Effect of the caspase inhibitor Z-VAD.fmk on aspirin-induced apoptosis in B-CLL cells. (A) Effect of Z-VAD.fmk on aspirin-induced DNA fragmentation. B lymphocytes from 2 B-CLL patients were incubated for 24 hours with 10 mmol/L aspirin (ASA) in the presence or absence of 200 μmol/L Z-VAD.fmk. DNA was extracted and subjected to agarose gel electrophoresis as described in the Materials and Methods. (B) Effect of Z-VAD.fmk on aspirin-induced PARP cleavage. Cells from patients no. 2 and 6 were incubated for 24 hours with 10 mmol/L aspirin (ASA) in the presence or absence of 200 μmol/L Z-VAD.fmk. Cells were lysed and analyzed by Western blot as described in the Materials and Methods. Z-VAD.fmk was added 1 hour before aspirin administration.