Large genomic rearrangements of the BRCA1 and BRCA2 genes: review of the literature and report of a novel BRCA1 mutation

Germline mutations of breast cancer susceptibility genes through expanded genetic analysis in unselected Colombian patients

BACKGROUND

In Colombia and worldwide, breast cancer (BC) is the most frequently diagnosed neoplasia and the leading cause of death from cancer among women. Studies predominantly involve hereditary and familial cases, demonstrating a gap in the literature regarding the identification of germline mutations in unselected patients from Latin-America. Identification of pathogenic/likely pathogenic (P/LP) variants is important for shaping national genetic analysis policies, genetic counseling, and early detection strategies. The present study included 400 women with unselected breast cancer (BC), in whom we analyzed ten genes, using Whole Exome Sequencing (WES), know to confer risk for BC, with the aim of determining the genomic profile of previously unreported P/LP variants in the affected population. Additionally, Multiplex Ligation-dependent Probe Amplification (MLPA) was performed to identify Large Genomic Rearrangements (LGRs) in the BRCA1/2 genes. To ascertain the functional impact of a recurrent intronic variant (ATM c.5496 + 2_5496 + 5delTAAG), a minigene assay was conducted.

RESULTS

We ascertained the frequency of P/LP germline variants in BRCA2 (2.5%), ATM (1.25%), BRCA1 (0.75%), PALB2 (0.50%), CHEK2 (0.50%), BARD1 (0.25%), and RAD51D (0.25%) genes in the population of study. P/LP variants account for 6% of the total population analyzed. No LGRs were detected in our study. We identified 1.75% of recurrent variants in BRCA2 and ATM genes. One of them corresponds to the ATM c.5496 + 2_5496 + 5delTAAG. Functional validation of this variant demonstrated a splicing alteration probably modifying the Pincer domain and subsequent protein structure.

CONCLUSION

This study described for the first time the genomic profile of ten risk genes in Colombian women with unselected BC. Our findings underscore the significance of population-based research, advocating the consideration of molecular testing in all women with cancer.

Assessment of BRCA1 and BRCA2 Germline Variant Data From Patients With Breast Cancer in a Real-World Data Registry

PURPOSE

The emergence of large real-world clinical databases and tools to mine electronic medical records has allowed for an unprecedented look at large data sets with clinical and epidemiologic correlates. In clinical cancer genetics, real-world databases allow for the investigation of prevalence and effectiveness of prevention strategies and targeted treatments and for the identification of barriers to better outcomes. However, real-world data sets have inherent biases and problems (eg, selection bias, incomplete data, measurement error) that may hamper adequate analysis and affect statistical power.

METHODS

Here, we leverage a real-world clinical data set from a large health network for patients with breast cancer tested for variants in BRCA1 and BRCA2 (N = 12,423). We conducted data cleaning and harmonization, cross-referenced with publicly available databases, performed variant reassessment and functional assays, and used functional data to inform a variant's clinical significance applying American College of Medical Geneticists and the Association of Molecular Pathology guidelines.

RESULTS

In the cohort, White and Black patients were over-represented, whereas non-White Hispanic and Asian patients were under-represented. Incorrect or missing variant designations were the most significant contributor to data loss. While manual curation corrected many incorrect designations, a sizable fraction of patient carriers remained with incorrect or missing variant designations. Despite the large number of patients with clinical significance not reported, original reported clinical significance assessments were accurate. Reassessment of variants in which clinical significance was not reported led to a marked improvement in data quality.

CONCLUSION

We identify the most common issues with BRCA1 and BRCA2 testing data entry and suggest approaches to minimize data loss and keep interpretation of clinical significance of variants up to date.

Circulating Tumor DNA Enables Sensitive Detection of Actionable Gene Fusions and Rearrangements Across Cancer Types

PURPOSE

Genomic rearrangements can generate potent oncogenic drivers or disrupt tumor suppressor genes. This study examines the landscape of fusions and rearrangements detected by liquid biopsy (LBx) of circulating tumor DNA (ctDNA) across different cancer types.

EXPERIMENTAL DESIGN

LBx from 53,842 patients with 66 solid tumor types were profiled using FoundationOneLiquid CDx, a hybrid-capture sequencing platform that queries 324 cancer-related genes. Tissue biopsies (TBx) profiled using FoundationOneCDx were used as a comparator.

RESULTS

Among all LBx, 7,377 (14%) had ≥1 pathogenic rearrangement detected. A total of 3,648 (6.8%) LBx had ≥1 gain-of-function (GOF) oncogene rearrangement, and 4,428 (8.2%) LBx had ≥1 loss-of-function rearrangement detected. Cancer types with higher prevalence of GOF rearrangements included those with canonical fusion drivers: prostate cancer (19%), cholangiocarcinoma (6.4%), bladder (5.5%), and non-small cell lung cancer (4.4%). Although the prevalence of driver rearrangements was lower in LBx than TBx overall, the frequency of detection was comparable in LBx with a tumor fraction (TF) ≥1%. Rearrangements in FGFR2, BRAF, RET, and ALK, were detected across cancer types, but tended to be clonal variants in some cancer types and potential acquired resistance variants in others.

CONCLUSIONS

In contrast to some prior literature, this study reports detection of a wide variety of rearrangements in ctDNA. The prevalence of driver rearrangements in tissue and LBx was comparable when TF ≥1%. LBx presents a viable alternative when TBx is not available, and there may be less value in confirmatory testing when TF is sufficient.

Gender-Specific Genetic Predisposition to Breast Cancer: BRCA Genes and Beyond

Among neoplastic diseases, breast cancer (BC) is one of the most influenced by gender. Despite common misconceptions associating BC as a women-only disease, BC can also occur in men. Additionally, transgender individuals may also experience BC. Genetic risk factors play a relevant role in BC predisposition, with important implications in precision prevention and treatment. The genetic architecture of BC susceptibility is similar in women and men, with high-, moderate-, and low-penetrance risk variants; however, some sex-specific features have emerged. Inherited high-penetrance pathogenic variants (PVs) in BRCA1 and BRCA2 genes are the strongest BC genetic risk factor. BRCA1 and BRCA2 PVs are more commonly associated with increased risk of female and male BC, respectively. Notably, BRCA-associated BCs are characterized by sex-specific pathologic features. Recently, next-generation sequencing technologies have helped to provide more insights on the role of moderate-penetrance BC risk variants, particularly in PALB2, CHEK2, and ATM genes, while international collaborative genome-wide association studies have contributed evidence on common low-penetrance BC risk variants, on their combined effect in polygenic models, and on their role as risk modulators in BRCA1/2 PV carriers. Overall, all these studies suggested that the genetic basis of male BC, although similar, may differ from female BC. Evaluating the genetic component of male BC as a distinct entity from female BC is the first step to improve both personalized risk assessment and therapeutic choices of patients of both sexes in order to reach gender equality in BC care. In this review, we summarize the latest research in the field of BC genetic predisposition with a particular focus on similarities and differences in male and female BC, and we also discuss the implications, challenges, and open issues that surround the establishment of a gender-oriented clinical management for BC.

A MALDI-TOF mass spectrometry-based method for detection of copy number variations in BRCA1 and BRCA2 genes

Background: Identifying germline mutations in BRCA1 and BRCA2 genes (BRCAs) would benefit the carriers in multiple aspects. In addition to single-nucleotide variations and small indels, copy number variations (CNVs) is also an indispensable component of identifiable mutations in BRCAs. A sensitive, rapid and throughput-flexible method to detect CNVs would be preferred to meet the rising clinical requirements for BRCAs testing. Methods: We developed a MALDI-TOF-MS-based method (MS assay) which included three steps: first, multiplex end-point PCR followed by a single base extension reaction; second, automated analyte transfer and data acquisition; third, data analysis. We applied MS assay to detect CNVs in BRCAs in 293 Chinese patients with ovarian or pancreatic cancer. All the samples were examined by targeted next-generation sequencing (TS) simultaneously. Samples were further cross-validated by multiplex ligation-dependent probe amplification (MLPA) if the results from MS assay and TS were inconsistent. Long range PCR was then applied to identify the exact breakpoints in BRCAs. Results: MS assay introduced highly multiplexed panels to detect CNVs of BRCAs semi-quantitatively. Simplified on-board data analysis was available for MS assay and no complex bioinformatics was needed. The turnaround time of MS assay was less than 8 hours with a hands-on time of only 40 min. Compared to TS, MS assay exhibited higher sensitivity (100% vs. 75%) and was more flexible in throughput, with the reagent cost per sample remaining constant no matter how many samples were examined per assay. A total of eight CNVs in BRCAs were detected from the 293 samples, and the molecular breakpoints were successfully identified in five samples through long-range PCR followed by Sanger sequencing. Conclusion: Our results suggested that MS assay might be an effective method in primary screening for CNVs in genes such as BRCAs, especially when short turnaround time and/or high sensitivity is a top priority.

Genetic medicine in companion diagnostics of germline BRCA testing of Japanese pancreatic cancer patients

In 2021, Japan's national health insurance made germline BRCA (g.BRCA) testing available to unresectable pancreatic cancer (PC) patients as a companion diagnostic (CD) of the PARP inhibitor. This study investigated the incidence of the g.BRCA variant (g.BRCAv.) and the status of the genetic medicine associated with its testing. A total of 110 PC patients underwent the testing, five of whom (4.5%) had a deleterious g.BRCA2v. (all truncations) but no g.BRCA1v. The turnaround time (TAT) to the doctors was 13 days, and to the patients, 17 days. A higher incidence of a BRCA-related family history and a shorter TAT were seen in the g.BRCAv. patients, but they were insignificant (p = 0.085 and p = 0.059, respectively). Genetic counseling was not performed for three g.BRCA2v. patients because two of them had no accessible relatives and one died of the cancer before the genetic report was completed. Two families underwent generic counseling and testing based on the patient's genetic data. g.BRCAv. is recognized in a small fraction of PC cases, and the following genetic counseling is done more for the relatives than for the patients. TAT was constant and did not affect much on the genetic counseling, but the earlier testing is expected for patients with a deadly cancer.

Case Report: Clinical benefit from multi-target tyrosine kinase inhibitor and PARP inhibitor in a patient with cancer of unknown primary with BRCA1 large genomic rearrangement

Background: Cancer of unknown primary (CUP), which accounts for 3%-5% of new cancer cases every year, involves the presence of a type of histologically confirmed metastatic tumors whose primary site cannot be confirmed by conventional diagnostic methods. This difficulty in identifying the primary site means that CUP patients fail to receive precisely targeted therapy. Most patients are treated with empiric chemotherapy, with a median survival of 6 months and even poorer prognosis within an unfavorable subset of CUP. Case report: An 80-year-old woman presented with masses in the abdomen. Following comprehensive imagological and immunohistochemical examinations, she was diagnosed with CUP. She emphatically declined chemotherapy; thus, anlotinib has been administered with patient consent since 02/07/2019, and stable disease (SD) was observed for 2 years. During subsequent treatment, a large genomic rearrangement in BRCA1 was identified in the patient via NGS, and SD was observed for a further 6 months following olaparib treatment. The type of LGR identified in this patient was discovered to be BRCA1 exon 17-18 inversion (inv), which has never been previously reported. Conclusion: For CUP patients, a chemo-free regimen seems to be acceptable as a first-line treatment, and NGS-guided targeted treatment could improve patient outcomes.

Copy Number Variants Are Ovarian Cancer Risk Alleles at Known and Novel Risk Loci

BACKGROUND

Known risk alleles for epithelial ovarian cancer (EOC) account for approximately 40% of the heritability for EOC. Copy number variants (CNVs) have not been investigated as EOC risk alleles in a large population cohort.

METHODS

Single nucleotide polymorphism array data from 13 071 EOC cases and 17 306 controls of White European ancestry were used to identify CNVs associated with EOC risk using a rare admixture maximum likelihood test for gene burden and a by-probe ratio test. We performed enrichment analysis of CNVs at known EOC risk loci and functional biofeatures in ovarian cancer-related cell types.

RESULTS

We identified statistically significant risk associations with CNVs at known EOC risk genes; BRCA1 (PEOC = 1.60E-21; OREOC = 8.24), RAD51C (Phigh-grade serous ovarian cancer [HGSOC] = 5.5E-4; odds ratio [OR]HGSOC = 5.74 del), and BRCA2 (PHGSOC = 7.0E-4; ORHGSOC = 3.31 deletion). Four suggestive associations (P < .001) were identified for rare CNVs. Risk-associated CNVs were enriched (P < .05) at known EOC risk loci identified by genome-wide association study. Noncoding CNVs were enriched in active promoters and insulators in EOC-related cell types.

CONCLUSIONS

CNVs in BRCA1 have been previously reported in smaller studies, but their observed frequency in this large population-based cohort, along with the CNVs observed at BRCA2 and RAD51C gene loci in EOC cases, suggests that these CNVs are potentially pathogenic and may contribute to the spectrum of disease-causing mutations in these genes. CNVs are likely to occur in a wider set of susceptibility regions, with potential implications for clinical genetic testing and disease prevention.

Next-generation sequencing based detection of BRCA1 and BRCA2 large genomic rearrangements in Chinese cancer patients

BRCA1/2 mutation is a biomarker for guiding multiple solid tumor treatment. However, the prevalence of BRCA1/2 large genomic rearrangements (LGRs) in Chinese cancer patients has not been well revealed partially due to technical difficulties in LGR detection. This study utilized next-generation sequencing (NGS) to analyze the BRCA1/2 mutation profile, including LGR, in 56126 Chinese cancer patients. We also reported that two ovarian and breast cancer patients with NGS-determined BRCA1/2 LGR benefited from PARP inhibitors (PARPi). DNA sequencing identified BRCA1/2 variants (including LGR, pathogenic and likely-pathogenic variants) in 2108 individuals. Seventy patients were discovered to harbor germline LGRs in BRCA1 and 14 had germline LGRs in BRCA2. Among the LGRs detected, exon 1-2 deletion was the predominant LGR (14/70) in BRCA1, and exon 22-24 deletion was the most frequent LGR (3/14) in BRCA2. Notably, the BRCA1 exon 7 deletion was a novel LGR and was identified in six patients, suggesting a specific LGR in Chinese cancer patients. The prevalence analysis of BRCA1 and BRCA2 LGRs across multiple cancers revealed that BRCA1 LGR more frequently occurred in ovarian cancer (1.31%, 33/2526), and BRCA2 LGR was more commonly seen in cholangiocarcinoma (0.47%, 2/425). Two ovarian and breast cancer patients with BRCA1/2 LGR benefited from PARPi therapy. This is the first study to reveal the BRCA1/2 LGR profile of a Chinese pan-cancer cohort by using an NGS-based assay. Two breast and ovarian cancer patients harboring NGS-determined BRCA1/2 LGR benefited from PARPi, indicating that NGS-based detection of BRCA1/2 LGR has the potential to guide PARPi treatment.

Clinical Benefits of Olaparib in Mexican Ovarian Cancer Patients With Founder Mutation BRCA1-Del ex9-12

Background: Ovarian cancer (OC) is gynecologic cancer with the highest mortality rate. It is estimated that 13–17% of ovarian cancers are due to heritable mutations in BRCA1 and BRCA2. The BRCA1 (BRCA1-Del ex9-12) Mexican founder mutation is responsible for 28–35% of the cases with ovarian cancer. The aim was to describe the PFS of OC patients treated with olaparib, emphasizing patients carrying the Mexican founder mutation (BRCA1-Del ex9-12).

Methods: In this observational study, of 107 patients with BRCAm, 35 patients were treated with olaparib from November 2016 to May 2021 at the Ovarian Cancer Program (COE) of Mexico; patient information was extracted from electronic medical records.

Results: Of 311 patients, 107 (34.4%) were with BRCAm; 71.9% (77/107) were with BRCA1, of which 27.3% (21/77) were with BRCA1-Del ex9-12, and 28.1% (30/107) were with BRCA2 mutations. Only 35 patients received olaparib treatment, and the median follow-up was 12.87 months. The PFS of BRCA1-Del ex9-12 was NR (non-reach); however, 73% of the patients received the treatment at 36 vs. 11.59 months (95% CI; 10.43–12.75) in patients with other BRCAm (p = 0.008). Almost 50% of patients required dose reduction due to toxicity; the most frequent adverse events were hematological in 76.5% and gastrointestinal in 4%.

Conclusion: Mexican OC BRCA1-Del ex9-12 patients treated with olaparib had a significant increase in PFS regardless of the line of treatment compared to other mutations in BRCA.

Prevalence of Clinically Relevant Germline BRCA Variants in a Large Unselected South African Breast and Ovarian Cancer Cohort: A Public Sector Experience

Breast cancer is a multifaceted disease that currently represents a leading cause of death in women worldwide. Over the past two decades (1998–2020), the National Health Laboratory Service’s Human Genetics Laboratory in central South Africa screened more than 2,974 breast and/or ovarian cancer patients for abnormalities characteristic of the widely known familial breast cancer genes, Breast Cancer gene 1 (BRCA1) and Breast Cancer gene 2 (BRCA2). Patients were stratified according to the presence of family history, age at onset, stage of the disease, ethnicity and mutation status relative to BRCA1/2. Collectively, 481 actionable (likely-to pathogenic) variants were detected in this cohort among the different ethnic/racial groups. A combination of old (pre-2014) and new (post-2014) laboratory techniques was used to identify these variants. Additionally, targeted genotyping was performed as translational research revealed the first three recurrent South African pathogenic variants, namely BRCA1 c.1374del (legacy name 1493delC), BRCA1 c.2641G&gt;T (legacy name E881X) and BRCA2 c.7934del (legacy name 8162delG). This initial flagship study resulted in a cost-effective diagnostic test that enabled screening of a particular ethnic group for these variants. Since then, various non-Afrikaner frequent variants were identified that were proven to represent recurrent variants. These include BRCA2 c.5771_5774del (legacy name 5999del4) and BRCA2 c.582G&gt;A, both Black African founder mutations. By performing innovative translational research, medical science in South Africa can adopt first-world technologies into its healthcare context as a developing country. Over the past two decades, the progress made in the public sector enabled a pivotal shift away from population-directed genetic testing to the screening of potentially all breast and ovarian cancer patients, irrespective of ethnicity, family history or immunohistochemical status. The modifications over the years complied with international standards and guidelines aimed at universal healthcare for all. This article shares all the cohort stratifications and the likely-to pathogenic variants detected.

Determining the Accuracy of Next Generation Sequencing Based Copy Number Variation Analysis in Hereditary Breast and Ovarian Cancer

BACKGROUND

Copy number variations (CNVs) are commonly associated with malignancies, including hereditary breast and ovarian cancers. Next generation sequencing (NGS) provides solutions for CNV detection in a single run. This study aimed to compare the accuracy of CNV detection by NGS analysing tool against Multiplex Ligation Dependent Probe Amplification (MLPA).

RESEARCH DESIGN AND METHODS

In total, 1276 cases were studied by targeted NGS panels and 691 cases (61 calls in 58 NGS-CNV positive and 633 NGS-CNV negative cases) were validated by MLPA.

RESULTS

Twenty-eight (46%) NGS-CNV positive calls were consistent, whereas 33 (54%) calls showed discordance with MLPA. Two cases were detected as SNV by the NGS and CNV by the MLPA analysis. In total, 2% of the cases showed an MLPA confirmed CNV region in BRCA1/2. The results of this study showed that despite the high false positive call rate of the NGS-CNV algorithm, there were no false negative calls. The cases that were determined to be negative by the NGS and positive by the MLPA were actually carrying SNVs that were located on the MLPA probe binding sites.

CONCLUSION

The diagnostic performance of NGS-CNV analysis is promising; however, the need for confirmation by different methods remains.

BRCA1/2 variants of unknown significance in hereditary breast and ovarian cancer (HBOC) syndrome: looking for the hidden meaning

Hereditary breast and ovarian cancer syndrome is caused by germline mutations in BRCA1/2 genes. These genes are very large and their mutations are heterogeneous and scattered throughout the coding sequence. In addition to the above-mentioned mutations, variants of uncertain/unknown significance (VUSs) have been identified in BRCA genes, which make more difficult the clinical management of the patient and risk assessment. In the last decades, several laboratories have developed different databases that contain more than 2000 variants for the two genes and integrated strategies which include multifactorial prediction models based on direct and indirect genetic evidence, to classify the VUS and attribute them a clinical significance associated with a deleterious, high-low or neutral risk. This review provides a comprehensive overview of literature studies concerning the VUSs, in order to assess their impact on the population and provide new insight for the appropriate patient management in clinical practice.

Implementation of Multigene Germline and Parallel Somatic Genetic Testing in Epithelial Ovarian Cancer: SIGNPOST Study

We present findings of a cancer multidisciplinary-team (MDT) coordinated mainstreaming pathway of unselected 5-panel germline BRCA1/BRCA2/RAD51C/RAD51D/BRIP1 and parallel somatic BRCA1/BRCA2 testing in all women with epithelial-OC and highlight the discordance between germline and somatic testing strategies across two cancer centres. Patients were counselled and consented by a cancer MDT member. The uptake of parallel multi-gene germline and somatic testing was 97.7%. Counselling by clinical-nurse-specialist more frequently needed >1 consultation (53.6% (30/56)) compared to a medical (15.0% (21/137)) or surgical oncologist (15.3% (17/110)) (p < 0.001). The median age was 54 (IQR = 51-62) years in germline pathogenic-variant (PV) versus 61 (IQR = 51-71) in BRCA wild-type (p = 0.001). There was no significant difference in distribution of PVs by ethnicity, stage, surgery timing or resection status. A total of 15.5% germline and 7.8% somatic BRCA1/BRCA2 PVs were identified. A total of 2.3% patients had RAD51C/RAD51D/BRIP1 PVs. A total of 11% germline PVs were large-genomic-rearrangements and missed by somatic testing. A total of 20% germline PVs are missed by somatic first BRCA-testing approach and 55.6% germline PVs missed by family history ascertainment. The somatic testing failure rate is higher (23%) for patients undergoing diagnostic biopsies. Our findings favour a prospective parallel somatic and germline panel testing approach as a clinically efficient strategy to maximise variant identification. UK Genomics test-directory criteria should be expanded to include a panel of OC genes.

Clinical Utility of Liquid Biopsy-Based Actionable Mutations Detected via ddPCR

Cancer is one of the leading causes of death worldwide and remains a major public health challenge. The introduction of more sensitive and powerful technologies has permitted the appearance of new tumor-specific molecular aberrations with a significant cancer management improvement. Therefore, molecular pathology profiling has become fundamental not only to guide tumor diagnosis and prognosis but also to assist with therapeutic decisions in daily practice. Although tumor biopsies continue to be mandatory in cancer diagnosis and classification, several studies have demonstrated that liquid biopsies could be used as a potential tool for the detection of cancer-specific biomarkers. One of the main advantages is that circulating free DNA (cfDNA) provides information about intra-tumoral heterogeneity, reflecting dynamic changes in tumor burden. This minimally invasive tool has become an accurate and reliable instrument for monitoring cancer genetics. However, implementing liquid biopsies across the clinical practice is still ongoing. The main challenge is to detect genomic alterations at low allele fractions. Droplet digital PCR (ddPCR) is a powerful approach that can overcome this issue due to its high sensitivity and specificity. Here we explore the real-world clinical utility of the liquid biopsy ddPCR assays in the most diagnosed cancer subtypes.

5' Region Large Genomic Rearrangements in the BRCA1 Gene in French Families: Identification of a Tandem Triplication and Nine Distinct Deletions with Five Recurrent Breakpoints

Simple Summary

Large genomic rearrangements in BRCA1 consisting of deletions/duplications of one or several exons are complex events, often occurring in the 5′ region. We characterized 10 events in 20 families: one large triplication classified as benign and nine large deletions classified as pathogenic. The breakpoint localization will certainly help to further understand the chromatin structure in regions sensitive to rearrangement.

Abstract

Background: Large genomic rearrangements (LGR) in BRCA1 consisting of deletions/duplications of one or several exons have been found throughout the gene with a large proportion occurring in the 5′ region from the promoter to exon 2. The aim of this study was to better characterize those LGR in French high-risk breast/ovarian cancer families. Methods: DNA from 20 families with one apparent duplication and nine deletions was analyzed with a dedicated comparative genomic hybridization (CGH) array, high-resolution BRCA1 Genomic Morse Codes analysis and Sanger sequencing. Results: The apparent duplication was in fact a tandem triplication of exons 1 and 2 and part of intron 2 of BRCA1, fully characterized here for the first time. We calculated a causality score with the multifactorial model from data obtained from six families, classifying this variant as benign. Among the nine deletions detected in this region, eight have never been identified. The breakpoints fell in six recurrent regions and could confirm some specific conformation of the chromatin. Conclusions: Taken together, our results firmly establish that the BRCA1 5′ region is a frequent site of different LGRs and highlight the importance of the segmental duplication and Alu sequences, particularly the very high homologous region, in the mechanism of a recombination event. This also confirmed that those events are not systematically deleterious.

A novel BRCA1 duplication and new insights on the spectrum and frequency of germline large genomic rearrangements in BRCA1/BRCA2

Heritable breast cancers account for 5% to 10% of all breast cancers, and monogenic, highly penetrant genes cause them. Around 90% of pathogenic variants in BRCA1 and BRCA2 are observed using gene sequencing, with another 10% identified through gene duplication/deletion analysis, which differs across various communities. In this study, we performed a next-generation sequencing panel and MLPA on 1484 patients to explain the importance of recurrent germline duplications/deletions of BRCA1-2 and their clinical results and determine how often BRCA gene LGRs were seen in people suspected of hereditary breast and ovarian cancer syndrome. The large genomic rearrangements (LGRs) frequency was approximately 1% (14/1484). All 14 mutations were heterozygous and detected in patients with breast cancer. BRCA1 mutations were more predominant (n = 8, 57.1%) than BRCA2 mutations (6, 42.9%). The most common recurrent mutations were BRCA2 exon three and BRCA1 exon 24 (23) deletions. To the best of our knowledge, BRCA1 5'UTR-exon11 duplication has never been reported before. Testing with MLPA is essential to identify patients at high risk. Our data demonstrate that BRCA1-2 LGRs should be considered when ordering genetic testing for individuals with a personal or family history of cancer, particularly breast cancer. Further research could shed light on BRCA1-2 LGRs' unique carcinogenesis roles.

Circulating Tumor DNA Testing for Homology Recombination Repair Genes in Prostate Cancer: From the Lab to the Clinic

Approximately 23% of metastatic castration-resistant prostate cancers (mCRPC) harbor deleterious aberrations in DNA repair genes. Poly (ADP-ribose) polymerase (PARP) inhibitors (PARPi) therapy has shown improvements in overall survival in patients with mCRPC who harbor somatic and/or germline alterations of homology recombination repair (HRR) genes. Peripheral blood samples are typically used for the germline mutation analysis test using the DNA extracted from peripheral blood leucocytes. Somatic alterations can be assessed by extracting DNA from a tumor tissue sample or using circulating tumor DNA (ctDNA) extracted from a plasma sample. Each of these genetic tests has its own benefits and limitations. The main advantages compared to the tissue test are that liquid biopsy is a non-invasive and easily repeatable test with the value of better representing tumor heterogeneity than primary biopsy and of capturing changes and/or resistance mutations in the genetic tumor profile during disease progression. Furthermore, ctDNA can inform about mutation status and guide treatment options in patients with mCRPC. Clinical validation and test implementation into routine clinical practice are currently very limited. In this review, we discuss the state of the art of the ctDNA test in prostate cancer compared to blood and tissue testing. We also illustrate the ctDNA testing workflow, the available techniques for ctDNA extraction, sequencing, and analysis, describing advantages and limits of each techniques.

Germline Structural Variations in Cancer Predisposition Genes

In addition to single nucleotide variations and small-scale indels, structural variations (SVs) also contribute to the genetic diversity of the genome. SVs, such as deletions, duplications, amplifications, or inversions may also affect coding regions of cancer-predisposing genes. These rearrangements may abrogate the open reading frame of these genes or adversely affect their expression and may thus act as germline mutations in hereditary cancer syndromes. With the capacity of disrupting the function of tumor suppressors, structural variations confer an increased risk of cancer and account for a remarkable fraction of heritability. The development of sequencing techniques enables the discovery of a constantly growing number of SVs of various types in cancer predisposition genes (CPGs). Here, we provide a comprehensive review of the landscape of germline SV types, detection methods, pathomechanisms, and frequency in CPGs, focusing on the two most common cancer syndromes: hereditary breast- and ovarian cancer and gastrointestinal cancers. Current knowledge about the possible molecular mechanisms driving to SVs is also summarized.

The landscape of kinase domain duplication in Chinese lung cancer patients

Background

Kinase domain duplication (KDD) is a special type of large genomic rearrangement (LGR), occurring in the kinase domain of protein kinase genes. KDD of some lung cancer driver genes, such as

EGFR

KDD, has been identified and implicated to be oncogenic in non-small cell lung cancer (NSCLC). The present study aims to interrogate the spectrum of KDD occurring on classic driver genes in Chinese lung cancer patients without the presence of classic lung cancer driver mutations.

Methods

We retrospectively enrolled 10,525 Chinese lung cancer patients who met the following inclusion criteria; (I) do not carry classic lung cancer driver mutations in any of the 8 driver genes and (II) tyrosine kinase inhibitor (TKI)-naïve. Capture-based targeted sequencing was performed on tissue or plasma samples. LGR and KDD were identified by using in-house analysis scripts. The prevalence and distribution of LGR and KDD in our cohort were analyzed.

Results

The median age of the cohort was 64 years with 68.7% being male. Among all patients, 23.2% and 51.8% were diagnosed with stage III and IV disease respectively. We identified 43 cases (0.41%) harboring LGR in one of the driver genes (EGFR/ERBB2/ALK/RET/ROS1/MET/BRAF), with 24 (0.23%) patients harboring KDD. Of the patients harboring KDD, a majority (n=19) harbored canonical EGFR-KDD involving exons 18–25, whilst one patient harbored duplications of EGFR exons 18–26. There were three MET-KDD patients; in two, the alteration occurred in exons 15–21 and in one, the alteration occurred in exons 3–21. One patient harbored RET-KDD involving exons 12–18. KDD showed a comparable prevalence in lung adenocarcinoma (LUAD) and lung squamous cell carcinoma (LUSC) (0.33% vs. 0.11%, P=0.118). Nineteen non-KDD LGRs, spanning six genes including EGFR (n=6), MET (n=3), ALK (n=4), ROS1 (n=2), ERBB2 (n=2) and BRAF (n=2), were found, each occurring in one patient. The prevalence of LGR in LUADs and LUSCs was comparable (0.55% vs. 0.38%, P=0.452).

Conclusions

We observed a prevalence of 0.41% and 0.23% for LGR and KDD, respectively. Twenty-four different LGR alterations, including 5 KDDs and 19 non-KDD LGRs, were observed. KDDs mainly occurred in EGFR involving exons 18–25 and non-KDD LGRs were distributed more randomly. The prevalence of LGR/KDD in LUSCs and LUADs was comparable.

Pathogenicity reclassification of two BRCA1/BRCA2 exonic duplications after identification of genomic breakpoints and tandem orientation

The genomic consequence and clinical interpretation of large duplications are difficult to infer without determining the location and orientation of the duplicated sequence. We aimed to characterize two intragenic duplications detected in two hereditary breast and ovarian cancer syndrome (HBOC) families, namely BRCA1 exon 4 to 6 and BRCA2 exon 17 to 18, previously detected by multiplex ligation probe amplification and initially classified as variants of unknown significance. Using long range PCR, with duplication-specific primers, we were able to ascertain the genomic breakpoints and observed that the two rearrangements occurred in tandem and in direct orientation. The BRCA1 c.134+440_441+870dup and BRCA2 c.7806-2083_8332-1512dup duplications here identified are predicted to cause frameshifts that create a premature stop codon and were reclassified as pathogenic. Furthermore, both families present phenotypic traits typical of HBOC syndrome. We also observed that the genomic breakpoints of these two duplications occurred within highly homologous Alu elements. Concluding, we characterized two in tandem BRCA1 and BRCA2 duplications that likely occurred by Alu-mediated homologous recombination, allowing identification of the underlying cause of the HBOC syndrome in these families.

Early-onset breast cancer in a woman with a germline mobile element insertion resulting in BRCA2 disruption: a case report

Mobile element insertions (MEIs) contribute to genomic diversity, but they can be responsible for human disease in some cases. Initial clinical testing (BRCA1, BRCA2 and PALB2) in a 40-year-old female with unilateral breast cancer did not detect any pathogenic variants. Subsequent reanalysis for MEIs detected a novel likely pathogenic insertion of the retrotransposon element (RE) c.7894_7895insSVA in BRCA2. This case highlights the importance of bioinformatic pipeline optimization for the detection of MEIs in genes associated with hereditary cancer, as early detection can significantly impact clinical management.

Genetic Counseling, Testing, and Management of HBOC in India: An Expert Consensus Document from Indian Society of Medical and Pediatric Oncology

PURPOSE

Hereditary breast and ovarian cancer (HBOC) syndrome is primarily characterized by mutations in the BRCA1/2 genes. There are several barriers to the implementation of genetic testing and counseling in India that may affect clinical decisions. These consensus recommendations were therefore convened as a collaborative effort to improve testing and management of HBOC in India.

DESIGN

Recommendations were developed by a multidisciplinary group of experts from the Indian Society of Medical and Pediatric Oncology and some invited experts on the basis of graded evidence from the literature and using a formal Delphi process to help reach consensus. PubMed and Google Scholar databases were searched to source relevant articles.

RESULTS

This consensus statement provides practical insight into identifying patients who should undergo genetic counseling and testing on the basis of assessments of family and ancestry and personal history of HBOC. It discusses the need and significance of genetic counselors and medical professionals who have the necessary expertise in genetic counseling and testing. Recommendations elucidate requirements of pretest counseling, including discussions on genetic variants of uncertain significance and risk reduction options. The group of experts recommended single-site mutation testing in families with a known mutation and next-generation sequencing coupled with multiplex ligation probe amplification for the detection of large genomic rearrangements for unknown mutations. Recommendations for surgical and lifestyle-related risk reduction approaches and management using poly (ADP-ribose) polymerase inhibitors are also detailed.

CONCLUSION

With rapid strides being made in the field of genetic testing/counseling in India, more oncologists are expected to include genetic testing/counseling as part of their clinical practice. These consensus recommendations are anticipated to help homogenize genetic testing and management of HBOC in India for improved patient care.

Complex Characterization of Germline Large Genomic Rearrangements of the BRCA1 and BRCA2 Genes in High-Risk Breast Cancer Patients-Novel Variants from a Large National Center

Large genomic rearrangements (LGRs) affecting one or more exons of BRCA1 and BRCA2 constitute a significant part of the mutation spectrum of these genes. Since 2004, the National Institute of Oncology, Hungary, has been involved in screening for LGRs of breast or ovarian cancer families enrolled for genetic testing. LGRs were detected by multiplex ligation probe amplification method, or next-generation sequencing. Where it was possible, transcript-level characterization of LGRs was performed. Phenotype data were collected and analyzed too. Altogether 28 different types of LGRs in 51 probands were detected. Sixteen LGRs were novel. Forty-nine cases were deletions or duplications in BRCA1 and two affected BRCA2. Rearrangements accounted for 10% of the BRCA1 mutations. Three exon copy gains, two complex rearrangements, and 23 exon losses were characterized by exact breakpoint determinations. The inferred mechanisms for LGR formation were mainly end-joining repairs utilizing short direct homologies. Comparing phenotype features of the LGR-carriers to that of the non-LGR BRCA1 mutation carriers, revealed no significant differences. Our study is the largest comprehensive report of LGRs of BRCA1/2 in familial breast and ovarian cancer patients in the Middle and Eastern European region. Our data add novel insights to genetic interpretation associated to the LGRs.

The contribution of large genomic rearrangements in BRCA1 and BRCA2 to South African familial breast cancer

BACKGROUND

Pathogenic variants that occur in the familial breast cancer genes (BRCA1/2) lead to truncated ineffective proteins in the majority of cases. These variants are mostly represented by small deletions/insertions, nonsense- and splice-site variants, although some larger pathogenic rearrangements occur. Currently, their contribution to familial breast cancer (BC) and ovarian cancer (OVC) in South Africa (SA) is unknown.

METHODS

Seven hundred and forty-four patients affected with BC or OVC were screened for larger genomic rearrangements (LGRs) by means of multiplex ligation-dependent probe amplification or Next Generation Sequencing using the Oncomine™ BRCA research assay.

RESULTS

The patients represented mostly medium to high-risk families, but also included lower risk patients without a family history of the disease, diagnosed at an early age of onset (< 40 years). Eight LGRs were detected (1.1%); seven in BRCA1 with a single whole gene deletion (WGD) detected for BRCA2. These eight LGRs accounted for 8.7% of the 92 BRCA1/2 pathogenic variants identified in the 744 cases. The pathogenic LGRs ranged from WGDs to the duplication of a single exon.

CONCLUSIONS

Larger rearrangements in BRCA1/2 contributed to the overall mutational burden of familial BC and OVC in SA. Almost a quarter of all pathogenic variants in BRCA1 were LGRs (7/30, 23%). The spectrum observed included two WGDs, one each for BRCA1 and BRCA2.

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.

Detection of BRCA1/2 large genomic rearrangement including BRCA1 promoter-region deletions using next-generation sequencing

BACKGROUND

Germline mutations in BRCA1 and BRCA2 (BRCA1/2) have been conventionally analyzed by Sanger sequencing and multiplex ligation-dependent probe amplification (MLPA). Nowadays, next-generation sequencing (NGS) is increasingly being used in clinical genetics. The aim of this study was to evaluate the performance of NGS BRCA1/2 assays by comparing them with the conventional method.

MATERIALS AND METHODS

We did BRCA1/2 NGS assays of 108 breast and/or ovarian cancer patients whose BRCA1/2 mutation had been previously analyzed by Sanger sequencing and MLPA using TruSeq Custom Amplicon Design AFP2. Single-nucleotide variations (SNVs) and small insertions or deletions (InDels) were evaluated. In addition, we analyzed large genomic rearrangements (LGRs) using a coverage-based algorithm as well as a revised BRCA1/2 NGS assay (BRCAaccuTest PLUS), which additionally covered a BRCA1 promoter region.

RESULTS

The NGS BRCA1/2 assay detected all 20 SNVs and 21 small InDels in 56 patients. Among seven LGRs detected by MLPA, six exonic LGRs were well identified by both NGS BRCA1/2 assays. One pathogenic LGR, located on a BRCA1 promoter region, was successfully identified using revised BRCAaccuTestPLUS.

CONCLUSIONS

These results indicated that an NGS BRCA1/2 assay could detect most LGRs including BRCA1 promoter-region deletion as well as SNVs and small InDels. Therefore, it was applicable to clinical BRCA1/2 mutation tests.

Identification of novel BRCA1 large genomic rearrangements by a computational algorithm of amplicon-based Next-Generation Sequencing data

Background

Genetic testing for BRCA1/2 germline mutations in hereditary breast/ovarian cancer patients requires screening for single nucleotide variants, small insertions/deletions and large genomic rearrangements (LGRs). These studies have long been run by Sanger sequencing and multiplex ligation-dependent probe amplification (MLPA). The recent introduction of next-generation sequencing (NGS) platforms dramatically improved the speed and the efficiency of DNA testing for nucleotide variants, while the possibility to correctly detect LGRs by this mean is still debated. The purpose of this study was to establish whether and to which extent the development of an analytical algorithm could help us translating NGS sequencing via an Ion Torrent PGM platform into a tool suitable to identify LGRs in hereditary breast-ovarian cancer patients.

Methods

We first used NGS data of a group of three patients (training set), previously screened in our laboratory by conventional methods, to develop an algorithm for the calculation of the dosage quotient (DQ) to be compared with the Ion Reporter (IR) analysis. Then, we tested the optimized pipeline with a consecutive cohort of 85 uncharacterized probands (validation set) also subjected to MLPA analysis. Characterization of the breakpoints of three novel BRCA1 LGRs was obtained via long-range PCR and direct sequencing of the DNA products.

Results

In our cohort, the newly defined DQ-based algorithm detected 3/3 BRCA1 LGRs, demonstrating 100% sensitivity and 100% negative predictive value (NPV) (95% CI [87.6–99.9]) compared to 2/3 cases detected by IR (66.7% sensitivity and 98.2% NPV (95% CI [85.6–99.9])). Interestingly, DQ and IR shared 12 positive results, but exons deletion calls matched only in five cases, two of which confirmed by MLPA. The breakpoints of the 3 novel BRCA1 deletions, involving exons 16–17, 21–22 and 20, have been characterized.

Conclusions

Our study defined a DQ-based algorithm to identify BRCA1 LGRs using NGS data. Whether confirmed on larger data sets, this tool could guide the selection of samples to be subjected to MLPA analysis, leading to significant savings in time and money.

Adapting ACMG/AMP sequence variant classification guidelines for single-gene copy number variants

PURPOSE

The ability of a single technology, next-generation sequencing, to provide both sequence and copy number variant (CNV) results has driven the merger of clinical cytogenetics and molecular genetics. Consequently, the distinction between the definition of a sequence variant and a CNV is blurry. As the 2015 American College of Medical Genetics and Genomics/Association for Molecular Pathology (ACMG/AMP) standards and guidelines for interpretation of sequence variants address CNV classification only sparingly, this study focused on adapting ACMG/AMP criteria for single-gene CNV interpretation.

METHODS

CNV-specific modifications of the 2015 ACMG/AMP criteria were developed and their utility was independently tested by three diagnostic laboratories. Each laboratory team interpreted the same 12 single-gene CNVs using three systems: (1) without ACMG/AMP guidance, (2) with ACMG/AMP criteria, and (3) with new modifications. A replication study of 12 different CNVs validated the modified criteria.

RESULTS

The adapted criteria system presented here showed improved concordance and usability for single-gene CNVs compared with using the ACMG/AMP interpretation guidelines focused on sequence variants.

CONCLUSION

These single-gene CNV criteria modifications could be used as a supplement to the ACMG/AMP guidelines for sequence variants, allowing for a streamlined workflow and a step toward a uniform classification system for both sequence and copy number alterations.

An update on genetic risk assessment and prevention: the role of genetic testing panels in breast cancer

Introduction: In the past 5 years, multi-gene panels have replaced the practice of BRCA1 and BRCA2 genetic testing in cases of suspected inherited breast cancer susceptibility. A variety of genes have been included on these panels without certainty of their clinical utility. Pertinent current and historical literature was reviewed to provide an up-to-date snapshot of the changing landscape of the use of gene panel tests in the context of breast cancer. Areas covered: Following a recent review of the evidence, 10 genes have been found to have definitive evidence of increased breast cancer risk with variable penetrance. Here, we review the recent changes to the practice of multi-gene panel use in breast cancer diagnoses, including an update on next generation sequencing, alternative models of genetic testing, considerations when ordering these panel tests, and recommendations for management in identified carriers for a variety of genes. A comparison of screening recommendations and carrier frequencies from recent studies is also explored. Lastly, we consider what the future of hereditary oncologic genetic testing holds. Expert opinion: The transition to multi-gene panels in breast cancer patients has improved the likelihood of capturing a rare variant in a well-established gene associated with hereditary breast cancer (e.g. BRCA1 and BRCA2, TP53). There is also an increase in the likelihood of uncovering an uncertain result. This could be in the form of a variant of uncertain significance, or a pathogenic variant in a gene with questionable breast cancer risk-association. Concurrently, a changing landscape of who orders genetic tests will improve access to genetic testing. This pervasiveness of genetic testing must be accompanied with increased genetic literacy in all health-care providers, and access to support from genetics professionals for management of patients and at-risk family members.

Detection of BRCA1/2 large genomic rearrangements in breast and ovarian cancer patients: an overview of the current methods

Introduction: Currently, genetic testing of BRCA1/2 genes includes screening for single-nucleotide variants, small insertions/deletions, and copy number variations (CNVs). In fact, many studies document the involvement of BRCA1/2 gene rearrangements in genetic predisposition to breast and ovarian cancer. Large genomic rearrangements (LGRs) of BRCA1 may account for up to one-third of all disease-causing alterations in various populations, while LGRs in BRCA2 are less frequently observed. Areas covered: We aimed to present an overview of current technologies employed in molecular diagnosis of BRCA1/2 LGRs. The most relevant literature papers, showing the application of new strategies, were considered. Expert opinion: Currently, the progress of next-generation sequencing (NGS) technologies allows for the validation of new pipelines able to provide rapid and effective results, ensuring the sensitivity and specificity requested for the detection of BRCA1/2 LGRs. Multiplex ligation-dependent probe amplification remains the gold standard to confirm NGS CNVs results and to perform fast screening in families where a pathogenic rearrangement has been detected in a proband.

Selective nanopore sequencing of human BRCA1 by Cas9-assisted targeting of chromosome segments (CATCH)

Next generation sequencing (NGS) is challenged by structural and copy number variations larger than the typical read length of several hundred bases. Third-generation sequencing platforms such as single-molecule real-time (SMRT) and nanopore sequencing provide longer reads and are able to characterize variations that are undetected in NGS data. Nevertheless, these technologies suffer from inherent low throughput which prohibits deep sequencing at reasonable cost without target enrichment. Here, we optimized Cas9-Assisted Targeting of CHromosome segments (CATCH) for nanopore sequencing of the breast cancer gene BRCA1. A 200 kb target containing the 80 kb BRCA1 gene body and its flanking regions was isolated intact from primary human peripheral blood cells, allowing long-range amplification and long-read nanopore sequencing. The target was enriched 237-fold and sequenced at up to 70× coverage on a single flow-cell. Overall performance and single-nucleotide polymorphism (SNP) calling were directly compared to Illumina sequencing of the same enriched sample, highlighting the benefits of CATCH for targeted sequencing. The CATCH enrichment scheme only requires knowledge of the target flanking sequence for Cas9 cleavage while providing contiguous data across both coding and non-coding sequence and holds promise for characterization of complex disease-related or highly variable genomic regions.

BRCA1/2 mutations, including large genomic rearrangements, among unselected ovarian cancer patients in Korea

Objective

We performed small-scale mutation and large genomic rearrangement (LGR) analysis of BRCA1/2 in ovarian cancer patients to determine the prevalence and the characteristics of the mutations.

Methods

All ovarian cancer patients who visited a single institution between September 2015 and April 2017 were included. Sanger sequencing, multiplex ligation-dependent probe amplification (MLPA), and long-range polymerase chain reaction (PCR) were performed to comprehensively study BRCA1/2. The genetic risk models BRCAPRO, Myriad, and BOADICEA were used to evaluate the mutation analysis.

Results

In total, 131 patients were enrolled. Of the 131 patients, Sanger sequencing identified 16 different BRCA1/2 small-scale mutations in 20 patients (15.3%). Two novel nonsense mutations were detected in 2 patients with a serous borderline tumor and a large-cell neuroendocrine carcinoma. MLPA analysis of BRCA1/2 in Sanger-negative patients revealed 2 LGRs. The LGRs accounted for 14.3% of all identified BRCA1 mutations, and the prevalence of LGRs identified in this study was 1.8% in 111 Sanger-negative patients. The genetic risk models showed statistically significant differences between mutation carriers and non-carriers. The 2 patients with LGRs had at least one blood relative with breast or ovarian cancer.

Conclusion

Twenty-two (16.8%) of the unselected ovarian cancer patients had BRCA1/2 mutations that were detected through comprehensive BRCA1/2 genetic testing. Ovarian cancer patients with Sanger-negative results should be considered for LGR detection if they have one blood relative with breast or ovarian cancer. The detection of more BRCA1/2 mutations in patients is important for efforts to provide targeted therapy to ovarian cancer patients.

Comprehensive mutation detection of BRCA1/2 genes reveals large genomic rearrangements contribute to hereditary breast and ovarian cancer in Chinese women

BACKGROUND

Mutated BRCA1/2 genes are associated with hereditary breast and ovarian cancer (HBOC). So far most of the identified BRCA1/2 pathogenic variants are single nucleotide variants (SNVs) or insertions/deletions (Indels). However, large genomic rearrangements (LGRs) such as copy number variants (CNVs) are also playing an important role in HBOC predisposition. Their frequency and spectrum have been well studied in western populations but remain largely unknown for Chinese population.

METHODS

Peripheral blood samples were collected from 218 unrelated familial breast and/or ovarian cancer (FBOC) patients living in Eastern China. PCR-based Sanger sequencing and panel-based next-generation sequencing (NGS) were performed to detect pathogenic SNVs and Indels in BRCA1/2 genes. For the patients lacking small pathogenic variants, multiplex ligation dependent probe amplification (MLPA) assay was conducted to screen for LGRs.

RESULTS

In total, we identified 44 samples (20.1%) carrying small pathogenic variants (26 in BRCA1 and 18 in BRCA2, respectively). Among the rest of 174 samples, five were found carrying novel deleterious LGRs in BRCA1 which are exon5-7dup (1 patient), exon13-14dup (2 patients), and exon1-22del (2 patients). No LGR was found in BRCA2. Overall, LGRs accounted for 16.1% (5/31) of BRCA1 pathogenic variants, and were detected in 2.3% (5/218) of all FBOC patients.

, CONCLUSIONS

LGR variants in BRCA1 gene play a significant role in Chinese HBOC patients. MLPA or other similar LGR-detecting methods should be recommended along with nucleotide sequencing as the initial screening approach for Chinese HBOC women.

Novel BRCA2 pathogenic variant c.5219 T > G; p.(Leu1740Ter) in a consanguineous Senegalese family with hereditary breast cancer

Background

Pathogenic variants associated with hereditary breast cancer have been reported for BRCA1 and BRCA2 (BRCA1/2) genes in patients from multiple ethnicities, but limited information is available from sub-Saharan African populations. We report a BRCA2 pathogenic variant in a Senegalese family with hereditary breast cancer.

Methods

An index case from a consanguineous family and nineteen healthy female relatives were recruited after informed consent. Along with this family, 14 other index cases with family history of breast cancer were also recruited. For the control populations we recruited 48 healthy women with no cancer diagnosis and 48 women diagnosed with sporadic breast cancer without family history. Genomic DNA was extracted from peripheral blood. All BRCA2 exons were amplified by PCR and sequenced. Sequences were compared to the BRCA2 GenBank reference sequence (NM_000059.3) using Alamut Software.

Results

We identified a novel nonsense pathogenic variant c.5219 T > G; p.(Leu1740Ter) in exon 11 of BRCA2 in the index case. The pathogenic variant was also identified in three sisters and one daughter, but was absent in the controls and unrelated cases.

Conclusions

This is the first report of a novel BRCA2 pathogenic variant in a Senegalese family with hereditary breast cancer. This result confirms the diversity of hereditary breast cancer pathogenic variants across populations and extends our knowledge of genetic susceptibility to breast cancer in Africa.

Electronic supplementary material

The online version of this article (10.1186/s12881-019-0814-y) contains supplementary material, which is available to authorized users.

Novel BRCA1 Large Genomic Rearrangements in Italian Breast/Ovarian Cancer Patients

BACKGROUND

In recent years, the number of patients being offered BRCA1/2 testing has changed dramatically. Advances in high-throughput sequencing technology have led many diagnostic laboratories to test next-generation sequencing (NGS)-based platforms as the main technology for clinical testing. As a consequence, the proportion of novel BRCA1/2 variants detected has greatly increased. Here, we describe two novel BRCA1 large deletions detected in Italian patients affected by hereditary breast and ovarian cancer syndrome (HBOC).

METHODS

We applied an NGS pipeline with a reliable copy number variation (CNV) prediction algorithm. Successively, samples were investigated using the Multiplex Amplicon Quantification (MAQ) assay and array comparative genomic hybridization (CGH). In a single case, long-range polymerase chain reaction (PCR) was employed for careful detection of the breakpoint region, while the RepeatMasker program was used to identify Alu sequences at the junction point.

RESULTS

A 137.8 kb deletion, involving the first six exons of BRCA1 and the full NBR2, BRCA1P1, NBR1, and TMEM106a genes, was detected in an Italian woman diagnosed with high-grade serous ovarian carcinoma. A second rearrangement, involving the deletion of BRCA1 11-14 exons, was detected in a breast cancer patient and was fully characterized and reported according to recommended Human Genome Variation Society (HGVS) nomenclature: NG_005905.2: g.125038_143266del; NM_007294.3: c.2817_4716del; NP_009225: p.Lys862Metfs?

CONCLUSION

Although it was not possible to perform a familial segregation analysis and more direct evidence of the relationship between genotype and phenotype is necessary, both of the novel reported rearrangements cause the loss of crucial functional domains of the BRCA1 protein and this event supports their pathogenicity.

Reflex Testing for Germline BRCA1, BRCA2, PALB2, and ATM Mutations in Pancreatic Cancer: Mutation Prevalence and Clinical Outcomes From Two Canadian Research Registries

Purpose

We investigated the translational value of reflex testing for germline mutations in four homology-directed DNA repair predisposition genes ( BRCA1, BRCA2, PALB2, and ATM) in consecutive patients with pancreatic adenocarcinoma.

Methods

One hundred fifty patients with French-Canadian (FC) ancestry were evaluated for founder mutations, and 114 patients were subsequently assessed by full gene sequencing and multiplex ligation-dependent probe amplification for nonfounder mutations. Two hundred thirty-six patients unselected for ancestry were also assessed for mutations by full gene sequencing.

Results

The FC founder mutation prevalence among the 150 patients was 5.3% (95% CI, 2.6% to 10.3%), and the nonfounder mutation prevalence across the four genes among the 114 patients tested was 2.6% (95% CI, 0.6% to 7.8%). In the case series unselected for ancestry, 10.0% (95% CI, 2.7% to 26.4%) of patients reporting Ashkenazi Jewish (AJ) ancestry carried an AJ founder mutation, with no nonfounder mutations identified. The mutation prevalence among patients without FC/AJ ancestry was 4.9% (95% CI, 2.6% to 8.8%). Mutations were more frequent in patients diagnosed at ≤ 50 years of age ( P = .03) and in patients with either two or more first- or second-degree relatives with pancreas, breast, ovarian or prostate cancer, or one such relative and a second primary of one of these cancer types ( P < .001). BRCA1, BRCA2, and PALB2 carriers with late-stage (III or IV) disease had an overall survival advantage ( P = .049), particularly if treated with platinum-based chemotherapies ( P = .030).

Conclusion

Considering these results, we recommend reflex founder mutation testing of patients with FC/AJ ancestry and full gene sequencing of patients who are ≤ 50 years or meet the identified family history criteria. Reflex testing of all incident patients for these four genes may become justified as full gene sequencing costs decline.

Rapid detection of copy number variations and point mutations in BRCA1/2 genes using a single workflow by ion semiconductor sequencing pipeline

Molecular analysis of BRCA1 (MIM# 604370) and BRCA2 (MIM #600185) genes is essential for familial breast and ovarian cancer prevention and treatment. An efficient, rapid, cost-effective accurate strategy for the detection of pathogenic variants is crucial. Mutations detection of BRCA1/2 genes includes screening for single nucleotide variants (SNVs), small insertions or deletions (indels), and Copy Number Variations (CNVs). Sanger sequencing is unable to identify CNVs and therefore Multiplex Ligation Probe amplification (MLPA) or Multiplex Amplicon Quantification (MAQ) is used to complete the BRCA1/2 genes analysis. The rapid evolution of Next Generation Sequencing (NGS) technologies allows the search for point mutations and CNVs with a single platform and workflow. In this study we test the possibilities of NGS technology to simultaneously detect point mutations and CNVs in BRCA1/2 genes, using the Oncomine^TM BRCA Research Assay on Personal Genome Machine (PGM) Platform with Ion Reporter Software for sequencing data analysis (Thermo Fisher Scientific). Comparison between the NGS-CNVs, MLPA and MAQ results shows how the NGS approach is the most complete and fast method for the simultaneous detection of all BRCA mutations, avoiding the usual time consuming multistep approach in the routine diagnostic testing of hereditary breast and ovarian cancers.

Molecular Diagnostics in Clinical Oncology

There are multiple applications of molecular tests in clinical oncology. Mutation analysis is now routinely utilized for the diagnosis of hereditary cancer syndromes. Healthy carriers of cancer-predisposing mutations benefit from tight medical surveillance and various preventive interventions. Cancers caused by germ-line mutations often require significant modification of the treatment strategy. Personalized selection of cancer drugs based on the presence of actionable mutations has become an integral part of cancer therapy. Molecular tests underlie the administration of EGFR, BRAF, ALK, ROS1, PARP inhibitors as well as the use of some other cytotoxic and targeted drugs. Tumors almost always shed their fragments (single cells or their clusters, DNA, RNA, proteins) into various body fluids. So-called liquid biopsy, i.e., the analysis of circulating DNA or some other tumor-derived molecules, holds a great promise for non-invasive monitoring of cancer disease, analysis of drug-sensitizing mutations and early cancer detection. Some tumor- or tissue-specific mutations and expression markers can be efficiently utilized for the diagnosis of cancers of unknown primary origin (CUPs). Systematic cataloging of tumor molecular portraits is likely to uncover a multitude of novel medically relevant DNA- and RNA-based markers.

DNA breakpoint assay reveals a majority of gross duplications occur in tandem reducing VUS classifications in breast cancer predisposition genes

PURPOSE

Gross duplications are ambiguous in terms of clinical interpretation due to the limitations of the detection methods that cannot infer their context, namely, whether they occur in tandem or are duplicated and inserted elsewhere in the genome. We investigated the proportion of gross duplications occurring in tandem in breast cancer predisposition genes with the intent of informing their classifications.

METHODS

The DNA breakpoint assay (DBA) is a custom, paired-end, next-generation sequencing (NGS) method designed to capture and detect deep-intronic DNA breakpoints in gross duplications in BRCA1, BRCA2, ATM, CDH1, PALB2, and CHEK2.

RESULTS

DBA allowed us to ascertain breakpoints for 44 unique gross duplications from 147 probands. We determined that the duplications occurred in tandem in 114 (78%) carriers from this cohort, while the remainder have unknown tandem status. Among the tandem gross duplications that were eligible for reclassification, 95% of them were upgraded to pathogenic.

CONCLUSION

DBA is a novel, high-throughput, NGS-based method that informs the tandem status, and thereby the classification of, gross duplications. This method revealed that most gross duplications in the investigated genes occurred in tandem and resulted in a pathogenic classification, which helps to secure the necessary treatment options for their carriers.

Identification and Characterization of a New BRCA2 Rearrangement in an Italian Family with Hereditary Breast and Ovarian Cancer Syndrome

INTRODUCTION

Many studies document the involvement of BRCA1/2 gene rearrangements in genetic predisposition to breast and ovarian cancer. Large genomic rearrangements (LGRs) of BRCA1 account for 0-27% of all disease-causing mutations in various populations, while LGRs in BRCA2 are rarer. Here, we describe a novel BRCA2 LGR, involving the duplication of exons 4-26, in an Italian family with hereditary breast and ovarian cancer (HBOC) syndrome.

OBJECTIVE

Our purpose was to provide an effective characterization of this variant using a combination of different methods able to establish the exact breakpoints of the duplication.

METHODS

A multiplex amplicon quantification (MAQ) assay was used as the primary screening method in the detection of LGRs. Array comparative genomic hybridization (CGH), reverse transcriptase polymerase chain reaction (RT-PCR) and long-range PCR were used for the careful characterization of the rearrangement and breakpoint regions. The Repeat Masker program was employed to identify Alu sequences at breakpoint junctions.

RESULTS

Array CGH and long-range PCR strategies revealed that the BRCA2 exons 4-26 duplication (g.12016_87170dup) involved exactly 75,154 bp nucleotides between intron 3 and intron 26 of the gene. Given that no Alu repeats were found at the junction sites, we support the hypothesis that the new duplication could be the result of a microhomology-mediated event (MH) involving very short homologous sequences at an upstream breakpoint.

DISCUSSION

LGR investigation is mandatory in BRCA1/2 routine testing in order to provide a complete result for a targeted therapeutic decision. Nevertheless, the characterization and classification of novel BRCA1/2 variants represents a crucial step in the support of genetic counselling. Our results, including a comprehensive co-segregation analysis, indicate that the novel duplication identifed has a pathogenic role and would be considered a causing-disease variant in genetic and oncologic counselling.

Frequency of Rearrangements Versus Small Indels Mutations in BRCA1 and BRCA2 Genes in Turkish Patients with High Risk Breast and Ovarian Cancer

Objective

The current rearrangement ratio of BRCA1 and BRCA2 genes is not known in the Turkish population. Rearrangements are not routinely investigated in many Turkish laboratories. This creates problems and contradictions between clinics. Therefore, the aim of this study was to evaluate the distribution and frequency of rearrangements in BRCA1 and BRCA2 genes in high-risk families and to clarify the limits of BRCA1 and BRCA2 testing in Turkey.

Materials and Methods

The study included 1809 patients at high risk of breast cancer or ovarian cancer. All patients were investigated for both small indels and rearrangements of BRCA genes using DNA sequencing and multiplex ligation-dependent probe amplification (MLPA) analysis.

Results

The overall frequency of rearrangements was 2% (25/1262). The frequency of rearrangements was 1.7% (18/1086) and 4% (9/206) in patients with breast cancer and ovarian cancer, respectively. The frequency of rearrangements was 3.7% (8/215) in patients with triple-negative breast cancer. The rearrangement rate was 7.7% (2/26) in patients with both breast and ovarian cancer.

Conclusions

Rearrangements were found with high rates and were strongly associated with bilateral and triple-negative status of patients with breast cancer, which are signs of high risk for breast and ovarian cancer. Analysis of rearrangements should definitely be included in routine clinical practice in Turkey for high-risk families and also for improved cancer risk prediction for families.

Fast Detection of a BRCA2 Large Genomic Duplication by Next Generation Sequencing as a Single Procedure: A Case Report

The aim of this study was to verify the reliability of a next generation sequencing (NGS)-based method as a strategy to detect all possible BRCA mutations, including large genomic rearrangements. Genomic DNA was obtained from a peripheral blood sample provided by a patient from Southern Italy with early onset breast cancer and a family history of diverse cancers. BRCA molecular analysis was performed by NGS, and sequence data were analyzed using two software packages. Comparative genomic hybridization (CGH) array was used as confirmatory method. A novel large duplication, involving exons 4-26, of BRCA2 was directly detected in the patient by NGS workflow including quantitative analysis of copy number variants. The duplication observed was also found by CGH array, thus confirming its extent. Large genomic rearrangements can affect the BRCA1/2 genes, and thus contribute to germline predisposition to familial breast and ovarian cancers. The frequency of these mutations could be underestimated because of technical limitations of several routinely used molecular analysis, while their evaluation should be included also in these molecular testing. The NGS-based strategy described herein is an effective procedure to screen for all kinds of BRCA mutations.

Next-Generation Sequencing-Based Detection of Germline Copy Number Variations in BRCA1/BRCA2: Validation of a One-Step Diagnostic Workflow

Genetic testing of BRCA1/2 includes screening for single nucleotide variants and small insertions/deletions and for larger copy number variations (CNVs), primarily by Sanger sequencing and multiplex ligation-dependent probe amplification (MLPA). With the advent of next-generation sequencing (NGS), it has become feasible to provide CNV information and sequence data using a single platform. We report the use of NGS gene panel sequencing on the Illumina MiSeq platform and JSI SeqPilot SeqNext software to call germline CNVs in BRCA1 and BRCA2. For validation 18 different BRCA1/BRCA2 CNVs previously identified by MLPA in 48 Danish breast and/or ovarian cancer families were analyzed. Moreover, 120 patient samples previously determined as negative for BRCA1/BRCA2 CNVs by MLPA were included in the analysis. Comparison of the NGS data with the data from MLPA revealed that the sensitivity was 100%, whereas the specificity was 95%. Taken together, this study validates a one-step bioinformatics work-flow to call germline BRCA1/2 CNVs using data obtained by NGS of a breast cancer gene panel. The work-flow represents a robust and easy-to-use method for full BRCA1/2 screening, which can be easily implemented in routine diagnostic testing and adapted to genes other than BRCA1/2.

Mutational analysis of BRCA1 and BRCA2 genes in Peruvian families with hereditary breast and ovarian cancer

Background

Breast cancer is one of the most prevalent malignancies in the world. In Peru, breast cancer is the second cause of death among women. Five to ten percent of patients present a high genetic predisposition due to BRCA1 and BRCA2 germline mutations.

Methods

We performed a comprehensive analysis of BRCA1 and BRCA2 genes by Sanger sequencing and multiplex ligation‐dependent probe amplification (MLPA) to detect large rearrangements in patients from 18 families, which met the criteria for hereditary breast cancer.

Results

In this series, we found four pathogenic mutations, three previously reported (BRCA1: c.302‐1G>C and c.815_824dup10; BRCA2: c.5946delT) and a duplication of adenines in exon 15 in BRCA1 gene (c.4647_4648dupAA, ClinVar SCV000256598.1). We also found two exonic and four intronic variants of unknown significance and 28 polymorphic variants.

Conclusion

This is the first report to determine the spectrum of mutations in the BRCA1/BRCA2 genes in Peruvian families selected by clinical and genetic criteria. The alteration rate in BRCA1/BRCA2 with proven pathogenic mutation was 22.2% (4 out 18) and this finding could be influenced by the reduced sample size or clinical criteria. In addition, we found three known BRCA1/BRCA2 mutations and a BRCA1 c.4647_4648dupAA as a novel pathogenic mutation.

Detection of BRCA1 gross rearrangements by droplet digital PCR

PURPOSE

Large genomic rearrangements (LGRs) constitute a significant share of pathogenic BRCA1 mutations. Multiplex ligation-dependent probe amplification (MLPA) is a leading method for LGR detection; however, it is entirely based on the use of commercial kits, includes relatively time-consuming hybridization step, and is not convenient for large-scale screening of recurrent LGRs.

MATERIALS AND METHODS

We developed and validated the droplet digital PCR (ddPCR) assay, which covers the entire coding region of BRCA1 gene and is capable to precisely quantitate the copy number for each exon.

RESULTS

141 breast cancer (BC) patients, who demonstrated evident clinical features of hereditary BC but turned out to be negative for founder BRCA1/2 mutations, were subjected to the LGR analysis. Four patients with LGR were identified, with three cases of exon 8 deletion and one women carrying the deletion of exons 5-7. Excellent concordance with MLPA test was observed. Exon 8 copy number was tested in additional 720 BC and 184 ovarian cancer (OC) high-risk patients, and another four cases with the deletion were revealed; MLPA re-analysis demonstrated that exon 8 loss was a part of a larger genetic alteration in two cases, while the remaining two patients had isolated defect of exon 8. Long-range PCR and next generation sequencing of DNA samples carrying exon 8 deletion revealed two types of recurrent LGRs.

CONCLUSION

Droplet digital PCR is a reliable tool for the detection of large genomic rearrangements.

Characterization of a new BRCA1 rearrangement in an Italian woman with hereditary breast and ovarian cancer syndrome

BACKGROUND

We report a novel BRCA1 LGR, involving the complete duplication of exon 3, in an Italian patient with a strong family history of breast and ovarian cancer. Our purpose is to provide an effective characterization of this LGR using a combination of different methods able to establish the exact breakpoints of the duplication.

METHODS

MAQ assay was used as primary screening method in LGRs detection. Array CGH, RT-PCR, and Long-PCR were used for a careful characterization of rearrangement and breakpoint regions. The Repeat Masker program was employed to identify Alu sequences at breakpoint junctions.

RESULTS

RNA analysis showed that this in tandem duplication of exon 3 causes an in frame insertion of 18 amino acids within the protein. Array CGH and Long-PCR strategies revealed that the duplication (g.100411_102863dup) involves exactly 2.452 nucleotides between intron 2 and intron 3 of the gene. In addition, while an Alu Sx sequence was identified at upstream breakpoint, no Alu repeats were found at downstream junction. This supports the hypothesis that the new duplication was the result of a non-homologous recombination event between Alu and Non-Alu sequences.

CONCLUSION

Our strategy, which combines a comprehensive set of methodologies, has been able to characterize the new BRCA1 duplication confirming, as previously reported, that MAQ assay represents a reliable and effective method for a primary screening of BRCA rearrangements. We underline the relevance of incorporating quantitative methods for BRCA genes dosage testing into routine diagnostic practice.

Transposable Elements in Human Cancer: Causes and Consequences of Deregulation

Transposable elements (TEs) comprise nearly half of the human genome and play an essential role in the maintenance of genomic stability, chromosomal architecture, and transcriptional regulation. TEs are repetitive sequences consisting of RNA transposons, DNA transposons, and endogenous retroviruses that can invade the human genome with a substantial contribution in human evolution and genomic diversity. TEs are therefore firmly regulated from early embryonic development and during the entire course of human life by epigenetic mechanisms, in particular DNA methylation and histone modifications. The deregulation of TEs has been reported in some developmental diseases, as well as for different types of human cancers. To date, the role of TEs, the mechanisms underlying TE reactivation, and the interplay with DNA methylation in human cancers remain largely unexplained. We reviewed the loss of epigenetic regulation and subsequent genomic instability, chromosomal aberrations, transcriptional deregulation, oncogenic activation, and aberrations of non-coding RNAs as the potential mechanisms underlying TE deregulation in human cancers.

Next-generation sequencing of BRCA1/2 in breast cancer patients: potential effects on clinical decision-making using rapid, high-accuracy genetic results

Purpose

We evaluated the clinical role of rapid next-generation sequencing (NGS) for identifying BRCA1/2 mutations compared to traditional Sanger sequencing.

Methods

Twenty-four paired samples from 12 patients were analyzed in this prospective study to compare the performance of NGS to the Sanger method. Both NGS and Sanger sequencing were performed in 2 different laboratories using blood samples from patients with breast cancer. We then analyzed the accuracy of NGS in terms of variant calling and determining concordance rates of BRCA1/2 mutation detection.

Results

The overall concordance rate of BRCA1/2 mutation identification was 100%. Variants of unknown significance (VUS) were reported in two cases of BRCA1 and 3 cases of BRCA2 after Sanger sequencing, whereas NGS reported only 1 case of BRCA1 VUS, likely due to differences in reference databases used for mutation identification. The median turnaround time of Sanger sequencing was 22 days (range, 14–26 days), while the median time of NGS was only 6 days (range, 3–21 days).

Conclusion

NGS yielded comparably accurate results to Sanger sequencing and in a much shorter time with respect to BRCA1/2 mutation identification. The shorter turnaround time and higher accuracy of NGS may help clinicians make more timely and informed decisions regarding surgery or neoadjuvant chemotherapy in patients with breast cancer.