Tracking adoptively transferred NK cells in rhesus macaques with 89Zr PET imaging.

225 Objectives Cell-based therapies against cancers have been rapidly progressing in recent years. Various techniques to enhance migration of transferred cells to the target have been explored. A non-invasive cell tracking method could help evaluate and optimize these techniques. We generated 89Zr-oxine complex cell labeling agent, evaluated the complex in rhesus macaque (RM) and human natural killer (NK) cells, and monitored an autologous NK cell transfer in RM by PET. Methods NK cells enriched from peripheral blood, by T-cell depletion, were expanded using irradiated feeder cells and human IL-2 for 14 days. 89Zr-oxine complex synthesized in an aqueous solution was used to label NK cells. Effects of labeling on surface phenotype and cytotoxicy were evaluated. 89Zr-labelled autologous NK cells (1.3×108 cells, 2.3 MBq) transferred to RM (5.7 kg) were tracked by a clinical PET/CT scanner up to 7 days. Deferoxamine was injected concurrently to chelate and enhance renal excretion of free 89Zr released from the dead cells. Results Expanded RM and human NK cells showed comparable surface phenotype and cytotoxic function. 89Zr-oxine readily permeabilized and was retained in NK cells. Labeling did not alter expression of CD16 and CD56 markers or cytotoxicity against K562 cells. PET/CT demonstrated that NK cells initially localized to the lungs, and gradually trafficked to the liver and spleen (SUV: 0.7, 17.0, and 20.1 for the lungs, liver and spleen on day 2) where they remained up to day 7. RM indicated no side effect. Conclusions The RM model indicated that 89Zr-oxine could visualize transferred cells at a low radioactivity dose on a clinical PET/CT imager. 89Zr-oxine complex would be a valuable tool for evaluating and optimizing various cell-based therapies and readily translational.