To investigate whether radiosensitization with combined HDAC inhibition and RT increases the expressions of NKG2D ligands in HCC cells and consequently enhances their susceptibility to NK cell-mediated cytotoxicity, the pan-HDAC inhibitor (panobinostat) or HDAC4 knockdown combined with various doses of RT were used to induce NKG2D ligands by flow cytometry with MICA/B expressions on PLC5 and Huh7 cells co-cultured with or without NK cells. Here, HDAC9 is linked to hepatocellular carcinoma.