MAPK1 and melanoma: Furthermore, fivefold reduction in RAF1 levels in YUFIC-BRAFWT melanoma cells by siRNA (Figure 3C, compare RAF1 bands with actin as the loading control, and Figure 3D, RAF1/actin ratio) caused a similar fold suppression in PLX4032 induced ERK activation compared with non-treated cells (Figure 3C, pERK and ERK, and Figure 3D, pERK/ERK ratio), lending support to the conclusion that RAF1 is the main kinase that caused ERK activation.