NUDT21 lactylation enhances its interaction with CPSF6, facilitating CFIm complex formation and inducing 3′ untranslated region (UTR) lengthening of FDX1. Extension of the FDX1 3′ UTR attenuates its protein output, thereby conferring resistance to cuproptosis in esophageal squamous cell carcinoma (ESCC). The gene discussed is CPSF6; the disease is esophageal squamous cell carcinoma.