Development of Novel 111-In-Labelled DOTA Urotensin II Analogues for Targeting the UT Receptor Overexpressed in Solid Tumours.

Benjamin Poret,Richard Leduc,Pierre Bohn,Hélène Castel,Marc-André Bonin,Martin Pedard,Romain Modzelewski,Pierrick Gandolfo,Martine Dubois,Fabrice Morin,Pierre Vera,Pierre Decazes,Laurence Desrues

doi:10.3390/biom10030471

Abstract

Overexpression of G protein-coupled receptors (GPCRs) in tumours is widely used to develop GPCR-targeting radioligands for solid tumour imaging in the context of diagnosis and even treatment. The human vasoactive neuropeptide urotensin II (hUII), which shares structural analogies with somatostatin, interacts with a single high affinity GPCR named UT. High expression of UT has been reported in several types of human solid tumours from lung, gut, prostate, or breast, suggesting that UT is a valuable novel target to design radiolabelled hUII analogues for cancer diagnosis. In this study, two original urotensinergic analogues were first conjugated to a DOTA chelator via an aminohexanoic acid (Ahx) hydrocarbon linker and then -hUII and DOTA-urantide, complexed to the radioactive metal indium isotope to successfully lead to radiolabelled DOTA-Ahx-hUII and DOTA-Ahx-urantide. The 111In-DOTA-hUII in human plasma revealed that only 30% of the radioligand was degraded after a 3-h period. DOTA-hUII and DOTA-urantide exhibited similar binding affinities as native peptides and relayed calcium mobilization in HEK293 cells expressing recombinant human UT. DOTA-hUII, not DOTA-urantide, was able to promote UT internalization in UT-expressing HEK293 cells, thus indicating that radiolabelled 111In-DOTA-hUII would allow sufficient retention of radioactivity within tumour cells or radiolabelled DOTA-urantide may lead to a persistent binding on UT at the plasma membrane. The potential of these radioligands as candidates to target UT was investigated in adenocarcinoma. We showed that hUII stimulated the migration and proliferation of both human lung A549 and colorectal DLD-1 adenocarcinoma cell lines endogenously expressing UT. In vivo intravenous injection of 111In-DOTA-hUII in C57BL/6 mice revealed modest organ signals, with important retention in kidney. 111In-DOTA-hUII or 111In-DOTA-urantide were also injected in nude mice bearing heterotopic xenografts of lung A549 cells or colorectal DLD-1 cells both expressing UT. The observed significant renal uptake and low tumour/muscle ratio (around 2.5) suggest fast tracer clearance from the organism. Together, DOTA-hUII and DOTA-urantide were successfully radiolabelled with 111Indium, the first one functioning as a UT agonist and the second one as a UT-biased ligand/antagonist. To allow tumour-specific targeting and prolong body distribution in preclinical models bearing some solid tumours, these radiolabelled urotensinergic analogues should be optimized for being used as potential molecular tools for diagnosis imaging or even treatment tools.

Highlights

For several years, natural or synthetic derivatives radiolabelled ligands for G protein-coupled receptors (GPCRs) have acquired a great clinical interest, mainly in nuclear medicine, for the diagnosis and treatment of some cancers such as neuroendocrine ones [1,2]
As a proof of concept for the use of UT as a functional target in solid tumours, we found that exposure of human vasoactive neuropeptide urotensin II (hUII) stimulated the migration and proliferation of both human lung adenocarcinoma A549 and colorectal DLD-1 cell lines endogenously expressing UT
Using an in vivo approach, we evaluated the pharmacokinetic of the 111In-DOTA-hUII in immunocompetent mice, and the tumour targeting of both 111In-DOTA-hUII and 111In-DOTA-urantide in A549 and DLD-1 human tumours xenografted in nude mice

Summary

Introduction

Natural or synthetic derivatives radiolabelled ligands for G protein-coupled receptors (GPCRs) have acquired a great clinical interest, mainly in nuclear medicine, for the diagnosis and treatment of some cancers such as neuroendocrine ones [1,2]. The other fundamental component for the development of GPCR radioligands for cancer diagnosis is the combination of commonly low expression and limited density of the targeted GPCR in most organs and the concurrent overexpression and high density of these receptors in tumour cells [2,6,7]. The use of radiotracers was extended to tumours that overexpress GPCRs, with the development of, for example, 99mTc-HABN or 99mTc-BBN both targeting Gastrin-releasing peptide receptor with high density in prostate tumour cells [17] and in breast cancer [18]

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Results

Conclusion