Asia Oceania Journal of Nuclear Medicine and Biology (Jul 2020)

Evaluation of D-isomer of 18F-FBPA for oncology PET focusing on the differentiation of glioma and inflammation

  • Nobuto Hirai,
  • Tadashi Watabe,
  • Shushi Nagamori,
  • Pattama Wiriyasermkul,
  • Yoko Tanaka,
  • Victor Romanov,
  • Sadahiro Naka,
  • Yasukazu Kanai,
  • Yuwei Liu,
  • Naoki Tani,
  • Tatsuya Sakai,
  • Mitsuaki Tatsumi,
  • Eku Shimosegawa,
  • Yoshikatsu Kanai,
  • Jun Hatazawa

DOI
https://doi.org/10.22038/aojnmb.2020.47399.1321
Journal volume & issue
Vol. 8, no. 2
pp. 102 – 108

Abstract

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Objective(s): L-4-borono-2-18F-fluoro-phenylalanine (L-[18F]FBPA), a substrate of L-type amino acid transporter 1 (LAT1), is a tumor-specific probe used in positron emission tomography (PET). On the other hand, it has not been examined whether another isomer D-[18F]FBPA accumulates specifically in the tumor. Here, we compared the accumulation of D-[18F]FBPA in C6 glioma and inflammation to evaluate the performance of D-[18F]FBPA as a tumor-specific probe. Methods: HEK293-LAT1 and HEK293-LAT2 cells were tested for [14C]-leucine or [14C]-alanine transport, and IC50 values of L- and D-FBPA were evaluated in both cell types. PET was conducted in rat xenograft model of C6 glioma with LAT1 expression and model of turpentine oil-induced subcutaneous inflammation (n=10 for both models). The concentrations of D-[18F]FBPA were compared between glioma and inflammatory lesion using standardized uptake value (SUV). Results: In contrast to L-FBPA, which inhibited substrate uptake in both HEK293-LAT1 and -LAT2 cells, D-FBPA showed no inhibitory effect on both cells, suggesting low transporter selectivity of D-[18F]FBPA against LAT1 and LAT2. Static PET analysis showed low accumulation of D-[18F]FBPA in C6 glioma and inflammatory lesion (SUVmax=0.80±0.16, 0.56±0.09, respectively). Although there was a statistical difference in SUVmax between these tissues, it was difficult to distinguish glioma from inflammation on the PET image due to its low uptake level. Therefore, it was suggested that D-[18F]FBPA is not a suitable tumor-specific probe for oncology PET in contrast to L-[18F]FBPA. Conclusion: This study demonstrated that D-[18F]FBPA is not a LAT1-specific PET probe and shows low uptake in C6 glioma, indicating its unsuitability as a tumor diagnosis PET probe.

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