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.     

Multiple founder effects and geographical clustering of BRCA1 and BRCA2 families in Finland

In the Finnish breast and ovarian cancer families six BRCA1 and five BRCA2 mutations have been found recurrently. Some of these recurrent mutations have also been seen elsewhere in the world, while others are exclusively of Finnish origin. A haplotype analysis of 26 Finnish families carrying a BRCA1 mutation and 20 families with a BRCA2 mutation indicated that the carriers of each recurrent mutation have common ancestors. The common ancestors were estimated to trace back to 7-36 generations (150-800 years). The time estimates and the geographical clustering of these founder mutations in Finland are in concordance with the population history of this country. Analysis of the cancer phenotypes showed differential ovarian cancer expression in families carrying mutations in the 5' and 3' ends of the BRCA1 gene, and earlier age of ovarian cancer onset in families with BRCA1 mutations compared with families with BRCA2 mutations. The identification of prominent and regional BRCA1 and BRCA2 founder mutations in Finland will have significant impact on diagnostics in Finnish breast and ovarian cancer families. An isolated population with known history and multiple local founder effects in multigenic disease may offer distinct advantages also for mapping novel predisposing genes.     

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.     

Analysis of BRCA1 and BRCA2 genes in Spanish breast/ovarian cancer patients: a high proportion of mutations unique to Spain and evidence of founder effects

We screened index cases from 410 Spanish breast/ovarian cancer families and 214 patients (19 of them males) with breast cancer for germ-line mutations in the BRCA1 and BRCA2 genes, using SSCP, PTT, CSGE, DGGE, and direct sequencing. We identified 60 mutations in BRCA1 and 53 in BRCA2. Of the 53 distinct mutations observed, 11 are novel and 12 have been reported only in Spanish families (41.5%). The prevalence of mutations in this set of families was 26.3%, but the percentage was higher in the families with breast and ovarian cancer (52.1%). The lowest proportion of mutations was found in the site-specific female breast cancer families (15.4%). Of the families with male breast cancer cases, 59.1% presented mutations in the BRCA2 gene. We found a higher frequency of ovarian cancer associated with mutations localized in the 5' end of the BRCA1 gene, but there was no association between the prevalence of this type of cancer and mutations situated in the ovarian cancer cluster region (OCCR) region of exon 11 of the BRCA2 gene. The mutations 187_188delAG, 330A>G, 5236G>A, 5242C>A, and 589_590del (numbered after GenBank U14680) account for 46.6% of BRCA1 detected mutations whereas 3036_3039del, 6857_6858del, 9254_9258del, and 9538_9539del (numbered after GenBank U43746) account for 56.6% of the BRCA2 mutations. The BRCA1 330A>G has a Galician origin (northwest Spain), and BRCA2 6857_6858del and 9254_9258del probably originated in Catalonia (northeast Spain). Knowledge of the spectrum of mutations and their geographical distribution in Spain will allow a more effective detection strategy in countries with large Spanish populations.     

Screening for BRCA1 and BRCA2 mutations in Eastern Finnish breast/ovarian cancer families

Familial aggregation is thought to account for 5-10% of all breast cancer cases, and high penetrance breast and ovarian cancer susceptibility genes BRCA1 and BRCA2 explain < or =20% of these. Hundreds of mutations among breast/ovarian cancer families have been found in these two genes. The mutation spectrum and prevalence, however, varies widely among populations. Thirty-six breast/ovarian cancer families were identified from a population sample of breast and ovarian cancer cases among a relatively isolated population in Eastern Finland, and the frequency of BRCA1/BRCA2 germline mutations were screened using heteroduplex analysis, protein truncation test and sequencing. Five different mutations were detected in seven families (19.4%). Two mutations were found in BRCA1 and three in BRCA2. One of the mutations (BRCA2 4088insA) has not been detected elsewhere in Finland while the other four, 4216-2nt A-->G and 5370 C-->T in BRCA1 and 999del5 and 6503delTT in BRCA2, are recurrent Finnish founder mutations. These results add to the evidence of the geographical differences in distribution of Finnish BRCA1/BRCA2 mutations. This screen also provides further evidence for the presumption that the majority of Finnish BRCA1/BRCA2 founder mutations have been found and that the proportion of BRCA1/BRCA2 mutations in Finnish breast/ovarian cancer families is around 20%.     

Analysis of BRCA1 and BRCA2 in breast and breast/ovarian cancer families shows population substructure in the Iberian peninsula

An estimated 5–10% of all breast and ovarian cancers are due to an inherited predisposition, representing a rather large number of patients. In Spain 1/13–1/14 women will be diagnosed with breast cancer during their lifetime. Two major breast cancer genes, BRCA1 and BRCA2 , have been identified. To date, several hundred pathogenic mutations in these two genes have been published or reported to the Breast Cancer Information Core, BIC database ( http://www.nhgri.nih.gov/Intramural_research_Labtransfer/Bic/index.html ). In the present study, 30 Spanish breast and breast/ovarian cancer families (29 from Galicia, NW Spain, and 1 from Catalonia, NE Spain) were screened for mutations in the BRCA1 and BRCA2 genes. The analysis of these genes was carried out by SSCP for shorter exons and direct sequencing in the case of longer ones. Mutations were found in 8 of the 30 families studied (26.66%). It is important to note that all mutations were detected within the BRCA1 gene: 330 A>G, 910_913delGTTC, 2121 C>T, 3958_3962delCTCAGinsAGGC, and 5530 T>A. The BRCA1 330 A>G mutation was found in four unrelated families and accounted for 50% of all identified mutations.     

Molecular analysis of the BRCA2 gene in 16 breast/ovarian cancer Spanish families

The recent isolated gene BRCA2 is responsible for about 45% of familial breast cancer and the majority of male breast cancer families. In order to evaluate the role of inherited BRCA2 mutations in Spanish families, the complete coding sequence of the gene was screened by SSCP/sequencing in 16 high-risk breast/ovarian cancer families. Four mutations were found that cause a premature termination codon. Two of them have been reported elsewhere and one is a novel mutation. In addition we have found seven polymorphisms, two of which have not been previously described. One of the mutations, 936delAAAC was found in two of our high-risk families. Because this mutation is considered as recurrent, we have tried to estimate its frequency in our breast cancer population. A total of 127 moderate- high-risk families were screened for this mutation and it was also found in another high-risk family. All the families carrying the 936delAAAC mutation harboured part of a common haplotype shared by other reported carriers, suggesting a possible founder effect for this mutation.     

A low frequency of non-founder BRCA1 mutations in Ashkenazi Jewish breast-ovarian cancer families

The 185delAG and 5382insC founder mutations account for the majority of mutations identified in BRCA1 in Ashkenazi Jewish breast and breast-ovarian cancer families. Few non-founder BRCA1 mutations have been identified to date in these families. We initially screened a panel of 245 Ashkenazi Jewish breast-ovarian cancer families with an affected proband and at least one other case of breast or ovarian cancer for founder mutations in BRCA1 and BRCA2. Founder mutations were identified in 85 families (185delAG in 44 families, 5382insC in 16 families, and the BRCA2 6174delT in 25 families). The 160 negative families were then screened for the entire BRCA1 gene by a combination of DGGE and PTT. We identified one novel frameshift mutation in BRCA1 in exon 14 (4572del22) that truncated the protein at codon 1485. The family contained three cases of early-onset ovarian cancer (41 years, 43 years, and 52 years) and one case of breast cancer (at age 54 years subsequent to an ovarian cancer). In addition, three missense variants of unknown significance (exon 11 C3832T (P1238L), exon 15 G4654T (S1512I), and exon 15 G4755A (D1546N)) were found in single families. These missense variants have been previously identified in other families [BIC Database] and are considered to be "unclassified variants, favoring polymorphism." Non-founder BRCA1 mutations are rare in Ashkenazi Jewish breast/ovarian cancer families.     

BRCA1 and BRCA2 mutations among 233 unselected Finnish ovarian carcinoma patients.

Germline mutations of BRCA1 and BRCA2 predispose to hereditary breast-ovarian cancer syndrome. In Finland, 20 different BRCA1/2 mutations have been identified, and 13 of them are founder mutations that account for the vast majority of Finnish BRCA1/2 families. The purpose of our study was to determine the prevalence of BRCA1/2 mutations in unselected Finnish ovarian carcinoma patients and to evaluate the relationship between mutation carrier status and personal/family history of cancer. Two hundred and thirty-three patients were screened for all the 20 BRCA1/2 mutations known in the Finnish population. Additionally, a subgroup of patients with personal history of breast cancer and/or family history of breast and/or ovarian cancer was screened for novel BRCA1/2 mutations. Thirteen patients (5.6%) had mutations: eleven in BRCA1 and two in BRCA2. All the mutation-positive patients were carriers of the previously known Finnish BRCA1/2 mutations, and seven recurrent founder mutations accounted for 12 of the 13 mutations detected. A logistic regression analysis was used to determine the odds of mutation for ovarian carcinoma patients. The most significant predictor of a mutation was the presence of both breast and ovarian cancer in the same woman, but family history of breast cancer was also strongly related to mutation carrier status. Although BRCA1/2 mutation testing is not warranted in the general Finnish ovarian cancer patient population, patients who have also been diagnosed with breast cancer or have family history of breast or breast and ovarian cancer could benefit from referral to genetic counselling and mutation testing.     

BRCA1 5272-1G>A and BRCA2 5374delTATG are founder mutations of high relevance for genetic counselling in breast/ovarian cancer families of Spanish origin

Infante M, Durán M, Acedo A, Pérez-Cabornero L, Sanz DJ, García-González M, Beristain E, Esteban-Cardeñosa E, de la Hoya M, Teulé A, Vega A, Tejada M-I, Lastra E, Miner C, Velasco EA. BRCA1 5272-1G>A and BRCA2 5374delTATG are founder mutations of high relevance for genetic counselling in breast/ovarian cancer families of Spanish origin.
The distribution of BRCA1 and BRCA2 germ line mutations in breast/ovarian cancer families varies among different populations, which typically present a wide spectrum of unique mutations. Splicing mutation 5272-1G>A of BRCA1 and frameshift mutation 5374delTATG of BRCA2 are highly prevalent mutations in Castilla-León (Spain), accounting for 18.4% and 13.6% of BRCA1 and BRCA2 positive families, respectively. To test the presence of founder effects, 9 Spanish 5272-1G>A and 13 5374delTATG families were genotyped with polymorphic markers linked to BRCA1 or BRCA2 . All the 5272-1G>A families shared a common haplotype in eight markers (1.1 Mb region) and the mutation age was estimated in 15 generations (∼380 years). A conserved haplotype associated to 5374delTATG was observed in four markers (0.82 Mb). The mutation occurred approximately 48 generations ago (∼1200 years). Each mutation likely arose from a common ancestor that could be traced to a small area of Castilla-León and expanded to other Spanish regions. They can have a significant impact on the clinical management of asymptomatic carriers as well as on the genetic screening strategy to be followed in populations with Spanish ancestries.     

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.     

BRCA1 and BRCA2 mutations in Russian familial breast cancer

We have screened index cases from 25 Russian breast/ovarian cancer families for germ‐line mutations in all coding exons of the BRCA1 and BRCA2 genes, using multiplex heteroduplex analysis. In addition we tested 22 patients with breast cancer diagnosed before age 40 without family history and 6 patients with bilateral breast cancer. The frequency of families with germline mutations in BRCA was 16% (4/25). One BRCA1 mutation, 5382insC, was found in three families. The results of present study, and those of a separate study of 19 breast‐ovarian cancer families, suggest that BRCA1 5382insC is a founder mutation in the Russian population. Three BRCA2 mutations were found in patients with breast cancer without family history: two in young patients and one in patients with bilateral breast cancer. Four novel BRCA2 mutations were identified: three frameshift (695insT, 1528del4, 9318del4) and one nonsense (S1099X). © 2002 Wiley‐Liss, Inc.     

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.     

Breast and ovarian cancer risks to carriers of the BRCA1 5382insC and 185delAG and BRCA2 6174delT mutations: a combined analysis of 22 population based studies

A recent report estimated the breast cancer risks in carriers of the three Ashkenazi founder mutations to be higher than previously published estimates derived from population based studies. In an attempt to confirm this, the breast and ovarian cancer risks associated with the three Ashkenazi founder mutations were estimated using families included in a previous meta-analysis of populatrion based studies. The estimated breast cancer risks for each of the founder BRCA1 and BRCA2 mutations were similar to the corresponding estimates based on all BRCA1 or BRCA2 mutations in the meta-analysis. These estimates appear to be consistent with the observed prevalence of the mutations in the Ashkenazi Jewish population.     

BRCA1 and BRCA2 mutation analysis in 86 early onset breast/ovarian cancer patients.

Eighty-six women fulfilling specific selection criteria were studied for germline mutations in two breast cancer susceptibility genes, BRCA1 and BRCA2, using the protein truncation test (PTT). Nine germline mutations were identified, six in BRCA1 and three in BRCA2. Of the six BRCA1 mutations, three have previously been described and three are new, and for BRCA2, one is a new mutation and the other two appear to occur at a site that has been described several times. Four kindreds were breast cancer families, one a breast/ovarian cancer family, and the sixth an ovarian cancer family. The three kindreds with BRCA2 mutations were classified as one breast/ovarian cancer family, one breast cancer family, and one family which harboured one early onset breast cancer patient and two melanoma patients. The mutations in BRCA1 were either insertions, deletions, or transitions which all resulted in a premature stop codon. Mutations in BRCA2 were all frameshift mutations as a result of either 2 or 4 bp deletions. Two BRCA2 mutations were identical, suggesting a Swiss founder effect which was confirmed by haplotype sharing. The 10% mutation detection rate is compatible with the relaxed criteria used for patient selection. Considering the relative ease with which coding sequences can be screened by PTT, this assay is useful as a first screen for BRCA1 and BRCA2 mutations.     

Low proportion of BRCA1 and BRCA2 mutations in Finnish breast cancer families: evidence for additional susceptibility genes

One hundred breast and breast-ovarian cancer families identified at the Helsinki University Central Hospital in southern Finland and previously screened for mutations in the BRCA2 gene were now analyzed for mutations in the BRCA1 gene. The coding region and splice boundaries of BRCA1 were analyzed by protein truncation test (PTT) and heteroduplex analysis (HA)/SSCP in all 100 families, and 70 were also screened by direct sequencing. Contrary to expectations based on Finnish population history and strong founder effects in several monogenic diseases in Finland, a wide spectrum of BRCA1 and BRCA2 mutations was found. In the BRCA1 gene, 10 different protein truncating mutations were found each in one family. Six of these are novel Finnish mutations and four have been previously found in other European populations. Six different BRCA2 mutations were found in 11 families. Altogether only 21% of the breast cancer families were accounted for by mutations in these two genes. Linkage to both chromosome 17q21 (BRCA1) and 13q12 (BRCA2) was also excluded in a subset of seven mutation-negative families with four or more cases of breast or ovarian cancer. These data indicate that additional breast and breast-ovarian cancer susceptibility genes are likely to be important in Finland.      

Mutational analysis of BRCA1 and BRCA2 in Mediterranean Spanish women with early-onset breast cancer: identification of three novel pathogenic mutations

In Spain, the contribution of BRCA mutations to the population incidence of early-onset breast cancer was unknown. We carried out a mutational analysis of the BRCA1 and BRCA2 genes in 124 Spanish women diagnosed with breast cancer before the age 41 and who were not selected for a family history of this disease. The genetic study was performed by PCR-SSCP analysis and DNA sequencing. We identified 6 pathogenic BRCA mutations in 7 unrelated probands (5.6%; 95% CI=2.3% to 11.3%): 1 BRCA1 (c.2080delA) and 5 BRCA2 (p.Y3006X, p.Q1994X, c.9204_9217del14, c.9254_9258del5 and c.295+2T>C). Three out of 6 mutations were novel (BRCA2 p.Y3006X, c.9204_9217del14, and c.295+2T>C), and two further mutations had not been previously found in Spain (BRCA1 c.2080delA and BRCA2 p.Q1994X). The one remaining (BRCA2 c.9254_9258del5) was detected in two probands of our sample. Additionally, we identified two new missense mutations: BRCA1 p.P1812A and BRCA2 p.G2044A. Our data support the notion that Spaniards represent a heterogeneous population with its own spectrum of BRCA mutations, some of which appear as founding mutations. We categorized patients into familial or non-familial groups on the basis of her family history of breast/ovarian cancer; this analysis indicated that among Spanish women with early-onset breast cancer, an even moderate family history is a good predictor of being a BRCA mutation carrier.     

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.     

Mutation analysis of the BRCA1 and BRCA2 genes in the Belgian patient population and identification of a Belgian founder mutation BRCA1 IVS5 + 3A > G

Since the identification of the BRCA1 and BRCA2 genes, several hundred different germline mutations in both genes have been reported. Recurrent mutations are rare and mainly due to founder effects. As the mutational spectrum of the BRCA1 and BRCA2 genes in the Belgian patient population is largely unknown, we initiated mutation analysis for the complete coding sequence of both genes in Belgian families with multiple breast and/or ovarian cancer patients and in "sporadic" patients with early onset disease. We completed the analysis in 49 families and in 19 "sporadic" female patients with early onset breast and/or ovarian cancer. In 15 families we identified a mutation (12 mutations in BRCA1 and 3 mutations in BRCA2). In 5 apparently unrelated families the same splice site mutation was identified (BRCA1 IVS5 + 3A > G). Haplotype analysis revealed a common haplotype immediately flanking the mutation in all families suggesting that disease alleles are identical by descent. In none of the 19 sporadic patients was a mutation found.     

Haplotype analysis of the BRCA2 9254delATCAT recurrent mutation in breast/ovarian cancer families from Spain

A frame-shift 9254del5 mutation was independently identified in 12 families, eleven of them with Spanish ancestors, in a BRCA2 screening performed in 841 breast and/or ovarian cancer families and in 339 women with breast cancer diagnosed before the age of 40 at different centers in France and Spain. We sought to analyze in detail the haplotype and founder effects of the 9254del5 and to estimate the time of origin of the mutation. Eight polymorphic microsatellite markers and two BRCA2 polymorphisms were used for the haplotype analyses. The markers were located flanking the BRCA2 gene spanning a region of 6.1 cM. Our results suggest that these families shared a common ancestry with BRCA2 9254del5, which is a founder mutation originating in the Northeast Spanish, with an estimated age of 92 (95% CI 56-141) generations.