Trimming of HCL projections by BRAF inhibition. Confocal immunofluorescence staining for phalloidin (green), annexin V/ANXA5 (red), and the nuclear dye Draq5 (blue) in HCL cells purified from the peripheral blood of a representative patient with HCL and treated in vitro with vehicle DMSO (Ctrl) or Drug (vemurafenib 1 µM) for 48 hours (363× optical magnification with oil immersion). Upon drug treatment, first the hairy projections (rich in filamentous actin and thus stained in green by phalloidin) almost completely disappear while the leukemic cells are still alive (ie, negative for annexin V; top 2 cells in the right panel); afterward, apoptosis ensues (bottom 4 cells in the right panel). This figure is reproduced from Falini et al.¹⁵ DMSO, dimethyl sulfoxide.