Ncoa5转录抑制ZEB1调控EMT在肝癌侵袭转移中的作用及机制研究

It is of great significance to explore the mechanism of recurrence and metastasis of hepatocellular carcinoma (HCC) to reduce the recurrence and improve the prognosis of liver cancer. Epithelial mesenchymal transformation (EMT) is closely related to the invasion and metastasis of liver cancer. ZEB1 is an important transcriptional factor in EMT process. Nuclear receptor coactivator 5 (Ncoa5) is a transcription factor that can inhibit or activate transcriptional activity. Our preliminary study showed that Ncoa5 was significantly down-regulated in the hepatocellular carcinoma tissues, and Ncoa5 inhibited the expression of ZEB1, a key molecule of EMT, in hepatocellular carcinoma cells. Based on these findings, we innovatively put forward the hypothesis that Ncoa5 by transcriptional suppression of ZEB1 affects EMT and consequent metastasis of hepatocellular carcinoma cells. This project aims to illustrate the following issues through multiple molecular biology methods: 1) the effect of Ncoa5 the invasion and metastasis of hepatocellular carcinoma cells; 2) the mechanism of Ncoa5 in modulating EMT by transcription suppression of ZEB1. This project is expected to reveal a new mechanism for the regulation of the invasion and metastasis of hepatocellular carcinoma by Ncoa5, which provides new targets and strategies for the inhibition of hepatocellular carcinoma metastasis.

探索肝癌（HCC）侵袭转移的机制对降低肝癌复发、改善预后具有重要意义。上皮间质转化（EMT）与肝癌侵袭转移密切相关，受关键转录因子ZEB1的调控。核受体共激活因子5（Ncoa5）是广泛表达的核受体辅助因子，具有转录激活或转录抑制功能。Ncoa5在肝癌中的表达及对肝癌侵袭转移的影响尚不清楚，亟待研究。本项目组前期初步研究表明Ncoa5的表达在肝癌组织中显著下调；Ncoa5能抑制EMT的关键分子ZEB1的表达并降低肝癌细胞侵袭能力。基于此，我们创新性地提出本研究假说：Ncoa5可转录抑制ZEB1影响EMT，从而调控肝癌的侵袭转移。本项目拟在前期研究基础上通过多种分子生物学手段在细胞水平和动物模型上揭示：1）Ncoa5对肝癌侵袭转移的影响；2）Ncoa5转录抑制ZEB1影响EMT的分子机制。本项目有望揭示Ncoa5调控肝癌侵袭转移的新机制，为抑制肝癌的侵袭转移提供新的靶点和策略。

我国是肝癌高发大国，肝癌由于其生物学行为，致死率仍非常高。核受体共激活因子（NCOA5）是广泛表达的核受体辅助因子，在肝癌组织中表达下调，但其在肝癌中的表达对肝癌侵袭转移的影响尚不明确。目前研究表明NCOA5低水平与肝癌临床病理表达有关联，并且NCOA5的过度表达显著抑制了肝癌细胞HCC-LM3在体外的迁移和侵袭以及在裸鼠体内的肝内转移以及肺转移；相反，敲除NCOA5后促进这些过程在肝癌细胞MHCC97L中进展。从机制上说，NCOA5抑制了肝癌细胞的上皮间质化，NCOA5过表达显著上调E-钙粘蛋白上皮标记物以及下调的N-钙粘蛋白间充质标记物和转录抑制因子ZEB1 ，EMT诱导转录因子（EMT-TF），而NCOA5基因敲除则表现出相反的效应；更重要的是，我们发现NCOA5直接与ZEB1基因启动子结合并阻止RNA聚合酶II（Pol II）的募集，从而抑制ZEB1的转录，我们的实验数据进一步显示，HCC组织中NCOA5的表达水平与E-钙粘蛋白呈正相关，而与N-钙粘蛋白和ZEB1呈负相关。我们的数据证明NCOA5的降低可能通过增强RNA Pol II对ZEB1启动子的募集，从而通过ZEB1的转录抑制促进HCC细胞EMT和转移，因此NCOA5调控肝癌侵袭转移的新机制变得明朗起来，也为肝癌的侵袭转移提供新的靶点和策略。