IFI44L/STAT1通路在化学致肺癌过程中的作用及机制研究

Epigenetic regulation is closely related to chemical carcinogenesis. Our previous studies showed that DNA hypermethylation accounting for IFI44L gene silencing is an important molecular biology event during the process of chemical-induced lung cancer. However, the relevant role and molecular mechanism was unclear. Preliminary experiments showed that IFI44L overexpression could significantly inhibit lung cancer cell growth and migration, and promote cell apoptosis. The tumor suppressor role of IFI44L was markedly decreased after the inhibition of STAT1. IFI44L expression was significantly positively correlated with the expression of STAT1 and the downstream key genes XAF1, TRAIL, and OAS. Further analysis suggests that IFI44L could interact with STAT1. Therefore, we speculate that IFI44L gene is a novel tumor suppressor gene regulated by DNA methylation, which may participate in the whole process of chemical-induced lung cancer through regulating STAT1 mediated downstream gene expression. This project is planned to reveal the epigenetic regulation and main biological functions of IFI44L gene and its role during the process of chemical-induced lung cancer through gene overexpression/knockdown and intervention experiments on gene knock-out animal model, chemical-induced lung cancer model and cell malignant transformation model, clinical lung cancer samples. Additionally, we will elucidate the role and molecular mechanism of IFI44L gene in regulating STAT1 pathway and downstream gene expression. This project may provide scientific basis for looking for early biomarkers and prevention strategies of lung cancer induced by environmental chemicals.

表观遗传调控与化学致癌密切相关。我们前期发现IFI44L受DNA甲基化调控导致表达沉默是化学致肺癌过程中的重要分子事件，但作用机制尚不明确。预实验发现：该基因过表达显著抑制肺癌细胞生长和迁移并促进其凋亡，而抑制STAT1后明显降低其抑癌作用；该基因与STAT1及下游XAF1、TRAIL、OAS表达呈显著正相关；进一步分析提示IFI44L与STAT1存在相互作用。由此推测：IFI44L是一个新的甲基化调控的抑癌基因，可能通过调控STAT1通路介导的下游关键基因的表达参与化学致肺癌过程。本项目拟利用基因敲除动物、化学致肺癌模型及细胞恶性转化模型并结合临床肺癌标本，通过基因过表达和干扰、干预等实验，全面揭示IFI44L基因的表观调控和主要生物学功能及在化学致肺癌过程中的作用，阐明该基因调控STAT1通路及下游基因表达的作用及分子机制，为寻找环境化学物致肺癌的早期生物标志物和预防策略提供科学依据。

表观遗传调控在化学致癌过程中发挥至关重要的作用。课题组前期通过高通量组学筛选出候选表观调控基因IFI44L，但其在化学致肺癌过程中的作用及分子机制尚不明确。本项目利用化学致肺癌动物模型、细胞恶性转化模型、临床肺癌标本并结合生物信息学分析，全面揭示IFI44L基因的表观调控和主要生物学功能及在化学致肺癌过程中的作用机制。研究发现，IFI44L基因在肺癌发生过程中表达显著下调且与甲基化状态呈显著负相关，去甲基化实验进一步证实DNA甲基化负调控该基因表达。IFI44L过表达明显抑制细胞生长并促进细胞凋亡，敲低IFI44L表达后其增殖能力明显增强，细胞凋亡明显减少。功能富集分析显示IFI44L参与了细胞凋亡和JAK/STAT1信号通路，并与下游关键分子高度相关。差异表达IFI44L后，P-STAT1和下游分子XAF1、OAS1、OAS2和OAS3的表达明显改变，而干预STAT1的表达可显著影响IFI44L的抑癌作用及对下游通路的调控。Co-IP结果显示IFI44L与STAT1存在蛋白相互作用，机制研究证实IFI44L通过直接与STAT1蛋白结合促进STAT1磷酸化，激活JAK/STAT1信号通路，从而导致细胞凋亡。进一步生信分析发现IFI44L与肺癌样本中的肿瘤免疫浸润细胞及多种免疫相关通路具有显著相关性，构建的IFI44L相关免疫预后模型可作为肺腺癌的独立预后因素。临床标本组织芯片分析表明，IFI44L的表达与肺癌患者的病理分期呈显著负相关，而与总体生存率呈显著正相关。本研究为筛选环境化学物致肺癌的生物标志物和精准预防/治疗的新靶点提供了科学依据。