治疗胰腺癌的新靶点–阻断肥大细胞和激活OX40联合调控免疫微环境的研究

胰腺癌是致命的难治性肿瘤之一，化疗、放疗、靶向治疗、或免疫治疗都没有取得满意的效果。申请人的前期工作揭示肿瘤微环境中的免疫抑制状态很可能是免疫治疗无效的原因；为此设计了一个独特的联合靶点进行免疫治疗：应用肥大细胞阻滞剂和OX40激活抗体，在胰腺癌的老鼠模型中，治疗后的原位接种肿瘤消失，达到长期无瘤生存；并显著延长自发胰腺癌鼠的带瘤生存期。但是，该策略的治疗机制尚待探讨。基于此，本项目提出肥大细胞诱导免疫抑制的假说。即：阻断肥大细胞后，上调的FCGR阳性细胞，是OX40激活抗体结合锚地和发挥疗效的必需细胞组分。将应用遗传学（肥大细胞敲除鼠）和药理学（肥大细胞阻滞剂）的互补手段，阻断肥大细胞的不同功能，增敏OX40共刺激信号的传递通路，优化抗肿瘤免疫。本课题应用免疫学体内体外干预手段和单细胞技术，深入研究肿瘤微环境中免疫记忆和表遗传调控的作用机制，为胰腺癌的免疫治疗提供新方案。

Advanced pancreatic ductal adenocarcinoma is uniformly fatal and resistant to current therapies, including single-agent immunotherapy. Our previous work demonstrated that immunosuppression in the tumor microenvironment may be a major obstacle to immunotherapy. Furthermore, we designed a potent combination immunotherapy using mast cell blockade and OX40 agonist antibody. This combination eradicated syngeneic orthotopic tumor and achieved long-term tumor-free survival. Notably, it significantly elongated the survival of mice with spontaneous tumor. However, potential mechanisms for the synergistic durable anti-tumor effects remain obscure. On the basis of our findings, we hypothesized that mast cells can foster an immunosuppression in pancreatic cancer, which can incapacitate endogenous anti-tumor immunity. While blocking mast cells, up-regulated FCGR positive cells are required for engaging OX40 agonist antibody to mediate anti-tumor immunity. We propose three specific aims: (1) By employing genetic (mast cell-deficient mice) and pharmacological (mast cell blockades) approaches complementarily, we will investigate the role of mast cells in the delivery of OX40 co-stimulatory signaling; (2) We will select the mast cell blockades for sensitizing OX40 agonist antibody, so that we can optimize the treatment strategies to eliminate pancreatic cancer ultimately; (3) Using the single cell technologies and in vitro and in vivo immunological tools to manipulate the dynamics of mast cells and OX40 pathways, we will identify the attribution of immunological memory and epigenetic regulation in the tumor microenvironment. Completion of this study will uncover the potential mechanisms of action that can guide the design of immune-based combinations for clinical studies in advanced pancreatic ductal adenocarcinoma.