lncRNA-CHDAT1介导HDAC2去乙酰化调控在结直肠癌肝转移中的作用机制研究

Our preliminary work has found one epigenetics enzyme, histone deacetylation enzyme 2 (HDAC2), which is relevant to colorectal cancer with liver metastases (CLM) by the next-generation sequencing and test in samples of CLM. This over-expressed enzyme was a prognosis fact of CLM, which could promote the migration and invasion in vitro. In the subsequent work we found that in some colorectal cancer cell lines, over-expressed HDAC2 couldn't improve deacetylation state of histone, which suggested that some collaborative factors may cooperate with HDAC2.Then,we found a new lncRNA—lncCHDAT1 (Colorectal cancer histone deacetylase associated transcript 1) through the RIP-Seq and RNA-pulldown, proved the collaboration with HDAC2.Therefore we propose that lnc-CHDAT1 would provide a scaffold structure for HDAC2, created an environment of deacetylation, which will promote CLM. On the above base, this project aimed to study the mechanism of lnc-CHDAT1 participate in deacetylation trigged by HDAC2, find the specific binding site and the downstream pathway, using clinical samples, cell lines and animal models. This study could clarify the mechanism of lnc-CHDAT1 participate in deacetylation trigged by HDAC2 and provide a new clues to personalized CLM treatment.

申请人在前期工作中鉴定了与结直肠癌肝转移（CLM）相关的表观遗传学分子—组蛋白去乙酰化酶2（HDAC2），并验证其能促进侵袭与转移。但在部分细胞系中过表达HDAC2，组蛋白的去乙酰化状态未发生明显变化与预期不符，提示存在与HDAC2共同作用的因子。随后我们通过RIP-Seq及RNA-pulldown技术发现与HDAC2相互作用的一个新的长链非编码RNA（lncRNA）—lnc-CHDAT1，并验证HDAC2发挥功能时需要依赖lnc-CHDAT1。据此，我们提出科学假设：lnc-CHDAT1在HDAC2介导的去乙酰化过程发挥“脚手架”作用，调节组蛋白乙酰化水平。在此基础上，本项目拟从分子、细胞、动物与临床四个层次，深入阐明lnc-CHDAT1与HDAC2在 CLM中的作用及其相互作用的分子机制。本项目研究结果将首次阐明LncRNA对组蛋白去乙酰化的调控作用，有可能为CLM的治疗提供新的线索。

结直肠癌的发病率及死亡率逐年上升，而肝转移是导致结直肠癌患者死亡的主要因素。对结直肠癌肝转移进行深入研究以提高结直肠癌的诊治水平，有着十分重要的意义。近年来，表观遗传学在肿瘤发生、发展过程中发挥的作用逐渐受到关注，本课题组前期筛选出了与结直肠癌肝转移相关的表观遗传相关分子——组蛋白去乙酰化酶2（HDAC2），它是组蛋白去乙酰化酶家族的一员，在各种癌症中起着重要作用。在本项目中，我们发现HDAC2的表达水平与结直肠癌的肝转移、较高的T分期和不良预后相关。通过慢病毒介导的HDAC2靶向shRNA表达下调HDAC2，降低了HCT116细胞的体外迁移和侵袭能力，并降低了其在裸鼠异种移植物中的肝转移。从机制上讲，HDAC2通过结合EZH2(一种关键的组蛋白甲基转移酶)促进结直肠癌细胞上皮-间质转化(Epithelial-mesenchymal transition, EMT)，这可能是通过一种新的lncRNA ENSG00000274093.1（Lnc-CHDAT1）的脚手架功能实现的。因此，HDAC2通过Lnc-CHDAT1结合HDAC1和EZH2促进结直肠癌细胞迁移和侵袭。