Binding of cetuximab to the EGFRvIII deletion mutant and its biological consequences in malignant glioma cells.
OBJECTIVE
Despite the clinical use of cetuximab, a chimeric antibody against EGFR, little is known regarding its interaction with EGFRvIII, a frequently expressed deletion mutant of EGFR. Therefore, we investigated the interaction and the functional consequences of cetuximab treatment on glioma cells stably expressing EGFRvIII.


METHODS
The human glioma cell line U373 genetically modified to express EGFRvIII was used to measure the binding of cetuximab and its internalization using flow cytometry and confocal microscopy. Proliferation and cell survival were analyzed by cell growth and clonogenic survival assays.


RESULTS
Cetuximab is able to bind to EGFRvIII and causes an internalization of the receptor and decreases its expression levels. Furthermore, in contrast to EGF, cetuximab was able to activate EGFRvIII which was evidenced by multiple phosphorylation sites and its downstream signaling targets. Despite this activation, the growth rate and the radiosensitivity of the EGFRvIII-expressing glioma cells were not modulated.


CONCLUSIONS
Cetuximab binds to EGFRvIII and leads to the initial activation, internalization and subsequent downregulation of EGFRvIII, but it does not seem to modulate the proliferation or radiosensitivity of EGFRvIII-expressing glioma cells. Thus, approaches to treat EGFRvIII-expressing glioma cells should be evaluated more carefully.
Jutten
Barry
B
Maastricht Radiation Oncology (MaastRO) Lab, GROW-School for Oncology and Developmental Biology, University of Maastricht, Maastricht, The Netherlands. b.jutten@maastro.unimaas.nl
Dubois
Ludwig
L
Li
Younan
Y
Aerts
Hugo
H
Wouters
Bradly G
BG
Lambin
Philippe
P
Theys
Jan
J
Lammering
Guido
G
D000911:Antibodies, Monoclonal / Q000494:pharmacology*; D061067:Antibodies, Monoclonal, Humanized; D001665:Binding Sites / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D000068818:Cetuximab; D066246:ErbB Receptors / Q000187:drug effects* / Q000235:genetics*; D005434:Flow Cytometry; D017353:Gene Deletion; D015972:Gene Expression Regulation, Neoplastic; D005910:Glioma / Q000188:drug therapy / Q000235:genetics; D006801:Humans; D018613:Microscopy, Confocal; D011336:Probability; D015398:Signal Transduction / Q000187:drug effects; D018709:Statistics, Nonparametric; D014407:Tumor Cells, Cultured / Q000187:drug effects
D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; C410723:epidermal growth factor receptor VIII; D066246:ErbB Receptors; D000068818:Cetuximab