Loss of the hairy morphology upon BRAF inhibition. Leukemic cells purified from patients with (A) HCL or (B) HCL-v were exposed in vitro to vemurafenib (vemuraf.) 1 µM or drug vehicle as control (Ctrl.) for 2 or 3 days, and then costained with phalloidin (labeling in green the cytoskeleton of hairy projections rich in F-actin), Annexin-V (ANXA5, labeling in red the dying cells), and Draq5 (labeling the nucleus), followed by confocal fluorescence microscopy showing 2-dimensional images of representative cells and their corresponding 3-dimensional reconstruction. After blocking BRAF V600E with vemurafenib, HCL (but not HCL-v) cells become smoother and smaller while being still alive (ANXA5⁻ HCL cells showing severely shortened green surface projections). This hair loss is then followed by apoptosis of HCL (but not HCL-v) cells, which become ANXA5⁺ (red) and lose any phalloidin-positive (green) cytoskeletal structures. These images were taken with a LSM510 laser-scanning confocal microscope (Zeiss) equipped with laser emission lines at 458, 488, 543, and 633 nm, using an objective Plan-Apocromat 63×/1.4 NA with oil immersion and LSM510 Zeiss software.