Opportunities and challenges for anti-CD73 cancer therapy

Cancer Stem Cell Transcriptome Profiling Reveals Seed Genes of Tumorigenesis: New Avenues for Cancer Precision Medicine

Cancer stem-like cells (CSCs) possess the ability to self-renew and differentiate, and they are among the major factors driving tumorigenesis, metastasis, and resistance to chemotherapy. Therefore, it is critical to understand the molecular substrates of CSC biology so as to discover novel molecular biosignatures that distinguish CSCs and tumor cells. Here, we report new findings and insights by employing four transcriptome datasets associated with CSCs, with CSC and tumor samples from breast, lung, oral, and ovarian tissues. The CSC samples were analyzed to identify differentially expressed genes between CSC and tumor phenotypes. Through comparative profiling of expression levels in different cancer types, we identified 17 "seed genes" that showed a mutual differential expression pattern. We showed that these seed genes were strongly associated with cancer-associated signaling pathways and biological processes, the immune system, and the key cancer hallmarks. Further, the seed genes presented significant changes in their expression profiles in different cancer types and diverse mutation rates, and they also demonstrated high potential as diagnostic and prognostic biomarkers in various cancers. We report a number of seed genes that represent significant potential as "systems biomarkers" for understanding the pathobiology of tumorigenesis. Seed genes offer a new innovation avenue for potential applications toward cancer precision medicine in a broad range of cancers in oncology in the future.

Adenosine Blockage in Tumor Microenvironment and Improvement of Cancer Immunotherapy

Immunotherapy has been introduced into cancer treatment methods, but different problems have restricted the efficacy of these protocols in clinical trials such as the presence of various immunomodulatory factors in the tumor microenvironment. Adenosine is an immunosuppressive metabolite produced by the tumor to promote growth, invasion, metastasis, and immune evasion. Many studies about adenosine and its metabolism in cancer have heightened interest in pursuing this treatment approach. It seems that targeting the adenosine pathway in combination with immunotherapy may lead to efficient antitumor response. In this review, we provide information on the roles of both adenosine and CD73 in the immune system and tumor development. We also describe recent studies about combination therapy with both purinergic inhibitors and other immunotherapeutic methods.

CD73 expression on effector T cells sustained by TGF-β facilitates tumor resistance to anti-4-1BB/CD137 therapy

Agonist antibodies (Ab) directed against costimulatory molecules on the surface of antigen-primed T cells are in various stages of pre-clinical and clinical trials, albeit with limited therapeutic benefit as single agents. The underlying mechanisms of action remain incompletely understood. Here, we demonstrate an inhibitory role of ecto-enzyme CD73 for agonistic anti-4-1BB/CD137 Ab therapy. In particular, anti-4-1BB treatment preferentially drives CD73- effector T cell response for tumor inhibition. Anti-CD73 neutralizing Ab further improves anti-4-1BB therapy associated with enhanced anti-tumor T cell immunity. However, the TGF-β-rich tumor milieu confers resistance to anti-4-1BB therapy by sustaining CD73 expression primarily on infiltrating CD8+ T cells across several tumor models. TGF-β blockade results in downregulation of CD73 expression on infiltrating T cells and sensitizes resistant tumors to agonistic anti-4-1BB therapy. Thus, our findings identify a mechanism of action for more effective clinical targeting of 4-1BB or likely other costimulatory molecules.

Metformin-Induced Reduction of CD39 and CD73 Blocks Myeloid-Derived Suppressor Cell Activity in Patients with Ovarian Cancer

Metformin is a broadly prescribed drug for type 2 diabetes that exerts antitumor activity, yet the mechanisms underlying this activity remain unclear. We show here that metformin treatment blocks the suppressive function of myeloid-derived suppressor cells (MDSC) in patients with ovarian cancer by downregulating the expression and ectoenzymatic activity of CD39 and CD73 on monocytic and polymononuclear MDSC subsets. Metformin triggered activation of AMP-activated protein kinase α and subsequently suppressed hypoxia-inducible factor α, which was critical for induction of CD39/CD73 expression in MDSC. Furthermore, metformin treatment correlated with longer overall survival in diabetic patients with ovarian cancer, which was accompanied by a metformin-induced reduction in the frequency of circulating CD39+CD73+ MDSC and a concomitant increase in the antitumor activities of circulating CD8+ T cells. Our results highlight a direct effect of metformin on MDSC and suggest that metformin may yield clinical benefit through improvement of antitumor T-cell immunity by dampening CD39/CD73-dependent MDSC immunosuppression in ovarian cancer patients.Significance: The antitumor activity of an antidiabetes drug is attributable to reduced immunosuppressive activity of myeloid-derived tumor suppressor cells. Cancer Res; 78(7); 1779-91. ©2018 AACR.

MiR-422a promotes loco-regional recurrence by targeting NT5E/CD73 in head and neck squamous cell carcinoma

At the time of diagnosis, 60% of patients with head and neck squamous cell carcinoma (HNSCC) present tumors in an advanced stage (III-IV) of disease and 80% will relapse within the first two years post-treatment, due to their frequent radio(chemo)resistance. To identify new molecular targets and companion biomarkers, we have investigated the miRNome of 75 stage III-IV oropharynx tumors without relapse (R) or with loco-regional relapse (non-responder, NR) within two years post-treatment. Interestingly, miR-422a was significantly downregulated in NR tumors, in agreement with the increase in cell proliferation and adhesion induced by miR-422a inhibition in vitro. Furthermore, we identified CD73/NT5E oncogene as target of miR-422a. Indeed, modulation of the endogenous level of miR-422a inversely influences the expression and the enzymatic activity of CD73. Moreover, knocking down CD73 mimics the effects of miR-422a upregulation. Importantly, in tumors, miR-422a and CD73 expression levels are inversely correlated, and both are predictive of relapse free survival - especially considering loco(regional) recurrence - in vitro two independent cohorts of advanced oropharynx or HNSCC (N=255) tumors. In all, we reported, for the first time, that MiR-422a and its target CD73 are involved in early loco(regional) recurrence of HNSCC tumors and are new targets for personalized medicine.

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.

CD73/NT5E is a target of miR-30a-5p and plays an important role in the pathogenesis of non-small cell lung cancer

Background

CD73 (ecto-5′-nucleotidase) is implicated in the development of many types of cancer. CD73 inhibitors are currently being tested in clinical trials for the treatment of cancer. Understanding the molecular and cellular actions of CD73 inhibitors is the key to improving this line of therapy.

Methods

Quantitative real-time PCR (qRT-PCR) was used to detect the expression of CD73 and miR-30a-5p; Western blot and immunohistochemical assays were used to investigate the levels of CD73 and other proteins. Flow cytometry was used to determine cell cycle stage and apoptosis. CCK-8 and clonogenic assays were used to investigate cell proliferation. Wound healing, migration and invasion assays were used to investigate the motility of cells. A lung carcinoma xenograft mouse model was used to investigate the in vivo effects of CD73 and miR-30a-5p.

Results

In the present study, we found that CD73 is overexpressed and miR-30a-5p is underexpressed in non-small cell lung cancer tissues compared with adjacent noncancerous. Further, we showed that CD73 is a direct target of miR-30a-5p by luciferase reporter assays, qRT-PCR and western blot analysis. We also found that overexpression of miR-30a-5p in these non-small cell lung cancer cell lines inhibited cell proliferation in vitro and in vivo. Moreover, the epithelial-to-mesenchymal phenotype was suppressed and cell migration and invasion were inhibited; these effects were brought about via the EGF signaling pathway.

Conclusions

Our findings reveal a new post-transcriptional mechanism of CD73 regulation via miR-30a-5p and EGFR-related drug resistance in non-small cell lung cancer.

Electronic supplementary material

The online version of this article (doi:10.1186/s12943-017-0591-1) contains supplementary material, which is available to authorized users.

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.

Reducing CD73 expression by IL1β-Programmed Th17 cells improves immunotherapeutic control of tumors

T cells of the T helper (Th)17 subset offer promise in adoptive T-cell therapy for cancer. However, current protocols for ex vivo programming of Th17 cells, which include TGFβ exposure, increase the expression of CD39 and CD73, two cell surface ATP ectonucleotidases that reduce T-cell effector functions and promote immunosuppression. Here, we report that ATP-mediated suppression of IFNγ production by Th17 cells can be overcome by genetic ablation of CD73 or by using IL1β instead of TGFβ to program Th17 cells ex vivo. Th17 cells cultured in IL1β were also highly polyfunctional, expressing high levels of effector molecules and exhibiting superior short-term control of melanoma in mice, despite reduced stem cell-like properties. TGFβ addition at low doses that did not upregulate CD73 expression but induced stemness properties drastically improved the antitumor effects of IL1β-cultured Th17 cells. Effector properties of IL1β-dependent Th17 cells were likely related to their high glycolytic capacity, since ex vivo programming in pyruvate impaired glycolysis and antitumor effects. Overall, we show that including TGFβ in ex vivo cultures used to program Th17 cells blunts their immunotherapeutic potential and demonstrate how this potential can be more fully realized for adoptive T-cell therapy.

Requirement of NK cells for selective A2A receptor blockade to suppress CD73+ tumor metastasis

Evaluation of: Beavis PA, Divisekera U, Paget C et al. Blockade of A2A receptors potently suppresses the metastasis of CD73(+) tumors. Proc. Natl Acad. Sci. USA 110(36), 14711-14716 (2013). CD73 is becoming an emerging therapeutic target for the prevention of tumor growth and metastasis. However, the mechanism by which CD73 promotes tumor metastasis is unclear. Beavis et al. evaluated the efficacy of A2A and A2B adenosine receptor antagonists in inhibiting the metastasis of tumors expressing CD73, either endogenously or ectopically. They demonstrate distinct mechanisms whereby A2A versus A2B adenosine receptors could contribute to CD73(+) tumor metastasis. As A2Areceptor (R)/A2BR antagonists have been tested in clinical trials in other disease settings, this study highlights the potential therapeutic application of an A2AR/A2BR blockade strategy for treatment of CD73(+) metastatic tumors.

Purinergic signalling and cancer

Receptors for extracellular nucleotides are widely expressed by mammalian cells. They mediate a large array of responses ranging from growth stimulation to apoptosis, from chemotaxis to cell differentiation and from nociception to cytokine release, as well as neurotransmission. Pharma industry is involved in the development and clinical testing of drugs selectively targeting the different P1 nucleoside and P2 nucleotide receptor subtypes. As described in detail in the present review, P2 receptors are expressed by all tumours, in some cases to a very high level. Activation or inhibition of selected P2 receptor subtypes brings about cancer cell death or growth inhibition. The field has been largely neglected by current research in oncology, yet the evidence presented in this review, most of which is based on in vitro studies, although with a limited amount from in vivo experiments and human studies, warrants further efforts to explore the therapeutic potential of purinoceptor targeting in cancer.

The roles of CD73 in cancer

Purinergic signaling has emerged as an important player in cancer progression and is regulated by a series of nucleotidases. Among the enzyme cascade, CD73, which catelyzes AMP breakdown to adenosine, has been found to be overexpressed in many types of cancer. Various factors and mechanisms are employed to regulate expression of CD73. Accumulating studies have shown that CD73 is a key regulatory molecule of cancer cells proliferation, migration and invasion in vitro, tumor angiogenesis, and tumor immune escape in vivo. With such important roles in cancer, CD73 has become an appealing therapy target. Recent evidences in mice models demonstrated that targeted blockade of CD73 could be a favorable therapeutic approach for cancer patients in the future. In this review, we will summarize the multiple roles of CD73 in cancer development, including its clinical significance, its promotive effects on tumor growth, metastasis, and angiogenesis, and its suppressive effects on immune response, regulatory mechanisms of CD73 expression, and current situation of anti-CD73 cancer therapy.

High expression of ecto-nucleotidases CD39 and CD73 in human endometrial tumors

One of the strategies used by tumors to evade immunosurveillance is the accumulation of extracellular adenosine, which has immunosupressive and tumor promoting effects. The study of the mechanisms leading to adenosine formation at the tumor interstitium are therefore of great interest in oncology. The dominant pathway generating extracellular adenosine in tumors is the dephosphorylation of ATP by ecto-nucleotidases. Two of these enzymes acting sequentially, CD39 and CD73, efficiently hydrolyze extracellular ATP to adenosine. They have been found to play a crucial role in a variety of tumors, but there were no data concerning endometrial cancer, the most frequent of the invasive tumors of the female genital tract. The aim of the present work is to study the expression of CD39 and CD73 in human endometrial cancer. We have analyzed protein and gene expression, as well as enzyme activity, in type I endometrioid adenocarcinomas and type II serous adenocarcinomas and their nonpathological endometrial counterparts. High levels of both enzymes were found in tumor samples, with significantly increased expression of CD39 in type II serous tumors, which also coincided with the higher tumor grade. Our results reinforce the involvement of the adenosinergic system in cancer, emphasizing the relevance of ecto-nucleotidases as emerging therapeutic targets in oncology.

NTPDase3 and ecto-5'-nucleotidase/CD73 are differentially expressed during mouse bladder cancer progression

According to the World Health Organization, bladder cancer is the seventh most common cancer among men in the world. The current treatments for this malignancy are not efficient to prevent the recurrence and progression of tumors. Then, researches continue looking for better therapeutic targets which can end up in new and more efficient treatments. One of the recent findings was the identification that the purinergic system was involved in bladder tumorigenesis. The ectonucleotidases, mainly ecto-5'-nucleotidase/CD73 have been revealed as new players in cancer progression and malignity. In this work, we investigated the NTPDase3 and ecto-5'-nucleotidase/CD73 expression in cancer progression in vivo. Bladder tumor was induced in mice by the addition of 0.05 % of N-butyl-N-(hydroxybutyl)-nitrosamine (BBN) in the drinking water for 4, 8, 12, 18, and 24 weeks. After this period, mice bladders were removed for histopathology analysis and immunofluorescence assays. The bladder of animals which has received BBN had alterations, mainly inflammation, in initial times of tumor induction. After 18 weeks, mice's bladder has developed histological alterations similar to human transitional cell carcinoma. The cancerous urothelium, from mice that received BBN for 18 and 24 weeks, presented a weak immunostaining to NTPDase3, in contrast to an increased expression of ecto-5'-nucleotidase/CD73. The altered expression of NTPDase3 and ecto-5'-nucleotidase/CD73 presented herein adds further evidence to support the idea that alterations in ectonucleotidases are involved in bladder tumorigenesis and reinforce the ecto-5'-nucleotidase/CD73 as a future biomarker and/or a target for pharmacological therapy of bladder cancer.