CD226 and glioblastoma: One may suggest that alterations such as reduced transcription of IFN-γ [132], decreased expression of some activating receptors (e.g., NKp30, NKG2D, DNAM-1, and CD2) [133], and the expression of transcripts associated with quiescent NK cells in GBM tissue [132] collectively represent tumor-modified NK cells, but the functional impact of these changes remains elusive in GBM.