Cell surface expressions of NKG2D ligands after treating irradiated A549 cells with HDAC inhibitors. NKG2D ligand cell surface expressions were analyzed by flow cytometry using specific mAbs against NKG2D ligands. A549 cells were irradiated with 8 Gy, allowed to recover for 6 hours, and then treated with or without 250nM TSA or 125 ng/ml apicidin. The cells were then incubated for 18 hours. In the figure, filled gray represents the isotype control and filled black represents the treated group (A). All experiments performed independently in triplicate and significant differences between the untreated control and treated cells are presented as * (p < 0.05) or ** (p < 0.01). Ratios of mean fluorescence intensities (MFI) obtained from treated cells and untreated control are shown (B). The further inductions of NKG2D ligands by combination treatment as compared with treatment with HDAC inhibitors only are marked # (p < 0.05) or ## (p < 0.01). Changes in the surface protein expressions of HLA-A/B/C were analyzed after ionizing radiation or TSA treatment (C).