nNOS-mediated S-nitrosylation of TCOF1 regulates KRAS proteostasis to suppress hepatoblastoma progression.

Neuronal nitric oxide synthase (nNOS) plays dual roles in tumorigenesis, but its function in hepatoblastoma (HB) remains unclear. Analysis of 30 clinical HB samples reveals significant nNOS downregulation, correlating with tumor malignancy. Overexpression of nNOS inhibits HB cell proliferation and tumor growth in vitro and in vivo. Multi-omics analysis identifies the MAPK pathway as a key target, with KRAS protein levels most prominently reduced. Mechanistically, nNOS induces S-nitrosylation of TCOF1 at cysteine 644, disrupting TCOF1-KRAS interaction and thereby accelerating KRAS protein degradation. These findings establish the nNOS-TCOF1-KRAS axis as a critical regulator of HB progression and propose a novel NO-based therapeutic strategy for KRAS-driven cancers.