In vitro growth inhibitory, apoptotic and cytodifferentiating activity of ATRA and AM580 in NB4 and NB4.437r cells. NB4 (open bars) or NB4.437r (solid bars) cells (2 × 105/mL) were treated with ATRA (10−6 mol/L), the powerful cytodifferentiating retinoid AM580 (10−8 mol/L) or vehicle (dimethyl sulfoxide, control) for 4 days. (A) The total number of cells was counted after staining with erythrosine (the percentage of viable cells is indicated in parentheses). (B) The proportion of apoptotic cells after staining with DAPI is shown. (C) NBT-reducing activity was measured spectrophotometrically after stimulation of cells with PMA for 30 minutes. Results are the mean ± SD of 3 separate culture dishes. (D) CD11a, CD11b, CD11c, CD13, and CD33 surface expression was measured by flow cytometry after staining with specific fluoresceinated antibodies. “Neg” indicates the level of background fluorescence observed in the different samples. Data are representative of at least 2 independent experiments with superimposable results. **Significantly higher or lower than the respective control values according to the Student t test (P < .01).
