BSO sensitized cells to ATO and enhanced up-regulation of the BH3-only protein Noxa. (A) MM.1s and KMS11 cells were treated with 1 μM ATO as a single agent or in combination with BSO (100 μM) or NAC (10 mM) for 48 hours. Viability was evaluated by annexin-V–FITC/PI staining. Data are presented as means (± SD) of 3 independent experiments. (B) MM.1s and KMS11 cells were treated for 24 hours. Protein expression was determined by Western blot. Membranes were reprobed with specific antibodies for Noxa, Puma, Bim, Mcl-1, Bcl-X_L, and actin. (C) KMS11 cells were treated with 2 μM ATO as a single agent or in combination with BSO and/or NAC for 24 and 48 hours. Viability was evaluated by annexin-V–FITC/PI staining. Data are presented as means (± SD) of 4 independent experiments. Noxa expression was determined by Western blot. t test was used to compare differences among samples, ATO, and experimental combinations unless otherwise indicated, with confidence intervals of 95%. ND indicates no difference; *P < .05; **P < .01; ***P < .001.