BTZ-resistant MM cells respond to GO-203 with increases in ROS and cell death. (A-D) U266/BR (A) and RPMI8226/BR (B) cells were left untreated (CTL) and treated with 5 μM GO-203 or CP-2 each day for 72 hours. The GO-203-treated cells were also incubated in the presence of 5 mM NAC for 72 hours. Cells were analyzed for relative hydrogen peroxide levels (mean ± SD of 3 determinations) as compared with that obtained with control cells (A-B). Cells were incubated with PI and annexin V and analyzed by flow cytometry. The results are expressed as the percentage (mean ± SD of 3 determinations) of dead cells (C-D). (E) ANBL-6 and ANBL-6/BR cells were treated with 5 μM GO-203 each day for 72 hours, incubated with PI and annexin V, and analyzed by flow cytometry. The results are expressed as the percentage (mean ± SD of 3 determinations) of dead cells. (F) OMP-2/BR cells were left untreated (CTL) and treated with 5 μM GO-203 or CP-2 each day for 72 hours. Percentage survival (mean ± SD of 3 determinations) was determined by Alamar blue staining.