Bortezomib inhibits proliferation of MyLa and SeAx cell lines. Cells were cultured in the presence of increasing concentrations of bortezomib (5, 10, 20, and 40 nM) for 24 and 48 hours. DNA synthesis was assessed by [³H] thymidine uptake during the last 16 hours of culture. The results expressed in cpm are the mean ± SEM of 6-way culture wells from 3 independent experiments.