DNA hypermethylation appears early and shows increased frequency with dysplasia in Lynch syndrome-associated colorectal adenomas and carcinomas

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dc.contributor.author Valo, Satu
dc.contributor.author Kaur, Sippy
dc.contributor.author Ristimäki, Ari
dc.contributor.author Renkonen-Sinisalo, Laura
dc.contributor.author Järvinen, Heikki
dc.contributor.author Mecklin, Jukka-Pekka
dc.contributor.author Nyström, Minna
dc.contributor.author Peltomäki, Päivi
dc.date.accessioned 2015-07-22T07:15:36Z
dc.date.available 2015-07-22T07:15:36Z
dc.date.issued 2015-07-22
dc.identifier.citation Clinical Epigenetics. 2015 Jul 22;7(1):71
dc.identifier.uri http://hdl.handle.net/10138/155696
dc.description.abstract Abstract Background Lynch syndrome (LS) is associated with germline mutations in DNA mismatch repair (MMR) genes. The first “hit” to inactivate one allele of the predisposing MMR gene is present in every cell, contributing to accelerated tumorigenesis. Less information is available of the nature, timing, and order of other molecular “hits” required for tumor development. To this end, MMR protein expression and coordinated promoter methylation were examined in colorectal specimens prospectively collected from LS mutation carriers (n = 55) during colonoscopy surveillance (10/2011–5/2013), supplemented with retrospective specimens. Results Loss of MMR protein corresponding to the gene mutated in the germline increased with dysplasia, with frequency of 0 % in normal mucosa, 50–68 % in low-grade dysplasia adenomas, and 100 % in high-grade dysplasia adenomas and carcinomas. Promoter methylation as a putative “second hit” occurred in 1/56 (2 %) of tumors with silenced MMR protein. A general hypermethylation tendency was evaluated by two gene sets, eight CpG island methylator phenotype (CIMP) genes, and seven candidate tumor suppressor genes linked to colorectal carcinoma (CRC). Hypermethylation followed the same trend as MMR protein loss and was present in some low-grade dysplasia adenomas that still expressed MMR protein suggesting the absence of a “second hit.” To assess prospectively collected normal mucosa for carcinogenic “fields,” the specimen donors were stratified according to age at biopsy (50 years or below vs. above 50 years) and further according to the absence vs. presence of a (previous or concurrent) diagnosis of CRC. In mutation carriers over 50 years old, two markers from the candidate gene panel (SFRP1 and SLC5A8) revealed a significantly elevated average degree of methylation in individuals with CRC diagnosis vs. those without. Conclusions Our findings emphasize the importance and early appearance of epigenetic alterations in LS-associated tumorigenesis. The results serve early detection and assessment of progression of CRC.
dc.language.iso eng
dc.publisher BioMed Central
dc.title DNA hypermethylation appears early and shows increased frequency with dysplasia in Lynch syndrome-associated colorectal adenomas and carcinomas en
dc.date.updated 2015-07-22T07:15:37Z
dc.type.uri http://purl.org/eprint/entityType/ScholarlyWork
dc.type.uri http://purl.org/eprint/entityType/Expression
dc.type.uri http://purl.org/eprint/type/JournalArticle
dc.rights.copyrightholder Valo et al.

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