title: Cyclopamine cooperates with EGFR inhibition to deplete stem-like cancer cells in glioblastoma-derived spheroid cultures.
abstract: Putative cancer stem cells have been identified in glioblastoma (GBM), associated with resistance to conventional therapies. Overcoming this resistance is a major challenge to manage this deadly brain tumor. Epidermal growth factor receptor (EGFR) is commonly amplified, over-expressed, and/or mutated in GBM, making it a compelling target for therapy. This study investigates the behavior of 3 primary neurosphere (NS) cell lines and their adherent counterparts originated from human GBM resections, when treated with EGFR-tyrosine kinase inhibitor erlotinib, associated or not with cyclopamine, a hedgehog pathway inhibitor. Adherent cells cultured in the presence of serum expressed the glial fibrillary acidic protein, whereas NS-forming cells cultured in serum-free medium expressed CD133, nestin, and Oct-4, markers of neural stem and progenitor cells. For the 3 adherent cell lines, erlotinib has a moderate effect (50% inhibitory concentration [IC50], >10 µM). Conversely, erlotinib induced a strong cell growth inhibition (IC50, <1 µM) on NS-forming cells, related to the EGFR gene amplification and EGFR protein expression. A short exposure to erlotinib reduced nestin-positive cell proliferation, but NS-initiating activity and self-renewal were not altered. EGFR pathway seems essential for GBM progenitor cell proliferation but dispensable for cancer stem-like cell self-renewal. Inhibition of hedgehog pathway with cyclopamine was evaluated in association with erlotinib on NS growth. Although each drug separately had no effect on sphere initiation, their combination significantly decreased the sphere number (P < .001). Our findings show synergic efficiency for erlotinib-cyclopamine association and provide a suitable in vitro model to explore drug combinations on GBM cells.
authors.affiliation: EA 2406 Histology and Molecular Pathology of Tumors Laboratory, Léo Saignat Victor Segalen University, Bordeaux, France. sandrine.eimer@chu-bordeaux.fr
authors.forename: Sandrine
authors.initials: S
authors.lastname: Eimer
authors.forename: Frédéric
authors.initials: F
authors.lastname: Dugay
authors.forename: Kelly
authors.initials: K
authors.lastname: Airiau
authors.forename: Tony
authors.initials: T
authors.lastname: Avril
authors.forename: Véronique
authors.initials: V
authors.lastname: Quillien
authors.forename: Marc-Antoine
authors.initials: MA
authors.lastname: Belaud-Rotureau
authors.forename: Francis
authors.initials: F
authors.lastname: Belloc
mesh_terms: D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D001932:Brain Neoplasms / Q000473:pathology*; D002454:Cell Differentiation / Q000187:drug effects*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D055028:Comparative Genomic Hybridization; D004357:Drug Synergism; D066246:ErbB Receptors / Q000037:antagonists & inhibitors; D000069347:Erlotinib Hydrochloride; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D005909:Glioblastoma / Q000473:pathology*; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D014411:Neoplastic Stem Cells / Q000187:drug effects* / Q000473:pathology; D011799:Quinazolines / Q000008:administration & dosage; D014704:Veratrum Alkaloids / Q000008:administration & dosage
chemical_list: D011799:Quinazolines; D014704:Veratrum Alkaloids; D000069347:Erlotinib Hydrochloride; C512478:EGFR protein, human; D066246:ErbB Receptors; C000541:cyclopamine