IGR-N91 neuroblasts sensitivity to 4-HPR-induced cell death. A) The IGR-N91-M control cells and IGR-N91-C8 clone 19 cells were treated with 2.5 or 5 μM 4HPR for 48 hrs. Cell lysates were analyzed by IB for caspase-8, -9 and β-actin as loading control. B) Cell death was determined by the MTS assay and the data represent the mean values of two representative experiments ± SD. **P < 0.01 indicates difference between 4HPR-treated cells and EtOH-treated cells.