title: Aptamer imaging with Cu-64 labeled AS1411: preliminary assessment in lung cancer.
abstract: BACKGROUND
  AS1411 is a 26-base guanine-rich oligonucleotide aptamer shown binding to surface nucleolin, a protein over-expressed in multiple cancer cells, thus AS1411 labeled with a PET isotope can be explored as a potential diagnostic imaging agent. Our objective was to perform preliminary biological characterization of (64)Cu-labeled AS1411 in vitro and in vivo.
  
  
  METHODS
  Four chelators (DOTA, CB-TE2A, DOTA-Bn and NOTA-Bn) were selected to label AS1411 with Cu-64. 185kBq (5μCi) of each tracer was incubated in each well with H460 cells at 37°C for 1, 3, 6, 12, 24 and 48h, respectively (n=4). For microPET/CT imaging, 7.4MBq (200μCi) of AS1411 labeled with either (64)Cu-DOTA or (64)Cu-CB-TE2A was I.V. injected and multiple scans were obtained at 1, 3, 6 and 24h post injection. Afterward in vivo biodistribution studies were performed.
  
  
  RESULTS
  Percent uptake of (64)Cu-DOTA-AS1411 and (64)Cu-CB-TE2A-AS1411 was significantly higher than that of (64)Cu-DOTA-Bn-AS1411 and (64)Cu-NOTA-Bn-AS1411. About 90% of uptake for (64)Cu-DOTA-AS1411 and (64)Cu-CB-TE2A-AS1411 was internalized into cells within 3h and the internalization process was completed before 24h. Both tracers demonstrated reasonable in vivo stability and high binding affinity to the cells. MicroPET imaging with (64)Cu-CB-TE2A-AS1411 showed clear tumor uptake at both legs from 1 to 24h post injection, whereas both tumors were undetectable for up to 24h with (64)Cu-DOTA-AS1411. In addition, (64)Cu-CB-TE2A-AS1411 had faster in vivo pharmacokinetics than (64)Cu-DOTA-AS1411 with lower liver uptake and higher tumor to background contrast.
  
  
  CONCLUSIONS
  CB-TE2A is a preferred chelator with higher tumor-to-background ratio, lower liver uptake and faster clearance than DOTA. Aptamer imaging with (64)Cu-CB-TE2A-AS1411 may be feasible for detecting lung cancer, if an appropriate chelator can be identified and further validation can be performed with a known control oligonucleotide. It may also be used as a companion diagnostic imaging agent for AS1411 in the treatment of cancer.
authors.affiliation: Department of Diagnostic Radiology, University of Louisville School of Medicine, Louisville, KY 40202, USA.
authors.forename: Junling
authors.initials: J
authors.lastname: Li
authors.affiliation: Department of Diagnostic Radiology, University of Louisville School of Medicine, Louisville, KY 40202, USA.
authors.forename: Huaiyu
authors.initials: H
authors.lastname: Zheng
authors.affiliation: Department of Medicine, University of Louisville School of Medicine, Louisville, KY 40202, USA; James Graham Brown Cancer Center, University of Louisville School of Medicine, Louisville, KY 40202, USA.
authors.forename: Paula J
authors.initials: PJ
authors.lastname: Bates
authors.affiliation: Department of Medicine, University of Louisville School of Medicine, Louisville, KY 40202, USA; James Graham Brown Cancer Center, University of Louisville School of Medicine, Louisville, KY 40202, USA.
authors.forename: Tariq
authors.initials: T
authors.lastname: Malik
authors.affiliation: Department of Diagnostic Radiology, University of Louisville School of Medicine, Louisville, KY 40202, USA.
authors.forename: Xiao-Feng
authors.initials: XF
authors.lastname: Li
authors.affiliation: Department of Medicine, University of Louisville School of Medicine, Louisville, KY 40202, USA; James Graham Brown Cancer Center, University of Louisville School of Medicine, Louisville, KY 40202, USA.
authors.forename: John O
authors.initials: JO
authors.lastname: Trent
authors.affiliation: Department of Diagnostic Radiology, University of Louisville School of Medicine, Louisville, KY 40202, USA. Electronic address: chin.ng@louisville.edu.
authors.forename: Chin K
authors.initials: CK
authors.lastname: Ng
mesh_terms: D000818:Animals; D052157:Aptamers, Nucleotide; D045744:Cell Line, Tumor; D003301:Copper Radioisotopes; D005260:Female; D006801:Humans; D007553:Isotope Labeling; D008175:Lung Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology*; D051379:Mice; D009838:Oligodeoxyribonucleotides / Q000378:metabolism / Q000493:pharmacokinetics; D049268:Positron-Emission Tomography / Q000379:methods*; D011854:Radiochemistry; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: C513936:AGRO 100; D052157:Aptamers, Nucleotide; D003301:Copper Radioisotopes; D009838:Oligodeoxyribonucleotides
keywords: AS1411; Aptamer; Chelators; Cu-64; Oligonucleotide; PET