PDXK and neoplasm: To further confirm the enhanced anti-tumor activity in pre-activated hypoxic NK cells in vivo, we adopted a peritoneal clearance model, where 5 × 106 PKH-stained live CEM tumor cells and 1 × 107 cultured human NK cells were co-injected intraperitoneally into immunocompromised NSG (NOD-scid IL2rγnull) mice.