Knockdown of Bmi-1 reduces the migration and invasion of glioma cells. A, Western blot analysis of Bmi-1 protein expression in vector-control cells and Bmi-1-shRNA-transduced glioma cell lines (Bmi-1-RNAi); β-actin was used as a loading control (upper). The fold changes of Bmi-1 expression were analyzed by densitometry quantification (lower). B, Wound healing assay of vector-control cells and Bmi-1-shRNA-transduced glioma cell lines. C, Representative micrographs and quantification of cell migration in the Transwell migration assay (without matrigel). D, Representative micrographs and quantification of cell invasion in the Transwell matrix penetration assay (with matrigel). E, Representative micrographs from the three-dimensional spheroid invasion assay on the 4th day after cells were planted. The experiments were repeated for at least three times with similar results. RNAi-Vector: pSuper-retro-puro-vector. Error bars represent the mean ± SD of three independent experiments; ** P < 0.01.