TY - JOUR
T1 - Characterization and evaluation of 64Cu-labeled A20FMDV2 conjugates for imaging the integrin αvβ6
AU - Hu, Lina Y.
AU - Bauer, Nadine
AU - Knight, Leah M.
AU - Li, Zibo
AU - Liu, Shuanglong
AU - Anderson, Carolyn J.
AU - Conti, Peter S.
AU - Sutcliffe, Julie
PY - 2014
Y1 - 2014
N2 - 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 αvβ 6 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 αvβ 6-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.
AB - 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 αvβ 6 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 αvβ 6-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.
KW - Copper-64
KW - PET imaging
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U2 - 10.1007/s11307-013-0717-9
DO - 10.1007/s11307-013-0717-9
M3 - Article
C2 - 24448825
AN - SCOPUS:84904409812
VL - 16
SP - 567
EP - 577
JO - Molecular Imaging and Biology
JF - Molecular Imaging and Biology
SN - 1536-1632
IS - 4
ER -