Analysis of PALB2 Gene in BRCA1/BRCA2 Negative Spanish Hereditary Breast/Ovarian Cancer Families with Pancreatic Cancer Cases

Background

The PALB2 gene, also known as FANCN, forms a bond and co-localizes with BRCA2 in DNA repair. Germline mutations in PALB2 have been identified in approximately 1% of familial breast cancer and 3–4% of familial pancreatic cancer. The goal of this study was to determine the prevalence of PALB2 mutations in a population of BRCA1/BRCA2 negative breast cancer patients selected from either a personal or family history of pancreatic cancer.

Methods

132 non-BRCA1/BRCA2 breast/ovarian cancer families with at least one pancreatic cancer case were included in the study. PALB2 mutational analysis was performed by direct sequencing of all coding exons and intron/exon boundaries, as well as multiplex ligation-dependent probe amplification.

Results

Two PALB2 truncating mutations, the c.1653T>A (p.Tyr551Stop) previously reported, and c.3362del (p.Gly1121ValfsX3) which is a novel frameshift mutation, were identified. Moreover, several PALB2 variants were detected; some of them were predicted as pathological by bioinformatic analysis. Considering truncating mutations, the prevalence rate of our population of BRCA1/2-negative breast cancer patients with pancreatic cancer is 1.5%.

Conclusions

The prevalence rate of PALB2 mutations in non-BRCA1/BRCA2 breast/ovarian cancer families, selected from either a personal or family pancreatic cancer history, is similar to that previously described for unselected breast/ovarian cancer families. Future research directed towards identifying other gene(s) involved in the development of breast/pancreatic cancer families is required.     

Detection of New Point Mutations of BRCA1 and BRCA2 in Breast Cancer Patients

This study included 20 selected female patients with breast cancer, 30 of their female relatives (sisters and daughters), and 10 healthy females as a control group. Genomic DNA was extracted from peripheral blood lymphocytes of all the subjects, and the polymerase chain reaction was carried out using specific primers for BRCA1 (exons 2 and 8) and BRCA2 (exons 9, 11, and 21). The mutations were detected using a single-strand conformation polymorphism assay and heteroduplex analysis. Finally, the sample variants and their controls were sequenced. Mutations were detected in 44% of the study population, with 18% found in the BRCA1 gene and 26% attributed to BRCA2. Five sequence variants were identified, including two frameshift mutations, one nonsense mutation, and two missense mutations. Therefore, we conclude that germline mutations in two major genes, BRCA1 and BRCA2, may have an important influence on the predisposition and development of familial breast cancer.     

家族性乳腺癌和健康遗传高危人群BRCA1/2基因突变研究

目的:研究中国汉族女性家族性乳腺癌患者和健康遗传性高危人群的BRCA1/2基因突变特征。方法:研究对象为2013年12月~2014年10月于解放军307医院乳腺外科确诊的54例汉族家族性乳腺癌患者及24例健康遗传性高危人群,应用PCR-DNA直接测序法检测乳腺癌易感基因BRCA1和BRCA2的全编码外显子基因序列。结果:54例家族性乳腺癌患者中共发现8例致病性突变,突变类型均为单个碱基置换,BRCA1和BRCA2的总突变率为14.8%,BRCA1突变率为11.1%,BRCA2突变率为3.7%;其中,三阴性乳腺癌患者BRCA总突变率高于非三阴性乳腺癌患者的总突变率(28.6%vs 12.8%),差异具有统计学意义(P0.05)。24例遗传性高危人群中共发现2例致病性突变,均为BRCA1基因突变,突变率为8.3%。结论:用BRCA1/2突变检测"金标准"的一代测序法再次发现在中国汉族女性家族性乳腺癌中存在的BRCA1/2突变,与三阴性乳腺癌有关,并发现碱基置换突变也是重要的突变类型;在健康遗传性高危人群中存在一定比例的BRCA1突变,值得关注。     

Clinical Evaluation of BRCA1/2 Mutation in Mexican Ovarian Cancer Patients

Ovarian cancer (OC) is an important cause of gynecologic cancer-related deaths. In Mexico, around 4700 new cases of OC are diagnosed per year and it represents the second cause of gynecological cancer mortality with more than 2700 deaths. Germline mutations in BRCA1/2 genes are present in 13–18% of OC cases. Few studies have evaluated the presence of mutations in BRCA genes in a population of OC Mexican patients and their relationship with clinical response and survival rates.A total of 179 OC patients were studied by molecular testing for BRCA1/2 through next-generation sequencing and multiplex ligation-dependent probe amplification. Recurrence-free survival (RFS) was estimated by the Kaplan–Meier method. BRCA mutation was detected in 33% of patients. A percentage of 66.1% were BRCA1 mutated and 33.9% were BRCA2 mutated. BRCA1 mutation carriers had a worst RFS compared with BRCA2 mutation carriers (37.6 [29–46.2] vs 72.7 [38.4–107.2]; P = 0.030). The most common mutation for BRCA1 was ex9-12del (28.2%) (Mexican founder mutation). The Mexican founder mutation had a better RFS than other BRCA1 mutations (86.1 [37.2–135.1] vs 34.5 [20.7–48.2]; P = 0.033). The presence of BRCA2 mutations in the ovarian cancer cluster region (OCCR) had a significantly better RFS than mutations in breast cancer cluster regions (BCCR) and not-related risk region (NRR) (NR vs 72.8 [39–106.6] vs 25.8 [8.3–43.2]; P = 0.013). These results demonstrate that the prevalence of BRCA1/2 positive patients in OC Mexican patients are the highest reported. Patients with mutations in BRCA2 have a better prognosis than those mutated in BRCA1. The Mexican founder mutation has an important role in clinical outcomes. These results highlight the importance to test all the HGSP (high-grade serous papillary) OC patients with or without cancer family history (CFH) in Mexican population.     

Tumor Mutation Burden Forecasts Outcome in Ovarian Cancer with BRCA1 or BRCA2 Mutations

Background

Increased number of single nucleotide substitutions is seen in breast and ovarian cancer genomes carrying disease-associated mutations in BRCA1 or BRCA2. The significance of these genome-wide mutations is unknown. We hypothesize genome-wide mutation burden mirrors deficiencies in DNA repair and is associated with treatment outcome in ovarian cancer.

Methods and Results

The total number of synonymous and non-synonymous exome mutations (Nmut), and the presence of germline or somatic mutation in BRCA1 or BRCA2 (mBRCA) were extracted from whole-exome sequences of high-grade serous ovarian cancers from The Cancer Genome Atlas (TCGA). Cox regression and Kaplan-Meier methods were used to correlate Nmut with chemotherapy response and outcome. Higher Nmut correlated with a better response to chemotherapy after surgery. In patients with mBRCA-associated cancer, low Nmut was associated with shorter progression-free survival (PFS) and overall survival (OS), independent of other prognostic factors in multivariate analysis. Patients with mBRCA-associated cancers and a high Nmut had remarkably favorable PFS and OS. The association with survival was similar in cancers with either BRCA1 or BRCA2 mutations. In cancers with wild-type BRCA, tumor Nmut was associated with treatment response in patients with no residual disease after surgery.

Conclusions

Tumor Nmut was associated with treatment response and with both PFS and OS in patients with high-grade serous ovarian cancer carrying BRCA1 or BRCA2 mutations. In the TCGA cohort, low Nmut predicted resistance to chemotherapy, and for shorter PFS and OS, while high Nmut forecasts a remarkably favorable outcome in mBRCA-associated ovarian cancer. Our observations suggest that the total mutation burden coupled with BRCA1 or BRCA2 mutations in ovarian cancer is a genomic marker of prognosis and predictor of treatment response. This marker may reflect the degree of deficiency in BRCA-mediated pathways, or the extent of compensation for the deficiency by alternative mechanisms.     

Assessing Associations between the AURKA-HMMR-TPX2-TUBG1 Functional Module and Breast Cancer Risk in BRCA1/2 Mutation Carriers

While interplay between BRCA1 and AURKA-RHAMM-TPX2-TUBG1 regulates mammary epithelial polarization, common genetic variation in HMMR (gene product RHAMM) may be associated with risk of breast cancer in BRCA1 mutation carriers. Following on these observations, we further assessed the link between the AURKA-HMMR-TPX2-TUBG1 functional module and risk of breast cancer in BRCA1 or BRCA2 mutation carriers. Forty-one single nucleotide polymorphisms (SNPs) were genotyped in 15,252 BRCA1 and 8,211 BRCA2 mutation carriers and subsequently analyzed using a retrospective likelihood approach. The association of HMMR rs299290 with breast cancer risk in BRCA1 mutation carriers was confirmed: per-allele hazard ratio (HR) = 1.10, 95% confidence interval (CI) 1.04 – 1.15, p = 1.9 x 10⁻⁴ (false discovery rate (FDR)-adjusted p = 0.043). Variation in CSTF1, located next to AURKA, was also found to be associated with breast cancer risk in BRCA2 mutation carriers: rs2426618 per-allele HR = 1.10, 95% CI 1.03 – 1.16, p = 0.005 (FDR-adjusted p = 0.045). Assessment of pairwise interactions provided suggestions (FDR-adjusted p_interaction values > 0.05) for deviations from the multiplicative model for rs299290 and CSTF1 rs6064391, and rs299290 and TUBG1 rs11649877 in both BRCA1 and BRCA2 mutation carriers. Following these suggestions, the expression of HMMR and AURKA or TUBG1 in sporadic breast tumors was found to potentially interact, influencing patients’ survival. Together, the results of this study support the hypothesis of a causative link between altered function of AURKA-HMMR-TPX2-TUBG1 and breast carcinogenesis in BRCA1/2 mutation carriers.     

Polymorphic Repeat Length in the AIB1 Gene and Breast Cancer Risk in BRCA1 and BRCA2 Mutation Carriers: A Meta-Analysis of Observational Studies

Objectives

We carried out a meta-analysis focusing on the relationship between length of AIB1 gene poly-Q repeat domain as a modifier of breast cancer (BC) susceptibility in patients with BRCA1 and BRCA2 mutation carriers.

Data sources

We searched MEDLINE and EMBASE for all medical literature published until February, 2012.

Study Eligibility criteria

Studies were included in the meta-analysis if they met all the predetermined criteria, such as: (a) case-control or cohort studies; (b) the primary outcome was clearly defined as BC; (c) the exposure of interest measured was AIB1 polyglutamine repeat length genotype; (d) provided relative risk (RR) or odds ratio (OR) estimates and their 95% confidence intervals (CIs).

Synthesis methods

Two of the authors independently evaluated the quality of the studies included and extracted the data. Meta-analyses were performed for case-control and cohort studies separately. Heterogeneity was examined and the publication bias was assessed with a funnel plot for asymmetry.

Result

7 studies met our predetermined inclusion criteria and were included in the meta-analysis. Overall quality ratings of the studies varied from 0.36 to 0.77, with a median of 0.5. The overall RR estimates of 29/29 poly-Q repeats on risk of BC in BRCA1/2, BRCA1, and BRCA2, were always greater than 1.00; however, this effect was not statistically significant. In the meta-analysis of studies reporting the effect of 28/28 poly-Q repeats on risk of BC in BRCA1/2, BRCA1, and BRCA2, the overall RR decreased below 1.00; however, this effect was not statistically significant. Similar estimates were shown for at least 1 allele of ≤26 repeats.

Conclusions

Genotypes of AIB1 polyglutamine polymorphism analyzed do not appear to be associated to a modified risk of BC development in BRCA1 and BRCA2 mutation carriers. Future research on length of poly-Q repeat domain and BC susceptibility should be discouraged and more promising potential sources of penetrance variation among BRCA1 and BRCA2 mutation carriers should be investigated.     

Prevalence of PALB2 Mutations in Breast Cancer Patients in Multi-Ethnic Asian Population in Malaysia and Singapore

Background

The partner and localizer of breast cancer 2 (PALB2) is responsible for facilitating BRCA2-mediated DNA repair by serving as a bridging molecule, acting as the physical and functional link between the breast cancer 1 (BRCA1) and breast cancer 2 (BRCA2) proteins. Truncating mutations in the PALB2 gene are rare but are thought to be associated with increased risks of developing breast cancer in various populations.

Methods

We evaluated the contribution of PALB2 germline mutations in 122 Asian women with breast cancer, all of whom had significant family history of breast and other cancers. Further screening for nine PALB2 mutations was conducted in 874 Malaysian and 532 Singaporean breast cancer patients, and in 1342 unaffected Malaysian and 541 unaffected Singaporean women.

Results

By analyzing the entire coding region of PALB2, we found two novel truncating mutations and ten missense mutations in families tested negative for BRCA1/2-mutations. One additional novel truncating PALB2 mutation was identified in one patient through genotyping analysis. Our results indicate a low prevalence of deleterious PALB2 mutations and a specific mutation profile within the Malaysian and Singaporean populations.     

Genome-Wide Association Study in BRCA1 Mutation Carriers Identifies Novel Loci Associated with Breast and Ovarian Cancer Risk

BRCA1-associated breast and ovarian cancer risks can be modified by common genetic variants. To identify further cancer risk-modifying loci, we performed a multi-stage GWAS of 11,705 BRCA1 carriers (of whom 5,920 were diagnosed with breast and 1,839 were diagnosed with ovarian cancer), with a further replication in an additional sample of 2,646 BRCA1 carriers. We identified a novel breast cancer risk modifier locus at 1q32 for BRCA1 carriers (rs2290854, P = 2.7×10⁻⁸, HR = 1.14, 95% CI: 1.09–1.20). In addition, we identified two novel ovarian cancer risk modifier loci: 17q21.31 (rs17631303, P = 1.4×10⁻⁸, HR = 1.27, 95% CI: 1.17–1.38) and 4q32.3 (rs4691139, P = 3.4×10⁻⁸, HR = 1.20, 95% CI: 1.17–1.38). The 4q32.3 locus was not associated with ovarian cancer risk in the general population or BRCA2 carriers, suggesting a BRCA1-specific association. The 17q21.31 locus was also associated with ovarian cancer risk in 8,211 BRCA2 carriers (P = 2×10⁻⁴). These loci may lead to an improved understanding of the etiology of breast and ovarian tumors in BRCA1 carriers. Based on the joint distribution of the known BRCA1 breast cancer risk-modifying loci, we estimated that the breast cancer lifetime risks for the 5% of BRCA1 carriers at lowest risk are 28%–50% compared to 81%–100% for the 5% at highest risk. Similarly, based on the known ovarian cancer risk-modifying loci, the 5% of BRCA1 carriers at lowest risk have an estimated lifetime risk of developing ovarian cancer of 28% or lower, whereas the 5% at highest risk will have a risk of 63% or higher. Such differences in risk may have important implications for risk prediction and clinical management for BRCA1 carriers.     

High Levels of Nucleolar Spindle-Associated Protein and Reduced Levels of BRCA1 Expression Predict Poor Prognosis in Triple-Negative Breast Cancer

Purpose

Nucleolar spindle-associated protein (NuSAP1) is an important mitosis-related protein, and aberrant NuSAP1 expression is associated with abnormal spindles and mitosis. This study investigated the prognostic value of NuSAP1 in breast cancer.

Methods

Two sets of tissue microarrays (TMAs) that included samples from 450 breast cancer patients were constructed, of which 250 patients were training set and the other 200 patients were validation set. Immunohistochemical staining was performed to determine the NuSAP1 levels. A Kaplan-Meier analysis was used to estimate the prognostic value of NuSAP1 in breast cancer. A stepwise Cox analysis was performed to construct a risk-prediction model for triple-negative breast cancer (TNBC). All statistical analysis was performed with SPSS software.

Results

There were 108 (43.5%) and 88 (44.0%) patients expressed NuSAP1 in the training set and validation set respectively. High levels of NuSAP1 expression were related to poor disease-free survival (DFS) in both training (P = 0.028) and validation (P = 0.006) cohorts, particularly in TNBC. With combination of two cohorts, both NuSAP1 (HR = 4.136, 95% CI: 1.956–8.747, P < 0.001) and BRCA1 (HR = 0.383, 95% CI: 0.160–0.915, P = 0.031) were independent prognostic indicators of DFS in TNBC. A receiver operating characteristic (ROC) analysis revealed that the combination of NuSAP1 and BRCA1 significantly improved the prognostic power compared with the traditional model (0.778 versus 0.612, P < 0.001).

Conclusions

Our study confirms the prognostic value of NuSAP1 in breast cancer. The combination of NuSAP1 and BRCA1 could improve the DFS prediction accuracy in TNBC.     

Copy Number Variation Analysis in Familial BRCA1/2-Negative Finnish Breast and Ovarian Cancer

Background

Inherited factors predisposing individuals to breast and ovarian cancer are largely unidentified in a majority of families with hereditary breast and ovarian cancer (HBOC). We aimed to identify germline copy number variations (CNVs) contributing to HBOC susceptibility in the Finnish population.

Methods

A cohort of 84 HBOC individuals (negative for BRCA1/2-founder mutations and pre-screened for the most common breast cancer genes) and 36 healthy controls were analysed with a genome-wide SNP array. CNV-affecting genes were further studied by Gene Ontology term enrichment, pathway analyses, and database searches to reveal genes with potential for breast and ovarian cancer predisposition. CNVs that were considered to be important were validated and genotyped in 20 additional HBOC individuals (6 CNVs) and in additional healthy controls (5 CNVs) by qPCR.

Results

An intronic deletion in the EPHA3 receptor tyrosine kinase was enriched in HBOC individuals (12 of 101, 11.9%) compared with controls (27 of 432, 6.3%) (OR = 1.96; P = 0.055). EPHA3 was identified in several enriched molecular functions including receptor activity. Both a novel intronic deletion in the CSMD1 tumor suppressor gene and a homozygous intergenic deletion at 5q15 were identified in 1 of 101 (1.0%) HBOC individuals but were very rare (1 of 436, 0.2% and 1 of 899, 0.1%, respectively) in healthy controls suggesting that these variants confer disease susceptibility.

Conclusion

This study reveals new information regarding the germline CNVs that likely contribute to HBOC susceptibility in Finland. This information may be used to facilitate the genetic counselling of HBOC individuals but the preliminary results warrant additional studies of a larger study group.     

Telomere Length Shows No Association with BRCA1 and BRCA2 Mutation Status

This study aimed to determine whether telomere length (TL) is a marker of cancer risk or genetic status amongst two cohorts of BRCA1 and BRCA2 mutation carriers and controls. The first group was a prospective set of 665 male BRCA1/2 mutation carriers and controls (mean age 53 years), all healthy at time of enrolment and blood donation, 21 of whom have developed prostate cancer whilst on study. The second group consisted of 283 female BRCA1/2 mutation carriers and controls (mean age 48 years), half of whom had been diagnosed with breast cancer prior to enrolment. TL was quantified by qPCR from DNA extracted from peripheral blood lymphocytes. Weighted and unweighted Cox regressions and linear regression analyses were used to assess whether TL was associated with BRCA1/2 mutation status or cancer risk. We found no evidence for association between developing cancer or being a BRCA1 or BRCA2 mutation carrier and telomere length. It is the first study investigating TL in a cohort of genetically predisposed males and although TL and BRCA status was previously studied in females our results don''t support the previous finding of association between hereditary breast cancer and shorter TL.     

DNA Glycosylases Involved in Base Excision Repair May Be Associated with Cancer Risk in BRCA1 and BRCA2 Mutation Carriers

Single Nucleotide Polymorphisms (SNPs) in genes involved in the DNA Base Excision Repair (BER) pathway could be associated with cancer risk in carriers of mutations in the high-penetrance susceptibility genes BRCA1 and BRCA2, given the relation of synthetic lethality that exists between one of the components of the BER pathway, PARP1 (poly ADP ribose polymerase), and both BRCA1 and BRCA2. In the present study, we have performed a comprehensive analysis of 18 genes involved in BER using a tagging SNP approach in a large series of BRCA1 and BRCA2 mutation carriers. 144 SNPs were analyzed in a two stage study involving 23,463 carriers from the CIMBA consortium (the Consortium of Investigators of Modifiers of BRCA1 and BRCA2). Eleven SNPs showed evidence of association with breast and/or ovarian cancer at p<0.05 in the combined analysis. Four of the five genes for which strongest evidence of association was observed were DNA glycosylases. The strongest evidence was for rs1466785 in the NEIL2 (endonuclease VIII-like 2) gene (HR: 1.09, 95% CI (1.03–1.16), p = 2.7×10⁻³) for association with breast cancer risk in BRCA2 mutation carriers, and rs2304277 in the OGG1 (8-guanine DNA glycosylase) gene, with ovarian cancer risk in BRCA1 mutation carriers (HR: 1.12 95%CI: 1.03–1.21, p = 4.8×10⁻³). DNA glycosylases involved in the first steps of the BER pathway may be associated with cancer risk in BRCA1/2 mutation carriers and should be more comprehensively studied.     

Mutation analysis of BRCA1 and BRCA2 in a male breast cancer population.

A population-based series of 54 male breast cancer cases from Southern California were analyzed for germ-line mutations in the inherited breast/ovarian cancer genes, BRCA1 and BRCA2. Nine (17%) of the patients had a family history of breast and/or ovarian cancer in at least one first-degree relative. A further seven (13%) of the patients reported breast/ovarian cancer in at least one second-degree relative and in no first-degree relatives. No germ-line BRCA1 mutations were found. Two male breast cancer patients (4% of the total) were found to carry novel truncating mutations in the BRCA2 gene. Only one of the two male breast cancer patients carrying a BRCA2 mutation had a family history of cancer, with one case of ovarian cancer in a first-degree relative. The remaining eight cases (89%) of male breast cancer with a family history of breast/ovarian cancer in first-degree relatives remain unaccounted for by mutations in either the BRCA1 gene or the BRCA2 gene.     

Control of BRCA2 cellular and clinical functions by a nuclear partner, PALB2

BRCA2 mutations predispose carriers to breast and ovarian cancer and can also cause other cancers and Fanconi anemia. BRCA2 acts as a "caretaker" of genome integrity by enabling homologous recombination (HR)-based, error-free DNA double-strand break repair (DSBR) and intra-S phase DNA damage checkpoint control. Described here is the identification of PALB2, a BRCA2 binding protein. PALB2 colocalizes with BRCA2 in nuclear foci, promotes its localization and stability in key nuclear structures (e.g., chromatin and nuclear matrix), and enables its recombinational repair and checkpoint functions. In addition, multiple, germline BRCA2 missense mutations identified in breast cancer patients but of heretofore unknown biological/clinical consequence appear to disrupt PALB2 binding and disable BRCA2 HR/DSBR function. Thus, PALB2 licenses key cellular biochemical properties of BRCA2 and ensures its tumor suppression function.     

Age-Related Disparity in Immediate Prognosis of Patients with Triple-Negative Breast Cancer: A Population-Based Study from SEER Cancer Registries

Background

Triple-negative breast cancer (TNBC) has been demonstrated to carry poor prognosis, but whether or not there exists any age-related variation in TNBC outcomes has yet to be elucidated. The current population-based study investigated the early survival pattern of elderly women with TNBC and identified outcome-correlated factors.

Patients and Methods

We searched the Surveillance, Epidemiology, and End Results (SEER) database and enrolled female primary non-metastatic TNBC cases. The patients were subdivided into elderly (≥70 years) and young groups (<70 years). The survival status of elderly patients was compared to that of the younger women. The primary and secondary endpoints were cancer-specific survival (CSS) and overall survival (OS) respectively.

Results

9908 female TNBC patients diagnosed from 2010 to 2011 were included in the current study (20.4% elderly). Elderly patients with relatively advanced diseases exhibited distinctly worse cancer-specific (log-rank, p<0.001) and overall survival (log-rank, p<0.001) than their young counterparts. Advanced age at diagnosis (≥70 years) was significantly predictive of poor outcome in terms of CSS (hazard ratio (HR), 2.125; 95% confidence interval (CI), 1.664 to 2.713; p<0.001) and OS (HR, 3.042; 95%CI, 2.474 to 3.740; p<0.001). Underuse of curative treatment especially radiotherapy was more prevalent in elderly women with stage II or III diseases than in younger patients.

Conclusion

Elderly patients with TNBC displayed elevated early mortality within the first two years of diagnosis compared to the younger individuals. The observed lower rate of loco-regional treatment might be associated with worse cancer-specific outcome for these patients.     

Identification of BRCA1/2 Founder Mutations in Southern Chinese Breast Cancer Patients Using Gene Sequencing and High Resolution DNA Melting Analysis

Background

Ethnic variations in breast cancer epidemiology and genetics have necessitated investigation of the spectra of BRCA1 and BRCA2 mutations in different populations. Knowledge of BRCA mutations in Chinese populations is still largely unknown. We conducted a multi-center study to characterize the spectra of BRCA mutations in Chinese breast and ovarian cancer patients from Southern China.

Methodology/Principal Findings

A total of 651 clinically high-risk breast and/or ovarian cancer patients were recruited from the Hong Kong Hereditary Breast Cancer Family Registry from 2007 to 2011. Comprehensive BRCA1 and BRCA2 mutation screening was performed using bi-directional sequencing of all coding exons of BRCA1 and BRCA2. Sequencing results were confirmed by in-house developed full high resolution DNA melting (HRM) analysis. Among the 451 probands analyzed, 69 (15.3%) deleterious BRCA mutations were identified, comprising 29 in BRCA1 and 40 in BRCA2. The four recurrent BRCA1 mutations (c.470_471delCT, c.3342_3345delAGAA, c.5406+1_5406+3delGTA and c.981_982delAT) accounted for 34.5% (10/29) of all BRCA1 mutations in this cohort. The four recurrent BRCA2 mutations (c.2808_2811delACAA, c.3109C>T, c.7436_7805del370 and c.9097_9098insA) accounted for 40% (16/40) of all BRCA2 mutations. Haplotype analysis was performed to confirm 1 BRCA1 and 3 BRCA2 mutations are putative founder mutations. Rapid HRM mutation screening for a panel of the founder mutations were developed and validated.

Conclusion

In this study, our findings suggest that BRCA mutations account for a substantial proportion of hereditary breast/ovarian cancer in Southern Chinese population. Knowing the spectrum and frequency of the founder mutations in this population will assist in the development of a cost-effective rapid screening assay, which in turn facilitates genetic counseling and testing for the purpose of cancer risk assessment.