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Evidence for an ancient BRCA1 pathogenic variant in inherited breast cancer patients from Senegal.

ABSTRACT: BRCA1 and BRCA2 are the most incriminated genes in inherited breast/ovarian cancers. Several pathogenic variants of these genes conferring genetic predisposition have been described in different populations but rarely in sub-Saharan Africa. The objectives of this study were to identify pathogenic variants of the BRCA genes involved in hereditary breast cancer in Senegal and to search for a founder effect. We recruited after free informed consent, 27 unrelated index cases diagnosed with breast cancer and each having a family history. Mutation screening of the genes identified a duplication of ten nucleotides c.815_824dupAGCCATGTGG, (p.Thr276Alafs) (NM_007294.3) located in exon 11 of BRCA1 gene, in 15 index cases (allelic frequency 27.7%). The pathogenic variant has been previously reported in African Americans as a founder mutation of West African origin. Haplotypes analysis of seven microsatellites surrounding the BRCA1 gene highlights a shared haplotype encompassing ~400?kb between D17S855 and D17S1325. This haplotype was not detected in none of 15 healthy controls. Estimation of the age of the pathogenic variant suggested that it occurred ~1400 years ago. Our study identified a founder pathogenic variant of BRCA1 predisposing to breast cancer and enabled the establishment of an affordable genetic test as a mean of prevention for Senegalese women at risk.

SUBMITTER: Ndiaye R

PROVIDER: S-EPMC6994613 | biostudies-literature | 2020

REPOSITORIES: biostudies-literature

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Evidence for an ancient BRCA1 pathogenic variant in inherited breast cancer patients from Senegal.

Ndiaye Rokhaya R Diop Jean Pascal Demba JPD Bourdon-Huguenin Violaine V Dem Ahmadou A Diouf Doudou D Dieng Mamadou Moustapha MM Diop Pape Saloum PS Kane Gueye Serigne Modou SM Ba Seydi Abdoul SA Dia Yacouba Y Ka Sidy S Mbengue Babacar B Thiam Alassane A Sylla Niang Maguette M Gueye Papa Madieye PM Faye Oumar O Lopez Sall Philomene P Cisse Aynina A Diop Papa Amadou PA Sobol Hagay H Dieye Alioune A

NPJ genomic medicine 20200131

BRCA1 and BRCA2 are the most incriminated genes in inherited breast/ovarian cancers. Several pathogenic variants of these genes conferring genetic predisposition have been described in different populations but rarely in sub-Saharan Africa. The objectives of this study were to identify pathogenic variants of the BRCA genes involved in hereditary breast cancer in Senegal and to search for a founder effect. We recruited after free informed consent, 27 unrelated index cases dia ...[more]

PMID: 32025337

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Project description:PurposeTalazoparib has demonstrated efficacy in patients with BRCA-positive metastatic breast cancer. This study evaluated the pathologic response of talazoparib alone for 6 months in patients with a known germline BRCA pathogenic variant (gBRCA-positive) and operable breast cancer.MethodsEligibility included 1 cm or larger invasive tumor and gBRCA-positive disease. Human epidermal growth factor receptor 2-positive tumors were excluded. Twenty patients underwent a pretreatment biopsy, 6 months of once per day oral talazoparib (1 mg), followed by definitive surgery. Patients received adjuvant therapy at physician's discretion. The primary end point was residual cancer burden (RCB). With 20 patients, the RCB-0 plus RCB-I response rate can be estimated with a 95% CI with half width less than 20%.ResultsTwenty patients were enrolled from August 2016 to September 2017. Median age was 38 years (range, 23 to 58 years); 16 patients were gBRCA1 positive and 4 patients were gBRCA2 positive. Fifteen patients had triple-negative breast cancer (estrogen receptor/progesterone receptor < 10%), and five had hormone receptor-positive disease. Five patients had clinical stage I disease, 12 had stage II, and three had stage III, including one patient with inflammatory breast carcinoma and one with metaplastic chondrosarcomatous carcinoma. One patient chose to receive chemotherapy before surgery and was not included in RCB analyses. RCB-0 (pathologic complete response) rate was 53% and RCB-0/I was 63%. Eight patients (40%) had grade 3 anemia and required a transfusion, three patients had grade 3 neutropenia, and 1 patient had grade 4 thrombocytopenia. Common grade 1 or 2 toxicities were nausea, fatigue, neutropenia, alopecia, dizziness, and dyspnea. Toxicities were managed by dose reduction and transfusions. Nine patients required dose reduction.ConclusionNeoadjuvant single-agent oral talazoparib once per day for 6 months without chemotherapy produced substantial RCB-0 rate with manageable toxicity. The substantive pathologic response to single-agent talazoparib supports the larger, ongoing neoadjuvant trial (ClinicalTrials.gov identifier: NCT03499353).

Project description:Simple Summary The Finnish population has evolved through multiple reductions in the population size, which have caused decreased genetic diversity in the population. This may affect the risk variant spectrum in diseases such as breast cancer (BC) so that a few variants may cover most of the pathogenic variation found in the risk genes. A dozen recurrent pathogenic variants have been identified in the moderate-risk BC susceptibility genes in Finnish BC patients. To evaluate the spectrum and frequency of the risk variants more comprehensively, we have, here, studied all variants in 1769 patients and copy number changes in 1511 patients both in the moderate-risk genes as well as in the high-risk BRCA1 and BRCA2 genes. While the overall pathogenic variant frequency was comparable to other populations, just a few variants accounted for most of the pathogenic burden in the risk genes. These results could be utilized in population screening strategies in Finland. Abstract Recurrent pathogenic variants have been detected in several breast and ovarian cancer (BC/OC) risk genes in the Finnish population. We conducted a gene-panel sequencing and copy number variant (CNV) analysis to define a more comprehensive spectrum of pathogenic variants in BRCA1, BRCA2, PALB2, CHEK2, ATM, BARD1, RAD51C, RAD51D, BRIP1, and FANCM genes in Finnish BC patients. The combined frequency of pathogenic variants in the BRCA1/2 genes was 1.8% in 1356 unselected patients, whereas variants in the other genes were detected altogether in 8.3% of 1356 unselected patients and in 12.9% of 699 familial patients. CNVs were detected in 0.3% of both 1137 unselected and 612 familial patients. A few variants covered most of the pathogenic burden in the studied genes. Of the BRCA1/2 carriers, 70.8% had 1 of 10 recurrent variants. In the other genes combined, 92.1% of the carrier patients had at least 1 of 11 recurrent variants. In particular, PALB2 c.1592delT and CHEK2 c.1100delC accounted for 88.9% and 82.9%, respectively, of the pathogenic variation in each gene. Our results highlight the importance of founder variants in the BC risk genes in the Finnish population and could be used in the designing of population screening for the risk variants.

Project description:BackgroundBreast cancer (BC) is the most common cancer and related cause of mortality among Hispanics, yet susceptibility has been understudied. BRCA1 and BRCA2 (BRCA) mutations explain less than one-half of hereditary BC, and the proportion associated with other BC susceptibility genes is unknown.MethodsGermline DNA from 1054 BRCA-mutation-negative Hispanic women with hereditary BC (BC diagnosed at age <51 years, bilateral BC, breast and ovarian cancer, or BC diagnosed at ages 51-70 years with ≥2 first-degree or second-degree relatives who had BC diagnosed at age <70 years), 312 local controls, and 887 multiethnic cohort controls was sequenced and analyzed for 12 known and suspected, high-penetrance and moderate-penetrance cancer susceptibility genes (ataxia telangiectasia mutated [ATM], breast cancer 1 interacting protein C-terminal helicase 1 [BRIP1], cadherin 1 [CDH1], checkpoint kinase 2 [CHEK2], nibrin [NBN], neurofibromatosis type 1 [NF1], partner and localizer of BRCA2 [PALB2], phosphatase and tensin homolog [PTEN], RAD51 paralog 3 [RAD51C], RAD51D, serine/threonine kinase 11 [STK11], and TP53).ResultsForty-nine (4.6%) pathogenic or likely pathogenic variants (PVs) in 47 of 1054 participants (4.5%), including 21 truncating frameshift, 20 missense, 5 nonsense, and 4 splice variants, were identified in CHEK2 (n = 20), PALB2 (n = 18), ATM (n = 5), TP53 (n = 3), BRIP1 (n = 2), and CDH1 and NF1 (both n = 1) and none were identified in NBN, PTEN, STK11, RAD51C, or RAD51D. Nine participants carried the PALB2 c.2167_2168del PV (0.85%), and 14 carried the CHEK2 c.707T>C PV (1.32%).ConclusionsOf 1054 BRCA-negative, high-risk Hispanic women, 4.5% carried a PV in a cancer susceptibility gene, increasing understanding of hereditary BC in this population. Recurrent PVs in PALB2 and CHEK2 represented 47% (23 of 49) of the total, suggesting a founder effect. Accurate classification of variants was enabled by carefully controlling for ancestry and the increased identification of at-risk Hispanics for screening and prevention.

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Evidence for an ancient BRCA1 pathogenic variant in inherited breast cancer patients from Senegal.

Publications

Evidence for an ancient <i>BRCA</i>1 pathogenic variant in inherited breast cancer patients from Senegal.

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