Differentiation of leukemic cells in response to doxycycline. (A) Fold accumulation (log10) in cell number of ME4 (□, ■), ME4a (▵, ▴), and ME4b (◇, ♦) with (□, ▵, ◇) or without (■, ▴, ♦) 2 μg/mL doxycycline. (B) Morphology of the cell lines (left panel, original magnification ×400) and p-iodonitrotetrazolium stains of methylcellulose cultures (right panel) after culture with or without doxycycline (DOX) for 4 and 8 days, respectively. (C) Relative level of neutrophil granule mRNA expression, measured by quantitative reverse-transcribed PCR, in ME4 and ME4a cells after culture with (□) or without (■) doxycycline for 3 days. Plots show a decrease in primary granule myeloperoxidase (Mpo) and an increase in secondary granule lactotransferrin (Ltf) and tertiary granule matrix metallopeptidase 9 (Mmp9) gene expression after doxycycline treatment. Values for each gene were normalized to untreated ME4 cells. Columns represent the mean of triplicate measurements; error bars represent the SD. (D) Changes in surface antigen expression in ME4 (left panel) and ME4a (right panel) cells after culture with or without doxycycline for 3 days. (Top panels) c-Kit and EGFP expression. (Bottom panels) Gr-1 and Mac-1 expression. Numbers in the plots refer to the percentages of cells within each quadrant.
