Knockdown of Gli1 by small-interfering RNA enhances the effects of BCNU on the proliferation and apoptosis of glioma U251 cells

Aims: The present study is to investigate the effect of the combination of small-interfering RNA (siRNA) treatment with bis-chloroethylnitrosourea (BCNU) on the proliferation and apoptosis of glioma cells. Methods: According to different treatments, glioma U251 cells were randomly divided into blank group, Lipofectamine group, siRNA-Gli1 group, BCNU group and combination group. After treatments, the morphology of U251 cells was visualized under the microscope. Afterwards, semi-quantitative real-time polymerase chain reaction and Western blotting were used to determine Gli1, Bcl-2, Bax and cyclin D1 mRNA levels and protein expression, respectively. MTT assay was used detect the proliferation of U251 cells, while flow cytometry was performed to determine cell apoptosis and cell cycle. Results: The combination of siRNA-Gli1 and BCNU caused more severe damages to U251 cell shapes compared with siRNA-Gli1 or BCNU alone. The combination of BCNU and siRNA-Gli1 altered mRNA level and protein expression of Bcl-2 and Bax, but not those of Gli1 and cyclin D1. The combination of siRNA-Gli1 and BCNU promoted U251 cell apoptosis. The combination of siRNA-Gli1 and BCNU enhanced the arrestment of U251 cells in G0/G1 phase. The combination of siRNA-Gli1 and BCNU significantly inhibited U251 cell proliferation. Conclusions: The present study demonstrates that combined treatment with siRNA-Gli1 and BCNU significantly inhibits the proliferation and promotes the apoptosis of glioma U251 cells, possibly by the up-regulation of Bax and the down-regulation of Bcl-2. The combination of siRNA-Gli1 and BCNU enhances the inhibition of cell cycles, but does not down-regulate the expression of cell cycle protein cyclin D1.