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.     

Mutational analysis of the BRCA1-interacting genes ZNF350/ZBRK1 and BRIP1/BACH1 among BRCA1 and BRCA2-negative probands from breast-ovarian cancer families and among early-onset breast cancer cases and reference individuals

Two potential breast cancer susceptibility genes, encoding the BRCA1-interacting proteins ZNF350 (or ZBRK1) and BRIP1 (or BACH1), have been identified in yeast two-hybrid screens. We sequenced these genes in probands from 21 families with potentially inherited breast/ovarian cancer, all of which were negative for BRCA1/BRCA2 mutations. Families had at least one case of male breast cancer, two cases of ovarian cancer, or three or more cases of breast and ovarian cancer. In addition, 58 early-onset (before age 35) breast cancer cases and 30 reference individuals were analyzed. Of 17 variants detected in ZBRK1, a missense mutation Val524Ile was identified in the proband of one high-risk family, but no other family members were available for testing. Of 25 variants identified in BRIP1, in addition to four common silent or missense mutations, we identified Gln540Leu, a non-conservative amino acid change, in a single familial proband with inflammatory breast cancer, but this mutation was not present in her three relatives with breast cancer. Haplotype analysis suggests that all ZBRK1 SNPs fall within a single block with two SNPs capturing 92% of the haplotype diversity, while the BRIP1 SNPs fall in two blocks, with five SNPs capturing 89% of the haplotype diversity. Based on sequencing of ZBRK1 and BRIP1 in 21 BRCA1/2-negative probands from inherited breast/ovarian cancer families, it appears unlikely that mutations in these genes account for a significant fraction of inherited breast cancer. Further analysis in unselected cases will be required to know whether the identified variants play a role in genetic predisposition to breast cancer in the general population. Hum Mutat 22:121-128, 2003. Published 2003 Wiley-Liss, Inc.     

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.     

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.     

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.     

Identification of germline BRCA1 and BRCA2 genetic alterations in Greek breast cancer moderate-risk and low-risk individuals--correlation with clinicopathological data

The current study was designed to evaluate the prevalence of BRCA1 and BRCA2 germline mutations in Greek moderate- and low-risk individuals with respect to clinicopathological phenotype and clinical outcome of breast cancer. Ninety-four consecutive individuals were prospectively recruited from two University Breast Cancer Clinics (Hippokrateion Hospitan and Laikon Hospital) between 1989 and 1999 and were categorized as moderate-risk and low-risk individuals for carrying BRCA1/2 germline mutations. To identify the underlying mutations, protein-truncation test and single-strand conformation polymorphism methods were used, followed by direct sequencing. Three novel BRCA1 missense mutations, one novel BRCA1 intronic deletion, three novel (previously reported) BRCA2 truncating mutations, and one novel BRCA2 missense mutation were identified in the moderate-risk group of individuals studied. The BRCA1/2 missense mutations as well as the single intronic variant identified were designated as unclassified genetic variants. Two BRCA1 unclassified genetic variants (missense mutations) were detected in two of the three (66.7%) male breast cancer patients analyzed, while the third one was identified in a sporadic (low-risk) breast cancer patient. Clinicopathological characteristics of breast carcinomas originating from BRCA1/2 heterozygotes were consistent with those already reported and not different from those observed in BRCA1/2 mutation (-) breast cancer patients. Furthermore, BRCA1/2 mutation carriers presented an excellent 4.5-year overall survival (100%). Our results reveal the unique characteristics of BRCA1/2 mutation status, genotype-phenotype correlations, and prognosis, in moderate- and low-risk individuals of Greek ancestry. Breast cancer due to mutations in BRCA1 and BRCA2 genes appears to be a heterogeneous syndrome in the Greek population.     

BRCA1 and BRCA2 sequence variants in Chinese breast cancer families

A series of 45 high-risk breast cancer patients, consisting of 25 affected individuals from 16 families in China with at least two cases of breast cancer and 20 cases of breast cancer diagnosed under age 35 without reported family history, were studied for germline mutations of the BRCA1 and BRCA2 genes. Thirteen of the 16 families contained at least one case diagnosed under age 50. Three distinct protein truncating sequence variants, likely to be disease-associated, were identified: two novel mutations in BRCA1 (1584G>T and 5028delC), and a previously reported mutation in BRCA2 (7883delTTAA). Additional sequence variants identified included common polymorphisms, and several variants of unknown clinical significance, including a novel BRCA1 alteration. Based on models for predictive testing using allele frequencies and risks estimated in Western populations, our results suggest that BRCA1/2 mutations account for a somewhat smaller fraction of breast cancer cases in Tianjin than in the Caucasian populations studied. This difference could be the result of a lower penetrance of BRCA1/2 mutations due to the surrounding environmental and hormonal milieu, or a lower frequency of mutations in this population. Larger, more detailed, studies will be necessary to determine which factors underlie this difference.     

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.     

A mutation analysis of the<Emphasis Type="Italic"> BRCA1</Emphasis> gene in 140 families from southeast France with a history of breast and/or ovarian cancer

A mutation analysis of the BRCA1 gene in 140 French families with a history of breast cancer or breast-ovarian cancer revealed several deleterious germline mutations, as well as rare sequence variants. The 19 genetics variants were of 15 different types, two of which had not been reported in the Breast cancer Information Core (BIC) database. Five distinct truncating mutations, leading to putative nonfunctional proteins, were identified out of 140 index cases (3.5%). One novel nonsense mutation, C4491T, was reported, whereas the four other BRCA1 deleterious mutations identified consisted of frequent frameshifts in the nucleotide sequence. One splice variant (331+3A>G) and thirteen missense variations leading to amino acid substitutions of unknown structural and functional importance were identified. Among these, two BRCA1 missense mutations, A120G and T243C could be considered as suspected deleterious. The first missense mutation modified the initiation codon (M1V) and the second (C39R) may have consequences on the structure and functioning of the BRCA1 protein by modifying cysteine ligands from the RING finger domain. As expected BRCA1 gene alteration, including missense mutations of unknown biological significance, were more frequent in families with a history of breast-ovarian-cancer (32%) than in breast-cancer-only families (12%).     

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.     

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.     

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.     

MLPA screening in the BRCA1 gene from 1,506 German hereditary breast cancer cases: novel deletions, frequent involvement of exon 17, and occurrence in single early-onset cases

We present a comprehensive analysis of 1,506 German families for large genomic rearrangements (LGRs) in the BRCA1 gene and of 450 families in the BRCA2 gene by the multiplex ligation-dependent probe amplification (MLPA) technique. A total of 32 pathogenic rearrangements in the BRCA1 gene were found, accounting for 1.6% of all mutations, but for 9.6% of all BRCA1 mutations identified in a total of 1,996 families, including 490 with small pathogenic BRCA1/2 mutations. Considering only high risk groups for hereditary breast/ovarian cancer, the prevalence of rearrangements is 2.1%. Interestingly, deletions involving exon 17 of the BRCA1 gene seem to be most frequent in Germany. Apart from recurrent aberrations like del ex17, dupl ex13, and del ex22, accounting for more than 50% of all BRCA1 LGRs, we could fully characterize 11 novel deletions. Moreover, one novel deletion involving exons 1-7 and one deletion affecting the entire BRCA1 gene were identified. All rearrangements were detected in families with: 1) at least two breast cancer cases prior to the age of 51 years; 2) breast and ovarian cancer cases; 3) ovarian cancer only families with at least two ovarian cancer cases; or 4) a single breast cancer case prior to the age of 36 years, while no mutations were detected in breast cancer only families with no or only one breast cancer case prior to the age of 51 years. Analysis for gross rearrangements in 412 high-risk individuals, revealed no event in the BRCA2 gene and only two known CHEK2 mutations. However, in an additional 38 high-risk families with cooccurrence of female breast/ovarian and male breast cancer, one rearrangement in the BRCA2 gene was found. In summary, we advise restricting BRCA1 MLPA screening to those subgroups that revealed LGRs and recommend BRCA2 MLPA screening only for families presenting with cooccurrence of female and male breast cancer.     

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.     

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%.     

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。     

中国早发性乳腺癌患者中BRCA1基因突变分析

目的研究中国早发性乳腺癌患者中BRCA1基因致病性突变的发生情况以及家族史在突变携带者识别中的作用。方法研究对象为来自中国4个乳腺癌临床医疗中心的188例早发性乳腺癌病例(发病年龄≤40岁),其中39例(20.1%)有乳腺/卵巢癌家族史。从外周静脉血提取基因组DNA,对BRCA1基因的全部编码区和外显子/内含子拼接区进行PCR扩增。其中22例通过单链构象多态方法进行突变初筛,166例用变性高效液相色谱分析进行初筛;对发现的异常片段通过DNA直接测序的方法进行确认。对发现重复出现突变的样本,选取5个与BRCA1基因连锁的标记(D17S855、D17S1322、D17S1323、D17S1326和D17S1327)进行等位基因型分析。结果在15例(8.0%)患者中发现有12个BRCA1基因的致病性突变,其中BRCA11100delAT和5589del8突变分别在3个和2个患者中发现。在39例同时伴有乳腺/卵巢癌家族史的病例中共发现有9例(23.1%)携带突变。有(无)乳腺癌家族史的早发性乳腺癌病例间BRCA1基因的突变率的差异有统计学意义(P=0.001)。重复出现的突变在所有检测病例中出现的频率为2.7%,在所有检测到的突变中占33.3%。两个来自中国北方的BRCA11100delAT突变携带病例有相同的等位基因型,而与来自上海地区的此突变携带者的等位基因型在D17S1322位点上有所差异。两例5589del8突变携带者在所检测的5个STR位点上有完全相同的等位基因型。结论这是到目前为止较大规模的关于中国早发性乳腺癌人群的BRCA1基因突变的研究,有助于增加对中国早发性乳腺癌人群中BRCA1基因致病性突变分布的全面认识。在中国早发性乳腺癌人群中,BRCA1基因致病性突变在肿瘤的发生中有比较重要的意义,尤其在伴有乳腺/卵巢癌家族史病例中该基因突变的意义尤为突出。两个重复出现的突变可能在中国人群中有始祖效应,在进行全基因检测前对其先进行检测可能非常合算。     

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.     

Recurrent mutations of BRCA1 and BRCA2 in Poland: an update

Three founder alleles of BRCA1 (C61G, 4153delA, 5382insC) were reported in Poland in 2000, and these three mutations have comprised the standard testing panel used throughout the country. However, since 2000, other recurrent mutations of BRCA1 and BRCA2 have been reported. To establish if the inclusion of one or more of these mutations will increase the sensitivity of the standard test panel, we studied 1164 Polish women with unselected breast cancer diagnosed at age of 50 or below. All women were genotyped for 12 recurrent mutations of BRCA1 and BRCA2. We identified a mutation in 83 of 1164 patients (7.1%) including 61 women with one of the original three mutations (C61G, 4153delA, 5382insC) and 22 women with a different mutation (1.9%). Three new mutations (3819del5, 185delAG and 5370C>T) were seen in multiple families. By including these three mutations in the extended panel, the mutant frequency increased from 5.2 to 6.7%. Polish women with breast cancer diagnosed at age of 50 or below should be screened with a panel of six founder mutations of BRCA1 (C61G, 4153delA, 5382insC, 3819del5, 185delAG and 5370C>T).     

A DGGE system for comprehensive mutation screening of BRCA1 and BRCA2: application in a Dutch cancer clinic setting

Rapid and reliable identification of deleterious changes in the breast cancer genes BRCA1 and BRCA2 has become one of the major issues in most DNA services laboratories. To rapidly detect all possible changes within the coding and splice site determining sequences of the breast cancer genes, we established a semiautomated denaturing gradient gel electrophoresis (DGGE) mutation scanning system. All exons of both genes are covered by the DGGE scan, comprising 120 amplicons. We use a semiautomated approach, amplifying all individual amplicons with the same PCR program, after which the amplicons are pooled. DGGE is performed using three slightly different gel conditions. Validation was performed using DNA samples with known sequence variants in 107 of the 120 amplicons; all variants were detected. This DGGE mutation scanning, in combination with a PCR test for two Dutch founder deletions in BRCA1 was then applied in 431 families in which 52 deleterious changes and 70 unclassified variants were found. Fifteen unclassified variants were not reported before. The system was easily adopted by five other laboratories, where in another 3,593 families both exons 11 were analyzed by the protein truncation test (PTT) and the remaining exons by DGGE. In total, a deleterious change (nonsense, frameshift, splice-site mutation, or large deletion) was found in 661 families (16.4%), 462 in BRCA1 (11.5%), 197 in BRCA2 (4.9%), and in two index cases a deleterious change in both BRCA1 and BRCA2 was identified. Eleven deleterious changes in BRCA1 and 36 in BRCA2 had not been reported before. In conclusion, this DGGE mutation screening method for BRCA1 and BRCA2 is proven to be highly sensitive and is easy to adopt, which makes screening of large numbers of patients feasible. The results of screening of BRCA1 and BRCA2 in more than 4,000 families present a valuable overview of mutations in the Dutch population.