miRNA-21对乳腺癌细胞放射敏感性的影响及其机制

目的：观察miRNA-21对乳腺癌细胞放射敏感性的影响，并初步探讨其作用机制。方法：乳腺癌T47D和MDA-MB-361细胞分别给予0.0、2.5和5.0 Gy γ射线照射，CCK8法检测细胞存活率，流式细胞术分析细胞周期进程，实时定量PCR法检测72 h内细胞中miRNA-21表达水平。T47D和MDA-MB-361细胞分别转染anti-miRNA-21序列（anti-miRNA-21组）和阴性对照序列（阴性对照组），并设置未转染细胞为空白对照组，实时定量PCR法检测各组细胞中miRNA-21表达水平；经0.0和5.0 Gy γ射线照射后，CCK8法检测细胞存活率，流式细胞术分析细胞周期进程。结果：经5.0 Gy γ射线照射后，T47D细胞存活率明显高于MDA-MB-361细胞（P<0.05）；与0.0 Gy照射组比较，5.0 Gy照射组T47D和MDA-MB-361细胞G₂/M期细胞百分率均明显升高（P<0.05），miRNA-21表达水平均明显升高（P<0.05）。与空白对照组比较，anti-miRNA-21组T47D和MDA-MB-361细胞中miRNA-21表达水平均明显降低（P<0.05或P<0.01）；给予5.0 Gy γ射线照射后，anti-miRNA-21组T47D和MDA-MB-361细胞存活率均明显降低（P<0.05或P<0.01），T47D细胞G₂/M期细胞百分率明显降低（P<0.05），而subG₁期细胞百分率明显升高（P<0.05）。结论：miRNA-21表达下调能够增强乳腺癌细胞的放射敏感性，其机制可能与抑制细胞周期G₂/M期阻滞有关。

Influence of miRNA-21 in radiosensitivity of breast cancer cells and its mechanism

Objective:To observe the influence of miRNA-21 in the radiosensitivity of the breast cancer cells, and to preliminarily explore its mechanism. Methods:The breast cancer T47D and MDA-MB-361 cells were irradiated with 0.0,2.5,and 5.0 Gy γ-ray,respectively; CCK8 assay was used to detect the survival rates of T47D and MDA-MB-361 cells and flow cytometry was used to analyze the cell cycle; real-time quantitative PCR was used to detect the expression levels of miRNA-21 in cells during 72 h. The T47D and MDA-MB-361 cells were transfected with anti-miRNA-21 sequence (anti-miRNA-21 group) and negative control sequence(negative control group), respectively; the untransfected cells were set as blank control group. Real-time quantitative PCR was used to detect the expression levels of miRNA-21 in cells in various groups. After irradiation with 0.0 and 5.0 Gy γ-ray, CCK8 assay was used to detect the survival rates, and flow cytometry was used to analyze the cell cycle. Results:After irradiation with 5.0 Gy γ-ray, the survival rate of T47D cells was significantly higher than that of the MDA-MB-361 cells (P<0.05). Compared with 0.0 Gy radiation group, the percentages of T47D and MDA-MB-361 cells in G₂/M phase in 5.0 Gy radiation group were significantly increased(P<0.05); the miRNA-21 expression levels in the T47D and MDA-MB-361 cells were significantly increased (P<0.05).The miRNA-21 expression levels in the T47D and MDA-MB-361 cells in anti-miRNA-21 group were lower than those in blank control group (P<0.05). After irradiation with 5.0 Gy γ-ray, the survival rates of T47D and MDA-MB-361 cells in anti-miRNA-21 group were significantly lower than those in blank control group(P<0.05 or P<0.01), and the percentage of T47D cells in G₂/M phase in anti-miRNA-21 group was significantly lower than that in blank control group (P<0.05), and the percentage of T47D cells in subG₁ phase was significantly higher than that in blank control group (P<0.05). Conclusion:The down-regulation of miRNA-21 may enhance the radiosensitivity of breast cancer cells, and its mechanism may be related to the inhibition of G₂/M phase arrest.