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Joo JE, Mahmood K, Walker R, Georgeson P, Candiloro I, Clendenning M, Como J, Joseland S, Preston S, Graversen L, Wilding M, Field M, Lemon M, Wakeling J, Marfan H, Susman R, Isbister J, Edwards E, Bowman M, Kirk J, Ip E, McKay L, Antill Y, Hopper JL, Boussioutas A, Macrae FA, Dobrovic A, Jenkins MA, Rosty C, Winship IM, Buchanan DD. Identifying primary and secondary MLH1 epimutation carriers displaying low-level constitutional MLH1 methylation using droplet digital PCR and genome-wide DNA methylation profiling of colorectal cancers. Clin Epigenetics 2023; 15:95. [PMID: 37270516 PMCID: PMC10239107 DOI: 10.1186/s13148-023-01511-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2023] [Accepted: 05/24/2023] [Indexed: 06/05/2023] Open
Abstract
BACKGROUND MLH1 epimutation is characterised by constitutional monoallelic MLH1 promoter hypermethylation, which can cause colorectal cancer (CRC). Tumour molecular profiles of MLH1 epimutation CRCs were used to classify germline MLH1 promoter variants of uncertain significance and MLH1 methylated early-onset CRCs (EOCRCs). Genome-wide DNA methylation and somatic mutational profiles of tumours from two germline MLH1: c.-11C > T and one MLH1: c.-[28A > G; 7C > T] carriers and three MLH1 methylated EOCRCs (< 45 years) were compared with 38 reference CRCs. Methylation-sensitive droplet digital PCR (ddPCR) was used to detect mosaic MLH1 methylation in blood, normal mucosa and buccal DNA. RESULTS Genome-wide methylation-based Consensus Clustering identified four clusters where the tumour methylation profiles of germline MLH1: c.-11C > T carriers and MLH1 methylated EOCRCs clustered with the constitutional MLH1 epimutation CRCs but not with the sporadic MLH1 methylated CRCs. Furthermore, monoallelic MLH1 methylation and APC promoter hypermethylation in tumour were observed in both MLH1 epimutation and germline MLH1: c.-11C > T carriers and MLH1 methylated EOCRCs. Mosaic constitutional MLH1 methylation in MLH1: c.-11C > T carriers and 1 of 3 MLH1 methylated EOCRCs was identified by methylation-sensitive ddPCR. CONCLUSIONS Mosaic MLH1 epimutation underlies the CRC aetiology in MLH1: c.-11C > T germline carriers and a subset of MLH1 methylated EOCRCs. Tumour profiling and ultra-sensitive ddPCR methylation testing can be used to identify mosaic MLH1 epimutation carriers.
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Affiliation(s)
- Jihoon E Joo
- Colorectal Oncogenomics Group, Department of Clinical Pathology, Victorian Comprehensive Cancer Centre, The University of Melbourne, 305 Grattan Street, Parkville, VIC, 3000, Australia.
- Victorian Comprehensive Cancer Centre, University of Melbourne Centre for Cancer Research, Parkville, VIC, Australia.
| | - Khalid Mahmood
- Colorectal Oncogenomics Group, Department of Clinical Pathology, Victorian Comprehensive Cancer Centre, The University of Melbourne, 305 Grattan Street, Parkville, VIC, 3000, Australia
- Victorian Comprehensive Cancer Centre, University of Melbourne Centre for Cancer Research, Parkville, VIC, Australia
- Melbourne Bioinformatics, The University of Melbourne, Melbourne, VIC, Australia
| | - Romy Walker
- Colorectal Oncogenomics Group, Department of Clinical Pathology, Victorian Comprehensive Cancer Centre, The University of Melbourne, 305 Grattan Street, Parkville, VIC, 3000, Australia
- Victorian Comprehensive Cancer Centre, University of Melbourne Centre for Cancer Research, Parkville, VIC, Australia
| | - Peter Georgeson
- Colorectal Oncogenomics Group, Department of Clinical Pathology, Victorian Comprehensive Cancer Centre, The University of Melbourne, 305 Grattan Street, Parkville, VIC, 3000, Australia
- Victorian Comprehensive Cancer Centre, University of Melbourne Centre for Cancer Research, Parkville, VIC, Australia
| | - Ida Candiloro
- Beacon Biomarkers Lab, Department of Surgery, Austin Health, University of Melbourne, Heidelberg, VIC, Australia
| | - Mark Clendenning
- Colorectal Oncogenomics Group, Department of Clinical Pathology, Victorian Comprehensive Cancer Centre, The University of Melbourne, 305 Grattan Street, Parkville, VIC, 3000, Australia
- Victorian Comprehensive Cancer Centre, University of Melbourne Centre for Cancer Research, Parkville, VIC, Australia
| | - Julia Como
- Colorectal Oncogenomics Group, Department of Clinical Pathology, Victorian Comprehensive Cancer Centre, The University of Melbourne, 305 Grattan Street, Parkville, VIC, 3000, Australia
- Victorian Comprehensive Cancer Centre, University of Melbourne Centre for Cancer Research, Parkville, VIC, Australia
| | - Sharelle Joseland
- Colorectal Oncogenomics Group, Department of Clinical Pathology, Victorian Comprehensive Cancer Centre, The University of Melbourne, 305 Grattan Street, Parkville, VIC, 3000, Australia
- Victorian Comprehensive Cancer Centre, University of Melbourne Centre for Cancer Research, Parkville, VIC, Australia
| | - Susan Preston
- Colorectal Oncogenomics Group, Department of Clinical Pathology, Victorian Comprehensive Cancer Centre, The University of Melbourne, 305 Grattan Street, Parkville, VIC, 3000, Australia
- Victorian Comprehensive Cancer Centre, University of Melbourne Centre for Cancer Research, Parkville, VIC, Australia
| | - Lise Graversen
- Department of Clinical Genetics, Aarhus University Hospital, Aarhus, Denmark
| | - Mathilda Wilding
- Department of Clinical Genetics, Royal North Shore Hospital, Sydney, NSW, Australia
| | - Michael Field
- Department of Clinical Genetics, Royal North Shore Hospital, Sydney, NSW, Australia
| | - Michelle Lemon
- Genetic Health Queensland, Royal Brisbane and Women's Hospital, Herston, QLD, Australia
| | - Janette Wakeling
- Genetic Health Queensland, Royal Brisbane and Women's Hospital, Herston, QLD, Australia
- Tasman Health Care, Southport, QLD, Australia
| | - Helen Marfan
- Genetic Health Queensland, Royal Brisbane and Women's Hospital, Herston, QLD, Australia
| | - Rachel Susman
- Genetic Health Queensland, Royal Brisbane and Women's Hospital, Herston, QLD, Australia
| | - Joanne Isbister
- Genomic Medicine and Family Cancer Clinic, Royal Melbourne Hospital, Parkville, Melbourne, VIC, Australia
| | - Emma Edwards
- Familial Cancer Service, Crown Princess Mary Cancer Centre, Westmead Hospital, Sydney, NSW, 2145, Australia
| | - Michelle Bowman
- Familial Cancer Service, Crown Princess Mary Cancer Centre, Westmead Hospital, Sydney, NSW, 2145, Australia
| | - Judy Kirk
- Familial Cancer Service, Crown Princess Mary Cancer Centre, Westmead Hospital, Sydney, NSW, 2145, Australia
| | - Emilia Ip
- Department of Cancer Genetics, Liverpool Hospital, Liverpool, NSW, Australia
| | - Lynne McKay
- The Cabrini Family Cancer Clinic, Cabrini Health, Malvern, VIC, Australia
| | - Yoland Antill
- Genomic Medicine and Family Cancer Clinic, Royal Melbourne Hospital, Parkville, Melbourne, VIC, Australia
- The Cabrini Family Cancer Clinic, Cabrini Health, Malvern, VIC, Australia
| | - John L Hopper
- Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, The University of Melbourne, Carlton, VIC, Australia
| | - Alex Boussioutas
- Department of Gastroenterology, The Alfred Hospital, Melbourne, Parkville, VIC, 3010, Australia
- Central Clinical School, Monash University, Melbourne, VIC, 3004, Australia
| | - Finlay A Macrae
- Genomic Medicine and Family Cancer Clinic, Royal Melbourne Hospital, Parkville, Melbourne, VIC, Australia
- Colorectal Medicine and Genetics, The Royal Melbourne Hospital, Parkville, VIC, Australia
- Department of Medicine, The University of Melbourne, Parkville, Australia
| | - Alexander Dobrovic
- Beacon Biomarkers Lab, Department of Surgery, Austin Health, University of Melbourne, Heidelberg, VIC, Australia
| | - Mark A Jenkins
- Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, The University of Melbourne, Carlton, VIC, Australia
| | - Christophe Rosty
- Colorectal Oncogenomics Group, Department of Clinical Pathology, Victorian Comprehensive Cancer Centre, The University of Melbourne, 305 Grattan Street, Parkville, VIC, 3000, Australia
- Victorian Comprehensive Cancer Centre, University of Melbourne Centre for Cancer Research, Parkville, VIC, Australia
- Envoi Specialist Pathologists, Brisbane, Australia
- University of Queensland, Brisbane, Australia
| | - Ingrid M Winship
- Genomic Medicine and Family Cancer Clinic, Royal Melbourne Hospital, Parkville, Melbourne, VIC, Australia
- Department of Medicine, The University of Melbourne, Parkville, Australia
| | - Daniel D Buchanan
- Colorectal Oncogenomics Group, Department of Clinical Pathology, Victorian Comprehensive Cancer Centre, The University of Melbourne, 305 Grattan Street, Parkville, VIC, 3000, Australia
- Victorian Comprehensive Cancer Centre, University of Melbourne Centre for Cancer Research, Parkville, VIC, Australia
- Genomic Medicine and Family Cancer Clinic, Royal Melbourne Hospital, Parkville, Melbourne, VIC, Australia
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Nugroho PP, Ghozali SAS, Buchanan DD, Pisano MI, Reece JC. Risk of cancer in individuals with Lynch-like syndrome and their families: a systematic review. J Cancer Res Clin Oncol 2023; 149:25-46. [PMID: 36251064 PMCID: PMC9889410 DOI: 10.1007/s00432-022-04397-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2022] [Accepted: 10/05/2022] [Indexed: 02/04/2023]
Abstract
BACKGROUND Lynch-like syndrome (LLS) tumors have similar clinicopathological features to Lynch syndrome (LS) tumors but have no identifiable pathogenic germline mismatch repair gene variant. However, cancer risks in LLS patients and first-degree relatives (FDRs) are not well defined. METHODS To clarify LLS-associated cancer risks, a systematic review of all studies examining all cancer risks in LLS was performed. Searching of Medline, Embase, Pubmed, Cochrane and CINAHL databases and reference/citation checking identified relevant studies published between January 1, 1980 and February 11, 2021. Joanna Briggs Institute Appraisal Tools assessed the risk of bias. RESULTS Six studies (five cohort/one cross-sectional) were eligible for study inclusion. One study found no difference in colorectal cancer (CRC) incidence between LLS and LS patients or CRC risks at aged 70 years. Three studies found CRC incidence in LLS FDRs was higher than the general population but lower than LS FDRs. Two studies showed no difference in CRC diagnosis age between LLS patients and LS patients. Endometrial cancer risks in LLS patients were higher than the general population but lower than LS patients. CONCLUSION Evidence of elevated CRC risks in LLS patients and FDRs supports increased colonoscopy surveillance strategies for LLS patients and FDRs in line with current recommendations for LS. Due to heterogeneity amongst LLS populations, extended intervals between screening may be advised for low-risk families. Studies to resolve the molecular characterization and definition of LLS are needed to clarify cancer risks associated with LLS which in turn may individualize surveillance strategies for LLS patients and families.
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Affiliation(s)
- Pandu P Nugroho
- Faculty of Medicine, Universitas Indonesia, Depok, West Java, Indonesia
- Melbourne Medical School, The University of Melbourne, Parkville, VIC, Australia
| | - Siti Alyaa S Ghozali
- Faculty of Medicine, Universitas Indonesia, Depok, West Java, Indonesia
- Melbourne Medical School, The University of Melbourne, Parkville, VIC, Australia
| | - Daniel D Buchanan
- Colorectal Oncogenomics Group, Department of Clinical Pathology, Melbourne Medical School, The University of Melbourne, Parkville, VIC, Australia
- University of Melbourne Centre for Cancer Research, Parkville, VIC, Australia
- Genomic Medicine and Family Cancer Clinic, Royal Melbourne Hospital, Parkville, VIC, Australia
| | - Mia I Pisano
- Faculty of Medicine, Dentistry and Health Sciences, The University of Melbourne, Parkville, VIC, Australia
| | - Jeanette C Reece
- Neuroepidemiology Unit, Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, The University of Melbourne, Level 3 207 Bouverie Street, Parkville, VIC, 3010, Australia.
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Lynch-like Syndrome: Potential Mechanisms and Management. Cancers (Basel) 2022; 14:cancers14051115. [PMID: 35267422 PMCID: PMC8909420 DOI: 10.3390/cancers14051115] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Revised: 02/20/2022] [Accepted: 02/21/2022] [Indexed: 02/05/2023] Open
Abstract
Simple Summary Lynch-like syndrome (LLS) is defined as colorectal cancer cases with microsatellite instability (MSI) and loss of expression of MLH1, MSH2, MSH6, or PMS2 by immunohistochemistry (IHC) in the absence of a germline mutation in these genes that cannot be explained by BRAF mutation or MLH1 hypermethylation. The application of the universal strategy for the diagnosis of Lynch syndrome (LS) in all CRCs is leading to an increase in the incidence of cases of LLS. It has been described that risk of cancer in relatives of LLS patients is in between of that found in Lynch syndrome families and sporadic cases. That makes LLS patients and their families a challenging group for which the origin of CRC is unknown, being a mixture between unidentified hereditary CRC and sporadic cases. The potential causes of LLS are discussed in this review, as well as methods for identification of truly hereditary cases. Abstract Lynch syndrome is an autosomal dominant disorder caused by germline mutations in DNA mismatch repair (MMR) system genes, such as MLH1, MSH2, MSH6, or PMS2. It is the most common hereditary colorectal cancer syndrome. Screening is regularly performed by using microsatellite instability (MSI) or immunohistochemistry for the MMR proteins in tumor samples. However, in a proportion of cases, MSI is found or MMR immunohistochemistry is impaired in the absence of a germline mutation in MMR genes, BRAF mutation, or MLH1 hypermethylation. These cases are defined as Lynch-like syndrome. Patients with Lynch-like syndrome represent a mixture of truly hereditary and sporadic cases, with a risk of colorectal cancer in first-degree relatives that is between the risk of Lynch syndrome in families and relatives of sporadic colon cancer cases. Although multiple approaches have been suggested to distinguish between hereditary and sporadic cases, a homogeneous testing protocol and consensus on the adequate classification of these patients is still lacking. For this reason, management of Lynch-like syndrome and prevention of cancer in these families is clinically challenging. This review explains the concept of Lynch-like syndrome, potential mechanisms for its development, and methods for adequately distinguishing between sporadic and hereditary cases of this entity.
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Norouzi M, Shafiei M, Abdollahi Z, Miar P, Galehdari H, Emami MH, Zeinalian M, Tabatabaiefar MA. WRN Germline Mutation Is the Likely Inherited Etiology of Various Cancer Types in One Iranian Family. Front Oncol 2021; 11:648649. [PMID: 34164337 PMCID: PMC8215443 DOI: 10.3389/fonc.2021.648649] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2021] [Accepted: 05/05/2021] [Indexed: 11/15/2022] Open
Abstract
Background Familial cancers comprise a considerable distribution of colorectal cancers (CRCs), of which only about 5% occurs through well-established hereditary syndromes. It has been demonstrated that deleterious variants at the newly identified cancer-predisposing genes could describe the etiology of undefined familial cancers. Methods The present study aimed to identify the genetic etiology in a 32-year-old man with early onset familial CRC employing several molecular diagnostic techniques. DNA was extracted from tumoral and normal formalin-fixed-paraffin-embedded (FFPE) blocks, and microsatellite instability (MSI) was evaluated. Immunohistochemistry staining of MMR proteins was performed on tumoral FFPE blocks. Next-generation sequencing (NGS), multiplex ligation-dependent amplification (MLPA) assay, and Sanger sequencing were applied on the genomic DNA extracted from peripheral blood. Data analysis was performed using bioinformatics tools. Genetic variants interpretation was based on ACMG. Results MSI analysis indicated MSI-H phenotype, and IHC staining proved no expressions of MSH2 and MSH6 proteins. MLPA and NGS data showed no pathogenic variants in MMR genes. Further analysis of NGS data revealed a candidate WRN frameshift variant (p.R389Efs*3), which was validated with Sanger sequencing. The variant was interpreted as pathogenic since it met the criteria based on the ACMG guideline including very strong (PVS1), strong (PS3), and moderate (PM2). Conclusion WRN is a DNA helicase participating in DNA repair pathways to sustain genomic stability. WRN deficient function may contribute to CRC development that is valuable for further investigation as a candidate gene in hereditary cancer syndrome diagnosis.
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Affiliation(s)
- Mahnaz Norouzi
- Department of Biology, Faculty of Sciences, Shahid Chamran University of Ahvaz, Ahvaz, Iran
| | - Mohammad Shafiei
- Department of Biology, Faculty of Sciences, Shahid Chamran University of Ahvaz, Ahvaz, Iran
| | - Zeinab Abdollahi
- Department of Genetics and Molecular Biology, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran
| | - Paniz Miar
- Department of Genetics and Molecular Biology, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran
| | - Hamid Galehdari
- Department of Biology, Faculty of Sciences, Shahid Chamran University of Ahvaz, Ahvaz, Iran
| | - Mohammad Hasan Emami
- Department of Gastroenterology, Poursina Hakim Digestive Disease Research Center, Isfahan University of Medical Sciences, Isfahan, Iran
| | - Mehrdad Zeinalian
- Department of Genetics and Molecular Biology, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran
| | - Mohammad Amin Tabatabaiefar
- Department of Genetics and Molecular Biology, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran.,Pediatric Inherited Diseases Research Center, Research Institute for Primordial Prevention of Noncommunicable Disease, Isfahan University of Medical Sciences, Isfahan, Iran
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5
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Xu Y, Huang Z, Li C, Zhu C, Zhang Y, Guo T, Liu F, Xu Y. Comparison of Molecular, Clinicopathological, and Pedigree Differences Between Lynch-Like and Lynch Syndromes. Front Genet 2020; 11:991. [PMID: 32973888 PMCID: PMC7466573 DOI: 10.3389/fgene.2020.00991] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2020] [Accepted: 08/05/2020] [Indexed: 12/12/2022] Open
Abstract
In this study, we compared the molecular, clinical, and pathological characteristics, as well as pedigrees, between patients with Lynch-like syndrome (LLS) and confirmed Lynch syndrome (LS) to develop appropriate management strategies for patients with LLS and their affected family members. Between June 2008 and September 2018, 81 patients with LLS and 47 patients with LS who developed colorectal cancer (CRC) were enrolled in this study. Multigene panel testing included 139 genes and was performed for all patients. The variants identified in each group were described, and clinicopathological characteristics and pedigrees were compared between the two groups. In the LLS group, a total of 52 variants were detected in 44 (54.3%) patients. Among the 52 variants, 17 were variants of unknown significance in mismatch repair genes, and the other most frequently mutated genes were MUYTH, POLE, BRCA2, and GJB2. The proportion of early-onset patients was significantly higher among the LS probands than among the LLS probands (74.5 and 53.1%, respectively; χ2 = 5.712, P = 0.017). On the other hand, the proportion of primary CRC developed in the rectum was higher in the LLS group than in the LS group (25.9 and 10.6%, respectively; χ2 = 2.358, P = 0.046). There were no significant differences in the occurrence of metachronous CRC (P = 0.632) and extra-colorectal cancer (extra-CRC) (P = 0.145) between the two groups. However, analysis of pedigrees showed that more patients developed CRC in the LS families (P = 0.013), whereas more patients with extra-CRC were observed in the LLS families (P = 0.045). A higher prevalence of male patients was observed in the LLS families (P = 0.036). In conclusion, LLS should be classified as a mixed entity, containing cases of LS, other hereditary cancer syndromes, and sporadic CRC. The high risks of CRC and extra-CRCs, which were found in this study, suggest tailored management policy and surveillance should be formulated based on individual and family risk. The surveillance regimen can be based on the presence of confirmed pathogenic/likely pathogenic germline variant(s) and family history.
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Affiliation(s)
- Yun Xu
- Department of Colorectal Surgery, Fudan University Shanghai Cancer Center, Shanghai, China.,Department of Oncology, Shanghai Medical College, Fudan University, Shanghai, China
| | - Zonghao Huang
- Hospital Information Centre, Fudan University Shanghai Cancer Center, Shanghai, China
| | - Cong Li
- Department of Colorectal Surgery, Fudan University Shanghai Cancer Center, Shanghai, China.,Department of Oncology, Shanghai Medical College, Fudan University, Shanghai, China
| | - Congcong Zhu
- Department of Oncology, Shanghai Medical College, Fudan University, Shanghai, China
| | - Yuqin Zhang
- Department of Oncology, Shanghai Medical College, Fudan University, Shanghai, China
| | - Tian'an Guo
- Department of Oncology, Shanghai Medical College, Fudan University, Shanghai, China
| | - Fangqi Liu
- Department of Colorectal Surgery, Fudan University Shanghai Cancer Center, Shanghai, China
| | - Ye Xu
- Department of Colorectal Surgery, Fudan University Shanghai Cancer Center, Shanghai, China.,Department of Oncology, Shanghai Medical College, Fudan University, Shanghai, China
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The Clinical Utility of Epigenetics: A Case Study. Clin Epigenetics 2019. [DOI: 10.1007/978-981-13-8958-0_11] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
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7
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Fraile-Bethencourt E, Valenzuela-Palomo A, Díez-Gómez B, Infante M, Durán M, Marcos G, Lastra E, Gómez-Barrero S, Velasco EA. Genetic dissection of the BRCA2 promoter and transcriptional impact of DNA variants. Breast Cancer Res Treat 2018; 171:53-63. [PMID: 29766361 DOI: 10.1007/s10549-018-4826-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2017] [Accepted: 04/16/2018] [Indexed: 11/28/2022]
Abstract
PURPOSE Promoter mutations may affect transcription and can be associated with human diseases. However, the promoters of the breast cancer (BC) genes are not regularly screened. Our goal was to investigate the BRCA2 promoter in order to study a possible correlation between impaired transcription and disease. METHODS The proximal and core promoter of the BRCA2 gene was sequenced in 95 high-risk BC patients. A BRCA2-promoter insert [- 938 to + 312 from the transcription start site (TSS)] was generated and cloned into the firefly luciferase vector pGL4.10. Promoter variants and deletions were introduced by site-directed mutagenesis and quantified by Dual-Luciferase assays and semi-quantitative RT-PCR. RESULTS Three different variants were detected in high-risk BC patients: rs3092989, rs206118, and rs563971900. Functional mapping of 13 overlapping deletions revealed four down-regulating segments (TSS positions): -59_-10del/µdel3 (16% of activity of the wild-type construct), -104_-55del/µdel4 (62%), -239_-190del/µdel7 (39%), -464_-415/µdel12 (78%), suggesting the presence therein of putative transcriptional activator motifs. Additionally, six microdeletions rendered luciferase overexpression: +32_+81del/µdel1 (356%), -14_+36del/µdel2 (180%), -194_-145del/µdel6 (154%), -284_-235del/µdel8 (168%), -329_-280del/µdel9 (111%), and -509_-460del/µdel13 (139%), which is indicative of repressor elements. Functional assays of 15 promoter variants (including those detected in patients) showed that ten of them significantly altered expression with seven up-regulating (113-163%) and three down-regulating (rs551887850_G, rs570548398_T, rs55880202_T; 72-83%) SNPs. Eight of them were located in an ENCODE-DNase Hypersensitive Cluster (TSS - 185 to + 105) where most active transcriptional motifs are known to be placed. CONCLUSIONS BRCA2 expression is highly sensitive to promoter variations as most of them induced relevant changes. Moreover, we mapped critical regions of the BRCA2 promoter that may constitute potential targets for regulatory variants. Three SNPs moderately decreased luciferase activity, but confirmation of its potential pathogenicity requires further analysis. These data reinforce the need to screen the promoter regions of breast cancer genes with a view to discovering novel deleterious mutations.
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Affiliation(s)
- Eugenia Fraile-Bethencourt
- Grupo de Splicing y Cáncer, Instituto de Biología y Genética Molecular (IBGM), Consejo Superior de Investigaciones Científicas (CSIC-UVa), Sanz y Forés 3, 47003, Valladolid, Spain
| | - Alberto Valenzuela-Palomo
- Grupo de Splicing y Cáncer, Instituto de Biología y Genética Molecular (IBGM), Consejo Superior de Investigaciones Científicas (CSIC-UVa), Sanz y Forés 3, 47003, Valladolid, Spain
| | - Beatriz Díez-Gómez
- Grupo de Splicing y Cáncer, Instituto de Biología y Genética Molecular (IBGM), Consejo Superior de Investigaciones Científicas (CSIC-UVa), Sanz y Forés 3, 47003, Valladolid, Spain
| | - Mar Infante
- Cancer Genetics, Instituto de Biología y Genética Molecular (UVa-CSIC), Valladolid, Spain
| | - Mercedes Durán
- Cancer Genetics, Instituto de Biología y Genética Molecular (UVa-CSIC), Valladolid, Spain
| | - Germán Marcos
- Servicio de Oncología, Hospital Río Hortega, Valladolid, Spain
| | - Enrique Lastra
- Servicio de Oncología, Hospital Universitario de Burgos, Burgos, Spain
| | | | - Eladio A Velasco
- Grupo de Splicing y Cáncer, Instituto de Biología y Genética Molecular (IBGM), Consejo Superior de Investigaciones Científicas (CSIC-UVa), Sanz y Forés 3, 47003, Valladolid, Spain.
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8
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Morak M, Ibisler A, Keller G, Jessen E, Laner A, Gonzales-Fassrainer D, Locher M, Massdorf T, Nissen AM, Benet-Pagès A, Holinski-Feder E. Comprehensive analysis of the MLH1 promoter region in 480 patients with colorectal cancer and 1150 controls reveals new variants including one with a heritable constitutional MLH1 epimutation. J Med Genet 2018; 55:240-248. [PMID: 29472279 DOI: 10.1136/jmedgenet-2017-104744] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2017] [Revised: 10/27/2017] [Accepted: 10/30/2017] [Indexed: 01/28/2023]
Abstract
BACKGROUND Germline defects in MLH1, MSH2, MSH6 and PMS2 predisposing for Lynch syndrome (LS) are mainly based on sequence changes, whereas a constitutional epimutation of MLH1(CEM) is exceptionally rare. This abnormal MLH1 promoter methylation is not hereditary when arising de novo, whereas a stably heritable and variant-induced CEM was described for one single allele. We searched for MLH1 promoter variants causing a germline or somatic methylation induction or transcriptional repression. METHODS We analysed the MLH1 promoter sequence in five different patient groups with colorectal cancer (CRC) (n=480) composed of patients with i) CEM (n=16), ii) unsolved loss of MLH1 expression in CRC (n=37), iii) CpG-island methylator-phenotype CRC (n=102), iv) patients with LS (n=83) and v) MLH1-proficient CRC (n=242) as controls. 1150 patients with non-LS tumours also served as controls to correctly judge the results. RESULTS We detected 10 rare MLH1 promoter variants. One novel, complex MLH1 variant c.-63_-58delins18 is present in a patient with CRC with CEM and his sister, both showing a complete allele-specific promoter methylation and transcriptional silencing. The other nine promoter variants detected in 17 individuals were not associated with methylation. For four of these, a normal, biallelic MLH1 expression was found in the patients' cDNA. CONCLUSION We report the second promoter variant stably inducing a hereditary CEM. Concerning the classification of promoter variants, we discuss contradictory results from the literature for two variants, describe classification discrepancies between existing rules for five variants, suggest the (re-)classification of five promoter variants to (likely) benign and regard four variants as functionally unclear.
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Affiliation(s)
- Monika Morak
- Medizinische Klinik und Poliklinik IV, Klinikum der Universität München, Munich, Bavaria, Germany.,Center of Medical Genetics, Medizinisch Genetisches Zentrum, Munich, Bavaria, Germany
| | - Ayseguel Ibisler
- Department of Human Genetics, Ruhr University Bochum, Bochum, North Rhine-Westphalia, Germany
| | - Gisela Keller
- Institute of Pathology, Technical University Munich, Munich, Bavaria, Germany
| | - Ellen Jessen
- Praxis für Humangenetik, Praxis für Humangenetik, Hamburg, Hamburg, Germany
| | - Andreas Laner
- Center of Medical Genetics, Medizinisch Genetisches Zentrum, Munich, Bavaria, Germany
| | | | - Melanie Locher
- Center of Medical Genetics, Medizinisch Genetisches Zentrum, Munich, Bavaria, Germany
| | - Trisari Massdorf
- Medizinische Klinik und Poliklinik IV, Klinikum der Universität München, Munich, Bavaria, Germany
| | - Anke M Nissen
- Center of Medical Genetics, Medizinisch Genetisches Zentrum, Munich, Bavaria, Germany
| | - Anna Benet-Pagès
- Center of Medical Genetics, Medizinisch Genetisches Zentrum, Munich, Bavaria, Germany
| | - Elke Holinski-Feder
- Medizinische Klinik und Poliklinik IV, Klinikum der Universität München, Munich, Bavaria, Germany.,Center of Medical Genetics, Medizinisch Genetisches Zentrum, Munich, Bavaria, Germany
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