The Characterization of 18 F-hGTS13 for Molecular Imaging of x C - Transporter Activity with PET

J Nucl Med. 2019 Dec;60(12):1812-1817. doi: 10.2967/jnumed.119.225870. Epub 2019 Jun 6.

Abstract

The aim of this study was development of an improved PET radiotracer for measuring xC - activity with increased tumor uptake and reduced uptake in inflammatory cells compared with (S)-4-(3-18F-fluoropropyl)-l-glutamate (18F-FSPG). Methods: A racemic glutamate derivative, 18F-hGTS13, was evaluated in cell culture and animal tumor models. 18F-hGTS13 was separated into C5 epimers, and the corresponding 18F-hGTS13-isomer1 and 18F-hGTS13-isomer2 were evaluated in H460 tumor-bearing rats. Preliminary studies investigated the cellular uptake of 18F-hGTS13-isomer2 in multiple immune cell populations and states. Results: 18F-hGTS13 demonstrated excellent H460 tumor visualization with high tumor-to-background ratios, confirmed by ex vivo biodistribution studies. Tumor-associated radioactivity was significantly higher for 18F-hGTS13 (7.5 ± 0.9 percentage injected dose [%ID]/g, n = 3) than for 18F-FSPG (4.6 ± 0.7 %ID/g, n = 3, P = 0.01). 18F-hGTS13-isomer2 exhibited excellent H460 tumor visualization (6.3 ± 1.1 %ID/g, n = 3) and significantly reduced uptake in multiple immune cell populations relative to 18F-FSPG. 18F-hGTS13-isomer2 exhibited increased liver uptake relative to 18F-FSPG (4.6 ± 0.8 vs. 0.7 ± 0.01 %ID/g), limiting its application in hepatocellular carcinoma. Conclusion: 18F-hGTS13-isomer2 is a new PET radiotracer for molecular imaging of xC - activity that may provide information on tumor oxidation states. 18F-hGTS13-isomer2 has potential for clinical translation for imaging cancers of the thorax because of the low background signal in healthy tissue.

Keywords: 18F-hGTS13; PET imaging; cancer metabolism; oxidative stress; xC− transporter.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • A549 Cells
  • Amino Acid Transport Systems / metabolism*
  • Biological Transport
  • Glutamic Acid*
  • Humans
  • Positron-Emission Tomography*

Substances

  • Amino Acid Transport Systems
  • Glutamic Acid