In this particular circumstance, we would envisage that the synergistic induction of cancer cell death with VSV infection and HDAC-inhibitor treatment prevails over the lack of NKG2D-ligand expression It is however noteworthy that the study uses Melanoma and Prostate cancer cells, which may express suppressive soluble NKG2D-ligands. This evidence concerns the gene HDAC9 and melanoma.