title: Antibody-based PET of uPA/uPAR signaling with broad applicability for cancer imaging.
abstract: Mounting evidence suggests that the urokinase plasminogen activator (uPA) and its receptor (uPAR) play a central role in tumor progression. The goal of this study was to develop an 89Zr-labeled, antibody-based positron emission tomography (PET) tracer for quantitative imaging of the uPA/uPAR system. An anti-uPA monoclonal antibody (ATN-291) was conjugated with a deferoxamine (Df) derivative and subsequently labeled with 89Zr. Flow cytometry, microscopy studies, and competitive binding assays were conducted to validate the binding specificity of Df-ATN-291 against uPA. PET imaging with 89Zr-Df-ATN-291 was carried out in different tumors with distinct expression levels of uPA. Biodistribution, histology examination, and Western blotting were performed to correlate tumor uptake with uPA or uPAR expression. ATN-291 retained uPA binding affinity and specificity after Df conjugation. 89Zr-labeling of ATN-291 was achieved in good radiochemical yield and high specific activity. Serial PET imaging demonstrated that, in most tumors studied (except uPA- LNCaP), the uptake of 89Zr-Df-ATN-291 was higher compared to major organs at 120 h post-injection, providing excellent tumor contrast. The tumor-to-muscle ratio of 89Zr-Df-ATN-291 in U87MG was as high as 45.2 ± 9.0 at 120 h p.i. In vivo uPA specificity of 89Zr-Df-ATN-291 was confirmed by successful pharmacological blocking of tumor uptake with ATN-291 in U87MG tumors. Although the detailed mechanisms behind in vivo 89Zr-Df-ATN-291 tumor uptake remained to be further elucidated, quantitative PET imaging with 89Zr-Df-ATN-291 in tumors can facilitate oncologists to adopt more relevant cancer treatment planning.
authors.affiliation: Center for Molecular Imaging, Department of Radiology, University of Michigan, Ann Arbor, Michigan 48109, United States.|Jiangsu Key Laboratory of New Drug Research and Clinical Pharmacy, Xuzhou Medical University, Xuzhou, Jiangsu 221004, China.
authors.forename: Dongzhi
authors.initials: D
authors.lastname: Yang
authors.affiliation: Center for Nuclear Technologies, Technical University of Denmark, 4000 Roskilde, Denmark.|Department of Chemistry, Facility for Rare Isotope Beams, Michigan State University, East Lansing, Michigan 48824, United States.
authors.forename: Gregory W
authors.initials: GW
authors.lastname: Severin
authors.affiliation: Center for Molecular Imaging, Department of Radiology, University of Michigan, Ann Arbor, Michigan 48109, United States.|Department of Chemistry, Iona College, New Rochelle, New York 10801, United States.
authors.forename: Casey A
authors.initials: CA
authors.lastname: Dougherty
authors.affiliation: Center for Molecular Imaging, Department of Radiology, University of Michigan, Ann Arbor, Michigan 48109, United States.
authors.forename: Rachel
authors.initials: R
authors.lastname: Lombardi
authors.affiliation: Center for Molecular Imaging, Department of Radiology, University of Michigan, Ann Arbor, Michigan 48109, United States.
authors.forename: Daiqin
authors.initials: D
authors.lastname: Chen
authors.affiliation: Center for Molecular Imaging, Department of Radiology, University of Michigan, Ann Arbor, Michigan 48109, United States.
authors.forename: Marcian E
authors.initials: ME
authors.lastname: Van Dort
authors.affiliation: Department of Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin 53705, United States.
authors.forename: Todd E
authors.initials: TE
authors.lastname: Barnhart
authors.affiliation: Center for Molecular Imaging, Department of Radiology, University of Michigan, Ann Arbor, Michigan 48109, United States.
authors.forename: Brian D
authors.initials: BD
authors.lastname: Ross
authors.affiliation: Department of Pharmacology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611, United States.
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Mazar
authors.affiliation: Center for Molecular Imaging, Department of Radiology, University of Michigan, Ann Arbor, Michigan 48109, United States.
authors.forename: Hao
authors.initials: H
authors.lastname: Hong
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal; D015415:Biomarkers; D045744:Cell Line, Tumor; D004195:Disease Models, Animal; D005455:Fluorescent Antibody Technique; D064593:Heterografts; D006801:Humans; D051379:Mice; D057054:Molecular Imaging / Q000379:methods; D009369:Neoplasms / Q000000981:diagnostic imaging* / Q000378:metabolism* / Q000473:pathology; D049268:Positron-Emission Tomography / Q000379:methods; D011485:Protein Binding; D019275:Radiopharmaceuticals; D055293:Receptors, Urokinase Plasminogen Activator / Q000378:metabolism*; D014018:Tissue Distribution; D014568:Urokinase-Type Plasminogen Activator / Q000378:metabolism*
chemical_list: D000911:Antibodies, Monoclonal; D015415:Biomarkers; D019275:Radiopharmaceuticals; D055293:Receptors, Urokinase Plasminogen Activator; D014568:Urokinase-Type Plasminogen Activator
keywords: cancer biomarkers; immunoPET; quantitative analysis; uPAR; urokinase plasminogen activator (uPA)