title: Positron emission tomography imaging of endometrial cancer using engineered anti-EMP2 antibody fragments.
abstract: OBJECTIVE
  As imaging of the cell surface tetraspan protein epithelial membrane protein-2 (EMP2) expression in malignant tumors may provide important prognostic and predictive diagnostic information, the goal of this study is to determine if antibody fragments to EMP2 may be useful for imaging EMP2 positive tumors.
  
  
  METHODS
  The normal tissue distribution of EMP2 protein expression was evaluated by immunohistochemistry and found to be discretely expressed in both mouse and human tissues. To detect EMP2 in tumors, a recombinant human anti-EMP2 minibody (scFv-hinge-C(H)3 dimer; 80 kDa) was designed to recognize a common epitope in mice and humans and characterized. In human tumor cell lines, the antibody binding induced EMP2 internalization and degradation, prompting the need for a residualizing imaging strategy. Following conjugation to DOTA (1,4,7,10-tetraazacyclododecane-N,N',N',N'″-tetraacetic acid), the minibody was radiolabeled with (64)Cu (t                   (1/2) = 12.7 h) and evaluated in mice as a positron emission tomography (PET) imaging agent for human EMP2-expressing endometrial tumor xenografts.
  
  
  RESULTS
  The residualizing agent, (64)Cu-DOTA anti-EMP2 minibody, achieved high uptake in endometrial cancer xenografts overexpressing EMP2 (10.2 ± 2.6, percent injected dose per gram (%ID/g) ± SD) with moderate uptake in wild-type HEC1A tumors (6.0 ± 0.1). In both cases, precise tumor delineation was observed from the PET images. In contrast, low uptake was observed with anti-EMP2 minibodies in EMP2-negative tumors (1.9 ± 0.5).
  
  
  CONCLUSIONS
  This new immune-PET agent may be useful for preclinical assessment of anti-EMP2 targeting in vivo. It may also have value for imaging of tumor localization and therapeutic response in patients with EMP2-positive malignancies.
authors.affiliation: Department of Pathology and Laboratory Medicine, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA.
authors.forename: Maoyong
authors.initials: M
authors.lastname: Fu
authors.forename: Sarah
authors.initials: S
authors.lastname: Brewer
authors.forename: Tove
authors.initials: T
authors.lastname: Olafsen
authors.forename: Anna M
authors.initials: AM
authors.lastname: Wu
authors.forename: Lynn K
authors.initials: LK
authors.lastname: Gordon
authors.forename: Jonathan
authors.initials: J
authors.lastname: Said
authors.forename: Jonathan
authors.initials: J
authors.lastname: Braun
authors.forename: Madhuri
authors.initials: M
authors.lastname: Wadehra
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D045744:Cell Line, Tumor; D003301:Copper Radioisotopes; D016889:Endometrial Neoplasms / Q000000981:diagnostic imaging* / Q000378:metabolism; D005260:Female; D006801:Humans; D007135:Immunoglobulin Variable Region / Q000235:genetics / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000032:analysis / Q000037:antagonists & inhibitors / Q000276:immunology* / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D057054:Molecular Imaging / Q000379:methods*; D049268:Positron-Emission Tomography / Q000379:methods*; D015202:Protein Engineering; D014018:Tissue Distribution
chemical_list: D003301:Copper Radioisotopes; C113388:Emp2 protein, mouse; D007135:Immunoglobulin Variable Region; D008562:Membrane Glycoproteins