Frequency Of Myeloid-derived Suppressor Cells Research Articles

Tumor-reactive immune cells protect against metastatic tumor and induce immunoediting of indolent but not quiescent tumor cells.

Two major barriers to cancer immunotherapy include tumor-induced immune suppression mediated by myeloid-derived suppressor cells and poor immunogenicity of the tumor-expressing self-antigens. To overcome these barriers, we reprogrammed tumor-immune cell cross-talk by combined use of decitabine and adoptive immunotherapy, containing tumor-sensitized T cells and CD25(+) NKT cells. Decitabine functioned to induce the expression of highly immunogenic cancer testis antigens in the tumor, while also reducing the frequency of myeloid-derived suppressor cells and the presence of CD25(+) NKT cells rendered T cells, resistant to remaining myeloid-derived suppressor cells. This combinatorial therapy significantly prolonged survival of animals bearing metastatic tumor cells. Adoptive immunotherapy also induced tumor immunoediting, resulting in tumor escape and associated disease-related mortality. To identify a tumor target that is incapable of escape from the immune response, we used dormant tumor cells. We used Adriamycin chemotherapy or radiation therapy, which simultaneously induce tumor cell death and tumor dormancy. Resultant dormant cells became refractory to additional doses of Adriamycin or radiation therapy, but they remained sensitive to tumor-reactive immune cells. Importantly, we discovered that dormant tumor cells contained indolent cells that expressed low levels of Ki67 and quiescent cells that were Ki67 negative. Whereas the former were prone to tumor immunoediting and escape, the latter did not demonstrate immunoediting. Our results suggest that immunotherapy could be highly effective against quiescent dormant tumor cells. The challenge is to develop combinatorial therapies that could establish a quiescent type of tumor dormancy, which would be the best target for immunotherapy.

The clinical and prognostic significance of CD14(+)HLA-DR(-/low) myeloid-derived suppressor cells in hepatocellular carcinoma patients receiving radiotherapy.

Myeloid-derived suppressor cells (MDSCs) are key player in mediating systemic immunosuppression, and their accumulation and expansion in the periphery and tumor have been iteratively observed in patients with various types of cancer. It has been reported that CD14(+)HLA-DR(-/low) MDSCs are increased in hepatocellular carcinoma (HCC) patients; however, the clinical significance of MDSC alteration in HCC patients after treatment is poorly studied. In this study, we examined the frequency of MDSCs in 92 HCC patients, 14 chronic liver disease patients without HCC, and 22 healthy controls by flow cytometric analysis. The associations between the clinical features and the frequency of MDSCs were analyzed. In particular, we further examined the prognostic impact of MDSCs on the overall survival of HCC patients receiving radiation therapy. The frequency of MDSCs in HCC patients was significantly increased and correlated with tumor stage, size, burden, and Child-Pugh classification but not with biochemical parameters of liver function. In HCC patients who received radiation therapy, the frequency of MDSCs after treatment significantly decreased and was inversely correlated with overall survival time. In multivariate analysis, only post-treatment MDSC ratio and Child-Pugh classification were correlated with the prognosis of HCC patients. Patients with a high frequency of MDSCs after radiotherapy should be closely followed, and the inhibition of MDSCs may improve the prognosis of patients.

Kinetics of human myeloid-derived suppressor cells after blood draw.

BackgroundHuman myeloid-derived suppressor cells (MDSC) have been described as a group of immature myeloid cells which exert immunosuppressive action by inhibiting function of T lymphocytes. While there is a huge scientific interest to study these cells in multiple human diseases, the methodological approach varies substantially between published studies. This is problematic as human MDSC seem to be a sensible cell type concerning not only cryopreservation but also time point after blood draw. To date data on delayed blood processing influencing cell numbers and phenotype is missing. We therefore evaluated the kinetics of granulocytic MDSC (gMDSC) and monocytic MDSC (mMDSC) frequencies after blood draw in order to determine the best time point for analysis of this recently defined cell type.MethodsIn this study, we isolated peripheral blood mononuclear cells (PBMC) of patients with HIV infection or solid tumors directly after blood draw. We then analyzed the frequencies of gMDSC and mMDSC 2, 4 and 6 h after blood draw and after an overnight rest by FACS analysis using the standard phenotypic markers. In addition, part of the cells was frozen directly after PBMC preparation and was measured after thawing.ResultsgMDSC levels showed no significant difference using fresh PBMC over time with a limitation for the overnight sample. However they were massively diminished after freezing (p = 0.0001 for all subjects). In contrast, frequencies of fresh mMDSC varied over time with no difference between time point 2 and 4 h but a significantly reduction after 6 h and overnight rest (p = 0.0005 and p = 0.005 respectively). Freezing of PBMC decreased the yield of mMDSC reaching statistical significance (p = 0.04). For both MDSC subgroups, FACS analysis became more difficult over time due to less sharp divisions between populations.ConclusionsAccording to our data human MDSC need to be studied on fresh PBMC. gMDSC can be studied with delay, mMDSC however should be studied no later than 4 h after blood draw. These results are crucial as an increasing number of clinical trials aim at analyzing MDSC nowadays and the logistics of blood processing implies delayed sample processing in some cases.Electronic supplementary materialThe online version of this article (doi:10.1186/s12967-015-0755-y) contains supplementary material, which is available to authorized users.

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

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.

Olive Leaf Extract Reduces Myeloid-Derived Suppressor Cells, and Modulates the Function of Residual Cells in Experimental Model of Melanoma

Background: Immunosuppression in melanoma is mediated by increased accumulation of Myeloid Derived Suppressor Cells (MDSCs). Olive Leaf Extract (OLE) has been developed as a natural anti-inflammatory, anti-oxidant, anti-proliferative and antiapoptotic agent on cancer immunotherapy. Objective: To investigate whether OLE could inhibit MDSCs, enhance anti-tumor activities and consequently increase the survival rate of the murine melanoma model. Methods: The C57BL/6 mice were inoculated subcutaneously with B16/F10 melanoma tumor cell lines. Induced mice were orally treated with 500 mgkg-1 of olive extract per kg of body weight for 8 consecutive days. The frequency and function of MDSCs and induction of inflammatory mediators as well as tumor growth and survival rate were assessed in treated and untreated mice. Results: The results of current study revealed that the optimal dose of OLE (500 mgkg-1) reduced the tumor growth (40%), and prolonged mice survival (25%) by significant decreasing (P<0.05) the number (over 50%), and suppressive function of MDSCs (over 60%) (P<0.05). OLE was also significantly (P<0.05) down regulated the induction of inflammatory agents in melanoma-bearing mice (over 50%) at the applied dose (500 mgkg-1). Conclusion: Therefore, these results altogether provided some evidence that regulation of immunosuppression were the possible therapeutic effects of OLE in tumor cells.

Dynamic Change and Impact of Circulating Myeloid-Derived Suppressor Cells in Patients Following Allogeneic Hematopoietic Stem Cell Transplantation

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous cell population involved in tumor-associated immunosuppression and played immune regulatory roles in malignancies, infectious disease, autoimmune disease, trauma and inflammatory disease. Based on the significant suppressive functions, MDSCs raises great interests in the field of allogenetic hematopoietic stem cell transplantation (allo-HSCT) and graft-versus-host disease (GVHD). In recent years, studies described the immunosuppressive functions of CD14+HLA-DR-/low MDSCs, one of the few well-characterized MDSC subsets in human. However, the studies in patients with allo-HSCT are still scanty. This study identified the phenotype of CD14+HLA-DR-/low MDSCs and systematically monitored the dynamic changes of MDSCs accumulation in patients during the first 100 days after allo-HSCT in order to evaluate possible effects of MDSCs on aGVHD development and clinical outcomes. We also detected the frequencies of other cell types and concentrations of relative cytokines during MDSCs accumulation. Results showed that accumulation of MDSCs in the graft and in peripheral blood when engraftment might contribute to patients' overall immune suppression and result in the successful control of severe aGVHD and long-term survival without influence on risk of recurrence after allo-HSCT. However, the level of MDSCs in the graft had more favorable predictive abilities compared with that in PBMCs when engraftment. Furthermore, MDSCs frequencies were significantly increased in patients developing aGVHD after allo-HSCT.In the patients with mild aGVHD (0-2), MDSCs accumulated at the time of engraftment after allo-HSCT and decreased to basal levels at about 4 weeks. MDSCs frequencies would keep in stable levels with slight fluctuations in the following weeks. But, in patients with severe aGVHD (3-4), MDSCs elevated slightly when engraftment. When aGVHD occurred, MDSCs frequencies would significantly increase. And a synchronized reduction of the levels of MDSCs was observed after effective management of aGVHD with immunosuppressive therapy. Besides, the levels of IL-10, IL-6, TNF-α, Arg-1, iNOS and HO-1 increased greatly both in patients with aGVHD and in high MDSCs group. It is speculated that MDSC accumulation at the onset of aGVHD might be caused by secondary inflammatory response, especially related to high concentrations of IL-6 and TNF-α. But the accumulation would not be able to counterbalance the aggravation of aGVHD and would not have influence on clinical outcomes and risk of relapse in future. Overall, we suggested that MDSCs might be considered as a potential new approaches to regulate transplant rejection and achieve the recipient host long-term acceptance and survival. [Display omitted] [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

The significance of G-CSF expression and myeloid-derived suppressor cells in the chemoresistance of uterine cervical cancer.

Granulocyte-colony stimulating factor (G-CSF) producing malignant tumor has been reported to occur in various organs, and has been associated with poor clinical outcome. The aim of this study is to investigate the significance of tumor G-CSF expression in the chemosensitivity of uterine cervical cancer. The clinical data of recurrent or advanced cervical cancer patients who were treated with platinum-based chemotherapy were analyzed. Clinical samples, cervical cancer cell lines, and a mouse model of cervical cancer were employed to examine the mechanisms responsible for the development of chemoresistance in G-CSF-producing cervical cancer, focusing on myeloid-derived suppressor cells (MDSC). As a result, the tumor G-CSF expression was significantly associated with increased MDSC frequencies and compromised survival. In vitro and in vivo experiments demonstrated that the increased MDSC induced by tumor-derived G-CSF is involved in the development of chemoresistance. The depletion of MDSC via splenectomy or the administration of anti-Gr-1 antibody sensitized G-CSF-producing cervical cancer to cisplatin. In conclusion, tumor G-CSF expression is an indicator of an extremely poor prognosis in cervical cancer patients that are treated with chemotherapy. Combining MDSC-targeting treatments with current standard chemotherapies might have therapeutic efficacy as a treatment for G-CSF-producing cervical cancer.

In HIV-positive patients, myeloid-derived suppressor cells induce T-cell anergy by suppressing CD3ζ expression through ELF-1 inhibition.

During HIV infection, a down-modulation of CD3ζ was found on T cells, contributing to T-cell anergy. In this work, we studied the correlation between myeloid-derived suppressor cells (MDSC) frequency and T-cell CD3ζ expression. Moreover, we investigated the mechanisms of CD3ζ decrease exploited by MDSC. CD3ζ expression and MDSC frequency were evaluated by flow cytometry on peripheral blood mononuclear cells from 105 HIV-positive (HIV+) patients. The role of MDSC in the modulation of the HIV-specific T-cell response was evaluated. The level of CD3ζ mRNA and ELF-1 protein were analysed by real-time-PCR and western blot, respectively. We found that granulocytic-MDSC (Gr-MDSC) were expanded in HIV+ patients compared with healthy donors; in particular, in cART-treated individuals a higher Gr-MDSC frequency was observed in patients with a CD4 T-cell count below 400 cells/μl. We found an inverse correlation between the percentage of Gr-MDSC and CD3ζ level. Moreover, in-vitro MDSC depletion induced the up-regulation of CD3ζ in T cells, restoring the functionality of αβ, but not γδ T cells. The in-vitro effect of isolated MDSC on CD3ζ expression was found cell contact-dependent, and was not mediated by previously described molecules. CD3ζ down-modulation corresponds to the decrease of its mRNA induced by silencing the transcription factor ELF-1. Our data provide new knowledge on mechanisms used by Gr-MDSC in immune-modulation and on their role in the immune reconstitution during antiviral treatments.

The immunobiology of myeloid-derived suppressor cells in cancer.

The tumor microenvironment is a complex and heterogeneous milieu in which multiple interactions occur between tumor and host cells. Immunosuppressive cells which are present in this microenvironment, such as regulatory T (Treg) cells and myeloid-derived suppressor cells (MDSCs), play an important role in tumor progression, via down-regulation of antitumor responses. MDSCs represent a heterogeneous group of cells originated from the myeloid lineage that are in the immature state. These cells markedly accumulate under pathologic conditions, such as cancer, infection, and inflammation, and use various mechanisms to inhibit both adaptive and innate immune responses. These immunosuppressive mechanisms include deprivation of T cells from essential amino acids, induction of oxidative stress, interference with viability and trafficking of T cells, induction of immunosuppressive cells, and finally polarizing immunity toward a tumor-promoting type 2 phenotype. In addition to suppression of antitumor immune responses, MDSCs can also enhance the tumor metastasis and angiogenesis. Previous studies have shown that increased frequency of MDSCs is related to the tumor progression. Moreover, various drugs that directly target these cells or reverse their suppressive activity can improve antitumor immune responses as well as increase the efficacy of immunotherapeutic intervention. In this review, we will first discuss on the immunobiology of MDSCs in an attempt to find the role of these cells in tumor progression and then discuss about therapeutic approaches to target these cells.

Immunological correlates of treatment and response in stage IV malignant melanoma patients treated with Ipilimumab

ABSTRACTIntroduction: Ipilimumab is effective in the treatment of metastatic malignant melanoma, but few biomarkers reliably predict treatment response. Methods: Patients were treated with Ipilimumab for metastatic malignant melanoma. Blood and serum samples were collected before and during treatment. Mononuclear cells in peripheral blood were subjected to immune phenotypic analyses and cytokine levels were measured in serum samples. Results were correlated with clinical data. Results: A total of 40 patients were included in the analyses. Clinical response were associated with an increase after one series of treatment in absolute lymphocyte count (ALC) (p = 0.008), absolute T cell count (p = 0.02) and the absolute number of activated T cells in peripheral blood (p = 0.003). A high frequency of myeloid derived suppressor cells (MDSC) and a higher level of IL6 were associated with treatment failure, though not significantly. Levels of IL6 in serum above the median showed a tendency to associate with reduced survival by the 4th treatment series. Finally, treatment with Ipilimumab led to a decreased frequency of FOXP3+ regulatory T cells (p = 0.009). Conclusion: Ipilimumab leads to increased ALC, T cell count and T cell activation in malignant melanoma patients responding to treatment. A high baseline frequency of myeloid-derived suppressor cells and high levels of IL6 is associated with a reduced chance of responding to therapy.

Cisplatin selectively downregulated the frequency and immunoinhibitory function of myeloid-derived suppressor cells in a murine B16 melanoma model.

The objective of this study was to investigate the immunomodulatory effect of cisplatin (DDP) on the frequency, phenotype and function of myeloid-derived suppressor cells (MDSC) in a murine B16 melanoma model. C57BL/6 mice were inoculated with B16 cells to establish the murine melanoma model and randomly received treatment with different doses of DDP. The percentages and phenotype of MDSC after DDP treatment were detected by flow cytometry. The immunoinhibitory function of MDSC was analyzed by assessing the immune responses of cocultured effector cells through CFSE-labeling assay, detection of interferon-γ production and MTT cytotoxic assay, respectively. Tumor growth and mice survival were monitored to evaluate the antitumor effect of combined DDP and adoptive cytokine-induced killer (CIK) cell therapy. DDP treatment selectively decreased the percentages, modulated the surface molecules and attenuated the immunoinhibitory effects of MDSC in murine melanoma model. The combination of DDP treatment and CIK therapy exerted synergistic antitumor effect against B16 melanoma. DDP treatment selectively downregulated the frequency and immunoinhibitory function of MDSC in B16 melanoma model, indicating the potential mechanisms mediating its immunomodulatory effect.

Cetuximab ameliorates suppressive phenotypes of myeloid antigen presenting cells in head and neck cancer patients.

BackgroundMyeloid-derived suppressor cells (MDSC) and M2 monocytes/macrophages are two types of suppressive myeloid antigen presenting cells that have been shown to promote tumor progression and correlate with poor prognosis in cancer patients. Tumor antigen specific monoclonal antibodies (mAb) have emerged as important agents for cancer therapy. In addition to the direct inhibition of tumor growth, the Fc portions of the therapeutic mAbs, such as the IgG1 portion of the anti-epidermal growth factor receptor (EGFR) mAb cetuximab, might interact with the Fc-gamma receptors (FcγR) on myeloid cells and modulate their suppressive activity.MethodsPatients with locally advanced head and neck squamous cell carcinoma (HNSCC) on the UPCI 08–013 NCT01218048 trial were treated with single-agent cetuximab before surgery. Blood were collected pre- and post-cetuximab treatment to analyze frequency of monocytic MDSC (CD11b+CD14+HLA-DRlo/-), granulocytic MDSC (LIN−CD11b+CD15+) and CD11b+CD14+HLA-DRhi monocytes by flow cytometry. Besides, CD11b+CD14+HLA-DRhi monocytes were sorted for qPCR analysis of IL-10 and IL-12B transcripts. MDSC were generated in vitro with or without coated hIgG1 and tested for suppressive activity in mixed leukocyte reaction (MLR). Naïve monocytes from HNSCC patients co-cultured with tumor cell lines in the presence of cetuximab or hIgG1 were analyzed for M1/2 surface markers and cytokines.ResultsWe observed significantly increased monocytic MDSC in non-responders and decreased granulocytic MDSC in responders after cetuximab treatment. In addition, circulating CD11b+CD14+HLA-DRhi monocytes of cetuximab responders displayed attenuated M2 polarization, with decreased CD163+ expression and IL-10 transcripts after cetuximab treatment. This beneficial effect appeared to be FcγR dependent, since CD16 ligation reproduced the reversal of suppressive activity of MDSC in vitro. CD14+ naïve monocytes from the co-cultures of tumor cells, cetuximab and HNSCC patient PBMC or purified monocytes were skewed to an M1-like phenotype, with increased expression of HLA-DR, CD86 and production of IL-12 p70. Likewise, reduced M2 features (expression of CD163 and production of IL-10) were found after crosslinking CD16 on the surface of monocytes to cetuximab-coated tumor cells.ConclusionOur studies demonstrate a novel function of cetuximab in ameliorating suppressive phenotypes of FcγR bearing myeloid cells in cancer patients, which is associated with better clinical outcome of cetuximab-treated patients.Clinical trial registry#NCT01218048. Registered 7 October 2010.Electronic supplementary materialThe online version of this article (doi:10.1186/s40425-015-0097-6) contains supplementary material, which is available to authorized users.

CD4+ T effector memory cell dysfunction is associated with the accumulation of granulocytic myeloid-derived suppressor cells in glioblastoma patients.

Myeloid-derived suppressor cells (MDSCs) comprise a heterogeneous population of myeloid cells that are significantly expanded in cancer patients and are associated with tumor progression. Multicolor flow cytometry was used to study the frequency, phenotype, and function of MDSCs in peripheral blood and freshly resected tumors of 52 participants with primary glioblastoma (GBM). The frequency of CD14(high)CD15(pos) monocytic and CD14(low)CD15(pos) granulocytic MDSCs was significantly higher in peripheral blood of GBM participants compared with healthy donors. The majority of granulocytic MDSCs consisted of CD14(low)CD15(high) neutrophilic MDSCs with high T-cell suppressive capacities. At the tumor side, we found an increase in CD14(high)CD15(pos) monocytic MDSCs and high frequencies of CD14(low)CD15(pos) granulocytic MDSCs that displayed an activated phenotype with downregulation of CD16 and upregulation of HLA-DR molecules, which did not inhibit T-cell proliferative responses in vitro. However, a strong association between granulocytic MDSCs and CD4(+) effector memory T-cells (TEM) within the tumors was detected. Tumor-derived CD4(+) TEM expressed high levels of PD-1 when compared with their blood-derived counterparts and were functionally exhausted. The respective ligand, PD-L1, was significantly upregulated on tumor-derived MDSCs, and T-cell co-culture experiments confirmed that glioma-infiltrating MDSCs can induce PD-1 expression on CD4(+) TEM. Our findings provide a detailed characterization of different MDSC subsets in GBM patients and indicate that both granulocytic MDSCs in peripheral blood and at the tumor site play a major role in GBM-induced T-cell suppression.

Polarization of Monocytic Myeloid-Derived Suppressor Cells by Hepatitis B Surface Antigen Is Mediated via ERK/IL-6/STAT3 Signaling Feedback and Restrains the Activation of T Cells in Chronic Hepatitis B Virus Infection.

Chronic hepatitis B virus (HBV) infection is characterized by T cell tolerance to virus. Although inhibition of T cell responses by myeloid-derived suppressor cells (MDSCs) has been observed in patients with chronic hepatitis B (CHB), the mechanism for expansion of MDSCs remains ambiguous. In this study, a significant increased frequency of monocytic MDSCs (mMDSCs) was shown positively correlated to level of HBsAg in the patients with CHB. We further found hepatitis B surface Ag (HBsAg) efficiently promoted differentiation of mMDSCs in vitro, and monocytes in PBMCs performed as the progenitors. This required the activation of ERK/IL-6/STAT3 signaling feedback. Importantly, the mMDSCs polarized by HBsAg in vitro acquired the ability to suppress T cell activation. Additionally, treatment of all-trans retinoic acid, an MDSC-targeted drug, restored the proliferation and IFN-γ production by HBV-specific CD4(+) and CD8(+) T cells in PBMCs from patients with CHB and prevented increase of viral load in mouse model. In summary, HBsAg maintains HBV persistence and suppresses T cell responses by promoting differentiation of monocytes into mMDSCs. A therapy aimed at the abrogation of MDSCs may help to disrupt immune suppression in patients with CHB.

CBM-06IMMUNE BIOMARKER RESULTS FROM A TRIAL OF NIVOLUMAB ± IPILIMUMAB IN PATIENTS WITH RECURRENT GLIOBLASTOMA: CHECKMATE-143

BACKGROUND: The prognosis for patients with glioblastoma (GBM) remains poor despite the availability of first-line therapies including surgery and chemoradiation. Recent evidence suggests that there are varying degrees of lymphocyte infiltration in GBM, and the composition may have prognostic significance. Expansion of regulatory T cells (CD4+FoxP3+, Treg) at the tumor site has been observed and is implicated in cancer-associated immunity in GBM. Immune checkpoint inhibitors, such as the fully human anti-PD-1 monoclonal antibody nivolumab, have shown promising antitumor activity in both solid tumors and preclinical glioma models. The CHECKMATE-143 study is evaluating nivolumab as monotherapy and in combination with ipilimumab (anti-CTLA-4) in patients with recurrent GBM (Cohorts 1 and 1b). As part of the initial phase of this study, T-cell maturation, activation, exhaustion, and effector function, as well as Treg frequencies and function and myeloid-derived suppressor cell frequencies were examined. METHODS: Analyses were performed on peripheral blood drawn from patients at pre-determined time points and upon tumor tissue samples obtained if resection was performed at the time of progression or suspected progression. Baseline and on-treatment samples were obtained from patients (n = 20) randomized 1:1 to receive either nivolumab 3 mg/kg Q2W or nivolumab 1 mg/kg + ipilimumab 3 mg/kg Q3W followed by nivolumab 3 mg/kg Q2W. Phenotypic analysis was determined by CyTOF and flow cytometry; Treg suppressive function by thymidine incorporation; cytokine release by multiplex immunoassay; and gene expression by RNAseq. RESULTS: Treatment-related changes in lymphocyte populations (including but not limited to T, B, and NK cells, granulocytes, and memory and effector T-cell subsets) in peripheral blood and resected tumor will be reported. CONCLUSIONS: Peripheral and tumor biomarker analyses of GBM subjects treated with checkpoint inhibitors will provide insights into treatment-related changes versus tumor progression.

Inhibition of iNOS activity enhances the anti-tumor effects of alpha-galactosylceramide in established murine cancer model.

Alpha-garactosylceramide (GalCer) has been shown to have anti-tumor effect in the basic research and clinical studies. However, anti-tumor effect of GalCer is limited. The administration of GalCer increases the production of IFN-γ which is involved in the suppression of tumor growth. On the other hand, the enhancement of IFN-γ production increases immunosuppressive factors such as nitric oxide. This suppressive action might impair the anti-tumor effect of GalCer. In the present study, we evaluated the anti-tumor effect of GalCer in the absence of inducible nitric oxide synthase (iNOS). In lung metastatic model, the number of tumor nodules in the lung of iNOS-KO mice treated with GalCer was significantly reduced compared with that of WT mice treated with GalCer. Moreover, L-NAME, which is the inhibitor for iNOS, enhanced the anti-tumor effect of GalCer in lung metastatic model. The frequency of CD8+ cells in bronchoalveolar lavage fluid increased in iNOS-KO mice treated with GalCer. The administration of GalCer increased the frequency of myeloid-derived suppressor cells (MDSCs) in the lung from tumor-bearing WT mice, but the increase of MDSCs in the lung was not induced in iNOS-KO mice. The subcutaneous tumor experiments revealed that the administration of GalCer in the absence of iNOS expression significantly enhanced the induction of tumor antigen-specific response. Finally, our results indicated that the inhibition of iNOS expression could enhance the therapeutic efficacy of GalCer via the increase of tumor antigen-specific immune response and the suppression of MDSCs.

17β-estradiol contributes to the accumulation of myeloid-derived suppressor cells in blood by promoting TNF-α secretion.

Estrogens are strongly implicated in gender differences in immune responses by influencing the development and activation of immune cells. Recent studies have shown that myeloid-derived suppressor cells (MDSCs), derived from CD11b(+)Gr-1(+) myeloid cells under pathological conditions, play vital roles in modulating immune responses. However, it is still unknown the effects of estrogens on MDSCs. In the present study, we investigated the effects and mechanisms of estrogens on regulating the accumulation of MDSCs. It was found that, compared with male patients with systemic lupus erythematosus (SLE), female patients with SLE showed a higher frequency of MDSCs in peripheral blood mononuclear cells and a higher level of tumor necrosis factor α (TNF-α) in serum. Notably, estradiol level in the serum of female patients with SLE was positively correlated with the frequency of MDSCs. Moreover, 17β-estradiol could promote TNF-α-induced accumulation of MDSCs in vivo by increasing the fundamental frequency of CD11b(+)Gr-1(+) cells. Furthermore, 17β-estradiol promoted the secretion of TNF-α in vivo, which contributed to the increase of the frequency of CD11b(+)Gr-1(+) cells. In addition, it was also found that female mice showed a higher frequency of CD11b(+)Gr-1(+) cells and a higher TNF-α level in blood than the age-matched male mice. These data indicate that 17β-estradiol contributes to the accumulation of MDSCs in blood by promoting TNF-α secretion, which increases the fundamental frequency of CD11b(+)Gr-1(+) cells. Our findings provide a new insight into the mechanism of gender difference in the prevalence of inflammation and autoimmune diseases.

Poly (I: C) modulates the immunosuppressive activity of myeloid-derived suppressor cells in a murine model of breast cancer.

Polyinosinic-polycytidylic acid [Poly (I: C)], a ligand for Toll-like receptor (TLR-3), is used as an adjuvant to enhance anti-tumor immunity because of its prominent effects on CD8 T cells and NK cells. Myeloid-derived suppressor cells (MDSCs) are one of the main immunosuppressive factors in cancer, and their abnormal accumulation is correlated with the clinical stage of breast cancer and is an important mechanism of tumor immune evasion. Although Poly (I: C) is thought to have direct anti-tumor activity in different cell lines, its effect on immunosuppressive MDSCs in tumor-bearing animals has not been studied. 4T1-Luc, a metastatic breast cancer mouse cell line, was injected into the left flank of female BALB/c mice. Tumor-bearing mice were treated with i.p. injection of Poly (I: C) or PBS beginning on day 7 after tumor inoculation. WBCs and MDSCs were counted using coulter counter and stained for flow cytometry, respectively. Bioluminescent imaging was used to monitor tumor burden at multiple time points during the course of tumor growth. Poly (I: C) treatment led to a decrease in MDSC frequencies in BM, blood, and tumor compared to saline-treated control mice. Poly (I: C) treatment also abrogated the immunosuppressive function of MDSCs, concomitant with an increase in local T cell response of the immune system in a murine model of breast cancer. Poly (I: C) treatment decreases MDSC frequency and immunosuppressive function in 4T1-tumor-bearing hosts and effectively augments the activity of breast cancer immunotherapy.

Myeloid-derived suppressor cells in major depression patients suppress T-cell responses through the production of reactive oxygen species

Major depression is closely associated with immune dysregulation. Myeloid-derived suppressor cells (MDSCs) are an important suppressor of immune responses. The aim of this study was to evaluate the possible role of MDSCs in major depression patients. We collected peripheral blood mononuclear cells (PBMCs) from 25 major depression patients and 25 healthy donors, and the frequency of MDSCs was determined by flow cytometric analysis. The proportion of MDSCs was increased in the peripheral blood of major depression patients, when compared with healthy controls. Further functional studies revealed that MDSCs from depression patients suppressed T cell function potently. We examined the reactive oxygen species (ROS) content in MDSCs from 6 major depression patients and 6 healthy controls. The ROS content in depression derived MDSCs was significantly elevated, when compared with those from healthy controls. We also examined the arginase activity and NO content in 5 major depression patients and 5 healthy controls, respectively. But no significant changes were detected between two groups. Administration of a ROS inhibitor completely abrogated the suppressive effect of MDSCs on T cells. In conclusion, our study revealed that MDSCs from depression patients suppress T cell reponses in ROS-dependent manner.

Increased circulating CD14(+)HLA-DR-/low myeloid-derived suppressor cells are associated with poor prognosis in patients with small-cell lung cancer.

High expression of CD14(+)HLA-DR-/low myeloid-derived suppressor cells (MDSCs) is correlated with immunosuppressive activity in various cancers, however, no studies have shown a correlation of these immunosuppressive cells with clinical outcomes in small-cell lung cancer (SCLC) patients. The purpose of the study was to investigate the number, frequency and clinical significance of CD14(+)HLA-DR-/low MDSCs in SCLC patients. The peripheral blood of 42 patients with SCLC and 37 healthy controls was analyzed by using flow cytometry. The relationships between the number and frequency of MDSCs, clinicopathological features and overall survival(OS) were analyzed. The prognostic value of MDSCs was tested by using univariate and multivariate analysis. Our results demonstrated that number and frequency of peripheral CD14(+)HLA-DR-/low MDSCs were significantly increased in SCLC patients than in controls (p< 0.0001 and p< 0.0001, respectively). The frequency of MDSCs correlated with tumor stage (p= 0.02), serum LDH levels (p= 0.001) and with the poorer OS (log-rank test, p= 0.017). Univariate and multivariate analyses suggested that frequency of CD14(+)HLA-DR-/low MDSCs as an independent biomarker for poor prognosis in SCLC patients during follow-up. Our study provides the first evidence that the frequency of CD14(+)HLA-DR-/low MDSCs negatively correlates with clinical outcomes in SCLC patients. The frequency of CD14(+)HLA-DR-/low MDSCs could be considered as a poor prognostic predictor in SCLC and the elimination of MDSCs during medical interventions may improve the prognosis of SCLC patients.