MAPK3 and melanoma: Real time RT-PCR demonstrated that known early response genes, FOS and JUNB, were activated within 30 min in YUDOSO-BRAFWT melanoma cells in response to PLX4032, an effect that was persistent for up to 8 h, whereas FOS was downregulated within 30 min in YULAC-BRAFV600E cells (Figure 4C), in agreement with the kinetics of ERK1/2 functional activation and inactivation in wild-type and mutant cells, respectively.