The Pivotal Role of Germline BRCA2 Pathogenic Variants in "Apparently Sporadic" Pancreatic Cancer.

In 1996, Goggins and colleagues demonstrated the importance of germline BRCA2 pathogenic variants in the development of apparently sporadic pancreatic ductal adenocarcinoma (PDAC). Previously, the group identified homozygous deletion of the 13q region in PDACs, enabling the identification of the BRCA2 gene. This 1996 article first revealed loss of BRCA2, both germline and somatic, as a key driver of PDAC at a time when there was still doubt if PDAC even had an inherited component. Contrary to the prevailing wisdom, not all individuals with inherited pathogenic BRCA2 variants had a family history of cancer. The innovative bedside-to-bench nature of this work revealed that individuals with these variants would be missed if genetic testing was limited only to those meeting the family history criteria. Therefore, Goggins and colleagues advocated that universal genetic testing may be indicated for pancreatic cancer at a time when genetic testing was in its infancy. Twenty-three years later, in 2019, universal testing for pancreatic cancer became standard of care in the United States. Additionally, this work and future-related publications by the Kern Laboratory set the stage for targeting BRCA2 and related DNA repair mutations in pancreatic cancer via a synthetic lethal therapeutic approach. The provocative discussion initiated by this team in this publication is still inspiring the field today. In this seminal publication, Goggins and colleagues profoundly impacted the direction of pancreatic cancer research, leading to a more sophisticated approach to designing earlier detection and precision treatment strategies for pancreatic cancer. See related article by Goggins and colleagues, Cancer Res 1996;56:5360-4.

The coexistence of a BRCA2 germline and a DICER1 somatic variant in two first-degree cousins suggests their potential synergic effect.

Cancer predisposition syndromes are recognized in about 10% of pediatric malignancies with several genes specifically involved in a subset of pediatric tumors such as DICER1, in pleuropulmonary blastoma, cystic nephroma, and brain sarcomas. By contrast, the role of BRCA1/2 in pediatric cancer predisposition is still under investigation. We present two cases of young first-degree cousins, both carrying a germline BRCA2 variant and developing tumors characterized by somatic DICER1 mutations. Patient 1 presented with a cystic nephroma harboring a somatic DICER1 variant (p.Asp1810Tyr), while patient 2 had a primary intracranial DICER1-mutated sarcoma showing a distinct somatic DICER1 variant (p.Asp1709Glu) as well as biallelic inactivation of TP53 (p.Val173Leu, VAF 91%) and APC (p.Ile1307Lys, VAF 95%) and a pathogenic variant in KRAS (p.Gln61His). Both patients carried the same germline BRCA2 variant (p.Arg2842Cys) of unknown significance. The same variant was found in the mother of patient 2 and in the father of patient 1, who are siblings. A homologous recombination deficiency signature was not identified in any of the two tumors, possibly suggesting a reduction of BRCA2 activity. The association of BRCA2 and DICER1 variants in our cases hints at a potential cooperative role in cancer pathogenesis. Further studies are warranted to elucidate the interplay between BRCA1/2 and DICER1 variants and their implications for cancer predisposition and treatment in pediatric patients.

BRCA2 stabilises RAD51 and DMC1 nucleoprotein filaments through a conserved interaction mode.

BRCA2 is essential for DNA repair by homologous recombination in mitosis and meiosis. It interacts with recombinases RAD51 and DMC1 to facilitate the formation of nucleoprotein filaments on resected DNA ends that catalyse recombination-mediated repair. BRCA2's BRC repeats bind and disrupt RAD51 and DMC1 filaments, whereas its PhePP motifs bind recombinases and stabilise their nucleoprotein filaments. However, the mechanism of filament stabilisation has hitherto remained unknown. Here, we report the crystal structure of a BRCA2-DMC1 complex, revealing how core interaction sites of PhePP motifs bind to recombinases. The interaction mode is conserved for RAD51 and DMC1, which selectively bind to BRCA2's two distinct PhePP motifs via subtly divergent binding pockets. PhePP motif sequences surrounding their core interaction sites protect nucleoprotein filaments from BRC-mediated disruption. Hence, we report the structural basis of how BRCA2's PhePP motifs stabilise RAD51 and DMC1 nucleoprotein filaments for their essential roles in mitotic and meiotic recombination.

Durable benefit from poly(ADP-ribose) polymerase inhibitors in metastatic prostate cancer in routine practice: biomarker associations and implications for optimal clinical next-generation sequencing testing.

BACKGROUND: Controlled trials have consistently demonstrated the efficacy of poly(ADP-ribose) polymerase inhibitors (PARPis) in patients with metastatic castration-resistant prostate cancer (mCRPC) and BRCA1 or BRCA2 alterations (BRCAalt). However, the reported efficacy of PARPi for alterations in other homologous recombination repair (HRR) genes is less consistent. We sought to evaluate the routine practice effectiveness of PARPi between and within these groups. DESIGN: Patient-level data from a deidentified nationwide (USA-based) cancer clinico-genomic database between January 2011 and September 2023 were extracted. Patients with mCRPC and comprehensive genomic profiling by liquid biopsy [circulating tumor DNA (ctDNA)] or tissue (tumor) biopsy and who received single-agent PARPi were included and grouped by BRCAalt, ATMalt, other HRR, or no HRR. We further subcategorized BRCAalt into homozygous loss (BRCAloss) and all other deleterious BRCAalt (otherBRCAalt). RESULTS: A total of 445 patients met inclusion criteria: 214 with tumor and 231 with ctDNA. BRCAalt had more favorable outcomes to PARPi compared with ATM, other HRR, and no HRR groups. Within the BRCAalt subgroup, compared with other BRCAalt, BRCAloss had a more favorable time to next treatment (median 9 versus 19.4 months, P = 0.005), time to treatment discontinuation (median 8 versus 14 months, P = 0.006), and routine practice overall survival (median 14.7 versus 19.4 months, P = 0.016). Tumor BRCAloss prevalence (3.1%) was similar to ctDNA prevalence in liquid biopsy specimens with high tumor fraction (>20%). BRCAloss was not detected in orthogonal germline testing. CONCLUSIONS: PARPi routine practice effectiveness between groups mirrors prospective trials. Within the BRCAalt group, BRCAloss had the best outcomes. Unless the ctDNA tumor fraction is very high, somatic tissue testing (archival or metastatic) should be prioritized to identify patients who may benefit most from PARPi. When tissue testing is not clinically feasible, sufficient ctDNA tumor fraction levels for detection are enriched at clinical timepoints associated with tumor progression.

Genomic Landscape in Prostate Cancer in a Latin American Population.

PURPOSE: This study aims to describe genomic characteristics of patients with metastatic prostate cancer (mPC). PATIENTS AND METHODS: This study is a retrospective, multicenter cohort study of patients with mPC and reports on genomic testing. Patients were included from 12 academic centers in five countries. RESULTS: A total of 349 patients with PC were included in this study. Most patients (209, 59.9%) were de novo metastatic. Genomic analysis was performed in 233 (66.6%) patients in the metastatic castration-resistant prostate cancer (mCRPC) setting, and only 115 (32.8%) patients had a tumor evaluation in the metastatic hormone sensitive prostate cancer scenario. The evaluation of somatic and/or germline mutations was performed through multigene panel analyses in 290 (83.09%) patients, and next-generation sequencing of BRCA1 and BRCA2 genes was performed in 59 (16.91%) patients. Analyzing the mCRPC subgroup, with a median follow-up of 15.6 months (IQR, 14-19.06), the median progression-free survival (PFS) was not reached (NR) and the PFS at 16 months was 58.7% (95% CI, 50.8 to 67.8). When comparing patients with BRCA mutations with those who are not BRCA-mutated in the mCRPC scenario, the median PFS was NR (95% CI, 14 to NR) and 26.3 months (95% CI, 16.7 to 36.5; P = .2), respectively. Two of six patients with BRCA mutations were treated with targeted therapies (poly-ADP-ribose polymerase inhibitors). CONCLUSION: Our study, to the best of our knowledge, represents one of the larger data sets for somatic testing in patients with PC in Latin America (LATAM). It adds valuable information to the growing body of knowledge about the genomic landscape of advanced PC in real-world daily practice scenarios in LATAM countries, which are not always well-represented in large-scale randomized clinical trials.

TMPRSS2:ERG Gene Fusion Might Predict Resistance to PARP Inhibitors in Metastatic Castration-resistant Prostate Cancer.

BACKGROUND/AIM: The emergence of novel DNA damage repair (DDR) pathways in molecular-target therapy drugs (MTTD) has shown promising outcomes in treating patients with metastatic castration-resistant prostate cancer (mCRPC). About 25% of mCRPC patients have actionable deleterious aberrations in DDR genes, primarily in the homologous recombination (HR) pathway. However, the response rate in patients with BRCA1/2 or mutations in HRR-related genes is only 45%-55%, when exposed to poly ADP ribose polymerase (PARP) inhibitor-based therapy (PARPi). A frequent characteristic feature of prostate cancer (PC) is the occurrence of genomic rearrangement that affects the transmembrane protease serine 2 (TMPRSS2) and E26 transformation-specific (ETS)- transcription factor-related gene (ERG). MATERIALS AND METHODS: In this study, a total of 114 patients with mCRPC had their RNA and DNA sequenced using next-generation sequencing. RESULTS: Based on their genetic profile of deleterious gene alterations of BRCA1/2 or ATM, six patients were selected for PARPi. Patients with TMPRSS2:ERG gene fusion and homozygous alteration in ATM or BRCA2 (n=2) or heterozygous alterations (BRCA1 or BRCA2) and lack of TMPRSS2:ERG gene fusion (n=2) did not show clinical benefit from PARPi (treatment duration <16 weeks). In contrast, patients (n=2) without TMPRSS2:ERG gene fusion and homozygous deleterious alterations in ATM or BRCA2 all had clinical benefit from PARPi (treatment duration ≥16 weeks). CONCLUSION: The TMPRSS2:ERG transcript product might be used as a PARPi resistance biomarker.

Fine mapping of RNA isoform diversity using an innovative targeted long-read RNA sequencing protocol with novel dedicated bioinformatics pipeline.

BACKGROUND: Solving the structure of mRNA transcripts is a major challenge for both research and molecular diagnostic purposes. Current approaches based on short-read RNA sequencing and RT-PCR techniques cannot fully explore the complexity of transcript structure. The emergence of third-generation long-read sequencing addresses this problem by solving this sequence directly. However, genes with low expression levels are difficult to study with the whole transcriptome sequencing approach. To fix this technical limitation, we propose a novel method to capture transcripts of a gene panel using a targeted enrichment approach suitable for Pacific Biosciences and Oxford Nanopore Technologies platforms. RESULTS: We designed a set of probes to capture transcripts of a panel of genes involved in hereditary breast and ovarian cancer syndrome. We present SOSTAR (iSofOrmS annoTAtoR), a versatile pipeline to assemble, quantify and annotate isoforms from long read sequencing using a new tool specially designed for this application. The significant enrichment of transcripts by our capture protocol, together with the SOSTAR annotation, allowed the identification of 1,231 unique transcripts within the gene panel from the eight patients sequenced. The structure of these transcripts was annotated with a resolution of one base relative to a reference transcript. All major alternative splicing events of the BRCA1 and BRCA2 genes described in the literature were found. Complex splicing events such as pseudoexons were correctly annotated. SOSTAR enabled the identification of abnormal transcripts in the positive controls. In addition, a case of unexplained inheritance in a family with a history of breast and ovarian cancer was solved by identifying an SVA retrotransposon in intron 13 of the BRCA1 gene. CONCLUSIONS: We have validated a new protocol for the enrichment of transcripts of interest using probes adapted to the ONT and PacBio platforms. This protocol allows a complete description of the alternative structures of transcripts, the estimation of their expression and the identification of aberrant transcripts in a single experiment. This proof-of-concept opens new possibilities for RNA structure exploration in both research and molecular diagnostics.

Prevalence, prognosis, and health care resource utilization in carriers of pathogenic germline variants in BRCA1/2 with incident early-stage breast cancer: a Finnish population-based study.

BACKGROUND AND PURPOSE: Data on real-world prevalence and outcomes in patients diagnosed with pathogenic germline variants in BRCA1 or BRCA2 (gBRCAm) breast cancer is sparse. MATERIAL AND METHODS: An observational cohort study including all patients diagnosed with incident early-stage breast cancer and recorded in Helsinki University Hospital data lake 2012-2022, accounting for one-third of the Finnish breast cancer patient population. RESULTS: Among 14,696 incident early-stage breast cancer patients, 11.2% (n = 1,644) were tested for gBRCAm. Of the tested population, 7.4% (n = 122) carried gBRCAm. Of the 122 gBRCAm patients, 95.1% (n = 116) were women, with a median age at diagnosis of 46.4 years. Among the same patient group, HER2 status was available for 87.7% (n = 107) of the patients. Among these, 49.5% (n = 53) had hormone receptor-positive (HR+), HER2-negative breast cancer, 13.1% were (n = 14) HER2-positive, and 37.3% (n = 40) of patients had triple-negative breast cancer. The tested patients were significantly younger compared with non-tested patients. No significant differences in overall survival or healthcare resource utilization between the tested patients with gBRCAm and gBRCA wild-type (gBRCAwt) were observed. INTERPRETATION: This comprehensive observational study supports previous findings of gBRCAm prevalence in the Western early-stage breast cancer population. While no differences in survival were observed between patients with gBRCAm and gBRCAwt, it is important to consider the potential influence of selection bias, particularly due to the younger gBRCAm testing target population and the overall low frequency of testing. Therefore, a substantial proportion of the patients carrying gBRCAm likely remained undiagnosed, and wider screening criteria are warranted.

Universal Genetic Testing for Newly Diagnosed Invasive Breast Cancer.

Importance: Between 5% and 10% of breast cancer cases are associated with an inherited germline pathogenic or likely pathogenic variant (GPV) in a breast cancer susceptibility gene (BCSG), which could alter local and systemic therapy recommendations. Traditional genetic testing criteria misses a proportion of these cases. Objective: To evaluate the prevalence and clinicopathological associations of GPVs in 2 groups of BCSGs among an ethnically diverse cohort of women with newly diagnosed breast cancer. Design, Setting, and Participants: This cross-sectional study, conducted at 3 Montreal hospitals between September 2019 and April 2022, offered universal genetic counseling and testing to all women with a first diagnosis of invasive breast cancer. Women were offered an obligatory primary panel of BRCA1, BRCA2, and PALB2 (B1B2P2) and an optional secondary panel of 14 additional BCSGs. Eligible participants were women 18 years of age or older who received a diagnosis of a first primary invasive breast cancer not more than 6 months before the time of referral to the study. Data were analyzed from November 2023 to June 2024. Results: Of 1017 referred patients, 805 were eligible and offered genetic counseling and testing, and 729 of those 805 (90.6%) consented to be tested. The median age at breast cancer diagnosis was 53 years (range, 23-91 years), and 65.4% were White and of European ancestry. Fifty-four GPVs were identified in 53 patients (7.3%), including 39 patients (5.3%) with B1B2P2 and 15 patients (2.1%) with 6 of the 14 secondary panel BCSGs (ATM, BARD1, BRIP1, CHEK2, RAD51D, and STK11). On multivariable analysis, clinical factors independently associated with B1B2P2-positive status included being younger than 40 years of age at diagnosis (odds ratio [OR], 6.83; 95% CI, 2.22-20.90), triple-negative breast cancer (OR, 3.19; 95% CI, 1.20-8.43), high grade disease (OR, 1.68; 95% CI, 1.05-2.70), and family history of ovarian cancer (OR, 9.75; 95% CI, 2.65-35.85). Of 39 B1B2P2-positive patients, 13 (33.3%) were eligible for poly(adenosine diphosphate-ribose) polymerase (PARP) inhibitors. Conclusions and Relevance: In this cross-sectional universal genetic testing study of women with newly diagnosed invasive breast cancer, the prevalence of GPVs was 7.3%, with 5.3% of patients testing positive for B1B2P2. Among B1B2P2-women women, one-third were eligible for PARP inhibitors.

Hyper-recombination in ribosomal DNA is driven by long-range resection-independent RAD51 accumulation.

Ribosomal DNA (rDNA) encodes the ribosomal RNA genes and represents an intrinsically unstable genomic region. However, the underlying mechanisms and implications for genome integrity remain elusive. Here, we use Bloom syndrome (BS), a rare genetic disease characterized by DNA repair defects and hyper-unstable rDNA, as a model to investigate the mechanisms leading to rDNA instability. We find that in Bloom helicase (BLM) proficient cells, the homologous recombination (HR) pathway in rDNA resembles that in nuclear chromatin; it is initiated by resection, replication protein A (RPA) loading and BRCA2-dependent RAD51 filament formation. However, BLM deficiency compromises RPA-loading and BRCA1/2 recruitment to rDNA, but not RAD51 accumulation. RAD51 accumulates at rDNA despite depletion of long-range resection nucleases and rDNA damage results in micronuclei when BLM is absent. In summary, our findings indicate that rDNA is permissive to RAD51 accumulation in the absence of BLM, leading to micronucleation and potentially global genomic instability.

Predicting BRCA mutation and stratifying targeted therapy response using multimodal learning: a multicenter study.

BACKGROUND: The status of BRCA1/2 genes plays a crucial role in the treatment decision-making process for multiple cancer types. However, due to high costs and limited resources, a demand for BRCA1/2 genetic testing among patients is currently unmet. Notably, not all patients with BRCA1/2 mutations achieve favorable outcomes with poly (ADP-ribose) polymerase inhibitors (PARPi), indicating the necessity for risk stratification. In this study, we aimed to develop and validate a multimodal model for predicting BRCA1/2 gene status and prognosis with PARPi treatment. METHODS: We included 1695 slides from 1417 patients with ovarian, breast, prostate, and pancreatic cancers across three independent cohorts. Using a self-attention mechanism, we constructed a multi-instance attention model (MIAM) to detect BRCA1/2 gene status from hematoxylin and eosin (H&E) pathological images. We further combined tissue features from the MIAM model, cell features, and clinical factors (the MIAM-C model) to predict BRCA1/2 mutations and progression-free survival (PFS) with PARPi therapy. Model performance was evaluated using area under the curve (AUC) and Kaplan-Meier analysis. Morphological features contributing to MIAM-C were analyzed for interpretability. RESULTS: Across the four cancer types, MIAM-C outperformed the deep learning-based MIAM in identifying the BRCA1/2 genotype. Interpretability analysis revealed that high-attention regions included high-grade tumors and lymphocytic infiltration, which correlated with BRCA1/2 mutations. Notably, high lymphocyte ratios appeared characteristic of BRCA1/2 mutations. Furthermore, MIAM-C predicted PARPi therapy response (log-rank p < 0.05) and served as an independent prognostic factor for patients with BRCA1/2-mutant ovarian cancer (p < 0.05, hazard ratio:0.4, 95% confidence interval: 0.16-0.99). CONCLUSIONS: The MIAM-C model accurately detected BRCA1/2 gene status and effectively stratified prognosis for patients with BRCA1/2 mutations.

The risk of endocrine interventions in carriers of a genetic predisposition for breast and gynecologic cancers: recommendations of the German Consortium for Hereditary Breast and Ovarian Cancer.

PURPOSE: To support doctors in counselling women with genetic predisposition for breast or gynecologic cancers on endocrine interventions. METHODS: Evidence on the safety of endocrine interventions for fertility treatment, contraception, hormone replacement therapy after risk-reducing salpingo-oophorectomy (RRSO) or treatment of symptoms during peri- and postmenopause was analysed for carriers of probably pathogenic and pathogenic variants in BRCA1 or BRCA2 (BRCA1/2-pV), in other breast and ovarian cancer genes and the Lynch Syndrome. Cancer risks were compared with data on risks for the general population. RESULTS: Data on risk modulation of endocrine interventions in women with genetic predisposition is limited. Ovarian hyperstimulation for fertility treatment may be performed. Oral contraceptives should not be used to reduce ovarian cancer risk in BRCA1/2-pV carriers. Premenopausal BRCA1/2-pV carriers and carriers of pV in Lynch Syndrome genes should be offered hormone replacement therapy (HRT) after RRSO, to prevent diseases caused by estrogen deficiency. CONCLUSION: Effect direction and strength of risk modulation by endocrine interventions is similar to the general population. Participation of individuals at risk in prospective registries is recommended.

Economic Evaluation of Population-Based BRCA1 and BRCA2 Testing in Canada.

Importance: Population-based BRCA testing can identify many more BRCA carriers who will be missed by the current practice of BRCA testing based on family history (FH) and clinical criteria. These carriers can benefit from screening and prevention, potentially preventing many more breast and ovarian cancers and deaths than the current practice. Objective: To estimate the incremental lifetime health outcomes, costs, and cost-effectiveness associated with population-based BRCA testing compared with FH-based testing in Canada. Design, Setting, and Participants: For this economic evaluation, a Markov model was developed to compare the lifetime costs and outcomes of BRCA1/BRCA2 testing for all general population women aged 30 years compared with FH-based testing. BRCA carriers are offered risk-reducing salpingo-oophorectomy to reduce their ovarian cancer risk and magnetic resonance imaging (MRI) and mammography screening, medical prevention, and risk-reducing mastectomy to reduce their breast cancer risk. The analyses were conducted from both payer and societal perspectives. This study was conducted from October 1, 2022, to February 20, 2024. Main Outcomes and Measures: Outcomes of interest were ovarian cancer, breast cancer, additional heart disease deaths, and incremental cost-effectiveness ratio ICER per quality-adjusted life-year (QALY). One-way and probabilistic-sensitivity-analyses (PSA) were undertaken to explore the uncertainty. Results: In the simulated cohort of 1 000 000 women aged 30 years in Canada, the base case ICERs of population-based BRCA testing were CAD $32 276 (US $23 402.84) per QALY from the payer perspective or CAD $16 416 (US $11 903.00) per QALY from the societal perspective compared with FH-based testing, well below the established Canadian cost-effectiveness thresholds. Population testing remained cost-effective for ages 40 to 60 years but not at age 70 years. The results were robust for multiple scenarios, 1-way sensitivity, and PSA. More than 99% of simulations from payer and societal perspectives were cost-effective on PSA (5000 simulations) at the CAD $50 000 (US $36 254.25) per QALY willingness-to-pay threshold. Population-based BRCA testing could potentially prevent an additional 2555 breast cancers and 485 ovarian cancers in the Canadian population, corresponding to averting 196 breast cancer deaths and 163 ovarian cancer deaths per 1 000 000 population. Conclusions and Relevance: In this economic evaluation, population-based BRCA testing was cost-effective compared with FH-based testing in Canada from payer and societal perspectives. These findings suggest that changing the genetic testing paradigm to population-based testing could prevent thousands of breast and ovarian cancers.

Utility of Clinical-Pathological Parameters for Exclusion of BRCA1/2 Mutation Carriers as Candidates for Partial Breast Irradiation.

PURPOSE: Several international groups have published guidelines to identify low-risk breast cancer (BC) patients who are eligible for partial breast irradiation (PBI). These include the American Society for Radiation Oncology (ASTRO), the European Society for Radiotherapy and Oncology (ESTRO), and ESTRO subgroups such as the Intraoperative radiation (IORT) Task Force and Groupe Européen de Curiethérapie (GEC) -ESTRO. Only ASTRO guidelines recommend against the use of PBI in known carriers of germline pathogenic variants (PVs) in BRCA1/2. The aim of this study was to evaluate the proportion of BC patients, subsequently found to be BRCA1/2 PV carriers who would be eligible for PBI based on clinical-pathologic criteria of the above-mentioned international guidelines. METHODS AND MATERIALS: Data were extracted from the medical records of consecutive BC BRCA1/2 PV carriers treated at a single institution between 2006 and 2023. Data included patient demographics, tumor characteristics, treatment, and disease outcomes. RESULTS: Overall, 498 patients with 518 primary tumors were analyzed. Of these, 282 (12 of them with synchronous bilateral disease) presented with unknown genetic status at diagnosis and formed the study cohort. The median age at diagnosis was 42.7 years (range, 23.8-77.9). Based on the recent ASTRO guidelines (not including conditionally recommended criteria), 17 of 294 (5.8%) of the carriers had tumors that would be eligible for PBI, including 3 Her2-positive tumors and 5 patients diagnosed between ages 40 and 49 years. Using the ESTRO IORT and the ACROP-ESTRO PBI criteria, 9 of 294 (3%) would be eligible, whereas with the GEC-ESTRO low-risk criteria, 31 of 294 (10.5%) of the carriers would be eligible, and their intermediate risk criteria would increase eligibility for PBI by an additional 8.2% (overall 18.7%). CONCLUSIONS: Using clinical-pathologic criteria published in international guidelines, 3% to 18% of BRCA1/2 PV carriers will have tumors eligible for PBI. Therefore, especially in populations who are at high risk for being BRCA1/2 PV carriers, we recommend adhering to stricter guidelines. In our cohort, ASTRO, ESTRO-IORT, and ESTRO PBI had the lowest probability of identifying BRCA1/2 PV carriers as eligible for PBI.

DSS1 restrains BRCA2's engagement with dsDNA for homologous recombination, replication fork protection, and R-loop homeostasis.

DSS1, essential for BRCA2-RAD51 dependent homologous recombination (HR), associates with the helical domain (HD) and OB fold 1 (OB1) of the BRCA2 DSS1/DNA-binding domain (DBD) which is frequently targeted by cancer-associated pathogenic variants. Herein, we reveal robust ss/dsDNA binding abilities in HD-OB1 subdomains and find that DSS1 shuts down HD-OB1's DNA binding to enable ssDNA targeting of the BRCA2-RAD51 complex. We show that C-terminal helix mutations of DSS1, including the cancer-associated R57Q mutation, disrupt this DSS1 regulation and permit dsDNA binding of HD-OB1/BRCA2-DBD. Importantly, these DSS1 mutations impair BRCA2/RAD51 ssDNA loading and focus formation and cause decreased HR efficiency, destabilization of stalled forks and R-loop accumulation, and hypersensitize cells to DNA-damaging agents. We propose that DSS1 restrains the intrinsic dsDNA binding of BRCA2-DBD to ensure BRCA2/RAD51 targeting to ssDNA, thereby promoting optimal execution of HR, and potentially replication fork protection and R-loop suppression.

Streamlined Genetic Education and Cascade Testing in Men from Hereditary Breast Ovarian Cancer Families: A Randomized Trial.

INTRODUCTION: When a pathogenic BRCA1 or BRCA2 mutation is identified in a family, cascade genetic testing of family members is recommended since the results may inform screening or treatment decisions in men and women. However, rates of cascade testing are low, and men are considerably less likely than women to pursue cascade testing. To facilitate cascade testing in men, we designed a Web-based genetic education tool that addressed barriers to cascade testing, was individually tailored, delivered proactively, and could be used in lieu of pretest genetic counseling to streamline the cascade testing process. METHODS: We randomized 63 untested men from hereditary cancer families to Web-based genetic education (WGE) versus enhanced usual care (EUC). WGE participants were provided access to a genetic education website after which they could accept or decline genetic testing or opt for pretest genetic counseling. EUC participants received an informational brochure and a letter informing them of their eligibility for genetic testing and recommending they schedule genetic counseling. The primary outcome was the uptake of genetic testing. RESULTS: Men in the WGE group were more likely to complete genetic counseling and/or genetic testing (43% vs. 12.1%; χ2 [n = 63, df = 1] = 7.77, p = 0.005). WGE participants were also more likely to complete genetic testing compared to men in the EUC group (30% vs. 9.1%; χ2 [n = 63, df = 1] = 4.46, p = 0.03). CONCLUSION: This preliminary trial suggests that a streamlined approach to genetic testing using proactively delivered genetic education may reduce barriers to cascade testing for at-risk men, leading to increased uptake. These results should be interpreted cautiously given the select sample and high rate of non-response.

Evidence-based recommendations for gene-specific ACMG/AMP variant classification from the ClinGen ENIGMA BRCA1 and BRCA2 Variant Curation Expert Panel.

The ENIGMA research consortium develops and applies methods to determine clinical significance of variants in hereditary breast and ovarian cancer genes. An ENIGMA BRCA1/2 classification sub-group, formed in 2015 as a ClinGen external expert panel, evolved into a ClinGen internal Variant Curation Expert Panel (VCEP) to align with Food and Drug Administration recognized processes for ClinVar contributions. The VCEP reviewed American College of Medical Genetics and Genomics/Association of Molecular Pathology (ACMG/AMP) classification criteria for relevance to interpreting BRCA1 and BRCA2 variants. Statistical methods were used to calibrate evidence strength for different data types. Pilot specifications were tested on 40 variants and documentation revised for clarity and ease of use. The original criterion descriptions for 13 evidence codes were considered non-applicable or overlapping with other criteria. Scenario of use was extended or re-purposed for eight codes. Extensive analysis and/or data review informed specification descriptions and weights for all codes. Specifications were applied to pilot variants with pre-existing ClinVar classification as follows: 13 uncertain significance or conflicting, 14 pathogenic and/or likely pathogenic, and 13 benign and/or likely benign. Review resolved classification for 11/13 uncertain significance or conflicting variants and retained or improved confidence in classification for the remaining variants. Alignment of pre-existing ENIGMA research classification processes with ACMG/AMP classification guidelines highlighted several gaps in the research processes and the baseline ACMG/AMP criteria. Calibration of evidence strength was key to justify utility and strength of different data types for gene-specific application. The gene-specific criteria demonstrated value for improving ACMG/AMP-aligned classification of BRCA1 and BRCA2 variants.

Low-dose abiraterone plus Olaparib as a late-line treatment for mCRPC patients without BRCA1/2 mutations: a multicenter retrospective pilot study.

Although overall survival data are still premature, the PROpel study found radiological progression-free survival (PFS) benefits of abiraterone and olaparib in patients with metastatic castration-resistant prostate cancer (mCRPC). However, for patients who have not been genetically tested or lack BRCA1/2 mutations (BRCAm), this combination therapy has been questioned as a first-line conventional treatment for mCRPC, mainly due to significant health economics and side effects. In our retrospective study, we found that treatment with low-dose abiraterone plus olaparib as a late-line treatment for mCRPC could lead to prostate-specific antigen (PSA) and symptom PFS in selective cases even without BRCAm. The median PSA-PFS was 8 months (IQR: 6.5-11.5), with a median follow-up duration of 39.0 months (IQR: 27.5-64.5). Gene tests were conducted in all patients, identifying non-BRCA mutations through ctDNA testing (24%), tumor tissue testing (12%), or both (64%). Adverse events occurred in 72% of patients, with 16% experiencing Grade ≥ 3 events. Common adverse events included anemia (64%), decreased appetite (48%), and fatigue (25%). Our findings support low-dose abiraterone plus olaparib as a potential option for mCRPC patients without BRCAm, offering manageable safety and efficacy profiles.

Histone-methyltransferase KMT2D deficiency impairs the Fanconi anemia/BRCA pathway upon glycolytic inhibition in squamous cell carcinoma.

Histone lysine methyltransferase 2D (KMT2D) is the most frequently mutated epigenetic modifier in head and neck squamous cell carcinoma (HNSCC). However, the role of KMT2D in HNSCC tumorigenesis and whether its mutations confer any therapeutic vulnerabilities remain unknown. Here we show that KMT2D deficiency promotes HNSCC growth through increasing glycolysis. Additionally, KMT2D loss decreases the expression of Fanconi Anemia (FA)/BRCA pathway genes under glycolytic inhibition. Mechanistically, glycolytic inhibition facilitates the occupancy of KMT2D to the promoter/enhancer regions of FA genes. KMT2D loss reprograms the epigenomic landscapes of FA genes by transiting their promoter/enhancer states from active to inactive under glycolytic inhibition. Therefore, combining the glycolysis inhibitor 2-DG with DNA crosslinking agents or poly (ADP-ribose) polymerase (PARP) inhibitors preferentially inhibits tumor growth of KMT2D-deficient mouse HNSCC and patient-derived xenografts (PDXs) harboring KMT2D-inactivating mutations. These findings provide an epigenomic basis for developing targeted therapies for HNSCC patients with KMT2D-inactivating mutations.

Strategies for the prevention or reversal of PARP inhibitor resistance.

INTRODUCTION: Advances in our understanding of tumor biology shed light on hallmarks of cancer development and progression that include dysregulated DNA damage repair (DDR) machinery. Leveraging the underlying tumor genomic instability and tumor-specific defects in DDR, Poly (ADP-ribose) polymerase (PARP) inhibitors (PARPi) induced DNA damage emerges as a novel non-chemotherapy therapeutic opportunity. PARPis are currently approved in multiple tumor types, with the largest benefit seen in tumors with homologous recombination repair (HRR) deficiency, including germline and somatic mutations in BRCA1/2 genes (BRCA) and other pathway members such as PALB2 and Rad51c. AREAS COVERED: This review article summarizes the current approval landscape and known and proposed mechanisms of resistance to PARPi. Further, therapeutic strategies to overcome PARPi resistance are discussed, including ongoing clinical trials. EXPERT OPINION: PARPi have proven to be a safe and effective therapy and represents a cornerstone treatment across multiple solid tumor types. Elucidating innate and acquired mechanisms of resistance, coupled with the emergence of novel therapeutic options to capitalize on the activity of PARPi and prevent or reverse the acquisition of resistance, provides an opportunity to further expand the role of PARPi in cancer therapy.