Flow cytometry analysis revealed that ectopic expression of Ago2 decreases the cell-surface level of MHC I and infiltration and cytotoxicity of CD8+ T cells in Mll4−/− melanomas (Fig. 3u, v, and Supplementary Fig. 3q), which probably underlie the rescuing effects of exogenous Ago2 expression on Mll4−/− melanoma progression in vivo. This evidence concerns the gene KMT2D and melanoma.