Wang Fang, Yang Chen, Zheng Fang, Yan Yang, Li Guifang, Feng Yanyan, Xu Hejia, He Zilong, Cai Dongyan, Sun Hairong, Qi Xiaowei, Mao Yong
Department of Cancer Diagnosis and Treatment Center, Affiliated Hospital of Jiangnan University, Wuxi, China.
Laboratory of Oncology Precision Diagnosis and Treatment, Wuxi Medical College of Jiangnan University, Wuxi, China.
J Transl Med. 2024 Dec 31;22(1):1161. doi: 10.1186/s12967-024-05991-1.
Colorectal cancer (CRC) is characterized by poor responsiveness to immune evasion and immunotherapy. RNA 7-methylguanine (m7G) modification plays a key role in tumorigenesis. However, the mechanisms by which m7G-modified RNA metabolism affects tumor progression are not fully understood, nor is the contribution of m7G-modified RNA to the CRC immune microenvironment.
The expression levels of Methyltransferase-like 1 (METTL1) and m7G in human tissues were determined. In this study, the effect of METTL1 on RNA m7G levels was evaluated, the effect of METTL1 on PKM mRNA modification was confirmed, the expression level of the PKM2 protein was detected, and the mechanism involved RT‒qPCR, Western blot, RNA stability analysis and RIP analysis. Lactate and H3K9 lactylation (H3K9la) induced by METTL1/PKM2 were analyzed via the extracellular acidification rate (ECAR) and lactic acid assays. Cut&Run was used to detect METTL1/PKM2-induced CD155 (PVR) transcription. In addition, METTL1 knockout mice were studied in vivo with CD155 blockers.
We demonstrated that m7G RNA METTL1 enhances PKM2 expression by acting on PKM mRNA, leading to tumor progression and increased glycolysis. Specifically, METTL1 mediates m7G methylation of PKM mRNA and enhances the expression of its encoded PKM2, which in turn enhances glycolysis, promotes H3K9la, and activates METTL1 transcription, creating a positive feedback loop. Moreover, increased PKM2 dimer expression and nuclear translocation activated CD155 expression and induced CRC immune evasion.
Our findings reveal a general mechanism by which METTL1/PKM2/H3K9la signaling regulates RNA metabolism and highlight METTL1 targeting as a potential strategy for CRC immunotherapy.
结直肠癌（CRC）的特点是对免疫逃逸和免疫治疗反应不佳。RNA 7-甲基鸟嘌呤（m7G）修饰在肿瘤发生中起关键作用。然而，m7G修饰的RNA代谢影响肿瘤进展的机制尚未完全阐明，m7G修饰的RNA对CRC免疫微环境的作用也不清楚。
测定人组织中甲基转移酶样蛋白1（METTL1）和m7G的表达水平。在本研究中，评估了METTL1对RNA m7G水平的影响，证实了METTL1对PKM mRNA修饰的作用，检测了PKM2蛋白的表达水平，所涉及的机制采用RT-qPCR、蛋白质免疫印迹法、RNA稳定性分析和RNA免疫沉淀分析。通过细胞外酸化率（ECAR）和乳酸测定分析METTL1/PKM2诱导的乳酸和组蛋白H3赖氨酸9乳酸化（H3K9la）。采用切割与运行技术检测METTL1/PKM2诱导的CD155（PVR）转录。此外，利用CD155阻滞剂对METTL1基因敲除小鼠进行体内研究。
我们证明m7G RNA甲基转移酶METTL1通过作用于PKM mRNA增强PKM2表达，导致肿瘤进展和糖酵解增加。具体而言，METTL1介导PKM mRNA的m7G甲基化并增强其编码的PKM2的表达，进而增强糖酵解，促进H3K9la，并激活METTL1转录，形成正反馈回路。此外，PKM2二聚体表达增加和核转位激活了CD155表达并诱导了CRC免疫逃逸。
我们的研究结果揭示了METTL1/PKM2/H3K9la信号通路调节RNA代谢的一般机制，并强调靶向METTL1作为CRC免疫治疗的潜在策略。
