CD11b+ Gr-1 + immature myeloid cells (

Evaluation of immune dysfunction during the tumor-bearing state is a critical issue in combating cancer. In this study, we initially found that IL-6, one of the cachectic factors, suppressed CD4+ T cell–mediated immunity through downregulation of MHC class II by enhanced arginase activity of dendritic cells (DC) in tumor-bearing mice. We demonstrated that administration of Ab against IL-6R (anti–IL-6R mAb) greatly enhanced T cell responses and inhibited the growth of tumor in vivo. We also found that IL-6 upregulated the expression of arginase-1 and arginase activity of DC in vitro. Tumor-infiltrating CD11c+ DC exhibited upregulated mRNA expression of arginase-1 but reduced expression of MHC class II in parallel with the increase in serum IL-6 levels at the late stage in tumor-bearing hosts. However, the administration of anti–IL-6R mAb into tumor-bearing mice inhibited both the downmodulation of MHC class II and the upregulation of arginase-1 mRNA levels in DC. Furthermore, we noted that Nω-hydroxy-L-arginine or L-arginine, an arginase-1 inhibitor, blocked the reduction in MHC class II levels on CD11c+ DC during the tumor-bearing state. Finally, we demonstrated that the administration of Nω-hydroxy-L-arginine at the peritumor site significantly enhanced CD4+ T cell responses and inhibited tumor growth. Thus, IL-6–mediated arginase activation and the subsequent reduction in MHC class II expression on DC appeared to be critical mechanisms for inducing dysfunction of the immune system in the tumor-bearing state. Blockade of the IL-6–arginase cascade is a promising tool to overcome the dysfunction of antitumor immunity in tumor-bearing hosts.

Background: Neurotransmitters, including substance P (SP) and neurokinin A (NKA),

No abstract

No abstract

No abstract

Various types of myeloid-derived suppressor cells (MDSCs) and tumor-associated macrophages (TAMs) were generated from immature myeloid cells (ImCs) according to the state of tumor microenvironments. In human cancer patients, MDSCs are generally defined as monocytic (CD11b+, CD14+, and HLA-DR-/low) or granulocytic (CD11b+ and CD15+) myeloid cells with antitumor and immunosuppressive activities. In order to develop the effective cancer immunotherapy, these immune suppressor populations should be restrictlly controlled in tumor bearing hosts. In the present research, we evaluated the immunological functions of monocytic or granulocytic myeloid cells, which were collected from tumor tissues of colorectal cancer patients. We found here that myeloid populations in tumor tissues significantly induced immuno-modulating factors such as IL-6, IL-10, VEGF, iNOS, ARG1, IDO1, and IDO2. In addition, we confirmed that tumor-infiltrating myeloid-populations exhibited a significant immunosuppressive activity than those prepared from peripheral blood mononuclear cells (PBMCs). To investigate how tumor-infiltrating MDSCs acquired the immunosuppressive activity, we focused on the effect of tumor-derived factors (TDFs) on immunosuppressive activity. PBMCs from healthy volunteers were cultured in the presence of IL-6, TGF-β, and granulocyte macrophage colony-stimulating factor (GM-CSF) for 6 days, and then differentiated into Mo-MDSCs (CD11b+CD14+CD33+)-like phenotype cells. The generated Mo-MDSCs were further isolated by using cell sorter system and cultured with donor matched T cells and stimulated with anti-CD3/CD28 beads for 3 days. As a result, we confirmed that T cell proliferation was significantly inhibited by the addition of Mo-MDSCs generated with IL-6, TGF-β and GM-CSF. On the other hand, these populations showed immunostimulating ability in the presence of IFN-g in vitro, suggesting the Mo-MDSCs might have multi-differencing potentials. These results indicated that tumor-infiltrating MDSCs acquired stronger immunosuppressive activity by tumor-derived IL-6 and TGF-β, however the function might be altered in response to cytokine conditions. Thus, we concluded that IL-6 and TGF-β induced functional maturation of MDSCs in tumor microenvironments, suggesting promising targets to improve the immunological responses by immunotherapy for cancer patients. Citation Format: Kentaro Sumida, Yosuke Ono, Junya Ohtake, Kazutaka Masuko, Satoshi Terada, Shun Kaneumi, Takuto Kishikawa, Toshiyuki Kita, Hidemitsu Kitamura. Crucial roles of cytokine-signaling for alteration in functions of myeloid-derived suppressor cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3661. doi:10.1158/1538-7445.AM2014-3661

Introduction Immunosuppression in tumor microenvironments is one of the critical issues for cancer immunotherapy. To develop more effective treatment, it is essential to overcome the dysfunction of immunity in cancer patients. Recently, it has been demonstrated that myeloid derived suppressor cells (MDSCs) have crucial roles for such immunosuppression. In the current reports, it was indicated that activation of STAT3 was required for immunosuppressive function of human MDSCs. In this study, we focused on IL-6/STAT3-signaling pathway in human monocyte-derived dendritic cells (DCs), and investigated the effects of IL-6 on antigen-presenting ability of DCs. Materials and Methods Tumor-infiltrating myeloid cells and PBMCs were collected from specimen of patients with colorectal cancers. Surface molecules , such as HLA-DR, of the cells were investigated by flowcytometry. Then, the surface molecules of monocyte-derived DCs from healthy volunteers were evaluated after the stimulation with IL-6 in vitro. IL-6-treated DCs were co-cultured with autologous T cells stimulated by using anti-CD3 antibody and cytokine production levels were investigated by ELISA. MAGE-A4-specific CD4+ T cells were generated from PBMCs ofhealthy healthy volunteers in vitro and co-cultured with IL-6-pretreated DCs in the presence of MAGE-A4 antigen. Cytokine production by antigen specific T cells were measured by ELISA. Results In this study, we found that expression levels of HLA-DR and CD86 are down regulated in tumor infiltrating CD11c+CD14+ DCs compared with peripheral monocytes. In addition, we confirmed that HLA-DR and CD86 expressions were significantly reduced by IL-6 treatment of CD11c+CD14+ DCs in vitro. The reduction of HLA-DR and CD86 expression levels were remarkably blocked in the presence of STAT3 inhibitor. IFN-γ production by T cells after TCR-stimulation was suppressed in the presence of IL-6-treated DCs compared with control DCs. Moreover, activation of MAGE-A4 antigen-specific CD4+ T cells were remarkably reduced by IL-6-treatment of DCs. Discussion Previously, it was reported that CD14+HLA-DRlow/- cells increased in peripheral blood of cancer patients and that these cells were an important population for immunosuppression. In this study, we demonstrated that IL-6/STAT3-signaling cascade was one of the regulating factors for surface expression levels of HLA-DR on DCs. In addition, we confirmed that IL-6-treatment significantly suppressed the antigen presentation by DCs for cancer antigen-specific CD4+ T cells. Generally, MDSCs were known to induce several immunosuppressive and tumor promoting factors such as VEGF, ARG1, and COX2. We are now investigating target molecules of IL-6 for dysfunction of DCs in tumor microenvironments. Conclusion IL-6/STAT3 signaling pathway regulates immunosuppressive function of human DCs, which would be a promising target for improving the effects of cancer immunotherapy. Citation Format: Yosuke Ono, Jyunya Ohtake, Shun Kaneumi, Kazutaka Masuko, Kentaro Sumida, Takuto Kishikawa, Satoshi Terada, Toshiyuki Kita, Norihiko Takahashi, Akinobu Taketomi, Hidemitsu Kitamura. IL-6/STAT3-dependent immunosuppressive function of tumor-infiltrating dendritic cells in colorectal cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3615. doi:10.1158/1538-7445.AM2014-3615