肝癌是中国高发的恶性肿瘤，死亡率高、预后差。发现新的肝癌相关基因有助于阐明其致病分子机理以及更有效的诊断和治疗。本实验室前期通过对肝癌组织样本的全外显子组测序发现了一系列新的候选肝癌相关基因，其中ZNF521的突变率最高；体外功能研究显示敲低ZNF521可抑制肝癌细胞的增殖；基因表达谱分析初步提示ZNF521突变与MAPK信号通路显著相关。目前，ZNF521在肝癌中的生物学功能和分子机制均未见公开发表。本项目拟在此基础上，首先通过体外和在体实验确证ZNF521的致瘤性，然后确定其潜在分子机制，验证其是否通过MAPK信号通路促进肝癌的发生发展，最后评价其在肝癌组织中的表达或突变与肝癌患者发生发展和预后的相关性。本项目的实施将有望阐明新型肝癌相关基因ZNF521在肝癌发生发展中的作用和潜在分子机制，补充和完善现有的细胞癌变理论体系，并为肝癌的诊治措施提供新的候选生物标志物和药物靶标。

Hepatocellular carcinoma (HCC) is one of the most common cancers worldwide, especially in China, with high morality and poor prognosis. Our previous studies have identified a list of novel candidate driver genes not previously implicated in this malignancy through whole-exome sequencing of liver tissues of hepatitis B virus (HBV)-associated HCC, on which the ZNF521 gene is the most frequently mutated. Furthermore, our in vitro functional study showed that downregulation of ZNF521 by shRNA suppressed the proliferation of liver cancer cell line HepG2, indicating that it may act as an oncogene in HCC. In addition, we performed a high - throughput gene expression profiling in 8 HCC tissues with ZNF521 mutations and 30 HCC tissues without ZNF521 mutations, followed by gene set enrichment analysis (GSEA). Intriguingly, our GSEA analysis showed that ZNF521 mutations were strongly negatively associated with the activity of negative regulators of Mitogen-activated protein Kinase (MAPK) pathway. However, there is no published study on the biological function and molecular mechanisms of ZNF521 in tumorigenesis and development of HCC. In this proposal, the biological function of ZNF521 in HCC will be confirmed by investigating the possible influence of ZNF521 on cell proliferation in multiple liver cancer cell lines (in vitro), and in human liver cancer xenograft (HepG2) transplanted nude mice with subcutaneous injection and in situ liver injection (in vivo) and in liver-specific gene knock-in mice by TALEN (in vivo). Furthermore, Expression profiling, ChIP-seq, IP-MASS, and yeast two-hybrid analysis will be used to search for genes targeted by, proteins interacted with, and signal pathways regulated by ZNF521 in HCC. Finally, q-PCR and immunohistochemistry will be used to detect mRNA and protein level of ZNF521 in a large number of HCC tissues and paired adjacent tissues, and the relations between ZNF521 expression and HCC occurrence, metastasis and prognosis will be evaluated. The present study on ZNF521 will provide experimental basis for understanding the role and molecular mechanisms of this gene in HCC, and for evaluating its clinical values in early diagnosis and therapeutic interventions of this malignancy.