MiR-424-503簇在肝细胞癌中的协同抑癌功能及其上下游调节机制研究

申请人既往研究证实miRNA在肝癌的发生发展中扮演重要角色，提示以miRNA为切入点是阐明肝癌发病机制的重要环节。检索miRBase数据库，我们发现人体约30%的miRNA以成簇的多顺反子形式存在于基因组中，在进化中通过协同增效机制调控基因表达，但其在肿瘤发生发展中的功能和机制尚待深入研究。课题组前期研究结果显示：miR-424-503簇的基因组上游含有肝富集转录因子c/EBPa的DNA结合基序，同时具有CpG岛，提示DNA高甲基化和肝富集转录因子的缺失可能是该簇在肝癌中低表达的原因。生物信息学分析结果显示miR-424和miR-503存在共有下游靶点，而各自独立的靶点在调控肿瘤信号网络中又具有互补性的特点。据此，本课题希望从分子、细胞、动物模型和临床样品等层面阐明该miRNA簇在肝癌中的协同抑癌功能及其上下游调节机制，揭示成簇表达miRNA在肝癌发生发展中的信号网络并挖掘新的治疗靶标。

Our previous studies showed that miRNA-mediated network plays an important role in development and progression of hepatocellular carcinoma (HCC). According to data from the miRbase resources，we found that about 30% miRNAs are polycistron. They frequently synergetically work together to drive a specific biological process. However, their regulatory mechanisms and synergetic functions are still elusive. Our preliminary data showed the existence of putative DNA binding motif of liver enriched transcriptional factor C/EBPa and CpG islands on the upstream of miR-424-503 cluster in the genome. These results indicate that loss of C/EBPa expression and DNA hypermethylation may be the important reasons for low levels of miR-424-503 in HCC. Our further bioinformatic analysis revealed that on the one side miR-424 and miR-503 have interaction target genes, and on the other side these two miRNAs can target different oncogenic pathways. In the present study, the following specific aims are proposed, 1). To identify that if C/EBPa is a direct transcriptional factor increasing miR-424-503 cluster in HCC; 2). To identify that if DNA hypermethylation is a major reason for low levels of miR-424-503 cluster in HCC. 3). To determine the roles and unknown mechanisms of miR-424-503 in HCC cells. 4). To confirm the significance of miR-424-503 cluster for prognosis in clinic. The objective of this proposal is to reveal regulatory mechanisms and synergetic functions of miR-424-503 cluster on the inhibition of hepatocellualr carcinoma. The proposed work is anticipated to define miR-424-503 cluster as a novel diagnostic marker and/or a therapeutic drug target for the treatment of advanced liver cancer.