Time-dependent drug-induced apoptosis in ALL. Freshly isolated ALL cells were cultured in the presence of 2.0 μg/mL daunorubicin (DNR; ), 50 μg/mL vincristine (VCR; •), 10 IU/mL l-asparaginase (ASP; ▵), or 250 μg/mL prednisolone (PRED; ♦) for the indicated time points. Drug-induced PS externalization (A), mitochondrial transmembrane disruption (B), caspase-3 activation (C), and PARP inactivation (D) were determined by flow cytometry and calculated by the formula described in “Materials and methods.” Results are expressed as mean ± SD of 5 patients with ALL.