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Baart VM, Houvast RD, de Geus-Oei LF, Quax PHA, Kuppen PJK, Vahrmeijer AL, Sier CFM. Molecular imaging of the urokinase plasminogen activator receptor: opportunities beyond cancer. EJNMMI Res 2020; 10:87. [PMID: 32725278 PMCID: PMC7387399 DOI: 10.1186/s13550-020-00673-7] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Accepted: 07/14/2020] [Indexed: 02/07/2023] Open
Abstract
The urokinase plasminogen activator receptor (uPAR) plays a multifaceted role in almost any process where migration of cells and tissue-remodeling is involved such as inflammation, but also in diseases as arthritis and cancer. Normally, uPAR is absent in healthy tissues. By its carefully orchestrated interaction with the protease urokinase plasminogen activator and its inhibitor (plasminogen activator inhibitor-1), uPAR localizes a cascade of proteolytic activities, enabling (patho)physiologic cell migration. Moreover, via the interaction with a broad range of cell membrane proteins, like vitronectin and various integrins, uPAR plays a significant, but not yet completely understood, role in differentiation and proliferation of cells, affecting also disease progression. The implications of these processes, either for diagnostics or therapeutics, have received much attention in oncology, but only limited beyond. Nonetheless, the role of uPAR in different diseases provides ample opportunity to exploit new applications for targeting. Especially in the fields of oncology, cardiology, rheumatology, neurology, and infectious diseases, uPAR-targeted molecular imaging could offer insights for new directions in diagnosis, surveillance, or treatment options.
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Affiliation(s)
- V M Baart
- Department of Surgery, Leiden University Medical Center, Albinusdreef 2, 2333 ZA, Leiden, The Netherlands
| | - R D Houvast
- Department of Surgery, Leiden University Medical Center, Albinusdreef 2, 2333 ZA, Leiden, The Netherlands
| | - L F de Geus-Oei
- Department of Radiology, Section of Nuclear Medicine, Leiden University Medical Center, Leiden, The Netherlands.,Biomedical Photonic Imaging Group, University of Twente, Enschede, The Netherlands
| | - P H A Quax
- Department of Surgery, Leiden University Medical Center, Albinusdreef 2, 2333 ZA, Leiden, The Netherlands
| | - P J K Kuppen
- Department of Surgery, Leiden University Medical Center, Albinusdreef 2, 2333 ZA, Leiden, The Netherlands
| | - A L Vahrmeijer
- Department of Surgery, Leiden University Medical Center, Albinusdreef 2, 2333 ZA, Leiden, The Netherlands
| | - C F M Sier
- Department of Surgery, Leiden University Medical Center, Albinusdreef 2, 2333 ZA, Leiden, The Netherlands. .,Percuros BV, Leiden, The Netherlands.
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Improved positron emission tomography imaging of glioblastoma cancer using novel 68Ga-labeled peptides targeting the urokinase-type plasminogen activator receptor (uPAR). Amino Acids 2017; 49:1089-1100. [PMID: 28316028 DOI: 10.1007/s00726-017-2407-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2017] [Accepted: 02/28/2017] [Indexed: 10/19/2022]
Abstract
The urokinase-type plasminogen activator receptor (uPAR) is overexpressed in several cancers including glioblastoma (GBM) and is an established biomarker for metastatic potential. The uPAR-targeting peptide AE105-NH2 (Ac-Asp-Cha-Phe-(D)Ser-(D)Arg-Tyr-Leu-Trp-Ser-CONH2) is a promising candidate for non-invasive positron emission tomography (PET) imaging of uPAR. Despite the optimal physical properties of 68Ga for peptide-based PET imaging, low tumor uptakes have previously been reported using 68Ga-labeled AE105-NH2-based tracers. In an attempt to optimize the tumor uptake, we developed three novel tracers with alkane (AOC) and polyethylene glycol (PEG) spacers inserted between AE105-NH2 and the radio metal chelator 2-(4,7-bis(carboxymethyl)-1,4,7-triazonan-1-yl)pentanedioic acid (NODAGA). The resulting tracers NODAGA-AOC-AE105-NH2, NODAGA-PEG3-AE105-NH2 and NODAGA-PEG8-AE105-NH2 were compared to the non-spacer version, NODAGA-AE105-NH2. Following radiolabeling with 68Ga, we evaluated the in vitro and in vivo performance in mice bearing subcutaneous tumors derived from the uPAR-expressing human GBM cell line U87MG. In vivo PET/CT imaging showed that introduction of PEG spacers more than doubled the in vivo tumor uptake after 1 h compared with the non-spacer version: 68Ga-NODAGA-PEG3-AE105-NH2 (2.08 ± 0.37%ID/g) and 68Ga-NODAGA-PEG8-AE105-NH2 (2.01 ± 0.22%ID/g) vs. 68Ga-NODAGA-AE105-NH2 (0.70 ± 0.40%ID/g), p < 0.05. In addition, 68Ga-NODAGA-PEG8-AE105-NH2 showed significantly higher (p < 0.05) tumor-to-background contrast (3.68 ± 0.23) than the other tracers. The specific tumor-targeting property of 68Ga-NODAGA-PEG8-AE105-NH2 was established by effectively blocking the tumor uptake with co-injection of unlabeled AE105-NH2 (1 h: unblocked 2.01 ± 0.22%ID/g vs. blocked 1.24 ± 0.09%ID/g, p < 0.05). Ex vivo biodistribution confirmed the improved tumor uptakes of the PEG-modified tracers. 68Ga-NODAGA-PEG8-AE105-NH2 is thus a promising candidate for human translation for PET imaging of GBM.
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