Cleavage of caspase substrates and zymogens in HL-60 cells treated with etoposide or DT388–GM-CSF.
(A) Whole cell lysates were prepared from HL-60 cells treated with 68 μM etoposide or 40 nM DT388–GM-CSF for the indicated times. After SDS-PAGE, samples were probed with reagents that recognize PARP, lamin B1, or PKCδ. Arrowheads indicate cleavage products as a result of caspase action. (B) Duplicate blots were probed with reagents that recognize procaspase-9, the epitope PEPD that becomes accessible on cleavage between the large and small subunits of caspase-9, the procaspase-8 splice variants expressed in HL-60 cells, the epitope VETD that becomes accessible on cleavage between the large and small subunits of caspase-8, the large subunit of caspase-3, or procaspase-2. Arrowheads indicate products that represent active caspase species in HL-60 cells.
