BRAF-mutant A375 and WM2664 cells were treated with vemurafenib or SCH772984 for 24 h and PREX1 mRNA levels were measured by Taqman qPCR using two independent probes (A,B). NRAS-mutant SK-MEL-119 and Mel224 cells were treated with trametinib or SCH772984 for 24 h, and PREX1 mRNA measured as above (C,D). Taqman analyses indicate compiled results of n=2 experiments for WM2664 and Mel224, and n=3 experiments for A375 and SK-MEL-119. To test posttranscriptional regulation, A375 cells were treated with vehicle or SCH772984 in the presence of 50 μg/ml cycloheximide, and lysates were probed by western blot for PREX1, pERK and MYC (E). Quantification of PREX1 levels using ImageJ (F) is representative of n=2 independent experiments. Data are represented as mean ± SD.