Ricolinostat displays antimyeloma activity and its efficacy is enhanced by knockdown of BRD4. (A) Ricolinostat decreases MM cell viability. A panel of MM cell lines was treated with the indicated concentrations of ricolinostat for 72 hours. Cell viability was measured by MTT assay. (B) Ricolinostat promotes the accumulation of acetylated (Ac) α-tubulin. MM cells were treated with the indicated concentrations of ricolinostat for 24 hours. Protein expression was measured by immunoblotting. (C) Silencing BRD4 decreases c-MYC and BCL-2 expression and induces p21 and HDAC6 levels. BRD4 was knocked down by using lentiviral shRNA, and positively infected cells were selected with puromycin. Immunoblotting confirmed knockdown of BRD4 and levels of c-MYC, BCL-2, p21, and HDAC6. (D) Silencing of BRD4 enhances the antimyeloma activity of ricolinostat. Cells transfected with NT control or BRD4 shRNA were treated with the indicated concentrations of ricolinostat for 72 hours, and cell viability was determined by MTT assay. Data are shown as mean ± SD; n = 3. *Indicates a significant difference compared with NT shRNA transfected cells treated with the same concentration. P < .05.