Ex vivo cell labeling with 64Cu–pyruvaldehyde-bis(N4-methylthiosemicarbazone) for imaging cell trafficking in mice with positron-emission tomography

doi:10.1073/pnas.052709599

Ex vivo cell labeling with ⁶⁴Cu–pyruvaldehyde-bis(N⁴-methylthiosemicarbazone) for imaging cell trafficking in mice with positron-emission tomography

^*The Crump Institute for Molecular Imaging, ^†University of California Los Angeles (UCLA)/Department of Energy Laboratory of Structural Biology and Molecular Medicine, ^‡Department of Molecular and Medical Pharmacology, ^§Department of Biomathematics, and ^‖UCLA-Jonsson Comprehensive Cancer Center, UCLA School of Medicine, Los Angeles, CA 90095-1770; and ^¶Washington University, St. Louis, MO 63110

Contributed by Michael E. Phelps

Abstract

We have used copper-64-pyruvaldehyde-bis(N ⁴-methylthiosemicarbazone) (⁶⁴Cu–PTSM) to radiolabel cells ex vivo for in vivo positron-emission tomography (PET) imaging studies of cell trafficking in mice and for eventual application in patients. 2-[¹⁸F]-Fluoro-2-deoxy-d-glucose (FDG) cell labeling also was evaluated for comparison. ⁶⁴Cu–PTSM uptake by C6 rat glioma (C6) cells increased for 180 min and then stabilized. The labeling efficiency was directly proportional to ⁶⁴Cu–PTSM concentration and influenced negatively by serum. Label uptake per cell was greater with ⁶⁴Cu–PTSM than with FDG. However, both ⁶⁴Cu–PTSM- and FDG-labeled cells showed efflux of cell activity into supernatant. The ⁶⁴Cu–PTSM labeling procedure did not interfere significantly with C6 cell viability and proliferation rate. MicroPET images of living mice indicate that tail-vein-injected labeled C6 cells traffic to the lungs and liver. In addition, transient splenic accumulation of radioactivity was clearly detectable in a mouse scanned at 3.33 h postinfusion of ⁶⁴Cu–PTSM-labeled lymphocytes. In contrast, the liver was the principal organ of tracer localization after tail-vein administration of ⁶⁴Cu–PTSM alone. These results indicate that in vivo imaging of cell trafficking is possible with ⁶⁴Cu–PTSM-labeled cells. Given the longer t _1/2 of ⁶⁴Cu (12.7 h) relative to ¹⁸F (110 min), longer cell-tracking periods (up to 24–36 h) should be possible now with PET.

cell tracking‖Cu–PTSM‖PET‖cell labeling

Footnotes

↵ ** To whom reprint requests should be addressed at: University of California Los Angeles School of Medicine, B3-399 BRI, Box 951770, Los Angeles, CA 90095-1770. E-mail: sgambhir{at}mednet.ucla.edu.
↵ ‡‡ Yu, M. D., Green, M. A., Mock, B. H. & Shaw, S. M., Society for Nuclear Medicine, Proceedings of the 36th Annual Meeting, June 13–16, 1989, St. Louis (abstr.).
Abbreviations:

PET,

positron-emission tomography;

FDG,

2-[18F]fluoro-2-deoxy-d-glucose;

PTSM,

pyruvaldehyde-bis(N4-methylthiosemicarbazone);

C6,

C6 rat glioma;

MTT,

3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide;

WB,

whole body;

DWBA,

digital WB autoradiography;

%ID/g,

percentage of injected dose per gram of tissue