MAPK3 and melanoma: To verify the hypothesis of ETS-1 functional shift, in connection with P-T38 constitutive activation, we treated the primary Me1007 and the metastatic A375M melanoma cell lines with the phorbol ester PMA, which induces ETS-1 phosphorylation by stimulating ERK1/2 through the RAF/MEK signaling pathway (Jørgensen et al., 2005).