The downregulation of CD48 by the AML fusion oncogenes is HDAC-dependent. (A-D) Flow cytometry analysis of CD48 expression in U937 cells transduced with the AML oncogenic proteins (indicated in the y-axis of the histograms). Cells were treated with either solvent control (black lines) or 4 different HDACi (indicated above the histograms, blue lines): TSA (A), sodium valproate (B), mocetinostat (C), and entinostat (D). The gray line represents the CD48 staining of U937 cells transduced with an empty vector. Gray shaded histogram, background staining with an isotype-matched control antibody. One representative experiment of at least 3 representative experiments performed is shown. (E and F) FACS analysis of CD48 expression without mutations (left histograms) or with mutations (right histograms) in the HDAC binding site (the specific mutation is indicated in the y-axis). Mutations were performed in (E) PML-RARA– and in (F) AML1-ETO–expressing cells. The expression of CD48 is compared between the GFP⁺ cells (black histograms) and the nontransduced cells (gray histograms) because not all cells were trandscuded (see supplemental Figure 4). Gray shaded histogram, background staining with an isotype-matched control antibody. One of 3 representative experiments is shown.