FIG. 2.

Drug treatment activates the p53-p21 pathway in breast cancer cells. (A) Subconfluent MCF-7 monolayers, serum starved for 2 days (Q), asynchronously growing (Log), or treated with 1 μM doxorubicin for 2 h, followed by a change to fresh media for the indicated times, were harvested for Western blotting or chromatin immunoprecipitation according to Materials and Methods. p53, p21, and actin immunoblots show increased p53 and p21 levels early after drug treatment, diminishing 8 days after drug treatment. Molecular weight markers are indicated at the right. (B) Chromatin immunoprecipitations with p53 (left chart), acetylated histone H4 (right chart), and a no-antibody control were performed on MCF-7 cells treated as indicated. Real-time PCR analysis was performed using primers for the p21 or acetylcholine receptor (AchR) promoter regions as indicated, and results are expressed as percentages of the input. Error bars represent standard errors of the mean for triplicates. Data are representative of at least two independent experiments.