KLRK1 and neoplasm: Other interesting results aimed at increasing NKG2D-mediated killing activity of NK cells against CRC liver metastases have been carried out from preclinical studies focused on the analysis of the anti-tumor activity of allogeneic healthy donors’ NK cells modified with a chimeric NKG2D receptor fused to co-stimulatory (OX40) and signaling (CD3ζ) domains (to enhance their intrinsic activity) and equipped with membrane-bound IL-15 (to enhance in vivo persistence) [139,140].