Targeting Axl and SFK induces apoptosis in CLLB cells. (A) Bosutinib (SKI-606) induces apoptosis in CLL B cells. Freshly isolated CLL B cells (n = 20) were treated with increasing doses of SKI-606 as indicated for 24 and 48 hours. Cells were harvested and stained with Annexin/PI for flow cytometric analysis. Mean values are presented with standard error bars. Effect of SKI-606 on normal B and T lymphocytes (n = 3) were also examined after a 24-hour incubation with the indicated doses of SKI-606. (B) Specific Axl inhibitor R428 induces apoptosis in CLL B cells. Freshly isolated CLL B cells (n = 10) were treated with increasing doses of R428 as indicated for 24 hours. Cells were stained with Annexin/PI for flow cytometric analysis as described. Mean values are presented with standard error bars. Effect of R428 on normal B and T lymphocytes and NK cells (n = 4) were also examined similarly after a 24-hour incubation with the indicated doses of R428.