Induction of apoptosis by aspirin on B-CLL cells. (A) Effect of aspirin on DNA fragmentation in B-CLL cells. Cells from patients no. 1 and 2 were incubated for 24 hours with 1 to 10 mmol/L aspirin (ASA). DNA was extracted and subjected to agarose gel electrophoresis as described in the Materials and Methods. (B) Effect of aspirin on PARP cleavage. Cells from patients no. 1 and 2 were incubated for 48 hours with 1 to 10 mmol/L aspirin (ASA). PARP cleavage was analyzed on protein extracts from these cells by Western blot as described in the Materials and Methods. The position of the native PARP (116 kD) and the proteolytic fragment (85 kD) is indicated. As an internal control, blots were also probed with -tubulin antibody. (C) Effect of aspirin on DNA content in a representative CLL patient. Cells from patient no. 1 were incubated for 48 hours with 1 to 10 mmol/L aspirin (ASA). DNA content was quantified by PI staining and flow cytometry analysis as described in the Materials and Methods. (D) Quantification of aspirin-induced apoptosis in cells from 4 patients by PI staining and FACS analysis after 48 hours of incubation with 1 to 10 mmol/L aspirin.