In vivo administration of HU results in accumulation of KTLS cells in the S/G2/M phases of the cell cycle. Mice were treated with HU (10, 50, or 100 mg/kg/d) for 3 days. The cell-cycle status of KTLS cells from HU-treated mice was examined by sorting KTLS cells from BM and staining with Hoechst 33342 for analysis of DNA content. FACS plots display Hoechst 33342 staining v forward scatter (a to d). The percentage of cells in G0/G1 or S/G2/M is indicated at the left or right of each FACS plot, respectively. (e and f ) Cells in G0/G1, S, and G2/M phases of the cell cycle were determined by DNA histogram modeling using ModFit (Verity Software House, Topsham, ME). Note that the calibration for the forward-scatter setting is different from the one used in Fig 1.