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In Vivo Imaging of Natural Killer Cell Trafficking in Tumors

2015; Society of Nuclear Medicine and Molecular Imaging; Volume: 56; Issue: 10 Linguagem: Inglês

10.2967/jnumed.114.152918

1535-5667

Filippo Galli, Anna Rapisarda, Helena Stabile, Gaurav Malviya, Isabella Manni, Elena Bonanno, Giulia Piaggio, Angela Gismondi, Angela Santoni, Alberto Signore,

CAR-T cell therapy research

Natural killer cells (NKs) are important effectors of the innate immune system, with marked antitumor activity. Imaging NK trafficking in vivo may be relevant to following up the efficacy of new therapeutic approaches aiming at increasing tumor-infiltrating NKs (TINKs). The specific aims of present study were to efficiently target NKs using a 99m Tc-anti-CD56 and to image human NK trafficking in SCID mice bearing human cancer. Methods: The anti-CD56 monoclonal antibody (mAb) was radiolabeled with 99m Tc, and in vitro quality controls were performed to test labeling efficiency, stability, and binding affinity to CD56. In vivo biodistribution was determined by injecting 5.5 MBq (104 ng) of radiolabeled antibody in the tail vein of SCID mice, which were then sacrificed at 1, 3, 6, and 24 h after injection. Targeting experiments were performed on 2 groups of SCID mice inoculated subcutaneously with increasing numbers of human NKs in the right thigh (from 2.5 × 10 6 to 40 × 10 6 ) and human granulocytes (CD56 − ) or anaplastic thyroid cancer (ARO) cells in the contralateral thigh as control. TINK trafficking imaging was achieved by injecting 5.5 MBq of 99m Tc-anti-CD56 mAb in SCID mice bearing ARO tumor xenografts in the right thigh, 24 h after being reconstituted with 10 5 , 10 6 , or 10 7 human NKs. Results: Anti-CD56 mAb was radiolabeled, achieving a radiochemical purity of more than 97% and a specific activity of 3,700 MBq/mg and retaining biochemical integrity and binding activity. In vivo studies revealed physiologic uptake in the liver and kidneys. Targeting experiments confirmed the specificity of labeled antibody to CD56 + cells. Human NK cells injected in CD1 nude mice accumulated in the ARO tumors within 24 h and were imaged as early as 3 h after intravenous administration of 99m Tc-anti-CD56. Conclusion: 99m Tc-anti-CD56 is a promising tool for in vivo imaging of TINK cell trafficking.