title: The DNA damage/repair cascade in glioblastoma cell lines after chemotherapeutic agent treatment.
abstract: Therapeutic resistance in glioblastoma multiforme (GBM) has been linked to a subpopulation of cells with stem cell-like properties, the glioma stem cells (GSCs), responsible for cancer progression and recurrence. This study investigated the in vitro cytotoxicity of three chemotherapeutics, temozolomide (TMZ), doxorubicin (Dox) and paclitaxel (PTX) on glioma cell lines, by analyzing the molecular mechanisms leading to DNA repair and cell resistance, or to cell death. The drugs were tested on 16 GBM cell lines, grown as neurospheres (NS) or adherent cells (AC), by studying DNA damage occurrence by Comet assay, the expression by immunofluorescence and western blotting of checkpoint/repair molecules and apoptosis. The three drugs were able to provoke a genotoxic injury and to inhibit dose- and time-dependently cell proliferation, more evidently in AC than in NS. The first cell response to DNA damage was the activation of the damage sensors (p-ATM, p-53BP1, γ-H2AX), followed by repair effectors; the expression of checkpoint/repair molecules appeared higher in NS than in AC. The non-homologous repair pathway (NHEJ) seemed more involved than the homologous one (HR). Apoptosis occurred after long treatment times, but only a small percentage of cells in NS underwent death, even at high drug concentration, whereas most cells survived in a quiescent state and resumed proliferation after drug removal. In tumor specimens, checkpoint/repair proteins were constitutively expressed in GBMs, but not in low-grade gliomas.
authors.affiliation: Neuro-Bio-Oncology Center, Policlinico di Monza Foundation (Vercelli), I-13100 Vercelli, Italy.
authors.forename: Laura
authors.initials: L
authors.lastname: Annovazzi
authors.affiliation: Neuro-Bio-Oncology Center, Policlinico di Monza Foundation (Vercelli), I-13100 Vercelli, Italy.
authors.forename: Valentina
authors.initials: V
authors.lastname: Caldera
authors.affiliation: Neuro-Bio-Oncology Center, Policlinico di Monza Foundation (Vercelli), I-13100 Vercelli, Italy.
authors.forename: Marta
authors.initials: M
authors.lastname: Mellai
authors.affiliation: Department of Oncology, University of Turin, I-10126 Turin, Italy.
authors.forename: Chiara
authors.initials: C
authors.lastname: Riganti
authors.affiliation: Department of Drug Science and Technology, University of Turin, I-10125 Turin, Italy.
authors.forename: Luigi
authors.initials: L
authors.lastname: Battaglia
authors.affiliation: Department of Drug Science and Technology, University of Turin, I-10125 Turin, Italy.
authors.forename: Daniela
authors.initials: D
authors.lastname: Chirio
authors.affiliation: Department of Neurosurgery, CTO Hospital, Città della Salute e della Scienza, I-10126 Turin, Italy.
authors.forename: Antonio
authors.initials: A
authors.lastname: Melcarne
authors.affiliation: Neuro-Bio-Oncology Center, Policlinico di Monza Foundation (Vercelli), I-13100 Vercelli, Italy.
authors.forename: Davide
authors.initials: D
authors.lastname: Schiffer
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis; D001932:Brain Neoplasms / Q000188:drug therapy / Q000235:genetics*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D004249:DNA Damage / Q000187:drug effects; D004260:DNA Repair / Q000187:drug effects*; D004273:DNA, Neoplasm / Q000187:drug effects*; D003606:Dacarbazine / Q000031:analogs & derivatives / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004317:Doxorubicin / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm; D005909:Glioblastoma / Q000188:drug therapy / Q000235:genetics*; D006801:Humans; D017239:Paclitaxel / Q000494:pharmacology; D000077204:Temozolomide
chemical_list: D000970:Antineoplastic Agents; D004273:DNA, Neoplasm; D003606:Dacarbazine; D004317:Doxorubicin; D017239:Paclitaxel; D000077204:Temozolomide