(A) MCF-7 cells were transfected with siMAD2 or the negative control siRNAs, and then treated with 2ME2 for additional 24 h. The protein levels of p-JNK, c-jun, cyclin B1, MAD2, and p-Cdc2(Thr161) were determined by Western blotting. (B) The degree of 2ME2-induced prometaphase arrest in cells with or without MAD2 knockdown. The quantitative value (percentage) was based on counting ≥ 200 nuclei in each treatment group. Each bar is the mean ± S.D. from three separate experiments. * P < 0.05 versus vehicle control; #P < 0.05 versus 2ME2 treatment.