Circular RNA circEYA3 promotes the radiation resistance of hepatocellular carcinoma via the IGF2BP2/DTX3L axis.

BACKGROUND: Hepatocellular carcinoma (HCC) has a high incidence and mortality rate despite various treatment options, including 125I seed implantation. However, recurrence and radiation resistance remain challenging issues. Hsa_circ_0007895 (circEYA3)-derived from exons 2-6 of EYA3-facilitates the proliferation and progression of pancreatic ductal adenocarcinoma. However, the role of circEYA3 in HCC 125I radiation resistance remains unclear. Thus, we aimed to investigate the functions and underlying molecular mechanisms of circEYA3 in HCC under 125I and X-ray irradiation conditions. METHODS: CircEYA3 was identified by RNA-seq in patients with HCC before and after 125I seed implantation treatment, followed by fluorescence in situ hybridization and RNase R assays. The radiosensitivity of HCC cell lines irradiated with 125I seeds or external irradiation were evaluated using the Cell Counting Kit 8, flow cytometry, γH2A.X immunofluorescence and comet assays. RNA pull-down and RNA immunoprecipitation assays were performed to explore the interactions between circEYA3 and IGF2BP2. DTX3L mRNA was identified by RNA-seq in PLC/PRF/5 cells with overexpressed circEYA3. The corresponding in vitro results were verified using a mouse xenograft model. RESULTS: CircEYA3 decreased the radiosensitivity of HCC cells both in vitro and in vivo. Notably, using a circRNA pulldown assay and RNA-binding protein immunoprecipitation, we identified IGF2BP2 as a novel and robust interacting protein of circEYA3. Mechanistically, circEYA3 binds to IGF2BP2 and enhances its ability to stabilize DTX3L mRNA, thereby specifically alleviating radiation-induced DNA damage in HCC cells. CONCLUSIONS: Our findings demonstrate that circEYA3 increases the radioresistance of HCC to 125I seeds and external irradiation via the IGF2BP2/DTX3L axis. Thus, circEYA3 might be a predictive indicator and intervention option for 125I brachytherapy or external radiotherapy in HCC.