Reanalysis of BRCA1/2 negative high risk ovarian cancer patients reveals novel germline risk loci and insights into missing heritability

Targeted DNA sequencing of high-grade serous ovarian carcinoma reveals association of TP53 mutations with platinum resistance when combined with gene expression

High-grade serous ovarian carcinoma (HGSC) is the most common subtype of ovarian cancer and is among the most fatal gynecological malignancies worldwide, due to late diagnosis at advanced stages and frequent therapy resistance. In 47 HGSC patients, we assessed somatic and germline genetic variability of a custom panel of 144 known or suspected HGSC-related genes by high-coverage targeted DNA sequencing to identify the genetic determinants associated with resistance to platinum-based therapy. In the germline, the most mutated genes were DNAH14 (17%), RAD51B (17%), CFTR (13%), BRCA1 (11%), and RAD51 (11%). Somatically, the most mutated gene was TP53 (98%), followed by CSMD1/2/3 (19/19/36%), and CFTR (23%). Results were compared with those from whole exome sequencing of a similar set of 35 HGSC patients. Somatic variants in TP53 were also validated using GENIE data of 1287 HGSC samples. Our approach showed increased prevalence of high impact somatic and germline mutations, especially those affecting splice sites of TP53, compared to validation datasets. Furthermore, nonsense TP53 somatic mutations were negatively associated with patient survival. Elevated TP53 transcript levels were associated with platinum resistance and presence of TP53 missense mutations, while decreased TP53 levels were found in tumors carrying mutations with predicted high impact, which was confirmed in The Cancer Genome Atlas data (n = 260). Targeted DNA sequencing of TP53 combined with transcript quantification may contribute to the concept of precision oncology of HGSC. Future studies should explore targeting the p53 pathway based on specific mutation types and co-analyze the expression and mutational profiles of other key cancer genes.

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 to 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.

Case report: A germline CHEK1 c.613 + 2T>C leads to a splicing error in a family with multiple cancer patients

Background

Genome instability plays a crucial role in promoting tumor development. Germline mutations in genes responsible for DNA repair are often associated with familial cancer syndromes. A noticeable exception is the CHEK1 gene. Despite its well-established role in homologous recombination, germline mutations in CHEK1 are rarely reported.

Case presentation

In this report, we present a patient diagnosed with ovarian clear cell carcinoma who has a family history of cancer. Her relatives include a grandfather with esophageal cancer, a father with gastric cancer, and an uncle with a brain tumor. The patient carried a typical genomic profile of clear cell carcinoma including mutations in KRAS, PPP2R1A, and PIK3R1. Importantly, her paired peripheral blood cells harbored a germline CHEK1 mutation, CHEK1 exon 6 c.613 + 2T>C, which was also found in her father. Unfortunately, the CHEK1 status of her grandfather and uncle remains unknown due to the unavailability of their specimens. Further evaluation via RT-PCR confirmed a splicing error in the CHEK1 gene, resulting in truncation at the kinase domain region, indicative of a loss-of-function mutation.

Conclusion

This case highlights a rare germline CHEK1 mutation within a family with a history of cancer. The confirmed splicing error at the mRNA level underscores the functional consequences of this mutation. Documenting such cases is vital for future evaluation of inheritance patterns, clinical penetrance of the mutation, and its association with specific cancer types.

"I don't need any more unknowns hanging over my head": Views of patients with cancer on variants of uncertain significance and low/moderate risk results from genomic sequencing

PURPOSE

We sought to explore patient-reported utility of all types of cancer results from genomic sequencing (GS).

METHODS

Qualitative study, using semi-structured interviews with patients who underwent GS within a trial. Thematic analysis employing constant comparison was used. Two coders coded transcripts, with use of a third coder to resolve conflicts.

RESULTS

25 patients participated: female (22), >50 years (18), European (12), Ashkenazi Jewish (5), Middle Eastern (3), or other ethnicity (5), with breast cancer history (20). Patients' perceptions of the utility of cancer GS results hinged on whether they triggered clinical action. For example, when patients were enrolled into high-risk breast cancer surveillance programs for low/moderate risk breast cancer genes, they perceived the results to be very "useful" and of moderate-high utility. In contrast, patients receiving low/moderate risk or primary variants of uncertain significance results without clinical action perceived results as "concerning," leading to harms, such as hypervigilance about cancer symptoms. Overall, having supportive relatives or providers enhanced perceptions of utility.

CONCLUSION

Patients' perceptions of cancer GS results hinged on whether they triggered clinical management. Consequently, patients who received results without clinical action became hypervigilant, experiencing harms. Our findings call for a need to develop practice interventions to support patients with cancer undergoing GS.

Prevalence of BRCA1 and BRCA2 germline variants in an unselected pancreatic cancer patient cohort in Pakistan

BACKGROUND

BRCA1 and BRCA2 (BRCA1/2) are the most frequently investigated genes among Caucasian pancreatic cancer patients, whereas limited reports are available among Asians. We aimed to investigate the prevalence of BRCA1/2 germline variants in Pakistani pancreatic cancer patients.

METHODS

One hundred and fifty unselected and prospectively enrolled pancreatic cancer patients were comprehensively screened for BRCA1/2 germline variants using denaturing high-performance liquid chromatography and high-resolution melting analyses, followed by DNA sequencing of the variant fragments. The novel variants were analyzed for their pathogenic effect using in-silico tools. Potentially functional variants were further screened in 200 cancer-free controls.

RESULTS

Protein truncating variant was detected in BRCA2 only, with a prevalence of 0.7% (1/150). A frameshift BRCA2 variant (p.Asp946Ilefs*14) was identified in a 71-year-old male patient of Pathan ethnicity, with a family history of abdominal cancer. Additionally, we found a novel variant in BRCA2 (p.Glu2650Gln), two previously reported variants in BRCA1 (p.Thr293Ser) and BRCA2 (p.Ile2296Leu) and a recurrent nonsense variant in BRCA2 (p.Lys3326Ter). These variants were classified as variants of uncertain significance (VUS). It is noteworthy that none of these VUS carriers had a family history of pancreatic or other cancers.

CONCLUSIONS

In this first study, BRCA1/2 pathogenic variant is identified with a low frequency in pancreatic cancer patients from Pakistan. Comprehensive multigene panel testing is recommended in the Pakistani pancreatic cancer patients to enhance genetic understanding in this population.

Partner and localizer of BRCA2 (PALB2) pathogenic variants and ovarian cancer: A systematic review and meta-analysis

OBJECTIVE

Approximately 20% of ovarian cancers are due to an underlying germline pathogenic variant. While pathogenic variants in several genes have been well-established in the development of hereditary ovarian cancer (e.g. BRCA1/2, RAD51C, RAD51D, BRIP1, mismatch repair genes), the role of partner and localizer of BRCA2 (PALB2) remains uncertain. We sought to utilize meta-analysis to evaluate the association between PALB2 germline pathogenic variants and ovarian cancer.

METHODS

We conducted a systematic review and meta-analysis. We searched key electronic databases to identify studies evaluating multigene panel testing in people with ovarian cancer. Eligible trials were subjected to meta-analysis.

RESULTS

Fifty-five studies met inclusion criteria, including 48,194 people with ovarian cancer and information available on germline PALB2 pathogenic variant status. Among people with ovarian cancer and available PALB2 sequencing data, 0.4% [95% CI 0.3-0.4] harbored a germline pathogenic variant in the PALB2 gene. The pooled odds ratio (OR) for carrying a PALB2 pathogenic variant among the ovarian cancer population of 20,474 individuals who underwent germline testing was 2.48 [95% CI 1.57-3.90] relative to 123,883 controls.

CONCLUSIONS

Our meta-analysis demonstrates that the pooled OR for harboring a PALB2 germline pathogenic variant among people with ovarian cancer compared to the general population is 2.48 [95% CI 1.57-3.90]. Prospective studies evaluating the role of germline PALB2 pathogenic variants in the development of ovarian cancer are warranted.

The "extreme phenotype approach" applied to male breast cancer allows the identification of rare variants of ATR as potential breast cancer susceptibility alleles

In oncogenetics, some patients could be considered as "extreme phenotypes", such as those with very early onset presentation or multiple primary malignancies, unusually high numbers of cancers of the same spectrum or rare cancer types in the same parental branch. For these cases, a genetic predisposition is very likely, but classical candidate gene panel analyses often and frustratingly remains negative. In the framework of the EX2TRICAN project, exploring unresolved extreme cancer phenotypes, we applied exome sequencing on rare familial cases with male breast cancer, identifying a novel pathogenic variant of ATR (p.Leu1808*). ATR has already been suspected as being a predisposing gene to breast cancer in women. We next identified 3 additional ATR variants in a cohort of both male and female with early onset and familial breast cancers (c.7762-2A>C; c.2078+1G>A; c.1A>G). Further molecular and cellular investigations showed impacts on transcripts for variants affecting splicing sites and reduction of ATR expression and phosphorylation of the ATR substrate CHEK1. This work further demonstrates the interest of an extended genetic analysis such as exome sequencing to identify very rare variants that can play a role in cancer predisposition in extreme phenotype cancer cases unexplained by classical cancer gene panels testing.

Prevalence of FANCM germline variants in BRCA1/2 negative breast and/or ovarian cancer patients from Pakistan

The Fanconi anemia complementation group M (FANCM) gene is a potential candidate for breast/ovarian cancer susceptibility in European populations. Here, we examined the contribution of FANCM germline variants to hereditary breast and/or ovarian cancer in Pakistan. Comprehensive FANCM variant screening was performed in 201 BRCA1 and BRCA2 (BRCA1/2) negative Pakistani patients with and without triple-negative breast cancer (TNBC) and/or ovarian cancer, using denaturing high-performance liquid chromatography analysis (DHPLC) followed by DNA sequencing. Novel variants were tested for their potential effect on protein function using in silico tools. Reverse transcription (RT)-PCR analysis of RNA extracted from one deletion/insertion (delins) variant (p.K1780delinsNGIT) carrier and three non-carriers was performed to evaluate the impact of this variant on splicing. Furthermore, potentially functional variants were evaluated in 200 healthy female controls. A missense variant (p.V1857M) was identified in a 50-year-old TNBC patient with a family history of breast cancer. It was also identified in the index patient´s daughter, who was diagnosed with osteosarcoma at 15 years of age. Further, one delins variant (p.K1780delinsNGIT) was identified in a 45-year-old non-TNBC patient, but not detected in her brother, who was diagnosed with Hodgkin's lymphoma at 38 years of age. Based on in silico and RNA analyses, p.V1857M and p.K1780delinsNGIT were predicted as variants of uncertain significance (VUS), respectively. Both variants were absent in 200 healthy controls. Our findings suggest a marginal contribution of FANCM variants to hereditary breast/ovarian cancer in Pakistan, which need to be confirmed in larger studies.

Homologous Recombination Deficiency in Ovarian, Breast, Colorectal, Pancreatic, Non-Small Cell Lung and Prostate Cancers, and the Mechanisms of Resistance to PARP Inhibitors

Homologous recombination (HR) is a highly conserved DNA repair mechanism that protects cells from exogenous and endogenous DNA damage. Breast cancer 1 (BRCA1) and breast cancer 2 (BRCA2) play an important role in the HR repair pathway by interacting with other DNA repair proteins such as Fanconi anemia (FA) proteins, ATM, RAD51, PALB2, MRE11A, RAD50, and NBN. These pathways are frequently aberrant in cancer, leading to the accumulation of DNA damage and genomic instability known as homologous recombination deficiency (HRD). HRD can be caused by chromosomal and subchromosomal aberrations, as well as by epigenetic inactivation of tumor suppressor gene promoters. Deficiency in one or more HR genes increases the risk of many malignancies. Another conserved mechanism involved in the repair of DNA single-strand breaks (SSBs) is base excision repair, in which poly (ADP-ribose) polymerase (PARP) enzymes play an important role. PARP inhibitors (PARPIs) convert SSBs to more cytotoxic double-strand breaks, which are repaired in HR-proficient cells, but remain unrepaired in HRD. The blockade of both HR and base excision repair pathways is the basis of PARPI therapy. The use of PARPIs can be expanded to sporadic cancers displaying the “BRCAness” phenotype. Although PARPIs are effective in many cancers, their efficacy is limited by the development of resistance. In this review, we summarize the prevalence of HRD due to mutation, loss of heterozygosity, and promoter hypermethylation of 35 DNA repair genes in ovarian, breast, colorectal, pancreatic, non-small cell lung cancer, and prostate cancer. The underlying mechanisms and strategies to overcome PARPI resistance are also discussed.

PMS2 variant results in loss of ATPase activity without compromising mismatch repair

Hereditary cancer syndromes account for approximately 5%-10% of all diagnosed cancer cases. Lynch syndrome (LS) is an autosomal dominant hereditary cancer condition that predisposes individuals to an elevated lifetime risk for developing colorectal, endometrial, and other cancers. LS results from a pathogenic mutation in one of four mismatch repair (MMR) genes (MSH2, MSH6, MLH1, and PMS2). The diagnosis of LS is often challenged by the identification of missense mutations, termed variants of uncertain significance, whose functional effect on the protein is not known. Of the eight PMS2 variants initially selected for this study, we identified a variant within the N-terminal domain where asparagine 335 is mutated to serine, p.Asn335Ser, which lacked ATPase activity, yet appears to be proficient in MMR. To expand our understanding of this functional dichotomy, we performed biophysical and structural studies, and noted that p.Asn335Ser binds to ATP but is unable to hydrolyze it to ADP. To examine the impact of p.Asn335Ser on MMR, we developed a novel in-cell fluorescent-based microsatellite instability reporter that revealed p.Asn335Ser maintained genomic stability. We conclude that in the absence of gross structural changes, PMS2 ATP hydrolysis is not necessary for proficient MMR and that the ATPase deficient p.Asn335Ser variant is likely benign.

Massive parallel sequencing in individuals with multiple primary tumours reveals the benefit of re-analysis

Multiple primary cancers, defined as three or more primary tumours, are rare, and there are few genetic studies concerning them. There is a need for increased knowledge on the heritability of multiple primary cancers and genotype-phenotype correlations. We have performed whole-genome/exome sequencing (WGS/WES) in ten individuals with three or more primary tumours, with no previous findings on standard clinical genetic investigations. In one individual with a clinical diagnosis of MEN1, a likely pathogenic cryptic splice site variant was detected in the MEN1 gene. The variant (c.654C > A) is synonymous but we showed in a cDNA analysis that it affects splicing and leads to a frameshift, with the theoretical new amino acid sequence p.(Gly219Glufs*13). In one individual with metachronous colorectal cancers, ovarian cancer, endometrial cancer and chronic lymphocytic leukaemia, we found a likely pathogenic variant in the MLH1 gene (c.27G > A), and two risk factor variants in the genes CHEK2 and HOXB13. The MLH1 variant is synonymous but has previously been shown to be associated to constitutional low-grade hypermethylation of the MLH1 promoter, and segregates with disease in families with colorectal and endometrial cancer. No pathogenic single nucleotide or structural variants were detected in the remaining eight individuals in the study. The pathogenic variants found by WGS/WES were in genes already sequenced by Sanger sequencing and WES in the clinic, without any findings. We conclude that, in individuals with an unequivocal clinical diagnosis of a specific hereditary cancer syndrome, where standard clinical testing failed to detect a causative variant, re-analysis may lead to a diagnosis.

Germline mutations in apoptosis pathway genes in ovarian cancer; the functional role of a TP53I3 (PIG3) variant in ROS production and DNA repair

Approximately 25% of all cases of ovarian cancer (OVCA) cases are associated with inherited risk. However, accurate risk assessment is limited by the presence of variants of unknown significance (VUS). Previously, we performed whole-exome sequencing on 48 OVCA patients with familial predisposition, yet negative for pathogenic BRCA1/2 mutations. In our cohort, we uncovered thirteen truncating mutations in genes associated with apoptosis (~35% of our patient cohort). The TP53I3 p.S252X premature stop gain was identified in two unrelated patients. TP53I3 is transcriptionally activated by p53 and believed to play a role in DNA damage response and reactive oxygen species-induced apoptosis. In addition, nonsense variants in apoptosis-related genes TP53AIP1, BCLAF1, and PIK3C2G were identified in our cohort; highlighting the potential relevance of genes involved in apoptotic processes to hereditary cancer. In the current study, we employed functional assays and demonstrated that cells expressing TP53I3 p.S252X displayed decreased homologous recombination repair efficiency and increased sensitivity to chemotherapeutic drugs bleomycin, mitomycin c, and etoposide. In addition, in the presence of oxidative stress from hydrogen peroxide or etoposide we observed a reduction in the formation of reactive oxygen species, an important precursor to apoptosis with this variant. Our findings suggest that the combination of in silico and wet laboratory approaches can better evaluate VUSs, establish novel germline predisposition genetic loci, and improve individual cancer risk estimates.

Application of Multilayer Evidence for Annotation of C-Terminal BRCA2 Variants

Simple Summary

The potential pathogenic role of germline BRCA2 c.9976A>T and c.10095delinsGAATTATATCT was evaluated in hereditary breast and ovarian cancer (HBOC) patients by investigating 2491 probands and verified in an independent cohort of 122,209 patients. Although the c.10095delinsGAATTATATCT variant was more prevalent among patients compared to control populations, no increased risk for cancer was found. No association between c.9976A>T and clinicopathological parameters or elevated risk for HBOC cases was detected. However, lung cancer was more prevalent in families carrying c.9976A>T compared to pathogenic BRCA1/BRCA2 carrier families. An increased frequency of pancreatic cancer was found in families where c.9976A>T occurred together with other pathogenic BRCA1 variants. The C-terminal stop codon variants showed no association with other pathogenic BRCA2 variants. No loss of heterozygosity (LOH) in tumor tissue and no allelic imbalance in RNA level were confirmed. The c.9976A>T variant may be considered as a potential risk for lung cancer, and a potential modifying factor in pancreatic cancer when it occurs along with the pathogenic BRCA1 variant, although this observation should be validated in a larger sample cohort.

Abstract

The clinical relevance of the BRCA2 C-terminal stop codon variants is controversial. The pathogenic role of the germline BRCA2 c.9976A>T and c.10095delinsGAATTATATCT variants in hereditary breast and ovarian cancer (HBOC) patients was evaluated. An association with clinicopathological parameters was performed in 2491 independent probands diagnosed with HBOC and in 122,209 cancer patients reported earlier. Loss-of-heterozygosity (LOH) in tumor samples and allelic imbalance in RNA extracted from peripheral blood cells were investigated. Neither c.10095delinsGAATTATATCT or c.9976A>T variants showed significant association with clinicopathological parameters or elevated risk for HBOC-associated tumors. Lung cancer was more prevalent in families carrying the c.9976A>T variant compared to pathogenic BRCA1 or BRCA2 carrier families. An increased prevalence of pancreatic cancer was found in families where c.9976A>T occurred together with other pathogenic BRCA1 variants. An increased risk for familial pancreatic, lung and upper aero-digestive tract cancers was confirmed in the validation set. Regarding BRCA2 C-terminal variants, no linkage with other pathogenic BRCA2 variants, no LOH in tumor tissue and no allelic imbalance in RNA level were confirmed. The c.9976A>T variant may be considered as a potential risk for lung cancer, and a potential modifying factor in pancreatic cancer when it occurs along with the pathogenic BRCA1 variant, although this observation should be validated in a larger sample cohort.

K3326X and Other C-Terminal BRCA2 Variants Implicated in Hereditary Cancer Syndromes: A Review

Simple Summary

The cancer associated protein BRCA2 is the subject of intense continual study. Because of this, new insights into the relation of specific variants of this gene and cancer are regularly generated. These discoveries shed light on cancer risk and management for patients carrying these mutations. Additionally, new techniques for variant discovery and investigation are developed and tested, further enhancing scientific and clinical understanding of this key protein. In this review we will investigate the recent literature associated with variants in the C-terminus of BRCA2 and their effect on health and cancer predisposition.

Abstract

Whole genome analysis and the search for mutations in germline and tumor DNAs is becoming a major tool in the evaluation of risk as well as the management of hereditary cancer syndromes. Because of the identification of cancer predisposition gene panels, thousands of such variants have been catalogued yet many remain unclassified, presenting a clinical challenge for the management of hereditary cancer syndromes. Although algorithms exist to estimate the likelihood of a variant being deleterious, these tools are rarely used for clinical decision-making. Here, we review the progress in classifying K3326X, a rare truncating variant on the C-terminus of BRCA2 and review recent literature on other novel single nucleotide polymorphisms, SNPs, on the C-terminus of the protein, defined in this review as the portion after the final BRC repeat (amino acids 2058–3418).

10H-3,6-Diazaphenothiazines triggered the mitochondrial-dependent and cell death receptor-dependent apoptosis pathways and further increased the chemosensitivity of MCF-7 breast cancer cells via inhibition of AKT1 pathways

Breast cancer is one of the leading causes of death in cancer categories, followed by lung, colorectal, and ovarian among the female gender across the world. 10H-3,6-diazaphenothiazine (PTZ) is a thiazine derivative compound that exhibits many pharmacological activities. Herein, we proceed to investigate the pharmacological activities of PTZ toward breast cancer MCF-7 cells as a representative in vitro breast cancer cell model. The PTZ exhibited a proliferation inhibition (IC50  = 0.895 µM) toward MCF-7 cells. Further, cell cycle analysis illustrated that the S-phase checkpoint was activated to achieve proliferation inhibition. In vitro cytotoxicity test on three normal cell lines (HEK293 normal kidney cells, MCF-10A normal breast cells, and H9C2 normal heart cells) demonstrated that PTZ was more potent toward cancer cells. Increase in the levels of reactive oxygen species results in polarization of mitochondrial membrane potential (ΔΨm), together with suppression of mitochondrial thioredoxin reductase enzymatic activity suggested that PTZ induced oxidative damages toward mitochondria and contributed to improved drug efficacy toward treatment. The RT2 PCR Profiler Array (human apoptosis pathways) proved that PTZ induced cell death via mitochondria-dependent and cell death receptor-dependent pathways, through a series of modulation of caspases, and the respective morphology of apoptosis was observed. Mechanistic studies of apoptosis suggested that PTZ inhibited AKT1 pathways resulting in enhanced drug efficacy despite it preventing invasion of cancer cells. These results showed the effectiveness of PTZ in initiation of apoptosis, programmed cell death, toward highly chemoresistant MCF-7 cells, thus suggesting its potential as a chemotherapeutic drug.

Summary of BARD1 Mutations and Precise Estimation of Breast and Ovarian Cancer Risks Associated with the Mutations

Over the last two decades, numerous BARD1 mutations/pathogenic variants (PVs) have been found in patients with breast cancer (BC) and ovarian cancer (OC). However, their role in BC and OC susceptibility remains controversial, and strong evidence-based guidelines for carriers are not yet available. Herein, we present a comprehensive catalog of BARD1 PVs identified in large cumulative cohorts of ~48,700 BC and ~20,800 OC cases (retrieved from 123 studies examining the whole coding sequence of BARD1). Using these resources, we compared the frequency of BARD1 PVs in the cases and ~134,100 controls from the gnomAD database and estimated the effect of the BARD1 PVs on BC and OC risks. The analysis revealed that BARD1 is a BC moderate-risk gene (odds ratio (OR) = 2.90, 95% CIs:2.25–3.75, p < 0.0001) but not an OC risk gene (OR = 1.36, 95% CIs:0.87–2.11, p = 0.1733). In addition, the BARD1 mutational spectrum outlined in this study allowed us to determine recurrent PVs and evaluate the variant-specific risk for the most frequent PVs. In conclusion, these precise estimates improve the understanding of the role of BARD1 PVs in BC and OC predisposition and support the need for BARD1 diagnostic testing in BC patients.

A Systematic Literature Review of Whole Exome and Genome Sequencing Population Studies of Genetic Susceptibility to Cancer

The application of next-generation sequencing (NGS) technologies in cancer research has accelerated the discovery of somatic mutations; however, progress in the identification of germline variation associated with cancer risk is less clear. We conducted a systematic literature review of cancer genetic susceptibility studies that used NGS technologies at an exome/genome-wide scale to obtain a fuller understanding of the research landscape to date and to inform future studies. The variability across studies on methodologies and reporting was considerable. Most studies sequenced few high-risk (mainly European) families, used a candidate analysis approach, and identified potential cancer-related germline variants or genes in a small fraction of the sequenced cancer cases. This review highlights the importance of establishing consensus on standards for the application and reporting of variants filtering strategies. It also describes the progress in the identification of cancer-related germline variation to date. These findings point to the untapped potential in conducting studies with appropriately sized and racially diverse families and populations, combining results across studies and expanding beyond a candidate analysis approach to advance the discovery of genetic variation that accounts for the unexplained cancer heritability.

BRIP1, RAD51C, and RAD51D mutations are associated with high susceptibility to ovarian cancer: mutation prevalence and precise risk estimates based on a pooled analysis of ~30,000 cases

Background

It is estimated that more than 20% of ovarian cancer cases are associated with a genetic predisposition that is only partially explained by germline mutations in the BRCA1 and BRCA2 genes. Recently, several pieces of evidence showed that mutations in three genes involved in the homologous recombination DNA repair pathway, i.e., BRIP1, RAD51C, and RAD51D, are associated with a high risk of ovarian cancer. To more precisely estimate the ovarian cancer risk attributed to BRIP1, RAD51C, and RAD51D mutations, we performed a meta-analysis based on a comparison of a total of ~ 29,400 ovarian cancer patients from 63 studies and a total of ~ 116,000 controls from the gnomAD database.

Results

The analysis allowed precise estimation of ovarian cancer risks attributed to mutations in BRIP1, RAD51C, and RAD51D, confirming that all three genes are ovarian cancer high-risk genes (odds ratio (OR) = 4.94, 95%CIs:4.07–6.00, p < 0.0001; OR = 5.59, 95%CIs:4.42–7.07, p < 0.0001; and OR = 6.94, 95%CIs:5.10–9.44, p < 0.0001, respectively). In the present report, we show, for the first time, a mutation-specific risk analysis associated with distinct, recurrent, mutations in the genes.

Conclusions

The meta-analysis provides evidence supporting the pathogenicity of BRIP1, RAD51C, and RAD51D mutations in relation to ovarian cancer. The level of ovarian cancer risk conferred by these mutations is relatively high, indicating that after BRCA1 and BRCA2, the BRIP1, RAD51C, and RAD51D genes are the most important ovarian cancer risk genes, cumulatively contributing to ~ 2% of ovarian cancer cases. The inclusion of the genes into routine diagnostic tests may influence both the prevention and the potential treatment of ovarian cancer.

Exome sequencing of familial high-grade serous ovarian carcinoma reveals heterogeneity for rare candidate susceptibility genes

High-grade serous ovarian carcinoma (HGSOC) has a significant hereditary component, approximately half of which cannot be explained by known genes. To discover genes, we analyse germline exome sequencing data from 516 BRCA1/2-negative women with HGSOC, focusing on genes enriched with rare, protein-coding loss-of-function (LoF) variants. Overall, there is a significant enrichment of rare protein-coding LoF variants in the cases (p < 0.0001, chi-squared test). Only thirty-four (6.6%) have a pathogenic variant in a known or proposed predisposition gene. Few genes have LoF mutations in more than four individuals and the majority are detected in one individual only. Forty-three highly-ranked genes are identified with three or more LoF variants that are enriched by three-fold or more compared to GnomAD. These genes represent diverse functional pathways with relatively few involved in DNA repair, suggesting that much of the remaining heritability is explained by previously under-explored genes and pathways.

The ectopic expression of meiCT genes promotes meiomitosis and may facilitate carcinogenesis

Cancer meiomitosis is defined as the concurrent activation of both mitotic and meiotic machineries in neoplastic cells that confer a selective advantage together with increased genomic instability. MeiCT (meiosis-specific cancer/testis) genes that perform specialized functions in the germline events required for the first meiotic division are ectopically expressed in several cancers. Here we describe the expression profiles of meiCT genes and proteins across a number of cancers and review the proposed mechanisms that increase aneuploidy and elicit reduction division in polyploid cells. These mechanisms are centered on the overexpression and function of meiCT proteins in cancers under various conditions that includes a response to genotoxic stress. Since meiCT genes are transcriptionally repressed in somatic cells, their target offers a promising therapeutic approach with limited toxicity to healthy tissues. Throughout the review, we provide a detailed description of the roles for each gene in the context of meiosis and we discuss proposed functions and outcomes resulting from their ectopic reactivation in cancer.

Inhibitors of the Fanconi anaemia pathway as potential antitumour agents for ovarian cancer

The Fanconi anaemia (FA) pathway is an important mechanism for cellular DNA damage repair, which functions to remove toxic DNA interstrand crosslinks. This is particularly relevant in the context of ovarian and other cancers which rely extensively on interstrand cross-link generating platinum chemotherapy as standard of care treatment. These cancers often respond well to initial treatment, but reoccur with resistant disease and upregulation of DNA damage repair pathways. The FA pathway is therefore of great interest as a target for therapies that aim to improve the efficacy of platinum chemotherapies, and reverse tumour resistance to these. In this review, we discuss recent advances in understanding the mechanism of interstrand cross-link repair by the FA pathway, and the potential of the component parts as targets for therapeutic agents. We then focus on the current state of play of inhibitor development, covering both the characterisation of broad spectrum inhibitors and high throughput screening approaches to identify novel small molecule inhibitors. We also consider synthetic lethality between the FA pathway and other DNA damage repair pathways as a therapeutic approach.

Effect of BRCA1 missense variants on gene reversion in DNA double-strand break repair mutants and cell cycle-arrested cells of Saccharomyces cerevisiae

Evaluation of the functional impact of germline BRCA1 variants that are likely to be associated to breast and ovarian cancer could help to investigate the mechanism of BRCA1 tumorigenesis. Expression of pathogenic BRCA1 missense variants increased homologous recombination (HR) and gene reversion (GR) in yeast. We thought to exploit yeast genetics to shed light on BRCA1-induced genome instability and tumorigenesis. We determined the effect on GR of several neutral and pathogenic BRCA1 variants in the yeast strain RSY6wt and its isogenic DSB repair mutants, such as mre11∆, rad50∆ and rad51∆. In the RSY6wt, four out of five pathogenic and two out of six neutral variants significantly increased GR; rad51∆ strain, the pathogenic variants C61G and A1708E induced a weak but significant increase in GR. On the other hand, in rad50∆ mutant expressing the pathogenic variants localised at the BRCT domain, a further GR increase was seen. The neutral variant N132K and the VUS A1789T induced a weak GR increase in mre11∆ mutant. Thus, BRCA1 missense variants require specific genetic functions and presumably induced GR by different mechanisms. As DNA repair is regulated by cell cycle, we determined the effect on GR of BRCA1 variants in cell cycle-arrested RSYwt cells. GR is highly BRCA1-inducible in S-phase-arrested cells as compared to G1 or G2. Sequence analysis of genomic DNA from ILV1 revertant clones showed that BRCA1-induced ilv1-92 reversion by base substitution when GR is at least 6-fold over the control. Our study demonstrated that BRCA1 may interfere with yeast DNA repair functions that are active in S-phase causing high level of GR. In addition, we confirmed here that yeast could be a reliable model to investigate the mechanism and genetic requirements of BRCA1-induced genome instability. Finally, developing yeast-based assays to characterise BRCA1 missense variants could be useful to design more precise therapies.

The Identification and Analysis of mRNA-lncRNA-miRNA Cliques From the Integrative Network of Ovarian Cancer

Ovarian cancer is one of the leading causes of cancer mortality in women. Since little clinical symptoms were shown in the early period of ovarian cancer, most patients were found in phases III-IV or with abdominal metastasis when diagnosed. The lack of effective early diagnosis biomarkers makes ovarian cancer difficult to screen. However, in essence, the fundamental problem is we know very little about the regulatory mechanisms during tumorigenesis of ovarian cancer. There are emerging regulatory factors, such as long noncoding RNAs (lncRNAs) and microRNAs (miRNAs), which have played important roles in cancers. Therefore, we analyzed the RNA-seq profiles of 407 ovarian cancer patients. An integrative network of 20,424 coding RNAs (mRNAs), 10,412 lncRNAs, and 742 miRNAs were construed with variance inflation factor (VIF) regression method. The mRNA-lncRNA-miRNA cliques were identified from the network and analyzed. Such promising cliques showed significant correlations with survival and stage of ovarian cancer and characterized the complex sponge regulatory mechanism, suggesting their contributions to tumorigenicity. Our results provided novel insights of the regulatory mechanisms among mRNAs, lncRNAs, and miRNAs and highlighted several promising regulators for ovarian cancer detection and treatment.

The identification of pathogenic variants in BRCA1/2 negative, high risk, hereditary breast and/or ovarian cancer patients: High frequency of FANCM pathogenic variants

NGS-based multiple gene panel resequencing in combination with a high resolution CGH-array was used to identify genetic risk factors for hereditary breast and/or ovarian cancer in 237 high risk patients who were previously tested negative for pathogenic BRCA1/2 variants. All patients were screened for pathogenic variants in 94 different cancer predisposing genes. We identified 32 pathogenic variants in 14 different genes (ATM, BLM, BRCA1, CDH1, CHEK2, FANCG, FANCM, FH, HRAS, PALB2, PMS2, PTEN, RAD51C and NBN) in 30 patients (12.7%). Two pathogenic BRCA1 variants that were previously undetected due to less comprehensive and sensitive methods were found. Five pathogenic variants are novel, three of which occur in genes yet unrelated to hereditary breast and/or ovarian cancer (FANCG, FH and HRAS). In our cohort we discovered a remarkably high frequency of truncating variants in FANCM (2.1%), which has recently been suggested as a susceptibility gene for hereditary breast cancer. Two patients of our cohort carried two different pathogenic variants each and 10 other patients in whom a pathogenic variant was confirmed also harbored a variant of unknown significance in a breast and ovarian cancer susceptibility gene. We were able to identify pathogenic variants predisposing for tumor formation in 12.3% of BRCA1/2 negative breast and/or ovarian cancer patients.

FANCM, RAD1, CHEK1 and TP53I3 act as BRCA-like tumor suppressors and are mutated in hereditary ovarian cancer

Although 25% of ovarian cancer cases are due to inherited factors, most of the genetic risk remains unexplained. We previously identified candidate genes through germline whole exome sequencing of BRCA1/BRCA2 negative ovarian cancer patients with familial risk. Here, we performed functional assessment to determine whether they act as BRCA-like tumor suppressors. Seven candidate risk genes were targeted by siRNA for mRNA depletion followed by functional assays for clonogenic survival, cytotoxicity to DNA damaging agents, and involvement in homologous recombination repair. BRCA1 and BRCA1 were targeted as standards for loss of function outcome. Knockdown of various candidate genes led to tumor suppressor phenotypes also observed in BRCA1/BRCA2 deficient cells. Deficiency of CHEK1, FANCM and TP53I3 led to reduced homologous recombination repair efficiency. Knockdown of RAD1, CHEK1 or FANCM led to a decrease in cellular viability and cells deficient in CHEK1, RAD1 or TP53I3 displayed increased sensitivity to cisplatin. Functional studies of candidate genes identified by whole exome sequencing complements bioinformatics techniques and aid the implication of novel risk loci. The results of this study suggest that genes found mutated in hereditary ovarian cancer, FANCM, RAD1, CHEK1 and TP53I3, act as BRCA-like tumor suppressors.

Utilizing iVariantGuide for Variant Assessment of Next-Generation Sequencing

Molecular genetic testing provides the capability for personalized prediction, diagnosis, and pharmacological treatments of disease and disorders. Variant assessment of next-generation sequencing (NGS) is a crucial component of genetic testing for clinicians to counsel patients on risk and management. The iVariantGuide application is a dynamic Web-based application made for the tertiary analysis of NGS. Along with variant assessment, iVariantGuide provides a unique interactive pathway impact analysis of genetic variants, as well as a unique Gene Ontology (GO) analysis. Here we provide a step-by-step guide on how to utilize iVariantGuide, employing a publicly available NGS dataset consisting of a cohort of germline DNAs from high-risk serous ovarian cancer (OVCA) patients. The application will be used to exhibit the ease in filtering down to a set of compelling novel variants and their impact on biological pathways and GO terms. © 2019 by John Wiley & Sons, Inc.

Guidelines for reporting secondary findings of genome sequencing in cancer genes: the SFMPP recommendations

In oncology, the expanding use of multi-gene panels to explore familial cancer predisposition and tumor genome analysis has led to increased secondary findings discoveries (SFs) and has given rise to important medical, ethical, and legal issues. The American College of Medical Genetics and Genomics published a policy statement for managing SFs for a list of genes, including 25 cancer-related genes. Currently, there are few recommendations in Europe. From June 2016 to May 2017, the French Society of Predictive and Personalized Medicine (SFMPP) established a working group of 47 experts to elaborate guidelines for managing information given on the SFs for genes related to cancers. A subgroup of ethicists, lawyers, patients' representatives, and psychologists provided ethical reflection, information guidelines, and materials (written consent form and video). A subgroup with medical expertise, including oncologists and clinical and molecular geneticists, provided independent evaluation and classification of 60 genes. The main criteria were the "actionability" of the genes (available screening or prevention strategies), the risk evaluation (severity, penetrance, and age of disease onset), and the level of evidence from published data. Genes were divided into three classes: for class 1 genes (n = 36), delivering the information on SFs was recommended; for class 2 genes (n = 5), delivering the information remained questionable because of insufficient data from the literature and/or level of evidence; and for class 3 genes (n = 19), delivering the information on SFs was not recommended. These guidelines for managing SFs for cancer-predisposing genes provide new insights for clinicians and laboratories to standardize clinical practices.

Family specific genetic predisposition to breast cancer: results from Tunisian whole exome sequenced breast cancer cases

BACKGROUND

A family history of breast cancer has long been thought to indicate the presence of inherited genetic events that predispose to this disease. In North Africa, many specific epidemio-genetic characteristics have been observed in breast cancer families when compared to Western populations. Despite these specificities, the majority of breast cancer genetics studies performed in North Africa remain restricted to the investigation of the BRCA1 and BRCA2 genes. Thus, comprehensive data at a whole exome or whole genome level from local patients are lacking.

METHODS

A whole exome sequencing (WES) of seven breast cancer Tunisian families have been performed using a family-based approach. We focused our analysis on BC-TN-F001 family that included two affected members that have been sequenced using WES. Relevant variants identified in BC-TN-F001 have been confirmed using Sanger sequencing. Then, we conducted an integrative analysis by combining our results with those from other WES studies in order to figure out the genetic transmission model of the newly identified genes. Biological network construction and protein-protein interactions analyses have been performed to decipher the molecular mechanisms likely accounting for the role of these genes in breast cancer risk.

RESULTS

Sequencing, filtering strategies, and validation analysis have been achieved. For BC-TN-F001, no deleterious mutations have been identified on known breast cancer genes. However, 373 heterozygous, exonic and rare variants have been identified on other candidate genes. After applying several filters, 12 relevant high-risk variants have been selected. Our results showed that these variants seem to be inherited in a family specific model. This hypothesis has been confirmed following a thorough analysis of the reported WES studies. Enriched biological process and protein-protein interaction networks resulted in the identification of four novel breast cancer candidate genes namely MMS19, DNAH3, POLK and KATB6.

CONCLUSIONS

In this first WES application on Tunisian breast cancer patients, we highlighted the impact of next generation sequencing technologies in the identification of novel breast cancer candidate genes which may bring new insights into the biological mechanisms of breast carcinogenesis. Our findings showed that the breast cancer predisposition in non-BRCA families may be ethnic and/or family specific.

Mutational analysis of candidate genes in Israeli male breast cancer cases

PURPOSE

To define the mutational spectrum of several candidate gene mutations in Israeli male breast cancer cases.

METHODS

MBC cases counselled at the Oncogenetics unit, Sheba Medical Center from January 1998 to June 2017 were included. Relevant clinical and oncological data and cancer phenotype were retrieved. All participants were genotyped for the predominant Jewish BRCA1 and BRCA2 germline mutations using a chip-based assay. Those who tested negative were further genotyped for three recurring mutations in CHEK2 (c.1100delC, p.S428F, p.I157T), and single mutations in the FANCM (c.5791C>T), and RAD51D (c.556C>T) genes, by direct sequencing. The ethics committee approved the study.

RESULTS

Overall, 61 MBC were identified and genotyped, 41 (67.2%) were Ashkenazim, age at diagnosis was 58.1 ± 12.6 years, and 31 (50.8%) had a family history of cancer. Of genotyped individuals, one (1.6%) harboured the 185delAG* BRCA1 mutation, 7 (11.4%) the 6174delT*BRCA2 mutation and 2 (3.2%) other recurring mutations in BRCA2 (overall 10/61-16.4% BRCA1/BRCA2 mutation carriers). Of BRCA-negative cases, 3/51 (5.9%) carried the p.S428F *CHEK2 mutation. None was a carrier of the other genotyped mutations in CHEK2, FANCM or RAD51D.

CONCLUSION

BRCA1, BRCA2 and CHEK2 germline mutations contribute to inherited predisposition to MBC in Israel.

Double Heterozygosity for BRCA1 Pathogenic Variant and BRCA2 Polymorphic Stop Codon K3326X: A Case Report in a Southern Italian Family

Here, we describe a patient with bilateral breast cancer and melanoma, and with a concomitant double variant, namely p.Gln563Ter in BRCA1 and p.Lys3326Ter in BRCA2. The BRCA2 p.Lys3326Ter (K3326X) (rs11571833) mutation identified in our patient is a debated substitution of thymidine for adenine which is currently regarded as benign polymorphism in main gene databases. Recent studies, however, describe this variant as associated with breast and ovarian tumors. Based on the observation of the cancer’s earliest age of onset in this subject, our purpose was to reevaluate this variant according to recent papers indicating a role of powerful modifier of the genetic penetrance. Genetic testing was performed in all consenting patient’s relatives, and in the collection of the clinical data particular attention was paid to the age of onset of the neoplasia. Following our observation that the our patient with double heterozygosis had an early age of onset for cancer similar to a few rare cases of double mutation for BRCA1 and BRCA2, we also performed an extensive review of the literature relative to patients carrying a double heterozygosity for both genes. In line with previous studies relative to the rare double heterozygosity in both BRCA1/2 genes, we found the earlier onset of breast cancer in our patient with both BRCA1/2 mutations with respect to other relatives carrying the single BRCA1 mutation. The presence of the second K3326X variant in our case induces a phenotype characterized by early onset of the neoplasia in a manner similar to the other cases of double heterozygosity previously described. Therefore, we suggest that during the genetic counseling, it should be recommendable to evaluate the presence of the K3326X variant in association with other pathogenic mutations.

Rethinking ovarian cancer genomics: where genome-wide association studies stand?

Genome-wide association studies (GWAS) allow the finding of genetic variants associated with several traits. Regarding ovarian cancer (OC), 15 GWAS have been conducted since 2009, with the discovery of 49 SNPs associated with disease susceptibility and 46 with impact in the clinical outcome of patients (p < 5.00 × 10-2). Among them, 14 variants reached the genome-wide significance (p < 5.00 × 10−8). Despite the results obtained, they should be validated in independent sets. So far, five validation studies have been conducted which could confirm the association of 12 OC susceptibility SNPs. Consequently, post-GWAS studies are crucial unravel the biological plausibility of GWAS’ findings and the allelic spectrum of OC.