SiRNA-mediated knockdown of YB-1 decreases proliferation rates and increases apoptotic cell death in MM.1s cells. (A) Western blot analysis of YB-1 protein expression in MM.1s cells 72 hours after transient transfection of siRNA expression constructs against YB-1. Staining of α-tubulin served as a loading control. (B) Viability of MM.1s cells was assayed with annexin V–FITC/PI staining (left), proliferation of MM.1s cells was detected by CFSE staining (center), and the S-phase cells of the cell cycle were detected by BrdU/PI staining, all 96 hours after transfection. (C) Western blot of p21^WAF1/CIP and cyclin B1 expression levels after 72 hours after transfection with YB-1 siRNA. Staining of α-tubulin served as a loading control. The error bars denote the range of values derived from 3 independent experiments.