<p>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 <sup>125</sup>I, EGF labelled with <sup>211</sup>At, and two EGF-chelates, DTPA-EGF and Bz-DTPA-EGF, labelled with the radioactive metals <sup>111</sup>In and <sup>177</sup>Lu. </p><p>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.</p><p>Targeting with <sup>211</sup>At-EGF was investigated in combination with the tyrosine kinase inhibitor gefitinib (Iressa™, ZD1839). The uptake of <sup>211</sup>At-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 <sup>211</sup>At-EGF treatment alone. In gefitinib sensitive cells, however, combined treatment increased the cell survival (i.e. a protective effect).</p><p>The EGF-chelates studied ([<sup>111</sup>In]DTPA-EGF, [<sup>111</sup>In]Bz-DTPA-EGF and [<sup>177</sup>Lu]Bz-DTPA-EGF) all bound specifically with high affinity (K<sub>d</sub>≈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 <i>in vivo</i>. A tumour-to-blood ratio of 25 was achieved in a preliminary study.</p>
| Identifer | oai:union.ndltd.org:UPSALLA/oai:DiVA.org:uu-4201 |
| Date | January 2004 |
| Creators | Sundberg, Åsa Liljegren |
| Publisher | Uppsala University, Biomedical Radiation Sciences, Uppsala : Acta Universitatis Upsaliensis |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Doctoral thesis, comprehensive summary, text |
| Relation | Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, 0282-7476 ; 1341 |
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