Induction of apoptosis by fludarabine, mafosfamide, and mitoxantrone on B-CLL cells. Cells from patient no. 17 were incubated for 48 hours with fludarabine (F; 1 μg/mL), mitoxantrone (M; 0.5 μg/mL), and/or mafosfamide (Mf; 1 μg/mL). DNA content was quantified by PI staining and flow cytometry analysis as described in Materials and Methods.