Effect of SKI-606 and R428 on stroma-mediated protection of CLLB cells. (A) SKI-606 is able to overcome stromal-mediated protection. Freshly isolated CLL B cells (n = 3) were cocultured with the primary CLL BMSCs or cultured alone and treated with increasing doses of SKI-606 for 24 hours. Cells were harvested and stained with CD19 antibody and Annexin/PI for flow cytometric analysis. Mean values are presented with standard error bars. (B) Coculture of CLL B cells with CLL BMSCs protects from R428-induced apoptosis. Freshly isolated CLL B cells (n = 3) were cocultured with the primary CLL BMSCs or cultured alone and treated with increasing doses of R428 for 24 hours. CLL B cells were harvested and stained with CD19 antibody and Annexin/PI for flow cytometric analysis. Mean values are presented with standard error bars.