Sildenafil- and vardenafil-induced apoptosis in CLL B cells is caspase dependent.

(A) B-CLL cells were cultured for 24 hours with or without sildenafil (50 μg/mL). Cell viability was determined by FSC/SSC (i,iv); double staining with FITC-labeled annexin V/PI (ii,v) or by DiOC6 staining (iii,vi). Percentage of dead cells (annexin⁺ cells) and percentage viable cells (DiOC6^high) are also shown. (B) B-CLL cells (n = 2) were cultured as in panel A in the absence or presence of the caspase inhibitor z-VAD.fmk (50 μM). (C) B-CLL lymphocytes were cultured for 24 hours with or without sildenafil (50 μg/mL) or vardenafil (10 μg/mL), and caspase 3 activity was detected by flow cytometry as described in “Patients, materials, and methods.” Results shown are from 1 experiment representative of 3 performed on samples from separate donors.