C/EBPα overexpression drives cells into differentiation and apoptosis. (A) C/EBPα-ER fusion translocates to the nucleus when bound to 17β-estradiol (E2). (B-C) Flow cytometry of mock or C/EBPα-ER–transduced Kasumi-1 or SKH-1 cells treated with either ethanol (ETOH) or 10 nM-1μM E2 for 2-4 days. (B) Mean fluorescence intensity (MFI) (median) of CD11b and annexin V conjugated to allophycocyanin (APC) staining relative to ethanol treated, mock transduced Kasumi-1 or SKH-1. The graph shows the mean of 3 independent experiments with standard error of the mean (SEM). *P < .05, paired Student t test. (C) Representative overlay of flow cytometry histograms of cells stained with CD11b-APC. (D-E) Annexin-V APC in mock-treated or C/EBPα-ER–transduced Kasumi-1 or SKH-1 cells treated with either vehicle (ethanol) or 10 nM E2 followed by flow cytometry (2 days in SKH-1, 4 days in Kasumi-1). (D) Percentage of Annexin-V–positive cells. Mean and SEM of 3 independent experiments. *P < .05 by paired Student t test. (E) Representative plots are shown. C/EBPα-ER–transduced cells express GFP. (F) Kasumi-1 or SKH-1 cells were either mock treated or transduced with C/EBPα-ER virus. Induced and uninduced transduced cells were treated (2 days in SKH-1, 4 days in Kasumi-1) before plating on methylcellulose culture. Colonies of >20 cells were counted between 7 and 11 days after plating. The graph shows the mean of at least 4 experiments, with error bars representing SEM. *P < .05 by paired Student t test.