Silvestrol cytotoxicity. (A) Silvestrol cytotoxicity in chronic lymphocytic leukemia (CLL) patient cells: CD19⁺ cells from CLL patients (n = 14) were incubated with or without silvestrol at various concentrations for 72 hours, and viability was determined by MTT assay. Viability was calculated relative to time-matched untreated controls. (B) Time dependency of silvestrol cytotoxicity: CLL patient samples (n = 4) were incubated with 0 or 80 nM silvestrol for 4, 24, or 72 hours. At each time point, cells were centrifuged and resuspended in fresh media without drug. Incubations were each continued to a total of 72 hours, at which point viability was determined by MTT assay. Results for each exposure time are shown relative to time-matched untreated cells, set at 100%. Bars show plus or minus SD. (C) Silvestrol cytotoxicity in del(17p13) cells: CLL cells from patients with or without the del(17p13) chromosomal abnormality (n = 7 for each subset) were incubated with silvestrol at 8 nM (approximate LC₅₀) or 1 μM F-ara A, and viability was determined by MTT assay at 72 hours. Results are shown relative to time-matched untreated cells. Bars show plus or minus SD.