Frequency of BRCA1 mutation 5382insC in German breast cancer patients

Prevalence of specific and recurrent/founder pathogenic variants in BRCA genes in breast and ovarian cancer in North Africa

Background

Elucidation of specific and recurrent/founder pathogenic variants (PVs) in BRCA (BRCA1 and BRCA2) genes can make the genetic testing, for breast cancer (BC) and/or ovarian cancer (OC), affordable for developing nations.

Methods

To establish the knowledge about BRCA PVs and to determine the prevalence of the specific and recurrent/founder variants in BRCA genes in BC and/or OC women in North Africa, a systematic review was conducted in Morocco, Algeria, and Tunisia.

Results

Search of the databases yielded 25 relevant references, including eleven studies in Morocco, five in Algeria, and nine in Tunisia. Overall, 15 studies investigated both BRCA1 and BRCA2 genes, four studies examined the entire coding region of the BRCA1 gene, and six studies in which the analysis was limited to a few BRCA1 and/or BRCA2 exons. Overall, 76 PVs (44 in BRCA1 and32 in BRCA2) were identified in 196 BC and/or OC patients (129 BRCA1 and 67 BRCA2 carriers). Eighteen of the 76 (23.7%) PVs [10/44 (22.7%) in BRCA1 and 8/32 (25%) in BRCA2] were reported for the first time and considered to be novel PVs. Among those identified as unlikely to be of North African origin, the BRCA1 c.68_69del and BRCA1 c.5266dupC Jewish founder alleles and PVs that have been reported as recurrent/founder variants in European populations (ex: BRCA1 c.181T>G, BRCA1 c1016dupA). The most well characterized PVs are four in BRCA1 gene [c.211dupA (14.7%), c.798_799detTT (14%), c.5266dup (8.5%), c.5309G>T (7.8%), c.3279delC (4.7%)] and one in BRCA2 [c.1310_1313detAAGA (38.9%)]. The c.211dupA and c.5309G>T PVs were identified as specific founder variants in Tunisia and Morocco, accounting for 35.2% (19/54) and 20.4% (10/49) of total established BRCA1 PVs, respectively. c.798_799delTT variant was identified in 14% (18/129) of all BRCA1 North African carriers, suggesting a founder allele. A broad spectrum of recurrent variants including BRCA1 3279delC, BRCA1 c.5266dup and BRCA2 c.1310_1313detAAGA was detected in 42 patients. BRCA1 founder variants explain around 36.4% (47/129) of BC and outnumber BRCA2 founder variants by a ratio of ≈3:1.

Conclusions

Testing BC and/or OC patients for the panel of specific and recurrent/founder PVs might be the most cost-effective molecular diagnosis strategy.

Analysis of Heterozygous BRCA1 5382ins Founder Mutation in a Cohort of Egyptian Breast Cancer Female Patients Using Pyrosequencing Technique

BACKGROUND

Up to half of the heritable mutations in breast cancer (BC) are attributed to BRCA1 and BRCA2 genes. The mutation prevalence is variable based on ethnicity and may be influenced by founder mutations. The aim of this pilot study is to determine for the first time, the prevalence of BRCA1 5382insC founder mutation in a cohort of Egyptian familial breast cancer patients (FBC).

METHODS

Female patients were selected to have familial type of breast cancer. Twenty healthy females were included as a control group. Peripheral blood samples were withdrawn from all studied females and were analyzed for BRCA1 5382insC founder mutation detection using pyrosequencing technique.

RESULTS

Eighty Egyptian FBC females were eligible to be enrolled in the study with a mean age of 48.31 ± 10.97years.We found a BRCA1 5382insC mutation carrier frequency of 5% of total studied FBC patients (4 out of 80 patients) with 95% confidence interval (1.61-12.99). There was a high statistical significant difference between carriers and non-carriers concerning the number of affected family members by BC, (p=0.001).  Conclusion: BRCA1 5382insC founder mutation is not uncommon among Egyptian FBC females. The carrier frequency is comparable to that reported worldwide; however it is lower than those from previous Egyptian studies using different molecular techniques. The strong association between the mutation and the number of affected family members suggest wider screening of the mutation among high risk families using the reliable pyrosequencing technique.

Addition of triple negativity of breast cancer as an indicator for germline mutations in predisposing genes increases sensitivity of clinical selection criteria

Background

Breast cancer is the most common cancer in women. 12–15% of all tumors are triple-negative breast cancers (TNBC). So far, TNBC has been mainly associated with mutations in BRCA1. The presence of other predisposing genes seems likely since DNA damage repair is a complex process that involves several genes. Therefore we investigated if mutations in other genes are involved in cancer development and whether TNBC is an additional indicator of mutational status besides family history and age of onset.

Methods

We performed a germline panel-based screening of 10 high and low-moderate penetrance breast cancer susceptibility genes (BRCA1, BRCA2, ATM, CDH1, CHEK2, NBN, PALB2, RAD51C, RAD51D and TP53) in 229 consecutive individuals affected with TNBC unselected for age, family history or bilateral disease. Within this cohort we compared the number of mutation carriers fulfilling clinical selection criteria with the total number of carriers identified.

Results

Age at diagnosis ranged from 23 to 80 years with an average age of 50.2 years. In 57 women (24.9%) we detected a pathogenic mutation, with a higher frequency (29.7%) in the group manifesting cancer before 60 years. Deleterious BRCA1 mutations occurred in 14.8% of TNBC patients. These were predominantly recurrent frameshift mutations (24/34, 70.6%). Deleterious BRCA2 mutations occurred in 5.7% of patients, all but one (c.1813dupA) being unique.

While no mutations were found in CDH1 and TP53, 10 mutations were detected in one of the six other predisposition genes. Remarkably, neither of the ATM, RAD51D, CHEK2 and PALB2 mutation carriers had a family history. Furthermore, patients with non-BRCA1/2 mutations were not significantly younger than mutation negative women (p = 0.3341). Most importantly, among the 57 mutation carriers, ten (17.5%) would be missed using current clinical testing criteria including five (8%) with BRCA1/2 mutations.

Conclusions

In summary, our data confirm and expand previous studies of a high frequency of germline mutations in genes associated with ineffective repair of DNA damage in women with TNBCs. Neither age of onset, contralateral disease nor family history were able to discern all mutation positive individuals. Therefore, TNBC should be considered as an additional criterion for panel based genetic testing.

Founder and Recurrent Mutations in BRCA1 and BRCA2 Genes in Latin American Countries: State of the Art and Literature Review

BACKGROUND

Numerous epidemiological factors affect the probability of developing breast or ovarian cancer, but no predictor is as determinant as inheriting a mutation in BRCA1 or BRCA2. The concept of the founder effect explains the reduced genetic variability in some populations, according to the theory that new populations can be formed from a reduced number of individuals, so the new population would carry only a small fraction of the genetic variability of the original population. The main purpose of this review is to provide an update on the state of the art in founder mutations and some recurrent mutations that have recently been described in Latin America.

METHODS

A literature search was performed in the electronic databases of PUBMED, EMBASE, LILACS, and BIREME using the terms BRCA1, BRCA2, founder mutation, Latin American population, and Hispanic. Sixty-two papers were identified, of which 38 were considered relevant for this review. Each result is shown per country.

RESULTS

In Latin America, clear founder effects have been reported in Mexico (BRCA1 del exons 9-12), Brazil (BRCA1 5382insC and BRCA2 c.156_157insAlu), and Colombia (BRCA1 3450del4, A1708E, and BRCA2 3034del4) and in Latinas residing in Southern California (BRCA1 185delAG, IVS5+1G>A, S955x, and R1443x). Of these, mutation BRCA1 3450del4 has also been reported in Brazil and Chile, whereas mutation BRCA2 3034del4 has been reported in Argentina and Peru. These data support the idea that although most Hispanic populations are the result of a mixture between Europeans, Africans, and Amerindians, the relative proportion of each genetic component varies throughout the Hispanic populations, making it necessary to identify the mutations characteristic of each population to generate mutation profiles adjusted to each one of them.

CONCLUSION

In Latin American countries, and even among regions of the same country, there is great heterogeneity of ancestors. Therefore, Latinas should not be analyzed like other population groups without taking into account their genetic ancestry. The presence of founder mutations in specific population groups represents a cost-effective analysis. The importance of determining the founder mutations lies mainly in the decrease in costs. If we manage to decrease costs, screenings could be offered more widely and cover a larger number of women.

IMPLICATIONS FOR PRACTICE

Hispanic and African-American populations are four to five times less likely than other populations worldwide to receive screening for BRCA mutations, a main reason being the high costs of these tools. The present study seeks to identify the prevalent mutations and the founder effect in the BRCA gene in the Hispanic population to address specific panels for this population group in the future and develop strategies for population screening.

Detection of somatic BRCA1/2 mutations in ovarian cancer - next-generation sequencing analysis of 100 cases

The overall prevalence of germline BRCA1/2 mutations is estimated between 11% and 15% of all ovarian cancers. Individuals with germline BRCA1/2 alterations treated with the PARP1 inhibitors (iPARP1) tend to respond better than patients with wild-type BRCA1/2. Additionally, also somatic BRCA1/2 alterations induce the sensitivity to iPARP1. Therefore, the detection of both germline and somatic BRCA1/2 mutations is required for effective iPARP1 treatment. The aim of this study was to identify the frequency and spectrum of germline and somatic BRCA1/2 alterations in a group of Polish patients with ovarian serous carcinoma. In total, 100 formalin-fixed paraffin-embedded (FFPE) ovarian serous carcinoma tissues were enrolled to the study. Mutational analysis of BRCA1/2 genes was performed by using next-generation sequencing. The presence of pathogenic variants was confirmed by Sanger sequencing. In addition, to confirm the germline or somatic status of the mutation, the nonneoplastic tissue was analyzed by bidirectional Sanger sequencing. In total, 27 (28% of patient samples) mutations (20 in BRCA1 and 7 in BRCA2) were identified. For 22 of 27 patients, nonneoplastic cells were available and sequencing revealed the somatic character of two BRCA1 (2/16; 12.5%) and two BRCA2 (2/6; 33%) mutations. Notably, we identified six novel frameshift or nonsense BRCA1/2 mutations. The heterogeneity of the detected mutations confirms the necessity of simultaneous analysis of BRCA1/2 genes in all patients diagnosed with serous ovarian carcinoma. Moreover, the use of tumor tissue for mutational analysis allowed the detection of both somatic and germline BRCA1/2 mutations.

Screening for common mutations in BRCA1 and BRCA2 genes: interest in genetic testing of Tunisian families with breast and/or ovarian cancer

BACKGROUND

In the Tunisian population, as yet a limited number of BRCA1/2 germline mutations have been reported in hereditary breast and/or ovarian cancer. These mutations are located in a few exons of BRCA1/2. The aim of the present study was to search for these mutations in 66 unrelated patients with hereditary breast and/or ovarian cancer in order to assess the interest in such a targeted approach for genetic testing in Tunisia.

MATERIALS AND METHODS

Blood specimens from the 66 Tunisian patients, with family history of breast and/or ovarian cancer, were collected at the Salah Azaiz Cancer Institute of Tunis. The exons 5, 20 and part of exon 11 of BRCA1 as well as part of exons 10 and 11 of BRCA2 were analyzed by Sanger sequencing.

RESULTS

12 patients had deleterious mutations in the BRCA1 or BRCA2 genes (18%), including a novel frame-shift mutation of BRCA1 (c.3751dup; 3780insT). Four distinct BRCA1 mutations were detected eight patients: c.5266dup (5382insC) and c.211dup (330insA) each in three patients, c.3751dup (3870insT) and c.4041_4042del (4160delAG) each in one patient. The four remaining cases all carried the same BRCA2 mutation, c.1310_1313del (1538delAAGA). Besides these deleterious mutations, eight polymorphisms and unclassified variants were detected, one of them being never reported (BRCA1c.3030T>G, p.Pro1010Pro).

CONCLUSION

In this study, we show that targeting relevant exons in BRCA1 and BRCA2 genes allows detection of a substantial percentage of mutations in the Tunisian population. Therefore such an approach may be of interest in genetic testing of high-risk breast and ovarian cancer families in Tunisia.

BRCA genetic screening in Middle Eastern and North African: mutational spectrum and founder BRCA1 mutation (c.798_799delTT) in North African

BACKGROUND

The contribution of BRCA1 mutations to both hereditary and sporadic breast and ovarian cancer (HBOC) has not yet been thoroughly investigated in MENA.

METHODS

To establish the knowledge about BRCA1 mutations and their correlation with the clinical aspect in diagnosed cases of HBOC in MENA populations. A systematic review of studies examining BRCA1 in BC women in Cyprus, Jordan, Egypt, Lebanon, Morocco, Algeria, and Tunisia was conducted.

RESULTS

Thirteen relevant references were identified, including ten studies which performed DNA sequencing of all BRCA1 exons. For the latter, 31 mutations were detected in 57 of the 547 patients ascertained. Familial history of BC was present in 388 (71%) patients, of whom 50 were mutation carriers. c.798_799delTT was identified in 11 North African families, accounting for 22% of total identified BRCA1 mutations, suggesting a founder allele. A broad spectrum of other mutations including c.68_69delAG, c.181T>G, c.5095C>T, and c.5266dupC, as well as sequence of unclassified variants and polymorphisms, was also detected.

CONCLUSION

The knowledge of genetic structure of BRCA1 in MENA should contribute to the assessment of the necessity of preventive programs for mutation carriers and clinical management. The high prevalence of BC and the presence of frequent mutations of the BRCA1 gene emphasize the need for improving screening programs and individual testing/counseling.

Identification of a novel BRCA2 and CHEK2 A-C-G-C haplotype in Turkish patients affected with breast cancer

BACKGROUND

Many breast cancers are caused by certain rare and familial mutations in the high or moderate penetrance genes BRCA1, BRCA2 and CHEK2. The aim of this study was to examine the allele and genotype frequencies of seven mutations in BRCA1, BRCA2 and CHEK2 genes in breast cancer patients and to investigate their isolated and combined associations with breast cancer risk.

METHODS

We genotyped seven mutations in BRCA1, BRCA2 and CHEK2 genes and then analyzed single variations and haplotype associations in 106 breast cancer patients and 80 healthy controls.

RESULTS

We found significant associations in the analyses of CHEK2- 1100delC (p=0.001) and BRCA1-5382insC (p=0.021) mutations in breast cancer patients compared to controls. The highest risk was observed among breast cancer patients carrying both CHEK2-1100delC and BRCA2- Met784Val mutations (OR=0.093; 95%CI 0.021-0.423; p=0.001). We identified one previously undescribed BRCA2 and a CHEK2 four-marker haplotype of A-C-G-C which was overrepresented (?2=7.655; p=0.0057) in the patient group compared to controls.

CONCLUSION

In this study, we identified a previously undescribed BRCA2 and CHEK2 A-C-G-C haplotype in association with the breast cancer in our population. Our results further suggest that the CHEK2-1100delC mutation in combination with BRCA2-Met784Val may lead to an unexpected high risk which needs to be confirmed in larger cohorts in order to better understand their role in the development and prognosis of breast cancer.

Frequency of 5382insC mutation of BRCA1 gene among breast cancer patients: an experience from Eastern India

The incidence of breast cancer in India is on the rise and is rapidly becoming the number one cancer in females pushing the cervical cancer to the second position. The mutations in two breast cancer susceptibility genes, BRCA1 and BRCA2, are frequently associated with familial breast cancer. The main objective of the study was to determine the frequency of the mutation 5382insC in BRCA1 of eastern Indian breast cancer patients and also study the hormonal receptor status and histopathology of the patients. Altogether 92 patients affected with breast cancer were included in this study. ARMS-PCR based amplification was used to detect the presence of mutation. The mutations were considered only after pedigree analysis. Out of 92 patients (age range: 20-77 years) with family history (57 individuals) and without family history (35 individuals) were screened. Fifty controls have been systematically investigated. Seven patients and two family members were found to be carriers of 5382insC mutation in BRCA1 gene. We have found 42.64 % ER(-)/PR(-) cancer and 20.58 % triple negative cancer. Invasive ductal carcinoma is the most common histology among the investigated individuals. The presented data confirm a noticeable contribution of BRCA1 5382insC mutation in BC development in Eastern India, which may justify an extended BRCA1 5382insC testing within this patient population. We found HER-2/neu negativity and BRCA1 positivity associated with familial breast cancer. From the hospital's patient history, it was revealed that the age of menarche plays an important role in development of breast cancer.

Mutation analysis of the ERCC4/FANCQ gene in hereditary breast cancer

The ERCC4 protein forms a structure-specific endonuclease involved in the DNA damage response. Different cancer syndromes such as a subtype of Xeroderma pigmentosum, XPF, and recently a subtype of Fanconi Anemia, FA-Q, have been attributed to biallelic ERCC4 gene mutations. To investigate whether monoallelic ERCC4 gene defects play some role in the inherited component of breast cancer susceptibility, we sequenced the whole ERCC4 coding region and flanking untranslated portions in a series of 101 Byelorussian and German breast cancer patients selected for familial disease (set 1, n = 63) or for the presence of the rs1800067 risk haplotype (set 2, n = 38). This study confirmed six known and one novel exonic variants, including four missense substitutions but no truncating mutation. Missense substitution p.R415Q (rs1800067), a previously postulated breast cancer susceptibility allele, was subsequently screened for in a total of 3,698 breast cancer cases and 2,868 controls from Germany, Belarus or Russia. The Gln415 allele appeared protective against breast cancer in the German series, with the strongest effect for ductal histology (OR 0.67; 95%CI 0.49; 0.92; p = 0.003), but this association was not confirmed in the other two series, with the combined analysis yielding an overall Mantel-Haenszel OR of 0.94 (95% CI 0.81; 1.08). There was no significant effect of p.R415Q on breast cancer survival in the German patient series. The other three detected ERCC4 missense mutations included two known rare variants as well as a novel substitution, p.E17V, that we identified on a p.R415Q haplotype background. The p.E17V mutation is predicted to be probably damaging but was present in just one heterozygous patient. We conclude that the contribution of ERCC4/FANCQ coding mutations to hereditary breast cancer in Central and Eastern Europe is likely to be small.

BRCA1 gene mutations frequency estimation by allele-specific real-time PCR of pooled genomic DNA samples

The frequencies of four mutations in the BRCA1 gene (185delAG, T300G, 4153delA, and 5382insC) were estimated in the Russian population. The mutations were analyzed in 7920 DNA samples obtained from randomly selected Novosibirsk citizens and 570 samples from breast cancer patients at Siberian hospitals. The mutations were detected by allele-specific real-time PCR. The mutation analysis was performed with pooled DNA samples to reduce the cost of the study. The 5382insC mutation was found in 20 of 7920 (0.25%) population DNA samples and in 14 of 570 (2.46%) breast cancer samples; the T300G mutation was detected in 4 population samples (0.05%) and in 2 breast cancer samples (0.35%); the 185delAG or 4153delA mutations were not identified in any of the 7920 samples and were detected in 1 (0.18%) breast cancer case each.

Validation of three BRCA1/2 mutation-carrier probability models Myriad, BRCAPRO and BOADICEA in a population-based series of 183 German families

Many studies have evaluated the performance of risk assessment models for BRCA1/2 mutation carrier probabilities in different populations, but to our knowledge very few studies have been conducted in the German population so far. In the recent study, we validated the performance of three risk calculation models by names BRCAPRO, Myriad and BOADICEA in 183 German families who had undergone molecular testing of mutations in BRCA1 and BRCA2 with an indication based on clinical criteria regarding their family history of cancer. The sensitivity and specificity at the conventional threshold of 10% as well as for a threshold of 20% were evaluated. The ability to discriminate between carriers and non-carriers was judged by the area under the receiver operating characteristics curve. We further focused on the performance characteristic of these models in patients carrying large genomic rearrangements as a subtype of mutations which is currently gaining increasing importance. BRCAPRO and BOADICEA performed almost equally well in our patient population, but we found a lack of agreement to Myriad. The results obtained from this study were consistent with previously published results from other population and racial/ethnic groups. We suggest using model specific decision thresholds instead of the recommended universal value of 10%. We further suggest integrating the CaGene5 software package, which includes BRCAPRO and Myriad, in the genetic counselling of German families with suspected inherited breast and ovarian cancer because of the good performance of BRCAPRO and the substantial ease of use of this software.

Mutation analysis of BRCA1, BRCA2, PALB2 and BRD7 in a hospital-based series of German patients with triple-negative breast cancer

Triple-negative breast cancer (TNBC) is an aggressive form of breast carcinoma with a poor prognosis. Recent evidence suggests that some patients with TNBC harbour germ-line mutations in DNA repair genes which may render their tumours susceptible to novel therapies such as treatment with PARP inhibitors. In the present study, we have investigated a hospital-based series of 40 German patients with TNBC for the presence of germ-line mutations in BRCA1, BRCA2, PALB2, and BRD7 genes. Microfluidic array PCR and next-generation sequencing was used for BRCA1 and BRCA2 analysis while conventional high-resolution melting and Sanger sequencing was applied to study the coding regions of PALB2 and BRD7, respectively. Truncating mutations in BRCA1 were found in six patients, and truncating mutations in BRCA2 and PALB2 were detected in one patient each, whereas no truncating mutation was identified in BRD7. One patient was a double heterozygote for the PALB2 mutation, c.758insT, and a BRCA1 mutation, c.927delA. Our results confirm in a hospital-based setting that a substantial proportion of German TNBC patients (17.5%) harbour germ-line mutations in genes involved in homology-directed DNA repair, with a preponderance of BRCA1 mutations. Triple-negative breast cancer should be considered as an additional criterion for future genetic counselling and diagnostic sequencing.

Prevalence of the BRCA1 founder mutation c.5266dupin Brazilian individuals at-risk for the hereditary breast and ovarian cancer syndrome

About 5-10% of breast and ovarian carcinomas are hereditary and most of these result from germline mutations in the BRCA1 and BRCA2 genes. In women of Ashkenazi Jewish ascendance, up to 30% of breast and ovarian carcinomas may be attributable to mutations in these genes, where 3 founder mutations, c.68_69del (185delAG) and c.5266dup (5382insC) in BRCA1 and c.5946del (6174delT) in BRCA2, are commonly encountered. It has been suggested by some authors that screening for founder mutations should be undertaken in all Brazilian women with breast cancer. Thus, the goal of this study was to determine the prevalence of three founder mutations, commonly identified in Ashkenazi individuals in a sample of non-Ashkenazi cancer-affected Brazilian women with clearly defined risk factors for hereditary breast and ovarian cancer (HBOC) syndrome. Among 137 unrelated Brazilian women from HBOC families, the BRCA1c.5266dup mutation was identified in seven individuals (5%). This prevalence is similar to that encountered in non-Ashkenazi HBOC families in other populations. However, among patients with bilateral breast cancer, the frequency of c.5266dup was significantly higher when compared to patients with unilateral breast tumors (12.1% vs 1.2%, p = 0.023). The BRCA1 c.68_69del and BRCA2 c.5946del mutations did not occur in this sample. We conclude that screening non-Ashkenazi breast cancer-affected women from the ethnically heterogeneous Brazilian populations for the BRCA1 c.68_69del and BRCA2 c.5946del is not justified, and that screening for BRCA1c.5266dup should be considered in high risk patients, given its prevalence as a single mutation. In high-risk patients, a negative screening result should always be followed by comprehensive BRCA gene testing. The finding of a significantly higher frequency of BRCA1 c.5266dup in women with bilateral breast cancer, as well as existence of other as yet unidentified founder mutations in this population, should be further assessed in a larger well characterized high-risk cohort.

Mutation analysis of the SLX4/FANCP gene in hereditary breast cancer

SLX4 coordinates three structure-specific endonucleases in the DNA damage response. One subtype of Fanconi anaemia, FA-P, has recently been attributed to biallelic SLX4 gene mutations. To investigate whether monoallelic SLX4 gene defects play some role in the inherited component of breast cancer susceptibility, in this study we resequenced the whole SLX4 coding region and flanking untranslated sections in genomic DNA samples obtained from a total of 52 German or Byelorussian patients with familial breast cancer. Selected variants were subsequently screened by RFLP or TaqMan-based assays in an extended set of 965 German breast cancer cases and 985 healthy female controls. The resequencing study uncovered four new SLX4 missense substitutions, each of them in a single breast cancer patient. Three missense substitutions (p.V197A, p.G700R and p.R1034H) were not found in a subsequent screening of 240 additional breast cancer patients, while one missense substitution (p.R237Q) was more common and was detected in a total of 12 cases (1.3%) and seven controls (0.7%) in the Hannover breast cancer study. The rare missense substitution, p.G700R, resides in the conserved BTB domain and was in silico predicted to be pathogenic. Seven additional missense polymorphisms were correlated and formed one haplotype which was, however, neither associated with breast cancer risk nor with survival from breast cancer. In summary, this study did not reveal truncating or clearly pathogenic mutations, but unravelled four new unclassified missense variants at a low frequency. We conclude that there is no evidence for a major role of SLX4 coding variants in the inherited susceptibility towards breast cancer in German and Byelorussian patients, although very rare mutations such as the p.G700R substitution could make a minor contribution.

Hereditary breast cancer in Middle Eastern and North African (MENA) populations: identification of novel, recurrent and founder BRCA1 mutations in the Tunisian population

Germ-line mutations in BRCA1 breast cancer susceptibility gene account for a large proportion of hereditary breast cancer families and show considerable ethnic and geographical variations. The contribution of BRCA1 mutations to hereditary breast cancer has not yet been thoroughly investigated in Middle Eastern and North African populations. In this study, 16 Tunisian high-risk breast cancer families were screened for germline mutations in the entire BRCA1 coding region and exon-intron boundaries using direct sequencing. Six families were found to carry BRCA1 mutations with a prevalence of 37.5%. Four different deleterious mutations were detected. Three truncating mutations were previously described: c.798_799delTT (916 delTT), c.3331_3334delCAAG (3450 delCAAG), c.5266dupC (5382 insC) and one splice site mutation which seems to be specific to the Tunisian population: c.212 + 2insG (IVS5 + 2insG). We also identified 15 variants of unknown clinical significance. The c.798_799delTT mutation occurred at an 18% frequency and was shared by three apparently unrelated families. Analyzing five microsatellite markers in and flanking the BRCA1 locus showed a common haplotype associated with this mutation. This suggests that the c.798_799delTT mutation is a Tunisian founder mutation. Our findings indicate that the Tunisian population has a spectrum of prevalent BRCA1 mutations, some of which appear as recurrent and founding mutations.

High frequency and allele-specific differences of BRCA1 founder mutations in breast cancer and ovarian cancer patients from Belarus

Breast cancer and ovarian cancer are common malignancies in Belarus accounting for about 3500 and 800 new cases per year, respectively. For breast cancer, the rates and age of onset appear to vary significantly in regions differentially affected by the Chernobyl accident. We assessed the frequency and distribution of three BRCA1 founder mutations 5382insC, 4153delA and Cys61Gly in two hospital-based series of 1945 unselected breast cancer patients and of 201 unselected ovarian cancer patients from Belarus as well as in 1019 healthy control females from the same population. Any of these mutations were identified in 4.4% of the breast cancer patients, 26.4% of the ovarian cancer patients and 0.5% of the controls. In the breast cancer patients, BRCA1 mutations were strongly associated with earlier age at diagnosis, with oestrogen receptor (ER) negative tumours and with a first-degree family history of breast cancer, although only 35% of the identified BRCA1 mutation carriers had such a family history. There were no marked differences in the regional distribution of BRCA1 mutations, so that the significant differences in age at diagnosis and family history of breast cancer patients from areas afflicted by the Chernobyl accident could not be explained by BRCA1. We next observed a higher impact and a shifted mutational spectrum of BRCA1 in the series of Byelorussian ovarian cancer patients where the three founder mutations accounted for 26.4% (53/201). While the Cys61Gly mutation appeared underrepresented in ovarian cancer as compared with breast cancer cases from the same population (p = 0.01), the 4153delA mutation made a higher contribution to ovarian cancer than to breast cancer (p < 0.01). BRCA1 mutations were significantly enriched among ovarian cancer cases with a first-degree family history of breast or ovarian cancer, whereas the median age at ovarian cancer diagnosis was not different between mutation carriers and non-carriers. Taken together, these results identify three BRCA1 founder mutations as key components of inherited breast and ovarian cancer susceptibility in Belarus and might have implications for cancer prevention, treatment and genetic counselling in this population.

On the origin and diffusion of BRCA1 c.5266dupC (5382insC) in European populations

The BRCA1 mutation c.5266dupC was originally described as a founder mutation in the Ashkenazi Jewish (AJ) population. However, this mutation is also present at appreciable frequency in several European countries, which raises intriguing questions about the origins of the mutation. We genotyped 245 carrier families from 14 different population groups (Russian, Latvian, Ukrainian, Czech, Slovak, Polish, Danish, Dutch, French, German, Italian, Greek, Brazilian and AJ) for seven microsatellite markers and confirmed that all mutation carriers share a common haplotype from a single founder individual. Using a maximum likelihood method that allows for both recombination and mutational events of marker loci, we estimated that the mutation arose some 1800 years ago in either Scandinavia or what is now northern Russia and subsequently spread to the various populations we genotyped during the following centuries, including the AJ population. Age estimates and the molecular evolution profile of the most common linked haplotype in the carrier populations studied further suggest that c.5266dupC likely entered the AJ gene pool in Poland approximately 400-500 years ago. Our results illustrate that (1) BRCA1 c.5266dupC originated from a single common ancestor and was a common European mutation long before becoming an AJ founder mutation and (2) the mutation is likely present in many additional European countries where genetic screening of BRCA1 may not yet be common practice.

Founder BRCA1/2 mutations in the Europe: implications for hereditary breast-ovarian cancer prevention and control

Detection of mutations in hereditary breast and ovarian cancer-related BRCA1 and BRCA2 genes is an effective method of cancer prevention and early detection. Different ethnic and geographical regions have different BRCA1 and BRCA2 mutation spectrum and prevalence. Along with the emerging targeted therapy, demand and uptake for rapid BRCA1/2 mutations testing will increase in a near future. However, current patients selection and genetic testing strategies in most countries impose significant lag in this practice. The knowledge of the genetic structure of particular populations is important for the developing of effective screening protocol and may provide more efficient approach for the individualization of genetic testing. Elucidating of founder effect in BRCA1/2 genes can have an impact on the management of hereditary cancer families on a national and international healthcare system level, making genetic testing more affordable and cost-effective. The purpose of this review is to summarize current evidence about the BRCA1/2 founder mutations diversity in European populations.

Contribution of BRCA1 germ-line mutations to breast cancer in Greece: a hospital-based study of 987 unselected breast cancer cases

Background:

In most Western populations, 5–10% of all breast cancer cases can be attributed to major genetic factors such as predisposing mutations in BRCA1 and BRCA2, with early-onset cases generally considered as an indicator of genetic susceptibility. Specific BRCA1 and BRCA2 mutations or different mutation frequencies have been identified in specific populations and ethnic groups. Previous studies in Greek breast and/or ovarian cancer patients with family history have shown that four specific BRCA1 mutations, c.5266dupC, G1738R, and two large genomic rearrangements involving deletions of exons 20 and 24, have a prominent function in the population's BRCA1 and BRCA2 mutation spectrum.

Methods:

To estimate the frequency of the above mutations in unselected Greek breast cancer women, we screened 987 unselected cases independently of their family history, collected from major Greek hospitals.

RESULTS: Of the 987 patients, 26 (2.6%) were found to carry one of the above mutations in the BRCA1 gene: 13 carried the c.5266dupC mutation (1.3%), 6 carried the exon 24 deletion (0.6%), 3 carried the exon 20 deletion (0.3%), and 4 carried the G1738R mutation (0.4%). Among 140 patients with early-onset breast cancer (<40 years), 14 carried one of the four mutations (10.0%).

Conclusion:

These results suggest that a low-cost genetic screening for only the four prominent BRCA1 mutations may be advisable to all early-onset breast cancer patients of Greek origin.

Founder effect of the BRCA1 5382insC mutation in Brazilian patients with hereditary breast ovary cancer syndrome

The 5382insC mutation in BRCA1 is a frequently reported mutation, being very prevalent in Central and Eastern Europe. This mutation was recurrently reported in Brazil and one case was reported Portugal, but not in Spain and other South-American countries,. We analyzed the haplotypic profile of seven Brazilian carriers of 5382insC to characterize a possible founder effect. The analyses indicated that mutation carriers shared an identical haplotype. The absence of this mutation in Spain, other South American countries, and sub-Saharan populations, as well as the patients' own ancestry, point to a significant Central or Eastern European contribution to the present genetic background of Brazilian population, different from the population structuring of remaining South American countries.

Rapid detection of carriers with BRCA1 and BRCA2 mutations using high resolution melting analysis

BACKGROUND

Germline inactivating mutations in BRCA1 and BRCA2 underlie a major proportion of the inherited predisposition to breast and ovarian cancer. These mutations are usually detected by DNA sequencing. Cost-effective and rapid methods to screen for these mutations would enable the extension of mutation testing to a broader population. High resolution melting (HRM) analysis is a rapid screening methodology with very low false negative rates. We therefore evaluated the use of HRM as a mutation scanning tool using, as a proof of principle, the three recurrent BRCA1 and BRCA2 founder mutations in the Ashkenazi Jewish population in addition to other mutations that occur in the same regions.

METHODS

We designed PCR amplicons for HRM scanning of BRCA1 exons 2 and 20 (carrying the founder mutations185delAG and 5382insC respectively) and the part of the BRCA2 exon 11 carrying the 6174delT founder mutation. The analysis was performed on an HRM-enabled real time PCR machine.

RESULTS

We tested DNA from the peripheral blood of 29 individuals heterozygous for known mutations. All the Ashkenazi founder mutations were readily identified. Other mutations in each region that were also readily detected included the recently identified Greek founder mutation 5331G>A in exon 20 of BRCA1. Each mutation had a reproducible melting profile.

CONCLUSION

HRM is a simple and rapid scanning method for known and unknown BRCA1 and BRCA2 germline mutations that can dramatically reduce the amount of sequencing required and reduce the turnaround time for mutation screening and testing. In some cases, such as tracking mutations through pedigrees, sequencing may only be necessary to confirm positive results. This methodology will allow for the economical screening of founder mutations not only in people of Ashkenazi Jewish ancestry but also in other populations with founder mutations such as Central and Eastern Europeans (BRCA1 5382insC) and Greek Europeans (BRCA1 5331G>A).

Mutation analysis of the MDM4 gene in German breast cancer patients

Background

MDM4 is a negative regulator of p53 and cooperates with MDM2 in the cellular response to DNA damage. It is unknown, however, whether MDM4 gene alterations play some role in the inherited component of breast cancer susceptibility.

Methods

We sequenced the whole MDM4 coding region and flanking untranslated regions in genomic DNA samples obtained from 40 German patients with familial breast cancer. Selected variants were subsequently screened by RFLP-based assays in an extended set of breast cancer cases and controls.

Results

Our resequencing study uncovered two MDM4 coding variants in 4/40 patients. Three patients carried a silent substitution at codon 74 that was linked with another rare variant in the 5'UTR. No association of this allele with breast cancer was found in a subsequent screening of 133 patients with bilateral breast cancer and 136 controls. The fourth patient was heterozygous for the missense substitution D153G which is located in a less conserved region of the MDM4 protein but may affect a predicted phosphorylation site. The D153G substitution only partially segregated with breast cancer in the family and was not identified on additional 680 chromosomes screened.

Conclusion

This study did not reveal clearly pathogenic mutations although it uncovered two new unclassified variants at a low frequency. We conclude that there is no evidence for a major role of MDM4 coding variants in the inherited susceptibility towards breast cancer in German patients.

Nijmegen Breakage Syndrome mutations and risk of breast cancer

Mutations in the NBS1 gene have been identified as disease-causing mutations in patients with Nijmegen Breakage Syndrome (NBS), but their clinical impact on breast cancer susceptibility has remained uncertain. We determined the frequency of 2 NBS mutations, 657del5 and R215W, in two large series of breast cancer cases and controls from Northern Germany and from the Republic of Belarus. The 5-bp-deletion 657del5 was identified in 15/1,588 cases (0.9%) from Belarus and in 1/1,076 cases (0.1%) from Germany but in only 1/1,014 population controls from Belarus and 0/1017 German controls (p < 0.01). The missense substitution R215W was observed in 9/1,588 Byelorussian and 9/1,076 German patients (0.6% and 0.8%, respectively) but was also present in 5/1,014 Byelorussian and 2/1,017 German control individuals (adjusted OR = 1.9, 95%CI 0.8-4.6, p = 0.18). Studies of lymphoblastoid cell lines revealed that NBS1/p95 protein levels were reduced to 70% in cells from a heterozygous breast cancer patient carrying R215W and to 15% in cells from a NBS patient compound heterozygous for 657del5/R215W suggesting that the R215W substitution may be associated with protein instability. Levels of radiation-induced phosphorylation of Nbs1/p95(Ser343) were reduced to 60% and 35% of wildtype, respectively. Neither age at diagnosis nor family history of breast cancer differed significantly between carriers and noncarriers of NBS mutations. The combined data are in line with an about 3-fold increase in breast cancer risk for female NBS heterozygotes (OR 3.1; 95%CI 1.4-6.6) and indicate that the 657del5 deletion and perhaps the R215W substitution contribute to inherited breast cancer susceptibility in Central and Eastern Europe.

Breast cancer risk associated with BRCA1 and BRCA2 in diverse populations

Germline mutations in the BRCA1 or BRCA2 tumour-suppressor genes are strong predictors of breast and/or ovarian cancer development. The contribution of these mutations to breast cancer risk within any specific population is a function of both their prevalence and their penetrance. Mutation prevalence varies among ethnic groups and may be influenced by founder mutations. Penetrance can be influenced by mutation-specific phenotypes and the potential modifying effects of the patient's own genetic and environmental background. Although estimates of both mutation prevalence and mutation penetrance rates are inconsistent and occasionally controversial, understanding them is crucial for providing accurate risk information to each patient.

NBS1 variant I171V and breast cancer risk

The NBS1/p95 protein has a pivotal role in the sensing and repair of chromosome breaks. A missense mutation in the NBS1 gene, I171V, has recently been associated with a ninefold increased risk of breast cancer in Polish patients. Positive associations have also been reported for leukaemia and larynx cancer suggesting that I171V could be a more general susceptibility factor for malignancies. We investigated the prevalence of this mutation in two large hospital-based case-control series from Germany and from the Republic of Belarus. The I171V substitution was detected in 20/1,636 Byelorussian breast cancer patients and in 18/1,014 Byelorussian controls (OR: 0.68; 95%CI: 0.36-1.30, P=0.3). The I171V substitution was furthermore detected in 10/1,048 German breast cancer patients and in 7/1,017 German controls (OR: 1.39; 95%CI: 0.53-3.67, P=0.7). There were no significant differences between I171V carriers and non-carriers among the cases with regard to age at diagnosis, family history or bilateral occurrence of disease. A meta-analysis of all hitherto available studies did not reveal a difference in the prevalence of I171V between breast cancer cases and controls (OR: 1.05; 95%CI: 0.64-1.74, P=0.9). We conclude that the I171V substitution is unlikely to constitute a strong risk factor for breast cancer in our study populations.

Founder mutations in BRCA1 and BRCA2 genes

BRCA1 and BRCA2 germline mutations contribute to a significant number of familial and hereditary breast and/or ovarian cancers. The proportion of high-risk families with breast and/or ovarian cancer cases due to mutations in these tumor suppressor genes varies widely among populations. In some population, a wide spectrum of different mutations in both genes are present, whereas in other groups specific mutations in BRCA1 and BRCA2 have been reported with high frequency. Most of these mutations are prevalent in restricted populations as consequence of a founder effect. The comparison of haplotypes between families with the same mutation can distinguish whether high-frequency alleles derive from an older or more recent single mutational event or whether they have arisen independently more than once. Here, we review some of the most well-known and significant examples of founder mutations in BRCA genes found in European and non-European populations. In conclusion, the identification of the ethnic group of families undergoing genetic counseling enables the geneticist and oncologist to make more specific choices, leading to simplify the clinical approach to genetic testing carried out on members of high-risk families. Futhermore, the high frequency of founder mutations, allowing to analyze a large number of cases, might provide accurate information regarding their penetrance.

Greek BRCA1 and BRCA2 mutation spectrum: two BRCA1 mutations account for half the carriers found among high-risk breast/ovarian cancer patients

127 Greek breast/ovarian cancer families were screened for germline BRCA1/2 mutations by dHPLC followed by direct sequencing. Our results indicated 16 and 5 breast/ovarian cancer families bearing deleterious mutations in the BRCA1 and BRCA2 genes, respectively. Two novel BRCA2 germline mutations (G4X and 3783del10) are reported here for the first time. Subsequent compilation of our present findings with previously reported mutation data reveals that in a total of 287 Greek breast/ovarian cancer families, 46 and 13 carry a deleterious mutation in BRCA1 and BRCA2, respectively. It should be noted that two BRCA1 mutations, 5382insC and G1738R, both located in exon 20, account for 46% of the families found to carry a mutation. Based on our mutation analysis results, we propose here a hierarchical, cost-effective BRCA1/2 mutation screening protocol for individuals of Greek ethnic origin. The suggested protocol can impact on the clinical management of breast-ovarian cancer families on a national healthcare system level.

Ashkenazi Jews and breast cancer: the consequences of linking ethnic identity to genetic disease

We explored the advantages and disadvantages of using ethnic categories in genetic research. With the discovery that certain breast cancer gene mutations appeared to be more prevalent in Ashkenazi Jews, breast cancer researchers moved their focus from high-risk families to ethnicity. The concept of Ashkenazi Jews as genetically unique, a legacy of Tay-Sachs disease research and a particular reading of history, shaped this new approach even as methodological imprecision and new genetic and historical research challenged it. Our findings cast doubt on the accuracy and desirability of linking ethnic groups to genetic disease. Such linkages exaggerate genetic differences among ethnic groups and lead to unequal access to testing and therapy.

High frequency of BRCA1 5382insC mutation in Russian breast cancer patients

BRCA1 5382insC variant was repeatedly detected in Jewish breast cancer (BC) families residing in USA and Israel as well as in non-Jewish familial BC patients from Poland, Latvia, Hungary, Russia and some other European countries. However, the distribution of BRCA1 5382insC mutation in unselected BC cases vs. controls has been systematically investigated mainly in Ashkenazi Jews. Here we applied a case-control study design in order to evaluate the impact of BRCA1 5382insC allele on BC incidence in St Petersburg, Russia. High frequency of the BRCA1 5382insC allele was detected in a group of bilateral breast cancer patients (10.4%; 15/144). Randomly selected unilateral BC cases demonstrated noticeable occurrence of BRCA1 5382insC mutation as well (3.7%; 32/857), with evident excess of the carriers in the early-onset (40 years) category (6.1%; 6/99) and in patients reporting breast and/or ovarian tumours in first-degree relatives (11.3%; 11/97). Strikingly, none of 478 middle-aged controls and 344 elderly tumour-free women carried the 5382insC variant. The presented data confirm a noticeable contribution of BRCA1 5382insC mutation in BC development in Russia, that may justify an extended BRCA1 5382insC testing within this population.

High prevalence of two BRCA1 mutations, 4154delA and 5382insC, in Latvia

Our aim was to characterise the germline BRCA1 mutation profile in Latvian breast cancer and ovarian cancer patients, to develop an effective BRCA1 gene mutation detection strategy, and to document genotype-phenotype correlations in mutation carriers. The entire BRCA1 gene was analysed in 75 breast cancer and 30 ovarian cancer patients. Screening for three mutations (5382insC, 4154delA and 300T>G) was carried out in 55 breast cancer and 66 ovarian cancer patients, and for two mutations, 5382insC and 4154delA, in 376 unselected patients with any cancer (including 51 breast cancer and 29 ovarian cancers) and 215 women with any gynaecological tumour. Mutation detection techniques used were SSCP/HD analysis or F-SSCP (ABI PRISM 310). Five different deleterious mutations were detected by analysis of the entire BRCA1 gene. The proportion of cases with mutations amongst 50 breast cancer patients diagnosed before 48 years was 26.0% (95% CI: 14.6-40.3%). Two mutations (5382insC and 4154delA) made up more than 80% of all mutations identified by the analysis of the entire BRCA1 gene in Latvia, at present. Further screening for only the prevalent mutations in different cancer patient groups resulted in the identification of 53 more mutation carriers. We conclude that breast cancer diagnosed before the age of 48 years and ovarian cancer before 65 years are criteria for DNA testing to be offered to women in Latvia, regardless of cancer history in the family. The observed associations of specific prevalent mutations with cancer site and age at onset of disease are discussed.

Association of two mutations in the CHEK2 gene with breast cancer

The 1100delC mutation of the cell cycle checkpoint kinase 2 (CHEK2) gene confers an increased risk for breast cancer, but the clinical impact of other CHEK2 gene variants remains unclear. We determined the frequency of two functionally relevant CHEK2 gene mutations, I157T and IVS2+1G > A, in two large series of breast cancer cases and controls from two independent populations. Our first series consisted of a hospital-based cohort of 996 German breast cancer cases and 486 population controls, and the second series consisted of 424 breast cancer patients and 307 population controls from the Republic of Belarus. The missense substitution I157T was identified in 22/996 cases (2.2%) vs. 3/486 controls (0.6%; OR = 3.6, 95% CI 1.1-12.2, p = 0.044) in the German population and in 24/424 cases (5.7%) vs. 4/307 controls (1.3%; OR = 4.5, 95% CI 1.6-13.2, p = 0.005) in the Byelorussian cohorts. The splicing mutation IVS2+1G > A was infrequent in both populations, being observed in 3/996 German and 4/424 Byelorussian patients (0.3% and 0.9%, respectively) and in 1/486 German controls (0.2%; adjusted OR = 4.0, 95% CI 0.5-30.8, p = 0.273). Heterozygous CHEK2 mutation carriers tended to be diagnosed at an earlier age in both populations, but these differences did not reach statistical significance. Family history of breast cancer did not differ between carriers and noncarriers. Our data indicate that the I157T allele, and possibly the IVS2+1G > A allele, of the CHEK2 gene contribute to inherited breast cancer susceptibility.

High proportion of recurrent germline mutations in the BRCA1 gene in breast and ovarian cancer patients from the Prague area

Background

Germline mutations in the BRCA1 and BRCA2 genes have been shown to account for the majority of hereditary breast and ovarian cancers. The purpose of our study was to estimate the incidence and spectrum of pathogenic mutations in BRCA1/2 genes in high-risk Czech families.

Methods

A total of 96 Czech families with recurrent breast and/or ovarian cancer and 55 patients considered to be at high-risk but with no reported family history of cancer were screened for mutations in the BRCA1/2 genes. The entire coding sequence of each gene was analyzed using a combination of the protein truncation test and direct DNA sequencing.

Results

A total of 35 mutations in the BRCA1/2 genes were identified in high-risk families (36.5%). Pathogenic mutations were found in 23.3% of breast cancer families and in 59.4% of families with the occurrence of both breast and ovarian cancer. In addition, four mutations were detected in 31 (12.9%) women with early onset breast cancer. One mutation was detected in seven (14.3%) patients affected with both a primary breast and ovarian cancer and another in three (33.3%) patients with a bilateral breast cancer. A total of 3 mutations in BRCA1 were identified among 14 (21.4%) women with a medullary breast carcinoma. Of 151 analyzed individuals, 35 (23.2%) carried a BRCA1 mutation and 9 (6.0%) a BRCA2 mutation. One novel truncating mutation was found in BRCA1 (c.1747A>T) and two in BRCA2 (c.3939delC and c.5763dupT). The 35 identified BRCA1 mutations comprised 13 different alterations. Three recurrent mutations accounted for 71.4% of unrelated individuals with detected gene alterations. The BRCA1 c.5266dupC (5382insC) was detected in 51.4% of mutation positive women. The mutations c.3700_3704del5 and c.181T>G (300T>G) contributed to 11.4% and 8.6% of pathogenic mutations, respectively. A total of eight different mutations were identified in BRCA2. The novel c.5763dupT mutation, which appeared in two unrelated families, was the only recurrent alteration of the BRCA2 gene identified in this study.

Conclusion

Mutational analysis of BRCA1/2 genes in 151 high-risk patients characterized the spectrum of gene alterations and demonstrated the dominant role of the BRCA1 c.5266dupC allele in hereditary breast and ovarian cancer.

BRCA1 Mutations in a Population-based Study of Breast Cancer in Stockholm County

The mutation frequency of BRCA1 and BRCA2 in women with breast cancer varies according to family history, age at diagnosis and ethnicity. The contribution of BRCA1 and BRCA2 mutations in breast cancer populations, unselected for age and family history, has been examined in several studies reporting mutation frequencies between 1% and 12% by screening methods, population sizes, and to what extent the gene/s were screened differed in the studies. We wanted to clarify the proportion of breast cancer attributable to mutations in BRCA1 in an unselected breast cancer population from the Stockholm region. All incident breast cancer patients treated surgically in a 19-month period were eligible for the study and 70% (489/696) participated. Exon 11 of BRCA1 was screened for mutations using the protein truncation test, and the mutation frequency was estimated from that. In previous studies on high-risk families from Stockholm, more than 70% of the mutations were detected in exon 11. Two mutations were found, both in patients with a family history or their own medical history of ovarian cancer, giving a mutation frequency in exon 11 of 0.4% and an estimated BRCA1 mutation frequency of <1%. Mutations in BRCA1 in unselected breast cancer cases in our region are rare and likely to be found only in high-risk families. Our BRCA1 prevalence is the lowest of all studies on unselected breast cancer patients, probably reflecting the comparatively low rates detected also in high-risk breast cancer families from the region.

BRCA1 and BRCA2 mutations among breast cancer patients from the Philippines

Age-adjusted incidence rates of breast cancer vary more than 10-fold worldwide, with the highest rates reported in North America and Europe. The highest breast cancer incidence rates in Southeast Asia have been reported for the Manila Cancer Registry in the Philippines, with an age-standardized rate of 47.7 per 100,000 per year. The possible contribution of hereditary factors to these elevated rates has not been investigated. We conducted a case-control study of 294 unselected incident breast cancer cases and 346 female controls from Manila, Philippines. Cases and controls were selected from women below the age of 65 undergoing evaluation at the PGH in Manila because of a suspicious breast mass. Molecular analysis identified 12 BRCA2 mutations and 3 BRCA1 mutations. We estimate the prevalence of BRCA mutations among unselected breast cancer cases in the Philippines to be 5.1% (95% CI: 2.6-7.6%), with a prevalence of 4.1% (95% CI: 1.8-6.4%) for BRCA2 mutations alone. The BRCA2 4265delCT and 4859delA mutations were found in 2 and 4 unrelated cases, respectively; haplotype analysis confirmed that these, and the BRCA1 5454delC mutation, are founder mutations. BRCA2 mutations were also found in 2 of 346 controls (0.6%; 95% CI: 0.2-1.4%). Compared with non-carrier cases, the cumulative risk of breast cancer for first-degree relatives of mutation carriers was 24.3% to age 50, compared with <4% for first-degree relatives of non-carrier cases (RR = 6.6; 95% CI: 2.6-17.2; p= 7.5 x 10(-6)). Our data suggest that penetrance of BRCA mutations is not reduced in the Philippines. Germline mutations in the BRCA2 gene contribute more than mutations BRCA1 to breast cancer in the Philippines, due in large part to the presence of 2 common founder mutations.

Comprehensive analysis of 989 patients with breast or ovarian cancer provides BRCA1 and BRCA2 mutation profiles and frequencies for the German population

The main focus of this German-wide multi-center study was to establish a BRCA1/2 mutation profile and to determine family types with high frequencies of mutations in these genes. In a comprehensive study, the entire coding sequences of the breast cancer genes BRCA1 and BRCA2 were analyzed in 989 unrelated patients from German breast/ovarian cancer families. A total of 77 BRCA1 and 63 BRCA2 distinct deleterious mutations were found in 302 patients. More than (1/3) of these mutations are novel and might be specific for the German population. Eighteen common mutations were found in 68% of cases in BRCA1 and 13 recurrent mutations in 44% of cases in BRCA2, facilitating prescreening approaches. Haplotype analysis indicate that 14 out of 20 recurrent mutations are likely originating from a common founder. An additional 50 different rare sequence variants with unknown relevance for tumorigenesis were found in 72 families. Correlation of BRCA1/BRCA2 detection rates with family history identified families with both breast and ovarian cancer to be at highest risk for BRCA1/BRCA2 mutations (43% and 10%, respectively), followed by families with at least 2 premenopausal cases of breast cancer (24% BRCA1 and 13% BRCA2 mutations). These data provide strong evidence for further predisposing genes in the German population. In breast cancer families with 2 or 3 affected females but only a single or no premenopausal case, mutations were detected with low frequencies (about 10% or less for both genes). The decision for or against molecular diagnosis is now aided by considering the expected mutation detection rates that greatly depend on family history and structure.

Uncovering functionally relevant signaling pathways using microarray-based expression profiling

The introduction of microarray technology to the scientific and medical communities has fundamentally altered the way in which we now address basic biomedical questions. Microarrays technology facilitates a more complete and inclusive experimental approach where alterations in the transcript level of entire genomes can be simultaneously assayed in response to a variety of stimuli. Conceptually different approaches to the development of microarray technology have resulted in the generation of two different array formats: oligonucleotide arrays and cDNA arrays. The application of microarray and related technologies to identify specific targets of defined genes that have clearly been implicated in cancer progression requires a specific experimental approach. The objective of this approach is to define changes in transcriptional profile that occur in response to modulating the expression level of the gene to be studied. The resulting altered expression profile can then be viewed as a blueprint by which that gene effects its cellular function. We have used oligonucleotide array-based expression profiling in collaboration with Affymetrix to identify downstream transcriptional targets of the BRCA1 tumor-suppressor gene as a means of defining its function. BRCA1 has been implicated in at least three functional pathways, namely, mediating the cellular response to DNA damage, as a cell cycle checkpoint protein and in the regulation of transcription. The physiological significance of these properties and their implications for the function of BRCA1 as a tumor-suppressor gene remain to be defined.

High frequency of recurrent mutations in BRCA1 and BRCA2 genes in Polish families with breast and ovarian cancer

Germ-line mutations in BRCA1 and BRCA2 genes result in a significantly increased risk of breast and ovarian cancer. Other genes involved in an increased predisposition to breast cancer include the TP53 gene, mutated in Li-Fraumeni syndrome. To estimate the frequency of germ-line mutations in these three genes in Upper Silesia, we have analyzed 47 breast/ovarian cancer families from that region. We found five different disease predisposing mutations in 17 (36%) families. Twelve families (25.5%) carried known BRCA1 mutations (5382insC and C61G), four families (8.5%) carried novel BRCA2 mutations (9631delC and 6886delGAAAA), and one family (2%) harbored novel mutation 1095del8 in the TP53 gene, which is the largest germline deletion in coding sequence of this gene identified thus far. The 5382insC mutation in BRCA1 was found in 11 families and the 9631delC mutation in BRCA2 occurred in three families. These two mutations taken together contribute to 82% of all mutations found in this study, and 30% of the families investigated harbor one of these mutations. The very high frequency of common mutations observed in these families can only be compared to that reported for Ashkenazi Jewish, Icelandic, and Russian high-risk families. This frequency, however, may not be representative for the entire Polish population. The observed distribution of mutations will favor routine pre-screening of predisposed families using a simple and cost-effective test.

Hereditary breast cancer: a review

Breast cancer is the most common female malignancy and a major cause of death in middle-aged women. A positive family history of breast cancer is one of the strongest risk factors for the disease. In addition, many afflicted breast cancer families are characterized by early onset and bilateral tumors, and also, in some cases, associated malignancies, most commonly ovarian cancer. It is estimated that 5-10% of all breast cancer cases are due to autosomal dominant genes segregating with the disease. Mutations in the BRCA1 and BRCA2 genes are known to predispose to breast and ovarian cancer in many families. Other genes are only involved in very rare syndromes, and additional genes remain to be disclosed.

Communicating genetic risk: pros, cons, and counsel

Shortly before his death in 1995, Kenneth B. Schwartz, a cancer patient at Massachusetts General Hospital (MGH), founded The Kenneth B. Schwartz Center at MGH. The Schwartz Center is a non-profit organization dedicated to supporting and advancing compassionate health care delivery, which provides hope to the patient, support to caregivers, and encourages the healing process. The center sponsors the Schwartz Center Rounds, a monthly multidisciplinary forum where caregivers reflect on important psychosocial issues faced by patients, their families, and their caregivers, and gain insight and support from fellow staff members. This case is of a woman with a personal, and a strong family history of breast cancer, who considered genetic testing for mutations in the BRCA1 and BRCA2 genes. The details of the case have been altered to protect the patient's anonymity. The patient was very anxious and there was disagreement between her healthcare providers about the potential benefits of genetic testing. The discussion of the case focused on several controversial issues, particularly the ownership of genetic information, and who is responsible for disseminating information to the family members at risk. The difficulties in communicating risk, providing emotional support and coping with the continuing uncertainties about screening and intervention are reviewed with an overview of the molecular biology, inheritance, and epidemiology of the BRCA1 and BRCA2 genes.

Prevalence of founder BRCA1 and BRCA2 mutations among breast and ovarian cancer patients in Hungary

We have investigated the impact of BRCA1 and BRCA2 mutations that were frequently identified among Hungarian high-risk breast-ovarian cancer families (Ramus et al., 1997b, AJHG), on the development of breast and ovarian cancer in the general Hungarian population. The prevalence of 3 BRCA1 mutations (185delAG, 300T-->G and 5382insC) and 2 BRCA2 mutations (6174delT and 9326insA) was evaluated in a hospital-based consecutive series of 500 female breast cancer patients and 90 ovarian cancer patients, not selected for age at diagnosis or family history of cancer, as well as in 350 controls. Among breast cancer patients, 3.6% (18/500) carried a founder mutation: 9 BRCA1 300T-->G, 7 BRCA1 5382insC, 1 BRCA1 185delAG and 1 BRCA2 9326insA. Among ovarian cancer patients, 11% (10/90) carried a founder mutation: 5 BRCA1 185delAG, 4 BRCA1 300T-->G and 1 BRCA1 5382insC. One control carried a mutation, BRCA1 5382insC. Inherited breast cancer was more frequent among women with younger age at diagnosis: 6.1% of women younger than age 50 but 2.4% of women diagnosed at age 50 or older carried one of the founder mutations. There was no association between mutation status and age at diagnosis of ovarian cancer. Three of 23 medullary breast cancers were inherited (p = 0.038). Carrier status was also associated with a non-significant trend toward advanced tumor stage at diagnosis. These mutations could be evaluated among all ovarian cancer patients and breast cancer patients younger than age 60 and of Hungarian ancestry.

Founder populations and their uses for breast cancer genetics

Numerous founder mutations have been reported in BRCA1 and BRCA2. For genetic screening of a population with a founder mutation, testing can be targeted to the mutation, allowing for a more rapid and less expensive test. In addition, more precise estimates of the prior probability of carrying a mutation and of the likelihood of a mutation carrier developing cancer should be possible. For a given founder mutation a large number of carriers are available, so that focused scientific studies of penetrance, expression, and genetic and environmental modifiers of risk can be performed. Finally, founder populations may be a powerful resource to localize additional breast cancer susceptibility loci, because of the reduction in locus heterogeneity.