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Andrianova MA, Seplyarskiy VB, Terradas M, Sánchez-Heras AB, Mur P, Soto JL, Aiza G, Borràs E, Kondrashov FA, Kondrashov AS, Bazykin GA, Valle L. Discovery of recessive effect of human polymerase δ proofreading deficiency through mutational analysis of POLD1-mutated normal and cancer cells. Eur J Hum Genet 2024; 32:837-845. [PMID: 38658779 PMCID: PMC11219999 DOI: 10.1038/s41431-024-01598-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Revised: 02/16/2024] [Accepted: 03/18/2024] [Indexed: 04/26/2024] Open
Abstract
Constitutional heterozygous pathogenic variants in the exonuclease domain of POLE and POLD1, which affect the proofreading activity of the corresponding polymerases, cause a cancer predisposition syndrome characterized by increased risk of gastrointestinal polyposis, colorectal cancer, endometrial cancer and other tumor types. The generally accepted explanation for the connection between the disruption of the proofreading activity of polymerases epsilon and delta and cancer development is through an increase in the somatic mutation rate. Here we studied an extended family with multiple members heterozygous for the pathogenic POLD1 variant c.1421T>C p.(Leu474Pro), which segregates with the polyposis and cancer phenotypes. Through the analysis of mutational patterns of patient-derived fibroblasts colonies and de novo mutations obtained by parent-offspring comparisons, we concluded that heterozygous POLD1 L474P just subtly increases the somatic and germline mutation burden. In contrast, tumors developed in individuals with a heterozygous mutation in the exonuclease domain of POLD1, including L474P, have an extremely high mutation rate (>100 mut/Mb) associated with signature SBS10d. We solved this contradiction through the observation that tumorigenesis involves somatic inactivation of the wildtype POLD1 allele. These results imply that exonuclease deficiency of polymerase delta has a recessive effect on mutation rate.
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Affiliation(s)
- Maria A Andrianova
- Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology, Barcelona, Spain
| | - Vladimir B Seplyarskiy
- Department of Biomedical Informatics, Harvard Medical School, Boston, MA, USA
- Division of Genetics, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA
| | - Mariona Terradas
- Hereditary Cancer Program, Catalan Institute of Oncology, Oncobell Program, IDIBELL, Hospitalet de Llobregat, Barcelona, Spain
| | - Ana Beatriz Sánchez-Heras
- Foundation for the Promotion of Health and Biomedical Research of Valencia Region (FISABIO), Elche Health Department, Elche, Spain
- Medical Oncology Department, Cancer Genetic Counseling Unit. Elche University Hospital, Elche, Spain
| | - Pilar Mur
- Hereditary Cancer Program, Catalan Institute of Oncology, Oncobell Program, IDIBELL, Hospitalet de Llobregat, Barcelona, Spain
- Department of Health of Catalonia, Catalan Cancer Plan, Barcelona, Spain
| | - José Luis Soto
- Foundation for the Promotion of Health and Biomedical Research of Valencia Region (FISABIO), Elche Health Department, Elche, Spain
- Molecular Genetics Unit, Elche University Hospital, Elche, Spain
| | - Gemma Aiza
- Hereditary Cancer Program, Catalan Institute of Oncology, Oncobell Program, IDIBELL, Hospitalet de Llobregat, Barcelona, Spain
| | - Emma Borràs
- Molecular Genetics Unit, Consorci Sanitari de Terrassa, Terrassa, Spain
| | - Fyodor A Kondrashov
- Institute of Science and Technology Austria, Klosterneuburg, Austria
- Evolutionary and Synthetic Biology Unit, Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan
| | - Alexey S Kondrashov
- Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI, USA
| | - Georgii A Bazykin
- Department of Biomedical Informatics, Harvard Medical School, Boston, MA, USA
- Division of Genetics, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA
| | - Laura Valle
- Hereditary Cancer Program, Catalan Institute of Oncology, Oncobell Program, IDIBELL, Hospitalet de Llobregat, Barcelona, Spain.
- Centro de Investigación Biomédica en Red de Cáncer (CIBERONC), Madrid, Spain.
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Lynch Syndrome: From Carcinogenesis to Prevention Interventions. Cancers (Basel) 2022; 14:cancers14174102. [PMID: 36077639 PMCID: PMC9454739 DOI: 10.3390/cancers14174102] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2022] [Revised: 08/23/2022] [Accepted: 08/23/2022] [Indexed: 11/25/2022] Open
Abstract
Simple Summary Promoting proper preventive interventions to reduce morbidity and mortality is one of the most important challenges pertaining to inherited conditions. Lynch syndrome (LS) is an inherited disorder that predisposes to several kinds of tumor and is responsible for a relevant proportion of human colorectal and endometrial cancers. Recent knowledge has allowed for a better understanding of the genetic cause, pathogenesis, underlying immunological mechanisms, epidemiological distribution, and prevalence of this disease. This opens up unpredictable perspectives of translating such knowledge into validated programs for prevention and surveillance, in order to reduce the health impact of this disease through medical interventions before cancer development. In our review, we summarize the updated guidelines of the screening, surveillance, and risk-reducing strategies for LS patients. Moreover, we present novel opportunities in the treatment and prevention of LS patients through harnessing the immune system using immunocheckpoint inhibitors and vaccines. Abstract Lynch syndrome (LS) is the most common inherited disorder responsible for an increased risk of developing cancers at different sites, most frequently in the gastrointestinal and genitourinary tracts, caused by a germline pathogenic variant affecting the DNA mismatch repair system. Surveillance and risk-reducing procedures are currently available and warranted for LS patients, depending on underlying germline mutation, and are focused on relevant targets for early cancer diagnosis or primary prevention. Although pharmacological approaches for preventing LS-associated cancer development were started many years ago, to date, aspirin remains the most studied drug intervention and the only one suggested by the main surveillance guidelines, despite the conflicting findings. Furthermore, we also note that remarkable advances in anticancer drug discovery have given a significant boost to the application of novel immunological strategies such as immunocheckpoint inhibitors and vaccines, not only for cancer treatment, but also in a preventive setting. In this review, we outline the clinical, biologic, genetic, and morphological features of LS as well as the recent three-pathways carcinogenesis model. Furthermore, we provide an update on the dedicated screening, surveillance, and risk-reducing strategies for LS patients and describe emerging opportunities of harnessing the immune system.
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Rath A, Mishra A, Ferreira VD, Hu C, Omerza G, Kelly K, Hesse A, Reddi HV, Grady JP, Heinen CD. Functional interrogation of Lynch syndrome-associated MSH2 missense variants via CRISPR-Cas9 gene editing in human embryonic stem cells. Hum Mutat 2019; 40:2044-2056. [PMID: 31237724 DOI: 10.1002/humu.23848] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2018] [Revised: 05/08/2019] [Accepted: 06/19/2019] [Indexed: 12/18/2022]
Abstract
Lynch syndrome (LS) predisposes patients to cancer and is caused by germline mutations in the DNA mismatch repair (MMR) genes. Identifying the deleterious mutation, such as a frameshift or nonsense mutation, is important for confirming an LS diagnosis. However, discovery of a missense variant is often inconclusive. The effects of these variants of uncertain significance (VUS) on disease pathogenesis are unclear, though understanding their impact on protein function can help determine their significance. Laboratory functional studies performed to date have been limited by their artificial nature. We report here an in-cellulo functional assay in which we engineered site-specific MSH2 VUS using clustered regularly interspaced short palindromic repeats-Cas9 gene editing in human embryonic stem cells. This approach introduces the variant into the endogenous MSH2 loci, while simultaneously eliminating the wild-type gene. We characterized the impact of the variants on cellular MMR functions including DNA damage response signaling and the repair of DNA microsatellites. We classified the MMR functional capability of eight of 10 VUS providing valuable information for determining their likelihood of being bona fide pathogenic LS variants. This human cell-based assay system for functional testing of MMR gene VUS will facilitate the identification of high-risk LS patients.
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Affiliation(s)
- Abhijit Rath
- Center for Molecular Oncology and Institute for Systems Genomics, UConn Health, Farmington, Connecticut
| | - Akriti Mishra
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, Connecticut
| | | | - Chaoran Hu
- Department of Statistics, University of Connecticut, Storrs, Connecticut.,Connecticut Institute for Clinical and Translational Science, UConn Health, Farmington, Connecticut
| | - Gregory Omerza
- Clinical Genomics Laboratory, The Jackson Laboratory for Genomic Medicine, Farmington, Connecticut
| | - Kevin Kelly
- Clinical Genomics Laboratory, The Jackson Laboratory for Genomic Medicine, Farmington, Connecticut
| | - Andrew Hesse
- Clinical Genomics Laboratory, The Jackson Laboratory for Genomic Medicine, Farmington, Connecticut
| | - Honey V Reddi
- Clinical Genomics Laboratory, The Jackson Laboratory for Genomic Medicine, Farmington, Connecticut
| | - James P Grady
- Connecticut Institute for Clinical and Translational Science, UConn Health, Farmington, Connecticut
| | - Christopher D Heinen
- Center for Molecular Oncology and Institute for Systems Genomics, UConn Health, Farmington, Connecticut
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4
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Martín-Morales L, Feldman M, Vershinin Z, Garre P, Caldés T, Levy D. SETD6 dominant negative mutation in familial colorectal cancer type X. Hum Mol Genet 2018; 26:4481-4493. [PMID: 28973356 DOI: 10.1093/hmg/ddx336] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2017] [Accepted: 08/15/2017] [Indexed: 01/01/2023] Open
Abstract
Familiar colorectal cancer type X (FCCTX) comprises families that fulfill the Amsterdam criteria for hereditary non-polyposis colorectal cancer, but that lack the mismatch repair deficiency that defines the Lynch syndrome. Thus, the genetic cause that increases the predisposition to colorectal and other related cancers in families with FCCTX remains to be elucidated. Using whole-exome sequencing, we have identified a truncating mutation in the SETD6 gene (c.791_792insA, p.Met264IlefsTer3) in all the affected members of a FCCTX family. SETD6 is a mono-methyltransferase previously shown to modulate the NF-κB and Wnt signaling pathways, among other. In the present study, we characterized the truncated version of SETD6, providing evidence that this SETD6 mutation may play a role in the cancer inheritance in this family. Here we demonstrate that the truncated SETD6 lacks its enzymatic activity as a methyltransferase, while maintaining other properties such as its expression, localization and substrate-binding ability. In addition, we show that the mutant allele is expressed and that the resulting protein competes with the wild type for their substrates, pointing to a dominant negative nature. These findings suggest that the identified mutation impairs the normal function of SETD6, which may result in the deregulation of the different pathways in which it is involved, contributing to the increased susceptibility to cancer in this FCCTX family.
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Affiliation(s)
- Lorena Martín-Morales
- Molecular Oncology Laboratory, Department of Medical Oncology, Hospital Clínico San Carlos, IdISSC, CIBERONC, 28040 Madrid, Spain
| | - Michal Feldman
- The Shraga Segal Department of Microbiology, Immunology and Genetics.,National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, Be'er-Sheva 84105, Israel
| | - Zlata Vershinin
- The Shraga Segal Department of Microbiology, Immunology and Genetics.,National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, Be'er-Sheva 84105, Israel
| | - Pilar Garre
- Molecular Oncology Laboratory, Department of Medical Oncology, Hospital Clínico San Carlos, IdISSC, CIBERONC, 28040 Madrid, Spain
| | - Trinidad Caldés
- Molecular Oncology Laboratory, Department of Medical Oncology, Hospital Clínico San Carlos, IdISSC, CIBERONC, 28040 Madrid, Spain
| | - Dan Levy
- The Shraga Segal Department of Microbiology, Immunology and Genetics.,National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, Be'er-Sheva 84105, Israel
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Porkka N, Valo S, Nieminen TT, Olkinuora A, Mäki-Nevala S, Eldfors S, Peltomäki P. Sequencing of Lynch syndrome tumors reveals the importance of epigenetic alterations. Oncotarget 2017; 8:108020-108030. [PMID: 29296220 PMCID: PMC5746122 DOI: 10.18632/oncotarget.22445] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2017] [Accepted: 10/27/2017] [Indexed: 02/07/2023] Open
Abstract
Genomic instability and epigenetic aberrations are important classifiers of human tumors, yet, their interrelations are poorly understood. We used Lynch syndrome (LS) to address such relationships. Forty-five tumors (11 colorectal adenomas, 18 colorectal carcinomas, and 16 ovarian carcinomas) were profiled for CpG Island Methylator Phenotype (CIMP) and somatic mutations. All tumors showed high-degree microsatellite instability. Panel sequencing of 578 cancer-relevant genes revealed the average number of 1433, 1124, and 657 non-synonymous somatic mutations per colorectal adenoma, colorectal carcinoma, and ovarian carcinoma, respectively. Genes harboring mutations with allele frequency 25 % or higher in at least 31 % of tumors were regarded to be possible drivers. Among 72 and 10 such genes identified in colorectal and ovarian tumors, respectively, the most frequently mutated genes BRD4 and MLL2 (62 % of colorectal tumors) and ARID1A (50 % of ovarian carcinomas) are involved in epigenetic regulation. The total number of somatic mutations or mutant genes per tumor were significantly associated with CIMP. Our results suggest that even in an inherited disease, tumor type-specific epigenetic changes are significant and may result from regulatory changes (CIMP) or structural events (mutations of epigenetic regulatory genes). The findings are clinically relevant since many of the affected pathways can be therapeutically targeted.
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Affiliation(s)
- Noora Porkka
- Department of Medical and Clinical Genetics, University of Helsinki, Helsinki, Finland
| | - Satu Valo
- Department of Medical and Clinical Genetics, University of Helsinki, Helsinki, Finland
| | - Taina T Nieminen
- Department of Medical and Clinical Genetics, University of Helsinki, Helsinki, Finland
| | - Alisa Olkinuora
- Department of Medical and Clinical Genetics, University of Helsinki, Helsinki, Finland
| | - Satu Mäki-Nevala
- Department of Medical and Clinical Genetics, University of Helsinki, Helsinki, Finland
| | - Samuli Eldfors
- Institute for Molecular Medicine Finland, University of Helsinki, Helsinki, Finland
| | - Päivi Peltomäki
- Department of Medical and Clinical Genetics, University of Helsinki, Helsinki, Finland
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6
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Abstract
Four main DNA mismatch repair (MMR) genes have been identified, MLH1, MSH2, MSH6, and PMS2, which when mutated cause susceptibility to Lynch syndrome (LS). LS is one of the most prevalent hereditary cancer syndromes in man and accounts for 1–3 % of unselected colorectal carcinomas and some 15 % of those with microsatellite instability and/or absent MMR protein. The International Society for Gastrointestinal Hereditary Tumours (InSiGHT) maintains a database for LS-associated mutations since 1996. The database was recently reorganized to efficiently gather published and unpublished data and to classify the variants according to a five-tiered scheme linked to clinical recommendations. This review provides an update of germline mutations causing susceptibility to LS based on information available in the InSiGHT database and the latest literature. MMR gene mutation profiles, correlations between genotype and phenotype, and possible mechanisms leading to the characteristic spectrum of tumors in LS are discussed in light of the different functions of MMR proteins, many of which directly serve cancer avoidance.
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7
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Shetzer Y, Napchan Y, Kaufman T, Molchadsky A, Tal P, Goldfinger N, Rotter V. Immune deficiency augments the prevalence of p53 loss of heterozygosity in spontaneous tumors but not bi-directional loss of heterozygosity in bone marrow progenitors. Int J Cancer 2017; 140:1364-1369. [PMID: 28008605 DOI: 10.1002/ijc.30554] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2016] [Accepted: 11/24/2016] [Indexed: 01/06/2023]
Abstract
p53 loss of heterozygosity (LOH) is a frequent event in tumors of somatic and Li-Fraumeni syndrome patients harboring p53 mutation. Here, we focused on resolving a possible crosstalk between the immune-system and p53 LOH. Previously, we reported that p53 heterozygous bone-marrow mesenchymal progenitor cells undergo p53 LOH in-vivo. Surprisingly, the loss of either the wild-type p53 allele or mutant p53 allele was detected with a three-to-one ratio in favor of losing the mutant allele. In this study, we examined whether the immune-system can affect the LOH directionality in bone marrow progenitors. We found that mesenchymal progenitor cells derived from immune-deficient mice exhibited the same preference of losing the mutant p53 allele as immune-competent matched cells, nevertheless, these animals showed a significantly shorter tumor-free survival, indicating the possible involvement of immune surveillance in this model. Surprisingly, spontaneous tumors of p53 heterozygous immune-deficient mice exhibited a significantly higher incidence of p53 LOH compared to that observed in tumors derived of p53 heterozygous immune-competent mice. These findings indicate that the immune-system may affect the p53 LOH prevalence in spontaneous tumors. Thus suggesting that the immune-system may recognize and clear cells that underwent p53 LOH, whereas in immune-compromised mice, those cells will form tumors with shorter latency. In individuals with a competent immune-system, p53 LOH independent pathways may induce malignant transformation which requires a longer tumor latency. Moreover, this data may imply that the current immunotherapy treatment aimed at abrogating the inhibition of cellular immune checkpoints may be beneficial for LFS patients.
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Affiliation(s)
- Yoav Shetzer
- Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot, 76100, Israel
| | - Yael Napchan
- Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot, 76100, Israel
| | - Tom Kaufman
- Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot, 76100, Israel
| | - Alina Molchadsky
- Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot, 76100, Israel
| | - Perry Tal
- Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot, 76100, Israel
| | - Naomi Goldfinger
- Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot, 76100, Israel
| | - Varda Rotter
- Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot, 76100, Israel
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8
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Shetzer Y, Kagan S, Koifman G, Sarig R, Kogan-Sakin I, Charni M, Kaufman T, Zapatka M, Molchadsky A, Rivlin N, Dinowitz N, Levin S, Landan G, Goldstein I, Goldfinger N, Pe'er D, Radlwimmer B, Lichter P, Rotter V, Aloni-Grinstein R. The onset of p53 loss of heterozygosity is differentially induced in various stem cell types and may involve the loss of either allele. Cell Death Differ 2014; 21:1419-31. [PMID: 24832469 DOI: 10.1038/cdd.2014.57] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2013] [Revised: 02/27/2014] [Accepted: 03/17/2014] [Indexed: 12/12/2022] Open
Abstract
p53 loss of heterozygosity (p53LOH) is frequently observed in Li-Fraumeni syndrome (LFS) patients who carry a mutant (Mut) p53 germ-line mutation. Here, we focused on elucidating the link between p53LOH and tumor development in stem cells (SCs). Although adult mesenchymal stem cells (MSCs) robustly underwent p53LOH, p53LOH in induced embryonic pluripotent stem cells (iPSCs) was significantly attenuated. Only SCs that underwent p53LOH induced malignant tumors in mice. These results may explain why LFS patients develop normally, yet acquire tumors in adulthood. Surprisingly, an analysis of single-cell sub-clones of iPSCs, MSCs and ex vivo bone marrow (BM) progenitors revealed that p53LOH is a bi-directional process, which may result in either the loss of wild-type (WT) or Mut p53 allele. Interestingly, most BM progenitors underwent Mutp53LOH. Our results suggest that the bi-directional p53LOH process may function as a cell-fate checkpoint. The loss of Mutp53 may be regarded as a DNA repair event leading to genome stability. Indeed, gene expression analysis of the p53LOH process revealed upregulation of a specific chromatin remodeler and a burst of DNA repair genes. However, in the case of loss of WTp53, cells are endowed with uncontrolled growth that promotes cancer.
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Affiliation(s)
- Y Shetzer
- Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot, Israel
| | - S Kagan
- Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot, Israel
| | - G Koifman
- Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot, Israel
| | - R Sarig
- Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot, Israel
| | - I Kogan-Sakin
- Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot, Israel
| | - M Charni
- Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot, Israel
| | - T Kaufman
- Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot, Israel
| | - M Zapatka
- Division of Molecular Genetics, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, Heidelberg, Germany
| | - A Molchadsky
- Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot, Israel
| | - N Rivlin
- Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot, Israel
| | - N Dinowitz
- Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot, Israel
| | - S Levin
- Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot, Israel
| | - G Landan
- Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot, Israel
| | - I Goldstein
- Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot, Israel
| | - N Goldfinger
- Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot, Israel
| | - D Pe'er
- Department of Biological Sciences, Columbia University, New York, NY, USA
| | - B Radlwimmer
- Division of Molecular Genetics, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, Heidelberg, Germany
| | - P Lichter
- Division of Molecular Genetics, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, Heidelberg, Germany
| | - V Rotter
- Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot, Israel
| | - R Aloni-Grinstein
- Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot, Israel
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Dwight T, Mann K, Benn DE, Robinson BG, McKelvie P, Gill AJ, Winship I, Clifton-Bligh RJ. Familial SDHA mutation associated with pituitary adenoma and pheochromocytoma/paraganglioma. J Clin Endocrinol Metab 2013; 98:E1103-8. [PMID: 23633203 DOI: 10.1210/jc.2013-1400] [Citation(s) in RCA: 90] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
CONTEXT Reports of the coexistence of pituitary adenomas and pheochromocytoma/paraganglioma are uncommon. Recently germline mutations in 2 of the genes encoding succinate dehydrogenase, SDHC and SDHD, were associated with pituitary tumors. OBJECTIVE Our aim was to determine whether the development of a pituitary adenoma was associated with SDHA mutation. PATIENTS A 46-year-old female presented with carotid body paraganglioma (proband). Subsequently the proband's son was diagnosed with a nonfunctioning pituitary macroadenoma at age 30 years. RESULTS An immunohistochemical analysis of the resected paraganglioma and pituitary adenoma revealed the loss of succinate dehydrogenase subunit B and succinate dehydrogenase subunit A (SDHA) expression in both tumors, with the preservation of staining in nonneoplastic tissue. Mutation analysis showed a novel SDHA mutation (c.1873C>T, p.His625Tyr) in the germline of the proband as well as in the proband's son. In the paraganglioma of the proband, in addition to the germline mutation, a somatic mutation was observed (c.1865G>A, p.Trp622*). In the pituitary adenoma of the proband's son, loss of SDHA immunoreactivity was paradoxically accompanied by loss of the mutant allele. CONCLUSIONS This is the first report of a pituitary adenoma arising in the setting of germline SDHA mutation. The loss of SDHA protein expression in both the paraganglioma (proband) and pituitary adenoma (proband's son) argues strongly for a causative role of SDHA mutation. This report further strengthens the link between pituitary neoplasia and germline SDH mutation. Although pituitary adenomas appear rare among patients carrying SDH subunit mutations, they may have been underrecognized due to the low penetrance of disease and lack of systematic surveillance.
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Affiliation(s)
- Trisha Dwight
- Cancer Genetics, Hormones and Cancer Group, Kolling Institute of Medical Research, Royal North Shore Hospital, Sydney, New South Wales 2065, Australia.
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Colas C, Coulet F, Svrcek M, Collura A, Fléjou JF, Duval A, Hamelin R. Lynch or not Lynch? Is that always a question? Adv Cancer Res 2012; 113:121-66. [PMID: 22429854 DOI: 10.1016/b978-0-12-394280-7.00004-x] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The familial cancer syndrome referred to as Lynch I and II was renamed hereditary nonpolyposis colorectal cancer (HNPCC) only to revert later to Lynch syndrome (LS). LS is the most frequent human predisposition for the development of colorectal cancer (CRC), and probably also for endometrial and gastric cancers, although it has yet to acquire a consensus name. Its estimated prevalence ranges widely from 2% to 7% of all CRCs due to the fact that tumors from patients with LS are difficult to recognize at both the clinical and molecular level. This review is based on two assumptions. First, all LS patients inherit a predisposition to develop CRC (without polyposis) and/or other tumors from the Lynch spectrum. Second, all LS patients have a germline defect in one of the DNA mismatch repair (MMR) genes. When a somatic second hit inactivates the relevant MMR gene, the consequence is instability of DNA repeat sequences such as microsatellites and the tumors are referred to as having the microsatellite instability (MSI) phenotype. However, some of the inherited predisposition to develop CRC without concurrent polyposis, termed HNPCC, is found in non-LS patients, while not all MSI tumors are from LS cases. LS tumors are therefore at the junction of inherited and MSI cases. We describe here the defining characteristics of LS tumors that differentiate them from inherited non-MSI tumors and from non-inherited MSI tumors.
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Affiliation(s)
- Chrystelle Colas
- INSERM, UMRS 938, Centre de Recherche Saint-Antoine, Equipe Instabilité des Microsatellites et Cancers, Paris, France
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Cordeiro AT, Silva CMGD, Bartchewsky Júnior W, Ribeiro ML, Martinez CAR. Avaliação da expressão do gene MGMT nos tecidos normal e neoplásico de doentes com câncer colorretal. Rev Col Bras Cir 2012. [DOI: 10.1590/s0100-69912012000100010] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
OBJETIVO: Avaliar a expressão tecidual do gene de reparo MGMT comparando a mucosa cólica normal e neoplásica em doentes com câncer colorretal. MÉTODOS: Foram estudados 44 portadores de adenocarcinoma colorretal confirmado por estudo histopatológico. Foram excluídos doentes suspeitos de pertencerem a famílias com câncer colorretal hereditário (HNPCC e PAF) e os portadores de câncer do reto médio e inferior submetidos a tratamento quimioradioterápico neoadjuvante. A expressão do gene MGMT foi avaliada pela técnica da reação de polimerase em cadeia em tempo real (RT-PCR). A comparação dos resultados encontrados para expressão do gene MGMT entre tecidos normais e neoplásicos foi feita pelo teste t de Student pareado, adotando-se nível de significância de 5% (p <0,05). RESULTADOS: A expressão tecidual do gene MGMT em todos os doentes foi menor no tecido neoplásico quando comparada a do tecido normal (p=0,002). CONCLUSÃO: O gene de reparo MGMT encontra-se menos expresso no tecido neoplásico quando comparados aos tecidos normais em portadores de CCR esporádico.
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12
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Zavodna K, Krivulcik T, Bujalkova MG, Slamka T, Martinicky D, Ilencikova D, Bartosova Z. Partial loss of heterozygosity events at the mutated gene in tumors from MLH1/MSH2 large genomic rearrangement carriers. BMC Cancer 2009; 9:405. [PMID: 19930554 PMCID: PMC2788582 DOI: 10.1186/1471-2407-9-405] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2009] [Accepted: 11/20/2009] [Indexed: 11/24/2022] Open
Abstract
Background Depending on the population studied, large genomic rearrangements (LGRs) of the mismatch repair (MMR) genes constitute various proportions of the germline mutations that predispose to hereditary non-polyposis colorectal cancer (HNPCC). It has been reported that loss of heterozygosity (LOH) at the LGR region occurs through a gene conversion mechanism in tumors from MLH1/MSH2 deletion carriers; however, the converted tracts were delineated only by extragenic microsatellite markers. We sought to determine the frequency of LGRs in Slovak HNPCC patients and to study LOH in tumors from LGR carriers at the LGR region, as well as at other heterozygous markers within the gene to more precisely define conversion tracts. Methods The main MMR genes responsible for HNPCC, MLH1, MSH2, MSH6, and PMS2, were analyzed by MLPA (multiplex ligation-dependent probe amplification) in a total of 37 unrelated HNPCC-suspected patients whose MLH1/MSH2 genes gave negative results in previous sequencing experiments. An LOH study was performed on six tumors from LGR carriers by combining MLPA to assess LOH at LGR regions and sequencing to examine LOH at 28 SNP markers from the MLH1 and MSH2 genes. Results We found six rearrangements in the MSH2 gene (five deletions and dup5-6), and one aberration in the MLH1 gene (del5-6). The MSH2 deletions were of three types (del1, del1-3, del1-7). We detected LOH at the LGR region in the single MLH1 case, which was determined in a previous study to be LOH-negative in the intragenic D3S1611 marker. Three tumors displayed LOH of at least one SNP marker, including two cases that were LOH-negative at the LGR region. Conclusion LGRs accounted for 25% of germline MMR mutations identified in 28 Slovakian HNPCC families. A high frequency of LGRs among the MSH2 mutations provides a rationale for a MLPA screening of the Slovakian HNPCC families prior scanning by DNA sequencing. LOH at part of the informative loci confined to the MLH1 or MSH2 gene (heterozygous LGR region, SNP, or microsatellite) is a novel finding and can be regarded as a partial LOH. The conversion begins within the gene, and the details of conversion tracts are discussed for each case.
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Affiliation(s)
- Katarina Zavodna
- Laboratory of Cancer Genetics, Cancer Research Institute of Slovak Academy of Sciences, Vlarska 7, 833 91 Bratislava, Slovak Republic.
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Martinez CAR, Cordeiro AT, Priolli DG, Miranda DDDC, Bartchewsky Júnior W, Margarido NF, Ribeiro ML. Avaliação da expressão tecidual do gene de reparo MLH1 e dos níveis de dano oxidativo ao DNA em doentes com câncer colorretal. ACTA ACUST UNITED AC 2009. [DOI: 10.1590/s0101-98802009000300004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
O dano oxidativo ao DNA provocado por radicais livres de oxigênio representa um dos principais mecanismos responsáveis pelas etapas iniciais da carcinogênese colorretal. O estresse oxidativo ocasiona erros de pareamento de bases possibilitando o aparecimento de mutações em genes controladores do ciclo celular. As células possuem um sistema de defesa representado pelos genes de reparo do DNA que corrigindo os erros de pareamento impedem o desenvolvimento de mutações. Poucos estudos avaliaram a relação entre dano oxidativo ao DNA e a expressão tecidual do gene de reparo MLH1. OBJETIVO: O objetivo do presente estudo foi avaliar os níveis de estresse oxidativo ao DNA e a expressão tecidual do gene de reparo MLH1 nas células da mucosa cólica normal e neoplásica de doentes com câncer colorretal. MATERIAL E MÉTODO: Foram estudados 44 doentes com diagnóstico de adenocarcinoma colorretal. Foram excluídos os doentes com câncer colorretal hereditário, portadores de câncer relacionado às doenças inflamatórias intestinais e os submetidos à radioquimioterapia neoadjuvante. Para a avaliação dos níveis de dano oxidativo ao DNA utilizou-se a técnica da eletroforese alcalina em gel de célula isolada (ensaio do cometa) avaliando 100 células obtidas dos tecidos normal e neoplásico. Para a avaliação da expressão do gene MLH1 utilizou-se a técnica de reação de polimerase em cadeia em tempo real (RT-PCR) com primer especificamente desenhados para amplificação do gene. A comparação dos resultados encontrados para os níveis de estresse oxidativo ao DNA, e expressão do gene MLH1 nos tecidos normais e neoplásicos foi feito pelo teste t de Student, adotando-se nível de significância de 5% (p<0,05). RESULTADOS: Os níveis de dano oxidativo ao DNA no tecido neoplásico foram significativamente mais elevados quando comparados ao tecido normal (p=0,0001). A expressão tecidual do gene MLH1 no tecido neoplásico foi significativamente menor quando comparado ao tecido normal (p=0,02). CONCLUSÃO: O gene de reparo MLH1 encontra-se menos expresso no tecido neoplásico e inversamente relacionado aos níveis de dano oxidativo ao DNA.
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Abstract
Colorectal cancers (CRC)--and probably all cancers--are caused by alterations in genes. This includes activation of oncogenes and inactivation of tumor suppressor genes (TSGs). There are many ways to achieve these alterations. Oncogenes are frequently activated by point mutation, gene amplification, or changes in the promoter (typically caused by chromosomal rearrangements). TSGs are typically inactivated by mutation, deletion, or promoter methylation, which silences gene expression. About 15% of CRC is associated with loss of the DNA mismatch repair system, and the resulting CRCs have a unique phenotype that is called microsatellite instability, or MSI. This paper reviews the types of genetic alterations that can be found in CRCs and hepatocellular carcinoma (HCC), and focuses upon the epigenetic alterations that result in promoter methylation and the CpG island methylator phenotype (CIMP). The challenge facing CRC research and clinical care at this time is to deal with the heterogeneity and complexity of these genetic and epigenetic alterations, and to use this information to direct rational prevention and treatment strategies.
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Affiliation(s)
- Clement Richard Boland
- Division of Gastroenterology, Department of Internal Medicine, Sammons Cancer Center, Baylor Research Institute, Baylor University Medical Center, 3500 Gaston Avenue, Dallas, TX 75246, USA.
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Hofstra RMW, Spurdle AB, Eccles D, Foulkes WD, de Wind N, Hoogerbrugge N, Hogervorst FBL. Tumor characteristics as an analytic tool for classifying genetic variants of uncertain clinical significance. Hum Mutat 2008; 29:1292-303. [PMID: 18951447 DOI: 10.1002/humu.20894] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
It is important to identify a germline mutation in a patient with an inherited cancer syndrome to allow mutation carriers to be included in cancer surveillance programs, which have been proven to save lives. Many of the mutations identified result in premature termination of translation, and thus in loss-of-function of the encoded mutated protein. However, the significance of a large proportion of the sequence changes reported is unknown. Some of these variants will be associated with a high risk of cancer and have direct clinical consequence. Many criteria can be used to classify variants with unknown significance; most criteria are based on the characteristics of the amino acid change, on segregation data and appearance of the variant, on the presence of the variant in controls, or on functional assays. In inherited cancers, tumor characteristics can also be used to classify variants. It is worthwhile to examine the clinical, morphological and molecular features of a patient, and his or her family, when assessing whether the role of a variant is likely to be neutral or pathogenic. Here we describe the advantages and disadvantages of using the tumor characteristics of patients carrying germline variants of uncertain significance (VUS) in BRCA1, BRCA2, or in one of the mismatch repair (MMR) genes, MLH1, MSH2, or MSH6, to infer pathogenicity.
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Affiliation(s)
- Robert M W Hofstra
- Department of Genetics, University Medical Center Groningen and University of Groningen, Groningen, the Netherlands.
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Genome-wide copy neutral LOH is infrequent in familial and sporadic microsatellite unstable carcinomas. Fam Cancer 2008; 7:319-30. [DOI: 10.1007/s10689-008-9194-8] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2008] [Accepted: 04/01/2008] [Indexed: 01/05/2023]
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Imai K, Yamamoto H. Carcinogenesis and microsatellite instability: the interrelationship between genetics and epigenetics. Carcinogenesis 2008; 29:673-80. [PMID: 17942460 DOI: 10.1093/carcin/bgm228] [Citation(s) in RCA: 307] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
DNA mismatch repair (MMR) deficiency results in a strong mutator phenotype and high-frequency microsatellite instability (MSI-H), which are the hallmarks of tumors arising within Lynch syndrome. MSI-H is characterized by length alterations within simple repeated sequences, microsatellites. Lynch syndrome is primarily due to germline mutations in one of the DNA MMR genes; mainly hMLH1 or hMSH2 and less frequently hMSH6 and rarely hPMS2. Germline hemiallelic methylation of MLH1, termed epimutation, has been reported to be a new cause of Lynch syndrome. MSI-H is also observed in approximately 15% of colorectal, gastric and endometrial cancers and in lower frequencies in a minority of other tumors, where it is associated with the hypermethylation of the promoter region of hMLH1. MSI-H underlies a distinctive tumorigenic pathway because cancers with MSI-H exhibit many differences in genotype and phenotype relative to cancers without MSI-H, irrespective of their hereditary or sporadic origins. Genetic, epigenetic and transcriptomic differences exist between cancers with and those without the MSI-H. The BRAF V600E mutation is associated with sporadic MSI-H colorectal cancers (CRCs) harboring hMLH1 methylation but not Lynch syndrome-related CRCs. The differences in genotype and phenotype between cancers with and those without MSI-H are likely to be causally linked to their differences in biological and clinical features. Therefore, the diagnosis of MSI-H in cancers is thus considered to be of increasing relevance, because MSI-H is a useful screening marker for identifying patients with Lynch syndrome, a better prognostic factor and could affect the efficacy of chemotherapy. This review addresses recent advances in the field of microsatellite instability research.
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Affiliation(s)
- Kohzoh Imai
- Sapporo Medical University, South 1, West 17, Chuo-ku, Sapporo 060-8556, Japan.
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Zhou CZ, Qiu GQ, Fan JW, Wang XL, Tang HM, Huang L, Sun YH, Peng ZH. Refined mapping of loss of heterozygosity on 1q31.1-32.1 in sporadic colorectal carcinoma. World J Gastroenterol 2008; 14:1582-7. [PMID: 18330952 PMCID: PMC2693756 DOI: 10.3748/wjg.14.1582] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
AIM: To explore precise deleted regions and screen the candidate tumor suppressor genes related to sporadic colorectal carcinoma.
METHODS: Six markers on 1q31.1-32.1 were chosen. These polymorphic microsatellite markers in 83 colorectal cancer patients tumor and normal DNA were analyzed via PCR. PCR products were electrophoresed on an ABI 377 DNA sequencer. Genescan 3.1 and Genotype 2.1 software were used for Loss of heterozygosity (LOH) scanning and analysis. Comparison between LOH frequency and clinicopathological factors was performed by χ2 test.
RESULTS: 1q31.1-32.1 exhibited higher LOH frequency in colorectal carcinoma. The average LOH frequency of 1q31.1-32.1 was 23.0%, with the highest frequency of 36.7% (18/49) at D1S2622, and the lowest of 16.4% (11/67) at D1S412, respectively. A minimal region of frequent deletion was located within a 2 cM genomic segment at D1S413-D1S2622 (1q31.3-32.1). There was no significant association between LOH of each marker on 1q31.1-32.1 and the clinicopathological data (patient sex, age, tumor size, growth pattern or Dukes stage), which indicated that on 1q31.1-32.1, LOH was a common phenomenon in all kinds of sporadic colorectal carcinoma.
CONCLUSION: Through our refined deletion mapping, the critical and precise deleted region was located within 2 cM chromosomal segment encompassing 2 loci (D1S413, D1S2622). No significant association was found between LOH and clinicopathologic features in 1q31.1-32.1.
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Yan H, Jin H, Xue G, Mei Q, Ding F, Hao L, Sun SH. Germline hMSH2 promoter mutation in a Chinese HNPCC kindred: evidence for dual role of LOH. Clin Genet 2007; 72:556-61. [PMID: 17894833 DOI: 10.1111/j.1399-0004.2007.00911.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Hereditary non-polyposis colorectal cancer (HNPCC) is a dominantly inherited cancer predisposition syndrome that is caused by germline mutations in mismatch repair genes. By screening the core promoters of hMSH2, hMLH1, and hMSH6 in 37 Chinese suspected HNPCC families, a novel germline mutation c.-78_-79delGT was found in the hMSH2 promoter. Its pathogenic effects were supported by the following findings: (a) it co-segregated with HNPCC-related cancers and was not present in the 220 control subjects, (b) tumors harboring the mutation lacked the expression of hMSH2 and showed high microsatellite instability, (c) it significantly decreased the promoter activity, and (d) it abolished the binding ability of the transcription factor E1A-F. Loss of heterozygosity (LOH) was found in three of the tumors studied. Intriguingly, in the tumors from patients II:1 and III:1, LOH occurred in the wild-type allele and agreed well with the traditional 'two-hit' model. In contrast, in the tumor from patient III:3, LOH occurred in the mutant allele. A pathogenic somatic mutation (c.2210+1G>A) was also found in this tumor; therefore, we proposed that the 'second hit' was inactivated by somatic mutation, and the mutant allele was lost during tumor progression; this provided evidence for the new hypothesis for the dual role of LOH.
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Affiliation(s)
- H Yan
- Department of Medical Genetics, College of Basic Medical Sciences, Second Military Medical University, Shanghai, 200433, China
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Kaz A, Kim YH, Dzieciatkowski S, Lynch H, Watson P, Kay Washington M, Lin L, Grady WM. Evidence for the role of aberrant DNA methylation in the pathogenesis of Lynch syndrome adenomas. Int J Cancer 2007; 120:1922-9. [PMID: 17278092 DOI: 10.1002/ijc.22544] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Colorectal cancer (CRC) forms through a series of histologic steps that are accompanied by mutations and epigenetic alterations, which is called the polyp-cancer sequence. The role of epigenetic alterations, such as aberrant DNA methylation, in the polyp-cancer sequence in sporadic CRC and particularly in hereditary colon cancer is not well understood. Consequently, we assessed the methylation status of CDKN2A/p16, MGMT, MLH1 and p14(ARF) in adenomas arising in the Lynch syndrome, a familial colon cancer syndrome caused by MLH1 and MSH2 mutations, to determine if DNA methylation is a "second hit" mechanism in CRC and to characterize the role of DNA methylation in the polyp phase of the Lynch syndrome. We found MLH1 and p14(ARF) are methylated in 53 and 60% of the Lynch syndrome adenomas and in 4 and 20% of sporadic adenomas, whereas CDKN2A/p16 and MGMT are methylated in 6 and 14% of the Lynch syndrome adenomas versus 50 and 64% of sporadic adenomas. Therefore, the frequency and pattern of gene methylation varies between the Lynch syndrome and sporadic colon adenomas, implying differences in the molecular pathogenesis of the tumors. MLH1 methylation in the Lynch syndrome adenomas suggests gene methylation might have a role in the initiation of these neoplasms.
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Affiliation(s)
- Andrew Kaz
- Clinical Research Division, Fred Hutchinson Cancer Research Center, Seattle, WA, USA
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Ollikainen M, Hannelius U, Lindgren CM, Abdel-Rahman WM, Kere J, Peltomäki P. Mechanisms of inactivation of MLH1 in hereditary nonpolyposis colorectal carcinoma: a novel approach. Oncogene 2007; 26:4541-9. [PMID: 17260015 DOI: 10.1038/sj.onc.1210236] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Mutations in the DNA mismatch repair gene MLH1 are a major cause of hereditary nonpolyposis colorectal cancer (HNPCC). No mutant phenotype is observed before the wild-type (wt) allele is somatically inactivated in target tissue. We addressed the mechanisms of MLH1 inactivation in 25 colorectal (CRC) and 32 endometrial cancers (ECs) from MLH1 mutation carriers (Mut1, in-frame genomic deletion; Mut2, out-of-frame splice site mutation; Mut3, missense mutation). By a quantitative method, matrix-assisted laser desorption/ionization-time-of-flight (MALDI-TOF), utilizing four intragenic single nucleotide polymorphisms and mutations, loss of heterozygosity (LOH) was present in 31/57 (54.4%) of tumors. The wt allele displayed LOH more often than the mutant allele (23/57 vs 8/57, P=0.006). For Mut1, LOH was more frequent in CRC than EC (10/11 vs 1/13, P<0.0001), whereas Mut2 and Mut3 displayed opposite LOH pattern. Moreover, although wt LOH predominated in CRC irrespective of the predisposing mutation, LOH often affected the mutant allele in EC from Mut2 and Mut3 carriers (6/19, 31.6%). MLH1 promoter methylation, which reflected a more widespread hypermethylation tendency, occurred in 4/55 (7.3%) of tumors and was inversely associated with LOH. In conclusion, the patterns of somatic events (LOH and promoter methylation) differ depending on the tissue and germline mutation, which may in part explain the differential tumor susceptibility of different organs in HNPCC. MALDI-TOF provides a novel approach for the detection and quantification of LOH.
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Affiliation(s)
- M Ollikainen
- Department of Medical Genetics, University of Helsinki, Helsinki, Finland.
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Ding DC, Huang RL, Chen CH, Chao CF, Chu TY. Novel germline and somatic mutations of the MSH2 gene in hereditary non-polyposis colorectal cancer. Clin Genet 2007; 71:190-2. [PMID: 17250671 DOI: 10.1111/j.1399-0004.2007.00749.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Tuupanen S, Karhu A, Järvinen H, Mecklin JP, Launonen V, Aaltonen LA. No evidence for dual role of loss of heterozygosity in hereditary non-polyposis colorectal cancer. Oncogene 2006; 26:2513-7. [PMID: 17043646 DOI: 10.1038/sj.onc.1210038] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Hereditary non-polyposis colorectal cancer (HNPCC) is caused by germline mutations in mismatch repair (MMR) genes, mostly MLH1 and MSH2. Somatic inactivation of the wild-type allele of the respective MMR gene is required for tumor development. Unexpectedly, a recent study utilizing DNA from paraffin-embedded tissue material detected frequent loss of the mutant MMR gene allele in HNPCC tumors. Dual role for loss of heterozygosity (LOH) was proposed. If somatic loss of the wild-type MMR gene allele had occurred through point mutation or promoter hypermethylation, frequent somatic deletions at the region of the MMR gene locus, perhaps targeting other relevant cancer genes, could quite commonly lead to loss of the mutant allele. To test this hypothesis, we studied a population-based series of 25 fresh-frozen HNPCC tumors with a germline mutation in MLH1 or MSH2 for LOH. Fourteen of the 25 tumors (56%) showed LOH at the respective locus, and all 14 losses targeted the wild-type allele (P=0.00006). These results strongly support the traditional two-hit model of HNPCC gene inactivation.
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Affiliation(s)
- S Tuupanen
- Department of Medical Genetics, Biomedicum Helsinki, University of Helsinki, Helsinki, Finland
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