Activation of MAPK (ERK1/2) and AKT in CLL cells. (A) CLL B cells were cultured for 3 or 10 minutes with SDF-1α (200 ng/mL), rhBAFF (50 ng/mL), or media, as indicated above the sample lanes. Cell lysates were prepared and analyzed by immunoblot using antibodies specific for phosphorylated ERK1/2 (P-ERK1/2), ERK1/2, phosphorylated AKT (P-AKT^Ser473), or AKT, as indicated on the left margin. Equal loading in the lanes was evaluated by stripping the blot and probing again with anti-ERK1/2 and an anti-AKT antibody. Five different CLL B cells gave similar results. (B) The CLL cells were stimulated for 3 minutes with either media (far left lane) or SDF-1α (200 ng/mL) (right 3 lanes). For samples treated with SDF-1α we included the CXCR4 antagonist 4F-benzoyl-TE14011²⁰  (4F) at 0 nM, 50 nM, or 500 nM. The samples were analyzed and the results presented as noted in panel A.