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- Ahlgren, Sara, et al.
(författare)
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Targeting of HER2-expressing tumors with a site-specifically 99mTc-labeled recombinant affibody molecule, ZHER2:2395, with C-terminally engineered cysteine
- 2009
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Ingår i: Journal of Nuclear Medicine. - : Society of Nuclear Medicine. - 0161-5505 .- 1535-5667 .- 2159-662X. ; 50:5, s. 781-789
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Tidskriftsartikel (refereegranskat)abstract
- The detection of human epidermal growth factor receptor type 2 (HER2) expression in malignant tumors provides important information influencing patient management. Radionuclide in vivo imaging of HER2 may permit the detection of HER2 in both primary tumors and metastases by a single noninvasive procedure. Small (7 kDa) high-affinity anti-HER2 Affibody molecules may be suitable tracers for SPECT visualization of HER2-expressing tumors. The use of generator-produced (99m)Tc as a label would facilitate the prompt translation of anti-HER2 Affibody molecules into use in clinics. METHODS: A C-terminal cysteine was introduced into the Affibody molecule Z(HER2:342) to enable site-specific labeling with (99m)Tc. Two recombinant variants, His(6)-Z(HER2:342)-Cys (dissociation constant [K(D)], 29 pM) and Z(HER2:2395)-Cys, lacking a His tag (K(D), 27 pM), were labeled with (99m)Tc in yields exceeding 90%. The binding specificity and the cellular processing of Affibody molecules were studied in vitro. Biodistribution and gamma-camera imaging studies were performed in mice bearing HER2-expressing xenografts. RESULTS: (99m)Tc-His(6)-Z(HER2:342)-Cys was capable of targeting HER2-expressing SKOV-3 xenografts in SCID mice, but the liver radioactivity uptake was high. A series of comparative biodistribution experiments indicated that the presence of the His tag caused elevated accumulation in the liver. (99m)Tc-Z(HER2:2395)-Cys, not containing a His tag, showed low uptake in the liver and high and specific uptake in HER2-expressing xenografts. Four hours after injection, the radioactivity uptake values (percentage of injected activity per gram of tissue [%IA/g]) were 6.9 +/- 2.5 (mean +/- SD) %IA/g in LS174T xenografts (moderate level of HER2 expression) and 15 +/- 3 %IA/g in SKOV-3 xenografts (high level of HER2 expression). The corresponding tumor-to-blood ratios were 88 +/- 24 and 121 +/- 24, respectively. Both LS174T and SKOV-3 xenografts were clearly visualized with a clinical gamma-camera 1 h after injection of (99m)Tc-Z(HER2:2395)-Cys. CONCLUSION: The Affibody molecule (99m)Tc-Z(HER2:2395)-Cys is a promising tracer for SPECT visualization of HER2-expressing tumors.
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| 2. |
- Tran, Thuy A., 1980-, et al.
(författare)
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Design, synthesis and biological evaluation of a multifunctional HER2-specific Affibody molecule for molecular imaging
- 2009
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Ingår i: European Journal of Nuclear Medicine and Molecular Imaging. - : Springer Science and Business Media LLC. - 1619-7070 .- 1619-7089. ; 36:11, s. 1864-1873
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: The purpose of this study was to design and evaluate a novel platform for labelling of Affibody molecules, enabling for both recombinant and synthetic production and for site-specific labelling with 99mTc or trivalent radiometals. Methods: The HER2-specific Affibody molecule PEP05352 was made by peptide synthesis. The chelator sequence SECG (serine-glutamic acid-cysteine-glycine) was anchored on the C-terminal to allow 99mTc-labelling. The cysteine can alternatively serve as a conjugation site of the chelator DOTA for indium-labelling. The resulting 99mTc- and 111In-labelled Affibody molecules were evaluated both in vitro and in vivo. Results: Both conjugates retained their capacity to bind to HER2 receptors in vitro and in vivo. The tumour-to-blood ratio in LS174T xenografts was 30 at 4 h p.i. for both conjugates. Biodistribution data showed that 99mTc-labelled Affibody molecule had 4-fold lower kidney accumulation compared with 111In-labelled Affibody molecule while the accumulation in other organs was similar. Gamma-camera imaging of the conjugates could clearly visualise the tumours 4 h after injection. Conclusions: Incorporation of C-terminal SECG sequence in Affibody molecules provides a general multifunctional platform for site-specific labelling with different nuclides (technetium, indium, gallium, cobalt, or yttrium) and for a flexible production (chemical synthesis or recombinant).
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