Journal of Human Genetics

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.

Returning genetic risk information for hereditary cancers to participants in a population-based cohort study in Japan

Abstract Large-scale population cohort studies that collect genomic information are tasked with returning an assessment of genetic risk for hereditary cancers to participants. While several studies have applied to return identified genetic risks to participants, comprehensive surveys of participants’ understanding, feelings, and behaviors toward cancer risk remain to be conducted. Here, we report our experience and surveys of returning genetic risks to 100 carriers of pathogenic variants for hereditary cancers identified through whole genome sequencing of 50 000 individuals from the Tohoku Medical Megabank project, a population cohort study. The participants were carriers of pathogenic variants associated with either hereditary breast and ovarian cancer (n = 79, median age=41) or Lynch syndrome (n = 21, median age=62). Of these, 28% and 38% had a history of cancer, respectively. We provided information on cancer risk, heritability, and clinical actionability to the participants in person. The comprehension assessment revealed that the information was better understood by younger (under 60 years) females than by older males. Scores on the cancer worry scale were positively related to cancer experiences and general psychological distress. Seventy-one participants were followed up at Tohoku University Hospital; six females underwent risk-reducing surgery triggered by study participation and three were newly diagnosed with cancer during surveillance. Among first-degree relatives of hereditary breast and ovarian cancer carriers, participants most commonly shared the information with daughters. This study showed the benefits of returning genetic risks to the general population and will provide insights into returning genetic risks to asymptomatic pathogenic variant carriers in both clinical and research settings.

Frequency and distribution of BRCA1/BRCA2 large genomic rearrangements in Turkish population with breast cancer

Germline mutations in BRCA1 and BRCA2 genes are mainly responsible for breast and/or ovarian cancer patients. Most of the mutations in these genes are single nucleotide changes or deletions/insertions of small numbers of bases, while a minority of mutations in these genes are large genomic rearrangements (LGRs). The frequency of LGRs in the Turkish population is not clearly known. Also insufficient awareness of the importance of LGRs in breast and/or ovarian cancer development can lead to some disruptions in patient management. So, we aimed to determine the frequency and distribution of the LGRs in the BRCA1/2 genes in the Turkish population. We investigated rearrangements of BRCA genes using multiplex ligation-dependent probe amplification (MLPA) analysis in 1540 patients with a personal and/or family history of breast and/or ovarian cancer or who had familial known large deletion/duplication and applied for segregation. The estimated overall frequency of LGRs in our group was 3,4% (52/1540) with 91% in BRCA1 gene and 9% in BRCA2 gene. 13 different rearrangements were detected (10 BRCA1, 3 BRCA2). To the best our knowledge, BRCA1 exon 1-16 duplication and BRCA2 exon 6 deletion have not been previously reported before. Our study results supported that the detection of rearrangements in BRCA genes is of great importance and it should be planned routinely in patients whose mutations cannot be detected by sequence analysis in screening programs.

A systematic review of predicted pathogenic PALB2 variants: an analysis of mutational overlap between epithelial cancers

Partner and localiser of BRCA2 forms part of a macromolecular complex with BRCA1 and BRCA2, which is critical for the repair of double-strand DNA breaks by homologous DNA recombination. Germline loss-of-function variants in the PALB2 gene may confer an increased lifetime risk of breast, pancreatic, ovarian and other cancers. However, the complete spectrum of predicted pathogenic PALB2 variants associated with each tissue type of cancer remains unknown. A systematic review is performed with the aim of cataloguing predicted pathogenic PALB2 variants in breast, ovary and pancreas cancers. All catalogued predicted pathogenic variants are analysed to assess for overlap and mutational "hotspots" within gene exons. Our results showed that 911 (92.5%) cases were described in breast cancer patients, 49 (5.0%) cases were described in ovarian cancer patients, and 24 (2.4%) cases were described in pancreatic cancer patients. The top five most frequently reported predicted pathogenic PALB2 variants were c.509_510delGA, c.3113G > A, c.1592delT, c.172_175delTTGT, and c.1240C > T, accounting for 57.3% of all cases. Breast and pancreatic cancers share five variants while breast and ovarian cancers share 12 variants. Breast, ovarian and pancreatic cancers share eight common variants. Exons with the highest mutation rates were exons 2 (6.7%), 1 (6.3%) and 3 (5.8%). This systematic review provides a quantitative catalogue of predicted pathogenic PALB2 variants described in cancers. This comprehensive analysis of the PALB2 mutational spectrum represents a useful resource for clinicians overseeing PALB2-related cancer surveillance and provides a valuable resource for future PALB2-specific research.

Functional evaluation of BRCA1/2 variants of unknown significance with homologous recombination assay and integrative in silico prediction model

Numerous variants of unknown significance (VUSs) exist in hereditary breast and ovarian cancers. Although multiple methods have been developed to assess the significance of BRCA1/2 variants, functional discrepancies among these approaches remain. Therefore, a comprehensive functional evaluation system for these variants should be established. We performed conventional homologous recombination (HR) assays for 50 BRCA1 and 108 BRCA2 VUSs and complementarily predicted VUSs using a statistical logistic regression prediction model that integrated six in silico functional prediction tools. BRCA1/2 VUSs were classified according to the results of the integrative in vitro and in silico analyses. Using HR assays, we identified 10 BRCA1 and 4 BRCA2 VUSs as low-functional pathogenic variants. For in silico prediction, the statistical prediction model showed high accuracy for both BRCA1 and BRCA2 compared with each in silico prediction tool individually and predicted nine BRCA1 and seven BRCA2 variants to be pathogenic. Integrative functional evaluation in this study and the American College of Medical Genetics and Genomics and the Association for Molecular Pathology (ACMG/AMP) guidelines strongly suggested that seven BRCA1 variants (p.Glu272Gly, p.Lys1095Glu, p.Val1653Leu, p.Thr1681Pro, p.Phe1761Val, p.Thr1773Ile, and p.Gly1803Ser) and four BRCA2 variants (p.Trp31Gly, p.Ser2616Phe, p.Tyr2660Cys, and p.Leu2792Arg) were pathogenic. This study demonstrates that integrative evaluation using conventional HR assays and optimized in silico prediction comprehensively classified the significance of BRCA VUSs for future clinical applications.

Ovarian cancer risk of Chinese women with BRCA1/2 germline pathogenic variants

Estimating the lifetime risk of ovarian cancer in Chinese women with BRCA1/2 germline pathogenic variants (PVs) is of great importance for the clinical management of BRCA1/2 carriers. This cohort study recruited 9903 unselected Chinese breast cancer patients whose BRCA1/2 status was determined. Of these, 3984 probands completed family history questionnaires, which investigated the health status of their relatives, including 11,997 female first-degree relatives. The ovarian cancer risk of BRCA1/2 germline pathogenic carriers was estimated using the ovarian cancer history of proband first-degree female relatives via the Kin-cohort method. Of the 3984 probands, 126 (3.2%) carried BRCA1 PVs, and 183 (4.6%) carried BRCA2 PVs. The estimated cumulative risks of ovarian cancer by age 70 were 15.3% (95% CI 8.4-18.6%) for BRCA1 carriers, 5.5% (95% CI 2.0-10.2%) for BRCA2 carriers, and 0.4% (95% CI 0.3-0.7%) for noncarriers. The cumulative risks of ovarian cancer were very low before the age of 40 for both BRCA1 and BRCA2 carriers and were an increase up to age 45. The cumulative ovarian cancer risk of BRCA1 carriers was approximately three times higher than that of BRCA2 carriers, and BRCA1 and BRCA2 carriers had 38- and 14-fold higher risks than non-BRCA carriers, respectively. The findings indicate that Chinese women with BRCA1/2 PVs have high risks of ovarian cancer in their lifetime, especially BRCA1 carriers. These results are useful for devising optimal strategies to reduce ovarian cancer risk in BRCA1/2 carriers.

Increased incidence of pathogenic variants in ATM in the context of testing for breast and ovarian cancer predisposition

Pathogenic Variants (PV) in major cancer predisposition genes are only identified in approximately 10% of patients with Hereditary Breast and Ovarian Cancer (HBOC) syndrome. Next Generation Sequencing (NGS) leads to the characterization of incidental variants in genes other than those known to be associated with HBOC syndrome. The aim of this study was to determine if such incidental PV were specific to a phenotype. The detection rates of HBOC-associated and incidental PV in 1812 patients who underwent genetic testing were compared with rates in control groups FLOSSIES and ExAC. The rates of incidental PV in the PALB2, ATM and CHEK2 genes were significantly increased in the HBOC group compared to controls with, respective odds ratios of 15.2 (95% CI = 5.6-47.6), 9.6 (95% CI = 4.8-19.6) and 2.7 (95% CI = 1.3-5.5). Unsupervised Hierarchical Clustering on Principle Components characterized 3 clusters: by HBOC (P = 0.01); by ExAC and FLOSSIES (P = 0.01 and 0.02 respectively); and by HBOC, ExAC and FLOSSIES (P = 0.01, 0.04 and 0.04 respectively). Interestingly, PALB2 and ATM were grouped in the same statistical cluster defined by the HBOC group, whereas CHEK2 was in a different cluster. We identified co-occurrences of PV in ATM and BRCA genes and confirmed the Manchester Scoring System as a reliable PV predictor tool for BRCA genes but not for ATM or PALB2. This study demonstrates that ATM PV, and to a lesser extent CHEK2 PV, are associated with HBOC syndrome. The co-occurrence of ATM PV with BRCA PV suggests that such ATM variants are not sufficient alone to induce cancer, supporting a multigenism hypothesis.

APOBEC mediated mutagenesis drives genomic heterogeneity in endometriosis

Endometriosis is a benign gynecologic condition, acting as a precursor of certain histological subtypes of ovarian cancers. The epithelial cells of endometriotic tissues and normal uterine endometrium accumulated somatic mutations in cancer-associated genes such as phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA) and Kirsten rat sarcoma (KRAS) proto-oncogene. To determine the genomic characteristic of endometriotic epithelial cells and normal uterine endometrium and to identify the predominant mutational process acting on them, we studied the somatic mutation profiles obtained from whole exome sequencing of 14 endometriotic epithelium and 11 normal uterine endometrium tissues and classified them into mutational signatures. We observed that single base substitutions 2/13 (SBS), attributed to Apolipoprotein B mRNA Editing Enzyme Catalytic Subunit (APOBEC) induced mutagenesis, were significant in endometriotic tissues, but not in the normal uterine endometrium. Additionally, the larger number and wider allele frequency distribution of APOBEC signature mutations, compared to cancer-associated driver mutations in endometriotic epithelium suggested APOBEC mutagenesis as an important source of mutational burden and heterogeneity in endometriosis. Further, the relative risk of enriched APOBEC signature mutations was higher in endometriosis patients who were carriers of APOBEC3A/3B germline deletion, a common polymorphism in East Asians which involves the complete loss of APOBEC3B coding region. Our results illustrate the significance of APOBEC induced mutagenesis in driving the genomic heterogeneity of endometriosis.

Correlation between the risk of ovarian cancer and BRCA recurrent pathogenic variants in Japan

We previously reported that L63X and Q934X are BRCA1 common founder variants in Japan. So far, there have been no reports of a correlation between such BRCA common variants and the risk of BRCA-related cancers. In this analysis, we investigated the correlation between the risk of ovarian cancer (OC) and BRCA recurrent pathogenic variants. We examined the database of the Japanese organization of hereditary breast and ovarian cancer. The database contained 3517 probands who underwent BRCA genetic testing. Among them, 11.1% (392/3517) had germline BRCA1 pathogenic variant, and 8.3% (293/3517) had BRCA2 pathogenic variant. We calculated the OC prevalence, breast cancer (BC) prevalence, and the ratio of OC to BC within second-degree relatives. The ratio of OC to BC in Q934X family members was significantly higher than that in the overall BRCA1 family members (0.80 vs.0.52: p = 0.038), and the ratio in STOP799 was 0.42, which was relatively lower than the overall BRCA1 value. Both Q934X and STOP799 are located in the ovarian cancer cluster region (OCCR), however there seems to be a difference in the risk of OC. R2318X family members had a significant higher ratio of OC to BC at 0.32 than the overall BRCA2 value of 0.13 (p = 0.012). R2318X is known to be located in the OCCR. This is the first report to investigate the correlation between BRCA recurrent variants and the risk of OC in Japan. The family members of probands with Q934X or R2318X have a higher risk of OC than that with other BRCA variants.

A random forest-based predictive model for classifying BRCA1 missense variants: a novel approach for evaluating the missense mutations effect

The right classification of variants is the key to pre-symptomatic detection of disease and conducting preventive actions. Since BRCA1 has a high incidence and penetrance in breast and ovarian cancers, a high-performance predictive tool can be employed to classify the clinical significance of its variants. Several tools have previously been developed for this purpose which poorly classify the significance in specific cases. The proposed tools commonly assign a score without providing any interpretation behind it. To reach an accurate predictive tool with interpretation abilities, in this study, we propose BRCA1-Forest which works based on random forest as a well-known machine learning technique for making interpretable decisions with high specificity and sensitivity in variants classification. The method involves narrowing down available options until reaching the final decision. To this end, a set of BRCA1 benign and pathogenic missense variants was collected first, and then, the dataset was prepared based on the effect of each variant on the protein sequence. The dataset was enriched by adding physicochemical changes and the conservation score of the amino acid position as pathogenicity criteria. The proposed model was trained based on the dataset to classify the clinical significance of variants. The performance of BRCA1-Forest was compared to four state-of-the-art methods, SIFT, PolyPhen2, CADD, and DANN, in terms of different evaluation metrics including precision, recall, false positive rate (FPR), the area under the receiver operator curve (AUC ROC), the area under the precision-recall curve (AUC-PR), and Mathew correlation coefficient (MCC). The results reveal that the proposed model outperforms the abovementioned tools in all metrics except for recall. The software of BRCA1-Forest is available at https://github.com/HamedKAAC/BRCA1Forest .

Hidden SVA retrotransposon insertion in BRCA1 revealed by nanopore targeted sequencing causes hereditary breast and ovarian cancer

In Japan, germline BRCA1/2 genetic testing is extensively used for the diagnosis of hereditary breast and ovarian cancer syndrome (HBOC). However, inconclusive results sometimes complicate clinical management. In this study, we identified an intronic SINE-VNTR-Alu (SVA) insertion in BRCA1 of a proband and her mother, both of whom had inconclusive conventional BRCA1/2 genetic test results, by targeted long-read sequencing (LRS) through the application of nanopore adaptive sampling and Flongle genome amplicon sequencing. We further confirmed splicing aberrations using cDNA quantitative PCR with TaqMan probes and Flongle cDNA amplicon sequencing. Our findings highlighted that, in addition to conventional BRCA1/2 genetic testing, structural variation analysis using targeted LRS is indispensable for the accurate diagnosis of HBOC in certain cases. Furthermore, Flongle amplicon sequencing was demonstrated to be effective for sequencing regions refractory to conventional PCR and Sanger sequencing, particularly repetitive and GC-rich regions, such as retrotransposons.

The frequency and pathogenicity of BRCA1 and BRCA2 variants in the general Japanese population

Hereditary breast and ovarian cancer syndrome (HBOC) resulting from pathogenic variants of BRCA1 or BRCA2 is the most common and well-documented hereditary tumor. Although founder variants have been identified in population-based surveys in various countries, the types of variants are not uniform across races and regions. Recently, the Tohoku Medical Megabank Organization (ToMMo) released whole-genome sequence data including approximately 54,000 individuals from the general population of the Tohoku area in Japan. We analyzed these data and comprehensively identified the prevalence of BRCA1/2 pathogenic and truncating variants. We believe that an accurate understanding of the unique distribution and characteristics of pathogenic BRCA1/2 variants in Japan through this analysis will enable better surveillance and intervention for HBOC patients, not only in Japan but also worldwide.

Recontact: a survey of current practices and BRCA1/2 testing in Japan

Genetic testing advances have enabled the provision of previously unavailable information on the pathogenicity of genetic variants, frequently necessitating the recontact of former patients by clinicians. In Japan, national health insurance coverage was extended to BRCA1/2 testing for the diagnosis of hereditary breast and ovarian cancer for patients who meet certain criteria in 2020, and conditions necessitating recontact were expected to increase. Studies and discussions regarding recontact have been conducted in the U.S. and Europe; however, in Japan, the national discussion around recontact remains undeveloped. We conducted a cross-sectional study by interviewing 73 facilities accredited by the Japanese Organization of Hereditary Breast and Ovarian Cancer regarding the practice of recontacting patients at these facilities. Sixty-six facilities responded that they recontact patients, but only 17 facilities had a protocol for this. The most common reason for recontact was that it could benefit the patient. Facilities that did not recontact stated that they lacked the necessary personnel or services. Most facilities indicated that a recontact system should be implemented in their practice. The increased burden on too few medical personnel, unestablished systems, patient confusion, and the right not to know were cited as barriers to implementing recontact. Although developing recommendations on recontact would be useful for providing equitable healthcare in Japan, there is an urgent need to deepen the discussion on recontacting, as negative opinions about recontacting patients were observed.

A Japanese case of ovarian mucinous adenocarcinoma with germline double variants of MSH2 and BRCA2

Germline double heterozygosity (GDH) is rarely reported in cases of inherited cancer syndromes, and GDH of a mismatch repair gene and BRCA has never been reported in Japan. Nonetheless, the current report demonstrates a case of ovarian mucinous adenocarcinoma with initiated Lynch syndrome (LS)-related surveillance because of a known germline MSH2 variant. Six and a half years after oophorectomy, multiple tumors developed in the patient's lungs, bones, and lymph nodes, and histology results confirmed mucinous adenocarcinoma. Systemic chemotherapy including an anti-PD-L1 antibody was effective for >1 year, but brain metastases developed. Pathology of the brain tumors showed mucinous adenocarcinoma without expression of MSH2 and MSH6, while multi-gene panel testing demonstrated not only high microsatellite instability and a high tumor mutation burden, but also germline BRCA2 variants. Further, germline testing in relatives confirmed both variants were from the paternal line, from which many LS-related cancers develop, but not BRCA-related cancer.

Genetic and epigenetic profiling of BRCA1/2 in ovarian tumors reveals additive diagnostic yield and evidence of a genomic BRCA1/2 DNA methylation signature

AbstractPoly-ADP-ribose-polymerase inhibitor (PARPi) treatment is indicated for advanced-stage ovarian tumors with BRCA1/2 deficiency. The “BRCAness” status is thought to be attributed to a tumor phenotype associated with a specific epigenomic DNA methylation profile. Here, we examined the diagnostic impact of combined BRCA1/2 sequence, copy number, and promoter DNA methylation analysis, and evaluated whether genomic DNA methylation patterns can predict the BRCAness in ovarian tumors. DNA sequencing of 172 human tissue samples of advanced-stage ovarian adenocarcinoma identified 36 samples with a clinically significant tier 1/2 sequence variants (point mutations and in/dels) and 9 samples with a CNV causing a loss of function in BRCA1/2. DNA methylation analysis of the promoter of BRCA1/2 identified promoter hypermethylation of BRCA1 in two mutation-negative samples. Computational modeling of genome-wide methylation markers, measured using Infinium EPIC arrays, resulted in a total accuracy of 0.75, sensitivity: 0.83, specificity: 0.64, positive predictive value: 0.76, negative predictive value: 0.74, and area under the receiver’s operating curve (AUC): 0.77, in classifying tumors harboring a BRCA1/2 defect from the rest. These findings indicate that the assessment of CNV and promoter DNA methylation in BRCA1/2 increases the cumulative diagnostic yield by 10%, compared with the 20% yield achieved by sequence variant analysis alone. Genomic DNA methylation data can partially predict BRCAness in ovarian tumors; however, further investigation in expanded BRCA1/2 cohorts is needed, and the effect of other double strand DNA repair gene defects in these tumors warrants further investigations.

The impact of public insurance on RRSO for HBOC in Japan: a nationwide data study

Abstract In Japan, risk management based on genetic disposition, such as risk-reducing surgery for hereditary breast and ovarian cancer (HBOC), is covered by public insurance only for some cancer patients. However, non-cancer clients are forced to pay a high co-payment. In this study, we examined the impact of risk-reducing salpingo-oophorectomy (RRSO), before and after the April 2020 public insurance coverage, using nationwide data from the Japanese Organization of Hereditary Breast and Ovarian Cancer. The period from March 2006 to March 2020 was defined as before insurance coverage (Pre), and the period from April 2020 to August 2021 was defined as after insurance coverage (Post). In addition, the period from April 2018 to March 2020 was designated as special (short-Pre) to coincide with the post-insurance coverage period. Of the 383 breast cancer patients who underwent genetic testing at Short-Pre, 42 (11.0%) underwent RRSO during that period. Of the 623 breast cancer patients who underwent genetic testing at Post, 142 (22.8%) underwent RRSO during that period. Significantly, this comparison shows an increase in RRSO rates in Post. Separating BRCA1 and BRCA2 also significantly increased RRSO in Post. This nationwide survey suggests that if RRSO is covered by insurance in Japan, the implementation rate will increase. As the number of cases increases in the future, the impact of insurance coverage will become clearer. If the insurance coverage for RRSO in Japan is determined to be useful, this information can be used to expand coverage for those who have not yet developed the disease.

Clinical risk management of breast, ovarian, pancreatic, and prostatic cancers for BRCA1/2 variant carriers in Japan

Opportunities for genetic counseling and germline BRCA1/2 (BRCA) testing are increasing in Japan owing to cancer genomic profiling testing and companion diagnostics being covered by national health insurance for patients with BRCA-related cancers. These tests are useful not only to judge whether platinum agents and PARP inhibitors are indicated but also to reveal an autosomal-dominant inherited cancer syndrome: hereditary breast and ovarian cancer. In individuals with germline BRCA variants, risk of cancers of the breast, ovary, pancreas, and prostate is significantly increased at various ages of onset, but the stomach, uterus, biliary tract, and skin might also be at risk. For women with pathogenic BRCA variants, breast awareness and image analyses should be initiated in their 20s, and risk-reducing procedures such as mastectomy are recommended starting in their 30s, with salpingo-oophorectomy in their late 30s. For male BRCA pathogenic variant carriers, prostatic surveillance should be applied using serum prostate-specific antigen starting in their 40s. For both sexes, image examinations ideally using endoscopic ultrasound and magnetic resonance cholangiopancreatography and blood testing should begin in their 50s for pancreatic surveillance. Homologous recombination pathway-associated genes are also causative candidates. Variant pathogenicity needs to be evaluated every 6-12 months when results are uncertain for clinical significance. Genetic counseling needs to be offered to the blood relatives of the pathogenic variant carriers with suitable timing. We review the recommended cross-organ BRCA risk management in Japan.

The relationship between BRCA-associated breast cancer and age factors: an analysis of the Japanese HBOC consortium database

BRCA1/2 pathogenic variant prevalence in Japanese breast cancer is unclear. Here, we analyzed BRCA1/2 pathogenic variant prevalence with a particular focus on age factors, using the Japanese HBOC consortium database. All registered subjects were Japanese individuals who underwent BRCA1/2 genetic testing from January 1996 to July 2017 according to the Japanese HBOC consortium database. Cases were extracted and analyzed for each evaluation item. Overall BRCA1 and BRCA2 pathogenic variant prevalence was 11.2% and 9.0% in the cohort of 2366 proband patients, respectively. The age at onset of breast cancer for patients with BRCA1/2 pathogenic variants was significantly lower than that for patients without a BRCA1/2 pathogenic variant. In both BRCA1/2 patients, ages at onset were not statistically significantly different between two subtype groups (ER-positive vs. TNBC). We analyzed the BRCA1/2 pathogenic variant prevalence among age groups in patients with no family history of breast or ovarian cancer. In the TNBC group, the rate of genetic variants was more frequent among younger patients. Our results demonstrated that early breast cancer onset is associated with a BRCA1/2 pathogenic variant in the Japanese population. Younger TNBC patients were more likely to have a BRCA1/2 pathogenic variant irrespective of a family history of breast or ovarian cancer.

Bypass of premature stop codons and generation of functional BRCA2 by exon skipping

A pathogenic mutation in BRCA2 significantly increases the risk of breast and ovarian cancers making it imperative to examine the functional consequences of variants of uncertain clinical significance. Variants that are predicted to result in a truncated protein are unambiguously classified as pathogenic. We have previously shown how a pathogenic splice site variant known to generate a premature termination codon (PTC) in exon 9 and a nonsense mutation at exon 7, can generate functional BRCA2 by skipping exons 4-7 and restoring the reading frame. Using a well-established mouse embryonic stem cell-based assay, we functionally characterize here one splice site mutation and 11 pathogenic BRCA2 variants that are either nonsense mutation or generate PTC in different exons ranging from exons 4 to 7. Our study shows that five variants can restore the open reading frame by exon skipping and generate a functional protein. This suggests further need to exercise prudence when classifying clearly pathogenic variants.

Impact of proactive high-throughput functional assay data on BRCA1 variant interpretation in 3684 patients with breast or ovarian cancer

The clinical utility of BRCA1/2 genotyping was recently extended from the selection of subjects at high risk for hereditary breast and ovary cancer to the identification of candidates for poly (ADP-ribose) polymerase (PARP) inhibitor treatment. This underscores the importance of accurate interpretation of BRCA1/2 genetic variants and of reducing the number of variants of uncertain significance (VUSs). Two recent studies by Findlay et al. and Starita et al. introduced high-throughput functional assays, and proactively analyzed variants in specific regions regardless of whether they had been previously observed. We retrospectively reviewed all BRCA1 and BRCA2 germline genetic test reports from patients with breast or ovarian cancer examined at Asan Medical Center (Seoul, Korea) between September 2011 and December 2018. Variants were assigned pathogenic or benign strong evidence codes according to the functional classification and were reclassified according to the ACMG/AMP 2015 guidelines. Among 3684 patients with available BRCA1 and BRCA2 germline genetic test reports, 429 unique variants (181 from BRCA1) were identified. Of 34 BRCA1 variants intersecting with the data reported by Findlay et al., three missense single-nucleotide variants from four patients (0.11%, 4/3684) were reclassified from VUSs to likely pathogenic variants. Four variants scored as functional were reclassified into benign or likely benign variants. Three variants that overlapped with the data reported by Starita et al. could not be reclassified. In conclusion, proactive high-throughput functional study data are useful for the reclassification of clinically observed VUSs. Integrating additional evidence, including functional assay results, may help reduce the number of VUSs.