Colorectal cancer (CRC) is a global health concern, and despite advances in radiotherapy, endogenous radioresistance in CRC patients remains a challenge. The present study delves into the role of miR-4274 and peroxisomal biogenesis factor 5 (PEX5) in CRC radioresistance, uncovering a potential molecular mechanism and therapeutic target. The research identified a significant association between a single-nucleotide polymorphism (SNP), rs1553867776, in the seed region of miR-4274 and CRC radiosensitivity. PEX5 was revealed as a target gene of miR-4274, with the deletion genotype of rs1553867776 leading to downregulation of PEX5 protein, which is associated with enhanced tumor response to radiotherapy. The study suggests that PEX5 interacts with Ku70 in the cytoplasm, preventing its nuclear entry and subsequent DNA damage repair, thereby increasing CRC cell radiosensitivity. Additionally, PEX5 was implicated in ferroptosis, an iron-dependent cell death program that modulates radiosensitivity. The findings propose that the miR-4274-PEX5 axis is crucial in CRC radioresistance and could serve as a novel clinical target for enhancing radiotherapy efficacy.

The study employed a comprehensive approach, utilizing CRC cell lines, reagents, and various assays to explore the molecular mechanisms of CRC radioresistance. Through luciferase reporter assays, it was confirmed that PEX5 is a direct target of miR-4274. The functional significance of PEX5 in CRC was further investigated through the establishment of CRC cell lines with PEX5 overexpression or knockout. The results indicated that PEX5 overexpression increased CRC cell radiosensitivity, while PEX5 silencing led to radioresistance. The role of PEX5 in DNA repair was investigated, revealing that PEX5 interacts with Ku70 and influences the formation of the Ku70/Ku80 complex, a key player in non-homologous end-joining (NHEJ) DNA repair. The study also examined the impact of PEX5 on ferroptosis, showing that PEX5 overexpression enhanced iron-induced cell death, suggesting its role in modulating ferroptosis in CRC cells.

Animal experiments further validated the in vivo effects of miR-4274 and PEX5 on CRC progression and radiosensitivity. The results demonstrated that the deletion-type miR-4274 agomiR-mimics enhanced tumor growth, while PEX5 knockout significantly improved tumor growth in mouse models. The study concluded that PEX5 is closely associated with high radiotherapy efficacy and improved survival outcomes in CRC patients, indicating its potential as an effective biomarker for cancer radiotherapy response.

This research contributes to the understanding of genetic variations in miRNA seed regions associated with CRC radiotherapy sensitivity and provides definitive proof for SNPs' prediction of treatment efficacy. It also highlights the therapeutic potential of targeting miR-4274 and PEX5 to overcome radioresistance in CRC. The study's findings have significant implications for developing precise and effective cancer radiotherapy strategies, offering new insights into the molecular mechanisms of CRC radioresistance and potential therapeutic targets.
DOI: 10.1007/s11684-024-1082-6