title: Anti-MET immunoPET for non-small cell lung cancer using novel fully human antibody fragments.
abstract: MET, the receptor of hepatocyte growth factor, plays important roles in tumorigenesis and drug resistance in numerous cancers, including non-small cell lung cancer (NSCLC). As increasing numbers of MET inhibitors are being developed for clinical applications, antibody fragment-based immunopositron emission tomography (immunoPET) has the potential to rapidly quantify in vivo MET expression levels for drug response evaluation and patient stratification for these targeted therapies. Here, fully human single-chain variable fragments (scFvs) isolated from a phage display library were reformatted into bivalent cys-diabodies (scFv-cys dimers) with affinities to MET ranging from 0.7 to 5.1 nmol/L. The candidate with the highest affinity, H2, was radiolabeled with (89)Zr for immunoPET studies targeting NSCLC xenografts: low MET-expressing Hcc827 and the gefitinib-resistant Hcc827-GR6 with 4-fold MET overexpression. ImmunoPET at as early as 4 hours after injection produced high-contrast images, and ex vivo biodistribution analysis at 20 hours after injection showed about 2-fold difference in tracer uptake levels between the parental and resistant tumors (P < 0.01). Further immunoPET studies using a larger fragment, the H2 minibody (scFv-CH3 dimer), produced similar results at later time points. Two of the antibody clones (H2 and H5) showed in vitro growth inhibitory effects on MET-dependent gefitinib-resistant cell lines, whereas no effects were observed on resistant lines lacking MET activation. In conclusion, these fully human antibody fragments inhibit MET-dependent cancer cells and enable rapid immunoPET imaging to assess MET expression levels, showing potential for both therapeutic and diagnostic applications.
authors.affiliation: Department of Molecular and Medical Pharmacology, Crump Institute for Molecular Imaging, David Geffen School of Medicine at UCLA, Los Angeles, California.
authors.forename: Keyu
authors.initials: K
authors.lastname: Li
authors.affiliation: Department of Molecular and Medical Pharmacology, Crump Institute for Molecular Imaging, David Geffen School of Medicine at UCLA, Los Angeles, California.
authors.forename: Richard
authors.initials: R
authors.lastname: Tavaré
authors.affiliation: Department of Molecular and Medical Pharmacology, Crump Institute for Molecular Imaging, David Geffen School of Medicine at UCLA, Los Angeles, California.
authors.forename: Kirstin A
authors.initials: KA
authors.lastname: Zettlitz
authors.affiliation: Center for Applied Molecular Medicine, Keck School of Medicine, University of Southern California, Los Angeles, California.
authors.forename: Shannon M
authors.initials: SM
authors.lastname: Mumenthaler
authors.affiliation: Center for Applied Molecular Medicine, Keck School of Medicine, University of Southern California, Los Angeles, California. Department of Radiology, School of Medicine, Stanford University, Stanford, California.
authors.forename: Parag
authors.initials: P
authors.lastname: Mallick
authors.affiliation: Department of Anesthesia, University of California, San Francisco, San Francisco General Hospital, San Francisco, California.
authors.forename: Yu
authors.initials: Y
authors.lastname: Zhou
authors.affiliation: Department of Anesthesia, University of California, San Francisco, San Francisco General Hospital, San Francisco, California.
authors.forename: James D
authors.initials: JD
authors.lastname: Marks
authors.affiliation: Department of Molecular and Medical Pharmacology, Crump Institute for Molecular Imaging, David Geffen School of Medicine at UCLA, Los Angeles, California. awu@mednet.ucla.edu.
authors.forename: Anna M
authors.initials: AM
authors.lastname: Wu
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000737:chemistry / Q000276:immunology; D002289:Carcinoma, Non-Small-Cell Lung / Q000000981:diagnostic imaging* / Q000276:immunology* / Q000473:pathology; D002471:Cell Transformation, Neoplastic; D005260:Female; D064593:Heterografts; D006801:Humans; D007128:Immunoglobulin Fragments / Q000737:chemistry* / Q000276:immunology; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000276:immunology* / Q000473:pathology; D051379:Mice; D016513:Mice, SCID; D049268:Positron-Emission Tomography; D019859:Proto-Oncogene Proteins c-met / Q000276:immunology*; D011868:Radioisotopes / Q000737:chemistry; D019275:Radiopharmaceuticals / Q000737:chemistry*; D015040:Zirconium / Q000737:chemistry
chemical_list: D000911:Antibodies, Monoclonal; D007128:Immunoglobulin Fragments; D011868:Radioisotopes; D019275:Radiopharmaceuticals; D015040:Zirconium; C491743:MET protein, human; D019859:Proto-Oncogene Proteins c-met