Browsing by Subject "MSH2"

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  • PLSD Collaborators; Dominguez-Valentin, Mev; Sampson, Julian R.; Møller, Pål; Seppälä, Toni T. (2021)
  • Ahadova, Aysel; Pfuderer, Pauline Luise; Ahtiainen, Maarit; Ballhausen, Alexej; Bohaumilitzky, Lena; Kösegi, Svenja; Müller, Nico; Tang, Yee Lin; Kosmalla, Kosima; Witt, Johannes; Endris, Volker; Stenzinger, Albrecht; von Knebel Doeberitz, Magnus; Bläker, Hendrik; Renkonen-Sinisalo, Laura; Lepistö, Anna; Böhm, Jan; Mecklin, Jukka-Pekka; Seppälä, Toni T.; Kloor, Matthias (2021)
    Regular colonoscopy even with short intervals does not prevent all colorectal cancers (CRC) in Lynch syndrome (LS). In the present study, we asked whether cancers detected under regular colonoscopy surveillance (incident cancers) are phenotypically different from cancers detected at first colonoscopy (prevalent cancers). We analyzed clinical, histological, immunological and mutational characteristics, including panel sequencing and high-throughput coding microsatellite (cMS) analysis, in 28 incident and 67 prevalent LS CRCs (n total = 95). Incident cancers presented with lower UICC and T stage compared to prevalent cancers (p < 0.0005). The majority of incident cancers (21/28) were detected after previous colonoscopy without any pathological findings. On the molecular level, incident cancers presented with a significantly lower KRAS codon 12/13 (1/23, 4.3% vs. 11/21, 52%; p = 0.0005) and pathogenic TP53 mutation frequency (0/17, 0% vs. 7/21, 33.3%; p = 0.0108,) compared to prevalent cancers; 10/17 (58.8%) incident cancers harbored one or more truncating APC mutations, all showing mutational signatures of mismatch repair (MMR) deficiency. The proportion of MMR deficiency-related mutational events was significantly higher in incident compared to prevalent CRC (p = 0.018). In conclusion, our study identifies a set of features indicative of biological differences between incident and prevalent cancers in LS, which should further be monitored in prospective LS screening studies to guide towards optimized prevention protocols.
  • Olkinuora, Alisa; Gylling, Annette; Almusa, Henrikki; Eldfors, Samuli; Lepistö, Anna; Mecklin, Jukka-Pekka; Nieminen, Taina Tuulikki; Peltomäki, Päivi (2020)
    Some 10-50% of Lynch-suspected cases with abnormal immunohistochemical (IHC) staining remain without any identifiable germline mutation of DNA mismatch repair (MMR) genes. MMR proteins form heterodimeric complexes, giving rise to distinct IHC patterns when mutant. Potential reasons for not finding a germline mutation include involvement of an MMR gene not predicted by the IHC pattern, epigenetic mechanism of predisposition, primary mutation in another DNA repair or replication-associated gene, and double somatic MMR gene mutations. We addressed these possibilities by germline and tumor studies in 60 Lynch-suspected cases ascertained through diagnostics (n= 55) or research (n= 5). All cases had abnormal MMR protein staining in tumors but no point mutation or large rearrangement of the suspected MMR genes in the germline. In diagnostic practice, MSH2/MSH6 (MutS Homolog 2/MutS Homolog 6) deficiency promptsMSH2mutation screening; in our study, 3/11 index individuals (27%) with this IHC pattern revealed pathogenic germline mutations inMSH6. Individuals with isolated absence of MSH6 are routinely screened forMSH6mutations alone; we found a predisposing mutation inMSH2in 1/7 such cases (14%). Somatic deletion of theMSH2-MSH6region, joint loss of MSH6 and MSH3 (MutS Homolog 3) proteins, and hindered MSH2/MSH6 dimerization offered explanations to misleading IHC patterns. Constitutional epimutation hypothesis was pursued in the MSH2 and/or MSH6-deficient cases plus 38 cases with MLH1 (MutL Homolog 1)-deficient tumors; a primaryMLH1epimutation was identified in one case with an MLH1-deficient tumor. We conclude that bothMSH2andMSH6should be screened in MSH2/6- and MSH6-deficient cases. In MLH1-deficient cases, constitutional epimutations ofMLH1warrant consideration.
  • PLSD; Dominguez-Valentin, Mev; Plazzer, John-Paul; Sampson, Julian R.; Renkonen-Sinisalo, Laura; Lepistö, Anna; Peltomäki, Päivi; Lindberg, Lars; Seppälä, Toni T. (2021)
    Background. Lynch syndrome is the most common genetic predisposition for hereditary cancer. Carriers of pathogenic changes in mismatch repair (MMR) genes have an increased risk of developing colorectal (CRC), endometrial, ovarian, urinary tract, prostate, and other cancers, depending on which gene is malfunctioning. In Lynch syndrome, differences in cancer incidence (penetrance) according to the gene involved have led to the stratification of cancer surveillance. By contrast, any differences in penetrance determined by the type of pathogenic variant remain unknown. Objective. To determine cumulative incidences of cancer in carriers of truncating and missense or aberrant splicing pathogenic variants of the MLH1 and MSH2 genes. Methods. Carriers of pathogenic variants of MLH1 (path_MLH1) and MSH2 (path_MSH2) genes filed in the Prospective Lynch Syndrome Database (PLSD) were categorized as truncating or missense/aberrant splicing according to the InSiGHT criteria for pathogenicity. Results. Among 5199 carriers, 1045 had missense or aberrant splicing variants, and 3930 had truncating variants. Prospective observation years for the two groups were 8205 and 34,141 years, respectively, after which there were no significant differences in incidences for cancer overall or for colorectal cancer or endometrial cancers separately. Conclusion. Truncating and missense or aberrant splicing pathogenic variants were associated with similar average cumulative incidences of cancer in carriers of path MLH1 and path_MSH2.
  • Shrestha, Kul; Aska, Elli; Tuominen, Minna; Kauppi, Liisa (2021)
    Tumors of Lynch syndrome (LS) patients display high levels of microsatellite instability (MSI), which results from complete loss of DNA mismatch repair (MMR), in line with Knudson’s two-hit hypothesis. Why some organs, in particular those of the gastrointestinal (GI) tract, are prone to tumorigenesis in LS remains unknown. We hypothesized that MMR is haploinsufficient in certain tissues, compromising microsatellite stability in a tissue-specific manner before tumorigenesis. Using mouse genetics, we tested how levels of MLH1, a central MMR protein, affect age- and tissue-specific microsatellite stability in vivo and whether elevated MSI is detectable prior to loss of MMR function and to neoplastic growth. To assess putative tissue-specific MMR haploinsufficiency, we determined relevant molecular phenotypes (MSI, Mlh1 promoter methylation status, MLH1 protein and RNA levels) in jejuna of Mlh1+/− mice and compared them to those in spleen, as well as to MMR-proficient and -deficient controls (Mlh1+/+ and Mlh1−/− mice). While spleen MLH1 levels of Mlh1+/− mice were, as expected, approximately 50 % compared to wildtype mice, MLH1 levels in jejunum varied substantially between individual Mlh1+/− mice and moreover, decreased with age. Mlh1+/− mice with soma-wide Mlh1 promoter methylation often displayed severe MLH1 depletion in jejunum. Reduced (but still detectable) MLH1 levels correlated with elevated MSI in Mlh1+/− jejunum. MSI in jejunum increased with age, while in spleens of the same mice, MLH1 levels and microsatellites remained stable. Thus, MLH1 expression levels are particularly labile in intestine of Mlh1+/− mice, giving rise to tissue-specific MSI long before neoplasia. A similar mechanism likely also operates also in the human GI epithelium and could explain the wide range in age-of-onset of LS-associated tumorigenesis.
  • Seppala, TT; Dominguez-Valentin, M; Crosbie, EJ; Engel, C; Aretz, S; Macrae, F; Winship, I; Capella, G; Thomas, H; Hovig, E; Nielsen, M; Sijmons, RH; Bertario, L; Bonanni, B; Tibiletti, MG; Cavestro, GM; Mints, M; Gluck, N; Katz, L; Heinimann, K; Vaccaro, CA; Green, K; Lalloo, F; Hill, J; Schmiegel, W; Vangala, D; Perne, C; Strauss, HG; Tecklenburg, J; Holinski-Feder, E; Steinke-Lange, V; Mecklin, JP; Plazzer, JP; Pineda, M; Navarro, M; Vida, JB; Kariv, R; Rosner, G; Pinero, TA; Pavicic, W; Kalfayan, P; Ten Broeke, SW; Jenkins, MA; Sunde, L; Bernstein, I; Burn, J; Greenblatt, M; Cappel, WHDTN; Della Valle, A; Lopez-Koestner, F; Alvarez, K; Buttner, R; Gorgens, H; Morak, M; Holzapfel, S; Huneburg, R; Doeberitz, MV; Loeffler, M; Redler, S; Weitz, J; Pylvanainen, K; Renkonen-Sinisalo, L; Lepisto, A; Hopper, JL; Win, AK; Lindor, NM; Gallinger, S; Marchand, LL; Newcomb, PA; Figueiredo, JC; Thibodeau, SN; Therkildsen, C; Wadt, KAW; Mourits, MJE; Ketabi, Z; Denton, OG; Rodland, EA; Vasen, H; Neffa, F; Esperon, P; Tjandra, D; Moslein, G; Rokkones, E; Sampson, JR; Evans, DG; Moller, P (2021)
    Purpose: This study aimed to report the uptake of hysterectomy and/or bilateral salpingo-oophorectomy (BSO) to prevent gynaecological cancers (risk-reducing surgery [RRS]) in carriers of pathogenic MMR (path_MMR) variants. Methods: The Prospective Lynch Syndrome Database (PLSD) was used to investigate RRS by a cross-sectional study in 2292 female path_MMR carriers aged 30-69 years. Results: Overall, 144, 79, and 517 carriers underwent risk-reducing hysterectomy, BSO, or both combined, respectively. Two-thirds of procedures before 50 years of age were combined hysterectomy and BSO, and 81% of all procedures included BSO. Risk-reducing hysterectomy was performed before age 50 years in 28%, 25%, 15%, and 9%, and BSO in 26%, 25%, 14% and 13% of path_MLH1, path_MSH2, path_MSH6, and path_PMS2 carriers, respectively. Before 50 years of age, 107 of 188 (57%) BSO and 126 of 204 (62%) hysterectomies were performed in women without any prior cancer, and only 5% (20/392) were performed simultaneously with colorectal cancer (CRC) surgery. Conclusion: Uptake of RRS before 50 years of age was low, and RRS was rarely undertaken in association with surgical treatment of CRC. Uptake of RRS aligned poorly with gene-and age-associated risk estimates for endometrial or ovarian cancer that were published recently from PLSD and did not correspond well with current clinical guidelines. The reasons should be clarified. Decision-making on opting for or against RRS and its timing should be better aligned with predicted risk and mortality for endometrial and ovarian cancer in Lynch syn-drome to improve outcomes. (C) 2021 The Author(s). Published by Elsevier Ltd.