Comparison of the uptake of [123/125I]-2-iodo-D-tyrosine and [123/125I]-2-iodo-L-tyrosine in R1M Rhabdomyosarcoma cells in vitro and in R1M tumor-bearing Wag/Rij rats in vivo

Matthias Bauwens, Tony Lahoutte, Ken Kersemans, Axel Bossuyt, John Mertens

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Introduction: Recently promising results concerning uptake in vivo in tumours of D-amino acids have been published. Therefore we decided to evaluate the tumour uptake of the D-analogue of [123I]-2-Iodo-L-Tyrosine, a tracer recently introduced by our group into clinical trials. The uptake of 2-Amino-3-(4-hydroxy-2-[123/125I]iodophenyl)-D-propanoic acid (2-Iodo-D-Tyrosine) was studied in vitro in LAT1 expressing R1M rat rhabdomyosarcoma cells and in vivo in R1M tumour bearing Wag/Rij rats.

Methods: The uptake of [125I]-2-Iodo-L-Tyrosine and [125I]-2-Iodo-D-Tyrosine into R1M cells was determined in appropriate buffers allowing the study of the involved transport systems. In vivo the biodistribution in R1M bearing rats of [123I]-2-Iodo-L-Tyrosine and [123I]-2-Iodo-D-Tyrosine was performed by both dynamic and static planar imaging with a gamma camera.

Results: In in vitro conditions, the uptake of both [125I]-2-Iodo-L-Tyrosine and [125I]-2-Iodo-D-Tyrosine in the HEPES buffer was 25% higher in presence of Na+ ions. In absence of Na+ ions [125I]-2-Iodo-D-Tyrosine was taken up reversibly in the R1M cells, with an apparent accumulation, probably for the larger part by the LAT1 system. Dynamic Planar Imaging showed that the uptake in the tumours of [123I]-2-Iodo-D-Tyrosine was somewhat lower than of [123I]-2-Iodo-L-Tyrosine. At 30 minutes p.i. the mean DUR values of the L- and D-enantiomers are respectively 2.5 _ 0.7 and 1.7 _ 0.6. Although the uptake of the D-isomer is lower, probably due to a faster clearance from the blood, the tumour / background ratio is the same as of the L-analogue.

Conclusion: [125I]-2-Iodo-D-Tyrosine in vitro and [123I]-2-Iodo-D-Tyrosine in vivo is reversibly highly taken up in R1M tumour cells for a large part (75%) by Na+ independent LAT transport systems, more likely by the LAT1. The clearance from the blood of [123I]-2-Iodo-D-Tyrosine in the rats is faster than of the L-analogue resulting in a slightly lower tumour uptake but a same tumour to background ratio.
Original languageEnglish
Pages (from-to)735-741
Number of pages7
JournalNucl Med Biol. 2006 Aug;33(6)
Publication statusPublished - 2006


  • D-amino acid
  • 123I
  • tumour


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