Combined TIM-3 blockade and CD137 activation affords the long-term protection in a murine model of ovarian cancer

Zhiqiang Guo,Zhijun Xia,Meng Luan,Shulan Zhang,Gang Wang,Dali Cheng,Liangliang Wu

doi:10.1186/1479-5876-11-215

Abstract

BackgroundT-cell immunoglobulin and mucin domain 3 (TIM-3) is known as a negative immune regulator and emerging data have implicated TIM-3 a pivotal role in suppressing antitumor immunity. The co-stimulatory receptor CD137 is transiently upregulated on T-cells following activation and increases their proliferation and survival when engaged. Although antagonistic anti-TIM-3 or agonistic anti-CD137 antibodies can promote the rejection of several murine tumors, some poorly immunogenic tumors were refractory to this treatment. In this study, we sought to evaluate whether combined TIM-3 blockade and CD137 activation would significantly improve the immunotherapy in the murine ID8 ovarian cancer model.MethodsMice with established ID8 tumor were intraperitoneally injected with single or combined anti-TIM-3/CD137 monoclonal antibody (mAb); mice survival was recorded, the composition and gene expression of tumor-infiltrating immune cells in these mice was analyzed by flow cytometry and quantitative RT-PCR respectively, and the function of CD8+ cells was evaluated by ELISA and cytotoxicity assay.ResultsEither anti-TIM-3 or CD137 mAb alone, although effective in 3 days established tumor, was unable to prevent tumor progression in mice bearing 10 days established tumor, however, combined anti-TIM-3/CD137 mAb significantly inhibited the growth of these tumors with 60% of mice tumor free 90 days after tumor inoculation. Therapeutic efficacy was associated with a systemic immune response with memory and antigen specificity, required CD4+ cells and CD8+ cells. The 2 mAb combination increased CD4+ and CD8+ cells and decreased immunosuppressive CD4+FoxP3+ regulatory T (Treg) cells and CD11b+Gr-1+ myeloid suppressor cells (MDSC) at tumor sites, giving rise to significantly elevated ratios of CD4+ and CD8+ cells to Treg and MDSC; This is consistent with biasing local immune response towards an immunostimulatory Th1 type and is further supported by quantitative RT-PCR data showing the increased Th1-associated genes by anti-TIM-3/CD137 treatment. The increased CD8+ T cells produced high level of IFN-γ upon tumor antigen stimulation and displayed antigen-specific cytotoxic activity.ConclusionsTo our knowledge, this is the first report investigating the effects of anti-TIM-3/CD137 combined mAb in a murine ovarian cancer model, and our results may aid the design of future trials for ovarian cancer immunotherapy.

Highlights

T-cell immunoglobulin and mucin domain 3 (TIM-3) is known as a negative immune regulator and emerging data have implicated TIM-3 a pivotal role in suppressing antitumor immunity
Combined treatment of anti-TIM-3 and anti-CD137 monoclonal antibody (mAb) significantly increased survival of mice bearing 10 days established tumor with 60% (6 out of 10 mice) of mice tumor free 90 days after tumor injection (Figure 1B; p < 0.01, combined mAb compared to single or control mAb), and even mice succumbed to tumor growth had significantly prolonged MTS compared with control or single mAb treated mice (Figure 1D; MTS 31.40, 32.80, 32.50 and 73.00 days for control, anti-TIM-3, anti-CD137 and antiTIM-3/CD137 group; p < 0.01, combined mAb compared to single or control mAb)
Combined anti-TIM-3/CD137 mAbs were even more efficacious in 3 days established ID8 tumor model with 100% of mice remaining free of tumor 90 days post-injection (Figure 1A; p < 0.001 compared to control mAb)

Summary

Introduction

T-cell immunoglobulin and mucin domain 3 (TIM-3) is known as a negative immune regulator and emerging data have implicated TIM-3 a pivotal role in suppressing antitumor immunity. Over 70% of women with EOC present with advanced stage disease and tumor dissemination throughout the peritoneal cavity [2]. The studies pioneered by Coukos and colleagues indicate tumor immune surveillance plays a role in clinical outcomes in EOC supported by the close correlation between survival and tumor infiltration with CD3+ T cells in the large annotated clinical samples [10]. EOC is a devastating disease, metastases are frequently restricted to the peritoneal cavity where the tumor microenvironment is directly accessible, which prevents the need for systemic delivery of immunostimulatory treatments [11]. Despite the abundant evidence that anti-tumor immunity could be effective, clinical success with immunebased therapies for EOC has generally been modest [12]

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