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Fibroblast-like synoviocytes (FLS) plays an important role in synovial inflammation and joint damage in rheumatoid arthritis (RA). As the most abundant mRNA modification, N6-methyladenosine (m 6 A) is involved in the development of various diseases; however, its role in RA remains to be defined. In this study, we reported the elevated expression of the m 6 A demethylase fat mass and obesity-associated protein (FTO) in FLS and synovium from RA patients. Functionally, FTO knockdown or treatment with FB23-2, an inhibitor of the mRNA m 6 A demethylase FTO, inhibited the migration, invasion and inflammatory response of RA FLS, however, FTO-overexpressed RA FLS exhibited increased migration, invasion and inflammatory response. We further demonstrated that FTO promoted ADAMTS15 mRNA stability in an m 6 A-IGF2BP1 dependent manner. Notably, the severity of arthritis was significantly reduced in CIA mice with FB23-2 administration or CIA rats with intra-articular injection of FTO shRNA. Our results illustrate the contribution of FTO-mediated m 6 A modification to joint damage and inflammation in RA and suggest that FTO might be a potential therapeutic target in RA., Competing Interests: Declaration of competing interest The authors declare no competing interests., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Cartilage maintains the structure and function of joints, with disturbances leading to potential osteoarthritis. N6-methyladenosine (m 6 A), the most widespread post-transcriptional modification in eukaryotes, plays a crucial role in regulating biological processes. While current research has indicated that m 6 A affects the progression of osteoarthritis, its function in the development and homeostasis of articular cartilage remains unclear. Here we report that Mettl3 deficiency in chondrocytes leads to mandibular condylar cartilage morphological alterations, early temporomandibular joint osteoarthritis, and diminished adaptive response to abnormal mechanical stimuli. Mechanistically, METTL3 modulates Lats1 mRNA methylation and facilitates its degradation in an m 6 A-YTHDF2-dependent manner, which subsequently influences the degradation and nuclear translocation of YAP1. Intervention with the Hippo pathway inhibitor XMU-MP-1 alleviates condylar abnormality caused by Mettl3 knockout. Our findings demonstrate the role of METTL3 in cartilage development and homeostasis, offering insights into potential treatment strategies for osteoarthritis., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

Studies on biological functions of N 6 -methyladenosine (m 6 A) modification in mRNA have sprung up in recent years. We find m 6 A can positively regulate the glycolysis of cancer cells. Specifically, m 6 A-sequencing and functional studies confirm that pyruvate dehydrogenase kinase 4 (PDK4) is involved in m 6 A regulated glycolysis and ATP generation. The m 6 A modified 5'UTR of PDK4 positively regulates its translation elongation and mRNA stability via binding with YTHDF1/eEF-2 complex and IGF2BP3, respectively. Targeted specific demethylation of PDK4 m 6 A by dm 6 ACRISPR system can significantly decrease the expression of PDK4 and glycolysis of cancer cells. Further, TATA-binding protein (TBP) can transcriptionally increase the expression of Mettl3 in cervical cancer cells via binding to its promoter. In vivo and clinical data confirm the positive roles of m 6 A/PDK4 in tumor growth and progression of cervical and liver cancer. Our study reveals that m 6 A regulates glycolysis of cancer cells through PDK4.

Background: Accumulating evidence has revealed the critical roles of N 6 -methyladenosine (m 6 A) modification of mRNA in various cancers. However, the biological function and regulation of m 6 A in bladder cancer (BC) are not yet fully understood., Methods: We performed cell phenotype analysis and established in vivo mouse xenograft models to assess the effects of m 6 A-modified ITGA6 on BC growth and progression. Methylated RNA immunoprecipitation (MeRIP), RNA immunoprecipitation and luciferase reporter and mutagenesis assays were used to define the mechanism of m 6 A-modified ITGA6. Immunohistochemical analysis was performed to assess the correlation between METTL3 and ITGA6 expression in bladder cancer patients., Findings: We show that the m 6 A writer METTL3 and eraser ALKBH5 altered cell adhesion by regulating ITGA6 expression in bladder cancer cells. Moreover, upregulation of ITGA6 is correlated with the increase in METTL3 expression in human BC tissues, and higher expression of ITGA6 in patients indicates a lower survival rate. Mechanistically, m 6 A is highly enriched within the ITGA6 transcripts, and increased m 6 A methylations of the ITGA6 mRNA 3'UTR promotes the translation of ITGA6 mRNA via binding of the m 6 A readers YTHDF1 and YTHDF3. Inhibition of ITGA6 results in decreased growth and progression of bladder cancer cells in vitro and in vivo. Furthermore, overexpression of ITGA6 in METTL3-depleted cells partially restores the BC adhesion, migration and invasion phenotypes., Interpretation: Our results demonstrate an oncogenic role of m 6 A-modified ITGA6 and show its regulatory mechanisms in BC development and progression, thus identifying a potential therapeutic target for BC. FUND: This work was supported by National Natural Science Foundation of China (81772699, 81472999)., (Copyright © 2019 The Authors. Published by Elsevier B.V. All rights reserved.)

N6-methyladenosine (m 6 A) is the most abundant internal modification in mammalian mRNAs. Despite its functional importance in various physiological events, the role of m 6 A in chemical carcinogenesis remains largely unknown. Here we profiled the dynamic m 6 A mRNA modification during cellular transformation induced by chemical carcinogens and identified a subset of cell transformation-related, concordantly modulated m 6 A sites. Notably, the increased m 6 A in 3'-UTR mRNA of oncogene CDCP1 was found in malignant transformed cells. Mechanistically, the m 6 A methyltransferase METTL3 and demethylases ALKBH5 mediate the m 6 A modification in 3'-UTR of CDCP1 mRNA. METTL3 and m 6 A reader YTHDF1 preferentially recognize m 6 A residues on CPCP1 3'-UTR and promote CDCP1 translation. We further showed that METTL3 and CDCP1 are upregulated in the bladder cancer patient samples and the expression of METTL3 and CDCP1 is correlated with the progression status of the bladder cancers. Inhibition of the METTL3-m 6 A-CDCP1 axis resulted in decreased growth and progression of chemical-transformed cells and bladder cancer cells. Most importantly, METTL3-m 6 A-CDCP1 axis has synergistic effect with chemical carcinogens in promoting malignant transformation of uroepithelial cells and bladder cancer tumorigenesis in vitro and in vivo. Taken together, our results identify dynamic m 6 A modification in chemical-induced malignant transformation and provide insight into critical roles of the METTL3-m 6 A-CDCP1 axis in chemical carcinogenesis.

N6-Methyladenosine (m 6 A) modification has been implicated in the progression of several cancers. We reveal that during epithelial-mesenchymal transition (EMT), one important step for cancer cell metastasis, m 6 A modification of mRNAs increases in cancer cells. Deletion of methyltransferase-like 3 (METTL3) down-regulates m 6 A, impairs the migration, invasion and EMT of cancer cells both in vitro and in vivo. m 6 A-sequencing and functional studies confirm that Snail, a key transcription factor of EMT, is involved in m 6 A-regulated EMT. m 6 A in Snail CDS, but not 3'UTR, triggers polysome-mediated translation of Snail mRNA in cancer cells. Loss and gain functional studies confirm that YTHDF1 mediates m 6 A-increased translation of Snail mRNA. Moreover, the upregulation of METTL3 and YTHDF1 act as adverse prognosis factors for overall survival (OS) rate of liver cancer patients. Our study highlights the critical roles of m 6 A on regulation of EMT in cancer cells and translation of Snail during this process.

Emerging data support that RNA methylation plays important roles in RNA processing and metabolism. The methyltransferases Mettl3 and Mettl14 are shown to catalyse N(6)-methyladenosine (m(6)A) RNA modification in embryonic stem cells (ESCs). This m(6)A modification controls RNA metabolism and functions to destabilize mRNAs encoding developmental regulators to help sustain ESC self-renewal.