RNA and DNA synthesis after treatment with bendamustine, fludarabine, or their combination in CLL cells. RNA and DNA synthesis after treatment with bendamustine alone (▼), fludarabine alone (▲), or their combination (▪) in CLL cells in suspension culture (A,C) and in CLL cells cocultured on human stromal cells (B,D). Cells were obtained from 3 patients (24, 25, and 26). After incubation for 0, 5, and 10 hours, RNA and DNA synthesis activity was measured by [³H]uridine incorporation assay (A-B) and [³H]thymidine incorporation assay (C-D) as described in “Materials and methods.” Values are mean ± SD from 3 patient samples, and each one was done in triplicate. Data are presented as percent of control, where control is the 0-hour untreated sample.