Project description:Our group and others have determined that immune effector cells from patients with advanced cancers exhibit reduced activation of IFN signaling pathways. We hypothesized that increases in immune regulatory cells termed myeloid-derived suppressor cells (MDSC) could interfere with the host immune response to tumors by inhibiting immune cell responsiveness to IFNs. The C26 murine adenocarcinoma model was employed to study immune function in advanced malignancy. C26-bearing mice had significantly elevated levels of GR1(+)CD11b(+) MDSC as compared with control mice, and splenocytes from tumor-bearing mice exhibited reduced phosphorylation of STAT1 (P-STAT1) on Tyr(701) in response to IFN-? or IFN-?. This inhibition was seen in splenic CD4(+) and CD8(+) T cells as well as natural killer cells. In vitro coculture experiments revealed that MDSC inhibited the IFN responsiveness of splenocytes from normal mice. Treatment of C26-bearing mice with gemcitabine or an anti-GR1 antibody led to depletion of MDSC and restored splenocyte IFN responsiveness. Spleens from C26-bearing animals displayed elevated levels of iNOS protein and nitric oxide. In vitro treatment of splenocytes with a nitric oxide donor led to a decreased STAT1 IFN response. The elevation in nitric oxide in C26-bearing mice was associated with increased levels of nitration on STAT1. Finally, splenocytes from iNOS knockout mice bearing C26 tumors exhibited a significantly elevated IFN response as compared with control C26 tumor-bearing mice. These data suggest that nitric oxide produced by MDSC can lead to reduced IFN responsiveness in immune cells.
Project description:MDSCs are a group of cells with potent immune-suppressive activity. These cells accumulate in many pathologic conditions and play a major role in the regulation of immune responses. The nature of MDSC remains highly debatable. In cancer, most MDSCs are represented by cells with granulocytic phenotype and morphology, G-MDSC. The relationship between G-MDSCs and Neu remains unclear. In this study, we have found that G-MDSCs, from tumor-bearing, and Neu, from tumor-free, mice share a common morphology and phenotype. However, in contrast to Neu, a substantial proportion of G-MDSCs expressed M-CSFR and a CD244 molecule. Neu had significantly higher phagocytic activity, expression of lysosomal proteins, and TNF-? than corresponding G-MDSCs, which had significantly higher activity of arginase, MPO, and ROS. In contrast to G-MDSC, neither rested nor mobilized Neu suppressed T cells. G-MDSC survived 2 days in culture in the presence of GM-CSF and within 24 h, became phenotypic and functionally similar to Neu. Tumor-associated G-MDSC shared most characteristics of splenic G-MDSC, rather then Neu. These data suggest that in cancer, despite morphological and phenotypic similarities, G-MDSCs are functionally distinct from Neu and are comprised of pathologically activated precursors of Neu.
Project description:Immune evasion is an emerging hallmark of cancer progression. However, functional studies to understand the role of myeloid-derived suppressor cells (MDSCs) in the tumor microenvironment are limited by the lack of available specific cell surface markers. We adapted a competitive peptide phage display platform to identify candidate peptides binding MDSCs specifically and generated peptide-Fc fusion proteins (peptibodies). In multiple tumor models, intravenous peptibody injection completely depleted blood, splenic and intratumoral MDSCs in tumor-bearing mice without affecting proinflammatory immune cell types, such as dendritic cells. Whereas control Gr-1-specific antibody primarily depleted granulocytic MDSCs, peptibodies depleted both granulocytic and monocytic MDSC subsets. Peptibody treatment was associated with inhibition of tumor growth in vivo, which was superior to that achieved with Gr-1-specific antibody. Immunoprecipitation of MDSC membrane proteins identified S100 family proteins as candidate targets. Our strategy may be useful to identify new diagnostic and therapeutic surface targets on rare cell subtypes, including human MDSCs.
Project description:In this study, using single-cell RNA-seq, cell mass spectrometry, flow cytometry, and functional analysis, we characterized the heterogeneity of polymorphonuclear neutrophils (PMNs) in cancer. We describe three populations of PMNs in tumor-bearing mice: classical PMNs, polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs), and activated PMN-MDSCs with potent immune suppressive activity. In spleens of mice, PMN-MDSCs gradually replaced PMNs during tumor progression. Activated PMN-MDSCs were found only in tumors, where they were present at the very early stages of the disease. These populations of PMNs in mice could be separated based on the expression of CD14. In peripheral blood of cancer patients, we identified two distinct populations of PMNs with characteristics of classical PMNs and PMN-MDSCs. The gene signature of tumor PMN-MDSCs was similar to that in mouse activated PMN-MDSCs and was closely associated with negative clinical outcome in cancer patients. Thus, we provide evidence that PMN-MDSCs are a distinct population of PMNs with unique features and potential for selective targeting opportunities.
Project description:BackgroundMyeloid-derived suppressor cells (MDSCs) participate in tumor-elicited immunosuppression by dramatically blocking T-cell-induced antitumor responses, thereby influencing the effectiveness of cancer immunotherapies. Treatments that alter the differentiation and function of MDSCs can partially restore antitumor immune responses. The long noncoding RNA plasmacytoma variant translocation 1 (lncRNA Pvt1) is a potential oncogene in a variety of cancer types. However, whether lncRNA Pvt1 is involved in the regulation of MDSCs has not been thoroughly elucidated to date.MethodsMDSCs or granulocytic MDSCs (G-MDSCs) were isolated by microbeads and flow cytometry. Bone marrow derived G-MDSCs were induced by IL-6 and GM-CSF. The expression of lncRNA Pvt1 was measured by qRT-PCR. Specific siRNA was used to knockdown the expression of lncRNA Pvt1 in G-MDSCs.ResultsIn this study, we found that knockdown of lncRNA Pvt1 significantly inhibited the immunosuppressive function of G-MDSCs in vitro. Additionally, lncRNA Pvt1 knockdown reduced the ability of G-MDSCs to delay tumor progression in tumor-bearing mice in vivo. Notably, lncRNA Pvt1 was upregulated by HIF-1α under hypoxia in G-MDSCs.ConclusionsTaken together, our results demonstrate a critical role for lncRNA Pvt1 in regulating the immunosuppression activity of G-MDSCs, and lncRNA Pvt1 might thus be a potential antitumor immunotherapy target.
Project description:The regulation of myeloid-derived suppressor cells (MDSCs) function is key for effective tumor immunotherapy. Recent lipidomics data revealed that MDSCs accumulate lipid species thereby promote their immunosuppressive activity on T cells. However, genetic manipulation of fatty acid transport protein 2 in mice reduced lipid accumulation in polymorphonuclear MDSCs. Herein we present for the first time lipidome of splenic MDSCs from B16F10 melanoma-bearing mice treated with FATP2 inhibitor - lipofermata compared to the control group. B16F10 were subcutaneously injected into the left flank of wild-type C57BL/6 mice, either lipofermata or vehicle was administered to the mice every day starting from day 7 post-tumor injection for 2 weeks. CD11b+Gr1+ cells from the spleen referred to as MDSCs were sorted on a flow cytometer machine for lipid extraction. Lipid was extracted using methyl‑tert‑butyl ether as previously described with slight modification, followed by liquid chromatography-mass spectrophotometry lipid profiling using a Q-Exactive instrument coupled with HPLC. The raw scans were identified and quantified with LipidSearch while raw data for various lipid species available on the Mendeley Data repository [1]. The lipid profiles reveal change in lipid species following blockade of FATP2 expression in MDSCs compared to the control. These data were collected in connection to a co-submitted paper [2].
Project description:The aim of the study is to evaluate whether the preoperative level of myeloid-derived suppressor cells is associated with postoperative complications classified by Clavien-Dindo categories. Levels of all MDSC, polymorphonuclear MDSC (PMNMDSC), monocytic MDSC (MMDSC), early-stage MDSC (EMDSC) and monocytic to polymorphonuclear MDSC ratio (M/PMN MDCS) were established and compared in patients with postoperative complications, severe postoperative complications (>= IIIA according to Clavien-Dindo) and severe septic complications.
Project description:Polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs) are implicated in the progression and outcome of a variety of pathological states, from cancer to infection. Our previous work has identified three antimicrobial peptides differentially expressed by PMN-MDSCs compared to conventional neutrophils isolated from dogs, mice, and human patients with cancer. We therefore hypothesized that PMN-MDSCs in dogs with cancer possess antimicrobial activity. In the current work, we observed that exposure of PMN-MDSCs to Gram-negative bacteria (Escherichia coli) increased the expression of reactive oxygen species by the PMN-MDSCs, indicating that they are capable of initiating an anti-microbial response. Electron microscopy revealed that the PMN-MDSCs phagocytosed Gram-negative and Gram-positive (Staphylococcus aureus) bacterial species. Lysis of bacteria within some of the PMN-MDSCs suggested bactericidal activity, which was confirmed by the recovery of significantly lower numbers of bacteria of both species following exposure to PMN-MDSCs isolated from tumor-bearing dogs. Our data therefore indicate that PMN-MDSCs isolated from dogs with cancer, in common with PMNs, have phagocytic and bactericidal activity. This nexus of immunosuppressive and antimicrobial activity reveals a hitherto unrecognized function of MDSCs.
Project description:Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of immature myeloid cells that suppress effector T cell responses and can reduce the efficacy of cancer immunotherapies. We previously showed that ultra-small polymer nanoparticles efficiently drain to the lymphatics after intradermal injection and target antigen-presenting cells, including Ly6c(hi) Ly6g(-) monocytic MDSCs (Mo-MDSCs), in skin-draining lymph nodes (LNs) and spleen. Here, we developed ultra-small polymer micelles loaded with 6-thioguanine (MC-TG), a cytotoxic drug used in the treatment of myelogenous leukemia, with the aim of killing Mo-MDSCs in tumor-bearing mice and thus enhancing T cell-mediated anti-tumor responses. We found that 2 days post-injection in tumor-bearing mice (B16-F10 melanoma or E.G7-OVA thymoma), MC-TG depleted Mo-MDSCs in the spleen, Ly6c(lo) Ly6g(+) granulocytic MDSCs (G-MDSCs) in the draining LNs, and Gr1(int) Mo-MDSCs in the tumor. In both tumor models, MC-TG decreased the numbers of circulating Mo- and G-MDSCs, as well as of Ly6c(hi) macrophages, for up to 7 days following a single administration. MDSC depletion was dose dependent and more effective with MC-TG than with equal doses of free TG. Finally, we tested whether this MDSC-depleting strategy might enhance cancer immunotherapies in the B16-F10 melanoma model. We found that MC-TG significantly improved the efficacy of adoptively transferred, OVA-specific CD8(+) T cells in melanoma cells expressing OVA. These findings highlight the capacity of MC-TG in depleting MDSCs in the tumor microenvironment and show promise in promoting anti-tumor immunity when used in combination with T cell immunotherapies.