Phenotypic characterization of cells treated with pharmaceutical BRAF inhibitors. A, B) Melanoma cells treated ± inhibitors 48 h with 0.5 μM SB-590885, 0.5 μM PLX-4720 or DMSO. Adherent cells were trypsinized and plated on top a collagen gel  for an additional 24 h in the continued presence of inhibitors. A) Cell morphology of control (DMSO) or BRAF inhibitor treated cultures, visualized using phase-contrast microscopy. B) Fluorescent visualization of F-actin organization, TRITC-conjugated phalloidin (P1951) was from Sigma-Aldrich (St. Louis, MO). C) Phase contrast images of melanoma spheroids that were embedded in a collagen gel for three days ± inhibitors . D) Quantitation of spheroids, shown in (C), that contains cells insensitive to BRAF inhibitors. (Graph shows average ± SD; *P < 0.05).