| 1. |
- Haylock, Anna-Karin, et al.
(författare)
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In vivo characterization of the novel CD44v6-targeting Fab fragment AbD15179 for molecular imaging of squamous cell carcinoma : a dual-isotope study
- 2014
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Ingår i: EJNMMI Research. - 2191-219X. ; 4
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Patients with squamous cell carcinoma in the head and neck region (HNSCC) offer a diagnostic challenge due to difficulties to detect small tumours and metastases. Imaging methods available are not sufficient, and radio-immunodiagnostics could increase specificity and sensitivity of diagnostics. The objective of this study was to evaluate, for the first time, the in vivo properties of the radiolabelled CD44v6-targeting fragment AbD15179 and to assess its utility as a targeting agent for radio-immunodiagnostics of CD44v6-expressing tumours.METHODS: The fully human CD44v6-targeting Fab fragment AbD15179 was labelled with 111In or 125I, as models for radionuclides suitable for imaging with SPECT or PET. Species specificity, antigen specificity and internalization properties were first assessed in vitro. In vivo specificity and biodistribution were then evaluated in tumour-bearing mice using a dual-tumour and dual-isotope setup.RESULTS: Both species-specific and antigen-specific binding of the conjugates were demonstrated in vitro, with no detectable internalization. The in vivo studies demonstrated specific tumour binding and favourable tumour targeting properties for both conjugates, albeit with higher tumour uptake, slower tumour dissociation, higher tumour-to-blood ratio and higher CD44v6 sensitivity for the 111In-labelled fragment. In contrast, the 125I-Fab demonstrated more favourable tumour-to-organ ratios for liver, spleen and kidneys.CONCLUSIONS: We conclude that AbD15179 efficiently targets CD44v6-expressing squamous cell carcinoma xenografts, and particularly, the 111In-Fab displayed high and specific tumour uptake. CD44v6 emerges as a suitable target for radio-immunodiagnostics, and a fully human antibody fragment such as AbD15179 can enable further clinical imaging studies.
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| 2. |
- Cheng, Qing, et al.
(författare)
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Preclinical PET imaging of EGFR levels : pairing a targeting with a non-targeting Sel-tagged Affibody-based tracer to estimate the specific uptake
- 2016
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Ingår i: EJNMMI Research. - : Springer. - 2191-219X. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- Background: Though overexpression of epidermal growth factor receptor (EGFR) in several forms of cancer is considered to be an important prognostic biomarker related to poor prognosis, clear correlations between biomarker assays and patient management have been difficult to establish. Here, we utilize a targeting directly followed by a non-targeting tracer-based positron emission tomography (PET) method to examine some of the aspects of determining specific EGFR binding in tumors. Methods: The EGFR-binding Affibody molecule Z(EGFR:2377) and its size-matched non-binding control Z(Taq:3638) were recombinantly fused with a C-terminal selenocysteine-containing Sel-tag (Z(EGFR:2377)-ST and Z(Taq:3638)-ST). The proteins were site-specifically labeled with DyLight488 for flow cytometry and ex vivo tissue analyses or with C-11 for in vivo PET studies. Kinetic scans with the C-11-labeled proteins were performed in healthy mice and in mice bearing xenografts from human FaDu (squamous cell carcinoma) and A431 (epidermoid carcinoma) cell lines. Changes in tracer uptake in A431 xenografts over time were also monitored, followed by ex vivo proximity ligation assays (PLA) of EGFR expressions. Results: Flow cytometry and ex vivo tissue analyses confirmed EGFR targeting by ZE(GFR:2377)-ST-DyLight488. [Methyl-C-11]-labeled Z(EGFR:2377)-ST-CH3 and Z(Taq:3638)-ST-CH3 showed similar distributions in vivo, except for notably higher concentrations of the former in particularly the liver and the blood. [Methyl-C-11]-Z(EGFR:2377)-ST-CH3 successfully visualized FaDu and A431 xenografts with moderate and high EGFR expression levels, respectively. However, in FaDu tumors, the non-specific uptake was large and sometimes equally large, illustrating the importance of proper controls. In the A431 group observed longitudinally, non-specific uptake remained at same level over the observation period. Specific uptake increased with tumor size, but changes varied widely over time in individual tumors. Total (membranous and cytoplasmic) EGFR in excised sections increased with tumor growth. There was no positive correlation between total EGFR and specific tracer uptake, which, since Z(EGFR:2377) binds extracellularly and is slowly internalized, indicates a discordance between available membranous and total EGFR expression levels. Conclusions: Same-day in vivo dual tracer imaging enabled by the Sel-tag technology and C-11-labeling provides a method to non-invasively monitor membrane-localized EGFR as well as factors affecting non-specific uptake of the PET ligand.
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| 3. |
- Cheung, Pierre, et al.
(författare)
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Preclinical evaluation of Affibody molecule for PET imaging of human pancreatic islets derived from stem cells
- 2023
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Ingår i: EJNMMI Research. - : Springer Nature. - 2191-219X. ; 13:1
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Tidskriftsartikel (refereegranskat)abstract
- Background: Beta-cell replacement methods such as transplantation of isolated donor islets have been proposed as a curative treatment of type 1 diabetes, but widespread application is challenging due to shortages of donor tissue and the need for continuous immunosuppressive treatments. Stem-cell-derived islets have been suggested as an alternative source of beta cells, but face transplantation protocols optimization difficulties, mainly due to a lack of available methods and markers to directly monitor grafts survival, as well as their localization and function. Molecular imaging techniques and particularly positron emission tomography has been suggested as a tool for monitoring the fate of islets after clinical transplantation. The integral membrane protein DGCR2 has been demonstrated to be a potential pancreatic islet biomarker, with specific expression on insulin-positive human embryonic stem-cell-derived pancreatic progenitor cells. The candidate Affibody molecule ZDGCR2:AM106 was radiolabeled with fluorine-18 using a novel click chemistry-based approach. The resulting positron emission tomography tracer [18F]ZDGCR2:AM106 was evaluated for binding to recombinant human DGCR2 and cryosections of stem-cell-derived islets, as well as in vivo using an immune-deficient mouse model transplanted with stem-cell-derived islets. Biodistribution of the [18F]ZDGCR2:AM106 was also assessed in healthy rats and pigs. Results: [18F]ZDGCR2:AM106 was successfully synthesized with high radiochemical purity and yield via a pretargeting approach. [18F]ZDGCR2:AM106 retained binding to recombinant human DCGR2 as well as to cryosectioned stem-cell-derived islets, but in vivo binding to native pancreatic tissue in both rat and pig was low. However, in vivo uptake of [18F]ZDGCR2:AM106 in stem-cell-derived islets transplanted in the immunodeficient mice was observed, albeit only within the early imaging frames after injection of the radiotracer. Conclusion: Targeting of DGCR2 is a promising approach for in vivo detection of stem-cell-derived islets grafts by molecular imaging. The synthesis of [18F]ZDGCR2:AM106 was successfully performed via a pretargeting method to label a site-specific covalently bonded fluorine-18 to the Affibody molecule. However, the rapid washout of [18F]ZDGCR2:AM106 from the stem-cell-derived islets graft indicates that dissociation kinetics can be improved. Further studies using alternative binders of similar classes with improved binding potential are warranted.
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