Figure 5. MK591 treatment triggers activation of c-Jun N-terminal Kinase which plays a critical role in apoptosis.

PCSCs (3 × 10⁵ per plate) were plated in complete growth medium supplemented with 10% serum in 60 mm diameter plates and allowed to grow for 48 hours. On the day of experiment, the spent culture medium was replaced with 2 ml fresh RPMI medium and the cells were treated with MK591 as described in Figure 2 for 24 hours. In (A and B), dose and time-dependent changes in phosphorylation of c-JNK by MK591 treatment were detected by Western blots using phospho-specific antibodies. In (C), cells were pre-treated with c-JNK inhibitor (SP = SP600125) for 30 minutes before treatment with MK591, and cell death was detected by staining with Annexin V-FITC as in Figure 4 above.