Extracellular Adenosine Production Research Articles

CD73/adenosine axis exerts cardioprotection against hypobaric hypoxia-induced metabolic shift and myocarditis in a sex-dependent manner

BackgroundClinical and experimental studies have shown that the myocardial inflammatory response during pathological events varies between males and females. However, the cellular and molecular mechanisms of these sex differences remain elusive. CD73/adenosine axis has been linked to anti-inflammatory responses, but its sex-specific cardioprotective role is unclear. The present study aimed to investigate whether the CD73/adenosine axis elicits sex-dependent cardioprotection during metabolic changes and myocarditis induced by hypobaric hypoxia.MethodsFor 7 days, male and female mice received daily injections of the CD73 inhibitor adenosine 5′- (α, β-methylene) diphosphate (APCP) 10 mg/kg/day while they were kept under normobaric normoxic and hypobaric hypoxic conditions. We evaluated the effects of hypobaric hypoxia on the CD73/adenosine axis, myocardial hypertrophy, and cardiac electrical activity and function. In addition, metabolic homeostasis and immunoregulation were investigated to clarify the sex-dependent cardioprotection of the CD73/adenosine axis.ResultsHypobaric hypoxia-induced cardiac dysfunction and adverse remodeling were more pronounced in male mice. Also, male mice had hyperactivity of the CD73/adenosine axis, which aggravated myocarditis and metabolic shift compared to female mice. In addition, CD73 inhibition triggered prostatic acid phosphatase ectonucleotidase enzymatic activity to sustain adenosine overproduction in male mice but not in female mice. Moreover, dual inhibition prostatic acid phosphatase and CD73 enzymatic activities in male mice moderated adenosine content, alleviating glycolytic shift and proinflammatory response.ConclusionThe CD73/adenosine axis confers a sex-dependent cardioprotection. In addition, extracellular adenosine production in the hearts of male mice is influenced by prostatic acid phosphatase and tissue nonspecific alkaline phosphatase.

SynNotch-programmed iPSC-derived NK cells usurp TIGIT and CD73 activities for glioblastoma therapy

Severe heterogeneity within glioblastoma has spurred the notion that disrupting the interplay between multiple elements on immunosuppression is at the core of meaningful anti-tumor responses. T cell immunoreceptor with Ig and ITIM domains (TIGIT) and its glioblastoma-associated antigen, CD155, form a highly immunosuppressive axis in glioblastoma and other solid tumors, yet targeting of TIGIT, a functionally heterogeneous receptor on tumor-infiltrating immune cells, has largely been ineffective as monotherapy, suggesting that disruption of its inhibitory network might be necessary for measurable responses. It is within this context that we show that the usurpation of the TIGIT − CD155 axis via engineered synNotch-mediated activation of induced pluripotent stem cell-derived natural killer (NK) cells promotes transcription factor-mediated activation of a downstream signaling cascade that results in the controlled, localized blockade of CD73 to disrupt purinergic activity otherwise resulting in the production and accumulation of immunosuppressive extracellular adenosine. Such “decoy” receptor engages CD155 binding to TIGIT, but tilts inhibitory TIGIT/CD155 interactions toward activation via downstream synNotch signaling. Usurping activities of TIGIT and CD73 promotes the function of adoptively transferred NK cells into intracranial patient-derived models of glioblastoma and enhances their natural cytolytic functions against this tumor to result in complete tumor eradication. In addition, targeting both receptors, in turn, reprograms the glioblastoma microenvironment via the recruitment of T cells and the downregulation of M2 macrophages. This study demonstrates that TIGIT/CD155 and CD73 are targetable receptor partners in glioblastoma. Our data show that synNotch-engineered pluripotent stem cell-derived NK cells are not only effective mediators of anti-glioblastoma responses within the setting of CD73 and TIGIT/CD155 co-targeting, but represent a powerful allogeneic treatment option for this tumor.

Unraveling the Intricacies of CD73/Adenosine Signaling: The Pulmonary Immune and Stromal Microenvironment in Lung Cancer

CD73 and adenosine have gained prominence in lung cancer research. The NT5E gene encodes CD73, known as an ectonucleotidase, which plays a crucial role within tumor cells, with immune-suppressive properties. Beyond cancer, CD73 exerts an influence on cardiac, neural, and renal functions, affecting cardiac, neural, and renal functions. CD73’s significance lies in its production of extracellular adenosine. It is notably expressed across diverse cell types within the immune and stromal lung microenvironment. CD73 expression amplifies in lung tumors, especially non-small cell lung cancer (NSCLC), often aligned with key oncogenic drivers like mutant EGFR and KRAS. CD73/adenosine pathway seems to be involved in tumoral immunoevasion, hampering the use of the immune checkpoint inhibitor (ICI) and correlating with therapy resistance. Despite the partial success of current ICI therapies, the CD73/adenosine pathway offers promise in enhancing their effectiveness. This comprehensive review explores recent insights into lung cancer’s CD73/adenosine pathway. It explores roles within tumor cells, the lung’s stromal environment, and the immune system. Ranging from pre-clinical models to clinical trials, potential therapies targeting the adenosine pathway for lung cancer treatment are discussed below.

Expression of functionally distinct ecto-5'-nucleotidase/CD73 glycovariants in reactive astrocytes in experimental autoimmune encephalomyelitis and neuroinflammatory conditions in vitro.

Ecto-5'-nucleotidase/CD73 (eN/CD73) is a membrane-bound enzyme involved in extracellular production of adenosine and a cell adhesion molecule involved in cell-cell interactions. In neuroinflammatory conditions such as experimental autoimmune encephalomyelitis (EAE), reactive astrocytes occupying active demyelination areas significantly upregulate eN/CD73 and express additional eN/CD73 variants. The present study investigated whether the different eN/CD73 variants represent distinct glycoforms and the functional consequences of their expression in neuroinflammatory states. The study was performed in animals at different stages of EAE and in primary astrocyte cultures treated with a range of inflammatory cytokines. Upregulation at the mRNA, protein, and functional levels, as well as the appearance of multiple eN/CD73 glycovariants were detected in the inflamed spinal cord tissue. At the peak of the disease, eN/CD73 exhibited higher AMP turnover and lower enzyme-substrate affinity than the control group, which was attributed to altered glycosylation under neuroinflammatory conditions. A subsequent in vitro study showed that primary astrocytes upregulated eN/CD73 and expressed the multiple glycovariants upon stimulation with TNFα, IL-1β, IL-6, and ATP, with the effect occurring at least in part via induction of JAK/STAT3 signaling. Experimental removal of glycan moieties from membrane glycoproteins by PNGaseF decreased eN/CD73 activity but had no effect on the enzyme's involvement in astrocyte migration. Our results suggest that neuroinflammatory states are associated with the appearance of functionally distinct eN/CD73 glycovariants, which may play a role in the development of the reactive astrocyte phenotype.

Heparins are potent inhibitors of ectonucleotide pyrophosphatase/phospho-diesterase-1 (NPP1) - a promising target for the immunotherapy of cancer.

Heparins, naturally occurring glycosaminoglycans, are widely used for thrombosis prevention. Upon application as anticoagulants in cancer patients, heparins were found to possess additional antitumor activities. Ectonucleotidases have recently been proposed as novel targets for cancerimmunotherapy. In the present study, we discovered that heparin and its derivatives act as potent, selective, allosteric inhibitors of the poorly investigated ectonucleotidase NPP1 (nucleotide pyrophosphatase/phosphodiesterase-1, CD203a). Structure-activity relationships indicated that NPP1 inhibition could be separated from the compounds' antithrombotic effect. Moreover, unfractionated heparin (UFH) and different low molecular weight heparins (LMWHs) inhibited extracellular adenosine production by the NPP1-expressing glioma cell line U87 at therapeutically relevant concentrations. As a consequence, heparins inhibited the ability of U87 cell supernatants to induce CD4+ T cell differentiation into immunosuppressive Treg cells. NPP1 inhibition likely contributes to the anti-cancer effects of heparins, and their specific optimization may lead to improved therapeutics for the immunotherapy of cancer.

Phase 3 study of durvalumab combined with oleclumab or monalizumab in patients with unresectable stage III NSCLC (PACIFIC-9).

TPS8610 Background: Based on the findings of the phase 3 PACIFIC trial, durvalumab as consolidation therapy is the standard of care for patients with unresectable Stage III NSCLC and no disease progression following chemoradiotherapy (CRT; the PACIFIC regimen). However, further improvements in outcomes are needed for this population and, to build upon the backbone of PD-L1 inhibition with durvalumab, immunotherapy combinations including anti-TIGIT, anti-CD73, and anti-NKG2a monoclonal antibodies (mAbs) are now being explored. Two potential candidates, oleclumab and monalizumab, have demonstrated encouraging clinical activity in a randomized, phase 2 trial when combined with durvalumab in this setting. Oleclumab (MEDI9447) is a human IgG1λ mAb that inhibits the function of CD73, to reduce extracellular adenosine production and thus promote antitumor immunity. Monalizumab (IPH2201) is a first-in-class, humanized, IgG4 mAb that prevents NKG2A from binding to HLA-E, which reduces inhibition of natural killer and CD8+ T cells. The combination of each of these molecules with durvalumab consolidation therapy was evaluated in the phase 2 COAST study (NCT03822351). In COAST (n = 189), patients receiving combination therapy reported numerically higher objective response rates (durvalumab plus oleclumab: 30.0%; durvalumab plus monalizumab: 35.5%; durvalumab monotherapy: 17.9%) and prolonged progression-free survival versus durvalumab alone, with no new/significant safety signals (Herbst, et al. 2022). Thus, the combination of oleclumab or monalizumab with consolidative durvalumab warrants further evaluation in a phase 3 trial. Methods: PACIFIC-9 (NCT05221840) is a phase 3, double-blind, placebo-controlled, randomized, international trial. Eligible patients (age ≥18 years) must have EGFR/ALK wild-type unresectable Stage III NSCLC, a WHO performance status of 0/1, documented PD-L1 status, and must not have progressed following ≥2 cycles of definitive, platinum-based concurrent CRT. Approximately 999 patients will be randomized (1:1:1) to receive up to 12 months of treatment (in 28-day cycles) with durvalumab plus either oleclumab (Arm A); monalizumab (Arm B); or placebo (Arm C). The primary endpoint is progression-free survival (RECIST v1.1) by blinded independent central review (BICR). Overall survival is a key secondary endpoint. Other secondary endpoints include objective response rate and duration of response (RECIST v1.1; BICR), patient-reported outcomes, PD-L1 expression on tumor cells relative to efficacy outcomes, and safety/tolerability (CTCAE v5.0). Trial enrollment is ongoing. Previously presented at the World Conference on Lung Cancer (WCLC) 2022, FPN (Final Publication Number): P1.10-01, Fabrice Barlesi et al. Clinical trial information: NCT05221840 .

Abstract PD2-07: Tumor CD73 regulates zoledronate induced TIL accumulation into triple negative breast cancer

Abstract Background: CD73 is a membrane-bound protein that by extracellular adenosine production, regulates immune cell function. Low CD73 expression is associated with better prognosis among triple-negative breast cancer (TNBC) patients. Adjuvant bisphosphonates (BPs, such as zoledronate) improve survival among post-menopausal breast cancer patients, but the mechanism for this is unknown. Since BPs also affect immune cells, we studied 1) whether zoledronate-treatment has an effect on tumor infiltrating lymphocytes (TILs) and 2) whether tumor CD73 expression affects these responses in TNBC tumors. Methods: 4T1 mouse mammary cells, stably expressing non-targeting shRNA (sh-NT, control cells) or sh-CD73 were inoculated into the mammary fat pads of Balb/c mice. The mice were treated with i.p. vehicle or zoledronate (ZOL) each 4th day for total of six times. Additionally, to deplete B-cells, the mice were treated with an anti-CD20 or control IgG antibody. Tumor sizes were assessed with a caliper, TILs were studied with immunostainings. Blood lymphocytes were analyzed with Flow cytometry. Results: Sh-CD73 cells formed significantly smaller tumors, than sh-NT cells. ZOL significantly inhibited the growth of both sh-CD73 and sh-NT tumors, but at sacrifice, this effect of ZOL was more significant against sh-CD73 tumors. ZOL increased the % of CD19+/CD21+ and CD19+/23+ in blood of both mice groups, and this effect was inhibited by anti-CD20 antibody. Although neither treatment alone had an effect, the % of CD3+/CD8+ cells in blood were increased in both mice groups by the combination of ZOL and anti-CD20-antibody. ZOL induced accumulation of B220+, CD4+ and CD8+ TILs into both tumor groups. These TIL effects were reduced with anti-CD20 antibody treatment. Anti-CD20 antibody alone inhibited significantly sh-CD73 tumor growth. Anti-CD20 antibody did not interfere with ZOL inhibition of tumor growth in either group. Conclusions: ZOL has inflammatory effects on blood lymphocytes and TILs, which may be affected by tumor expression of immune system regulating proteins, such as CD73. B cell depletion may further prevent tumor growth, in the context of CD73 inhibition. Further studies are needed to investigate whether B-cell inhibition affects ZOL-induced tumor growth inhibition. Citation Format: Nataliia Petruk, Arafat Siddiqui, Sina Tadayon, Arja Jukkola, Jorma Määttä, Pieta Mattila, Jouko Sandholm, Katri S. Selander. Tumor CD73 regulates zoledronate induced TIL accumulation into triple negative breast cancer. [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr PD2-07.

Abstract IA013: Preclinical testing of CD73 inhibitors for pancreatic cancer immunoprevention

Abstract Introduction: The all stages combined five-year survival rate for pancreatic adenocarcinoma (PDA) is 11%; however, the five-year survival rate for localized PDA is 42%. These statistics highlight the importance of early prevention strategies to prevent disease progression and metastatic dissemination. Through the NCI PREVENT program, this research program explores immunoprevention strategies for PDA by targeting CD73, a gatekeeper ectoenzyme responsible for production of extracellular adenosine. We have recently shown aggressive subtypes of pancreatic intraepithelial neoplasia (PanIN) and PDA arising in ductal pancreatic epithelium have elevated CD73 and intrapancreatic adenosine indicating adenosine generation may be an early trigger of immunosuppression. We hypothesize inhibition of CD73 and adenosine generation will promote a more robust anti-tumor immune response and prevent PanIN and PDA progression. Methods: We tested three small molecule CD73 inhibitors (APCP, OP-5244, and AB680) in a syngeneic PDA mouse model by injecting 100-200k murine PDA cells derived from KrasG12D;Trp53R172H/+;Pdx:Cre (KPC) mice in the flanks of C57BL/6 female mice. Tumor sizes were measured weekly and tumor volume and mass were recorded at time of death. Dosage: APCP oral gavage (3x/week at 20mg/kg) and intraperitoneal (IP) (3x/week at 20 mg/kg). OP-5244 oral (3x/week at 25mg/kg and 10mg/kg). AB680 oral gavage (3x/week at 10mg/kg). HPLC analysis was performed for each inhibitor to quantify adenosine levels. Results: IP delivery of APCP significantly reduced tumor growth and intratumoral adenosine levels; however oral gavage delivery did not reduce tumor growth. Similarly, oral gavage delivery of OP-5244 did not reduce tumor growth. AB680 significantly reduced tumor volume and intratumoral adenosine levels and CyTOF immunoprofiling showed activated CD8+ T cells, dendritic cells, and macrophages were significantly increased in the tumors from AB680 treated mice. Conclusion: APCP IP delivery is more effective than oral gavage delivery and OP-5244 oral gavage delivery does not significantly decrease tumor growth. AB680 oral gavage delivery significantly decreases tumor growth and tumor adenosine concentrations. We observed a significant increase in infiltration of activated CD8+ T cells. AB680 shows high translational potential for preclinical testing in spontaneous GEM models. Citation Format: Lincoln Ballew, Kanchan Singh, Vidhi Chandra, Tingting Mills, Erika Y. Faraoni, Victoria Mota, Trent Clark, Lana Vornik, Michelle I. Savage, Shizuko Sei, Altaf Mohammed, Holger K. Eltzschig, Powel H. Brown, Florencia McAllister, Jennifer M. Bailey-Lundberg. Preclinical testing of CD73 inhibitors for pancreatic cancer immunoprevention [abstract]. In: Proceedings of the Second Biennial NCI Meeting: Translational Advances in Cancer Prevention Agent Development (TACPAD); 2022 Sep 7-9. Philadelphia (PA): AACR; Can Prev Res 2022;15(12 Suppl_2): Abstract nr IA013.

SNAI1-dependent upregulation of CD73 increases extracellular adenosine release to mediate immune suppression in TNBC

Triple-negative subtype of breast cancer (TNBC) is hallmarked by frequent disease relapse and shows highest mortality rate. Although PD-1/PD-L1 immune checkpoint blockades have recently shown promising clinical benefits, the overall response rate remains largely insufficient. Hence, alternative therapeutic approaches are warranted. Given the immunosuppressive properties of CD73-mediated adenosine release, CD73 blocking approaches are emerging as attractive strategies in cancer immunotherapy. Understanding the precise mechanism regulating the expression of CD73 is required to develop effective anti-CD73-based therapy. Our previous observations demonstrate that the transcription factors driving epithelial-to-mesenchymal transition (EMT-TF) can regulate the expression of several inhibitory immune checkpoints. Here we analyzed the role of the EMT-TF SNAI1 in the regulation of CD73 in TNBC cells. We found that doxycycline-driven SNAI1 expression in the epithelial -like TNBC cell line MDA-MB-468 results in CD73 upregulation by direct binding to the CD73 proximal promoter. SNAI1-dependent upregulation of CD73 leads to increased production and release of extracellular adenosine by TNBC cells and contributes to the enhancement of TNBC immunosuppressive properties. Our data are validated in TNBC samples by showing a positive correlation between the mRNA expression of CD73 and SNAI1. Overall, our results reveal a new CD73 regulation mechanism in TNBC that participates in TNBC-mediated immunosuppression and paves the way for developing new treatment opportunities for CD73-positive TNBC.

The Hypoxia-Adenosine Link during Myocardial Ischemia-Reperfusion Injury.

Despite increasing availability and more successful interventional approaches to restore coronary reperfusion, myocardial ischemia-reperfusion injury is a substantial cause of morbidity and mortality worldwide. During myocardial ischemia, the myocardium becomes profoundly hypoxic, thus causing stabilization of hypoxia-inducible transcription factors (HIF). Stabilization of HIF leads to a transcriptional program that promotes adaptation to hypoxia and cellular survival. Transcriptional consequences of HIF stabilization include increases in extracellular production and signaling effects of adenosine. Extracellular adenosine functions as a signaling molecule via the activation of adenosine receptors. Several studies implicated adenosine signaling in cardioprotection, particularly through the activation of the Adora2a and Adora2b receptors. Adenosine receptor activation can lead to metabolic adaptation to enhance ischemia tolerance or dampen myocardial reperfusion injury via signaling events on immune cells. Many studies highlight that clinical strategies to target the hypoxia-adenosine link could be considered for clinical trials. This could be achieved by using pharmacologic HIF activators or by directly enhancing extracellular adenosine production or signaling as a therapy for patients with acute myocardial infarction, or undergoing cardiac surgery.

Abstract 12528: Intima Thickening, Adenosine Reduction and Calcification in CD73-Deficient Mice

Introduction and Hypothesis: The 5' exonucleotidase, CD73, is a key enzyme for extracellular adenosine production. Mutations of the CD73 gene NT5E have been recently reported to cause a rare arterial disease named Arterial Calcification due to Deficiency of CD73 (ACDC). Using a murine model of ACDC, we tested the hypothesis that CD73 protects the arterial wall from hyperplasia and inhibits calcification of vascular smooth muscle cells (SMC). Methods and Results: Echocardiography showed that CD73 deficient mice ( CD73 -/- , n=11) (1.5 yr old, both sexes) had significantly increased aortic intima thickness than C57BL/6J wild type mice (WT, n=8). In culture with inorganic phosphate (Pi, 3.6mM) for 9 days CD73 -/- aortic SMC exhibited elevation of intracellular calcium contents than WT cells (Fig. 1a). HPLC analysis revealed more than 50% reduction of extracellular adenosine in CD73 -/- SMC compared to that in WT SMC (Fig. 1b). Addition of recombinant apolipoprotein-J (Apo-J, 6μg/mL) diminished Pi-induced calcification and restored extracellular adenosine levels in both CD73 -/- - and WT SMC. Conclusions: CD73 plays a key role in maintaining arterial intimal normality, adenosine production and de-calcification. Apo-J serves a regulator of vascular adenosine production and calcification in CD73 -/- mice.

Immunotherapy Strategy Targeting Programmed Cell Death Ligand 1 and CD73 with Macrophage-Derived Mimetic Nanovesicles to Treat Bladder Cancer.

Combination immunotherapy is a promising strategy to remove the inhibitory effect of the tumor microenvironment on immune effector cells, improving the efficacy of immune checkpoint inhibitor treatment in bladder cancer. However, it is challenging to deliver multiple drugs to the tumor tissue effectively and simultaneously to ensure optimal therapeutic effects. Macrophage-derived exosome-mimetic nanovesicles (EMVs) were designed and validated as a nanoplatform for coloading and delivery of the CD73 inhibitor (AB680) and the monoclonal antibody to programmed cell death ligand 1 (aPDL1). The tumor-targeting, biosafety, and therapeutic effects of these nanocomplexes (AB680@EMVs-aPDL1), as a combined immunotherapy strategy for bladder cancer, were assessed in vitro and in vivo. Our results indicate that the nanodrug system was highly stable, provided adequate biosafety, and enhanced tumor targeting in a mouse model of bladder cancer. Moreover, the CD73 inhibitor reduced extracellular adenosine production, and the combination therapy significantly promoted the activation and infiltration of cytotoxic T-lymphocytes, which helped to optimally suppress tumor growth and extend median survival in vivo. Therefore, using EMVs to deliver a combination of aPDL1 and the CD73 inhibitor may be a useful combined immunotherapy strategy for treating bladder cancer.

CD73 Promotes Tumor Progression in Patients with Esophageal Squamous Cell Carcinoma

Simple SummaryThe immune system plays important roles in antitumor activities. However, increasing evidence shows that tumor cells develop several mechanisms to escape the immune attack, resulting in immunosuppression. One of the most important immunosuppressive pathways is the CD73-adenosinergic pathway. In addition, this pathway participates in the development of cancer, including tumor cell proliferation, angiogenesis, and anti-inflammation mechanisms. Moreover, CD73 can mediate the invasion and metastasis of tumor cells via the regulation of cell interactions with the extracellular matrix components. Therefore, overcoming immunosuppression to restore the antitumor functions of T cells may be explored as a potential treatment strategy. Overexpression of CD73 promotes the malignant properties of cancers and is associated with specific clinical characteristics and worse prognosis in many types of cancers. The current study is the first to investigate the role of CD73 in determining the clinical outcomes of patients with esophageal squamous cell carcinoma.Cluster of differentiation (CD)-73 plays pivotal roles in the regulation of immune reactions via the production of extracellular adenosine, and the overexpression of CD73 is associated with worse outcomes in several types of cancers. Here, we identified 167 esophageal squamous cell carcinoma (ESCC) patients who underwent esophagectomy, including 64 and 103 patients with high and low expression levels of CD73, respectively. Univariate and multivariate analyses showed high expression of CD73 was an independent prognostic factor for worse disease-free survival and overall survival. In addition, we selected another cohort consisting of 38 ESCC patients receiving nivolumab or pembrolizumab and found that treatment response and survival benefit to immunotherapy were strongly correlated with the expression levels of CD73/programmed death ligand 1. Moreover, the transwell assay revealed knockdown of CD73 in two ESCC cell lines, TE1 and KYSE30, exhibited significantly reduced abilities of cell invasion and migration. CD73 silencing also showed that the protein expression levels of CD73, vimentin, and snail were downregulated, while those of E-cadherin were upregulated in Western blotting. The findings of our study indicate CD73 may be an independent prognostic factor for ESCC patients who underwent esophagectomy. Furthermore, it may be associated with the patient responses to immunotherapy.

Hyper-Activation of the Adenosinergic Axis in the Eμ-TCL1 Chronic Lymphocytic Leukemia Mouse Model Offers Therapeutic Opportunities

Background. Tumor immunosuppression is a major cause for treatment failure and disease relapse, both in solid tumors and leukemia. Several indications suggest that increased extracellular adenosine levels, which potently suppress T cell responses and skew macrophages towards an M2 phenotype, characterize the tumor microenvironment. Hence, there is intense investigation to identify drugs that target this axis.We previously showed that CLL cells, particularly those endowed in the proliferation centers, express CD39 and CD73, the enzymes that lead to extracellular adenosine production. We also showed that the A2A adenosine receptor is expressed at high levels in CLL lymph nodes, likely due to the effect of hypoxia in positively modulating adenosine production.Aim of the work. The main aim of this work is to study the expression and the role of the adenosinergic axis in vivo, determining the impact of this signaling pathway in CLL progression and modulation of immune responses. To this purpose, we exploited the Eμ-TCL1 (TCL1) mouse model based on the adoptive transfer of spleen-purified leukemic cells in naïve C57BL/6 immunocompetent recipients (WT).Results. Firstly, expression of the adenosinergic axis (CD39, CD73, CD26 and A2A) both on the leukemic side and on bystander immune cells was assessed by comparing cells obtained from the spleen, the bone marrow (BM) and peripheral blood (PB) of TCL1 and WT mice. Flow cytometry analysis of B220+/CD5+ leukemic cells showed that CD39 was constantly expressed at high levels, in contrast to normal circulating B cells from naïve mice. CD73 expression was more heterogeneous, with both CD73+ and CD73- leukemic clones. These data recapitulate the phenotype observed in CLL patients and sustain the hypothesis of variable levels of adenosine in tissues colonized by leukemic cells. In contrast, CD26, the adenosine deaminase-anchoring protein was poorly detected, as opposed to WT B cells. Real-time PCR data obtained from purified cell populations confirmed this expression pattern and also indicated dramatic up-regulation in the expression of the A2A receptor, suggesting that leukemia development is accompanied by increased ability to respond to extracellular adenosine. The development of CLL is usually associated with specific T cell and myeloid subset changes. Multiparametric flow cytometry analyses, with selective markers, were adopted to identify naïve, memory, central memory, effector memory and effector T cells, as well as inflammatory, intermediate or patrolling monocytes. Data obtained confirm that in TCL1 mice the naïve T cell subset was dramatically reduced compared to WT mice, with the simultaneous increase in memory, exhausted and regulatory T cell sub-populations. Both CD4+ and CD8+ lymphocyte subsets in TCL1 mice were highly CD39+ compared to the normal counterpart, as opposed to CD73 that was expressed in distinct subpopulation of cells, including regulatory T cells. No significant differences were highlighted for CD26, in all the tissues considered, while the A2A receptor became expressed at very high levels in all cellular components of the leukemic niche. In the monocyte compartment, we observed a reduction of the inflammatory subset, with a parallel increase of patrolling population, functionally similar to M2 tumor-supportive macrophages.Given the role of low oxygen tension as a critical modulator of the adenosinergic system, hypoxia levels were determined, comparing tumor-bearing and WT mice. Mice were treated with pimonidazole hydrochloride, a hypoxia marker, 2 hours prior euthanasia. Flow cytometry and immuno-histochemistry analyses indicated that leukemic engraftment is paralleled by increased hypoxia levels in the lymphoid tissues, such as spleen or BM.Conclusions.Taken together, these results show that the adenosinergic axis is over-expressed in the TCL1 mouse model and confirm that the presence of leukemic cells polarizes the host immune cells, favoring the establishment of a tumor supportive environment. This could be due, at least partly, to the presence of a highly hypoxic leukemic niche. These observations confirm what described for CLL patients, indicating that this animal model can be used to test the impact of adenosine-targeting therapies, in combination with drugs that directly target the clone. DisclosuresNo relevant conflicts of interest to declare.

Ecto-5'-Nucleotidase (CD73) Regulates the Survival of CD8+ T Cells.

Ecto-5′-nucleotidase (CD73) is an enzyme present on the surface of tumor cells whose primary described function is the production of extracellular adenosine. Due to the immunosuppressive properties of adenosine, CD73 is being investigated as a target for new antitumor therapies. We and others have described that CD73 is present at the surface of different CD8+ T cell subsets. Nonetheless, there is limited information as to whether CD73 affects CD8+ T cell proliferation and survival. In this study, we assessed the impact of CD73 deficiency on CD8+ T cells by analyzing their proliferation and survival in antigenic and homeostatic conditions. Results obtained from adoptive transfer experiments demonstrate a paradoxical role of CD73. On one side, it favors the expression of interleukin-7 receptor α chain on CD8+ T cells and their homeostatic survival; on the other side, it reduces the survival of activated CD8+ T cells under antigenic stimulation. Also, upon in vitro antigenic stimulation, CD73 decreases the expression of interleukin-2 receptor α chain and the anti-apoptotic molecule Bcl-2, findings that may explain the reduced CD8+ T cell survival observed in this condition. These results indicate that CD73 has a dual effect on CD8+ T cells depending on whether they are subject to an antigenic or homeostatic stimulus, and thus, special attention should be given to these aspects when considering CD73 blockade in the design of novel antitumor therapies.

Clustering of adenosine A2B receptors with ectonucleotidases in caveolin-rich lipid rafts underlies immunomodulation by Leishmania amazonensis.

Extracellular adenosine plays important roles in modulating the immune responses. We have previously demonstrated that infection of dendritic cells (DC) by Leishmania amazonensis leads to increased expression of CD39 and CD73 and to the selective activation of the low affinity A2B receptors (A2B R), which contributes to DC inhibition, without involvement of the high affinity A2A R. To understand this apparent paradox, we now characterized the alterations of both adenosine receptors in infected cells. With this aim, bone marrow-derived DC from C57BL/6J mice were infected with metacyclic promastigotes of L. amazonensis. Fluorescence microscopy revealed that L. amazonensis infection stimulates the recruitment of A2B R, but not of A2A R, to the surface of infected DC, without altering the amount of mRNA or the total A2B R density, an effect dependent on lipophosphoglycan (LPG). Log-phase promastigotes or axenic amastigotes of L. amazonensis do not stimulate A2B R recruitment. A2B R clusters are localized in caveolin-rich lipid rafts and the disruption of these membrane domains impairs A2B R recruitment and activation. More importantly, our results show that A2B R co-localize with CD39 and CD73 forming a "purinergic cluster" that allows for the production of extracellular adenosine in close proximity with these receptors. We conclude that A2B R activation by locally produced adenosine constitutes an elegant and powerful evasion mechanism used by L. amazonensis to down-modulate the DC activation.

ARC-8: Phase I/Ib study to evaluate safety and tolerability of AB680 + chemotherapy + zimberelimab (AB122) in patients with treatment-naive metastatic pancreatic adenocarcinoma (mPDAC).

404 Background: AB680, a potent, selective small-molecule inhibitor of soluble and membrane-bound CD73, targets a major pathway of extracellular adenosine production with the aim of eliminating adenosine-mediated immunosuppression within the tumor microenvironment. In mPDAC, programmed cell death protein-1 (PD-1) axis inhibitors have limited clinical activity as monotherapies or combined with standard-of-care (SOC) chemotherapy. KRAS mutations, present in >90% of invasive PDACs, are associated with significantly elevated CD73 expression and poor clinical outcomes. Thus, mPDAC may be particularly sensitive to CD73 inhibition combined with SOC chemotherapy + anti–PD-1 antibody (zimberelimab [Zim]) treatment. Methods: ARC-8 (NCT04104672) is an ongoing phase 1b, dose escalation and expansion study in patients (pts) with treatment-naive mPDAC. In the dose escalation, AB680 (25, 50, 75, or 100 mg) is administered intravenously once every 2 weeks (Q2W) with standard doses of nab-paclitaxel/gemcitabine (NP/Gem) + Zim (240 mg) in a 3+3 design to determine the recommended dose for expansion (RDE). In the dose expansion, AB680 will be administered at the RDE with NP/Gem + Zim. Adverse events (AEs) and dose-limiting toxicities (DLTs) are recorded and graded per NCI CTCAE 5.0. AB680 pharmacokinetics, pharmacodynamics, and biomarker evaluations are also being performed throughout the study. Clinical activity is assessed every 8 weeks per RECIST v1.1. Results: As of 04SEPT2020, enrolled patients include 4 in Cohort 1 (25 mg AB680), 6 in Cohort 2 (50 mg AB680), and 3 in Cohort 3 (75 mg AB680). Initial AE profiles were similar to those observed for NP/Gem. The most common treatment-related AEs were fatigue (n=6, 43%), anemia (n=4, 29%), and neutrophil count decrease (n=4, 29%); anemia (n=2, 14%) was the most common treatment-related grade 3/4 AE. Initial pharmacodynamic data (50 mg dose) indicated excellent peripheral target coverage at AB680 trough concentrations. Best overall responses for 9 evaluable pts were 3 with partial response (1 in Cohort 1; 2 in Cohort 2), including a complete response of a target lesion, and 5 with stable disease (1 in Cohort 1; 4 in Cohort 2). One pt in Cohort 1 discontinued the study due to progressive disease. As of the cutoff date, 1 DLT (Grade 2 autoimmune hepatitis) occurred in Cohort 2; the event completely resolved with steroids and the pt was able to resume study treatment. No DLTs were reported in Cohort 3. Conclusions: Preliminary results from ARC-8 indicate that AB680, the first clinical-stage small-molecule CD73 inhibitor, in combination with SOC chemotherapy + Zim has a manageable safety profile consistent with that expected for each agent alone and demonstrates early signals of clinical activity. Dose escalation to 100 mg AB680 (Cohort 4) is ongoing to inform RDE selection. Clinical trial information: NCT04104672.

Serum CD73 is a prognostic factor in patients with metastatic melanoma and is associated with response to anti-PD-1 therapy

BackgroundInhibitors of immune checkpoint programmed cell death protein 1 (PD-1) receptor on T cells have shown remarkable clinical outcomes in metastatic melanoma. However, most patients are resistant to therapy. Production...

CD73 contributes to anti-inflammatory properties of afferent lymphatic endothelial cells in humans and mice.

CD73 is an important ectoenzyme responsible for the production of extracellular adenosine. It is involved in regulating inflammatory responses and cell migration and is overexpressed in various cancers. The functions of CD73 in blood endothelial cells are understood in detail, but its role on afferent lymphatics remains unknown. Moreover, anti‐CD73 antibodies are now used in multiple clinical cancer trials, but their effects on different endothelial cell types have not been studied. This study reveals that a previously unknown role of CD73 on afferent lymphatics is to dampen immune responses. Knocking it out or suppressing it by siRNA leads to the upregulation of inflammation‐associated genes on lymphatic endothelial cells and a more pro‐inflammatory phenotype of interacting dendritic cells in vitro and in vivo. In striking contrast, anti‐CD73 antibodies had only negligible effects on the gene expression of lymphatic‐ and blood‐endothelial cells. Our data thus reveal new functions of lymphatic CD73 and indicate a low likelihood of endothelial cell–related adverse effects by CD73 targeting therapeutic antibodies.

Protective effect of CD73 inhibitor α, β-methylene ADP against amyloid-β-induced cognitive impairment by inhibiting adenosine production in hippocampus

Alzheimer's disease (AD) is a chronic, progressive neurodegenerative disease. Recent studies have reported the close association between cognitive function in AD and purinergic receptors in the central nervous system. In the current study, we investigated the effect of CD73 inhibitor α, β-methylene ADP (APCP) on cognitive impairment of AD in mice, and to explore the potential underlying mechanisms. We found that acute administration of Aβ 1 – 42 (i.c.v.) resulted in a significant increase in adenosine release by using microdialysis study. Chronic administration of APCP (10, 30 mg/kg) for 20 d obviously mitigated the spatial working memory impairment of Aβ 1 – 42 -treated mice in both Morris water maze (MWM) test and Y-maze test. In addition, the extracellular adenosine production in the hippocampus was inhibited by APCP in Aβ-treated mice. Further analyses indicated expression of acetyltransferase (ChAT) in hippocampus of mice of was significantly reduced, while acetylcholinesterase (AChE) expression increased, which compared to model group. We observed that APCP did not significantly alter the NLRP3 inflammasome activity in hippocampus, indicating that anti-central inflammation seems not to be involved in APCP effect. In conclusion, we report for the first time that inhibition of CD73 by APCP was able to protect against memory loss induced by Aβ 1 – 42 in mice, which may be due to the decrease of CD73-driven adenosine production in hippocampus. Enhancement of central cholinergic function of the central nervous system may also be involved in the effects of APCP. How to cite: Song W, Tang Y, Wei L, et al. Protective effect of CD73 inhibitor α, β-methylene ADP against amyloid-β-Induced cognitive impairment by inhibiting adenosine production in hippocampus. Electron J Biotechnol 2020;48. https://doi.org/10.1016/j.ejbt.2020.09.002