Effect of bone marrow stroma coculturing on the induction of apoptosis in CLL cells by the simultaneous combination of bendamustine and fludarabine. CLL cells were cultured in suspension (white bar) or cocultured with bone marrow stroma cells (gray bar) and incubated with 30 µM bendamustine and 10 µM fludarabine simultaneously for 24 (A) or 48 hours (B). Cell death was measured using a DiOC6 assay as described in “Materials and methods.” Data are from individual patient samples, and results are corrected to a time-matched control (untreated sample) for each patient sample.