CD39/ENTPD1 expression by CD4+Foxp3+ regulatory T cells promotes hepatic metastatic tumor growth in mice

Harnessing the tumor microenvironment to boost adoptive T cell therapy with engineered lymphocytes for solid tumors

Adoptive cell therapy (ACT) using Chimeric Antigen Receptor (CAR) and T Cell Receptor (TCR) engineered T cells represents an innovative therapeutic approach for the treatment of hematological malignancies, yet its application for solid tumors is still suboptimal. The tumor microenvironment (TME) places several challenges to overcome for a satisfactory therapeutic effect, such as physical barriers (fibrotic capsule and stroma), and inhibitory signals impeding T cell function. Some of these obstacles can be faced by combining ACT with other anti-tumor approaches, such as chemo/radiotherapy and checkpoint inhibitors. On the other hand, cutting edge technological tools offer the opportunity to overcome and, in some cases, take advantage of TME intrinsic characteristics to boost ACT efficacy. These include: the exploitation of chemokine gradients and integrin expression for preferential T-cell homing and extravasation; metabolic changes that have direct or indirect effects on TCR-T and CAR-T cells by increasing antigen presentation and reshaping T cell phenotype; introduction of additional synthetic receptors on TCR-T and CAR-T cells with the aim of increasing T cells survival and fitness.

Identification of clinically relevant subsets CD39+PD-1+CD8+ T cells and CD39+ regulatory T cells in intrahepatic cholangiocarcinoma using single-cell CyTOF

Intrahepatic cholangiocarcinoma (iCCA) is an aggressive liver malignancy with limited treatment options and a dismal prognosis. The tumor immune microenvironment (TIME) is crucial for iCCA progression, yet its comprehensive characterization remains incomplete. This study utilized mass cytometry by time of flight (CyTOF) to comprehensively analyze immune cell populations in fresh iCCA tumor samples and adjacent peritumor liver tissues. Notably, NK cell percentages significantly decreased in iCCA lesions compared to peritumor liver tissues. Conversely, an enrichment of immunosuppressive CD39+Foxp3+CD4+ regulatory T cells (CD39+T-regs) and exhausted-like CD8+T cells (with pronounced CD39 and PD-1 expression) within TIME was identified and confirmed by multiplex immunofluorescence staining in an independent patient cohort (n = 140). Crucially, tumor-infiltrating CD39+T-regs and CD39+PD-1+CD8+T cells emerged as independent prognostic indicators associated with an unfavorable prognosis in iCCA. These findings unveil the intricate immune landscape within iCCA, offering valuable insights for disease management and novel cancer immunotherapies.

Platelets induce CD39 expression in tumor cells to facilitate tumor metastasis

BACKGROUND

Tumor cells continue to evolve the metastatic potential in response to signals provided by the external microenvironment during metastasis. Platelets closely interact with tumor cells during hematogenous metastasis and facilitate tumor development. However, the molecular mechanisms underlying this process are not fully understood.

METHODS

RNA-sequencing was performed to screen differentially expressed genes mediated by platelets. The effects of platelet and CD39 on tumor metastasis were determined by experimental metastasis models with WT, NCG and CD39-/- mice.

RESULTS

RNA-sequencing results showed that platelets significantly up-regulated CD39 expression in tumor cells. CD39 is a novel immune checkpoint molecule and a key driver of immunosuppression. Our data provided evidence that the expression of CD39 was enhanced by platelets in a platelet-tumor cell contact dependent manner. Although the role of CD39 expressed by immune cells is well established, the effect of CD39 expressed by tumor cells on tumor cell behavior, anti-tumor immunity and tumor metastasis is unclear. We found that CD39 promoted tumor cell invasion, but had no effect on proliferation and migration. Notably, we showed that the ability of platelets to prime tumor cells for metastasis depends on CD39 in the experimental tumor metastasis model. CD39 silencing resulted in fewer experimental metastasis formation, and this anti-metastasis effect was significantly reduced in platelet-depleted mice. Furthermore, overexpression of CD39 in tumor cells promoted metastasis. In order to eliminate the effect of CD39 expressed in cells other than tumor cells, we detected tumor metastasis in CD39-/- mice and obtained similar results. Moreover, overexpression of CD39 in tumor cells inhibited antitumor immunity. Finally, the data from human samples also supported our findings.

CONCLUSIONS

Our study shows that direct contact with platelets induces CD39 expression in tumor cells, leading to immune suppression and promotion of metastasis.

Regulatory T cell-mediated immunosuppression orchestrated by cancer: towards an immuno-genomic paradigm for precision medicine

Accumulating evidence indicates that aberrant signalling stemming from genetic abnormalities in cancer cells has a fundamental role in their evasion of antitumour immunity. Immune escape mechanisms include enhanced expression of immunosuppressive molecules, such as immune-checkpoint proteins, and the accumulation of immunosuppressive cells, including regulatory T (Treg) cells, in the tumour microenvironment. Therefore, Treg cells are key targets for cancer immunotherapy. Given that therapies targeting molecules predominantly expressed by Treg cells, such as CD25 or GITR, have thus far had limited antitumour efficacy, elucidating how certain characteristics of cancer, particularly genetic abnormalities, influence Treg cells is necessary to develop novel immunotherapeutic strategies. Hence, Treg cell-targeted strategies based on the particular characteristics of cancer in each patient, such as the combination of immune-checkpoint inhibitors with molecularly targeted agents that disrupt the immunosuppressive networks mediating Treg cell recruitment and/or activation, could become a new paradigm of cancer therapy. In this Review, we discuss new insights on the mechanisms by which cancers generate immunosuppressive networks that attenuate antitumour immunity and how these networks confer resistance to cancer immunotherapy, with a focus on Treg cells. These insights lead us to propose the concept of 'immuno-genomic precision medicine' based on specific characteristics of cancer, especially genetic profiles, that correlate with particular mechanisms of tumour immune escape and might, therefore, inform the optimal choice of immunotherapy for individual patients.

Upregulation of CD39 During Gout Attacks Promotes Spontaneous Remission of Acute Gouty Inflammation

Gout is a self-limiting form of inflammatory arthropathy caused by the formation of urate crystals due to hyperuricemia. The resolution of gout involves the transition of proinflammatory M1-type macrophages to anti-inflammatory M2-type macrophages, as well as neutrophil-mediated extracellular trap (NET) formation. However, the underlying mechanisms of these changes are not clear. Studies have confirmed that high expression of CD39 on macrophages and neutrophils can trigger the polarization of macrophages from a proinflammatory state to an anti-inflammatory state. Recent studies have shown that the pathogenesis of gout involves extracellular ATP (eATP), and the synergistic effect of MSU and extracellular ATP can cause gout. CD39 is a kind of ATP hydrolysis enzyme that can degrade eATP, suggesting that CD39 may inhibit the aggravation of inflammation in gout and participate in the remission mechanism of gout. To confirm this hypothesis, using data mining and flow cytometry, we first found that CD39 expression was significantly upregulated on CD14 + monocytes and neutrophils in gout patients during the acute phase. Inhibition of CD39 by lentivirus or a CD39 inhibitor in acute gout models aggravated gouty arthritis and delayed gout remission. Apyrase, a functional analog of CD39, can significantly reduce the inflammatory response and promote gout remission in acute gout model mice. Our findings confirm that the upregulation of CD39 during gout flare-ups promotes spontaneous remission of acute gouty inflammation.

Interrogations of single-cell RNA splicing landscapes with SCASL define new cell identities with physiological relevance

RNA splicing shapes the gene regulatory programs that underlie various physiological and disease processes. Here, we present the SCASL (single-cell clustering based on alternative splicing landscapes) method for interrogating the heterogeneity of RNA splicing with single-cell RNA-seq data. SCASL resolves the issue of biased and sparse data coverage on single-cell RNA splicing and provides a new scheme for classifications of cell identities. With previously published datasets as examples, SCASL identifies new cell clusters indicating potentially precancerous and early-tumor stages in triple-negative breast cancer, illustrates cell lineages of embryonic liver development, and provides fine clusters of highly heterogeneous tumor-associated CD4 and CD8 T cells with functional and physiological relevance. Most of these findings are not readily available via conventional cell clustering based on single-cell gene expression data. Our study shows the potential of SCASL in revealing the intrinsic RNA splicing heterogeneity and generating biological insights into the dynamic and functional cell landscapes in complex tissues.

The Prognostic Value of CD39 as a Marker of Tumor-Specific T Cells in Triple-Negative Breast Cancer in Asian Women

Triple-negative breast cancer (TNBC) has a poor prognosis with limited therapeutic options available for affected patients. Efforts are ongoing to identify surrogate markers for tumor-specific CD8+ T cells that can predict the response to immune checkpoint inhibitor (ICI) therapies, such as programmed cell death protein 1 or programmed cell death ligand-1 blockade. We have previously identified tumor-specific CD39+CD8+ T cells in non-small cell lung cancer that might help predict patient responses to programmed cell death protein 1 or programmed cell death ligand-1 blockade. Based on this finding, we conducted a comparative interrogation of TNBC in an Asian cohort to evaluate the potential of CD39 as a surrogate marker of tumor-specific CD8+ T cells. Using ICI-treated TNBC mouse models (n = 24), flow cytometric analyses of peripheral blood mononuclear cells and tumor-infiltrating lymphocytes revealed that >99% of tumor-specific CD8+ T cells also expressed CD39. To investigate the relationship between CD39+CD8+ T-cell density and CD39 expression with disease prognosis, we performed multiplex immunohistochemistry staining on treatment-naive human TNBC tissues (n = 315). We saw that the proportion of CD39+CD8+ T cells in human TNBC tumors correlated with improved overall survival, as did the densities of other CD39+ immune cell infiltrates, such as CD39+CD68+ macrophages. Finally, increased CD39 expression on CD8+ T cells was also found to predict the response to ICI therapy (pembrolizumab) in a separate cohort of 11 TNBC patients. These findings support the potential of CD39+CD8+ T-cell density as a prognostic factor in Asian TNBC patients.

CD39+ tumor infiltrating T cells from colorectal cancers exhibit dysfunctional phenotype

Recent studies revealed that CD39 was highly expressed in tumor-specific CD4+ tumor infiltrating lymphocytes (TILs). However, the divergent function of CD39+ T cells remains to be elucidated in colorectal cancer (CRC). In this study, T cells from CRC patients and tumor-bearing mice were isolated to evaluate the function of CD39 in T cells. We found that CD39 was elevated in intratumoral T cells from CRC patients, and negatively correlated with cytokine secretion capacity. T cell activation induced CD39 expression, and CD39+ T cells produced more IFN-γ in response to CRC tumor antigens. In addition, CD39+ T cells in the spleens of tumor-bearing mice exhibited a stronger anti-tumor activity in vitro than CD39- T cells, but there was no significant difference in the anti-tumor activities between CD39- TILs and CD39+ TILs. Moreover, we found that CD39+ T cells expressed higher checkpoint molecules and contained a higher proportion of Treg cells than CD39- T cells, suggesting that CD39+ T cells may be correlated with an immunosuppressive phenotype. And CD39 expression on T cells could convert pro-inflammatory eATP to immunosuppressive eADO. However, both T cells from the vaccinated-wild-type mice and CD39-/- mice could recognize and eliminate tumor cells in vitro, and adoptive transfer of these T cells resulted in tumor growth inhibition in tumor-bearing mice. In conclusion, our study revealed the divergent functions of CD39+ T cells, which were reactive to tumor antigen but exhibited a dysfunctional phenotype.

Adenosine A2a receptor inhibition increases the anti-tumor efficacy of anti-PD1 treatment in murine hepatobiliary cancers

Backgrounds & Aims

The efficacy of immune checkpoint inhibitor (ICI) therapy for liver cancer remains limited. As the hypoxic liver environment regulates adenosine signaling, we tested the efficacy of adenosine A2a receptor (A2aR) inhibition in combination with ICI treatment in murine models of liver cancer.

Methods

RNA expression related to the adenosine pathway was analyzed from public databases. Peripheral blood mononuclear cells of 13 patients with hepatocellular carcinoma (HCC) were examined by flow cytometry. The following murine cell lines were used: SB-1, RIL175, and Hep55.1c (liver cancer), CT26 (colon cancer), and B16-F10 (melanoma). C57BL/6 and BALB/c mice were used for orthotopic tumor models and were treated with SCH58261, an A2aR inhibitor, in combination with anti-PD1 therapy.

Results

RNA expression of ADORA2A in tumor tissues derived from patients with HCC was higher than in tissues from other cancer types. A2aR+ T cells in peripheral blood from patients with HCC were highly proliferative after immunotherapy. Likewise, in an orthotopic murine model, A2aR expression on T cells increased following anti-PD1 treatment, and the expression of A2aR on T cells increased more in tumor-bearing mice compared with tumor-free mice. The combination of SCH58261 and anti-PD1 led to activation of T cells and reductions in tumor size in orthotopic liver cancer models. In contrast, SCH58261 monotherapy was ineffective in orthotopic liver cancer models and the combination was ineffective in the subcutaneous tumor models tested. CD4+ T-cell depletion attenuated the efficacy of the combination therapy.

Conclusion

A2aR inhibition and anti-PD1 therapy had a synergistic anti-tumor effect in murine liver cancer models.

Impact and implications

Adenosine A2a receptor (A2aR)-expressing T cells in the liver increased in tumor-bearing mice and after anti-PD1 treatment. The combination of an A2aR inhibitor and anti-PD1 treatment had potent anti-tumor effects in two murine models of orthotopic liver cancer. Adenosine A2a receptor blockade promotes immunotherapy efficacy in murine models, highlighting putative clinical benefits for advanced stage liver cancer patients.

Istradefylline modulates purinergic enzymes and reduces malignancy-associated factors in B16F10 melanoma cells

ATP and adenosine exert pivotal roles in the development, maintenance, and metastatic spreading of melanoma. The action of such key melanoma tumor microenvironment (TME) constituents might be complementary or opposed, and their effects are not exclusive to immune cells but also to other host cells and tumor cells. The effects of ATP are controlled by the axis CD39/73, resulting in adenosine, the main actor in the TME, and A2A is the crucial mediator of its effects. We evaluated ATP and adenosine signaling through A2A on B16F10 melanoma cells using istradefylline (IST) (antiparkinsonian A2A antagonist) and caffeine (CAF) treatments after exposure to ATP and adenosine. Adenosine increased melanoma cell viability and proliferation in a concentration-dependent manner. ATP increases viability only as a substrate by CD39 to produce adenosine. Both IST and CAF are toxic to B16F10 cells, but only IST potentialized paclitaxel-induced cytotoxic effects, even decreasing its IC50 value. IST positively modulated CD39 and CD73 expression. CD39 activity was increased, and E-ADA was reduced, indicating that the melanoma cells promoted compensatory feedback in the production and maintenance of adenosine levels. A2A antagonism by IST reduced the factors associated with malignancy, like migration, adhesion, colony formation, and the capacity to produce melanin. Moreover, IST significantly increases nitric oxide (NO) production, which correlates to a decline in melanoma cell viability by apoptotic events. Altogether, our results suggest that adenosine signaling through A2A is essential for B16F10 cells, and its inhibition by IST causes compensatory purinergic enzymatic modulations. Furthermore, IST is a promising therapy that provides new ways to improve current melanoma treatments.

Purinergic signaling: decoding its role in COVID-19 pathogenesis and promising treatment strategies

The pathogenesis of coronavirus disease (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS‑CoV‑2), is complex and involves dysregulated immune responses, inflammation, and coagulopathy. Purinergic signaling, mediated by extracellular nucleotides and nucleosides, has emerged as a significant player in the pathogenesis of COVID-19. Extracellular adenosine triphosphate (ATP), released from damaged or infected cells, is a danger signal triggering immune responses. It activates immune cells, releasing pro-inflammatory cytokines, contributing to the cytokine storm observed in severe COVID-19 cases. ATP also promotes platelet activation and thrombus formation, contributing to the hypercoagulability seen in COVID-19 patients. On the other hand, adenosine, an immunosuppressive nucleoside, can impair anti-viral immune responses and promote tissue damage through its anti-inflammatory effects. Modulating purinergic receptors represents a promising therapeutic strategy for COVID-19. Understanding the role of purinergic signaling in COVID-19 pathogenesis and developing targeted therapeutic approaches can potentially improve patient outcomes. This review focuses on the part of purinergic signaling in COVID-19 pathogenesis and highlights potential therapeutic approaches targeting purinergic receptors.

Adenosine in cancer immunotherapy: Taking off on a new plane

As a new pillar of cancer therapy, tumor immunotherapy has brought irreplaceable durable responses in tumors. Considering its low response rate, additional immune regulatory mechanisms will be critical for the development of next-generation immune therapeutics. As a key regulatory mechanism, adenosine (ADO) protects tissues from excessive immune responses, but as a metabolite highly concentrated in tumor microenvironments, extracellular adenosine acts on adenosine receptors (mainly A2A receptors) expressed on MDSCs, Tregs, NK cells, effector T cells, DCs, and macrophages to promote tumor cell escape from immune surveillance by inhibiting the immune response. Amounting preclinical studies have demonstrated the adenosine pathway as a novel checkpoint for immunotherapy. Large number of adenosine pathway targeting clinical trials are now underway, including antibodies against CD39 and CD73 as well as A2A receptor inhibitors. There has been evidence of antitumor efficacy of these inhibitors in early clinical trials among a variety of tumors such as breast cancer, prostate cancer, non-small cell lung cancer, etc. As more clinical trial results are published, the combination of blockade of this pathway with immune checkpoint inhibitors, targeted drugs, traditional chemotherapy medications, radiotherapy and endocrine therapy will provide cancer patients with better clinical outcomes. We would elaborate on the role of CD39-CD73-A2AR pathway in the contribution of tumor microenvironment and the targeting of the adenosinergic pathway for cancer therapy in the review.

Adenosine, bridging chronic inflammation and tumor growth

Adenosine (Ado) is a well-known immunosuppressive agent that may be released or generated extracellularly by cells, via degrading ATP by the sequential actions of the ectonucleotides CD39 and CD73. During inflammation Ado is produced by leukocytes and tissue cells by different means to initiate the healing phase. Ado downregulates the activation and the effector functions of different leukocyte (sub-) populations and stimulates proliferation of fibroblasts for re-establishment of intact tissues. Therefore, the anti-inflammatory actions of Ado are already intrinsically triggered during each episode of inflammation. These tissue-regenerating and inflammation-tempering purposes of Ado can become counterproductive. In chronic inflammation, it is possible that Ado-driven anti-inflammatory actions sustain the inflammation and prevent the final clearance of the tissues from possible pathogens. These chronic infections are characterized by increased tissue damage, remodeling and accumulating DNA damage, and are thus prone for tumor formation. Developing tumors may further enhance immunosuppressive actions by producing Ado by themselves, or by "hijacking" CD39+/CD73+ cells that had already developed during chronic inflammation. This review describes different and mostly convergent mechanisms of how Ado-induced immune suppression, initially induced in inflammation, can lead to tumor formation and outgrowth.

Unlocking antitumor immunity with adenosine receptor blockers

Tumors survive by creating a tumor microenvironment (TME) that suppresses antitumor immunity. The TME suppresses the immune system by limiting antigen presentation, inhibiting lymphocyte and natural killer (NK) cell activation, and facilitating T cell exhaustion. Checkpoint inhibitors like anti-PD-1 and anti-CTLA4 are immunostimulatory antibodies, and their blockade extends the survival of some but not all cancer patients. Extracellular adenosine triphosphate (ATP) is abundant in inflamed tumors, and its metabolite, adenosine (ADO), is a driver of immunosuppression mediated by adenosine A2A receptors (A2AR) and adenosine A2B receptors (A2BR) found on tumor-associated lymphoid and myeloid cells. This review will focus on adenosine as a key checkpoint inhibitor-like immunosuppressive player in the TME and how reducing adenosine production or blocking A2AR and A2BR enhances antitumor immunity.

Adenosine A2A receptor is a tumor suppressor of NASH-associated hepatocellular carcinoma

Inhibition of adenosine A2A receptor (A2AR) is a promising approach for cancer immunotherapy currently evaluated in several clinical trials. We here report that anti-obesogenic and anti-inflammatory functions of A2AR, however, significantly restrain hepatocellular carcinoma (HCC) development. Adora2a deletion in mice triggers obesity, non-alcoholic steatohepatitis (NASH), and systemic inflammation, leading to spontaneous HCC and promoting dimethylbenzyl-anthracene (DMBA)- or diethylnitrosamine (DEN)-induced HCC. Conditional Adora2a deletion reveals critical roles of myeloid and hepatocyte-derived A2AR signaling in restraining HCC by limiting hepatic inflammation and steatosis. Remarkably, the impact of A2AR pharmacological blockade on HCC development is dependent on pre-existing NASH. In support of our animal studies, low ADORA2A gene expression in human HCC is associated with cirrhosis, hepatic inflammation, and poor survival. Together, our study uncovers a previously unappreciated tumor-suppressive function for A2AR in the liver and suggests caution in the use of A2AR antagonists in patients with NASH and NASH-associated HCC.

Targeting chemoresistance and mitochondria-dependent metabolic reprogramming in acute myeloid leukemia

Chemoresistance often complicates the management of cancer, as noted in the instance of acute myeloid leukemia (AML). Mitochondrial function is considered important for the viability of AML blasts and appears to also modulate chemoresistance. As mitochondrial metabolism is aberrant in AML, any distinct pathways could be directly targeted to impact both cell viability and chemoresistance. Therefore, identifying and targeting those precise rogue elements of mitochondrial metabolism could be a valid therapeutic strategy in leukemia. Here, we review the evidence for abnormalities in mitochondria metabolic processes in AML cells, that likely impact chemoresistance. We further address several therapeutic approaches targeting isocitrate dehydrogenase 2 (IDH2), CD39, nicotinamide phosphoribosyl transferase (NAMPT), electron transport chain (ETC) complex in AML and also consider the roles of mesenchymal stromal cells. We propose the term "mitotherapy" to collectively refer to such regimens that attempt to override mitochondria-mediated metabolic reprogramming, as used by cancer cells. Mounting evidence suggests that mitotherapy could provide a complementary strategy to overcome chemoresistance in liquid cancers, as well as in solid tumors.

Defining the spatial distribution of extracellular adenosine revealed a myeloid-dependent immunosuppressive microenvironment in pancreatic ductal adenocarcinoma

BACKGROUND

The prognosis for patients with pancreatic ductal adenocarcinoma (PDAC) remains extremely poor. It has been suggested that the adenosine pathway contributes to the ability of PDAC to evade the immune system and hence, its resistance to immuno-oncology therapies (IOT), by generating extracellular adenosine (eAdo).

METHODS

Using genetically engineered allograft models of PDAC in syngeneic mice with defined and different immune infiltration and response to IOT and autochthonous tumors in KPC mice we investigated the impact of the adenosine pathway on the PDAC tumor microenvironment (TME). Flow cytometry and imaging mass cytometry (IMC) were used to characterize the subpopulation frequency and spatial distribution of tumor-infiltrating immune cells. Mass spectrometry imaging (MSI) was used to visualize adenosine compartmentalization in the PDAC tumors. RNA sequencing was used to evaluate the influence of the adenosine pathway on the shaping of the immune milieu and correlate our findings to published data sets in human PDAC.

RESULTS

We demonstrated high expression of adenosine pathway components in tumor-infiltrating immune cells (particularly myeloid populations) in the murine models. MSI demonstrated that extracellular adenosine distribution is heterogeneous in tumors, with high concentrations in peri-necrotic, hypoxic regions, associated with rich myeloid infiltration, demonstrated using IMC. Protumorigenic M2 macrophages express high levels of the Adora2a receptor; particularly in the IOT resistant model. Blocking the in vivo formation and function of eAdo (Adoi), using a combination of anti-CD73 antibody and an Adora2a inhibitor slowed tumor growth and reduced metastatic burden. Additionally, blocking the adenosine pathway improved the efficacy of combinations of cytotoxic agents or immunotherapy. Adoi remodeled the TME, by reducing the infiltration of M2 macrophages and regulatory T cells. RNA sequencing analysis showed that genes related to immune modulation, hypoxia and tumor stroma were downregulated following Adoi and a specific adenosine signature derived from this is associated with a poorer prognosis in patients with PDAC.

CONCLUSIONS

The formation of eAdo promotes the development of the immunosuppressive TME in PDAC, contributing to its resistance to conventional and novel therapies. Therefore, inhibition of the adenosine pathway may represent a strategy to modulate the PDAC immune milieu and improve therapy response in patients with PDAC.

Heterogeneity of the tumor immune microenvironment and clinical interventions

The tumor immune microenvironment (TIME) is broadly composed of various immune cells, and its heterogeneity is characterized by both immune cells and stromal cells. During the course of tumor formation and progression and anti-tumor treatment, the composition of the TIME becomes heterogeneous. Such immunological heterogeneity is not only present between populations but also exists on temporal and spatial scales. Owing to the existence of TIME, clinical outcomes can differ when a similar treatment strategy is provided to patients. Therefore, a comprehensive assessment of TIME heterogeneity is essential for developing precise and effective therapies. Facilitated by advanced technologies, it is possible to understand the complexity and diversity of the TIME and its influence on therapy responses. In this review, we discuss the potential reasons for TIME heterogeneity and the current approaches used to explore it. We also summarize clinical intervention strategies based on associated mechanisms or targets to control immunological heterogeneity.

Review immune response of targeting CD39 in cancer

The ATP-adenosine pathway has emerged as a promising target for cancer therapy, but challenges remain in achieving effective tumor control. Early research focused on blocking the adenosine generating enzyme CD73 and the adenosine receptors A2AR or A2BR in cancer. However, recent studies have shown that targeting CD39, the rate-limiting ecto-enzyme of the ATP-adenosine pathway, can provide more profound anti-tumor efficacy by reducing immune-suppressive adenosine accumulation and increasing pro-inflammatory ATP levels. In addition, combining CD39 blocking antibody with PD-1 immune checkpoint therapy may have synergistic anti-tumor effects and improve patient survival. This review will discuss the immune components that respond to CD39 targeting in the tumor microenvironment. Targeting CD39 in cancer has been shown to not only decrease adenosine levels in the tumor microenvironment (TME), but also increase ATP levels. Additionally, targeting CD39 can limit the function of Treg cells, which are known to express high levels of CD39. With phase I clinical trials of CD39 targeting currently underway, further understanding and rational design of this approach for cancer therapy are expected.

SRF617 Is a Potent Inhibitor of CD39 with Immunomodulatory and Antitumor Properties

CD39 (ENTPD1) is a key enzyme responsible for degradation of extracellular ATP and is upregulated in the tumor microenvironment (TME). Extracellular ATP accumulates in the TME from tissue damage and immunogenic cell death, potentially initiating proinflammatory responses that are reduced by the enzymatic activity of CD39. Degradation of ATP by CD39 and other ectonucleotidases (e.g., CD73) results in extracellular adenosine accumulation, constituting an important mechanism for tumor immune escape, angiogenesis induction, and metastasis. Thus, inhibiting CD39 enzymatic activity can inhibit tumor growth by converting a suppressive TME to a proinflammatory environment. SRF617 is an investigational, anti-CD39, fully human IgG4 Ab that binds to human CD39 with nanomolar affinity and potently inhibits its ATPase activity. In vitro functional assays using primary human immune cells demonstrate that inhibiting CD39 enhances T-cell proliferation, dendritic cell maturation/activation, and release of IL-1β and IL-18 from macrophages. In vivo, SRF617 has significant single-agent antitumor activity in human cell line-derived xenograft models that express CD39. Pharmacodynamic studies demonstrate that target engagement of CD39 by SRF617 in the TME inhibits ATPase activity, inducing proinflammatory mechanistic changes in tumor-infiltrating leukocytes. Syngeneic tumor studies using human CD39 knock-in mice show that SRF617 can modulate CD39 levels on immune cells in vivo and can penetrate the TME of an orthotopic tumor, leading to increased CD8+ T-cell infiltration. Targeting CD39 is an attractive approach for treating cancer, and, as such, the properties of SRF617 make it an excellent drug development candidate.

The Function of NK Cells in Tumor Metastasis and NK Cell-Based Immunotherapy

Metastatic tumors cause the most deaths in cancer patients. Treating metastasis remains the primary goal of current cancer research. Although the immune system prevents and kills the tumor cells, the function of the immune system in metastatic cancer has been unappreciated for decades because tumors are able to develop complex signaling pathways to suppress immune responses, leading them to escape detection and elimination. Studies showed NK cell-based therapies have many advantages and promise for fighting metastatic cancers. We here review the function of the immune system in tumor progression, specifically focusing on the ability of NK cells in antimetastasis, how metastatic tumors escape the NK cell attack, as well as the recent development of effective antimetastatic immunotherapies.

Comprehensive analysis of immunogenic cell death associated genes expression, tumor microenvironment, and prognosis in hepatocellular carcinoma

Background: Immunogenic cell death (ICD) plays an important role in the development of cancers. This study attempted to explore the role of ICD in the prognosis of hepatocellular carcinoma (HCC).

Methods: Gene expression and clinical data were downloaded from The Cancer Genome Alas and Gene Expression Omnibus dataset. The immune/stromal/Estimate scores of the tumor microenvironment (TME) were calculated by ESTIMATE and CIBERSORT algorithms. Kaplan-Meier analysis, functional enrichment analysis, least absolute shrinkage and selection operator (LASSO) analysis, and univariate and multivariate Cox regression analysis were used for prognostic gene screening and prognostic model construction. The correlation of immune cell infiltration and risk scores was analyzed as well. Molecular docking was used to explore the relevance of related genes to anti-cancer drugs.

Results: Ten ICD associated differentially expressed genes in HCC were found, and all of them had good predictive ability for HCC. ICD gene high amount of expression group was associated with poor prognosis (p = 0.015). The TME, immune cell infiltration and gene expression were different between ICD high and low groups (all p < 0.05). Six ICD associated genes (BAX, CASP8, IFNB1, LY96, NT5E and PIK3CA) which could predict the survival status were identified and used to construct the prognostic model for HCC. A risk score was calculated and it could be used as an independent prognostic factor in HCC patients (p < 0.001). In addition, the risk score had a positive correlation with macrophage M0 (r = 0.33, p = 0.0086). Molecular docking indicated that sorafenib could bind strongly to the target protein, representing that sorafenib may exert anticancer effects through these six ICD associated genes.

Conclusion: This study established a prognostic model including six ICD associated genes for HCC, which may deepen our understanding of ICD and guide therapy for HCC patients.

Tumor-infiltrating regulatory T cells as targets of cancer immunotherapy

Regulatory T cells (Tregs) are abundant in tumor tissues, raising a question of whether immunosuppressive tumor-infiltrating Tregs (TI-Tregs) can be selectively depleted or functionally attenuated to evoke effective anti-tumor immune responses by conventional T cells (Tconvs), without perturbing Treg-dependent immune homeostasis in healthy organs and causing autoimmunity. Here, we review current cancer immunotherapy strategies, including immune checkpoint blockade (ICB) antibodies against CTLA-4 and PD-1 and discuss their effects on TI-Tregs. We also discuss approaches that exploit differentially regulated molecules on the cell surface (e.g., CTLA-4) and intracellularly (e.g., T cell receptor signaling molecules) between TI-Tregs and Tconvs as well as their dependence on cytokines (e.g., IL-2) and metabolites (e.g., lactate). We envisage that targeting TI-Tregs could be effective as a monotherapy and/or when combined with ICB antibodies.

Targets of Immune Escape Mechanisms in Cancer: Basis for Development and Evolution of Cancer Immune Checkpoint Inhibitors

Immune checkpoint blockade (ICB) has emerged as a novel therapeutic tool for cancer therapy in the last decade. Unfortunately, a small number of patients benefit from approved immune checkpoint inhibitors (ICIs). Therefore, multiple studies are being conducted to find new ICIs and combination strategies to improve the current ICIs. In this review, we discuss some approved immune checkpoints, such as PD-L1, PD-1, and CTLA-4, and also highlight newer emerging ICIs. For instance, HLA-E, overexpressed by tumor cells, represents an immune-suppressive feature by binding CD94/NKG2A, on NK and T cells. NKG2A blockade recruits CD8+ T cells and activates NK cells to decrease the tumor burden. NKG2D acts as an NK cell activating receptor that can also be a potential ICI. The adenosine A2A and A2B receptors, CD47-SIRPα, TIM-3, LAG-3, TIGIT, and VISTA are targets that also contribute to cancer immunoresistance and have been considered for clinical trials. Their antitumor immunosuppressive functions can be used to develop blocking antibodies. PARPs, mARTs, and B7-H3 are also other potential targets for immunosuppression. Additionally, miRNA, mRNA, and CRISPR-Cas9-mediated immunotherapeutic approaches are being investigated with great interest. Pre-clinical and clinical studies project these targets as potential immunotherapeutic candidates in different cancer types for their robust antitumor modulation.

The exploitation of enzyme-based cancer immunotherapy

Cancer immunotherapy utilizes the immune system and its wide-ranging components to deliver anti-tumor responses. In immune escape mechanisms, tumor microenvironment-associated soluble factors and cell surface-bound molecules are mainly accountable for the dysfunctional activity of tumor-specific CD8⁺ T cells, natural killer (NK) cells, tumor associated macrophages (TAMs) and stromal cells. The myeloid-derived suppressor cells (MDSCs) and Foxp3⁺ regulatory T cells (Tregs), are also key tumor-promoting immune cells. These potent immunosuppressive networks avert tumor rejection at various stages, affecting immunotherapies' outcomes. Numerous clinical trials have elucidated that disruption of immunosuppression could be achieved via checkpoint inhibitors. Another approach utilizes enzymes that can restore the body's potential to counter cancer by triggering the immune system inhibited by the tumor microenvironment. These immunotherapeutic enzymes can catalyze an immunostimulatory signal and modulate the tumor microenvironment via effector molecules. Herein, we have discussed the immuno-metabolic roles of various enzymes like ATP-dephosphorylating ectoenzymes, inducible Nitric Oxide Synthase, phenylamine, tryptophan, and arginine catabolizing enzymes in cancer immunotherapy. Understanding the detailed molecular mechanisms of the enzymes involved in modulating the tumor microenvironment may help find new opportunities for cancer therapeutics.

The potential of regulatory T cell-based therapies for alopecia areata

Cytotoxic T lymphocyte has been a concern for the etiopathogenesis of alopecia areata (AA), some recent evidence suggests that the regulatory T (T_reg) cell deficiency is also a contributing factor. In the lesional scalp of AA, T_reg cells residing in the follicles are impaired, leading to dysregulated local immunity and hair follicle (HF) regeneration disorders. New strategies are emerging to modulate T_reg cells' number and function for autoimmune diseases. There is much interest to boost T_reg cells in AA patients to suppress the abnormal autoimmunity of HF and stimulate hair regeneration. With few satisfactory therapeutic regimens available for AA, T_reg cell-based therapies could be the way forward. Specifically, CAR-T_reg cells and novel formulations of low-dose IL-2 are the alternatives.

Secreted immune metabolites that mediate immune cell communication and function

Metabolites are emerging as essential factors for the immune system that are involved in both metabolic circuits and signaling cascades. Accumulated evidence suggests that altered metabolic programs initiated by the activation and maturation of immune cell types are accompanied by the delivery of various metabolites into the local environment. We propose that, in addition to protein/peptide ligands, secreted immune metabolites (SIMets) are essential components of immune communication networks that fine-tune immune responses under homeostatic and pathological conditions. We summarize recent advances in our understanding of SIMets and discuss the potential mechanisms by which some metabolites engage in immunological responses through receptor-, transporter-, and post-translational-mediated regulation. These insights may contribute to understanding physiology and developing effective therapeutics for inflammatory and immune-mediated diseases.

Metabolic modulation of immune checkpoints and novel therapeutic strategies in cancer

Cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4) or programmed death-1 (PD-1)/programmed death-ligand 1 (PD-L1)-based immune checkpoint inhibitors (ICIs) have led to significant improvements in the overall survival of patients with certain cancers and are expected to benefit patients by achieving complete, long-lasting remissions and cure. However, some patients who receive ICIs either fail treatment or eventually develop immunotherapy resistance. The existence of such patients necessitates a deeper understanding of cancer progression, specifically nutrient regulation in the tumor microenvironment (TME), which includes both metabolic cross-talk between metabolites and tumor cells, and intracellular metabolism in immune and cancer cells. Here we review the features and behaviors of the TME and discuss the recently identified major immune checkpoints. We comprehensively and systematically summarize the metabolic modulation of tumor immunity and immune checkpoints in the TME, including glycolysis, amino acid metabolism, lipid metabolism, and other metabolic pathways, and further discuss the potential metabolism-based therapeutic strategies tested in preclinical and clinical settings. These findings will help to determine the existence of a link or crosstalk between tumor metabolism and immunotherapy, which will provide an important insight into cancer treatment and cancer research.

NK cells and solid tumors: therapeutic potential and persisting obstacles

Natural killer (NK) cells, which are innate lymphocytes endowed with potent cytotoxic activity, have recently attracted attention as potential anticancer therapeutics. While NK cells mediate encouraging responses in patients with leukemia, the therapeutic effects of NK cell infusion in patients with solid tumors are limited. Preclinical and clinical data suggest that the efficacy of NK cell infusion against solid malignancies is hampered by several factors including inadequate tumor infiltration and persistence/activation in the tumor microenvironment (TME). A number of metabolic features of the TME including hypoxia as well as elevated levels of adenosine, reactive oxygen species, and prostaglandins negatively affect NK cell activity. Moreover, cancer-associated fibroblasts, tumor-associated macrophages, myeloid-derived suppressor cells, and regulatory T cells actively suppress NK cell-dependent anticancer immunity. Here, we review the metabolic and cellular barriers that inhibit NK cells in solid neoplasms as we discuss potential strategies to circumvent such obstacles towards superior therapeutic activity.

CD38+CD39+ NK cells associate with HIV disease progression and negatively regulate T cell proliferation

The ectonucleotidases CD38 and CD39 have a critical regulatory effect on tumors and viral infections via the adenosine axis. Natural killer (NK) cells produce cytokines, induce cytotoxic responses against viral infection, and acquire immunoregulatory properties. However, the roles of CD38 and CD39 expressed NK cells in HIV disease require elucidation. Our study showed that the proportions of CD38⁺CD39⁺ NK cells in HIV-infected individuals were positively associated with HIV viral loads and negatively associated with the CD4⁺ T cell count. Furthermore, CD38⁺CD39⁺ NK cells expressed additional inhibitory receptors, TIM-3 and LAG-3, and produced more TGF-β. Moreover, autologous NK cells suppressed the proliferation of CD8⁺ T and CD4⁺ T cells of HIV-infected individuals, and inhibiting CD38 and CD39 on NK cells restored CD8⁺ T and CD4⁺ T cell proliferation in vitro. In conclusion, these data support a critical role for CD38 and CD39 on NK cells in HIV infection and targeting CD38 and CD39 on NK cells may be a potential therapeutic strategy against HIV infection.

FOXP family DNA methylation correlates with immune infiltration and prognostic value in NSCLC

Background: Forkhead box P (FOXP) family was introduced as a double-edged sword in tumorigenesis and influenced immunotherapy response by modulating host immunity. This study aimed to summarize the involvement of the FOXP family in non-small cell lung cancer (NSCLC).

Methods: The UALCAN, Gene Expression Profiling Interactive Analysis (GEPIA), and Reverse transcription-quantitative polymerase chain reaction (RT‒qPCR) were used to analyse the expression levels of the FOXP family in NSCLC. The prognostic impact was evaluated using Kaplan-Meier Plotter. MethSurv, UALCAN, and cBioPortal were applied to analyse the DNA methylation and mutation status of the FOXP family respectively. COEXPEDIA, STRING, and GeneMANIA were used to explore the interaction mechanism. Finally, TISIDB was used to investigate all of the immune-related characteristics regulated by the FOXP family.

Results: The expression levels of FOXP1/3/4 were dysregulated in NSCLC tissues than that in normal tissues. Groups with low expression levels of FOXP1/4 and high expression levels of FOXP2/3 were associated with poor prognosis in NSCLC. The transcriptional levels of FOXP2/3/4 were correlated with DNA methylation in NSCLC. FOXP1/3/4 DNA methylation were correlated with prognosis. Pathway enrichment analysis indicated the FOXP family was mainly related to immune-related pathways. After DNA methylation, the correlations between FOXP family and immune factors were opposite to that before alteration in NSCLC.

Conclusion: This study elucidated FOXP family could serve as vital diagnostic and prognostic biomarkers in NSCLC. Our study highlighted novel potential functions of FOXP family DNA methylation in regulation of immune-related signatures in NSCLC.

Adenosinergic axis and immune checkpoint combination therapy in tumor: A new perspective for immunotherapy strategy

There are two figures and one table in this review, the review consists of 5823 words, without the description of figures and table, but including references.

Tumor cells escape anti-tumor immune responses in various ways, including functionally shaping the microenvironment through the secretion of various chemokines and, cytokines. Adenosine is a powerful immunosuppressive metabolite, that is frequently elevated in the extracellular tumor microenvironment (TME). Thus, it has recently been proposed as a novel antitumor immunoassay for targeting adenosine- generating enzymes, such as CD39, CD73, and adenosine receptors. In recent years, the discovery of the immune checkpoints, such as programmed cell death 1(PD-1) and cytotoxic T lymphocyte antigen 4 (CTLA-4), has also greatly changed treatment methods and ideas for malignant tumors. Malignant tumor immunotherapy has been developed from point-to-point therapy targeting immune checkpoints, combining different points of different pathways to create a therapy based on the macroscopic immune regulatory system network. This article reviews the theoretical basis of the adenosine energy axis and immune checkpoint combined therapy for malignant tumors and the latest advances in malignant tumors.

ENTPD1/CD39 as a predictive marker of treatment response to gemogenovatucel-T as maintenance therapy in newly diagnosed ovarian cancer

Background

Broadened use of predictive molecular and phenotypic profiling amongst oncologists has facilitated optimal integration of targeted- and immuno-therapeutics into clinical care. However, the use of predictive immunomarkers in ovarian cancer (OC) has not consistently translated into clinical benefit. Vigil (gemogenovatucel-T) is a novel plasmid engineered autologous tumor cell immunotherapy designed to knock down the tumor suppressor cytokines, TGFβ1 and TGFβ2, augment local immune function via increased GMCSF expression and enhance presentation of clonal neoantigen epitopes. Methods: All patients enrolled in the VITAL trial (NCT02346747) of maintenance Vigil vs. placebo as front-line therapy with homologous recombination proficient (HRP) stage IIIB-IV newly diagnosed ovarian cancer underwent NanoString gene expression analysis. Tissue was obtained from surgically resected ovarian tumor tissue following surgical debulking. A statistical algorithm was used to analyze the NanoString gene expression data.

Results

Using the NanoString Statistical Algorithm (NSA), we identify high expression of ENTPD1/CD39 (which functions as the rate-limiting step in the production of the immune suppressor adenosine from ATP to ADP) as a presumptive predictor of response to Vigil versus placebo regardless of HRP status on the basis of relapse free survival (median not achieved vs 8.1 months, p = 0.00007) and overall survival (median not achieved vs 41.4 months, p = 0.013) extension.

Conclusion

NSA should be considered for application to investigational targeted therapies in order to identify populations most likely to benefit from treatment, in preparation for efficacy conclusive trials.

Immunotherapy: Reshape the Tumor Immune Microenvironment

Tumor immune microenvironment (TIME) include tumor cells, immune cells, cytokines, etc. The interactions between these components, which are divided into anti-tumor and pro-tumor, determine the trend of anti-tumor immunity. Although the immune system can eliminate tumor through the cancer-immune cycle, tumors appear to eventually evade from immune surveillance by shaping an immunosuppressive microenvironment. Immunotherapy reshapes the TIME and restores the tumor killing ability of anti-tumor immune cells. Herein, we review the function of immune cells within the TIME and discuss the contribution of current mainstream immunotherapeutic approaches to remolding the TIME. Changes in the immune microenvironment in different forms under the intervention of immunotherapy can shed light on better combination treatment strategies.

Regulatory T-cell development in the tumor microenvironment

Regulatory T (Treg) cells are required for maintaining self-tolerance and preventing the development of autoimmune diseases. However, Treg cells are abundant in tumors and suppress antitumor immunity, contributing to tumor development and growth. Thus, the selective deletion of tumor-infiltrating Treg cells is important for successful Treg cell-targeted therapies, providing effective antitumor immunity without inducing deleterious autoimmune disorders. Advancements in sequencing technologies have exposed the diversity and heterogeneity of human Treg cells during activation and differentiation, further emphasizing the importance of understanding tumor-infiltrating Treg cells for the development of Treg cell-targeted therapies. This review provides an overview of the classification and function of Treg cells and summarizes recent knowledge on the activation and differentiation of Treg cells in the tumor microenvironment.

Alternative adenosine Receptor activation: The netrin-Adora2b link

During hypoxia or inflammation, extracellular adenosine levels are elevated. Studies using pharmacologic approaches or genetic animal models pertinent to extracellular adenosine signaling implicate this pathway in attenuating hypoxia-associated inflammation. There are four distinct adenosine receptors. Of these, it is not surprising that the Adora2b adenosine receptor functions as an endogenous feedback loop to control hypoxia-associated inflammation. First, Adora2b activation requires higher adenosine concentrations compared to other adenosine receptors, similar to those achieved during hypoxic inflammation. Second, Adora2b is transcriptionally induced during hypoxia or inflammation by hypoxia-inducible transcription factor HIF1A. Studies seeking an alternative adenosine receptor activation mechanism have linked netrin-1 with Adora2b. Netrin-1 was originally discovered as a neuronal guidance molecule but also functions as an immune-modulatory signaling molecule. Similar to Adora2b, netrin-1 is induced by HIF1A, and has been shown to enhance Adora2b signaling. Studies of acute respiratory distress syndrome (ARDS), intestinal inflammation, myocardial or hepatic ischemia and reperfusion implicate the netrin-Adora2b link in tissue protection. In this review, we will discuss the potential molecular linkage between netrin-1 and Adora2b, and explore studies demonstrating interactions between netrin-1 and Adora2b in attenuating tissue inflammation.

Colorectal Cancer-Infiltrating Regulatory T Cells: Functional Heterogeneity, Metabolic Adaptation, and Therapeutic Targeting

Colorectal cancer (CRC) is a heterogeneous disease with one of the highest rates of incidence and mortality among cancers worldwide. Understanding the CRC tumor microenvironment (TME) is essential to improve diagnosis and treatment. Within the CRC TME, tumor-infiltrating lymphocytes (TILs) consist of a heterogeneous mixture of adaptive immune cells composed of mainly anti-tumor effector T cells (CD4+ and CD8+ subpopulations), and suppressive regulatory CD4+ T (Treg) cells. The balance between these two populations is critical in anti-tumor immunity. In general, while tumor antigen-specific T cell responses are observed, tumor clearance frequently does not occur. Treg cells are considered to play an important role in tumor immune escape by hampering effective anti-tumor immune responses. Therefore, CRC-tumors with increased numbers of Treg cells have been associated with promoting tumor development, immunotherapy failure, and a poorer prognosis. Enrichment of Treg cells in CRC can have multiple causes including their differentiation, recruitment, and preferential transcriptional and metabolic adaptation to the TME. Targeting tumor-associated Treg cell may be an effective addition to current immunotherapy approaches. Strategies for depleting Treg cells, such as low-dose cyclophosphamide treatment, or targeting one or more checkpoint receptors such as CTLA-4 with PD-1 with monoclonal antibodies, have been explored. These have resulted in activation of anti-tumor immune responses in CRC-patients. Overall, it seems likely that CRC-associated Treg cells play an important role in determining the success of such therapeutic approaches. Here, we review our understanding of the role of Treg cells in CRC, the possible mechanisms that support their homeostasis in the tumor microenvironment, and current approaches for manipulating Treg cells function in cancer.

CD39 - A bright target for cancer immunotherapy

The ATP-adenosine pathway functions as a key modulator of innate and adaptive immunity within the tumor microenvironment, and cancer immune evasion largely involves the generation of high amounts of immunosuppressive extracellular adenosine (eADO). Consequently, inhibition of eADO-generating enzymes and/or eADO receptors can effectively restore the antitumor immunity of multiple immune cells. With several clinical strategies currently being explored to modulating the eADO pathway in patients with cancer, recent clinical data with antagonists targeting CD73 and A_2A receptor have demonstrated a promising therapeutic potential in cancer. Recent findings reveal that the ectonucleotidase CD39, the limiting enzyme been viewed as "immunological switch", converts ATP-driven pro-inflammatory milieu to an anti-inflammatory state mediated by adenosine. Owing to its superior feature of CD39 antagonism that rely not only on preventing the accumulation of adenosine but also on the stabilization of extracellular ATP to restore antitumor immunity, several inhibitors and clinical trials based on CD39 are being evaluated. Consequently, there is currently a focus on understanding the role of CD39 in governing immunity and how therapeutic strategies targeting this pathway alter the antitumor potential. We herein review the impact of CD39 on tumor microenvironment with a focus on treatment preference. Additionally, we also discuss the implication for rational combination therapies, molecular regulation, as well as potential limitations.

Glycoengineered anti-CD39 promotes anticancer responses by depleting suppressive cells and inhibiting angiogenesis in tumor models

Immunosuppressive cells accumulating in the tumor microenvironment constitute a formidable barrier that interferes with current immunotherapeutic approaches. A unifying feature of these tumor-associated immune and vascular endothelial cells appears to be the elevated expression of ectonucleotidase CD39, which in tandem with ecto-5'-nucleotidase CD73, catalyzes the conversion of extracellular ATP into adenosine. We glycoengineered an afucosylated anti-CD39 IgG2c and tested this reagent in mouse melanoma and colorectal tumor models. We identified major biological effects of this approach on cancer growth, associated with depletion of immunosuppressive cells, mediated through enhanced Fcγ receptor-directed (FcγR-directed), antibody-dependent cellular cytotoxicity (ADCC). Furthermore, regulatory/exhausted T cells lost CD39 expression, as a consequence of antibody-mediated trogocytosis. Most strikingly, tumor-associated macrophages and endothelial cells with high CD39 expression were effectively depleted following antibody treatment, thereby blocking angiogenesis. Tumor site-specific cellular modulation and lack of angiogenesis synergized with chemotherapy and anti-PD-L1 immunotherapy in experimental tumor models. We conclude that depleting suppressive cells and targeting tumor vasculature, through administration of afucosylated anti-CD39 antibody and the activation of ADCC, comprises an improved, purinergic system-modulating strategy for cancer therapy.

ATP and Adenosine Metabolism in Cancer: Exploitation for Therapeutic Gain

Adenosine is an evolutionary ancient metabolic regulator linking energy state to physiologic processes, including immunomodulation and cell proliferation. Tumors create an adenosine-rich immunosuppressive microenvironment through the increased release of ATP from dying and stressed cells and its ectoenzymatic conversion into adenosine. Therefore, the adenosine pathway becomes an important therapeutic target to improve the effectiveness of immune therapies. Prior research has focused largely on the two major ectonucleotidases, ectonucleoside triphosphate diphosphohydrolase 1/cluster of differentiation (CD)39 and ecto-5'-nucleotidase/CD73, which catalyze the breakdown of extracellular ATP into adenosine, and on the subsequent activation of different subtypes of adenosine receptors with mixed findings of antitumor and protumor effects. New findings, needed for more effective therapeutic approaches, require consideration of redundant pathways controlling intratumoral adenosine levels, including the alternative NAD-inactivating pathway through the CD38-ectonucleotide pyrophosphatase phosphodiesterase (ENPP)1-CD73 axis, the counteracting ATP-regenerating ectoenzymatic pathway, and cellular adenosine uptake and its phosphorylation by adenosine kinase. This review provides a holistic view of extracellular and intracellular adenosine metabolism as an integrated complex network and summarizes recent data on the underlying mechanisms through which adenosine and its precursors ATP and ADP control cancer immunosurveillance, tumor angiogenesis, lymphangiogenesis, cancer-associated thrombosis, blood flow, and tumor perfusion. Special attention is given to differences and commonalities in the purinome of different cancers, heterogeneity of the tumor microenvironment, subcellular compartmentalization of the adenosine system, and novel roles of purine-converting enzymes as targets for cancer therapy. SIGNIFICANCE STATEMENT: The discovery of the role of adenosine as immune checkpoint regulator in cancer has led to the development of novel therapeutic strategies targeting extracellular adenosine metabolism and signaling in multiple clinical trials and preclinical models. Here we identify major gaps in knowledge that need to be filled to improve the therapeutic gain from agents targeting key components of the adenosine metabolic network and, on this basis, provide a holistic view of the cancer purinome as a complex and integrated network.

Promising application of polyoxometalates in the treatment of cancer, infectious diseases and Alzheimer's disease

As shown in studies conducted in recent decades, polyoxometalates (POMs), as inorganic metal oxides, have promising biological activities, including antitumor, anti-infectious and anti-Alzheimer’s activities, due to their special structures and properties. However, some side effects impede their clinical applications to a certain extent. Compared with unmodified POMs, POM-based inorganic–organic hybrids and POM-based nanocomposite structures show significantly enhanced bioactivity and reduced side effects. In this review, we introduce the biological activities of POMs and their derivatives and highlight the side effects of POMs on normal cells and organisms and their possible mechanisms of action. We then propose a development direction for overcoming their side effects. POMs are expected to constitute a new generation of inorganic metal drugs for the treatment of cancer, infectious diseases, and Alzheimer's disease.

Graphical abstract

Adenosine-A2A Receptor Pathway in Cancer Immunotherapy

A2A receptors (A2AR), a typical GPCR with a high affinity for adenosine, was expressed in many immune cells, such as regulatory T cells, cytotoxic T cells, macrophages, etc. Adenosine binding to the A2AR receptor activates the typical G protein and triggers the cAMP/PKA/CREB pathway. The adenosine-A2AR pathway plays an important role in protecting normal organs and tissues from the autoimmune response of immune cells. However, many solid tumors hijack the adenosine-A2AR pathway by promoting adenosine accumulation. The activation of the A2AR pathway inhibited the immune response of immune cells and then promotes the immune escape of tumor cells in the tumor microenvironment. Recently, both animal experiments and clinical trials indicated that blocking the adenosine pathway can inhibit the progression of a variety of solid tumors. In addition, it is encouraging that A2AR blockade combined with CAR T cells therapy showed better anti-tumor efficacy. Therefore, this review will discuss the role of the adenosine-A2AR pathway in the tumor microenvironment and summarize recent advances of A2AR-cancer related studies.

Purinergic and Adenosinergic Signaling in Pancreatobiliary Diseases

Adenosine 5'-triphosphate (ATP), other nucleotides, and the nucleoside analogue, adenosine, all have the capacity to modulate cellular signaling pathways. The cellular processes linked to extracellular purinergic signaling are crucial in the initiation, evolution, and resolution of inflammation. Injured or dying cells in the pancreatobiliary tract secrete or release ATP, which results in sustained purinergic signaling mediated through ATP type-2 purinergic receptors (P2R). This process can result in chronic inflammation, fibrosis, and tumor development. In contrast, signaling via the extracellular nucleoside derivative adenosine via type-1 purinergic receptors (P1R) is largely anti-inflammatory, promoting healing. Failure to resolve inflammation, as in the context of primary sclerosing cholangitis or chronic pancreatitis, is a risk factor for parenchymal and end-organ scarring with the associated risk of pancreatobiliary malignancies. Emerging immunotherapeutic strategies suggest that targeting purinergic and adenosinergic signaling can impact the growth and invasive properties of cancer cells, potentiate anti-tumor immunity, and also block angiogenesis. In this review, we dissect out implications of disordered purinergic responses in scar formation, end-organ injury, and in tumor development. We conclude by addressing promising opportunities for modulation of purinergic/adenosinergic signaling in the prevention and treatment of pancreatobiliary diseases, inclusive of cancer.

New Developments in T Cell Immunometabolism and Implications for Cancer Immunotherapy

Despite rapid advances in the field of immunotherapy, the elimination of established tumors has not been achieved. Many promising new treatments such as adoptive cell therapy (ACT) fall short, primarily due to the loss of T cell effector function or the failure of long-term T cell persistence. With the availability of new tools and advancements in technology, our understanding of metabolic processes has increased enormously in the last decade. Redundancy in metabolic pathways and overlapping targets that could address the plasticity and heterogenous phenotypes of various T cell subsets have illuminated the need for understanding immunometabolism in the context of multiple disease states, including cancer immunology. Herein, we discuss the developing field of T cell immunometabolism and its crucial relevance to improving immunotherapeutic approaches. This in-depth review details the metabolic pathways and preferences of the antitumor immune system and the state of various metabolism-targeting therapeutic approaches.

Next steps for clinical translation of adenosine pathway inhibition in cancer immunotherapy

Increasing evidence supports targeting the adenosine pathway in immuno-oncology with several clinical programs directed at adenosine A2 receptor (A2AR, A2BR), CD73 and CD39 in development. Through a cyclic-AMP-mediated intracellular cascade, adenosine shifts the cytokine and cellular profile of the tumor microenvironment away from cytotoxic T cell inflammation toward one of immune tolerance. A perpetuating cycle of tumor cell proliferation, tissue injury, dysregulated angiogenesis, and hypoxia promote adenosine accumulation via ATP catabolism. Adenosine receptor (eg, A2AR, A2BR) stimulation of both the innate and adaptive cellular precursors lead to immunosuppressive phenotypic differentiation. Preclinical work in various tumor models with adenosine receptor inhibition has demonstrated restoration of immune cell function and tumor regression. Given the broad activity but known limitations of anti-programmed cell death protein (PD1) therapy and other checkpoint inhibitors, ongoing studies have sought to augment the successful outcomes of anti-PD1 therapy with combinatorial approaches, particularly adenosine signaling blockade. Preliminary data have demonstrated an optimal safety profile and enhanced overall response rates in several early phase clinical trials with A2AR and more recently CD73 inhibitors. However, beneficial outcomes for both monotherapy and combinations have been mostly lower than expected based on preclinical studies, indicating a need for more nuanced patient selection or biomarker integration that might predict and optimize patient outcomes. In the context of known immuno-oncology biomarkers such as tumor mutational burden and interferon-associated gene expression, a comparison of adenosine-related gene signatures associated with clinical response indicates an underlying biology related to immunosuppression, angiogenesis, and T cell inflammation. Importantly, though, adenosine associated gene expression may point to a unique intratumoral phenotype independent from IFN-γ related pathways. Here, we discuss the cellular and molecular mechanisms of adenosine-mediated immunosuppression, preclinical investigation of adenosine signaling blockade, recent response data from clinical trials with A2AR, CD73, CD39 and PD1/L1 inhibitors, and ongoing development of predictive gene signatures to enhance combinatorial immune-based therapies.

Cancer metabolism and tumor microenvironment: fostering each other?

The changes associated with malignancy are not only in cancer cells but also in environment in which cancer cells live. Metabolic reprogramming supports tumor cell high demand of biogenesis for their rapid proliferation, and helps tumor cell to survive under certain genetic or environmental stresses. Emerging evidence suggests that metabolic alteration is ultimately and tightly associated with genetic changes, in particular the dysregulation of key oncogenic and tumor suppressive signaling pathways. Cancer cells activate HIF signaling even in the presence of oxygen and in the absence of growth factor stimulation. This cancer metabolic phenotype, described firstly by German physiologist Otto Warburg, insures enhanced glycolytic metabolism for the biosynthesis of macromolecules. The conception of metabolite signaling, i.e., metabolites are regulators of cell signaling, provides novel insights into how reactive oxygen species (ROS) and other metabolites deregulation may regulate redox homeostasis, epigenetics, and proliferation of cancer cells. Moreover, the unveiling of noncanonical functions of metabolic enzymes, such as the moonlighting functions of phosphoglycerate kinase 1 (PGK1), reassures the importance of metabolism in cancer development. The metabolic, microRNAs, and ncRNAs alterations in cancer cells can be sorted and delivered either to intercellular matrix or to cancer adjacent cells to shape cancer microenvironment via media such as exosome. Among them, cancer microenvironmental cells are immune cells which exert profound effects on cancer cells. Understanding of all these processes is a prerequisite for the development of a more effective strategy to contain cancers.

Inflammation and Myeloid Cells in Cancer Progression and Metastasis

To date, the most immunotherapy drugs act upon T cell surface proteins to promote tumoricidal T cell activity. However, this approach has to date been unsuccessful in certain solid tumor types including pancreatic, prostate cancer and glioblastoma. Myeloid-related innate immunity can promote tumor progression through direct and indirect effects on T cell activity; improved understanding of this field may provide another therapeutic avenue for patients with these tumors. Myeloid cells can differentiate into both pro-inflammatory and anti-inflammatory mature form depending upon the microenvironment. Most cancer type exhibit oncogenic activating point mutations (ex. P53 and KRAS) that trigger cytokines production. In addition, tumor environment (ex. Collagen, Hypoxia, and adenosine) also regulated inflammatory signaling cascade. Both the intrinsic and extrinsic factor driving the tumor immune microenvironment and regulating the differentiation and function of myeloid cells, T cells activity and tumor progression. In this review, we will discuss the relationship between cancer cells and myeloid cells-mediated tumor immune microenvironment to promote cancer progression and immunotherapeutic resistance. Furthermore, we will describe how cytokines and chemokines produced by cancer cells influence myeloid cells within immunosuppressive environment. Finally, we will comment on the development of immunotherapeutic strategies with respect to myeloid-related innate immunity.

Overexpression of PD-1 and CD39 in tumor-infiltrating lymphocytes compared with peripheral blood lymphocytes in triple-negative breast cancer

BACKGROUND AND AIM

Growing evidence highlighted the primary role of the immune system in the disease course of triple-negative breast cancer (TNBC). The study aim was to investigate the expression of PD-1 and CD39 on CD4+ and CD8+ cells infiltrating tumor tissue compared to their counterparts in peripheral blood and explore its association with tumor characteristics, disease progression, and prognosis in females with TNBC.

PATIENTS AND METHODS

The study included 30 TNBC patients and 20 healthy controls. Cancer and normal breast tissue and peripheral blood samples were collected for evaluation of the expression of PD-1 and CD39 on CD4+ and CD8+T cells by flow cytometry.

RESULTS

A marked reduction in the percentage of CD8+ T lymphocytes and a significant increase in the frequencies of CD4+ T lymphocytes and CD4+ and CD8+ T lymphocytes expressing PD1 and CD39 were evident in tumor tissue in comparison with the normal breast tissue. The DFS was inversely related to the cancer tissue PD1+CD8+ and CD39+CD8+ T lymphocytes. Almost all studied cells were significantly increased in the tumor tissue than in peripheral blood. Positive correlations were detected among peripheral PD1+CD4+T lymphocytes and each of cancer tissue PD1+CD4+, PD1+CD8+and CD39+CD8+T cells, and among peripheral and cancer tissue CD39+CD4+and CD39+CD8+ T cells.

CONCLUSIONS

The CD39 and PD1 inhibitory pathways are synergistically utilized by TNBC cells to evade host immune response causing poor survival. Hence, combinational immunotherapy blocking these pathways might be a promising treatment strategy in this type of cancer.

What Happens to the Immune Microenvironment After PD-1 Inhibitor Therapy?

The fruitful results of tumor immunotherapy establish its indispensable status in the regulation of the tumorous immune context. It seems that the treatment of programmed cell death receptor 1 (PD-1) blockade is one of the most promising approaches for cancer control. The significant efficacy of PD-1 inhibitor therapy has been made in several cancer types, such as breast cancer, lung cancer, and multiple myeloma. Even so, the mechanisms of how anti-PD-1 therapy takes effect by impacting the immune microenvironment and how partial patients acquire the resistance to PD-1 blockade have yet to be studied. In this review, we discuss the cross talk between immune cells and how they promote PD-1 blockade efficacy. In addition, we also depict factors that may underlie tumor resistance to PD-1 blockade and feasible solutions in combination with it.