Effect of MEK162 treatment on ERK1/2 phosphorylation and clonogenic survival of melanoma cells. (A) WT (YUVON and YUROB), B-RAF mutant (YUKSI and YUMAC) and N-RAS mutant (YUDOSO and YUKIM) cells were treated with increasing doses (10-1000 nM) of MEK162 inhibitor or left untreated for 4 and 24 hours. Western blot analysis was performed using phospho-ERK1/2, total ERK1/2 and β-actin antibodies. (B) The panel of six melanoma cultures was treated with increasing concentrations of MEK162. Cells were grown until well-defined colonies were formed. Colonies were visualized by crystal violet staining and counted. Colonies were counted and data are presented as percent of treated cells relative to the untreated cells. Each data point represents a mean of four independent experiments +/- standard error.