Fig. 2
circCDYL2 promotes radiotherapy resistance in vitro and in vivo. A. Colony formation assay was performed to measure the survival rates after ionizing radiation in NPC cells. Cells were irradiated with X-rays at doses of 0, 2, 4, 6, or 8 Gy, respectively, after overexpression or knockdown of circCDYL2. The cell survival curve was obtained by using the irradiation dose as the abscissa (arithmetic coordinates), and the survival fraction as the ordinate (logarithmic coordinates). The results were analyzed and plotted using a linear-quadratic model. B. In vivo experiments were performed by subcutaneously injecting 3 × 106 CNE2 cells after overexpression or knockdown for circCDYL2 (n = 5). Tumor sites were irradiated with 6 Gy on day 18. Tumor volumes were measured every 2 days until day 28. C. Representative images of subcutaneous tumors. D & E. Tumor volumes (D) and weights (E) were measured in each group. F. Immunofluorescence was performed to measure the level of γ-H2AX in HNE2 cells after overexpression or knockdown of circCDYL2 with 6 Gy irradiation for 2, 6, 12, or 24 hours. The results showed that overexpression of circCDYL2 reduced the accumulation of radiation-induced foci (IRIF) of γ-H2AX in HNE2 cells post-irradiation, while knockdown of circCDYL2 had the opposite effect. Scale bar = 10 μm. The right graph represents the number of radiation-induced foci (IRIF) in 30 cells. G. Western blotting revealed that circCDYL2 promoted the disappearance of γ-H2AX foci in HNE2 cells with circCDYL2 overexpression or knockdown after irradiation. H. Comet assays showed that circCDYL2 promoted DNA damage repair in NPC cells with circCDYL2 overexpression or knockdown after radiation. Representative comet images were shown above, and the scale bar = 20 μm. The lower panel represented statistical analysis. Data were represented as mean ± SD. ns, not significant; *, p < 0.05; **, p < 0.01; ***, p < 0.001