NSUN2/ALYREF stabilizes m5C-modified circCEP70 to enhance radioresistance in rectal cancer through NEDD8-dependent neddylation and ubiquitination regulation.

BACKGROUND

5-Methylcytosine (m5C) is an important RNA methylation modification implicated in tumor initiation and progression through its effects on RNA transcription, structural conformation, and stability. However, the role of the interaction between circular RNAs (circRNAs) and m5C modification in oncogenesis remains limited. This study aimed to elucidate the molecular mechanism by which m5C-modified circCEP70 facilitates radioresistance in rectal cancer (RC).

METHODS

Differentially expressed circRNAs were identified in radiosensitive and radioresistant RC tissues and cell lines. The radiosensitivity of the candidate circRNA was subsequently evaluated. RNA pull-down assays followed by mass spectrometry were employed to investigate the underlying mechanism.

RESULTS

circCEP70 was identified as a candidate circRNA. Assessment of clinical samples showed that patients with RC and low circCEP70 expression had a better response to neoadjuvant chemoradiotherapy and significantly longer disease-free survival than those with high circCEP70 expression. Both in vitro and in vivo experiments confirmed that circCEP70 enhanced radioresistance in RC cells. Mechanistically, NSUN2 and ALYREF mediated m5C modification to regulate the stability and expression of circCEP70. By binding to NEDD8, circCEP70 impeded its ubiquitination and subsequent degradation, thereby enhancing neddylation modification.

CONCLUSIONS

This study identifies circCEP70 as a previously unrecognized m5C-modified circRNA and suggests that the NSUN2/ALYREF/circCEP70/NEDD8 axis may serve as a potential therapeutic target for radiotherapy in RC.