title: High level of microsatellite instability but not hypermethylation of mismatch repair genes in therapy-related and secondary acute myeloid leukaemia and myelodysplastic syndrome.
abstract: Microsatellite instability (MSI) is associated with defects in the DNA mismatch repair (MMR) system, such as mutation or epigenetic silencing of the genes by promoter hypermethylation. We investigated the presence of MSI and promoter hypermethylation of hMLH1 and hMSH2 genes in 82 patients (68 acute myeloid leukaemia, AML; 14 myelodysplastic syndromes, MDS). Twelve separate microsatellite loci, including three mononucleotide repeat markers, were used. Mutator phenotype (RER+) was detected in 20 AML (29.4%) and 3 MDS (21.4%) patients. RER+ rate was much higher in the therapy-related and secondary cases compared with the de novo cases. Three out of 7 (42.9%) secondary (s-AML) and 8 out of 17 (47.1%) therapy-related (t-AML) showed RER+ in comparison with 9 out of 44 (20.5%) de novo cases. Similar rates were detected in MDS patients (2/2 therapy-related and 1/12 de novo). The promoter hypermethylation was found in three hMLH1 (3.7%) and two hMSH2 (2.4%) genes. All these five patients had AML and were older than 60 years of age. Two of them had s-AML and one had t-AML. RER+ was detected in three of these five patients. Our data suggest that genetic instability is associated with AML and MDS, especially t-AML and s-AML. In addition, our results indicate that the hMSH2 and hMLH1 promoter hypermethylation is not a common event in these malignancies, but may play a role in the development of AML in elderly patients.
authors.affiliation: Molecular Oncology Group, University Department of Haematology, Manchester Royal Infirmary, Cobbett House, Oxford Road, Manchester M13 9WL, UK.
authors.forename: Mohammad H
authors.initials: MH
authors.lastname: Sheikhha
authors.forename: Khalid
authors.initials: K
authors.lastname: Tobal
authors.forename: John A
authors.initials: JA
authors.lastname: Liu Yin
mesh_terms: D000208:Acute Disease; D048868:Adaptor Proteins, Signal Transducing; D000328:Adult; D000368:Aged; D020137:Base Pair Mismatch; D002352:Carrier Proteins; D019175:DNA Methylation; D004260:DNA Repair; D004268:DNA-Binding Proteins; D005260:Female; D006801:Humans; D007951:Leukemia, Myeloid / Q000235:genetics* / Q000628:therapy; D008297:Male; D018895:Microsatellite Repeats; D008875:Middle Aged; D000070957:MutL Protein Homolog 1; D051718:MutS Homolog 2 Protein; D009190:Myelodysplastic Syndromes / Q000235:genetics* / Q000628:therapy; D009363:Neoplasm Proteins / Q000378:metabolism; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins / Q000378:metabolism
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