Feasibility of real-time in vivo 89Zr-DFO-labeled CAR T-cell trafficking using PET imaging

Abstract

IntroductionChimeric antigen receptor (CAR) T-cells have been developed recently, producing impressive outcomes in patients with hematologic malignancies. However, there is no standardized method for cell trafficking and in vivo CAR T-cell monitoring. We assessed the feasibility of real-time in vivo 89Zr-p-Isothiocyanatobenzyl-desferrioxamine (Df-Bz-NCS, DFO) labeled CAR T-cell trafficking using positron emission tomography (PET).\n\nResultsThe 89Zr-DFO radiolabeling efficiency of Jurkat/CAR and human peripheral blood mononuclear cells (hPBMC)/CAR T-cells was 70-79%, and cell radiolabeling activity was 98.1-103.6 kBq/106 cells. Cell viability after radiolabeling was >95%. Compared with unlabeled cells, cell proliferation was not significantly different during the early period after injection; however, the proliferative capacity decreased over time (p = 0.02, day 7 after labeling). IL-2 or IFN-{gamma} secretion was not significantly different between unlabeled and labeled CAR T-cells. PET/magnetic resonance images in the xenograft model showed that most of the 89Zr-DFO-labeled Jurkat/CAR T-cells were distributed in the lung (24.4% {+/-} 3.4%ID) and liver (22.9% {+/-} 5.6%ID) by 1 hour after injection. The cells gradually migrated from lung to the liver and spleen by day 1, and remained stably until day 7 (on day 7: lung 3.9% {+/-} 0.3%ID, liver 36.4% {+/-} 2.7%ID, spleen 1.4% {+/-} 0.3%ID). No significant accumulation of labeled cells was identified in tumors. A similar pattern was observed in ex vivo biodistributions on day 7 (lung 3.0% {+/-} 1.0%ID, liver 19.8% {+/-} 2.2%ID, spleen 2.3% {+/-} 1.7%ID). 89Zr-DFO-labeled hPBMC/CAR T-cells showed the similar distribution on serial PET images as Jurkat/CAR T-cells. The distribution of CAR T-cells was cross-confirmed by flow cytometry, Alu polymerase chain reaction, and immunohistochemistry.\n\nConclusionUsing PET imaging of 89Zr-DFO-labeled CAR T-cells, real time in vivo cell trafficking is feasible. It can be used to investigate cellular kinetics, initial in vivo biodistribution, and the safety profile in future CAR T-cell development.