Myeloid-derived Suppressor Cells In Peripheral Blood Research Articles

Polysaccharide from Lentinus edodes Inhibits the Immunosuppressive Function of Myeloid-Derived Suppressor Cells

Reversing the function of immune suppressor cells may improve the efficacy of cancer therapy. Here, we have isolated a novel polysaccharide MPSSS (577.2 Kd) from Lentinus edodes and examined its effects on differentiation and function of myeloid-derived suppressor cells (MDSCs). MPSSS is composed of glucose (75.0%), galactose (11.7%), mannose (7.8%), and xylose (0.4%). In vivo, it inhibits the growth of McgR32 tumor cells, which is correlated with a reduced percentage of MDSCs in peripheral blood. In vitro, it induces both morphological and biophysical changes in MDSCs. Importantly, MPSSS up-regulates MHC II and F4/80 expression on MDSCs, and reverses their inhibition effect on CD4+ T cells in a dose-dependent manner. The mechanism study shows that MPSSS may stimulate MDSCs through a MyD88 dependent NF-κB signaling pathway. Together, we demonstrated for the first time that MPSSS stimulates the differentiation of MDSCs and reverses its immunosuppressive functions, shedding new light on developing novel anti-cancer strategies by targeting MDSCs.

CD14+S100A9+ Myeloid-derived Suppressor Cells Portend Decreased Survival in Patients with Advanced Lung Cancer

It has been clearly shown from multiple preclinical studies that myeloid-derived suppressor cells (MDSC) serve as a target for inhibiting tumor growth (1–3). Although studies in humans have shown the presence of MDSC in different pathological conditions, understanding their clinical significance in cancer requires the full characterization of these cells. The characteristics of MDSC have been described for several human malignancies, including melanoma, colon cancer, and renal cell carcinoma, but the identification of a unique set of markers for human MDSC has been challenging because MDSC gene expression varies in different tumor types. Feng and colleagues in this issue of the Journal (pp. ) describe the characteristics of the CD11b+CD14+S100A9+ monocytic MDSC and their clinical relevance in patients with advanced non–small cell lung cancer (NSCLC) (4). The identification of markers for the characterization of MDSC in lung cancer is useful because only limited data are available on specific markers. The authors evaluated the characteristics of MDSC in the peripheral blood of patients with NSCLC [adenocarcinoma, 40; squamous cell carcinoma, 6; and nonclassified NSCLC, 6] in comparison to 17 healthy control subjects. In addition, 40 patients who received cisplatin-based chemotherapy in a randomized prospective trial were evaluated for the predictive role of MDSC. The authors demonstrated that there was a higher proportion of CD11b+CD14+ than CD11b+CD14− MDSC in the peripheral blood mononuclear cells of patients with NSCLC, and the frequencies of both subsets were higher in patients with NSCLC in comparison to healthy control subjects. Both subsets of MDSC had similar suppressive activity on CD8 T-cell proliferation and IFN-γ production. In contrast, CD11b+CD14+ cells from healthy donors showed no suppressive ability on CD8+ T-cell proliferation or IFN-γ production. Through inhibitor and antibody-mediated blocking experiments, the authors showed that the CD11b+CD14+ MDSC–mediated suppression of CD8 T cells in vitro was via arginase, inducible nitric oxide synthase, the IL-13/IL-4Rα axis, and IL-10. The levels of S100A9+ expression by CD11b+CD14+ correlated with their suppressive ability. Furthermore, high levels of CD11b+CD14+S100A9+ MDSC were associated with poor response to cisplatin-based chemotherapy and predicted shorter progression-free survival. Although the CD11b+CD14− subpopulation of MDSC had an inhibitory ability that was comparable to the CD11b+CD14+ cells, there was no association of these cells with performance status or treatment response of patients with NSCLC to chemotherapy. The findings of this study are significant as they show that S100A9 can serve as an important marker for the further characterization of the CD11b+CD14+ MDSC in patients with advanced NSCLC. The results of this study corroborate the findings from a previous study that demonstrated an increase in the population of CD14+ S100A9+ MDSC in the peripheral blood from patients with colon cancer in comparison with healthy control subjects (5). Since solid tumors contain a significant population of tumor-infiltrating myeloid cells that promote tumor growth, the lack of evaluation of the characteristics of MDSC from the NSCLC samples is a limitation of this study. It is not known if the CD11b+CD14+S100A9+ MDSC are present in the lung tumor microenvironment of the patients with advanced NSCLC. Nevertheless, the results of this study demonstrate that levels of CD11b+CD14+S100A9+ MDSC in peripheral blood can serve as a predictor of response to chemotherapy in patients with advanced lung cancer. Further investigations are required to determine whether modulating the levels and activities of CD11b+CD14+S100A9+ MDSC would improve patient outcome in advanced lung cancer. MDSC play a central role in immune suppressive pathways and tumor progression, and modulating the activities of this population could prove beneficial as an innovative therapeutic strategy against lung cancer.

Murine Pancreatic Adenocarcinoma Dampens SHIP-1 Expression and Alters MDSC Homeostasis and Function

BackgroundPancreatic cancer is one of the most aggressive cancers, with tumor-induced myeloid-derived suppressor cells (MDSC) contributing to its pathogenesis and ineffective therapies. In response to cytokine/chemokine receptor activation, src homology 2 domain-containing inositol 5′-phosphatase-1 (SHIP-1) influences phosphatidylinositol-3-kinase (PI3K) signaling events, which regulate immunohomeostasis. We hypothesize that factors from murine pancreatic cancer cells cause the down-regulation of SHIP-1 expression, which may potentially contribute to MDSC expansion, and the suppression of CD8+ T cell immune responses. Therefore, we sought to determine the role of SHIP-1 in solid tumor progression, such as murine pancreatic cancer.Methodology and Principal FindingsImmunocompetent C57BL/6 mice were inoculated with either murine Panc02 cells (tumor-bearing [TB] mice) or Phosphate Buffer Saline (PBS) (control mice). Cytometric Bead Array (CBA) analysis of supernatants of cultured Panc02 detected pro-inflammatory cytokines such as IL-6, IL-10 and MCP-1. TB mice showed a significant increase in serum levels of pro-inflammatory factors IL-6 and MCP-1 measured by CBA. qRT-PCR and Western blot analyses revealed the in vivo down-regulation of SHIP-1 expression in splenocytes from TB mice. Western blot analyses also detected reduced SHIP-1 activity, increased AKT-1 and BAD hyper-phosphorylation and up-regulation of BCL-2 expression in splenocytes from TB mice. In vitro, qRT-PCR and Western blot analyses detected reduced SHIP-1 mRNA and protein expression in control splenocytes co-cultured with Panc02 cells. Flow cytometry results showed significant expansion of MDSC in peripheral blood and splenocytes from TB mice. AutoMACS sorted TB MDSC exhibited hyper-phosphorylation of AKT-1 and over-expression of BCL-2 detected by western blot analysis. TB MDSC significantly suppressed antigen-specific CD8+ T cell immune responses in vitro.Conclusion/SignificanceSHIP-1 may regulate immune development that impacts MDSC expansion and function, contributing to pancreatic tumor progression. Thus, SHIP-1 can be a potential therapeutic target to help restore immunohomeostasis and improve therapeutic responses in patients with pancreatic cancer.

Myeloid-derived suppressor cell accumulation and function in patients with newly diagnosed glioblastoma

To assess the accumulation of myeloid-derived suppressor cells (MDSCs) in the peripheral blood of patients with glioma and to define their heterogeneity and their immunosuppressive function. Peripheral blood mononuclear cells (PBMCs) from healthy control subjects and from patients with newly diagnosed glioma were stimulated with anti-CD3/anti-CD28 and T cells assessed for intracellular expression of interferon (IFN)-γ. Antibody staining of PBMCs from glioma patients and healthy donors (CD33, HLADR, CD15, and CD14) followed by 4-color flow cytometry analysis-defined MDSC levels in the peripheral blood. To assess the role of MDSCs in suppressing T cell IFNγ production, PBMCs were depleted of MDSCs using anti-CD33 and anti-CD15 antibody-coated beads prior to T cell stimulation. Enzyme-linked immunosorbent assays were used to assess plasma arginase activity and the level of granulocyte colony-stimulating factor (G-CSF). Patients with glioblastoma have increased MDSC counts (CD33+HLADR-) in their blood that are composed of neutrophilic (CD15(+); >60%), lineage-negative (CD15(-)CD14(-); 31%), and monocytic (CD14(+); 6%) subsets. After stimulation, T cells from patients with glioblastoma had suppressed IFN-γ production when compared with healthy, age-matched donor T cells. Removal of MDSCs from the PBMCs with anti-CD33/CD15-coated beads significantly restored T cell function. Significant increases in arginase activity and G-CSF levels were observed in plasma specimens obtained from patients with glioblastoma. The accumulation of MDSCs in peripheral blood in patients with glioma likely promotes T cell immune suppression that is observed in this patient population. Increased plasma levels of arginase and G-CSF may relate to MDSC suppressor function and MDSC expansion, respectively, in patients with glioma.

Reduction of myeloid-derived suppressor cells in peripheral blood by local hyperthermia in patients with advanced solid tumors.

e21058 Background: Circulating levels of myeloid-derived suppressor cells (MDSCs) correlate with clinical cancer stage, metastatic tumor burden and tumor immune evasion. The potential contribution of MDSCs to thermotherapy has not been explored. The aim of this study was to investigate the impact of treatment of local hyperthermia on the levels of MDSCs in peripheral blood. Methods: Thirty patients with advanced solid tumors treated with local hyperthermia were enrolled. Peripheral blood samples were obtained before and after treatment immediately. Circulating MDSCs (identified as HLA-Dr-/low, CD11b+, CD33+ cells) were measured by flow cytometry. Meanwhile lymphocyte subpopulations in peripheral blood samples (T-helper-/T4-cells, T-suppressor-/T8-cells, natural-killer-/NK-cells, CD19+cells) were also analyzed using the same method. The association between MDSCs and the other lymphocyte subpopulation was examined by ultivariate linear regression analysis. Results: The percentage of MDSCs and other lymphocyte subpopulations before and after treatment are shown in the Table1. MDSCs were significantly reduced after local hyperthermia, so were the T-suppressor cells and the NK cells. But the T-helper cells and the ratio of T-helper/T-suppressor cells were increased. The numbers of CD3+ cells and CD19+ cells were not significantly affected by the treatment. This reduction of MDSCs is not associated with any other lymphocyte subtype. Conclusions: It was demonstrated that local hyperthermia can reduce abnormal accumulation of circulating MDSCs. The reduction of MDSCs was not associated with the other lymphocyte subpopulation. The percentage of MDSCs and lymphocyte subpopulations before and after treatment. MDSC CD3+CD4+ CD3+CD8+ CD4+/CD8+ CD3+ NK CD19+ B# 7.71±5.92 38.84±10.72 28.26±10.05 1.56±0.71 65.65±13.49 23.77±11.37 5.69±5.13 A* 6.45±4.85 43.80±10.89 26.92±9.93 1.98±1.26 68.80±14.23 19.37±10.58 6.37±6.25 P value 0.042 0.003 0.006 0.004 0.052 0.004 0.150 B# Before Local Hyperthermia. A* After Local Hyperthermia.

The Effect of Rhg-CSF on MDSC In Bone Marrow and Peripheral Blood Cells

AbstractAbstract 4709 Objective:As granulocyte colony-stimulating factor, recombinant human granulocyte colony stimulating factor (rhG-CSF) is widely used in neutropenic patients. In addition to stimulating the growth of granulocyte, rhG-CSF can promote hematopoietic stem cells from bone marrow (BM) to peripheral blood (PB) and has the effect of immune regulation. Myeloid-derived suppressor cells (MDSC) are a group of heterogeneous cells, derived from bone marrow progenitor cells and immature myeloid cells. Recently, MDSC is researched in the field of solid tumor, but not in the field of hematopoietic stem cell transplantation. Here, we investigate rhG-CSF's effect on MDSC in healthy donors' BM, PB and the relationship between MDSC and graft-verse-host disease (GVHD). Methods:We obtained the BM and PB samples before mobilization and the BM APB and peripheral blood stem cell collection (PBSC) on the 5th day after the rhG-CSF mobilization from 12 healthy donors, respectively. Then we used the flow cytometry to check the absolute number of MDSC. Finally, we analyzed the relationship between the number of MDSC and the incidence of GVHD. Results:In normal physiological conditions, the MDSC could be detected in healthy donor's PB and BM. In PB, the proportion of MDSC in the mononuclear cells was 1.35 ± 0.35%. In BM, the proportion was 2.44 ± 1.11%. The proportion in BM is higher than that in PB, the difference was statistically significant (P=0.047). On the 5th day after the rhG-CSF mobilization, the MDSC ratio of mononuclear cell in PB were 4.01 ± 1.82%. In BM, the ratio was 4.38 ± 2.19%. The difference between the ratio of MDSC in BM and PB was no significant (P=0.076). The number of mobilized peripheral blood MDSC was significantly higher than that before mobilization (P=0.015), while the difference between the numbers of bone marrow MDSC cells before and after mobilization was not significant (P=0.083). The numbers of MDSC in collection and the incidence of GVHD had a significant negative correlation (P=0.048). Conclusion:MDSC could be detected in the healthy donors' PB and BM, the numbers of MDSC in BM were higher than that in PB. The rhG-CSF could mobilize more MDSC from BM to the peripheral blood, and the increased s of MDSC in PB after rhG-CSF mobilization might be related to the low incidence of GVHD in hematopoietic stem cell transplantation.Supported by National Natural Science Foundation of China (30971300), Science and Technology Planning Project of Guangdong Province of China (2009A030200007) and China Postdoctoral Science Foundation (200902332, 20080440776). Disclosures:No relevant conflicts of interest to declare.

Anti-inflammatory Triterpenoid Blocks Immune Suppressive Function of MDSCs and Improves Immune Response in Cancer

Myeloid-derived suppressor cells (MDSC) are one of the major factors responsible for immune suppression in cancer. Therefore, it would be important to identify effective therapeutic means to modulate these cells. We evaluated the effect of the synthetic triterpenoid C-28 methyl ester of 2-cyano-3,12-dioxooleana-1,9,-dien-28-oic acid (CDDO-Me; bardoxolone methyl) in MC38 colon carcinoma, Lewis lung carcinoma, and EL-4 thymoma mouse tumor models, as well as blood samples from patients with renal cell cancer and soft tissue sarcoma. Samples were also analyzed from patients with pancreatic cancer treated with CDDO-Me in combination with gemcitabine. CDDO-Me at concentrations of 25 to 100 nmol/L completely abrogated immune suppressive activity of MDSC in vitro. CDDO-Me reduced reactive oxygen species in MDSCs but did not affect their viability or the levels of nitric oxide and arginase. Treatment of tumor-bearing mice with CDDO-Me did not affect the proportion of MDSCs in the spleens but eliminated their suppressive activity. This effect was independent of antitumor activity. CDDO-Me treatment decreased tumor growth in mice. Experiments with severe combined immunodeficient-beige mice indicated that this effect was largely mediated by the immune system. CDDO-Me substantially enhanced the antitumor effect of a cancer vaccines. Treatment of pancreatic cancer patients with CDDO-Me did not affect the number of MDSCs in peripheral blood but significantly improved the immune response. CDDO-Me abrogated the immune suppressive effect of MDSCs and improved immune responses in tumor-bearing mice and cancer patients. It may represent an attractive therapeutic option by enhancing the effect of cancer immunotherapy.

Elevated Circulating Myeloid Derived Suppressor Cells (MDSC) Are Associated with Inferior Overall Survival (OS) and Correlate with Circulating Tumor Cells (CTC) in Patients with Metastatic Breast Cancer.

Abstract Background: MDSC acumulation is an important mechanism of tumor escape from immune surveillance and cancer progression. Pre-clinical studies have shown a correlation between tumor progression and MDSC. While we and others have shown that circulating MDSC correlate with clinical stage, to date there are few clinical studies that have explored the correlation of MDSC with metastatic tumor burden or as an adverse prognostic factor. Consequently, the goal of this study was to determine whether levels of MDSC in patients with stage IV breast cancer correlate with tumor burden using CTC and Swenerton Scores (SS) as surrogates for metastatic disease burden, and if circulating MDSC levels were predictive of overall survival.Methods: Flow cytometric analysis was performed on peripheral whole blood from 25 patients with stage IV breast cancer prior to initiation of therapy and at defined intervals during therapy. The MDSC population was defined as lineage-, CD33+, HLA-DR-, CD11b+. CTC (CellSearch®) and MDSC were drawn simultaneously and SS were calculated using a standardized scoring system previously defined and published in the literature. A generalized estimating equation regression model was created and fitted individually for each predictor. OS was defined as time of study enrollment to date of death.Results: Using a generalized estimating equation regression model the percentage of MDSC in peripheral blood was found to have a close correlation with CTC (Pearson correlation 0.62, p=0.0001) and a coefficient of 0.29 (0.14, 0.43 95%CI). The correlation between percent MDSC and SS was not significant (Pearson 0.31, p=0.12). Interestingly, no significant correlation between CTC and SS was noted either. MDSC levels were also found to predict OS in patients with the highest percentages at the first visit having significantly decreased median overall survival [6.8 vs. 19.6 months; p=0.05]Similarly, high MDSC levels at the final blood draw was also found to correlate with significantly shorter median OS [p=0.023].Conclusions. MDSC correlated well with CTC but not SS. High circulating MDSC levels were associated with significantly decreased overall survival in patients with metastatic breast cancer. MDSC appear to be a promising prognostic immunologic biomarker in metastatic breast cancer. Further studies are needed to better define the role of MDSCs in breast cancer progression and may be a useful therapeutic target to enhance the effectiveness of immune based therapies in breast cancer. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 4135.

A New Population of Myeloid-Derived Suppressor Cells in Hepatocellular Carcinoma Patients Induces CD4+CD25+Foxp3+ T Cells

Several studies have shown that development of hepatocellular carcinoma (HCC) generates a number of immune suppressive mechanisms in these patients. Myeloid-derived suppressor cells (MDSC) are a heterogeneous population of cells that have been shown to inhibit T-cell responses in tumor-bearing mice, but little is known about these cells in humans owing to a lack of specific markers. In this study, we have investigated the frequency and function of a new population of MDSC denoted here as CD14(+)HLA-DR(-/low) in HCC patients. We have also identified a novel, MDSC-mediated immune regulatory pathway in these patients. We have directly isolated and characterized MDSCs for phenotype and function from peripheral blood (n = 111) and tumor (n = 12) of patients with HCC. The frequency of CD14(+)HLA-DR(-/low) cells in peripheral blood mononuclear cells (PBMC) from HCC patients was significantly increased in comparison with healthy controls. CD14(+) HLA-DR(-/low) cells were unable to stimulate an allogeneic T-cell response, suppressed autologous T-cell proliferation, and had high arginase activity, a hallmark characteristic of MDSC. Most important, CD14(+)HLA-DR(-/low) cells from HCC patients induced a CD4(+)CD25(+)Foxp3(+) regulatory T-cell population when cocultured with autologous T cells. CD14(+)HLA-DR(-/low) cells are a new population of MDSC increased in blood and tumor of HCC patients. We propose a new mechanism by which MDSC exert their immunosuppressive function, through the induction of CD4(+)CD25(+)Foxp3(+) regulatory T cells in cocultured CD4(+) T cells. Understanding the mechanism of action of MDSC in HCC patients is important in the design of effective immunotherapeutic protocols.