A high frequency of BRCA2 gene mutations in Polish families with ovarian and stomach cancer

Germ-line mutations in the BRCA2 gene are associated with a wide range of cancer types, including the breast, ovary, pancreas, prostate and melanoma. In this study, we evaluated the importance of a family history of stomach cancer in predicting the presence of a BRCA2 mutation in Polish patients with ovarian cancer. A BRCA2 mutation was found in eight of 34 women with ovarian cancer and a family history of stomach cancer versus three of 75 women with ovarian cancer and a family history of ovarian cancer, but not of stomach cancer (odds ratio=7.4; 95% CI 1.8-30; P=0.004). The results of this study suggest that, in the Polish population, the constellation of ovarian and stomach cancer predicts the presence of a germ-line BRCA2 mutation and confirms that stomach cancer is part of the spectrum of BRCA2 mutations. It is expected that the penetrance of BRCA2 mutations for stomach cancer will vary from country to country, reflecting local environmental and lifestyle factors.     

High proportion of missense mutations of the BRCA1 and BRCA2 genes in Japanese breast cancer families

Mutations in either of two recently identified genes, BRCA1 and BRCA2, are thought to be responsible for approximately two-thirds of all cases of autosomal-dominantly inherited breast cancer. To examine the nature and frequency of BRCA1 and BRCA2 mutations in Japanese families exhibiting a high incidence of breast cancer, we screened 78 unrelated families in this category for mutations of these two genes. Examining the entire coding sequences as well as exon–intron boundaries of both genes by polymerase chain reaction (PCR) single-strand conformation polymorphism (SSCP) and multiplex-SSCP analysis, we identified possible disease-causing alterations in BRCA1 among affected members of 15 families and in BRCA2 in another 14 families. In 15 of those 29 families, the affected individuals carried missense mutations, although most germline mutations reported worldwide have been deletions or nonsense mutations. Our results, indicating that missense mutations of BRCA1 and BRCA2 tend to predominate over frameshifts or nonsense mutations in Japanese breast cancer families, will contribute signifi-cantly to an understanding of mammary tumorigenesis in Japan, and will be of vital importance for future genetic testing. Received: September 4, 1997 / Accepted: October 28, 1997     

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%.     

Germline mutations of BRCA1 and BRCA2 in Korean breast and/or ovarian cancer families

Germline mutations in the BRCA1 and BRCA2 genes are responsible for the predisposition and development of familial breast and/or ovarian cancer. Most mutations of BRCA1 and BRCA2 associated with breast and/or ovarian cancer result in truncated proteins. To investigate the presence of BRCA1 and BRCA2 germline mutations in Korean breast and/or ovarian cancer families, we screened a total of 27 cases from 21 families including two or more affected first- or second-degree relatives with breast and/or ovarian cancer. PTT, PCR-SSCP, and DHPLC analysis, followed by sequencing were used in the screening process. In nine families, we found BRCA1 and BRCA2 germline mutations that comprised four frameshift mutations and five nonsense mutations. All nine mutations led to premature termination producing shortened proteins. Among the nine mutations, three novel BRCA1 mutations (E1114X, Q1299X, 4159delGA) and two novel BRCA2 mutations (K467X, 8945delAA) were identified in this work.     

Low frequency of BRCA1 germline mutations in 45 German breast/ovarian cancer families.

In this study we investigated 45 German breast/ovarian cancer families for germline mutations in the BRCA1 gene. We identified four germline mutations in three breast cancer families and in one breast-ovarian cancer family. among these were one frameshift mutation, one nonsense mutation, one novel splice site mutation, and one missense mutation. The missense mutation was also found in 2.8% of the general population, suggesting that it is not disease associated. The average age of disease onset in those families harbouring causative mutations was between 32.3 and 37.4 years, whereas the family harbouring the missense mutation had an average age of onset of 51.2 years. These findings show that BRCA1 is implicated in a small fraction of breast/ovarian cancer families suggesting the involvement of another susceptibility gene(s).     

Frequency of BRCA1 and BRCA2 mutations in a clinic-based series of breast and ovarian cancer families

Mutations in BRCA1 and BRCA2 account for a significant proportion of hereditary breast and ovarian cancer cases. In this study, we sought to determine the frequency of BRCA1- and BRCA2-mutation carrier families in a hospital-based cancer family registry. The frequency of families with germline truncating mutations in BRCA1 and BRCA2 was 17.3% (18/104) and 1.9% (2/104), respectively. Two novel truncating mutations, BRCA1 1848delGA and BRCA2 5694insT, were identified. We also sought to determine the carrier frequency of other affected family members for which the mutation lineage could be established within these families. Not including the probands, 72% (18/25) of the affected family members within the BRCA1 mutation-associated families were carriers, and all four affected members of the BRCA2 families were carriers. These data imply that risk evaluation based on cancer family history alone may result in inaccurate estimates, and where possible, mutation testing should be considered in other affected family members to verify carrier status.     

Novel germline BRCA1 and BRCA2 mutations in breast and breast/ovarian cancer families from the Czech Republic

Germline mutations in breast cancer susceptibility genes, BRCA1 and BRCA2, are responsible for a substantial proportion of high‐risk breast and breast/ovarian cancer families. To characterize the spectrum of BRCA1 and BRCA2 mutations, we screened Czech families with breast/ovarian cancer using the non‐radioactive protein truncation test, heteroduplex analysis and direct sequencing. In a group of 100 high‐risk breast and breast/ovarian cancer families, four novel frame shift mutations were identified in BRCA1 and BRCA2 genes. In BRCA1, two novel frame shift mutations were identified as 3761‐3762delGA and 2616‐2617ins10; in BRCA2, two novel frame shift mutations were identified as 5073‐5074delCT and 6866delC. Furthermore, a novel missense substitution M18K in BRCA1 gene in a breast/ovarian cancer family was identified which lies adjacent just upstream of the most highly conserved C3HC4 RING zinc finger motif. To examine the tertiary structure of the RING zinc finger domain and possible effects of M18K substitution on its stability, we used threading techniques according to the crystal structure of RAG1 dimerization domain of the DNA‐binding protein. © 2000 Wiley‐Liss, Inc.     

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.     

Novel germline mutations in the BRCA1 and BRCA2 genes in Indian breast and breast-ovarian cancer families

The two major hereditary breast/ovarian cancer predisposition tumor suppressor genes, BRCA1 and BRCA2 that perform apparently generic cellular functions nonetheless cause tissue-specific syndromes in the human population when they are altered, or mutated in the germline. However, little is known about the contribution of BRCA1 and BRCA2 mutations to breast and/or ovarian cancers in the Indian population. We have screened for mutations the entire BRCA1 and BRCA2 coding sequences, and intron-exon boundaries, as well as their flanking intronic regions in sixteen breast or breast and ovarian cancer families of Indian origin. We have also analyzed 20 female patients with sporadic breast cancer regardless of age and family history, and 69 unrelated normal individuals as control. Thus a total of 154 samples were screened for BRCA1 and BRCA2 mutations using a combination of polymerase chain reaction-mediated site directed mutagenesis (PSM), polymerase chain reaction-single stranded conformation polymorphism assay (PCR-SSCP) and direct DNA sequencing of PCR products (DS). Twenty-one sequence variants including fifteen point mutations were identified. Five deleterious pathogenic, protein truncating frameshift and non-sense mutations were detected in exon 2 (c.187_188delAG); and exon 11 (c.3672G>T) [p.Glu1185X] of BRCA1 and in exon 11 (c.5227dupT, c.5242dupT, c.6180dupA) of BRCA2 (putative mutations - four novel) as well as fourteen amino acid substitutions were identified. Twelve BRCA1 and BRCA2 missense variants were identified as unique and novel. In the cohort of 20 sporadic female patients no mutations were found.     

Ten novel BRCA1 and BRCA2 mutations in breast and/or ovarian cancer families from northern Germany

Germline mutations in the BRCA1 and BRCA2 gene account for the majority of high-risk breast/ovarian cancer families. We have screened such families from Northern Germany by using DHPLC analysis and subsequent direct sequencing techniques. In ten families we identified six novel BRCA1 and 4 novel BRCA2 mutations comprising four frame shift mutations, one nonsense and one splice site mutation in the BRCA1 gene as well as three frameshift mutations and one nonsense mutation in the BRCA2 gene. Our analysis contributes to the further characterisation of the mutational spectrum of BRCA1 and BRCA2.     

Founder BRCA1 mutations and two novel germline BRCA2 mutations in breast and/or ovarian cancer families from North-Eastern Poland

Germline mutations in the BRCA1 and BRCA2 genes account for the majority of high-risk breast/ovarian cancer families, depending on the population studied. Previously, BRCA1 mutations were described in women from Western Poland. To further characterize the spectrum of BRCA1 mutations and the impact of BRCA2 mutations in Poland, we have analyzed 25 high-risk breast and/or ovarian cancer families from North-Eastern Poland for mutations in all coding exons of the BRCA1 and BRCA2 genes, using combined heteroduplex analysis/SSCP followed by direct DNA sequence analysis. Out of 25 probands a total of five (20%) carried three recurrent BRCA1 mutations (300T>G, 3819del5, 5382insC). The 300T>G mutation accounted for 60% (3/5) of BRCA1 mutations and allelotyping suggested a common founder of this mutation. No unique mutations were found. In addition, we identified three BRCA2 (12%) mutations, one recurrent 4075delGT, and two novel frameshift mutations, 7327ins/dupl19 and 9068delA. We conclude that 30% of high-risk families from North-Eastern Poland may be due to recurrent BRCA1 and unique BRCA2 mutations. Intriguingly, the BRCA1 mutation spectrum seems to be different within subregions of Poland.     

Germline mutations of BRCA1 and BRCA2 genes in Turkish breast, ovarian, and prostate cancer patients

Distribution and prevalence of germline mutations in BRCA1 and BRCA2 differ among different populations. For the Turkish population, several studies have addressed high-risk breast cancer and ovarian cancer (BC–OC) patients. In most studies, both genes were analyzed in part, and a quite heterogeneous mutation spectrum was observed. For high-risk Turkish prostate cancer (PCa) patients, however, there are no data available about mutations of germline BRCA genes. To accurately determine the contribution of germline mutations in BRCA1 and BRCA2 in Turkish BC, OC, and PCa high-risk patients, 106 high-risk BC–OC patients, 50 high-risk PCa patients, and 50 control subjects were recruited. The study represents the only full screening, to date, of a large series of Turkish high-risk BC–OC patients and the only study in Turkish high-risk PCa patients. Mutation screenings were performed on coding exons of both genes with either denaturing gradient gel electrophoresis or denaturing high performance liquid chromatography, or with both techniques. Three deleterious mutations in BRCA1 and three deleterious mutations in BRCA2 were detected in different BC–OC patients, and one truncating mutation was detected in a high-risk PCa patient. In addition, 28 different unclassified and mostly novel variants were detected in both genes, as well as several silent polymorphisms. These findings reflect the genetic heterogeneity of the Turkish population and are relevant to genetic counseling and clinical management.     

Hereditary breast and ovarian cancer due to mutations in BRCA1 and BRCA2

Hereditary breast and ovarian cancer due to mutations in the BRCA1 and BRCA2 genes is the most common cause of hereditary forms of both breast and ovarian cancer. The overall prevalence of BRCA1/2 mutations is estimated to be from 1 in 400 to 1 in 800 with a higher prevalence in the Ashkenazi Jewish population (1 in 40). Estimates of penetrance (cancer risk) vary considerably depending on the context in which they were derived and have been shown to vary within families with the same BRCA1/2 mutation. This suggests there is no exact risk estimate that can be applied to all individuals with a BRCA1/2 mutation. The likelihood of harboring a BRCA1 or BRCA2 mutation is dependent on one's personal and/or family history of cancer and can be estimated using various mutation probability models. For those individuals who have a BRCA1 or BRCA2 mutation, several screening and primary prevention options have been suggested, including prophylactic surgery and chemoprevention. Once a BRCA1 or BRCA2 mutation has been identified in a family, testing of at-risk relatives can identify those family members who also have the familial mutation and thus need increased surveillance and early intervention when a cancer is diagnosed.     

Low frequency of recurrent BRCA1 and BRCA2 mutations in Spain

BRCA1 and BRCA2 mutations underlie a substantial proportion of all hereditary breast cancer. The mutational spectrum in these genes is very broad, with hundreds of different BRCA mutations reported worldwide. However, high frequency founder mutations make up a substantial fraction of all mutations in some ethnic groups. We directly sequenced BRCA1 and BRCA2 in 35 Spanish breast/ovarian cancer families and found 13 mutations of which 3 had been reported previously in Spain. The ten novel mutations are: IVS5+1 G>A, 1491delA, Leu1086Ter, and Gln895Ter in BRCA1; Glu49Ter, 5373delGTAT, 5947delCTCT, 6672delTA, 8281insA, and Pro3039Leu (which also involves a splice site) in BRCA2. Our data, in combination with previous reports, indicate that 14 mutations have been seen recurrently in Spanish families. Analyzing these 14 mutations in 42 previously untested breast/ovarian cancer families revealed only two families testing positive, one for BRCA1 185delAG and one for BRCA2 9254delATCAT. While several mutations have been found recurrently in Spain, none appear to be high frequency founder mutations based on studies of breast and ovarian cancer families.     

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.      

Prevalence of BRCA1 genomic rearrangements in a large cohort of Italian breast and breast/ovarian cancer families without detectable BRCA1 and BRCA2 point mutations

The presence of genomic rearrangements of the BRCA1 gene in breast and/or ovarian cancer families has been intensively investigated in patients from various countries over the last years. A number of different rearrangements have been reported by several studies that clearly document the involvement of this mutation type in genetic predisposition to breast and ovarian cancer. Population-specific studies are now needed to evaluate the prevalence of genomic rearrangements before deciding whether to include ad hoc screening procedures into standard diagnostic mutation detection approaches. Indeed, the vast majority of the studies have been performed on small, highly selected, sample sets because of the limitations imposed by the laborious technical approaches. Moreover, prevalence figures are likely to differ across different countries according to the ethnic origin of each specific population. Here we analyze a large cohort of 653 Italian probands, negative for BRCA1 and BRCA2 point mutations, gathered from four National Institutions. We report the identification of BRCA1 genomic rearrangements in 12 independent families. Noteworthy, half of the probands carry mutations that recur in more than one Italian family. Considering the whole spectrum of Italian BRCA1 gene rearrangements identified thus far in consecutive patients, we estimate that alterations of this type account for 19% (95% CI: 0.11 < 0.19 < 0.28) of the BRCA1 mutation positive families. We conclude that the search for major genomic rearrangements is essential for an accurate and comprehensive BRCA1 mutation detection strategy in Italy.     

BRCA1 and BRCA2 mutations in breast/ovarian cancer patients from central Italy

We report on the screening of the entire BRCA1/BRCA2 coding sequence by SSCP, PTT, and direct sequencing in 68 Italian families with recurrent breast or ovarian cancer. For each investigated proband, the probability of being carrier of a BRCA1/BRCA2 mutation was evaluated using the BRCAPRO software. We detected BRCA1/BRCA2 mutations in 8 patients (11.7%). However, if considering only patients with a carrier probability >10%, the detection rate was 36.8%, confirming the usefulness of the BRCAPRO software. One change (BRCA1 4172insT) was a novel mutation not reported in BIC database.