MOE Key Laboratory of Gene Function and Regulation, School of Life Sciences, Collaborative Innovation Center for Cancer Medicine, Sun Yat-sen University, Guangzhou, China.
Key Laboratory of Liver Disease of Guangdong Province, The Third Affiliated Hospital, Sun Yat-sen University, Guangzhou, China.
Hepatology. 2019 Jul;70(1):259-275. doi: 10.1002/hep.30613. Epub 2019 Apr 29.
Although thousands of long noncoding RNAs (lncRNAs) have been annotated, only a limited number of them have been functionally characterized. Here, we identified an oncogenic lncRNA, named lnc-UCID (lncRNA up-regulating CDK6 by interacting with DHX9). Lnc-UCID was up-regulated in hepatocellular carcinoma (HCC), and a higher lnc-UCID level was correlated with shorter recurrence-free survival of HCC patients. Both gain-of-function and loss-of function studies revealed that lnc-UCID enhanced cyclin-dependent kinase 6 (CDK6) expression and thereby promoted G1/S transition and cell proliferation. Studies from mouse xenograft models revealed that tumors derived from lnc-UCID-silenced HCC cells had a much smaller size than those from control cells, and intratumoral injection of lnc-UCID small interfering RNA suppressed xenograft growth. Mechanistically, the 850-1030-nt domain of lnc-UCID interacted physically with DEAH (Asp-Glu-Ala-His) box helicase 9 (DHX9), an RNA helicase. On the other hand, DHX9 post-transcriptionally suppressed CDK6 expression by binding to the 3'-untranslated region (3'UTR) of CDK6 mRNA. Further investigation disclosed that lnc-UCID enhanced CDK6 expression by competitively binding to DHX9 and sequestering DHX9 from CDK6-3'UTR. In an attempt to explore the mechanisms responsible for lnc-UCID up-regulation in HCC, we found that the lnc-UCID gene was frequently amplified in HCC. Furthermore, miR-148a, whose down-regulation was associated with an increase of lnc-UCID in HCC, could bind lnc-UCID and inhibit its expression. Conclusion: Up-regulation of lnc-UCID, which may result from amplification of its gene locus and down-regulation of miR-148a, can promote HCC growth by preventing the interaction of DHX9 with CDK6 and subsequently enhancing CDK6 expression. These findings provide insights into the biological functions of lncRNAs, the regulatory network of cell cycle control, and the mechanisms of HCC development, which may be exploited for anticancer therapy.
尽管已经注释了数千个长非编码 RNA（lncRNA），但仅有少数具有功能特征。在这里，我们鉴定了一种致癌 lncRNA，命名为 lnc-UCID（通过与 DHX9 相互作用上调 CDK6 的 lncRNA）。lnc-UCID 在肝细胞癌（HCC）中上调，并且 lnc-UCID 水平较高与 HCC 患者无复发生存时间较短相关。功能获得和功能丧失研究表明，lnc-UCID 增强了细胞周期蛋白依赖性激酶 6（CDK6）的表达，从而促进了 G1/S 期转换和细胞增殖。来自小鼠异种移植模型的研究表明，源自 lnc-UCID 沉默 HCC 细胞的肿瘤比源自对照细胞的肿瘤小得多，并且肿瘤内注射 lnc-UCID 小干扰 RNA 抑制了异种移植瘤的生长。从机制上讲，lnc-UCID 的 850-1030nt 结构域与 RNA 解旋酶 DEAH（Asp-Glu-Ala-His）盒解旋酶 9（DHX9）物理相互作用。另一方面，DHX9 通过与 CDK6 mRNA 的 3'-非翻译区（3'UTR）结合，转录后抑制 CDK6 的表达。进一步的研究揭示，lnc-UCID 通过竞争性结合 DHX9 并将 DHX9 从 CDK6-3'UTR 中隔离出来，增强 CDK6 的表达。为了探索 lnc-UCID 在 HCC 中上调的机制，我们发现 lnc-UCID 基因在 HCC 中经常扩增。此外，miR-148a 的下调与 HCC 中 lnc-UCID 的增加有关，它可以与 lnc-UCID 结合并抑制其表达。结论：lnc-UCID 的上调，可能是由于其基因座的扩增和 miR-148a 的下调，通过防止 DHX9 与 CDK6 相互作用并随后增强 CDK6 的表达，促进 HCC 生长。这些发现为 lncRNA 的生物学功能、细胞周期调控的调控网络以及 HCC 发展的机制提供了新的见解，这些机制可能被用于癌症治疗。
