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GLP-1 receptor expression in human tumors and human normal tissues: potential for in vivo targeting
Meike Körner1, Martin Stöckli, Beatrice Waser
1Division of Cell Biology and Experimental Cancer Research, Institute of Pathology, University of Bern, Bern, Switzerland.
Unlabelled:
Peptide hormone receptors overexpressed in human tumors, such as somatostatin receptors, can be used for in vivo targeting for diagnostic and therapeutic purposes. A novel promising candidate in this field is the GLP-1 receptor, which was recently shown to be massively overexpressed in gut and lung neuroendocrine tumors--in particular, in insulinomas. Anticipating a major development of GLP-1 receptor targeting in nuclear medicine, our aim was to evaluate in vitro the GLP-1 receptor expression in a large variety of other tumors and to compare it with that in nonneoplastic tissues.
Methods:
The GLP-1 receptor protein expression was qualitatively and quantitatively investigated in a broad spectrum of human tumors (n=419) and nonneoplastic human tissues (n=209) with receptor autoradiography using (125)I-GLP-1(7-36)amide. Pharmacologic competition experiments were performed to provide proof of specificity of the procedure.
Results:
GLP-1 receptors were expressed in various endocrine tumors, with particularly high amounts in pheochromocytomas, as well as in brain tumors and embryonic tumors but not in carcinomas or lymphomas. In nonneoplastic tissues, GLP-1 receptors were present in generally low amounts in specific tissue compartments of several organs--namely, pancreas, intestine, lung, kidney, breast, and brain; no receptors were identified in lymph nodes, spleen, liver, or the adrenal gland. The rank order of potencies for receptor binding--namely, GLP-1(7-36)amide = exendin-4 >> GLP-2 = glucagon(1-29)--provided proof of specific GLP-1 receptor identification.
Conclusion:
The GLP-1 receptors may represent a novel molecular target for in vivo scintigraphy and targeted radiotherapy for a variety of GLP-1 receptor-expressing tumors. For GLP-1 receptor scintigraphy, a low-background signal can be expected, on the basis of the low receptor expression in the normal tissues surrounding tumors.
Insights
Glucagon-like peptide-1 (GLP-1) receptors are highly expressed in various tumors, making them a promising target for nuclear medicine imaging and therapy. Low expression in normal tissues suggests potential for specific tumor targeting with reduced side effects.
Area of Science:
- Oncology
- Nuclear Medicine
- Molecular Imaging
Background:
- Peptide hormone receptors like somatostatin receptors are utilized for in vivo tumor targeting.
- Glucagon-like peptide-1 (GLP-1) receptors are overexpressed in neuroendocrine tumors, particularly insulinomas.
- GLP-1 receptor targeting shows promise for diagnostic and therapeutic applications in oncology.
Purpose of the Study:
- To evaluate GLP-1 receptor expression in a wide range of human tumors and non-neoplastic tissues.
- To compare GLP-1 receptor expression levels between cancerous and normal tissues.
- To assess the potential of GLP-1 receptors as a molecular target for nuclear medicine.
Main Methods:
- Receptor autoradiography using (125)I-GLP-1(7-36)amide on 419 human tumors and 209 non-neoplastic tissues.
- Qualitative and quantitative investigation of GLP-1 receptor protein expression.
- Pharmacologic competition experiments to confirm receptor specificity.
Main Results:
- GLP-1 receptors were highly expressed in endocrine tumors (pheochromocytomas), brain tumors, and embryonic tumors.
- Carcinomas and lymphomas showed no GLP-1 receptor expression.
- Low GLP-1 receptor expression was observed in specific compartments of pancreas, intestine, lung, kidney, breast, and brain tissues; absent in lymph nodes, spleen, liver, and adrenal gland.
- Specificity was confirmed by binding affinities: GLP-1(7-36)amide = exendin-4 >> GLP-2 = glucagon(1-29).
Conclusions:
- GLP-1 receptors represent a novel molecular target for in vivo scintigraphy and targeted radiotherapy.
- The low expression of GLP-1 receptors in surrounding normal tissues suggests a low-background signal for scintigraphy.
- GLP-1 receptor targeting offers potential for improved diagnostics and therapeutics in various tumor types.
