HNF 4α的SUMO化修饰调节蛋白稳定性在肝细胞分化中的机制研究

End stage liver disease (ESLD) is an irreversible condition that leads to the eventual failure of liver, with poor prognosis and high mortality. Researchers have proposed that human stem cells are very attractive in vitro cellular resource and in theory provide unlimited amounts of hepatocytes for the treatment of ESLD. HNF 4a is an important factor required in the hepatic differentiation and SUMOylation seems to play a critical role in this process. Our study showed some promising clues between SUMOylation and the stability of HNF4a but the mechanism is still unknown. Therefore, some further researches need to be initiated to extend this project and clarify the possible mechanism of SUMOylation on HNF4a. Based on our previous research, this project is designed to alter the expression level of HNF4a and SUMO by transfection of lentiviral vectors to hepatocytes from human embryonic stem cells and to observe the subsequent impact on hepatic function in living system. We will further identify this mechanism and hunt for possible genetic treatment in hepatocellular carcinoma mouse model by overexpression or knockdown of HNF4a and SUMOylation-raleted proteins. This project will provide deep research on the role of SUMOylation on HNF4a in hepatic differentiation and their promising application in modern medicine.

终末期肝病是预后差、死亡率高的严重疾病，肝细胞核因子4a(hepatocyte nuclear factor 4a, HNF4α)作为重要的肝细胞分化转录因子能提高肝细胞功能而为其治疗带来了希望。我们前期研究发现，在肝细胞分化过程中，小泛素相关修饰物（small ubiquitin-related modifier，SUMO）与HNF4α存在相互作用并影响肝细胞功能基因表达，目前已明确HNF4α的SUMO化位点，但SUMO如何调控HNF4α的表达还需进一步研究。本课题拟在前期工作基础上利用干细胞向肝细胞分化细胞模型，通过上调、下调HNF4a及SUMO化调控相关蛋白表达寻找HNF4a的SUMO化修饰的直接证据和验证SUMO化调节HNF4a稳定性的假说，并通过动物实验进一步验证该机制和探索基于此机制治疗肝癌的可能性和有效性，可为终末期肝病特别是肝癌的治疗提供生物学新思路。

终末期肝病是预后差、死亡率高的严重疾病，肝细胞核因子4a(hepatocyte nuclear factor 4a, HNF4α)作为重要的肝细胞分化转录因子能提高肝细胞功能而为其治疗带来了希望。我们前期研究发现，小泛素相关修饰物（small ubiquitin-related modifier，SUMO）与HNF4α存在相互作用并在肝细胞分化发育过程中具有重要调控作用。本课题在前期研究基础上利用干细胞向肝细胞分化细胞模型和裸鼠肝癌细胞皮下种植瘤模型，发现了通过抑制HNF4a的SUMO化的方式可以显著地提高其肝细胞的功能水平（ALB和CYP1A2的表达水平相对于Amar Sharma实验室获得的iHeps分别为1.7和3倍，2016 Cell Stem Cell）和显著延长其功能持续时间，并在裸鼠肝癌细胞皮下种植瘤模型中基于该调控机制通过病毒转染的方式验证了上调HNF4a或抑制SUMO2进行基因治疗肝癌的可能性和有效性。基于本项目研究2016年申请并获批中英国际合作交流项目Developing and Optimizing Hepatic Differentiation ‘on a chip’，将于2017年赴英进行合作研究，进一步筛选SUMO2抑制剂用于改善肝细胞功能，为终末期肝病特别是肝癌的治疗提供新思路。目前发表相关论文2篇，项目资助待发表论文2篇；培养博士生1名，硕士生2名，1名博士及1名硕士已取得学位，1名硕士在读。项目投入经费23万元，支出18.7903万元，各项支出基本与预算相符，剩余经费4.2097万元，计划用于本项目研究的后续支出。