Cell-cycle analysis of purified murine KTLS cells after HU treatment in vitro. KTLS cells were isolated from BM and cultured for 24 hours with (a) no cytokines (72% viable), (b) the cytokines IL-6, SLF, and TPO (95% viable), (c) HU (100 μg/mL) and cytokines (78% viable), or (d) HU (100 μg/mL) and cytokines, and then cells were washed to remove HU and cultured with cytokines for another 24 hours (92% viable). FACS plots display Hoechst 33342 staining forward scatter. The percentage of cells in G0/G1 or S/G2/M is indicated at the left or right of each FACS plot, respectively. About 6% of KTLS cells were in the S/G2/M phases before culture initiation. During this experiment, the fine-gain setting of forward-scatter measurement was normalized using calibration beads.