TIM-3抑制促进MUC1-VNTR6核酸疫苗抗胰腺癌作用的研究

Pancreatic cancer (PC) is a highly aggressive and notoriously difficult to treat, less than 5% of people with pancreatic cancer do survive beyond 5 years. As the vast majority of patients are diagnosed at advanced stage of the disease, only a small population is curative by surgical resection. Although gemcitabine-based chemotherapy is typically offered as standard of care, most patients do not survive longer than 6 months. Thus, new therapeutic approaches are needed. Nucleic acid vaccine, also called DNA vaccine, is one of the most promising immunotherapeutic approaches because it can provide prolonged antigen expression, leading to amplification of immune responses and inducing memory responses through both endogenous and exogenous pathways. However, the anti-tumor effect of DNA vaccine is limited by its weak antigen-specificity.. Mucin 1 (MUC1), a mucins family protein, is a heavily O-glycosylated protein characterized by the presence of short stretches of amino acid sequences repeated several times in tandem. It is overexpressed in more than 90% of pancreatic cancer cells and acts as a potential target for immunotherapy with wide public concern over the recent years. Recently, we have screened out a nucleic acid vaccine which targets the variable number tandem repeat of mucin1 (MUC1-VNTR6) through our work supported by National Natural Scientific Foundation of China (No. 81000917). However, although we found that MUC1-VNTR6 was highly specific and robust immune response in vitro, its immune response was still impeded in vivo. . Recent data suggested that TIM-3 which is high-expressed on dendritic cells (DCs) in tumor microenvironment was responsible for tumor immune tolerance of nucleic acid vaccine by suppressing the activation of both innate immune response and adaptive immune response. Interestingly, our previous data showed that abundant dendritic cells expressing TIM-3 were infiltrating in peritumor region. Thus then, it is reasonable to assume that TIM-3 may play a part in function of our vaccine in vivo. Therefore, our study is conducted to explore the reasons why our vaccine against MUC1-VNTR6 poorly raised immune response in vivo, and the mechanism how TIM-3 was involved in activation of innate immune response and adaptive immune response raised by nucleic acid vaccine against MUC1-VNTR6 in pancreatic cancer. Further, based on our previous findings, a new model combining vaccine against MUC1-VNTR6, anti-TIM-3 and chemotherapy was proposed for the comprehensive treatment of pancreatic cancer.. Overall, this project is intended to clarify the mechanism that DCs in pancreatic cancer microenvironment suppress the immune response elicited by MUC1-VNTR6 nucleic acid vaccine through Tim-3 associated pathway, and suggest a new combination therapy method of “MUC1-VNTR6 DNA vaccine, plus TIM-3 monoclonal antibody, and plus Chemotherapy” which may offer a new approach to treat pancreatic cancer and improve the prognosis.

胰腺癌恶性度高，疗效差，肿瘤核酸疫苗治疗最具应用前景，但存在抗原特异性不强、体内抗瘤作用远弱于体外研究的主要问题，其中的机制尚不明确。申请者在研国家青年科学基金（项目编号：81000917）已筛选出了体外抗瘤作用较强的胰腺癌特异性MUC1-VNTR6核酸疫苗，但其在体内的抗瘤效果仍欠理想。结合最新研究发现肿瘤微环境中负性免疫调节蛋白TIM-3介导的免疫抑制与核酸疫苗抗瘤效应密切相关。本项目通过构建TIM-3基因敲除小鼠的成瘤模型，探讨胰腺癌肿瘤微环境中的TIM-3抑制促进MUC1-VNTR6核酸疫苗激活先天性和特异性抗瘤免疫应答的机制，并提出“MUC1-VNTR6核酸疫苗+TIM-3单抗+化疗”的综合治疗模式。本课题为MUC1-VNTR6核酸疫苗体内抗瘤效果不佳的机制研究提供重要依据，提出胰腺癌综合治疗新模式，有望改善胰腺癌治疗效果不佳的现状。

胰腺癌恶性度高，疗效差，肿瘤核酸疫苗治疗最具应用前景，但存在抗原特异性不强、体内抗瘤作用远弱于体外研究的主要问题。实验组前期研究已筛选出了体外抗瘤作用较强的胰腺癌特异性MUC1-VNTR6核酸疫苗，但其在体内的抗瘤效果仍欠理想。本课题组研究发现肿瘤微环境中负性免疫调节蛋白TIM-3介导的免疫抑制与核酸疫苗抗瘤效应密切相关，拟通过构建TIM-3基因敲除小鼠的成瘤模型，探讨胰腺癌肿瘤微环境中的TIM-3抑制促进MUC1-VNTR6核酸疫苗激活先天性和特异性抗瘤免疫应答的机制。目前本课题组已经按照设计思路，验证了阻断TIM3联合MUC1-VNTRn核酸疫苗小鼠体内抗胰腺癌实验效果，并探讨了可能的机制，我们认为TIM3阻断剂主要通过增强了肿瘤微环境中树突状细胞的固有免疫应答来抑制Tregs的产生增强，从而促进MUC1-VNTRn核酸疫苗对抗肿瘤效应。