Treatment with trametinib decreases PD-L1 and PD-L2 expression. After proliferation assays were performed by using murine or human samples, PD-L1 expression was assessed via flow cytometry on CD11b⁺ or CD33⁺ cells, respectively. (A-B) Representative plots of the treatment effect of trametinib on PD-L1 expression on CD11b⁺ cells from an AML mouse. (C) Mean ± SD percent change in PD-L1 GMFI on CD11b⁺ cells from AML mice (n = 3) after treatment with trametinib 10 nM and 100 nM. (D) Flow cytometry plot of PD-L1 expression on CD33⁺ cells after treatment with trametinib from 1 of 9 independent experiments using patient samples. (E) Mean ± SD percent change in PD-L1 and PD-L2 GMFI on CD33⁺ cells from patient samples after treatment with trametinib 10 or 100 nM. (F) Percent change in PD-L1 GMFI between no treatment and after treatment with IFN-γ, and percent change in PD-L1 GMFI between treatment with IFN-γ and treatment with IFN-γ plus trametinib 100 nM. (C,E-F) Two-sided, 1-sample Student t tests. (C,E) Statistically significant results displayed as: *P < .05; **P < .01.