Targeting NSUN5-mediated m5C-RNA modification overcomes sunitinib resistance in renal cell carcinoma by suppressing Fibronectin/PI3K/AKT signaling

Abstract Sunitinib resistance represents a dominating obstacle for clinical pharmacotherapy of renal cell carcinoma (RCC). Dysregulation of the RNA 5-methylcytosine (m 5 C) modification exerts an important influence on tumor pathogenesis, yet its role and the mechanism underlying RCC sunitinib resistance remain unknown. Here, we demonstrate that the global level of RNA m 5 C and expression of its methyltransferase NSUN5 (“writer”) are increased in sunitinib-resistant RCC cells/tissues. Upregulated NSUN5 correlates with RCC sunitinib resistance and poor prognosis of patients after receiving surgery or sunitinib treatment. Functional studies confirmed the biological significance of NSUN5 in RCC development and sunitinib resistance. Mechanistically, NSUN5 catalyzes m 5 C modification on Fibronectin 1 (FN1) mRNA, enabling recognition by the m 5 C “reader” YBX1 and subsequently stabilizing FN1 transcripts, thereby stimulating PI3K/AKT signaling and augmenting oncogenic effects. Furthermore, a small-molecular inhibitor targeting NSUN5 was discovered by virtual and high-throughput screening to reduce RNA m 5 C levels, and treatment with this inhibitor significantly inhibits growth and sunitinib resistance in RCC cells and patient-derived xenografts. These findings illustrate that RNA m 5 C modification and the NSUN5/YBX1-FN1-PI3K/AKT axis play vital roles in modulating sunitinib resistance and progression of RCC, and imply that NSUN5 may serve as a prospective indicator and therapeutic target for sunitinib response.