title: Combined EGFR and autophagy modulation impairs cell migration and enhances radiosensitivity in human glioblastoma cells.
abstract: Glioblastoma (GBM) remains the most aggressive and lethal brain tumor due to its molecular heterogeneity and high motility and invasion capabilities of its cells, resulting in high resistance to current standard treatments (surgery, followed by ionizing radiation combined with Temozolomide chemotherapy administration). Locus amplification, gene overexpression, and genetic mutations of epidermal growth factor receptor (EGFR) are hallmarks of GBM that can ectopically activate downstream signaling oncogenic cascades such as PI3K/Akt/mTOR pathway. Importantly, alteration of this pathway, involved also in the regulation of autophagy process, can improve radioresistance in GBM cells, thus promoting the aggressive phenotype of this tumor. In this work, the endogenous EGFR expression profile and autophagy were modulated to increase radiosensitivity behavior of human T98G and U373MG GBM cells. Our results primarily indicated that EGFR interfering induced radiosensitivity according to a decrease of the clonogenic capability of the investigated cells, and an effective reduction of the in vitro migratory features. Moreover, EGFR interfering resulted in an increase of Temozolomide (TMZ) cytotoxicity in T98G TMZ-resistant cells. In order to elucidate the involvement of the autophagy process as pro-death or pro-survival role in cells subjected to EGFR interfering, the key autophagic gene ATG7 was silenced, thereby producing a transient block of the autophagy process. This autophagy inhibition rescued clonogenic capability of irradiated and EGFR-silenced T98G cells, suggesting a pro-death autophagy contribution. To further confirm the functional interplay between EGFR and autophagy pathways, Rapamycin-mediated autophagy induction during EGFR modulation promoted further impairment of irradiated cells, in terms of clonogenic and migration capabilities. Taken together, these results might suggest a novel combined EGFR-autophagy modulation strategy, to overcome intrinsic GBM radioresistance, thus improving the efficacy of standard treatments. J. Cell. Physiol. 229: 1863-1873, 2014. © 2014 Wiley Periodicals, Inc.
authors.affiliation: Department of Biology and Biotechnology, University of Pavia, Pavia, Italy.
authors.forename: Silvia
authors.initials: S
authors.lastname: Palumbo
authors.forename: Paolo
authors.initials: P
authors.lastname: Tini
authors.forename: Marzia
authors.initials: M
authors.lastname: Toscano
authors.forename: Giulia
authors.initials: G
authors.lastname: Allavena
authors.forename: Francesca
authors.initials: F
authors.lastname: Angeletti
authors.forename: Federico
authors.initials: F
authors.lastname: Manai
authors.forename: Clelia
authors.initials: C
authors.lastname: Miracco
authors.forename: Sergio
authors.initials: S
authors.lastname: Comincini
authors.forename: Luigi
authors.initials: L
authors.lastname: Pirtoli
mesh_terms: D001343:Autophagy / Q000187:drug effects / Q000528:radiation effects; D000071193:Autophagy-Related Protein 7; D001932:Brain Neoplasms / Q000378:metabolism / Q000473:pathology*; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects / Q000528:radiation effects; D002999:Clone Cells; D003606:Dacarbazine / Q000031:analogs & derivatives / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm / Q000187:drug effects; D066246:ErbB Receptors / Q000378:metabolism*; D020868:Gene Silencing / Q000187:drug effects / Q000528:radiation effects; D005909:Glioblastoma / Q000378:metabolism* / Q000473:pathology*; D006801:Humans; D034741:RNA, Small Interfering / Q000378:metabolism; D011836:Radiation Tolerance / Q000187:drug effects / Q000528:radiation effects; D011839:Radiation, Ionizing; D020123:Sirolimus / Q000494:pharmacology; D000077204:Temozolomide; D014162:Transfection; D044764:Ubiquitin-Activating Enzymes / Q000235:genetics / Q000378:metabolism
chemical_list: D034741:RNA, Small Interfering; D003606:Dacarbazine; D066246:ErbB Receptors; C509349:ATG7 protein, human; D000071193:Autophagy-Related Protein 7; D044764:Ubiquitin-Activating Enzymes; D020123:Sirolimus; D000077204:Temozolomide