KLRK1 and neoplasm: These authors found that SeCys2 was the main functional metabolite of Se nanoparticles and not only significantly prolonged the persistence of CIK cells in vivo but also effectively enhanced the cytotoxicity of CIK cells through upregulating the expression of NKG2D/NKG2DLs and PD-1/PD-L1 and reshaping the TME in multiple mouse tumor models (hepatic, breast and prostate tumors) 80.