HHT induced apoptosis in CLL cells. (A) HHT induced apoptosis in CLL cells in a time- and concentration-dependent manner. CLL cells were incubated with 0nM (○), 50nM (□), 100nM (▵), 200nM (□), or 400nM (◇) HHT for 6, 12, or 24 hours (left). Apoptosis was detected by annexin V–PI double staining and quantitated by flow cytometric analysis. Each concentration represents the mean ± SEM of 8 patient samples. HHT induced apoptosis in CLL cells with an IC50 of 105nM at 24 hours (right). CLL cells were incubated with various concentrations of HHT for 24 hours. Each data point represents the mean ± SEM of 28 patient samples. (B) HHT (100nM) induced significant apoptosis in CLL cells at 24 hours (P < .0001, paired t test). CLL cells from 51 patients were mock-incubated or with 100nM HHT for 24 hours, and apoptosis was detected by annexin V–PI staining. Bars indicate medium values of each group; 17.5% cell death for the control group and 59.9% for the HHT-treated group. (C) HHT induced similar cell death regardless of patient characteristics and treatment history. Cell death induced by 100nM HHT after 24-our incubation was compared in CLL cells from patients with poor (□) or favorable (▩) prognostic factors. A P ≤ .05 from an unpaired t test was considered significant. Induced cell death was the difference of cell death between HHT-treated samples and that of time-matched controls. Each data point represents the mean ± SEM. (D) HHT-induced apoptosis required the continuous presence of HHT. CLL cells were incubated with 200nM HHT (□) for 6, 12, or 24 hours and compared with control (○). At 6 hours, a portion of the culture was washed into drug-free medium (▵). Apoptosis was detected by annexin V–PI staining. Each data point represents the mean ± SEM of 4 patient samples. (E) HHT induced loss of mitochondrial transmembrane potential. CLL cells were incubated with 100nM HHT for 24 hours. Mitochondrial transmembrane potential and viability were measured by DiOC6(3) and PI double staining. Representative figures from 3 independent experiments were shown.