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Identification and characterization of B220⁺/B220^- subpopulations in murine Gr1⁺CD11b⁺ cells during tumorigenesis.

ABSTRACT: Although all murine MDSCs are defined as Gr1⁺CD11b⁺, their true immunophenotype remains elusive. In this study, we found murine Gr1⁺CD11b⁺ cells can be divided into two subsets: Gr1⁺CD11b⁺B220^- and Gr1⁺CD11b⁺B220⁺, especially in the spleen tissues. Unlike the dominant B220^- subset, the B220⁺ subpopulation was not induced by tumor in vivo. Moreover, Gr1⁺CD11b⁺B220⁺ cells from tumor-bearing mice spleens were unable to induce arginase 1 and inducible nitric oxide synthase expression, inhibit T cell proliferation, or promote tumor growth in primary tumor site. Nevertheless, these cells suppressed tumor metastasis in vivo and reduced cancer cell motility in vitro, while Gr1⁺CD11b⁺B220^- cells from tumor-bearing mice spleens promoted tumor metastasis and enhanced cancer cell motility. Furthermore, both the polymorphonuclear (PMN-MDSCs) and monocytic MDSCs (Mo-MDSCs) could be further divided into B220^- and B220⁺ subsets; interestingly, tumor only induced the expansion of B220^- PMN-MDSCs and B220^- Mo-MDSCs, but not the B220⁺ counterparts. Compared with B220^- PMN-MDSCs and B220^- Mo-MDSCs, the Ly6G⁺Ly6C^-CD11b⁺B220⁺ and Ly6G^-Ly6C⁺CD11b⁺B220⁺ cells from tumor-bearing mice spleens exhibited a more mature phenotype without immunosuppressive activity. Additionally, IL-6 deficiency attenuated the tumor-induced accumulation of MDSCs, B220^- MDSCs and B220^- PMN-MDSCs but increased the percentages of Gr1⁺CD11b⁺B220⁺, Ly6G⁺Ly6C^-CD11b⁺B220⁺, and Ly6G^-Ly6C⁺CD11b⁺B220⁺ cells, indicating the opposing roles of the IL-6 signaling pathway in the expansion of B220^- MDSCs and their B220⁺ counterparts. Taken together, our findings indicate that the B220⁺ subset is a distinct subset of Gr1⁺CD11b⁺ cells functionally different from the B220^- subpopulation during tumorigenesis and induction of MDSCs to B220⁺ cells may be helpful for cancer therapy.

SUBMITTER: Zhang Z

PROVIDER: S-EPMC8057082 | biostudies-literature | 2021 Apr

REPOSITORIES: biostudies-literature

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Identification and characterization of B220+/B220- subpopulations in murine Gr1+CD11b+ cells during tumorigenesis.

Zhang Zhiqian Z Huang Xu X Wang Enlin E Huang Yugang Y Yang Rongcun R

Oncoimmunology 20210414 1

Although all murine MDSCs are defined as Gr1+CD11b+, their true immunophenotype remains elusive. In this study, we found murine Gr1+CD11b+ cells can be divided into two subsets: Gr1+CD11b+B220- and Gr1+CD11b+B220+, especially in the spleen tissues. Unlike the dominant B220- subset, the B220+ subpopulation was not induced by tumor in vivo. Moreover, Gr1+< ...[more]

PMID: 33948392

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Project description:ObjectiveImmature CD11b + Gr1+ myeloid cells that acquire immunosuppressive capability, also known as myeloid-derived suppressor cells (MDSCs), are a heterogeneous population of cells that regulate immune responses. Our study's objective was to elucidate the role of ovarian cancer microenvironment in regulating the immunosuppressive function of CD11b+Gr1+ myeloid cells.MethodsAll studies were performed using the intraperitoneal ID8 syngeneic epithelial ovarian cancer mouse model. Myeloid cell depletion and immunotherapy were carried out using anti-Gr1 mAb, gemcitabine treatments, and/or anti-PD1 mAb. The treatment effect was assessed by a survival curve, in situ luciferase-guided imaging, and histopathologic evaluation. Adoptive transfer assays were carried out between congenic CD45.2 and CD45.1 mice. Immune surface and intracellular markers were assessed by flow cytometry. ELISA, western blot, and RT-PCR techniques were employed to assess the protein and RNA expression of various markers. Bone marrow-derived myeloid cells were used for ex-vivo studies.ResultsThe depletion of Gr1+ immunosuppressive myeloid cells alone and in combination with anti-PD1 immunotherapy inhibited ovarian cancer growth. In addition to the adoptive transfer studies, these findings validate the role of immunosuppressive CD11b+Gr1+ myeloid cells in promoting ovarian cancer. Mechanistic investigations showed that ID8 tumor cells and their microenvironments produced recruitment and regulatory factors for immunosuppressive CD11b+Gr1+ myeloid cells. CD11b+Gr1+ myeloid cells primed by ID8 tumors showed increased immunosuppressive marker expression and acquired an energetic metabolic phenotype promoted primarily by increased oxidative phosphorylation fueled by glutamine. Inhibiting the glutamine metabolic pathway reduced the increased oxidative phosphorylation and decreased immunosuppressive markers' expression and function. Dihydrolipoamide succinyl transferase (DLST), a subunit of α-KGDC in the TCA cycle, was found to be the most significantly elevated gene in tumor-primed myeloid cells. The inhibition of DLST reduced oxidative phosphorylation, immunosuppressive marker expression and function in myeloid cells.ConclusionOur study shows that the ovarian cancer microenvironment can regulate the metabolism and function of immunosuppressive CD11b + Gr1+ myeloid cells and modulate its immune microenvironment. Targeting glutamine metabolism via DLST in immunosuppressive myeloid cells decreased their activity, leading to a reduction in the immunosuppressive tumor microenvironment. Thus, targeting glutamine metabolism has the potential to enhance the success of immunotherapy in ovarian cancer.

Project description:RationaleThe accumulation of macrophages in the airways and the pulmonary interstitium is a hallmark of cigarette smoke-associated inflammation. Notably, pulmonary macrophages are not a homogenous population but consist of several subpopulations. To date, the manner in which cigarette smoke exposure affects the relative composition and functional capacity of macrophage subpopulations has not been elucidated.MethodsUsing a whole-body cigarette smoke exposure system, we investigated the impact of cigarette smoke on macrophage subpopulations in C57BL/6 mice using flow cytometry-based approaches. Moreover, we used bromodeoxyuridine labelling plus Il1a-/- and Il1r1-/- mice to assess the relative contribution of local proliferation and monocyte recruitment to macrophage accumulation. To assess the functional consequences of altered macrophage subpopulations, we used a model of concurrent bleomycin-induced lung injury and cigarette smoke exposure to examine tissue remodelling processes.Main resultsCigarette smoke exposure altered the composition of pulmonary macrophages increasing CD11b+ subpopulations including monocyte-derived alveolar macrophages (Mo-AM) as well as interstitial macrophages (IM)1, -2 and -3. The increase in CD11b+ subpopulations was observed at multiple cigarette smoke exposure timepoints. Bromodeoxyuridine labelling and studies in Il1a-/- mice demonstrated that increased Mo-AM and IM3 turnover in the lungs of cigarette smoke-exposed mice was IL-1α dependent. Compositional changes in macrophage subpopulations were associated with impaired induction of fibrogenesis including decreased α-smooth muscle actin positive cells following intratracheal bleomycin treatment. Mechanistically, in vivo and ex vivo assays demonstrated predominant macrophage M1 polarisation and reduced matrix metallopeptidase 9 activity in cigarette smoke-exposed mice.ConclusionCigarette smoke exposure modified the composition of pulmonary macrophage by expanding CD11b+ subpopulations. These compositional changes were associated with attenuated fibrogenesis, as well as predominant M1 polarisation and decreased fibrotic activity. Overall, these data suggest that cigarette smoke exposure altered the composition of pulmonary macrophage subpopulations contributing to impaired tissue remodelling.

Project description:The gene expression of murine splenic myeloid derived suppressor cells treated with Tff2 is characterized. The motivation of the study originates in the fact that Gr1+Cd11b+ myeloid-derived suppressor cells (MDSCs), which resemble immature myeloid cells (IMCs), expand during cancer in response to inflammatory cytokines and accumulate in the spleen. MDSCs promote neoplastic progression through their suppression of anti-tumourigenic cytotoxic T-cells. MDSCs are also rapidly expanded following acute insults, but in cancer as opposed to acute inflammation, MDSCs persist. It is now recognized that a vagally-mediated, anti-inflammatory reflex arc promoting acetylcholine secretion by Cd4+ (Cd44hiSelllo) T cells, is necessary for a return to homeostasis after an acute insult. Failure of this restorative neural circuit might contribute to unabated procarcinogenic inflammation, with the chronic expansion of MDSCs driving carcinogenesis. Trefoil factor 2 (Tff2) is a secreted anti-inflammatory peptide produced by both epithelial cells and a small subset of splenic T cell. In this study, we show that splenic Tff2 is induced in vagally-modulated memory T cells to suppress the expansion of MDSCs in response to chemical and carcinogenic injury. Deletion of Tff2 interrupts this anti-inflammatory neural arc and leads to expanded MDSCs and a dramatically increased incidence of colorectal cancer. Tff2 directly suppresses proliferation of myeloid progenitors, in a large part through upregulation of cell-bound Apolipoprotein E (ApoE), which has previously been shown to suppress proliferation of haematopoietic stem and progenitor cells. The predisposition to inflammation-associated cancer can be rescued through transgenic overexpression of splenic Tff2, adenoviral transfer of Tff2 expression or transplantation of Tff2-expressing haematopoietic cells. Thus, Tff2 production in memory T cells, is regulated by the vagus nerve, plays a central role in arresting procarcinogenic MDSC proliferation, and offers a novel approach to the prevention and treatment.

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Identification and characterization of B220⁺/B220^- subpopulations in murine Gr1⁺CD11b⁺ cells during tumorigenesis.

Publications

Identification and characterization of B220<sup>+</sup>/B220<sup>-</sup> subpopulations in murine Gr1<sup>+</sup>CD11b<sup>+</sup> cells during tumorigenesis.

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