Germline hypermethylation of MLH1 and EPCAM deletions are a frequent cause of Lynch syndrome
ABSTRACT It was shown that Lynch syndrome can be caused by germline hypermethylation of the MLH1 and MSH2 promoters. Furthermore, it has been demonstrated very recently that germline deletions of the 3' region of EPCAM cause transcriptional read-through which results in silencing of MSH2 by hypermethylation. We wanted to determine the prevalence of germline MLH1 promoter hypermethylation and of germline and somatic MSH2 promoter hypermethylation in a large group of Lynch syndrome-suspected patients. From a group of 331 Lynch Syndrome-suspected patients we selected cases, who had no germline MLH1, MSH2, or MSH6 mutation and whose tumors showed loss of MLH1 or MSH2, or, if staining was unavailable, had a tumor with microsatellite instability. Methylation assays were performed to test these patients for germline MLH1 and/or MSH2 promoter hypermethylation. Two patients with germline MLH1 promoter hypermethylation and no patients with germline MSH2 promoter hypermethylation were identified. In the subgroup screened for germline MSH2 promoter hypermethylation, we identified 3 patients with somatic MSH2 promoter hypermethylation in their tumors, which was caused by a germline EPCAM deletion. In the group of 331 Lynch Syndrome-suspected patients, the frequencies of germline MLH1 promoter hypermethylation and somatic MSH2 promoter hypermethylation caused by germline EPCAM deletions are 0.6 and 0.9%, respectively. These mutations, therefore, seem to be rather infrequent. However, the contribution of germline MLH1 hypermethylation and EPCAM deletions to the genetically proven Lynch syndrome cases in this cohort is very high. Previously 27 pathogenic mutations were identified; the newly identified mutations now represent 16% of all mutations.
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ABSTRACT: Objective: The primary aim of this study was to determine the prevalence of occult gynecologic malignancy at the time of risk reducing surgery in patients with Lynch Syndrome. A secondary aim was to determine the prevalence of occult gynecologic malignancy at the time of surgery for non-prophylactic indications in patients with Lynch Syndrome. Methods: A retrospective review of an Inherited Colorectal Cancer Registry found 76 patients with Lynch syndrome (defined by a germline mutation in a DNA mismatch repair gene) or hereditary nonpolyposis colorectal cancer (HNPCC) (defined by Amsterdam criteria) who had undergone hysterectomy and/or salpingo-oophorectomy for a prophylactic or non-prophylactic indication. Indications for surgery and the prevalence of cancer at the time of each operation were reviewed. Results: 24 of 76 patients underwent prophylactic hysterectomy and/or bilateral salpingo-oophorectomy for Lynch syndrome or HNPCC. In 9 of these patients, a benign indication for surgery was also noted. 4 of 24 patients (17%, 95% CI=5-38%) were noted to have cancer on final pathology. 20 of 76 patients (26%) undergoing operative management for any indication were noted to have occult malignancy on final pathology. Conclusions: Patients should be counseled about the risks of finding gynecologic cancer at the time of prophylactic or non-prophylactic surgery for Lynch syndrome and HNPCC, and the potential need for additional surgery.Gynecologic Oncology 11/2013; 132(2). DOI:10.1016/j.ygyno.2013.10.033 · 3.69 Impact Factor
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ABSTRACT: Identifying individuals who have Lynch syndrome (LS) involves a complex diagnostic work up that includes taking a detailed family history and a combination of various genetic and immunohistochemical tests. The National Society of Genetic Counselors (NSGC) and the Collaborative Group of the Americas on Inherited Colorectal Cancer (CGA-ICC) have come together to publish this clinical practice testing guideline for the evaluation of LS. The purpose of this practice guideline is to provide guidance and a testing algorithm for LS as well as recommendations on when to offer testing. This guideline does not replace a consultation with a genetics professional. This guideline includes explanations in support of this and a summary of background data. While this guideline is not intended to serve as a review of LS, it includes a discussion of background information on LS, and cites a number of key publications which should be reviewed for a more in-depth understanding of LS. These guidelines are intended for genetic counselors, geneticists, gastroenterologists, surgeons, medical oncologists, obstetricians and gynecologists, nurses and other healthcare providers who evaluate patients for LS.Journal of Genetic Counseling 12/2011; 21(4):484-93. DOI:10.1007/s10897-011-9465-7 · 1.75 Impact Factor