CAL-101 cytotoxicity against CLL cells is partially dependent on caspase activity. (A) CD19⁺ cells from patients with CLL (n = 4) were incubated with or without 1 or 10μM CAL-101 or 25μM LY294002 (pan-PI3K inhibitor) for 12 hours, and caspase-3 and PARP were assessed by immunoblot. Results are shown from 1 of 4 experiments. (B) CD19⁺ cells from patients with CLL (n = 7) were incubated with or without 1 or 10μM CAL-101 for 12 hours. Cells were lysed, and caspase activity was determined by the amino trifluoromethyl coumarin assay. Results were calculated relative to microgram of protein. Each symbol represents an individual patient. (C) CD19⁺ cells from patients with CLL (n = 6) were incubated with or without 1 or 10μM CAL-101 and 100μM z-VAD-fmk for 48 hours. Viability was determined by annexin/PI flow cytometry and is shown relative to time-matched untreated controls. Each symbol represents an individual patient. Horizontal lines represent the mean. (D) CD19⁺ cells from patients with CLL (n = 4) were incubated with or without CAL-101 (1-10μM) and 100μM z-VAD-fmk for 12 hours. PARP cleavage was assessed by immunoblot. Results are shown from 1 of 4 experiments.