Effect of combinations of ST1346 and RARα agonist or RXR agonists on NBT-reducing activity in NB4 cells.

NB4 cells were seeded at an initial concentration of 200 000/mL, and aliquots of the cell cultures were used for the determination of NBT-reducing activity. In all cases the cellular viability was above 80%, as assessed by the erythrosin exclusion test. (A) Cells were treated with the RARα agonist AM580 or the RXR agonist CD2915 at the indicated concentrations in the presence or absence of ST1346 (10 μM). (B) Cells were treated for 3 days with vehicle, ST1346 (5 μM), the RXR agonist CD2809 (1 μM), or the combination of the 2 compounds. Results are expressed as the means ± SD of 3 separate culture dishes and are representative of at least 2 independent experiments. *Significantly higher than the corresponding group treated with vehicle (P < .01 according to the Studentt test). °Significantly higher than the sum of the effects observed in the corresponding ST1346- and RARα- or RXR-agonist–treated groups, following 2-way analysis of variance and measurement of the F of interaction (P < .01 according to Tukey test).