MAPK1 and melanoma: Of note, unlike c-Myc and c-Jun, the EGR1 and c-Fos protein expression was low in untreated melanoma cells but was significantly induced in response to eiF4Fi, indicating that the increased EGR1 and c-Fos levels might be a sign of a disrupted control of the MAPK optimum or a shift of the MAPK optimum toward higher ERK activity levels.