Figure 2.

Comparative activity of MEK mutants found in BRAF^V600E inhibitor-resistant melanoma. (a) An immunoblot for MAPK pathway components in 293 FT cells transfected with plasmid DNA containing wild-type MEK, MEK^Indel55RT, MEK^Q56P, MEK^V60E, MEK^C121S, MEK^P124L, MEK^G128V, MEK^V154L and BRAF^V600E or empty vector controls. Both the transfections and immunoblotting were performed in triplicate. Tubulin was used as a loading control. (b) Densitometry measurements from three experimental replicates showing MEK^GF had higher activity than any of the naturally occurring mutants (P<0.05). Although MEK V60, Q56P and 55RT had similar activity, C121s trended toward lower activity, but this was not statistically significant. MEK^G128V had lower activity than C121S (P<0.05). P-ERK and P-RSK were not observed for P124L or V154L although P-MEK was detected.