Selective killing of primary CLL cells by PEITC. (A) Cytotoxicity of PEITC in primary CLL cells (n = 6, black solid symbols) and normal lymphocytes (n = 4, open symbols), after 30-hour incubation detected by MTT assay. Each data point represents the mean of duplicate measurements. (B) Comparison of the mean IC₅₀ of PEITC in CLL cells (n = 13) and normal lymphocytes (n = 11). Each bar represents the mean and 95% CI. (C) Cell death induced by 5 μM PEITC (24 hours) in primary CLL cells and normal lymphocytes detected by flow cytometric analysis (annexin V/PI double staining). Representative dot plots are shown. (D) Quantitative comparison of cell death induced by PEITC (5 μM, 24 hours) as in C. Percentage of drug-induced cell death was calculated by subtracting the spontaneous death in the control from the overall cell death in the PEITC-treated samples for each time point. The black and white bar represents the mean and 95% CI of 18 CLL patient samples and 7 normal blood samples, respectively. (E) Induction of ROS increase in primary CLL cells and normal lymphocytes by PEITC (5 μM, 2 hours), detected by flow cytometry using 1 μM DCF-DA. Representative histograms for CLL cells and normal lymphocytes are shown.