Familial Cancer

, Volume 9, Issue 2, pp 167–172

Selection of patients with germline MLH1 mutated Lynch syndrome by determination of MLH1 methylation and BRAF mutation

  • Hanifa Bouzourene
  • Pierre Hutter
  • Lorena Losi
  • Patricia Martin
  • Jean Benhattar
Article

DOI: 10.1007/s10689-009-9302-4

Cite this article as:
Bouzourene, H., Hutter, P., Losi, L. et al. Familial Cancer (2010) 9: 167. doi:10.1007/s10689-009-9302-4
  • 333 Downloads

Abstract

Lynch syndrome is one of the most common hereditary colorectal cancer (CRC) syndrome and is caused by germline mutations of MLH1, MSH2 and more rarely MSH6, PMS2, MLH3 genes. Whereas the absence of MSH2 protein is predictive of Lynch syndrome, it is not the case for the absence of MLH1 protein. The purpose of this study was to develop a sensitive and cost effective algorithm to select Lynch syndrome cases among patients with MLH1 immunohistochemical silencing. Eleven sporadic CRC and 16 Lynch syndrome cases with MLH1 protein abnormalities were selected. The BRAF c.1799T> A mutation (p.Val600Glu) was analyzed by direct sequencing after PCR amplification of exon 15. Methylation of MLH1 promoter was determined by Methylation-Sensitive Single-Strand Conformation Analysis. In patients with Lynch syndrome, there was no BRAF mutation and only one case showed MLH1 methylation (6%). In sporadic CRC, all cases were MLH1 methylated (100%) and 8 out of 11 cases carried the above BRAF mutation (73%) whereas only 3 cases were BRAF wild type (27%). We propose the following algorithm: (1) no further molecular analysis should be performed for CRC exhibiting MLH1 methylation and BRAF mutation, and these cases should be considered as sporadic CRC; (2) CRC with unmethylated MLH1 and negative for BRAF mutation should be considered as Lynch syndrome; and (3) only a small fraction of CRC with MLH1 promoter methylation but negative for BRAF mutation should be true Lynch syndrome patients. These potentially Lynch syndrome patients should be offered genetic counselling before searching for MLH1 gene mutations.

Keywords

BRAF gene BRAF mutation Germline mutations Hereditary colorectal cancer Lynch syndrome MLH1 gene MLH1 methylation 

Abbreviations

CRC

Colorectal cancer

HNPCC

Hereditary nonpolyposis colorectal cancer

MMR

Mismatch repair

MSI

Microsatellite instability

MSI-H

MSI-high

IHC

Immunohistochemistry

Copyright information

© Springer Science+Business Media B.V. 2009

Authors and Affiliations

  • Hanifa Bouzourene
    • 1
  • Pierre Hutter
    • 2
  • Lorena Losi
    • 3
  • Patricia Martin
    • 1
  • Jean Benhattar
    • 1
  1. 1.Institute of Pathology, Centre Hospitalier Universitaire VaudoisUniversity of LausanneLausanneSwitzerland
  2. 2.Unit of GeneticsInstitut Central des Hôpitaux valaisansSionSwitzerland
  3. 3.Department of Pathological AnatomyUniversity of Modena and Reggio EmiliaModenaItaly

Personalised recommendations