Imaging of EGFR expression in murine xenografts using site-specifically labelled anti-EGFR 111In-DOTA-ZEGFR:2377 Affibody molecule: aspect of the injected tracer amount
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Overexpression of epidermal growth factor receptor (EGFR) is a prognostic and predictive biomarker in a number of malignant tumours. Radionuclide molecular imaging of EGFR expression in cancer could influence patient management. However, EGFR expression in normal tissues might complicate in vivo imaging. The aim of this study was to evaluate if optimization of the injected protein dose might improve imaging of EGFR expression in tumours using a novel EGFR-targeting protein, the DOTA-ZEGFR:2377 Affibody molecule.
An anti-EGFR Affibody molecule, ZEGFR:2377, was labelled with 111In via the DOTA chelator site-specifically conjugated to a C-terminal cysteine. The affinity of DOTA-ZEGFR:2377 for murine and human EGFR was measured by surface plasmon resonance. The cellular processing of 111In-DOTA-ZEGFR:2377 was evaluated in vitro. The biodistribution of radiolabelled Affibody molecules injected in a broad range of injected Affibody protein doses was evaluated in mice bearing EGFR-expressing A431 xenografts.
Site-specific coupling of DOTA provided a uniform conjugate possessing equal affinity for human and murine EGFR. The internalization of 111In-DOTA-ZEGFR:2377 by A431 cells was slow. In vivo, the conjugate accumulated specifically in xenografts and in EGFR-expressing tissues. The curve representing the dependence of tumour uptake on the injected Affibody protein dose was bell-shaped. The highest specific radioactivity (lowest injected protein dose) provided a suboptimal tumour-to-blood ratio. The results of the biodistribution study were confirmed by γ-camera imaging.
The 111In-DOTA-ZEGFR:2377 Affibody molecule is a promising tracer for radionuclide molecular imaging of EGFR expression in malignant tumours. Careful optimization of protein dose is required for high-contrast imaging of EGFR expression in vivo.
KeywordsAffibody molecules EGFR Indium-111 Gamma-camera imaging
This study was supported by grants from the Swedish Cancer Society (Cancerfonden) and the Swedish Research Council (Vetenskapsrådet). We thank Veronika Eriksson and the staff of the animal facility at Rudbeck Laboratory for technical assistance.
The authors, Orlova Anna, Helena Wållberg and Vladimir Tolmachev had earlier, and Daniel Rosik, Anna Sjöberg, Monika Hansson, Anders Wennborg have currently an affiliation (employment) with Affibody AB, Bromma, Sweden, which holds the intellectual property rights and trademarks for Affibody molecules.
- 9.Bentzen SM, Atasoy BM, Daley FM, Dische S, Richman PI, Saunders MI, et al. Epidermal growth factor receptor expression in pretreatment biopsies from head and neck squamous cell carcinoma as a predictive factor for a benefit from accelerated radiation therapy in a randomized controlled trial. J Clin Oncol. 2005;23:5560–7.CrossRefPubMedGoogle Scholar
- 10.Giralt J, de las Heras M, Cerezo L, Eraso A, Hermosilla E, Velez D, et al. The expression of epidermal growth factor receptor results in a worse prognosis for patients with rectal cancer treated with preoperative radiotherapy: a multicenter, retrospective analysis. Radiother Oncol. 2005;74:101–8.CrossRefPubMedGoogle Scholar
- 12.Scartozzi M, Bearzi I, Berardi R, Mandolesi A, Fabris G, Cascinu S. Epidermal growth factor receptor (EGFR) status in primary colorectal tumors does not correlate with EGFR expression in related metastatic sites: implications for treatment with EGFR-targeted monoclonal antibodies. J Clin Oncol. 2004;22:4772–8.CrossRefPubMedGoogle Scholar
- 43.Wållberg H, Ahlgren S, Widström C, Orlova A. Evaluation of the radiocobalt-labeled [MMA-DOTA-Cys61]-ZHER2:2395-Cys Affibody molecule for targeting of HER2-expressing tumors. Mol Imaging Biol 2009. doi: 10.1007/s11307-009-0238-8.
- 44.ImClone Systems Incorporated. Cetuximab: epidermal growth factor receptor (EGFR) antibody, version 9.0. ImClone Investigator Brochure. New York: ImClone Systems, 2003.Google Scholar