Molecular Imaging and Biology

, Volume 16, Issue 4, pp 567–577 | Cite as

Characterization and Evaluation of 64Cu-Labeled A20FMDV2 Conjugates for Imaging the Integrin αvβ6

  • Lina Y. Hu
  • Nadine Bauer
  • Leah M. Knight
  • Zibo Li
  • Shuanglong Liu
  • Carolyn J. Anderson
  • Peter S. Conti
  • Julie L. Sutcliffe
Research Article

Abstract

Purpose

The integrin αvβ6 is overexpressed in a variety of aggressive cancers and serves as a prognosis marker. This study describes the conjugation, radiolabeling, and in vitro and in vivo evaluation of four chelators to determine the best candidate for 64Cu radiolabeling of A20FMDV2, an αvβ6 targeting peptide.

Procedures

Four chelators were conjugated onto PEG28-A20FMDV2 (1): 11-carboxymethyl-1,4,8,11-tetraazabicyclo[6.6.2]hexadecane-4-methanephosphonic acid (CB-TE1A1P), 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA), 1,4,7-triazacyclononane-1,4,7-triacetic acid (NOTA), and 4,4′-((3,6,10,13,16,19-hexazazbicyclo[6.6.6]ico-sane-1,8-diylbis(aza-nediyl))bis(methylene)dibenzoic acid (BaBaSar). All peptides were radiolabeled with 64Cu in ammonium acetate buffer at pH 6 and formulated to pH 7.2 in PBS for use. The radiotracers were evaluated using in vitro cell binding and internalization assays and serum stability assays. In vivo studies conducted include blocking, biodistribution, and small animal PET imaging. Autoradiography and histology were also conducted.

Results

All radiotracers were radiolabeled in good radiochemical purity (>95 %) under mild conditions (37–50 °C for 15 min) with high specific activity (0.58–0.60 Ci/μmol). All radiotracers demonstrated αvβ6-directed cell binding (>46 %) with similar internalization levels (>23 %). The radiotracers 64Cu-CB-TE1A1P-1 and 64Cu-BaBaSar-1 showed improved specificity for the αvβ6 positive tumor in vivo over 64Cu-DOTA-1 and 64Cu-NOTA-1 (+/− tumor uptake ratios—3.82 +/- 0.44, 3.82 ± 0.41, 2.58 ± 0.58, and 1.29 ± 0.14, respectively). Of the four radiotracers, 64Cu-NOTA-1 exhibited the highest liver uptake (10.83 ± 0.1 % ID/g at 4 h).

Conclusions

We have successfully conjugated, radiolabeled, and assessed the four chelates CB-TE1A1P, DOTA, NOTA, and BaBaSar both in vitro and in vivo. However, the data suggests no clear “best candidate” for the 64Cu-radiolabeling of A20FMDV2, but instead a trade-off between the different properties (e.g., stability, selectivity, pharmacokinetics, etc.) with no obvious effects of the individual chelators.

Key words

Integrin αvβ6 Copper-64 PET imaging 

Supplementary material

11307_2013_717_MOESM1_ESM.docx (2.5 mb)
ESM 1(DOCX 2531 kb)

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Copyright information

© World Molecular Imaging Society 2014

Authors and Affiliations

  • Lina Y. Hu
    • 1
  • Nadine Bauer
    • 1
  • Leah M. Knight
    • 1
  • Zibo Li
    • 2
  • Shuanglong Liu
    • 2
  • Carolyn J. Anderson
    • 3
  • Peter S. Conti
    • 2
  • Julie L. Sutcliffe
    • 1
    • 4
    • 5
  1. 1.Department of Biomedical EngineeringUniversity of California DavisDavisUSA
  2. 2.Department of RadiologyUniversity of Southern CaliforniaLos AngelesUSA
  3. 3.Department of RadiologyUniversity of PittsburghPittsburghUSA
  4. 4.Department of Internal Medicine, Division of Hematology/OncologyUniversity of California Davis, School of MedicineSacramentoUSA
  5. 5.Center for Molecular and Genomic ImagingUniversity of California DavisDavisUSA

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