Increased proliferation and induction of replating activity of committed myeloid progenitors on VPA and VPA + Li treatment. Primary myeloid progenitor subpopulations were sorted by flow cytometry, and the effect of VPA + Li exposure on proliferation, colony-forming ability, and self-renewal potential was tested. (A) Influence of VPA and/or Li on CFU-GM activity of distinct myeloid subpopulations. Data are presented as colony forming cells per 10 000 cells. Shown is the mean ± SD. (B) Single-cell proliferation potential of distinct myeloid progenitor subpopulations in liquid culture with SCF and GM-CSF in the presence or absence of VPA and Li. After 7 days of culture, the number of wells with dead cells and the size of clones derived from single cells were scored. Clone size was classified as small (1-100 cells), medium (101-30 000 cells), or large (30 000 to < 150 000; n = 192-288). Cell death, defined by the percentage of wells with dead cells, was not significantly different from control conditions (GFs only) on the compound treatment in any of the tested cell populations (Welch t test, LSK + Li, P = .8; LSK + VPA, P = .13; LSK + VPA + Li, P = .13). (C) Effects of the adding compounds on single-cell colony-plating efficiency of distinct myeloid progenitors. Data are shown as the percentage of cells with colony-forming ability. (D) Ability of distinct myeloid progenitors to generate secondary CFU-GM colonies derived from a single cell (n = 20-48). The bars represent the percentage of single cell–derived primary colonies that gave rise to secondary CFU-GM colonies. The individual colors in the bars indicate the number of secondary CFU-GM colonies derived from the single cell. The differences between groups were evaluated by Welch t test, *P < .05, **P < .01, and ***P < .001.