Effect of SAHA and bortezomib on NF-κB activation in K562 cells. (A) K562 cells were exposed to 1.5 μM SAHA ± 4.5 nM bortezomib for one hour, after which EMSA analysis was used to monitor NF-κB DNA binding as described in “Materials and methods.” The first lane corresponds to control extracts exposed to an unlabeled competitor to exclude nonspecific DNA binding. (B) NF-κB DNA binding activity was quantified densitometrically as described in “Materials and methods,” and values for each condition were expressed in relation to untreated controls. Values represent the means for triplicate determinations ± SEM. P < .01 (^*) or < .005 (^**) relative to untreated controls. (C) K562 cells were exposed to SAHA (2.0 μM) ± the NF-κB inhibitor BAY 11-7082 for 48 hours, after which the percentage of apoptotic cells was determined by examining Wright Giemsa-stained specimens under light microscopy as described in “Materials and methods.” Values represent the means ± SD for 3 separate experiments performed in triplicate.