Drug-induced apoptosis inversely correlates with cellular drug resistance in pediatric ALL. Freshly isolated ALL cells were incubated in the presence of vincristine (B) or daunorubicin (D) for 18 hours or prednisolone (A) or l-asparaginase (C) for 42 hours at 37°C in a humidified incubator in 5% CO₂. See Figure 2 for drug concentrations used. Each dot corresponds to a patient with ALL.