Compartmentalization of adenosine metabolism in cancer cells and its modulation during acute hypoxia

Targeting ENPP1 for cancer immunotherapy: Killing two birds with one stone

Cancer immunotherapy, particularly with immune checkpoint inhibitors, has revolutionized the paradigm of cancer treatment. Nevertheless, the efficacy of cancer immunotherapy remains limited in most clinical settings due to the lack of a preexisting antitumor T-cell response in tumors. Therefore, the clinical outcomes of cancer immunotherapy must be improved crucially. With increased awareness of the importance of the innate immune response in the recruitment of T cells, as well as the onset and maintenance of the T cell response, great interest has been shown in activating the cGAS-STING signaling pathway to awaken the innate immune response, thereby orchestrating both innate and adaptive immune responses to induce tumor clearance. However, tumor cells have evolved to overexpress ectonucleotide pyrophosphate phosphodiesterase 1 (ENPP1), which degrades the immunotransmitter 2',3'-cGAMP and promotes the production of immune-suppressing adenosine, resulting in inhibition of the anticancer immune response in the tumor microenvironment. Clinically, ENPP1 overexpression is closely associated with poor prognosis in patients with cancer. Conversely, depleting or inhibiting ENPP1 has been verified to elevate extracellular 2',3'-cGAMP levels and inhibit the generation of adenosine, thereby reinvigorating the anticancer immune response for tumor elimination. A variety of ENPP1 inhibitors have recently been developed and have demonstrated significant promise for cancer immunotherapy. In this review, we provide an overview of ENPP1, dissect its immunosuppressive mechanisms, and discuss the development of ENPP1 inhibitors with the potential to further improve the efficacy of cancer immunotherapy.

Deterministic reprogramming of neutrophils within tumors

Neutrophils are increasingly recognized as key players in the tumor immune response and are associated with poor clinical outcomes. Despite recent advances characterizing the diversity of neutrophil states in cancer, common trajectories and mechanisms governing the ontogeny and relationship between these neutrophil states remain undefined. Here, we demonstrate that immature and mature neutrophils that enter tumors undergo irreversible epigenetic, transcriptional, and proteomic modifications to converge into a distinct, terminally differentiated dcTRAIL-R1+ state. Reprogrammed dcTRAIL-R1+ neutrophils predominantly localize to a glycolytic and hypoxic niche at the tumor core and exert pro-angiogenic function that favors tumor growth. We found similar trajectories in neutrophils across multiple tumor types and in humans, suggesting that targeting this program may provide a means of enhancing certain cancer immunotherapies.

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.

Purine Intake and All-Cause Mortality in Ovarian Cancer: Results from a Prospective Cohort Study

BACKGROUND

Current biological evidence suggests that purine involvement in purine metabolism may contribute to the development and progression of ovarian cancer (OC), but the epidemiological association is currently unknown.

METHODS

A total of 703 newly diagnosed patients with OC aged 18-79 years were included in this prospective cohort study. Utilizing a verified food-frequency questionnaire, the participants' dietary consumption was gathered. Using medical records and ongoing follow-up, the deaths up until 31 March 2021 were determined. To assess the hazard ratios (HRs) and 95% confidence intervals (CIs) of purine intake with OC mortality, Cox proportional-hazard models were utilized.

RESULTS

During the median follow-up of 31 months (interquartile: 20-47 months), 130 deaths occurred. We observed an improved survival for the highest tercile of total purine intake compared with the lowest tercile (HR = 0.39, 95% CI = 0.19-0.80; p trend < 0.05), and this protective association was mainly attributed to xanthine intake (HR = 0.52, 95% CI = 0.29-0.94, p trend < 0.05). Additionally, we observed a curving relationship in which OC mortality decreased with total purine intake, and the magnitude of the decrease was negatively correlated with intake (p non-linear < 0.05). Significant inverse associations were also observed in subgroup analyses and sensitivity analyses according to demographic and clinical characteristics. Moreover, we observed that xanthine intake and hypoxanthine intake had a multiplicative interaction with ER and PR expression (p < 0.05), respectively.

CONCLUSION

A high total purine and xanthine intake was linked to a lower risk of OC mortality. Further clarification of these findings is warranted.

Overcoming high level adenosine-mediated immunosuppression by DZD2269, a potent and selective A2aR antagonist

BACKGROUND

Adenosine is a potent immunosuppressant whose levels in the tumor microenvironment (TME) are often much higher than those in normal tissues. Binding of adenosine to its receptor A2aR activates a cascade of genes and leads to immunosuppression. In addition, immune checkpoint blockage markedly increases A2aR expression in T cells, which could dampen their anti-tumor response. Several A2aR antagonists are under clinical development, but with limited clinical benefit reported so far. These A2aR antagonists showed much diminished activity at high adenosine levels found in TME, which may explain their clinical underperformance. We report the discovery and early clinical development of DZD2269, a novel A2aR antagonist which can fully block A2aR mediated immunosuppression commonly found in TME. Adenosine stimulates phosphorylation of cyclic AMP response element binding protein (CREB) in T cells and inhibits anti-tumor cytokine secretion in PBMCs in a dose-dependent manner. DZD2269 was able to reverse the immunosuppression induced by high concentrations of adenosine, as demonstrated by inhibiting CREB phosphorylation in T cells, restoring Th1 cytokine secretion in PBMCs, and stimulating dendritic cells (DCs) maturation. As a single agent, DZD2269 showed anti-tumor growth in multiple syngeneic mouse tumor models, and more profound anti-tumor effects were observed when DZD2269 was in combination with immune checkpoint inhibitors, radiotherapy, or chemotherapy. A good PK/PD relationship was observed in these animal models. In the phase 1 clinical study, downregulation of pCREB was detected in human T cells, consistent with preclinical prediction. Our data support further clinical development of DZD2269 in patients with cancer.

METHODS

The selectivity of DZD2269 for adenosine receptors was tested in engineered cell lines, and its efficacy in blocking A2aR signaling and reversing adenosine-mediated immunosuppression was assessed in human T cells and peripheral blood mononuclear cells (PBMCs). The anti-tumor effects of DZD2269 were evaluated in multiple syngeneic mouse models as a single agent as well as in combination with chemotherapy, radiotherapy, or immune checkpoint inhibitors. A phase 1 study in healthy volunteers (NCT04932005) has been initiated to assess safety, pharmacokinetics (PK) and pharmacodynamics (PD) of DZD2269.

RESULTS

Adenosine stimulates phosphorylation of cyclic AMP response element binding protein (CREB) in T cells and inhibits anti-tumor cytokine secretion in PBMCs in a dose-dependent manner. DZD2269 was able to reverse the immunosuppression induced by high concentrations of adenosine, as demonstrated by inhibiting CREB phosphorylation in T cells, restoring Th1 cytokine secretion in PBMCs, and stimulating dendritic cells (DCs) maturation. As a single agent, DZD2269 showed anti-tumor growth in multiple syngeneic mouse tumor models, and more profound anti-tumor effects were observed when DZD2269 was in combination with immune checkpoint inhibitors, radiotherapy, or chemotherapy. A good PK/PD relationship was observed in these animal models. In the phase 1 clinical study, downregulation of pCREB was detected in human T cells, consistent with preclinical prediction.

CONCLUSION

DZD2269 is a novel A2aR antagonist which can fully block A2aR mediated immunosuppression commonly found in TME. Clinical development of DZD2269 in patients with cancer is warranted (NCT04634344).

Purinergic Signaling in Oral Tissues

The role of the purinergic signal has been extensively investigated in many tissues and related organs, including the central and peripheral nervous systems as well as the gastrointestinal, cardiovascular, respiratory, renal, and immune systems. Less attention has been paid to the influence of purines in the oral cavity, which is the first part of the digestive apparatus and also acts as the body’s first antimicrobial barrier. In this review, evidence is provided of the presence and possible physiological role of the purinergic system in the different structures forming the oral cavity including teeth, tongue, hard palate, and soft palate with their annexes such as taste buds, salivary glands, and nervous fibers innervating the oral structures. We also report findings on the involvement of the purinergic signal in pathological conditions affecting the oral apparatus such as Sjögren’s syndrome or following irradiation for the treatment of head and neck cancer, and the use of experimental drugs interfering with the purine system to improve bone healing after damage. Further investigations are required to translate the results obtained so far into the clinical setting in order to pave the way for a wider application of purine-based treatments in oral diseases.

ATP and Adenosine Metabolism in Cancer: Exploitation for Therapeutic Gain

Adenosine is an evolutionary ancient metabolic regulator linking energy state to physiologic processes, including immunomodulation and cell proliferation. Tumors create an adenosine-rich immunosuppressive microenvironment through the increased release of ATP from dying and stressed cells and its ectoenzymatic conversion into adenosine. Therefore, the adenosine pathway becomes an important therapeutic target to improve the effectiveness of immune therapies. Prior research has focused largely on the two major ectonucleotidases, ectonucleoside triphosphate diphosphohydrolase 1/cluster of differentiation (CD)39 and ecto-5'-nucleotidase/CD73, which catalyze the breakdown of extracellular ATP into adenosine, and on the subsequent activation of different subtypes of adenosine receptors with mixed findings of antitumor and protumor effects. New findings, needed for more effective therapeutic approaches, require consideration of redundant pathways controlling intratumoral adenosine levels, including the alternative NAD-inactivating pathway through the CD38-ectonucleotide pyrophosphatase phosphodiesterase (ENPP)1-CD73 axis, the counteracting ATP-regenerating ectoenzymatic pathway, and cellular adenosine uptake and its phosphorylation by adenosine kinase. This review provides a holistic view of extracellular and intracellular adenosine metabolism as an integrated complex network and summarizes recent data on the underlying mechanisms through which adenosine and its precursors ATP and ADP control cancer immunosurveillance, tumor angiogenesis, lymphangiogenesis, cancer-associated thrombosis, blood flow, and tumor perfusion. Special attention is given to differences and commonalities in the purinome of different cancers, heterogeneity of the tumor microenvironment, subcellular compartmentalization of the adenosine system, and novel roles of purine-converting enzymes as targets for cancer therapy. SIGNIFICANCE STATEMENT: The discovery of the role of adenosine as immune checkpoint regulator in cancer has led to the development of novel therapeutic strategies targeting extracellular adenosine metabolism and signaling in multiple clinical trials and preclinical models. Here we identify major gaps in knowledge that need to be filled to improve the therapeutic gain from agents targeting key components of the adenosine metabolic network and, on this basis, provide a holistic view of the cancer purinome as a complex and integrated network.

Adenosine Kinase on Deoxyribonucleic Acid Methylation: Adenosine Receptor-Independent Pathway in Cancer Therapy

Methylation is an important mechanism contributing to cancer pathology. Methylation of tumor suppressor genes and oncogenes has been closely associated with tumor occurrence and development. New insights regarding the potential role of the adenosine receptor-independent pathway in the epigenetic modulation of DNA methylation offer the possibility of new interventional strategies for cancer therapy. Targeting DNA methylation of cancer-related genes is a promising therapeutic strategy; drugs like 5-Aza-2′-deoxycytidine (5-AZA-CdR, decitabine) effectively reverse DNA methylation and cancer cell growth. However, current anti-methylation (or methylation modifiers) are associated with severe side effects; thus, there is an urgent need for safer and more specific inhibitors of DNA methylation (or DNA methylation modifiers). The adenosine signaling pathway is reported to be involved in cancer pathology and participates in the development of tumors by altering DNA methylation. Most recently, an adenosine metabolic clearance enzyme, adenosine kinase (ADK), has been shown to influence methylation on tumor suppressor genes and tumor development and progression. This review article focuses on recent updates on ADK and its two isoforms, and its actions in adenosine receptor-independent pathways, including methylation modification and epigenetic changes in cancer pathology.

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

The immunosuppressive effect of adenosine in the microenvironment of a tumor is well established. Presently, researchers are developing approaches in immune therapy that target inhibition of adenosine or its signaling such as CD39 or CD73 inhibiting antibodies or adenosine A2A receptor antagonists. However, numerous enzymatic pathways that control ATP-adenosine balance, as well as understudied intracellular adenosine regulation, can prevent successful immunotherapy. This review contains the latest data on two adenosine-lowering enzymes: adenosine kinase (ADK) and adenosine deaminase (ADA). ADK deletes adenosine by its phosphorylation into 5′-adenosine monophosphate. Recent studies have revealed an association between a long nuclear ADK isoform and an increase in global DNA methylation, which explains epigenetic receptor-independent role of adenosine. ADA regulates the level of adenosine by converting it to inosine. The changes in the activity of ADA are detected in patients with various cancer types. The article focuses on the biological significance of these enzymes and their roles in the development of cancer. Perspectives of future studies on these enzymes in therapy for cancer are discussed.

Pros and Cons of Pharmacological Manipulation of cGMP-PDEs in the Prevention and Treatment of Breast Cancer

The cyclic nucleotides, cAMP and cGMP, are ubiquitous second messengers responsible for translating extracellular signals to intracellular biological responses in both normal and tumor cells. When these signals are aberrant or missing, cells may undergo neoplastic transformation or become resistant to chemotherapy. cGMP-hydrolyzing phosphodiesterases (PDEs) are attracting tremendous interest as drug targets for many diseases, including cancer, where they regulate cell growth, apoptosis and sensitization to radio- and chemotherapy. In breast cancer, PDE5 inhibition is associated with increased intracellular cGMP levels, which is responsible for the phosphorylation of PKG and other downstream molecules involved in cell proliferation or apoptosis. In this review, we provide an overview of the most relevant studies regarding the controversial role of PDE inhibitors as off-label adjuvants in cancer therapy.

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.

Adenosine kinase: An epigenetic modulator in development and disease

Adenosine kinase (ADK) is the key regulator of adenosine and catalyzes the metabolism of adenosine to 5'-adenosine monophosphate. The enzyme exists in two isoforms: a long isoform (ADK-long, ADK-L) and a short isoform (ADK-short, ADK-S). The two isoforms are developmentally regulated and are differentially expressed in distinct subcellular compartments with ADK-L localized in the nucleus and ADK-S localized in the cytoplasm. The nuclear localization of ADK-L and its biochemical link to the transmethylation pathway suggest a specific role for gene regulation via epigenetic mechanisms. Recent evidence reveals an adenosine receptor-independent role of ADK in determining the global methylation status of DNA and thereby contributing to epigenomic regulation. Here we summarize recent progress in understanding the biochemical interactions between adenosine metabolism by ADK-L and epigenetic modifications linked to transmethylation reactions. This review will provide a comprehensive overview of ADK-associated changes in DNA methylation in developmental, as well as in pathological conditions including brain injury, epilepsy, vascular diseases, cancer, and diabetes. Challenges in investigating the epigenetic role of ADK for therapeutic gains are briefly discussed.

In Search of a Role for Extracellular Purine Enzymes in Bone Function

Bone is one of the major tissues that undergoes continuous remodeling throughout life, thus ensuring both organic body growth during development and protection of internal organs as well as repair of trauma during adulthood. Many endogenous substances contribute to bone homeostasis, including purines. Their role has increasingly emerged in recent decades as compounds which, by interacting with specific receptors, can help determine adequate responses of bone cells to physiological or pathological stimuli. Equally, it is recognized that the activity of purines is closely dependent on their interconversion or metabolic degradation ensured by a series of enzymes present at extracellular level as predominantly bound to the cell membrane or, also, as soluble isoforms. While the effects of purines mediated by their receptor interactions have sufficiently, even though not entirely, been characterized in many tissues including bone, those promoted by the extracellular enzymes providing for purine metabolism have not been. In this review, we will try to circumstantiate the presence and the role of these enzymes in bone to define their close relationship with purine activities in maintaining bone homeostasis in normal or pathological conditions.

Exosomes: Small EVs with Large Immunomodulatory Effect in Glioblastoma

Glioblastomas are among the most aggressive tumors, and with low survival rates. They are characterized by the ability to create a highly immunosuppressive tumor microenvironment. Exosomes, small extracellular vesicles (EVs), mediate intercellular communication in the tumor microenvironment by transporting various biomolecules (RNA, DNA, proteins, and lipids), therefore playing a prominent role in tumor proliferation, differentiation, metastasis, and resistance to chemotherapy or radiation. Exosomes are found in all body fluids and can cross the blood–brain barrier due to their nanoscale size. Recent studies have highlighted the multiple influences of tumor-derived exosomes on immune cells. Owing to their structural and functional properties, exosomes can be an important instrument for gaining a better molecular understanding of tumors. Furthermore, they qualify not only as diagnostic and prognostic markers, but also as tools in therapies specifically targeting aggressive tumor cells, like glioblastomas.

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.

Adenosine Kinase Expression Determines DNA Methylation in Cancer Cell Lines

DNA methylation has a major role in cancer, and its inhibitors are used therapeutically. DNA methylation depends on methyl group flux through the transmethylation pathway, which forms adenosine. We hypothesized that an adenosine kinase isoform with nuclear expression (ADK-L) determines global DNA methylation in cancer cells. We quantified ADK-L expression (Western Blot) and global DNA methylation as percent 5-methyldeoxycytidine (5mdC, LC-MS/MS) in three cancer lines (HeLa, HepG2, and U373). ADK-L expression and global DNA methylation correlated positively with the highest levels in HeLa cells compared to U373 and HepG2 cells. To determine whether ADK increases global DNA methylation and to validate its potential therapeutics, we treated HeLa cells with potent ADK inhibitors MRS4203 and MRS4380 (IC₅₀ 88 and 140 nM, respectively). Both nucleosides, but not a structurally related poor ADK inhibitor, significantly reduced global DNA methylation in HeLa cells in a concentration-dependent manner. Thus, ADK-L is a potential target for the therapeutic manipulation of DNA methylation levels in cancer.

Adenosine metabolism in the vascular system

The concept of extracellular purinergic signaling was first proposed by Geoffrey Burnstock in the early 1970s. Since then, extracellular ATP and its metabolites ADP and adenosine have attracted an enormous amount of attention in terms of their involvement in a wide range of immunomodulatory, thromboregulatory, angiogenic, vasoactive and other pathophysiological activities in different organs and tissues, including the vascular system. In addition to significant progress in understanding the properties of nucleotide- and adenosine-selective receptors, recent studies have begun to uncover the complexity of regulatory mechanisms governing the duration and magnitude of the purinergic signaling cascade. This knowledge has led to the development of new paradigms in understanding the entire purinome by taking into account the multitude of signaling and metabolic pathways involved in biological effects of ATP and adenosine and compartmentalization of the adenosine system. Along with the "canonical route" of ATP breakdown to adenosine via sequential ecto-nucleoside triphosphate diphosphohydrolase-1 (NTPDase1/CD39) and ecto-5'-nucleotidase/CD73 activities, it has now become clear that purine metabolism is the result of concerted effort between ATP release, its metabolism through redundant nucleotide-inactivating and counteracting ATP-regenerating ectoenzymatic pathways, as well as cellular nucleoside uptake and phosphorylation of adenosine to ATP through complex phosphotransfer reactions. In this review I provide an overview of key enzymes involved in adenosine metabolic network, with special emphasis on the emerging roles of purine-converting ectoenzymes as novel targets for cancer and vascular therapies.

Fluorescent Probes for Ecto-5'-nucleotidase (CD73)

Ecto-5'-nucleotidase (CD73) catalyzes the hydrolysis of AMP to anti-inflammatory, immunosuppressive adenosine. It is expressed on vascular endothelial, epithelial, and also numerous cancer cells where it strongly contributes to an immunosuppressive microenvironment. In the present study we designed and synthesized fluorescent-labeled CD73 inhibitors with low nanomolar affinity and high selectivity based on N ⁶ -benzyl-α,β-methylene-ADP (PSB-12379) as a lead structure. Fluorescein was attached to the benzyl residue via different linkers resulting in PSB-19416 (14b, K _i 12.6 nM) and PSB-18332 (14a, K _i 2.98 nM) as fluorescent high-affinity probes for CD73. These compounds are anticipated to become useful tools for biological studies, drug screening, and diagnostic applications.

Immune checkpoint molecules in natural killer cells as potential targets for cancer immunotherapy

Recent studies have demonstrated the potential of natural killer (NK) cells in immunotherapy to treat multiple types of cancer. NK cells are innate lymphoid cells that play essential roles in tumor surveillance and control that efficiently kill the tumor and do not require the major histocompatibility complex. The discovery of the NK’s potential as a promising therapeutic target for cancer is a relief to oncologists as they face the challenge of increased chemo-resistant cancers. NK cells show great potential against solid and hematologic tumors and have progressively shown promise as a therapeutic target for cancer immunotherapy. The effector role of these cells is reliant on the balance of inhibitory and activating signals. Understanding the role of various immune checkpoint molecules in the exhaustion and impairment of NK cells when their inhibitory receptors are excessively expressed is particularly important in cancer immunotherapy studies and clinical implementation. Emerging immune checkpoint receptors and molecules have been found to mediate NK cell dysfunction in the tumor microenvironment; this has brought up the need to explore further additional NK cell-related immune checkpoints that may be exploited to enhance the immune response to refractory cancers. Accordingly, this review will focus on the recent findings concerning the roles of immune checkpoint molecules and receptors in the regulation of NK cell function, as well as their potential application in tumor immunotherapy.

Targeting Metabolism of Extracellular Nucleotides via Inhibition of Ectonucleotidases CD73 and CD39

In the tumor microenvironment, unusually high concentrations of extracellular adenosine promote tumor proliferation through various immunosuppressive mechanisms. Blocking adenosine production by inhibiting nucleotide-metabolizing enzymes, such as ectonucleotidases CD73 and CD39, represents a promising therapeutic strategy that may synergize with other immuno-oncology mechanisms and chemotherapies. Emerging small-molecule ectonucleotidase inhibitors have recently entered clinical trials. This Perspective will outline challenges, strategies, and recent advancements in targeting this class with small-molecule inhibitors, including AB680, the first small-molecule CD73 inhibitor to enter clinical development. Specific case studies, including structure-based drug design and lead optimization, will be outlined. Preclinical data on these molecules and their ability to enhance antitumor immunity will be discussed.

De novo transcriptome sequencing of Paecilomyces tenuipes revealed genes involved in adenosine biosynthesis

The use of Paecilomyces tenuipes (P. tenuipes), a Chinese medicinal fungus in scientific research, is limited due to its low adenosine content. To improve adenosine production, the present study investigated the gene network of adenosine biosynthesis in P. tenuipes via transcriptome analysis. Mycelia of P. tenuipes cultured for 24 h (PT24), 102 h (PT102) and 196 h (PT192) were subjected to RNA sequencing. In total, 13,353 unigenes were obtained. Based on sequence similarity, 8,099 unigenes were annotated with known proteins. Of these 8,099 unigenes, 5,123 had functions assigned based on Gene Ontology terms while 4,158 were annotated based on the Eukaryotic Orthologous Groups database. Moreover, 1,272 unigenes were mapped to 281 Kyoto Encyclopedia of Genes and Genomes pathways. In addition, the differential gene expression of the three libraries was also performed. A total of 601, 1,658 and 628 differentially expressed genes (DEGs) were detected in PT24 vs. PT102, PT24 vs. PT192 and PT102 vs. PT192 groups, respectively. Reverse transcription‑quantitative PCR was performed to analyze the expression levels of 14 DEGs putatively associated with adenosine biosynthesis in P. tenuipes. The results showed that two DEGs were closely associated with adenosine accumulation of P. tenuipes. The present study not only provides an improved understanding of the genetic information of P. tenuipes but also the findings can be used to aid research into P. tenuipes.

First person – Karolina Losenkova

First Person is a series of interviews with the first authors of a selection of papers published in Journal of Cell Science, helping early-career researchers promote themselves alongside their papers. Karolina Losenkova is first author on ‘Compartmentalization of adenosine metabolism in cancer cells and its modulation during acute hypoxia’, published in JCS. Karolina is a PhD student in the lab of Gennady Yegutkin at Medicity Research Laboratory, University of Turku, Finland, investigating the role of purine-converting enzymes in tumorigenesis.