title: PET Imaging of VEGFR-2 Expression in Lung Cancer with 64Cu-Labeled Ramucirumab.
abstract: Lung cancer accounts for 17% of cancer-related deaths worldwide, and most patients present with locally advanced or metastatic disease. Novel PET imaging agents for assessing vascular endothelial growth factor receptor-2 (VEGFR-2) expression can be used for detecting VEGFR-2-positive malignancies and subsequent monitoring of therapeutic response to VEGFR-2-targeted therapies. Here, we report the synthesis and characterization of an antibody-based imaging agent for PET imaging of VEGFR-2 expression in vivo.
  
  
  METHODS
  Ramucirumab (named RamAb), a fully humanized IgG1 monoclonal antibody, was conjugated to 2-S-(4-isothiocyanatobenzyl)-1,4,7-triazacyclononane-1,4,7-triacetic acid (p-SCN-Bn-NOTA) and labeled with (64)Cu. Flow cytometry analysis and microscopy studies were performed to compare the VEGFR-2 binding affinity of RamAb and NOTA-RamAb. PET imaging and biodistribution studies were performed in nude mice bearing HCC4006 and A549 xenograft tumors. Ex vivo histopathology was performed to elucidate the expression patterns of VEGFR-2 in different tissues and organs to validate in vivo results.
  
  
  RESULTS
  Flow cytometry examination revealed the specific binding capacity of fluorescein isothiocyanate-RamAb to VEGFR-2, and no difference in VEGFR-2 binding affinity was seen between RamAb and NOTA-RamAb. After being labeled with (64)Cu, PET imaging revealed specific and prominent uptake of (64)Cu-NOTA-RamAb in VEGFR-2-positive HCC4006 tumors (9.4 ± 0.5 percentage injected dose per gram at 48 h after injection; n = 4) and significantly lower uptake in VEGFR-2-negative A549 tumors (4.3 ± 0.2 percentage injected dose per gram at 48 h after injection; n = 3). Blocking experiments revealed significantly lower uptake in HCC4006 tumors, along with histology analysis, further confirming the VEGFR-2 specificity of (64)Cu-NOTA-RamAb.
  
  
  CONCLUSIONS
  This study provides initial evidence that (64)Cu-NOTA-RamAb can function as a PET imaging agent for visualizing VEGFR-2 expression in vivo, which may also find potential applications in monitoring the treatment response of VEGFR-2-targeted cancer therapy.
authors.affiliation: Department of Radiology, University of Wisconsin-Madison, Madison, Wisconsin.
authors.forename: Haiming
authors.initials: H
authors.lastname: Luo
authors.affiliation: Department of Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin; and.
authors.forename: Christopher G
authors.initials: CG
authors.lastname: England
authors.affiliation: Department of Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin; and.
authors.forename: Stephen A
authors.initials: SA
authors.lastname: Graves
authors.affiliation: Department of Radiology, University of Wisconsin-Madison, Madison, Wisconsin.
authors.forename: Haiyan
authors.initials: H
authors.lastname: Sun
authors.affiliation: University of Wisconsin Carbone Cancer Center, Madison, Wisconsin.
authors.forename: Glenn
authors.initials: G
authors.lastname: Liu
authors.affiliation: Department of Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin; and.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Nickles
authors.affiliation: Department of Radiology, University of Wisconsin-Madison, Madison, Wisconsin Department of Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin; and University of Wisconsin Carbone Cancer Center, Madison, Wisconsin wcai@uwhealth.org.
authors.forename: Weibo
authors.initials: W
authors.lastname: Cai
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000493:pharmacokinetics; D061067:Antibodies, Monoclonal, Humanized; D045744:Cell Line, Tumor; D003301:Copper Radioisotopes; D006571:Heterocyclic Compounds; D006573:Heterocyclic Compounds, 1-Ring; D006801:Humans; D007553:Isotope Labeling; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000378:metabolism*; D051379:Mice; D008819:Mice, Nude; D057054:Molecular Imaging; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D014018:Tissue Distribution; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000096:biosynthesis* / Q000235:genetics; D023041:Xenograft Model Antitumor Assays; D000096662:Ramucirumab
chemical_list: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D003301:Copper Radioisotopes; D006571:Heterocyclic Compounds; D006573:Heterocyclic Compounds, 1-Ring; D019275:Radiopharmaceuticals; D040301:Vascular Endothelial Growth Factor Receptor-2; D000096662:Ramucirumab; C048993:1,4,7-triazacyclononane-N,N',N''-triacetic acid; C000588866:KDR protein, human
keywords: 64Cu; molecular imaging; positron emission tomography (PET); ramucirumab; vascular endothelial growth factor receptor-2 (VEGFR-2)