染色质重塑调节因子ARID1A缺失在肝癌发生发展过程中的作用及其机制研究

The tumor is a genetic disease caused by genomic instability, especially somatic mutations. Among somatic mutations, there are a few mutations called driver mutations which can endow the tumor cells with ability of rapid proliferation, tissue invasion and metastasis. So, the finding and identification of these crucial genes with mutations is very important to understanding of tumorigeneisis. Liver cancer is the sixth-most-common cancer overall but the third-most-frequent cause of cancer death. Among primary liver cancers, hepatocellular carcinoma (HCC), the major histological subtype, is associated with multiple risk factors, including hepatitis B (HBV）and C virus infection, alcohol consumption, obesity, and diet contamination. Although previous studies have revealed that certain genetic and epigenetic changes, such as TP53, occur in HCC cells, the pathogenesis of this cancer remains obscure. Recently,we employed whole-exome sequencing to identify somatic mutations in ten HBV-positive individuals with HCC with portal vein tumor thromboses (PVTTs), intrahepatic metastases. Notably, ARID1A (AT-rich interactive domain-containing protein 1A), which encodes a component of the SWI/SNF chromatin remodeling complex, was mutated in 13% HBV-associated HCC specimens. So far, ARID1A has recently been considered as a new type of tumor suppressor gene for its loss of function somatic mutation frequently found in various human tumors. However, the role and mechanism of the loss of function ARID1A mutation in tumorigenesis remain unclear. To explore the role of ARID1A mutations in tumorigenesis, we constructed the hepatocyte-specific Arid1a deletion mice by crossing Arid1a floxed mice with albumin (Alb)-Cre transgenic mice. Interestingly, the hepatocyte-specific Arid1a deficiency results in steatohepatitis, and finally HCC development. To explore the role of p53 in Arid1a deficient mice, we generated Arid1a-/- Tp53-/- mice. Surprisingly, these mice rapidly develop liver cancer or adenocarcinoma. Based on these animal models, We will identify the roles as well as cellular and molecualr mechanisms of Arid1a deficiency alone in oncogenesis of liver cancer; adderss the effect of both Arid1a and Tp53 deficiency on initiation and progression of HCC; and develop potential prevention and treatment methods for HCC. This study will provide the cellular and molecular mechanisms for understanding of role of the loss of function ARID1A mutation in tumorigenesis, as well as the identification of novel diagnostic biomarkers and therapeutic targets for cancer.

体细胞基因突变是肿瘤形成的重要机制之一,发现和鉴定驱动基因异常是理解肿瘤发生发展分子机制的关键，也是发展新型肿瘤靶向治疗的前提条件。本课题前期利用大规模DNA测序技术对乙型肝炎病毒感染相关肝癌进行了外显子组分析，除已知抑癌基因TP53高突变外，表观遗传相关调控因子ARID1A基因也呈高突变；单独ARID1A剔除小鼠可自发产生肝癌，如同时TP53剔除则加速肝癌发生，但机制尚不清楚。本课题拟基于多种ARID1A和TP53剔除小鼠模型，研究新型抑癌基因ARID1A单独缺失以及与TP53协同在肝癌细胞发生、发展和转移中的过程中作用；探讨其内在遗传学、表观遗传学以及相关的分子和细胞学机制，重点阐明ARID1A异常以及协同TP53缺失对基因组稳定性、肝脏炎症微环境、肝癌干/祖细胞等影响；探索针对ARID1A及相关分子和细胞异常的靶向治疗策略和方法。本研究为理解抑癌基因ARID1A在肿瘤作用奠定基础。

体细胞基因突变是肿瘤形成的重要机制之一,发现和鉴定驱动基因异常是理解肿瘤发生发展分子机制的关键，也是发展新型肿瘤靶向治疗的前提条件。本课题前期利用大规模DNA测序技术对乙型肝炎病毒感染相关肝癌进行了外显子组分析，除已知抑癌基因TP53高突变外，表观遗传相关调控因子ARID1A基因也呈高突变，但关于ARID1A在肝癌发生和发展过程中发挥的作用并不清楚。本项目的研究目的便是利用Arid1a基因剔除的小鼠为模型，研究新型抑癌基因ARID1A单独缺失以及与TP53协同在肝癌细胞发生、发展和转移中的过程中作用；探讨其内在遗传学、表观遗传学以及相关的分子和细胞学机制，重点阐明ARID1A异常以及协同TP53缺失对基因组稳定性、肝脏炎症微环境、肝癌干/祖细胞等影响。本项目目前已发现：1）单独Arid1a剔除小鼠可自发产生肝炎甚至肝癌；2）Arid1a的剔除导致小鼠肝细胞DNA损伤和p53信号系统路的激活，Arid1a缺失引起的肝细胞DNA损伤、死亡和炎症反应是通过p53信号通路发挥作用；3）我们进一步探究了Arid1a缺失引起肝癌的分子机制，发现Arid1a缺失可能降低SWI/SNF复合物的功能，引起与细胞分化相关的重要信号通路的基因调节区域染色质开放性改变，从而导致这些关键基因的表达异常，使得在肝细胞中，与分化成熟肝细胞和肝脏功能相关的基因表达下降，与肝干/祖细胞相关的基因表达上升，使得肝细胞逆分化为一种接近肝干/祖细胞或肿瘤干细胞的细胞，最终导致细胞恶性增殖为肿瘤。4）ARID1A通过抑制长链非编码RNA MVIH抑制肝癌细胞的增殖和迁移。我们的工作进一步揭示了ARID1A缺失在肿瘤发生和发展过程中起作用的分子机制，探索针对ARID1A及相关分子和细胞异常的靶向治疗策略和方法，为理解抑癌基因ARID1A在肿瘤作用奠定基础。