title: Molecular and clinical characteristics of MSH6 variants: an analysis of 25 index carriers of a germline variant.
abstract: The MSH6 gene is one of the mismatch-repair genes involved in hereditary nonpolyposis colorectal cancer (HNPCC). Three hundred sixteen individuals who were known or suspected to have HNPCC were analyzed for MSH6 germline mutations. For 25 index patients and 8 relatives with MSH6 variants, molecular and clinical features are described. For analysis of microsatellite instability (MSI), the five consensus markers were used. Immunohistochemical analysis of the MLH1, MSH2, and MSH6 proteins was performed. Five truncating MSH6 mutations, of which one was detected seven times, were found in 12 index patients, and 10 MSH6 variants with unknown pathogenicity were found in 13 index patients. Fourteen (54%) of 26 colorectal cancers (CRCs) and endometrial cancers showed no, or only weak, MSI. Twelve of 18 tumors of truncating-mutation carriers and 3 of 17 tumors of missense-mutation carriers showed loss of MSH6 staining. Six of the families that we studied fulfilled the original Amsterdam criteria; most families with MSH6, however, were only suspected to have HNPCC. In families that did not fulfill the revised Amsterdam criteria, the prevalence of MSH6 variants is about the same as the prevalence of those in MLH1/MSH2. Endometrial cancer and/or atypical hyperplasia were diagnosed in 8 of 12 female carriers of MSH6 truncating mutations. Most CRCs were localized distally in the colon. Although, molecularly, missense variants are labeled as doubtfully pathogenic, clinical data disclose a great resemblance between missense-variant carriers and truncating-mutation carriers. We conclude that, in all patients suspected to have HNPCC, MSH6-mutation analysis should be considered. Neither MSI nor immunohistochemistry should be a definitive selection criterion for MSH6-mutation analysis.
authors.affiliation: Department of Gastroenterology, University Hospital Groningen, Groningen, The Netherlands.
authors.forename: Maran J W
authors.initials: MJ
authors.lastname: Berends
authors.forename: Ying
authors.initials: Y
authors.lastname: Wu
authors.forename: Rolf H
authors.initials: RH
authors.lastname: Sijmons
authors.forename: Rob G J
authors.initials: RG
authors.lastname: Mensink
authors.forename: Tineke
authors.initials: T
authors.lastname: van der Sluis
authors.forename: Jannet M
authors.initials: JM
authors.lastname: Hordijk-Hos
authors.forename: Elisabeth G E
authors.initials: EG
authors.lastname: de Vries
authors.forename: Harry
authors.initials: H
authors.lastname: Hollema
authors.forename: Arend
authors.initials: A
authors.lastname: Karrenbeld
authors.forename: Charles H C M
authors.initials: CH
authors.lastname: Buys
authors.forename: Ate G J
authors.initials: AG
authors.lastname: van der Zee
authors.forename: Robert M W
authors.initials: RM
authors.lastname: Hofstra
authors.forename: Jan H
authors.initials: JH
authors.lastname: Kleibeuker
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000328:Adult; D017668:Age of Onset; D000368:Aged; D000369:Aged, 80 and over; D002352:Carrier Proteins; D015179:Colorectal Neoplasms / Q000453:epidemiology / Q000235:genetics*; D003123:Colorectal Neoplasms, Hereditary Nonpolyposis / Q000453:epidemiology / Q000235:genetics; D004252:DNA Mutational Analysis; D004268:DNA-Binding Proteins / Q000032:analysis / Q000235:genetics*; D016889:Endometrial Neoplasms / Q000453:epidemiology / Q000235:genetics*; D005260:Female; D014644:Genetic Variation / Q000235:genetics*; D018095:Germ-Line Mutation / Q000235:genetics*; D006579:Heterozygote; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D018895:Microsatellite Repeats / Q000235:genetics; D008875:Middle Aged; D000070957:MutL Protein Homolog 1; D051718:MutS Homolog 2 Protein; D009363:Neoplasm Proteins / Q000032:analysis; D009687:Nuclear Proteins; D010641:Phenotype; D011518:Proto-Oncogene Proteins / Q000032:analysis
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; C094443:G-T mismatch-binding protein; 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