GA101 induces actin-dependent PCD and HA in primary B-CLL. (A) Primary B-CLL cells were isolated from patient blood samples as described in “Primary tumor samples,” preincubated with vehicle control (DMSO) or latrunculin B (Lat B, 10μM) then treated with anti-CD20 mAbs (5 μg/mL) for 4 hours, and cell death was assessed using annexin V-Cy5.5/7-AAD staining. Mean ± SEM of 4 independent patient samples are shown. Because of the heterogeneous levels of background cell death in individual patient samples, death was expressed as percentage above control. GA101 and GA101 (NG), the non-glycoengineered derivative of GA101, both induced significantly higher cell death than rituximab and ofatumumab. Cell death was completely ablated by latrunculin B (*P < .005, **P < .0001). (B) Primary B-CLL cells were treated as above and assessed for HA using light microscopy. Figure shows representative images from patient CLL31 (scale bar, 50 μm). GA101-induced HA correlates with PCD, and is blocked by the disruption of the actin cytoskeleton with latrunculin B.