title: Glutathione depletion sensitizes cisplatin- and temozolomide-resistant glioma cells in vitro and in vivo.
abstract: Malignant glioma is a severe type of brain tumor with a poor prognosis and few options for therapy. The main chemotherapy protocol for this type of tumor is based on temozolomide (TMZ), albeit with limited success. Cisplatin is widely used to treat several types of tumor and, in association with TMZ, is also used to treat recurrent glioma. However, several mechanisms of cellular resistance to cisplatin restrict therapy efficiency. In that sense, enhanced DNA repair, high glutathione levels and functional p53 have a critical role on cisplatin resistance. In this work, we explored several mechanisms of cisplatin resistance in human glioma. We showed that cellular survival was independent of the p53 status of those cells. In addition, in a host-cell reactivation assay using cisplatin-treated plasmid, we did not detect any difference in DNA repair capacity. We demonstrated that cisplatin-treated U138MG cells suffered fewer DNA double-strand breaks and DNA platination. Interestingly, the resistant cells carried higher levels of intracellular glutathione. Thus, preincubation with the glutathione inhibitor buthionine sulfoximine (BSO) induced massive cell death, whereas N-acetyl cysteine, a precursor of glutathione synthesis, improved the resistance to cisplatin treatment. In addition, BSO sensitized glioma cells to TMZ alone or in combination with cisplatin. Furthermore, using an in vivo model the combination of BSO, cisplatin and TMZ activated the caspase 3-7 apoptotic pathway. Remarkably, the combined treatment did not lead to severe side effects, while causing a huge impact on tumor progression. In fact, we noted a remarkable threefold increase in survival rate compared with other treatment regimens. Thus, the intracellular glutathione concentration is a potential molecular marker for cisplatin resistance in glioma, and the use of glutathione inhibitors, such as BSO, in association with cisplatin and TMZ seems a promising approach for the therapy of such devastating tumors.
authors.affiliation: Department of Microbiology, Institute of Biomedical Sciences, University of São Paulao, Av. Prof. Lineu Prestes, 1374, São Paulo 05505-900, Brazil.
authors.forename: C R R
authors.initials: CR
authors.lastname: Rocha
authors.affiliation: Department of Microbiology, Institute of Biomedical Sciences, University of São Paulao, Av. Prof. Lineu Prestes, 1374, São Paulo 05505-900, Brazil.
authors.forename: C C M
authors.initials: CC
authors.lastname: Garcia
authors.affiliation: Department of Microbiology, Institute of Biomedical Sciences, University of São Paulao, Av. Prof. Lineu Prestes, 1374, São Paulo 05505-900, Brazil.
authors.forename: D B
authors.initials: DB
authors.lastname: Vieira
authors.affiliation: Department of Microbiology, Institute of Biomedical Sciences, University of São Paulao, Av. Prof. Lineu Prestes, 1374, São Paulo 05505-900, Brazil.
authors.forename: A
authors.initials: A
authors.lastname: Quinet
authors.affiliation: Department of Microbiology, Institute of Biomedical Sciences, University of São Paulao, Av. Prof. Lineu Prestes, 1374, São Paulo 05505-900, Brazil.
authors.forename: L C
authors.initials: LC
authors.lastname: de Andrade-Lima
authors.affiliation: Department of Microbiology, Institute of Biomedical Sciences, University of São Paulao, Av. Prof. Lineu Prestes, 1374, São Paulo 05505-900, Brazil.
authors.forename: V
authors.initials: V
authors.lastname: Munford
authors.affiliation: Department of Pharmacology, Institute of Biomedical Sciences, University of São Paulo, Av. Prof. Lineu Prestes, 1374, São Paulo 05508-900, Brazil.
authors.forename: J E
authors.initials: JE
authors.lastname: Belizário
authors.affiliation: Department of Microbiology, Institute of Biomedical Sciences, University of São Paulao, Av. Prof. Lineu Prestes, 1374, São Paulo 05505-900, Brazil.
authors.forename: C F M
authors.initials: CF
authors.lastname: Menck
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001932:Brain Neoplasms / Q000473:pathology*; D019328:Buthionine Sulfoximine / Q000494:pharmacology; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D002945:Cisplatin / Q000494:pharmacology*; D004249:DNA Damage; D004260:DNA Repair / Q000187:drug effects; D003606:Dacarbazine / Q000031:analogs & derivatives* / Q000494:pharmacology; D018450:Disease Progression; D019008:Drug Resistance, Neoplasm / Q000187:drug effects*; D005260:Female; D005910:Glioma / Q000473:pathology*; D005978:Glutathione / Q000172:deficiency*; D006801:Humans; D008819:Mice, Nude; D000077204:Temozolomide; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism
chemical_list: D016159:Tumor Suppressor Protein p53; D019328:Buthionine Sulfoximine; D003606:Dacarbazine; D005978:Glutathione; D002945:Cisplatin; D000077204:Temozolomide