Enhanced Ku70 acetylation sensitizes H358 cells to gefitinib. (a) H358 cells were transfected with a plasmid control encoding green fluorescent protein (GFP) or with a plasmid encoding CREB-binding protein-hemagglutinin (CBP-HA) and treated or not with 0.5 µmol/l gefitinib as indicated. The expression of GFP or CBP-HA was revealed by immunofluorescence 96 hours after transfection and apoptosis of transfected cells was analyzed after counting Hoechst-stained cells. (b–d) H358 cells were treated or not with (b) TSA, (c) vorinostat, (d) nicotinamide, and/or 0.5 µmol/l gefitinib. Apoptosis was scored after counting Hoechst-stained cells. Results are expressed as mean ± SD (n ≥ 3). *P < 0.05, **P < 0.01, ***P < 0.001, more significant than control, NT, untreated.