Effects of PLX4032 on cell cycle and apoptosis. a-c) Melanoma cell lines were cultured with 1 μM of PLX4032 for 20 hours and stained with propidium iodide for cell cycle analysis gated on live cells. a) NRAS Q61L mutants, b) BRAFV600E mutants resistant to PLX4032, c) BRAFV600E mutants sensitive to PLX4032. d-e) Melanoma cell lines were cultured with 1 μM of PLX4032, vehicle control, or 1 μM of staurosporine (SSP - positive control to induce apoptosis) for 120 hours and analyzed by flow cytometry for apoptotic cell death upon double-staining with Annexin V and propidium iodide. Testing included a PLX4032-resistant cell line (M233) and a highly sensitive cell line (M249), both of which are BRAFV600E mutants.