METTL1/WDR4-mediated m7G Hypermethylation of <i>SCLT1</i> mRNA Promotes Gefitinib Resistance in NSCLC

Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) have produced durable complete responses, but the eventual development of acquired resistance presents a major challenge in the treatment of non-small cell lung cancer (NSCLC). N7-methylguanosine (m7G), a prevalent post-transcriptional modification within RNA, plays regulatory roles in RNA stability, expression dynamics, and functional diversity. Despite these insights, the contribution of m7G methylation to EGFR-TKIs resistance remains poorly characterized. Here, we demonstrate that internal m7G modifications of mRNA and their associated methyltransferase complex, methyltransferase-like 1 (METTL1)/WD repeat domain 4 (WDR4), are significantly elevated in NSCLC specimens, which correlates with therapeutic resistance. Functional assays confirmed that METTL1/WDR4 enhances gefitinib resistance in both cellular and animal models through internal RNA m7G methyltransferase activity in NSCLC. Mechanistically, m7G MeRIP-seq combined with RNA-seq identified sodium channel and clathrin linker 1 (SCLT1) as the m7G target of METTL1/WDR4. METTL1/WDR4 knockdown led to decreased methylation level and mRNA stability of the SCLT1 transcript. Importantly, overexpression of wild-type METTL1, but not its catalytically inactive mutant, restored mRNA stability. Furthermore, METTL1/WDR4-mediated m7G modification of SCLT1 regulates gefitinib resistance by activating the NF-κB signaling. Our findings reveal the crucial role of aberrant mRNA internal m7G modification in EGFR-TKIs resistance, suggesting that targeting the METTL1/WDR4-SCLT1-NF-κB axis holds a promising therapeutic potential for overcoming EGFR-TKIs resistance.