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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Public Library of Science (PLoS)
2019-01-01
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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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last_indexed | 2024-12-14T19:07:58Z |
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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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