lncRNA MEG3 inhibits the growth of hepatocellular carcinoma cells by sponging miR-9-5p to upregulate SOX11

The long non-coding RNA (lncRNA) maternally expressed gene 3 (MEG3), a tumor suppressor, is critical for the carcinogenesis and progression of different cancers, including hepatocellular carcinoma (HCC). To date, the roles of lncRNA MEG3 in HCC are not well illustrated. Therefore, this study used western blot and qRT-PCR to evaluate the expression of MEG3, miR-9-5p, and Sex determining Region Y-related HMG-box 11 (SOX11) in HCC tissues and cell lines. RNA pull-down and luciferase reporter assay were used to evaluate these molecular interactions. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and flow cytometry detected the viability and apoptosis of HCC cells, respectively. The results showed that MEG3 and SOX11 were poorly expressed but miR-9-5p was highly expressed in HCC. The expression levels of these molecules suggested a negative correlation between MEG3 and miR-9-5p and a positive correlation with SOX11, confirmed by Pearson's correlation analysis and biology experiments. Furthermore, MEG3 could combine with miR-9-5p, and SOX11 was a direct target of miR-9-5p. Moreover, MEG3 over-expression promoted cell apoptosis and growth inhibition in HCC cells through sponging miR-9-5p to up-regulate SOX11. Therefore, the interactions among MEG3, miR-9-5p, and SOX11 might offer a novel insight for understanding HCC pathogeny and provide potential diagnostic markers and therapeutic targets for HCC.

长链非编码RNA（long non-coding RNA，lncRNA）母系表达基因3（maternally expressed gene 3，MEG3）作为一种抑癌基因，在包括肝细胞癌（hepatocellular carcinoma，HCC）在内的多种癌症的发生与进展中发挥关键作用。迄今为止，lncRNA MEG3在肝细胞癌中的作用尚未得到充分阐明。因此，本研究采用蛋白质印迹法（western blot）与实时定量聚合酶链反应（qRT-PCR），检测了肝细胞癌组织及细胞系中MEG3、miR-9-5p以及性别决定区Y框蛋白11（Sex determining Region Y-related HMG-box 11，SOX11）的表达水平。通过RNA下拉实验（RNA pull-down）与荧光素酶报告基因实验，分析了上述分子间的相互作用。分别采用噻唑蓝（3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide，MTT）法与流式细胞术检测肝细胞癌细胞的活力与凋亡情况。结果显示，在肝细胞癌组织与细胞中，MEG3与SOX11呈低表达状态，而miR-9-5p呈高表达状态。经Pearson相关分析与生物学实验证实，三者的表达水平存在显著关联：MEG3与miR-9-5p呈负相关，而MEG3与SOX11呈正相关。进一步研究发现，MEG3可与miR-9-5p直接结合，且SOX11是miR-9-5p的直接靶基因。此外，MEG3过表达可通过海绵吸附miR-9-5p上调SOX11的表达，进而促进肝细胞癌细胞的凋亡并抑制其增殖。综上，MEG3、miR-9-5p与SOX11之间的相互作用，可为阐明肝细胞癌的发病机制提供全新视角，同时为肝细胞癌的潜在诊断标志物与治疗靶点提供新思路。