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Radiolabelled GLP-1 receptor antagonist binds to GLP-1 receptor-expressing human tissues

Waser, Beatrice ; Reubi, Jean

In: European Journal of Nuclear Medicine and Molecular Imaging, 2014, vol. 41, no. 6, p. 1166-1171

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    Title
    • Radiolabelled GLP-1 receptor antagonist binds to GLP-1 receptor-expressing human tissues
    Author
    • Waser, Beatrice. Division of Cell Biology and Experimental Cancer Research, Institute of Pathology, University of Berne, Murtenstrasse 31, PO Box 62, 3010, Berne, Switzerland
    • Reubi, Jean. Division of Cell Biology and Experimental Cancer Research, Institute of Pathology, University of Berne, Murtenstrasse 31, PO Box 62, 3010, Berne, Switzerland
    Document Type
    • Postprint
    Language
    • English
    Published in
    • European Journal of Nuclear Medicine and Molecular Imaging, 2014, vol. 41, no. 6, p. 1166-1171. Springer Berlin Heidelberg
    Other Version
    OAI-PMH Identifier
    • oai:doc.rero.ch:324955
    Summary
    Purpose: Radiolabelled glucagon-like peptide 1 (GLP-1) receptor agonists have recently been shown to successfully image benign insulinomas in patients. For the somatostatin receptor targeting of tumours, however, it was recently reported that antagonist tracers were superior to agonist tracers. The present study therefore evaluated various forms of the 125iodinated-Bolton-Hunter (BH)-exendin(9-39) antagonist tracer for the in vitro visualization of GLP-1 receptor-expressing tissues in rats and humans and compared it with the agonist tracer 125I-GLP-1(7-36)amide. Methods: Receptor autoradiography studies with 125I-GLP-1(7-36)amide agonist or 125I-BH-exendin(9-39) antagonist radioligands were performed in human and rat tissues. Results: The antagonist 125I-BH-exendin(9-39) labelled at lysine 19 identifies all human and rat GLP-1 target tissues and GLP-1 receptor-expressing tumours. Binding is of high affinity and is comparable in all tested tissues in its binding properties with the agonist tracer 125I-GLP-1(7-36)amide. For comparison, 125I-BH-exendin(9-39) with the BH labelled at lysine 4 did identify the GLP-1 receptor in rat tissues but not in human tissues. Conclusion: The GLP-1 receptor antagonist exendin(9-39) labelled with 125I-BH at lysine 19 is an excellent GLP-1 radioligand that identifies human and rat GLP-1 receptors in normal and tumoural tissues. It may therefore be the molecular basis to develop suitable GLP-1 receptor antagonist radioligands for in vivo imaging of GLP-1 receptor-expressing tissues in patients.