PCI-32765 cytotoxicity against CLL cells is dependent on caspase pathway activation. (A) CD19⁺ cells from CLL patients (N = 4) were incubated with or without various concentrations of PCI-32765 (1μM-50μM) for 8 hours and PARP cleavage was assessed by immunoblot. Results are shown from 1 of 4 experiments. (B) CD19⁺ cells from CLL patients (N = 7) were incubated with or without various concentrations of PCI-32765 (1μM-50μM) for 8 hours. Cells were lysed and caspase activity was determined by the amino trifluoromethyl coumarin assay. Results were calculated relative to micrograms of protein. Each symbol represents an individual patient and dark lines represent averages. (C) CD19⁺ cells from CLL patients (N = 10) were incubated with or without various concentrations of PCI-32765 (1μM-50μM) and 100μM z-VAD-fmk for 48 hours. Viability was determined by annexin-V/PI flow cytometry, and is shown relative to time-matched untreated controls. Each symbol represents an individual patient and dark lines represent averages. (D) CD19⁺ cells from CLL patients (N = 3) were incubated with or without various concentrations of PCI-32765 (1μM-50μM) and 100μM z-VAD-fmk for 8 hours. PARP cleavage was assessed by immunoblot. Results are shown from 1 of 4 experiments.