LncRNA GAS8-AS1对抑癌基因GAS8的表观遗传学调控机制研究

A large number of human diseases related long non-coding RNAs (lncRNA) were recently identified via the Next Generation Sequencing technology. However, only a small amount of lncRNAs' biological functions have been clearly studied. In our previous study, we for the first time identified lncRNA GAS8-AS1 as a significant mutated gene in Chinese papillary thyroid carcinoma (PTC) patients after whole-exome sequencing (WES) of 91 clinically and pathologically characterized PTC tissues and 91 paired normal samples. We also found that expression of lncRNA GAS8-AS1 was significantly down-regulated and positively correlated with its host gene GAS8 in thyroid cancer and other cancer tissues compared with normal tissues. After silencing lncRNA GAS8-AS1 expression, the H3K4me3 modification levels and expression of the tumor suppressor gene GAS8 were significantly suppressed. LncRNA GAS8-AS1 can interact with WDR5 protein. Moreover, there is one CpG island in the GAS8 regulatory region. Based on the aforementioned results, we aimed to reveal the exact epigenetic mechanisms on how lncRNA GAS8-AS1 regulates the expression of GAS8 in cancer cells. Also, the biological role of lncRNA GAS8-AS1 during malignant transformation of normal cells will be investigated. The results of this study will initially explain how lncRNA GAS8-AS1 is involved in cancer development, which may extend our understanding on the etiology of cancers.

二代测序技术的出现导致大量人类疾病相关长链非编码RNA(lncRNA)被发现，然而仅少量lncRNA的生物学功能得到了清晰阐释。我们前期利用全外显子组测序技术检测了91例甲状腺癌组织基因突变谱，意外发现lncRNA GAS8-AS1是中国人群特有的显著突变基因。后继研究显示：与正常组织相比，lncRNA GAS8-AS1在甲癌等多种癌组织中的表达显著下调，并与其宿主基因GAS8的表达呈正相关；基因沉默GAS8-AS1后，癌细胞中抑癌基因GAS8调控区H3K4me3修饰及其表达均被显著抑制；GAS8-AS1可与WDR5蛋白相互作用；GAS8调控区中存在1个CpG岛。基于此，本项目拟深入研究GAS8-AS1调控GAS8表达的表观遗传机制，揭示GAS8-AS1在肿瘤恶变中的生物学功能。研究结果将初步阐明抑癌lncRNA GAS8-AS1在肿瘤发生发展中的重要作用，对深入理解肿瘤发病机制打下基础。

二代测序技术的出现导致大量人类疾病相关长链非编码RNA (lncRNA)被发现，然而仅少量lncRNA的生物学功能得到了清晰阐释。我们首次发现lncRNA GAS8-AS1是一种新的肿瘤抑癌基因。在本项目的资助下，我们发现肝癌细胞中基因沉默lncRNA GAS8-AS1表达可显著下调GAS8基因调控区组蛋白H3K4me3修饰；分子机制研究显示lncRNA GAS8-AS1可募集MLL1和WDR5组蛋白甲基化酶至GAS8基因调控区，导致该区域H3K4me3修饰增强，GAS8基因表达上调。利用重亚硫酸盐处理DNA+质谱分析，发现基因沉默肝癌细胞中lncRNA GAS8-AS1表达后GAS8基因调控区的CpG岛中的CpG二核苷酸DNA甲基化状态没有显著变化。我们发现过表达GAS8-AS1显著抑制肝癌细胞增殖、凋亡和克隆形成能力、及裸鼠移植瘤成瘤；基因沉默GAS8-AS1显著促进肝癌细胞增殖、凋亡和克隆形成能力、及裸鼠移植瘤成瘤。过表达GAS8-AS1显著抑制肝癌细胞运动及侵袭转移能力；基因沉默GAS8-AS1显著促进肝癌细胞运动及侵袭转移能力。本项目研究结果揭示了抑癌lncRNA GAS8-AS1在肝癌发生发展中的重要作用，以及lncRNA GAS8-AS1作为逆转肝癌靶向治疗药物索拉菲尼耐药的分子治疗靶标的潜能。本项目结果对深入理解恶性肿瘤的表观遗传学发病机制打下坚实的基础。