Founder BRCA1 and BRCA2 mutations in French Canadian ovarian cancer cases unselected for family history

The breast cancer susceptibility genes, BRCA1 and BRCA2, differ in their contribution to ovarian cancer. Recently, founder mutations in each of these genes were identified in Canadian breast cancer and breast ovarian cancer families of French ancestry. We have examined the prevalence of the founder mutations in a series of 113 French Canadian women with ovarian cancer unselected for family history. Germline mutations were found in eight of 99 invasive carcinomas and in none of the 14 tumors of borderline malignancy. Five cases carried the BRCA1 C4446T mutation and two cases carried the BRCA2 8765delAG mutation which are the most common mutations that have been described in French Canadian breast cancer and breast ovarian cancer families. All of these cases reported a family history of at least one first-degree relative with breast cancer, diagnosed below age 60 years, or with ovarian cancer. The identification of founder BRCA1 and BRCA2 mutations in ovarian cancer cases unselected for family history can facilitate carrier detection when the expected yield of a comprehensive screen may be low.     

Anticipation in hereditary breast cancer

To determine whether familial breast cancer occurs at a younger age in successive generations, we reviewed the clinical records of 435 Ashkenazi women with breast cancer referred to our cancer genetic clinic. Ninety-eight who reported a maternal history of breast cancer were selected for further investigation. All women were genotyped for founder BRCA1/2 mutations (185delAG, 5382insC and 6174delT). Mean age at dignosis was 55.35 +/- 14.21 years in the maternal generation and 48.17 +/- 9.32 years in the daughters (t = - 4.144; p < 0.001). Seventeen women carried a BRCA1 mutation and 12 the 6174delT mutation in BRCA2. Among carriers of the BRCA1 mutation, mean age at diagnosis in the mothers' generation (44 +/- 10.18 years) did not differ from that recorded in the daughters (40.76 +/- 76 years). Among BRCA2 mutation carriers and non-carriers, the mean age at diagnosis in the daughters' generation (41.4 +/- 7.2 and 50.7 +/- 8.8 years, respectively) was younger than in the mothers (61.75 +/- 14.1 and 57.08 +/- 13.7 years, respectively) (t = - 4.29; p < 0.001 for BRCA2 carriers and t = -3.76; p < 0.001 for non-BRCA1/2 carriers). Daughters who were carriers of BRCA1/2 mutations developed breast cancer at a significantly younger age than non-carriers, whilst in the mothers' generation, carriers of BRCA1 mutations developed breast cancer at a significantly younger age than carriers of BRCA2 mutations and non-carriers. BRCA1 mutations predispose to breast cancer at an early age in both mothers and daughters, whereas mutations in BRCA2 were associated with significantly younger age at diagnosis in the second generation. This observation could be related to gene-environmental interactions causing anticipation in BRCA2 mutation carriers.     

维吾尔族和汉族散发性乳腺癌患者BRCA1/2基因突变的检测

目的探讨新疆维吾尔族和汉族散发性乳腺癌患者乳腺癌易感基因1/2(BRCA1/2)突变情况及与临床病理参数的关系。方法采用PCR和DNA直接测序法,对新疆地区230例散发性乳腺癌患者(维吾尔族、汉族各115例)石蜡组织进行BRCA1基因第2、11(11A和11B)、20号外显子和BRCA2基因第11号部分外显子,共5对引物进行突变检测。结果 230例乳腺癌患者中,BRCA基因突变率为6.96%(16/230),其中1例BRCA1基因-5 382位点的突变及7例新发突变位点;维吾尔族和汉族患者中BRCA基因突变检出率分别为7.83%(9/115)和6.09%(7/115);BRCA基因突变组发病年龄均≤50岁;突变组16例患者中绝经前患者(13例)的突变率明显高于绝经后患者(3例)(P0.05)。结论 BRCA1基因突变可能与新疆地区散发性乳腺癌发生相关。     

Analysis of breast cancer susceptibility genes BRCA1 and BRCA2 in Thai familial and isolated early-onset breast and ovarian cancer

Here we report the study on BRCA1 and BRCA2 mutations in 12 Thai breast and/or ovarian cancer families and 6 early-onset breast or breast/ovarian cancer cases without a family history of cancer. Five distinct rare alterations were identified in each gene: four introducing premature stop codons, one in-frame deletion, two missense changes, two intronic alterations and one silent rare variant. The BRCA1 or BRCA2 truncating mutations were detected in four of seven patients with familial or personal history of breast and ovarian cancer, in one of four isolated early onset breast cancer cases and in none of seven breast cancer site specific families. The BRCA1 and BRCA2 mutation yield in Thai patients is consistent with that reported from Europe and North America in similar groups of patients, being particularly high in individuals with personal or family history of breast and ovarian cancer. The BRCA1 and BRCA2 alterations found in this series are different from those identified in other Asian studies, and all but two have never been reported before. We report at least three novel deleterious mutations, the BRCA1 3300delA, BRCA1 744ins20 and BRCA2 6382delT. One in-frame deletion was also found, the BRCA2 5527del9, which seggregated within family members of breast-only cancer patients and was thought to be a cancer-related mutation. BRCA1 3300delA and Asp67Glu alterations were detected each in at least two families and thus could represent founder mutations in Thais.     

The contribution of founder mutations in BRCA1 to breast cancer in Belarus

Uglanitsa N, Oszurek O, Uglanitsa K, Savonievich E, Lubiński J, Cybulski C, Debniak T, Narod SA, Gronwald J. The contribution of founder mutations in BRCA1 to breast cancer in Belarus. Mutations in the BRCA1 gene increase susceptibility to both breast and ovarian cancer. In some countries, including several in Eastern Europe, founder mutations in the BRCA1 gene are responsible for a significant proportion of breast cancer cases. To estimate the hereditary proportion of breast cancer in Belarus, we sought the presence of any of three founder mutations in BRCA1 (4153delA, 5382insC and C61G) in 500 unselected cases of breast cancer. These mutations have previously been identified in breast/ovarian cancer families from Belarus and from other Slavic countries, including Poland and Russia. One of the three founder mutations in BRCA1 was present in 38 of 500 unselected cases of breast cancer (7.6%). A mutation was found in 12.6% of women diagnosed before age 50 and 5.6% of women diagnosed after age 50. A mutation was identified in 2 of 251 newborn controls (0.8%). The hereditary proportion of breast cancers in Belarus is among the highest of any countries studied to date.     

BRCA1 and BRCA2 mutations in women with familial or early-onset breast/ovarian cancer in the Czech Republic

Germline mutations in BRCA1 and BRCA2 account for majority of hereditary breast and ovarian cancer. The complete coding sequence analysis of both genes was carried out in 197 breast/ovarian cancer patients from high-risk families and 53 patients with sporadic breast/ovarian cancer. In summary, 59 mutations (16 different) in BRCA1 and 29 mutations (17 different) in BRCA2 were identified in unrelated breast and/or ovarian index cases. Using the BIC Database numbering, the most frequently found mutations in BRCA1 were c.5385dupC (22 cases), c.3819_3823delGTAAA (8 cases) and c.300T>G (6 cases). The most frequently found mutations in BRCA2 were c.8138_8142delCCTTT (7 cases) and c.8765_8766delAG (7 cases). Altogether, these 5 mutations represented 56.8% of all detected mutations. A broad spectrum of other mutations was detected including four novel mutations (c.2881delA in BRCA1; and c. 6677_6678delAA, c.6982dupT and c.8397_8400dupTGGG in BRCA2). Deleterious mutations were found in 80 (40.6%) of 197 high risk-families, in 6 (37.5%) of 16 patients with sporadic bilateral breast, ovarian or both cancers and in 2 (6.2%) of 32 women with sporadic early-onset unilateral breast cancer. No mutation was detected in 5 cases of sporadic early-onset unilateral ovarian cancer.     

The contribution of founder mutations to early-onset breast cancer in French-Canadian women

In an ethnically‐homogeneous population, it is valuable to identify founder mutations in cancer‐predisposing genes. Founder mutations have been found in four breast‐cancer‐predisposing genes in French‐Canadian breast cancer families. The frequencies of the mutant alleles have been measured neither in a large series of unselected breast cancer patients from Quebec, nor in healthy controls. These estimates are necessary to measure their contribution to the hereditary burden of breast cancer in Quebec and to help develop genetic screening policies which are appropriate for the province. We studied 564 French‐Canadian women with early‐onset invasive breast cancer who were treated at a single Montreal hospital. Patients had been diagnosed at age 50 or less, and were ascertained between 2004 and 2008. We screened all 564 patients for nine founder mutations: four in BRCA1, three in BRCA2 and one each in PALB2 and CHEK2. We also studied 6433 DNA samples from newborn infants from the Quebec City area to estimate the frequency of the nine variant alleles in the French‐Canadian population. We identified a mutation in 36 of the 564 breast cancer cases (6.4%) and in 35 of 6443 controls (0.5%). In the breast cancer patients, the majority of mutations were in BRCA2 (54%). However, in the general population (newborn infants), the majority of mutations were in CHEK2 (54%). The odds ratio for breast cancer to age 50, given a BRCA1 mutation, was 10.1 (95% CI: 3.7–28) and given a BRCA2 mutation was 29.5 (95% CI: 12.9–67). The odds ratio for breast cancer to age 50, given a CHEK2 mutation, was 3.6 (95% CI: 1.4–9.1). One‐half of the women with a mutation had a first‐ or second‐degree relative diagnosed with breast or ovarian cancer. Thus, it can be concluded that a predisposing mutation in BRCA1, BRCA2, CHEK2 or PALB2 is present in approximately 6% of French‐Canadian women with early‐onset breast cancer. It is reasonable to offer screening for founder mutations to all French‐Canadian women with breast cancer before age 50. The frequency of these mutations in the general population (0.5%) is too low to advocate population‐based screening.     

Spectrum of Mutations in BRCA1 Gene in Hereditary Forms of Breast and Ovarian Cancer in Russian Families

The 5382insC mutation predominated (94%) in the spectrum of detected mutations of BRCA1 gene. High incidence of this mutation in familial breast cancer detected for the first time attested to origination of 5382insC mutation from the European part of Russia. The percentage of families with mutations in BRCA1 gene and familial predisposition to ovarian cancer was significantly higher than in hereditary predisposition to breast cancer (p<0.007). These data suggest that clinical manifestation of the mutation depends on genotypical factors other than the position of this mutation in BRCA1 gene. The results prompt screening for hereditary predisposition to these diseases.     

Histopathological features of 'BRCAX' familial breast cancers in the kConFab resource

AIMS: In recent years histopathology has made an important contribution to the study of familial breast cancer, largely on the basis of the distinctive cancer phenotype commonly identified in BRCA1-mutation carriers. The aim of this study was to identify this phenotype amongst index cases from families in the kConFab familial breast cancer resource with no known pathogenic mutation ('BRCAX' families). METHODS: The histopathology of breast cancer from 180 individuals was reviewed: 132 members of individual BRCAX families, 26 BRCA1 and 15 BRCA2 mutation carriers and seven mutation negative individuals from families with a known pathogenic mutation. RESULTS: BRCAX breast cancers were a heterogeneous group with 25.8% grade 1, 37.9% grade 2 and 36.4% grade 3. Overall, 45/180 (25%) cases were designated 'BRCA1-phenotype' including 22/132 (16.7%) BRCAX cases, 18/26 (69.2%) BRCA1 and 5/15 (33.3%) BRCA2 mutation carriers. For BRCAX cases, a BRCA1 phenotype designation was negatively correlated with age. CONCLUSIONS: Characteristic breast cancer pathology is not diagnostic of a germline BRCA1 mutation, but it does indicate a pathogenic mechanism that occurs with increased frequency in BRCA1 mutation carriers. In BRCAX families, BRCA1 tumour phenotype may signal the presence of an unidentified BRCA1 mutation. However, this finding must be interpreted with regard to limits of the association between histopathology and genotype, and the importance of clinical context.     

Contribution of BRCA1 and BRCA2 mutations to inherited ovarian cancer

A total of 283 epithelial ovarian cancer families from the United Kingdom (UK) and the United States (US) were screened for coding sequence changes and large genomic alterations (rearrangements and deletions) in the BRCA1 and BRCA2 genes. Deleterious BRCA1 mutations were identified in 104 families (37%) and BRCA2 mutations in 25 families (9%). Of the 104 BRCA1 mutations, 12 were large genomic alterations; thus this type of change represented 12% of all BRCA1 mutations. Six families carried a previously described exon 13 duplication, known to be a UK founder mutation. The remaining six BRCA1 genomic alterations were previously unreported and comprised five deletions and an amplification of exon 15. One of the 25 BRCA2 mutations identified was a large genomic deletion of exons 19-20. The prevalence of BRCA1/2 mutations correlated with the extent of ovarian and breast cancer in families. Of 37 families containing more than two ovarian cancer cases and at least one breast cancer case with diagnosis at less than 60 years of age, 30 (81%) had a BRCA1/2 mutation. The mutation prevalence was appreciably less in families without breast cancer; mutations were found in only 38 out of 141 families (27%) containing two ovarian cancer cases only, and in 37 out of 59 families (63%) containing three or more ovarian cancer cases. These data indicate that BRCA1 and BRCA2 are the major susceptibility genes for ovarian cancer but that other susceptibility genes may exist. Finally, it is likely that these data will be of clinical importance for individuals in families with a history of epithelial ovarian cancer, in providing accurate estimates of their disease risks.     

CHEK2基因c.1100delC与中国人遗传性乳腺癌易感性的关联研究

目的研究上海地区非BRCA1／2基因突变的遗传倾向乳腺癌中CHEK2基因c．1100delC突变的携带情况及可能的作用。方法研究对象来自114例遗传倾向性乳腺癌，包括家族性乳腺癌76例，其中8例发病年龄低于40岁；38例单纯早发性乳腺癌（发病年龄〈40岁）。对照组为121名无乳腺癌的健康女性，静脉血中提取基因组DNA，对CHEK2基因的第10～14外显子进行长片段PCR扩增，PCR产物再进行含突变的第10外显子的扩增。突变分析全部由DNA直接测序进行鉴定。结果研究人群和对照人群中都没有发现c．1100delC的突变；在3例（3／114，2．6％）家族性乳腺癌中发现邻近c．1100delC的新的错义突变位点1111C〉T（p-His371 Tyr），对照组中则无此突变发现。结论CHEK2基因c．1100delC突变可能是中国人群罕见的突变位点，在中国人乳腺癌遗传易感性中的作用非常有限；1111C〉T可能与中国上海地区遗传倾向乳腺癌低度外显的易感性有关，需要进行进一步研究确认。     

Mutation analysis of the BRCA1 gene in 23 families with cases of cancer of the breast, ovary, and multiple other sites.

Germline mutations in the BRCA1 tumour suppressor gene on chromosome 17q21 are responsible for approximately half of the cases of hereditary breast cancer, including the majority of familial breast/ovarian cancers. To increase our knowledge of the spectrum of BRCA1 mutations, we have extended our analysis to include patients with varied family histories of cancer of the breast, ovary, and at multiple other sites. We have analysed 23 unrelated familial cases using direct sequencing or a combination of dideoxy fingerprinting and sequencing procedures. Twenty one of these families contained three or more cases of breast or ovarian cancer and two families had one case of breast cancer diagnosed before the age of 40 and one case of ovarian cancer. The common frameshift mutation 5382insC was detected in two patients, and the 185delAG mutation was found in a family of Ashkenazi Jewish descent. The novel frameshift mutation 3450del4 (CAAG) was detected in a patient who developed breast cancer at the age of 28 and ovarian cancer at the age of 34. Three other women in this family were diagnosed with breast cancer at the ages of 26, 29, and 40. The novel framshift mutation 2953del3+C was found in a French Canadian woman who had developed two primary cancers of the breast at the age of 37 and 38 and renal cancer at the age of 38.     

BRCA1 and BRCA2 mutation analysis in breast-ovarian cancer families from northeastern Poland

Sixty high-risk breast and/or ovarian cancer families from North-Eastern Poland were screened for germline mutations in BRCA1 (MIM# 113705) and BRCA2 (MIM# 600185), using a combination of protein truncation test, denaturing high-performance liquid chromatography and direct sequencing. Sixteen (27%) of the families were found to carry nine different BRCA mutations, including 14 families with BRCA1 mutation and two families with BRCA2 mutation. The results suggest the presence of two strong BRCA1 founder mutations in the Polish population - 5382insC (6 families) and 300T>G (Cys61Gly; 3 families). The remaining seven mutations were found in single families and included three previously reported BRCA1 mutations (185delAG, 2682C>T [Gln855Ter] and 3819del5), a novel BRCA1 mutation (IVS14+1G>A), as well as two BRCA2 mutations (4088delA and 7985G>A [Trp2586Ter]) not previously observed in Polish families. We confirm the strong influence of two Central-Eastern European BRCA1 founder mutations in familial breast and/or ovarian cancer in Poland. We also conclude that the Polish population has a more dispersed BRCA mutation spectrum than had been earlier thought. This warrants further careful BRCA mutation screening in order to optimise genetic counselling and disease prevention in affected families.     

Strong founder effects in BRCA1 mutation carrier breast cancer patients from Latvia

Germ‐line mutations of the BRCA1 gene account for approximately half of the cases of hereditary breast/ovarian cancers. We have screened index patients from 15 breast cancer families and 8 sporadic breast cancer patients from Latvia for mutations in all coding exons of the BRCA1 gene, using combined Heteroduplex Analysis/SSCP followed by direct sequencing of the variants. BRCA1 germ‐line mutations proved to be frequent in Latvian breast cancer patients, also in moderate‐risk families and sporadic patients. Out of 23 cases a total of 8 patients (35%) exhibited three different mutations (5382insC, C61G, 4153delA). Interestingly, these three recurrent mutations accounted for all mutations in our sample set and no unique mutation was found. The 5382insC and C61G mutations accounted for 63% (5/8) and 25% (2/8) of all mutations, respectively. Allelotyping suggested a common founder in each recurrent mutation. Additional one‐hundred hospital‐based incident breast cancer patients were screened for the three mutations and 4 other 5382insC mutation carriers were identified (4%). Patients with C61G and 4153delA mutations were all Latvians, whilst the majority of 5382insC carriers (7/9=78%) were of Russian ethnicity, which is intriguing for the supposed Baltic origin of this mutation. Hum Mutat 14:92, 1999. © 1999 Wiley‐Liss, Inc.     

BRCA1 germline mutations in Indian familial breast cancer

Germline mutation analysis of BRCA1 gene has demonstrated significant allelic heterogeneity. These differences represent historical influences of migration, population structure and geographic or cultural isolation. To date, there have been no reports of Indian families with mutations in BRCA1. We have screened for mutations in selected coding exons of BRCA1 and their flanking intron regions in three breast or breast and ovarian cancer families with family history of three or more cases of breast cancer under age 45 and/or ovarian cancer at any age. We have also analyzed 10 female patients with sporadic breast cancer regardless of age and family history, as well as 50 unrelated normal individuals as controls. Thus a total of 90 samples were analyzed for BRCA1 mutations using polymerase chain reaction-mediated site directed mutagenesis (PSM) and single stranded conformation polymorphism (SSCP) analysis for various selected exons followed by sequencing of variant bands. Eight point mutations were identified. Two deleterious pathogenic, protein truncating non-sense mutations were detected in exon 11 (E1250X) and exon 20 (E1754X) and six novel and unique amino acid substitutions (F1734S, D1739Y, V1741G, Q1747H, P1749A, R1753K). One complex missense mutation of exon 20 [V1741G; P1749A] was seen in two out of three families and another complex combination of missense and non-sense mutations of the same exon [V1741G; E1754X] was observed in only one family. These complex mutations exist only in breast cancer families but not in control populations of women. Three splice site variants (IVS20+3A>C, IVS20+4A>T, IVS20+5A>T) and two intronic variants (IVS20+21_22insG, IVS20+21T>G) were also detected. In the group of 10 sporadic female patients no mutations were found.     

Low prevalence of SLX4 loss-of-function mutations in non-BRCA1/2 breast and/or ovarian cancer families

Fanconi anemia is a genetically heterogeneous autosomal recessive disorder characterized by development abnormalities, bone marrow failure, and childhood cancers. Compelling evidence indicates a common genetic basis for FA and breast/ovarian cancer susceptibility. Recently, biallelic germ-line mutations in SLX4 have been demonstrated to cause a previously unknown FA subtype (FA-P). We address the role of SLX4/FANCP in breast/ovarian cancer susceptibility by conducting a comprehensive mutation scanning in 486 index cases from non-BRCA1/BRCA2 multiple-case breast and/or ovarian cancer families (non-BRCA1/2 families) from Spain. We detected one unequivocal loss-of-function mutation (p.Glu1517X). In addition, one missense change (p.Arg372Trp) predicted to be pathogenic by in silico analysis co-segregates with disease in one family. Overall, the study indicates that SLX4 mutation screening will have a very low impact (if any) in the genetic counseling of non-BRCA1/2 families.     

Routine testing for PALB2 mutations in familial pancreatic cancer families and breast cancer families with pancreatic cancer is not indicated

PALB2-mutation carriers not only have an increased risk for breast cancer (BC) but also for pancreatic cancer (PC). Thus far, PALB2 mutations have been mainly found in PC patients from families affected by both PC and BC. As it is well known that the prevalence of gene mutations varies between different populations, we studied the prevalence of PALB2 mutations in a Dutch cohort of non-BRCA1/2 familial PC (FPC) families and in non-BRCA1/2 familial BC (FBC) families with at least one PC case. Mutation analysis included direct sequencing and multiplex ligation-dependent probe amplification (MLPA) and was performed in a total of 64 patients from 56 distinct families (28 FPC families, 28 FBC families). In total, 31 patients (48%) originated from FPC families; 24 were FPC patients (77%), 6 had a personal history of BC (19%) and 1 was a suspected carrier (3.2%). The remaining 33 patients (52%) were all female BC patients of whom 31 (94%) had a family history of PC and 2 (6.1%) had a personal history of PC. In none of these 64 patients a PALB2 mutation was found. Therefore, PALB2 does not have a major causal role in familial clustering of PC and BC in non-BRCA1/2 families in the Dutch population.     

Germline mutations in the BRCA1 and BRCA2 genes in Turkish breast/ovarian cancer patients

In this study we genotyped Turkish breast/ovarian cancer patients for BRCA1/BRCA2 mutations: protein truncation test (PTT) for exon 11 BRCA1 of and, multiplex PCR and denaturing gradient gel electrophoresis (DGGE) for BRCA2, complemented by DNA sequencing. In addition, a modified restriction assay was used for analysis of the predominant Jewish mutations: 185delAG, 5382InsC, Tyr978X (BRCA1) and 6174delT (BRCA2). Eighty three breast/ovarian cancer patients were screened: twenty three had a positive family history of breast/ovarian cancer, ten were males with breast cancer at any age, in eighteen the disease was diagnosed under 40 years of age, one patient had ovarian cancer in addition to breast cancer and one patient had ovarian cancer. All the rest (n=30) were considered sporadic breast cancer cases. Overall, 3 pathogenic mutations (3/53-5.7%) were detected, all in high risk individuals (3/23-13%): a novel (2990insA) and a previously described mutation (R1203X) in BRCA1, and a novel mutation (9255delT) in BRCA2. In addition, three missense mutations [two novel (T42S, N2742S) and a previously published one (S384F)] and two neutral polymorphisms (P9P, P2532P) were detected in BRCA2. Notably none of the male breast cancer patients harbored any mutation, and none of the tested individuals carried any of the Jewish mutations. Our findings suggest that there are no predominant mutations within exon 11 of the BRCA1 and in BRCA2 gene in Turkish high risk families.