Figure 1.

Trametinib exerts moderate cytotoxic effect on human HNSCC cell lines and increases MHC class I and PD-L1 expression in surviving cells. (A) Cells were incubated with 10 pM – 10 µM of trametinib for 72 hours and cell growth inhibition was analyzed using a cell viability assay. Data are shown as the mean ± SD from three independent experiments. (B and C) Cells were treated with trametinib (50 nM), IFN-γ (1 ng/ml; 10 ng/ml to examine PD-L1 expression in SNU-1066 cells) or the combination of trametinib and IFN-γ (pretreated with DMSO or trametinib one hour prior to the addition of IFN-γ) for 72 hours. Expression of MHC class I (B) and PD-L1 (C) were assessed by flow cytometry. The fold change in mean fluorescence intensity (MFI) was averaged from three independent experiments. Error bars indicate SD. (D) Changes in PD-L1 expression shown in Figure 1C were confirmed by Western blotting. Data show one of three independent experiments with comparable results.