Let-7g调节染色质重塑关键酶CHD4抑制肝细胞癌转移

Traditional epigenetic mechanisms include DNA methylation, histone modification and chromatin remodeling, which play pivotal roles in the pathogenesis and progression of hepatocellular carcinoma (HCC). Recently it has been reported that microRNAs (miRNA) can regulate DNA methylation and histone modification, if miRNAs also target ATP-dependent chromatin remodeling remains unknown. Our previous project proved that let-7g inhibits HCC metastasis by, at least in part, targeting COL1A2. The following pilot study discovered that let-7g target and inhibit ATP-dependent chromatin remodeling enzyme CHD4 (also known as Mi-2β) in HCC cell lines, which indicated that let-7g may broaden the range of regulated genes via chromatin remodeling and affect metastasis. In this project, we plan to further validate the targeting regulatory effect of let-7g to CHD4, and the consequent epigenetic effects that affect the metastatic potential of HCC, till the difference in the expression of metastasis-related proteins; we will also explore the feasibility of the clinical application based on this regulatory mechanism. By this project, we aim to elucidate if miRNA can regulate ATP-dependent chromatin remodeling, and to expand the understanding of the gene-regulatory function as well as the anti-metastatic effect of miRNA let-7g in HCC.

表观遗传学在肝细胞癌（HCC）发生与进展中具有重要作用；其主要机制包括DNA甲基化、组蛋白修饰及染色质重塑。近年发现microRNA（miRNA）可调节DNA甲基化与组蛋白修饰，但尚无miRNA调节ATP依赖染色质重塑的报道。我们前期的研究初步证实 let-7g在HCC细胞株中靶向抑制ATP依赖染色质重塑酶CHD4（即Mi-2β）的表达，提示let-7g可能靶向调控CHD4，通过染色质重塑这一表观遗传学机制调节更广泛的基因表达，进而影响HCC的转移。本课题拟进一步验证let-7g对CHD4的负性靶向调控作用，研究随之产生的影响HCC转移的表观遗传学效应，并初步探讨针对这一调控机制的临床应用的可能性。本课题目的在于阐明miRNA对ATP依赖染色质重塑机制的调控作用，扩展对miRNA调控基因表达的机制，及miRNA调节肿瘤转移的途径的新认识。

表观遗传学在肝细胞癌（HCC）发生与进展中具有重要作用；其主要机制包括DNA甲基化、组蛋白修饰及染色质重塑。近年发现microRNA（miRNA）可调节DNA甲基化与组蛋白修饰，但尚无miRNA调节ATP依赖染色质重塑的报道。本研究中，通过蛋白质组研究发现，let-7g上调可致HCC细胞株中染色质重塑关键酶CHD4表达下调，该结果经蛋白印迹及定量PCR实验验证，而CHD4经信息学预测为let-7g的潜在靶基因；luciferase assay研究确证let-7g靶向调控CHD4；临床标本及TCGA数据库分析也证实二者表达负相关。以let-7g与CHD4质粒双转染HCC细胞系，以空白质粒或单转染为对照，通过蛋白质组分析，筛选出一组let-7g通过CHD4调控HCC转移的候选蛋白，进而通过对其生物学功能的文献分析与功能实验验证，确定let-7g通过染色质重塑机制级联放大，调控HCC转移的机制。本课题目的在于阐明miRNA对ATP依赖染色质重塑机制的调控作用，扩展对miRNA调控基因表达的机制，及miRNA调节肿瘤转移的途径的新认识。