CXCR4 and B-cell chronic lymphocytic leukemia: PIM1 phosphorylates CXCR4 on serine 339 (S339) and increases CXCR4 surface expression and recycling.8, 9, 25 We thus explored whether pan‐PIM inhibitor SEL24‐B489 affects p‐CXCR4 levels and CXCR4‐driven migration in CLL cells.