General Clinical Research Center, Nanjing First Hospital, Nanjing Medical University, No. 68, Changle Road, Nanjing, 210006, China.
Department of oncology, Nanjing First Hospital, Nanjing Medical University, Nanjing, 210006, Jiangsu, China.
Mol Cancer. 2020 Jun 17;19(1):106. doi: 10.1186/s12943-020-01220-7.
Colorectal cancer (CRC) is one of the leading causes of tumor-related death worldwide, and its main cause of death is distant metastasis. Methyltransferase-like 14(METTL14), a major RNA N6-adenosine methyltransferase, is involved in tumor progression via regulating RNA function. The goal of the study is to uncover the biological function and molecular mechanism of METTL14 in CRC.
Quantitative real-time PCR (qRT-PCR), western blot and immunohistochemical (IHC) assays were employed to detect METTL14 and SOX4 in CRC cell lines and tissues. The biological functions of METTL14 were demonstrated using in vitro and in vivo experiments. Chromatin immunoprecipitation (ChIP), Transcrptomic RNA sequencing (RNA-Seq), m6A-RNA immunoprecipitation sequencing (MeRIP-Seq), RNA immunoprecipitation and luciferase reporter assays were used to explore the mechanism of METTL14 action.
METTL14 expression was significantly downregulated in CRC and decreased METTL14 was associated with poor overall survival (OS). Both the univariate and multivariate Cox regression analysis indicated that METTL14 was an independent prognostic factor in CRC. Moreover, lysine-specific histone demethylase 5C(KDM5C)-mediated demethylation of histone H3 lysine 4 tri-methylation(H3K4me3) in the promoter of METTL14 inhibited METTL14 transcription. Functionally, we verified that METTL14 inhibited CRC cells migration, invasion and metastasis through in vitro and in vivo assays, respectively. Furthermore, we identified SRY-related high-mobility-group box 4(SOX4) as a target of METTL14-mediated m6A modification. Knockdown of METTL14 markedly abolished SOX4 mRNA m6A modification and elevated SOX4 mRNA expression. We also revealed that METTL14-mediated SOX4 mRNA degradation relied on the YTHDF2-dependent pathway. Lastly, we demonstrated that METTL14 might inhibit CRC malignant process partly through SOX4-mediated EMT process and PI3K/Akt signals.
Decreased METTL14 facilitates tumor metastasis in CRC, suggesting that METTL14 might be a potential prognostic biomarker and effective therapeutic target for CRC.
结直肠癌（CRC）是全球肿瘤相关死亡的主要原因之一，其主要死因是远处转移。甲基转移酶样 14（METTL14）是一种主要的 RNA N6-腺苷甲基转移酶，通过调节 RNA 功能参与肿瘤进展。本研究旨在揭示 METTL14 在 CRC 中的生物学功能和分子机制。
采用定量实时 PCR（qRT-PCR）、western blot 和免疫组织化学（IHC）检测 CRC 细胞系和组织中的 METTL14 和 SOX4。通过体外和体内实验证明 METTL14 的生物学功能。采用染色质免疫沉淀（ChIP）、转录组 RNA 测序（RNA-Seq）、m6A-RNA 免疫沉淀测序（MeRIP-Seq）、RNA 免疫沉淀和荧光素酶报告基因检测等方法探讨 METTL14 作用的机制。
METTL14 在 CRC 中表达明显下调，降低的 METTL14与总体生存（OS）不良相关。单因素和多因素 Cox 回归分析均表明 METTL14 是 CRC 的独立预后因素。此外，赖氨酸特异性组蛋白去甲基酶 5C（KDM5C）介导的 METTL14 启动子中组蛋白 H3 赖氨酸 4 三甲基化（H3K4me3）去甲基化抑制 METTL14 转录。功能上，我们通过体外和体内实验分别证实 METTL14 通过抑制 CRC 细胞迁移、侵袭和转移来发挥作用。此外，我们确定性别决定区 Y 框 4（SOX4）是 METTL14 介导的 m6A 修饰的靶标。METTL14 的敲低显著消除了 SOX4 mRNA m6A 修饰并增加了 SOX4 mRNA 的表达。我们还揭示了 METTL14 介导的 SOX4 mRNA 降解依赖于 YTHDF2 依赖性途径。最后，我们证明 METTL14 可能通过 SOX4 介导的 EMT 过程和 PI3K/Akt 信号部分抑制 CRC 恶性进程。
METTL14 的减少促进 CRC 中的肿瘤转移，提示 METTL14 可能是 CRC 的一个有潜力的预后生物标志物和有效治疗靶点。
