HDAC inhibitors (HDACi) such as valproic acid (VPA) and entinostat have been shown to sensitize NK cell-mediated killing by upregulating expression of NKG2D ligands MICA/B or ULBP1on cancer cells10, 11, 12, 13, 14, 15, suggesting that HDACi might have promising applications in cancer immunotherapy, especially in combination with adoptive NK cell therapy. This evidence concerns the gene HDAC9 and cancer.