title: Contribution of ATM and ATR to the resistance of glioblastoma and malignant melanoma cells to the methylating anticancer drug temozolomide.
abstract: The major cytotoxic DNA adduct induced by temozolomide and other methylating agents used in malignant glioma and metastasized melanoma therapy is O(6)-methylguanine (O(6)-MeG). This primary DNA damage is converted by mismatch repair into secondary lesions, which block replication and in turn induce DNA double-strand breaks that trigger the DNA damage response (DDR). Key upstream players in the DDR are the phosphoinositide 3-kinases ataxia telangiectasia mutated (ATM) and ataxia telangiectasia and Rad3 related (ATR). Here, we addressed the question of the importance of ATM and ATR in the cell death response following temozolomide. We show that (i) ATM- and ATR-mutated cells are hypersensitive to temozolomide, (ii) O(6)-MeG triggers ATM and ATR activation, (iii) knockdown of ATM and ATR enhances cell kill in gliobalstoma and malignant melanoma cells with a stronger and significant effect in ATR knockdown cells, (iv) ATR, but not ATM, knockdown abolished phosphorylation of H2AX, CHK1, and CHK2 in glioma cells, and (v) temozolomide-induced cell death was more prominently enhanced by pharmacologic inhibition of CHK1 compared with CHK2. The data suggest that ATM and, even better, ATR inhibition is a useful strategy in sensitizing cancer cells to temozolomide and presumably also other anticancer drugs.
authors: Corresponding Author: Bernd Kaina, Institute of Toxicology, Medical Center of the University Mainz, Obere Zahlbacher Str. 67, D-55131 Mainz, Germany. kaina@uni-mainz.de.
authors: Marcus
authors: M
authors: Eich
authors: Wynand Paul
authors: WP
authors: Roos
authors: Teodora
authors: T
authors: Nikolova
authors: Bernd
authors: B
authors: Kaina
mesh_terms: D018906:Antineoplastic Agents, Alkylating / Q000494:pharmacology*; D064007:Ataxia Telangiectasia Mutated Proteins / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D000071877:Checkpoint Kinase 1; D053903:DNA Breaks, Double-Stranded / Q000187:drug effects; D015254:DNA Modification Methylases / Q000235:genetics / Q000378:metabolism; D045643:DNA Repair Enzymes / Q000235:genetics / Q000378:metabolism; D003606:Dacarbazine / Q000031:analogs & derivatives* / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm; D055785:Gene Knockdown Techniques; D005909:Glioblastoma / Q000178:diet therapy / Q000235:genetics / Q000378:metabolism*; D006147:Guanine / Q000031:analogs & derivatives / Q000494:pharmacology; D006801:Humans; D008545:Melanoma / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism*; D008769:Methylnitronitrosoguanidine / Q000494:pharmacology; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D000077204:Temozolomide; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D018906:Antineoplastic Agents, Alkylating; D025521:Tumor Suppressor Proteins; D008769:Methylnitronitrosoguanidine; D006147:Guanine; D003606:Dacarbazine; C008449:O-(6)-methylguanine; D015254:DNA Modification Methylases; C515491:MGMT protein, human; D011494:Protein Kinases; C576324:ATM protein, human; C576597:ATR protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; C000605867:CHEK1 protein, human; D000071877:Checkpoint Kinase 1; D045643:DNA Repair Enzymes; D000077204:Temozolomide