Abstract 2108: Prevalence of mutations in MSH6, PMS1 and PMS2 gene in Brazilian families with Lynch syndrome

Abstract

Background: Lynch syndrome (LS) is an autosomal dominant disorder predisposing to colorectal cancer and increased risk for cancers of the stomach, small intestine, hepatobiliary system, kidney, ureter, ovary, and sebaceous tumors. Germline mutations in the MMR genes MutL homolog 1 (MLH1), MutS homolog 2 (MSH2), MutS homolog 6 (MSH6), post- meiotic segregation increased 1 (PMS1) or post- meiotic segregation increased 2 (PMS2), are known to cause LS. While mutations in MLH1 and MSH2 gene, account for 70% - 80% of all Lynch syndrome colorectal cancers, the involvement of the MSH6, PMS2 and PMS1 gene is continually rising. Altogether, MSH6, PMS1 and PMS2 mutations account for 5-20% of kindreds in which MSH2 and MLH1 mutations are excluded. Objective: The aim of the study was evaluate the frequency of mutations in MSH6, PMS1 and PMS2 gene. Methods: Seventy one unrelated patients without MLH1/MSH2 mutations were eligible for this study. Genomic DNA was obtained from peripheral blood and primers were designed within introns of all exons of MSH6, PMS1 gene. In order to avoid the amplification of pseudogenes for the PMS2 gene, a set of four primer pairs were design. Results: Out of 71 patients, 20 fulfilled the Amsterdam criteria and other 51 fulfilled the Bethesda guideline. Four novel pathogenic mutations were detected, three in MSH6 and 1 in PMS2. In addition, 7 variants of uncertain significance were encountered, in which two of them were previously described as pathogenic. No mutations were found in PMS1 gene. Conclusion: Our data shows that 8.5% (6/71) of the individuals have mutations in MSH6 and PMS2 gene and these results strongly suggest that MSH6 and PMS2 should not be excluded from the MMR screening in Brazilian families suspected for Lynch syndrome. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2108. doi:1538-7445.AM2012-2108