shRNA沉默Sp1对胶质瘤细胞放射敏感性的影响

目的 探讨下调Sp1基因表达对胶质瘤细胞放射敏感性的影响。方法 设计并合成编码shRNA的寡核苷酸序列,克隆入LV3（H1/GFP&Puro）载体中构建重组体。然后重组慢病毒分别感染U251和U87细胞,嘌呤霉素筛选得到稳定转染细胞株。荧光定量RT-PCR和蛋白质印迹法分别检测细胞中Sp1 mRNA和蛋白表达水平;克隆存活法检测细胞存活;流式法检测细胞周期;免疫荧光法检测DNA损伤程度。结果 两株胶质瘤细胞在感染72 h后荧光显微镜观察Sp1慢病毒载体均高表达,RT-PCR和蛋白质印迹法结果显示转染后shRNA-U87和shRNA-U251细胞Sp1 mRMA和蛋白表达量均明显降低（P<0.01）,Sp1敲除率达90%以上。shRNA-U251和shRNA-U87细胞在10%细胞存活水平下的放射增敏比（SER）分别为1.39和1.18;两株Sp1敲除组细胞经辐照后G₂/M期比率及γ-H2AX foci数目与对照组相比均极显著增大。结论 shRNA沉默Sp1增大了X线诱导的G₂/M期阻滞,加重了DNA双链断裂程度,提高了胶质瘤细胞的放射敏感性。

Effect of shRNA silencing of Sp1on radiosensitivity of glioma cells

Objective To evaluate the effect of down-regulation of Sp1 expression on the radiosensitivity of glioma cells. Methods The oligonucleotide sequence encoding shRNA was designed and synthesized, and cloned into LV3 (H1/GFP & Puro) vector to construct the recombinant. U251 and U87 cells were infected with recombinant lentivirus, then the stably-transfected cell lines were obtained by puromycin screening. The expression levels of Sp1 mRNA and protein were detected by RT-PCR and Western blot. Cell survival was detected by clonal survival assay, cell cycle was determined by flow cytometry, and DNA damage was measured by immunofluorescence assay, respectively. Results At 72 h after infection, high expression of Sp1 lentiviral vector was observed in two cell lines under fluorescence microscope. RT-PCR and Western blot confirmed that the expression levels of Sp1 mRNA and protein were significantly down-regulated in both transfected cells (both P<0.01) and the silencing rates of Sp1 were above 90%. The sensitization enhancement ratio (SER) of shRNA-U251 and shRNA-U87 cells at 10% cell survival level were 1.39 and 1.18, respectively. After irradiation, the G₂/M phase ratio and the number of γ-H2AX foci in two Sp1 knockout groups were significantly increased. Conclusions hRNA silencing of Sp1 increases the G₂/M phase arrest induced by X-ray, aggravates the degree of DNA double-strand breaks, and improves the radiosensitivity of glioma cells.