PF-04691502 inhibits CXCL12 signaling and subsequent migration. (A) CLL cells were treated with 200 ng/mL CXCL12 for the times indicated in the presence or absence of PF-04691502 (0.25-2.5 μM). PF-04691502 was added 30 minutes prior to the addition of CXCL12. Immunoblotting was performed for pAKT^S473, pS6K^T389, pS6^S235/236, pERK^T202/Y204, total proteins, and the loading control HSC70. Blot is representative of 6 independent experiments. (B) Using a transwell migration assay, we evaluated the migration of CLL cells toward 200 ng/mL CXCL12 in the presence or absence of PF-04691502 (1.25-2.5 μM). Flow cytometry was used to count the number of CD5⁺CD19⁺cells that had passed through the transwell filter (n = 5) (see supplemental Methods). Error bars represent SEM. *P < .03.