信使RNA-m6A修饰对树突状细胞抗肿瘤免疫反应的调控机制研究

Emerging evidence emphasizes the important role of spontaneous antitumor immune response during tumorigenesis. Therefore, identifying the molecular pathway that can be manipulated to increase tumor specific immune response could provide potential target for enhancing the clinical benefit of immunotherapy. On the other hand, m6A, the most abundant internal mRNA modification responsible for posttranscriptional regulation of mRNA in diverse cell types, is proved to be critical during multiple biological processes. Emerging evidence has revealed a link between m6A and tumorigenesis as evidenced by abnormal translation of tumor oncogenes under control of m6A program. While most study focus on tumor intrinsic oncogenic pathway, the roles of m6A and m6A binding protein in regulating host antitumor immune response remain elusive. To understand the in vivo functions of m6A, we will use conditional knock out mice that lack m6A methytransferase METTL14 and m6A binding protein YTHDF1 in dendritic cells. We will determine the cross-priming capacity of dendritic cells in both knock out and wild-type mice. While integrating multiple m6A-related sequencing methods, we will in depth dissect the functional role of m6A marked mRNA and test their function during anti-tumor immune response. Overall, our study will identify several new immunotherapy targets and opens up a promising avenue of study into epitranscriptomic marker m6A involved in anti-tumor immunity.

肿瘤微环境中的免疫细胞在肿瘤发生发展及抗肿瘤治疗中发挥着极其重要作用。免疫系统如何识别肿瘤是当今肿瘤免疫治疗领域的研究热点。另一方面，近年来信使RNA（mRNA）N6-腺嘌呤甲基化（m6A）修饰的发现，提出了转录后修饰的调控新层次。m6A能够通过影响mRNA的剪切、翻译和降解等加工过程，调控发育和生殖等重要生理过程。然而RNAm6A对免疫细胞的调控机制研究还极为稀少，这一交叉学科仍是几乎空白。本项目拟研究m6A及其相关蛋白在抗肿瘤免疫反应过程中对树突状细胞功能的作用机制。以m6A甲基化转移酶METTL14及结合蛋白YTHDF1条件敲除小鼠为模型，分析m6A对肿瘤生长及肿瘤侵润树突状细胞抗原提呈能力的影响。结合m6A相关测序技术，进一步寻找受m6A调控的核心靶基因。探讨m6A相关蛋白及靶基因与PD-L1抗体的协同治疗效果。加深我们对抗肿瘤免疫反应精密调控机制的理解，为免疫治疗提供新靶点。

尽管越来越多的证据表明RNAm6A修饰异常与肿瘤生长密切相关，RNA甲基化修饰对肿瘤免疫微环境的影响目前尚未有过报道。更重要的是，m6A相关RNA表观转录组学在免疫反应，尤其是肿瘤免疫反应中的调节机制作为交叉学科仍是空白。我们的研究结果发现，RNA m6A书写器METTL14和阅读器YTHDF1的表达水平与T细胞浸润程度呈负相关。同时，YTHDF1基因敲除小鼠的抗肿瘤免疫反应显著高于野生型小鼠，树突状细胞对新抗原的提呈能力大大增强。RNA m6A能够通过调节机体的抗原提呈能力，进而影响机体的抗肿瘤免疫反应。本研究以抗肿瘤免疫反应为出发点，首次从RNA甲基化修饰这一新的维度上解析肿瘤免疫识别机制，解析RNA甲基化m6A修饰及其结合蛋白在抗肿瘤免疫反应中的生物学功能和分子机制。为免疫治疗提供新靶点及联合治疗新策略，为未来的临床转化提供重要的理论基础。