title: Different response of human glioma tumor-initiating cells to epidermal growth factor receptor kinase inhibitors.
abstract: Because a subpopulation of cancer stem cells (tumor-initiating cells, TICs) is believed to be responsible for the development, progression, and recurrence of many tumors, we evaluated the in vitro sensitivity of human glioma TICs to epidermal growth factor receptor (EGFR) kinase inhibitors (erlotinib and gefitinib) and possible molecular determinants for their effects. Cells isolated from seven glioblastomas (GBM 1-7) and grown using neural stem cell permissive conditions were characterized for in vivo tumorigenicity, expression of tumor stem cell markers (CD133, nestin), and multilineage differentiation properties, confirming that these cultures are enriched in TICs. TIC cultures were challenged with increasing concentrations of erlotinib and gefitinib, and their survival was evaluated after 1-4 days. In most cases, a time- and concentration-dependent cell death was observed, although GBM 2 was completely insensitive to both drugs, and GBM 7 was responsive only to the highest concentrations tested. Using a radioligand binding assay, we show that all GBM TICs express EGFR. Erlotinib and gefitinib inhibited EGFR and ERK1/2 phosphorylation/activation in all GBMs, irrespective of the antiproliferative response observed. However, under basal conditions GBM 2 showed a high Akt phosphorylation that was completely insensitive to both drugs, whereas GBM 7 was completely insensitive to gefitinib, and Akt inactivation occurred only for the highest erlotinib concentration tested, showing a precise relationship with the antiproliferative effects of the drug. Interestingly, in GBM 2, phosphatase and tensin homolog expression was significantly down-regulated, possibly accounting for the insensitivity to the drugs. In conclusion, glioma TICs are responsive to anti-EGFR drugs, but phosphatase and tensin homolog expression and Akt inhibition seem to be necessary for such effect.
authors.affiliation: Department of Translational Oncology, National Institute for Cancer Research, 16132 Genova, Italy.
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Griffero
authors.forename: Antonio
authors.initials: A
authors.lastname: Daga
authors.forename: Daniela
authors.initials: D
authors.lastname: Marubbi
authors.forename: Maria Cristina
authors.initials: MC
authors.lastname: Capra
authors.forename: Alice
authors.initials: A
authors.lastname: Melotti
authors.forename: Alessandra
authors.initials: A
authors.lastname: Pattarozzi
authors.forename: Monica
authors.initials: M
authors.lastname: Gatti
authors.forename: Adriana
authors.initials: A
authors.lastname: Bajetto
authors.forename: Carola
authors.initials: C
authors.lastname: Porcile
authors.forename: Federica
authors.initials: F
authors.lastname: Barbieri
authors.forename: Roberto E
authors.initials: RE
authors.lastname: Favoni
authors.forename: Michele
authors.initials: M
authors.lastname: Lo Casto
authors.forename: Gianluigi
authors.initials: G
authors.lastname: Zona
authors.forename: Renato
authors.initials: R
authors.lastname: Spaziante
authors.forename: Tullio
authors.initials: T
authors.lastname: Florio
authors.forename: Giorgio
authors.initials: G
authors.lastname: Corte
mesh_terms: D000368:Aged; D000818:Animals; D066246:ErbB Receptors / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000069347:Erlotinib Hydrochloride; D005260:Female; D000077156:Gefitinib; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D005910:Glioma / Q000188:drug therapy / Q000378:metabolism*; D006801:Humans; D008297:Male; D051379:Mice; D016688:Mice, Inbred NOD; D016513:Mice, SCID; D008840:Microfilament Proteins / Q000096:biosynthesis; D008875:Middle Aged; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D014411:Neoplastic Stem Cells / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D011799:Quinazolines / Q000494:pharmacology*; D000070876:Tensins; D013997:Time Factors; D014407:Tumor Cells, Cultured
chemical_list: D008840:Microfilament Proteins; D047428:Protein Kinase Inhibitors; D011799:Quinazolines; D000070876:Tensins; D000069347:Erlotinib Hydrochloride; C512478:EGFR protein, human; D066246:ErbB Receptors; D051057:Proto-Oncogene Proteins c-akt; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D000077156:Gefitinib