Zhejiang Provincial Key Laboratory of Pancreatic Disease, The First Affiliated Hospital of Zhejiang University School of Medicine, No.79 Qingchun Road, Hangzhou, 310003, Zhejiang, China.
Institute of Translational Medicine, Zhejiang University School of Medicine, Hangzhou, 310058, Zhejiang, China.
J Exp Clin Cancer Res. 2024 Nov 20;43(1):307. doi: 10.1186/s13046-024-03225-2.
Triple-negative breast cancer (TNBC) has pronounced stemness that is associated with relapse. N-methyladenosine (mA) plays a crucial role in shaping cellular behavior by modulating transcript expression. However, the role of mA in TNBC stemness, as well as the mechanisms governing its abundance, has yet to be elucidated.
We analyzed proteomic and transcriptomic data derived from breast cancer cohorts, with an emphasis on mA regulators. To unravel the role of mA in TNBC, we employed RNA sequencing, methylated RNA immunoprecipitation sequencing, RNA immunoprecipitation, chromatin immunoprecipitation, and luciferase reporter assays with mesenchymal stem-like (MSL) TNBC models. The clinical relevance was validated using human tissue microarrays and publicly accessible databases.
Our findings indicate that the global level of mA modification in MSL TNBC is downregulated primarily due to the loss of methyltransferase-like 14 (METTL14). The diminished mA modification is crucial for the maintenance of TNBC stemness, as it increases the expression of yes-associated protein 1 (YAP1) by blocking YTH domain-containing family protein 2 (YTHDF2)-mediated transcript decay, thereby promoting the activation of Hippo-independent YAP1 signaling. YAP1 is essential for sustaining the stemness regulated by METTL14. Furthermore, we demonstrated that the loss of METTL14 expression results from lysine-specific demethylase 1 (LSD1)-mediated removal of histone H3 lysine 4 methylation at the promoter region, which is critical for LSD1-driven stemness in TNBC.
These findings present an epi-transcriptional mechanism that maintains Hippo-independent YAP1 signaling and plays a role in preserving the undifferentiated state of TNBC, which indicates the potential for targeting the LSD1-METTL14 axis to address TNBC stemness.
三阴性乳腺癌（TNBC）具有明显的干性，与复发相关。N6-甲基腺苷（mA）通过调节转录本表达在塑造细胞行为方面发挥着关键作用。然而，mA 在 TNBC 干性中的作用以及控制其丰度的机制尚未阐明。
我们分析了来自乳腺癌队列的蛋白质组学和转录组学数据，重点关注 mA 调节因子。为了揭示 mA 在 TNBC 中的作用，我们采用了 RNA 测序、甲基化 RNA 免疫沉淀测序、RNA 免疫沉淀、染色质免疫沉淀和带有间充质干细胞样（MSL）TNBC 模型的荧光素酶报告基因检测。使用人组织微阵列和公开可访问的数据库验证了临床相关性。
我们的研究结果表明，MSL TNBC 中 mA 修饰的整体水平主要由于甲基转移酶样 14（METTL14）的缺失而下调。mA 修饰的减少对于维持 TNBC 干性至关重要，因为它通过阻止 YTH 结构域家族蛋白 2（YTHDF2）介导的转录本降解来增加 YAP1 的表达，从而促进 Hippo 非依赖性 YAP1 信号的激活。YAP1 对于维持由 METTL14 调节的干性是必不可少的。此外，我们证明 METTL14 表达的缺失是由于赖氨酸特异性去甲基酶 1（LSD1）介导的启动子区域组蛋白 H3 赖氨酸 4 甲基化的去除所致，这对于 LSD1 驱动的 TNBC 干性至关重要。
这些发现提出了一种表观转录机制，可维持 Hippo 非依赖性 YAP1 信号，并在维持 TNBC 的未分化状态中发挥作用，这表明靶向 LSD1-METTL14 轴可能是解决 TNBC 干性的一种策略。
