title: EGFR signaling is differentially activated in patient-derived glioblastoma stem cells.
abstract: Evidence suggests that stem-like cells are responsible for initiation, maintenance and recurrence of solid tumors, including Glioblastoma Multiforme (GBM). GBM is an intractable, highly lethal tumor of the central nervous system. Although epidermal growth factor receptor (EGFR) is highly expressed in many GBMs, anti-EGFR therapies have been unsuccessful as treatment. Few studies have examined EGFR activation in GBM stem cells (GSCs) to determine if patient-specific GSCs are amenable to anti-EGFR therapy pre-clinically. We hypothesized that EGFR activation in GSCs varied between patients and was an important determinant of responsiveness to anti-EGFR therapy. Cell cycle and apoptosis analysis was performed on tumor-spheres by immuncytochemistry in the presence and absence of the AG1478. Second messenger pathways operative in these processes were elucidated by immunoblotting. EGFR activated AKT and inactivated GSK3beta in EGFR+/PTEN+ GSCs. AG1478 and erlotinib significantly decreased the total number of tumor-spheres that EGFR+/ PTEN+ GSCs generated and the rate of sphere formation. Inhibition of EGFR signaling by AG1478 increased GSC senescence and apoptosis, likely via inhibition of AKT and activation of GSK3beta. Sphere formation by EGFR-/ PTEN- GSCs was independent of EGF stimulation, but dependant on B27 growth supplement. Our data suggest that EGFR+/PTEN+ GSCs are susceptible to anti-EGFR therapy in vitro.
authors.affiliation: Laboratory for Translational Stem Cell Research, Weill Cornell Brain Tumor Center, Department of Neurological Surgery, Weill Cornell Medical College, New York, New York, 10065, USA.
authors.forename: Brian M
authors.initials: BM
authors.lastname: Howard
authors.forename: Demirkan B
authors.initials: DB
authors.lastname: Gursel
authors.forename: Anne-Marie
authors.initials: AM
authors.lastname: Bleau
authors.forename: Robel T
authors.initials: RT
authors.lastname: Beyene
authors.forename: Eric C
authors.initials: EC
authors.lastname: Holland
authors.forename: John A
authors.initials: JA
authors.lastname: Boockvar
mesh_terms: D045744:Cell Line, Tumor; D066246:ErbB Receptors / Q000037:antagonists & inhibitors / Q000502:physiology*; D000069347:Erlotinib Hydrochloride; D005909:Glioblastoma / Q000188:drug therapy / Q000473:pathology*; D038362:Glycogen Synthase Kinase 3 / Q000502:physiology; D000071679:Glycogen Synthase Kinase 3 beta; D006801:Humans; D014411:Neoplastic Stem Cells / Q000502:physiology*; D051059:PTEN Phosphohydrolase / Q000502:physiology; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D051057:Proto-Oncogene Proteins c-akt / Q000502:physiology; D011799:Quinazolines / Q000494:pharmacology; D015398:Signal Transduction / Q000502:physiology*; D020032:Tyrphostins / Q000494:pharmacology
chemical_list: D047428:Protein Kinase Inhibitors; D011799:Quinazolines; D020032:Tyrphostins; C101044:RTKI cpd; D000069347:Erlotinib Hydrochloride; D019869:Phosphatidylinositol 3-Kinases; D066246:ErbB Receptors; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; D051057:Proto-Oncogene Proteins c-akt; D038362:Glycogen Synthase Kinase 3; D051059:PTEN Phosphohydrolase; C494929:PTEN protein, human