CXCL12-mediated MEK and ERK activation in ZAP-70⁺ CLL cells is RAF dependent. (A) CLL cells were pretreated with 10μM sorafenib or DMSO as solvent control for 30 minutes before the addition of CXCL12 or media control. After exposure of CLL cells to CXCL12 for 3 minutes, the cells were harvested, lysed, and analyzed for the presence of the indicated proteins by immunoblot. Results are shown from 3 ZAP-70⁺ CLL samples. (B) ZAP-70⁺ CLL cells were pretreated with 10μM sorafenib, 10μM sunitinib, or DMSO as solvent control for 30 minutes before the addition of CXCL12 or media control. After exposure of CLL cells to CXCL12 for 3 minutes, cells were harvested and analyzed as above. Results are shown from 1 representative of 3 ZAP-70⁺ CLL samples, all showing similar responses. (C) ZAP-70⁺ CLL cells were pretreated with sorafenib, GW5074, KG1, KG5 (all inhibitors were used at 10μM), or DMSO as solvent control for 30 minutes before the addition of CXCL12 or media control. After exposure of CLL cells to CXCL12 for 3 minutes, cells were harvested and analyzed as above. Results are shown from 1 representative of 6 ZAP-70⁺ CLL samples; all but 1 sample showed similar responses. GAPDH indicates glyceraldehyde-3-phosphate dehydrogenase.