(a) Western blot analysis vector control and stable mBRAF expressing SK-MEL-2 metastatic melanoma cells. Actin shows equal loading. (b) Cells (1 × 10⁵) were plated in a six-well plate and growth was measured by crystal violet assay. (c) Clonogenicity of control and mBRAF SK-MEL-2 cells. Crystal violet-stained colonies were counted and the number of colonies is shown.

(a) Immunofluorescence staining of autophagic marker MAP1LC3 in 451Lu-mBRAF cells shows punctate staining of autophagic vesicles (arrows). Cells plated on cover glass were incubated with LC3 antibody followed by anti-mouse IgG-FITC and visualized in a confocal microscope. Nuclei were stained with propidium iodide (upper). Representative confocal images of GFP-LC3-transfected vector control 451Lu and control cells treated with 10 μM brefeldin A (BFA) and untreated 451Lu-mBRAF3 (lower). Arrows indicate GFP-LC3-positive autophagosomal structures. Inset shows higher magnification. (Bar = 50 μm). (b) Induction of autophagic marker LC3-II isoform in mBRAF-expressing cells. Western blot analysis of total cell lysate from 451Lu mBRAF, vector, and 451Lu treated with 10 μM BFA for 24 hours and probed with LC3 antibody. Actin was used as a loading control. (c) Transmission electron microscopy of control and mBRAF3 cells. Arrows and inset show double membrane autophagic vesicles. (Bar = 2 μm). (d) Inhibition of autophagy decreases cell death in mBRAF-expressing cells. Cells were treated with 1 mM 3MA and dead cells were measured after 24 hours using the Cytotox-glo assay kit. Representative data (mean±SEM) from three independent experiments are shown. (e) Western blot analysis of mTORC1 and mTORC2 complexes in vector control, mBRAF2 and -3 clones, and BFA-treated 451Lu cells. Numbers on the left indicate the position of molecular weight markers. (Numbers below the bands indicate densitometric quantitation of the bands normalized to actin). (f) Western blot analysis of upstream and downstream targets of mTORC1 complex in vector control, and mBRAF2 and -3 clones.

451Lu vector control and mBRAF cells (1 × 10⁶) were injected subcutaneously in the right flank of nu/nu athymic mice. Tumors were measured twice a week for 6 weeks in control (n =9), mBRAF2 (n = 10), and mBRAF3 (n = 9) mice. (a) Left: Kinetics of tumor growth shown as mean (±SEM) tumor volume (mm³) (Two-tailed Student’s t-test *P = 0.03). In all three groups, mice with the largest and smallest tumor volume were removed from the analysis. Right: Kaplan–Meier survival analysis. Percent mice that reached tumor size of 1000 mm³ were plotted against time (*P = 0.0035 and **P = 0.0003). (b) Necrosis of mBRAF tumors. By 3–4 weeks, most 451Lu-mBRAF tumors were red (hemorrhagic) in color and became progressively necrotic (black) with a recessed or concave surface contour. Necrosis was graded (0, +1 to +3) as the surface area of the tumor showing black color, and the numbers in the table represent the number of animals with particular necrosis score at day 60. (c) Histology and expression of autophagy marker LC3 in vivo. Formalin-fixed 451Lu vector control and mBRAF tumors were sectioned and stained with hematoxylin and eosin (H&E) (bars = 4 mm; top and middle panels) and immunostained for LC3 (bar = 50 μm; bottom panel). Representative H&E and immunostained sections of a control and mBRAF tumors are shown. Arrows indicate necrosis and arrowheads show red hemorrhagic areas. (d) Ultrastructure of 451Lu vector control and mBRAF tumors show necrotic features in mBRAF tumors. Excised tumor tissues were fixed and processed for transmission electron microscopy. Upper panels: low magnification (bar = 5 and 10 μm for vector and mBRAF, respectively); lower panels: higher magnification (bar = 2 μm). N: nuclei; *: vacuoles, and arrowheads: plasma membrane.

(a) 451Lu metastatic melanoma cells harboring BRAF V600E mutation were transfected with empty vector (pMCEFplink) or mBRAF (pMCEFBRAF^V600E) expression plasmid using Nucleofector (Amaxa) and two G418-resistant clones were selected from two separate transfections. Puromycin-resistant stable clones from empty vector or pLXSP3-G BRAF^VE:ER^T2 plasmid transfections of 451Lu were generated. Cell lysates were analyzed by western blots using the anti-BRAF antibody. (Numbers below the bands indicate fold increase in BRAF protein.) Actin shows equal loading. (b) MTT assay for cell proliferation. Left: 451Lu-mBRAF clones; right: 4-OHT (4-hydroxytamoxifen)-inducible ER-mBRAF clone. Representative data from three independent experiments are shown (*P<0.001). (c) Colony-forming ability of 451Lu control and mBRAF clones. Cells (5000 per well) were plated in triplicate, and 2 weeks later crystal violet-stained colonies were counted. Representative data from three independent experiments are shown (*P<0.001).

(a) Cells (5,000 per well) were plated in triplicate and stained to detect senescence-associated-β-galactosidase (SA-β-gal) (insets), and percent SA-β-gal-positive cells were counted. Representative data from three independent experiments are shown (*P<0.001). (Bar = 4 mm). (b) Immunoblot analysis of p16^INK4A and acetylated H3K9. Actin was used as a loading control. (c) Expression of mBRAF does not inhibit cell cycle. 451Lu vector and mBRAF-expressing cells were stained with propidium iodide and analyzed by flow cytometry for cell cycle distribution (upper) and TUNEL-positive cells (lower). (d) Inhibition of apoptosis does not rescue the growth of high mBRAF cells. Control and 451Lu-mBRAF cells were treated with pan-caspase inhibitor fmk-ZVAD, and cell survival was measured by MTT assay. Representative data from three independent experiments are shown.

(a) Partial knockdown of BRAF by shRNA lentivirus. Vector control and mBRAF cells were infected with (equal MOI) scrambled (control) and BRAF shRNA lentivirus. Transduced cells were selected by treating the cells with 1 μg ml⁻¹ of puromycin for 10 days. Western blot analysis shows total BRAF protein levels in control and mBRAF cells. Actin control for equal protein loading is shown. (b) Partial knockdown of BRAF restores growth of 451Lu-mBRAF cells. BRAF shRNA-transduced, puromycin-selected cells were plated in a 96-well plate, and the cell growth was measured after 1 and 3 days using MTT dye. Representative data of three independent experiments are shown (N = 5, *P<0.05; **P< 0.001). (c) Partial knockdown of BRAF in mBRAF3 by shRNA plasmid (BRAF9 and BRAF10) transfection. Western blot analysis of total BRAF and p16 in control and BRAF shRNA-transduced cells. Actin control for equal protein loading is shown. (d) Inhibition MAPK signaling does not rescue growth of 451Lu-mBRAF cells. Vector control and 451Lu-mBRAF cells were treated with MEK inhibitor (0.5–10 μM, U0126) and growth was measured by MTT assay. Representative data of three experiments are shown.

A melanoma trial tissues array (obtained from the National Cancer Institute, NIH, USA) was used for immunofluorescent staining. The staining intensity was analyzed using AQUA. Melanoma was masked with S100 antibody and visualized with Alexa Fluor 555 (green) tagged secondary antibodies. BRAF and LC3 were stained and visualized with Alexa Fluor 647 (red) tagged secondary antibodies. 4,6-Diamidino-2-phenylindole (DAPI) was used to stain and visualize the nuclei (blue). Representative images of primary melanoma tissues stained with BRAF (upper), LC3 (lower), S100, and DAPI are shown (bar = 200 pi).