Perazzoli, GloriaPrados, JoseOrtiz, RaulCaba, OctavioCabeza, LauraBerdasco, MariaGónzalez, BeatrizMelguizo, Consolación2017-03-242017-03-242015-10-08Perazzoli G, Prados J, Ortiz R, Caba O, Cabeza L, Berdasco M, et al. Temozolomide Resistance in Glioblastoma Cell Lines: Implication of MGMT, MMR, P-Glycoprotein and CD133 Expression. PLoS ONE. 2015; 10(10):e0140131http://hdl.handle.net/10668/2596Journal Article; Research Support, Non-U.S. Gov't;BACKGROUND The use of temozolomide (TMZ) has improved the prognosis for glioblastoma multiforme patients. However, TMZ resistance may be one of the main reasons why treatment fails. Although this resistance has frequently been linked to the expression of O6-methylguanine-DNA methyltransferase (MGMT) it seems that this enzyme is not the only molecular mechanism that may account for the appearance of drug resistance in glioblastoma multiforme patients as the mismatch repair (MMR) complex, P-glycoprotein, and/or the presence of cancer stem cells may also be implicated. METHODS Four nervous system tumor cell lines were used to analyze the modulation of MGMT expression and MGMT promoter methylation by TMZ treatment. Furthermore, 5-aza-2'-deoxycytidine was used to demethylate the MGMT promoter and O(6)-benzylguanine to block GMT activity. In addition, MMR complex and P-glycoprotein expression were studied before and after TMZ exposure and correlated with MGMT expression. Finally, the effect of TMZ exposure on CD133 expression was analyzed. RESULTS Our results showed two clearly differentiated groups of tumor cells characterized by low (A172 and LN229) and high (SF268 and SK-N-SH) basal MGMT expression. Interestingly, cell lines with no MGMT expression and low TMZ IC50 showed a high MMR complex expression, whereas cell lines with high MGMT expression and high TMZ IC50 did not express the MMR complex. In addition, modulation of MGMT expression in A172 and LN229 cell lines was accompanied by a significant increase in the TMZ IC50, whereas no differences were observed in SF268 and SK-N-SH cell lines. In contrast, P-glycoprotein and CD133 was found to be unrelated to TMZ resistance in these cell lines. CONCLUSIONS These results may be relevant in understanding the phenomenon of TMZ resistance, especially in glioblastoma multiforme patients laking MGMT expression, and may also aid in the design of new therapeutic strategies to improve the efficacy of TMZ in glioblastoma multiforme patients.enAntineoplásicos alquilantesAzacitidinaLínea celular tumoralMetilación de ADNMetilasas de modificación del ADNEnzimas reparadoras del ADNTumor Suppressor ProteinsDacarbazinaResistencia a antineoplásicosEpigénesis genéticaExpresión génicaRegulación neoplásica de la expresión génicaGlicoproteínasGuaninaConcentración 50 inhibidoraGlicoproteína PPéptidosRegiones promotoras genéticasProteínas supresoras de tumorAntígenos CDRegiones promotoras genéticasMedical Subject Headings::Chemicals and Drugs::Chemical Actions and Uses::Pharmacologic Actions::Therapeutic Uses::Antineoplastic Agents::Antineoplastic Agents, AlkylatingMedical Subject Headings::Chemicals and Drugs::Organic Chemicals::Aza Compounds::AzacitidineMedical Subject Headings::Anatomy::Cells::Cells, Cultured::Cell Line::Cell Line, TumorMedical Subject Headings::Phenomena and Processes::Chemical Phenomena::Biochemical Phenomena::Biochemical Processes::DNA MethylationMedical Subject Headings::Chemicals and Drugs::Enzymes and Coenzymes::Enzymes::DNA Restriction-Modification Enzymes::DNA Modification MethylasesMedical Subject Headings::Chemicals and Drugs::Enzymes and Coenzymes::Enzymes::DNA Repair EnzymesMedical Subject Headings::Chemicals and Drugs::Organic Chemicals::Triazenes::DacarbazineMedical Subject Headings::Phenomena and Processes::Physiological Phenomena::Pharmacological Phenomena::Drug Resistance::Drug Resistance, NeoplasmMedical Subject Headings::Phenomena and Processes::Genetic Phenomena::Genetic Processes::Gene Expression Regulation::Epigenesis, GeneticMedical Subject Headings::Phenomena and Processes::Genetic Phenomena::Genetic Processes::Gene ExpressionMedical Subject Headings::Phenomena and Processes::Genetic Phenomena::Genetic Processes::Gene Expression Regulation::Gene Expression Regulation, NeoplasticMedical Subject Headings::Diseases::Neoplasms::Neoplasms by Histologic Type::Neoplasms, Germ Cell and Embryonal::Neuroectodermal Tumors::Neoplasms, Neuroepithelial::Glioma::Astrocytoma::GlioblastomaMedical Subject Headings::Chemicals and Drugs::Carbohydrates::Glycoconjugates::GlycoproteinsMedical Subject Headings::Chemicals and Drugs::Heterocyclic Compounds::Heterocyclic Compounds, 2-Ring::Purines::Purinones::Hypoxanthines::GuanineMedical Subject Headings::Organisms::Eukaryota::Animals::Chordata::Vertebrates::Mammals::Primates::Haplorhini::Catarrhini::Hominidae::HumansMedical Subject Headings::Analytical, Diagnostic and Therapeutic Techniques and Equipment::Investigative Techniques::Toxicity Tests::Inhibitory Concentration 50Medical Subject Headings::Chemicals and Drugs::Amino Acids, Peptides, and Proteins::Proteins::Carrier Proteins::Membrane Transport Proteins::ATP-Binding Cassette Transporters::P-GlycoproteinsMedical Subject Headings::Chemicals and Drugs::Amino Acids, Peptides, and Proteins::PeptidesMedical Subject Headings::Chemicals and Drugs::Amino Acids, Peptides, and Proteins::Proteins::Neoplasm Proteins::Tumor Suppressor ProteinsMedical Subject Headings::Chemicals and Drugs::Biological Factors::Biological Markers::Antigens, Differentiation::Antigens, CDMedical Subject Headings::Phenomena and Processes::Chemical Phenomena::Biochemical Phenomena::Molecular Structure::Base Sequence::Regulatory Sequences, Nucleic Acid::Promoter Regions, Geneticresearch article26447477open access10.1371/journal.pone.01401311932-6203PMC4598115