A Whole Germline BRCA2 Gene Deletion: How to Learn from CNV In Silico Analysis

Implementation of BRCA mutations testing in formalin-fixed paraffin-embedded (FFPE) samples of different cancer types

BRCA1 and BRCA2 are onco-suppressor genes involved in the DNA repair mechanism. The presence of BRCA1/2 mutations confers a higher risk of developing several cancer types. To date, the FDA approved various PARP inhibitors to treat selected BRCA1/2 mutated oncologic patients. At first, PARP inhibitors were approved for patients with ovarian and breast cancers, and subsequently for metastatic pancreatic adenocarcinoma and metastatic castration-resistant prostate cancer after the treatment with chemotherapy. The current guidelines for BRCA testing are very heterogeneous between the different types of tumors regarding the diagnostic algorithm and the type of sample to analyze, such as the blood for the germline mutations and the tumoral tissue for the somatic mutations. Few data have currently been described regarding the detection of BRCA1/2 somatic mutations in formalin-fixed paraffin-embedded (FFPE) samples. In this review, we propose an overview of the BRCA mutations in FFPE samples of several cancers, including breast, ovarian, fallopian tube, primary peritoneal, prostate, and pancreatic cancer. We summarize the types and the frequency of BRCA mutations, the guidelines approved for the test, the molecular assays used for the detection and the PARP inhibitors approved for each tumor type.

The performance of multi-gene panels for breast/ovarian cancer predisposition

BRCA1 and BRCA2 are the most mutated genes in breast cancer. We analyzed 48 breast cancer subjects using two methods that differ in terms of number of genes investigated and strategy used (primers: Panel A - 12 genes - vs probes: Panel B - 48 genes). Both the panels and procedures identified "pathogenic" or "likely pathogenic" variants in TP53, ATM, CHEK2 and BARD1 besides BRCA1 and BRCA2. Panel B identified two other putatively pathogenic variants in RNASEL and in RAD50. Identification of variants other than the BRCA genes can be useful in patient management. A total of 121 variants were distributed within the 12 genes and were correctly detected by both panels. However, the number of calls without divergence, namely ± 0.10 difference of allelic frequency, was 78.3%, while calls with a divergence below 0.10 was 16.7%, thus indicating that only 5% (n = 275) of 5,412 calls had a divergence above 0.10. Although these panels differ from each other, both are useful in different situations, particularly when patients should be tested for genes other than BRCA1/2 (as occurs in patients affected by a so called hereditary syndrome) or for therapeutic purposes.

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.

Implementation of preventive and predictive BRCA testing in patients with breast, ovarian, pancreatic, and prostate cancer: a position paper of Italian Scientific Societies

Constitutional BRCA1/BRCA2 pathogenic or likely pathogenic variants (PVs) are associated with an increased risk for developing breast and ovarian cancers. Current evidence indicates that BRCA1/2 PVs are also associated with pancreatic cancer, and that BRCA2 PVs are associated with prostate cancer risk. The identification of carriers of constitutional PVs in the BRCA1/2 genes allows the implementation of individual and family prevention pathways, through validated screening programs and risk-reducing strategies. According to the relevant and increasing therapeutic predictive implications, the inclusion of BRCA testing in the routine management of patients with breast, ovarian, pancreatic and prostate cancers represent a key requirement to optimize medical or surgical therapeutic and prevention decision-making, and access to specific anticancer therapies. Therefore, accurate patient selection, the use of standardized and harmonized procedures, and adherence to homogeneous testing criteria, are essential elements to implement BRCA testing in clinical practice.

This consensus position paper has been developed and approved by a multidisciplinary Expert Panel of 64 professionals on behalf of the AIOM–AIRO–AISP–ANISC–AURO–Fondazione AIOM–SIAPEC/IAP–SIBioC–SICO–SIF–SIGE–SIGU–SIU–SIURO–UROP Italian Scientific Societies, and a patient association (aBRCAdaBRA Onlus). The working group included medical, surgical and radiation oncologists, medical and molecular geneticists, clinical molecular biologists, surgical and molecular pathologists, organ specialists such as gynecologists, gastroenterologists and urologists, and pharmacologists. The manuscript is based on the expert consensus and reports the best available evidence, according to the current eligibility criteria for BRCA testing and counseling, it also harmonizes with current Italian National Guidelines and Clinical Recommendations.

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The rapid technologic and medical progress on BRCA-related cancers produced a clinical need for BRCA testing optimization.

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To incorporate BRCA testing in the routine management is a key requirement to help medical or surgical decision-making

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Standardized procedures and harmonized testing criteria are needed to implement BRCA testing in clinical practice.

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Adequate training and qualification for multidisciplinary team members are crucial for the success of the patient care path.

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.

Droplet digital PCR for large genomic rearrangements detection: A promising strategy in tissue BRCA1 testing

BACKGROUND AND AIMS

With the introduction of Olaparib as target therapy for High Grade Serous Ovarian Cancer (HGSOC) patients with germline and somatic BRCA1/2 mutations, the genetic test performed on tumor tissue has become important like the germline test. In somatic testing the evaluation of Large Genomic Rearrangements (LGRs) represents the main challenge. We describe a droplet digital PCR (ddPCR) assay for the evaluation of target BRCA1 LGRs on blood and formalin-fixed paraffin-embedded (FFPE)/Fresh Frozen Tissue (FFT) samples.

MATERIALS AND METHODS

We analyzed blood, FFPE and FFT samples in a validation setting of n = 78 HGSOC patients. We applied the ddPCR to BRCA1 exons 2, 20 and 21 as some of the most common BRCA1 exons involved in LGRs in our cohort of patients.

RESULTS

The ddPCR custom assays allowed the identification of LGRs in all sample types, including FFPE specimens. Moreover, we were able to clearly detect LGRs accounted as somatic event.

CONCLUSION

The introduction of ddPCR in a comprehensive workflow, encompassing both germline and somatic tests, represents an improvement in BRCA1/2 testing. ddPCR can overcome challenges related to BRCA testing, especially on FFPE analysis. Finally, ddPCR represents a promising alternative strategy to the established standard methods currently used in clinical setting.

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.

From a variant of unknown significance to pathogenic: Reclassification of a large novel duplication in BRCA2 by high-throughput sequencing

Background

Germline mutations in BRCA1/2 significantly contribute to hereditary breast and/or ovarian cancer. Here, we report a novel BRCA2 duplication of exons 22–24 in a female patient with bilateral breast cancer at age 35 and 44. The duplicated region was initially detected by gene panel sequencing and multiplex ligation‐dependent probe amplification. However, the location and orientation of the duplicated region was unknown. Therefore, it was initially classified as a variant of unknown significance.

Methods

The spatial directional characterization of the BRCA2 duplication was achieved by targeted enrichment of the whole‐genomic BRCA2 locus including exons and introns, and subsequent high‐throughput sequencing. Subsequently, bioinformatics tools and a breakpoint‐spanning PCR were used for identification of location and orientation of the duplication.

Results

The duplicated region was arranged in tandem and direct orientation (Chr13(GRCh37):g.32951579_32960394dup; NM_000059.3 c.8754 + 651_9256+6112dup p.(Ala3088Phefs*3)). It is predicted to result in a frameshift and a premature stop codon likely triggering nonsense‐mediated mRNA decay. Consequently, it is regarded as pathogenic.

Conclusion

This case study demonstrates that a comprehensive characterization of a structural variant by breakpoint assessment is crucial for its correct classification. Therefore, sequencing strategies including non‐coding regions might be necessary to identify cancer predispositions in affected families.

Automated Workflow for Somatic and Germline Next Generation Sequencing Analysis in Routine Clinical Cancer Diagnostics

Thanks to personalized medicine trends and collaborations between industry, clinical research groups and regulatory agencies, next generation sequencing (NGS) is turning into a common practice faster than one could have originally expected. When considering clinical applications of NGS in oncology, a rapid workflow for DNA extraction from formalin-fixed paraffin-embedded (FFPE) tissue samples, as well as producing high quality library preparation, can be real challenges. Here we consider these targets and how applying effective automation technology to NGS workflows may help improve yield, timing and quality-control. We firstly evaluated DNA recovery from archived FFPE blocks from three different manual extraction methods and two automated extraction workstations. The workflow was then implemented to somatic (lung/colon panel) and germline (BRCA1/2) library preparation for NGS analysis exploiting two automated workstations. All commercial kits gave good results in terms of DNA yield and quality. On the other hand, the automated workstation workflow has been proven to be a valid automatic extraction system to obtain high quality DNA suitable for NGS analysis (lung/colon Ampli-seq panel). Moreover, it can be efficiently integrated with an open liquid handling platform to provide high-quality libraries from germline DNA with more reproducibility and high coverage for targeted sequences in less time (BRCA1/2). The introduction of automation in routine workflow leads to an improvement of NGS standardization and increased scale up of sample preparations, reducing labor and timing, with optimization of reagents and management.

BRCA1/2 Molecular Assay for Ovarian Cancer Patients: A Survey through Italian Departments of Oncology and Molecular and Genomic Diagnostic Laboratories

In Italy, 5200 new ovarian cancers were diagnosed in 2018, highlighting an increasing need to test women for BRCA1/2. The number of labs offering this test is continuously increasing. The aim of this study was to show the results coming from the intersociety survey coordinated by four different Clinical and Laboratory Italian Scientific Societies (AIOM, SIAPEC-IAP, SIBIOC, and SIGU). A multidisciplinary team belonging to the four scientific societies drew up two different questionnaires: One was targeted toward all Italian Departments of Medical Oncology, and the second toward laboratories of clinical molecular biology. This survey was implemented from September 2017 to March 2018. Seventy-seven out of 305 (25%) Departments of Medical Oncology filled our survey form. Indeed, 59 molecular laboratories were invited. A total of 41 laboratories (70%) filled in the questionnaire. From 2014 to 2017, 16 new molecular laboratories were activated. A total of 12,559 tests were performed in the year 2016, with a mean of 339 tests and a median of 254 tests per laboratory, showing a glimpse of an extreme low number of tests performed per year by some laboratories. In terms of the type and number of professionals involved in the pre- and post-test counseling, results among the onco-genetic team were heterogeneous. Our data show that the number of laboratories providing BRCA1/2 germline assays is significantly increased with further implementation of the somatic test coming soon. The harmonization of the complete laboratory diagnostic path should be encouraged, particularly in order to reduce the gap between laboratories with high and low throughput.

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.