Myeloid-derived Suppressor Cells Subsets Research Articles

Monocytic myeloid-derived suppressor cells as an immune indicator of early diagnosis and prognosis in patients with sepsis

BackgroundImmunosuppression is a leading cause of septic death. Therefore, it is necessary to search for biomarkers that can evaluate the immune status of patients with sepsis. We assessed the diagnostic and prognostic value of low-density neutrophils (LDNs) and myeloid-derived suppressor cells (MDSCs) subsets in the peripheral blood mononuclear cells (PBMCs) of patients with sepsis.MethodsLDNs and MDSC subsets were compared among 52 inpatients with sepsis, 33 inpatients with infection, and 32 healthy controls to investigate their potential as immune indicators of sepsis. The percentages of LDNs, monocytic MDSCs (M-MDSCs), and polymorphonuclear MDSCs (PMN-MDSCs) in PBMCs were analyzed. Sequential organ failure assessment (SOFA) scores, C-reactive protein (CRP), and procalcitonin (PCT) levels were measured concurrently.ResultsThe percentages of LDNs and MDSC subsets were significantly increased in infection and sepsis as compared to control. MDSCs performed similarly to CRP and PCT in diagnosing infection or sepsis. LDNs and MDSC subsets positively correlated with PCT and CRP levels and showed an upward trend with the number of dysfunctional organs and SOFA score. Non-survivors had elevated M-MDSCs compared with that of patients who survived sepsis within 28 days after enrollment.ConclusionsMDSCs show potential as a diagnostic biomarker comparable to CRP and PCT, in infection and sepsis, even in distinguishing sepsis from infection. M-MDSCs show potential as a prognostic biomarker of sepsis and may be useful to predict 28-day hospital mortality in patients with sepsis.

The clinical association of programmed death-1/PD-L1 axis, myeloid derived suppressor cells subsets and regulatory T cells in peripheral blood of stable COPD patients.

Myeloid-derived suppressor cells (MDSCs) have crucial immunosuppressive role in T cell dysfunction in various disease processes. However, the role of MDSCs and their impact on Tregs in COPD have not been fully understood. The aim of the present study is to investigate the immunomodulatory role of MDSCs and their potential impact on the expansion and function of Tregs in COPD patients. Peripheral blood samples were collected to analyze circulating MDSCs, Tregs, PD-1/PD-L1 expression to assess the immunomodulatory role of MDSC and their potential impact on the expansion and function of Treg in COPD. A total of 54 COPD patients and 24 healthy individuals were enrolled in our study. Flow cytometric analyses were performed to identify granulocytic MDSCs (G-MDSCs), monocytic MDSCs (M-MDSCs), Tregs, and the expression of PD-1/PD-L1(L2) on MDSCs and Tregs in peripheral blood. Our results revealed a significantly higher percentage of G-MDSCs and M-MDSCs (p < 0.001) in COPD patients compared to the healthy controls. Additionally, a significantly higher proportion of peripheral blood Tregs was observed in COPD patients. Furthermore, an increased expression of cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) on Tregs (p < 0.01) was detected in COPD patients. The expression of PD-1 on CD4+ Tcells and Tregs, but not CD8+Tcells, was found to be increased in patients with COPD compared to controls. Furthermore, an elevated expression of PD-L1 on M-MDSCs (p < 0.01) was also observed in COPD patients. A positive correlation was observed between the accumulation of M-MDSCs and Tregs in COPD patients. Additionally, the percentage of circulating M-MDSCs is positively associated with the level of PD-1 (r = 0.51, p < 0.0001) and CTLA-4 (r = 0.42, p = 0.0014) on Tregs in COPD. The recruitment of MDSCs, accumulation of Tregs, and up-regulation of CTLA-4 on Treg in COPD, accompanied by an increased level of PD-1/PD-L1, suggest PD-1/PD-L1 axis may be potentially involved in MDSCs-induced the expansion and activation of Treg at least partially in COPD.

Abstract 5355: A novel subset of Treg-like MDSCs expressing LAG-3 found in advanced gastric cancer

Abstract The development and progression of cancers are frequently promoted by immunosuppressive cells, such as Treg and myeloid-derived suppressor cells (MDSCs) mediated by various immune checkpoint molecules. Therefore, MDSCs are potential diagnostic and therapeutic targets in cancer. However, the definitive cell surface markers for defining MDSC and the subset that correlates with cancer progression are not clear. In our previous studies, there was no difference in the amount of total granulocyte MDSCs (G-MDSCs) between early and advanced gastric cancer. We inferred that there is a novel subset of G-MDSCs involved in cancer progression rather than the previous marker-based classification. The purpose of this study is to analyze MDSCs in gastric cancer patients at different stages of progression and to identify subsets of G-MDSCs that are involved in cancer progression. As a result, we identified a subset of novel G-MDSCs that correlate with cancer progression by expressing LAG-3. LAG-3 is a molecule that is expressed in Tregs and causes strong immunosuppression, suggesting that it is involved in the immunosuppressive potential of MDSCs. Citation Format: Takumi Iwasawa, Suguru Yamauchi, Tetsu Fukunaga, Hajime Orita, Tomoaki Ito, Kato Kazunori. A novel subset of Treg-like MDSCs expressing LAG-3 found in advanced gastric cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5355.

Abstract 104: Profiling peripheral blood to predict response to targeted androgen receptor axis therapy in mice

Abstract Background: Targeting the androgen receptor (AR) signaling axis (ARAT) continues to be the mainstay treatment for advanced-stage prostate cancer. Using second-generation antiandrogens like abiraterone acetate (Abi) and apalutamide (Apa) has contributed to the survival of prostate cancer patients. However, resistance to these therapies remains a problem and most of these patients progress to castration-resistant prostate cancer (CRPC). Myeloid-derived suppressor cells (MDSCs) have been shown to drive CRPC. We previously showed that unfavorable responses to androgen deprivation therapy (ADT) or ADT plus Apa were associated with polymorphonuclear MDSCs (PMN-MDSCs) cells enriched in prostate tumors from conditional Pten/Trp53-double knockout (DKO) mice. Here, we explore the association between pre-treatment immune cell subsets blood and antitumor to ARAT therapy DKO mice. Methods: Twenty-eight-week-old DKO mice were surgically castrated and after four weeks were randomized to treatments with vehicle, Apa or Abi for an additional four weeks (n=20). Individual treatment responses were assessed and classified according to tumor burden as follows: high tumor burden (HTB), ≥20% of median; moderate tumor burden (MTB), -20% to 20% of median; or low tumor burden (LTB), ≤-20% of median. Peripheral blood was collected both before and after treatment and analyzed by multi-color flow cytometry panels for lymphoid and myeloid subsets. Blood samples from healthy wildtype and untreated DKO mice with castration-naïve prostate tumors were collected as reference samples. Subsets of PMN-MDSCs and monocytic-MDCSs (m-MDSCs) were represented as % of total abundance and 5 of parental population. revealed a signature that was correlated with treatment responses. Profiles were constructed and the data was used to train supervised learning models to predict treatment responses. Shapely additive explanations (ShAP) were used to determine feature importance. The model was tested and validated on an independent cohort of 20 DKO mice treated with ADT and ADT plus Abi. Results: Moderate prediction from baseline blood could be identified for tumor burden following ARAT using a Naïve Bayes classifier. Model evaluation, using an independent cohort, yielded favorable performance with area under the curve (AUC) mean, 0.707; HTB, 0.627; MTB, 0.750; and LTB, 0.745. The most important features for prediction were identified. Conclusion: Our study revealed that MDSC subsets present in blood were associated with treatment responses to ARAT. Citation Format: Marco A. De Velasco, Yurie Kura, Kazuko Sakai, Yoshitaka Saito, Takafumi Minami, Kazuhiro Yoshimura, Kazutoshi Fujita, Kazuto Nishio, Hirotsugu Uemura. Profiling peripheral blood to predict response to targeted androgen receptor axis therapy in mice [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 104.

Myeloid‑derived suppressor cell accumulation induces Treg expansion and modulates lung malignancy progression.

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous family of myeloid cells that suppress T cell immunity in tumor-bearing hosts. The present study aimed to examine roles of T and MDSC subsets in lung malignancy. The study analyzed 102 cases with lung malignancy and 34 healthy individuals. Flow cytometry was performed for identification of T cell and MDSC subsets and their phenotypic characteristics in peripheral blood. The lung malignancy cases exhibited lower frequencies of granulocyte-like MDSCs (G-MDSCs) expressing PD-L2 and PD-L1 than healthy controls (P=0.013 and P<0.001, respectively). Additionally, there was a higher frequency of monocyte-like MDSCs (M-MDSCs) expressing PD-L1 in the peripheral blood of patients with lung malignancy than healthy controls (P<0.001). The frequencies of G-MDSCs and M-MDSCs were positively correlated with proportions of PD-1+ and CTLA-4+ regulatory T cells (Tregs). In vitro co-culture assay demonstrated M-MDSCs of lung malignancy enhanced naive T cell apoptosis and promoted Treg subset differentiation compared with M-MDSCs of healthy controls. The findings suggested accumulation of MDSC subsets in lung malignancy and MDSCs expressing PD-L2 and PD-L1 induced Treg expansion by binding to PD-1 on the surface of Tregs.

Accumulation of circulating myeloid-derived suppressor cell subsets: predicting poor clinical efficacy and prognosis through T cell suppression in non-Hodgkin's lymphoma.

Myeloid-derived suppressor cells (MDSC) are implicated in the regulation of immune responses closely associated with poor clinical outcomes in cancer. However, the MDSC subtypes in non-Hodgkin's Lymphoma (NHL) has not been systematically investigated. So we investigated the percentage of MDSC subsets in 78 newly diagnosed NHL patients by flow cytometry. The results showed that all MDSC subsets increased in NHL patients compared to healthy donors. Notably, MDSC, M-MDSC, and CD14+CD66b+MDSC significantly increased in NHL patients compared to those with lymphadenitis. PMN-MDSC, e-MDSC and IPI were independent risk factors for poor clinical efficacy and were involved in constructing the nomogram for predicting clinical efficacy. Progression-free survival (PFS) was significantly shorter in patients with high level of MDSC subsets, and PMN-MDSC emerged as an independent prognostic factor for PFS. PMN-MDSC, e-MDSC and IPI were involved in constructing the nomogram for predicting PFS. Patients with a higher percentage of MDSC, PMN-MDSC, e-MDSC, and CD14+CD66b+MDSC experienced a shorter OS compared to those with lower percentages. In addition, research on mechanisms found that T cell function was suppressed and mediated by the expansion of MDSC via involving Arg-1 and IL-10 in vitro and in vivo. In conclusion, our study demonstrates that the increased circulating MDSC subsets predict poor clinical efficacy and prognosis in NHL, potentially involving T cell suppression through MDSC subsets expansion. These findings indicate the potential of MDSC subsets as comprehensive diagnostic, prognostic biomarkers, and therapeutic targets for NHL.

Decreased circulating myeloid-derived suppressor cell count at the engraftment is one of the risk factors for multiple myeloma relapse after autologous hematopoietic stem cell transplantation

Recent studies demonstrated that myeloid-derived suppressor cells (MDSCs) are involved in the pathogenesis and progression of multiple myeloma (MM). Nevertheless, data on the quantitative and functional changes in MDSCs during standard MM treatment remain poorly understood. Here, we determined that monocytic MDSCs (M-MDSC; CD14+HLA-DRlow/–) and granulocytic MDSCs (PMN-MDSC; Lin–HLA-DR–CD33+CD66b+) in MM patients in remission following induction therapy (IT) were significantly increased, while early MDSCs (E-MDSCs; Lin–HLA-DR–CD33+CD66b–) were decreased compared to the donor group. In progression, MM patients had the most pronounced decrease in E-MDSCs and enhanced levels of PMN-MDSCs. IT was accompanied with a decrease in the expression of arginase-1 (Arg-1). In MM patients with relapse or resistance to IT, Arg-1+ cell frequency in M-MDSCs and E-MDSCs, as well as PD-L1+ M-MDSCs, was increased, which may facilitate tumor immunosuppression. G-CSF administration led to a significant increment in the MDSC subsets. At the engraftment, circulating M-MDSC and PMN-MDSCs were temporarily increased, with a gradual decline to the pre-transplant levels in 12 months. The percentage of E-MDSCs was decreased at the leukocyte recovery. Patients with a higher (>Me) M-MDSC count at the engraftment had a shorter post-transplant leukopenia duration (Me 11 vs. 13 days; pU = 0.0086). The advanced MM stage, depth of response, and lower relative count of circulating E-MDSCs at the engraftment were independent risk factors associated with a lower progression-free survival.The obtained data allow us to hypothesize that MDSCs may play a positive role at the stage of leukocyte recovery by ameliorating the long-term anti-tumor response in MM.

Myeloid derived suppressor cells in peripheral blood can be a prognostic factor in canine transitional cell carcinoma

Myeloid-derived suppressor cells (MDSCs) are immature cells with immunosuppressive properties found in the tumor microenvironment. MDSCs are divided into two major subsets: polymorphonuclear MDSCs (PMN-MDSCs) and monocytic MDSCs (M-MDSCs). Both MDSC subsets contribute to the creation of an immunosuppressive environment for tumor progression. In humans, patients with high levels of MDSCs show worse outcomes for several types of cancers. However, the association between MDSCs and clinical features has rarely been investigated in canine studies. In the present study, we measured the proportion of PMN-MDSCs and M-MDSCs in the peripheral blood and tumor tissue of dogs with hepatocellular carcinoma (HCC), prostate cancer (PC), transitional cell carcinoma (TCC), lymphoma, and pulmonary adenocarcinoma. Additionally, we examined immunosuppressive ability of PMN-MDSCs and M-MDSCs in peripheral blood mononuclear cells of TCC case on CD4+, CD8+ and interferon-γ+ cells and investigated the relationships of MDSCs with clinical features and outcomes. PMN-MDSCs increased in HCC, PC, TCC, and lymphoma. In contrast, M-MDSCs increased in the TCC. Both PMN-MDSCs and M-MDSCs exhibited immunosuppressive effects on CD8+, CD4+ and interferon-γ+ cells. In dogs with TCC, lymph node metastasis was associated with high level of PMN-MDSCs but not with M-MDSCs. High levels of both PMN-MDSCs and M-MDSCs were related to advanced tumor stage. Kaplan-Meier analysis revealed that high levels of both PMN-MDSCs and M-MDSCs were significantly associated with shorter overall survival. In addition, the Cox proportional hazard regression model showed that M-MDSCs and the tumor stage were independent prognostic factors for TCC. These results suggest that PMN-MDSCs and M-MDSCs may be involved in tumor progression and could be prognostic factors and promising therapeutic targets in dogs with TCC.

Phenotypic Analysis of Circulating Myeloid Derived Suppressor Cells and Their Subpopulations in Egyptian Females with Breast Cancer: A Single-Centre Case-Control Study.

Myeloid-derived suppressor cells (MDSC) are immature myeloid cells with suppressive function that has been thoroughly documented in the setting of cancer. Our purpose was to evaluate levels of MDSC and their subsets in a cohort of Egyptian patients with breast cancer. Evaluation of peripheral blood total MDSC and its subset was done using multicolor flowcytometry in 30 malignant, 10 benign breast tumor patients and 10 healthy control females. BC patients had higher total MDSC levels compared to controls (p= 0.01) particularly the Monocytic MDSC (M-MDSC) and abnormal MDSC subsets (p = 0.001 and p <0.001, respectively). A tumor size > 2 cm exhibited significantly higher granulocytic MDSCs (G-MDSCs) compared to tumor size < 2 cm (p= 0.02) whereas abnormal MDSCs were significantly higher in patients with a tumor size < 2 cm (p = 0.037). MDSC and its subsets can be used as a prognostic marker of tumor size as well as a potential targets for treatment in breast cancer patients.

Assessment of myeloid-derived suppressor cell differentiation ex vivo.

Myeloid-derived suppressor cells (MDSCs) are major promoters of progression and metastasis in cancer. MDSCs inhibit the anti-tumor immune response through multiple mechanisms. The main MDSC functions in cancer are related to the inactivation of T cells and the establishment of an immunosuppressive tumor microenvironment (TME) through the production of pro-inflammatory cytokines, among other mechanisms. MDSCs are phenotypically similar to conventional myeloid cells, so their identification is challenging. Moreover, they infiltrate the tumors in limited numbers, and their purification from within the tumors is technically difficult and makes their study a challenge. Therefore, several ex vivo differentiation methods have been established. Our differentiation method leads to MDSCs that closely model tumor-infiltrating counterparts. In this protocol, MDSCs are differentiated from bone marrow precursors by incubation in differentiation medium produced by murine tumor cell lines engineered to constitutively express granulocyte-monocyte colony stimulating factor (GM-CSF). These ex vivo-generated MDSC subsets show high fidelity compared to their natural tumor-infiltrated counterparts. Moreover, the high yields of purification from these ex vivo differentiated MDSC enable their use for validation of new treatments in high-throughput assays. In this chapter we describe the engineering of a stable cell line overexpressing GM-CSF, followed by production and collection of conditioned media supporting MDSC differentiation. Finally, we detail the isolation procedure of bone marrow cells and the specific MDSC differentiation protocol.

Trichosanthin alleviates streptozotocin-induced type 1 diabetes mellitus in mice by regulating the balance between bone marrow-derived IL6+ and IL10+ MDSCs

Myeloid-derived suppressor cells (MDSCs) occupy a pivotal role in the intricate pathogenesis of the autoimmune disorder, Type 1 diabetes mellitus (T1DM). Since our previous work demonstrated that trichosanthin (TCS), an active compound of Chinese herb medicine Tian Hua Fen, regulated immune response, we aimed to clarify the efficacy and molecular mechanism of TCS in the treatment of T1DM. To this end, T1DM mouse model was established by streptozotocin (STZ) induction. The mice were randomly divided into normal control group (Ctl), T1DM group (STZ), TCS treated diabetic group (STZ + TCS) and insulin-treated diabetic group (STZ + insulin). Our comprehensive evaluation encompassed variables such as blood glucose, glycosylated hemoglobin, body weight, pertinent biochemical markers, pancreatic histopathology, and the distribution of immune cell populations. Furthermore, we meticulously isolated MDSCs from the bone marrow of T1DM mice, probing into the expressions of genes pertaining to the advanced glycation end product receptor (RAGE)/NF-κB signaling pathway through RT-qPCR. Evidently, TCS exhibited a substantial capacity to effectively counteract the T1DM-induced elevation in random blood glucose, glycosylated hemoglobin, and IL-6 levels in plasma. Pathological scrutiny underscored the ability of TCS to mitigate the damage incurred by islets. Intriguingly, TCS interventions engendered a reduction in the proportion of MDSCs within the bone marrow, particularly within the IL-6+ MDSC subset. In contrast, IL-10+ MDSCs exhibited an elevation following TCS treatment. Moreover, we observed a significant down-regulation of relative mRNA of pro-inflammatory genes, including arginase 1 (Arg1), inducible nitric oxide synthase (iNOS), RAGE and NF-κB, within MDSCs due to the influence of TCS. It decreases total MDSCs and regulates the balance between IL-6+ and IL-10+ MDSCs thus alleviating the symptoms of T1DM. TCS also down-regulates the RAGE/NF-κB signaling pathway, making it a promising alternative therapeutic treatment for T1DM. Collectively, our study offered novel insights into the underlying mechanism by which TCS serves as a promising therapeutic intervention for T1DM.

Mass cytometry and transcriptomic profiling reveal PD1 blockade induced alterations in oral carcinogenesis.

Oral squamous cell carcinoma is the predominant subtype of head and neck squamous cell carcinoma, characterized by a challenging prognosis. In this study, we established a murine model of oral carcinogenesis using 4-nitroquinoline-1-oxide (4-NQO) induction to investigate the impact of immunotherapy on microenvironmental alterations. Mice in the precancerous condition were randomly divided into two groups:one receiving programmed death-1 (PD1) monoclonal antibody treatment and the other, control immunoglobulin G. Our observations showed that while PD1 blockade effectively delayed the progression of carcinogenesis, it did not completely impede or reverse it. To unravel the underlying reasons for the limited effectiveness of PD1 blockade, we collected tongue lesions and applied mass cytometry (CyTOF) and RNA sequencing (RNA-seq) to characterize the microenvironment. CyTOF analysis revealed an increased macrophage subset (expressing high levels of IFNγ and iNOS) alongside a diminished Th1-like subset (exhibiting low expression of TCF7) and three myeloid-derived suppressor cell subsets (displaying low expression of MHC Class II or IFNγ) following anti-PD1 treatment. Notably, we observed an increased presence of cancer-associated fibroblasts (CAFs) expressing collagen-related genes after PD1 blockade. Furthermore, we found a negative correlation between the infiltration levels of CAFs and CD8+ T cells. These findings were validated in murine tongue tissue slides, and publicly available multi-omics datasets. Our results suggest that CAFs may impair the therapeutic efficacy of PD1 blockade in oral carcinogenesis by the remodeling of the extracellular matrix.

Comparison of Myeloid-Derived Suppressor Cells (MDSC) in children with RSV vs. COVID-19

Abstract Introduction Lower respiratory tract infections (LRTI) caused by respiratory syncytial virus (RSV) result in over 100,000 deaths of infants globally. Though adults account for most COVID-19 hospitalizations, children also develop severe disease due to SARS-CoV-2. Children with severe illness due to LRTI demonstrate evidence of impaired adaptive immune function. MDSC are an immature, heterogenous cell population that expands significantly during inflammatory conditions. MDSC suppress T cell proliferation and function resulting in immunosuppression. MDSC subsets (granulocytic (G) MDSC and the monocytic (M-)MDSC) suppress T cells via distinct mechanisms. In a previous study, we observed a significant increase in G-MDSC in children with septic shock. We hypothesize that children with severe LRTI with RSV or COVID-19 will have expansion of MDSC that will be associated with differences in T cell subset composition and worse clinical outcomes. Methods Prospective, observational study in children admitted to the pediatric intensive care unit (PICU) with symptomatic RSV or COVID-19, defined by a positive polymerase chain reaction test. Children with multi-system inflammatory syndrome or positive for both RSV and COVID-19 were excluded. Pre-pandemic healthy control samples were obtained from children requiring IV placement for outpatient MRI. Peripheral blood mononuclear cells were isolated by ficoll gradient and stained for surface markers to identify MDSC (CD45+, HLA-DR-, CD33+ and CD11b+), including G- (CD15+, CD14-) and M-MDSC (CD14+, CD15-), and T cell populations. Clinical and demographic data were collected from the electronic medical record and stored in a secure database. Results We enrolled 30 children, 20 with RSV (50% male, median age 2 [1.2-5] months), 10 with COVID-19 (30 % male, median age 25 [ 3.8 – 215] months), and 30 healthy controls (64% male, median age 73.2 [57.6, 98.4] months. Children with severe LRTI due to RSV or COVID-19 have significantly increased percentage MDSC of PBMC compared to healthy controls (13% [5.6,22] vs 9.9% [5.2, 23] vs 0.95 [0.34, 2.8] respectively). Compared to children with COVID-19, children with RSV had higher percentage M-MDSC of total MDSC (90% [87,97] vs 45% (8.4, 71], p&amp;lt; 0.0001) and lower G-MDSC (1.1% [0.44, 3.0] vs 38% [17,90], p&amp;lt;0.0001). Children with RSV had a larger percentage of T regulatory cells of total CD4+ T cells (8.0% [6.1, 9.0] vs 4.3% [3.3, 5.8], p=0.01) and were more likely require non-invasive or invasive ventilatory respiratory support than those with COVID-19 (75% vs 30%, p=0.04). Conclusions Total MDSC are significantly expanded in children with severe LRTI due to RSV and COVID-19 compared to healthy controls, but with significantly different subset distributions. Children with RSV demonstrate a predominance of M-MDSC, while children with COVID-19 demonstrate significantly higher G-MDSC. Children with RSV were also more likely to have expanded Treg cell population and require higher level respiratory support. These findings suggest that MDSC composition and suppressive mechanisms may be partially driven by viral pathogen. Larger studies are needed to confirm these findings and to investigate the role of MDSC-mediated immune suppression in children with severe LRTI to identify this cell population as a potential therapeutic target.

IMMU-35. G-AMINOBUTYRIC ACID DRIVES GLIOBLASTOMA IN FEMALES BY ACTIVATING THE COMPLEMENT SYSTEM

Abstract Interaction between tumor and neural cells drives the progression of glioblastoma (GBM), which is characterized by enhanced immunosuppressive myeloid cell accumulation. Our previous results revealed that myeloid-derived suppressor cell subsets (MDSCs) play a central role in tumorigenesis in a sex-specific manner, with monocytic MDSCs (mMDSCs) accumulating in male tumors and granulocytic MDSCs (gMDSCs) correlating with a worse outcome in females. However, host factors governing sex differences in MDSC subset activity remained unknown. Here, we report that g-aminobutyric acid (GABA) receptor expression by gMDSCs informs their sex-specific behavior. We observed that only female gMDSCs but not male gMDSCs or mMDSCs from either sex respond to GABA by upregulating the antiviral innate immune pathway. As part of this signature, GABA-stimulated female gMDSCs had higher complement 1qa (C1qa) expression. To test the potential role of the GABA pathway on GBM outcome, we tested the GABA analogue pregabalin in preclinical models. Female mice treated with pregabalin succumbed to disease earlier, consistent with our previous observation that gMDSCs have a central role in GBM progression in females. In contrast, pregabalin treatment had no effect in male mice with tumors or immunocompromised female mice. To further evaluate whether C1q is a relevant physiological target, we performed single-cell sequencing of tumor-infiltrating versus circulating MDSC subsets and detected high levels of C1q expression in gMDSCs from tumors. C1q KO transgenic female mice had significantly better outcomes compared to wild-type littermates upon implantation with syngeneic mouse GBM lines, while C1q expression status did not impact the outcome in males. Correspondingly, only in female patients C1q expression correlated with poor prognosis. Collectively, these results identify a neuron-immune-cancer communication axis and indicate that GABA and C1q alter anti-tumor immune responses in a sex-specific manner. These results support the future assessment of the GABA pathway and complement inhibitors as potential immunotherapy agents.

MDSCs-derived GPR84 induces CD8+ T-cell senescence via p53 activation to suppress the antitumor response

BackgroundsG-protein-coupled receptor 84 (GPR84) marks a subset of myeloid-derived suppressor cells (MDSCs) with stronger immunosuppression in the tumor microenvironment. Yet, how GPR84 endowed the stronger inhibition of MDSCs to CD8+...

The Effects of Adjuvant Chemoradiotherapy (CRT) on Myeloid-Derived Suppressor Cell (MDSC) Subsets in Glioblastoma (GBM)

GBM continues to be a diagnosis with an exceedingly low survival rate despite standard therapy of resection followed by concurrent CRT. MDSC, immunosuppressive myeloid cells that aid immune system evasion by the tumor, expand during fractionated RT. To date, little is known about the effects of CRT on MDSC subsets. The goal of our pilot study is to compare peripheral blood MDSC subset frequency in patients (pts) undergoing CRT. We hypothesize that the pro-tumor, monocytic MDSC (M-MDSC) subset increases following CRT. Pts over the age of 18 yo with a new diagnosis of GBM from a single institution participated in the study between 7/2022 -1/2023. Exclusion criteria included prior history of brain RT. Baseline peripheral blood samples were collected within one week prior to CRT start and post-CRT samples were collected within the last week of CRT. Peripheral blood mononuclear cells (PBMC) were isolated from whole blood and freshly stained for intracellular flow cytometric analyses. Total MDSC (singlet, viable, non-lymphocyte, CD11b+CD33+ HLA-DR- cells) and subsets (M-MDSC, granulocytic (G-MDSC), and early MDSC (eMDSC)) were identified. Percent frequency (%fx) of total and MDSC subsets as well as MDSC activation status (n = 3) (interleukin (IL)-10, transforming growth factor-β (TGF-β), interferon gamma (IFNγ)) was compared before and after CRT. The average age of pts receiving CRT (n = 4) was 70 yo. Fractionated RT consisted of CF RT (n = 2), 6000 cGy in 30 fractions, and HF RT (n = 2), 4005 cGy in 15 fractions. All pts received concurrent chemotherapy with temozolomide. The %fx of MDSC of non-lymphocytes started at 29.2% prior to CRT and decreased to 9.9% at the end of CRT. The fold change of %fx of total MDSC in CF RT and HF RT was 0.39 and 0.29, respectively. The mean change in %fx of MDSC subsets before and after CRT are shown in Table 1. The mean %fx of TGF-β-expressing MDSC in all GBM pts increased by 3.5% after CRT. The mean IFNγ+ MDSC %fx for all GBM pts decreased after CRT from 24.2% to 16.2% with a corresponding decrease in geometric mean fluorescence intensity (GMFI). The mean %fx of IL-10+ MDSC decreased by 1.5% at the end of CRT with a decrease in GMFI from 5550 to 1806. In this limited dataset of pts with GBM receiving standard of care adjuvant therapy, we identified an expansion in the eMDSC and decrease in the M-MDSC subsets. These early results suggest HF RT may promote immunity that is more supportive of anti-tumor function, with a lesser increase in fold change of total MDSC after CRT. A more detailed understanding of the effect of RT on myeloid subpopulations is essential to addressing immune suppression in pts with GBM.

Effect of External Beam Radiation Therapy (EBRT) and Brachytherapy (BT) on Circulating MDSC Populations in Patients Treated Definitively for Cervical Cancer

The immunosuppressive function of myeloid derived suppressor cells (MDSCs) has been implicated in the regulation of immune responses against cancer. MDSCs have been associated with progression and poor response to therapy in various types of cancer, including cervical cancer. Radiation treatment (RT) alters immune cell populations within the tumor and is thought to augment antitumor responses. However, whether RT also recruits immunosuppressive MDSC populations is not well understood. Here, we investigate how circulating MDSC populations change in response to RT and if changes in MDSC frequency or subsets is predictive of RT responses in cervical cancer patients. Newly diagnosed, treatment-naïve pts with locally advanced carcinoma of the cervix will be enrolled from July 2022 to July 2023. EBRT to the pelvis was delivered at a dose of 45 Gy in 25 fractions with a simultaneous integrated boost of 52-55 Gy to involved regional lymph nodes and parametria and concurrent weekly cisplatin. Gross tumor was boosted via interstitial or tandem ring BT (22.5-27.5 Gy) after completion of EBRT. Serial blood samples were collected prior to initiating therapy (T0), post-EBRT and pre-BT (T1), and one-month post-BT (T2). Treatment response was determined based on pre-treatment MRI compared to MRI post-EBRT. Peripheral blood mononuclear cells (PBMCs) were isolated from whole blood using density gradient centrifugation and stained for analysis via flow cytometry. MDSC populations were identified by Live/Dead-CD11b+CD33+HLA-DR- staining. MDSC subsets were further subdivided into granulocytic (G-, CD15+CD14-), monocytic (M-, CD15-CD14+), or early-MDSCs (e-, CD15-CD14-). Blood samples were collected at indicated time points for four patients (FIGO stage IIA-IIB). Three had partial responses to chemoradiotherapy (CRT), while one had a complete response. All three patients with partial response had an increase in total frequency of circulating MDSCs in response to EBRT/BT (mean %fx MDSC 16.6 at T0 to 35.9 at T2), and an increase in total MDSCs in two of these patients occurred with EBRT alone. Interestingly, the patient that had a complete response had fewer MDSCs at T2 relative to T0 (35.8% at T0 to 27% at T2). Proportion of MDSC subsets varied considerably among the patients, and all had altered distribution of subsets in response to RT. G-MDSCs expanded the most to RT while M-MDSCs and e-MDSCs were less affected (mean fold change from T0 to T2 G-MDSC 4.75, M-MDSC 1.27, e-MDSC 0.942). In this cohort of patients, an increase in MDSC frequency occurred after RT and altered subset distribution. Only the patient with a complete response had fewer total MDSCs following completion of CRT, suggesting further studies are needed to determine if circulating MDSCs could be a biomarker for treatment response to RT in cervical cancer.

Myeloid-derived suppressor cells in the therapy of autoimmune diseases.

Myeloid-derived suppressor cells (MDSCs) are well recognized as critical factors in the pathology of tumors. However, their roles in autoimmune diseases are still unclear, which hampers the development of efficient immunotherapies. The role of different MDSCs subsets in multiple sclerosis, inflammatory bowel diseases, rheumatoid arthritis, type 1 diabetes, and systemic lupus erythematosus displayed different mechanisms of immune suppression, and several studies pointed to MDSCs' capacity to induce T-helper (Th)17 cells and tissue damage. These results also suggested that MDSCs could be present in different functional states and utilize different mechanisms for controlling the activity of T and B cells. Therefore, various therapeutic strategies should be employed to restore homeostasis in autoimmune diseases. The therapies harnessing MDSCs could be designed either as cell therapy or rely on the expansion and activation of MDSCs in vivo, or their depletion. Cumulatively, MDSCs are inevitable players in autoimmunity, and rational approaches in developing therapies are required to avoid the adverse effects of MDSCs and harness their suppressive mechanisms to improve the overall efficacy of autoimmunity therapy.

The distribution of myeloid-derived suppressor cells subsets and up-regulation of programmed death-1/PD-L1 axis in peripheral blood of adult CAP patients.

Myeloid-derived suppressor cells (MDSCs) have been reported to expand and have a potent ability in the expansion of regulatory T cells in malignant and infectious disease. The current study was performed to investigate the role of MDSCs and possible immune mechanisms in dampening immune responses of community acquired pneumonia (CAP). This was a single-center cross-sectional study. The distribution of MDSCs subsets, the PD-1/PD-L1(L2) level of MDSCs subsets and Tregs in the peripheral blood of adult CAP patients and healthy control were measured by flow cytometry analysis. Peripheral blood mononuclear cells (PBMCs) from 63 adult CAP patients contained an elevated frequency of both G-MDSC (4.92±0.30 vs 2.25±0.21,p<0.0001) and M-MDSC (19.40±1.30 vs 9.64±0.57,p<0.001) compared to healthy controls. Treg in the peripheral blood of CAP patients exhibited increased expression of PD-1 and CTLA-4, accompanied by no difference of their frequency. Moreover, up-regulated expression of PD-L1 on MDSC subsets in the peripheral blood of CAP patients was also revealed. Of note, the frequency of circulating MDSCs subset displayed a positive correlation with neutrophil count percentage in blood in CAP patients. In summary, the significant expansion of circulating MDSCs subsets and the up-regulated expression of PD-1/PD-L1 level in CAP patients may suggest the possible involvement of PD-1/PD-L1axis in MDSCs mediated immune regulation on Treg at least partially in CAP patients.

Decreased programmed cell death ligand 2-positive monocytic myeloid-derived suppressor cells and programmed cell death protein 1-positive T-regulatory cells in patients with type 2 diabetes: implications for immunopathogenesis.

The activation of immune cells plays a significant role in the progression of type 2 diabetes. This study aimed to investigate the potential role of myeloid-derived suppressor cells (MDSCs) and T-regulatory cells (Tregs) in type 2 diabetes. A total of 61 patients diagnosed with type 2 diabetes were recruited. Clinical characteristics were reviewed and peripheral blood samples were collected. We calculated the percentage of different cells. Frequencies of MDSC subsets refered to the percentage of G-MDSCs (CD15+CD33+CD11b+CD14-HLA-DR-/low) in CD45 positive cells and the percentage of M-MDSCs (CD14+CD15-CD11b+CD33+HLA-DR-/low) in lymphocytes plus monocytes. Frequencies of programmed cell death ligand 1-positive granulocytic MDSCs (PD-L1+ G-MDSCs), programmed cell death ligand 2-positive monocytic MDSCs (PD-L2+ M-MDSCs), PD-L2+ G-MDSC, and programmed cell death protein 1-positive Tregs (PD-1+Tregs) were decreased in patients with type 2 diabetes. The frequency of PD-1+ Tregs was positively related to PD-L2+ M-MDSCs (r= 0.357, P = 0.009) and negatively related to HbA1c (r = -0.265, P = 0.042), fasting insulin level (r = -0.260, P = 0.047), and waist circumference (r = -0.373, P = 0.005). Decreased PD-L2+ M-MDSCs and PD-1+ Tregs may promote effector T cell activation, leading to chronic low-grade inflammation in type 2 diabetes. These findings highlight the contribution of MDSCs and Tregs to the immunopathogenesis of type 2 diabetes and suggest their potential as targets for new therapeutic approaches.