Adenosine 2B Receptor Expression on Cancer Cells Promotes Metastasis

The adenosine A2b receptor promotes tumor progression of bladder urothelial carcinoma by enhancing MAPK signaling pathway

The adenosine A2b receptor (A2bR) was considered to play an oncogenic role in many human malignancies. However, the expression and molecular function of A2bR in bladder urothelial carcinoma (BUC) have not been well elucidated. Herein, we found that the expression of A2bR was higher than other adenosine receptors in BUC tissues and cells, and it was upregulated in BUC tissues compared with matched normal bladder tissues. Furthermore, high expression of A2bR was associated with poor prognosis of patients with BUC. In addition, suppression of A2bR inhibited the proliferation, migration and invasion of BUC cells and arrested the cell cycle at the G1 phase. Finally, we demonstrated that downregulation of A2bR inhibited the proliferation, migration and invasion of BUC in part via the MAPK signaling pathway, increasing the levels of P21 but decreasing the levels of cyclin B1, D, E1, MMP-2 and MMP-9. Overexpression of MMP-2 could rescue BUC cells migration and invasion. Thus, the present study indicates that A2bR may play a potential oncogenic role in BUC progression and act as a potential biomarker to identify BUC patients with poor clinical outcomes.

Cep55 overexpression causes male-specific sterility in mice by suppressing Foxo1 nuclear retention through sustained activation of PI3K/Akt signaling

Spermatogenesis is a dynamic process involving self-renewal and differentiation of spermatogonial stem cells, meiosis, and ultimately, the differentiation of haploid spermatids into sperm. Centrosomal protein 55 kDa (CEP55) is necessary for somatic cell abscission during cytokinesis. It facilitates equal segregation of cytoplasmic contents between daughter cells by recruiting endosomal sorting complex required for transport machinery (ESCRT) at the midbody. In germ cells, CEP55, in partnership with testes expressed-14 (TEX14) protein, has also been shown to be an integral component of intercellular bridge before meiosis. Various in vitro studies have demonstrated a role for CEP55 in multiple cancers and other diseases. However, its oncogenic potential in vivo remains elusive. To investigate, we generated ubiquitously overexpressing Cep55 transgenic ( Cep55^Tg/Tg) mice aiming to characterize its oncogenic role in cancer. Unexpectedly, we found that Cep55^Tg/Tg male mice were sterile and had severe and progressive defects in spermatogenesis related to spermatogenic arrest and lack of spermatids in the testes. In this study, we characterized this male-specific phenotype and showed that excessively high levels of Cep55 results in hyperactivation of PI3K/protein kinase B (Akt) signaling in testis. In line with this finding, we observed increased phosphorylation of forkhead box protein O1 (FoxO1), and suppression of its nuclear retention, along with the relative enrichment of promyelocytic leukemia zinc finger (PLZF) -positive cells. Independently, we observed that Cep55 amplification favored upregulation of ret ( Ret) proto-oncogene and glial-derived neurotrophic factor family receptor α-1 ( Gfra1). Consistent with these data, we observed selective down-regulation of genes associated with germ cell differentiation in Cep55-overexpressing testes at postnatal day 10, including early growth response-4 ( Egr4) and spermatogenesis and oogenesis specific basic helix-loop-helix-1 ( Sohlh1). Thus, Cep55 amplification leads to a shift toward the initial maintenance of undifferentiated spermatogonia and ultimately results in progressive germ cell loss. Collectively, our findings demonstrate that Cep55 overexpression causes change in germ cell proportions and manifests as a Sertoli cell only tubule phenotype, similar to that seen in many azoospermic men.-Sinha, D., Kalimutho, M., Bowles, J., Chan, A.-L., Merriner, D. J., Bain, A. L., Simmons, J. L., Freire, R., Lopez, J. A., Hobbs, R. M., O'Bryan, M. K., Khanna, K. K. Cep55 overexpression causes male-specific sterility in mice by suppressing Foxo1 nuclear retention through sustained activation of PI3K/Akt signaling.

Targeting the Adenosinergic Axis in Chronic Lymphocytic Leukemia: A Way to Disrupt the Tumor Niche?

Targeting adenosine triphosphate (ATP) metabolism and adenosinergic signaling in cancer is gaining momentum, as increasing evidence is showing their relevance in tumor immunology and biology. Chronic lymphocytic leukemia (CLL) results from the expansion of a population of mature B cells that progressively occupies the bone marrow (BM), the blood, and peripheral lymphoid organs. Notwithstanding significant progress in the treatment of these patients, the cure remains an unmet clinical need, suggesting that novel drugs or drug combinations are needed. A unique feature of CLL is its reliance on micro-environmental signals for proliferation and cell survival. We and others have shown that the lymphoid niche, an area of intense interactions between leukemic and bystander non-tumor cells, is a typically hypoxic environment. Here adenosine is generated by leukemic cells, as well as by cells of myeloid origin, acting through autocrine and paracrine mechanisms, ultimately affecting tumor growth, limiting drug responses, and skewing the immune cells towards a tolerant phenotype. Hence, understanding the mechanisms through which this complex network of enzymes, receptors, and metabolites functions in CLL, will pave the way to the use of pharmacological agents targeting the system, which, in combination with drugs targeting leukemic cells, may get us one step closer to curing these patients.

Canonical and non-canonical adenosinergic pathways

Adenosine (ADO) is an immunosuppressive molecule with multiple functions in different human organs. ADO is released through the concerted action of surface molecules endowed with enzymatic functions, that belong to two different adenosinergic pathways. The canonical pathway is started by CD39, that converts ATP to AMP. On the other hand, the non-canonical pathway metabolizes NAD⁺ to ADPR, through the action of CD38. The latter byproduct is then converted to AMP by CD203a/PC-1. Both pathways converge to CD73, that fully degrades AMP to the final product ADO. In this Review we take into account the most relevant finding regarding the expression of ectoenzymes belonging to both adenosinergic pathways in different cell types, including regulatory cell subsets and neoplastic cells. Moreover, we summarize the role of these molecules in different physiological and pathological settings. Finally, we discuss potential therapeutic application of specific inhibitors of ectoenzymes and/or ADO receptors.

Activation of the A2B adenosine receptor in B16 melanomas induces CXCL12 expression in FAP-positive tumor stromal cells, enhancing tumor progression

The A2B receptor (A2BR) can mediate adenosine-induced tumor proliferation, immunosuppression and angiogenesis. Targeting the A2BR has proved to be therapeutically effective in some murine tumor models, but the mechanisms of these effects are still incompletely understood. Here, we report that pharmacologic inhibition of A2BR with PSB1115, which inhibits tumor growth, decreased the number of fibroblast activation protein (FAP)-expressing cells in tumors in a mouse model of melanoma. This effect was associated with reduced expression of fibroblast growth factor (FGF)-2. Treatment of melanoma-associated fibroblasts with the A2BR agonist Bay60-6583 enhanced CXCL12 and FGF2 expression. This effect was abrogated by PSB1115. The A2AR agonist CGS21680 did not induce CXCL12 or FGF2 expression in tumor associated fibroblasts. Similar results were obtained under hypoxic conditions in skin-derived fibroblasts, which responded to Bay60-6583 in an A2BR-dependent manner, by stimulating pERK1/2. FGF2 produced by Bay60-6583-treated fibroblasts directly enhanced the proliferation of melanoma cells. This effect could be reversed by PSB1115 or an anti-FGF2 antibody. Interestingly, melanoma growth in mice receiving Bay60-6583 was attenuated by inhibition of the CXCL12/CXCR4 pathway with AMD3100. CXCL12 and its receptor CXCR4 are involved in angiogenesis and immune-suppression. Treatment of mice with AMD3100 reduced the number of CD31+ cells induced by Bay60-6583. Conversely, CXCR4 blockade did not affect the accumulation of tumor-infiltrating MDSCs or Tregs. Together, our data reveal an important role for A2BR in stimulating FGF2 and CXCL12 expression in melanoma-associated fibroblasts. These factors contribute to create a tumor-promoting microenvironment. Our findings support the therapeutic potential of PSB1115 for melanoma.

The A2B Adenosine Receptor Modulates the Epithelial- Mesenchymal Transition through the Balance of cAMP/PKA and MAPK/ERK Pathway Activation in Human Epithelial Lung Cells

The epithelial-mesenchymal transition (EMT) is a complex process in which cell phenotype switches from the epithelial to mesenchymal one. The deregulations of this process have been related with the occurrence of different diseases such as lung cancer and fibrosis. In the last decade, several efforts have been devoted in understanding the mechanisms that trigger and sustain this transition process. Adenosine is a purinergic signaling molecule that has been involved in the onset and progression of chronic lung diseases and cancer through the A_2B adenosine receptor subtype activation, too. However, the relationship between A_2BAR and EMT has not been investigated, yet. Herein, the A_2BAR characterization was carried out in human epithelial lung cells. Moreover, the effects of receptor activation on EMT were investigated in the absence and presence of transforming growth factor-beta (TGF-β1), which has been known to promote the transition. The A_2BAR activation alone decreased and increased the expression of epithelial markers (E-cadherin) and the mesenchymal one (Vimentin, N-cadherin), respectively, nevertheless a complete EMT was not observed. Surprisingly, the receptor activation counteracted the EMT induced by TGF-β1. Several intracellular pathways regulate the EMT: high levels of cAMP and ERK1/2 phosphorylation has been demonstrated to counteract and promote the transition, respectively. The A_2BAR stimulation was able to modulated these two pathways, cAMP/PKA and MAPK/ERK, shifting the fine balance toward activation or inhibition of EMT. In fact, using a selective PKA inhibitor, which blocks the cAMP pathway, the A_2BAR-mediated EMT promotion were exacerbated, and conversely the selective inhibition of MAPK/ERK counteracted the receptor-induced transition. These results highlighted the A_2BAR as one of the receptors involved in the modulation of EMT process. Nevertheless, its activation is not enough to trigger a complete transition, its ability to affect different intracellular pathways could represent a mechanism at the basis of EMT maintenance/inhibition based on the extracellular microenvironment. Despite further investigations are needed, herein for the first time the A_2BAR has been related to the EMT process, and therefore to the different EMT-related pathologies.

A2B adenosine receptor agonist induces cell cycle arrest and apoptosis in breast cancer stem cells via ERK1/2 phosphorylation

PURPOSE

It has been reported that cancer stem cells (CSCs) may play a crucial role in the development, recurrence and metastasis of breast cancer. Targeting signaling pathways in CSCs is considered to be a promising strategy for the treatment of cancer. Here, we investigated the role of the A2B adenosine receptor (A2BAR) and its associated signaling pathways in governing the proliferation and viability of breast cancer cell line derived CSCs.

METHODS

CSCs were isolated from the breast cancer cell lines MCF-7 and MDA-MB-231 using a mammosphere assay. The effect of the A2BAR agonist BAY606583 on cell proliferation was evaluated using XTT and mammosphere formation assays, respectively. Apoptosis was assessed using Annexin-V staining and cell cycle analyses were performed using flow cytometry. The expression levels of Bax, Bcl-2, cyclin-D1, CDK-4 and (phosphorylated) ERK1/2 were assessed using Western blotting.

RESULTS

Our data revealed that the breast cancer cell line derived mammospheres were enriched for CSCs. We also found that A2BAR stimulation with its agonist BAY606583 inhibited mammosphere formation and CSC viability. In addition, we found that the application of BAY606583 led to CSC cell cycle arrest and apoptosis through the cyclin-D1/Cdk-4 and Bax/Bcl-2 pathways, respectively. Notably, we found that BAY606583 significantly down-regulated ERK1/2 phosphorylation in the breast cancer cell line derived CSCs.

CONCLUSIONS

From our results we conclude that A2BAR induces breast CSC cell cycle arrest and apoptosis through downregulation of the ERK1/2 cascade. As such, A2BAR may be considered as a novel target for the treatment of breast cancer.

Targeting immunosuppressive adenosine in cancer

Despite the success of anti-programmed cell death protein 1 (PD1), anti-PD1 ligand 1 (PDL1) and anti-cytotoxic T lymphocyte antigen 4 (CTLA4) therapies in advanced cancer, a considerable proportion of patients remain unresponsive to these treatments (known as innate resistance). In addition, one-third of patients relapse after initial response (known as adaptive resistance), which suggests that multiple non-redundant immunosuppressive mechanisms coexist within the tumour microenvironment. A major immunosuppressive mechanism is the adenosinergic pathway, which now represents an attractive new therapeutic target for cancer therapy. Activation of this pathway occurs within hypoxic tumours, where extracellular adenosine exerts local suppression through tumour-intrinsic and host-mediated mechanisms. Preclinical studies in mice with adenosine receptor antagonists and antibodies have reported favourable antitumour immune responses with some definition of the mechanism of action. Currently, agents targeting the adenosinergic pathway are undergoing first-in-human clinical trials as single agents and in combination with anti-PD1 or anti-PDL1 therapies. In this Review, we describe the complex interplay of adenosine and adenosine receptors in the development of primary tumours and metastases and discuss the merits of targeting one or more components that compose the adenosinergic pathway. We also review the early clinical data relating to therapeutic agents inhibiting the adenosinergic pathway.

Interleukin-12 from CD103+ Batf3-Dependent Dendritic Cells Required for NK-Cell Suppression of Metastasis

Several host factors may affect the spread of cancer to distant organs; however, the intrinsic role of dendritic cells (DC) in controlling metastasis is poorly described. Here, we show in several tumor models that although the growth of primary tumors in Batf3-deficient mice, which lack cross-presenting DCs, was not different from primary tumors in wild-type (WT) control mice, Batf3-deficient mice had increased experimental and spontaneous metastasis and poorer survival. The increased metastasis was independent of CD4⁺ and CD8⁺ T lymphocytes, but required NK cells and IFNγ. Chimeric mice in which Batf3-dependent DCs uniformly lacked the capacity to produce IL12 had metastatic burdens similar to the Batf3-deficient mice, suggesting that Batf3⁺ DCs were the only cell type whose IL12 production was critical for controlling metastasis. We found that IL12-YFP reporter mice, whose lungs were injected with B16F10 melanoma, had increased numbers of IL12-expressing CD103⁺ DCs with enhanced CD86 expression. Bone-marrow-derived DCs from WT, but not Batf3-deficient, mice activated NK cells to produce IFNγ in an IL12-dependent manner and therapeutic injection of recombinant mouse IL12 decreased metastasis in both WT and Batf3-deficient mice. Analysis of TCGA datasets revealed an association between high expression of BATF3 and IRF8 and improved survival of breast cancer patients; BATF3 expression also significantly correlated with NK-cell receptor genes, IL12, and IFNG Collectively, our findings show that IL12 from CD103⁺ DCs is critical for NK cell-mediated control of tumor metastasis. Cancer Immunol Res; 5(12); 1098-108. ©2017 AACR.

New Combination Strategies Using Programmed Cell Death 1/Programmed Cell Death Ligand 1 Checkpoint Inhibitors as a Backbone

The discovery of immune checkpoints and subsequent clinical development of checkpoint inhibitors have revolutionized the field of oncology. The durability of the antitumor immune responses has raised the hope for long-term patient survival and potential cure; however, currently, only a minority of patients respond. Combination strategies to help increase antigen release and T-cell priming, promote T-cell activation and homing, and improve the tumor immune microenvironment, all guided by predictive biomarkers, can help overcome the tumor immune-evasive mechanisms and maximize efficacy to ultimately benefit the majority of patients. Great challenges remain because of the complex underlying biology, unpredictable toxicity, and accurate assessment of response. Carefully designed clinical trials guided by translational studies of paired biopsies will be key to develop reliable predictive biomarkers to choose which patients would most likely benefit from each strategy.

Primary, Adaptive, and Acquired Resistance to Cancer Immunotherapy

Cancer immunotherapy can induce long lasting responses in patients with metastatic cancers of a wide range of histologies. Broadening the clinical applicability of these treatments requires an improved understanding of the mechanisms limiting cancer immunotherapy. The interactions between the immune system and cancer cells are continuous, dynamic, and evolving from the initial establishment of a cancer cell to the development of metastatic disease, which is dependent on immune evasion. As the molecular mechanisms of resistance to immunotherapy are elucidated, actionable strategies to prevent or treat them may be derived to improve clinical outcomes for patients.

Role of adenosine signaling in the pathogenesis of breast cancer

The plasma level of adenosine increases under ischemic and inflamed conditions in tumor microenvironment. Adenosine elicits a range of signaling pathways in tumors, resulting in either inhibition or enhancement of tumor growth depending upon different subtypes of adenosine receptors activation and type of cancer. Metabolism of adenosine-5'-triphosphate (ATP) and its derivatives including adenosine is dysregulated in the breast tumor microenvironment, supporting the role of this metabolite in the pathogenesis of breast cancer. Adenosine regulates inflammation, apoptosis, cell proliferation, and metastasis in breast cancer cells. This review summarizes the role of adenosine in the pathogenesis of breast cancer for a better understanding and hence a better management of this disease.

Function and Clinical Implications of Long Non-Coding RNAs in Melanoma

Metastatic melanoma is the most deadly type of skin cancer. Despite the success of immunotherapy and targeted agents, the majority of patients experience disease recurrence upon treatment and die due to their disease. Long non-coding RNAs (lncRNAs) are a new subclass of non-protein coding RNAs involved in (epigenetic) regulation of cell growth, invasion, and other important cellular functions. Consequently, recent research activities focused on the discovery of these lncRNAs in a broad spectrum of human diseases, especially cancer. Additional efforts have been undertaken to dissect the underlying molecular mechanisms employed by lncRNAs. In this review, we will summarize the growing evidence of deregulated lncRNA expression in melanoma, which is linked to tumor growth and progression. Moreover, we will highlight specific molecular pathways and modes of action for some well-studied lncRNAs and discuss their potential clinical implications.

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.

Targeting A2 adenosine receptors in cancer

Tumor cells use various ways to evade anti-tumor immune responses. Adenosine, a potent immunosuppressive metabolite, is often found elevated in the extracellular tumor microenvironment. Therefore, targeting adenosine-generating enzymes (CD39 and CD73) or adenosine receptors has emerged as a novel means to stimulate anti-tumor immunity. In particular, the A2 (A2a and A2b) adenosine receptors exhibit similar immunosuppressive and pro-angiogenic functions, yet have distinct biological roles in cancer. In this review, we describe the common and distinct biological consequences of A2a and A2b adenosine receptor signaling in cancer. We discuss recent pre-clinical studies and summarize the different mechanisms-of-action of adenosine-targeting drugs. We also review the rationale for combining inhibitors of the adenosine pathway with other anticancer therapies such immune checkpoint inhibitors, tumor vaccines, chemotherapy and adoptive T cell therapy.

For robust big data analyses: a collection of 150 important pro-metastatic genes

Metastasis is the greatest contributor to cancer-related death. In the era of precision medicine, it is essential to predict and to prevent the spread of cancer cells to significantly improve patient survival. Thanks to the application of a variety of high-throughput technologies, accumulating big data enables researchers and clinicians to identify aggressive tumors as well as patients with a high risk of cancer metastasis. However, there have been few large-scale gene collection studies to enable metastasis-related analyses. In the last several years, emerging efforts have identified pro-metastatic genes in a variety of cancers, providing us the ability to generate a pro-metastatic gene cluster for big data analyses. We carefully selected 285 genes with in vivo evidence of promoting metastasis reported in the literature. These genes have been investigated in different tumor types. We used two datasets downloaded from The Cancer Genome Atlas database, specifically, datasets of clear cell renal cell carcinoma and hepatocellular carcinoma, for validation tests, and excluded any genes for which elevated expression level correlated with longer overall survival in any of the datasets. Ultimately, 150 pro-metastatic genes remained in our analyses. We believe this collection of pro-metastatic genes will be helpful for big data analyses, and eventually will accelerate anti-metastasis research and clinical intervention.

A Purinergic Trail for Metastases

Nucleotides and nucleosides have emerged as important modulators of tumor biology. Recently acquired evidence shows that, when these molecules are released by cancer cells or surrounding tissues, they act as potent prometastatic factors, favoring tumor cell migration and tissue colonization. Therefore, nucleotides and nucleosides should be considered as a new class of prometastatic factors. In this review, we focus on the prometastatic roles of nucleotides and discuss future applications of purinergic signaling modulation in view of antimetastatic therapies.

Adenosine Stimulate Proliferation and Migration in Triple Negative Breast Cancer Cells

Emerging evidence suggests that the adenosine (Ado) receptors may play crucial roles in tumor progression. Here, we show that Ado increases proliferation and migration in a triple negative breast cancer model, the MDA-MB 231 cell line. The use of specific agonists and antagonists evidenced that these effects depend on the activation of the A_2B receptor, which then triggers an intracellular response mediated by the adenylate cyclase/PKA/cAMP signaling pathway. Ado also increases the expression of Na_V1.5 channels, a potential biomarker in breast cancer. Together, these data suggest important roles of the A_2B receptors and Na_V1.5 channels in the Ado-induced increase in proliferation and migration of the MDA-MB 231 cells.

Combination Approaches with Immune-Checkpoint Blockade in Cancer Therapy

In healthy individuals, immune-checkpoint molecules prevent autoimmune responses and limit immune cell-mediated tissue damage. Tumors frequently exploit these molecules to evade eradication by the immune system. Over the past years, immune-checkpoint blockade of cytotoxic T lymphocyte antigen-4 and programed death-1 emerged as promising strategies to activate antitumor cytotoxic T cell responses. Although complete regression and long-term survival is achieved in some patients, not all patients respond. This review describes promising, novel combination approaches involving immune-checkpoint blockade in the context of the cancer-immunity cycle, aimed at increasing response rates to the single treatments. Specifically, we discuss combinations that promote antigen release and presentation, that further amplify T cell activation, that inhibit trafficking of regulatory T cells or MSDCs, that stimulate intratumoral T cell infiltration, that increase cancer recognition by T cells, and that stimulate tumor killing.