GO-203 is synergistic with BTZ and decreases survival of BTZ-resistant cells. U266 (A) and RPMI8226 (B) cells were treated with (1) the indicated concentrations of GO-203 alone each day for 72 hours, (2) the indicated concentrations of BTZ alone for 24 hours, and (3) GO-203 for 48 hours combined with BTZ for an additional 24 hours. Mean cell survival was assessed in triplicate by Alamar blue assays. Numbers 1 to 6 in the graphs (left) represent combinations listed in the tables (right). FA, fraction affected. (C-D) The indicated drug-naïve U266 and BTZ-resistant U266/BR (C) and drug-naïve RPMI8226 and BTZ-resistant RPMI8226/BR (D) cells were left untreated (CTL) and treated with 20 nM BTZ and 16 nM BTZ, respectively, for 24 hours. 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. (E-F) The indicated cells were left untreated (CTL) and treated with 5 μM GO-203 each day for 72 hours. Percentage survival (mean ± SD of 3 determinations) was determined by Alamar blue staining.