Cytotoxic effect of aspirin on B-CLL cells. (A) Dose-response of the cytotoxic effect of aspirin on B-CLL cells. Cells from 5 patients were incubated for 48 hours with various concentrations of aspirin that ranged from 1 to 10 mmol/L. (B) Time course of aspirin-induced cytotoxicity. Cells from patients no. 1 and 2 were incubated with 2.5, 5, and 10 mmol/L aspirin (ASA) for the times indicated. Cell viability was determined by the MTT assay as described in the Materials and Methods and is expressed as a percentage of the viability of control cells at the beginning of the culture. Data are shown as the mean value ± SD of 3 independent experiments.