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Dissertation zugänglich unter
URN: urn:nbn:de:gbv:18-50230
URL: http://ediss.sub.uni-hamburg.de/volltexte/2011/5023/

Radiation-Induced Activation of the Epidermal Growth Factor Receptor in Lung Cancer

Strahleninduzierte Aktivierung des Epidermalen Wachstumsfaktor-Rezeptors bei Lungenkarzinom

Sander, David

 Dokument 1.pdf (2.793 KB) 

SWD-Schlagwörter: Epidermaler Wachstumsfaktor-Rezeptor , Nicht-kleinzelliges Bronchialkarzinom , Strahlentherapie
Freie Schlagwörter (Deutsch): pEGFR , Strahlenresistenz , Strahleninduziert , Erlotinib
Freie Schlagwörter (Englisch): Radioresitance , K-RAS , Tarceva , Erlotinib
Basisklassifikation: 44.64 , 44.81 , 44.97
Institut: Medizin
DDC-Sachgruppe: Medizin, Gesundheit
Dokumentart: Dissertation
Hauptberichter: Dahm-Daphi, Jochen (Prof. Dr.)
Sprache: Englisch
Tag der mündlichen Prüfung: 25.01.2011
Erstellungsjahr: 2010
Publikationsdatum: 01.03.2011
Kurzfassung auf Englisch: This thesis project studied the use of a KRAS mutation present in three NSCLC cell lines, A549, NCI-H460 and Calu-6, as a positive predictive marker for achieving radiosensitization by a combined treatment with the tyrosine kinase inhibitor (TKI) erlotinib followed by irradiation. After validating the method using the KRAS wild type PC-9 cell line, Western blots for phosphorylated EGFR were performed for the three cell lines. In A549 cells, Western blots revealed an early pEGFR signal 5 minutes after irradiation with 5 Gy, but within 1.5 and 3.5 hours after irradiation, no late pEGFR signal was present. In contrast, both the NCI-H460 and Calu-6 cell line did not show a pEGFR signal 5 minutes after irradiation with 5 Gy. In colony formation assays performed for A549, NCI-H460 and Calu-6 cell lines, radiosensitization by treatment with the TKI erlotinib prior to irradiation was only achieved in A549 cells, reaching a dose enhancement factor (DEF) of 1.4 at the 10% survival level. For NCI-H460 and Calu-6 cells, no radioenhancement was detected in colony formation assays. In addition, short-term proliferation assays of the three cell lines were conducted. While erlotinib alone compared to the untreated control had only a small impact on cell proliferation, the combined treatment of erlotinib followed by 2 Gy of irradiation showed a clear antiproliferative effect on the A549 cell line. Corresponding with the findings of the colony formation assays, the proliferation of NCI-H460 and Calu-6 cells was not significantly decreased by the combined treatment regime. Even though the KRAS mutant A549 cell line was radiosensitized in colony formation and proliferation assays, the other two KRAS mutant cell lines NCI-H460 and Calu-6 did not respond to EGFR inhibition. Taken together, the presence of a KRAS mutation in those three NSCLC cell lines was not predictive for cellular response to EGFR inhibition combined with irradiation. Therefore, a KRAS mutation present in NSCLC cell lines cannot be used as a general positive predictive marker for achieving radiosensitization with the TKI erlotinib.
Also, the presence of a KRAS mutation in A549 cells was not associated with a late phase pEGFR signal after irradiation, questioning whether a KRAS mutation always leads to an increased pEGFR signaling via ligand production. Furthermore, the experimental data showing that a pEGFR signaling within minutes after irradiation was only present in A549, but not in NCI-H460 and Calu-6 cell lines implies that irradiation-induced pEGFR might not be a universal phenomenon, but rather influenced by yet unknown cellular properties. The fact that an early pEGFR signaling was only present in A549 cells, which also was the only cell line to be radiosensitized by erlotinib, implies that the early generation of a pEGFR signal after irradiation might be important for cellular radioresistance and therefore being an important target for EGFR inhibitory strategies. While the conducted experiments demonstrated that the KRAS mutation present in the NSCLC cell lines A549, NCI-H460 and Calu-6 was not predictive for the cells response to erlotinib and irradiation treatment, the early pEGFR signaling after irradiation might be of predictive value. For future individualized therapies of NSCLC, further studies are needed to possibly find a cellular marker predicting the response to combined EGFR inhibition and irradiation, ultimately providing an easy and fast screening method of cancer patients to identify those who will benefit of adding EGFR inhibitors to their irradiation treatment regime.


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