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Tumour Targeting Using Radiolabelled EGF Conjugates: Preclinical Studies
Uppsala University, Medicinska vetenskapsområdet, Faculty of Medicine, Department of Oncology, Radiology and Clinical Immunology, Biomedical Radiation Sciences.
2004 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Tumour targeted radiotherapy is an appealing approach for treatment of disseminated tumour cells. A targeting agent that specifically binds to a structure on tumour cells is then used to transport therapeutically relevant radionuclides. The epidermal growth factor receptor, EGFR, is overexpressed on tumour cells in several malignancies, e.g. highly malignant gliomas. In this thesis, three types of radiolabelled EGF-conjugates, aimed for targeting to EGFR-expressing tumour cells, were developed and studied: EGF-dextran labelled with 125I, EGF labelled with 211At, and two EGF-chelates, DTPA-EGF and Bz-DTPA-EGF, labelled with the radioactive metals 111In and 177Lu.

The targeting properties of radioiodinated EGF-dextran were first studied in cultured glioma cells. Radioiodine coupled to the dextran part of EGF-dextran was retained in cells appreciably longer than radioiodine coupled to EGF. This can give about 100 times increased radiation dose to tumour cells.

Targeting with 211At-EGF was investigated in combination with the tyrosine kinase inhibitor gefitinib (Iressa™, ZD1839). The uptake of 211At-EGF in EGFR-expressing tumour cells increased with increasing gefitinib concentrations. This was the case for both gefitinib-resistant and gefitinib-sensitive cell lines. The effect of the combined treatment on cell survival, however, differed between the cell lines in an unexpected way. In gefitinib resistant cells, combined treatment decreased cell survival approximately 3.5 times relative to 211At-EGF treatment alone. In gefitinib sensitive cells, however, combined treatment increased the cell survival (i.e. a protective effect).

The EGF-chelates studied ([111In]DTPA-EGF, [111In]Bz-DTPA-EGF and [177Lu]Bz-DTPA-EGF) all bound specifically with high affinity (Kd≈2 nM) to EGFR on cultured glioma cells. They were internalised after binding, and the cellular retention of radionuclides was high (60% remained after 45 h). A biodistribution study in mice showed that liver and kidneys accumulated a majority of the radioactivity. The EGF-chelates bound EGFR specifically also in vivo. A tumour-to-blood ratio of 25 was achieved in a preliminary study.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis , 2004. , p. 63
Series
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 0282-7476 ; 1341
Keywords [en]
Radiation sciences, targeting, tumour, EGF, radionuclide, gefitinib, Iressa, ZD1839, glioma, therapy, diagnostics
Keywords [sv]
Strålningsvetenskap
National Category
Radiology, Nuclear Medicine and Medical Imaging
Identifiers
URN: urn:nbn:se:uu:diva-4201ISBN: 91-554-5932-3 (print)OAI: oai:DiVA.org:uu-4201DiVA, id: diva2:164387
Public defence
2004-05-08, Rudbecksalen, Rudbecklaboratoriet, Dag Hammarskjölds väg 20, Uppsala, 09:15
Opponent
Supervisors
Available from: 2004-04-15 Created: 2004-04-15Bibliographically approved
List of papers
1.
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2. EGF and dextran-conjugated EGF induces differential phosphorylation of the EGF receptor
Open this publication in new window or tab >>EGF and dextran-conjugated EGF induces differential phosphorylation of the EGF receptor
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2002 (English)In: International Journal of Molecular Medicine, ISSN 1107-3756, E-ISSN 1791-244X, Vol. 10, no 5, p. 655-659Article in journal (Refereed) Published
Abstract [en]

Dextran-conjugated EGF (EGF-dextran) has a potential use for targeted radionuclide therapy of tumors that overexpress the epidermal growth factor receptor (EGFR). There are plans to treat both bladder carcinomas and malignant gliomas with local injections of radiolabeled EGF-dextran since these tumors often express high levels of EGFR. In this report we show that EGF and EGF-dextran differentially activate the EGFR. In the human glioma cell line U-343, activation of the serine/threonine kinases Erk and Akt is identical upon stimulation with EGF or EGF-dextran. However, the effect on phospholipase Cgamma1 (PLCgamma1) phosphorylation differs. In cells stimulated with EGF-dextran, the PLCgamma1 phosphorylation is lower than in cells stimulated with EGF. This observation could be explained by the fact that the PLCgamma1 association sites in the EGFR, tyrosine residues 992 and 1173, were phosphorylated to a lower degree when the receptor was stimulated with EGF-dextran as compared to with EGF.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:uu:diva-91593 (URN)12373311 (PubMedID)
Available from: 2004-04-15 Created: 2004-04-15 Last updated: 2017-12-14Bibliographically approved
3.
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4.
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5. [111In]Bz-DTPA-hEGF: Preparation and in vitro characterization of a potential anti-glioblastoma targeting agent
Open this publication in new window or tab >>[111In]Bz-DTPA-hEGF: Preparation and in vitro characterization of a potential anti-glioblastoma targeting agent
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2003 (English)In: Cancer Biotherapy and Radiopharmaceuticals, ISSN 1084-9785, E-ISSN 1557-8852, Vol. 18, no 4, p. 643-54Article in journal (Refereed) Published
Abstract [en]

The overexpression of epidermal growth factor receptors, EGFR, in glioblastomas is well documented. Hence, the EGFR can be used as target structure for a specific targeting of glioblastomas. Both radiolabeled anti-EGFR antibodies and the natural ligand EGF are candidate agents for targeting. However, EGF, which has a rather low molecular weight (6 kDa), might have better tissue penetration properties through both normal tissue and tumors in comparison with anti-EGF antibodies and their fragments. The aim of this study was to prepare and evaluate in vitro an EGF-based antiglioma conjugate with residualizing label. Human recombinant EGF (hEGF) was coupled to isothiocyanate-benzyl-DTPA. The conjugate was purified from unreacted chelator using solid-phase extraction and labeled with (111)In. The labeling yield was 87% +/- 7%. The label was reasonably stable; the transchelation of (111)In to serum proteins was about 5% after incubation at 37 degrees C during 24 hours. The obtained [(111)In]benzyl-DTPA-hEGF conjugate was characterized in vitro using the EGFR expressing glioma cell line U343MGaCl2:6. The binding affinity, internalization, and retention of the conjugate were studied. The conjugate had receptor specific binding and the radioactivity was quickly internalized. The intracellular retention of radioactivity after interrupted incubation with conjugate was 71% +/- 1% and 59% +/- 1.5% at 24 and 45 hours, respectively. The dissociation constant was estimated to 2.0 nM. The results indicate that [(111)In]benzyl-DTPA-hEGF is a potential candidate for targeting glioblastoma cells, possibly using locoregional injection.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:uu:diva-91596 (URN)10.1089/108497803322287736 (DOI)14503960 (PubMedID)
Available from: 2004-04-15 Created: 2004-04-15 Last updated: 2017-12-14Bibliographically approved
6.
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