Foxo1调控NK细胞成熟和恶性转化的作用及机制研究

NK cell maturation is tightly associated with the function of immune surveillance in vivo. NK cell leukemia is highly aggressive and of no response to current any treatment. Therefore, to identify the key factor involved in NK cell maturation and leukemia is not only helpful for NK cell usage, but also for preventing and treating NK cell malignant transformation. T-bet is a critical transcription factor regulating NK cell maturation. We found that Foxo1 was specifically overexpressed in T-bet knockout murine NK cells. On the contrary, mature NK cell subpopulation was largely increased after conditional depletion of Foxo1 in NK cells, which means that Foxo1 can inhibit NK cell maturation. Meanwhile, Foxo1 expression was lower in NK cell leukemia cell lines than that in normal control NK cells. Based on our previous investigation, we will continue to explore the crucial role and corresponding potential mechanism of Foxo1 in NK cell maturation and leukemia in vivo by virtue of conditional knockout of Foxo1 in NK cells and IL-15 transgenic mice and other phenotypes of mice, and we will also try to identify the molecular mechanism associated with Foxo1 function by promoter analysis and chromatin IP in vitro. These studies are helpful for providing new clues for acknowledging NK cell differentiation and maturation and new theoretical evidence for NK cell leukemia diagnosis and treatment.

NK细胞成熟与其免疫监视功能密切相关，NK细胞白血病侵袭度高且无确切有效的治疗方法，明确参与其中的关键分子既有助于NK细胞的合理利用，还可为防治其恶性转化提供新的对策。T-bet是调控NK细胞成熟的关键转录分子，我们发现Foxo1特异性高表达于T-bet敲基因小鼠NK细胞中，反之在NK细胞中特异敲除Foxo1，其成熟亚群比例则大大增加；另外Foxo1在NK细胞白血病中表达也明显低于正常NK细胞。结合Foxo1具有调控NK细胞成熟和抑癌基因的作用，本课题拟继续利用特异性敲除NK细胞Foxo1基因的小鼠和可自发NK细胞白血病的IL-15转基因小鼠等模型，从体内探讨Foxo1在NK细胞成熟和白血病发病中的关键作用和可能机制，并利用启动子分析和染色质IP等技术，从体外验证与Foxo1功能相应的分子机制。该研究有望为了解NK细胞的分化和成熟提供新的线索，并为NK细胞白血病的诊治提供新的理论依据。

NK细胞的成熟与其免疫监视功能密切相关，由NK细胞发生恶性转化生成的NK/T细胞淋巴瘤迄今为止其发病机制尚不明确，因而也缺乏针对性治疗措施。我们在初期的预实验中发现Foxo1可能具有负调NK细胞功能和抑制NK/T细胞淋巴瘤发生的作用。为此，在国家自然科学基金委的资助下，本项目利用可在小鼠NK细胞中实现敲基因的NKp46icre工具小鼠，首先发现Foxo1是负调NK细胞成熟的关键分子，并与转录因子T-bet之间存在着相互拮抗的作用，Foxo1还具有负调NK细胞杀伤作用的功能，缺失Foxo1的NK细胞体内杀瘤效果明显增强，提示在未来利用CAR-NK或者CAR-T细胞进行免疫治疗时可能可以通过抑制Foxo1的功能从而达到促进CAR-NK或者CAR-T细胞抗肿瘤的效果；随后，我们继续利用NKp46icre小鼠逐一证实在NK细胞中单独缺失Shp1、13q14、Pten、Foxo1、Foxo3a后，与人NK/T细胞淋巴瘤的研究结果不一致的是，这些基因的缺失并不能引起小鼠NK/T细胞淋巴瘤，提示可能还有其他更重要的基因参与了NK/T细胞淋巴瘤的发生发展，值得我们做进一步的深入探讨。总之，本课题研究对于未来利用NK和T细胞抗肿瘤免疫治疗、探讨NK/T细胞淋巴瘤发生发展的分子机制以及对NK/T细胞淋巴瘤实施精准治疗提供了新的实验依据。