MAP2K1 and melanoma: In early passage murine melanoma cell lines with homozygous BRAFV600E mutation, derived from our genetically engineered murine melanoma models8, 12, proteomic analysis showed higher levels of BRAFV600E protein, and increased phosphorylated MEK1, ERK, RSK and Jun, in cells expressing constitutively active ARF6-GTP (ARF6Q67L) compared to ARF6WT (Fig. 1a).