3-Cl-AHPC and tRA induction of apoptosis of leukemic blasts. Leukemia cells obtained from patients were cultured as described in “Materials and methods.” The results represent the mean of 3 independent experiments, with the variation between the experiments being less than 10% if error bars are not shown. Error bars represent standard deviations. (A) The 3-Cl-AHPC or tRA induction of apoptosis. The 3-Cl-AHPC and tRA were added to a final concentration of 1 μM; the cells were harvested at various times, and the percentage of apoptotic cells was assessed as described in “Materials and methods.” (B) Leukemic cells of patient 1 were exposed to varying concentrations of 3-Cl-AHPC for up to 5 days.