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Vol 14, No 2 (2011)
Original articles
Published online: 2012-01-04
Submitted: 2012-01-23
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Comparison of receptor affinity of natSc-DOTA-TATE versus natGa-DOTA-TATE

Eftychia Koumarianou, Dariusz Pawlak, Agnieszka Korsak, Renata Mikolajczak
Nucl. Med. Rev 2011;14(2):85-89.

open access

Vol 14, No 2 (2011)
Original articles
Published online: 2012-01-04
Submitted: 2012-01-23

Abstract

BACKGROUND: 44Sc as a positron emitter can be an interesting alternative to 68Ga (T½ = 67.71 min) due to its longer half-life (T½ = 3.97 h). Moreover, the b– emitter 47Sc can be used for therapy when attached to the same biomolecule vectors. DOTA as a chelating agent has been proven suitable for the radiolabelling of peptides recognising tumour cell receptors in vivo with M3+ radiometals. DOTA-derivatized peptides have been successfully labelled with 90Y and 177Lu for therapy, and with 68Ga for PET imaging. However, published data on 44Sc-labelled DOTA-biomolecules as potential PET radiotracers are still very limited. The aim of this study was to compare the affinity of natGa- and natSc-labelled DOTA-TATE to somatostatin receptors subtype 2 expressed in rat pancreatic cancer cell line AR42J.
MATERIAL AND METHODS: The cold complexes of DOTA-TATE with natGa and natSc were synthesized and identified by HPLC and MS analysis and evaluated in vitro for competitive binding to cancer cell line AR42J expressing somatostatin receptors subtype 2 (sstr2).
RESULTS: The IC50 values calculated from the displacement curve of {125I-Tyr11}-SST-14 were: 0.20 ± 0.18, 0.70 ± 0.20, 0.64 ± 0.22 and 0.67 ± 0.12 for natGa-DOTA-TATE, natSc-DOTA-TATE, DOTA-TATE, and {Tyr11}-SST-14 complexes, respectively, with the affinity lowering in the decreasing order: natGa-DOTA-TATE > DOTA-TATE > Tyr11-SST-14 > natSc-DOTA-TATE.
CONCLUSIONS: The binding affinity of natGa-DOTA-TATE appeared higher than that of natSc-DOTA-TATE. Further in vitro and in vivo studies are needed to verify the influence of the chelated metal on the affinity and uptake of the respective radiolabelled compounds. This information might be crucial when the in vivo applications of peptides labelled with 68Ga and 44Sc for PET, as well as the use of 47Sc for radiotherapy are considered.
Nuclear Med Rev 2011; 14, 2: 85–89

Abstract

BACKGROUND: 44Sc as a positron emitter can be an interesting alternative to 68Ga (T½ = 67.71 min) due to its longer half-life (T½ = 3.97 h). Moreover, the b– emitter 47Sc can be used for therapy when attached to the same biomolecule vectors. DOTA as a chelating agent has been proven suitable for the radiolabelling of peptides recognising tumour cell receptors in vivo with M3+ radiometals. DOTA-derivatized peptides have been successfully labelled with 90Y and 177Lu for therapy, and with 68Ga for PET imaging. However, published data on 44Sc-labelled DOTA-biomolecules as potential PET radiotracers are still very limited. The aim of this study was to compare the affinity of natGa- and natSc-labelled DOTA-TATE to somatostatin receptors subtype 2 expressed in rat pancreatic cancer cell line AR42J.
MATERIAL AND METHODS: The cold complexes of DOTA-TATE with natGa and natSc were synthesized and identified by HPLC and MS analysis and evaluated in vitro for competitive binding to cancer cell line AR42J expressing somatostatin receptors subtype 2 (sstr2).
RESULTS: The IC50 values calculated from the displacement curve of {125I-Tyr11}-SST-14 were: 0.20 ± 0.18, 0.70 ± 0.20, 0.64 ± 0.22 and 0.67 ± 0.12 for natGa-DOTA-TATE, natSc-DOTA-TATE, DOTA-TATE, and {Tyr11}-SST-14 complexes, respectively, with the affinity lowering in the decreasing order: natGa-DOTA-TATE > DOTA-TATE > Tyr11-SST-14 > natSc-DOTA-TATE.
CONCLUSIONS: The binding affinity of natGa-DOTA-TATE appeared higher than that of natSc-DOTA-TATE. Further in vitro and in vivo studies are needed to verify the influence of the chelated metal on the affinity and uptake of the respective radiolabelled compounds. This information might be crucial when the in vivo applications of peptides labelled with 68Ga and 44Sc for PET, as well as the use of 47Sc for radiotherapy are considered.
Nuclear Med Rev 2011; 14, 2: 85–89
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Keywords

scandium-44; gallium-68; PET tracers; receptor affinity; DOTA-derivatised peptides

About this article
Title

Comparison of receptor affinity of natSc-DOTA-TATE versus natGa-DOTA-TATE

Journal

Nuclear Medicine Review

Issue

Vol 14, No 2 (2011)

Pages

85-89

Published online

2012-01-04

Bibliographic record

Nucl. Med. Rev 2011;14(2):85-89.

Keywords

scandium-44
gallium-68
PET tracers
receptor affinity
DOTA-derivatised peptides

Authors

Eftychia Koumarianou
Dariusz Pawlak
Agnieszka Korsak
Renata Mikolajczak

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