Germline EPCAM (epithelial cell adhesion molecule, TACSTD1)
Gene Deletion MLPA analysis
Hereditary nonpolyposis colorectal cancer (HNPCC), also known as Lynch syndrome patients are at an increased risk for colorectal and several other cancers owing to inactivating germline mutations in mismatch repair genes (MMR), including MLH1, MSH2, MSH6 and PMS2. Recently, several groups reported that germline EPCAM deletions in 3’ region can cause HNPCC. The EPCAM deletions result in loss of the exons 8 and 9 (the last two exons), including the polyadenylation signal, which abolished transcription termination. This leads to transcription read-through into the downstream of MSH2 gene causing methylation of the MSH2 promoter and ultimately silencing of MSH2 gene1.
Kovacs M. E. et al reported that the EPCAM deletion was found in about 19% HNPCC families without identifiable pathogenic variant in MMR genes3. Niessen R.C. et al found that the overall contribution of EPCAM deletion to the HNPCC cases is about 6.3% 2. The mean age of diagnosis in the patients is 43 years, which is comparable with the average age of onset in patients with HNPCC with a germline MMR gene mutation 1, 2. Although more clinical data will be needed to set up criteria of the clinical managements, it seems reasonable to provide EPCAM deletion patients the standard HNPCC surveillance protocols.
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- Ligtenberg M. J. et al., (2009) Nat Genet. 41(1):112-7
- Niessen R.C. et al., (2009) Genes Chromosomes Cancer; 48(8): 737-44
- Kovacs M. E. et al., (2009) Hum Mutat. 30(2):197-203