title: The role of mismatch repair in small-cell lung cancer cells.
abstract: The role of mismatch repair (MMR) in small-cell lung cancer (SCLC) is controversial, as the phenotype of a MMR-deficiency, microsatellite instability (MSI), has been reported to range from 0 to 76%. We studied the MMR pathway in a panel of 21 SCLC cell lines and observed a highly heterogeneous pattern of MMR gene expression. A significant correlation between the mRNA and protein levels was found. We demonstrate that low hMLH1 gene expression was not linked to promoter CpG methylation. One cell line (86MI) was found to be deficient in MMR and exhibited resistance to the alkylating agent MNNG. Surprisingly, MSI was not detected in 86MI and it appears to express all the major MMR components hMSH2, hMSH6, hMLH1, hPMS2, hMSH3, hMLH3, MBD4 (MED1) and hExo1. These data are consistent with at least two possibilities: (1) A missense mutation in one of the MMR genes, which dissociates MSI from drug resistance, or (2) inactivation of a second pathway that leads to MMR-deficiency and MNNG resistance, but induces negligible levels of MSI. We conclude that MMR deficiency is largely not associated with the pathogenesis of SCLC.
authors.affiliation: Institute of Molecular Pathology, University of Copenhagen, DK-2100 Copenhagen, Denmark. riis@pai.ku.dk
authors.forename: L T
authors.initials: LT
authors.lastname: Hansen
authors.forename: T
authors.initials: T
authors.lastname: Thykjaer
authors.forename: T F
authors.initials: TF
authors.lastname: Ørntoft
authors.forename: L J
authors.initials: LJ
authors.lastname: Rasmussen
authors.forename: P
authors.initials: P
authors.lastname: Keller
authors.forename: M
authors.initials: M
authors.lastname: Spang-Thomsen
authors.forename: T Bocker
authors.initials: TB
authors.lastname: Edmonston
authors.forename: C
authors.initials: C
authors.lastname: Schmutte
authors.forename: R
authors.initials: R
authors.lastname: Fishel
authors.forename: L Nørgård
authors.initials: LN
authors.lastname: Petersen
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D020137:Base Pair Mismatch / Q000235:genetics*; D015152:Blotting, Northern; D015153:Blotting, Western; D002289:Carcinoma, Non-Small-Cell Lung / Q000235:genetics*; D002352:Carrier Proteins; D019175:DNA Methylation; D004268:DNA-Binding Proteins; D006801:Humans; D008175:Lung Neoplasms / Q000235:genetics*; D018895:Microsatellite Repeats; D000070957:MutL Protein Homolog 1; D051718:MutS Homolog 2 Protein; D009363:Neoplasm Proteins / Q000235:genetics; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins / Q000235:genetics; D014407:Tumor Cells, Cultured
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; C501486:MLH1 protein, human; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; C497172:MSH2 protein, human; D000070957:MutL Protein Homolog 1; D051718:MutS Homolog 2 Protein