SOX4-HNF3a/ERα-miR-26-SOX4反馈环路在肝细胞癌发生发展中的功能及机制研究

Dysregulation of miRNA plays an important role in the development and progression of human hepatocellular carcinomas (HCCs). The systematic investigation on biological functions and regulatory mechanisms of miRNA-involved network in HCCs can help us to deeply understand this complicated progression and to establish novel therapeutic strategies. Previous studies demonstrated that miRNA-26a plays a potential role in inhibition of hepatocarcinogenesis by reducing proliferation and inducing apoptosis of HCCs cells. A series of cyclin-dependent kinase (CDK) and cyclin genes controlling cell cycle progression were identified as miR-26a’s downstream targets. However, it may not be a reasonable explanation for its potent inhibitory effect on malignant behaviors of HCCs. What is the auto-regulatory mechanism of low level of miR-26a expression in HCCs? What is the impact of miR-26a on other malignant behaviors in HCCs besides regulation of proliferation and apoptosis? And what are the novel target genes of miR-26a in HCCs? Here, according to our preliminary data and previous reports from other groups, we suspect that SOX4-HNF3a/ERα-miR-26-SOX4, a novel feedback loop-involved regulatory network could function in initiation and progression of liver cancer. We plan to use approaches in molecular biology and cell biology in vitro and in vivo, a transgenic mouse model with liver specific expression of miR-26a and the resources in clinical samples to demonstrate the biological contribution of the SOX4-HNF3a/ERα-miR-26-SOX4 feedback loop-involved regulatory network in HCCs. Deeply understanding the biological functions and regulatory mechanisms of tumor suppressor miR-26 involved regulatory network will provide significant advances for the treatment of HCCs.

MicroRNA表达失衡在肝癌发生发展中扮演重要角色。系统分析miRNA介导信号网络对深刻理解肝癌进程和建立干预手段至关重要。以往研究证明miR-26a通过靶向细胞周期蛋白发挥强大抑瘤作用，但现有研究尚无法充分揭示其作用机制。它在肝癌进程中自身表达调控机制如何？对肝癌的众多恶性表型作用如何？发挥功能调控的下游靶分子群又是什么？以上问题均未得到系统回答。本研究基于前期工作基础和既往文献支持，提出肝癌中可能存在以miR-26抑癌功能为核心的 SOX4-HNF3a/ERα-miR-26-SOX4反馈环路。拟利用体内外生物学实验，肝脏特异过表达miR-26a转基因小鼠和临床样本明确该环路在肝癌发生发展中的生物学贡献；进而系统阐明miR-26介导的信号网络对调控肝癌恶性表型的影响和机制。这对于深刻理解抑癌miRNA分子调控网络和建立肿瘤靶向治疗策略具有重要的理论价值和临床指导意义。

miR-26家族分子被证明在包括肝癌在内的多种肿瘤中发挥重要的抑癌功能，通过回补策略能够显著抑制小鼠原发性肝癌和裸鼠移植瘤的生长，在肿瘤治疗学中具有重要的科学意义。但是miR-26在肝癌发生发展进程中表达水平降低原因和其主要调控的下游靶分子群尚未得到系统的研究。在本项目中，我们有一下重要发现：①miR-26在肝癌组织中的表达水平与促癌转录因子c-myc和表观遗传学抑制复合物PRC2的核心酶EZH2呈现显著的负相关关系；②miR-26负向调控c-myc的机制主要是通过靶向抑制经典Wnt信号通路的激活分子CDK8来实现的。同时，miR-26直接靶向结合EZH2的3’UTR区域是导致EZH2降低的直接机制；③c-myc通过募集EZH2介导的H3K27的高甲基化导致miR-26a1/2表达水平的降低；④在对miE-26抑制肝癌体内转移的研究中，我们鉴定出PAK2激酶是miR-26a的一个新的现有靶分子，而PAK2的活性对于促进肿瘤细胞的侵袭转移具有重要的生物学功能；⑤利用重组AAV病毒介导的体内转基因技术将miR-26导入自发现肺转移肝癌小鼠体内，显著抑制了自发现肝癌的肺转移。上述研究发现为我们将具有抑癌功能的miRNA分子应用于临床治疗提供了重要的理论支持。在研究过程中，我们围绕肿瘤相关miRNA的功能表达调控展开了系列研究。共发表SCI论文8篇。包括:Nucleic Acids Research；Cancer Letters；Cell Death & Disease；Biochim Biophys Acta Rev Cancer；BBRC（四篇）。同时，修回两篇（Theranostics；Cancer Letters）。培养研究生四人，博士后两人。邀请国内外知名学者交流讲学四次。受邀国内学术会议大会报告三次。