BRAF and melanoma: To compare the activity of a panel of MEK1 mutations found in BRAF inhibitor-resistant melanoma cell lines, 293FT cells, which have low basal MAPK activity, were transfected with a bicistronic green fluorescent protein (GFP) vector containing either wild-type MEK, MEKIndel55RT, MEKQ56P, MEKV60E, MEKC121S, MEKG128V MEKP124L, MEKV154L, MEKGF or BRAFV600E.