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(99m)Tc-maEEE-Z(HER2:342), an Affibody molecule-based tracer for the detection of HER2 expression in malignant tumors
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Oncology, Radiology and Clinical Immunology, Biomedical Radiation Sciences.
School of Biotechnology, Royal Institute of Technology, Stockholm, Sweden.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Oncology, Radiology and Clinical Immunology.ORCID iD: 0000-0001-6120-2683
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Oncology, Radiology and Clinical Immunology.
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2007 (English)In: Bioconjugate chemistry, ISSN 1043-1802, E-ISSN 1520-4812, Vol. 18, no 6, 1956-1964 p.Article in journal (Refereed) Published
Abstract [en]

Detection of HER2-overexpression in tumors and metastases is important for the selection of patients who will benefit from trastuzumab treatment. Earlier investigations showed successful imaging of HER2-positive tumors in patients using indium- or gallium-labeled Affibody molecules. The goal of this study was to evaluate the use of (99m)Tc-labeled Affibody molecules for the detection of HER2 expression. The Affibody molecule Z(HER2:342) with the chelator sequences mercaptoacetyl-Gly-Glu-Gly (maGEG) and mercaptoacetyl-Glu-Glu-Glu (maEEE) was synthesized by peptide synthesis and labeled with technetium-99m. Binding specificity, cellular retention, and in vitro stability were investigated. The biodistribution of (99m)Tc-maGEG-Z(HER2:342) and (99m)Tc-maEEE-Z(HER2:342) was compared with (99m)Tc-maGGG-Z(HER2:342) in normal mice, and the tumor targeting properties of (99m)Tc-maEEE-Z(HER2:342) were determined in SKOV-3 xenografted nude mice. The results showed that the Affibody molecules were efficiently labeled with technetium-99m. The labeled conjugates were highly stable in vitro with preserved HER2-binding capacity. The use of glutamic acid in the chelator sequences for (99m)Tc-labeling of Z(HER2:342) reduced the hepatobiliary excretion 3-fold with a single Gly-to-Glu substitution and 10-fold with three Gly-to-Glu substitutions. (99m)Tc-maEEE-Z(HER2:342) showed a receptor-specific tumor uptake of 7.9 +/- 1.0 %IA/g and a tumor-to-blood ratio of 38 at 4 h pi. Gamma-camera imaging with (99m)Tc-maEEE-Z(HER2:342) could detect HER2-expressing tumors in xenografts already at 1 h pi. It was concluded that peptide synthesis for the coupling of chelator sequences to Affibody molecules for (99m)Tc labeling is an efficient way to modify the in vivo kinetics. Increased hydrophilicity, combined with improved stability of the mercaptoacetyl-triglutamyl chelator, resulted in favorable biodistribution, making (99m)Tc-maEEE-Z(HER2:342) a promising tracer for clinical imaging of HER2 overexpression in tumors.

Place, publisher, year, edition, pages
2007. Vol. 18, no 6, 1956-1964 p.
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:uu:diva-17053DOI: 10.1021/bc7002617ISI: 000251166400035PubMedID: 17944527OAI: oai:DiVA.org:uu-17053DiVA: diva2:44824
Available from: 2008-06-16 Created: 2009-03-25 Last updated: 2017-12-08Bibliographically approved
In thesis
1. Molecular Imaging of HER2 Expression using Synthetic Affibody Molecules: Design, Synthesis and Biological Evaluation
Open this publication in new window or tab >>Molecular Imaging of HER2 Expression using Synthetic Affibody Molecules: Design, Synthesis and Biological Evaluation
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Molecular imaging is an emerging multidisciplinary field that addresses the visualisation of diseases at the cellular and molecular levels. This thesis focuses on the development of a synthetic Affibody molecule-based imaging tracer for the detection of HER2 expression in malignant tumours.

Papers I-IV report the development of the HER2-specific Affibody molecule, ZHER2:342 by peptide synthesis and the use of different chelators attached to the N-terminus to allow 99mTc-labelling. Paper I described the optimisation of labelling of Affibody molecules using cysteine-based chelator sequences, in which the direct labelling method under alkaline conditions was the most suitable one. Papers II-IV report the development and optimisation of the in vivo properties of the HER2-specific Affibody molecule for high-contrast imaging. By using an array of mercaptoacetyl-based chelators, it was found that the substitution of a single amino acid in a 60 amino acid-long Affibody molecule can dramatically change the pharmacokinetics of the tracer. Strategic approaches that utilised hydrophilic amino acids, such as serine, glutamate and lysine, changed the excretion pathway from hepatobiliary to renal excretion. Problems with the high accumulation of radioactivity in the abdomen area and restricted imaging were resolved by the use of mercaptoacetyl-triglutamyl, maEEE or mercaptoacetyl-seryl-lysyl-seryl, maSKS chelators.

Paper V reports the re-engineering of the HER2-specific Affibody molecule to provide a C-terminal SECG sequence using peptide synthesis. Incorporation of this sequence provided a multifunctional platform for labelling (with technetium or trivalent radiometals) and a flexible production route (recombinant or chemical synthesis). Combination of a serine, a glutamic acid and a thiol-bearing group in the chelating sequence reduced the renal accumulation of Affibody molecules.

Altogether, the in vivo efficiency of Affibody molecules to target tumours and their biodistribution properties can be improved by strategic design and suitable chemistry. Hopefully, these observations will be applicable to other small peptide and protein scaffold-based tracers.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2009. 53 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 445
Series
National Category
Medical and Health Sciences
Research subject
Biomedical Radiation Science
Identifiers
urn:nbn:se:uu:diva-99248 (URN)978-91-554-7489-8 (ISBN)
Public defence
2009-05-16, Rudbecksalen, Rudbecklaboratoriet, Uppsala, 09:15 (English)
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Available from: 2009-04-24 Created: 2009-03-10 Last updated: 2009-04-24Bibliographically approved

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Tran, ThuyOrlova, AnnaTolmachev, Vladimir

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