Effect of ATRA and STI571 alone or in combination on the growth, granulocytic maturation, and apoptosis in NB4 cells.
NB4 cells were seeded at an initial concentration of 2 × 105/mL and treated for the indicated amount of time with medium alone (▵) or medium containing ATRA (10−7 M) (○), STI571 (5 × 10−6 M) (▴), and STI571 + ATRA (●). Aliquots of the cultures were withdrawn at each time point and subjected to counting, following erythrosin staining for the determination of the total number of viable cells (A), the percentage of viable cells (B), the degree of apoptosis as assessed by DAPI staining (C), and the level of granulocytic maturation, as assessed by measuring the percentage of NBT-positive cells (D) or cell-associated NBT-reducing activity (E). Results are the mean ± SD of 3 separate culture dishes and are representative of at least 3 independent experiments. *, significantly higher or lower than the untreated control (P < .01 according to the Studentt test). °, significantly higher or lower than the sum of the effects observed in the corresponding STI571- and ATRA-treated groups, following 2-way analysis of variance and measurement of the F of interaction (P < .01 according to Tukey test).
