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Drenner K, Basu GD, Goodman LJ, Ozols AA, LoBello JR, Royce T, Gordon MS, Borazanci EH, Steinbach MA, Trent J, Sharma S. The value of comprehensive genomic sequencing to maximize the identification of clinically actionable alterations in advanced cancer patients: a case series. Oncotarget 2021; 12:1836-1847. [PMID: 34504655 PMCID: PMC8416559 DOI: 10.18632/oncotarget.28046] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2021] [Accepted: 07/27/2021] [Indexed: 01/10/2023] Open
Abstract
PURPOSE We present seven cases of advanced cancer patients who initially underwent tumor testing utilizing smaller, panel-based tests, followed by a variety of therapeutic treatments which ultimately resulted in progression of their disease. These cases demonstrate the value of utilizing WES/RNA seq and characterization following disease progression in these patients and the determination of clinically targetable alterations as well as acquired resistance mutations. MATERIALS AND METHODS All patients are part of an IRB approved observational study. WES and RNA sequencing were performed, using GEM ExTra® on tumor and blood samples obtained during routine clinical care. To accurately determine somatic versus germline alterations the test was performed with paired normal testing from peripheral blood. RESULTS The presented cases demonstrate the clinical impact of actionable findings uncovered using GEM ExTra® in patients with advanced disease who failed many rounds of treatment. Unique alterations were identified resulting in newly identified potential targeted therapies, mechanisms of resistance, and variation in the genomic characterization of the primary versus the metastatic tumor. CONCLUSIONS Taken together our results demonstrate that GEM ExTra® maximizes detection of actionable mutations, thus allowing for appropriate treatment selection for patients harboring both common and rare genomic alterations.
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Affiliation(s)
- Kevin Drenner
- Translational Genomic Research Institute (Tgen), Phoenix, AZ 85004, USA
- These authors contributed equally to this work
| | - Gargi D. Basu
- Ashion Analytics, LLC, Phoenix, AZ 85004, USA
- These authors contributed equally to this work
| | | | | | | | | | | | | | | | - Jeffrey Trent
- Translational Genomic Research Institute (Tgen), Phoenix, AZ 85004, USA
| | - Sunil Sharma
- Translational Genomic Research Institute (Tgen), Phoenix, AZ 85004, USA
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Weiderpass E, Tyczynski JE. Epidemiology of Patients with Ovarian Cancer with and Without a BRCA1/2 Mutation. Mol Diagn Ther 2016; 19:351-64. [PMID: 26476542 DOI: 10.1007/s40291-015-0168-x] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Ovarian cancer survival rates have improved only slightly in recent decades; however, treatment of this disease is expected to undergo rapid change as strategies incorporating molecular-targeted therapies enter clinical practice. Carriers of deleterious mutations (defined as a harmful mutation) in either the BRCA1 or BRCA2 gene (BRCAm) have a significantly increased risk of developing ovarian cancer. Epidemiology data in large (>500 patients) unselected ovarian cancer populations suggest that the expected incidence rate for BRCAm in this population is 12-14 %. Patients with a BRCAm are typically diagnosed at a younger age than those without a BRCAm. Associations with BRCAm vary according to ethnicity, with women of Ashkenazi Jewish descent being 10 times more likely to have a BRCAm than the general population. In terms of survival, patients with invasive epithelial ovarian cancer who have a BRCAm may have improved overall survival compared with patients who do not carry a BRCAm. Although genetic testing for BRCAm remains relatively uncommon in ovarian cancer patients, testing is becoming cheaper and increasingly accessible; however, this approach is not without numerous social, ethical and policy issues. Current guidelines recommend BRCAm testing in specific ovarian cancer patients only; however, with the emergence of treatments that are targeted at patients with a BRCAm, genetic testing of all patients with high-grade serous ovarian cancer may lead to improved patient outcomes in this patient population. Knowledge of BRCAm status could, therefore, help to inform treatment decisions and identify relatives at increased risk of developing cancer.
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Affiliation(s)
- Elisabete Weiderpass
- Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, PO Box 281, 171 77, Stockholm, Sweden. .,Department of Community Medicine, Faculty of Health Sciences, University of Tromsø, The Arctic University of Norway, Tromsø, Norway. .,Department of Research, Cancer Registry of Norway, Oslo, Norway. .,Genetic Epidemiology Group, Folkhälsan Research Center, Helsinki, Finland.
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Jhuraney A, Velkova A, Johnson RC, Kessing B, Carvalho RS, Whiley P, Spurdle AB, Vreeswijk MPG, Caputo SM, Millot GA, Vega A, Coquelle N, Galli A, Eccles D, Blok MJ, Pal T, van der Luijt RB, Santamariña Pena M, Neuhausen SL, Donenberg T, Machackova E, Thomas S, Vallée M, Couch FJ, Tavtigian SV, Glover JNM, Carvalho MA, Brody LC, Sharan SK, Monteiro AN. BRCA1 Circos: a visualisation resource for functional analysis of missense variants. J Med Genet 2015; 52:224-30. [PMID: 25643705 PMCID: PMC4392196 DOI: 10.1136/jmedgenet-2014-102766] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2014] [Revised: 11/29/2014] [Accepted: 12/05/2014] [Indexed: 11/17/2022]
Abstract
BACKGROUND Inactivating germline mutations in the tumour suppressor gene BRCA1 are associated with a significantly increased risk of developing breast and ovarian cancer. A large number (>1500) of unique BRCA1 variants have been identified in the population and can be classified as pathogenic, non-pathogenic or as variants of unknown significance (VUS). Many VUS are rare missense variants leading to single amino acid changes. Their impact on protein function cannot be directly inferred from sequence information, precluding assessment of their pathogenicity. Thus, functional assays are critical to assess the impact of these VUS on protein activity. BRCA1 is a multifunctional protein and different assays have been used to assess the impact of variants on different biochemical activities and biological processes. METHODS AND RESULTS To facilitate VUS analysis, we have developed a visualisation resource that compiles and displays functional data on all documented BRCA1 missense variants. BRCA1 Circos is a web-based visualisation tool based on the freely available Circos software package. The BRCA1 Circos web tool (http://research.nhgri.nih.gov/bic/circos/) aggregates data from all published BRCA1 missense variants for functional studies, harmonises their results and presents various functionalities to search and interpret individual-level functional information for each BRCA1 missense variant. CONCLUSIONS This research visualisation tool will serve as a quick one-stop publically available reference for all the BRCA1 missense variants that have been functionally assessed. It will facilitate meta-analysis of functional data and improve assessment of pathogenicity of VUS.
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Affiliation(s)
- Ankita Jhuraney
- Cancer Epidemiology Program, H. Lee Moffitt Cancer Center and Research Institute, Tampa, Florida, USA
- University of South Florida Cancer Biology PhD Program, Tampa, Florida, USA
| | - Aneliya Velkova
- Cancer Epidemiology Program, H. Lee Moffitt Cancer Center and Research Institute, Tampa, Florida, USA
- Genome Technology Branch, National Human Genome Research Institute, Bethesda, Maryland, USA
| | - Randall C Johnson
- Frederick National Laboratory for Cancer Research, National Cancer Institute, Fredrick, Maryland, USA
| | - Bailey Kessing
- Frederick National Laboratory for Cancer Research, National Cancer Institute, Fredrick, Maryland, USA
| | - Renato S Carvalho
- Instituto Federal de Educação, Ciência e Tecnologia, Rio de Janeiro, RJ, Brazil
- Instituto Nacional de Câncer, Divisão de Farmacologia, Rio de Janeiro, Brazil
| | - Phillip Whiley
- Genetics and Population Health Division, QIMR, BNE, Brisbane, Queensland, Australia
| | - Amanda B Spurdle
- Genetics and Population Health Division, QIMR, BNE, Brisbane, Queensland, Australia
| | - Maaike P G Vreeswijk
- Department of Human Genetics, Center for Human and Clinical Genetics, Leiden University Medical Center, Leiden, the Netherlands
| | - Sandrine M Caputo
- Service de Génétique, Institut Curie, Hôpital René Huguenin, Paris, France
| | - Gael A Millot
- Institut Curie, Université Pierre et Marie Curie, Paris, France
| | - Ana Vega
- Fundación Pública Galega de Medicina Xenómica, Santiago, Spain
| | - Nicolas Coquelle
- Department of Biochemistry, University of Alberta, Alberta, Canada
| | - Alvaro Galli
- Instituto di Fisiologia Clinica, Consiglio Nazionale delle Ricerche, Pisa, Italy
| | | | - Marinus J Blok
- Department of Clinical Genetics, Maastricht University Medical Centre, Maastricht, the Netherlands
| | - Tuya Pal
- Cancer Epidemiology Program, H. Lee Moffitt Cancer Center and Research Institute, Tampa, Florida, USA
| | - Rob B van der Luijt
- Department of Medical Genetics, University Medical Center Utrecht, Utrecht, the Netherlands
| | | | - Susan L Neuhausen
- Department of Population Sciences, Beckman Research Institute of the City of Hope, Duarte, California, USA
| | | | - Eva Machackova
- Department of Cancer Epidemiology and Genetics, Masaryk Memorial Cancer Institute, Brno, Czech Republic
| | - Simon Thomas
- Salisbury District Hospital, Salisbury, Wiltshire, UK
| | - Maxime Vallée
- International Agency for Research on Cancer, Lyon, France
| | - Fergus J Couch
- Department of Laboratory Medicine and Pathology, and Health Sciences Research, Mayo Clinic, Rochester, Minnesota, USA
| | - Sean V Tavtigian
- Huntsman Cancer Institute, University of Utah School of Medicine, Salt Lake City, Utah, USA
| | - J N Mark Glover
- Department of Biochemistry, University of Alberta, Alberta, Canada
| | - Marcelo A Carvalho
- Instituto Federal de Educação, Ciência e Tecnologia, Rio de Janeiro, RJ, Brazil
- Instituto Nacional de Câncer, Divisão de Farmacologia, Rio de Janeiro, Brazil
| | - Lawrence C Brody
- Genome Technology Branch, National Human Genome Research Institute, Bethesda, Maryland, USA
| | - Shyam K Sharan
- Center for Cancer Research, National Cancer Institute, Frederick, Maryland, USA
| | - Alvaro N Monteiro
- Cancer Epidemiology Program, H. Lee Moffitt Cancer Center and Research Institute, Tampa, Florida, USA
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Bodian DL, McCutcheon JN, Kothiyal P, Huddleston KC, Iyer RK, Vockley JG, Niederhuber JE. Germline variation in cancer-susceptibility genes in a healthy, ancestrally diverse cohort: implications for individual genome sequencing. PLoS One 2014; 9:e94554. [PMID: 24728327 PMCID: PMC3984285 DOI: 10.1371/journal.pone.0094554] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2013] [Accepted: 02/17/2014] [Indexed: 01/05/2023] Open
Abstract
Technological advances coupled with decreasing costs are bringing whole genome and whole exome sequencing closer to routine clinical use. One of the hurdles to clinical implementation is the high number of variants of unknown significance. For cancer-susceptibility genes, the difficulty in interpreting the clinical relevance of the genomic variants is compounded by the fact that most of what is known about these variants comes from the study of highly selected populations, such as cancer patients or individuals with a family history of cancer. The genetic variation in known cancer-susceptibility genes in the general population has not been well characterized to date. To address this gap, we profiled the nonsynonymous genomic variation in 158 genes causally implicated in carcinogenesis using high-quality whole genome sequences from an ancestrally diverse cohort of 681 healthy individuals. We found that all individuals carry multiple variants that may impact cancer susceptibility, with an average of 68 variants per individual. Of the 2,688 allelic variants identified within the cohort, most are very rare, with 75% found in only 1 or 2 individuals in our population. Allele frequencies vary between ancestral groups, and there are 21 variants for which the minor allele in one population is the major allele in another. Detailed analysis of a selected subset of 5 clinically important cancer genes, BRCA1, BRCA2, KRAS, TP53, and PTEN, highlights differences between germline variants and reported somatic mutations. The dataset can serve a resource of genetic variation in cancer-susceptibility genes in 6 ancestry groups, an important foundation for the interpretation of cancer risk from personal genome sequences.
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Affiliation(s)
- Dale L. Bodian
- Inova Translational Medicine Institute, Inova Health System, Falls Church, Virginia, United States of America
| | - Justine N. McCutcheon
- Inova Translational Medicine Institute, Inova Health System, Falls Church, Virginia, United States of America
| | - Prachi Kothiyal
- Inova Translational Medicine Institute, Inova Health System, Falls Church, Virginia, United States of America
| | - Kathi C. Huddleston
- Inova Translational Medicine Institute, Inova Health System, Falls Church, Virginia, United States of America
| | - Ramaswamy K. Iyer
- Inova Translational Medicine Institute, Inova Health System, Falls Church, Virginia, United States of America
| | - Joseph G. Vockley
- Inova Translational Medicine Institute, Inova Health System, Falls Church, Virginia, United States of America
- * E-mail:
| | - John E. Niederhuber
- Inova Translational Medicine Institute, Inova Health System, Falls Church, Virginia, United States of America
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Rath MG, Fathali-Zadeh F, Langheinz A, Tchatchou S, Voigtländer T, Heil J, Golatta M, Schott S, Drasseck T, Behnecke A, Burgemeister AL, Evers C, Bugert P, Junkermann H, Schneeweiss A, Bartram CR, Sohn C, Sutter C, Burwinkel B. Molecular and clinical characterization of an in frame deletion of uncertain clinical significance in the BRCA2 gene. Breast Cancer Res Treat 2012; 133:725-34. [PMID: 22228431 DOI: 10.1007/s10549-011-1917-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2011] [Accepted: 12/08/2011] [Indexed: 01/07/2023]
Abstract
In this study, we analyzed a "variant of uncertain significance" (VUS) located in exon 23 of the BRCA2 gene exhibited by six members of five distinct families with hereditary breast cancer (BC). The variant was identified by DNA sequencing, and cDNA analysis revealed its co-expression with wild-type mRNA. We analyzed co-occurrence with other pathological mutations in BRCA1/2, performed a case-control study, looked for evolutionary data and used in-silico analyses to predict its potential clinical significance. Sequencing revealed an in frame deletion of 126 nucleotides in exon 23, leading to a deletion of 42 amino acids (c.9203_9328del126, p.Pro2992_Thr3033del). All of the VUS-carriers suffered from either BC or ovarian/pancreatic cancer. No other definite pathologic mutation of BRCA genes was found in the five families. The identified deletion could not be observed in a control cohort of 2,652 healthy individuals, but in 5 out of 916 (0.5%) tested BC families without a bona fide pathogenic BRCA1/2 mutation (P = 0.0011). According to these results, the in frame deletion c.9203_9328del126 is a rare mutation strongly associated with familial BC. In summary, our investigations indicate that this BRCA2 deletion is pathogenic.
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Affiliation(s)
- Michelle G Rath
- Division Molecular Biology of Breast Cancer, Department of Gynecology and Obstetrics, University of Heidelberg, Heidelberg, Germany
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Kuusisto KM, Bebel A, Vihinen M, Schleutker J, Sallinen SL. Screening for BRCA1, BRCA2, CHEK2, PALB2, BRIP1, RAD50, and CDH1 mutations in high-risk Finnish BRCA1/2-founder mutation-negative breast and/or ovarian cancer individuals. Breast Cancer Res 2011; 13:R20. [PMID: 21356067 PMCID: PMC3109589 DOI: 10.1186/bcr2832] [Citation(s) in RCA: 89] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2010] [Revised: 12/14/2010] [Accepted: 02/28/2011] [Indexed: 12/18/2022] Open
Abstract
INTRODUCTION Two major high-penetrance breast cancer genes, BRCA1 and BRCA2, are responsible for approximately 20% of hereditary breast cancer (HBC) cases in Finland. Additionally, rare mutations in several other genes that interact with BRCA1 and BRCA2 increase the risk of HBC. Still, a majority of HBC cases remain unexplained which is challenging for genetic counseling. We aimed to analyze additional mutations in HBC-associated genes and to define the sensitivity of our current BRCA1/2 mutation analysis protocol used in genetic counseling. METHODS Eighty-two well-characterized, high-risk hereditary breast and/or ovarian cancer (HBOC) BRCA1/2-founder mutation-negative Finnish individuals, were screened for germline alterations in seven breast cancer susceptibility genes, BRCA1, BRCA2, CHEK2, PALB2, BRIP1, RAD50, and CDH1. BRCA1/2 were analyzed by multiplex ligation-dependent probe amplification (MLPA) and direct sequencing. CHEK2 was analyzed by the high resolution melt (HRM) method and PALB2, RAD50, BRIP1 and CDH1 were analyzed by direct sequencing. Carrier frequencies between 82 (HBOC) BRCA1/2-founder mutation-negative Finnish individuals and 384 healthy Finnish population controls were compared by using Fisher's exact test. In silico prediction for novel missense variants effects was carried out by using Pathogenic-Or-Not -Pipeline (PON-P). RESULTS Three previously reported breast cancer-associated variants, BRCA1 c.5095C > T, CHEK2 c.470T > C, and CHEK2 c.1100delC, were observed in eleven (13.4%) individuals. Ten of these individuals (12.2%) had CHEK2 variants, c.470T > C and/or c.1100delC. Fourteen novel sequence alterations and nine individuals with more than one non-synonymous variant were identified. One of the novel variants, BRCA2 c.72A > T (Leu24Phe) was predicted to be likely pathogenic in silico. No large genomic rearrangements were detected in BRCA1/2 by multiplex ligation-dependent probe amplification (MLPA). CONCLUSIONS In this study, mutations in previously known breast cancer susceptibility genes can explain 13.4% of the analyzed high-risk BRCA1/2-negative HBOC individuals. CHEK2 mutations, c.470T > C and c.1100delC, make a considerable contribution (12.2%) to these high-risk individuals but further segregation analysis is needed to evaluate the clinical significance of these mutations before applying them in clinical use. Additionally, we identified novel variants that warrant additional studies. Our current genetic testing protocol for 28 Finnish BRCA1/2-founder mutations and protein truncation test (PTT) of the largest exons is sensitive enough for clinical use as a primary screening tool.
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Affiliation(s)
- Kirsi M Kuusisto
- Institute of Biomedical Technology, University of Tampere, Biokatu 8, Tampere, 33520, Finland
- Centre for Laboratory Medicine, Tampere University Hospital, Biokatu 4, Tampere, 33520, Finland
| | - Aleksandra Bebel
- Institute of Biomedical Technology, University of Tampere, Biokatu 8, Tampere, 33520, Finland
| | - Mauno Vihinen
- Institute of Biomedical Technology, University of Tampere, Biokatu 8, Tampere, 33520, Finland
| | - Johanna Schleutker
- Institute of Biomedical Technology, University of Tampere, Biokatu 8, Tampere, 33520, Finland
- Centre for Laboratory Medicine, Tampere University Hospital, Biokatu 4, Tampere, 33520, Finland
| | - Satu-Leena Sallinen
- Department of Pediatrics, Genetics Outpatient Clinic, Tampere University Hospital, Biokatu 8, Tampere, 33520, Finland
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Lovelock PK, Spurdle AB, Mok MTS, Farrugia DJ, Lakhani SR, Healey S, Arnold S, Buchanan D, Couch FJ, Henderson BR, Goldgar DE, Tavtigian SV, Chenevix-Trench G, Brown MA. Identification of BRCA1 missense substitutions that confer partial functional activity: potential moderate risk variants? Breast Cancer Res 2008; 9:R82. [PMID: 18036263 PMCID: PMC2246181 DOI: 10.1186/bcr1826] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2007] [Revised: 10/16/2007] [Accepted: 11/26/2007] [Indexed: 12/03/2022] Open
Abstract
Introduction Many of the DNA sequence variants identified in the breast cancer susceptibility gene BRCA1 remain unclassified in terms of their potential pathogenicity. Both multifactorial likelihood analysis and functional approaches have been proposed as a means to elucidate likely clinical significance of such variants, but analysis of the comparative value of these methods for classifying all sequence variants has been limited. Methods We have compared the results from multifactorial likelihood analysis with those from several functional analyses for the four BRCA1 sequence variants A1708E, G1738R, R1699Q, and A1708V. Results Our results show that multifactorial likelihood analysis, which incorporates sequence conservation, co-inheritance, segregation, and tumour immunohistochemical analysis, may improve classification of variants. For A1708E, previously shown to be functionally compromised, analysis of oestrogen receptor, cytokeratin 5/6, and cytokeratin 14 tumour expression data significantly strengthened the prediction of pathogenicity, giving a posterior probability of pathogenicity of 99%. For G1738R, shown to be functionally defective in this study, immunohistochemistry analysis confirmed previous findings of inconsistent 'BRCA1-like' phenotypes for the two tumours studied, and the posterior probability for this variant was 96%. The posterior probabilities of R1699Q and A1708V were 54% and 69%, respectively, only moderately suggestive of increased risk. Interestingly, results from functional analyses suggest that both of these variants have only partial functional activity. R1699Q was defective in foci formation in response to DNA damage and displayed intermediate transcriptional transactivation activity but showed no evidence for centrosome amplification. In contrast, A1708V displayed an intermediate transcriptional transactivation activity and a normal foci formation response in response to DNA damage but induced centrosome amplification. Conclusion These data highlight the need for a range of functional studies to be performed in order to identify variants with partially compromised function. The results also raise the possibility that A1708V and R1699Q may be associated with a low or moderate risk of cancer. While data pooling strategies may provide more information for multifactorial analysis to improve the interpretation of the clinical significance of these variants, it is likely that the development of current multifactorial likelihood approaches and the consideration of alternative statistical approaches will be needed to determine whether these individually rare variants do confer a low or moderate risk of breast cancer.
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Affiliation(s)
- Paul K Lovelock
- Queensland Institute of Medical Research, PO Royal Brisbane Hospital, Herston Road, Queensland 4029, Australia
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8
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Easton DF, Deffenbaugh AM, Pruss D, Frye C, Wenstrup RJ, Allen-Brady K, Tavtigian SV, Monteiro ANA, Iversen ES, Couch FJ, Goldgar DE. A systematic genetic assessment of 1,433 sequence variants of unknown clinical significance in the BRCA1 and BRCA2 breast cancer-predisposition genes. Am J Hum Genet 2007; 81:873-83. [PMID: 17924331 DOI: 10.1086/521032] [Citation(s) in RCA: 348] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2007] [Accepted: 06/06/2007] [Indexed: 12/31/2022] Open
Abstract
Mutation screening of the breast and ovarian cancer-predisposition genes BRCA1 and BRCA2 is becoming an increasingly important part of clinical practice. Classification of rare nontruncating sequence variants in these genes is problematic, because it is not known whether these subtle changes alter function sufficiently to predispose cells to cancer development. Using data from the Myriad Genetic Laboratories database of nearly 70,000 full-sequence tests, we assessed the clinical significance of 1,433 sequence variants of unknown significance (VUSs) in the BRCA genes. Three independent measures were employed in the assessment: co-occurrence in trans of a VUS with known deleterious mutations; detailed analysis, by logistic regression, of personal and family history of cancer in VUS-carrying probands; and, in a subset of probands, an analysis of cosegregation with disease in pedigrees. For each of these factors, a likelihood ratio was computed under the hypothesis that the VUSs were equivalent to an "average" deleterious mutation, compared with neutral, with respect to risk. The likelihood ratios derived from each component were combined to provide an overall assessment for each VUS. A total of 133 VUSs had odds of at least 100 : 1 in favor of neutrality with respect to risk, whereas 43 had odds of at least 20 : 1 in favor of being deleterious. VUSs with evidence in favor of causality were those that were predicted to affect splicing, fell at positions that are highly conserved among BRCA orthologs, and were more likely to be located in specific domains of the proteins. In addition to their utility for improved genetics counseling of patients and their families, the global assessment reported here will be invaluable for validation of functional assays, structural models, and in silico analyses.
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Affiliation(s)
- Douglas F Easton
- Genetic Epidemiology Unit, Strangeways Research Laboratories, University of Cambridge, Cambridge, UK.
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Chenevix-Trench G, Healey S, Lakhani S, Waring P, Cummings M, Brinkworth R, Deffenbaugh AM, Burbidge LA, Pruss D, Judkins T, Scholl T, Bekessy A, Marsh A, Lovelock P, Wong M, Tesoriero A, Renard H, Southey M, Hopper JL, Yannoukakos K, Brown M, Easton D, Tavtigian SV, Goldgar D, Spurdle AB. Genetic and histopathologic evaluation of BRCA1 and BRCA2 DNA sequence variants of unknown clinical significance. Cancer Res 2006; 66:2019-27. [PMID: 16489001 DOI: 10.1158/0008-5472.can-05-3546] [Citation(s) in RCA: 134] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Classification of rare missense variants as neutral or disease causing is a challenge and has important implications for genetic counseling. A multifactorial likelihood model for classification of unclassified variants in BRCA1 and BRCA2 has previously been developed, which uses data on co-occurrence of the unclassified variant with pathogenic mutations in the same gene, cosegregation of the unclassified variant with affected status, and Grantham analysis of the fit between the missense substitution and the evolutionary range of variation observed at its position in the protein. We have further developed this model to take into account relevant features of BRCA1- and BRCA2-associated tumors, such as the characteristic histopathology and immunochemical profiles associated with pathogenic mutations in BRCA1, and the fact that approximately 80% of tumors from BRCA1 and BRCA2 carriers undergo inactivation of the wild-type allele by loss of heterozygosity. We examined 10 BRCA1 and 15 BRCA2 unclassified variants identified in Australian, multiple-case breast cancer families. By a combination of genetic, in silico, and histopathologic analyses, we were able to classify one BRCA1 variant as pathogenic and six BRCA1 and seven BRCA2 variants as neutral. Five of these neutral variants were also found in at least 1 of 180 healthy controls, suggesting that screening a large number of appropriate controls might be a useful adjunct to other methods for evaluation of unclassified variants.
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Lovelock PK, Healey S, Au W, Sum EYM, Tesoriero A, Wong EM, Hinson S, Brinkworth R, Bekessy A, Diez O, Izatt L, Solomon E, Jenkins M, Renard H, Hopper J, Waring P, Tavtigian SV, Goldgar D, Lindeman GJ, Visvader JE, Couch FJ, Henderson BR, Southey M, Chenevix-Trench G, Spurdle AB, Brown MA. Genetic, functional, and histopathological evaluation of two C-terminal BRCA1 missense variants. J Med Genet 2005; 43:74-83. [PMID: 15923272 PMCID: PMC2564506 DOI: 10.1136/jmg.2005.033258] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
BACKGROUND The vast majority of BRCA1 missense sequence variants remain uncharacterized for their possible effect on protein expression and function, and therefore are unclassified in terms of their pathogenicity. BRCA1 plays diverse cellular roles and it is unlikely that any single functional assay will accurately reflect the total cellular implications of missense mutations in this gene. OBJECTIVE To elucidate the effect of two BRCA1 variants, 5236G>C (G1706A) and 5242C>A (A1708E) on BRCA1 function, and to survey the relative usefulness of several assays to direct the characterisation of other unclassified variants in BRCA genes. METHODS AND RESULTS Data from a range of bioinformatic, genetic, and histopathological analyses, and in vitro functional assays indicated that the 1708E variant was associated with the disruption of different cellular functions of BRCA1. In transient transfection experiments in T47D and 293T cells, the 1708E product was mislocalised to the cytoplasm and induced centrosome amplification in 293T cells. The 1708E variant also failed to transactivate transcription of reporter constructs in mammalian transcriptional transactivation assays. In contrast, the 1706A variant displayed a phenotype comparable to wildtype BRCA1 in these assays. Consistent with functional data, tumours from 1708E carriers showed typical BRCA1 pathology, while tumour material from 1706A carriers displayed few histopathological features associated with BRCA1 related tumours. CONCLUSIONS A comprehensive range of genetic, bioinformatic, and functional analyses have been combined for the characterisation of BRCA1 unclassified sequence variants. Consistent with the functional analyses, the combined odds of causality calculated for the 1706A variant after multifactorial likelihood analysis (1:142) indicates a definitive classification of this variant as "benign". In contrast, functional assays of the 1708E variant indicate that it is pathogenic, possibly through subcellular mislocalisation. However, the combined odds of 262:1 in favour of causality of this variant does not meet the minimal ratio of 1000:1 for classification as pathogenic, and A1708E remains formally designated as unclassified. Our findings highlight the importance of comprehensive genetic information, together with detailed functional analysis for the definitive categorisation of unclassified sequence variants. This combination of analyses may have direct application to the characterisation of other unclassified variants in BRCA1 and BRCA2.
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