WAS and B-cell chronic lymphocytic leukemia: For CCL19-driven directional cell steering and chemotaxis, CLL cells depend on CIP4 to modulate the Wiskott-Aldrich syndrome protein (WASP), p21-activated kinase 1 (PAK1), and p38 MAPK pathways to control the assembly of highly structured actin-rich protrusions, including lamellipodia.