CD73 Activity Research Articles

Effect of hyperoxic and hyperbaric conditions on the adenosinergic pathway and CD26 expression in rat

The nucleoside adenosine acts on the nervous and cardiovascular systems via the A2A receptor (A2AR). In response to oxygen level in tissues, adenosine plasma concentration is regulated in particular via its synthesis by CD73 and via its degradation by adenosine deaminase (ADA). The cell-surface endopeptidase CD26 controls the concentration of vasoactive and antioxidant peptides and hence regulates the oxygen supply to tissues and oxidative stress response. Although overexpression of adenosine, CD73, ADA, A2AR, and CD26 in response to hypoxia is well documented, the effects of hyperoxic and hyperbaric conditions on these elements deserve further consideration. Rats and a murine Chem-3 cell line that expresses A2AR were exposed to 0.21 bar O2, 0.79 bar N2 (terrestrial conditions; normoxia); 1 bar O2 (hyperoxia); 2 bar O2 (hyperbaric hyperoxia); 0.21 bar O2, 1.79 bar N2 (hyperbaria). Adenosine plasma concentration, CD73, ADA, A2AR expression, and CD26 activity were addressed in vivo, and cAMP production was addressed in cellulo. For in vivo conditions, 1) hyperoxia decreased adenosine plasma level and T cell surface CD26 activity, whereas it increased CD73 expression and ADA level; 2) hyperbaric hyperoxia tended to amplify the trend; and 3) hyperbaria alone lacked significant influence on these parameters. In the brain and in cellulo, 1) hyperoxia decreased A2AR expression; 2) hyperbaric hyperoxia amplified the trend; and 3) hyperbaria alone exhibited the strongest effect. We found a similar pattern regarding both A2AR mRNA synthesis in the brain and cAMP production in Chem-3 cells. Thus a high oxygen level tended to downregulate the adenosinergic pathway and CD26 activity. Hyperbaria alone affected only A2AR expression and cAMP production. We discuss how such mechanisms triggered by hyperoxygenation can limit, through vasoconstriction, the oxygen supply to tissues and the production of reactive oxygen species.

The role of ecto-5'-nucleotidase in endothelial dysfunction and vascular pathologies.

Ecto-5'-nucleotidase (e5NT, CD73) is an enzyme that is highly expressed in endothelium and is involved in the extracellular nucleotide catabolism. CD73 converts AMP to adenosine that via specific subtypes of P1 receptor mediates cytoprotection involving diverse mechanisms such as vasodilatation, suppression of inflammation, inhibition of thrombosis and anti-adrenergic effect. Physiological intravascular concentration of adenosine is in nanomolar range, but could become micromolar in response to various forms of stress. Endothelium is a major site for both CD73 mediated production of adenosine and its cytoprotective effect. Nucleotides (predominantly ATP or ADP) that could be released from different cells via controlled specific of unspecific mechanisms constitute a major source of substrate for adenosine production via CD73. Direct effects of extracellular nucleotides (mediated by P2 receptors) are typically opposite to adenosine P1 mediated activities. Retention of nucleotides and decreased adenosine production due to loss of CD73 function may have negative implications and could be important cause of various pathologies. Protective role of CD73 was indicated in ectopic calcification, atherosclerosis, rejection after xenotransplantation and thrombosis. Reduced activity of CD73 due to lymphocyte contact with endothelium increases its permeability that leads to enhanced leukocyte transmigration. Upregulation of endothelial CD73 may therefore be protective in a number of cardiovascular pathologies. Such effect has been confirmed for some common drugs such as statins and it could be part of its pleiotropic portfolio. Activation of CD73 could be a new target for specific treatment strategy that in particular will enhance endothelial protection.

CD39+ regulatory T cells attenuate allergic airway inflammation.

The suppressive mechanism of regulatory T cells (Tregs) has remained incompletely clarified. Recent studies found that CD39 expressed by Tregs may participate in the immunoregulatory role of Tregs. CD39-induced ATP hydrolysis and/or adenosine generation contribute to the suppressive mechanism of Tregs. Previous studies suggested that ATP is involved in allergic airway inflammation by acting on type 2 purinergic (P2) receptors, but the role of CD39 and CD39(+) Tregs in allergic airway inflammation has not been elaborated. To investigate the role and underlying mechanism of CD39 expression by Tregs in allergic airway inflammation. A model of allergic asthma was developed with ovalbumin-alum in female Cd39 wild type (Cd39(+/+) ) and deficient (Cd39(-/-) ) C57BL/6 mice. Foxp3-GFP knock-in Cd39(+/+) and Cd39(-/-) mice were used to sort CD4(+) GFP(+) cells (Tregs) for exploring the role of CD39 expression by Tregs in allergic asthma. The effects of modulating CD39 activity with ARL67156 (inhibitor) or apyrase were also observed. ARL67156 greatly worsened airway inflammation including increased lung inflammatory cells infiltration, goblet cell hyperplasia, and higher levels of Th2 and Th17 cytokines in bronchoalveolar lavage fluid (BALF), accompanied by an increment in transcription factor (GATA-3 and RORγt) and P2R (P2Y2, P2Y4 and P2Y6) mRNA expression in lungs. This potentiating effect was rescued by intratracheal injection of apyrase. Airway inflammation was markedly increased in Cd39(-/-) mice compared to Cd39(+/+) mice. In contrast to CD39(-) Tregs, CD39(+) Tregs showed stronger suppressive effects on airway inflammation. In vitro suppression assay suggested that CD39(+) Tregs have more potent suppressive effect on cytokines secretion from CD4(+) CD25(-) responder T cells and the inhibitory effects were reduced by addition of adenosine A2A receptor antagonist. CD39 expressed on Tregs participates in the regulation of limiting allergic airway inflammation by regulating extracellular ATP and/or adenosine. CD39 may represent a new therapeutic target for asthma.

The quantity of CD26 on helper T cells correlates with the efficacy of adoptive cancer immunotherapy (TUM2P.1008)

Abstract Although Th17 cells cause striking tumor eradication upon transfer into mice bearing established melanoma, their translation into the clinic is barred by a lack of FDA-approved cytokines. Consequently, we sought to determine if IL-17-producing CD4+ cells could be enriched from peripheral blood. We found that functional Th17 cells could be isolated from blood, without the need for polarization, by using the surface marker CD26. Excitingly, very few CD26-rich cells, termed CD26high T cells, displayed striking antitumor activity and survival upon transfer into melanoma-bearing mice compared to CD26negative or bulk CD4+ T cells. Of translational significance, we found that human CD26high cells had heightened cytotoxicity and caused greater cancer cell death in vitro. Interestingly, human CD26high T cells have enhanced expression of cytokines (IL-17, IFN-γ, IL-2, TNFα), transcription factors (RORγ, Tbet), integrins (LFA-1, VLA-1) and chemokines (RANTES). Given the unique phenotype of CD26high T cells compared to cells with decreased CD26 expression, the question of this marker's importance is raised. Our preliminary studies reveal that the enzymatic activity of CD26 may be important for the enhanced function, cytotoxicity and migration of these cells and could possibly be targeted to enhance future therapies. Not only do CD26high T cells give hope for Th17 clinical translation, but also provide a potential mechanism by which to improve the T cells used for cancer immunotherapies.

Viral Interference with Functions of the Cellular Receptor Tyrosine Phosphatase CD45

The receptor tyrosine phosphatase CD45 is expressed on the surface of almost all cells of hematopoietic origin. CD45 functions are central to the development of T cells and determine the threshold at which T and B lymphocytes can become activated. Given this pivotal role of CD45 in the immune system, it is probably not surprising that viruses interfere with the activity of CD45 in lymphocytes to dampen the immune response and that they also utilize this molecule to accomplish their replication cycle. Here we report what is known about the interaction of viral proteins with CD45. Moreover, we debate putative interactions of viruses with CD45 in myeloid cells and the resulting consequences—subjects that remain to be investigated. Finally, we summarize the evidence that pathogens were the driving force for the evolution of CD45.

Ecto-5′-nucleotidase (CD73) is involved in chronic cerebral hypoperfusion-induced white matter lesions and cognitive impairment by regulating glial cell activation and pro-inflammatory cytokines

Recent studies have demonstrated that inflammatory and immune mechanisms play important roles in the progression of chronic cerebral hypoperfusion (CCH)-induced white matter lesions (WMLs). As an endogenous neuromodulator in the brain, the extracellular levels of adenosine represent a critical endogenous mechanism for the regulation of immune and inflammatory responses. Ecto-5′-nucleotidase (CD73), which dephosphorylates AMP to adenosine, is considered to catalyze the rate-limiting step in the generation of extracellular adenosine. However, the role of CD73 in the development of CCH-induced WMLs remains unclear. In the present study, we investigated the expression and activity of CD73 using immunohistochemistry, Western blot analysis and measurements of the rate of AMP hydrolysis in a mouse model of CCH via bilateral common carotid artery stenosis (BCAS) surgery. Moreover, C57BL/6-CD73 knockout (KO) and their wild-type littermates were subjected to BCAS surgery to further investigate the functional roles of CD73 in the WMLs. White matter (WM) changes, astrocyte and microglia proliferation, proinflammatory cytokine levels in the corpus callosum and cognitive function were assessed on the 30th day after BCAS. The results indicated that CD73 expression and activities significantly increased in the corpus callosum on the 30th day after BCAS. Moreover, CD73 deficiency exacerbated CCH-induced WMLs and cognitive impairment. More reactive astrocytes and microglia were observed in the corpus callosum in CD73-KO mice. CD73 deficiency significantly increased the levels of proinflammatory cytokines, including tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and interleukin-1β (IL-1β) in the BCAS model of CCH. These findings suggest that CD73 plays a protective role in the development of CCH-induced WMLs and cognitive impairment via the regulation of glial cell activation and proinflammatory cytokine expression.

CD73 plays a protective role in collagen-induced arthritis.

Rheumatoid arthritis (RA) is a chronic autoimmune disease with significant morbidity and mortality. Recent studies suggest that modulation of adenosine signaling, a potent immunosuppressive pathway, is a promising approach for treatment of RA. Extracellular adenosine can come from two sources: transport of intracellular adenosine and hydrolysis of extracellular adenine nucleotides by CD73. In this study, we investigated the susceptibility of CD73-deficient C57BL/6 mice to collagen-induced arthritis (CIA), a well-established mouse model of RA. Our data demonstrated that CD73-deficient mice are significantly more susceptible to CIA than wild-type mice. CD73 deficiency resulted in an increased production of proinflammatory cytokines in the joints, increased Th1 T cell responses, and increased joint destruction. Surprisingly, this was accompanied by delayed anticollagen IgG responses, suggesting defective isotype class switching in CD73-deficient mice. Using bone marrow chimera mice, we demonstrated that CD73 expression on nonhematopoietic cells, but not on hematopoietic cells, was important for protection from CIA. We further demonstrated that administration of a selective A2A adenosine receptor agonist to CD73-deficient mice resulted in arthritis incidence similar to wild-type mice in support of a protective role for A2A signaling. Taken together, our study identifies CD73 as an important regulator of CIA in mice. It also strengthens the notion that CD73-generated adenosine by nonhematopoietic cells plays a protective role in RA and suggests that strategies able to enhance CD73 activity or expression levels may be a valid therapeutic option.

Abstract B06: Chemotherapeutic agents attenuate subsequent CXCL12-induced migration of colon cancer cells by selecting for CXCR4-negative cells and increasing peptidase CD26

Abstract Conventional chemotherapy eliminates the bulk of colorectal cancer (CRC) following surgery. However, recurrence may occur due to the persistence of drug-resistant and cancer-initiating cells that survive exposure to the chemotherapeutic agents. The residual effects of chemotherapy on such surviving cancer cells, and the possible implication for subsequent evolution of metastatic disease, are not well understood. We evaluated the expression and function of the chemokine receptor CXCR4, which is known to enable CRC metastasis, as well as the cancer-initiating cell marker and peptidase CD26, which terminates activity of its chemokine CXCL12. The major CRC chemotherapeutics 5-fluorouracil, oxaliplatin and SN-38 (the active metabolite of irinotecan), as well as cisplatin, doxorubicin, methotrexate and vinblastine, each caused decreases in cell-surface CXCR4 and concomitant increases in CD26 on surviving viable cells from HT-29, T84, HRT-18, SW480 and SW620 CRC cell lines. Flow cytometry revealed that the decline in CXCR4 was associated with a significant loss of CXCR4+ cells. Elevations in CD26 were observed across the entire cell population and were paralleled by increases in both the intrinsic dipeptidyl peptidase activity of CD26 as well as its capacity to bind extracellular adenosine deaminase. CD26-annexin V-propidium iodide co-staining confirmed that CD26 was elevated only on live cells. Orthotopic HT-29 xenografts treated with standard CRC chemotherapeutics 5-fluorouracil, irinotecan, or oxaliplatin showed dramatic increases in CD26 compared to untreated tumors. Consistent with the loss of CXCR4 and gain in CD26, migratory responses to exogenous CXCL12 were eliminated in cells pretreated with cytotoxic agents, although cells retained basal motility. Analysis of cancer-initiating cell CD44 and CD133 subsets showed that drug treatment and elevated CD26 was most closely associated with enrichment of the CD44+CD133- cell population, suggesting benefits of standard chemotherapy may be derived from selective elimination of cell populations by the combination of complementary drugs 5-fluorouracil and oxaliplatin. Our results indicate that conventional anticancer agents may act to inhibit chemokine-mediated migration through eradication of CXCR4+ cells and attenuation of chemokine gradients through elevation of CD26 activity. Citation Format: Murray J. Cutler, Erica L. Lowthers, Cynthia L. Richard, Dagmar M. Hajducek, Paul A. Spagnuolo, Jonathan Blay. Chemotherapeutic agents attenuate subsequent CXCL12-induced migration of colon cancer cells by selecting for CXCR4-negative cells and increasing peptidase CD26. [abstract]. In: Proceedings of the AACR Precision Medicine Series: Drug Sensitivity and Resistance: Improving Cancer Therapy; Jun 18-21, 2014; Orlando, FL. Philadelphia (PA): AACR; Clin Cancer Res 2015;21(4 Suppl): Abstract nr B06.

5'-Ectonucleotidase/CD73 expression on lymph-circulating lymphocytes and lymphatic endothelial cells offers new paths to explore barrier function.

5'-Nucleotidase/CD73 is a key enzyme in the regulation of purinergic signaling, hydrolyzing extracellular AMP to produce adenosine, which is critical in the blood vascular system and in immunosuppression. CD73 is expressed by both blood endothelial cells and lymphatic endothelial cells. Although the role of CD73 on blood endothelial cells in controlling vascular permeability and leukocyte trafficking has been studied, the role of lymphatic CD73 has thus far remained unknown. In this issue of European Journal of Immunology, Yegutkin etal. [Eur. J. Immunol. 2015. 45: 562-573] compare CD73 activity in the endothelia of lymphatics and blood vessels and investigate the CD73(+) lymphocyte subpopulations possibly involved in immunoregulation. This Commentary will discuss how the authors' work sheds light on the differential use of CD73 by these two cell populations to control endothelial permeability and sprouting.

Correlation of low CD73 expression on synovial lymphocytes with reduced adenosine generation and higher disease severity in juvenile idiopathic arthritis.

ObjectiveTo investigate the expression and adenosine‐generating activity of the ecto‐5′‐nucleotidase CD73 on synovial fluid mononuclear cells (SFMCs) and peripheral blood mononuclear cells (PBMCs) from children with juvenile idiopathic arthritis (JIA).MethodsGiven the role of CD73 protein in the production of antiinflammatory adenosine and its intersection with inflammatory biologic pathways, the expression of CD73 on SF and PB lymphocytes from patients with JIA and PB lymphocytes from healthy control subjects was determined by flow cytometry. The AMPase activity of CD73 on PBMCs and SFMCs was measured by high‐performance liquid chromatography. The effects of cell activation on CD73 expression were examined by in vitro culture of PBMCs.ResultsCD8+ and CD19+ SFMCs from patients with JIA expressed decreased levels of CD73 when compared to paired PBMCs from JIA patients and PBMCs from healthy controls. When the percentages of CD73+ synovial lymphocytes were compared between the 2 clinical forms of oligoarthritis, children with extended oligoarthritis showed lower CD73 expression compared to those with the milder form of the disease. CD8+ SFMCs had a lower ability to produce adenosine from etheno‐AMP compared to CD8+ PBMCs. T cell activation through the T cell receptor (TLR) of CD8+CD73+ cells and B cell activation through TLR‐9 resulted in reduced expression of CD73. This down‐regulation occurred on dividing cells.ConclusionThese findings show that low CD73 expression on T and B cells in the inflamed site is related to cell proliferation and is correlated with the clinical severity of oligoarticular JIA. The decreased CD73 expression on SFMCs, in turn, results in reduced adenosine production, which leads to a decreased potential for antiinflammatory activity.

Inactivation of Protein Tyrosine Phosphatases by Peracids Correlates with the Hydrocarbon Chain Length

Background/Aims: Protein tyrosine phosphatases are crucial enzymes controlling numerous physiological and pathophysiological events and can be regulated by oxidation of the catalytic domain cysteine residue. Peracids are highly oxidizing compounds, and thus may induce inactivation of PTPs. The aim of the present study was to evaluate the inhibitory effect of peracids with different length of hydrocarbon chain on the activity of selected PTPs. Methods: The enzymatic activity of human CD45, PTP1B, LAR, bacterial YopH was assayed under the cell-free conditions, and activity of cellular CD45 in human Jurkat cell lysates. The molecular docking and molecular dynamics were performed to evaluate the peracids binding to the CD45 active site. Results: Here we demonstrate that peracids reduce enzymatic activity of recombinant CD45, PTP1B, LAR, YopH and cellular CD45. Our studies indicate that peracids are more potent inhibitors of CD45 than hydrogen peroxide (with an IC50 value equal to 25 nM for peroctanoic acid and 8 µM for hydrogen peroxide). The experimental data show that the inactivation caused by peracids is dependent on hydrocarbon chain length of peracids with maximum inhibitory effect of medium-chain peracids (C8-C12 acyl chain), which correlates with calculated binding affinities to the CD45 active site. Conclusion: Peracids are potent inhibitors of PTPs with the strongest inhibitory effect observed for medium-chain peracids.

New molecules controlling endothelial barrier

Acute lung injury (ALI) and its hypoxemic form, acute respiratory distress syndrome (ARDS), has no approved pharma cological treatment and is a condition with high mortality. Vascular leakage is one of the early events of ALI/ARDS. CD73 activity (ecto5'-nucleotidase) maintains the endothelial barrier function of lung capillaries via its enzymatic endproduct adenosine. Interferon-beta (IFNβ) increases synthesis of CD73 and has been effective in a mouse model of ALI [1].

Contribution of Nrf2 to Atherogenic Phenotype Switching of Coronary Arterial Smooth Muscle Cells Lacking CD38 Gene

Background/Aims: Recent studies have indicated that CD38 gene deficiency results in dedifferentiation or transdifferentiation of arterial smooth muscle cells upon atherogenic stimulations. However, the molecular mechanisms mediating this vascular smooth muscle (SMC) phenotypic switching remain unknown. Methods & Results: In the present study, we first characterized the phenotypic change in the primary cultures of coronary arterial myocytes (CAMs) from CD38^-/- mice. It was shown that CD38 deficiency decreased the expression of contractile marker calponin, SM22α and α-SMA but increased the expression of SMC dedifferentiation marker, vimentin, which was accompanied by enhanced cell proliferation. This phenotypic change in CD38^-/- CAMs was enhanced by 7-ketocholesterol (7-Ket), an atherogenic stimulus. We further found that the CD38 deficiency decreased the expression and activity of nuclear factor E2-related factor 2 (Nrf2), a basic leucine zipper (bZIP) transcription factor sensitive to redox regulation. Similar to CD38 deletion, Nrf2 gene silencing increased CAM dedifferentiation upon 7-Ket stimulation. In contrast, the overexpression of Nrf2 gene abolished 7-Ket-induced dedifferentiation in CD38^-/- CAMs. Given the sensitivity of Nrf2 to oxidative stress, we determined the role of redox signaling in the regulation of Nrf2 expression and activity associated with CD38 effect in CAM phenotype changes. It was demonstrated that in CD38^-/- CAMs, 7-Ket failed to stimulate the production of O₂^-., while in CD38^+/+ CAMs 7-Ket induced marked O₂^-. production and enhancement of Nrf2 activity, which was substantially attenuated by NOX4 gene silencing. Finally, we demonstrated that 7-Ket-induced and NOX4-dependent O₂^-. production was inhibited by 8-Br-cADPR, an antagonist of cADPR or NED-19, an antagonist of NAADP as product of CD38 ADP-ribosylcyclase, which significantly inhibited the level of cytosolic Ca²⁺ and the activation of Nrf2 under 7-Ket. Conclusion: Taken together, these results suggest that CD38 activity is required for 7-Ket-induced Ca²⁺ and consequently O₂^-. production in CAMs, which increases Nrf2 activity to maintain their differentiated status. When CD38 gene expression and function are deficient, the Nrf2 activity is suppressed, thereby leading to phenotypic switching of CAMs.

Human peripheral blood CD34+ cells attenuate oleic acid–induced acute lung injury in rats

Background aimsAdult stem cell–based therapy is a promising novel approach for treatment of acute lung injury (ALI). In this study, we evaluated the therapeutic effect of isolated human peripheral blood CD34+ progenitor cells in an ALI rat model, induced by oleic acid (OA) injection. MethodsSeventy-five adult female rats were used in this study. Group A, control without treatment, and group B, control injected with phosphate-buffered saline, comprised 15 rats each; the remaining 45 rats were injected with OA to induce ALI and were further subdivided into 3 groups: group C (ALI group, 15 rats), group D (ALI and fibroblast group, 15 rats) and group E (ALI and CD34+ cell group, 15 rats). ResultsCD34+ cells transplantation in rats with OA-induced lung injury improves the arterial PaO2 and wet/dry ratio, reduces infiltration of inflammatory cells and decreases lung vascular permeability as determined by reduced intra-alveolar and interstitial patchy congestion and hemorrhage as well as decreased interstitial edema. Additionally, lung inflammation determined by expression of the pro-inflammatory mediators intercellular adhesion molecule 1 and tumor necrosis factor-α was attenuated in CD34+ cell–treated rats at 6, 24 and 48 h post-OA challenge compared with non-treated rats. Moreover, the expression of anti-inflammatory molecule interleukin-10 was up-regulated in the lung of OA-induced ALI rats after administration of CD34+ cells. The important finding was that human TNF-α-induced protein 6 (TSG-6) gene expression was significantly up-regulated in rats treated with CD34+ cells. ConclusionsThe freshly isolated human peripheral blood–derived CD34+ cells may be used as an important source of stem cells that improve ALI. The anti-inflammatory properties of CD34+ cells in the lung are explained, at least in part, by activation of CD34+ cells to express TSG-6.

Ecto-5'-nucleotidase/CD73 enhances endothelial barrier function and sprouting in blood but not lymphatic vasculature.

CD73/ecto-5'-nucleotidase is a key enzyme in the regulation of purinergic signaling and inflammatory reactions. It hydrolyzes extracellular AMP into adenosine, which dampens immune cell activation, and reduces leukocyte trafficking. By comparing CD73 expression and function in mononuclear and endothelial cells (ECs) of blood and lymph, we show that extracellular purines and CD73 activity have differential effects in these two vascular systems. We found that CD8-positive T lymphocytes and CD19-positive B lymphocytes in human lymph expressed high levels of CD73 and other purinergic enzymes and adenosine receptors. Soluble CD73 was less abundant in human lymph than in serum, whereas CD73 activity was higher in afferent lymphatic ECs than in blood ECs. Adenosine signaling improved barrier function and induced sprouting of human blood, but not lymphatic, ECs in vitro. Similarly, using CD73-deficient mice we found that CD73 controls only blood vascular permeability at selected lymphoid organs under physiological conditions. Thus, both vascular and lymphatic arms of the immune system synthesize the components of purinergic signaling system, but surprisingly they use CD73 differentially to control endothelial permeability and sprouting.

CD38 and airway hyper-responsiveness: studies on human airway smooth muscle cells and mouse models.

Asthma is an inflammatory disease in which altered calcium regulation, contractility, and airway smooth muscle (ASM) proliferation contribute to airway hyper-responsiveness and airway wall remodeling. The enzymatic activity of CD38, a cell-surface protein expressed in human ASM cells, generates calcium mobilizing second messenger molecules such as cyclic ADP-ribose. CD38 expression in human ASM cells is augmented by cytokines (e.g., TNF-α) that requires the activation of MAP kinases and the transcription factors, NF-κB and AP-1, and is post-transcriptionally regulated by miR-140-3p and miR-708 by binding to 3' Untranslated Region of CD38 as well as by modulating the activation of signaling mechanisms involved in its regulation. Mice deficient in Cd38 exhibit reduced airway responsiveness to inhaled methacholine relative to the response in wild-type mice. Intranasal challenge of Cd38-deficient mice with TNF-α or IL-13, or the environmental fungus Alternaria alternata, causes significantly attenuated methacholine responsiveness compared with wild-type mice, with comparable airway inflammation. Reciprocal bone marrow transfer studies revealed partial restoration of airway hyper-responsiveness to inhaled methacholine in the Cd38-deficient mice. These studies provide evidence for CD38 involvement in the development of airway hyper-responsiveness; a hallmark feature of asthma. Future studies aimed at drug discovery and delivery targeting CD38 expression and (or) activity are warranted.

Aberrant Hedgehog Pathway Activity Marks Clinical MDS Progression and Accelerates Leukemic Transformation in Vivo

Introduction:Myelodysplastic Syndromes (MDS) represent a heterogeneous group of hematopoietic stem cell (HSC) disorders with varying clinical outcomes, but prognosis uniformly worsens with transformation to secondary acute myeloid leukemia (AML). Despite recent progress in genomics, the mechanisms responsible for disease progression are not fully understood as most of the somatic mutations defined thus far can be found at early stages of the disease. Previous studies have identified aberrant activation of the Hedgehog (Hh) signaling pathway in a subset of AML patients and the expression of the Hh-regulated transcription factor GLI2 correlated with inferior overall and progression free survival. In solid tumors, Hh pathway activation has been associated with metastatic disease progression, and we examined its role in MDS progression and transformation to AML.Methods/Results: We initially quantified changes in Hh pathway activity in CD34+ cells isolated from serial bone marrow samples collected from MDS patients at the time of diagnosis and following progression to AML. We found that the expression of the Hh target genes GLI1 and PTCH1 was increased in 67% of patients (4/6) suggesting that pathway activation was involved in the development of secondary AML. We also analyzed gene expression in 135 MDS patients and found significantly higher GLI2 expression in high-risk MDS (N=80) compared to low-risk MDS (N=55) (p=0.036). In addition, bone marrow blast percentage was significantly higher in the MDS cohort with higher GLI2 expression (mean±SEM=7.1±0.7%) than with lower expression (5.4±0.5%, p=0.039).In order to mechanistically study the effects of Hh pathway activation on MDS progression, we studied mice expressing the Nup98-HoxD13 (NHD13) fusion gene under the control of the vav promoter that generates progressive cytopenia and, in some animals, progression to AML. We crossed NHD13 mice with mice conditionally expressing the constitutively active mutant of the Hh signal transduction regulator Smoothened (SmoM2) in hematopoietic cells expressing Mx1-Cre. The survival of double transgenic animals (NHD13/SmoM2) was significantly shorter compared to mice expressing NHD13 (median survival of 3 months vs. 12 months, p<0.001, Fig. 1). Similar to previous reports we found that the expression of SmoM2 alone had no significant effect on survival or hematologic phenotype. Compared to NHD13 mice, NHD13/SmoM2 mice had significantly higher peripheral blood WBC (93.9k vs. 5.2k, p<0.001) and splenomegaly (633mg vs. 462mg, p=0.006) at the time of disease progression. Furthermore, an immature population of myeloid cells (Mac1+/Gr1 dim) was widely present in peripheral blood, bone marrow and spleen of NHD13/SmoM2 mice. We also examined mice prior to the onset of disease (4-8 weeks post Smo M2 induction) and found an increased frequency of myeloid cells (Mac1+/Gr1+) within the peripheral blood compared to wild type and NHD13/Smo M2 mice (wild type – 17.2%, NHD13 - 40.5%, NHD13/SmoM2 - 68%, p<0.01).Within the bone marrow, hematopoietic stem/progenitor cells (Lin-Sca1+cKit+) were depleted within both NHD13 and NHD13/SmoM2 mice. To examine the impact of Hh activation on clonogenic growth and self-renewal potential, we plated bone marrow cells in methylcellulose and found that NHD13/SmoM2 cells contained a significantly higher number of CFU compared to NHD13 cells (37 vs. 2, p=0.002) that was sustained with subsequent passages (400 vs. 30, p<0.001). In order to define the compartment enriched for leukemia initiating potential (LIC) we transplanted Lin- and Lin+ leukemic fractions from NHD13/SmoM2 mice into naive recipients and found that Lin+ cells led to death within 3 months suggesting that the Lin+ compartment has acquired self- renewal potential.Conclusions:We found that the Hh signaling pathway may be aberrantly activated in a subset of secondary AML patients progressing from MDS. We also demonstrated that activation of Hh signaling induces fatal AML in a mouse model of MDS characterized by inferior survival and widespread expansion of immature myeloid cells. This disease progression is driven by the acquisition of self-renewal and tumor initiating potential in differentiated Lin+ hematopoietic cells. Our findings suggest that Hh pathway inhibition may be a promising approach for AML arising from MDS. [Display omitted] DisclosuresMaciejewski:Alexion: Speakers Bureau; Celgene: Speakers Bureau.

Direct in Vitro Comparison of Daratumumab with Surrogate Analogs of CD38 Antibodies MOR03087, SAR650984 and Ab79

The CD38 molecule, with its high expression on Multiple Myeloma (MM), is considered a suitable target for antibody therapy of MM. We developed daratumumab (DARA), a human CD38 monoclonal antibody (mAb) with direct and Fc-mediated cell killing activity. DARA induces killing of tumor cells, mainly via complement-dependent cytotoxicity (CDC), antibody-dependent cell-mediated cytotoxicity (ADCC) (de Weers M. J Immunol 2011), and antibody-dependent cellular phagocytosis (ADCP) by macrophages (both murine and human). In addition, DARA induces apoptosis upon secondary cross-linking and modulates CD38 enzymatic function. DARA is currently in phase I, II and III clinical evaluation in patients with MM.Besides DARA, several other anti-CD38 mAb are in development; SAR650894 (SAR; clone 38SB19; Sanofi-Aventis) for MM and other CD38+ hematological malignancies, MOR03087 (MOR; Morphosys) for relapsed/refractory MM and Ab79 (Millenium/Takeda) which is in preclinical development. Similar mechanisms of action (MoA) are described for these mAb; nevertheless direct comparison studies would be critical for differentiation among these antibodies. .In this study, the efficacy of these anti-CD38 mAb was directly compared to DARA with respect to binding, apoptosis, CD38 ectoenzyme activity, and the induction of ADCC, ADCP and CDC. Surrogate antibodies of MOR, SAR and Ab79 were generated on the basis of protein sequences, as published in their corresponding patents families, and were attached to the backbone of DARA.Binding to CD38 expressing Daudi tumor cells was assessed by flow cytomery. All CD38 antibodies showed similar EC50 (~0.1 µg/mL) and maximal binding, except MOR which showed a lower apparent affinity (~0.3 µg/mL). Previously, CD38 amino acid residues Q272 and S274 were reported as critical for DARA binding. ELISA analyses using CD38 point mutants revealed MOR, SAR and Ab79 not to be affected by mutation of these residues. All CD38 mAb were equally potent in inducing ADCC of Daudi cells (40-60% lysis, 0.02 µg/mL), in classic Cr51-release ADCC assay using human PBMC effector cells (E:T ratio 100:1). Important differences were observed with respect to induction of CDC. SAR was unable to induce CDC in Daudi cells at concentrations up to 30 µg/mL, while DARA induced more than 80% lysis at concentrations above 1 µg/mL. Ab79 and MOR induced CDC, yet maximum lysis was 50% and 20%, respectively.Evaluation of Annexin V/propidium iodide (AnnV/PI) staining and activation of caspase-3 showed that only SAR induced AnnV/PI+ in Ramos cells (~40%) after 48 h exposure without Fc crosslinking, but did not activate caspase-3. In the presence of Fc crosslinking antibodies, all anti-CD38 mAb induced AnnV/PI+, caspase-3 mediated apoptosis.In enzyme activity assays using purified CD38 protein, SAR inhibited generation of cGDPR (indicative of the combined CD38 cyclase activity generating fluorescent cGDPR and hydrolase activity converting cGDPR into GDPR)more effectively than DARA (~70% vs. ~20% inhibition at 30 µg/mL). Ab79 had a modest effect on CD38 enzyme activity (~10% inhibition). MOR did not affect CD38 enzyme activity at all.The capacity to induce ADCP was only tested for DARA, MOR and Ab79 using mouse macrophages (mϕ) as effector cells and Daudi target cells. mϕ, isolated and matured from bone marrow cells, and calcein-AM labelled target cells (E:T ratio 1:1) were cultured in the presence of 0.0006-5 µg/mL antibody for 4 h. Non-phagocytosed target cells and mϕ were collected and ADCP was evaluated by flow cytometry. All CD38 mAb induced mϕ-mediated phagocytosis, as observed by a concentration dependent increase in the number of double positive mϕ and killing of target cells. Ab79 was as effective as DARA (EC50 ~0.01 µg/mL) in ADCP induction, whereas MOR was less effective (EC50 0.04 µg/mL).In summary, DARA and surrogate mAb of MOR, SAR and Ab79 showed similar binding to cells and induced similar amounts of ADCC. Differences between these mAb involved the ability to directly induce apoptosis, to inhibit the enzymatic activity of CD38 and to induce ADCP. The most striking difference was observed for the ability to induce CDC, the MoA which is currently believed the most important mechanism of MM cell killing in the clinic. DARA efficiently induced high levels of CDC at low concentrations, whereas the other CD38 mAb were unable or less capable to induce CDC. DisclosuresLammerts van Bueren:Genmab: Employment, warrents Other. Jakobs:Genmab: Employment, warrents Other. Kaldenhoven:Genmab: Employment, warrents Other. Roza:Genmab: Employment, warrents Other. Hiddingh:Genmab: Employment. Meesters:Genmab: Employment, warrents Other. Voorhorst:Genmab: Employment, warrents Other. Gresnigt:Genmab: Employment, warrents Other. Wiegman:Genmab: Employment, warrents Other. Ortiz Buijsse:Genmab: Employment, warrents Other. Andringa:Genmab: Employment, warrents Other. Overdijk:Genmab: Employment, warrents Other. Doshi:Janssen R&D: Employment. Sasser:Janssen R&D: Employment. de Weers:Genmab: Employment, warrents Other. Parren:Genmab: Employment, inventor on patents regarding daratumumab Patents & Royalties, stock and warrents Other.

Erythrocyte Adenosine A2B Receptor-Mediated AMP-Activated Protein Kinase Prevents Hypoxia-Induced Tissue Injury in High Altitude By Inducing 2,3-Bisphosphoglycerate

To function effectively in O2 uptake, delivery and release, erythrocytes rely on sophisticated regulation of hemoglobin (Hb)-O2 affinity by allosteric modulators, especially 2,3-bisphophosphoglycerate (2,3-BPG). Earlier studies had shown that elevated erythrocyte 2,3-BPG level is correlated to increased availability of oxygen to tissues in high altitudes. However, nothing is known how 2,3-BPG is induced in high altitude. Recent study revealed that plasma adenosine is increased in patient and mice with sickle cell disease and elevated adenosine signaling via A2B receptor (ADORA2B) induces 2,3-BPG and thereby promotes deoxy-sickle hemoglobin and subsequent sickling. However, whether adenosine is induced and its effect in 2,3-BPG induction in high altitude are unknown. To address this question, we recruited 24 low-land volunteers and placed them in high altitude for different time points. Here we report that: 1) plasma adenosine, a molecule well known to be induced under hypoxia, is increased and its elevation is correlated to elevated erythrocyte 2,3-BPG levels and decreased Hb-O2 affinity; and 2) elevated plasma adenosine is correlated to increased circulating ecto-5’-nucleotidase (CD73), a key enzyme responsible for generation of extracellular adenosine. Similar to humans, increased circulating CD73 activity, plasma adenosine levels and erythrocyte 2,3-BPG and decreased Hb-O2 binding affinity were observed in wild type (WT) mice under hypoxia condition mimicking our human high altitude studies. Moreover, we found that hypoxia-induced increased plasma adenosine, erythrocyte 2,3-BPG and decreased Hb-O2 binding affinity were significantly attenuated in CD73-deficient mice (CD73-/-). As such, hypoxia-induced tissue injury and cell apoptosis were significantly elevated in CD73-/- mice compared to WT mice. Mechanistically, we provide both in vitro and in vivo genetic evidence that erythrocyte adenosine A2B receptor (ADORA2B) is essential for 2,3-BPG induction and subsequent O2 release. This finding led us to further discover that AMP-Activated Protein Kinase (AMPK) functions downstream of ADORA2B underlying adenosine-induced 2,3-BPG induction and O2 release by direct phosphorylation of 2,3-BPG mutase, a key enzyme for 2,3-BPG production. Finally, we demonstrated that treatment of metformin, a FDA approved potent AMPK agonist, induced erythrocyte 2,3-BPG levels and triggered O2 release and thereby prevented hypoxia-induced tissue injury in both CD73-/- mice and erythrocyte specific ADORA2B-deficient mice. Overall, our studies have revealed that erythrocyte ADORA2B-mediated AMPK activation is a novel mechanism underlying hypoxia-induced 2,3-BPG levels and thereby highlight its beneficial role to prevent hypoxia-induced tissue injury. DisclosuresNo relevant conflicts of interest to declare.

Growth and metastasis of B16-F10 melanoma cells is not critically dependent on host CD73 expression in mice.

BackgroundRecent studies have suggested that adenosine generated by ecto-5′-nucleotidase (CD73) in the tumor microenvironment plays a major role in promoting tumor growth by suppressing the immune response and stimulating angiogenesis via A2A and A2B receptors. However, adenosine has also been reported to inhibit tumor growth acting via A1 and A3 receptors. Therefore the aim of this study was to clarify the role of host CD73, which catalyzes the extracellular hydrolysis of AMP to adenosine, on tumor growth and metastasis of B16-F10 melanoma cells.MethodsCD73 and alkaline phosphatase (AP) activity of B16-F10 melanoma cells were measured by HPLC. Tumor cells were injected either subcutaneously or intradermally in WT and CD73−/− mice and tumor growth was monitored by MRI at 9.4 T. Immune cell subpopulations within tumors were assessed by FACS after enzymatic digestion. An endothelium specific CD73−/− was created using Tie2-Cre+ mice and CD73flox/flox (loxP) mice. Chimeric mice lacking CD73−/− on hematopoietic cells was generated by bone marrow transplantation. Lung metastatic spread was measured after intravenous B16-F10 application.ResultsB16-F10 cells showed very little CD73 and negligible AP activity. Neither complete loss of host CD73 nor specific knockout of CD73 on endothelial cells or hematopoietic cells affected tumor growth after subcutaneous or intradermal tumor cell application. Only peritumoral edema formation was significantly attenuated in global CD73−/− mice in the intradermal model. Immune cell composition revealed no differences in the different transgenic mice models. Also lung metastasis after intravenous B16-F10 injection was not altered in CD73−/− mice.ConclusionsCD73 expression on host cells, particularly on endothelial and hematopoietic cells, does not modulate tumor growth and metastatic spread of B16-F10 melanoma cells most likely because of insufficient adenosine formation by the tumor itself.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2407-14-898) contains supplementary material, which is available to authorized users.