Yumiko Matsumura

Negative regulation of cytokine signaling and immune responses by SOCS proteins

Immune and inflammatory systems are controlled by multiple cytokines, including interleukins and interferons. Many of these cytokines exert their biological functions through JAKs (Janus tyrosine kinases) and STAT (signal transduction and activators of transcription) transcription factors. CIS (cytokine-inducible SH2 (Src homology 2) protein) and SOCS (suppressor of cytokine signaling) are a family of intracellular proteins, several of which have emerged as key physiological regulators of cytokine-mediated homeostasis, including innate and adaptive immunity. In this review we focus on the molecular mechanism of the action of CIS/SOCS family proteins and their roles in immune regulation and inflammatory diseases including rheumatoid arthritis.

Selective expansion of foxp3-positive regulatory T cells and immunosuppression by suppressors of cytokine signaling 3-deficient dendritic cells.

Dendritic cells (DCs) induce immunity and immunological tolerance as APCs. It has been shown that DCs secreting IL-10 induce IL-10+ Tr1-type regulatory T (Treg) cells, whereas Foxp3-positive Treg cells are expanded from naive CD4+ T cells by coculturing with mature DCs. However, the regulatory mechanism of expansion of Foxp3+ Treg cells by DCs has not been clarified. In this study, we demonstrated that suppressors of cytokine signaling (SOCS)-3-deficient DCs have a strong potential as Foxp3+ T cell-inducing tolerogenic DCs. SOCS3−/− DCs expressed lower levels of class II MHC, CD40, CD86, and IL-12 than wild-type (WT)-DCs both in vitro and in vivo, and showed constitutive activation of STAT3. Foxp3− effector T cells were predominantly expanded by the priming with WT-DCs, whereas Foxp3+ Treg cells were selectively expanded by SOCS3−/− DCs. Adoptive transfer of SOCS3−/− DCs reduced the severity of experimental autoimmune encephalomyelitis. Foxp3+ T cell expansion was blocked by anti-TGF-β Ab, and SOCS3−/− DCs produced higher levels of TGF-β than WT-DCs, suggesting that TGF-β plays an essential role in the expansion of Foxp3+ Treg cells. These results indicate an important role of SOCS3 in determining on immunity or tolerance by DCs.

Induction of Hyper Th1 Cell-Type Immune Responses by Dendritic Cells Lacking the Suppressor of Cytokine Signaling-1 Gene

Suppressor of cytokine signaling (SOCS1/JAB) has been shown to play an important role in regulating dendritic cell (DC) function and suppressing inflammatory diseases and systemic autoimmunity. However, role of SOCS1 in DCs for the initiation of Th cell response has not been clarified. Here we demonstrate that SOCS1-deficient DCs induce stronger Th1-type responses both in vitro and in vivo. SOCS1-deficient DCs induced higher IFN-γ production from naive T cells than wild-type (WT) DCs in vitro. Lymph node T cells also produced a higher amount of IFN-γ when SOCS1-deficient bone marrow-derived DCs (BMDCs) were transferred in vivo. Moreover, SOCS1−/− BMDCs raised more effective anti-tumor immunity than WT BMDCs. Microarray analysis revealed that IFN-inducible genes were highly expressed in SOCS1-deficient DCs without IFN stimulation, suggesting hyper STAT1 activation in SOCS1−/− DCs. These phenotypes of SOCS1-deficient DCs were similar to those of CD8α+ DCs, and in the WT spleen, SOCS1 is expressed at higher levels in the Th2-inducing CD4+ DC subset, relative to the Th1-inducing CD8α+ DC subset. We propose that reduction of the SOCS1 gene expression in DCs leads to CD8α+ DC-like phenotype which promotes Th1-type hyperresponses.

Suppressors of Cytokine Signaling-1 and -3 Regulate Osteoclastogenesis in the Presence of Inflammatory Cytokines

Bone metabolism and the immune system have a correlative relationship, and both are controlled by various common cytokines, such as IFNs and ILs, produced in the bone microenvironments. The suppressor of cytokine signaling-1 (SOCS1) and SOCS3 are negative regulators of such cytokines. Although SOCSs are shown to be induced during osteoclast differentiation, their physiological roles in osteoclast differentiation and function have not been clarified. Thus, we examined the roles of SOCS1 and SOCS3 in osteoclastogenesis using SOCS1- and SOCS3-deficient mice. IFN-γ-mediated inhibition of osteoclast differentiation from bone marrow-derived monocytes (BMMs) was strongly enhanced in SOCS1-deficient BMMs, but was diminished in SOCS1-overexpressing BMMs. Moreover, LPS-induced osteoclastogenesis and bone destruction in vivo were suppressed in SOCS1+/− mice compared with those in wild-type mice, suggesting that SOCS1 antagonizes the inhibitory effect of IFN-γ on osteoclastogenesis. SOCS3 did not alter the inhibitory effect of IFNs in osteoclastogenesis in both gain and loss of functional assays; however, the suppressive effect of IL-6 on osteoclast differentiation was greater in SOCS3-deficient BMMs than in wild-type BMMs in vitro. In addition, IL-6 significantly prevented LPS-induced bone destruction in SOCS3-deficient mice, although it failed in wild-type mice in vivo. In SOCS3-deficient BMMs, expression levels of TNF-receptor-associated factor-6 and IκB were drastically reduced and receptor activator of the NF-κB ligand-induced IκB phosphorylation was severely impaired in the presence of IL-6. These data suggest that both SOCS1 and SOCS3 regulate osteoclastogenesis by blocking the inhibitory effect of inflammatory cytokines on receptor activator of the NF-κB ligand-mediated osteoclast differentiation signals. Selective suppression of SOCS1 and SOCS3 in osteoclast precursors may be a possible therapeutic strategy for inflammatory bone destruction.

A Major Lipid Raft Protein Raftlin Modulates T Cell Receptor Signaling and Enhances Th17-Mediated Autoimmune Responses

The membrane microdomains known as lipid rafts have been shown to act as platforms for the initiation of various receptor signals. Through proteomic analysis, we have identified a novel protein termed Raftlin (raft-linking protein) as a major protein in lipid rafts. To determine the physiological and immunological functions of Raftlin in mammals, we generated Raftlin-deficient mice, as well as Raftlin-transgenic (Tg) mice. Although Raftlin was originally identified in B cells, we observe no severe abnormalities in the B cells of these mice, presumably due to a high expression of Raftlin-homologue (Raftlin-2). T cells, in contrast, expressed a substantial amount of Raftlin but no Raftlin-2. In Raftlin-deficient mice, T cell-dependent Ab production was reduced, and experimental autoimmune encephalomyelitis, a Th17-dependent autoimmune disease model, was ameliorated. In Raftlin-Tg mice, in contrast, Ab production was enhanced and experimental autoimmune encephalomyelitis was more severe. Cytokine production, especially that of IL-17, was reduced in Raftlin-deficient T cells, while it was enhanced in Raftlin-Tg T cells. We found that these changes were associated with the strength of the TCR-mediated signals. Importantly, localization of Lck protein in the lipid rafts was enhanced by Raftlin overexpression and reduced by Raftlin deficiency. These data indicate that Raftlin modulates TCR signals and is necessary for the fine-tuning of T cell-mediated immune responses.

Absence of LTB4/BLT1 axis facilitates generation of mouse GM-CSF-induced long-lasting antitumor immunologic memory by enhancing innate and adaptive immune systems.

BLT1 is a high-affinity receptor for leukotriene B4 (LTB4) that is a potent lipid chemoattractant for myeloid leukocytes. The role of LTB4/BLT1 axis in tumor immunology, including cytokine-based tumor vaccine, however, remains unknown. We here demonstrated that BLT1-deficient mice rejected subcutaneous tumor challenge of GM-CSF gene-transduced WEHI3B (WGM) leukemia cells (KO/WGM) and elicited robust antitumor responses against second tumor challenge with WEHI3B cells. During GM-CSF-induced tumor regression, the defective LTB4/BLT1 signaling significantly reduced tumor-infiltrating myeloid-derived suppressor cells, increased the maturation status of dendritic cells in tumor tissues, enhanced their CD4(+) T-cell stimulation capacity and migration rate of dendritic cells that had phagocytosed tumor-associated antigens into tumor-draining lymph nodes, suggesting a positive impact on GM-CSF-sensitized innate immunity. Furthermore, KO/WGM mice displayed activated adaptive immunity by attenuating regulatory CD4(+) T subsets and increasing numbers of Th17 and memory CD44(hi)CD4(+) T subsets, both of which elicited superior antitumor effects as evidenced by adoptive cell transfer. In vivo depletion assays also revealed that CD4(+) T cells were the main effectors of the persistent antitumor immunity. Our data collectively underscore a negative role of LTB4/BLT1 signaling in effective generation and maintenance of GM-CSF-induced antitumor memory CD4(+) T cells.

TLR7 ligand augments GM-CSF-initiated antitumor immunity through activation of plasmacytoid dendritic cells

Narusawa and colleagues found that type 1 IFNs and plasmacytoid dendritic cells in the tumor-draining lymph nodes mediate GM-CSF–induced antitumor immunity in immunocompetent mice, and they report that the synthetic TLR7 ligand imiquimod could overcome tolerance and enhance autologous GM-CSF antitumor effects. Vaccination with irradiated granulocyte macrophage colony-stimulating factor (GM-CSF)–transduced autologous tumor cells (GVAX) has been shown to induce therapeutic antitumor immunity. However, its effectiveness is limited. We therefore attempted to improve the antitumor effect by identifying little-known key pathways in GM-CSF–sensitized dendritic cells (GM-DC) in tumor-draining lymph nodes (TDLN). We initially confirmed that syngeneic mice subcutaneously injected with poorly immunogenic Lewis lung carcinoma (LLC) cells transduced with Sendai virus encoding GM-CSF (LLC/SeV/GM) remarkably rejected the tumor growth. Using cDNA microarrays, we found that expression levels of type I interferon (IFN)–related genes, predominantly expressed in plasmacytoid DCs (pDC), were significantly upregulated in TDLN-derived GM-DCs and focused on pDCs. Indeed, mouse experiments demonstrated that the effective induction of GM-CSF–induced antitumor immunity observed in immunocompetent mice treated with LLC/SeV/GM cells was significantly attenuated when pDC-depleted or IFNα receptor knockout (IFNAR−/−) mice were used. Importantly, in both LLC and CT26 colon cancer–bearing mice, the combinational use of imiquimod with autologous GVAX therapy overcame the refractoriness to GVAX monotherapy accompanied by tolerability. Mechanistically, mice treated with the combined vaccination displayed increased expression levels of CD86, CD9, and Siglec-H, which correlate with an antitumor phenotype, in pDCs, but decreased the ratio of CD4+CD25+FoxP3+ regulatory T cells in TDLNs. Collectively, these findings indicate that the additional use of imiquimod to activate pDCs with type I IFN production, as a positive regulator of T-cell priming, could enhance the immunologic antitumor effects of GVAX therapy, shedding promising light on the understanding and treatment of GM-CSF–based cancer immunotherapy. Cancer Immunol Res; 2(6); 568–80. ©2014 AACR.

A novel, polymer-coated oncolytic measles virus overcomes immune suppression and induces robust antitumor activity

Although various therapies are available to treat cancers, including surgery, chemotherapy, and radiotherapy, cancer has been the leading cause of death in Japan for the last 30 years, and new therapeutic modalities are urgently needed. As a new modality, there has recently been great interest in oncolytic virotherapy, with measles virus being a candidate virus expected to show strong antitumor effects. The efficacy of virotherapy, however, was strongly limited by the host immune response in previous clinical trials. To enhance and prolong the antitumor activity of virotherapy, we combined the use of two newly developed tools: the genetically engineered measles virus (MV-NPL) and the multilayer virus-coating method of layer-by-layer deposition of ionic polymers. We compared the oncolytic effects of this polymer-coated MV-NPL with the naked MV-NPL, both in vitro and in vivo. In the presence of anti-MV neutralizing antibodies, the polymer-coated virus showed more enhanced oncolytic activity than did the naked MV-NPL in vitro. We also examined antitumor activities in virus-treated mice. Complement-dependent cytotoxicity and antitumor activities were higher in mice treated with polymer-coated MV-NPL than in mice treated with the naked virus. This novel, polymer-coated MV-NPL is promising for clinical cancer therapy in the future.

IL-21 inhibits IL-17A-producing γδ T-cell response after infection with Bacillus Calmette-Guérin via induction of apoptosis.

Innate γδ T cells expressing Vγ6 produce IL-17A at an early stage following infection with Mycobacterium bovis Bacillus Calmette-Guérin (BCG). In this study, we used IL-21 receptor knockout (IL-21R KO) mice and IL-21-producing recombinant BCG mice (rBCG-Ag85B-IL-21) to examine the role of IL-21 in the regulation of IL-17A-producing innate γδ T-cell response following BCG infection. IL-17A-producing Vγ6+ γδ T cells increased in the peritoneal cavity of IL-21R KO mice more than in wild type mice after BCG infection. In contrast, the number of IL-17A-producing Vγ6+ γδ T cells was significantly lower after inoculation with rBCG-Ag85B-IL-21 compared with control rBCG-Ag85B. Notably, exogenous IL-21 selectively induced apoptosis of IL-17A-producing Vγ6+ γδ T cells via Bim. Thus, these results suggest that IL-21 acts as a potent inhibitor of a IL-17A-producing γδ T-cell subset during BCG infection.

631. Novel Polymer-Coated Stealth Oncolytic Measles Virus Overcame Immune Suppression and Induced Stronger Antitumor Activity

Background: Although there have recently been much progress in cancer treatment including surgery, chemotherapy and radiotherapy, cancers have long been the leading cause of death in Japan in the last 30 years and the development of new therapeutic modalities is imminently required. As a new modality, there has recently been great interest in oncolytic virotherapy. Particularly, measles virus is one of the candidate viruses expected for strong antitumor effects. The efficacy of virotherapy, however, was strongly limited by the immune response of the host in previous clinical trials.Methods: To enhance and prolong the antitumor activity of the virotherapy in vivo, we combined newly developed tools of the genetically engineered measles virus (MV-NPL) and multilayer virus coating method of layer-by-layer deposition of ionic polymers. We compared the oncolytic effects of this polymer-coated MV-NPL with naked MV-NPL in vitro and in vivo.Results: In the presence of anti-MV neutralizing antibodies, the polymer-coated virus showed more enhanced oncolytic activity than naked MV-NPL in vitro. We also examined the antitumor immunity in virus treated mice. Complement-dependent cytotoxicity activities in mice treated with polymer-coated MV-NPL were higher than those with naked virus and stronger antitumor activity was observed in these mice.Conclusion: This novel polymer-coated MV-NPL may be promising for future clinical cancer therapy.