Increasing molar activity by HPLC purification improves 68Ga-DOTA-NAPamide tumor accumulation in a B16/F1 melanoma xenograft model.

<h4>Purpose</h4>Melanocortin receptor 1 (MC1R) is overexpressed in melanoma and may be a molecular target for imaging and peptide receptor radionuclide therapy. 68Gallium (68Ga) labeling of DOTA-conjugated peptides is an established procedure in the clinic for use in positron emission to...

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Main Authors: Jan Lennart von Hacht, Sarah Erdmann, Lars Niederstadt, Sonal Prasad, Asja Wagener, Samantha Exner, Nicola Beindorff, Winfried Brenner, Carsten Grötzinger
Format: Article
Language:English
Published: Public Library of Science (PLoS) 2019-01-01
Series:PLoS ONE
Online Access:https://doi.org/10.1371/journal.pone.0217883
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author Jan Lennart von Hacht
Sarah Erdmann
Lars Niederstadt
Sonal Prasad
Asja Wagener
Samantha Exner
Nicola Beindorff
Winfried Brenner
Carsten Grötzinger
author_facet Jan Lennart von Hacht
Sarah Erdmann
Lars Niederstadt
Sonal Prasad
Asja Wagener
Samantha Exner
Nicola Beindorff
Winfried Brenner
Carsten Grötzinger
author_sort Jan Lennart von Hacht
collection DOAJ
description <h4>Purpose</h4>Melanocortin receptor 1 (MC1R) is overexpressed in melanoma and may be a molecular target for imaging and peptide receptor radionuclide therapy. 68Gallium (68Ga) labeling of DOTA-conjugated peptides is an established procedure in the clinic for use in positron emission tomography (PET) imaging. Aim of this study was to compare a standard labeling protocol against the 68Ga-DOTA peptide purified from the excess of unlabeled peptide.<h4>Procedures</h4>The MC1R ligand DOTA-NAPamide was labeled with 68Ga using a standard clinical protocol. Radioactive peptide was separated from the excess of unlabeled DOTA-NAPamide by HPLC. Immediately after the incubation of peptide and 68Ga (95°C, 15 min), the reaction was loaded on a C18 column and separated by a water/acetonitrile gradient, allowing fractionation in less than 20 minutes. Radiolabeled products were compared in biodistribution studies and PET imaging using nude mice bearing MC1R-expressing B16/F1 xenograft tumors.<h4>Results</h4>In biodistribution studies, non-purified 68Ga-DOTA-NAPamide did not show significant uptake in the tumor at 1 h post injection (0.78% IA/g). By the additional HPLC step, the molar activity was raised around 10,000-fold by completely removing unlabeled peptide. Application of this rapid purification strategy led to a more than 8-fold increase in tumor uptake (7.0% IA/g). The addition of various amounts of unlabeled DOTA-NAPamide to the purified product led to a blocking effect and decreased specific tumor uptake, similar to the result seen with non-purified radiopeptide. PET imaging was performed using the same tracer preparations. Purified 68Ga-DOTA-NAPamide, in comparison, showed superior tumor uptake.<h4>Conclusions</h4>We demonstrated that chromatographic separation of radiolabeled from excess unlabeled peptide is technically feasible and beneficial, even for short-lived isotopes such as 68Ga. Unlabeled peptide molecules compete with receptor binding sites in the target tissue. Purification of the radiopeptide therefore improved tumor uptake.
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spelling doaj.art-85be88c523684bb79d093da540bcff572022-12-21T22:50:48ZengPublic Library of Science (PLoS)PLoS ONE1932-62032019-01-01146e021788310.1371/journal.pone.0217883Increasing molar activity by HPLC purification improves 68Ga-DOTA-NAPamide tumor accumulation in a B16/F1 melanoma xenograft model.Jan Lennart von HachtSarah ErdmannLars NiederstadtSonal PrasadAsja WagenerSamantha ExnerNicola BeindorffWinfried BrennerCarsten Grötzinger<h4>Purpose</h4>Melanocortin receptor 1 (MC1R) is overexpressed in melanoma and may be a molecular target for imaging and peptide receptor radionuclide therapy. 68Gallium (68Ga) labeling of DOTA-conjugated peptides is an established procedure in the clinic for use in positron emission tomography (PET) imaging. Aim of this study was to compare a standard labeling protocol against the 68Ga-DOTA peptide purified from the excess of unlabeled peptide.<h4>Procedures</h4>The MC1R ligand DOTA-NAPamide was labeled with 68Ga using a standard clinical protocol. Radioactive peptide was separated from the excess of unlabeled DOTA-NAPamide by HPLC. Immediately after the incubation of peptide and 68Ga (95°C, 15 min), the reaction was loaded on a C18 column and separated by a water/acetonitrile gradient, allowing fractionation in less than 20 minutes. Radiolabeled products were compared in biodistribution studies and PET imaging using nude mice bearing MC1R-expressing B16/F1 xenograft tumors.<h4>Results</h4>In biodistribution studies, non-purified 68Ga-DOTA-NAPamide did not show significant uptake in the tumor at 1 h post injection (0.78% IA/g). By the additional HPLC step, the molar activity was raised around 10,000-fold by completely removing unlabeled peptide. Application of this rapid purification strategy led to a more than 8-fold increase in tumor uptake (7.0% IA/g). The addition of various amounts of unlabeled DOTA-NAPamide to the purified product led to a blocking effect and decreased specific tumor uptake, similar to the result seen with non-purified radiopeptide. PET imaging was performed using the same tracer preparations. Purified 68Ga-DOTA-NAPamide, in comparison, showed superior tumor uptake.<h4>Conclusions</h4>We demonstrated that chromatographic separation of radiolabeled from excess unlabeled peptide is technically feasible and beneficial, even for short-lived isotopes such as 68Ga. Unlabeled peptide molecules compete with receptor binding sites in the target tissue. Purification of the radiopeptide therefore improved tumor uptake.https://doi.org/10.1371/journal.pone.0217883
spellingShingle Jan Lennart von Hacht
Sarah Erdmann
Lars Niederstadt
Sonal Prasad
Asja Wagener
Samantha Exner
Nicola Beindorff
Winfried Brenner
Carsten Grötzinger
Increasing molar activity by HPLC purification improves 68Ga-DOTA-NAPamide tumor accumulation in a B16/F1 melanoma xenograft model.
PLoS ONE
title Increasing molar activity by HPLC purification improves 68Ga-DOTA-NAPamide tumor accumulation in a B16/F1 melanoma xenograft model.
title_full Increasing molar activity by HPLC purification improves 68Ga-DOTA-NAPamide tumor accumulation in a B16/F1 melanoma xenograft model.
title_fullStr Increasing molar activity by HPLC purification improves 68Ga-DOTA-NAPamide tumor accumulation in a B16/F1 melanoma xenograft model.
title_full_unstemmed Increasing molar activity by HPLC purification improves 68Ga-DOTA-NAPamide tumor accumulation in a B16/F1 melanoma xenograft model.
title_short Increasing molar activity by HPLC purification improves 68Ga-DOTA-NAPamide tumor accumulation in a B16/F1 melanoma xenograft model.
title_sort increasing molar activity by hplc purification improves 68ga dota napamide tumor accumulation in a b16 f1 melanoma xenograft model
url https://doi.org/10.1371/journal.pone.0217883
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