Co-inhibition of CD73 and A2AR Adenosine Signaling Improves Anti-tumor Immune Responses

The proliferation/migration ability mediated by CD151/PI3K/AKT pathway determines the therapeutic effect of hUC-MSCs transplantation on rheumatoid arthritis

OBJECTIVE

To elucidate the underlying mechanism by which the proliferation and migration abilities of human umbilical cord mesenchymal stem cells (hUC-MSCs) determine their therapeutic efficacy in rheumatoid arthritis treatment.

METHODS

The DBA/1J mice were utilized to establish a collagen-induced RA (CIA) mouse model and to validate the therapeutic efficacy of hUC-MSCs transfected with CD151 siRNA. RNA-seq, QT-PCR and western blotting were utilized to evaluate the mRNA and protein levels of the PI3K/AKT pathway, respectively.

RESULTS

IFN-γ significantly enhanced the proliferation and migration abilities of hUC-MSCs, up-regulating the expression of CD151, a gene related to cell proliferation and migration. Effective inhibition of this effect was achieved through CD151 siRNA treatment. However, IFN-γ did not affect hUC-MSCs differentiation or changes in cell surface markers. Additionally, transplantation of CD151-interfered hUC-MSCs (siRNA-CD151-hUC-MSCs) resulted in decreased colonization in the toes of CIA mice and worse therapeutic effects compared to empty vector treatment (siRNA-NC-hUC-MSCs).

CONCLUSION

IFN-γ facilitates the proliferation and migration of hUC-MSCs through the CD151/PI3K/AKT pathway. The therapeutic efficacy of siRNA-CD151-hUC-MSCs was found to be inferior to that of siRNA-NC-hUC-MSCs.

Caffeine reduces viability, induces apoptosis, inhibits migration and modulates the CD39/CD73 axis in metastatic cutaneous melanoma cells

We aimed to evaluate the effect of caffeine on viability, apoptosis, migration, redox profile and modulatory effect of the purinergic system of cutaneous melanoma cells. The melanoma cells SK-MEL-28 and non-tumoural CCD-1059sk cells were treated for 24 h with different concentrations of caffeine. Cell viability was evaluated by a biochemical assay and fluorescence microscopy, and flow cytometry assessed apoptosis induction. A wound-healing assay assessed cell migration. The redox profile was evaluated by the levels of markers of reactive oxygen species (ROS), nitric oxide (NOx), total thiols (PSH) and non-protein thiols (NPSH). RT-qPCR and flow cytometry assessed the expression of CD39 and CD73. ATPase/ADPase and AMPase enzyme activities were evaluated by hydrolysis of ATP, ADP and AMP nucleotides. A bioluminescent assay assessed extracellular ATP levels. Caffeine significantly reduced melanoma cell viability and migration and did not affect non-tumoural cells. Caffeine increased ROS levels and improved PSH levels in melanoma cells. Furthermore, caffeine reduced CD39 and CD73 expression, decreased ATP, ADP and AMP nucleotide hydrolysis and increased extracellular ATP levels. We have shown that caffeine reduces metastatic cutaneous melanoma cell viability and migration, induces ROS generation and improves PSH levels. In an unprecedented manner, we also showed that caffeine reduces the expression of CD39 and CD73 and, consequently, ATPase/ADPase/AMPase hydrolytic activity of ectonucleotidases, thus displacing the CD39/CD73 axis and increasing extracellular ATP levels. Therefore, caffeine may be an interesting compound for clinical trials with the CD39/CD73 axis as a therapeutic target.

Current Understanding of the Role of Adenosine Receptors in Cancer

Cancer, a complex array of diseases, involves the unbridled proliferation and dissemination of aberrant cells in the body, forming tumors that can infiltrate neighboring tissues and metastasize to distant sites. With over 200 types, each cancer has unique attributes, risks, and treatment avenues. Therapeutic options encompass surgery, chemotherapy, radiation therapy, hormone therapy, immunotherapy, targeted therapy, or a blend of these methods. Yet, these treatments face challenges like late-stage diagnoses, tumor diversity, severe side effects, drug resistance, targeted drug delivery hurdles, and cost barriers. Despite these hurdles, advancements in cancer research, encompassing biology, genetics, and treatment, have enhanced early detection methods, treatment options, and survival rates. Adenosine receptors (ARs), including A1, A2A, A2B, and A3 subtypes, exhibit diverse roles in cancer progression, sometimes promoting or inhibiting tumor growth depending on the receptor subtype, cancer type, and tumor microenvironment. Research on AR ligands has revealed promising anticancer effects in lab studies and animal models, hinting at their potential as cancer therapeutics. Understanding the intricate signaling pathways and interactions of adenosine receptors in cancer is pivotal for crafting targeted therapies that optimize benefits while mitigating drawbacks. This review delves into each adenosine receptor subtype's distinct roles and signaling pathways in cancer, shedding light on their potential as targets for improving cancer treatment outcomes.

Interference of ATP-Adenosine Axis by Engineered Biohybrid for Amplifying Immunogenic Cell Death-Mediated Antitumor Immunotherapy

Immunogenic cell death (ICD) often results in the production and accumulation of adenosine (ADO), a byproduct that negatively impacts the therapeutic effect as well as facilitates tumor development and metastasis. Here, an innovative strategy is elaborately developed to effectively activate ICD while avoiding the generation of immunosuppressive adenosine. Specifically, ZIF-90, an ATP-responsive consumer, is synthesized as the core carrier to encapsulate AB680 (CD73 inhibitor) and then coated with an iron-polyphenol layer to prepare the ICD inducer (AZTF), which is further grafted onto prebiotic bacteria via the esterification reaction to obtain the engineered biohybrid (Bc@AZTF). Particularly, the designed Bc@AZTF can actively enrich in tumor sites and respond to the acidic tumor microenvironment to offload AZTF nanoparticles, which can consume intracellular ATP (iATP) content and simultaneously inhibit the ATP-adenosine axis to reduce the accumulation of adenosine, thereby alleviating adenosine-mediated immunosuppression and strikingly amplifying ICD effect. Importantly, the synergy of anti-PD-1 (αPD-1) with Bc@AZTF not only establishes a collaborative antitumor immune network to potentiate effective tumoricidal immunity but also activates long-lasting immune memory effects to manage tumor recurrence and rechallenge, presenting a new paradigm for ICD treatment combined with adenosine metabolism.

Discovery of a potent, selective, and tumor-suppressing antibody antagonist of adenosine A2A receptor

New immune checkpoints are emerging in a bid to improve response rates to immunotherapeutic drugs. The adenosine A2A receptor (A2AR) has been proposed as a target for immunotherapeutic development due to its participation in immunosuppression of the tumor microenvironment. Blockade of A2AR could restore tumor immunity and, consequently, improve patient outcomes. Here, we describe the discovery of a potent, selective, and tumor-suppressing antibody antagonist of human A2AR (hA2AR) by phage display. We constructed and screened four single-chain variable fragment (scFv) libraries-two synthetic and two immunized-against hA2AR and antagonist-stabilized hA2AR. After biopanning and ELISA screening, scFv hits were reformatted to human IgG and triaged in a series of cellular binding and functional assays to identify a lead candidate. Lead candidate TB206-001 displayed nanomolar binding of hA2AR-overexpressing HEK293 cells; cross-reactivity with mouse and cynomolgus A2AR but not human A1, A2B, or A3 receptors; functional antagonism of hA2AR in hA2AR-overexpressing HEK293 cells and peripheral blood mononuclear cells (PBMCs); and tumor-suppressing activity in colon tumor-bearing HuCD34-NCG mice. Given its therapeutic properties, TB206-001 is a good candidate for incorporation into next-generation bispecific immunotherapeutics.

GRHL2 suppression of NT5E/CD73 in breast cancer cells modulates CD73-mediated adenosine production and T cell recruitment

Tumor tissues often contain high extracellular adenosine, promoting an immunosuppressed environment linked to mesenchymal transition and immune evasion. Here, we show that loss of the epithelial transcription factor, GRHL2, triggers NT5E/CD73 ecto-enzyme expression, augmenting the conversion of AMP to adenosine. GRHL2 binds an intronic NT5E sequence and is negatively correlated with NT5E/CD73 in breast cancer cell lines and patients. Remarkably, the increased adenosine levels triggered by GRHL2 depletion in MCF-7 breast cancer cells do not suppress but mildly increase CD8 T cell recruitment, a response mimicked by a stable adenosine analog but prevented by CD73 inhibition. Indeed, NT5E expression shows a positive rather than negative association with CD8 T cell infiltration in breast cancer patients. These findings reveal a GRHL2-regulated immune modulation mechanism in breast cancers and show that extracellular adenosine, besides its established role as a suppressor of T cell-mediated cytotoxicity, is associated with enhanced T cell recruitment.

Immune Cell Migration to Cancer

Immune cell migration is required for the development of an effective and robust immune response. This elegant process is regulated by both cellular and environmental factors, with variables such as immune cell state, anatomical location, and disease state that govern differences in migration patterns. In all cases, a major factor is the expression of cell surface receptors and their cognate ligands. Rapid adaptation to environmental conditions partly depends on intrinsic cellular immune factors that affect a cell's ability to adjust to new environment. In this review, we discuss both myeloid and lymphoid cells and outline key determinants that govern immune cell migration, including molecules required for immune cell adhesion, modes of migration, chemotaxis, and specific chemokine signaling. Furthermore, we summarize tumor-specific elements that contribute to immune cell trafficking to cancer, while also exploring microenvironment factors that can alter these cellular dynamics within the tumor in both a pro and antitumor fashion. Specifically, we highlight the importance of the secretome in these later aspects. This review considers a myriad of factors that impact immune cell trajectory in cancer. We aim to highlight the immunotherapeutic targets that can be harnessed to achieve controlled immune trafficking to and within tumors.

The inhibitory effect of adenosine on tumor adaptive immunity and intervention strategies

Adenosine (Ado) is significantly elevated in the tumor microenvironment (TME) compared to normal tissues. It binds to adenosine receptors (AdoRs), suppressing tumor antigen presentation and immune cell activation, thereby inhibiting tumor adaptive immunity. Ado downregulates major histocompatibility complex II (MHC II) and co-stimulatory factors on dendritic cells (DCs) and macrophages, inhibiting antigen presentation. It suppresses anti-tumor cytokine secretion and T cell activation by disrupting T cell receptor (TCR) binding and signal transduction. Ado also inhibits chemokine secretion and KCa3.1 channel activity, impeding effector T cell trafficking and infiltration into the tumor site. Furthermore, Ado diminishes T cell cytotoxicity against tumor cells by promoting immune-suppressive cytokine secretion, upregulating immune checkpoint proteins, and enhancing immune-suppressive cell activity. Reducing Ado production in the TME can significantly enhance anti-tumor immune responses and improve the efficacy of other immunotherapies. Preclinical and clinical development of inhibitors targeting Ado generation or AdoRs is underway. Therefore, this article will summarize and analyze the inhibitory effects and molecular mechanisms of Ado on tumor adaptive immunity, as well as provide an overview of the latest advancements in targeting Ado pathways in anti-tumor immune responses.

Evolving Tumor Characteristics and Smart Nanodrugs for Tumor Immunotherapy

Typical physiological characteristics of tumors, such as weak acidity, low oxygen content, and upregulation of certain enzymes in the tumor microenvironment (TME), provide survival advantages when exposed to targeted attacks by drugs and responsive nanomedicines. Consequently, cancer treatment has significantly progressed in recent years. However, the evolution and adaptation of tumor characteristics still pose many challenges for current treatment methods. Therefore, efficient and precise cancer treatments require an understanding of the heterogeneity degree of various factors in cancer cells during tumor evolution to exploit the typical TME characteristics and manage the mutation process. The highly heterogeneous tumor and infiltrating stromal cells, immune cells, and extracellular components collectively form a unique TME, which plays a crucial role in tumor malignancy, including proliferation, invasion, metastasis, and immune escape. Therefore, the development of new treatment methods that can adapt to the evolutionary characteristics of tumors has become an intense focus in current cancer treatment research. This paper explores the latest understanding of cancer evolution, focusing on how tumors use new antigens to shape their "new faces"; how immune system cells, such as cytotoxic T cells, regulatory T cells, macrophages, and natural killer cells, help tumors become "invisible", that is, immune escape; whether the diverse cancer-associated fibroblasts provide support and coordination for tumors; and whether it is possible to attack tumors in reverse. This paper discusses the limitations of targeted therapy driven by tumor evolution factors and explores future strategies and the potential of intelligent nanomedicines, including the systematic coordination of tumor evolution factors and adaptive methods, to meet this therapeutic challenge.

Clinical and Biologic Correlates of ADORA2A Transcriptomic Expression in Cancer

ADORA2A (adenosine A2a receptor) and ADORA2B propagate immunoregulatory signals, including restricting both innate and adaptive immunity, though recent data also suggest a tumor suppressor effect in certain settings. We evaluated the RNA expression from 514 tumors in a clinical-grade laboratory; 489 patients with advanced/metastatic disease had clinical outcome correlates. Transcript expression was standardized to internal housekeeping genes and ranked (0-100 scale) relative to 735 specimens from 35 different cancer types. Transcript abundance rank values were defined as "low/moderate" (0-74) or "high" (75-100) percentile RNA expression ranks. Overall, 20.8% of tumors had high ADORA2A (≥75 percentile RNA rank). The greatest proportion of high ADORA2A expressors was found in neuroendocrine and breast cancers and sarcomas, whereas the lowest was found in colorectal and ovarian cancers, albeit with patient-to-patient variability. In multivariable logistic regression analysis, there was a significant positive correlation between high ADORA2A RNA expression and a high expression of the immune checkpoint-related molecules PD-1 (p = 0.015), VISTA (p ≤ 0.001), CD38 (p = 0.031), and CD39 (p ≤ 0.001). In 217 immunotherapy-treated patients, high ADORA2A did not correlate significantly with progression-free (p = 0.51) or overall survival (OS) (p = 0.09) from the initiation of the checkpoint blockade. However, high versus not-high ADORA2A transcript expression correlated with longer OS from the time of advanced/metastatic disease (N = 489 patients; (HR 0.69 (95% CI 0.51-0.95) (p = 0.02)). Therefore, high ADORA2A transcript levels may be a favorable prognostic factor, unrelated to immunotherapy. Importantly, ascertaining co-expression patterns of ADORA2A with PD-1 and VISTA in individual tumors as a basis for the precision co-targeting of ADORA2A and these other checkpoint-related molecules warrants investigation in clinical trials.

Regulatory role of CD39 and CD73 in tumor immunity

CD39 is the rate-limiting enzyme for the molecular signal cascade leading to the generation of ADP and adenosine monophosphate (AMP). In conjunction with CD73, CD39 converts adenosine triphosphate (ATP) to ADP and AMP, which leads to the accumulation of immunosuppressive adenosine in the tumor microenvironment. This review focuses on the role of CD39 and CD73 in immune response and malignant progression, including the expression of CD39 within the tumor microenvironment and its relationship to immune effector cells, and its role in antigen presentation. The role of CD39- and CD73-targeting therapeutics and cancer-directed clinical trials investigating CD39 modulation are also explored.

Cancer cell metabolism and antitumour immunity

Accumulating evidence suggests that metabolic rewiring in malignant cells supports tumour progression not only by providing cancer cells with increased proliferative potential and an improved ability to adapt to adverse microenvironmental conditions but also by favouring the evasion of natural and therapy-driven antitumour immune responses. Here, we review cancer cell-intrinsic and cancer cell-extrinsic mechanisms through which alterations of metabolism in malignant cells interfere with innate and adaptive immune functions in support of accelerated disease progression. Further, we discuss the potential of targeting such alterations to enhance anticancer immunity for therapeutic purposes.

Targeting metabolism to improve CAR-T cells therapeutic efficacy

ABSTRACT

Chimeric antigen receptor T (CAR-T) cell therapy achieved advanced progress in the treatment of hematological tumors. However, the application of CAR-T cell therapy for solid tumors still faces many challenges. Competition with tumor cells for metabolic resources in an already nutrient-poor tumor microenvironment is a major contributing cause to CAR-T cell therapy's low effectiveness. Abnormal metabolic processes are now acknowledged to shape the tumor microenvironment, which is characterized by increased interstitial fluid pressure, low pH level, hypoxia, accumulation of immunosuppressive metabolites, and mitochondrial dysfunction. These factors are important contributors to restriction of T cell proliferation, cytokine release, and suppression of tumor cell-killing ability. This review provides an overview of how different metabolites regulate T cell activity, analyzes the current dilemmas, and proposes key strategies to reestablish the CAR-T cell therapy's effectiveness through targeting metabolism, with the aim of providing new strategies to surmount the obstacle in the way of solid tumor CAR-T cell treatment.

Cutaneous melanoma and purinergic modulation by phenolic compounds

Cutaneous melanoma is a complex pathology that still has only treatments that lack efficiency and offer many adverse effects. Due to this scenario emerges the need to analyze other possible treatments against this disease, such as the effect of phenolic compounds. These substances have proven antitumor effects, but still have not been fully explored as a form of therapy to combat melanoma. Also, the purinergic receptors, along with its system molecules, take part in the formation of tumors from many pathways, such as the actions of ectoenzymes and receptors activity, especially P2Rs family, and are formed by structures that can be modulated by the phenolic compounds. Therefore, more studies have to be made with the aim of explaining the purinergic system activity in carcinogenesis of cutaneous melanoma and the effects of its modulation by phenolic compound, in order to enable the development of new therapies to combat this aggressive and feared cancer.

Brain hypothyroidism silences the immune response of microglia in Alzheimer's disease animal model

Thyroid hormone (TH) imbalance is linked to the pathophysiology of reversible dementia and Alzheimer's disease (AD). It is unclear whether tissue hypothyroidism occurs in the AD brain and how it affects on AD pathology. We find that decreased iodothyronine deiodinase 2 is correlated with hippocampal hypothyroidism in early AD model mice before TH alterations in the blood. TH deficiency leads to spontaneous activation of microglia in wild-type mice under nonstimulated conditions, resulting in lowered innate immune responses of microglia in response to inflammatory stimuli or amyloid-β. In AD model mice, TH deficiency aggravates AD pathology by reducing the disease-associated microglia population and microglial phagocytosis. We find that TH deficiency reduces microglial ecto-5'-nucleotidase (CD73) and inhibition of CD73 leads to impaired innate immune responses in microglia. Our findings reveal that TH shapes microglial responses to inflammatory stimuli including amyloid-β, and brain hypothyroidism in early AD model mice aggravates AD pathology by microglial dysfunction.

A phase 2 study of AZD4635 in combination with durvalumab or oleclumab in patients with metastatic castration-resistant prostate cancer

BACKGROUND

Inhibition of the adenosine 2A receptor (A2AR) diminishes the immunosuppressive effects of adenosine and may complement immune-targeting drugs. This phase 2 study evaluated the A2AR antagonist AZD4635 in combination with durvalumab or oleclumab in patients with metastatic castration-resistant prostate cancer.

METHODS

Patients with histologically/cytologically confirmed disease progressing within 6 months on ≥ 2 therapy lines were randomly assigned to either Module 1 (AZD4635 + durvalumab) or Module 2 (AZD4635 + oleclumab). Primary endpoints were objective response rate per RECIST v1.1 and prostate-specific antigen (PSA) response rate. Secondary endpoints included radiological progression-free survival (rPFS), overall survival, safety, and pharmacokinetics.

RESULTS

Fifty-nine patients were treated (Module 1, n = 29; Module 2, n = 30). Median number of prior therapies was 4. One confirmed complete response by RECIST (Module 1) and 2 confirmed PSA responses (1 per module) were observed. The most frequent adverse events (AEs) possibly related to AZD4635 were nausea (37.9%), fatigue (20.7%), and decreased appetite (17.2%) in Module 1; nausea (50%), fatigue (30%), and vomiting (23.3%) in Module 2. No dose-limiting toxicities or treatment-related serious AEs were observed. In Module 1, AZD4635 geometric mean trough concentration was 124.9 ng/mL (geometric CV% 69.84; n = 22); exposures were similar in Module 2. In Modules 1 and 2, median (95% CI) rPFS was 2.3 (1.6 -3.8) and 1.5 (1.3- 4.0) months, respectively. Median PFS was 1.7 versus 2.3 months for patients with high versus low blood-based adenosine signature.

CONCLUSION

In this heavily pretreated population, AZD4635 with durvalumab or oleclumab demonstrated minimal antitumor activity with a manageable safety profile.

CLINICAL TRIAL

gov identifier: NCT04089553.

Adenosine-modulating synthetic high-density lipoprotein for chemoimmunotherapy of triple-negative breast cancer

Adenosine (ADO) is a common chemotherapy-associated immune checkpoint that hinders anti-tumor immunity-mediated efficacy of chemotherapy. Herein, we created a synthetic high-density lipoprotein (sHDL) by co-assembly of a doxorubicin (DOX)-apolipoprotein A1 mimetic peptide conjugate, PSB-603 (an A2BR inhibitor), phospholipid, and cholesterol oleate with a microfluidic-based method. The obtained DP-sHDL showed a self-promoted drug delivery to cancer cells via remodeling tumor microenvironment. DP-sHDL could trigger the release of ATP from cancer cells and inhibit its conversion into ADO. Consequently, DP-sHDL, while increasing immunogenic cell death, reduced intratumoral ADO levels by 58%. This treatment improved both the density and activity of CD8+ T cells as well as NK cells and relieved the immunosuppressive microenvironment, and led to a substantial inhibition of 4T1 tumor growth, thereby extending the survival of mice. The efficacy of DP-sHDL could be further improved when used in combination with immune checkpoint blockade therapy. We envision that this platform provides a simple yet promising strategy to enhance anti-tumor response of chemotherapy by relieving treatment-associated immunosuppression.

Metabolic engineering for optimized CAR-T cell therapy

The broad effectiveness of T cell-based therapy for treating solid tumour cancers remains limited. This is partly due to the growing appreciation that immune cells must inhabit and traverse a metabolically demanding tumour environment. Accordingly, recent efforts have centred on using genome-editing technologies to augment T cell-mediated cytotoxicity by manipulating specific metabolic genes. However, solid tumours exhibit numerous characteristics restricting immune cell-mediated cytotoxicity, implying a need for metabolic engineering at the pathway level rather than single gene targets. This emerging concept has yet to be put into clinical practice as many questions concerning the complex interplay between metabolic networks and T cell function remain unsolved. This Perspective will highlight key foundational studies that examine the relevant metabolic pathways required for effective T cell cytotoxicity and persistence in the human tumour microenvironment, feasible strategies for metabolic engineering to increase the efficiency of chimeric antigen receptor T cell-based approaches, and the challenges lying ahead for clinical implementation.

CD73 contributes to the pathogenesis of fusion-negative rhabdomyosarcoma through the purinergic signaling pathway

Rhabdomyosarcoma (RMS) is the most common type of soft tissue sarcoma in children and adolescents. Fusion-negative RMS (FN-RMS) accounts for more than 80% of all RMS cases. The long-term event-free survival rate for patients with high-grade FN-RMS is below 30%, highlighting the need for improved therapeutic strategies. CD73 is a 5' ectonucleotidase that hydrolyzes AMP to adenosine and regulates the purinergic signaling pathway. We found that CD73 is elevated in FN-RMS tumors that express high levels of TWIST2. While high expression of CD73 contributes to the pathogenesis of multiple cancers, its role in FN-RMS has not been investigated. We found that CD73 knockdown decreased FN-RMS cell growth while up-regulating the myogenic differentiation program. Moreover, mutation of the catalytic residues of CD73 rendered the protein enzymatically inactive and abolished its ability to stimulate FN-RMS growth. Overexpression of wildtype CD73, but not the catalytically inactive mutant, in CD73 knockdown FN-RMS cells restored their growth capacity. Likewise, treatment with an adenosine receptor A2A-B agonist partially rescued FN-RMS cell proliferation and bypassed the CD73 knockdown defective growth phenotype. These results demonstrate that the catalytic activity of CD73 contributes to the pathogenic growth of FN-RMS through the activation of the purinergic signaling pathway. Therefore, targeting CD73 and the purinergic signaling pathway represents a potential therapeutic approach for FN-RMS patients.

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.

Breakthroughs in Cancer Immunotherapy: An Overview of T Cell, NK Cell, Mφ, and DC-Based Treatments

Efforts to treat cancer using chimeric antigen receptor (CAR)-T therapy have made astonishing progress and clinical trials against hematopoietic malignancies have demonstrated their use. However, there are still disadvantages which need to be addressed: high costs, and side effects such as Graft-versus-Host Disease (GvHD) and Cytokine Release Syndrome (CRS). Therefore, recent efforts have been made to harness the properties of certain immune cells to treat cancer-not just T cells, but also natural killer (NK) cells, macrophages (Mφ), dendritic cells (DC), etc. In this paper, we will introduce immune cell-based cellular therapies that use various immune cells and describe their characteristics and their clinical situation. The development of immune cell-based cancer therapy fully utilizing the unique advantages of each and every immune cell is expected to enhance the survival of tumor patients owing to their high efficiency and fewer side effects.

SIKs Regulate HDAC7 Stabilization and Cytokine Recall in Late-Stage T Cell Effector Differentiation

Understanding the mechanisms underlying the acquisition and maintenance of effector function during T cell differentiation is important to unraveling how these processes can be dysregulated in the context of disease and manipulated for therapeutic intervention. In this study, we report the identification of a previously unappreciated regulator of murine T cell differentiation through the evaluation of a previously unreported activity of the kinase inhibitor, BioE-1197. Specifically, we demonstrate that liver kinase B1 (LKB1)-mediated activation of salt-inducible kinases epigenetically regulates cytokine recall potential in effector CD8+ and Th1 cells. Evaluation of this phenotype revealed that salt-inducible kinase-mediated phosphorylation-dependent stabilization of histone deacetylase 7 (HDAC7) occurred during late-stage effector differentiation. HDAC7 stabilization increased nuclear HDAC7 levels, which correlated with total and cytokine loci-specific reductions in the activating transcription mark histone 3 lysine 27 acetylation (H3K27Ac). Accordingly, HDAC7 stabilization diminished transcriptional induction of cytokine genes upon restimulation. Inhibition of this pathway during differentiation produced effector T cells epigenetically poised for enhanced cytokine recall. This work identifies a previously unrecognized target for enhancing effector T cell functionality.

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.

Chimeric antigen receptor natural killer cells: a promising antitumor immunotherapy

Chimeric antigen receptor (CAR) T cells have been successfully used in adoptive cell therapy for malignancies. However, some obstacles, including side effects such as graft-versus-host disease and cytokine release syndrome, therapy resistance, limited sources, as well as high cost, limited the application of CAR T cells. Recently, CAR natural killer (NK) cells have been pursued as the effector cells for adoptive immunotherapy for their attractive merits of strong intrinsic antitumor activity and relatively mild side effects. Additionally, CAR NK cells can be available from various sources and do not require strict human leukocyte antigen matching, which suggests them as promising "off-the-shelf" products for clinical application. Although the use of CAR NK cells is restrained by the limited proliferation and impaired efficiency within the immunosuppressive tumor microenvironment, further investigation in optimizing CAR structure and combination therapies will overcome these challenges. This review will summarize the advancement of CAR NK cells, CAR NK cell manufacture, the clinical outcomes of CAR NK therapy, the challenges in the field, and prospective solutions. Besides, we will discuss the emerging application of other immune cells for CAR engineering. Collectively, this comprehensive review will provide a valuable and informative summary of current progress and evaluate challenges and future opportunities of CAR NK cells in tumor treatment.

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.

CD73 controls Myosin II-driven invasion, metastasis, and immunosuppression in amoeboid pancreatic cancer cells

Pancreatic ductal adenocarcinoma (PDAC) has a very poor prognosis because of its high propensity to metastasize and its immunosuppressive microenvironment. Using a panel of pancreatic cancer cell lines, three-dimensional (3D) invasion systems, microarray gene signatures, microfluidic devices, mouse models, and intravital imaging, we demonstrate that ROCK-Myosin II activity in PDAC cells supports a transcriptional program conferring amoeboid invasive and immunosuppressive traits and in vivo metastatic abilities. Moreover, we find that immune checkpoint CD73 is highly expressed in amoeboid PDAC cells and drives their invasive, metastatic, and immunomodulatory traits. Mechanistically, CD73 activates RhoA-ROCK-Myosin II downstream of PI3K. Tissue microarrays of human PDAC biopsies combined with bioinformatic analysis reveal that rounded-amoeboid invasive cells with high CD73-ROCK-Myosin II activity and their immunosuppressive microenvironment confer poor prognosis to patients. We propose targeting amoeboid PDAC cells as a therapeutic strategy.

Integrated single-cell and bulk RNA sequencing in pancreatic cancer identifies disulfidptosis-associated molecular subtypes and prognostic signature

Pancreatic cancer (PC) is known for its high degree of heterogeneity and exceptionally adverse outcome. While disulfidptosis is the most recently identified form of cell death, the predictive and therapeutic value of disulfidptosis-related genes (DRGs) for PC remains unknown. RNA sequencing data with the follow-up information, were retrieved from the TCGA and ICGC databases. Consensus clustering analysis was conducted on patient data using R software. Subsequently, the LASSO regression analysis was conducted to create a prognostic signature for foreseeing the outcome of PC. Differences in relevant pathways, mutational landscape, and tumor immune microenvironment were compared between PC samples with different risk levels. Finally, we experimentally confirmed the impact of DSG3 on the invasion and migration abilities of PC cells. All twenty DRGs were found to be hyperexpressed in PC tissues, and fourteen of them significantly associated with PC survival. Using consensus clustering analysis based on these DRGs, four DRclusters were identified. Additionally, altogether 223 differential genes were evaluated between clusters, indicating potential biological differences between them. Four gene clusters (geneClusters) were recognized according to these genes, and a 10-gene prognostic signature was created. High-risk patients were found to be primarily enriched in signaling pathways related to the cell cycle and p53. Furthermore, the rate of mutations was markedly higher in high-risk patients, besides important variations were present in terms of immune microenvironment and chemotherapy sensitivity among patients with different risk levels. DSG3 could appreciably enhance the invasion and migration of PC cells. This work, based on disulfidoptosis-related genes (DRGs), holds the promise of classifying PC patients and predicting their prognosis, mutational landscape, immune microenvironment, and drug therapy. These insights could boost an improvement in a better comprehension of the role of DRGs in PC as well as provide new opportunities for prognostic prediction and more effective treatment strategies.

Inhibitory effect of adenosine on adaptive antitumor immunity and intervention strategies

Tumors in which the microenvironment is characterized by lack of immune cell infiltration are referred as "cold tumors" and typically exhibit low responsiveness to immune therapy. Targeting the factors contributing to "cold tumors" formation and converting them into "hot tumors" is a novel strategy for improving the efficacy of immunotherapy. Adenosine, a hydrolysis product of ATP, accumulates with a significantly higher concentration in the tumor microenvironments compared with normal tissue and exerts inhibitory effects on tumor-specific adaptive immunity. Tumor cells, dendritic cells, macrophages, and T cells express abundant adenosine receptors on their surfaces. The binding of adenosine to these receptors initiates downstream signaling pathways that suppress tumor antigen presentation and immune cell activation, consequently dampening adaptive immune responses against tumors. Adenosine down-regulates the expression of major histocompatibility complex Ⅱ and co-stimulatory factors on dendritic cells and macrophages, thereby inhibiting antigen presentation to T cells. Adenosine also inhibits ligand-receptor binding and transmembrane signaling on T cells, concomitantly suppressing the secretion of anti-tumor cytokines and impairing T cell activation. Furthermore, adenosine hinders effector T cell trafficking to tumor sites and infiltration by inhibiting chemokine secretion and KCa3.1 channels. Additionally, adenosine promotes the secretion of immunosuppressive cytokines, increases immune checkpoint protein expression, and enhances the activity of immunosuppressive cells, collectively curbing cytotoxic T cell-mediated tumor cell killing. Given the immunosuppressive role of adenosine in adaptive antitumor immunity, several inhibitors targeting adenosine generation or adenosine receptor blockade are currently in preclinical or clinical development with the aim of enhancing the effectiveness of immunotherapies. This review provides an overview of the inhibitory effects of adenosine on adaptive antitumor immunity, elucidate the molecular mechanisms involved, and summarizes the latest advances in application of adenosine inhibition strategies for antitumor immunotherapy.

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.

The immune checkpoint adenosine 2A receptor is associated with aggressive clinical outcomes and reflects an immunosuppressive tumor microenvironment in human breast cancer

Background

The crosstalk between the immune system and cancer cells has aroused considerable interest over the past decades. To escape immune surveillance cancer cells evolve various strategies orchestrating tumor microenvironment. The discovery of the inhibitory immune checkpoints was a major breakthrough due to their crucial contribution to immune evasion. The A2AR receptor represents one of the most essential pathways within the TME. It is involved in several processes such as hypoxia, tumor progression, and chemoresistance. However, its clinical and immunological significance in human breast cancer remains elusive.

Methods

The mRNA expression and protein analysis were performed by RT-qPCR and immunohistochemistry. The log-rank (Mantel-Cox) test was used to estimate Kaplan-Meier analysis for overall survival. Using large-scale microarray data (METABRIC), digital cytometry was conducted to estimate cell abundance. Analysis was performed using RStudio software (7.8 + 2023.03.0) with EPIC, CIBERSORT, and ImmuneCellAI algorithms. Tumor purity, stromal and immune scores were calculated using the ESTIMATE computational method. Finally, analysis of gene set enrichment (GSEA) and the TISCH2 scRNA-seq database were carried out.

Results

Gene and protein analysis showed that A2AR was overexpressed in breast tumors and was significantly associated with high grade, elevated Ki-67, aggressive molecular and histological subtypes, as well as poor survival. On tumor infiltrating immune cells, A2AR was found to correlate positively with PD-1 and negatively with CTLA-4. On the other hand, our findings disclosed more profuse infiltration of protumoral cells such as M0 and M2 macrophages, Tregs, endothelial and exhausted CD8+ T cells within A2ARhigh tumors. According to the Single-Cell database, A2AR is expressed in malignant, stromal and immune cells. Moreover, it is related to tumor purity, stromal and immune scores. Our results also revealed that CD8+T cells from A2ARhigh patients exhibited an exhausted functional profile. Finally, GSEA analysis highlighted the association of A2AR with biological mechanisms involved in tumor escape and progression.

Conclusion

The present study is the first to elucidate the clinical and immunological relevance of A2AR in breast cancer patients. In light of these findings, A2AR could be deemed a promising therapeutic target to overcome immune evasion prevailing within the TME of breast cancer patients.

Rational engineering of an improved adenosine deaminase 2 enzyme for weaponizing T-cell therapies

Adenosine is a potent immunosuppressive metabolite that accumulates in the extracellular space within solid tumors and inhibits the antitumor function of native immune cell responses as well as chimeric antigen receptor (CAR) T-cell therapies. Here, we show that engineered human cells can degrade extracellular adenosine through secretion of adenosine deaminase (ADA) enzymes-a possible therapeutic enhancement for CAR T cells. We first determine that the high-activity ADA1 isoform is naturally intracellularly restricted and show that the addition of canonical or computationally predicted secretory peptides did not allow for improved secretion. We did, however, determine that the lower-activity ADA2 isoform is naturally secreted. Thus, we utilized phylogenetic-based structural comparisons to guide a mutational survey of ADA2 active site residues, which when coupled with a high-throughput screen for enhanced ADA2-mediated extracellular adenosine rate allowed isolation of the most catalytically efficient ADA2 variant reported to date. When expressed by human cells, this variant exhibits 30× higher extracellular adenosine degradation activity than the wild-type enzyme. Finally, we demonstrate that Jurkat and CAR T cells engineered to express this secreted, high-activity ADA2 variant can degrade significant amounts of extracellular adenosine in vitro.

Autotaxin suppresses cytotoxic T cells via LPAR5 to promote anti-PD-1 resistance in non-small cell lung cancer

Non-small cell lung cancers that harbor concurrent KRAS and TP53 (KP) mutations are immunologically warm tumors with partial responsiveness to anti-PD-(L)1 blockade; however, most patients observe little or no durable clinical benefit. To identify novel tumor-driven resistance mechanisms, we developed a panel of KP murine lung cancer models with intrinsic resistance to anti-PD-1 and queried differential gene expression between these tumors and anti-PD-1-sensitive tumors. We found that the enzyme autotaxin (ATX), and the metabolite it produces, lysophosphatidic acid (LPA), were significantly upregulated in resistant tumors and that ATX directly modulated antitumor immunity, with its expression negatively correlating with total and effector tumor-infiltrating CD8+ T cells. Pharmacological inhibition of ATX, or the downstream receptor LPAR5, in combination with anti-PD-1 was sufficient to restore the antitumor immune response and efficaciously control lung tumor growth in multiple KP tumor models. Additionally, ATX was significantly correlated with inflammatory gene signatures, including a CD8+ cytolytic score in multiple lung adenocarcinoma patient data sets, suggesting that an activated tumor-immune microenvironment upregulates ATX and thus provides an opportunity for cotargeting to prevent acquired resistance to anti-PD-1 treatment. These data reveal the ATX/LPA axis as an immunosuppressive pathway that diminishes the immune checkpoint blockade response in lung cancer.

Chimeric antigen receptor engineered natural killer cells for cancer therapy

Natural killer (NK) cells, a unique component of the innate immune system, are inherent killers of stressed and transformed cells. Based on their potent capacity to kill cancer cells and good tolerance of healthy cells, NK cells have been successfully employed in adoptive cell therapy to treat cancer patients. In recent years, the clinical success of chimeric antigen receptor (CAR)-T cells has proven the vast potential of gene-manipulated immune cells as the main force to fight cancer. Following the lessons learned from mature gene-transfer technologies and advanced strategies in CAR-T therapy, NK cells have been rapidly explored as a promising candidate for CAR-based therapy. An exponentially growing number of studies have employed multiple sources of CAR-NK cells to target a wide range of cancer-related antigens, showing remarkable outcomes and encouraging safety profiles. Clinical trials of CAR-NK cells have also shown their impressive therapeutic efficacy in the treatment of hematological tumors, but CAR-NK cell therapy for solid tumors is still in the initial stages. In this review, we present the favorable profile of NK cells as a potential platform for CAR-based engineering and then summarize the outcomes and strategies of CAR-NK therapies in up-to-date preclinical and clinical investigations. Finally, we evaluate the challenges remaining in CAR-NK therapy and describe existing strategies that can assist us in devising future prospective solutions.

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.

The Clinical Significance of CD73 in Cancer

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

Dual mechanisms of cholesterol-GPCR interactions that depend on membrane phospholipid composition

Cholesterol is a critical component of mammalian cell membranes and an allosteric modulator of G protein-coupled receptors (GPCRs), but divergent views exist on the mechanisms by which cholesterol influences receptor functions. Leveraging the benefits of lipid nanodiscs, i.e., quantitative control of lipid composition, we observe distinct impacts of cholesterol in the presence and absence of anionic phospholipids on the function-related conformational dynamics of the human A2A adenosine receptor (A2AAR). Direct receptor-cholesterol interactions drive activation of agonist-bound A2AAR in membranes containing zwitterionic phospholipids. Intriguingly, the presence of anionic lipids attenuates cholesterol's impact through direct interactions with the receptor, highlighting a more complex role for cholesterol that depends on membrane phospholipid composition. Targeted amino acid replacements at two frequently predicted cholesterol interaction sites showed distinct impacts of cholesterol at different receptor locations, demonstrating the ability to delineate different roles of cholesterol in modulating receptor signaling and maintaining receptor structural integrity.

Enhancing immunotherapy response in melanoma: myeloid-derived suppressor cells as a therapeutic target

Despite the remarkable success of immune checkpoint inhibitors (ICIs) in melanoma treatment, resistance to them remains a substantial clinical challenge. Myeloid-derived suppressor cells (MDSCs) represent a heterogeneous population of myeloid cells that can suppress antitumor immune responses mediated by T and natural killer cells and promote tumor growth. They are major contributors to ICI resistance and play a crucial role in creating an immunosuppressive tumor microenvironment. Therefore, targeting MDSCs is considered a promising strategy to improve the therapeutic efficacy of ICIs. This Review describes the mechanism of MDSC-mediated immune suppression, preclinical and clinical studies on MDSC targeting, and potential strategies for inhibiting MDSC functions to improve melanoma immunotherapy.

Inhibitors of the CD73-adenosinergic checkpoint as promising combinatory agents for conventional and advanced cancer immunotherapy

The cell surface enzyme CD73 is increasingly appreciated as a pivotal non-redundant immune checkpoint (IC) in addition to PD-1/PD-L1 and CTLA-4. CD73 produces extracellular adenosine (eADO), which not only inhibits antitumor T cell activity via the adenosine receptor (AR) A_2AR, but also enhances the immune inhibitory function of cancer-associated fibroblasts and myeloid cells via A_2BR. Preclinical studies show that inhibition of the CD73-adenosinergic pathway in experimental models of many solid tumors either as a monotherapy or, more effectively, in combination with PD-1/PD-L1 or CTLA-4 IC blockades, improves antitumor immunity and tumor control. Consequently, approximately 50 ongoing phase I/II clinical trials targeting the CD73-adenosinergic IC are currently listed on https://clinicaltrials.gov. Most of the listed trials employ CD73 inhibitors or anti-CD73 antibodies alone, in combination with A_2AR antagonists, and/or with PD-1/PD-L1 blockade. Recent evidence suggests that the distribution of CD73, A_2AR and A_2BR in tumor microenvironments (TME) is heterogeneous, and this distribution affects CD73-adenosinergic IC function. The new insights have implications for the optimally effective, carefully tailored approaches to therapeutic targeting of this essential IC. In the mini-review, we briefly discuss the cellular and molecular mechanisms of CD73/eADO-mediated immunosuppression during tumor progression and therapy in the spatial context of the TME. We include preclinical data regarding therapeutic CD73-eADO blockade in tumor models as well as available clinical data from completed trials that targeted CD73-adenosinergic IC with or without PD-1/PD-L1 inhibitors and discuss factors that are potentially important for optimal therapeutic outcomes in cancer patients.

ENPP1 Immunobiology as a Therapeutic Target

ENPP1 (ecto-nucleotide pyrophosphatase/phosphodiesterase) participates in the hydrolysis of different purine nucleotides in an array of physiologic processes. However, ENPP1 is frequently overexpressed in local relapses and tumor metastases, which are associated with poor prognosis and survival in a range of solid tumors. ENPP1 promotes an immunosuppressive tumor microenvironment (TME) by tilting the balance of ATP/adenosine (Ado) in conjunction with other components (CD38, CD39/ENTPD1, and CD73/NT5E). Moreover, ENPP1 intersects with the stimulator of interferon genes (STING), impairing its robust immune response through the hydrolysis of the effector 2´,3´-cyclic GMP-AMP. Thus, ENPP1 blockade emerges as a unique target eliciting immune remodeling and leveraging the STING pathway. Several ENPP1 inhibitors have shown an immunostimulatory effect, and their combination with other therapeutic modalities, such as immune-checkpoint blockade, STING activation, DNA damage response (DDR) inhibitors, and radiotherapy (RT), represents a promising avenue to boost antitumor-immune responses and to improve current clinical outcomes in several tumors. This comprehensive review summarizes the current state of the art and opens new perspectives for novel treatment strategies.

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.

Advances in CD73 inhibitors for immunotherapy: Antibodies, synthetic small molecule compounds, and natural compounds

Tumors, a disease with a high mortality rate worldwide, have become a serious threat to human health. Exonucleotide-5'-nucleotidase (CD73) is an emerging target for tumor therapy. Its inhibition can significantly reduce adenosine levels in the tumor microenvironment. It has a better therapeutic effect on adenosine-induced immunosuppression. In the immune response, extracellular ATP exerts immune efficacy by activating T cells. However, dead tumor cells release excess ATP, overexpress CD39 and CD73 on the cell membrane and catabolize this ATP to adenosine. This leads to further immunosuppression. There are a number of inhibitors of CD73 currently under investigation. These include antibodies, synthetic small molecule inhibitors and a number of natural compounds with prominent roles in the anti-tumor field. However, only a small proportion of the CD73 inhibitors studied to date have successfully reached the clinical stage. Therefore, effective and safe inhibition of CD73 in oncology therapy still holds great therapeutic potential. This review summarizes the currently reported CD73 inhibitors, describes their inhibitory effects and pharmacological mechanisms, and provides a brief review of them. It aims to provide more information for further research and development of CD73 inhibitors.

Metabolic codependencies in the tumor microenvironment and gastric cancer: Difficulties and opportunities

Oncogenesis and the development of tumors affect metabolism throughout the body. Metabolic reprogramming (also known as metabolic remodeling) is a feature of malignant tumors that is driven by oncogenic changes in the cancer cells themselves as well as by cytokines in the tumor microenvironment. These include endothelial cells, matrix fibroblasts, immune cells, and malignant tumor cells. The heterogeneity of mutant clones is affected by the actions of other cells in the tumor and by metabolites and cytokines in the microenvironment. Metabolism can also influence immune cell phenotype and function. Metabolic reprogramming of cancer cells is the result of a convergence of both internal and external signals. The basal metabolic state is maintained by internal signaling, while external signaling fine-tunes the metabolic process based on metabolite availability and cellular needs. This paper reviews the metabolic characteristics of gastric cancer, focusing on the intrinsic and extrinsic mechanisms that drive cancer metabolism in the tumor microenvironment, and interactions between tumor cell metabolic changes and microenvironment metabolic changes. This information will be helpful for the individualized metabolic treatment of gastric cancers.

Targeting Immunosuppressive Adenosine Signaling: A Review of Potential Immunotherapy Combination Strategies

The tumor microenvironment regulates many aspects of cancer progression and anti-tumor immunity. Cancer cells employ a variety of immunosuppressive mechanisms to dampen immune cell function in the tumor microenvironment. While immunotherapies that target these mechanisms, such as immune checkpoint blockade, have had notable clinical success, resistance is common, and there is an urgent need to identify additional targets. Extracellular adenosine, a metabolite of ATP, is found at high levels in the tumor microenvironment and has potent immunosuppressive properties. Targeting members of the adenosine signaling pathway represents a promising immunotherapeutic modality that can potentially synergize with conventional anti-cancer treatment strategies. In this review, we discuss the role of adenosine in cancer, present preclinical and clinical data on the efficacy adenosine pathway inhibition, and discuss possible combinatorial approaches.

The resurgence of the Adora2b receptor as an immunotherapeutic target in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is characterized by a dense desmoplastic stroma that impedes drug delivery, reduces parenchymal blood flow, and suppresses the anti-tumor immune response. The extracellular matrix and abundance of stromal cells result in severe hypoxia within the tumor microenvironment (TME), and emerging publications evaluating PDAC tumorigenesis have shown the adenosine signaling pathway promotes an immunosuppressive TME and contributes to the overall low survival rate. Hypoxia increases many elements of the adenosine signaling pathway, resulting in higher adenosine levels in the TME, further contributing to immune suppression. Extracellular adenosine signals through 4 adenosine receptors (Adora1, Adora2a, Adora2b, Adora3). Of the 4 receptors, Adora2b has the lowest affinity for adenosine and thus, has important consequences when stimulated by adenosine binding in the hypoxic TME. We and others have shown that Adora2b is present in normal pancreas tissue, and in injured or diseased pancreatic tissue, Adora2b levels are significantly elevated. The Adora2b receptor is present on many immune cells, including macrophages, dendritic cells, natural killer cells, natural killer T cells, γδ T cells, B cells, T cells, CD4+ T cells, and CD8+ T cells. In these immune cell types, adenosine signaling through Adora2b can reduce the adaptive anti-tumor response, augmenting immune suppression, or may contribute to transformation and changes in fibrosis, perineural invasion, or the vasculature by binding the Adora2b receptor on neoplastic epithelial cells, cancer-associated fibroblasts, blood vessels, lymphatic vessels, and nerves. In this review, we discuss the mechanistic consequences of Adora2b activation on cell types in the tumor microenvironment. As the cell-autonomous role of adenosine signaling through Adora2b has not been comprehensively studied in pancreatic cancer cells, we will also discuss published data from other malignancies to infer emerging therapeutic considerations for targeting the Adora2b adenosine receptor to reduce the proliferative, invasive, and metastatic potential of PDAC cells.

The role of tumor metabolism in modulating T-Cell activity and in optimizing immunotherapy

Immunotherapy has revolutionized cancer treatment and revitalized efforts to harness the power of the immune system to combat a variety of cancer types more effectively. However, low clinical response rates and differences in outcomes due to variations in the immune landscape among patients with cancer continue to be major limitations to immunotherapy. Recent efforts to improve responses to immunotherapy have focused on targeting cellular metabolism, as the metabolic characteristics of cancer cells can directly influence the activity and metabolism of immune cells, particularly T cells. Although the metabolic pathways of various cancer cells and T cells have been extensively reviewed, the intersections among these pathways, and their potential use as targets for improving responses to immune-checkpoint blockade therapies, are not completely understood. This review focuses on the interplay between tumor metabolites and T-cell dysfunction as well as the relationship between several T-cell metabolic patterns and T-cell activity/function in tumor immunology. Understanding these relationships could offer new avenues for improving responses to immunotherapy on a metabolic basis.

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.

Novel strategies for cancer immunotherapy: counter-immunoediting therapy

The advent of immunotherapy has made an indelible mark on the field of cancer therapy, especially the application of immune checkpoint inhibitors in clinical practice. Although immunotherapy has proven its efficacy and safety in some tumors, many patients still have innate or acquired resistance to immunotherapy. The emergence of this phenomenon is closely related to the highly heterogeneous immune microenvironment formed by tumor cells after undergoing cancer immunoediting. The process of cancer immunoediting refers to the cooperative interaction between tumor cells and the immune system that involves three phases: elimination, equilibrium, and escape. During these phases, conflicting interactions between the immune system and tumor cells result in the formation of a complex immune microenvironment, which contributes to the acquisition of different levels of immunotherapy resistance in tumor cells. In this review, we summarize the characteristics of different phases of cancer immunoediting and the corresponding therapeutic tools, and we propose normalized therapeutic strategies based on immunophenotyping. The process of cancer immunoediting is retrograded through targeted interventions in different phases of cancer immunoediting, making immunotherapy in the context of precision therapy the most promising therapy to cure cancer.

Dendritic Cell Subsets in Melanoma: Pathophysiology, Clinical Prognosis and Therapeutic Exploitation

Evasion from immunity is a hallmark of cancer development. Dendritic cells (DCs) are strategic immune cells shaping anti-tumor immune responses, but tumor cells exploit DC versatility to subvert their functions. Unveiling the puzzling role of DCs in the control of tumor development and mechanisms of tumor-induced DC hijacking is critical to optimize current therapies and to design future efficient immunotherapies for melanoma. Dendritic cells, crucially positioned at the center of anti-tumor immunity, represent attractive targets to develop new therapeutic approaches. Harnessing the potencies of each DC subset to trigger appropriate immune responses while avoiding their subversion is a challenging yet promising step to achieve tumor immune control. This review focuses on advances regarding the diversity of DC subsets, their pathophysiology and impact on clinical outcome in melanoma patients. We provide insights into the regulation mechanisms of DCs by the tumor, and overview DC-based therapeutic developments for melanoma. Further insights into DCs' diversity, features, networking, regulation and shaping by the tumor microenvironment will allow designing novel effective cancer therapies. The DCs deserve to be positioned in the current melanoma immunotherapeutic landscape. Recent discoveries strongly motivate exploitation of the exceptional potential of DCs to drive robust anti-tumor immunity, offering promising tracks for clinical successes.

Role of adenosine A2a receptor in cancers and autoimmune diseases

Adenosine receptors are P1 class of purinergic receptors that belong to G protein-coupled receptors. There are 4 subtypes of adenosine receptors, namely A1, A2A, A2B, and A3. A2AR has a high affinity for the ligand adenosine. Under pathological conditions or external stimuli, ATP is sequentially hydrolyzed to adenosine by CD39 and CD73. The combination of adenosine and A2AR can increase the concentration of cAMP and activate a series of downstream signaling pathways, and further playing the role of immunosuppression and promotion of tumor invasion. A2AR is expressed to some extent on various immune cells, where it is abnormally expressed on immune cells in cancers and autoimmune diseases. A2AR expression also correlates with disease progression. Inhibitors and agonists of A2AR may be potential new strategies for treatment of cancers and autoimmune diseases. We herein briefly reviewed the expression and distribution of A2AR, adenosine/A2AR signaling pathway, expression, and potential as a therapeutic target.