Germline MLH1 and MSH2 mutational spectrum including frequent large genomic aberrations in Hungarian hereditary non-polyposis colorectal cancer families: implications for genetic testing.

AIM

To analyze the prevalence of germline MLH1 and MSH2 gene mutations and evaluate the clinical characteristics of Hungarian hereditary non-polyposis colorectal cancer (HNPCC) families.

METHODS

Thirty-six kindreds were tested for mutations using conformation sensitive gel electrophoreses, direct sequencing and also screening for genomic rearrangements applying multiplex ligation-dependent probe amplification (MLPA).

RESULTS

Eighteen germline mutations (50%) were identified, 9 in MLH1 and 9 in MSH2. Sixteen of these sequence alterations were considered pathogenic, the remaining two were non-conservative missense alterations occurring at highly conserved functional motifs. The majority of the definite pathogenic mutations (81%, 13/16) were found in families fulfilling the stringent Amsterdam I/II criteria, including three rearrangements revealed by MLPA (two in MSH2 and one in MLH1). However, in three out of sixteen HNPCC-suspected families (19%), a disease-causing alteration could be revealed. Furthermore, nine mutations described here are novel, and none of the sequence changes were found in more than one family.

CONCLUSION

Our study describes for the first time the prevalence and spectrum of germline mismatch repair gene mutations in Hungarian HNPCC and suspected-HNPCC families. The results presented here suggest that clinical selection criteria should be relaxed and detection of genomic rearrangements should be included in genetic screening in this population.