Effects of AML1a expression on growth of hematopoietic cells ex vivo. (A) Fold-increases of cumulative cell number are presented on a logarithmic scale versus time. BM cells infected with TetOFF-GFP-tetO-AML1a (●) or control (○) retrovirus were sorted for GFP+ and cultured in the presence of SCF and IL-3. Cells were counted and replated at 105 cells/mL every 7 days. After 4 weeks, Dox was added to an aliquot of culture of TetOFF-GFP-tetO-AML1a–infected cells (■), which showed inhibited cell growth. Three experiments yielded similar results. (B) Frequency of colony-forming cells in serial replating experiments. BM cells infected with the indicated retrovirus, sorted for GFP+ and plated in the multimyeloid condition in the presence or absence of Dox. Colonies were counted and cells were harvested on day 7; 1 × 104 cells were replated. Representative data from 3 independent experiments conducted in triplicate are presented. (C) Photomicrographs show relative sizes of colonies generated in the multimyeloid condition. BM cells infected with the indicated retrovirus, sorted for GFP+, and assayed for colony formation in the presence or absence of Dox. Original magnification ×40 (UPlan FLN4×/0.13 PhP objective).
