NKTR (natural killer cell triggering receptor) is a peptidyl-prolyl cis-trans isomerase that catalyzes proline isomerization to assist protein folding 1. The protein is a 150-kDa NK-cell-specific molecule homologous to cyclophilin 2 and functions as a component of a putative tumor-recognition complex critical for NK cell lytic activity 3. NKTR expression is essential for maintaining NK cell cytotoxic function, as downregulation increases cancer cell proliferation, migration, and invasion 4. Clinically, NKTR serves as a biomarker for colorectal cancer liver metastasis, with reduced expression correlating with metastatic disease 4. The NKTR gene exhibits complex posttranscriptional regulation through alternative splicing, with differential expression patterns in developing versus mature NK cells 2. Beyond its direct function, NKTR-based therapeutics have emerged as immunotherapy agents. NKTR-358 selectively expands regulatory T cells for autoimmune disease treatment 5, while NKTR-214 (bempegaldesleukin) biases IL-2 signaling toward CD8+ T and NK cell activation without excessive Treg expansion in cancer immunotherapy 6. NKTR-255, an IL-15 agonist, enhances NK cell persistence and trafficking, improving outcomes in CAR-T cell therapy for leukemia 7 and combinatorial NK cell immunotherapy for pediatric solid tumors 89.