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

A cost-benefit analysis of genetic screening test for breast cancer in Iran

BACKGROUND

This study aimed to evaluate the implementation of the population- and family history (FH) -based screening for BReast CAncer (BRCA) in Iran, a country where less than 10% of breast cancer cases are attributable to a gene mutation.

METHODS

This was an economic evaluation study. The Benefit-Cost Ratio (BCR) for genetic screening test strategies in Iranian women older than 30 was calculated. To this end, the monetary value of the test was estimated using the willingness-to-pay (WTP) approach using the contingent valuation method (CVM) by payment card. From a healthcare perspective, direct medical and non-medical costs were considered and a decision model for the strategies was developed to simulate the costs. A one-way sensitivity analysis assessed the robustness of the analysis. The data were analyzed using Excel 2010.

RESULTS

660 women were included for estimating WTP and 2,176,919 women were considered in the costing model. The cost per genetic screening test for population- and FH-based strategies was $167 and $8, respectively. The monetary value of a genetic screening test was $20 and it was $27 for women with a family history or gene mutation in breast cancer. The BCR for population-based and FH-based screening strategies was 0.12 and 3.37, respectively. Sensitivity analyses confirmed the robustness of the results.

CONCLUSIONS

This study recommends the implementation of a FH-based strategy instead of a population-based genetic screening strategy in Iran, although a cascade genetic screening test strategy should be evaluated in future studies.

A Cost Decision Model Supporting Treatment Strategy Selection in BRCA1/2 Mutation Carriers in Breast Cancer

In this paper, a cost decision-making model that compares the healthcare costs for diverse treatment strategies is built for BRCA-mutated women with breast cancer. Moreover, this model calculates the cancer treatment costs that could potentially be prevented, if the treatment strategy with the lowest total cost, along the entire lifetime of the patient, is chosen for high-risk women with breast cancer. The benchmark of the healthcare costs for diverse treatment strategies is selected in the presence of uncertainty, i.e., considering, throughout the lifetime of the patient, the risks and complications that may arise in each strategy and, therefore, the costs associated with the management of such events. Our results reveal a clear economic advantage of adopting the cost decision-making model for benchmarking the healthcare costs for various treatment strategies for BRCA-mutated women with breast cancer. The cost savings were higher when all breast cancer patients underwent counseling and genetic testing before deciding on any diagnostic-therapeutic path, with a probability of obtaining savings of over 75%.

Screening of BRCA1 variants c.190T>C, 1307delT, g.5331G>A and c.2612C>T in breast cancer patients from North India

The polymorphic variants of BRCA1, which lead to amino acid substitutions, have a known pathogenic role in breast cancer. The present study investigated in North Indian breast cancer patients the association of risk with four reported pathogenic variants of BRCA1: c.190T>C (p.Cys64Arg), 1307delT, g.5331G>A (p.G1738R) and c.2612C>T (p.Pro871Leu). Genotyping was done by PCR-RFLP method in 255 clinically confirmed breast cancer patients and 255 age and gender matched healthy individuals. For c.190T>C, 1307delT and g.5331G>A, all the patients and controls had the wild-type genotype indicating no association with breast cancer risk. For c.2612C>T polymorphism, the frequency of the CC, CT, and TT genotypes was 14.5 vs 15.7%, 59.6 vs 53.7% and 25.9 vs 30.6% in breast cancer patients and controls respectively. The frequency of heterozygotes (CT genotype) was higher in cases than controls but the difference was not statistically significant. Genetic model analysis showed no association of the four analyzed BRCA1 variants with breast cancer risk with any model. The studied variants were not associated with the risk of breast cancer in Punjab, North west India, suggesting a need for further screening of other BRCA1 variants. It is the first reported study on these 4 variants from India.

BRCA1 and BRCA2 germline testing in Cretan isolates reveals novel and strong founder effects

Germline BRCA1 and BRCA2 loss-of-function variants have been linked to increased breast and ovarian cancer risk, with more than 5,000 distinct pathogenic variants being reported worldwide. Among individuals of Greek descent, the BRCA1/2 variant spectrum is heterogeneous, but characterized by strong founder effects. As patients from certain geographical regions of Greece (like Crete) were underrepresented in previous studies, we hypothesized that isolated Cretans, a southern Greece islanders' population with distinct demographic, cultural and genetic features, could harbor founder BRCA1/2 mutations. A total of 304 breast or/and ovarian cancer patients of Cretan descent, fulfilling NCCN criteria for genetic testing, were tested by NGS or Sanger sequencing, followed by MLPA. Haplotype analysis was subsequently performed to investigate potential founder effects of recurrent alleles. Overall, 16.5% (50/304) of the tested patients carried 22 different pathogenic variants; 48% in BRCA1, 52% in BRCA2. Three variants, namely two in BRCA2 (Δexons 12 and 13 and c.7806-2A>T) and one in BRCA1 (c.5492del), constituting approximately half (48%) of all detected pathogenic variants, were shown to have a founder effect, with all carriers sharing common haplotypes. Remarkably, these variants were confined to Cretans and have not been identified in other regions of Greece. The high prevalence of specific BRCA1/2 pathogenic variants among Cretans, provides the possibility of cost- and time-efficient screening of the Cretan population. Integrating this knowledge in local public health services may have a significant impact on cancer prevention, and may serve as a starting point for the implementation of testing on a population level.

Non-BRCA1/2 Variants Detected in a High-Risk Chilean Cohort With a History of Breast and/or Ovarian Cancer

METHODS

Data were retrospectively collected from the registry of the High-Risk Breast and Ovarian Cancer Program at Clínica Las Condes, Santiago, Chile. Data captured included index case diagnosis, ancestry, family history, and genetic test results.

RESULTS

Three hundred fifteen individuals underwent genetic testing during the study period. The frequency of germline pathogenic and likely pathogenic variants in a breast or ovarian cancer predisposition gene was 20.3%. Of those patients who underwent testing with a panel of both high- and moderate-penetrance genes, 10.5% were found to have pathogenic or likely pathogenic variants in non-BRCA1/2 genes.

CONCLUSION

Testing for non-BRCA1 and -2 mutations may be clinically relevant for individuals who are suspected to have a hereditary breast or ovarian cancer syndrome in Chile. Comprehensive genetic testing of individuals who are at high risk is necessary to further characterize the genetic susceptibility to cancer in Chile.

BRCA1 and BRCA2 germline variants in breast cancer patients from the Republic of Macedonia

PURPOSE

We aimed to establish the spectrum of BRCA1/2 mutations among the breast cancer (BC) patients from the Republic of Macedonia.

METHODS

We used targeted next-generation sequencing (NGS), Sanger DNA sequencing, and multiplex ligation probe amplification analysis (MLPA) to search for point mutations and deletions/duplications involving BRCA1 and BRCA2-coding regions.

RESULTS

We have analyzed a total of 313 BC patients, enriched for family history of cancer, early age of onset and bilateral and/or triple negative (TN) BC. A total of 26 pathogenic mutations were observed in 49 unrelated BC patients (49/313, 15.7%). BRCA2 mutations (27/49, 55.1%) were more common than BRCA1 mutations (22/49, 44.9%). We identified five novel point mutations, one in BRCA1 (c.4352_4356delA) and four in BRCA2 (c.151G>T, c.4707_4708delCA, c.7811_7814delTGTG, and c.9304_9305delG), as well as two novel deletions involving parts of the BRCA1 gene (c.81-?_593+?del and c.5470-?_5530+?del). The most common mutations were c.181T>G, c.5266dupC, and c.3700_3704del5 in BRCA1 and c.7879A>T, c.8317_8330del14 and c.5722_5723delCT in BRCA2 gene. Thus far, BRCA2 c.7879A>T and c.8317_8330del14 mutations have been described in several isolated cases; however, our study is the first one showing that they have a founder effect among Macedonian population. Nine recurrent mutations account for 65.3% of all of the detected mutations allowing for implementation of a fast first-step BRCA1/2 mutational screening strategy in our country.

CONCLUSION

This study provides a comprehensive view of known and novel BRCA1/2 mutations in BC patients from the Republic of Macedonia and contributes to the global spectrum of BRCA1/2 mutations in breast cancer.

Haplotype analysis reveals that the recurrent BRCA1 deletion of exons 23 and 24 is a Greek founder mutation

A recurrent large genomic rearrangement (LGR) encompassing exons 23 and 24 of the BRCA1 gene has been identified in breast-ovarian cancer families of Greek origin. Its breakpoints have been determined as c.5406 + 664_*8273del11052 (RefSeq: NM_007294.3) and a diagnostic polymerase chain reaction (PCR) has been set up for rapid screening. In a series of 2,092 high-risk families completely screened for BRCA1 and BRCA2 germline mutations, we have found the deletion in 35 families (1.68%), representing 7.83% of the mutations identified in both genes and 10.3% of the total BRCA1 mutations. In order to characterize this deletion as a founder mutation, haplotype analysis was conducted in 60 carriers from 35 families, using three BRCA1 intragenic microsatellite markers and four markers surrounding the BRCA1 locus. Our results demonstrate a common shared core disease-associated haplotype of 2.89Mb. Our calculations estimate that the deletion has originated from a common ancestor 1450 years ago, which most probably inhabited the Asia Minor area. The particular (LGR) is the third mutation of such type that is proven to have a Greek founder effect in the Greek population, illustrating the necessity for LGRs testing in individuals of Greek descent.

Cumulative BRCA mutation analysis in the Greek population confirms that homogenous ethnic background facilitates genetic testing

Screening for BRCA 1 and BRCA 2 mutations has long moved from the research lab to the clinic as a routine clinical genetic testing. BRCA molecular alteration pattern varies among ethnic groups which makes it already a less straightforward process to select the appropriate mutations for routine genetic testing on the basis of known clinical significance. The present report comprises an in depth literature review of the so far reported BRCA 1 and BRCA 2 molecular alterations in Greek families. Our analysis of Greek cumulative BRCA 1 and 2 molecular data, produced by several independent groups, confirmed that six recurrent deleterious mutations account for almost 60 % and 70 % of all BRCA 1 and 2 and BRCA 1 mutations, respectively. As a result, it makes more sense to perform BRCA mutation analysis in the clinic in two sequential steps, first conventional analysis for the six most prevalent pathogenic mutations and if none identified, a second step of New Generation Sequencing-based whole genome or whole exome sequencing would follow. Our suggested approach would enable more clinically meaningful, considerably easier and less expensive BRCA analysis in the Greek population which is considered homogenous.

Spectrum and frequencies of BRCA1/2 mutations in Bulgarian high risk breast cancer patients

BACKGROUND

About 3885 women are diagnosed with breast cancer and 1285 die from the disease each year in Bulgaria. However no genetic testing to identify the mutations in high-risk families has been provided so far.

METHODS

We evaluated 200 Bulgarian women with primary invasive breast cancer and with personal/ family history of breast cancer for the presence of unequivocally damaging germline mutations in BRCA1/2 using Sanger sequencing.

RESULTS

Of the 200 patients, 39 (19.5 %) carried a disease predisposing mutation, including 28 (14 %) with a BRCA1 mutation and 11 (5.5 %) with a BRCA2 mutation. At BRCA1, 6 different mutations were identified, including 2 frameshifts, 1 nonsense and 1 missense that had been previously reported (c.5030_5033delCTAA, c.5263_5264insC, c.4603G > T, c.181 T > G), and 2 frameshifts, which were novel to this study (c.464delA, c.5397_5403delCCCTTGG). At BRCA2, 7 different frameshift mutations were identified, including 5 previously reported (5851_5854delAGTT, c.5946delT, c.5718_5719delCT, c.7910_7914delCCTTT,c.9098_9099insA) and 2 novel (c.8532_8533delAA, c.9682delA). A BRCA1 mutation was found in 18.4 % of women diagnosed with breast cancer at/or under the age of 40 compared to 11.2 % of women diagnosed at a later age; a BRCA2 mutation was found in 4 % of women diagnosed at/or under the age of 40 compared to 6.5 % of women diagnosed at a later age. A mutation was present in 26.8 % patients with a positive family history and in 14.4 % of women with a negative family history. The most prevalent mutation observed in 22 patients (11 %) was BRCA1 c.5263_5264insC, a known Slavic mutation with founder effect in Eastern European and AJ communities. Other recurrent mutations were BRCA2 c.9098-9099insA (2 %), BRCA1 c.181T > G (1 %) and BRCA2 c.5851_5854delAGTT (1 %). Notably, BRCA1 c.5263_5264insC represented 56 % of all mutations identified in this series. Of the 22 patients with BRCA1 c.5263_5264insC, 9 were diagnosed with early onset breast cancer, 11 with TNBCs, 4 with bilateral breast cancer, and 6 with both breast and ovarian cancer.

CONCLUSIONS

This is the first comprehensive study of the BRCA1/2 mutation spectrum in Bulgaria and will assist the establishment of efficient protocols for genetic testing and individualized risk assessment for Bulgarian breast/ovarian cancer patients and healthy individuals at a high-risk.

Hereditary breast cancer: the era of new susceptibility genes

Breast cancer is the most common malignancy among females. 5%-10% of breast cancer cases are hereditary and are caused by pathogenic mutations in the considered reference BRCA1 and BRCA2 genes. As sequencing technologies evolve, more susceptible genes have been discovered and BRCA1 and BRCA2 predisposition seems to be only a part of the story. These new findings include rare germline mutations in other high penetrant genes, the most important of which include TP53 mutations in Li-Fraumeni syndrome, STK11 mutations in Peutz-Jeghers syndrome, and PTEN mutations in Cowden syndrome. Furthermore, more frequent, but less penetrant, mutations have been identified in families with breast cancer clustering, in moderate or low penetrant genes, such as CHEK2, ATM, PALB2, and BRIP1. This paper will summarize all current data on new findings in breast cancer susceptibility genes.

Prevalence of BRCA1 mutations in familial and sporadic greek ovarian cancer cases

Germline mutations in the BRCA1 and BRCA2 genes contribute to approximately 18% of hereditary ovarian cancers conferring an estimated lifetime risk from 15% to 50%. A variable incidence of mutations has been reported for these genes in ovarian cancer cases from different populations. In Greece, six mutations in BRCA1 account for 63% of all mutations detected in both BRCA1 and BRCA2 genes. This study aimed to determine the prevalence of BRCA1 mutations in a Greek cohort of 106 familial ovarian cancer patients that had strong family history or metachronous breast cancer and 592 sporadic ovarian cancer cases. All 698 patients were screened for the six recurrent Greek mutations (including founder mutations c.5266dupC, p.G1738R and the three large deletions of exon 20, exons 23-24 and exon 24). In familial cases, the BRCA1 gene was consequently screened for exons 5, 11, 12, 20, 21, 22, 23, 24. A deleterious BRCA1 mutation was found in 43/106 (40.6%) of familial cancer cases and in 27/592 (4.6%) of sporadic cases. The variant of unknown clinical significance p.V1833M was identified in 9/698 patients (1.3%). The majority of BRCA1 carriers (71.2%) presented a high-grade serous phenotype. Identifying a mutation in the BRCA1 gene among breast and/or ovarian cancer families is important, as it enables carriers to take preventive measures. All ovarian cancer patients with a serous phenotype should be considered for genetic testing. Further studies are warranted to determine the prevalence of mutations in the rest of the BRCA1 gene, in the BRCA2 gene, and other novel predisposing genes for breast and ovarian cancer.

Three novel BRCA1/BRCA2 mutations in breast/ovarian cancer families in Croatia

BRCA1 and BRCA2 genes from 167 candidates (145 families) were scanned for mutations. We identified 14 pathogenic point mutations in 17 candidates, 9 in BRCA1 and 5 in BRCA2. Of those, 11 have been previously described and 3 were novel (c.5335C>T in BRCA1 and c.4139_4140dupTT and c.8175G>A in BRCA2). No large deletions or duplications involving BRCA1 and BRCA2 genes were identified. No founder mutations were detected for the Croatian population. Croatia shares most of the mutations with neighboring Slovenia and also with Germany, Austria and Poland. Two common sequence variants in BRCA1, c.2077G>A and c.4956G>A, were found more frequently in mutation carriers compared to healthy controls. No difference in BRCA2 variants was detected between the groups. Haplotype inference showed no difference in haplotype distributions between deleterious mutation carriers and non-carriers in neither BRCA1 nor BRCA2. In silico analyses identified one BRCA1 sequence variant (c.4039A>G) and two BRCA2 variants (c.5986G>A and c.6884G>C) as harmful with high probability, and inconclusive results were obtained for our novel BRCA2 variant c.3864_3866delTAA. Combination of QMPSF and HRMA methods provides high detection rate and complete coverage of BRCA1/2 genes. Benefit of BRCA1/2 mutation testing is clear, since we detected mutations in young unaffected women, who will be closely monitored for breast and ovarian cancer.

Prevalence of BRCA1 mutations among 403 women with triple-negative breast cancer: implications for genetic screening selection criteria: a Hellenic Cooperative Oncology Group Study

In spite the close association of the triple-negative breast cancer immunophenotype with hereditary breast cancers and the BRCA1 pathway, there is a lack of population studies that determine the frequency of BRCA1 mutations among triple-negative breast cancer patients. To address this, we have screened a large sample of 403 women diagnosed with triple-negative invasive breast cancer, independently of their age or family history, for germline BRCA1 mutations. Median age at diagnosis was 50 years (range 20-83). The overall prevalence of triple-negative cases among the initial patient group with invasive breast cancer was 8%. BRCA1 was screened by direct DNA sequencing in all patients, including all exons where a mutation was previously found in the Greek population (exons 5, 11, 12, 16, 20, 21, 22, 23, 24-77% of the BRCA1 coding region), including diagnostic PCRs to detect the three Greek founder large genomic rearrangements. Sixty-five deleterious BRCA1 mutations were identified among the 403 triple-negative breast cancer patients (16%). Median age of onset for mutation carriers was 39 years. Among a total of 106 women with early-onset triple-negative breast cancer (<40 years), 38 (36%) had a BRCA1 mutation, while 27% of women with triple-negative breast cancer diagnosed before 50 years (56/208) had a BRCA1 mutation. A mutation was found in 48% (50/105) of the triple-negative breast cancer patients with family history of breast or ovarian cancer. It is noteworthy, however, that of the 65 carriers, 15 (23%) had no reported family history of related cancers. All but one of the carriers had grade III tumors (98%). These results indicate that women with early-onset triple-negative breast cancer, and ideally all triple-negative breast cancer patients, are candidates for BRCA1 genetic testing even in the absence of a family history of breast or ovarian cancer.

Prevalence of BRCA1 and BRCA2 mutations in unselected breast cancer patients from Greece

BACKGROUND

Inheritance of a mutation in either BRCA1 or BRCA2 accounts for approximately 5% of all breast cancer cases, but varies by country. Investigations into the contribution of BRCA mutations to breast cancer incidence in Greece have been, for the most part, limited by small sample sizes and by the use of cases selected for their family history of cancer. The aim of the current study was to estimate BRCA mutation frequencies in breast cancer patients unselected for family history.

METHODS

To do so, we enrolled 127 unselected women with breast cancer from the Alexandra Hospital in Athens, Greece, a large public hospital in the city. Mutations in BRCA1 and BRCA2 were detected using a combination of techniques and were confirmed by direct sequencing. Two large genomic deletions were sought using mutation-specific assays. A detailed family history of cancer was obtained from each patient.

RESULTS

We were able to successfully complete testing on samples from 127 women. Among these, six mutations were identified (four in BRCA1 and two in BRCA2) representing 4.7% of the total or 9.5% of cases diagnosed before age forty. None of the mutation carriers had a family history of breast or ovarian cancer. Three of the four BRCA1 mutations were in exon 20: two were a G5331A mutation and the third was a 3.2 kb deletion. The fourth BRCA1 mutation was the 3819delGTAAA in exon 11. The two BRCA2 mutations were in exon 11 (3782del10 and 4512insT).

CONCLUSIONS

The G5331A mutation in BRCA1 appears to be a founder mutation in the Greek population.

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.

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

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

Fully integrated monolithic optoelectronic transducer for real-time protein and DNA detection: the NEMOSLAB approach

The development and testing of a portable bioanalytical device which was capable for real-time monitoring of binding assays was demonstrated. The device was based on arrays of nine optoelectronic transducers monolithically integrated on silicon chips. The optocouplers consisted of nine silicon avalanche diodes self-aligned to nine silicon nitride waveguides all converging to a single silicon detector. The waveguides were biofunctionalized by appropriate recognition molecules. Integrated thick polymer microchannels provided the necessary fluidic functions to the chip. A single sided direct contact scheme through a board-to-board receptacle was developed and combined with a portable customized readout and control instrument. Real-time detection of deleterious mutations in BRCA1 gene related to predisposition to hereditary breast/ovarian cancer was performed with the instrument developed using PCR products. Detection was based on waveguided photons elimination through interaction with fluorescently labeled PCR products. Detection of single biomolecular binding events was also demonstrated using nanoparticles as labels. In addition, label-free monitoring of bioreactions in real time was achieved by exploiting wavelength filtering on photonic crystal engineered waveguides. The proposed miniaturized sensing device with proper packaging and accompanied by a portable instrument can find wide application as a platform for reliable and cost effective point-of-care diagnosis.

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.

BRCA1 gene mutations may explain more than 80% of excess number of ovarian cancer cases after breast cancer - a population based study from the Western Sweden Health Care region

AIM

In a previous cohort study, we showed that there was a significant variation in the frequency of ovarian cancer after having breast cancer in Sweden, with the highest risk occuring in the Western region. The present study aimed to evaluate whether the high prevalence of the founder mutation BRCA1 3171ins5 may explain the excess number of ovarian cancer.

METHOD

Among more than 26 000 women with breast cancer in the Western Swedish Health Care Region, 159 cases were subsequently diagnosed with ovarian cancer, whereas the expected number was 96. Archived tissue material was analysed for six common Scandinavian BRCA1 and BRCA2 gene mutations.

RESULTS

The excess number of cases was 63 (95% CI 47-77), based on person-years at risk and national incidence rates of ovarian cancer. A BRCA1 gene mutation was detected in 33 cases corresponding to 52% of the excess number. The founder mutation, BRCA1 3171ins5, was detected in 44% of the excess number. The identified mutations decreased from 45% in women less than 50 years of age at follow-up to 14% at 60+ years at follow-up. There was no obvious decrease in mutation frequency by excess numbers with age. Age at follow-up and first-degree relatives with breast and/or ovarian cancer were the best predictors of a mutation in this material.

CONCLUSION

The founder mutation, BRCA1 3171ins5, explains the excess of ovarian cancer after breast cancer in the region. From the relative frequency of the studied mutations found at the cancer genetic counselling clinic, it is estimated that BRCA1 gene mutations are associated with about 80-85% of the excess cases. This means that a negative screening for these mutations in similar cases may have a predictive value and could strongly reduce the risk of ovarian cancer in relatives.

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.

The c.156_157insAlu BRCA2 rearrangement accounts for more than one-fourth of deleterious BRCA mutations in northern/central Portugal

We evaluated the contribution of an Alu insertion in BRCA2 exon 3 (c.156_157insAlu) to inherited predisposition to breast/ovarian cancer in 208 families originated mostly from northern/central Portugal. We identified the c.156_157insAlu BRCA2 mutation in 14 families and showed that it accounts for more that one-fourth of deleterious BRCA1/BRCA2 mutations in breast/ovarian cancer families originated from this part of the country. This mutation originates BRCA2 exon 3 skipping and we demonstrated its pathogenic effect by showing that the BRCA2 full length transcript is derived only from the wild type allele in carriers, that it is absent in 262 chromosomes from healthy blood donors, and that it co-segregates with the disease. Polymorphic microsatellite markers were used for haplotype analysis in three informative families. In two of the three families one haplotype was shared for all but two markers, whereas in the third family all markers telomeric to BRCA2 differed from that observed in the other two. Although the c.156_157insAlu BRCA2 mutation has so far only been identified in Portuguese breast/ovarian cancer families, screening of this rearrangement in other populations will allow evaluation of whether or not it is a population-specific founder mutation and a more accurate estimation of its distribution and age.

Identification of BRCA1 missense substitutions that confer partial functional activity: potential moderate risk variants?

Introduction

Many of the DNA sequence variants identified in the breast cancer susceptibility gene BRCA1 remain unclassified in terms of their potential pathogenicity. Both multifactorial likelihood analysis and functional approaches have been proposed as a means to elucidate likely clinical significance of such variants, but analysis of the comparative value of these methods for classifying all sequence variants has been limited.

Methods

We have compared the results from multifactorial likelihood analysis with those from several functional analyses for the four BRCA1 sequence variants A1708E, G1738R, R1699Q, and A1708V.

Results

Our results show that multifactorial likelihood analysis, which incorporates sequence conservation, co-inheritance, segregation, and tumour immunohistochemical analysis, may improve classification of variants. For A1708E, previously shown to be functionally compromised, analysis of oestrogen receptor, cytokeratin 5/6, and cytokeratin 14 tumour expression data significantly strengthened the prediction of pathogenicity, giving a posterior probability of pathogenicity of 99%. For G1738R, shown to be functionally defective in this study, immunohistochemistry analysis confirmed previous findings of inconsistent 'BRCA1-like' phenotypes for the two tumours studied, and the posterior probability for this variant was 96%. The posterior probabilities of R1699Q and A1708V were 54% and 69%, respectively, only moderately suggestive of increased risk. Interestingly, results from functional analyses suggest that both of these variants have only partial functional activity. R1699Q was defective in foci formation in response to DNA damage and displayed intermediate transcriptional transactivation activity but showed no evidence for centrosome amplification. In contrast, A1708V displayed an intermediate transcriptional transactivation activity and a normal foci formation response in response to DNA damage but induced centrosome amplification.

Conclusion

These data highlight the need for a range of functional studies to be performed in order to identify variants with partially compromised function. The results also raise the possibility that A1708V and R1699Q may be associated with a low or moderate risk of cancer. While data pooling strategies may provide more information for multifactorial analysis to improve the interpretation of the clinical significance of these variants, it is likely that the development of current multifactorial likelihood approaches and the consideration of alternative statistical approaches will be needed to determine whether these individually rare variants do confer a low or moderate risk of breast cancer.

New sequence variants in BRCA1 and BRCA2 genes detected by high-resolution melting analysis in an elderly healthy female population in Croatia

BACKGROUND

Mutations in BRCA1 and BRCA2 genes are associated with family predisposition to breast and ovarian cancer. Novel screening methods are required for efficient and rapid detection of sequence variants in cancer patients and their family members.

METHODS

The screening for variants in the breast and ovarian cancer susceptibility genes BRCA1 and BRCA2 in Croatia was performed by a high-resolution melting approach, which is based on differences in melting curves caused by variations in nucleotide sequence. This is the first screening in Croatia on elderly healthy women with no family history of cancer. BRCA1 screening was performed on 220 and BRCA2 screening on 115 samples.

RESULTS

In a population well beyond the average age of breast/ovarian cancer onset, 21 different sequence variants in the BRCA1 gene (one novel: c.5193+49_50delTA) and 36 variants in the BRCA2 gene (7 novel: c.459A>C, c.3318C>A, c.4412_ 4414delGAA, c.4790C>A, c.6264T>C, c.9087G>A, and c.9864A>G) were detected.

CONCLUSIONS

Nine BRCA1 and seven BRCA2 known variants appeared with such high frequencies that they could be declared as harmless in this population. Eight BRCA1 high frequency variants, located further from the promoter region, appear to be strongly correlated. Three novel variants that changed the amino acid sequence of the BRCA2 protein (two missense base substitutions, c.3318C>A and c.4790C>A, and one codon deletion c.4412_4414delGAA), appearing only once, were predicted to have no potential effect on protein structure and function.

G1738R is a BRCA1 founder mutation in Greek breast/ovarian cancer patients: evaluation of its pathogenicity and inferences on its genealogical history

We have performed screening in 287 breast/ovarian cancer families in Greece which has revealed that approximately 12% (8/65) of all index patients-carriers of a deleterious mutation in BRCA1 and BRCA2 genes, contain the base substitution G to A at position 5331 of BRCA1 gene. This generates the amino acid change G1738R for which based on a combination of genetic, in silico and histopathological analysis there are strong suggestions that it is a causative mutation. In this paper, we present further evidence suggesting the pathogenicity of this variant. Forty breast/ovarian cancer patients were reported in 11 Greek families: the above eight living in Greece, two living in Australia and one in USA, all containing G1738R. Twenty of these patients were screened and were all found to be carriers of the same base substitution. In addition, we have detected the same base change in five breast/ovarian cancer patients after screening 475 unselected patient samples with no apparent family history. The mean age of onset for all the above patients was 39.4 and 53.6 years for breast and ovarian cancer cases, respectively. A multi-factorial likelihood model for classification of unclassified variants in BRCA1 and BRCA2 developed previously was applied on G1738R and the odds of it being a deleterious mutation was estimated to be 11470:1. In order to explain the prevalence of this mutation mainly in the Greek population, its genealogical history was examined. DNA samples were collected from 11 carrier families living in Greece, Australia and USA. Screening of eight intragenic SNPs, three intragenic and seven extragenic microsatellite markers and comparison with control individuals, suggested a common origin for the mutation while the time to its most recent common ancestor was estimated to be 11 generations (about 275 years assuming a generational interval of 25 years) with a 1-lod support interval of 4-24 generations (100-600 years). Considering the large degree of genetic heterogeneity in the Greek population, the identification of a frequent founder mutation greatly facilitates genetic screening.