Dose-dependent effects of STI571 and ATRA on the growth and granulocytic maturation of NB4 cells.
NB4 cells were seeded at an initial concentration of 2 × 105/mL and treated for 4 days with vehicle alone, STI571, ATRA, or the combination of the 2 compounds. In (A) and (C), cells were treated with the indicated concentrations of STI571 in the absence (○) or presence of ATRA (10−7 M) (●). In (B) and (D), cells were treated with the indicated concentrations of ATRA in the absence (○) or presence of STI571 (5 × 10−6 M) (●). The level of NBT-reducing activity is presented in (A) and (B), whereas the number of viable cells is shown in (C) and (D). Results are the mean ± SD of 3 separate culture dishes and are representative of 2 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).
