title: O6-methylguanine DNA methyltransferase and p53 status predict temozolomide sensitivity in human malignant glioma cells.
abstract: Temozolomide (TMZ) is a methylating agent which prolongs survival when administered during and after radiotherapy in the first-line treatment of glioblastoma and which also has significant activity in recurrent disease. O6-methylguanine DNA methyltransferase (MGMT) is a DNA repair enzyme attributed a role in cancer cell resistance to O6-alkylating agent-based chemotherapy. Using a panel of 12 human glioma cell lines, we here defined the sensitivity to TMZ in acute cytotoxicity and clonogenic survival assays in relation to MGMT, mismatch repair and p53 status and its modulation by dexamethasone, irradiation and BCL-X(L). We found that the levels of MGMT expression were a major predictor of TMZ sensitivity in human glioma cells. MGMT activity and clonogenic survival after TMZ exposure are highly correlated (p < 0.0001, r2 = 0.92). In contrast, clonogenic survival after TMZ exposure does not correlate with the expression levels of the mismatch repair proteins mutS homologue 2, mutS homologue 6 or post-meiotic segregation increased 2. The MGMT inhibitor O6-benzylguanine sensitizes MGMT-positive glioma cells to TMZ whereas MGMT gene transfer into MGMT-negative cells confers protection. The antiapoptotic BCL-X(L) protein attenuates TMZ cytotoxicity in MGMT-negative LNT-229 but not in MGMT-positive LN-18 cells. Neither ionizing radiation (4 Gy) nor clinically relevant concentrations of dexamethasone modulate MGMT activity or TMZ sensitivity. Abrogation of p53 wild-type function strongly attenuates TMZ cytotoxicity. Conversely, p53 mimetic agents designed to stabilize the wild-type conformation of p53 sensitize glioma cells for TMZ cytotoxicity. Collectively, these results suggest that the determination of MGMT expression and p53 status will help to identify glioma patients who will or will not respond to TMZ.
authors.affiliation: Laboratory of Molecular Neuro-Oncology, Department of General Neurology, Hertie Institute for Clinical Brain Research, University of Tübingen, School of Medicine, Tübingen, Germany. mirjam.hermisson@uni-tuebingen.de
authors.forename: Mirjam
authors.initials: M
authors.lastname: Hermisson
authors.forename: Andrea
authors.initials: A
authors.lastname: Klumpp
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Wick
authors.forename: Jörg
authors.initials: J
authors.lastname: Wischhusen
authors.forename: Georg
authors.initials: G
authors.lastname: Nagel
authors.forename: Wynand
authors.initials: W
authors.lastname: Roos
authors.forename: Bernd
authors.initials: B
authors.lastname: Kaina
authors.forename: Michael
authors.initials: M
authors.lastname: Weller
mesh_terms: D018906:Antineoplastic Agents, Alkylating / Q000494:pharmacology*; D002330:Carmustine / Q000494:pharmacology; D016923:Cell Death / Q000187:drug effects; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D003606:Dacarbazine / Q000031:analogs & derivatives* / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D005910:Glioma / Q000201:enzymology*; D006801:Humans; D019853:O(6)-Methylguanine-DNA Methyltransferase / Q000378:metabolism*; D000077204:Temozolomide; D014162:Transfection / Q000379:methods; D014410:Tumor Stem Cell Assay / Q000379:methods; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D051020:bcl-X Protein / Q000378:metabolism
chemical_list: D018906:Antineoplastic Agents, Alkylating; C494811:BCL2L1 protein, human; D016159:Tumor Suppressor Protein p53; D051020:bcl-X Protein; D003606:Dacarbazine; D019853:O(6)-Methylguanine-DNA Methyltransferase; D002330:Carmustine; D000077204:Temozolomide