A comprehensive focus on global spectrum of BRCA1 and BRCA2 mutations in breast cancer

Haplotype analysis of BRCA1 intragenic markers in Iranian patients with familial breast and ovarian cancer

BACKGROUND

Breast cancer is the most common malignancy in women. Breast Cancer Type 1 Susceptibility gene (BRCA1) is a tumor suppressor gene, involved in DNA damage repair and in 81% of the breast-ovarian cancer families were due to BRCA1. In some clinically investigated genes, the intragenic marker polymorphism is important and the screening of such mutations is faster by using short tandem repeat (STR) polymorphism. Individual polymorphism of STR is a good evidence for following inheritance of repeat polymorphism.

OBJECTIVE

The aim of this study was to evaluate three intragenic BRCA1 marker polymorphisms in families, which have two or more patients with breast/ovarian cancer in comparison to healthy women.

MATERIALS AND METHODS

A total of 107 breast and/or ovarian cancer patients and 93 unrelated healthy women with no clinical phenotype of any malignancy or familial cancer history constitute the study groups. Haplotyping analysis, at 3 intragenic BRCA1 microsatellite markers (D17S855, D17S1322 and D17S1323), were performed for all subject and control groups using labeled primers.

RESULTS

After fragment analysis, significance differences were observed as follows: two alleles of D17S855; allele 146 (p=0.02) and 150 (p=0.006), and two alleles of D17S1322, allele 121 (p=0.015) and 142 (p=0.043). These differences were compared with control group. There was significance difference in 8 di/tri allelic haplotypes in present experimental subjects. Some haplotypes were observed to have approximately twice the relation risk for breast cancer.

CONCLUSION

According to recent results, assessment of presence or absence of mentioned alleles in BRCA1 microsatellite can be used for prognosis in individuals, suspected of having or not having the breast cancer.

Hereditary truncating mutations of DNA repair and other genes in BRCA1/BRCA2/PALB2-negatively tested breast cancer patients

Hereditary breast cancer comprises a minor but clinically meaningful breast cancer (BC) subgroup. Mutations in the major BC-susceptibility genes are important prognostic and predictive markers; however, their carriers represent only 25% of high-risk BC patients. To further characterize variants influencing BC risk, we performed SOLiD sequencing of 581 genes in 325 BC patients (negatively tested in previous BRCA1/BRCA2/PALB2 analyses). In 105 (32%) patients, we identified and confirmed 127 truncating variants (89 unique; nonsense, frameshift indels, and splice site), 19 patients harbored more than one truncation. Forty-six (36 unique) truncating variants in 25 DNA repair genes were found in 41 (12%) patients, including 16 variants in the Fanconi anemia (FA) genes. The most frequent variant in FA genes was c.1096_1099dupATTA in FANCL that also show a borderline association with increased BC risk in subsequent analysis of enlarged groups of BC patients and controls. Another 81 (53 unique) truncating variants were identified in 48 non-DNA repair genes in 74 patients (23%) including 16 patients carrying variants in genes coding proteins of estrogen metabolism/signaling. Our results highlight the importance of mutations in the FA genes' family, and indicate that estrogen metabolism genes may reveal a novel candidate genetic component for BC susceptibility.

Detection of high frequency of mutations in a breast and/or ovarian cancer cohort: implications of embracing a multi-gene panel in molecular diagnosis in India

Breast and/or ovarian cancer (BOC) are among the most frequently diagnosed forms of hereditary cancers and leading cause of death in India. This emphasizes on the need for a cost-effective method for early detection of these cancers. We sequenced 141 unrelated patients and families with BOC using the TruSight Cancer panel, which includes 13 genes strongly associated with risk of inherited BOC. Multi-gene sequencing was done on the Illumina MiSeq platform. Genetic variations were identified using the Strand NGS software and interpreted using the StrandOmics platform. We were able to detect pathogenic mutations in 51 (36.2%) cases, out of which 19 were novel mutations. When we considered familial breast cancer cases only, the detection rate increased to 52%. When cases were stratified based on age of diagnosis into three categories, ⩽40 years, 40-50 years and >50 years, the detection rates were higher in the first two categories (44.4% and 53.4%, respectively) as compared with the third category, in which it was 26.9%. Our study suggests that next-generation sequencing-based multi-gene panels increase the sensitivity of mutation detection and help in identifying patients with a high risk of developing cancer as compared with sequential tests of individual genes.

The frequency of BRCA1 founder mutation c.5266dupC (5382insC) in breast cancer patients from Ukraine

Germ-line mutations in several genes, such as BRCA1 and BRCA2, are known to increase the risk of breast cancer. These heritable mutations are unequally represented among populations with different ethnic background due to founder effects and thereby contribute to differences in breast cancer rates in different populations. The BRCA1 mutation c.5266dupC (also known as 5382insC or 5385insC) was detected in a sample of 193 breast cancer patients in Ukraine by multiplex mutagenically separated PCR using published specific primers. Nine BRCA1 mutations 5382insC were detected (4.7 %). The difference in age of diagnosis (35 years in 5382insC carriers versus 45 years in non-carriers) we observed is consistent with other reports indicating that the 5382insC mutation is a factor of genetic predisposition to breast cancer, which is consistent with reports from other countries.

Double Heterozygosity of BRCA2 and STK11 in Familial Breast Cancer Detected by Exome Sequencing

BACKGROUND

Germ-line mutations of BRCA1 and BRCA2 genes are responsible for approximately 25-30% of dominantly inherited familial breast cancers; still a big part of genetic component is unknown. The aim of this study was to investigate genetic causes of familial breast cancer in a pedigree with recessive pattern of inheritance.

METHODS

We applied exome sequencing as a useful approach in heterogeneous diseases gene identification in present study for familial breast cancer. Sanger sequencing was applied for validation and segregation analysis of mutations.

RESULTS

Here, we describe a family with three affected sisters of early-onset invasive ductal carcinoma due to heterozygous frame shift mutation rs80359352 in BRCA2 gene as the first report in Iranian patients in association with a novel missense SNP of STK11 (p.S422G). These mutations are inherited from their normal father.

CONCLUSION

Despite apparent recessive pattern of inheritance a dominant gene (here BRCA2) can be involved in pathogenesis of hereditary breast cancer which can be explained by incomplete penetrance of BRCA2 mutations.

BRCA1 and BRCA2 mutations in ethnic Lebanese Arab women with high hereditary risk breast cancer

PURPOSE

Breast cancer is the most common malignancy among women in Lebanon and in Arab countries, with 50% of cases presenting before the age of 50 years.

METHODS

Between 2009 and 2012, 250 Lebanese women with breast cancer who were considered to be at high risk of carrying BRCA1 or BRCA2 mutations because of presentation at young age and/or positive family history (FH) of breast or ovarian cancer were recruited. Clinical data were analyzed statistically. Coding exons and intron-exon boundaries of BRCA1 and BRCA2 were sequenced from peripheral blood DNA. All patients were tested for BRCA1 rearrangements using multiplex ligation-dependent probe amplification (MLPA). BRCA2 MLPA was done in selected cases.

RESULTS

Overall, 14 of 250 patients (5.6%) carried a deleterious BRCA mutation (7 BRCA1, 7 BRCA2) and 31 (12.4%) carried a variant of uncertain significance. Eight of 74 patients (10.8%) aged ≤40 years with positive FH and only 1 of 74 patients (1.4%) aged ≤40 years without FH had a mutated BRCA. Four of 75 patients (5.3%) aged 41-50 years with FH had a deleterious mutation. Only 1 of 27 patients aged >50 years at diagnosis had a BRCA mutation. All seven patients with BRCA1 mutations had grade 3 infiltrating ductal carcinoma and triple-negative breast cancer. Nine BRCA1 and 17 BRCA2 common haplotypes were observed.

CONCLUSION

Prevalence of deleterious BRCA mutations is lower than expected and does not support the hypothesis that BRCA mutations alone cause the observed high percentage of breast cancer in young women of Lebanese and Arab descent. Studies to search for other genetic mutations are recommended.

BRCA1 and BRCA2 mutations in Iranian breast cancer patients: A systematic review

BACKGROUND

BRCA1/2 genes mutation prevalence varies among ethnic groups and may be influenced by founder mutations. Understanding BRCA1/2 genes mutations is important for reducing breast cancer (BC) incidence, accurate risk assessment and counseling. This systematic review of the literature was conducted to addressing BRCA1/2 mutations in Iranian BC patients.

MATERIALS AND METHODS

A search for relevant articles was run on before January 2014 using MedLine, PubMed, Science Iranian Database, Google, and Web sites related to the study topic. The key words included: BC and Iran with Genes, BRCA Genes, BRCA1 and BRCA2; "Cancer Genes," and "Iran."

RESULTS

Thirteen articles retrieved from this search strategy were eligible for this review. The overall BRCA1 mutation rate for Iranian female BC patients was detected 31.8% (377/1183). Although this gene mutation rate for male patients is <0.01%. Eight BRCA1 mutations (c. 4837A > G, c. 3419G > A, c. 3119G > A, c. 2612C > T, c. 3113A > G, c. 2311T > C, c. 4301T > C and c. 4308T > C in BRCA1, and one BRCA2 mutation (c. 6494G > C) were found in multiple case subjects and represent candidate founder mutations.

CONCLUSION

According to these studies, there is heterogeneity in BRCA mutations in Iranian BC patients.

Disparities in breast cancer and african ancestry: a global perspective

Recognition of breast cancer disparities between African-American and White American women has generated exciting research opportunities investigating the biologic and hereditary factors that contribute to the observed outcome differences, leading to international studies of breast cancer in Africa. The study of breast cancer in women with African ancestry has opened the door to unique investigations regarding breast cancer subtypes and the genetics of this disease. International research efforts can advance our understanding of race/ethnicity-associated breast cancer disparities within the USA; the pathogenesis of triple negative breast cancer; and hereditary susceptibility for breast cancer.

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.

Mismatch repair genes founder mutations and cancer susceptibility in Lynch syndrome

Founder mutations in specific populations are common in several Mendelian disorders. They are shared by apparently unrelated families that inherited them from a common ancestor that existed hundreds to thousands of years ago. They have been proven to impact in molecular diagnostics strategies in specific populations, where they can be assessed as the first screening step and, if positive, avoid further expensive gene scanning. In Lynch syndrome (LS), a dominantly inherited colorectal cancer disease, more than 50 founder pathogenic mutations have been described so far in the mismatch repair (MMR) genes (MLH1, MSH2, MSH6 and PMS2). We here provide a comprehensive summary of the founder mutations found in the MMR genes and an overview of their main characteristics. At a time when high-throughput strategies are being introduced in the molecular diagnostics of cancer, genetic testing for founder mutations can complement next generation sequencing (NGS) technologies to most efficiently identify MMR gene mutations in any given population. Additionally, special attention is paid to MMR founder mutations with interesting anthropological significance.

Novel treatment strategies in triple-negative breast cancer: specific role of poly(adenosine diphosphate-ribose) polymerase inhibition

Inhibitors of the poly(adenosine triphosphate-ribose) polymerase (PARP)-1 enzyme induce synthetic lethality in cancers with ineffective DNA (DNA) repair or homologous repair deficiency, and have shown promising clinical activity in cancers deficient in DNA repair due to germ-line mutation in BRCA1 and BRCA2. The majority of breast cancers arising in carriers of BRCA1 germ-line mutations, as well as half of those in BRCA2 carriers, are classified as triple-negative breast cancer (TNBC). TNBC is a biologically heterogeneous group of breast cancers characterized by the lack of immunohistochemical expression of the ER, PR, or HER2 proteins, and for which the current standard of care in systemic therapy is cytotoxic chemotherapy. Many "sporadic" cases of TNBC appear to have indicators of DNA repair dysfunction similar to those in BRCA-mutation carriers, suggesting the possible utility of PARP inhibitors in a subset of TNBC. Significant genetic heterogeneity has been observed within the TNBC cohort, creating challenges for interpretation of prior clinical trial data, and for the design of future clinical trials. Several PARP inhibitors are currently in clinical development in BRCA-mutated breast cancer. The use of PARP inhibitors in TNBC without BRCA mutation will require biomarkers that identify cancers with homologous repair deficiency in order to select patients likely to respond. Beyond mutations in the BRCA genes, dysfunction in other genes that interact with the homologous repair pathway may offer opportunities to induce synthetic lethality when combined with PARP inhibition.

Transcriptional profiling and dynamical regulation analysis identify potential kernel target genes of SCYL1-BP1 in HEK293T cells

SCYL1-BP1 is thought to function in the p53 pathway through Mdm2 and hPirh2, and mutations in SCYL1-BP1 are associated with premature aging syndromes such as Geroderma Osteodysplasticum; however, these mechanisms are unclear. Here, we report significant alterations in miRNA expression levels when SCYL1-BP1 expression was inhibited by RNA interference in HEK293T cells. We functionally characterized the effects of potential kernel miRNA-target genes by miRNA-target network and protein-protein interaction network analysis. Importantly, we showed the diminished SCYL1-BP1 dramatically reduced the expression levels of EEA1, BMPR2 and BRCA2 in HEK293T cells. Thus, we infer that SCYL1-BP1 plays a critical function in HEK293T cell development and directly regulates miRNA-target genes, including, but not limited to, EEA1, BMPR2, and BRCA2, suggesting a new strategy for investigating the molecular mechanism of SCYL1-BP1.