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A putative Lynch syndrome family carrying MSH2 and MSH6 variants of uncertain significance—functional analysis reveals the pathogenic one

Familial Cancer volume 10, pages 515–520 (2011)Cite this article

Abstract

Inherited pathogenic mutations in the mismatch repair (MMR) genes, MSH2, MLH1, MSH6, and PMS2 predispose to Lynch syndrome (LS). However, the finding of a variant or variants of uncertain significance (VUS) in affected family members complicates the risk assessment. Here, we describe a putative LS family carrying VUS in both MSH2 (c.2768T>A, p.Val923Glu) and MSH6 (c.3563G>A, p.Ser1188Asn). Two colorectal cancer (CRC) patients were studied for mutations and identified as carriers of both variants. In spite of a relatively high mean age of cancer onset (59.5 years) in the family, many CRC patients and the tumor pathological data suggested that the missense variation in MSH2, the more common susceptibility gene in LS, would be the predisposing alteration. However, MSH2 VUS was surprisingly found to be MMR proficient in an in vitro MMR assay and a tolerant alteration in silico. By supplying evidence that instead of MSH2 p.Val923Glu the MSH6 p.Ser1188Asn variant is completely MMR-deficient, the present study confirms the previous findings, and suggests that MSH6 (c.3563G>A, p.Ser1188Asn) is the pathogenic mutation in the family. Moreover, our results strongly support the strategy to functionally assess all identified VUS before predictive gene testing and genetic counseling are offered to a family.

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Abbreviations

AC:

Amsterdam criteria

CRC:

Colorectal cancer

EPCAM:

Epithelial cell adhesion molecule

HNPCC:

Hereditary non-polyposis colorectal cancer

IHC:

Immunohistochemical

LS:

Lynch syndrome

MMR:

Mismatch repair

MSI:

Microsatellite instability

NE:

Nuclear extract

TE:

Total extract

VUS:

Variants of uncertain significance

WT:

Wild type

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Acknowledgments

We thank Mikko Frilander for providing the HeLa cell line and Merja Salmitie for the preparation of 5′IDL1. Friedrik Wikman at Molecular Diagnostics at Skejby Hospital and Henrik Okkels at Clinical Biochemistry at Aalborg Hospital are acknowledged for their contributions to the molecular genetics analyses. Claus Fenger at Pathologic Department at Odense University Hospital is acknowledged for performing the immunohistochemical analyses. This study was supported by grants: Sigrid Juselius Foundation; European Research Council (2008-AdG-232635); Finnish Cancer Organisations, The Biocentrum Helsinki Organisation; The Research Foundation of the University of Helsinki and Kuopio Naturalists’ Society.

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Affiliations

  1. Department of Biosciences, Genetics, University of Helsinki, P.O. Box 56 (Viikinkaari 5), 00014, Helsinki, Finland

    Jukka Kantelinen, Minttu Kansikas, Mari K. Korhonen, Saara Ollila, Minna Nyström & Reetta Kariola

  2. Department of Clinical Biochemistry, Section of Genomic Medicine, Rigshospitalet and Copenhagen University, Copenhagen, Denmark

    Thomas v. O. Hansen

  3. Department of Clinical Genetics, Rigshospital and Copenhagen University, Copenhagen, Denmark

    Anne-Marie Gerdes

  4. Department of Clinical Genetics, Odense University Hospital, Odense, Denmark

    Lotte Nylandsted Krogh

Authors
  1. Jukka Kantelinen
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  2. Thomas v. O. Hansen
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  3. Minttu Kansikas
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  4. Lotte Nylandsted Krogh
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  5. Mari K. Korhonen
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  6. Saara Ollila
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  7. Minna Nyström
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  8. Anne-Marie Gerdes
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  9. Reetta Kariola
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Correspondence to Reetta Kariola.

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Kantelinen, J., Hansen, T.v.O., Kansikas, M. et al. A putative Lynch syndrome family carrying MSH2 and MSH6 variants of uncertain significance—functional analysis reveals the pathogenic one. Familial Cancer 10, 515–520 (2011). https://doi.org/10.1007/s10689-011-9436-z

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Keywords

  • Functional analysis
  • Lynch syndrome
  • MSH2
  • MSH6
  • Variants of uncertain significance (VUS)