Effect of ST2062, ST2064, ST2065, and ST2067 on ST1926-dependent apoptosis in NB4 cells. NB4 cells (300 000/mL) were pretreated for 1 hour with vehicle, ST2062 (A), ST2064 (A), ST2065 (B), and ST2067 (B) at the indicated concentrations before addition of vehicle or ST1926 for an additional 6 hours. The apoptotic index was determined on aliquots of the cell cultures. Results are expressed as the mean ± SD of 3 replicate cultures. The data are representative of at least 2 independent experiments. °Significantly higher than the corresponding vehicle-treated group (P < .01 according to the Student t test). *Significantly lower than the corresponding ST1926-treated group (P < .01 according to the Student t test).