RPMI8226, MM.1S, and H929 cells transduced with V-miR-26a-GFP or V-GFP were treated with bortezomib at different doses. A. Apoptosis was analyzed by flow cytometry with annexin V B. protein levels of PARP1, c-PARP1, caspase3 and c-caspase3 were detected by western blot. Β-actin was the internal control. C. Cell viability assay showing the effect of miR-26a enforced expression on RPMI8226, MM.1S, and H929 cells with bortezomib (BTZ) or DMSO treatment. miR-26a enhanced the effect of bortezomib in a dose-dependent fashion. (*p<0.05, **p<0.01, ***p<0.001, ****p<0.0001) D. RPMI8226, MM.1S, and H929 cells were transfected with 500 nM miR-26a or treated with 2 nM bortezomib or combined with miR-26a plus bortezomib and then assessed for viability using cell viability assay. Isobologram analysis was performed using the CompuSyn software program. A combination index (CI) of less than 1.0 indicates synergism.