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.     

Screening for large rearrangements of the BRCA1 gene in German breast or ovarian cancer families using semi-quantitative multiplex PCR method

Since the identification of the breast and ovarian cancer susceptibility genes BRCA1 and BRCA2, a large number of different germline mutations in both genes have been found by conventional PCR-based mutation detection methods. Complex germline rearrangements such as those reported in the BRCA1 gene are often not detectable by these standard diagnostic techniques. To detect large deletions or duplications encompassing one or more exons of the BRCA1 gene and in order to estimate the frequency of BRCA1 rearrangements in German breast or ovarian cancer families, a semi-quantitative multiplex PCR method was developed and applied to DNA samples of patients from families negatively tested for disease causing mutations in the BRCA1 and BRCA2 coding regions by direct sequencing. Out of 59 families analysed, one family was found to carry a rearrangement in the BRCA1 gene (duplication of exon 13). The results indicate that the semi-quantitative multiplex PCR method is useful for the detection of large rearrangements in the BRCA1 gene and therefore represents an additional valuable tool for mutation analysis of BRCA1 and BRCA2.     

Family history, BRCA mutations and breast cancer in Vietnamese women

The purpose of this report is to estimate the proportions of familial and hereditary breast cancers among unselected cases of breast cancer in Vietnam. Two hundred and ninety-two unselected cases of incident breast cancer were recruited from the National Cancer Hospital, Hanoi, the largest cancer centre in Vietnam. Family histories were collected for 292 cases and a DNA sample was obtained for 259 cases. DNA samples were screened for mutations in the large exons of BRCA1 and BRCA2 using the protein truncation test and by allele-specific testing for 17 founder mutations which have been reported in other Asian populations. Complete gene sequencing was performed on two cases of familial breast cancer. Seven of 292 cases reported a relative with breast cancer and one patient reported a relative with ovarian cancer. A pathogenic BRCA mutation was detected in 2 of 259 cases; one BRCA1 carrier was diagnosed at age 51 and one BRCA2 carrier was diagnosed at age 42. Neither case reported a relative with breast or ovarian cancer. A family history of breast cancer is very uncommon among Vietnamese breast cancer patients. The frequency of pathogenic BRCA mutations in Vietnamese breast cancer patients is among the lowest reported worldwide.     

Prevalence of five previously reported and recurrent BRCA1 genetic rearrangement mutations in 20,000 patients from hereditary breast/ovarian cancer families

Many rearrangement mutations in the BRCA1 gene have been identified. It is becoming clear that some of these mutations are prevalent, and therefore their detection is necessary in order for clinical genetic tests to have high sensitivity. Published information on particular rearrangements is frequently limited to a single patient, small groups of patients, or patients of a particular ethnicity. The objectives of this work included characterizing the prevalence of five specific rearrangement mutations in a large North American patient population. A mutation-specific multiplex PCR assay was used for determining the prevalence of five BRCA1 rearrangement mutations that previously had been reported to occur in unrelated patients. The mutation status of these rearrangements, which came from 20,712 patients at high risk for hereditary breast and/or ovarian cancers who had submitted specimens for clinical genetic testing, is presented. The results, obtained from 2,634 mutation carriers, showed a 6-kb duplication of exon 13, identified in 53 patients (2.01%); a 26-kb deletion encompassing exons 14-20, detected in seven patients (0.27%); a 510-bp deletion of exon 22, detected in 5 patients (0.19%); and a 3.4-kb deletion of exon 13, detected in one patient (0.04%). A previously reported 7.1-kb deletion of exons 8-9 was not found. The high frequency of the exon 13 duplication makes it the fourth most prevalent mutation in these patients. These results provide an accurate picture of the prevalence of these mutations in hereditary breast/ovarian cancer patients undergoing genetic testing in North America.     

Complex germline rearrangement of BRCA1 associated with breast and ovarian cancer

Germline mutations in BRCA1 predispose to breast and ovarian cancer. Most germline BRCA1 mutations are small insertions, deletions, or single base pair (bp) substitutions. These mutation classes are rarely found as somatic mutations in BRCA1. On the other hand, somatic deletions of multiple mega-base pairs (Mb) including BRCA1, as reflected by loss of heterozygosity, occur frequently in both inherited and sporadic breast and ovarian cancers. To determine whether deletions or rearrangements of hundreds to thousands of bps might contribute to inherited mutation in BRCA1, we developed a Long PCR strategy for screening the entire genomic BRCA1 locus in high-risk families. We evaluated genomic DNA from one high-risk family of European ancestry with BRCA1-linked cancer in which no genomic mutations had been detected using conventional methods. Long PCR revealed a complex mutation, g.12977 ins10 del1039 (based on GenBank L78833), comprising an inverted duplication and deletion in BRCA1 that removes portions of exon 3 and intron 3, including the 5' splice site for intron 3. As a result of the deletion, exon 3 is skipped, leading to a truncated protein and disease predisposition. Unlike previously reported large germline deletions in BRCA1, neither breakpoint resides within an Alu element. The g.12977 ins10 del1039 mutation was not detected among 11 other breast cancer families, nor among 406 breast cancer patients unselected for family history.     

Haplotype analysis of two recurrent genomic rearrangements in the BRCA1 gene suggests they are founder mutations for the Greek population

Pertesi M, Konstantopoulou I, Yannoukakos D. Haplotype analysis of two recurrent genomic rearrangements in the BRCA1 gene suggests they are founder mutations for the Greek population. The deletions of 4.4 and 3.2 kb identified in exons 24 and 20, respectively, are two of the four most common mutations in the BRCA1 gene in Greek breast cancer patients. They have been reported previously six and three times, respectively, in unrelated Greek families. A total of 11 more families have been identified in the present study. In order to characterize these recurrent mutations as founder mutations, it is necessary to identify the disease‐associated haplotype and prove that it is shared by all the mutation carriers, suggesting that it occurred only once in a common ancestor. Haplotype analysis was performed on 24 mutation carriers and 66 healthy individuals using 10 short tandem repeat markers located within and flanking the BRCA1 gene locus, spanning a 5.9 Mb interval. Results indicate that most of the carriers of the exon 24 deletion share a common core haplotype ‘4‐7‐6‐6‐1‐3’ between markers D17S951 and D17S1299, for a stretch of 2.9 Mb, while the common haplotype for the exon 20 deletion is ‘6‐7‐4‐2‐6‐7‐1‐3’ between markers D17S579 and D17S1299, for a stretch of 3.9 Mb. Both genomic rearrangements in BRCA1 gene are Greek founder mutations, as carriers share the same, for each mutation, disease‐associated haplotype, suggesting the presence of a distinct common ancestor for both mutations.     

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.     

Large BRCA1 gene deletions are found in 3% of German high-risk breast cancer families

We have tested for large BRCA1 gene rearrangements in German high-risk breast and ovarian cancer families previously screened negative for point mutations by dHPLC and sequencing. Using the novel MLPA method, two deletions of exons 1A, 1B and 2 and exon 17, respectively, were detected in four out of 75 families investigated in Southern Germany. An identical exon 17 deletion with the same breakpoints and a deletion of exons 1A, 1B and 2 were found by fluorescent multiplex PCR in two out of 30 families investigated in Northern Germany. Combining both populations, genomic rearrangements were found in 6% of the mutation-negative families and 3% of all high-risk families and account for 8% of all BRCA1 mutations. Our data indicate that the exon 17 deletion may be a founder mutation in the German population. The prevalence of BRCA1 gene deletions or duplications in our patients is similar to previous reports from Germany and France. Genomic quantification by MLPA is a useful method for molecular diagnostics in high-risk breast cancer families.     

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.     

Hereditary breast and ovarian cancer in Asia: genetic epidemiology of BRCA1 and BRCA2

Ethnic differences in cancer incidence and mortality result from differences in genetic and epidemiologic risk factors. Mutations in BRCA1 and BRCA2 account for a small proportion of all breast cancer cases, but for a much higher proportion of cases with a strong family history of breast or ovarian cancer. Germline mutations in BRCA1 and BRCA2 have been identified in individuals of many races and ethnic groups and the frequency of mutations varies between these groups. Some of the differences in cancer risk between populations may be the result of founder mutations in these genes. The cost and time required for mutation analysis are reduced considerably when founder mutations are identified for a specific ethnic group. The BRCA2 999del5 mutation in Iceland and three BRCA mutations in Ashkenazi Jews are well characterized. However, considerably less is known about the contribution of mutations in the BRCA1 and BRCA2 genes outside of European groups. Studies conducted on the Asian populations described here have expanded our current knowledge of genetic susceptibility and its contribution to breast and ovarian cancer rates in Asian populations.     

Gross rearrangements in BRCA1 but not BRCA2 play a notable role in predisposition to breast and ovarian cancer in high-risk families of German origin

A total of 226 index cases from high-risk hereditary breast and ovarian cancer families of German origin who had tested negative for small nucleotide alterations in BRCA1 and BRCA2 were analyzed for gross genomic rearrangements at the two gene loci by the multiplex ligation-dependent probe amplification technique. Six large genomic alterations were identified in BRCA1, while no gross rearrangements were found in BRCA2. The six BRCA1 mutations included two novel mutations including a deletion of exon 5, and a deletion comprising exons 5-7, as well as three distinct gross alterations previously reported, including a deletion of exons 1A, 1B, and 2, two duplications of exon 13, and a deletion of exon 17. To understand the mechanisms underlying the genomic rearrangements within the BRCA1 gene and to provide a simple PCR-based assay for further diagnostic applications, we have defined the molecular breakpoints of the deletion/insertion mutations. In all cases, our data point to a mechanism by which illegitimate crossing over between stretches of direct repeat sequences as small as 9 base pairs (bp) and up to 188 bp may have occurred. Overall, we provide evidence that gross rearrangements within the BRCA1 gene locus may be as frequent as 3% in primarily mutation-negative tested high-risk familial breast and ovarian cancer of German ancestry, while large alterations involving the BRCA2 locus do not appear to play a significant role in disease etiology. These findings have important implications for genetic counseling and testing of high-risk breast and ovarian cancer families.     

Genomic rearrangements account for more than one-third of the BRCA1 mutations in northern Italian breast/ovarian cancer families

The recent identification of major genomic rearrangements in breast and breast/ovarian cancer families has widened the mutational spectrum of the BRCA1 gene, thus increasing the number of informative patients who can benefit from molecular screening. Numerous types of alterations have been identified in different populations with variable frequencies, probably due to both ethnic diversity and the technical approach employed. In fact, although several methods have been successfully used to detect large genomic deletions and insertions, most are laborious, time-consuming, and of variable sensitivity. In order to estimate the contribution of BRCA1 genomic rearrangements to breast/ovarian cancer predisposition in Italian families, we applied, for the first time as a diagnostic tool, the recently described multiplex ligation-dependent probe amplification (MLPA) methodology. Among the 37 hereditary breast/ovarian cancer (HBOC) families selected, all had a high prior probability of BRCA1 mutation, and 15 were previously shown to carry a mutation in either the BRCA2 (five families) or BRCA1 gene (10 families, including one genomic rearrangement). The application of BRCA1-MLPA to the remaining 22 uninformative families allowed the identification of five additional genomic rearrangements. Moreover, we observed that loss of constitutive heterozygosity of polymorphic markers in linkage disequilibrium is predictive of such BRCA1 alterations. By means of this approach, we demonstrate that BRCA1 genomic deletions account for more than one-third (6/15) of the pathogenic BRCA1 mutations in our series. We therefore propose to systematically include MLPA in the BRCA1 mutational analysis of breast/ovarian cancer families.     

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 and BRCA2 Germline Mutations Screening in Algerian Breast/Ovarian Cancer Families

Background: Breast cancer is the leading cause of cancer death in women in Algeria. The contribution of BRCA1 and BRCA2 mutations to hereditary breast/ovarian cancer in Algerian population is largely unknown. Here, we describe analysis of BRCA1 and BRCA2 genes in 86 individuals from 70 families from an Algerian cohort with a personal and family history suggestive of genetic predisposition to breast cancer. Methods: The approach used is based on BRCA1 and BRCA2 mutations screening by High-Resolution Melting (HRM) curve analysis followed by direct sequencing. All samples for which no pathogenic mutation was found were analyzed by MLPA for large deletions or duplications. Results: Three distinct pathogenic mutations c.83_84delTG, c.181T>G, c.798_799delTT and two large rearrangements involving deletion of exon 2 and exon 8 respectively, were detected in BRCA1 gene. Moreover 17 unclassified variants and polymorphisms were detected in BRCA1 gene (6 described for the first time). Two pathogenic mutations, c.1310_1313delAAGA and c.5722_5723delCT and 40 unclassified variants and polymorphisms (14 never described before) were identified in BRCA2 gene. Conclusions: For the first time, we used HRM and MLPA to identify BRCA1 and BRCA2 mutations in Algerian patients with a personal and family history suggestive of genetic predisposition to breast cancer. The implications of these new findings in regard to genetic testing and counseling are substantial for the Algerian population.     

Comprehensive mutational analysis of BRCA1/BRCA2 for Korean breast cancer patients: evidence of a founder mutation

The BRCA1 and BRCA2 genes are the strongest susceptibility genes identified for breast cancer worldwide. However, BRCA1 / BRCA2 have been incompletely investigated due to their large size and the genomic rearrangements that occasionally occur within them. Here we performed a comprehensive mutational analysis for BRCA1 / BRCA2 in 206 Korean patients with breast cancer.
We analyzed all exons and flanking regions of BRCA1 / BRCA2 by direct sequencing and screened deletions or duplications involving BRCA1 / BRCA2 by multiplex ligation-dependent probe amplification. We reconstructed haplotypes using intragenic single nucleotide polymorphisms (SNPs) to investigate the possibility of a founder effect among recurrent mutations. In our series, 38 patients (18.4%) had one or more BRCA1 / BRCA2 mutations including 10 novel ones. Three additional patients carried novel distinct unclassified variants with potentially harmful effects. No large deletions or duplications involving BRCA1 / BRCA2 were identified in our series. Haplotype analyses and allele separation suggested that the most frequent mutation in Koreans, BRCA2 :c.7480C>T, might have originated from a common ancestor. BRCA1 / BRCA2 mutations were more frequent in a group with family history, bilateral cancer or multiple site cancer than in a group without the risk factors described or an unknown risk group. In contrast, mutation frequencies in the early-onset cancer group were not higher than in the unknown risk group.
Our results will be helpful to understand the mutation spectrum in BRCA1 / BRCA2 genes and establish a genetic screening strategy. In addition, this study suggests the possibility of the first true founder mutation of BRCA1/BRCA2 identified in the Korean population.     

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.     

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.     

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。     

维吾尔族和汉族散发性乳腺癌患者BRCA1/2基因突变的检测

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