Evaluation of viability in U937 human leukemia cells treated with PTX, MG132 and PTX + MG132. U937 cells were incubated in the presence of PTX, MG132, or PTX + MG132 for 18, 24, 36, and 48 hours as previously indicated. After incubation, WST-1 was added and 3 hours later, viability was assessed by spectrophotometry at 450 nm. The results represent mean ± standard deviation of three independent experiments performed in triplicate. Statistical analysis Mann-Whitney U test. ♦ p <0.05 PTX or PTX + MG132 vs untreated control group or MG132 group. ● p <0.05 PTX + MG132 vs all groups. * p < 0.05 PTX, MG132 or PTX + MG132 vs untreated control group.