PI3K inhibitors PIK-90 and PI-103 reduce actin polymerization in response to CXCL12 stimulation. Intracellular F-actin was measured in CLL cells using fluorescein isothiocyanate–labeled phalloidin after adding 200 ng/mL CXCL12 at time 0. Results at the time points indicated on the horizontal axis are shown as percentage of intracellular F-actin relative to the value of F-actin before addition of CXCL12. Each data point represents the mean (± SEM) of 4 different patients. Pretreatment of CLL cells with Ly294002 and PIK-90 reduces intracellular F-actin to approximately 70% of controls, whereas PI-103 had only a minor effect with an approximate 10% reduction.