Preliminary results of targeted sequencing of BRCA1 and BRCA2 in a cohort of breast cancer families: New insight into pathogenic variants in patients and at‑risk relatives
- Authors:
- Published online on: July 23, 2021 https://doi.org/10.3892/mmr.2021.12317
- Article Number: 678
Abstract
Introduction
Breast cancer type 1 and type 2 susceptibility genes (BRCA1 and BRCA2) are located at chromosomes 17q21.31 and 13q12-q13, respectively; these are tumor suppressor genes that share a common pathway in protecting cell fidelity (1). Both genes repair double-strand DNA breaks in homologous recombination patterns (2). Inheriting a germline mutation of a single copy of either gene increases the risk of developing several types of cancer, including breast cancer (BC). BRCA1 and BRCA2 genes have 24 and 27 exons, respectively. Exon 11 is the largest exon in both genes and is the location of the most common mutations found in patients with BC (3).
It is known that 4–5% of BC cases are hereditary (hereditary breast and ovarian cancer syndrome) (4), which is autosomal dominant and is characterized by an early onset of BC with the occurrence of multiple tumors successively, such as in the ovaries, pancreas and stomach (5). Furthermore, 5–10% of cases are familial BC (FBC), whereby BC affects family members usually <50 years of age, in clusters, and with a different pattern from that observed in hereditary BC (6). The majority of BC cases are sporadic (SBC), whereby mutations are acquired with an increased risk with age, environment, lifestyle or medical factors (7).
According to the American Society of Medical Genetics and Genomics, variants/mutations in cancer can be classified into five categories: i) Pathogenic; ii) likely pathogenic; iii) variant of uncertain significance (VUS); iv) likely benign; and v) benign (8). Individuals who carry pathogenic variants should undergo a follow-up scheme, including mammography at short time intervals, or possibly prophylactic surgeries, such as bilateral mastectomy or salpingo-oophorectomy (9). In addition, tamoxifen administration may be used as a protective strategy against tumor development in hormone-dependent BC (10).
Studies on BRCA1 and BRCA2 were previously conducted in various groups of Egyptian patients with BC. However, these studies were performed either at the genetic level targeting well-known variants (11–13), or at the genomic level in a limited number of patient families (14). Therefore, the present study aimed to include more BC families (patients and their first-degree, at-risk relatives) to investigate the frequency of BRCA1 and BRCA2 variants using targeted next-generation sequencing.
Patients and methods
Patients
The present study was based on residents of the city of Alexandria, located on the northern coast of Egypt. The majority of the included participants were educated, working women. A total of 11 families were included as follows: Six patients with FBC with a family history of BC (at least one first-degree relative affected before the age of 50 years) and 10 high-risk relatives. All the patients with FBC had a history of BC from the maternal side, apart from patient no. 4, who had a history of BC from both the maternal and paternal side. Additionally, there were five patients with SBC without a known family history of BC and six high-risk relatives. The clinicopathological characteristics of the patients are summarized in Table I. Patients were recruited between October 2018 and October 2019 from the Clinical Oncology Department, Faculty of Medicine and Medical Research Institute, Alexandria University (Alexandria, Egypt). There were no specific exclusion criteria, and all patients were included regardless of hormonal status and metastatic state. Patients and relatives signed a formal consent form to participate in the study. The present study was approved by the Ethical Committee, Faculty of Medicine, Alexandria University (approval no. 0304918).
DNA extraction
For patients with both FBC and SBC, formalin-fixed paraffin-embedded (FFPE) tissue blocks were collected; the fixative used for those archived blocks was 10% buffered formalin overnight at room temperature for breast lumpectomy and modified radical mastectomy specimens at room temperature. The immunohistochemistry data were collected from the pathological reports of the cases, and the previously obtained slides were reviewed to confirm the correct interpretation. Following a pathological examination, DNA extraction was performed using a QIAamp DNA FFPE Tissue kit (cat. no. 56404; Qiagen GmbH). For relatives, genomic DNA was extracted from the peripheral blood using a PureLink™ Genomic DNA Mini kit (cat. no. K1820-00; Invitrogen; Thermo Fisher Scientific, Inc.). DNA was quantified using a Qubit™ 1X dsDNA HS (High Sensitivity) Assay kit Q33231 with a Qubit Fluorometer version 4 (Thermo Fisher Scientific, Inc.), according to the manufacturer's instructions.
Library preparation and next-generation sequencing
A total of 10 ng DNA per sample was used for library preparation using the Ion AmpliSeq™ Library Kit Plus (cat. no. 4488990; Ion Torrent; Thermo Fisher Scientific, Inc.) and the Oncomine™ BRCA Research assay (cat. no. A32842; Ion Torrent; Thermo Fisher Scientific, Inc.), according to the manufacturer's instructions. Coding regions from BRAC1 and BRCA2 were amplified using 167 primer pairs divided into two pools. Each library was barcoded using the Ion Xpress™ Barcode Adapters 1–16 kit (cat. no. 4471250; Ion Torrent; Thermo Fisher Scientific, Inc.). An Ion Library TaqMan™ Quantitation kit (cat. no. 4468802; Ion Torrent; Thermo Fisher Scientific, Inc.) was used to quantify the libraries against a standard curve of serial dilutions of the E. coli DH10B Control Library provided (Thermo Fisher Scientific, Inc.). Barcoded libraries were pooled and diluted to a final concentration of 100 pM.
Template preparation by emulsion PCR on Ion Sphere Particles (ISPs) was performed using the Ion 520™ & Ion 530™ Kit-OT2 kit (cat. no. A27751) and the Ion OneTouch™ 2 System (Ion Torrent; Thermo Fisher Scientific, Inc.). The samples were loaded on Ion 520 Chip kit v2 (Ion Torrent; Thermo Fisher Scientific, Inc.). Sequencing primer and polymerase were added to the final enriched ISPs prior to loading onto an Ion 520 chip, according to the Ion 520 & Ion 530 kit-OT2 protocol.
Sequencing was performed using the Ion S5™ next generation sequencing system (Ion Torrent; Thermo Fisher Scientific, Inc.). Sequencing coverage for reporting were ≥20 unique reads (×20) for each base. Allelic frequency for somatic variants ranged from 0.05 to 1%, while for germline variants, the allele frequency was between 0.4 and 1%. Median coverage typically ranged between ×200 and ×300.
Statistical analysis
Sequencing data were processed using Torrent Suite software 5.12.1 (Ion Torrent; Thermo Fisher Scientific, Inc.) to analyze barcode reads; to align reads to the hg19 reference genome; and to generate run metrics, which include chip loading efficiency, total read counts and quality. Following statistical analysis, the annotation of single-nucleotide variants, insertions, deletions and splice site alterations, was performed using the Ion Reporter Server System (Oncomine BRCA Research Assay; Thermo Fisher Scientific, Inc.). The variants identified were further analyzed using Oncomine Reporter.
All mutations reported were confirmed in the Human Gene Mutation Database (HGMD; http://www.hgmd.cf.ac.uk/ac/index.php), Catalogue Of Somatic Mutations In Cancer (https://cancer.sanger.ac.uk/cosmic), the algorithms SIFT 6.2.1 (https://sift.bii.a-star.edu.sg/www/code.html) PolyPhen-2 (version 2) (http://genetics.bwh.harvard.edu/pph2/) and Align-GVGD (http://agvgd.hci.utah.edu/agvgd_input.php) and ClinVar (http://www.ncbi.nlm.nih.gov/clinvar/), and reviewed by the BRCA Exchange (https://brcaexchange.org). The mutation function and mutation classes were further investigated using the Consortium of Investigators of Modifiers of BRCA1/2 (CIMBA) (15).
Results
Patient characteristics and mutational status
The median age of patients with FBC and SBC was 35.5 and 66 years, respectively. Each patient had a history of unilateral BC, apart from FBC patient no. 6, who had a history of contralateral BC. With regards to first-degree relatives, no one had experienced a health issue, apart from the daughter of SBC patient no. 9, who had a history of fibroadenoma in the right breast (Tables I and II). The investigation of BRCA1 and BRCA2 variants in patients revealed 22 mutations, namely 9 in BRCA1 and 13 in BRCA2 (Table II).
All patients with FBC and SBC carried BRCA1 and BRCA2 mutations, apart from patients no. 6 and 11 who were carriers of BRCA2. Generally, no significant associations were detected between BRCA1 and BRCA2 mutations and patient age (data not shown). In total, ~82% of patients had infiltrating ductal carcinoma, 46% of patients had estrogen receptor (ER)- and progesterone receptor (PR)-positive BC of varying histological grades. In addition, three patients had triple-negative (ER, PR and Her2/neu) BC; two had FBC and one had SBC with a high histological grade (Table I). No significant association was observed between the hormonal status of the tumor, and BRCA1 and BRCA2 mutations (data not shown).
Pathogenic variants in patients are more frequent in BRCA2 than in BRCA1
The analysis of pathogenic variants in patients revealed two variants in BRCA1 and five variants in BRCA2 with no preference to a specific exon (Table II). Pathogenic variants were mainly found in patients with FBC (five with FBC and three with SBC) (Table II). A pathogenic variant c.9089del BRCA2, located in exon 23 was shared by three patients with FBC (nos. 2, 3 and 6) with a median age of 34 years and who presented with early-onset BC: Two of them had triple-negative BC of high histological grade (III/IV) (Tables I and II). The variant c.9089del is a frameshift class 1 mutation that is predicted to encode a truncated non-functional protein (15). This variant was previously detected in Chinese patients with early-onset BC (16). Additionally, a missense pathogenic variant, c.8243G>A BRCA2, located in exon 18, was shared by FBC patient no. 5 and two patients with SBC (nos. 9 and 10) with medium to high-histological grades (II/III). Variant c.8243G>A is a class 2 mutation with a stable mutant protein (17). A class 2 missense pathogenic variant c.5053A>G BRCA1, located in exon 16, was found in FBC patient no. 3 and SBC patient no. 10 (grade II/III). This variant is linked to an increased risk of breast and ovarian cancer (18,19). Other pathogenic variants were detected, such as a class 1 frameshift c.5583_5584insA BRCA2 variant, located in exon 11 and observed in SBC patient no. 11 (grade II). Two intronic variants (BRCA2 c.7008-2A>T intron 13 with non-functional transcript, BRCA1 c.4097-1G>A intron 10) were identified in FBC patient no. 4 with a very high histological grade (III/IV). Both variants have been found to have splicing aberrations (20,21). In addition, one in-frame class 2 c.7976G>A BRCA2 located in exon 17 was found in FBC patient no. 5 (grade II). This variant has been previously reported in patients with BC and/or ovarian cancer (19,22).
Furthermore, as presented in Table II, four VUS were identified in four patients: Three variants in patients with FBC (two in BRCA2 and one in BRCA1) and one variant in BRCA2 in a patient with SBC. The variants were distributed among different exons: 11, 13, 20, 23 and intron 2. The BRCA exchange revealed that the synonymous substitution variant c.9087G>A had a low bioinformatic likelihood of resulting in a splicing aberration. Variant c.68-16delT has no existing functional assay data. The algorithms SIFT, PolyPhen-2 and Align-GVGD that predict the effect of missense changes on protein structure and function, all suggested that the variants c.4412G>T and c.6556T>A were likely to be tolerated.
One patient with SBC (patient no. 8) had a probable benign variant c.8503T>C BRCA2 in exon 20. This variant has previously been identified in two North African countries: Tunisia and Algeria (23).
Cold spot benign variants identified in both BRCA1 and BRCA2
Missense benign mutations with amino acid replacement were also identified: Six variants in BRCA1 and four variants in BRCA2. These benign variants were observed in both FBC and patients with SBC (Table II). Benign missense mutations were found in exon 10 (40%) and exon 11 (20%) followed by 10% each in exons 13, 14, 15 and 16. These benign variants located in exon 10 and exon 11 are considered ‘cold spots’ since they are tolerant to variations (24).
Pathogenic variants are confined to relatives of patients with FBC
The investigation of BRCA1 and BRCA2 variants in first-degree relatives revealed three pathogenic variants, with all of these found in relatives of patients with FBC (Table III). Variant c.1278delA (GA>A) BRCA2 in exon 10 was detected in a daughter of patient no. 2, where the G allele is predicted to cause a frameshift deletion mutation with an amino acid change. Both relatives of FBC patient no. 4 had pathogenic variants: The mother had c.1960_1961delA, (CT>C, CTT) and the daughter had c.1224del, (CT>C). The last two variants were frameshift mutations located in BRCA1 exon 10. Variant c.1960_1961delA was also found in a sister of FBC patient no. 3. No pathogenic variants were identified in the relatives of patients with SBC.
Moreover, VUS, likely benign, or conflicting interpretation of pathogenicity variants were identified in 9/16 relatives: Six relatives with FBC and three with SBC. Three variants were detected in BRCA1 (exons 10 and 16) and four variants in BRCA2 (exons 10, 11 and intron 2). Notably, BRCA2 intron 2 c.68-16delT was observed in six at-risk relatives in four families (familial and sporadic). This variant was repeated in family no. 6 (patient and two relatives) and in both relatives of patient no. 4. The A allele in c.68-16delT (AT>A), is predicted to cause an unknown/non-coding mutation in the BRCA2 gene. This variant was previously selected as one of the specific deletions in BC microarray analyses (25). In addition, a daughter of FBC patient no. 1 had a likely benign BRCA1 exon 10 missense mutation. This locus is linked to adenocarcinoma in the Catalogue Of Somatic Mutations In Cancer (https://cancer.sanger.ac.uk/cosmic). Furthermore, one sister of FBC patient no. 3 had a BRCA1 exon 10 c.2733A>G synonymous variant that was previously detected only in patients with unilateral BC (24). One daughter of SBC patient no. 11 had a missense BRCA2 mutation c.5640T>G with a conflicting interpretation of pathogenicity that was previously identified as an unclassified variant in both contralateral and unilateral BC (26). Finally, both daughters of SBC patient no. 9 shared a BRCA2 exon 10 c.1011C>T synonymous variant. One of these daughters had a fibroadenoma in one breast and a history of pregnancy and lactation.
Common benign missense variants identified in relatives of patients with FBC and SBC
Seven out of 11 families had repeated benign BRCA missense mutations found in both patients and their relatives. Two benign mutations, c.3113A>G BRCA1 in exon 10 and c.4837A>G BRCA1 in exon 16, were detected in 8/16 relatives (50%). Variants c.3113A>G and c.4837A>G were previously reported as candidate founder mutations in an Iranian population (27).
Discussion
The present study was conducted on 11 families: Six with FBC and five with SBC. A similar previous study on BRCA1 and BRCA2 in five Egyptian families with a history of BC was previously performed using exome sequencing (14), where the families were selected from a more rural population in the Gharbiah district of the Delta region of Egypt. In the present study, various benign missense variants that were identified either in patients or their relatives, have been previously reported in Egyptian patients with BC (14) and in other BC populations, such as Indian, Greek, Turkish and Italian (3). However, in contrast to the findings of the present study, pathogenic/likely pathogenic variants were not observed using exome sequencing of the five patients with FBC (14), and where the median age for FBC was 48.5 years, which was higher than the median age of 35.5 years for FBC in the present study.
In the current study, no significant associations were found between the clinicopathological characteristics of the patients and BRCA mutations. Nevertheless, a broad-scale research including a greater number of patients is required to improve the characterization of BRCA1 and BRCA2 mutation carriers among the Egyptian population.
Certain pathogenic variants in the present study were repeated in more than one patient, such as c.8243G>A, c.9089del and c.5053A>G. However, no inherited pathogenic variant was found in the same family. Those recurrent loci may be used as a suggested targeted panel for genetic testing in Egyptian patients (28).
In the present study, only one pathogenic variant was found in exon 11 and the remaining variants were located outside exons 10 or 11, such as in exons 16, 17, 18 and 23, and introns 3 and 10. Therefore, screening for pathogenic variants in exons beyond exons 10 and 11 is crucial (29).
Additionally, one VUS: BRCA2 intron 2 c.68-16delT was repeated in the relatives of both the sporadic and familial cases. This variant has not been previously reported in Egyptian patients (14), at least to the best of our knowledge. A very recent screening of BRCA1 and BRCA2 in 103 Egyptian female patients with BC using high resolution melting analysis revealed novel VUS that were different from the results of the present study, as they screened only exons 2 and 20 of BRCA1, and exons 9 and 11 of BRCA2 (30). Nevertheless, the observation of the present study that VUS were frequent in patients with FBC and their relatives drew attention to the potential role of VUS in FBC. This necessitates further genetic analyses in order to fully elucidate the role of these variants in BC and to determine guidelines for the follow-up of relatives who are at a high risk (31).
Moreover, pathogenic variants that were detected in the relatives of patients with FBC, have been previously reported in other populations. For example, c.1278delA and c.1224delT were previously detected in the Japanese population (32,33) and c.1960_1961delA was observed in the Brazilian population (0.3% of a total 441 variants identified) (34). Variant c.1960_1961delA was also repeated in two relatives and may thus be added to the suggested targeted panel for genetic screening, as aforementioned. The association between FBC and pathogenic variants in BRCA or even in other BC predisposition genes, such as P53 and ATM, has been previously elucidated (35).
The data presented herein demonstrated that there was no specific pattern of inheritance of variants between patients with FBC and their relatives. However, the presence of pathogenic variants only in relatives of patients with FBC confirmed a genetic predisposition to the familial type of the tumor and thus, these BRCA pathogenic carriers must undergo close surveillance. Similarly, for the family of FBC patient no. 4, who has a history of BC from the paternal and maternal side, and the identification of BRCA1 pathogenic variants in both the unaffected mother and sister, genetic counseling and follow-up are mandatory (36).
In conclusion, to the best of our knowledge, the present study was the first to identify pathogenic variants in BRCA1 and BRCA2 in an Egyptian population, with a spotlight on pathogenic variants and VUS in at-risk relatives of patients with FBC. The present data and the results of previous studies on Egyptian families must be integrated in order to further understand the characteristics of BRCA1 and BRCA2 mutations in Egyptian families with BC.
Acknowledgements
The authors acknowledge the continuous follow-up and supervision from department chairs: Professor Dr Mostafa Rizk, Professor Dr Ola Sharaki, Professor Dr Magdy Elbordiny and Professor Dr Akram Deghady the heads of the Clinical Pathology Department, Alexandria for the success of this work.
Funding
This research was supported by a grant from the Science, Technology, and Innovation Funding Authority (STDF) (grant no. 22832) for establishing the Cancer Genetics Unit at the Clinical Pathology Department, Faculty of Medicine, Alexandria University, Egypt.
Availability of data and materials
The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.
Authors' contributions
MHS conceived the study, participated in its design and coordination, carried out the molecular genetics and sequencing studies, analyzed the data, and drafted the manuscript. DEK and ET participated in conception, design, molecular genetics, sequencing studies and revised the manuscript. RF, RAH, AR, AEK and MT participated in conception, design and practical sequencing work, and revised the manuscript. II participated in design and performed the pathological examination of the FFPE sections. MS and ET confirm the authenticity of all the raw data. All the authors read and approved the final manuscript.
Ethics approval and consent to participate
This research was conducted on human participants. The study was approved by the Ethics Committee of Alexandria University (approval no. 0304918; Alexandria, Egypt). Patients and relatives signed a formal consent form to participate in the study.
Patient consent for publication
Not applicable.
Competing interests
The authors declare that they have no competing interests.
References
|
Roy R, Chun J and Powell SN: BRCA1 and BRCA2: Different roles in a common pathway of genome protection. Nat Rev Cancer. 12:68–78. 2011. View Article : Google Scholar : PubMed/NCBI | |
|
Powell SN and Kachnic LA: Roles of BRCA1 and BRCA2 in homologous recombination, DNA replication fidelity and the cellular response to ionizing radiation. Oncogene. 22:5784–5791. 2003. View Article : Google Scholar : PubMed/NCBI | |
|
Karami F and Mehdipour P: A comprehensive focus on global spectrum of BRCA1 and BRCA2 mutations in breast cancer. Biomed Res Int. 2013:9285622013. View Article : Google Scholar : PubMed/NCBI | |
|
Yoshida R: Hereditary breast and ovarian cancer (HBOC): Review of its molecular characteristics, screening, treatment, and prognosis. Breast Cancer. Aug 29–2020.(Epub ahead of print). View Article : Google Scholar | |
|
Vogt A, Schmid S, Heinimann K, Frick H, Herrmann C, Cerny T and Omlin A: Multiple primary tumours: Challenges and approaches, a review. ESMO Open. 2:e0001722017. View Article : Google Scholar : PubMed/NCBI | |
|
Apostolou P and Fostira F: Hereditary breast cancer: The era of new susceptibility genes. Biomed Res Int. 2013:7473182013. View Article : Google Scholar : PubMed/NCBI | |
|
Burgess M and Puhalla S: BRCA 1/2-mutation related and sporadic breast and ovarian cancers: More alike than different. Front Oncol. 4:192014. View Article : Google Scholar : PubMed/NCBI | |
|
Richards S, Aziz N, Bale S, Bick D, Das S, Gastier-Foster J, Grody WW, Hegde M, Lyon E, Spector E, et al: Standards and guidelines for the interpretation of sequence variants: a joint consensus recommendation of the American college of medical genetics and genomics and the association for molecular pathology. Genet Med. 17:405–424. 2015. View Article : Google Scholar : PubMed/NCBI | |
|
Kauff ND, Satagopan JM, Robson ME, Scheuer L, Hensley M, Hudis CA, Ellis NA, Boyd J, Borgen PI, Barakat RR, et al: Risk-reducing salpingo-oophorectomy in women with a BRCA1 or BRCA2 mutation. N Engl J Med. 346:1609–1615. 2002. View Article : Google Scholar : PubMed/NCBI | |
|
King MC, Wieand S, Hale K, Lee M, Walsh T, Owens K, Tait J, Ford L, Dunn BK, Costantino J, et al: Tamoxifen and breast cancer incidence among women with inherited mutations in BRCA1 and BRCA2: National surgical adjuvant breast and bowel project (NSABP-P1) breast cancer prevention trial. JAMA. 286:2251–2256. 2001. View Article : Google Scholar : PubMed/NCBI | |
|
Fattouh M, Ahmed H and Hafez Eel S: Detection of BRCA1 and BRCA2 gene mutation in Egyptian females with breast cancer and their relatives by PCR-SSCP method. Egypt J Immunol. 18:9–16. 2011.PubMed/NCBI | |
|
Ibrahim SS, Hafez EE and Hashishe MM: Presymptomatic breast cancer in Egypt: Role of BRCA1 and BRCA2 tumor suppressor genes mutations detection. J Exp Clin Cancer Res. 29:822010. View Article : Google Scholar : PubMed/NCBI | |
|
Laraqui A, Uhrhammer N, Rhaffouli HE, Sekhsokh Y, Lahlou-Amine I, Bajjou T, Hilali F, El Baghdadi J, Al Bouzidi A, Bakri Y, et al: BRCA genetic screening in Middle Eastern and North African: Mutational spectrum and founder BRCA1 mutation (c.798_799delTT) in North African. Dis Markers. 2015:1942932015. View Article : Google Scholar : PubMed/NCBI | |
|
Kim YC, Soliman AS, Cui J, Ramadan M, Hablas A, Abouelhoda M, Hussien N, Ahmed O, Zekri AN, Seifeldin IA and Wang SM: Unique features of germline variation in five Egyptian familial breast cancer families revealed by exome sequencing. PLoS One. 12:e01675812017. View Article : Google Scholar : PubMed/NCBI | |
|
Rebbeck TR, Friebel TM, Friedman E, Hamann U, Huo D, Kwong A, Olah E, Olopade OI, Solano AR, Teo SH, et al: Mutational spectrum in a worldwide study of 29,700 families with BRCA1 or BRCA2 mutations. Hum Mutat. 39:593–620. 2018. View Article : Google Scholar : PubMed/NCBI | |
|
Wei H, Wang M, Ou J, Jiang W, Tian F, Sheng Y, Li H, Xu H, Zhang R, Guan A, et al: Multicenter cross-sectional screening of the BRCA gene for Chinese high hereditary risk breast cancer populations. Oncol Lett. 15:9420–9428. 2018.PubMed/NCBI | |
|
Mesman RLS, Calléja FMGR, Hendriks G, Morolli B, Misovic B, Devilee P, van Asperen CJ, Vrieling H and Vreeswijk MPG: The functional impact of variants of uncertain significance in BRCA2. Genet Med. 21:293–302. 2019. View Article : Google Scholar : PubMed/NCBI | |
|
Fernandes VC, Golubeva VA, Di Pietro G, Shields C, Amankwah K, Nepomuceno TC, de Gregoriis G, Abreu RBV, Harro C, Gomes TT, et al: Impact of amino acid substitutions at secondary structures in the BRCT domains of the tumor suppressor BRCA1: Implications for clinical annotation. J Biol Chem. 294:5980–5992. 2019. View Article : Google Scholar : PubMed/NCBI | |
|
Balabanski L, Antov G, Dimova I, Ivanov S, Nacheva M, Gavrilov I, Nesheva D, Rukova B, Hadjidekova S, Malinov M and Toncheva D: Next-generation sequencing of BRCA1 and BRCA2 in breast cancer patients and control subjects. Mol Clin Oncol. 2:435–439. 2014. View Article : Google Scholar : PubMed/NCBI | |
|
Concolino P, Gelli G, Rizza R, Costella A, Scambia G and Capoluongo E: BRCA1 and BRCA2 testing through next generation sequencing in a small cohort of Italian breast/ovarian cancer patients: Novel pathogenic and unknown clinical significance variants. Int J Mol Sci. 20:34422019. View Article : Google Scholar : PubMed/NCBI | |
|
Lindor NM, Guidugli L, Wang X, Vallee MP, Monteiro AN, Tavtigian S, Goldgar DE and Couch FJ: A review of a multifactorial probability-based model for classification of BRCA1 and BRCA2 variants of uncertain significance (VUS). Hum Mutat. 33:8–21. 2012. View Article : Google Scholar : PubMed/NCBI | |
|
Konstantopoulou I, Tsitlaidou M, Fostira F, Pertesi M, Stavropoulou AV, Triantafyllidou O, Tsotra E, Tsiftsoglou AP, Tsionou C, Droufakou S, et al: High prevalence of BRCA1 founder mutations in Greek breast/ovarian families. Clin Genet. 85:36–42. 2014. View Article : Google Scholar : PubMed/NCBI | |
|
Abbad A, Baba H, Dehbi H, Elmessaoudi-Idrissi M, Elyazghi Z, Abidi O and Radouani F: Genetics of breast cancer in African populations: A literature review. Glob Health Epidemiol Genom. 3:e82018. View Article : Google Scholar : PubMed/NCBI | |
|
Dines JN, Shirts BH, Slavin TP, Walsh T, King MC, Fowler DM and Pritchard CC: Systematic misclassification of missense variants in BRCA1 and BRCA2 ‘coldspots’. Genet Med. 22:825–830. 2020. View Article : Google Scholar : PubMed/NCBI | |
|
Schroeder C, Stutzmann F, Weber BH, Riess O and Bonin M: High-throughput resequencing in the diagnosis of BRCA1/2 mutations using oligonucleotide resequencing microarrays. Breast Cancer Res Treat. 122:287–297. 2010. View Article : Google Scholar : PubMed/NCBI | |
|
Borg A, Haile RW, Malone KE, Capanu M, Diep A, Törngren T, Teraoka S, Begg CB, Thomas DC, Concannon P, et al: Characterization of BRCA1 and BRCA2 deleterious mutations and variants of unknown clinical significance in unilateral and bilateral breast cancer: The WECARE study. Hum Mutat. 31:E1200–E1240. 2010. View Article : Google Scholar : PubMed/NCBI | |
|
Forat-Yazdi M, Neamatzadeh H, Sheikhha MH, Zare-Shehneh M and Fattahi M: BRCA1 and BRCA2 common mutations in iranian breast cancer patients: A meta analysis. Asian Pac J Cancer Prev. 16:1219–1224. 2015. View Article : Google Scholar : PubMed/NCBI | |
|
Jiang Y, Tian T, Yu C, Zhou W, Yang J, Wang Y, Wen Y, Chen J, Dai J, Jin G, et al: Identification of recurrent variants in BRCA1 and BRCA2 across multiple cancers in the Chinese population. Biomed Res Int. 2020:67398232020. View Article : Google Scholar : PubMed/NCBI | |
|
Li J, Wen WX, Eklund M, Kvist A, Eriksson M, Christensen HN, Torstensson A, Bajalica-Lagercrantz S, Dunning AM, Decker B, et al: Prevalence of BRCA1 and BRCA2 pathogenic variants in a large, unselected breast cancer cohort. Int J Cancer. 144:1195–1204. 2019. View Article : Google Scholar : PubMed/NCBI | |
|
AbdelHamid SG, Zekri AN, AbdelAziz HM and El-Mesallamy HO: BRCA1 and BRCA2 truncating mutations and variants of unknown significance in Egyptian female breast cancer patients. Clin Chim Acta. 512:66–73. 2021. View Article : Google Scholar : PubMed/NCBI | |
|
Eccles BK, Copson E, Maishman T, Abraham JE and Eccles DM: Understanding of BRCA VUS genetic results by breast cancer specialists. BMC Cancer. 15:9362015. View Article : Google Scholar : PubMed/NCBI | |
|
Arai M, Yokoyama S, Watanabe C, Yoshida R, Kita M, Okawa M, Sakurai A, Sekine M, Yotsumoto J, Nomura H, et al: Genetic and clinical characteristics in Japanese hereditary breast and ovarian cancer: First report after establishment of HBOC registration system in Japan. J Hum Genet. 63:447–457. 2018. View Article : Google Scholar : PubMed/NCBI | |
|
Yoshida R, Watanabe C, Yokoyama S, Inuzuka M, Yotsumoto J, Arai M and Nakamura S; Registration Committee of the Japanese HBOC consortium, : Analysis of clinical characteristics of breast cancer patients with the Japanese founder mutation BRCA1 L63X. Oncotarget. 10:3276–3284. 2019. View Article : Google Scholar : PubMed/NCBI | |
|
Palmero EI, Carraro DM, Alemar B, Moreira MAM, Ribeiro-Dos-Santos Â, Abe-Sandes K, Galvão HCR, Reis RM, de Pádua Souza C, Campacci N, et al: The germline mutational landscape of BRCA1 and BRCA2 in Brazil. Sci Rep. 8:91882018. View Article : Google Scholar : PubMed/NCBI | |
|
Slavin TP, Maxwell KN, Lilyquist J, Vijai J, Neuhausen SL, Hart SN, Ravichandran V, Thomas T, Maria A, Villano D, et al: The contribution of pathogenic variants in breast cancer susceptibility genes to familial breast cancer risk. NPJ Breast Cancer. 3:222017. View Article : Google Scholar : PubMed/NCBI | |
|
Petrucelli N, Daly MB and Pal T: BRCA1- and BRCA2-associated hereditary breast and ovarian cancer. GeneReviews® [Internet]. Adam MP, Ardinger HH, Pagon RA, Wallace SE, Bean LJH, Mirzaa G and Amemiya A: University of Washington; Seattle, WA: 1993 |
