Fig. 4

C2orf40 overexpression promotes the sensitivity of NPC cells to radiotherapy in vitro. A GSEA was performed using two GEO datasets (GSE12452 and GSE53819) as mentioned previously. The results demonstrated the enrichment of the gene signatures associated with DNA repair. B‒C HONE-1 and SUNE-1 cells stably overexpressing C2orf40 or controls were submitted to X-ray irradiation (IR). B Concurrent staining for the DNA damage marker γH2AX and endogenous control DAPI revealed that γH2AX expression, as measured by immunofluorescence, was significantly higher after 24 h of 6-Gy IR in NPC cells with C2orf40 overexpression. C Endogenous DNA damage and repair were assessed by the comet assay, indicating that overexpression of C2orf40 impaired the ability of NPC cells to repair DNA damage. D HONE-1 and SUNE-1 cells stably overexpressing C2orf40 or controls were exposed to a range of X-ray doses: 0, 2, 4, 6, and 8 Gy. Then, the clonogenic cell survival was measured to evaluate the radiation sensitivity of NPC cells. E Western blotting showed the γH2AX protein levels in HONE-1 and SUNE-1 cells after exposure to 6-Gy IR for 0, 1, and 12 h, with β-actin as an internal reference. The experiments were performed in triplicate and repeated twice. Data are presented as the mean ± SD. *P < 0.05, **P < 0.01, ***P < 0.001