Monocytic Myeloid-derived Suppressor Cells Research Articles

IMMU-58. BCAT1 TARGETED METABOLIC REPROGRAMMING PLAYS CRITICAL ROLES IN MODULATING MYELOID DERIVED SUPPRESSOR CELL FUNCTION IN GLIOBLASTOMA

Abstract A key component that has limited the efficacy of immunotherapy in glioblastoma (GBM) is the significant infiltration of immunosuppressive myeloid cells. Our previous work characterized myeloid derived suppressor cells (MDSCs) unique to GBM that drive tumor growth and immune suppression. Transcriptomic and flow cytometric analyses demonstrated that the most induced programs in these MDSCs are dominated by metabolic and mTOR pathways. Therefore, we aimed to understand the role of metabolic reprogramming in MDSC differentiation and immunosuppressive function. Using single cell RNA sequencing, we identified overexpression of enzymes and transporters involved in branched-chain amino acid (BCAA) metabolism, notably branched chain aminotransferase 1 (BCAT1), the first enzyme in the metabolic pathway. Intriguingly, this was only found in specific populations of early and monocytic MDSCs (E-MDSCs, M-MDSCs), and not polymorphonuclear MDSCs (PMN-MDSCs). Using established MDSC modeling systems, we found that M-MDSC differentiation and T cell suppressive function are dependent on BCAAs and can be hindered by pharmacological inhibition of BCAT1 activity or genetic knockout of BCAT1. We also establish that the influence of BCAA on M-MDSC function is specifically reliant on the BCAT1-mediated step of BCAA metabolism. To determine the underlying mechanism driving BCAT1’s impact on M-MDSC function, we evaluated the activity of signaling pathways known to be critical to M-MDSCs including the mTORC1 pathway. We found that the impact of BCAA and BCAT1 activity on M-MDSC function is abrogated by inhibition of mTORC1 pathway with reduction in M-MDSC differentiation and activity. Consistent with our single cell RNA sequencing analysis, modulation of BCAA levels and BCAT1 activity had no impact on PMN-MDSCs. Our results underscore the critical role of BCAT1 in preferentially modulating M-MDSC activity through mTORC1 signaling. Our finding paves the way for discovery of a targetable therapeutic approach to harness immunometabolism in myeloid cells to develop novel immune therapies.

TMIC-32. INFIGRATINIB INHIBITION OF THE THBS1 PATHWAY IN MELANOMA BRAIN METASTASIS

Abstract INTRODUCTION Despite promising preclinical studies, BRAF/MEK inhibition with vemurafenib in melanoma brain metastases (MBM) has suboptimal durable response in humans. Thrombospondin 1 (THBS1), a matricellular protein, is upregulated in vemurafenib-resistant metastatic melanoma, and its inhibition reverses BRAF inhibitor chemoresistance. However, the characteristics of THBS1-mediated signaling pathways as well as methods of inhibition require further exploration in the context of MBM. OBJECTIVE To characterize THBS1-mediated signaling pathways in MBM and evaluate the therapeutic potential of targeting THBS1 pathways. METHODS We analyzed human parenchymal MBM samples using publicly available single-cell RNA sequencing (scRNA-seq) data. Protein-protein interaction networks were assessed using the STRING database. Syngeneic B16 melanoma cells were intracranially implanted in C57BL/6J mice and treated with intraperitoneal injection of FGF7/FGFR2 small-molecule inhibitor Infigratinib or PBS (sham). Mice were immunophenotyped using flow cytometry and monitored for survival. RESULTS THBS1 is highly upregulated in immunosuppressive MBM-associated cell populations such as S100A8+ Metastasis-Associated Macrophages and Mesenchymal Stromal Cell-like cells. Gene set enrichment analysis of THBS1-positive cells paradoxically revealed upregulation of inflammation-associated gene sets. Differential expression analysis identified Fibroblast Growth Factor 7 (FGF7) as strongly co-expressed in THBS1-positive MBM cells, and STRING-DB confirmed close protein-protein interactions between FGF7 and THBS1. In vivo inhibition using Infigratinib for FGF7’s receptor, FGFR2, decreased the proportion of monocytic myeloid-derived suppressor cells (M-MDSCs) (P=0.030), increased T-cell activation marker IFN-y (P=0.027) and proliferation marker CD69 (P=0.047), and resulted in improved overall survival (P=0.0001). CONCLUSION MBM scRNA-seq data suggests that THBS1 is associated with inflammation-induced immunosuppression. Inhibiting the FGF7/FGFR2-THBS1 axis with Infigratinib modulates the tumor microenvironment by reducing immunosuppressive M-MDSCs and increasing T cell activation and proliferation. This data supports THBS1 inhibition as a viable therapeutic option that in the future can also be combined with other current immunotherapeutic strategies.

IMMU-56. THE TIGIT/CD155 AXIS PLAYS A CRITICAL ROLE IN EXTRACELLULAR VESICLE-MEDIATED PROGRAMMING OF THE GLIOBLASTOMA MICROENVIRONMENT

Abstract Glioblastoma (GBM), the most common and deadly primary brain tumor, exerts profound local and systemic immunosuppressive effects through a variety of mechanisms. Tumor-derived extracellular vesicles (EVs) are increasingly appreciated as critical mediators of these effects. In surveying the tumor-immune microenvironment in samples of ultrasonic aspirate collected during surgical resection of GBM (n=13), we identified several key immunomodulatory markers expressed across a range of myeloid cell populations. Particularly, we found TIGIT, classically understood as a T cell inhibitory protein, expressed across a range of myeloid cell populations in patient samples, including in myeloid-derived suppressor cells (MDSCs, 46.84±16.78% of total monocytic MDSCs). Using EVs collected from patient-derived cell lines, we were able to recapitulate these effects upon co-culture with monocytes derived from the peripheral blood of healthy donors (n=7). Furthermore, Induced MDSCs significantly inhibit T cells proliferation (70.97±8.454%, compared to control 19.4±5.71; p<0.03), concomitant with a surge in Th2 immune responses via TIGIT/CD155 axis. This effect was reversed after TIGIT silencing, indicating a TIGIT-dependent immune suppression in the GBM microenvironment. Our study indicates EV-induced TIGIT upregulation in myeloid cells as a crucial immunosuppressive mechanism in glioblastoma, with potential therapeutic applications.

TMIC-61. DEVELOPMENT OF A NOVEL NOTCH-TARGETING ONCOLYTIC HSV FOR GBM TUMORS

Abstract Glioblastoma (GBM) is the most aggressive brain malignancy, which despite continuing worldwide efforts to develop new therapies, remains a deadly disease with limited treatment options. The NOTCH signaling pathway is often hyperactive in GBM tumors, and its activity contributes to tumor progression and resistance to treatment. The role of NOTCH signaling in tumor growth and resistance is well studied, but the significance of this pathway for immunotherapy of GBM is not very well understood. We have recently shown that NOTCH activation following virotherapy contributes to tumor regrowth and induces recruitment of monocytic MDSC cells into the tumor, which limit optimal immune activation to kill tumor cells. For this study, we have discovered a NOTCH interfering intracellular ligand (NIIL) that blocks NOTCH activation from inside glioma cells. RNA sequencing shows the expression of NIIL downregulates NOTCH signaling in vitro. To evaluate the effect of NIIL on virotherapy, we generated an oncolytic herpes simplex virus (oHSV) that also encodes for NIIL. This virus showed a slower spread in vitro but improved therapeutic efficacy in vivo in multiple models of intracranial tumors. In immune competent mice there was a significant improvement in the survival of mice treated with the NIIL-encoding virus, with a fraction of mice showing a complete response after a single treatment. Single-cell RNA sequencing analysis of immune infiltrates is ongoing to understand how NIIL impacts tumor microenvironment and anti-tumor immune therapy.

TMIC-54. OHSV-MEDIATED NOTCH BLOCKADE FOR BRAIN TUMORS

Abstract Primary brain tumors such as glioblastoma (GBM) are refractory to current standard-of-care, and so there is an urgent need to develop novel therapies to treat brain tumors. NOTCH is a cell-cell communication pathway that is exploited by GBM stem cells to bypass treatment. The role of NOTCH signaling in tumor growth and resistance is well studied, but the significance of this pathway for immunotherapy of GBM is not very well understood. We have recently shown that NOTCH activation with viro-immunotherapy contributes to tumor regrowth and induces recruitment of monocytic MDSC cells into the tumor, which limit optimal immune activation to kill tumor cells. Herein, we evaluated the impact of blocking NOTCH signaling using two different peptides: NIX1 and NIX2 that can interfere with NOTCH ligand binding with their receptors. Both NIX1 and NIX2 could effectively block the ligation of NOTCH ligands with Notch receptors in the tumor microenvironment. Secretion of both NIX1 and NIX2 was confirmed by western blot (WB) and ELISA. Functionality of NIX1 and NIX2 to block NOTCH signaling was assessed by western blot analysis for NOTCH cleaved intracellular domain (NICD). RNA sequencing and PCR based assays were utilized to evaluate the impact of NIX1 and NIX2 on global pathways that were enriched. Gene therapy using oncolytic immunotherapy vectors revealed that both NIX1 and NIX2 could suppress NOTCH signaling. In vitro, NIX1 and NIX2 did not increase the benefit of viro-immunotherapy. Treatment of mice bearing intracranial tumors with NIX1 or NIX2 armed viro-immunotherapy revealed a significant increase in therapeutic benefit with some long-term survivors. Both NIX1 and NIX2-expressing viruses induced macrophage migration relative to unarmed viro-immunotherapy in two different glioma models. Role of macrophages in guiding therapeutic benefit is currently being explored.

Single cell RNA-seq reveals cellular and transcriptional heterogeneity in the splenic CD11b+Ly6Chigh monocyte population expanded in sepsis-surviving mice

BackgroundSepsis survivors exhibit immune dysregulation that contributes to poor long-term outcomes. Phenotypic and functional alterations within the myeloid compartment are believed to be a contributing factor. Here we dissect the cellular and transcriptional heterogeneity of splenic CD11b+Ly6Chigh myeloid cells that are expanded in mice that survive the cecal ligation and puncture (CLP) murine model of polymicrobial sepsis to better understand the basis of immune dysregulation in sepsis survivors.MethodsSham or CLP surgeries were performed on C57BL/6J and BALB/c mice. Four weeks later splenic CD11b+Ly6Chigh cells from both groups were isolated for phenotypic (flow cytometry) and functional (phagocytosis and glycolysis) characterization and RNA was obtained for single-cell RNA-seq (scRNA-seq) and subsequent analysis.ResultsCD11b+Ly6Chigh cells from sham and CLP surviving mice exhibit phenotypic and functional differences that relate to immune function, some of which are observed in both C57BL/6J and BALB/c strains and others that are not. To dissect disease-specific and strain-specific distinctions within the myeloid compartment, scRNA-seq analysis was performed on CD11b+Ly6Chigh cells from C57BL/6J and BALB/c sham and CLP mice. Uniform Manifold Approximation and Projection from both strains identified 13 distinct clusters of sorted CD11b+Ly6Chigh cells demonstrating significant transcriptional heterogeneity and expressing gene signatures corresponding to classical-monocytes, non-classical monocytes, M1- or M2-like macrophages, dendritic-like cells, monocyte-derived dendritic-like cells, and proliferating monocytic myeloid-derived suppressor cells (M-MDSCs). Frequency plots showed that the percentages of proliferating M-MDSCs (clusters 8, 11 and 12) were increased in CLP mice compared to sham mice in both strains. Pathway and UCell score analysis in CLP mice revealed that cell cycle and glycolytic pathways were upregulated in proliferating M-MDSCs in both strains. Notably, granule protease genes were upregulated in M-MDSCs from CLP mice. ScRNA-seq analyses also showed that phagocytic pathways were upregulated in multiple clusters including the classical monocyte cluster, confirming the increased phagocytic capacity in CD11b+Ly6Chigh cells from CLP mice observed in ex vivo functional assays in C57BL/6J mice.ConclusionThe splenic CD11b+Ly6Chigh myeloid populations expanded in survivors of CLP sepsis correspond to proliferating cells that have an increased metabolic demand and gene signatures consistent with M-MDSCs, a population known to have immunosuppressive capacity.

FoxO1 Deficiency in M-MDSCs Exacerbates B Cell Dysfunction in Systemic Lupus Erythematosus.

Myeloid-derived suppressor cells (MDSCs) contribute to the pathogenesis of systemic lupus erythematosus (SLE), in part due to promoting the survival of plasma cells. Forkhead box protein O1 (FoxO1) expression in monocytic MDSCs (M-MDSCs) exhibits a negative correlation with the SLE Disease Activity Index (SLEDAI) score. This study aimed to investigate the hypothesis that M-MDSCs specific FoxO1 deficiency enhances aberrant B cell function in aggressive SLE. We used GEO datasets and clinical cohorts to verify the FoxO1 expression and circulating M-MDSCs clinical significance. Using Cre-LoxP technology, we generated myeloid FoxO1 deficiency mice (mFoxO1-/-) to establish murine lupus-prone models. The transcriptional stage was assessed by integrating ChIP-seq with transcriptomic analysis, luciferase reporter assay and ChIP-qPCR. Methylated RNA immunoprecipitation sequencing, RNA sequencing and CRISPR-dCas9 were used to identify m6A modification. In vitro B cell co-culture experiments, Capmatinib intragastric administration, m6A-modulated MDSCs adoptive transfer, and SLE patient sample validation were performed to determine the role of FoxO1 on M-MDSCs dysregulation during B cell autoreacted with SLE. We present evidence that low FoxO1 is predominantly expressed in M-MDSCs in both SLE patients and lupus mice, and mice with myeloid FoxO1 deficiency (mFoxO1-/-) are more prone to B cell dysfunction. Mechanically, FoxO1 inhibits Met transcription by binding to the promoter region. M-MDSCs FoxO1 deficiency blocks the Met/COX2/PGE2 secretion pathway, promoting B cell proliferation and hyperactivation. Met antagonist Capmatinib effectively mitigates lupus exacerbation. Furthermore, ALKBH5 targeting catalyzes m6A modification on FoxO1 mRNA in CDS and 3'-UTR regions. Upregulation of FoxO1 mediated by ALKBH5 overexpression in M-MDSCs improves lupus progression. Finally, these correlations were confirmed in untreated SLE patients. Our findings indicate that effective inhibition of B cells mediated by ALKBH5/FoxO1/Met axis in M-MDSCs could offer a novel therapeutic approach to manage SLE.

Mediating role of circulating inflammatory proteins in the effect of immune cells on esophageal cancer risk: A Mendelian randomization study.

The immune system and inflammatory processes play crucial roles in the development of esophageal cancer (EC). This study aimed to investigate the causal relationships between 731 immune cell phenotypes, 91 circulating inflammatory proteins, and EC, with a particular focus on the mediating role of circulating inflammatory proteins. Utilizing public genetic data, we applied a 2-sample Mendelian Randomization (MR) method to examine the causal relationships between 731 immune cell phenotypes, 91 circulating inflammatory proteins, and EC. Comprehensive sensitivity analyses were conducted to assess the robustness, heterogeneity, and horizontal pleiotropy of the MR results. Additionally, a 2-step MR method was employed to quantify the impact and proportion of immune cell phenotypes mediated by circulating inflammatory proteins on EC. Eleven immune cell phenotypes and 1 inflammatory cytokine were found to have causal relationships with EC, with results stable across all sensitivity analyses. Mediation analyses revealed that only 2 cell phenotypes had causal relationships with EC through interleukin-10: CD3 on human leukocyte antigen-DR (HLA-DR)+ T cells (mediation effect = -0.009; mediation proportion = 12.01%) and monocytic myeloid-derived suppressor cell absolute count (mediation effect = 0.018; mediation proportion = 18.97%). This study enhances the understanding of the causal relationships between immune cells, circulating inflammatory proteins, and EC. The findings highlight the potential mediating role of interleukin-10, providing new insights into the mechanisms by which immune cells may influence esophageal tumorigenesis.

Intermittent Fasting and Fasting-mimicking Diet: Promising Strategies in Cancer Management.

In the current review, we aim to elucidate the advancements concerning the roles and fundamental mechanisms of intermittent fasting (IF) and fasting-mimicking diet (FMD) in cancers. As a dietary intervention,IF and FMD potentially impede tumor growth by modulating multiple signaling pathways, such as AKT, Nrf2, and AMPK pathways.Moreover, IF and FMD have been reported to be associated with the tumor immune response by regulating various immune cells including tumor-associated macrophages (TAMs), monocytic myeloid-derived suppressor cells (MDSCs), T cells, and B cells.Additionally, IF and FMD can enhance the efficacy and tolerability of therapy, concurrently reducing therapy-induced side effects. Furthermore, several clinical trials have underscored the safety, feasibility, and positive impact on the quality of life associated with IF and FMD, thereby augmenting the effectiveness of conventional anti-- tumor therapies while ameliorating treatment-related side effects. This review provides a comprehensive synthesis of findings and elucidates the underlying mechanisms of IF and FMD in cancer progression and therapy.

Increased CD14+HLA-DR-/low myeloid-derived suppressor cells can be regarded as a biomarker on disease severity and response to therapy in acute coronary syndrome.

This study aimed to investigate the dynamic changes in monocytic myeloid-derived suppressor cells (M-MDSCs) and their implications in the pathogenesis of acute coronary syndrome (ACS), shedding light on potential therapeutic targets. Peripheral blood samples were collected from 68 ACS patients, 35 stable angina pectoris (SAP) patients, and 30 healthy controls (HC). Multi-parameter flow cytometry was employed for analysis of M-MDSCs, explored with disease characteristics and progression. ACS patients exhibited an increased frequency of circulating M-MDSCs compared to SAP patients and HC. M-MDSCs levels demonstrated associations with ACS type, coronary artery lesions, multi-vessel disease, and cardiac dysfunction severity. Higher M-MDSCs levels were found in obese patients. Notably, therapy led to a significant decrease in M-MDSCs frequency. Furthermore, ACS patients exhibited elevated levels of interleukin (IL)-6, IL-10, granulocyte-macrophage colony-stimulating factor (GM-CSF), and tumor necrosis factor-α (TNF-α) in the cytokine profile associated with M-MDSCs. Increased expression of arginase-1(Arg-1) was observed in ACS patients, with positive correlations between M-MDSCs levels and IL-6, GM-CSF, and Arg-1 expression. The diagnostic performance of triglycerides (TG), high-density lipoprotein cholesterol (HDL-C), and M-MDSCs levels varied in predicting the severity of coronary artery stenosis, with TG showing higher specificity, HDL-C displaying higher sensitivity, and M-MDSCs levels demonstrating balanced sensitivity and specificity. Assessment of M-MDSCs frequency holds promise as a predictive marker for disease progression and therapy response of coronary artery stenosis. The elevated presence of M-MDSCs suggests their potential role in modulating ACS-related inflammation.

Resolvin D2/GPR18 signaling enhances monocytic myeloid-derived suppressor cell function to mitigate abdominal aortic aneurysm formation.

Abdominal aortic aneurysm (AAA) formation is a chronic vascular pathology characterized by inflammation, leukocyte infiltration, and vascular remodeling. The aim of this study was to delineate the protective role of Resolvin D2 (RvD2), a bioactive isoform of specialized pro-resolving lipid mediators, via G-protein-coupled receptor 18 (GPR18) receptor signaling in attenuating AAAs. Importantly, RvD2 and GPR18 levels were significantly decreased in aortic tissue of AAA patients compared with controls. Furthermore, using an established murine model of AAA in C57BL/6 (WT) mice, we observed that treatment with RvD2 significantly attenuated aortic diameter, pro-inflammatory cytokine production, immune cell infiltration (neutrophils and macrophages), elastic fiber disruption, and increased smooth muscle cell α-actin expression as well as increased TGF-β2 and IL-10 expressions compared to untreated mice. Moreover, the RvD2-mediated protection from vascular remodeling and AAA formation was blocked when mice were previously treated with siRNA for GPR18 signifying the importance of RvD2/GPR18 signaling in vascular inflammation. Mechanistically, RvD2-mediated protection significantly enhanced infiltration and activation of monocytic myeloid-derived suppressor cells (M-MDSCs) by increasing TGF-β2 and IL-10 secretions in a GPR18-dependent manner to attenuate aortic inflammation and vascular remodeling. Collectively, this study demonstrates that RvD2 treatment induces an expansion of myeloid-lineage committed progenitors, such as M-MDSCs, activates GPR18-dependent signaling to enhance TGF-β2 and IL-10 secretion, and mitigates SMC activation that contributes to resolution of aortic inflammation and remodeling during AAA formation.

Immunological responses to brain metastasis stereotactic radiosurgery in patient-matched longitudinal blood and tumour samples

BackgroundStereotactic radiosurgery (SRS) is highly effective as focal treatment for brain metastases (BrMs), but whether it can promote anti-tumour immune responses that synergise with immunotherapy remains unclear. We investigated this by examining blood samples from a clinical trial for HER2-amplified breast cancer (HER2-BC) BrMs, matched with longitudinal HER2-BC BrM samples resected from the same location in the same patient. MethodsBlood samples from 10 patients taken pre- and 7–14 days post-SRS were analysed by mass and flow cytometry. One patient received pre-operative SRS for a BrM that recurred 7 months after resection, followed by planned re-resection 8 days post-SRS. Pre- and post-SRS tumours from this patient were analysed by bulk RNAseq, multiplex immunohistochemistry (mIHC), and TCR sequencing. ResultsMonocytes, central memory CD8+ T and regulatory T cells were enriched in blood post-SRS, together with increased MHC-II expression on monocytes, conventional DCs, and monocytic MDSCs. In tumour, SRS upregulated antigen presentation, T cell proliferation and T cell co-stimulation signatures, alongside an influx of tumour-associated macrophages (TAMs) and CD4+ T cells. Specifically, TAMs and CD4+ T cells, but not CD8+ T cells, demonstrated spatial co-localisation post-SRS. These TAMs were lowly PD-L1 expressing, but CD4+ T cells showed increased PD-1 expression. A sizeable proportion of T cell clonotypes were retained post-SRS, and four clones demonstrated significant, non-stochastic expansion. ConclusionSystemic and local immunological changes in this homogenous patient cohort suggest that SRS may facilitate MHC-II-restricted T cell priming responses involving the monocyte-macrophage lineage and CD4+ T cells, which should be further explored.

The Interactions of T Cells with Myeloid-Derived Suppressor Cells in Peripheral Blood Stem Cell Grafts.

The interaction of myeloid-derived suppressor cells (MDSCs) with T cells within G-CSF-mobilized peripheral blood stem cell (PBSC) grafts in patients undergoing autologous or allogeneic hematopoietic stem cell transplantation remains to be elucidated. Through studying allo- and auto-PBSC grafts, we observed grafts containing large numbers of T cells and MDSCs with intergraft variability in their percentage and number. T cells from autologous grafts compared to allografts expressed relative higher percentages of inhibitory receptors PD-1, CTLA-4, TIM-3, LAG-3, TIGIT and BTLA. Autograft T cells had decreased cell proliferation and IFN-γ secretion, which supported the possible presence of T cell exhaustion. On the contrary, graft monocytic MDSCs (M-MDSCs) expressed multiple inhibitory receptor ligands, including PD-L1, CD86, Galectin-9, HVEM and CD155. The expression of inhibitory receptor ligands on M-MDSCs was correlated with their corresponding inhibitory receptors on T cells in the grafts. Isolated M-MDSCs had the ability to suppress T cell proliferation and IFN-γ secretion and/or promote Treg expansion. Blocking the PD-L1-PD-1 signaling pathway partially reversed the functions of M-MDSCs. Taken together, our data indicated that T cells and M-MDSCs in PBSC grafts express complementary inhibitory receptor-ligand pairing, which may impact the quality of immune recovery and clinical outcome post transplantation.

CCR5-mediated homing of regulatory T cells and monocytic-myeloid derived suppressor cells to dysfunctional endothelium contributes to early atherosclerosis.

A disbalance between immune regulatory cells and inflammatory cells is known to drive atherosclerosis. However, the exact mechanism is not clear. Here, we investigated the homing of immune regulatory cells, mainly, regulatory T cells (Tregs) and myeloid-derived suppressor cells (MDSCs) subsets in asymptomatic coronary artery disease (CAD) risk factor-exposed young individuals (dyslipidemia [DLP] group) and stable CAD patients (CAD group). Compared with healthy controls (HCs), Tregs frequency was reduced in both DLP and CAD groups but expressed high levels of CCR5 in both groups. The frequency of monocytic-myeloid-derived suppressor cells (M-MDSCs) was increased while polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs) were decreased in CAD patients only. Interestingly, although unchanged in frequency, M-MDSCs of the DLP group expressed high levels of CCR5. Serum levels of chemokines (CCL5, CX3CL1, CCL26) and inflammatory cytokines (IL-6, IL-1β, IFN-γ, TNF-α) were higher in the DLP group. Stimulation with inflammatory cytokines augmented CCR5 expression in Tregs and M-MDSCs isolated from HCs. Activated endothelial cells showed elevated levels of CX3CL1 and CCL5 in vitro. Blocking CCR5 with D-Ala-peptide T-amide (DAPTA) increased Treg and M-MDSC frequency in C57Bl6 mice fed a high-fat diet. In accelerated atherosclerosis model, DAPTA treatment led to the formation of smooth muscle-rich plaque with less macrophages. Thus, we show that CCR5-CCL5 axis is instrumental in recruiting Tregs and M-MDSCs to dysfunctional endothelium in the asymptomatic phase of atherosclerosis contributing to atherosclerosis progression. Drugs targeting CCR5 in asymptomatic and CAD risk-factor/s-exposed individuals might be a novel therapeutic regime to diminish atherogenesis.

The expansion of MDSCs induced by exosomal PD-L1 promotes the progression of gastric cancer

BackgroundMyeloid-derived suppressor cells (MDSCs) are the major factor in gastric cancer (GC) immune evasion. Nevertheless, the molecular process underlying the expansion of MDSCs induced by tumor-derived exosomes (TDEs) remains elusive.MethodsThe levels of exosomal and soluble PD-L1 in ninety GC patients were examined via enzyme-linked immunosorbent assay (ELISA) to determine their prognostic value. To investigate the correlation between exosomal PD-L1 and MDSCs, the percentage of MDSCs in the peripheral blood of 57 GC patients was assessed via flow cytometry. Through ultracentrifugation, the exosomes were separated from the GC cell supernatant and detected via Western blotting, nanoparticle tracking analysis (NTA), and transmission electron microscopy (TEM). The function of exosomal PD-L1 in MDSCs was evaluated via immunofluorescence, Western blotting and flow cytometry in a GC cell-derived xenograft (CDX) model.ResultsThe overall survival (OS) of GC patients in the high exosomal PD-L1 group was significantly lower than that of patients in the low exosomal PD-L1 group (P = 0.0042); however, there was no significant correlation between soluble PD-L1 and OS in GC patients (P = 0.0501). Furthermore, we found that the expression of exosomal PD-L1 was positively correlated with the proportions of polymorphonuclear MDSCs (PMN-MDSCs, r = 0.4944, P < 0.001) and monocytic MDSCs (M-MDSCs, r = 0.3663, P = 0.005) in GC patients, indicating that exosomal PD-L1 might induce immune suppression by promoting the aggregation of MDSCs. In addition, we found that exosomal PD-L1 might stimulate MDSC proliferation by triggering the IL-6/STAT3 signaling pathway in vitro. The CDX model confirmed that exosomal PD-L1 could stimulate tumor development and MDSC amplification.ConclusionsExosomal PD-L1 has the potential to become a prognostic and diagnostic biomarker for GC patients. Mechanistically, MDSCs can be activated by exosomal PD-L1 through IL-6/STAT3 signaling and provide a new strategy against GC through the use of exosomal PD-L1 as a treatment target.

The causal relationship between immune cells and diabetic retinopathy: a Mendelian randomization study.

This article explored the causal relationship between immune cells and diabetic retinopathy (DR) using single nucleotide polymorphisms (SNPs) as an instrumental variable and Mendelian randomization (MR). Statistical data were collected from a publicly available genome-wide association study (GWAS), and SNPs that were significantly associated with immune cells were used as instrumental variables (IVs). Inverse variance weighted (IVW) and MR-Egger regression were used for MR analysis. A sensitivity analysis was used to test the heterogeneity, horizontal pleiotropy, and stability of the results. We investigated the causal relationship between 731 immune cells and DR risk. All the GWAS data were obtained from European populations and from men and women. The IVW analysis revealed that HLA DR on CD14+ CD16- monocytes, HLA DR on CD14+ monocytes, HLA DR on CD33-HLA DR+, HLA DR on CD33+ HLA DR+ CD14- on CD33+ HLA DR+ CD14dim, and HLA DR on myeloid dendritic cells may increase the risk of DR (P<0.05). HLA DR to CD14-CD16- cells, the monocytic myeloid-derived suppressor cell absolute count, the SSC-A count of CD4+ T cells, and terminally differentiated CD4+ T cells may be protective factors against DR (P<0.05). The sensitivity analysis indicated no heterogeneity or pleiotropy among the selected SNPs. Furthermore, gene annotation of the SNPs revealed significant associations with 10 genes related to the risk of developing PDR and potential connections with 12 other genes related to PDR. Monocytes and T cells may serve as new biomarkers or therapeutic targets, leading to the development of new treatment options for managing DR.

Depletion of monocytic myeloid-derived suppressor cells in LP-BM5 murine retroviral infection has a positive impact on virus-induced host immunodeficiency

We have shown the induction of CD11b+Ly6C+ monocytic myeloid-derived suppressor cells (M-MDSCs) during infection of B6 mice by LP-BM5 immunodeficiency-inducing retrovirus. We published that the molecular mechanisms of these M-MDSCs vary, and depend on the cell type targeted by the suppression –defined by use of biochemical inhibitors, mouse M-MDSCs knock-out strains and blocking antibodies. These M-MDSCs suppressed proliferation and function of T cells, via nitric oxide synthase/nitric oxide; and that of B cells, ∼50% via INOS/NO along with the negative checkpoint regulator VISTA, reactive nitrogen and oxygen species, and other soluble mediators. Here, LP-BM5 infected mice were treated weekly with 5-Fluorouracil (5-FU), resulting in depletion of peripheral blood and splenic M-MDSCs, reduced MDSC activity, and significantly decreased standard disease parameters of: splenomegaly, impaired B-and T-cell ex vivo polyclonal responses, and viral load. In addition, 5-FU treatment significantly increased percentages of CD4+ and CD8+ T cells.

Impact of Microparticle Transarterial Chemoembolization (mTACE) on myeloid-derived suppressor cell subtypes in hepatocellular carcinoma: Clinical correlations and therapeutic implications.

Myeloid-derived suppressor cells (MDSCs) play a pivotal role in immunosuppression and tumor progression in hepatocellular carcinoma (HCC). While various treatments like surgical resection, ablation, and radiotherapy have been studied for their effects on circulating MDSC frequencies in HCC patients, the findings remain inconclusive. Transarterial Chemoembolization (TACE) stands as the standard care for unresectable HCC, with Microparticle TACE (mTACE) gaining prominence for its capacity to induce significant tumor necrosis. However, the immunological ramifications of such pathological outcomes are scarcely reported. This study aims to elucidate the alterations in MDSC subtypes, specifically monocytic MDSCs (mMDSCs) and early-stage MDSCs (eMDSCs), post-mTACE and to investigate their clinical correlations in HCC patients. A cohort comprising 75 HCC patients, 16 liver cirrhosis patients, and 20 healthy controls (HC) was studied. Peripheral blood samples were collected and analyzed for MDSC subtypes. The study also explored the associations between MDSC frequencies and various clinical parameters in HCC patients. The frequency of mMDSCs was significantly elevated in the HCC group compared to liver cirrhosis and HC. Importantly, mMDSC levels were strongly correlated with aggressive clinical features of HCC, including tumor size, vascular invasion, and distant metastasis. Post-mTACE, a marked reduction in mMDSC frequencies was observed, while eMDSC levels remained stable. Our findings underscore the critical role of mMDSCs in HCC pathogenesis and their potential as a therapeutic target. The study also highlights the efficacy of mTACE in modulating the immunosuppressive tumor microenvironment, thereby opening new avenues for combinatorial immunotherapeutic strategies in HCC management.

Decreased serum levels of IL-4 correlate with the efficacy of the PAI-1 inhibitor TM5614 in patients with malignant melanoma refractory to anti-PD-1 antibodies: post hoc study of TM5614-MM trial.

We previously reported that a combination of the PAI-1 inhibitor TM5614 and nivolumab resulted in a 25.9% response rate in patients with anti-PD-1 antibody failure. We therefore comprehensively evaluated the serum levels of chemokines and cytokines in patients enrolled in the protocol per set cohort of the TM5614-MM clinical trial (jRCT2021210029). Our present study revealed significant reductions in IL-4, IL-16 and CXCL2 in the response group treated with TM5614. Our findings suggest that the induction of an antitumour response in our previous clinical trial was due to the activation of tumour-associated macrophages through the blockade of M2 polarization and the reduction of monocytic myeloid-derived suppressor cells in the tumour-bearing host.

Age-related increase of CD38 directs osteoclastogenic potential of monocytic myeloid-derived suppressor cells through mitochondrial dysfunction in male mice.

An aged immune system undergoes substantial changes where myelopoiesis dominates within the bone marrow. Monocytic-MDSCs (M-MDSCs) have been found to play an important role in osteoclastogenesis and bone resorption. In this study, we sought to provide a more comprehensive understanding of the osteoclastogenic potential of bone marrow M-MDSCs during normal aging through transcriptomic and metabolic changes. Using young mature and aged mice, detailed immunophenotypic analyses of myeloid cells revealed that the M-MDSCs were not increased in bone marrow, however M-MDSCS were significantly expanded in peripheral tissues. Although aged mice exhibited a similar number of M-MDSCs in bone marrow, these M-MDSCs had significantly higher osteoclastogenic potential and greater demineralization activity. Intriguingly, osteoclast progenitors from aged bone marrow M-MDSCs exhibited greater mitochondrial respiration rate and glucose metabolism. Further, transcriptomic analyses revealed the upregulation of mitochondrial oxidative phosphorylation and glucose metabolism genes. Interestingly, there was 8-fold increase in Cd38 mRNA gene expression, consistent with the Mouse Aging Cell Atlas transcriptomic database, and confirmed by qRT-PCR. CD38 regulates NAD+ availability, and 78c, a small molecule inhibitor of CD38, reduced the mitochondrial oxygen consumption rate and glucose metabolism and inhibited the osteoclastogenic potential of aged mice bone marrow-derived M-MDSCs. These results indicate that the age-related increase in Cd38 expression in M-MDSCs bias the transcriptome of M-MDSCs towards osteoclastogenesis. This enhanced understanding of the mechanistic underpinnings of M-MDSCs and their osteoclastogenesis during aging could lead to new therapeutic approaches for age-related bone loss and promote healthy aging.