Induction of apoptosis by bendamustine, fludarabine, or their combination in CLL or CD34-positive cells. (A-C) CLL cells from 3 patients (1, 2, and 3) were incubated with bendamustine, fludarabine, or their combination for 24, 48, and 72 hours. Induction of apoptosis by bendamustine (white bars), fludarabine (gray bars), or their combination (black bars) in CLL (A-C) or CD34-positive (D) cells is shown. Cell death was measured by DiOC6 assay as described in “Materials and methods.” Concentrations of the drugs were 3 µM (A), 10 µM (B), or 30 µM (C), and data are from 3 patient samples. Measurements for patients 2 and 3 were done in triplicate. (D) Purified CD34-positive cells from CB were incubated with 30 µM bendamustine, 10 µM fludarabine, or their combination for 24 or 48 hours. All data are presented as mean ± standard deviation (SD). Results are corrected to a time-matched control (untreated sample). B, bendamustine; F, fludarabine.