SNORA23-KDM5C epigenetic axis mediates dual DNA repair pathways to drive radioresistance in esophageal squamous cell carcinoma

Radioresistance remains a major barrier in esophageal squamous cell carcinoma (ESCC). This study demonstrates small nucleolar RNA SNORA23 as a pathogenic epigenetic driver of intrinsic radioresistance, with its overexpression tightly correlating with advanced T-stage, lymph node metastasis, and adverse clinical outcomes in a chemoradiotherapy cohort. Mechanistically, SNORA23 directly binds the ARID domain of histone demethylase KDM5C via a structurally defined G11-Ser169 interface-obstructing KDM5C chromatin binding to derepress DNA repair scaffolding gene SFPQ. This chromatin reprogramming enables SFPQ-facilitated recruitment of RAD51 and Ku80 to DNA double-strand breaks, accelerating homologous recombination (HR) and non-homologous end joining (NHEJ). SFPQ high expression recapitulates SNORA23-mediated repair enhancement and reduced radiosensitivity. Therapeutically, SNORA23-targeting antisense oligonucleotides (ASOs) disrupt this axis, impair DNA repair, and synergize with radiotherapy to suppress tumor growth and prolong survival in vivo without evident systemic toxicity These findings define a snoRNA-chromatin-repair axis driving therapeutic resistance and support SNORA23 inhibition as a promising strategy to overcome radioresistance in ESCC.