Acceleration of chlorambucil-induced caspase 3 activation and PARP cleavage by LY.

CLL cells cultured in basal medium containing 10% FCS were incubated for 1 hour at 37°C in the absence or presence of 60 μM chlorambucil. The cells were recovered by centrifugation, washed once in Hanks saline, and resuspended in basal medium containing either 50% serum or 50% plasma. Each culture was divided into 2 aliquots, one of which received no further additions, and 20 μM LY was added to the other. Cells were processed for Western blot analysis at the indicated times. Blots were probed with caspase 3, p85 PARP, and p116 PARP antibodies. Pro indicates caspase 3 proenzyme; and su, caspase 3 subunits. The 0-hour sample expressed no detectable p116 PARP. This finding is attributable to the storage of these cells at 4°C prior to commencement of the experiment.