The cell-surface 5'-nucleotidase CD73 defines a functional T memory cell subset that declines with age

Mapping cell diversity in human sporadic cerebral cavernous malformations

BACKGROUND

Cerebral cavernous malformation (CCM) is a low-flow, bleeding-prone vascular disease that can cause cerebral hemorrhage, seizure and neurological deficits. Its inheritance mode includes sporadic or autosomal dominant inheritance with incomplete penetrance, namely sporadic CCM (SCCM) and familial CCM. SCCM is featured by single lesion and single affection in a family. Among CCM patients especially SCCM, the pathogenesis of the corresponding phenotypes and pathological features or candidate genes have not been fully elucidated yet.

METHODS

Here, we performed in-depth single-cell RNA sequencing (scRNA-Seq) and bulk assay for transposase-accessible chromatin sequencing (ATAC-Seq) in SCCM and control patients. Further validation was conducted for the gene of interest using qPCR and RNA in situ hybridization (RNA FISH) techniques to provide further atlas and evidence for SCCM generative process.

RESULTS

We identified six cell types in the SCCM and control vessels and found that the expression of NEK1, RNPC3, FBRSL1, IQGAP2, MCUB, AP3B1, ESCO1, MYO9B and PVT1 were up-regulated in SCCM tissues. Among the six cell types, we found that compared with control conditions, PVT1 showed a rising peak which followed the pseudo-time axis in endothelial cell clusters of SCCM samples, while showed an increasing trend in smooth muscle cell clusters of SCCM samples. Further experiments indicated that, compared with the control vessels, PVT1 exhibited significantly elevated expression in SCCM samples.

CONCLUSION

In SCCM conditions, We found that in the process of development from control to lesion conditions, PVT1 showed a rising peak in endothelial cells and showed an increasing trend in smooth muscle cells at the same time. Overall, there was a significantly elevated expression of NEK1, RNPC3, FBRSL1, IQGAP2, MCUB, AP3B1, ESCO1, MYO9B and PVT1 in SCCM specimens compared to control samples.

Spatial transcriptomic brain imaging reveals the effects of immunomodulation therapy on specific regional brain cells in a mouse dementia model

Increasing evidence of brain-immune crosstalk raises expectations for the efficacy of novel immunotherapies in Alzheimer's disease (AD), but the lack of methods to examine brain tissues makes it difficult to evaluate therapeutics. Here, we investigated the changes in spatial transcriptomic signatures and brain cell types using the 10x Genomics Visium platform in immune-modulated AD models after various treatments. To proceed with an analysis suitable for barcode-based spatial transcriptomics, we first organized a workflow for segmentation of neuroanatomical regions, establishment of appropriate gene combinations, and comprehensive review of altered brain cell signatures. Ultimately, we investigated spatial transcriptomic changes following administration of immunomodulators, NK cell supplements and an anti-CD4 antibody, which ameliorated behavior impairment, and designated brain cells and regions showing probable associations with behavior changes. We provided the customized analytic pipeline into an application named STquantool. Thus, we anticipate that our approach can help researchers interpret the real action of drug candidates by simultaneously investigating the dynamics of all transcripts for the development of novel AD therapeutics.

Purification and analysis of kidney-infiltrating leukocytes in a mouse model of lupus nephritis

Renal injury often occurs as a complication in autoimmune diseases such as systemic lupus erythematosus (SLE). It is estimated that a minimum of 20% SLE patients develop lupus nephritis, a condition that can be fatal when the pathology progresses to end-stage renal disease. Studies in animal models showed that incidence of immune cell infiltrates in the kidney was linked to pathological injury and correlated with severe lupus nephritis. Thus, preventing immune cell infiltration into the kidney is a potential approach to impede the progression to an end-stage disease. A requirement to investigate the role of kidney-infiltrating leukocytes is the development of reproducible and efficient protocols for purification and characterization of immune cells in kidney samples. This chapter describes a detailed methodology that discriminates tissue-resident leukocytes from blood-circulating cells that are found in kidney. Our protocol was designed to maximize cell viability and to reduce variability among samples, with a combination of intravascular staining and magnetic bead separation for leukocyte enrichment. Experiments included as example were performed with FcγRIIb[KO] mice, a well-characterized murine model of SLE. We identified T cells and macrophages as the primary leukocyte subsets infiltrating into the kidney during severe nephritis, and we extensively characterized them phenotypically by flow cytometry.

CD39 is expressed on functional effector and tissue resident memory CD8+ T cells

The ecto-ATPase CD39 is expressed on exhausted CD8+ T cells in chronic viral infection and has been proposed as a marker of tumor-specific CD8+ T cells in cancer, but the role of CD39 in an effector and memory T cell response has not been clearly defined. We report that CD39 is expressed on antigen-specific CD8+ short-lived effector cells (SLECs), while it's co-ecto-enzyme, CD73, is found on memory precursor effector cells (MPEC) in vivo . Inhibition of CD39 enzymatic activity during in vitro T cell priming enhances MPEC differentiation in vivo after transfer and infection. The enriched MPEC phenotype is associated with enhanced tissue resident memory (T RM ) establishment in the brain and salivary gland following an acute intranasal viral infection, suggesting that CD39 ATPase activity plays a role in memory CD8+ T cell differentiation. We also show that CD39 is expressed on human and murine T RM across several non-lymphoid tissues and melanoma, while CD73 is expressed on both circulating and resident memory subsets in mice. In contrast to exhausted CD39+ T cells in chronic infection, CD39+ T RM are fully functional when stimulated ex vivo with cognate antigen. This work further expands the identity of CD39 beyond a T cell exhaustion marker.

CD73 as a T cell dysfunction marker predicting cardiovascular and infection events in patients undergoing hemodialysis

BACKGROUND

T cell dysfunction observed in patients undergoing hemodialysis (HD) has been linked to an extremely high morbidity of cardiovascular events (CVEs) and infections. The cell-surface 5'-nucleotidase CD73 sets the balance between pro-inflammatory nucleotides and anti-inflammatory adenosine.

METHODS

A total of 395 patients who had been receiving HD for at least six months were evaluated for proportions of CD73+ cells in both the CD4+ T cell and CD8+ T cell compartment and followed for one year to document CVEs and infections. Differences in the proportions of CD73-expressingT cells between healthy controls and patients undergoing HD were compared. The relationship between CD73+ T cells and clinical outcomes was analyzed using the Kaplan-Meier curve and Cox regression.

RESULTS

HD was significantly related to a lower fraction of CD4+CD73+ T cells. In patients on HD, lower proportions of CD4+ CD73+T cells and CD8+ CD73+T cells were both associated with systemic inflammation and T cell terminal differentiation. More importantly, a lower CD4+CD73+T cell ratio independently predicted CVEs and infection in these patients.

CONCLUSION

We identified CD73 as a T cell dysfunction marker predicting cardiovascular and infection events in patients undergoing HD, which provides a potential target in future studies of uremia-related immune dysfunction.

T cell fate decisions during memory cell generation with aging

The defense against infectious diseases, either through natural immunity or after vaccinations, relies on the generation and maintenance of protective T cell memory. Naïve T cells are at the center of memory T cell generation during primary responses. Upon activation, they undergo a complex, highly regulated differentiation process towards different functional states. Naïve T cells maintained into older age have undergone epigenetic adaptations that influence their fate decisions during differentiation. We review age-sensitive, molecular pathways and gene regulatory networks that bias naïve T cell differentiation towards effector cell generation at the expense of memory and Tfh cells. As a result, T cell differentiation in older adults is associated with release of bioactive waste products into the microenvironment, higher stress sensitivity as well as skewing towards pro-inflammatory signatures and shorter life spans. These maladaptations not only contribute to poor vaccine responses in older adults but also fuel a more inflammatory state.

The interplay between the DNA damage response and ectonucleotidases modulates tumor response to therapy

The extracellular nucleoside adenosine reduces tissue inflammation and is generated by irreversible dephosphorylation of adenosine monophosphate (AMP) mediated by the ectonucleotidase CD73. The pro-inflammatory nucleotides adenosine triphosphate, nicotinamide adenine dinucleotide, and cyclic guanosine -monophosphate-AMP (cGAMP), which are produced in the tumor microenvironment (TME) during therapy-induced immunogenic cell death and activation of innate immune signaling, can be converted into AMP by ectonucleotidases CD39, CD38, and CD203a/ENPP1. Thus, ectonucleotidases shape the TME by converting immune-activating signals into an immunosuppressive one. Ectonucleotidases also hinder the ability of therapies including radiation therapy, which enhance the release of pro-inflammatory nucleotides in the extracellular milieu, to induce immune-mediated tumor rejection. Here, we review the immunosuppressive effects of adenosine and the role of different ectonucleotidases in modulating antitumor immune responses. We discuss emerging opportunities to target adenosine generation and/or its ability to signal via adenosine receptors expressed by immune and cancer cells in the context of combination immunotherapy and radiotherapy.

Optimal dosing regimen of CD73 blockade improves tumor response to radiotherapy through iCOS downregulation

BACKGROUND

Irradiation (IR) and immune checkpoint inhibitor (ICI) combination is a promising treatment modality. However, local and distance treatment failure and resistance can occur. To counteract this resistance, several studies propose CD73, an ectoenzyme, as a potential target to improve the antitumor efficiency of IR and ICI. Although CD73 targeting in combination with IR and ICI has shown attractive antitumor effects in preclinical models, the rationale for CD73 targeting based on CD73 tumor expression level deserves further investigations.

METHODS

Here we evaluated for the first time the efficacy of two administration regimens of CD73 neutralizing antibody (one dose vs four doses) in combination with IR according to the expression level of CD73 in two subcutaneous tumor models expressing different levels of CD73.

RESULTS

We showed that CD73 is weakly expressed by MC38 tumors even after IR, when compared with the TS/A model that highly expressed CD73. Treatment with four doses of anti-CD73 improved the TS/A tumor response to IR, while it was ineffective against the CD73 low-expressing MC38 tumors. Surprisingly, a single dose of anti-CD73 exerted a significant antitumor activity against MC38 tumors. On CD73 overexpression in MC38 cells, four doses of anti-CD73 were required to improve the efficacy of IR. Mechanistically, a correlation between a downregulation of iCOS expression in CD4⁺ T cells and an improved response to IR after anti-CD73 treatment was observed and iCOS targeting could restore an impaired benefit from anti-CD73 treatment.

CONCLUSIONS

These data emphasize the importance of the dosing regimen for anti-CD73 treatment to improve tumor response to IR and identify iCOS as part of the underlying molecular mechanisms. Our data suggest that the selection of appropriate dosing regimen is required to optimize the therapeutic efficacy of immunotherapy-radiotherapy combinations.

CD73-Dependent Adenosine Signaling through Adora2b Drives Immunosuppression in Ductal Pancreatic Cancer

The microenvironment that surrounds pancreatic ductal adenocarcinoma (PDAC) is profoundly desmoplastic and immunosuppressive. Understanding triggers of immunosuppression during the process of pancreatic tumorigenesis would aid in establishing targets for effective prevention and therapy. Here, we interrogated differential molecular mechanisms dependent on cell of origin and subtype that promote immunosuppression during PDAC initiation and in established tumors. Transcriptomic analysis of cell-of-origin-dependent epithelial gene signatures revealed that Nt5e/CD73, a cell-surface enzyme required for extracellular adenosine generation, is one of the top 10% of genes overexpressed in murine tumors arising from the ductal pancreatic epithelium as opposed to those rising from acinar cells. These findings were confirmed by IHC and high-performance liquid chromatography. Analysis in human PDAC subtypes indicated that high Nt5e in murine ductal PDAC models overlaps with high NT5E in human PDAC squamous and basal subtypes, considered to have the highest immunosuppression and worst prognosis. Multiplex immunofluorescent analysis showed that activated CD8+ T cells in the PDAC tumor microenvironment express high levels of CD73, indicating an opportunity for immunotherapeutic targeting. Delivery of CD73 small-molecule inhibitors through various delivery routes reduced tumor development and growth in genetically engineered and syngeneic mouse models. In addition, the adenosine receptor Adora2b was a determinant of adenosine-mediated immunosuppression in PDAC. These findings highlight a molecular trigger of the immunosuppressive PDAC microenvironment elevated in the ductal cell of origin, linking biology with subtype classification, critical components for PDAC immunoprevention and personalized approaches for immunotherapeutic intervention.

SIGNIFICANCE

Ductal-derived pancreatic tumors have elevated epithelial and CD8+GZM+ T-cell CD73 expression that confers sensitivity to small-molecule inhibition of CD73 or Adora2b to promote CD8+ T-cell-mediated tumor regression. See related commentary by DelGiorno, p. 977.

T cell aging and Alzheimer’s disease

The brain has long been considered an immune-privileged organ due to the presence of the blood-brain barrier (BBB). However, recent discoveries have revealed the underestimated role of T cells in the brain through the meningeal lymphatic system. Age is the primary risk factor for Alzheimer’s disease (AD), resulting in marked age-dependent changes in T cells. Manipulating peripheral T cell immune response has been shown to impact AD, but the relationship between T cell aging and AD remains poorly understood. Given the limited success of targeting amyloid beta (Aβ) and the growing evidence of T cells’ involvement in non-lymphoid organ aging, a deeper understanding of the relationship between T cells and AD in the context of aging is crucial for advancing therapeutic progress. In this review, we comprehensively examine existing studies on T cells and AD and offer an integrated perspective on their interconnections in the context of aging. This understanding can inform the development of new interventions to prevent or treat AD.

Pharmacology, pharmacokinetics, and toxicity characterization of a novel anti-CD73 therapeutic antibody IBI325 for cancer immunotherapy

It is an intriguing approach to target the ecto-5'-nucleotidase CD73 to confer synergetic beneficial survival in cancer patients, along with clinically established immunotherapy targets. In this study, a fully human, subnanomolar affinity CD73 antibody IBI325 was developed using the yeast display platform. Compared with Oleclumab, IBI325 was equivalent in hCD73 affinity and more potent in cell-bound and soluble CD73 enzymatic inhibition, and no hook effects were observed. Correspondingly, adenosine monophosphate-mediated immune suppression was reversed by IBI325, and significant T cell proliferation and release of cytokines were observed. Also, IBI325 enhanced the T cell recall response by inducing interferon-γ secretion. The antitumor efficacy of IBI325 was investigated in a hPBMC-reconstituted NOG mouse model, and a hCD73 knock-in mouse model. Consequently, IBI325 induced a significant tumor regression by inducing intratumoral immune cell expansion, and a combo therapy of IBI325 and aPD-1 was superior in efficacy than aCD73 or aPD-1 monotherapy. Additionally, the binding epitopes of CD73 to IBI325 were distinct from previously reported aCD73 therapeutics. IBI325 displayed acceptable pharmacokinetics and sufficient tolerable safety profiles to support clinical development. In conclusion, the pharmacology, pharmacokinetics, and toxicity profiles of IBI325 with complete CD73 inhibition were characterized, and encouraging preclinical outcomes were reported.

Prognostic relevance of tumor-resident memory T cells in metastatic lymph nodes of esophageal squamous cell carcinoma

Tumor-resident memory T (T_RM ) cells in primary tumors are reportedly associated with a favorable prognosis in several malignancies. However, the behaviors and functions of T_RM cells in regional lymph nodes (LNs) of esophageal cancer remain poorly understood. The aim of this study was to elucidate the effects of T_RM cells in regional LNs of esophageal cancer on clinicopathological findings and prognosis. Specimens of esophageal cancer and primary metastatic LNs (recurrent nerve LNs) were obtained from 84 patients who underwent radical esophagectomy between 2011 and 2017. We performed immunohistochemistry to enumerate and analyze T_RM cells, and used flow cytometry to investigate the function of T_RM cells. T_RM cells were observed in both metastatic LNs and primary tumors. T_RM cell-rich specimens exhibited reduced lymphatic invasion and LN metastasis and prolonged survival compared with T_RM cell-poor specimens. T_RM cells in metastatic LNs were more significantly associated with enhanced survival than T_RM cells in primary tumors. T_RM cells expressed high levels of granzyme B as a cytotoxicity marker. Our results suggested that high T_RM cell infiltration in metastatic LNs improves survival even though LN metastasis is commonly associated with poor prognosis. T_RM cells possibly contribute to antitumor immunity in regional LNs.

Virtual Memory CD8+ T Cells: Origin and Beyond

The presence of CD8+ T cells with a memory phenotype in nonimmunized mice has been noted for decades, but it was not until about 2 decades ago that they began to be studied in greater depth. Currently called virtual memory CD8+ T cells, they consist of a heterogeneous group of cells with memory characteristics, without any previous contact with their specific antigens. These cells were identified in mice, but a few years ago, a cell type with characteristics equivalent to the murine ones was described in healthy humans. In this review, we address the different aspects of its biology mainly developed in murine models and what is currently known about its cellular equivalent in humans.

Tumor-Induced T Cell Polarization by Schwann Cells

Nerve-cancer crosstalk resulting in either tumor neurogenesis or intratumoral neurodegeneration is critically controlled by Schwann cells, the principal glial cells of the peripheral nervous system. Though the direct stimulating effect of Schwann cells on malignant cell proliferation, motility, epithelial-mesenchymal transition, and the formation of metastases have been intensively investigated, the ability of Schwann cells to affect the effector and regulatory immune cells in the tumor environment is significantly less studied. Here, we demonstrated that tumor cells could stimulate Schwann cells to produce high levels of prostaglandin E, which could be blocked by COX-2 inhibitors. This effect was mediated by tumor-derived TGF-β as neutralization of this cytokine in the tumor-conditioned medium completely blocked the inducible prostaglandin E production by Schwann cells. Similar protective effects were also induced by the Schwann cell pretreatment with TGF-βR1/ALK4/5/7 and MAPK/ERK kinase inhibitors of the canonical and non-canonical TGF-β signaling pathways, respectively. Furthermore, prostaglandin E derived from tumor-activated Schwann cells blocked the proliferation of CD3/CD28-activated T cells and upregulated the expression of CD73 and PD-1 on both CD4+ and CD8+ T cells, suggesting T cell polarization to the exhausted phenotype. This new pathway of tumor-induced T cell inhibition via the activation of neuroglial cells represents new evidence of the importance of nerve-cancer crosstalk in controlling tumor development and progression. A better understanding of the tumor-neuro-immune axis supports the development of efficient targets for harnessing this axis and improving the efficacy of cancer therapy.

IL-4 prevents adenosine-mediated immunoregulation by inhibiting CD39 expression

The ectonucleotidase CD39 functions as a checkpoint in purinergic signaling on effector T cells. By depleting eATP and initiating the generation of adenosine, it impairs memory cell development and contributes to T cell exhaustion, thereby causing defective tumor immunity and deficient T cell responses in older adults who have increased CD39 expression. Tuning enzymatic activity of CD39 and targeting the transcriptional regulation of ENTPD1 can be used to modulate purinergic signaling. Here, we describe that STAT6 phosphorylation downstream of IL-4 signaling represses CD39 expression on activated T cells by inducing a transcription factor network including GATA3, GFI1, and YY1. GATA3 suppresses ENTPD1 transcription through prevention of RUNX3 recruitment to the ENTPD1 promoter. Conversely, pharmacological STAT6 inhibition decreases T cell effector functions via increased CD39 expression, resulting in the defective signaling of P2X receptors by ATP and stimulation of A2A receptors by adenosine. Our studies suggest that inhibiting the STAT6 pathway to increase CD39 expression has the potential to treat autoimmune disease while stimulation of the pathway could improve T cell immunity.

The Multifaceted Actions of CD73 During Development and Suppressive Actions of Regulatory T Cells

Adenosine (Ado) has been shown to have immunosuppressive effects in a variety of diseases. It can either be released directly into the extracellular environment by cells, or it can be produced by degradation of ATP within the extracellular spaces. This extracellular pathway is facilitated by the concerted actions of the ectoenzymes CD39 and CD73. In a first step CD39 dephosphorylates ATP to ADP and AMP, respectively, and in a second step CD73 converts AMP to Ado. Thus, activity of CD73 on the cell surface of cells is the rate limiting step in the generation of extracellular Ado. Among T cells, CD73 is most abundantly expressed by regulatory T cells (Tregs) and is even upregulated after their activation. Functionally, the generation of Ado by CD73+ Tregs has been shown to play a role in immune suppression of dendritic cells, monocytes and T cells, and the defined expression of CD73 by Tregs in immunosuppressive environments, such as tumors, made CD73 a novel checkpoint inhibitor. Therefore, therapeutical intervention by anti-CD73 antibodies or by chemical inhibitors of the enzymatic function is currently under investigation in some preclinical animal models. In the following we summarize the expression pattern and the possible functions of CD73 in T cells and Tregs, and exemplify novel ways to manipulate CD73 functions in Tregs to stimulate anti-tumor immunity.