(A) Cell cycle status of CD34⁺ primary cells at 42 hours after siRNA treatment. Cells treated with p21 siRNA and control siRNAs were examined by Hoechst (DNA dye) and PY (RNA dye) staining. Cell cycle status was examined at both 10 hours (not shown) and 42 hours after siRNA treatment. No significant changes in the cell cycle status were observed at both time points among CD34⁺ primary cells that were treated with p21 siRNA or control siRNA or those that were mock treated. (B) Cell cycle status of CMK cells at 42 hours after siRNA treatment. No significant changes were observed in the cell cycle status in megakaryoblasts treated with p21 siRNA (Si-1, Si-2), control siRNA, p21 shRNA, or vector only or those that were mock treated. (C and D) Cell cycle status determined by BrdU incorporation assay. (C) Cell cycle status of CD34⁺ primary cells was examined at both 10 hours (not shown) and 42 hours after siRNA treatment. No significant changes were observed between cells treated with p21 siRNA and cells treated with control siRNA. Cells incorporating BrdU (UL + UR) consisted of 23.75% and 23.72% p21 siRNA– or control siRNA–treated cells, respectively. (D) Mean values of cells incorporating BrdU in each condition from 4 independent assays are shown.