PVR and neoplasm: The interaction of NK cell-activating receptors such as DNAX accessory molecule 1 (DNAM-1) and natural killer group 2D (NKG2D), with their respective ligands expressed on tumor cells, poliovirus receptor (PVR) and Nectin-2 for DNAM-1, major histocompatibility complex class I-related chain A/B (MICA/B), and UL16-binding proteins (ULBPs) for NKG2D, triggers the release of cytolytic granules by NK cells, leading to tumor cell death.