The ERK pathway is growth-promoting in Grey horse melanoma cells. (A) Grey horse and human melanoma cell lines were cultured in the presence of DMSO as vehicle control (-) or 10 μM MEK1/2 inhibitor U0126 (+) for 12 h following a 2 h serum-free preincubation. The effect of U0126 on ERK1/2 activation was analyzed by Western blot. Similar results were obtained in three independent experiments. (B) The effect of U0126 on cell growth was measured in relation to DMSO-treated control by Alamar Blue assay 72 h post-treatment. The data show the mean ± s.e. of a representative experiment of three independent experiments performed in triplicates. (C) The efficiency of U0126 treatment on cell growth was determined by calculating the concentration necessary to achieve a 50% reduction in cell proliferation (IC50). The data represent the mean ± s.e. of three independent experiments performed in triplicates. (B, C) *P <0.05; **P <0.01; ***P <0.001.