방사선의학 웹진

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Abstract

The epidermal growth factor receptor (EGFR) is a member of the erbB family of receptors and is overexpressed in many tumor types. A repebody is a newly designed nonantibody protein scaffold for tumor targeting that contains leucine-rich repeat modules. In this study, 3 64Cu-labeled anti-EGFR repebodies with different chelators were synthesized, and their biologic characteristics were assessed in cultured cells and tumor-bearing mice. Methods: Repebodies were synthesized with the chelators 2-(p-isothiocyanatobenzyl)-1,4,7-triazacyclononane-N,N',N,″-triacetic acid trihydrochloride ([p-SCN-Bn]-NOTA), 2,2',2″-(10-(2-(2,5-dioxopyrrolidin-1-yloxy)-2-oxoethyl)-1,4,7,10-tetraazacyclododecane-1,4,7-triyl) triacetic acid (DOTA-N-hydroxysuccinimide ester), or 1-(p-isothiocyanatobenzyl)diethylenetriamine pentaacetic acid trihydrochloride ([p-SCN-Bn]-DTPA) in 1.0 M NaHCO3 buffer (pH 9.2) for 24 h. Purified NOTA-, DOTA-, and DTPA-conjugated repebody were radiolabeled with 64Cu in 0.1 M NH4OAc buffer (pH 5.5). To compare the EGFR-binding affinities of the repebodies, cellular uptake studies were performed with the human non-small cell lung cancer cell line H1650 (high expression of EGFR) and the human colon adenocarcinoma cell line SW620 (low expression of EGFR). Biodistribution and small-animal PET imaging studies were performed using H1650 tumor-bearing mice. Results: Radiochemical yields of the 64Cu-labeled repebodies were approximately 70%-80%. Cellular uptake of the NOTA-, DOTA-, and DTPA-repebodies was over 4-fold higher in H1650 cells than in SW620 cells at 1 h. The 3 repebodies had accumulated specifically in H1650 tumor-bearing nude mice by 1 h after intravenous injection and were retained for over 24 h, as measured by the percentage injected dose per gram of tissue (%ID/g). Tumor uptake of all repebodies increased from 1 to 6 h (at 1 h, 6.28, 8.46, and 6.91 %ID/g for NOTA-, DOTA-, and DTPA-repebody, respectively; at 6 h, 9.4, 8.28, and 10.1 %ID/g, respectively). H1650 tumors were clearly visible after injection of each repebody, with high tumor-to-background ratios (at 1 h, 3.43, 4.89, and 2.38 for NOTA-, DOTA-, and DTPA-repebody, respectively; at 6 h, 3.05, 4.36, and 2.08; at 24 h, 3.81, 4.58, and 2.86). Conclusion: The 3 64Cu-repebody complexes demonstrated specific and rapid uptake in EGFR-expressing tumorswithin 1 h and may have potential as novel EGFR imaging agents for PET.

Author information

Pyo A1,2, Yun M1,3, Kim HS1, Kim TY4, Lee JJ4, Kim JY5, Lee S2, Kwon SY1, Bom HS1, Kim HS4, Kim DY1, Min JJ6.

1 Department of Nuclear Medicine, Chonnam National University Hwasun Hospital, Hwasun, Korea.
2 Department of Chemistry, Chonnam National University, Gwangju, Korea.
3 Chair for Biological Imaging, Technische Universitat München, Munich, Germany.
4 Department of Biological Sciences, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, Korea; and.
5 Division of RI-Convergence Research, Korea Institute of Radiological and Medical Sciences, Seoul, Korea.
6 Department of Nuclear Medicine, Chonnam National University Hwasun Hospital, Hwasun, Korea jjmin@jnu.ac.kr blueburr@gmail.com.