Ecto-5'-nucleotidase (CD73) promotes tumor angiogenesis

CD73-positive pediatric urethral mesenchymal stem-like cell-derived small extracellular vesicles stimulate angiogenesis

Introduction

Angiogenesis plays an important role in the repair of urethral injury, and stem cells and their secretomes can promote angiogenesis. We obtained pediatric urethral mesenchymal stem-like cells (PU-MSLCs) in an earlier study. This project studied the pro-angiogenic effect of PU-MSLC-derived small extracellular vesicles (PUMSLC-sEVs) and the underlying mechanisms.

Materials and methods

PUMSLCs and PUMSLC-sEVs were cultivated and identified. Then, biological methods such as the ethynyl deoxyuridine (EdU) incorporation assay, Cell Counting Kit-8 (CCK-8) assay, scratch wound assay, Transwell assay, and tube formation assay were used to study the effect of PUMSLC-sEVs on the proliferation, migration, and tube formation of human umbilical vein endothelial cells (HUVECs). We explored whether the proangiogenic effect of PUMSLC-sEVs is related to CD73 and whether adenosine (ADO, a CD73 metabolite) promoted angiogenesis. GraphPad Prism 8 software was used for data analysis.

Results

We observed that PUMSLC-sEVs significantly promoted the proliferation, migration, and tube-forming abilities of HUVECs. PUMSLC-sEVs delivered CD73 molecules to HUVECs to promote angiogenesis. The angiogenic ability of HUVECs was enhanced after treatment with extracellular ADO produced by CD73, and PUMSLC-sEVs further promoted angiogenesis by activating Adenosine Receptor A2A (A2AR).

Conclusions

These observations suggest that PUMSLC-sEVs promote angiogenesis, possibly through activation of the CD73/ADO/A2AR signaling axis.

Bioprocess development for cord blood mesenchymal stromal cells on microcarriers in Vertical-Wheel bioreactors

Equine mesenchymal stromal cells (MSCs) have been found to be beneficial for the treatment of many ailments, including orthopedic injuries, due to their superior differentiation potential and immunomodulating properties. Cell therapies require large cell numbers, which are not efficiently generated using conventional static expansion methods. Expansion of equine cord blood-derived MSCs (eCB-MSCs) in bioreactors, using microcarriers as an attachment surface, has the potential to generate large numbers of cells with increased reproducibility and homogeneity compared with static T-flask expansion. This study investigated the development of an expansion process using Vertical-Wheel (VW) bioreactors, a single-use bioreactor technology that incorporates a wheel instead of an impeller. Initially, microcarriers were screened at small scale to assess eCB-MSC attachment and growth and then in bioreactors to assess cell expansion and harvesting. The effect of different donors, serial passaging, and batch versus fed batch were all examined in 0.1 L VW bioreactors. The use of VW bioreactors with an appropriate microcarrier was shown to be able to produce cell densities of up to 1E6 cells/mL, while maintaining cell phenotype and functionality, thus demonstrating great potential for the use of these bioreactors to produce large cell numbers for cell therapies.

5'-Ectonucleotidase CD73/NT5E supports EGFR-mediated invasion of HPV-negative head and neck carcinoma cells

BACKGROUND

Epithelial-to-mesenchymal transition (EMT) of malignant cells is a driving force of disease progression in human papillomavirus-negative (HPV-negative) head and neck squamous cell carcinomas (HNSCC). Sustained hyper-activation of epidermal growth factor receptor (EGFR) induces an invasion-promoting subtype of EMT (EGFR-EMT) characterized by a gene signature ("'EGFR-EMT_Signature'") comprising 5´-ectonucleotidase CD73. Generally, CD73 promotes immune evasion via adenosine (ADO) formation and associates with EMT and metastases. However, CD73 regulation through EGFR signaling remains under-explored and targeting options are amiss.

METHODS

CD73 functions in EGFR-mediated tumor cell dissemination were addressed in 2D and 3D cellular models of migration and invasion. The novel antagonizing antibody 22E6 and therapeutic antibody Cetuximab served as inhibitors of CD73 and EGFR, respectively, in combinatorial treatment. Specificity for CD73 and its role as effector or regulator of EGFR-EMT were assessed upon CD73 knock-down and over-expression. CD73 correlation to tumor budding was studied in an in-house primary HNSCC cohort. Expression correlations, and prognostic and predictive values were analyzed using machine learning-based algorithms and Kaplan-Meier survival curves in single cell and bulk RNA sequencing datasets.

RESULTS

CD73/NT5E is induced by the EGF/EGFR-EMT-axis and blocked by Cetuximab and MEK inhibitor. Inhibition of CD73 with the novel antagonizing antibody 22E6 specifically repressed EGFR-dependent migration and invasion of HNSCC cells in 2D. Cetuximab and 22E6 alone reduced local invasion in a 3D-model. Interestingly, combining inefficient low-dose concentrations of Cetuximab and 22E6 revealed highly potent in invasion inhibition, substantially reducing the functional IC50 of Cetuximab regarding local invasion. A role for CD73 as an effector of EGFR-EMT in local invasion was further supported by knock-down and over-expression experiments in vitro and by high expression in malignant cells budding from primary tumors. CD73 expression correlated with EGFR pathway activity, EMT, and partial EMT (p-EMT) in malignant single HNSCC cells and in large patient cohorts. Contrary to published data, CD73 was not a prognostic marker of overall survival (OS) in the TCGA-HNSCC cohort when patients were stratified for HPV-status. However, CD73 prognosticated OS of oral cavity carcinomas. Furthermore, CD73 expression levels correlated with response to Cetuximab in HPV-negative advanced, metastasized HNSCC patients.

CONCLUSIONS

In sum, CD73 is an effector of EGF/EGFR-mediated local invasion and a potential therapeutic target and candidate predictive marker for advanced HPV-negative HNSCC.

The Clinical Significance of CD73 in Cancer

The search for new and effective treatment targets for cancer immunotherapy is an ongoing challenge. Alongside the more established inhibitory immune checkpoints, a novel potential target is CD73. As one of the key enzymes in the purinergic signalling pathway CD73 is responsible for the generation of immune suppressive adenosine. The expression of CD73 is higher in tumours than in the corresponding healthy tissues and associated with a poor prognosis. CD73, mainly by the production of adenosine, is critical in the suppression of an adequate anti-tumour immune response, but also in promoting cancer cell proliferation, tumour growth, angiogenesis, and metastasis. The upregulation of CD73 and generation of adenosine by tumour or tumour-associated immune cells is a common resistance mechanism to many cancer treatments such as chemotherapy, radiotherapy, targeted therapy, and immunotherapy. Therefore, the inhibition of CD73 represents a new and promising approach to increase therapy efficacy. Several CD73 inhibitors have already been developed and successfully demonstrated anti-cancer activity in preclinical studies. Currently, clinical studies evaluate CD73 inhibitors in different therapy combinations and tumour entities. The initial results suggest that inhibiting CD73 could be an effective option to augment anti-cancer immunotherapeutic strategies. This review provides an overview of the rationale behind the CD73 inhibition in different treatment combinations and the role of CD73 as a prognostic marker.

CD73 (NT5E) Promotes the Proliferation and Metastasis of Lung Adenocarcinoma through the EGFR/AKT/mTOR Pathway

Introduction

Lung cancer is the most common malignant tumor and the main cause of tumor-related death globally. As the 5-year survival rate of lung adenocarcinoma (LUAD) remains low, it is necessary to investigate novel molecular markers and therapeutic targets for LUAD.

Materials and Methods

The protein expression of CD73 (NT5E) in LUAD specimens was analyzed using immunohistochemistry. Reverse transcription-quantitative PCR and western blot analysis were used to analyze the mRNA and protein expression levels of several genes in LUAD cells. The proliferation of LUAD cells was evaluated using proliferation and colony formation assays and apoptosis analysis. Wound healing and Transwell invasion assays were used to analyze the migration and invasion of the A549 cells, respectively. In addition, overexpression plasmids and small interfering RNAs were used to overexpress or knockdown the expression levels of CD73 in the A549 cell line, respectively. Finally, the interaction between CD73 and EGFR in the A549 cell line was analyzed using immunoprecipitation.

Results

Our research emphasized the importance of CD73 in the prognosis of LUAD and highlighted it as a potential therapeutic target. We also found that the mRNA and protein expression levels of CD73 are increased in LUAD specimens and cell lines and were associated with a poor prognosis in patients with LUAD. Furthermore, it was revealed that CD73 may promote the proliferation, migration, and invasion of the A549 cell line. Finally, we demonstrated that CD73 could bind epidermal growth factor receptor (EGFR) to further regulate the activation of the AKT/mTOR signaling pathway.

Conclusions

CD73 promotes LUAD proliferation and metastasis through EGFR/AKT/mTOR axis.

The Effects of CD73 on Gastrointestinal Cancer Progression and Treatment

Gastrointestinal (GI) cancer is a common and deadly malignant tumor. CD73, a cell-surface protein, acts as a switch of the adenosine-related signaling pathway that can cause significant immunosuppression. Recent evidence has emerged that CD73 is a promising immunotherapy target for regaining immune cell function and restraining tumorigenesis, and a growing stream of research indicates that combining immunotherapy with other therapies can effectively improve the prognosis and survival of GI cancer patients. Several immune checkpoint inhibitors have been approved for use in GI cancer recently; however, they have demonstrated limited efficacy. Solving the problem of immunosuppression in GI cancer is the key to developing an effective therapeutic option and the modulation of CD73 expression may provide an answer. In this review, we discuss current research on CD73 in gastric, liver, pancreatic, and colorectal cancer to evaluate its therapeutic potential as an immunotherapy target in GI cancers.

CD73-Positive Small Extracellular Vesicles Derived From Umbilical Cord Mesenchymal Stem Cells Promote the Proliferation and Migration of Pediatric Urethral Smooth Muscle Cells Through Adenosine Pathway

Smooth muscle cells (SMCs) are the main functional component of urethral tissue, but are difficult to proliferate in vitro. Mesenchymal stem cells (MSCs) and mesenchymal stem cell-derived small extracellular vesicles (MSC-sEV) have been shown to promote tissue repair by regulating the proliferation and migration of different types of cells. In this study, we investigated the effect of umbilical cord mesenchymal stem cell-derived sEV (UCMSC-sEV) on the proliferation and migration of pediatric urethral smooth muscle cells (PUSMCs) and the mechanism by which sEV regulates the function of PUSMCs. We observed that UCMSC-sEV can significantly promote the proliferation and migration of PUSMCs in vitro. UCMSC-sEV exerted proliferation and migration promotion effects by carrying the CD73 to PUSMCs and catalyzing the production of adenosine. Conversely, the effect of UCMSC-sEV on the proliferation and migration of PUSMCs were no longer observed with addition of the PSB12379 as a CD73 inhibitor. It was found that the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT) signaling pathway in PUSMCs was activated by adenosine or UCMSC-sEV intervention. In summary, UCMSC-sEV promoted proliferation and migration of PUSMCs in vitro by activating CD73/adenosine signaling axis and downstream PI3K/AKT pathway. Thus, we concluded that UCMSC-sEV may be suggested as a new solution strategy for the urethral tissue repair.

Emerging antibody therapies for pancreatic adenocarcinoma: a review of recent phase 2 trials

Introduction: Pancreatic adenocarcinoma is now the third-leading cause of cancer-related deaths in the US which can be attributed to rising incidence, diagnosis at advanced stages and early development of metastasis. Systemic therapy remains palliative with early development of resistance possibly related to the constitutive activation of 'undruggable' KRAS, immunosuppressive microenvironment, and intense desmoplasia. The advancements in molecular biology has led to the development and investigation of targeted and immune therapeutics.Areas covered: This study provides a comprehensive review of the literature to further the understanding of molecular targets with their respective antibody-based therapies in clinical development in pancreatic cancer. PubMed was systematically searched for English-language articles discussing antibody-based therapies under phase 2 clinical trial investigation in pancreatic adenocarcinoma.Expert opinion: PDAC remains highly resistant to chemotherapy with no significant improvement in survival for patients with advanced or metastatic cancer. Unfortunately, the majority of the antibody-based targeted and immune therapeutics have failed to meet their primary efficacy endpoints in early phase trials. However, there are a few promising antibody-based drugs with intriguing preliminary data that merit further investigation, while many more continue to be developed and investigated preclinically, and in early phase trials.

Review of novel tissue-based biomarkers for prostate cancer: towards personalised and targeted medicine

Background:

Prostate cancer is the most commonly diagnosed cancer in men and responsible for about 10% of all cancer mortality in both Canadian and American men. Currently, serum PSA level is the most commonly used test for the detection of prostate cancer, though the levels can also be elevated in benign conditions, has limited specificity and has a high rate of overdiagnosis and treatment of indolent disease. Consequently, in recent years, several investigations have been conducted to identify novel cancer biomarkers capable of both effective screening and diagnosis, as well as assisting to shift the diagnostic and treatment paradigm of prostate cancer towards more patient-specific and targeted medicine. The goal of this narrative review paper is to describe eleven novel and promising tissue-based biomarkers for prostate cancer capable to account for individual patient variabilities and have the potential for risk assessment, early detection and diagnosis, identification of patients who will benefit from a particular treatment and monitoring patient response to treatment.

Materials and methods:

We searched several databases from August to December 2020 for relevant studies published in English between 2000 and 2020 and reporting on tissue-based biomarkers for screening and early diagnosis, treatment and monitoring of prostate cancer.

Conclusions:

Emerging prostate cancer biomarkers have the potential to guide clinical decision-making since they have the potential to detect the disease early, measure the risk of developing the disease and the risk of progression, provide accurate information of patient response to a specific treatment and are capable of informing clinicians about the likely outcome of a cancer diagnosis independent of the treatment received. Therefore, the future holds promise for personalised and targeted medicine from prevention to diagnosis and treatment that considers the individual patient’s variabilities in the management of prostate cancer.

Enzymology of extracellular NAD metabolism

Extracellular NAD represents a key signaling molecule in different physiological and pathological conditions. It exerts such function both directly, through the activation of specific purinergic receptors, or indirectly, serving as substrate of ectoenzymes, such as CD73, nucleotide pyrophosphatase/phosphodiesterase 1, CD38 and its paralog CD157, and ecto ADP ribosyltransferases. By hydrolyzing NAD, these enzymes dictate extracellular NAD availability, thus regulating its direct signaling role. In addition, they can generate from NAD smaller signaling molecules, like the immunomodulator adenosine, or they can use NAD to ADP-ribosylate various extracellular proteins and membrane receptors, with significant impact on the control of immunity, inflammatory response, tumorigenesis, and other diseases. Besides, they release from NAD several pyridine metabolites that can be taken up by the cell for the intracellular regeneration of NAD itself. The extracellular environment also hosts nicotinamide phosphoribosyltransferase and nicotinic acid phosphoribosyltransferase, which inside the cell catalyze key reactions in NAD salvaging pathways. The extracellular forms of these enzymes behave as cytokines, with pro-inflammatory functions. This review summarizes the current knowledge on the extracellular NAD metabolome and describes the major biochemical properties of the enzymes involved in extracellular NAD metabolism, focusing on the contribution of their catalytic activities to the biological function. By uncovering the controversies and gaps in their characterization, further research directions are suggested, also to better exploit the great potential of these enzymes as therapeutic targets in various human diseases.

Tackling Immune Targets for Breast Cancer: Beyond PD-1/PD-L1 Axis

The burden of breast cancer is imposing a huge global problem. Drug discovery research and novel approaches to treat breast cancer have been carried out extensively over the last decades. Although immune checkpoint inhibitors are showing promising preclinical and clinical results in treating breast cancer, they are facing multiple limitations. From an immunological perspective, a recent report highlighted breast cancer as an "inflamed tumor" with an immunosuppressive microenvironment. Consequently, researchers have been focusing on identifying novel immunological targets that can tune up the tumor immune microenvironment. In this context, several novel non-classical immune targets have been targeted to determine their ability to uncouple immunoregulatory pathways at play in the tumor microenvironment. This article will highlight strategies designed to increase the immunogenicity of the breast tumor microenvironment. It also addresses the latest studies on targets which can enhance immune responses to breast cancer and discusses examples of preclinical and clinical trial landscapes that utilize these targets.

Adenosine Signaling in the Tumor Microenvironment

Adenosine, deriving from ATP released by dying cancer cells and then degradated in the tumor environment by CD39/CD73 enzyme axis, is linked to the generation of an immunosuppressed niche favoring the onset of neoplasia. Signals delivered by extracellular adenosine are detected and transduced by G-protein-coupled cell surface receptors, classified into four subtypes: A₁, A_2A, A_2B, and A₃. A critical role of this nucleoside is emerging in the modulation of several immune and nonimmune cells defining the tumor microenvironment, providing novel insights about the development of novel therapeutic strategies aimed at undermining the immune-privileged sites where cancer cells grow and proliferate.

CD73 Overexpression Promotes Progression and Recurrence of Papillary Thyroid Carcinoma

Simple Summary

This study aimed to evaluate the clinicopathologic significance of CD73 expression in patients with papillary thyroid carcinoma (PTC) and the potential for CD73 to serve as a therapeutic target of PTC. CD73 was highly expressed in PTC, but not in the normal thyroid tissue. Overexpression of CD73 was associated with unfavorable clinicopathologic characteristics and a shorter recurrence-free survival. The expression level of CD73 mRNA was associated with the abundance of Tregs and dendritic cells, depletion of natural killer (NK) cells, and high expression of immune checkpoint genes and epithelial-to-mesenchymal transition-related genes. CD73 inhibitor attenuated PTC cell proliferation, migration, and invasion in vitro, and suppressed PTC xenograft tumor growth in nude mice. These results suggest that CD73 expression is an unfavorable prognostic marker for patients with PTC. CD73 blockade would be an attractive candidate for therapeutic strategies in patients with advanced PTC.

Abstract

CD73 is involved in tumor immune escape and promotes the growth and progression of cancer cells. The functional role of CD73 expression in papillary thyroid carcinoma (PTC) has not yet been established. In 511 patients with PTC, immunohistochemistry for CD73 on tissue microarrays showed that the high expression of CD73 was associated with an aggressive histologic variant (p = 0.002), extrathyroidal extension (p < 0.001), lymph node metastasis (p < 0.001), and BRAF^V600E mutation (p = 0.015). Survival analysis results showed that patients with high CD73 expression had worse recurrence-free survival (p = 0.023). CD73 inhibitors induced G1 cell cycle arrest and apoptosis, inhibited the migration and invasion of PTC cells, and suppressed tumor growth in PTC xenograft nude mice. High expression of CD73 (NT5E) mRNA was associated with unfavorable clinicopathologic characteristics, the abundance of Tregs and dendritic cells, depletion of natural killer (NK) cells, and high expression of immune checkpoint genes and epithelial-to-mesenchymal transition-related genes in The Cancer Genome Atlas (TCGA) dataset. Taken together, CD73 expression promotes tumor progression and predicts low recurrence-free survival. Targeting the CD73–adenosine axis in the tumor microenvironment offers an attractive pathway for therapeutic strategies aimed at advanced PTC.

The adenosine pathway in immuno-oncology

Cancer immunotherapy based on immune-checkpoint inhibition or adoptive cell therapy has revolutionized cancer care. Nevertheless, a large proportion of patients do not benefit from such treatments. Over the past decade, remarkable progress has been made in the development of 'next-generation' therapeutics in immuno-oncology, with inhibitors of extracellular adenosine (eADO) signalling constituting an expanding class of agents. Induced by tissue hypoxia, inflammation, tissue repair and specific oncogenic pathways, the adenosinergic axis is a broadly immunosuppressive pathway that regulates both innate and adaptive immune responses. Inhibition of eADO-generating enzymes and/or eADO receptors can promote antitumour immunity through multiple mechanisms, including enhancement of T cell and natural killer cell function, suppression of the pro-tumourigenic effects of myeloid cells and other immunoregulatory cells, and promotion of antigen presentation. With several clinical trials currently evaluating inhibitors of the eADO pathway in patients with cancer, we herein review the pathophysiological function of eADO with a focus on effects on antitumour immunity. We also discuss the treatment opportunities, potential limitations and biomarker-based strategies related to adenosine-targeted therapy in oncology.

5-Fluorouracil Conversion Pathway Mutations in Gastric Cancer

To date, 5-Fluorouracil (5FU) is a major component of several chemotherapy regimens, thus its study is of fundamental importance to better understand all the causes that may lead to chemoresistance and treatment failure. Given the evident differences between prognosis in Asian and Caucasian populations, triggered by clear genetic discordances and given the extreme genetic heterogeneity of gastric cancer (GC), the evaluation of the most frequent mutations in every single member of the 5FU conversion and activation pathway might reveal several important results. Here, we exploited the cBioPortal analysis software to query a large databank of clinical and wide-genome studies to evaluate the components of the three major 5FU transformation pathways. We demonstrated that mutations in such ways were associated with a poor prognosis and reduced overall survival, often caused by a deletion in the TYMP gene and amplification in TYMS. The use of prodrugs and dihydropyrimidine dehydrogenase (DPD) inhibitors, which normally catabolizes 5FU into inactive metabolites, improved such chemotherapies, but several steps forward still need to be taken to select better therapies to target the chemoresistant pools of cells with high anaplastic features and genomic instability.

Targeting CD73 to augment cancer immunotherapy

CD73 (ecto-5'-nucleotidase) is a novel immunoinhibitory protein that plays a key role for tumor growth and metastasis. Its main function is to convert extracellular ATP to immunosuppressive adenosine in concert with CD39 in normal tissues to limit excessive immune response. However, tumors take advantage of the CD73-mediated adenosinergic mechanism to protect them from immune attack. In particular, inducible expression of CD73 along with other adenosinergic molecules on both cancer cells and host cells sustains immunosuppressive tumor microenvironment by affecting multiple aspects of the immune response. Owing to its multifaceted capacity to tumor promotion as an emerging immune checkpoint, CD73 is an ideal therapeutic target for cancer treatment especially in combination with conventional therapy and/or other immune checkpoint inhibitors. In this review, we will discuss the roles of CD73 on tumor and immune cells and will highlight the therapeutic value of CD73 for combination therapy.

Tumorigenesis and Progression As A Consequence of Hypoxic TME：A Prospective View upon Breast Cancer Therapeutic Targets

Intratumoral hypoxia has a significant impact on the development and progression of breast cancer (BC). Rather than exerting limited regional impact, hypoxia create an aggressive macroenvironment for BC. Hypoxia-inducible factors-1(HIF-1) is extensively induced under hypoxia condition of BC, activating the transcription of multiple oncogenes. Thereinto, CD73 is the one which could be secreted into the microenvironment and is in favor of the growth, metastasis, resistance to therapies, as well as the stemness maintenance of BC. In this review, we address the significance of hypoxia/HIF-1/CD73 axis for BC, and provide a novel perspective into BC therapeutic strategies.

Angiogenic Potential of Bone Marrow Derived CD133+ and CD271+ Intramyocardial Stem Cell Trans- Plantation Post MI

Background: Bone marrow (BM)-derived stem cells with their various functions and characteristics have become a well-recognized source for the cell-based therapies. However, knowledge on their therapeutic potential and the shortage for a cross-link between distinct BM-derived stem cells, primed after the onset of myocardial infarction (MI), seems to be still rudimentary. Therefore, the post-examination of the therapeutic characteristics of such primed hematopoietic CD133⁺ and mesenchymal CD271⁺ stem cells was the object of the present study. Methods and Results: The effects of respective CD133⁺ and CD271⁺ mononuclear cells alone as well as in the co-culture model have been explored with focus on their angiogenic potential. The phenotypic analysis revealed a small percentage of isolated cells expressing both surface markers. Moreover, target stem cells isolated with our standardized immunomagnetic isolation procedure did not show any negative alterations following BM storage in regard to cell numbers and/or quality. In vitro network formation relied predominantly on CD271⁺ stem cells when compared with single CD133⁺ culture. Interestingly, CD133⁺ cells contributed in the tube formation, only if they were cultivated in combination with CD271⁺ cells. Additional to the in vitro examination, therapeutic effects of the primed stem cells were investigated 48 h post MI in a murine model. Hence, we have found a lower expression of transforming growth factor βeta 3 (TGFβ3) as well as an increase of the proangiogenic factors after CD133⁺ cell treatment in contrast to CD271⁺ cell treatment. On the other hand, the CD271⁺ cell therapy led to a lower expression of the inflammatory cytokines. Conclusion: The interactions between CD271⁺ and CD133⁺ subpopulations the extent to which the combination may enhance cardiac regeneration has still not been investigated so far. We expect that the multiple characteristics and various regenerative effects of CD271⁺ cells alone as well as in combination with CD133⁺ will result in an improved therapeutic impact on ischemic heart disease.

CD73: an emerging checkpoint for cancer immunotherapy

CD73 is a novel immune checkpoint associated with adenosine metabolism that promotes tumor progression by suppressing antitumor immune response and promoting angiogenesis. The inhibition of CD73, in combination with immune checkpoint blockade, targeted therapy or conventional therapy, improves antitumor effects in numerous preclinical mouse models of cancer. Emerging evidence suggests that the combination of anti-CD73 and immune checkpoint blockade has promising clinical activity in patients with advanced solid tumors. In this review, we will discuss the specific role of CD73 on both tumor cells and nontumor cells in regulating tumor immunity and tumorigenesis and provide an update on the current view of the antitumor activity of targeting CD73 by mAb or small molecule selective inhibitors in preclinical and clinical settings.

Ecto-5'-nucleotidase (CD73) is a potential target of hepatocellular carcinoma

High expression of ecto-5'-nucleotidase (CD73) has been reported in a number of epithelium origin malignancies. Here, we hypothesize that CD73 promotes hepatocellular carcinoma (HCC) growth and metastasis and that the effect is mediated by epithelial growth factor receptor (EGFR). HCC cells with different malignancies and Tissue microarrays of the tumor and peritumoral liver tissues from 30 independent patients were used to examine CD73 and EGFR expression. Then, MTT and Ki67 detection, together with cell adhesion, invasion, and migration assays were used to evaluate the effects of CD73 on cell growth and metastasis. The expression of EGFR in HCC cells was also tested after suppressing or overexpressing CD73. Lastly, tumor tissues from nude mice, which had been injected subcutaneously with HCC cells, were transplanted subcutaneously into CD73^-/- and wild-type (WT) C57 mice. CD73 expression was higher in HCC cells with greater metastatic potentials and tumor tissues compared with low metastatic cells and peritumor tissues. CD73 and EGFR were coexpressed and positively correlated in tumor and peritumor liver tissues in HCC tissue microarrays. Up-regulationof CD73 by plasmid transfection or by pharmacological agents promoted EGFR expression in HCC cells, whereas suppression of CD73 inhibited these effects. The growth of transplanted tumor tissues was dramatically slower in CD73^-/- mice than in WT type mice in the in vivo experiments. CD73 promotes HCC growth and metastasis and upregulated the expression of EGFR in HCC. Thus, CD73 and EGFR are potential targets in the treatment of HCC.

Controlling the Immune Suppressor: Transcription Factors and MicroRNAs Regulating CD73/NT5E

The NT5E (CD73) molecule represents an ecto-5′-nucleotidase expressed on the cell surface of various cell types. Hydrolyzing extracellular adenosine monophosphate into adenosine and inorganic phosphate, NT5E performs numerous homeostatic functions in healthy organs and tissues. Importantly, NT5E can act as inhibitory immune checkpoint molecule, since free adenosine generated by NT5E inhibits cellular immune responses, thereby promoting immune escape of tumor cells. MicroRNAs (miRNAs) are small non-coding RNA molecules regulating gene expression on posttranscriptional level through binding to mRNAs, resulting in translational repression or degradation of the targeted mRNA molecule. In tumor cells, miRNA expression patterns are often altered which in turn might affect NT5E surface expression and eventually influence the efficacy of antitumor immune responses. This review describes the diverse roles of NT5E, summarizes current knowledge about transcription factors controlling NT5E expression, and highlights the significance of miRNAs involved in the posttranscriptional regulation of NT5E expression.

Gut microbiome modulates efficacy of immune checkpoint inhibitors

Immune checkpoint inhibitors (ICIs) therapy is a novel strategy for cancer treatments in recent years. However, it was observed that most patients treated with ICIs could not get benefit from the therapy, which led to the limitation of clinical application. Motivated by potent and durable efficacy of ICIs, oncologists endeavor to explore the mechanisms of resistance to ICIs and increase the drug sensitivity. It is known that heterogeneity of gut microbiome in populations may result in different outcomes of therapy. In xenograft model, bacteria in gut have been proved as a crucial factor regulating immunotherapy efficacy. And the similar phenomenon was obtained in patients. In this review, we summarized relevant advancements about gut microbiome and ICIs. Furthermore, we focused on modulatory function of gut microbiome in ICIs therapy and possible antitumor mechanism of specific commensals in ICIs treatment. We propose that gut microbiome is an important predictive factor, and manipulation of gut microbiome is feasible to elevate response rate in ICIs therapy.

Comparative Analysis of Mesenchymal Stem Cells from Bone Marrow, Adipose Tissue, and Dental Pulp as Sources of Cell Therapy for Zone of Stasis Burns

Introduction: The implantation of mesenchymal stem cells (MSCs) has been shown to exert benefits for the survival of the zone-of-stasis. However, the clinical experience indicates the importance of selecting the right source and type of stem cells. Therefore, we planned the current study to perform a quantitative comparison of MSCs isolated from three different sources to provide information useful in selection of the optimal source and to see whether critical mechanisms are conserved between different populations. Methods: The protective effects of MSCs derived from bone marrow, adipose tissue and dental pulp were compared in a rat model of thermal trauma. The stasis zones were evaluated 72 h after the burn using histochemistry, immunohistochemistry and biochemistry. Results: Gross evaluation of burn wounds revealed that the differences between the mean percentages of the calculated necrotic areas weren't statistically significant. Semi-quantitative grading of the histopathological findings revealed that there were no significant differences between damage scores. Immunohistochemical assessment of apoptotic and necrotic cell deaths revealed that the differences between the mean numbers of apoptotic and necrotic cells weren't statistically significant. Myeloperoxidase activity was found to be significantly lower in the adipose tissue group. Biochemical and immunohistochemical assessment of tissue malondialdehyde revealed that the differences between the groups weren't statistically significant. Finally, the number of neo-vessels in the dental pulp group was found to be significantly higher. Conclusion: Our findings suggest that bone marrow, adipose tissue and dental pulp may serve as a universal donor MSC source for the prevention of burn wound progression.

CD73 expression in lymph node metastases in patients with head and neck cancer

INTRODUCTION

CD73 is an enzyme crucial in the metabolism of immunosuppressive adenosine. In cancer, it has various functions including tumor growth and metastases. Squamous cell carcinoma of the head and neck has an overall poor prognosis, also due to early spread of metastatic cells.

MATERIALS AND METHODS

Tumor and lymph node specimens of 65 patients with HNSCC were subjected to immunohistochemical and H-score analysis of CD73 expression. Demographics, diagnoses, histopathology and subsequent outcome were analyzed.

RESULTS

The primary cancer was squamous cell carcinoma in all patients (male/female 55:10) with the following locations: oral cavity n:16, oropharynx n:28, hypopharynx n:11 and larynx n:10. H-score for CD73 expression in the primary lesion and metastatic lymph nodes was significantly higher in advanced compared to early stages with no significant differences among tumor locations. High CD73 expression was associated with reduced overall survival rates at a mean follow-up of 83.4 months (6-204 months).

CONCLUSIONS

CD73 expression in HNSCC correlated positively with tumor stage and was associated with poor prognosis. Therefore, CD73 expression in primary lesions and regional metastases appears to predict HNSCC patients at high risk of all tumor sites. Therapeutic approaches targeting CD73 might seem promising for this patient population.

Multifaceted Effects of Extracellular Adenosine Triphosphate and Adenosine in the Tumor-Host Interaction and Therapeutic Perspectives

Cancer is still one of the world's most pressing health-care challenges, leading to a high number of deaths worldwide. Immunotherapy is a new developing therapy that boosts patient's immune system to fight cancer by modifying tumor-immune cells interaction in the tumor microenvironment (TME). Extracellular adenosine triphosphate (eATP) and adenosine (Ado) are signaling molecules released in the TME that act as modulators of both immune and tumor cell responses. Extracellular adenosine triphosphate and Ado activate purinergic type 2 (P2) and type 1 (P1) receptors, respectively, triggering the so-called purinergic signaling. The concentration of eATP and Ado within the TME is tightly controlled by several cell-surface ectonucleotidases, such as CD39 and CD73, the major ecto-enzymes expressed in cancer cells, immune cells, stromal cells, and vasculature, being CD73 also expressed on tumor-associated fibroblasts. Once accumulated in the TME, eATP boosts antitumor immune response, while Ado attenuates or suppresses immunity against the tumor. In addition, both molecules can mediate growth stimulation or inhibition of the tumor, depending on the specific receptor activated. Therefore, purinergic signaling is able to modulate both tumor and immune cells behavior and, consequently, the tumor-host interaction and disease progression. In this review, we discuss the role of purinergic signaling in the host-tumor interaction detailing the multifaceted effects of eATP and Ado in the inflammatory TME. Moreover, we present recent findings into the application of purinergic-targeting therapy as a potential novel option to boost antitumor immune responses in cancer.

Extracellular 5'-nucleotidase (CD73) promotes human breast cancer cells growth through AKT/GSK-3β/β-catenin/cyclinD1 signaling pathway

To identify the role and to explore the mechanism of extracellular 5'-nucleotidase (CD73) in human breast cancer growth, CD73 expression was measured firstly in breast cancer tissues and cell lines, and then interfered with or over-expressed by recombinant lentivirus in cell lines. Impacts of CD73 on breast cancer cell proliferation and cell cycle were investigated with colony formation assay, CCK-8 and flow cytometry. The relationship between CD73 and AKT/GSK-3β/β-catenin pathway was assessed with adenosine, adenosine 2A receptor antagonist (SCH-58261), adenosine 2A receptor agonist (NECA), CD73 enzyme inhibitor (APCP) and Akt inhibitor (MK-2206). Moreover, the effect of CD73 on breast cancer growth in vivo was examined with human breast cancer transplanting model of nude mice. The results showed that the expression of CD73 was high in breast cancer tissues and increased with advanced tumor grades and lympho-node status. CD73 expression was higher in more malignant cells, and CD73 overexpression promoted breast cancer cell proliferation in both in vivo and in vitro. It activated AKT/GSK-3β/β-catenin/cyclinD1 signaling pathway through CD73 enzyme activity and other mechanism.

Mesenchymal Stem/Multipotent Stromal Cells from Human Decidua Basalis Reduce Endothelial Cell Activation

Recently, we reported the isolation and characterization of mesenchymal stem cells from the decidua basalis of human placenta (DBMSCs). These cells express a unique combination of molecules involved in many important cellular functions, which make them good candidates for cell-based therapies. The endothelium is a highly specialized, metabolically active interface between blood and the underlying tissues. Inflammatory factors stimulate the endothelium to undergo a change to a proinflammatory and procoagulant state (ie, endothelial cell activation). An initial response to endothelial cell activation is monocyte adhesion. Activation typically involves increased proliferation and enhanced expression of adhesion and inflammatory markers by endothelial cells. Sustained endothelial cell activation leads to a type of damage to the body associated with inflammatory diseases, such as atherosclerosis. In this study, we examined the ability of DBMSCs to protect endothelial cells from activation through monocyte adhesion, by modulating endothelial proliferation, migration, adhesion, and inflammatory marker expression. Endothelial cells were cocultured with DBMSCs, monocytes, monocyte-pretreated with DBMSCs and DBMSC-pretreated with monocytes were also evaluated. Monocyte adhesion to endothelial cells was examined following treatment with DBMSCs. Expression of endothelial cell adhesion and inflammatory markers was also analyzed. The interaction between DBMSCs and monocytes reduced endothelial cell proliferation and monocyte adhesion to endothelial cells. In contrast, endothelial cell migration increased in response to DBMSCs and monocytes. Endothelial cell expression of adhesion and inflammatory molecules was reduced by DBMSCs and DBMSC-pretreated with monocytes. The mechanism of reduced endothelial proliferation involved enhanced phosphorylation of the tumor suppressor protein p53. Our study shows for the first time that DBMSCs protect endothelial cells from activation by inflammation triggered by monocyte adhesion and increased endothelial cell proliferation. These events are manifest in inflammatory diseases, such as atherosclerosis. Therefore, our results suggest that DBMSCs could be usefully employed as a therapeutic strategy for atherosclerosis.

Switching off CD73: a way to boost the activity of conventional and targeted antineoplastic therapies

Over the past few years, several preclinical studies have highlighted the value of CD73 (ecto-5'-nucleotidase) as a potential therapeutic target for cancer therapy. Indeed, the pharmacological blockade of CD73, via monoclonal antibodies or small molecules, has promise in counteracting cancer development, growth and spread. Synergistic combinations of anti-CD73 drugs with conventional cancer treatments (i.e., chemotherapy, radiation therapy, immunotherapy, targeted therapy) have increased therapeutic potential. In this review, we discuss the potential synergistic effects of CD73 blockers and conventional antineoplastic therapies in the treatment of cancer.

Tiamulin inhibits breast cancer growth and pulmonary metastasis by decreasing the activity of CD73

BACKGROUND

Metastasis is the leading cause of death in breast cancer patients. CD73, also known as ecto-5'-nucleotidase, plays a critical role in cancer development including metastasis. The existing researches indicate that overexpression of CD73 promotes growth and metastasis of breast cancer. Therefore, CD73 inhibitor can offer a promising treatment for breast cancer. Here, we determined whether tiamulin, which was found to inhibit CD73, was able to suppress breast cancer development and explored the related mechanisms.

METHODS

We firstly measured the effect of tiamulin hydrogen fumarate (THF) on CD73 using high performance liquid chromatography (HPLC). Then, we investigated cell proliferation, migration and invasion in MDA-MB-231 human breast cancer cell line and 4 T1 mouse breast cancer cell line treated with THF by migration assay, invasion assay and activity assay. Besides, we examined the effect of THF on syngeneic mammary tumors of mice by immunohistochemistry.

RESULTS

Our data demonstrated that THF inhibited CD73 by decreasing the activity instead of the expression of CD73. In vitro, THF inhibited the proliferation, migration and invasion of MDA-MB-231 and 4 T1 cells by suppressing CD73 activity. In vivo, animal experiments showed that THF treatment resulted in significant reduction in syngeneic tumor growth, microvascular density and lung metastasis rate.

CONCLUSIONS

Our results indicate that THF inhibits growth and metastasis of breast cancer by blocking the activity of CD73, which may offer a promising treatment for breast cancer therapy.

Increased efficacy of a dendritic cell–based therapeutic cancer vaccine with adenosine receptor antagonist and CD73 inhibitor

Dendritic cells are important in initiating immune responses; therefore, a range of dendritic cell–based approaches have been established to induce immune response against cancer cells. However, the presence of immunosuppressive mediators such as adenosine in the tumor microenvironment reduces the efficacy of dendritic cell–based cancer immunotherapy. In this study, we investigated whether blockade of the A2A adenosine receptor with a selective antagonist and a CD73 inhibitor may increase the efficacy of a dendritic cell–based cancer vaccine. According to the findings, this therapeutic combination reduced tumor growth, prolonged survival of tumor-bearing mice, and enhanced specific antitumor immune responses. Thus, we suggest that targeting cancer-derived adenosine improves the outcomes of dendritic cell–based cancer immunotherapy.

miR-193a-3p interaction with HMGB1 downregulates human endothelial cell proliferation and migration

Circulating endothelial colony forming cells (ECFCs) contribute to vascular repair where they are a target for therapy. Since ECFC proliferative potential is increased in cord versus peripheral blood and to define regulatory factors controlling this proliferation, we compared the miRNA profiles of cord blood and peripheral blood ECFC-derived cells. Of the top 25 differentially regulated miRNAs selected, 22 were more highly expressed in peripheral blood ECFC-derived cells. After validating candidate miRNAs by q-RT-PCR, we selected miR-193a-3p for further investigation. The miR-193a-3p mimic reduced cord blood ECFC-derived cell proliferation, migration and vascular tubule formation, while the miR-193a-3p inhibitor significantly enhanced these parameters in peripheral blood ECFC-derived cells. Using in silico miRNA target database analyses combined with proteome arrays and luciferase reporter assays of miR-193a-3p mimic treated cord blood ECFC-derived cells, we identified 2 novel miR-193a-3p targets, the high mobility group box-1 (HMGB1) and the hypoxia upregulated-1 (HYOU1) gene products. HMGB1 silencing in cord blood ECFC-derived cells confirmed its role in regulating vascular function. Thus, we show, for the first time, that miR-193a-3p negatively regulates human ECFC vasculo/angiogenesis and propose that antagonising miR-193a-3p in less proliferative and less angiogenic ECFC-derived cells will enhance their vasculo/angiogenic function.

The ectonucleotidases CD39 and CD73: Novel checkpoint inhibitor targets

Cancers are able to grow by subverting immune suppressive pathways, to prevent the malignant cells as being recognized as dangerous or foreign. This mechanism prevents the cancer from being eliminated by the immune system and allows disease to progress from a very early stage to a lethal state. Immunotherapies are newly developing interventions that modify the patient's immune system to fight cancer, by either directly stimulating rejection-type processes or blocking suppressive pathways. Extracellular adenosine generated by the ectonucleotidases CD39 and CD73 is a newly recognized "immune checkpoint mediator" that interferes with anti-tumor immune responses. In this review, we focus on CD39 and CD73 ectoenzymes and encompass aspects of the biochemistry of these molecules as well as detailing the distribution and function on immune cells. Effects of CD39 and CD73 inhibition in preclinical and clinical studies are discussed. Finally, we provide insights into potential clinical application of adenosinergic and other purinergic-targeting therapies and forecast how these might develop in combination with other anti-cancer modalities.

The ectonucleotidases CD39 and CD73: Novel checkpoint inhibitor targets

Cancers are able to grow by subverting immune suppressive pathways, to prevent the malignant cells as being recognized as dangerous or foreign. This mechanism prevents the cancer from being eliminated by the immune system and allows disease to progress from a very early stage to a lethal state. Immunotherapies are newly developing interventions that modify the patient's immune system to fight cancer, by either directly stimulating rejection-type processes or blocking suppressive pathways. Extracellular adenosine generated by the ectonucleotidases CD39 and CD73 is a newly recognized "immune checkpoint mediator" that interferes with anti-tumor immune responses. In this review, we focus on CD39 and CD73 ectoenzymes and encompass aspects of the biochemistry of these molecules as well as detailing the distribution and function on immune cells. Effects of CD39 and CD73 inhibition in preclinical and clinical studies are discussed. Finally, we provide insights into potential clinical application of adenosinergic and other purinergic-targeting therapies and forecast how these might develop in combination with other anti-cancer modalities.

The ectonucleotidases CD39 and CD73: Novel checkpoint inhibitor targets

Cancers are able to grow by subverting immune suppressive pathways, to prevent the malignant cells as being recognized as dangerous or foreign. This mechanism prevents the cancer from being eliminated by the immune system and allows disease to progress from a very early stage to a lethal state. Immunotherapies are newly developing interventions that modify the patient's immune system to fight cancer, by either directly stimulating rejection-type processes or blocking suppressive pathways. Extracellular adenosine generated by the ectonucleotidases CD39 and CD73 is a newly recognized "immune checkpoint mediator" that interferes with anti-tumor immune responses. In this review, we focus on CD39 and CD73 ectoenzymes and encompass aspects of the biochemistry of these molecules as well as detailing the distribution and function on immune cells. Effects of CD39 and CD73 inhibition in preclinical and clinical studies are discussed. Finally, we provide insights into potential clinical application of adenosinergic and other purinergic-targeting therapies and forecast how these might develop in combination with other anti-cancer modalities.

Amelioration of experimental colitis after short-term therapy with glucocorticoid and its relationship to the induction of different regulatory markers

The clinical benefits of short-term therapy with glucocorticoids (GC) in patients with inflammatory bowel disease (IBD) are widely known. However, the effects of this treatment towards the re-establishment of the regulatory network in IBD are not fully explored. We have evaluated the immunological effects of the abbreviated GC therapy in experimental colitis induced by 3% dextran sulphate sodium in C57BL/6 mice. Treatment with GC improved disease outcome, constrained circulating leucocytes and ameliorated intestinal inflammation. The control of the local inflammatory responses involved a reduction in the expression of interferon-γ and interleukin-1β, associated with augmented mRNA levels of peroxisome proliferator-activated receptors (α and γ) in intestine. Furthermore, there was a reduction of CD4⁺ T cells producing interferon-γ, together with an increased frequency of the putative regulatory population of T cells producing interleukin-10, in spleen. These systemic alterations were accompanied by a decrease in the proliferative potential of splenocytes of mice treated in vivo with GC. Notably, treatment with GC also led to an increase in the frequency of the regulatory markers GITR, CTLA-4, PD-1, CD73 and FoxP3, more prominently in spleen. Taken together, our results pointed to a role of GC in the control of leucocyte responsiveness and re-establishment of a regulatory system, which probably contributed to disease control and the restoration of immune balance. Finally, this is the first time that GC treatment was associated with the modulation of a broad number of regulatory markers in an experimental model of colitis.

CD73 as a novel marker for poor prognosis of oral squamous cell carcinoma

Ecto-5′-nucleotidase [cluster of differentiation (CD)73] has important functions in several types of cancer, however, its expression in squamous cell carcinoma (SCC) remains unknown. The present study was designed to investigate CD73 expression in SCC. CD73 expression was assessed by immunohistochemistry in 113 patients with oral SCC (OSCC). The association between CD73 expression and clinicopathological features, overall survival (OS) and disease-free survival (DFS) times of patients were statistically analyzed. CD73 expression was detected in 58.4% (66/113) of OSCC patients, with the immunostaining predominantly localized in the cytomembrane and a little in the cytoplasm. Statistical analysis revealed that CD73 expression was more frequently detected in patients with larger tumors (P=0.021). The overexpression of CD73 was significantly associated with clinical stage (P=0.047). Furthermore, immunohistochemical staining showed that overexpression of CD73 was inversely correlated with DFS (P=0.002) and OS (P=0.002) times. Multivariate Cox regression analysis revealed that CD73 expression was an independent prognostic factor for poor DFS (P=0.018) and OS (P=0.021). The current study is the first to evaluate the clinical significance and prognostic value of CD73 in patients with OSCC. The findings suggest that CD73 is a potential prognostic marker for OSCC.

Immunosuppressive activities of adenosine in cancer

Multiple immunosuppressive mechanisms impede anti-tumor immunity. Among them, the accumulation of extracellular adenosine is a potent and widespread strategy exploited by tumors to escape immunosurveillance through the activation of purinergic receptors. In the immune system, engagement of A2a and A2b adenosine receptors is a critical regulatory mechanism that protects tissues against excessive immune reactions. In tumors, this pathway is hijacked and hinders anti-tumor immunity, promoting cancer progression. Different groups have highlighted the therapeutic potential of blocking CD73-dependent adenosine-mediated immunosuppression to reinstate anti-tumor immunity. Phase clinical trials evaluating anti-CD73 antibodies and A2a receptor antagonists in cancer patients are currently ongoing. We here review the recent literature on the immunosuppressive effects of extracellular adenosine and discuss the development of adenosine inhibitors.

Specific Activation of A3, A2A and A1 Adenosine Receptors in CD73-Knockout Mice Affects B16F10 Melanoma Growth, Neovascularization, Angiogenesis and Macrophage Infiltration

CD73 (ecto-5'-nucleotidase), a cell surface enzyme hydrolyzing AMP to adenosine, was lately demonstrated to play a direct role in tumor progression including regulation of tumor vascularization. It was also shown to stimulate tumor macrophage infiltration. Interstitial adenosine, accumulating in solid tumors due to CD73 enzymatic activity, is recognized as a main mediator regulating the production of pro- and anti-angiogenic factors, but the engagement of specific adenosine receptors in tumor progression in vivo is still poorly researched. We have analyzed the role of high affinity adenosine receptors A₁, A_2A, and A₃ in B16F10 melanoma progression using specific agonists (CCPA, CGS-21680 and IB-MECA, respectively). We limited endogenous extracellular adenosine background using CD73 knockout mice treated with CD73 chemical inhibitor, AOPCP (adenosine α,β-methylene 5’-diphosphate). Activation of any adenosine receptor significantly inhibited B16F10 melanoma growth but only at its early stage. At 14th day of growth, the decrease in tumor neovascularization and MAPK pathway activation induced by CD73 depletion was reversed by all agonists. Activation of A₁AR primarily increased angiogenic activation measured by expression of VEGF-R2 on tumor blood vessels. However, mainly A₃AR activation increased both the microvessel density and expression of pro-angiogenic factors. All agonists induced significant increase in macrophage tumor infiltration, with IB-MECA being most effective. This effect was accompanied by substantial changes in cytokines regulating macrophage polarization between pro-inflammatory and pro-angiogenic phenotype. Our results demonstrate an evidence that each of the analyzed receptors has a specific role in the stimulation of tumor angiogenesis and confirm significantly more multifaceted role of adenosine in its regulation than was already observed. They also reveal previously unexplored consequences to extracellular adenosine signaling depletion in recently proposed anti-CD73 cancer therapy.

The role of extracellular-5'-nucleotidase/CD73 in glioma peritumoural brain edema

During pathological conditions, extracellular-5'-nucleotidase/CD73 can protect neurons by reducing the permeability of the blood brain barrier. In recent years, it has been demonstrated that CD73 can negatively contribute to the growth of gliomas; however, the function of CD73 in glioma blood vessels is not clear. We analysed the expression of CD73 in 72 glioma patients using immunohistochemistry and correspondingly compared the results with the Edema index (EI). We established an in vitro model of the blood-tumour barrier and analysed the expression of CD73 in vascular endothelial cells. Lastly, CD73 expression was inhibited in endothelial cells, and the effects of this inhibition on tight junction structure and transendothelial resistance were observed. Compared to normal brains, the expression of CD73 in blood vessels of glioma patients was significantly decreased, and the amount was lower in the centre of the tumour than the periphery. The proportion of CD73-positive blood vessels had a positive correlation with the EI. The expression of CD73 in the in vitro endothelial cell blood-tumour barrier model was decreased. Lastly, inhibiting CD73 was found to decrease the expression of tight junction related proteins in endothelial cells and to decrease the value of transendothelial electric resistance. The expression of CD73 in glioma blood vessels was significantly decreased, which may play a multi-functional role in decreasing the expression of tight junction related proteins of brain microvascular endothelial cells and may also increase blood-tumour barrier permeability and accelerate the formation of PTBE.

Anti-CD73 in cancer immunotherapy: awakening new opportunities

In recent years, cancer immunotherapy made significant advances due to a better understanding of the principles underlying tumor biology and immunology. In this context, CD73 is a key molecule, since via degradation of adenosine monophosphate into adenosine, endorses the generation of an immunosuppressed and pro-angiogenic niche within the tumor microenvironment that promotes the onset and progression of cancer. Targeting CD73 results in favorable antitumor effects in pre-clinical models and combined treatments of CD73 blockade with other immune-modulating agents (i.e. anti-CTLA-4 mAb or anti-PD1 mAb) is particularly attractive. Although there is still a long way to go, anti-CD73 therapy, through the development of CD73 monoclonal antibodies, can potentially constitute a new biologic therapy for cancer patients. In this review, we discuss the link between CD73 and the onset, development and spread of tumors, highlighting the potential value of this molecule as a target and as a novel biomarker in the context of personalized cancer therapy.

CD73-adenosine: a next-generation target in immuno-oncology

Cancer immunotherapy has entered in a new era with the development of first-generation immune checkpoint inhibitors targeting the PD1/PD-L1 and CTLA-4 pathways. In this context, considerable research effort is being deployed to find the next generation of cancer immunotherapeutics. The CD73-adenosine axis constitutes one of the most promising pathways in immuno-oncology. We and others have demonstrated the immunosuppressive role of CD73-adenosine in cancer and established proof-of-concept that the targeted blockade of CD73 or adenosine receptors could effectively promote anti-tumor immunity and enhance the activity of first-generation immune checkpoint blockers. With Phase I clinical trials now underway evaluating anti-CD73 or anti-A2A therapies in cancer patients, we here discuss the fundamental, preclinical and clinical findings related to the role of the CD73-adenosinergic pathway in tumor immunity.

Human induced pluripotent stem cells derived endothelial cells mimicking vascular inflammatory response under flow

Endothelial cells (ECs) have great potential in vascular diseases research and regenerative medicine. Autologous human ECs are difficult to acquire in sufficient numbers in vitro, and human induced pluripotent stem cells (iPSCs) offer unique opportunity to generate ECs for these purposes. In this work, we present a new and efficient method to simply differentiate human iPSCs into functional ECs, which can respond to physiological level of flow and inflammatory stimulation on a fabricated microdevice. The endothelial-like cells were differentiated from human iPSCs within only one week, according to the inducing development principle. The expression of endothelial progenitor and endothelial marker genes (GATA2, RUNX1, CD34, and CD31) increased on the second and fourth days after the initial inducing process. The differentiated ECs exhibited strong expression of cells-specific markers (CD31 and von Willebrand factor antibody), similar to that present in human umbilical vein endothelial cells. In addition, the hiPSC derived ECs were able to form tubular structure and respond to vascular-like flow generated on a microdevice. Furthermore, the human induced pluripotent stem cell-endothelial cells (hiPSC-ECs) pretreated with tumor necrosis factor (TNF-α) were susceptible to adhesion to human monocyte line U937 under flow condition, indicating the feasibility of this hiPSCs derived microsystem for mimicking the inflammatory response of endothelial cells under physiological and pathological process.