Uhrf1调控II型NKT细胞抑制抗肿瘤免疫的作用及机制研究

Nature killer T cells （NKT cells） as the bridging system between innate immunity and adaptive immunity play important roles in tumor immunity. Till now, the molecular mechanism of type II NKT cells-mediated inhibition of anti-tumor immunity remains unknown. Recently, we found for the first time that Uhrf1 was upregulated in tumor infiltrating type II NKT cells. Moreover, type II NKT cells were hyperactivated, expression of factors related to cell killing capacity were significantly increased and tumor growth was significantly inhibited in Uhrf1-deficient mice compared to WT littermates. These observations prompted us to hypothesize that Uhrf1 may promote type II NKT cells-mediated inhibition of anti-tumor immunity via epigenetic regulation. In the present project, we will use Uhrf1 conditional knockout mice and the constructed melanoma model to investigate the following topics: First, we will analyze the signaling that promotes Uhrf1 upregulation in tumor infiltrating type II NKT cells. Second, we will test the specificity and way of inhibition of Uhrf1-deficient type II NKT cells in tumor immunity. Finally, we will investigate the molecular mechanism of Uhrf1-mediated inhibition of type II NKT cell activation by promoting PKM2 (Pyruvate kinase muscle isozyme M2) methylation based on whole genome DNA methylation and RNA-seq data. The findings of this project are expected to lay theoretical basis for NKT cell-mediated cancer immunotherapy.

NKT细胞作为固有免疫与适应性免疫的桥梁，在肿瘤免疫中发挥重要调控作用。目前，肿瘤微环境中II型NKT细胞抑制抗肿瘤免疫的机制尚不清楚。我们近期首次发现：表观遗传调控因子Uhrf1在肿瘤浸润的II型NKT细胞中表达上调；Uhrf1敲除小鼠的II型NKT细胞显著活化，细胞杀伤相关指标表达升高，小鼠抗肿瘤能力明显增强。因此我们推断：Uhrf1可能通过表观遗传调控抑制II型NKT细胞的活化，进而抑制抗肿瘤免疫。本项目拟利用已有的Uhrf1条件敲除小鼠及构建的黑色素瘤模型：①检测引起肿瘤微环境II型NKT细胞中Uhrf1上调的信号；②探究缺失Uhrf1的II型NKT细胞促进抗肿瘤免疫的特异性及作用方式；③结合全基因组甲基化及RNA测序结果，阐明Uhrf1通过促进PKM2的甲基化进而抑制II型NKT细胞活化的分子机制。预期研究成果将为NKT细胞介导的肿瘤免疫治疗提供理论依据。

NKT细胞作为固有免疫与适应性免疫的桥梁，在肿瘤免疫中发挥重要调控作用。目前，肿瘤微环境中II型NKT细胞抑制抗肿瘤免疫的机制尚不清楚。我们前期首次发现：表观遗传调控因子Uhrf1在肿瘤浸润的II型NKT细胞中表达上调；Uhrf1敲除小鼠的II型NKT细胞显著活化，细胞杀伤相关指标表达升高，小鼠抗肿瘤能力明显增强。本项目主要利用已有的Uhrf1条件敲除小鼠及构建的黑色素瘤模型：①阐明了肿瘤微环境中的腺苷（Adenosine）可以引起肿瘤微环境II型NKT细胞中Uhrf1的表达上调；②揭示了缺失Uhrf1的II型NKT细胞可以通过释放一些因子特异地促进肿瘤免疫，且直接对肿瘤进行杀伤；③通过结合甲基化及RNA测序结果，阐明了Uhrf1通过促进PKM2的启动子的甲基化进而抑制其表达，Uhrf1缺失的II型NKT细胞中，PKM2可以入核促进CD44、CD69、TRAIL、FASL及Granzyme B等跟细胞活化及杀伤相关的基因的转录，发挥杀伤肿瘤细胞的作用。总之，本项目基本揭示Uhrf1可能通过表观遗传调控抑制II型NKT细胞的活化，进而抑制抗肿瘤免疫。该项目成果可能为NKT细胞介导的肿瘤免疫治疗提供理论依据。