Forodesine decreased the antiapoptotic MCL-1 protein levels and induced proapoptotic BIM protein independent of p53 status. (A) Cells from 4 representative CLL cases were treated with forodesine (2 μM) and dGuo (10-20 μM) for 16 hours, and MCL-1, BIM EL, BIM L, and BCL-2 proteins were analyzed by Western blot in total protein extracts. α-Tubulin was used as internal loading control. Cell viability was assessed by annexin V labeling as described in “Methods.” Densitometric protein quantification of MCL-1 and BIM EL protein levels with respect to control was performed. (B-C) Protein basal levels of MCL-1, BIM EL, BCL-2, and the ratio between MCL-1 and BIM EL were quantified by densitometric analysis on Western blot of total protein extracts in 35 CLL cases and plotted against the cytotoxicity of forodesine 2 μM and dGuo 20 μM at 48 hours. β-Actin was used as internal loading control. Correlation coefficient and P value are shown. (D) Primary cells from 3 representative patients with CLL were treated with forodesine (2 μM) and dGuo (20 μM) for 16 hours. Activation of BAX and BAK (conformational change) and loss of ΔΨ_m (DIOC₆ staining) were analyzed by flow cytometry as described in “Methods.”