. This article is part of the Special Issue on "Purinergic Signaling: 50 years".

Determination of adenosine by CRISPR-Cas12a system based on duplexed aptamer and molecular beacon reporter linked to gold nanoparticles

Adenosine as a potential tumor marker is of great value for clinical disease diagnosis. Since the CRISPR-cas12a system is only capable of recognizing nucleic acid targets we expanded the CRISPR-cas12a system to determine small molecules by designing a duplexed aptamer (DA) converting g-RNA recognition of adenosine to recognition of aptamer complementary DNA strands (ACD). To further improve the sensitivity of determination, we designed a molecule beacon (MB)/gold nanoparticle (AuNP)-based reporter, which has higher sensitivity than traditional ssDNA reporter. In addition, the AuNP-based reporter enables more efficient and fast determination. The determination of adenosine under 488-nm excitation can be realized within 7 min, which is more than 4 times faster than traditional ssDNA reporter. The linear determination range of the assay to adenosine was 0.5-100 μM with the determination limit of 15.67 nM. The  assay was applied to recovery determination of adenosine in serum samples with satisfactory results. The recoveries were between 91 and 106% and the RSD values of different concertation were below  4.8%. This sensitive, highly selective, and stable sensing system is expected to play a role in the clinical determination of adenosine and other biomolecules.

Relationship between the Gene Expression of Adenosine Kinase Isoforms and the Expression of CD39 and CD73 Ectonucleotidases in Colorectal Cancer

Tumor cells have the capacity to create an adenosine-rich immunosuppressive environment, which can interfere with antitumor immunotherapy. Approaches are currently being developed with a view to suppressing the production of adenosine or its signals. Such approaches include the use of antibodies to inhibit CD39, CD73, and adenosine-receptor antagonists. However, the abundance of enzymatic pathways that control the ATP-adenosine balance, as well as the still poorly understood intracellular adenosine regulation, makes the hoped-for success unlikely. In the present study, the enzyme adenosine kinase (ADK) needed to convert adenosine to adenosine monophosphate, thereby regulating its levels, was investigated. To do so, peripheral blood samples from patients with colorectal cancer (CRC) (n = 31) were collected with blood samples from healthy donors (n = 17) used as controls. ADK gene expression levels and those of its long (ADK-L) and short (ADK-S) isoforms were measured. The relationship between the levels of ADK gene expression and that of CD39, CD73, and A2aR genes was analyzed. It turned out that in the group of CRC patients (stages III-IV), the level of ADK-L mRNA was lower (p < 0.0011) when compared to that of the control. For the first time, an average correlation was found between the level of expression of CD39 and ADK-S (r = -0.468 at p = 0.043) and between CD73 and ADK-L (r = 0.518 at p = 0.0232) in CRC patients. Flow cytometry was used to assess the content of CD39/CD73-expressing CD8+, CD4+ and Treg lymphocytes, as well as their relationship with the level of ADK gene expression in CRC patients. But no significant correlations were found.

Tumor intrinsic and extrinsic functions of CD73 and the adenosine pathway in lung cancer

The adenosine pathway is an exciting new target in the field of cancer immunotherapy. CD73 is the main producer of extracellular adenosine. Non-small cell lung cancer (NSCLC) has one of the highest CD73 expression signatures among all cancer types and the presence of common oncogenic drivers of NSCLC, such as mutant epidermal growth factor receptor (EGFR) and KRAS, correlate with increased CD73 expression. Current immune checkpoint blockade (ICB) therapies only benefit a subset of patients, and it has proved challenging to understand which patients might respond even with the current understanding of predictive biomarkers. The adenosine pathway is well known to disrupt cytotoxic function of T cells, which is currently the main target of most clinical agents. Data thus far suggests that combining ICB therapies already in the clinic with adenosine pathway inhibitors provides promise for the treatment of lung cancer. However, antigen loss or lack of good antigens limits efficacy of ICB; simultaneous activation of other cytotoxic immune cells such as natural killer (NK) cells can be explored in these tumors. Clinical trials harnessing both T and NK cell activating treatments are still in their early stages with results expected in the coming years. In this review we provide an overview of new literature on the adenosine pathway and specifically CD73. CD73 is thought of mainly for its role as an immune modulator, however recent studies have demonstrated the tumor cell intrinsic properties of CD73 are potentially as important as its role in immune suppression. We also highlight the current understanding of this pathway in lung cancer, outline ongoing studies examining therapies in combination with adenosine pathway targeting, and discuss future prospects.

Decreased circulating CD73 and adenosine deaminase are associated with disease severity in hospitalized patients with COVID-19

OBJECTIVE

SARS-CoV-2 infection has been shown to result in increased circulating levels of adenosine triphosphate and adenosine diphosphate and decreased levels of adenosine, which has important anti-inflammatory activity. The goal of this pilot project was to assess the levels of soluble CD73 and soluble Adenosine Deaminase (ADA) in hospitalized patients with COVID-19 and determine if levels of these molecules are associated with disease severity.

METHODS

Plasma from 28 PCR-confirmed hospitalized COVID-19 patients who had varied disease severity based on WHO classification (6 mild/moderate, 10 severe, 12 critical) had concentrations of both soluble CD73 and ADA determined by ELISA. These concentrations were compared to healthy control plasma that is commercially available and was biobanked prior to the start of the pandemic. Additionally, outcomes such as WHO ordinal scale for disease severity, ICU admission, needed for invasive ventilation, hospital length of stay, and development of thrombosis during admission were used as markers of disease severity.

RESULTS

Our results show that both CD73 and ADA are decreased during SARS-CoV-2 infection. The level of circulating CD73 is directly correlated to the severity of the disease defined by the need for ICU admission, invasive ventilation, and hospital length of stay. Low level of CD73 is also associated with clinical thrombosis, a severe complication of SARS-CoV-2 infection.

CONCLUSION

Our study indicates that adenosine metabolism is down-regulated in patients with COVID-19 and associated with severe infection. Further large-scale studies are warranted to investigate the role of the adenosinergic anti-inflammatory CD73/ADA axis in protection against COVID-19.

The impaired distribution of adenosine deaminase isoenzymes in multiple sclerosis plasma and cerebrospinal fluid

Background

Adenosine deaminase (ADA) via two isoenzymes, ADA1 and ADA2, regulates intra- and extracellular adenosine concentrations by converting it to inosine. In the central nervous system (CNS), adenosine modulates the processes of neuroinflammation and demyelination that together play a critical role in the pathophysiology of multiple sclerosis (MS). Except for their catalytic activities, ADA isoenzymes display extra-enzymatic properties acting as an adhesion molecule or a growth factor.

Aims

This study aimed to explore the distribution and activity of ADA1 and ADA2 in the plasma and the CSF of MS patients as well as in the human brain microvascular endothelial cells (HBMEC), human brain vascular pericytes and human astrocytes.

Methods and results

The enzyme assay following reverse phase-high performance liquid chromatography (HPLC) analysis was used to detect the ADA1 and ADA2 activities and revealed an increased ratio of ADA1 to ADA2 in both the plasma and the CSF of MS patients. Plasma ADA1 activity was significantly induced in MS, while ADA2 was decreased in the CSF, but significance was not reached. The brain astrocytes, pericytes and endothelial cells revealed on their surface the activity of ADA1, with its basal level being five times higher in the endothelial cells than in the astrocytes or the pericytes. In turn, ADA2 activity was only observed in pericytes and endothelial cells. Stimulation of the cells with pro-inflammatory cytokines TNFα/IL17 for 18 h decreased intracellular nucleotide levels measured by HPLC only in pericytes. The treatment with TNFα/IL17 did not modulate cell-surface ATP and AMP hydrolysis nor adenosine deamination in pericytes or astrocytes. Whereas in endothelial cells it downregulated AMP hydrolysis and ADA2 activity and upregulated the ADA1, which reflects the ADA isoenzyme pattern observed here in the CSF of MS patients.

Conclusion

In this study, we determined the impaired distribution of both ADA isoenzymes in the plasma and the CSF of patients with MS. The increased ADA1 to ADA2 ratio in the CSF and plasma may translate to unfavorable phenotype that triggers ADA1-mediated pro-inflammatory mechanisms and decreases ADA2-dependent neuroprotective and growth-promoting effects in MS.

Dipeptidyl Peptidase 4 (DPP4) as A Novel Adipokine: Role in Metabolism and Fat Homeostasis

Dipeptidyl peptidase 4 (DPP4) is a molecule implicated in the regulation of metabolic homeostasis and inflammatory processes, and it exerts its main action through its enzymatic activity. DPP4 represents the enzyme most involved in the catabolism of incretin hormones; thus, its activity impacts appetite, energy balance, and the fine regulation of glucose homeostasis. Indeed, DPP4 inhibitors represent a class of antidiabetic agents widely used for the treatment of Type 2 diabetes mellitus (T2DM). DPP4 also acts as an adipokine and is mainly secreted by the adipose tissue, mostly from mature adipocytes of the visceral compartment, where it exerts autocrine and paracrine activities. DPP4 can disrupt insulin signaling within the adipocyte and in other target cells and tissues, where it also favors the development of a proinflammatory environment. This is likely at the basis of the presence of elevated circulating DPP4 levels in several metabolic diseases. In this review, we summarize the most recent evidence of the role of the DPP4 as an adipokine-regulating glucose/insulin metabolism and fat homeostasis, with a particular focus on clinical outcomes associated with its increased secretion in the presence of adipose tissue accumulation and dysfunction.

LC-MS/MS Phytochemical Profiling, Antioxidant Activity, and Cytotoxicity of the Ethanolic Extract of Atriplex halimus L. against Breast Cancer Cell Lines: Computational Studies and Experimental Validation

Atriplex halimus L., also known as Mediterranean saltbush, and locally as "Lgtef", an halophytic shrub, is used extensively to treat a wide variety of ailments in Morocco. The present study was undertaken to determine the antioxidant activity and cytotoxicity of the ethanolic extract of A. halimus leaves (AHEE). We first determined the phytochemical composition of AHEE using a liquid chromatography (LC)-tandem mass spectrometry (MS/MS) technique. The antioxidant activity was evaluated using different methods including DPPH scavenging capacity, β-carotene bleaching assay, ABTS scavenging, iron chelation, and the total antioxidant capacity assays. Cytotoxicity was investigated against human cancer breast cells lines MCF-7 and MDA-MB-231. The results showed that the components of the extract are composed of phenolic acids and flavonoids. The DPPH test showed strong scavenging capacity for the leaf extract (IC₅₀ of 0.36 ± 0.05 mg/mL) in comparison to ascorbic acid (IC₅₀ of 0.19 ± 0.02 mg/mL). The β-carotene test determined an IC₅₀ of 2.91 ± 0.14 mg/mL. The IC₅₀ values of ABTS, iron chelation, and TAC tests were 44.10 ± 2.92 TE µmol/mL, 27.40 ± 1.46 mg/mL, and 124 ± 1.27 µg AAE/mg, respectively. In vitro, the AHE extract showed significant inhibitory activity in all tested tumor cell lines, and the inhibition activity was found in a dose-dependent manner. Furthermore, computational techniques such as molecular docking and ADMET analysis were used in this work. Moreover, the physicochemical parameters related to the compounds' pharmacokinetic indicators were evaluated, including absorption, distribution, metabolism, excretion, and toxicity prediction (Pro-Tox II).

Adenosine signaling: Optimal target for gastric cancer immunotherapy

Gastric cancer (GC) is one of the most common malignancy and leading cause of cancer-related deaths worldwide. Due to asymptomatic or only nonspecific early symptoms, GC patients are usually in the advanced stage at first diagnosis and miss the best opportunity of treatment. Immunotherapies, especially immune checkpoint inhibitors (ICIs), have dramatically changed the landscape of available treatment options for advanced-stage cancer patients. However, with regards to existing ICIs, the clinical benefit of monotherapy for advanced gastric cancer (AGC) is quite limited. Therefore, it is urgent to explore an optimal target for the treatment of GC. In this review, we summarize the expression profiles and prognostic value of 20 common immune checkpoint-related genes in GC from Gene Expression Profiling Interactive Analysis (GEPIA) database, and then find that the adenosinergic pathway plays an indispensable role in the occurrence and development of GC. Moreover, we discuss the pathophysiological function of adenosinergic pathway in cancers. The accumulation of extracellular adenosine inhibits the normal function of immune effector cells and facilitate the effect of immunosuppressive cells to foster GC cells proliferation and migration. Finally, we provide insights into potential clinical application of adenosinergic-targeting therapies for GC patients.

Resveratrol enhances A1 and hinders A2A adenosine receptors signaling in both HeLa and SH-SY5Y cells: Potential mechanism of its antitumoral action

Despite great efforts, effective treatment against cancer has not yet been found. However, natural compounds such as the polyphenol resveratrol have emerged as promising preventive agent in cancer therapy. The mode of action of resveratrol is still poorly understood, but it can modulate many signaling pathways related to the initiation and progression of cancer. Adenosinergic signaling may be involved in the antitumoral action of resveratrol since resveratrol binds to the orthosteric binding site of adenosine A_2A receptors and acts as a non-selective agonist for adenosine receptors. In the present study, we measured the impact of resveratrol treatment on different adenosinergic pathway components (i.e. adenosine receptors levels, 5'-nucleotidase, adenosine deaminase, and adenylyl cyclase activities, protein kinase A levels, intracellular adenosine and other related metabolites levels) and cell viability and proliferation in HeLa and SH-SY5Y cell lines. Results revealed changes leading to turning off cAMP signaling such as decreased levels of A_2A receptors and reduced adenylyl cyclase activation, increased levels of A₁ receptors and increased adenylyl cyclase inhibition, and lower levels of PKA. All these changes could contribute to the antitumoral action of resveratrol. Interestingly, these effects were almost identical in HeLa and SH-SY5Y cells suggesting that resveratrol enhances A₁ and hinders A_2A adenosine receptors signaling as part of a potential mechanism of antitumoral action.