B. Tian, X. Huang, J. Yu, and D. Chen; Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, Shandong, China
Purpose/Objective(s): Radioresistance was a paramount challenge affecting the therapeutic efficancy and improving prognosis in the treatment of esophageal squamous cell carcinoma (ESCC). There was an urgent need to identify key radioresistance genes. Although small nucleolar RNAs (snoRNAs) are recognized for their crucial role in oncogenesis, their contribution to radioresistance has not been delineated. This project aimed to clarify the mechanism of snoRNAs in ESCC radiotherapy. Materials/
Methods: KYSE30 and KYSE450 cell lines were subjected to fractionated irradiation at 2 Gy for a total of 60 Gy to establish radioresistant cell model. SnoRNA sequencing was followed to identify differential snoRNAs in the radioresistant cell lines. QPCR and FISH identified SNORA23 as the principal candidate. The radioresistant functions of SNORA23 were examined by survival fraction assay, comet assay, flow cytometry, WB and nude mice xenograft tumor model. Further mechanistic studies were conducted using RIP coupled with MS, CHIP, IHC, and rescue assays. Results: Expression profiling of snoRNAs in radioresistant ESCC cell lines exhibited significant deviation from parental cell, with SNORA23 being markedly upregulated among the 45 differentially snoRNAs identified. Experimental manipulations demonstrated SNORA23 enhanced radioresistance both in vitro and in vivo. Clinical sample analysis revealed that SNORA23 were significantly higher in ESCC tumors with T3+T4 staging compared to T1+T2 staging (P=0.0036). Following radiotherapy, a pronounced disparity was observed in the complete response (CR) rates, with a CR rate of 70% in patients exhibiting low SNORA23, significantly exceeding the 52% CR rate in high SNORA23 cohort (P=0.0059). Kaplan-Meier survival analysis further highlighted the prognostic value of SNORA23, high SNORA23 levels experiencing a significantly reduced median overall survival time of 20 months, compared to 34 months in the lower SNORA23 cohort. Mechanistically, SNORA23 interacted with the DNA binding domain ARID of KDM5C, effectively hindering KDM5Cs ability to demethylate H3K4me3 of the SFPQ promoter to H3K4me, which in turn elevated SFPQ transcription. Subsequently high expression level of SFPQ promoted DNA damage repair. Silencing SFPQ resulted in increased radiosensitivity in ESCC, partially reversed radioresistant induced by SNORA23. Moreover, there was a significantly correlation between the expression of SNORA23 and SFPQ, and ESCC tumors with co-elevated levels of SNORA23 and SFPQ are more difficult to achieve CR to radiotherapy. Conclusion: These results defined the integral role of SNORA23 in the context of radioresistance and delineated a sophisticated mechanistic linkage between snoRNAs and the DNA damage repair. Importantly, the SNORA23-KDM5C-SFPQ regulatory axis furnished compelling evidence for its potential as a strategic target and biomarker in mitigating radioresistance in ESCC.
