CD226 and neuroblastoma: MYCN amplification, a well-established predictor of poor prognosis in NB, may serve as a negative regulator of NKG2D ligands, that is, MIC-A, MIC-B, ULBP-1, ULBP-2, and ULBP-3, and DNAM-1 ligand, for example, PVR [45, 46], thus supporting the role of MYCN as an immunosuppressive oncogene in high-risk NB patients.