title: Biochemical changes associated with a multidrug-resistant phenotype of a human glioma cell line with temozolomide-acquired resistance.
abstract: Temozolomide (TMZ) is a newly approved alkylating agent for the treatment of malignant gliomas. To investigate resistance mechanisms in a multidrug therapeutic approach, a TMZ-resistant human glioma cell line, SF188/TR, was established by stepwise exposure of human SF188 parental cells to TMZ for approximately 6 months. SF188/TR showed 6-fold resistance to TMZ and cross-resistance to a broad spectrum of other anticancer agents that included 3-5-fold resistance to melphalan (MEL), gemcitabine (GEM), paclitaxel (PAC), methotrexate (MTX), and doxorubicin (DOX), and 1.6-2-fold resistance to cisplatin (CDDP) and topotecan (TPT). Alkylguanine alkyltransferase (AGT) activity was increased significantly in the resistant cell line compared with the parental cell line (P<0.05), whereas no significant differences occurred in the cellular uptake of TMZ and PAC between resistant and parental cells. Depletion of AGT by O(6)-benzylguanine significantly increased the cytotoxicity of TMZ in both the sensitive and resistant cell lines, but did not influence the cytotoxicity of the other drugs tested. Treatment with TMZ caused SF188 cells to accumulate in S phase, whereas SF188/TR cells were unaffected. Expression of Bcl-2 family members in SF188/TR cells compared with SF188 cells indicated that the pro-apoptotic proteins (i.e. Bad, Bax, Bcl-X(S)) were reduced 2-4-fold in the resistant cell line, whereas the anti-apoptotic proteins Bcl-2 and Bcl-X(L) were expressed at similar levels in both cell lines. In conclusion, the mechanism of resistance of SF188/TR cells to TMZ involved increased activity of AGT, a primary resistance mechanism, whereas the broad cross-resistance pattern to other anticancer drugs was due to a common secondary resistance mechanism related to alterations in the relative expression of the pro-apoptotic and anti-apoptotic proteins.
authors.affiliation: Department of Pharmacology, Fox Chase Cancer Center, 7701 Burholme Ave., Philadelphia, PA 19111, USA.
authors.forename: Jianguo
authors.initials: J
authors.lastname: Ma
authors.forename: Maureen
authors.initials: M
authors.lastname: Murphy
authors.forename: Peter J
authors.initials: PJ
authors.lastname: O'Dwyer
authors.forename: Eric
authors.initials: E
authors.lastname: Berman
authors.forename: Karin
authors.initials: K
authors.lastname: Reed
authors.forename: James M
authors.initials: JM
authors.lastname: Gallo
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000251:Adenosine Triphosphatases / Q000096:biosynthesis; D018906:Antineoplastic Agents, Alkylating / Q000494:pharmacology*; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology; D002352:Carrier Proteins; D002453:Cell Cycle / Q000187:drug effects; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000096:biosynthesis; D045643:DNA Repair Enzymes; D004268:DNA-Binding Proteins / Q000096:biosynthesis; D003606:Dacarbazine / Q000031:analogs & derivatives / Q000494:pharmacology*; D004317:Doxorubicin / Q000494:pharmacology; D004347:Drug Interactions; D018432:Drug Resistance, Multiple / Q000502:physiology*; D004354:Drug Screening Assays, Antitumor; D005910:Glioma / Q000473:pathology*; D006147:Guanine / Q000031:analogs & derivatives* / Q000494:pharmacology; D006801:Humans; D000070976:Mismatch Repair Endonuclease PMS2; D000070957:MutL Protein Homolog 1; D009363:Neoplasm Proteins / Q000096:biosynthesis; D009687:Nuclear Proteins; D019853:O(6)-Methylguanine-DNA Methyltransferase / Q000378:metabolism; D017239:Paclitaxel / Q000494:pharmacology; D010641:Phenotype; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D000077204:Temozolomide; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000096:biosynthesis
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D018906:Antineoplastic Agents, Alkylating; D000972:Antineoplastic Agents, Phytogenic; C493956:CDKN1A protein, human; D002352:Carrier Proteins; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D004268:DNA-Binding Proteins; C501486:MLH1 protein, human; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D016159:Tumor Suppressor Protein p53; C064976:O(6)-benzylguanine; D006147:Guanine; D003606:Dacarbazine; D004317:Doxorubicin; D019853:O(6)-Methylguanine-DNA Methyltransferase; D000251:Adenosine Triphosphatases; C094934:PMS2 protein, human; D000070976:Mismatch Repair Endonuclease PMS2; D000070957:MutL Protein Homolog 1; D045643:DNA Repair Enzymes; D017239:Paclitaxel; D000077204:Temozolomide