A. MTT cell viability assays of WT/WT, BRAF and NRAS mutant lines treated for four days with single agent (trametinib or palbociclib) or a fixed-ratio (1:100) combination (trametinib plus palbociclib) of both compounds (error bars represent SD). B. Calcusyn combination indices at median effective dose (ED50) generated from MTT assays in Figure A. C. Melanoma cells were plated at low density, treated with DMSO, trametinib (10 nM), palbociclib (1 μM) or the combination. After 1 week, cultures were stained with crystal violet.