Figure 5.

Treatment of FLT3/ITD cells with FLT3 inhibitors overcomes the block of B-cell development. (A-B) In vitro culture of early pro-B cells from FLT3/ITD mice with lestaurtinib generates a higher frequency of the more differentiated B220⁺CD19⁺ cells compared with the wild-type control group. A total of 20 000 events were acquired using FACSCalibur (BD Biosciences). Analysis was based on gated viable populations according to forward/side scatter. (C-D) Treatment with 2nM lestaurtinib improves DNA repair efficiency and reduces repair errors in B220⁺ cells generated from in vitro culture of early pro-B cells with FLT3/ITD mutation but not from wild-type cells. Results of PUC18-based in vivo DNA repair assay are shown. Graphs show the repair efficiency (C) and misrepair errors (D) (n = 3). (E-F) BM from sorafenib-treated FLT3/ITD mice shows a higher frequency of B220⁺CD19⁺ cells compared with the vehicle-treated group. Data are representative of 5 independent experiments. Data are expressed as mean ± SEM (error bars). Quantitative RT-PCR (G) and Western blotting analysis (H) demonstrate that treatment with sorafenib increases expression of Ku86 in B220⁺ cells from FLT3/ITD mice. Data are mean ± SEM (error bars); n = 3. Values below the gel image indicate relative fold changes of protein levels normalized to lamin-B.