Chloroquine augments SAHA-induced superoxide generation, which mediates cell death. (A) Quantification of cellular superoxide generation. K562 and LAMA 84 CML cells were treated with 25 μM CQ, 2 μM SAHA, or the combination for 12 hours. Superoxide production was determined by hydroethidine staining in conjunction with flow cytometry as described in Quantitation of intracellular superoxide generation in P‘Patients, materials, and methods.” n = 3; error bars represent the SEM. *P < .05. (B) Effects of NAC on drug-induced cell death. K562 and LAMA 84 cells were pretreated with 10 mM NAC for 3 hours. Following pretreatment with NAC, cells were exposed to 25 μM CQ, 2 μM SAHA, or the combination for 48 hours. Drug-induced apoptosis was quantified by PI/FACS. n = 3; error bars represent the SEM.