The expression of p53 is regulated by miR-125b in glioma cells. (A) miR-125 downregulates p53 expression in U87 cells. U87 cells were transfected with NC-DP, 125b-DP, NC-AS or 125b-AS, respectively. After incubation for 72 h, the expression level of p53 was analysed by western blot as described in Materials and Methods. P53-specific siRNA was used as a positive control. (B) Quantitative results of p53 expression. Quantitation of signal intensities was performed using densitometry on a Hewlett-Packard ScanJet 5370 C. The percentage of p53 is calculated using the formula: the value of densitometry of p53/the value of densitometry β-actin expression (n⩾3) × 100%. The relative p53 expression level in nontransfected U87 cells was defined as 1.0. The relative expression level of p53 siRNA-treated group was used as a positive control. The two-tail Student t-test was employed to statistically analyse the results: **P<0.01. (C) Downregulation of miR-125b activates the p53 and p53 related gene expression dominant cell apoptosis. U87 cells were transfected with NC-DP, 125b-DP or 125b-AS. After incubation for 72 h, cells were collected by centrifugation at 1000 r.p.m. for 5 min and cell protein was isolated. The expression level of p53, p21, Bax, Bcl-2, caspase-3 and capsase-9 were detected by western blot. The expression of β-actin was used as a loading control.