title: ImmunoPET and Near-Infrared Fluorescence Imaging of Pancreatic Cancer with a Dual-Labeled Bispecific Antibody Fragment.
abstract: Dual-targeted imaging agents have shown improved targeting efficiencies in comparison to single-targeted entities. The purpose of this study was to quantitatively assess the tumor accumulation of a dual-labeled heterobifunctional imaging agent, targeting two overexpressed biomarkers in pancreatic cancer, using positron emission tomography (PET) and near-infrared fluorescence (NIRF) imaging modalities. A bispecific immunoconjugate (heterodimer) of CD105 and tissue factor (TF) Fab' antibody fragments was developed using click chemistry. The heterodimer was dual-labeled with a radionuclide (64Cu) and fluorescent dye. PET/NIRF imaging and biodistribution studies were performed in four-to-five week old nude athymic mice bearing BxPC-3 (CD105/TF+/+) or PANC-1 (CD105/TF-/-) tumor xenografts. A blocking study was conducted to investigate the specificity of the tracer. Ex vivo tissue staining was performed to compare TF/CD105 expression in tissues with PET tracer uptake to validate in vivo results. PET imaging of64Cu-NOTA-heterodimer-ZW800 in BxPC-3 tumor xenografts revealed enhanced tumor uptake (21.0 ± 3.4%ID/g; n = 4) compared to the homodimer of TRC-105 (9.6 ± 2.0%ID/g; n = 4; p < 0.01) and ALT-836 (7.6 ± 3.7%ID/g; n = 4; p < 0.01) at 24 h postinjection. Blocking studies revealed that tracer uptake in BxPC-3 tumors could be decreased by 4-fold with TF blocking and 2-fold with CD105 blocking. In the negative model (PANC-1), heterodimer uptake was significantly lower than that found in the BxPC-3 model (3.5 ± 1.1%ID/g; n = 4; p < 0.01). The specificity was confirmed by the successful blocking of CD105 or TF, which demonstrated that the dual targeting with64Cu-NOTA-heterodimer-ZW800 provided an improvement in overall tumor accumulation. Also, fluorescence imaging validated the PET imaging, allowing for clear delineation of the xenograft tumors. Dual-labeled heterodimeric imaging agents, like64Cu-NOTA-heterodimer-ZW800, may increase the overall tumor accumulation in comparison to single-targeted homodimers, leading to improved imaging of cancer and other related diseases.
authors.affiliation: Department of Radiology, University of Wisconsin-Madison , Madison, Wisconsin 53705, United States.
authors.forename: Haiming
authors.initials: H
authors.lastname: Luo
authors.affiliation: Department of Medical Physics, University of Wisconsin-Madison , Madison, Wisconsin 53705, United States.
authors.forename: Christopher G
authors.initials: CG
authors.lastname: England
authors.affiliation: Materials Science Program, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States.
authors.forename: Shreya
authors.initials: S
authors.lastname: Goel
authors.affiliation: Department of Medical Physics, University of Wisconsin-Madison , Madison, Wisconsin 53705, United States.
authors.forename: Stephen A
authors.initials: SA
authors.lastname: Graves
authors.affiliation: Department of Radiology, University of Wisconsin-Madison , Madison, Wisconsin 53705, United States.
authors.forename: Fanrong
authors.initials: F
authors.lastname: Ai
authors.affiliation: Altor BioScience Corporation , Miramar, Florida 33025, United States.
authors.forename: Bai
authors.initials: B
authors.lastname: Liu
authors.affiliation: TRACON Pharmaceuticals Incorporation , San Diego, California 92122, United States.
authors.forename: Charles P
authors.initials: CP
authors.lastname: Theuer
authors.affiliation: Altor BioScience Corporation , Miramar, Florida 33025, United States.
authors.forename: Hing C
authors.initials: HC
authors.lastname: Wong
authors.affiliation: Department of Medical Physics, University of Wisconsin-Madison , Madison, Wisconsin 53705, United States.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Nickles
authors.affiliation: Department of Radiology, University of Wisconsin-Madison , Madison, Wisconsin 53705, United States.|Department of Medical Physics, University of Wisconsin-Madison , Madison, Wisconsin 53705, United States.|Materials Science Program, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States.|University of Wisconsin Carbone Cancer Center , Madison, Wisconsin 53705, United States.
authors.forename: Weibo
authors.identifier: 0000-0003-4641-0833
authors.initials: W
authors.lastname: Cai
mesh_terms: D000818:Animals; D018033:Antibodies, Bispecific / Q000737:chemistry*; D045744:Cell Line, Tumor; D003301:Copper Radioisotopes / Q000737:chemistry*; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000737:chemistry*; D051379:Mice; D008819:Mice, Nude; D010190:Pancreatic Neoplasms / Q000000981:diagnostic imaging*; D049268:Positron-Emission Tomography / Q000379:methods*
chemical_list: D018033:Antibodies, Bispecific; D003301:Copper Radioisotopes; D007140:Immunoglobulin Fab Fragments
keywords: CD105; copper-64 (64Cu); dual-targeting; heterodimer; positron emission tomography (PET); tissue factor