双重促渗机制协同提高特异性杀伤T细胞在肿瘤部位的浸润并用于免疫豁免型肿瘤的治疗

免疫检查点抑制剂（ICI）在实体瘤特别是免疫豁免型肿瘤（IET）中总体响应率低，主要原因在于该表型肿瘤内缺乏特异性杀伤T细胞（CTL）的招募信号，及其细胞外基质（ECM）和肿瘤相关成纤维细胞（CAF）共同形成致密的生物学屏障，导致瘤内CTL浸润不足。现有的直接和间接提高CTL浸润的策略均不能解决上述问题且在安全性上存在隐患。本研究拟以胰腺癌为模型，在课题组研究基础上构建共载p-sLIGHT质粒和天然产物a-倒捻子素（a-M）的靶向长循环脂质体（CaP-Lip）：①转染CAF使之分泌sLIGHT蛋白，作为瘤内三级淋巴组织的生成信号，招募CTL；②a-M降低CAF和ECM的屏障作用，两种机制合力增加CTL浸润，最终提高该表型肿瘤对ICI的响应。拟采用体内外模型系统研究CaP-Lip的协同治疗效果及安全性，并探讨其机制。该研究有望为IET的免疫治疗提供新策略，也为其他实体瘤的综合治疗提供新思路。

The overall response rate of immune-excluded tumors (IET) to immune checkpoint inhibitor (ICI) is very low. This is mainly due to the insufficient intra-tumor CTL infiltration that induced by the lack of tumor specific killer T cells (CTL) recruitment signals and the biological barrier which consist of extracellular matrix (ECM) and tumor-associated fibroblasts (CAF) inside tumor. Existing strategies for both direct and indirect enhancement of CTL infiltration cannot solve the above problems in terms of effectiveness and safety. In this study, with pancreatic cancer as the tumor model, we propose to construct targeted long-circulating calcium phosphate liposomes (CaP-Lip) that contains plasmid p-sLIGHT and natural product α-mangostin (α-M) to address the above challenges. By transfecting CAF to secrete sLIGHT protein to serve as a signal for CTL recruitment and the formation of tertiary lymphoid systems (TLSs), and enabling α-M-mediated reduction of the barrier formed by CAF and ECM, this designed nanostructure is expected to synergistically increase CTL infiltration, and finally raise the response to ICI and eliminate tumor cells. Both in vitro and in vivo experiments will be performed to study the efficacy and safety of CaP-Lip for combination immunotherapy, and to explore the mechanism. Through this study, we aim to provide a novel strategy for improving the efficacy of immunotherapy in IET, and also bring new hope for the combination therapy of other solid tumors.