Lactylation enhances YTHDF3 stability to promote cisplatin resistance via m6A-dependent KDM6B decay in bladder cancer.

Acquired resistance to cisplatin remains a major therapeutic challenge in muscle-invasive bladder cancer. Here, we demonstrate for the first time that lactate accumulation induces AARS2-dependent lactylation of the m6A reader YTHDF3, establishing lactylation as a previously unrecognized regulatory layer of this epitranscriptomic factor. YTHDF3 lactylation stabilizes the protein by antagonizing ubiquitin-mediated degradation. Importantly, a lactylation-deficient YTHDF3 mutant fails to confer cisplatin resistance, underscoring the functional importance of this modification. Mechanistically, lactylated YTHDF3 enhances its m6A-dependent recognition and decay of KDM6B RNA. The resulting downregulation of KDM6B suppresses CDKN1A transcription through impaired H3K27me3 demethylation, representing an epigenetic mechanism that weakens the DNA damage response and promotes chemoresistance. Functional assays further demonstrate that YTHDF3 knockdown enhances cisplatin sensitivity in bladder cancer cells and xenograft tumors, whereas enforced expression of KDM6B or CDKN1A phenocopies the cisplatin-sensitizing effect of YTHDF3 knockdown. Collectively, our findings define a lactate-AARS2-YTHDF3-KDM6B-CDKN1A axis that integrates metabolic reprogramming, m6A-dependent epitranscriptomic regulation, and epigenetic chromatin remodeling to drive cisplatin resistance in bladder cancer.