Bortezomib and dexamethasone exert an additive downregulation of chemokine (CXC motif) ligand 12 (CXCL12) levels in MS-5 cells. (A) MS-5 cells were treated with dexamethasone for 24 hr prior to western blotting for CXCL12. (B) Concentrations of CXCL12α in 3-day MS-5 culture media were measured by ELISA. Data are the mean±SD of 3 independent experiments. ^a)P<0.05, compared with the control (no bortezomib). (C) MS-5 cells were treated with bortezomib (5 nM) and/or dexamethasone (Dexa; 0.1 µM) and CXCL12 mRNA was measured by quantitative reverse transcription-PCR. (D) MS-5 cells were incubated with bortezomib (5 nM) and/or dexamethasone (0.1 µM) in X-VIVO medium for 72 hr. Media concentrations of CXCL12α were measured by ELISA. ^a)P<0.05.