title: Poly(ADP-ribose) polymerase inhibitor increases growth inhibition and reduces G(2)/M cell accumulation induced by temozolomide in malignant glioma cells.
abstract: Temozolomide (TZM) is a novel methylating agent currently under investigation for treatment of recurrent high-grade gliomas. Although TZM generates a wide spectrum of methyl adducts, its cytotoxicity has been attributed to mismatch repair (MR)-mediated processing of O(6)-methylguanine:T mispairs. N3-methyladenine and N7-methylguanine adducts are promptly repaired by the base excision repair system, unless a poly(ADP-ribose) polymerase (PARP) inhibitor is combined to TZM. In this case, the repair process of N-methylpurines cannot be completed and the deriving DNA strand breaks contribute to cytotoxicity. In this study, we investigated the influence on cell growth and cell cycle of treatment with TZM + PARP inhibitor in glioma cells characterized by different susceptibility to TZM. The results indicated that PARP inhibitor increases growth inhibition induced by TZM in either p53-wild-type or p53-mutant glioblastoma cells, as early as 24 h after drug exposure. The enhancing effect exerted by PARP inhibitor was particularly evident in glioma cells characterized by a defective expression of MR, since these cells are tolerant to O(6)-methylguanine damage and show low sensitivity to TZM. In O(6)-alkylguanine-DNA alkyltransferase (OGAT)-deficient and MR-proficient tumor cells bearing wild-type p53, the drug combination markedly reduced cell accumulation in the G(2)/M phase of cell cycle and induction of the G(2) checkpoint regulator Chk1 kinase. In short-term cultures of glioma cells derived from surgical specimens, PARP inhibitor enhanced chemosensitivity to TZM and this effect was especially evident in OGAT-proficient tumors. Thus, a pharmacological strategy based on the interruption of N-methylpurine repair might represent a novel strategy to restore or increase glioma sensitivity to TZM.
authors.affiliation: Department of Neuroscience, University of Rome Tor Vergata, Rome, Italy.
authors.forename: Lucio
authors.initials: L
authors.lastname: Tentori
authors.forename: Ilaria
authors.initials: I
authors.lastname: Portarena
authors.forename: Francesco
authors.initials: F
authors.lastname: Torino
authors.forename: Massimo
authors.initials: M
authors.lastname: Scerrati
authors.forename: Pierluigi
authors.initials: P
authors.lastname: Navarra
authors.forename: Grazia
authors.initials: G
authors.lastname: Graziani
mesh_terms: D018906:Antineoplastic Agents, Alkylating / Q000494:pharmacology*; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology; D001549:Benzamides / Q000494:pharmacology*; D001932:Brain Neoplasms / Q000188:drug therapy* / Q000201:enzymology / Q000235:genetics; D018797:Cell Cycle Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D000071877:Checkpoint Kinase 1; D004260:DNA Repair / Q000187:drug effects / Q000235:genetics; D003606:Dacarbazine / Q000031:analogs & derivatives* / Q000494:pharmacology*; D015536:Down-Regulation / Q000187:drug effects / Q000235:genetics; D004347:Drug Interactions; D019008:Drug Resistance, Neoplasm / Q000235:genetics; D004359:Drug Therapy, Combination; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D016195:G2 Phase / Q000187:drug effects / Q000235:genetics; D005909:Glioblastoma / Q000188:drug therapy / Q000201:enzymology / Q000235:genetics; D005910:Glioma / Q000188:drug therapy* / Q000201:enzymology / Q000235:genetics; D006801:Humans; D008938:Mitosis / Q000187:drug effects / Q000235:genetics; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases; D011494:Protein Kinases / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D011506:Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D000077204:Temozolomide; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D015854:Up-Regulation / Q000187:drug effects / Q000235:genetics; D020687:cdc25 Phosphatases / Q000187:drug effects / Q000235:genetics / Q000378:metabolism
chemical_list: D018906:Antineoplastic Agents, Alkylating; D001549:Benzamides; D018797:Cell Cycle Proteins; D004791:Enzyme Inhibitors; D011506:Proteins; D016159:Tumor Suppressor Protein p53; D003606:Dacarbazine; C025160:3-aminobenzamide; C499320:PARP1 protein, human; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases; D011494:Protein Kinases; C000605867:CHEK1 protein, human; D000071877:Checkpoint Kinase 1; C517009:CDC25C protein, human; D020687:cdc25 Phosphatases; D000077204:Temozolomide