scholarly journals T-Cell Defect in Diffuse Large B-Cell Lymphomas Involves Expansion of Myeloid Derived Suppressor Cells Expressing IL-10, PD-L1, and S100A12

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 1478-1478 ◽  
Author(s):  
Imane Azzaoui ◽  
Fabrice Uhel ◽  
Delphine Rossille ◽  
Céline Pangault ◽  
Joelle Dulong ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
Cell Proliferation ◽  
T Cell ◽  
B Cell ◽  
Suppressor Cells ◽  
T Cell Proliferation ◽  
Myeloid Derived Suppressor Cells ◽  
Arginase 1 ◽  
Culture Supernatants ◽  
Large B Cell

Abstract Introduction: In diffuse large B-cell lymphoma (DLBCL), the number of circulating monocytes and neutrophils represents an independent prognostic factor. These cells include monocytic and granulocytic myeloid derived suppressor cells (M- and G-MDSCs) defined by their ability to suppress T-cell responses. MDSCs are a heterogeneous population described in inflammatory or infectious diseases as well as in numerous tumors including multiple myeloma, chronic lymphocytic leukemia and DLBCL. However, their mechanisms of action in DLBCL remain unclear. The aim of the study was to investigate the presence and mechanisms of suppression of MDSC subsets in DLBCL. Methods: Whole blood from 56 DLBCL at diagnosis and 45 healthy donors (HD) were analyzed by flow cytometry. Quantitative Real Time PCR were analyzed on Taqman@ array microfluidic cards. Cytokine levels in plasma and culture supernatants were measured by Luminex and Elisa. T-cell proliferation after monocyte depletion or treatment with inhibitors, was analyzed by CFSE assay. Results: By flow cytometry, we identified an expansion of G-MDSC (Linneg HLA-DRneg CD33pos CD11bpos) and M-MDSC (CD14pos HLA-DRlow) in DLBCL compared to HD (p<0.001). Interestingly, only M-MDSC number was correlated with the International Prognostic Index (IPI), the event-free survival (EFS), and the number of circulating Treg. Furthermore, T-cell proliferation was restored after monocyte depletion. To identify the mechanism of suppression involved, we evaluated the gene expression of key enzymes (ARG1, IDO1, NOS2, HO-1 and PTGS2) or immunomodulatory molecules (IL10, TGF β1, CD274/PD-L1, S100A8, S100A9, S100A12) involved in MDSC biology. ARG1, IDO1, IL10, CD274/PD-L1 and S100A12 were significantly up-regulated in DLBCL (p<0.05). At the protein level arginase 1, IL-10 and S100A12 were increased in DLBCL plasma, whereas PD-L1 expression on monocyte was increased in DLBCL compared to HD (p=0.03). Arginase 1 and IDO activities where increased in DLBCL patients. In DLBCL, IL-10 and S100A12 were detected in culture supernatants from stimulated PBMC and these molecules were decreased after CD14pos depletion (p<0.05). Finally, we defined 2 groups of DLBCL depending on M-MDSC content and analyzed the percentage of proliferating T cells after CD3/CD28 stimulation in the presence of various inhibitors or blocking antibodies (L-1MT, nor-NOHA, anti-IL-10, anti-PD-1 and anti-S100A12). In the group of patients with circulating MDSC, neutralizing IL-10, PDL-1 and S100A12 resulted in an increase of CD4 and/or CD8 T-cell proliferation. Conclusion: In summary, we identified MDSC subsets expanded in DLBCL as well as new mechanisms of immunosuppression in DLBCL. Myeloid-dependent T-cell suppression is attributed to a release of IL-10 and S100A12 and an increase of PD-L1 expression. Disclosures Cartron: Roche: Consultancy, Honoraria; GSK: Honoraria; Celgene: Honoraria; Sanofi: Honoraria; Gilead: Honoraria.

473 Mavrilimumab, a human monoclonal antibody targeting GM-CSFRα, inhibits polarization to myeloid-derived suppressor cells (MDSCs) that express PD-L1 and restores T-cell proliferation in vitro

2020 ◽  
Vol 8 (Suppl 3) ◽  
pp. A504-A504
Author(s):  
Luis Carvajal ◽  
Luciana Gneo ◽  
Carmela De Santo ◽  
Matt Perez ◽  
Tracy Garron ◽  
...  
Keyword(s):  
Pancreatic Cancer ◽  
Cell Proliferation ◽  
T Cell ◽  
Cancer Cell ◽  
Suppressor Cells ◽  
T Cell Proliferation ◽  
Myeloid Derived Suppressor Cells ◽  
Gm Csf ◽  
Macrophage Colony Stimulating Factor ◽  
Macrophage Colony

BackgroundMyeloid-derived suppressor cells (MDSCs) accumulate in the blood and tumor microenvironment (TME) and suppress anti-tumor immune responses.1 Cancer cells express the granulocyte-macrophage colony-stimulating factor (GM-CSF), which drives MDSC differentiation and function.2 3 4 It is upregulated in several cancers, including mesothelioma, pancreatic and colorectal, and it is linked to higher levels of intra-tumoral MDSCs and poorer overall survival.2 4 5 In animal models, knockdown of GM-CSF in pancreatic epithelium or pancreatic mesenchymal stem cells inhibits tumorigenesis, reduces intra-tumor MDSCs and enhances CD8+ T cell accumulation.6 7 8 Therefore, targeting the GM-CSF receptor alpha (GM-CSFRα) on MDSCs is an attractive strategy to restore anti-tumor immunity. Mavrilimumab is a clinical stage fully human monoclonal antibody that blocks GM-CSFRα. It has demonstrated efficacy and acceptable safety profile in patients with rheumatoid arthritis, and it’s currently undergoing investigation in phase II studies in giant cell arteritis and in patients with severe COVID-19 pneumonia and hyper-inflammation (NCT03827018, NCT04397497, respectively). The present study investigates its potential as a therapeutic strategy to target MDSCs in the TME as an adjuvant to immunotherapy.MethodsCancer cell supernatants were collected when cells reached confluency. Human GM-CSF was measured by ELISA. Healthy donor CD14+ monocytes were incubated (± mavrilimumab) with cancer cell supernatants for either 3 or 6 days followed by phenotypic analysis (CD14, CD33, HLA-DR, CD11b, CD206, CD80, PD-L1, Arginase-1) by flow cytometry. On day 3, autologous CD3+ T cells were stimulated with CD3/CD28 and IL-2 and co-cultured with putative MDSCs for 5 days. T-cell proliferation was evaluated by measuring carboxyfluorescein succinimidyl ester (CFSE) dilution in CD4+ and CD8+ T cells by flow cytometry.ResultsGM-CSF is expressed in the supernatant of cancer cell lines (HCT116, SW-480, Panc-1, Capan-1). Human monocytes cultured with conditioned medium from colorectal carcinoma (SW-480) or pancreatic adenocarcinoma (Capan-1) show downregulation of HLA-DR, increased expression of PD-L1, Arg-1, CD206, and can suppress T-cell proliferation in-vitro. Similarly, peripheral blood monocytes purified from pancreatic cancer patients suppress T-cell proliferation ex-vivo. Notably, Mavrilimumab inhibits the polarization of healthy donor monocytes to M-MDSCs and restores T-cell proliferation.ConclusionsTargeting of GM-CSFRα with mavrilimumab may alleviate the pro-tumorigenic and immunosuppressive functions of MDSCs in the TME. Future clinical studies should evaluate whether targeting of the GM-CSFRα in combination with immune checkpoint inhibitors is a viable therapeutic option to bolster their efficacy.Ethics ApprovalThe study was approved by the Institute of Immunology and Immunotherapy, University of Birmingham, UK Ethics Board. Healthy volunteer human material was obtained from commercial sources and approved by Stemexpress Institutional Review Board (IRB).ReferencesLaw AMK, Valdes-Mora F, Gallego-Ortega D. Myeloid-Derived Suppressor Cells as a Therapeutic Target for Cancer. Cells 2020;9(3):561.Khanna S, Graef S, Mussai F, et al. Tumor-Derived GM-CSF Promotes Granulocyte Immunosuppression in Mesothelioma Patients. Clin Cancer Res 2018;24(12):2859–2872.Dolcetti L, Peranzoni E, Ugel S, et al. Hierarchy of immunosuppressive strength among myeloid-derived suppressor cell subsets is determined by GM-CSF. Eur J Immunol 2010;40(1):22–35.Takeuchi S, Baghdadi M, Tsuchikawa T, et al. Chemotherapy-derived inflammatory responses accelerate the formation of immunosuppressive myeloid cells in the tissue microenvironment of human pancreatic cancer. Cancer Res 2015;75(13):2629–2640.Chen Y, Zhao Z, Chen Y, et al. An epithelial-to-mesenchymal transition-inducing potential of granulocyte macrophage colony-stimulating factor in colon cancer. Sci Rep 2017;7(1):8265.Bayne LJ, Beatty GL, Jhala N, et al. Tumor-derived granulocyte-macrophage colony-stimulating factor regulates myeloid inflammation and T cell immunity in pancreatic cancer. Cancer Cell 2012;21(6):822–835.Pylayeva-Gupta Y, Lee KE, Hajdu CH, Miller G, Bar-Sagi D. Oncogenic Kras-induced GM-CSF production promotes the development of pancreatic neoplasia. Cancer Cell 2012;21(6):836–847.Waghray M, Yalamanchili M, Dziubinski M, et al. GM-CSF mediates mesenchymal-epithelial cross-talk in pancreatic cancer. Cancer Discov 2016;6(8):886–899.

scholarly journals Expansion of Functional Myeloid-Derived Suppressor Cells in Controlled Human Malaria Infection

2021 ◽  
Vol 12 ◽  
Author(s):  
Carlos Lamsfus Calle ◽  
Rolf Fendel ◽  
Anurag Singh ◽  
Thomas L. Richie ◽  
Stephen L. Hoffman ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
T Cells ◽  
T Cell ◽  
Immune Responses ◽  
Malaria Infection ◽  
Malaria Vaccine ◽  
Suppressor Cells ◽  
T Cell Proliferation ◽  
Myeloid Derived Suppressor Cells ◽  
Controlled Human Malaria Infection

Malaria can cause life-threatening complications which are often associated with inflammatory reactions. More subtle, but also contributing to the burden of disease are chronic, often subclinical infections, which result in conditions like anemia and immunologic hyporesponsiveness. Although very frequent, such infections are difficult to study in endemic regions because of interaction with concurrent infections and immune responses. In particular, knowledge about mechanisms of malaria-induced immunosuppression is scarce. We measured circulating immune cells by cytometry in healthy, malaria-naïve, adult volunteers undergoing controlled human malaria infection (CHMI) with a focus on potentially immunosuppressive cells. Infectious Plasmodium falciparum (Pf) sporozoites (SPZ) (PfSPZ Challenge) were inoculated during two independent studies to assess malaria vaccine efficacy. Volunteers were followed daily until parasites were detected in the circulation by RT-qPCR. This allowed us to analyze immune responses during pre-patency and at very low parasite densities in malaria-naïve healthy adults. We observed a consistent increase in circulating polymorphonuclear myeloid-derived suppressor cells (PMN-MDSC) in volunteers who developed P. falciparum blood stage parasitemia. The increase was independent of preceding vaccination with a pre-erythrocytic malaria vaccine. PMN-MDSC were functional, they suppressed CD4+ and CD8+ T cell proliferation as shown by ex-vivo co-cultivation with stimulated T cells. PMN-MDSC reduced T cell proliferation upon stimulation by about 50%. Interestingly, high circulating PMN-MDSC numbers were associated with lymphocytopenia. The number of circulating regulatory T cells (Treg) and monocytic MDSC (M-MDSC) showed no significant parasitemia-dependent variation. These results highlight PMN-MDSC in the peripheral circulation as an early indicator of infection during malaria. They suppress CD4+ and CD8+ T cell proliferation in vitro. Their contribution to immunosuppression in vivo in subclinical and uncomplicated malaria will be the subject of further research. Pre-emptive antimalarial pre-treatment of vaccinees to reverse malaria-associated PMN-MDSC immunosuppression could improve vaccine response in exposed individuals.

Endoplasmic reticulum stress induced Lox-1+ CD15+ polymorphonuclear myeloid-derived suppressor cells in hepatocellular carcinoma and associated with poor prognsis.

2018 ◽  
Vol 36 (5_suppl) ◽  
pp. 38-38
Author(s):  
Xing Li ◽  
Xiang-yuan Wu ◽  
Nan Jiang ◽  
Yan-Fang Xing ◽  
Jie Chen ◽  
...  
Keyword(s):  
Hepatocellular Carcinoma ◽  
Cell Proliferation ◽  
T Cell ◽  
Binding Protein ◽  
Suppressor Cells ◽  
T Cell Proliferation ◽  
Mrna Levels ◽  
Dependent Manner ◽  
Myeloid Derived Suppressor Cells ◽  
Ifn Γ

38 Background: A recent study indicated that Lectin-type oxidized LDL receptor-1 (LOX-1) was a distinct surface marker for human polymorphonuclears myeloid-derived suppressor cells (PMN-MDSC). The present study was aimed to investigate the existence LOX-1 PMN-MDSC in hepatocellular carcinoma (HCC) patients, the latent mechanism and their association with clinical parameters. Methods: 30 HCC patients and 30 health control were included. LOX-1+CD15+ PMN-MDSCs were investigated. Results: LOX-1+CD15+ PMN-MDSC were significantly elevated in both WB and PBMC of HCC patients compared with healthy control. LOX-1+CD15+ PMN-MDSC were more abundant in PBMC than WB. Addition of PMN-MDSCs resulted in significantly reduced proliferation and IFN-γ production of T cells with a dosage dependent manner. LOX-1-CD15+ PMNs present no suppressive function. The suppression on T cell proliferation and IFN-γ production was reversed by ROS inhibitor and Arginase inhibitor. ROS level of LOX-1+CD15+ PMN by DCFDA were higher in LOX-1+CD15+ PMN-MDSCs than LOX-1-CD15+ PMNs, as well as the mRNA levels of the NADPH oxidase NOX2. Meanwhile, the expression of arginase I and activity of arginase were also significantly raised in LOX-1+CD15+ PMN-MDSCs. LOX-1+CD15+ PMN-MDSCs displayed significantly higher expression of spliced X-box–binding protein 1 (sXBP1), ATF3 and CCAAT/enhancer binding protein (CHOP) were higher. For HCC patients, LOX-1+CD15+ PMN-MDSCs in WB were positively related to Cancer of the Liver Italian Program (CLIP) score. Conclusions: LOX-1+CD15+ PMN-MDSC were elevated in HCC patients and suppressed T cell proliferation through ROS/Arg I pathway with ER stress as a potential feature. LOX-1+CD15+ PMN-MDSC presented positive association with the prognosis of HCC patients.

scholarly journals Inhibition of Arginase 1 Liberates Potent T Cell Immunostimulatory Activity of Human Neutrophil Granulocytes

2021 ◽  
Vol 11 ◽  
Author(s):  
Verena Vonwirth ◽  
Yagmur Bülbül ◽  
Anke Werner ◽  
Hakim Echchannaoui ◽  
Johannes Windschmitt ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
T Cells ◽  
T Cell ◽  
Immune Escape ◽  
Suppressor Cells ◽  
T Cell Proliferation ◽  
Neutrophil Granulocytes ◽  
Tumor Immune Escape ◽  
Cell Functions ◽  
Arginase 1

Myeloid cell arginase-mediated arginine depletion with consecutive inhibition of T cell functions is a key component of tumor immune escape. Both, granulocytic myeloid-derived suppressor cells (G-MDSC) and conventional mature human polymorphonuclear neutrophil granulocytes (PMN) express high levels of arginase 1 and can act as suppressor cells of adaptive anti-cancer immunity. Here we demonstrate that pharmacological inhibition of PMN-derived arginase 1 not only prevents the suppression of T cell functions but rather leads to a strong hyperactivation of T cells. Human PMN were incubated in cell culture medium in the absence or presence of an arginase inhibitor. T cells from healthy donors were then activated either polyclonally or in an antigen-specific manner in the supernatants of the PMN cultures at different PMN-T cell ratios. T cell proliferation was completely suppressed in these supernatants in the absence of an arginase inhibitor. Arginase inhibition led to a strong hyperinduction of T cell proliferation, which exceeded control activation conditions up to 25-fold. The hyperinduction was correlated with higher PMN-T cell ratios and was only apparent when PMN arginase activity was blocked sufficiently. The T cell stimulatory factor was liberated very early by PMN and was present in the &lt; 3 kDa fraction of the PMN supernatants. Increased T cell production of specific proinflammatory cytokines by PMN supernatant in the presence of arginase inhibitor was apparent. Upon arginase inhibition, downregulation of important T cell membrane activation and costimulation proteins was completely prevented or de novo induction accelerated. Antigen-specific T cell cytotoxicity against tumor cells was enhanced by PMN supernatant itself and could be further increased by PMN arginase blockade. Finally, we analyzed anergic T cells from multiple myeloma patients and noticed a complete reversal of anergy and the induction of strong proliferation upon T cell activation in PMN supernatants by arginase inhibition. In summary, we discovered a potent PMN-mediated hyperactivation of human T cells, which is apparent only when PMN arginase-mediated arginine depletion is concurrently inhibited. Our findings are clearly relevant for the analysis and prevention of human tumor immune escape in conjunction with the application of arginase inhibitors already being developed clinically.

scholarly journals Activated Circulating Myeloid-Derived Suppressor Cells in Patients with Dilated Cardiomyopathy

2016 ◽  
Vol 38 (6) ◽  
pp. 2438-2451 ◽  
Author(s):  
Wen-Cai Zhang ◽  
Yan-Ge Wang ◽  
Wen-Hui Wei ◽  
Xin Xiong ◽  
Kan-Ling Liu ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
T Cell ◽  
Dilated Cardiomyopathy ◽  
Suppressor Cells ◽  
Left Ventricular Ejection ◽  
T Cell Proliferation ◽  
Healthy Controls ◽  
Myeloid Derived Suppressor Cells ◽  
Hla Dr ◽  
Ifn Γ

Background/Aims: Myeloid-derived suppressor cells (MDSCs) are increased in inflammatory and autoimmune disorders. This study aims to evaluate the significance of MDSCs in dilated cardiomyopathy (DCM) patients. Methods: In total, 42 newly hospitalized DCM patients and 39 healthy controls were enrolled in the study. The frequencies of circulating CD14+HLA-DR-/low MDSCs were determined by flow cytometry. Then, the functional properties of MDSCs in suppressing T cell proliferation and interferon-gamma (IFN-γ) production were measured in a co-culture model. Then, mRNA expression levels of various important molecules in peripheral blood mononuclear cells were measured by real time polymerase chain reaction. Furthermore, correlation analyses between MDSC frequencies and cardiac function parameters were also performed. Results: The frequencies of circulating CD14+HLA-DR-/low MDSCs were significantly elevated in DCM patients compared with healthy controls. It showed that MDSCs from DCM patients more effectively suppressed T cell proliferation and IFN-γ production compared with those from healthy controls, which was partially mediated by arginase-1 (Arg-1). In addition, the correlation analysis suggested that MDSC frequencies were negatively correlated with left ventricular ejection fraction (LVEF), while positively with N-terminal pro-brain natriuretic peptide (NT-proBNP) in patients with DCM. Conclusions: Circulating activated MDSCs might play significant immunomodulatory roles in the pathogenesis of DCM.

scholarly journals Myeloid-derived suppressor cells are bound and inhibited by anti-thymocyte globulin

2019 ◽  
Vol 25 (1) ◽  
pp. 46-59 ◽  
Author(s):  
Young Suk Lee ◽  
Eduardo Davila ◽  
Tianshu Zhang ◽  
Hugh P Milmoe ◽  
Stefanie N Vogel ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
T Cells ◽  
T Cell ◽  
Suppressor Cells ◽  
Arginase Activity ◽  
T Cell Proliferation ◽  
Myeloid Derived Suppressor Cells ◽  
Tumor Bearing ◽  
And Function

Myeloid-derived suppressor cells (MDSCs) inhibit T cell responses and are relevant to cancer, autoimmunity and transplant biology. Anti-thymocyte globulin (ATG) is a commonly used T cell depletion agent, yet the effect of ATG on MDSCs has not been investigated. MDSCs were generated in Lewis Lung Carcinoma 1 tumor-bearing mice. MDSC development and function were assessed in vivo and in vitro with and without ATG administration. T cell suppression assays, RT-PCR, flow cytometry and arginase activity assays were used to assess MDSC phenotype and function. MDSCs increased dramatically in tumor-bearing mice and the majority of splenic MDSCs were of the polymorphonuclear subset. MDSCs potently suppressed T cell proliferation. ATG-treated mice developed 50% fewer MDSCs and these MDSCs were significantly less suppressive of T cell proliferation. In vitro, ATG directly bound 99.6% of MDSCs. CCR7, L-selectin and LFA-1 were expressed by both T cells and MDSCs, and binding of LFA-1 was inhibited by ATG pre-treatment. Arg-1 and PD-L1 transcript expression were reduced 30–40% and arginase activity decreased in ATG-pretreated MDSCs. MDSCs were bound and functionally inhibited by ATG. T cells and MDSCs expressed common Ags which were also targets of ATG. ATG may be helpful in tumor models seeking to suppress MDSCs. Alternatively, ATG may inadvertently inhibit important T cell regulatory events in autoimmunity and transplantation.

scholarly journals T-cell defect in diffuse large B-cell lymphomas involves expansion of myeloid-derived suppressor cells

Blood ◽  
2016 ◽  
Vol 128 (8) ◽  
pp. 1081-1092 ◽  
Author(s):  
Imane Azzaoui ◽  
Fabrice Uhel ◽  
Delphine Rossille ◽  
Celine Pangault ◽  
Joelle Dulong ◽  
...  
Keyword(s):  
T Cell ◽  
B Cell ◽  
Clinical Outcomes ◽  
Suppressor Cells ◽  
Myeloid Derived Suppressor Cells ◽  
B Cell Lymphomas ◽  
Key Points ◽  
Cell Inhibition ◽  
Large B Cell ◽  
Cell Defect

Key Points Expansion of circulating monocytic myeloid-derived suppressor cells (MDSCs) correlates with clinical outcomes in patients with DLBCL. Mechanisms of MDSC-dependent T-cell inhibition in DLBCL are related to IL-10, PD-L1, and S100A12.

Mesenchymal STEM CELLS Favor Tumor Growth By Generating Granulocyte-like Myeloid Derived Suppressor CELLS in CML Patients

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 4018-4018
Author(s):  
Cesarina Giallongo ◽  
Nunziatina L Parrinello ◽  
Daniele Tibullo ◽  
Claudia Bellofiore ◽  
Piera La Cava ◽  
...  
Keyword(s):  
Stem Cells ◽  
Cell Proliferation ◽  
T Cells ◽  
Mesenchymal Stem Cells ◽  
T Cell ◽  
Peripheral Blood ◽  
Suppressor Cells ◽  
T Cell Proliferation ◽  
Myeloid Derived Suppressor Cells ◽  
Healthy Donors

Abstract INTRODUCTION. The complex interplay between cancer cells and immune system allows neoplastic cells to evade immune surveillance and expand. Recently, our and another group have demonstrated that a subpopulation of myeloid cells, defined as "granulocytic myeloid-derived suppressor cells" (G-MDSC), plays an important role for immune escape in chronic myeloid leukemia (CML) patients by reducing T cell activation. The aim of this study was to evaluate the influence of Mesenchymal stem cells (MSC) on generation of MDSCs by comparing CML MSCs (n=10) with healthy donors (HD) MSC (n=8). METHODS. G-MDSC (CD11b+CD33+CD14-HLADR- cells) were analyzed in peripheral blood (PB) of 20 healthy donors (HD) and 30 CML patients at diagnosis by cytofluorimetric analysis. Immuno-suppressive activity was tested through incubation of G-MDSC with autologous CFSE-labeled T cells and stimulation with phytohaemagglutinin (PHA). Controls included a positive T cell proliferation control (T cells plus PHA) and a negative one (T cells only). After three days, T cell proliferation was analyzed by flow cytometry. For G-MDSC generation, human peripheral blood mononucleated cells (PBMC) from HD were cultured alone and with MSC of CML (n=10) or HD (n=8) (1:100 ratio). After one week, G-MDSC were isolated using anti-CD66b magnetic microbeads and the phenotype was confirmed by cytofluorimetric analysis. Expression of ARG1, NOS2, PTGS2, TNFα, TGFβ, IL6, IL10, IL1β was also evaluated using real time PCR. RESULTS. Percentage of cells with a G-MDSC phenotype was greater in PB obtained from CML patients than HD (82.5±9.6% vs 56,2±5.4%, p<0.0001). G-MDSC were able to inhibit T cell proliferation compared to positive control (25±5% vs 48±7.6%, p=0.0057). To investigate if CML MSC may be involved in G-MDSC generation, we incubated HD PBMC with CML or HD MSC for one week. After magnetic isolation, we found that only CML MSC-educated G-MDSC acquired immune-suppressive ability, inhibiting T cell proliferation compared to G-MDSCs control (isolated from PBMC cultured in medium alone) (32±12% vs 63±5.9%, p=0.003). On the contrary, HD MSC-educated G-MDSC did not show any suppressive effect. We also found that CML MSC-educated G-MDSC expressed higher level of the following immune modulatory factors: TNFα (20.8±19.3, p=0.006), IL1β (47.3±25.2, p=0.001), PTGS2 (20.7±10.9, p=0.002) and IL6 (33.8±13.9, p=0.004) compared to HD MSC-educated G-MDSCs (arbitrarily 2-ΔΔCt value: 1). MSC WE also observed ane an up-regulation of PTGS2 (19±4.4, p=0.04), TGFβ (6±3, p=0.01) and IL6 (5±2.8, p=0.04) in CML MSCs at time 0 with a great variability among the patients (calculated value of 2-ΔΔCt in HD MSC was 1). After 48 h of co-culture with PBMC, CML MSC showed statistically significant up-regulation of ARG1 (23.5±11.9, p=0.02), TGFβ (4.8±3, p=0.04), IL10 (5.6±2.8, p=0.03) and IL6 (54.3±23, p=0.02) expression, suggesting that multiple mechanisms are involved in MDSC induction by CML MSC. CONCLUSION. Our work demonstrates that CML MSCs are able to activate MDSCs favoring cancer immune evasion in CML patients. Disclosures Palumbo: Novartis: Honoraria, Other: Advisory Board.

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