Epithelial-to-mesenchymal transition and c-myc expression are the determinants of cetuximab-induced enhancement of squamous cell carcinoma radioresponse.
OBJECTIVE
Radiation therapy cures malignant tumors of the head and neck region more effectively when it is combined with application of the anti-EGFR monoclonal antibody cetuximab. Despite the successes achieved, we still do not know how to select patients who will respond to this combination of anti-EGFR monoclonal antibody and radiation. This study was conducted to elucidate possible mechanisms which cause the combined treatment with cetuximab and irradiation to fail in some cases of squamous cell carcinomas.


METHODS
Mice bearing FaDu and A431 squamous cell carcinoma xenograft tumors were treated with cetuximab (total dose 3 mg, intraperitoneally), irradiation (10 Gy) or their combination at the same doses. Treatment was applied when tumors reached 8mm in size. To collect samples for further protein analysis (two-dimensional differential gel electrophoresis (2-D DIGE), mass spectrometry MALDI-TOF/TOF, Western blot analysis, and ELISA), mice from each group were sacrificed on the 8th day after the first injection of cetuximab. Other mice were subjected to tumor growth delay assay.


RESULTS
In FaDu xenografts, treatment with cetuximab alone was nearly as effective as cetuximab combined with ionizing radiation, whereas A431 tumors responded to the combined treatment with significantly enhanced delay in tumor growth. Tumors extracted from the untreated FaDu and A431 xenografts were analysed for protein expression, and 34 proteins that were differently expressed in the two tumor types were identified. The majority of these proteins are closely related to intratumoral angiogenesis, cell adhesion, motility, differentiation, epithelial-to-mesenchymal transition (EMT), c-myc signaling and DNA repair.


CONCLUSIONS
The failure of cetuximab to enhance radiation response in FaDu xenografts was associated with the initiation of the program of EMT and with c-myc up-regulation in the carcinoma cells. For this reason, c-myc and EMT-related proteins (E-cadherin, vimentin) may be considered as potential biomarkers to predict squamous cell carcinoma response after treatment with cetuximab in combination with radiation.
Skvortsova
Ira
I
Department of Therapeutic Radiology and Oncology, Innsbruck Medical University, Austria. Ira.Skvortsova@i-med.ac.at
Skvortsov
Sergej
S
Raju
Uma
U
Stasyk
Taras
T
Riesterer
Oliver
O
Schottdorf
Eva-Maria
EM
Popper
Bela-Andre
BA
Schiestl
Bernhard
B
Eichberger
Paul
P
Debbage
Paul
P
Neher
Andreas
A
Bonn
Guenther K
GK
Huber
Lukas A
LA
Milas
Luka
L
Lukas
Peter
P
D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology*; D061067:Antibodies, Monoclonal, Humanized; D015153:Blotting, Western; D015820:Cadherins / Q000378:metabolism; D002294:Carcinoma, Squamous Cell / Q000188:drug therapy* / Q000235:genetics / Q000532:radiotherapy*; D002455:Cell Division / Q000235:genetics; D045744:Cell Line, Tumor; D000068818:Cetuximab; D004195:Disease Models, Animal; D004797:Enzyme-Linked Immunosorbent Assay; D005786:Gene Expression Regulation / Q000187:drug effects / Q000528:radiation effects; D006258:Head and Neck Neoplasms / Q000188:drug therapy / Q000235:genetics / Q000532:radiotherapy; D008297:Male; D051379:Mice; D008819:Mice, Nude; D011836:Radiation Tolerance / Q000235:genetics; D011839:Radiation, Ionizing; D055291:Salivary alpha-Amylases / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction; D015854:Up-Regulation; D023041:Xenograft Model Antitumor Assays
D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D015820:Cadherins; C524799:Amy1 protein, mouse; D055291:Salivary alpha-Amylases; D000068818:Cetuximab