Ectopic expression of Bmi-1 enhances the migration and invasion of glioma cells. A, Western blot of Bmi-1 protein expression in A172-vector, A172-Bmi-1, LN229-vector and LN229-Bmi-1 cells; 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 A172-vector, A172-Bmi-1, LN229-vector and LN229-Bmi-1 cells. C, Representative micrographs (left) and quantification (right) of cell migration in the Transwell migration assay (without matrigel). D, Representative micrographs (left) and quantification (right) 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; these experiments were repeated at least three times with similar results. Vector: pMSCV-vector. Error bars represent the mean ± SD of three independent experiments; ** P < 0.01.