Caspase 8-negative SH-EP neuroblasts are resistant to 4-HPR-induced cell death. A) SH-EP cells infected with shRNA targeting caspase-8 (shC8) or nonsilencing control (nsc) were treated with 5, 10 or 15 μM 4-HPR for 48 hrs. Cell lysates were analyzed by western blotting for caspase-8 and β-actin used as loading control. B) Cell death was measured by MTS cell proliferation assays in the SH-EP cell lines. Mean values of three independent experiments ± SD are shown. ** P< 0.01 indicates difference between SHEP-nsc and SHEP-shC8 cells.