Hereditary Breast Cancer Families Research Articles

Targeted sequencing for hereditary breast and ovarian cancer in BRCA1/2-negative families reveals complex genetic architecture and phenocopies

Approximately 20% of breast cancer cases are attributed to increased family risk; yet variation in BRCA1/2 can only explain 20-25% of cases. Historically, only single gene or single variant testing were common in at-risk family members, and further sequencing studies were rarely offered after negative results. In this study, we applied an efficient and inexpensive targeted sequencing approach to provide molecular diagnoses in 245 human samples representing 134 BRCA mutation negative (BRCAX) hereditary breast and ovarian cancer (HBOC) families recruited from 1973-2019 by Dr. Henry Lynch. Sequencing identified 391 variants, which were functionally annotated and ranked based on their predicted clinical impact. Known pathogenic CHEK2 breast cancer variants were identified in five BRCAX families in this study. While BRCAX was an inclusion criterion for this study, we still identified a pathogenic BRCA2 variant (p.Met192ValfsTer13) in one family. A portion of BRCAX families could be explained by other hereditary cancer syndromes that increase HBOC risk: Li-Fraumeni Syndrome (gene: TP53) and Lynch Syndrome (gene: MSH6). Interestingly, many families carried additional Variants of Undetermined Significance (VOUSs) that may further modify phenotypes of syndromic family members. Ten families carried more than one potential VOUS suggesting the presence of complex multi-variant families. Overall, nine BRCAX HBOC families in our study may be explained by known likely-pathogenic/pathogenic variants, and six families carried potential VOUSs, which require further functional testing. To address this, we developed a functional assay where we successfully re-classified one family’s PMS2 VOUS as benign.

Effect on Germline Mutation Rate in a High-Risk Chinese Breast Cancer Cohort after Compliance with The National Comprehensive Cancer Network (NCCN) 2023 v.1 Testing Criteria.

The National Comprehensive Cancer Network (NCCN) testing criteria for the high-penetrance breast cancer susceptibility genes, specifically BRCA1, BRCA2, CDH1, PALB2, PTEN, and TP53, have been recently modified in 2023 to 2023 v.1. The following criteria have been changed: (1) from a person diagnosed with breast cancer at ≤45 to ≤50; (2) from aged 45-50 of personal breast diagnosis to any age of diagnosis with multiple breast cancers; and (3) from aged ≥51 of personal breast diagnosis to any age of diagnosis with family history listed in NCCN 2022 v.2. High-risk breast cancer patients (n = 3797) were recruited from the Hong Kong Hereditary Breast Cancer Family Registry between 2007 and 2022. Patients were grouped according to NCCN testing criteria 2023 v.1 and 2022 v.2. A 30-gene panel for hereditary breast cancer was performed. The mutation rates on high-penetrance breast cancer susceptibility genes were compared. About 91.2% of the patients met the 2022 v.2 criteria, while 97.5% of the patients met the 2023 v.1 criteria. An extra 6.4% of the patients were included after the revision of the criteria, and 2.5% of the patients did not meet both testing criteria. The germline BRCA1/2 mutation rates for patients meeting the 2022 v.2 and 2023 v.1 criteria were 10.1% and 9.6%, respectively. The germline mutation rates of all 6 high-penetrance genes in these two groups were 12.2% and 11.6%, respectively. Among the additional 242 patients who were included using the new selection criteria, the mutation rates were 2.1% and 2.5% for BRCA1/2 and all 6 high-penetrance genes, respectively. Patients who did not meet both testing criteria were those with multiple personal cancers, a strong family history of cancers not listed in the NCCN, unclear pathology information, or the patient's voluntary intention to be tested. The mutation rates of BRCA1/2 and the 6 high-penetrance genes in these patients were 5.3% and 6.4%, respectively. This study provided a real-world application of the revision of NCCN guidelines and its effect on the germline mutation rate in the Chinese population. Applying the updated criteria for further genetic investigation would increase the positive detection rate, and potentially more patients would benefit. The balance between the resource and outcome requires careful consideration.

Abstract B088: The Alabama Hereditary Cancer Cohort – New strategies for African American recruitment

Abstract Our group has established the Alabama Hereditary Cancer Cohort and primarily investigates breast cancer genetics in African American, an underrepresented group in biomedical research. Alabama has double the national percentage of African Americans and is the location of the infamous and unethical Tuskegee Syphilis Study. Therefore, strategic protocols were developed to break research participation barriers, effectively recruiting African American hereditary breast cancer cases and families. Our initial recruitment strategies involved both hospital-based and community-based recruitment; the latter involved our recruitment bus, the Gene Machine, and focused on African American engagement. Since our initial publication, our community-based recruitment protocol has been modified. Many of the modifications were due to the pandemic, limiting in-person community engagement. In-person education seminars and enrollment sessions transitioned to virtual meetings, using various video-conferencing platforms. Regarding virtual enrollments, upon agreement to proceed with the virtual consent process, study participants are mailed an enrollment kit containing study consent forms, saliva collection kits, return mailing materials, and instructions. Once received, an enrollment appointment is made, and the consent process follows the procedure for in-person study enrollment, concluding with the saliva sample collection. Once collected, the sample is packaged with the consent forms and returned to our laboratory in the postage-paid mailer. Community-based recruitment has also been enhanced by partnering with the Alabama Department of Public Health to identify study participants through the Alabama Statewide Cancer Registry, similar to the very successful Carolina Breast Cancer Study. Furthermore, Research Champions have been added to the protocol, defined as primary healthcare providers and specialists who aid in recruitment by identifying individuals who fit the study criteria. The concept of Research Champions was developed after recognizing that the requirements to execute hospital-based recruitment are arduous on partnering hospitals. Thus, the sole function of a Research Champion is identifying prospective study participants, relieving the burden on physicians and hospital staff. Lastly, our Gene Machine Facebook page and newly designed website, tailored towards laypeople/study participants, facilitate additional engagement through ads, videos, and photos. Ultimately, these processes reduce the travel burden, aid in social distancing, and expand our reach, enhancing recruitment and enrollment efforts and breaking barriers to African American research. Citation Format: Nancy Merner, Elizabeth Stallworth, Erica Reasor, Katia Khoury, Lily Gutnik, Meagan Farmer, Brandon Johnson. The Alabama Hereditary Cancer Cohort – New strategies for African American recruitment [abstract]. In: Proceedings of the 15th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2022 Sep 16-19; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2022;31(1 Suppl):Abstract nr B088.

Relatives from Hereditary Breast and Ovarian Cancer and Lynch Syndrome Families Forgoing Genetic Testing: Findings from the Swiss CASCADE Cohort.

Cascade genetic testing of relatives from families with pathogenic variants associated with hereditary breast and ovarian cancer (HBOC) or Lynch syndrome (LS) has important implications for cancer prevention. We compared the characteristics of relatives from HBOC or LS families who did not have genetic testing (GT (−) group) with those who had genetic testing (GT (+) group), regardless of the outcome. Self-administered surveys collected cross-sectional data between September 2017 and December 2021 from relatives participating in the CASCADE cohort. We used multivariable logistic regression with LASSO variable selection. Among n = 115 relatives who completed the baseline survey, 38% (n = 44) were in the GT (−) group. Being male (OR: 2.79, 95% CI: 1.10–7.10) and without a previous cancer diagnosis (OR: 4.47, 95% CI: 1.03–19.42) increased the odds of being untested by almost three times. Individuals from families with fewer tested relatives had 29% higher odds of being untested (OR: 0.71, 95% CI: 0.55–0.92). Reasons for forgoing cascade testing were: lack of provider recommendation, lack of time and interest in testing, being afraid of discrimination, and high out-of-pocket costs. Multilevel interventions designed to increase awareness about clinical implications of HBOC and LS in males, referrals from non-specialists, and support for testing multiple family members could improve the uptake of cascade testing.

Investigation of discordant sibling pairs from hereditary breast cancer families and analysis of a rare PMS1 variant

BackgroundIt is likely that additional genes for hereditary breast cancer can be identified using a discordant sib pair design. Using this design we identified individuals harboring a rare PMS1 c.605G>A variant previously predicted to result in loss of function. ObjectivesA family-based design and predictive algorithms were used to prioritize candidate variants possibly associated with an increased risk of hereditary breast cancer. Functional analyses were performed for one of the candidate variants, PMS1 c.605G>A. Methods1) 14 discordant sister-pairs from hereditary breast cancer families were identified. 2) Whole exome sequencing was performed and candidate risk variants identified. 3) A rare PMS variant was identified in 2 unrelated affected sisters but no unaffected siblings. 4) Functional analysis of this variant was carried out using targeted mRNA sequencing. ResultsGenotype-phenotype correlation did not demonstrate tracking of the variant with cancer in the family. Functional analysis revealed no difference in exon 6 incorporation, which was validated by analyzing PMS1 allele specific expression. ConclusionsThe PMS1 c.605G>A variant did not segregate with disease, and there was no variant-dependent impact on PMS1 exon 6 splicing, supporting this variant is likely benign. Functional analyses are imperative to understanding the clinical significance of predictive algorithms.

TUMOSPEC: A Nation-Wide Study of Hereditary Breast and Ovarian Cancer Families with a Predicted Pathogenic Variant Identified through Multigene Panel Testing.

Simple SummaryTUMOSPEC was designed for estimating the risk of cancer for carriers of a predicted pathogenic variant (PPV) in a gene usually tested in a hereditary breast and ovarian cancer context. Index cases are enrolled consecutively among patients who undergo genetic testing as part of their care plan in France. First- and second-degree relatives and cousins of PPV carriers are invited to participate whether they are affected by cancer or not, and are tested for the familial PPV. Genetic, clinical, family and epidemiological data are centralized at the coordinating centre. The three-year feasibility study included 4431 prospective index cases, with 19.1% of them carrying a PPV. This showed that the study logistics are well adapted to clinical and laboratory constraints, and collaboration between partners (clinicians, biologists, coordinating centre and participants) is smooth. Hence, TUMOSPEC is being pursued, with the aim of optimizing clinical management guidelines specific to each gene.Assessment of age-dependent cancer risk for carriers of a predicted pathogenic variant (PPV) is often hampered by biases in data collection, with a frequent under-representation of cancer-free PPV carriers. TUMOSPEC was designed to estimate the cumulative risk of cancer for carriers of a PPV in a gene that is usually tested in a hereditary breast and ovarian cancer context. Index cases are enrolled consecutively among patients who undergo genetic testing as part of their care plan in France. First- and second-degree relatives and cousins of PPV carriers are invited to participate whether they are affected by cancer or not, and genotyped for the familial PPV. Clinical, family and epidemiological data are collected, and all data including sequencing data are centralized at the coordinating centre. The three-year feasibility study included 4431 prospective index cases, with 19.1% of them carrying a PPV. When invited by the coordinating centre, 65.3% of the relatives of index cases (5.7 relatives per family, on average) accepted the invitation to participate. The study logistics were well adapted to clinical and laboratory constraints, and collaboration between partners (clinicians, biologists, coordinating centre and participants) was smooth. Hence, TUMOSPEC is being pursued, with the aim of optimizing clinical management guidelines specific to each gene.

Haplotype analysis of the internationally distributed BRCA1 c.3331_3334delCAAG founder mutation reveals a common ancestral origin in Iberia

BackgroundThe BRCA1 c.3331_3334delCAAG founder mutation has been reported in hereditary breast and ovarian cancer families from multiple Hispanic groups. We aimed to evaluate BRCA1 c.3331_3334delCAAG haplotype diversity in cases of European, African, and Latin American ancestry.MethodsBC mutation carrier cases from Colombia (n = 32), Spain (n = 13), Portugal (n = 2), Chile (n = 10), Africa (n = 1), and Brazil (n = 2) were genotyped with the genome-wide single nucleotide polymorphism (SNP) arrays to evaluate haplotype diversity around BRCA1 c.3331_3334delCAAG. Additional Portuguese (n = 13) and Brazilian (n = 18) BC mutation carriers were genotyped for 15 informative SNPs surrounding BRCA1. Data were phased using SHAPEIT2, and identical by descent regions were determined using BEAGLE and GERMLINE. DMLE+ was used to date the mutation in Colombia and Iberia.ResultsThe haplotype reconstruction revealed a shared 264.4-kb region among carriers from all six countries. The estimated mutation age was ~ 100 generations in Iberia and that it was introduced to South America early during the European colonization period.ConclusionsOur results suggest that this mutation originated in Iberia and later introduced to Colombia and South America at the time of Spanish colonization during the early 1500s. We also found that the Colombian mutation carriers had higher European ancestry, at the BRCA1 gene harboring chromosome 17, than controls, which further supported the European origin of the mutation. Understanding founder mutations in diverse populations has implications in implementing cost-effective, ancestry-informed screening.

Abstract 1211: Recurrent germline mutations in RAD51D and PALB2 are present in Colombian hereditary breast and ovarian cancer families

Abstract Hereditary breast cancer (BC) syndromes corresponds to 10% - 15% of all cases diagnosed worldwide. Most of these cases are due to deleterious germline genetic variants in BRCA1/2 genes; nevertheless, multipanel testing have contribute to the identification of other risk genes, including other homologous recombination (HR) repair genes, such as PALB2, ATM, CHEK2 and RAD51D. Here we explore the mutation spectrum of Hereditary Breast and Ovarian Cancer (HBOC) Colombian cases as part of the Hereditary Cancer Program from the National Cancer Institute from Colombia, the largest reference cancer center in the country, that seeks to identified high risk families to offer preventive measures and screening recommendations. A total of 358 patients fulfilling criteria for HBOC have been so far analyzed with Next Generation Sequencing using a multigene panel. Overall, 47% have negative results and in the 33% we identified VUSs. In general, 20% have a pathogenic or potentially pathogenic genetic variant; from those, BRCA1 (n = 17) and BRCA2 (n = 17) were the most frequently mutated genes (47.2% among all positive results). Deleterious mutations in RAD51D and PALB2 (also important HR repair genes) were found in 7% and 5.6% of the cases tested. Interestingly, genotype:phenotype correlations were found for these genes, as breast cancer molecular subtypes were distributed differently depending on the gene affected. In concordance with other reports, triple negative breast cancers (TNBC) were more frequent in BRCA1 (9/17, 53%) and PALB2 (4/4, 100%) carriers, and luminal subtypes were more frequent in BRCA2 carriers (10/17, 59%). Mutations in RAD51D: c.94_95del (p.Val32Phefs*67) and PALB2: c.2288_2291del (p.Leu763Ter), were both recurrent mutations in our Colombian cases. Further haplotype analysis will help us to determine if mutation carriers shared a common ancestry. Citation Format: Maria Carolina Sanabria-Salas, Ana Lucía Rivera-Herrera, Ana Milena Gómez-Camargo, Luis G. Carvajal-Carmona, Martha Lucía Serrano-López. Recurrent germline mutations in RAD51D and PALB2 are present in Colombian hereditary breast and ovarian cancer families [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1211.

Germline Mutation in 1338 BRCA-Negative Chinese Hereditary Breast and/or Ovarian Cancer Patients: Clinical Testing with a Multigene Test Panel

Differences in the mutation spectrum across ethnicities suggest the importance of identifying genes in addition to common high penetrant genes to estimate the associated breast cancer risk in China. A total of 1338 high-risk breast cancer patients who tested negative for germline BRCA1, BRCA2, TP53, and PTEN mutations between 2007 and 2017 were selected from the Hong Kong Hereditary Breast Cancer Family Registry. Patient samples were subjected to next-generation DNA sequencing using a multigene panel (Color Genomics). All detected pathogenic variants were validated by bidirectional DNA sequencing. The sequencing data were coanalyzed by a bioinformatics pipeline developed in-house. Sixty-one pathogenic variants (4.6%) were identified in this cohort in 11 cancer predisposition genes. Most carriers (77.1%) had early onset of breast cancer (age <45 years), 32.8% had family members with breast cancer, and 11.5% had triple-negative breast cancer. The most common mutated genes were PALB2 (1.4%), RAD51D (0.8%), and ATM (0.8%). A total of 612 variants of unknown significance were identified in 494 patients, and 87.4% of the variants of unknown significance were missense mutations. Pathogenic variants in cancer predisposition genes beyond BRCA1, BRCA2, TP53, and PTEN were detected in an additional 4.6% of patients using the multigene panel. PALB2 (1.4%) and RAD51D (0.8%) were the most commonly mutated genes in patients who tested mutation negative by a four-gene panel.

Detecting Large Germline Rearrangements of BRCA1 by Next Generation Tumor Sequencing

A majority of BRCA1/2 (BRCA) pathogenic variants (PVs) are single nucleotide substitutions or small insertions/deletions. Copy number variations (CNVs), also known as large genomic rearrangements (LGRs), have been identified in BRCA genes. LGRs detection is a mandatory analysis in hereditary breast and ovarian cancer families, if no predisposing PVs are found by sequencing. Next generation sequencing (NGS) may be used to detect structural variation, since quantitative analysis of sequencing reads, when coupled with appropriate bioinformatics tools, is capable of estimating and predicting germline LGRs (gLGRs). However, applying this approach to tumor tissue is challenging, and the pipelines for determination of CNV are yet to be optimized. The aim of this study was to validate the Next Generation Tumor Sequencing (NGTS) technology to detect various gLGRs of BRCA1 locus in surgical tumor tissue samples. In this study, seven different BRCA1 gLGRs, previously found in high-grade serous ovarian cancers (HGSOC) patients, were detected in tumor samples collected from the patients at a time of HGSOC surgery. This study demonstrated that NGS can accurately detect BRCA1 gLGRs in primary tumors, suggesting that gLGR evaluation in BRCA1 locus should be performed in cases when the screening for BRCA alterations starts from tumor instead of blood. NGS sequencing of tumor samples may become the preferred method to detect both somatic and germline gLGRs in BRCA-encoding loci.

SEOM clinical guidelines in hereditary breast and ovarian cancer (2019)

Mutations in BRCA1 and BRCA2 high penetrance genes account for most hereditary breast and ovarian cancer, although other new high-moderate penetrance genes included in multigene panels have increased the genetic diagnosis of hereditary breast and ovarian cancer families by 50%. Multigene cancer panels provide new challenges related to increased frequency of variants of uncertain significance, new gene-specific cancer risk assessments, and clinical recommendations for carriers of mutations of new genes. Although clinical criteria for genetic testing continue to be largely based on personal and family history with around a 10% detection rate, broader criteria are being applied with a lower threshold for detecting mutations when there are therapeutic implications for patients with breast or ovarian cancer. In this regard, new models of genetic counselling and testing are being implemented following the registration of PARP inhibitors for individuals who display BRCA mutations. Massive sequencing techniques in tumor tissue is also driving a paradigm shift in genetic testing and potential identification of germline mutations. In this paper, we review the current clinical criteria for genetic testing, as well as surveillance recommendations in healthy carriers, risk reduction surgical options, and new treatment strategies in breast cancer gene-mutated carriers.

Study on the differences of opinions and choices of high-risk breast cancer populations in China before and after genetic testing.

BackgroundIn recent years, genetic testing (GT) has developed rapidly in China. However, the cancer genetic service system is still immature in China. Little is known about the opinions around genetic counseling (GC) and GT in Chinese individuals at high risk of breast cancer. This work aims to understand the changes in awareness, attitudes, and willingness of high-risk populations before and after GT, as well as the possible barriers to GC/GT.MethodsSeveral questionnaires for the high-risk populations of breast cancer were completed. Then, some patients were selected for free single/multi-gene testing as well as further survey and statistical analysis.ResultsDespite low levels of awareness, Chinese high-risk breast cancer groups hold positive attitudes about GC/GT. There were differences in the willingness of different groups of high-risk people. After GT, different testing results led to different views and choices for the patients than before GT. Lack of genetic knowledge of breast cancer, misunderstanding, cost, fear of adverse effects, and policy market factors are obstacles to accepting GC/GT for the participants.ConclusionsChinese doctors need to communicate according to the specific situation of high-risk individuals in pre-test counseling and post-test counseling. The national policy and GT market also need to be improved to support the hereditary breast cancer families’ follow-up service system.

The spectrum of mutations predisposing to familial breast cancer in Poland.

To optimize genetic testing, it is necessary to establish the spectrum of breast cancer-predisposing mutations in particular ethnic groups. We studied 1,018 women with a strong family history for breast cancer (families with hereditary breast cancer; HBC) from genetically homogenous population of Poland, which is populated by ethnic Slavs, for mutations in 14 cancer susceptibility genes. Additionally, we compared the frequency of candidate pathogenic variants in breast cancer cases and controls. Germline mutations were detected in 512 of 1,018 probands with breast cancer (50.3%), including BRCA1/2 mutations detected in 420 families and non-BRCA mutations seen in 92 families. Thirteen BRCA1/2 founder mutations represented 84% of all BRCA1/2-positive cases. Seven founder mutations of CHEK2, PALB2, NBN and RECQL represented 73% of all non-BRCA-positive cases. Odds ratios for hereditary breast cancer were 87.6 for BRCA1, 15.4 for PALB2, 7.2 for CHEK2, 2.8 for NBN and 15.8 for RECQL. Odds ratios for XRCC2, BLM and BARD1 were below 1.3. In summary, we found that 20 founder mutations in six genes (BRCA1/2, CHEK2, PALB2, NBN and RECQL) are responsible for 82% of Polish hereditary breast cancer families. A simple test for these 20 mutations will facilitate genetic testing for breast cancer susceptibility in Poland. It may also facilitate genetic testing for breast cancer susceptibility in other Slavic populations and women of Slavic descent worldwide.

Enhancing access to genetic cancer risk assessment (GCRA) in Monterrey, Mexico: The beginning of a prevention program.

e13150 Background: In limited-resource countries like Mexico, GCRA is not routinely provided due to elevated costs, lack of public coverage for testing and prophylactic surgeries, and limited GCRA expertise or awareness among providers and patients. Thus, GCRA services in Mexico are 20 years behind higher income countries, resulting in suboptimal care and limited opportunity for prevention. The Breast Cancer Center TecSalud established formal GCRA services for underserved patients by recruiting a cancer geneticist who provides care at no added expense to patients, building academic collaborations for training and research with City of Hope, and enabling free genetic testing through the Clinical Cancer Genomics Community Research Network, supported in part by the Breast Cancer Research Foundation. Aim: To report the uptake of the GCRA program by patients and relatives at TecSalud from January 2016 - December 2018. Methods: Eligibility includes Mexican women who meet hereditary breast cancer testing criteria and family members of mutation carriers. Risk reduction procedures are covered by Seguro Popular and/or the NGO Fundación Santos y de la Garza Evia. Results: GCRA was offered to 255 patients and 74 at risk relatives, with an increasing reach (proportion of those eligible who access the program). A significant growth of cascade testing and access to risk reduction surgery over time are noted. Conclusions: A growing number of referrals and GCRA visits shows improving reach, possibly due to engagement of the multidisciplinary team and increased patient awareness. The expansion of cascade testing and performance of risk-appropriate surgeries reflects a maturing prevention program. Key determinants of our progress are collaborations that provided us with crucial mentorship, access to genetic assays, as well as the increasing involvement of local leaders, administrators and benefactors for the establishment of vital clinical and research capacity. Multilevel efforts should continue to enhance the delivery of standard of medical care for the most vulnerable and underserved high-risk patients and families. [Table: see text]

A PALB2 truncating mutation: Implication in cancer prevention and therapy of Hereditary Breast and Ovarian Cancer

Explaining genetic predisposition in Hereditary Breast and Ovarian Cancer (HBOC) families without BRCA mutations is crucial. Germline PALB2 inactivating mutations were associated with an increased risk of HBOC due to its role in DNA repair through cooperation with BRCA proteins. The prevalence and penetrance of PALB2 mutations in Spanish HBOC patients remains unexplained. PALB2 mutation screening has been conducted in 160 high-risk BRCA-negative patients and 320 controls. We evaluated four predicted splicing disruption variants and large genomic rearrangements by multiplex ligation-dependent probe amplification. We have found a frameshift mutation which segregates in an early onset cancer family; and four rare missense variants. None of the variants tested for a predicted splicing disruption showed an aberrant transcript pattern. No large genomic rearrangements were detected. Although PALB2 truncating mutations are rarely identified, segregation analysis and early onset cancer suggest a significant contribution to HBOC susceptibility in the Spanish population. PALB2 screening may improve genetic counselling through prevention measures, pedigree management and PARP inhibitor therapy selection.

Familial breast cancer and DNA repair genes: Insights into known and novel susceptibility genes from the GENESIS study, and implications for multigene panel testing.

Pathogenic variants in BRCA1 and BRCA2 only explain the underlying genetic cause of about 10% of hereditary breast and ovarian cancer families. Because of cost‐effectiveness, multigene panel testing is often performed even if the clinical utility of testing most of the genes remains questionable. The purpose of our study was to assess the contribution of rare, deleterious‐predicted variants in DNA repair genes in familial breast cancer (BC) in a well‐characterized and homogeneous population. We analyzed 113 DNA repair genes selected from either an exome sequencing or a candidate gene approach in the GENESIS study, which includes familial BC cases with no BRCA1 or BRCA2 mutation and having a sister with BC (N = 1,207), and general population controls (N = 1,199). Sequencing data were filtered for rare loss‐of‐function variants (LoF) and likely deleterious missense variants (MV). We confirmed associations between LoF and MV in PALB2, ATM and CHEK2 and BC occurrence. We also identified for the first time associations between FANCI, MAST1, POLH and RTEL1 and BC susceptibility. Unlike other associated genes, carriers of an ATM LoF had a significantly higher risk of developing BC than carriers of an ATM MV (ORLoF = 17.4 vs. ORMV = 1.6; p Het = 0.002). Hence, our approach allowed us to specify BC relative risks associated with deleterious‐predicted variants in PALB2, ATM and CHEK2 and to add MAST1, POLH, RTEL1 and FANCI to the list of DNA repair genes possibly involved in BC susceptibility. We also highlight that different types of variants within the same gene can lead to different risk estimates.

GEMO, a National Resource to Study Genetic Modifiers of Breast and Ovarian Cancer Risk in BRCA1 and BRCA2 Pathogenic Variant Carriers.

Women carrying a pathogenic variant (PV) in the BRCA1 or BRCA2 (BRCA1/2) genes are at high lifetime risk of developing breast cancer (BC) and ovarian cancer (OC), but estimation of the cumulative risk of cancer to age 70 years varies substantially between studies and populations. Initial estimations were obtained from selected high-risk families with multiple cases, such as those ascertained through the Breast Cancer Linkage Consortium used to identify disease loci (1). In the first retrospective studies conducted on such families, estimates for BC ranged from 40 to 87% for BRCA1 PV carriers and from 27 to 84% for BRCA2 PV carriers and estimates for OC ranged from 16 to 68% for BRCA1 PV carriers and from 11 to 27% for BRCA2 PV carriers (1–4). Recently, the largest prospective cohort conducted to date reported cumulative risks of BC to age 80 years of 72% for BRCA1 PV carriers and 69% for BRCA2 PV carriers (5). In the same study, cumulative risks of OC to age 80 years were 44% for BRCA1 PV carriers and 17% for BRCA2 PV carriers. Variation in cancer risks within or between BRCA1/2 families, with respect to age at diagnosis or type of cancer, can be explained by other genetic factors and/or lifestyle and reproductive factors (6–10). Genome-wide association studies (GWAS) conducted by the Breast Cancer Association Consortium (BCAC) have identified 172 common single-nucleotide polymorphisms (SNPs) associated with small increases in breast and/or ovarian cancer risk in the general population (11). A subset of these SNPs modifies the risk of breast and ovarian cancer risk for BRCA1/2 PV carriers (12–14) but most of the variability has not been explained yet (15). Breast and ovarian cancer risks in BRCA1/2 PV carriers might also vary according to the location of the variant and/or its origin (14, 16–19). Genetic testing for BRCA1 and BRCA2 has been part of genetic counseling in European Union countries and North America since their discovery in the 90's, and has greatly improved recommendations about clinical management options and the most appropriate treatments. Nonetheless, both retrospective and prospective studies on large datasets of BRCA1/2 PV carrier families are still very much needed to refine individual cancer risk estimates by considering other genetic and lifestyle/environmental factors, and they will also contribute to a better understanding of the correlation between mutant BRCA1/2 alleles and phenotype. In particular, accurate age-specific risk estimates for the different types of cancer would be useful when choosing risk reduction strategies such as prophylactic bilateral mastectomy or salphingo-oophorectomy. The Genetic Modifiers of BRCA1 and BRCA2 (GEMO) Group is the French multidisciplinary, collaborative framework for the investigation of genetic factors modifying cancer risk in Hereditary Breast and Ovarian cancer (HBOC) families segregating BRCA1/2 PVs. Its primary aims are to contribute to large-scale national and international projects to identify genetic modifiers and to facilitate the translation of research results to the clinical setting. This is achieved by establishing a resource of blood DNA samples from individuals carrying a PV together with family and clinical data through the nation-wide network of cancer genetic clinics. Here we report on the progress of the GEMO study, the characteristics of the 5,303 actual participants and the prevalence and spectrum of BRCA1/2 cancer-associated variants identified so far.

Abstract 4415: Characterization of tumor-derived exosomes in BRCA-associated breast tumors

Abstract Background: BRCA-mutated tumors are usually with higher grade than sporadic tumors and the biology is poorly understood. Exosomes are small membrane-derived vesicles that function to mediate cell-cell communication via the transfer of tumor-promoting microRNAs (miRNAs), RNAs and proteins. Interestingly, different spectrum of miRNAs is released by cancer cells to promote tumor growth and metastasis in breast cancer. However, the selectivity of miRNA released from tumor-derived exosomes and its relevance in cancer treatment has not been widely studied. Hence, this study is sought to characterize the role of exosomal-miRNA (exo-miR) for the development of BRCA-associated tumors. Methods: Plasma samples from patients with BRCA-positive and non-BRCA carriers were recruited and selected from the Hong Kong Hereditary Breast Cancer Family Registry. By using miRCURY LNA array, the exosomal-miRNA expressions in plasma of patient with BRCA-positive (n=4) and non-carriers (n=4), as well as healthy controls (n=4) were profiled. Selected miRNAs were further validated in pre- and post-operative plasma and paired primary tissues (n=40) using real-time RT-PCR. Functional study of miRNA was also carried out in the cell lines. Results: LNA array data showed that differential expressed BRCA-associated exo-miRNAs were identified. Upregulated miRs (miR-106a, miR-20a, miR-23a, miR-451 and miR-486) were validated in BRCA-positive, BRCA-negative and healthy controls by real-time RT-PCR. In addition, the expression levels of miR-106a, miR-451 and miR-486 were significantly lower in post-operative plasma of BRCA-carriers than non-carriers. Importantly, the expression of miR-451 was reduced after tumor resection in BRCA mutation carriers. In parallel, high expression of exo-miR-106a, miR-20a, miR-23a, miR-451 and miR-486 were also seen in breast cancer cell lines (MB-231 and MB-468) relative to normal breast cells (MCF-10A). We found that cells transfected with miR-451 inhibitor significantly reduce cell proliferation. Conclusions: These preliminary results reveal differential exo-miRNA profiles between BRCA carriers and non-carriers with breast cancer, and identify potential targets of dysregulated miRNAs which is crucial in disease progression of BRCA-associated breast cancers. Citation Format: Vivian Y. Shin, Man-Ting Siu, Isabella Cheuk, Ava Kwong. Characterization of tumor-derived exosomes in BRCA-associated breast tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4415.

Investigation of discordant sibling pairs from hereditary breast cancer (HBC) families.

1538Background: Women who undergo testing for hereditary breast cancer (HBC) may be offered a panel of up to 40 genes but the majority of women tested have no mutation identified on these panels. T...

Morphology and genomic hallmarks of breast tumours developed by ATM deleterious variant carriers

BackgroundThe ataxia telangiectasia mutated (ATM) gene is a moderate-risk breast cancer susceptibility gene; germline loss-of-function variants are found in up to 3% of hereditary breast and ovarian cancer (HBOC) families who undergo genetic testing. So far, no clear histopathological and molecular features of breast tumours occurring in ATM deleterious variant carriers have been described, but identification of an ATM-associated tumour signature may help in patient management.MethodsTo characterise hallmarks of ATM-associated tumours, we performed systematic pathology review of tumours from 21 participants from ataxia-telangiectasia families and 18 participants from HBOC families, as well as copy number profiling on a subset of 23 tumours. Morphology of ATM-associated tumours was compared with that of 599 patients with no BRCA1 and BRCA2 mutations from a hospital-based series, as well as with data from The Cancer Genome Atlas. Absolute copy number and loss of heterozygosity (LOH) profiles were obtained from the OncoScan SNP array. In addition, we performed whole-genome sequencing on four tumours from ATM loss-of-function variant carriers with available frozen material.ResultsWe found that ATM-associated tumours belong mostly to the luminal B subtype, are tetraploid and show LOH at the ATM locus at 11q22–23. Unlike tumours in which BRCA1 or BRCA2 is inactivated, tumours arising in ATM deleterious variant carriers are not associated with increased large-scale genomic instability as measured by the large-scale state transitions signature. Losses at 13q14.11-q14.3, 17p13.2-p12, 21p11.2-p11.1 and 22q11.23 were observed. Somatic alterations at these loci may therefore represent biomarkers for ATM testing and harbour driver mutations in potentially ‘druggable’ genes that would allow patients to be directed towards tailored therapeutic strategies.ConclusionsAlthough ATM is involved in the DNA damage response, ATM-associated tumours are distinct from BRCA1-associated tumours in terms of morphological characteristics and genomic alterations, and they are also distinguishable from sporadic breast tumours, thus opening up the possibility to identify ATM variant carriers outside the ataxia-telangiectasia disorder and direct them towards effective cancer risk management and therapeutic strategies.