PK + bortezomib does not affect the viability of patient MM-derived bone marrow stroma cells (BMSCs) and overcome the antiapoptotic effects of interleukin-6 (IL-6) or insulin growth factor-1 (IGF-1). (A) Patient MM BMSCs (patient nos. 1-3) were treated with indicated concentrations of PK + bortezomib for 24 hours and analyzed for viability by MTT assays. Results are the mean ± SD of 3 independent experiments; P < .005. (B) MM.1S cells were treated with indicated concentrations of PK + bortezomib or Dex (0.5 μM) in the presence or absence of either IL-6 (10 ng/mL) or IGF (50 ng/mL). At 24 hours, cells were harvested and viability was analyzed by MTT assays. Results are means ± SDs of 3 independent experiments.