BRCA1 mutations in South African breast and/or ovarian cancer families: evidence of a novel founder mutation in Afrikaner families

Germ-line mutations within BRCA1 are responsible for different proportions of inherited susceptibility to breast/ovarian cancer, and the spectrum of mutations within this gene is often unique to certain populations. At this time, there have been no reports regarding the role of BRCA1 in South African breast and/or ovarian cancer families. We therefore screened 90 South African breast/ovarian cancer families for BRCA1 mutations by means of PCR-based mutation detection assays. Eighteen families (20%) were identified with BRCA1 disease-causing mutations. Four Ashkenazi Jewish families were identified with the 185delAG mutation, whereas 2 Afrikaner and 1 Ashkenazi Jewish family were found to harbor the 5382insC mutation. Five of the families (5.56%), all of whom are Afrikaners, were found to carry the novel E881X mutation. Genotype analyses show that these patients share a common ancestor. Genealogic studies have identified 3 possible founding couples for this mutation, all of whom arrived in the Cape from France in the late 1600s. Of the remaining mutations detected, 3 have not been reported previously and include the S451X, 1493delC (detected twice) and 4957insC mutations.     

A high proportion of founder BRCA1 mutations in Polish breast cancer families

Three mutations in BRCA1 (5382insC, C61G and 4153delA) are common in Poland and account for the majority of mutations identified to date in Polish breast and breast-ovarian cancer families. It is not known, however, to what extent these 3 founder mutations account for all of the BRCA mutations distributed throughout the country. This question has important implications for health policy and the design of epidemiologic studies. To establish the relative contributions of founder and nonfounder BRCA mutations, we established the entire spectrum of BRCA1 and BRCA2 mutations in a large set of breast-ovarian cancer families with origins in all regions of Poland. We sequenced the entire coding regions of the BRCA1 and BRCA2 genes in 100 Polish families with 3 or more cases of breast cancer and in 100 families with cases of both breast and ovarian cancer. A mutation in BRCA1 or BRCA2 was detected in 66% of breast cancer families and in 63% of breast-ovarian cancer families. Of 129 mutations, 122 (94.6%) were in BRCA1 and 7 (5.4%) were in BRCA2. Of the 122 families with BRCA1 mutations, 119 (97.5%) had a recurrent mutation (i.e., one that was seen in at least 2 families). In particular, 111 families (91.0%) carried one of the 3 common founder mutations. The mutation spectrum was not different between families with and without ovarian cancer. These findings suggest that a rapid and inexpensive assay directed at identifying the 3 common founder mutations will have a sensitivity of 86% compared to a much more costly and labor-intensive full-sequence analysis of both genes. This rapid test will facilitate large-scale national epidemiologic and clinical studies of hereditary breast cancer, potentially including studies of chemoprevention.     

Significant proportion of breast and/or ovarian cancer families of French Canadian descent harbor 1 of 5 BRCA1 and BRCA2 mutations

In 1998, we reported that a significant proportion of breast and/or ovarian cancer families of French Canadian descent harbor specific germline mutations in BRCA1 or BRCA2 attributed to common founders. Here we report the frequency of previously described mutations (n = 7) and 13 mutations identified in French Canadian families since 1998, in a new group of families (n = 88). Four of the previously described mutations, 4446C>T, 2953delGTAinsC, 8765delAG and 6085C>T, account for 72% and 69% of mutation-positive families in previously (n = 81) and recently ascertained groups, respectively. Only 2 of 13 recently identified mutations were found in more than 1 family: 3875delGTCT (n = 2) and 3398delAAAAG (n = 4). The 2 groups (ascertained pre- and post-gene discovery) did not differ significantly when distribution of mutations based on cancer syndrome phenotype and age of diagnosis or number of breast cancer cases were compared. Five common mutations accounted for a significant proportion (84%) of all mutation-positive families. The age of diagnosis of female breast cancer in mutation-negative families was significantly higher than that of the mutation-positive families (p<0.0001). The total number of cases of cancer per family was significantly lower in mutation-negative than mutation-positive families (p<0.001). Our results define a new mutation panel for screening BRCA1/2 mutations and the phenotype of mutation-positive families harboring the common mutations in the French Canadian population.     

Screening for common mutations in BRCA1 and BRCA2 genes: interest in genetic testing of Tunisian families with breast and/or ovarian cancer

BackgroundIn the Tunisian population, as yet a limited number of BRCA1/2 germline mutations have been reported in hereditary breast and/or ovarian cancer. These mutations are located in a few exons of BRCA1/2. The aim of the present study was to search for these mutations in 66 unrelated patients with hereditary breast and/or ovarian cancer in order to assess the interest in such a targeted approach for genetic testing in Tunisia.Materials and MethodsBlood specimens from the 66 Tunisian patients, with family history of breast and/or ovarian cancer, were collected at the Salah Azaiz Cancer Institute of Tunis. The exons 5, 20 and part of exon 11 of BRCA1 as well as part of exons 10 and 11 of BRCA2 were analyzed by Sanger sequencing.Results12 patients had deleterious mutations in the BRCA1 or BRCA2 genes (18%), including a novel frame-shift mutation of BRCA1 (c.3751dup; 3780insT). Four distinct BRCA1 mutations were detected eight patients: c.5266dup (5382insC) and c.211dup (330insA) each in three patients, c.3751dup (3870insT) and c.4041_4042del (4160delAG) each in one patient. The four remaining cases all carried the same BRCA2 mutation, c.1310_1313del (1538delAAGA). Besides these deleterious mutations, eight polymorphisms and unclassified variants were detected, one of them being never reported (BRCA1c.3030T>G, p.Pro1010Pro).ConclusionIn this study, we show that targeting relevant exons in BRCA1 and BRCA2 genes allows detection of a substantial percentage of mutations in the Tunisian population. Therefore such an approach may be of interest in genetic testing of high-risk breast and ovarian cancer families in Tunisia.     

Molecular analysis of the BRCA1 and BRCA2 genes in 32 breast and/or ovarian cancer Spanish families

It is estimated that about 5-10% of breast cancer cases may be due to inherited predisposition. Until now, two main susceptibility genes have been identified: BRCA1 and BRCA2. The first linkage and mutational studies suggested that mutations in these two genes would account for the majority of high-risk breast cancer families, but recent studies show how the proportion of families due to BRCA1 or BRCA2 mutations strongly depends on the population and the types of family analyzed. It is now clear that, in the context of families with a modest cancer profile, which are the most commonly found in the clinical practice, the percentage of mutations found is much lower than that suggested by the first studies. In the present study, we analyze a group of 32 Spanish families, which contained at least three cases of female breast cancer (at least one of them diagnosed before the age of 50 years), for the presence of mutations in the BRCA genes. The total proportion of mutations was low (25%), although the percentage of mutations in the BRCA1 and BRCA2 genes was higher, considering the breast and ovarian cancer families and the male breast cancer families respectively. Our results are in agreement with the idea that a great proportion of moderate-risk cancer families could be due to low penetrance susceptibility genes distinct from BRCA1 or BRCA2.     

BRCA1 4153delA founder mutation in Russian ovarian cancer patients

The BRCA1 4153delA allele is frequently referred to as the Russian founder mutation, as it was initially detected in several cancer families from Moscow. Our earlier studies have demonstrated 1% occurrence of BRCA1 4153delA heterozygosity in familial and/or early-onset and/or bilateral Russian breast cancer (BC) patients. Since literature data suggest that the 4153delA variant is more associated with ovarian cancer (OC) than with BC, we expected to reveal a highly elevated frequency of this genotype in Russian ovarian cancer series. However, real-time allele-specific PCR genotyping has detected only two BRCA1 4153delA carriers out of 177 unselected OC patients (1.1%). Both these carriers were early-onset and had serous carcinomas of grade 3. Thus, our study supports neither the Russian origin of BRCA1 4153delA mutation, nor its selectivity towards ovarian versus breast cancer predisposition.     

BRCA1 and BRCA2 mutations in ovarian cancer patients from China: ethnic‐related mutations in BRCA1 associated with an increased risk of ovarian cancer

BRCA1/2 are cancer predisposition genes involved in hereditary breast and ovarian cancer (HBOC). Mutation carriers display an increased sensitivity to inhibitors of poly(ADP‐ribose) polymerase (PARP). Despite a number of small‐size hospital‐based studies being previously reported, there is not yet, to our knowledge, precise data of BRCA1/2 mutations among Chinese ovarian cancer patients. We performed a multicenter cohort study including 916 unselected consecutive epithelial ovarian cancer (EOC) patients from eastern China to screen for BRCA1/2 mutations using the next‐generation sequencing approach. A total of 153 EOC patients were found to carry pathogenic germline mutations in BRCA1/2, accounting for an overall mutation incidence of 16.7% with the predominance in BRCA1 (13.1%) compared with BRCA2 (3.9%). We identified 53 novel pathogenic mutations, among which the c.283_286delCTTG and the c.4573C > T of BRCA1 were both found in two unrelated patients. More importantly, the most common mutation found in this study, c.5470_5477del8 was most likely to be Chinese population‐related without an apparent founder origin. This hot‐spot mutation was presumably associated with an increased risk of ovarian cancer. Taken together, germline BRCA1/2 mutations were common in Chinese EOC patients with distinct mutational spectrum compared to Western populations. Our study contributes to the current understanding of BRCA1/2 mutation prevalence worldwide. We recommend BRCA1/2 genetic testing to all Chinese women diagnosed with EOC to identify HBOC families, to provide genetic counseling and clinical management for at‐risk relatives. Mutation carriers may also benefit from PARP‐targeted therapies.     

BRCA1 Gene Mutations in Chinese Families with Breast Cancer

OBJECTIVE To investigate the frequency of BRCA1 gene mutations in breast cancer families in China.METHODS Genomic DNA was obtained by conventional techniques from the peripheral blood mononuclear cells collected from 94 persons derived from 45 breast cancer families. All participants gave written informed consent. The mutations in the BRCA1 gene were detected by the polymerase chain reaction and single stranded conformation polymorphism(PCR-SSCP). Then , the samples of interest were sent for direct DNA sequencing.RESULTS No mutation sites were found in exon 2 or 20 by DNA sequencing.Eight sites were found in exon 11 such as 2201C>T (Ser694Ser),3232A>G(Glu 1038Gly), 2201C >A/G (Ser694Arg), 2731C >T (Pro871Leu),2086A >T(Asn591lle) and three sites of 1584G>T (Glu424Stop). Three mutation sites were found in exon 16 which included 5106A >G (Met1663Val),5208delT(Stop 1639) and 4956A>G (Ser 1613Gly).CONCLUSION These mutation sites may be related to breast cancer, but more investigation is needed to determine whether the mutation sites are hot spots of mutations in Chinese familial breast cancer patients.     

BRCA1 and BRCA2 mutations in Turkish breast/ovarian families and young breast cancer patients

To date, BRCA1 and BRCA2 mutations in breast and/or ovarian patients have not been characterized in the Turkish population. We investigated the presence of BRCA mutations in 53 individuals with a personal and family history of breast and/or ovarian cancer, and 52 individuals with a personal history of breast cancer diagnosed below age 50 without additional family history. We have identified 11 mutations (nine BRCA1 and two BRCA2) using combined techniques involving protein truncation test, direct sequencing and heteroduplex analysis. We found eight out of 53 patients (15.1%) with a family history to carry BRCA gene mutations (seven BRCA1 and one BRCA2). Of these, four were found in 43 families presenting only breast cancer histories, and four were found in families presenting ovarian cancer with or without breast cancer. We also demonstrated two BRCA1 and one BRCA2 mutations in three out of 52 (5.8%) early-onset breast cancer cases without additional family history. Three of nine BRCA1 and both BRCA2 mutations detected in this study were not reported previously. These mutations may be specific to the Turkish population. The BRCA1 5382insC mutation, specific to Ashkenazi and Russian populations, was found twice in our study group, representing a possible founder mutation in the Turkish population.     

BRCA1 mutation testing for Japanese patients with ovarian cancer in breast cancer screening

From February 1996 to April 1998, 2967 women received screening for breast cancer in the gynecologic ambulatory practice of the Hokkaido University Hospital. In 116 Japanese women with epithelial ovarian cancer, mutation analysis of BRCA1 exon 11 in genomic DNA was performed by the stop codon (SC) assay and DNA sequence analysis. Clinicopathological factors were also investigated in these patients. The aim of this study was to examine the advantages of performing BRCA1 mutation testing for ovarian cancer patients during breast cancer screening. We achieved a high detection rate (6.0) of patients with germline mutations in BRCA1. The high frequencies of breast ovarian cancer syndrome, serous adenocarcinoma, high histological grades, advanced FIGO stages, and breast cancer as double cancer were found to be characteristic of ovarian cancer with germline mutations in BRCA1. These characteristics may assist physicians in selecting BRCA1 mutation testing for ovarian cancer patients. The mean age at diagnosis of ovarian cancer was 51.0 and 51.2 years in the groups with and without mutation, respectively, and no difference was found in age at diagnosis. All of the nine living female mutation carriers were offered the options of increased surveillance or prophylactic surgery, and all chose the former. We have performed breast cancer screening and/or ovarian cancer screening every 6 months for these carriers. This may allow another advantage in establishing a relationship of mutual trust with a patient from a series of responsible follow-ups.     

BRCA1 c.5470_5477del,a founder mutation in Chinese Han breast cancer patients

The spectrum and frequency of BRCA1/2 pathogenic variants may be ethnicity-specific. Whether high-frequency founder mutations are present in Chinese women remains largely unknown. In the current study, germline pathogenic variants in the BRCA1/2 genes were determined in 9,505 unselected Chinese Han breast cancer (BC) patients by next-generation and/ or Sanger sequencing. Four hundred and seventy-one (5.0%) BC patients carried BRCA1/2 pathogenic variants in this cohort. A total of 25 recurrent pathogenic variants (at least found in four unrelated patients) were identified in this cohort (8 BRCA1 and 17 BRCA2 recurrent pathogenic variants), 161 patients carried one of these recurrent pathogenic variants in this cohort of 9,505 patients. All of these 25 recurrent pathogenic variants were further explored whether they had founder effect through haplotype analysis. The most common pathogenic variant, BRCA1 c.5470_5477del, was found in 30 BC patients from 29 unrelated families. Twenty-seven of these 29 unrelated patients who carried this BRCA1 c.5470_5477del mutation shared an identical haplotype, indicating that BRCA1 c.5470_5477del was a founder mutation in the Chinese Han population. Furthermore, BRCA1 c.5470_5477del mutation carriers had a significantly worse survival than noncarriers (disease-free survival, p = 0.049; overall survival, p = 0.029). Taken together, our data suggested that BRCA1 c.5470_5477del is a founder mutation in the Chinese Han population and BRCA1 c.5470_5477del mutation carriers have a poor survival.     

Evidence of a founder BRCA1 mutation in Scotland

BRCA1 mutations have been identified in breast and ovarian cancer families from diverse ethnic backgrounds. We studied 17 different families with the BRCA1 2800delAA mutation; seven were ascertained in Scotland (Dundee, Edinburgh, Glasgow, St Andrews), five in Canada (Toronto, Victoria) and five in the United States (Chicago, Philadelphia, Seattle). Overall there was a clear preponderance of Scottish ancestry. Genotype analysis performed on key members from 17 families was consistent with a common haplotype, strongly suggesting a single ancestral origin. A possible link was established between two families by tracing their genealogies through the records of the Registrar General for Scotland. This is the first example of a BRCA1 mutation likely to be derived from a common founder in Scotland. Further studies will be necessary to estimate more accurately the population frequency of the BRCA1 2800delAA mutation among unselected cases of breast and ovarian cancer in Scotland and the UK.     

Gene panel sequencing in familial breast/ovarian cancer patients identifies multiple novel mutations also in genes others than BRCA1/2

Breast and ovarian cancer (BC/OC) predisposition has been attributed to a number of high‐ and moderate to low‐penetrance susceptibility genes. With the advent of next generation sequencing (NGS) simultaneous testing of these genes has become feasible. In this monocentric study, we report results of panel‐based screening of 14 BC/OC susceptibility genes (BRCA1, BRCA2, RAD51C, RAD51D, CHEK2, PALB2, ATM, NBN, CDH1, TP53, MLH1, MSH2, MSH6 and PMS2) in a group of 581 consecutive individuals from a German population with BC and/or OC fulfilling diagnostic criteria for BRCA1 and BRCA2 testing including 179 with a triple‐negative tumor. Altogether we identified 106 deleterious mutations in 105 (18%) patients in 10 different genes, including seven different exon deletions. Of these 106 mutations, 16 (15%) were novel and only six were found in BRCA1/2. To further characterize mutations located in or nearby splicing consensus sites we performed RT‐PCR analysis which allowed confirmation of pathogenicity in 7 of 9 mutations analyzed. In PALB2, we identified a deleterious variant in six cases. All but one were associated with early onset BC and a positive family history indicating that penetrance for PALB2 mutations is comparable to BRCA2. Overall, extended testing beyond BRCA1/2 identified a deleterious mutation in further 6% of patients. As a downside, 89 variants of uncertain significance were identified highlighting the need for comprehensive variant databases. In conclusion, panel testing yields more accurate information on genetic cancer risk than assessing BRCA1/2 alone and wide‐spread testing will help improve penetrance assessment of variants in these risk genes.     

Prevalence of BRCA1 and BRCA2 mutations in Pakistani breast and ovarian cancer patients

Among Asian countries, Pakistan has the highest rates of breast and ovarian cancer. To assess the contribution of the BRCA1 and BRCA2 germ line mutations to these high rates, we conducted the first study of 176 Pakistani breast and ovarian cancer patients, selected on family history and on age of diagnosis. Comprehensive BRCA mutation screening was performed using a range of techniques, including denaturing high-pressure liquid chromatography, single strand conformational polymorphism analysis and protein truncation test, followed by DNA sequencing. Thirty deleterious germ-line mutations were identified in the 176 families (17.0%), including 23 in BRCA1 and 7 in BRCA2. Four mutations, 185delAG, 185insA, S1503X and R1835X, were recurrent; these accounted for 52% of all identified BRCA1 mutations. Haplotype analyses suggested founder effects for 3 of these. The prevalence of BRCA1 or BRCA2 mutations was 42.8% for families with multiple cases of breast cancer, and was 50.0% for the breast/ovarian cancer families. The prevalence of mutations was 11.9% for single cases of early-onset breast cancer (< or =30 years) and was 9.0% for single cases of early-onset ovarian cancer (< or =45 years). Our findings show that BRCA mutations account for a substantial proportion of hereditary breast/ovarian cancer and early-onset breast and ovarian cancer cases in Pakistan.     

家族性乳腺癌患者及家系成员乳腺癌易感基因携带情况调查

目的 乳腺癌易感基因1(breast cancer susceptibility gene 1,BRCA1)和BRCA2基因已经证实与家族性乳腺癌密切相关.本研究旨在分析中国汉族家族性乳腺癌患者及家系成员BRCA1和BRCA2突变特征及携带情况.方法 收集2013 12-02-2015-06-08军事医学科学院附属医院确诊的中国汉族家族性乳腺癌患者55例及家系成员48名,共计103例样本.柚取外周静脉血提取DNA,应用聚合酶链反应(polymerase chain reaction,PCR) DNA直接测序方法检测BRCA1和BRCA2基因全编码外显子序列.结果 55例家族性乳腺癌患者中发现5个BRCA基因致病性突变位点,1个突变位点乳腺癌信息库中见报道(BRCA1:4730insG),4个为新发现突变位点(BRCA1:1937insC,4538insAG;BRCA2:1382delA,2820delA).家族性乳腺癌患者BRCA1/2突变率为9.09％(BRCA1,5.45％;BRCA2,3.64％),其中三阴性乳腺癌患者突变率为22.22％(x2 =1.99,P=0.20),早发性乳腺癌患者(≤35岁)突变率为20.00％,x2=0.79,P=0.39.48例家系成员检测到3个新发现突变位点(BRCA1:1370insA,3459insA;BRCA2:6502insT),总突变率为6.25％.结论 中国汉族家族性乳腺癌患者BRCA基因突变率显著低于国外,应重点关注有家族史的三阴性乳腺癌患者和早发性乳腺癌患者;家系成员中发现BRCA基因致病性突变,家系成员突变率和发病风险有待进一步研究,应引起重视.     

Prevalence of BRCA1 and BRCA2 mutations in Ashkenazi Jewish families with breast and pancreatic cancer

BACKGROUND:

Germline mutations in the BRCA2 cancer susceptibility gene are associated with an increased risk of pancreatic cancer (PC). Breast‐pancreas cancer families with BRCA1 mutations have also been observed. The influence of a family history (FH) of PC on BRCA mutation prevalence in patients with breast cancer (BC) is unknown.

METHODS:

A clinical database review (2000‐2009) identified 211 Ashkenazi Jewish (AJ) BC probands who 1) underwent BRCA1/2 mutation analysis by full gene sequencing or directed testing for Ashkenazi founder mutations (BRCA1: 185delAG and 5382insC; BRCA2: 6174delT) and 2) had a FH of PC in a first‐, second‐, or third‐degree relative. For each proband, the pretest probability of identifying a BRCA1/2 mutation was estimated using the Myriad II model. The observed‐to‐expected (O:E) mutation prevalence was calculated for the entire group.

RESULTS:

Of the 211 AJ BC probands with a FH of PC, 30 (14.2%) harbored a BRCA mutation. Fourteen (47%) of the mutations were in BRCA1 and 16 (53%) were in BRCA2. Patients diagnosed with BC at age ≤ 50 years were found to have a higher BRCA1/2 mutation prevalence than probands with BC who were diagnosed at age > 50 years (21.1% vs 6.9%; P = .003). In patients with a first‐, second‐, or third‐degree relative with PC, mutation prevalences were 15.4%, 15.3%, and 8.6%, respectively (P = .58). In the overall group, the observed BRCA1/2 mutation prevalence was 14.2% versus an expected prevalence of 11.8% (O:E ratio, 1.21; P = .15).

CONCLUSIONS:

BRCA1 and BRCA2 mutations are observed with nearly equal distribution in AJ breast‐pancreas cancer families, suggesting that both genes are associated with PC risk. In this population, a FH of PC was found to have a limited effect on mutation prevalence. Cancer 2011;. © 2011 American Cancer Society.     

Identification of novel BRCA founder mutations in Middle Eastern breast cancer patients using capture and Sanger sequencing analysis

Ethnic differences of breast cancer genomics have prompted us to investigate the spectra of BRCA1 and BRCA2 mutations in different populations. The prevalence and effect of BRCA 1 and BRCA 2 mutations in Middle Eastern population is not fully explored. To characterize the prevalence of BRCA mutations in Middle Eastern breast cancer patients, BRCA mutation screening was performed in 818 unselected breast cancer patients using Capture and/or Sanger sequencing. 19 short tandem repeat (STR) markers were used for founder mutation analysis. In our study, nine different types of deleterious mutation were identified in 28 (3.4%) cases, 25 (89.3%) cases in BRCA 1 and 3 (10.7%) cases in BRCA 2. Seven recurrent mutations identified accounted for 92.9% (26/28) of all the mutant cases. Haplotype analysis was performed to confirm c.1140 dupG and c.4136_4137delCT mutations as novel putative founder mutation, accounting for 46.4% (13/28) of all BRCA mutant cases and 1.6% (13/818) of all the breast cancer cases, respectively. Moreover, BRCA 1 mutation was significantly associated with BRCA 1 protein expression loss (p = 0.0005). Our finding revealed that a substantial number of BRCA mutations were identified in clinically high risk breast cancer from Middle East region. Identification of the mutation spectrum, prevalence and founder effect in Middle Eastern population facilitates genetic counseling, risk assessment and development of cost‐effective screening strategy.     

219例中国汉族遗传性乳腺癌患者BRCA1和BRCA2突变的研究

  目的  分析中国新疆多民族地区的高风险遗传性乳腺癌BRCA1/2基因突变位点情况。  方法  以2009年1月到2010年12月新疆医科大学附属肿瘤医院收治的来自新疆地区的68例符合高风险遗传性乳腺癌标准的患者为研究对象,其中HBC 12例,HBOC 4例,E-BC 25例,BI-BC 10例,TNB 17例。通过外周静脉血提取基因组DNA,对BRCA1/2基因的全部编码序列进行扩增。用高效液相色谱分析（DHPLC）进行突变分析预筛,结果经DNA测序验证。  结果  BRCA1/2致病性突变在新疆地区高风险遗传性乳腺癌的突变率为8.8%（6/68）。其中BRCA1的突变率为4.4%（3/68）,BRCA2的突变率为4.4%（3/68）。不同民族之间BRCA1/2突变率无统计学差异。  结论  中国新疆多民族地区的高风险遗传性乳腺癌患者部分病例具有与内地汉族人群不同的BRCA基因突变谱。BRCA1 2073delA,BRCA2 6873del CTCC及BRCA2 9481del A可能是新疆遗传性乳腺癌特有的突变位点。     

BRCA1 and BRCA2 germline testing in Cretan isolates reveals novel and strong founder effects

Germline BRCA1 and BRCA2 loss-of-function variants have been linked to increased breast and ovarian cancer risk, with more than 5,000 distinct pathogenic variants being reported worldwide. Among individuals of Greek descent, the BRCA1/2 variant spectrum is heterogeneous, but characterized by strong founder effects. As patients from certain geographical regions of Greece (like Crete) were underrepresented in previous studies, we hypothesized that isolated Cretans, a southern Greece islanders' population with distinct demographic, cultural and genetic features, could harbor founder BRCA1/2 mutations. A total of 304 breast or/and ovarian cancer patients of Cretan descent, fulfilling NCCN criteria for genetic testing, were tested by NGS or Sanger sequencing, followed by MLPA. Haplotype analysis was subsequently performed to investigate potential founder effects of recurrent alleles. Overall, 16.5% (50/304) of the tested patients carried 22 different pathogenic variants; 48% in BRCA1, 52% in BRCA2. Three variants, namely two in BRCA2 (Δexons 12 and 13 and c.7806-2A>T) and one in BRCA1 (c.5492del), constituting approximately half (48%) of all detected pathogenic variants, were shown to have a founder effect, with all carriers sharing common haplotypes. Remarkably, these variants were confined to Cretans and have not been identified in other regions of Greece. The high prevalence of specific BRCA1/2 pathogenic variants among Cretans, provides the possibility of cost- and time-efficient screening of the Cretan population. Integrating this knowledge in local public health services may have a significant impact on cancer prevention, and may serve as a starting point for the implementation of testing on a population level.