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PDF file, 65K, mAb-mediated depletion of T-cells.

PDF file, 66K, Murine glioma-derived CD11b+ cells inhibit CD8+ T-cells in vitro.

PDF file, 129K, Critical role of IL-4Ralpha in T-cell-suppressing function of BM-derived myeloid cells.

PDF file, 65K, Confirmation of chimerism using enhanced green fluorescence protein (EGFP+) donor BM cells.

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Malignant gliomas are lethal cancers in the brain and heavily infiltrated by myeloid cells. Interleukin-4 receptor-α (IL-4Rα) mediates the immunosuppressive functions of myeloid cells, and polymorphisms in the IL-4Rα gene are associated with altered glioma risk and prognosis. In this study, we sought to evaluate a hypothesized causal role for IL-4Rα and myeloid suppressor cells in glioma development. In both mouse de novo gliomas and human glioblastoma cases, IL-4Rα was upregulated on glioma-infiltrating myeloid cells but not in the periphery or in normal brain. Mice genetically deficient for IL-4Rα exhibited a slower growth of glioma associated with reduced production in the glioma microenvironment of arginase, a marker of myeloid suppressor cells, which is critical for their T-cell inhibitory function. Supporting this result, investigations using bone marrow-derived myeloid cells showed that IL-4Rα mediates IL-13–induced production of arginase. Furthermore, glioma-derived myeloid cells suppressed T-cell proliferation in an IL-4Rα–dependent manner, consistent with their identification as myeloid-derived suppressor cells (MDSC). Granulocyte macrophage colony-stimulating factor (GM-CSF) plays a central role for the induction of IL-4Rα expression on myeloid cells, and we found that GM-CSF is upregulated in both human and mouse glioma microenvironments compared with normal brain or peripheral blood samples. Together, our findings establish a GM-CSF–induced mechanism of immunosuppression in the glioma microenvironment via upregulation of IL-4Rα on MDSCs. Cancer Res; 73(21); 6413–23. ©2013 AACR.

PDF file, 129K, IL-4Ralpha on CD11b+Gr1+ BILs and SPCs.

We have previously reported that the single nucleotide polymorphism (SNP) rs12553612 in IFNA8 is associated with better overall survival of glioma patients with the AA-genotype compared with patients with the AC-genotype. As rs12553612 is located in the IFNA8 promoter, we hypothesized that the A-allele allows for an enhanced IFNA8 promoter activity compared with the C-allele. Reporter assays in the human monocyte derived THP-1 cell line demonstrated a superior promoter activity of the A-allele compared with the C-allele. Electrophoretic mobility shift assays (EMSA) further demonstrated that the A-genotype specifically binds to more nuclear proteins than the C-genotype, including the transcription factor Oct-1. Further, co-transfection of plasmids encoding Oct-1 and the reporter constructs revealed that Oct-1 enhanced the promoter activity with the A- but not the C-allele. Taken together, our data demonstrate that the A-allele in the rs12553612 SNP, which is associated with better glioma patient survival, allows for IFNA8 transcription by allowing for Oct-1 binding, which is absent in patients with C allele, and suggests a molecular mechanism of IFNA8 mediated immune-surveillance of glioma progression., OncoImmunology is the official journal of the European Academy of Tumor Immunology

Malignant gliomas are lethal cancers in the brain and heavily infiltrated by myeloid cells. Interleukin-4 receptor-α (IL-4Rα) mediates the immunosuppressive functions of myeloid cells, and polymorphisms in the IL-4Rα gene are associated with altered glioma risk and prognosis. In this study, we sought to evaluate a hypothesized causal role for IL-4Rα and myeloid suppressor cells in glioma development. In both mouse de novo gliomas and human glioblastoma cases, IL-4Rα was upregulated on glioma-infiltrating myeloid cells but not in the periphery or in normal brain. Mice genetically deficient for IL-4Rα exhibited a slower growth of glioma associated with reduced production in the glioma microenvironment of arginase, a marker of myeloid suppressor cells, which is critical for their T-cell inhibitory function. Supporting this result, investigations using bone marrow-derived myeloid cells showed that IL-4Rα mediates IL-13–induced production of arginase. Furthermore, glioma-derived myeloid cells suppressed T-cell proliferation in an IL-4Rα–dependent manner, consistent with their identification as myeloid-derived suppressor cells (MDSC). Granulocyte macrophage colony-stimulating factor (GM-CSF) plays a central role for the induction of IL-4Rα expression on myeloid cells, and we found that GM-CSF is upregulated in both human and mouse glioma microenvironments compared with normal brain or peripheral blood samples. Together, our findings establish a GM-CSF–induced mechanism of immunosuppression in the glioma microenvironment via upregulation of IL-4Rα on MDSCs. Cancer Res; 73(21); 6413–23. ©2013 AACR.

Several studies have demonstrated a significant immunological impact of single nucleotide polymorphisms in Interferon (IFN)-related genes, such as Toll-Like Receptor (TLR)3 and TLR4. We recently reported that patients with the AA-genotype of a SNP in the IFN-alpha8 (IFNA8) promoter region was associated with better overall survival of patients with WHO grade 2 and 3 gliomas compared to patients with the AC-genotype. Based on these observations we hypothesized that the A-allele in the promoter of IFNA8 allows for enhanced transcription factor binding and expression levels of IFNA8 compared with the C-allele. Analyses of THP-1 cells transfected with a luciferase gene downstream of a short sequence containing the SNP in the IFNA8 promoter demonstrated that the A-allele results in enhanced promoter activity. In silico analysis suggested c-Krox and ELK-1 as likely transcription factors that bind to the IFNA8 polymorphic region. Co-transfection of plasmids encoding the c-Krox or ELK-1 and the luciferase constructs revealed that ELK-1 negatively regulated promoter activity with the A but not C-allele, while c-Krox could not affect activity regardless of allele. Consistently, transfection of ELK-1 siRNA into THP-1 cells resulted in increased promoter activity. To further identify factors that contribute to the enhanced A-allele promoter activity we assessed the effect drugs that inhibit intracellular signaling pathways: PD98059 for inhibiting MEK/ERK, SB203580 a p38 inhibitor, and PPase-2B for de-phosphorylating small molecules. Use of any of the inhibitor resulted in decreased activity of the A-allele promoter activity indicating that multiple proteins or a protein common to multiple pathways seems to be involved. Taken together our data demonstrates that the A-allele in the IFNA8 promoter, which is associated with better glioma patient survival, allows for enhances promoter activation which is negatively regulated by ELK-1 and further regulate by multiple signaling pathways. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1246. doi:1538-7445.AM2012-1246