title: Role of mismatch repair proteins in the processing of cisplatin interstrand cross-links.
abstract: Mismatch repair (MMR) deficiency gives rise to cisplatin resistance and can lead to poor prognosis in cancers. Various models have been proposed to explain this low level of resistance caused due to loss of MMR proteins. We have shown that MMR proteins are required to maintain cisplatin interstrand cross-links (ICLs) on the DNA leading to increased cellular sensitivity. In our previous studies, we have shown that BER processing of the cisplatin ICLs is mutagenic. Polymerase β (Polβ) can generate mismatches which leads to the activation and the recruitment of mismatch repair proteins. In this paper, we distinguished between the requirement of different downstream MMR proteins for maintaining cisplatin sensitivity. We show that the MutSα (MSH2-MSH6) heterocomplex is required to maintain cisplatin sensitivity, whereas the Mutsβ complex has no effect. These results can be correlated with the increased repair of cisplatin ICLs and ICL induced DNA double strand breaks (DSBs) in the resistant cells. Moreover, we show that MLH1 proficient cells displayed a cisplatin sensitive phenotype when compared with the MLH1 deficient cells and the ATPase activity of MLH1 is essential to mediate this effect. Based on these results, we propose that MutSα as well as the downstream MMR pathway proteins are essential to maintain a cisplatin sensitive phenotype as a consequence of processing Polβ induced mismatches at sites flanking cisplatin ICLs.
authors.affiliation: Department of Biochemistry and Cancer Biology, University of Toledo-Health Science Campus, Toledo, OH 43614, USA.
authors.forename: Akshada
authors.initials: A
authors.lastname: Sawant
authors.affiliation: Department of Biochemistry and Cancer Biology, University of Toledo-Health Science Campus, Toledo, OH 43614, USA.
authors.forename: Anbarasi
authors.initials: A
authors.lastname: Kothandapani
authors.affiliation: Department of Pathology and Laboratory Medicine, Alpert Medical School, Brown University, Providence, RI 02912, USA.
authors.forename: Anatoly
authors.initials: A
authors.lastname: Zhitkovich
authors.affiliation: Department of Pharmacology & Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA; University of Pittsburgh Cancer Institute, Hillman Cancer Center, Pittsburgh, PA 15213, USA; Department of Human Genetics, University of Pittsburgh Graduate School of Public Health, Pittsburgh, PA 15213, USA; Department of Oncologic Sciences, Molecular & Metabolic Oncology Program, University of South Alabama Mitchell Cancer Institute, 1660 Springhill Avenue, Mobile, AL 36604, USA.
authors.forename: Robert W
authors.initials: RW
authors.lastname: Sobol
authors.affiliation: Department of Oncology, Karmanos Cancer Institute, Wayne State University, Detroit, MI 48201, USA. Electronic address: patricks@karmanos.org.
authors.forename: Steve M
authors.initials: SM
authors.lastname: Patrick
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D045744:Cell Line, Tumor; D002945:Cisplatin / Q000494:pharmacology*; D003432:Cross-Linking Reagents / Q000494:pharmacology*; D053903:DNA Breaks, Double-Stranded; D053843:DNA Mismatch Repair; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D019008:Drug Resistance, Neoplasm; D055785:Gene Knockdown Techniques; D006801:Humans; D051379:Mice; D000070957:MutL Protein Homolog 1; D051718:MutS Homolog 2 Protein / Q000235:genetics / Q000378:metabolism; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D000970:Antineoplastic Agents; D003432:Cross-Linking Reagents; D004268:DNA-Binding Proteins; C094443:G-T mismatch-binding protein; C501486:MLH1 protein, human; D009687:Nuclear Proteins; C497172:MSH2 protein, human; D000070957:MutL Protein Homolog 1; D051718:MutS Homolog 2 Protein; D002945:Cisplatin
keywords: ATPase; BER; Cisplatin; MMR; Resistance