Effect of the antioxidant LNAC on the response of K562 cells to SAHA and bortezomib. (A) K562 cells were exposed to 1.5 μM SAHA ± 4.5 nM bortezomib in the presence or absence of 15 mM LNAC for 4 hours, after which ROS production was assayed by monitoring the percentage of cells displaying increased uptake of dichlorohydrofluoroscein diacetate (DCF) as described in “Materials and methods.” (B) Cells were treated with SAHA + bortezomib as shown in panel A ± 15 mM LNAC for 24 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.” For panels A-B, values represent the means ± SD for 3 separate experiments. (C) K562 cells were exposed to 4.5 nM bortezomib + 1.5 μ SAHA for 24 hours in the presence or absence of 15 mM LNAC, after which Western analysis was used to assess expression of JNK, phospho-JNK, p21^CIP1, and cleaved caspase-3. Each lane contained 25 μg protein; blots were stripped and reprobed for tubulin to ensure equivalent loading and transfer. An additional 2 studies yielded equivalent results.