Hereditary breast and ovarian cancer in Cyprus: identification of a founder BRCA2 mutation

The entire coding regions of the two breast cancer susceptibility genes BRCA1 and BRCA2 from breast cancer patients from 40 Cypriot families with multiple cases of breast and ovarian cancer were sequenced. A total of four protein-truncating mutations were found in six families. In BRCA1, a novel truncating mutation 5429delG was found in exon 21. In BRCA2, three truncating mutations were detected: a frameshift 8984delG in exon 22 and two nonsense mutations C1913X in exon 11 and K3326X in exon 27. It is noted that mutation 8984delG was found in three separate families, and haplotype analysis showed that this may be a founder mutation in the Cypriot population. In addition, a pair of rare variants, Q356R and S1512I, was detected in BRCA1 in patients belonging to two Cypriot families. The simultaneous presence of this pair of missense mutations may be associated with the breast cancer phenotype in the Cypriot population. We conclude that the BRCA2 gene appears to play a more important role in familial breast cancer in the Cypriot population than BRCA1.     

中国上海家族性乳腺癌BRCA1和BRCA2基因的突变

目的研究上海地区家族性乳腺癌中BRCA1／BRCA2基因的突变位点及携带情况。方法研究对象来自35个汉族家族性乳腺癌家系，家系中至少有一个一级亲属乳腺癌患病史。共35例患者，其中13例发病年龄≤加岁。由静脉血提取基因组DNA，对BRCA1／BRCA2基因的全部编码序列进行扩增。扩增产物突变分析先由变性高效液相色谱分析进行筛查，之后进行DNA直接测序证实。结果在BRCA1基因中发现有4个突变位点，其中2个为新发现位点——拼接点突变（IVS17-1G〉T；IVS21＋1G〉C）；另两个为已报道的致病突变位点——移码突变（1100delAT；5640delA）。BRCA2基因的1个致病突变位点位于11号外显子上，为移码突变（5802delAATT）。另外，共发现有12个新的单核苷重复多态位点，都未引起氨基酸编码改变；其中，8个在BRCA1基因上，4个在BRCA2基因上。在家族性乳腺癌中，BRCA1突变频率（11．4％）高于BRCA2基因（2．9％）。结论新发现的2个BRCA1基因的拼接点突变可能是中国上海人群家族性乳腺癌的特有突变位点；在我国上海地区人群中，BRCA1基因突变起着比BRCA2基因更大的作用；该研究丰富了中国人群中BRCA基因的突变谱，并为未来的临床基因检测提供了筛查模式。     

BRCA1 mutation analysis in breast/ovarian cancer families from Greece

Germline mutations in BRCA1 gene account for varying proportions of breast/ovarian cancer families, and demonstrate considerable variation in mutational spectra coincident with ethnic and geographical diversity. We have screened for mutations the entire coding sequence of BRCA1 in 30 breast/ovarian cancer women with family history of two or more cases of breast cancer under age 50 and/or ovarian cancer at any age. Genomic DNA from patient was initially analyzed for truncating mutations in exon 11 with PTT followed by DNA sequencing. In the cases where no frameshift mutation was observed in exon 11, all other exons were screened with direct sequencing. Two novel (3099delT, 3277insG) and three already described (3741insA, 1623del5-TTAAA, 5382insC-twice) truncating mutations were identified. In addition, 6 point mutations (L771L, P871L, E1038G, K1183R, S1436S, S1613G) which are already classified as polymorphisms were identified. Three unclassified intronic variants (IVS16-68 G>A, IVS16-92 G>A, IVS18+65G>A) were also detected. These results show that BRCA1 deleterious mutations are present in a fraction (20%) of Greek breast/ovarian cancer families similar to other European countries. Mutations were detected in high- (>/=3 members) as well as in moderate-risk (2 members) families. This is the first report of BRCA1 mutation analysis in Greece.     

Contribution of BRCA1 and BRCA2 germline mutations to the incidence of early-onset breast cancer in Cyprus

In Cyprus, the prevalence of breast cancer associated with BRCA1 and BRCA2 mutations in young women is unknown. In this study, we present the results of mutational analysis of the BRCA1 and BRCA2 genes in 26 Cypriot women diagnosed with breast cancer by the age of 40. The entire coding regions, including splice sites, of the BRCA1 and BRCA2 genes were sequenced using cycle sequencing. We identified four pathogenic mutations: two in BRCA1 [c.1840A>T (K614X), c.5310delG (5429delG)] and two in BRCA2 [c.3531-3534delCAGC (3758del4), c.8755delG (8984delG)] in six of 26 unrelated patients. The BRCA2 mutation c.3531-3534delCAGC (3758del4) is novel and the BRCA1 mutation c.1840A>T (K614X) is reported for the first time in Cypriot patients. The BRCA2 Cypriot founder mutation c.8755delG (8984delG) was detected in three unrelated patients. Additionally, we identified one novel BRCA1 missense mutation, two novel polymorphisms and three novel intronic variants of which BRCA1 c.4185+3A>G (IVS12+3A>G) may be pathogenic. Of the six BRCA1/2 mutation carriers, only four had a family history. These results show that the prevalence of BRCA1 and BRCA2 mutations in Cypriot women diagnosed with early-onset breast cancer is high. We conclude that Cypriot women with early-onset breast cancer should be offered BRCA1/2 testing irrespective of their family history.     

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.     

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.     

ATM germline mutations in Spanish early-onset breast cancer patients negative for BRCA1/BRCA2 mutations

Heterozygous carriers of ATM (ataxia telangiectasia mutated gene) mutations have increased risk of breast cancer (BC). We have estimated the prevalence of mutations in the ATM gene among Spanish patients with early-onset BC. Forty-three patients diagnosed with BC before the age of 46 years, and negative for BRCA1 and BRCA2 mutations, were analysed for the presence of ATM mutations. A total of 34 ATM sequence variants were detected: 1 deleterious mutation, 10 unclassified variants and 23 polymorphisms. One patient (2.3%) carried the ATM deleterious mutation (3802delG that causes ataxia telangiectasia in the homozygous state) and 13 patients carried the 10 ATM unclassified variants. The truncating mutation 3802delG and eight of the rare variants were not detected in a control group of 150 individuals. Different bioinformatic sequence analysis tools were used to evaluate the effects of the unclassified ATM changes on RNA splicing and function protein. This in silico analysis predicted that the missense variants 7653 T>C and 8156 G>A could alter the splicing by disrupting an exonic splicing enhancer motif and the 3763 T>G, 6314 G>C, and 8156 G>A variants would affect the ATM protein function. These are the initial results concerning the prevalence of germline mutations in the ATM gene among BC cases in a Spanish population, and they suggest that ATM mutations can confer increased susceptibility to early-onset BC.     

Contribution of germline BRCA1 and BRCA2 sequence alterations to breast cancer in Northern India

Background

A large number of distinct mutations in the BRCA1 and BRCA2 genes have been reported worldwide, but little is known regarding the role of these inherited susceptibility genes in breast cancer risk among Indian women. We investigated the distribution and the nature of BRCA1 and BRCA2 germline mutations and polymorphisms in a cohort of 204 Indian breast cancer patients and 140 age-matched controls.

Method

Cases were selected with regard to early onset disease (≤40 years) and family history of breast and ovarian cancer. Two hundred four breast cancer cases along with 140 age-matched controls were analyzed for mutations. All coding regions and exon-intron boundaries of the BRCA1 and BRCA2 genes were screened by heteroduplex analysis followed by direct sequencing of detected variants.

Results

In total, 18 genetic alterations were identified. Three deleterious frame-shift mutations (185delAG in exon 2; 4184del4 and 3596del4 in exon 11) were identified in BRCA1, along with one missense mutation (K1667R), one 5'UTR alteration (22C>G), three intronic variants (IVS10-12delG, IVS13+2T>C, IVS7+38T>C) and one silent substitution (5154C>T). Similarly three pathogenic protein-truncating mutations (6376insAA in exon 11, 8576insC in exon19, and 9999delA in exon 27) along with one missense mutation (A2951T), four intronic alterations (IVS2+90T>A, IVS7+75A>T, IVS8+56C>T, IVS25+58insG) and one silent substitution (1593A>G) were identified in BRCA2. Four previously reported polymorphisms (K1183R, S1613G, and M1652I in BRCA1, and 7470A>G in BRCA2) were detected in both controls and breast cancer patients. Rare BRCA1/2 sequence alterations were observed in 15 out of 105 (14.2%) early-onset cases without family history and 11.7% (4/34) breast cancer cases with family history. Of these, six were pathogenic protein truncating mutations. In addition, several variants of uncertain clinical significance were identified. Among these are two missense variants, one alteration of a consensus splice donor sequence, and a variant that potentially disrupts translational initiation.

Conclusion

BRCA1 and BRCA2 mutations appear to account for a lower proportion of breast cancer patients at increased risk of harboring such mutations in Northern India (6/204, 2.9%) than has been reported in other populations. However, given the limited extent of reported family history among these patients, the observed mutation frequency is not dissimilar from that reported in other cohorts of early onset breast cancer patients. Several of the identified mutations are unique and novel to Indian patients.     

Novel somatic mutations in the BRCA1 gene in sporadic breast tumors

Germline mutations in two major susceptibility genes BRCA1 and BRCA2 contribute to the majority of inherited breast and ovarian cancers. Besides the germline mutation, tumor progression depends on the loss of a wild-type allele. Allelic losses in the BRCA1 and BRCA2 loci have also been detected in a high proportion of sporadic breast tumors, suggesting the role of these genes in the development of non-inherited breast cancer. Forty unselected breast tumors were analyzed for the loss of heterozygosity (LOH) at BRCA1 and BRCA2 regions and tumors with allelic deletions were screened for the presence of acquired genetic alterations in respective genes. 21.1% of 38 informative tumor samples carried LOH at the BRCA1 locus whereas 33.3% of 39 informative samples showed LOH at the BRCA2 locus. Pathogenic truncating mutations in the BRCA1 gene were found in two tumor samples with allelic losses, whereas no mutations were identified in the BRCA2 gene. Mutations were not detected in non-tumor samples from the same individuals, which indicated that the BRCA1 allele was inactivated by somatic mutations in tumor tissue. The c.1116G>A (1235G>A) nonsense mutation (p.W372X) belongs to the genetic abnormalities detected infrequently in hereditary tumors; the c.3862delG (3981delG) frameshift mutation (p.E1288fsX1306) is a novel gene alteration. The occurrence of inactivating somatic mutations in sporadic breast tumors suggested the role of the BRCA1 gene in tumorigenesis in at least a minor group of patients with non-familial breast cancer.     

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.     

Contribution of the BRCA1 and BRCA2 mutations to breast cancer in Tunisia

Hereditary breast cancer accounts for 3–8% of all breast cancers, with mutations in the BRCA1 and BRCA2 genes responsible for up to 30% of these. To investigate the prevalence of BRCA1 and BRCA2 gene mutations in breast cancer patients with affected relatives in Tunisia, we studied 36 patients who had at least one first degree relative with breast and/or ovarian cancer Thirty-four 34 patients were suggestive of the BRCA1 mutation and two were suggestive of the BRCA2 mutation, based on the presence of male breast cancer detected in their corresponding pedigrees. Four mutations in BRCA1 were detected, including a novel frame-shift mutation (c.211dupA) in two unrelated patients and three other frameshift mutations – c.4041delAG, c.2551delG and c.5266dupC. Our study is the first to describe the c.5266dupC mutation in a non-Jewish Ashkenazi population. Two frameshift mutations (c.1309del4 and c.5682insA) were observed in BRCA2. Nineteen percent (7/36) of the familial cases had deleterious mutations of the BRCA1 or BRCA2 genes. Almost all patients with deleterious mutations of BRCA1 reported a family history of breast and/or ovarian cancer in the index case or in their relatives. Our data are the first to contribute to information on the mutation spectrum of BRCA genes in Tunisia, and we give a recommendation for improving clinical genetic testing policy.     

BRCA1 and BRCA2 germline mutations in Korean patients with sporadic breast cancer

In order to evaluate the role of BRCA1 and BRCA2 germline mutations in Korean patients with sporadic breast cancer, 97 patients with sporadic breast cancer were analyzed for mutations in the BRCA1 and BRCA2 coding regions, by using a combination of fluorescent-conformation sensitive gel electrophoresis (F-CSGE) and direct sequencing. Fifty-five distinct sequence variants were detected, which included three pathogenic truncating mutations, 15 missense mutations, 16 polymorphisms, and 21 intronic variants. Twenty-six of these variants have never been previously reported and may be of Korean-specific origin. Two pathogenic BRCA1 mutations (c.922_924delinsT, c.5445G>A) and one pathogenic BRCA2 mutation (c.2259delT) were observed, and two of these (BRCA1 c.5445G>A and BRCA2 c.2259delT) are novel. The total prevalence of germline pathogenic mutations in BRCA1 and/or BRCA2 in Korean sporadic breast cancer is estimated to be about 3.1%. Considering that the majority of breast cancer cases are sporadic, the present study will be helpful in the evaluation of the need for the genetic screening of germline BRCA mutations in sporadic breast cancer patients. Further study using a larger sample size is required to determine the merits of genetic diagnosis and counseling in breast cancer patients.     

BRCA1 and BRCA2 mutation analysis of early-onset and familial breast cancer cases in Mexico

The entire coding regions of BRCA1 and BRCA2 were screened for mutations by heteroduplex analysis in 51 Mexican breast cancer patients. One BRCA1 and one BRCA2 truncating mutation each was identified in the group of 32 (6%) early-onset breast cancer patients (< or =35 years). Besides these two likely deleterious mutations, eight rare variants of unknown significance, mostly in the BRCA2 gene, were detected in six of 32 (19%) early-onset breast cancer cases and in three of 17 (18%) site-specific breast cancer families, one containing a male breast cancer case. No mutations or rare sequence variants have been identified in two additional families including each an early-onset breast cancer case and an ovarian cancer patient. The two truncating mutations (BRCA1 3857delT; BRCA2 2663-2664insA) and six of the rare variants have never been reported before and may be of country-specific origin. The majority of the alterations appeared to be distinct, with only one of them being observed in more than one family.     

Mutation analysis of the BRCA1 and BRCA2 genes results in the identification of novel and recurrent mutations in 6/16 flemish families with breast and/or ovarian cancer but not in 12 sporadic patients with early-onset disease. Mutations in brief no. 224. Online

Since the identification of the BRCA1 and BRCA2 genes (MIM#s 113705 and 600185), more than hundred different mutations throughout both genes have been reported. Recurrent mutations are rare and mainly due to founder effects. We analyzed 12 sporadic female patients with breast cancer before age 35, as well as 16 unrelated families, presenting with either (i) at least 3 first degree relatives with breast and/or ovarian cancer diagnosed at any age, or (ii) at least 2 first and/or second degree relatives with breast and/or ovarian cancer before age 45 years. We performed a protein truncation test for BRCA1 exon 11 and BRCA2 exons 10 and 11 and heteroduplex analysis for all the remaining exons of BRCA1 and 2. Presence of genomic deletions encompassing exons 13 or 22 of BRCA1, known to be Dutch founder mutations, was investigated by PCR. In 6/16 (37.5%) unrelated families the causal mutation in either the BRCA1 or BRCA2 gene was identified. Four different mutations were found in the BRCA1 gene: IVS5+3A>G (intron 5), 1191delC (exon 11), R1443X (exon 13), IVS22+5G>A (intron 22) and two in the BRCA2 gene: 6503delTT (exon 11), 6831delTG (exon 11). 1191delC (BRCA1) and 6831delTG (BRCA2) are novel mutations. IVS5+3A>G in exon 5 of BRCA1 published by Peelen et al. (1997) as a novel Belgian mutation, was identified in one additional family, not fulfilling our inclusion criteria. In the group of 12 sporadic female patients no mutations were found.     

Mutations predisposing to breast cancer in 12 candidate genes in breast cancer patients from Poland

A number of genes other than BRCA1 and BRCA2 have been associated with breast cancer predisposition, and extended genetic testing panels have been proposed. It is of interest to establish the full spectrum of deleterious mutations in women with familial breast cancer.We performed whole‐exome sequencing of 144 women with familial breast cancer and negative for 11 Polish founder mutations in BRCA1, CHEK2 and NBS1, and we evaluated the sequences of 12 known breast cancer susceptibility genes. A truncating mutation in a breast cancer gene was detected in 24 of 144 women (17%) with familial breast cancer. A BRCA2 mutation was detected in 12 cases, a (non‐founder) BRCA1 mutation was detected in 5 cases, a PALB2 mutation was detected in 4 cases and an ATM mutation was detected in 2 cases. Polish women with familial breast cancer who are negative for founder mutations in BRCA1, CHEK2 and NBS1 should be fully screened for mutations in BRCA1, BRCA2 and PALB2. The PALB2 founder mutation c.509_519delGA should be included in the panel of Polish founder mutations.     

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.     

Similar contributions of BRCA1 and BRCA2 germline mutations to early-onset breast cancer in Germany

This study was undertaken to investigate the prevalence of BRCA1 and BRCA2 germline mutations in 91 German patients unselected for family history, who were diagnosed with breast cancer before the age of 41 years. Clinical information and blood samples were obtained from all patients. A comprehensive BRCA1 and BRCA2 mutational analysis was performed using the protein truncation assay and single-strand conformational polymorphism analysis followed by DNA sequencing of variant signals detected by these assays. Five different deleterious germline mutations including four frameshift mutations and one missense mutation were identified, three in BRCA1 (3.3%) and two mutations (2.2%) in BRCA2. Both BRCA2 mutations are novel and might be specific for the German population. An additional BRCA1 missense mutation previously described and classified as an unknown variant was found. This mutation was also detected in two breast cancer patients of family P 328 and not in 140 healthy controls suggesting that it is disease associated. In addition, one common polymorphism and five novel intronic sequence variants with unknown significance were found. Our findings show that mutations in BRCA1 and BRCA2 may contribute similarly to early-onset breast cancer in Germany. Given current constraints on health-care resources, these results support the notion that BRCA1 and BRCA2 mutation screening may have the strongest impact on health-care when targeted to high-risk populations.