Rosmarinic acid induces ferroptosis in oral squamous cell carcinoma by targeting METTL5-mediated m6A modification

Background: Oral squamous cell carcinoma (OSCC) is a most prevalent malignancies,with high recurrence rates and poor prognosis. METTL5 catalyzes m6A modification of ribosomal RNA, and exhibits oncogenic properties in several cancers. However, the function of METTL5 in OSCC pathogenesis remain uncharacterized. Rosmarinic acid (RA) have shown promise in cancer treatment due to their ability to modulate multiple molecular pathways with low toxicity. Methods: METTL5 was analyzed in OSCC patient tissues and cell lines. The OSCC cells were transfected with specific constructs to achieve METTL5 overexpression and knockdown, and their functional impact on cellular proliferation, migration, and invasion was assessed through standard assays. In addition, the levels of ferroptosis markers, including reactive oxygen species (ROS), Fe2+, glutathione (GSH), glutathione peroxidase 4 (GPX4), nuclear factor erythroid 2-related factor 2 (NRF2), solute carrier family 7 member 11 (SLC7A11), and ferritin light chain (FTL) were measured. Moreover, natural inhibitors of METTL5 were screened through virtual molecular docking, and the anti-cancer efficacy of RA was validated both in vitro and in vivo. Results: METTL5 was significantly upregulated in OSCC tissues and cell lines, and its elevated expression correlated with adverse patient prognosis. Overexpression of METTL5 enhanced the proliferation and invasion of OSCC cells, whereas its knockdown triggered ferroptosis, as indicated by the increase in ROS levels, decrease in Fe2+ and GSH content, and downregulation of the NRF2/SLC7A11/GPX4 axis. RA was identified as a selective METTL5 inhibitor that directly binds to the protein and suppresses its methyltransferase activity. RA treatment sensitized OSCC cells to ferroptosis, and significantly inhibited tumor growth both in vitro and in vivo. Conclusion: This study demonstrates that METTL5 promotes OSCC progression and regulates ferroptosis sensitivity through rRNA modification. Furthermore, we have identified RA as a promising natural inhibitor of METTL5. Our findings indicate that METTL5 is a novel target for OSCC.