Fig. 1. Mitogen-activated extracellular signal-regulated kinase (MEK) inhibitor trametinib fails to inhibit the viability of human gastric cancer (GC) cells and pancreatic ductal adeno carcinoma (PDAC) cells sufficiently due to activation of Janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) signaling. MGC803 (a), MIA PaCa-2 (b), and PANC-1 (c) cells were exposed to trametinib at the concentrations of 5 and 10 μmol/L for 24, 48, or 72 h. Cell survival was measured using a Cell Counting Kit-8 (CCK-8) assay. (d) Trametinib was added to MGC803, MIA PaCa-2, and PANC-1 cells at different concentrations for 8 h, after which the states of the JAK2/STAT3 and extracellular signal-regulated kinase (ERK) pathways were measured by western blot. (e) MGC803 cells were treated with 10 μmol/L trametinib at the indicated time points, and the tyrosine phosphorylation levels of JAK2 and STAT3 were measured by western blot. The results are presented as mean±standard deviation (SD) from three independent experiments. ^** P<0.01 and ^*** P<0.001 vs. control (no trametinib).