Familial Ovarian Cancer Cases Research Articles

Genetic analyses of DNA repair pathway associated genes implicate new candidate cancer predisposing genes in ancestrally defined ovarian cancer cases.

Not all familial ovarian cancer (OC) cases are explained by pathogenic germline variants in known risk genes. A candidate gene approach involving DNA repair pathway genes was applied to identify rare recurring pathogenic variants in familial OC cases not associated with known OC risk genes from a population exhibiting genetic drift. Whole exome sequencing (WES) data of 15 OC cases from 13 families tested negative for pathogenic variants in known OC risk genes were investigated for candidate variants in 468 DNA repair pathway genes. Filtering and prioritization criteria were applied to WES data to select top candidates for further analyses. Candidates were genotyped in ancestry defined study groups of 214 familial and 998 sporadic OC or breast cancer (BC) cases and 1025 population-matched controls and screened for additional carriers in 605 population-matched OC cases. The candidate genes were also analyzed in WES data from 937 familial or sporadic OC cases of diverse ancestries. Top candidate variants in ERCC5, EXO1, FANCC, NEIL1 and NTHL1 were identified in 5/13 (39%) OC families. Collectively, candidate variants were identified in 7/435 (1.6%) sporadic OC cases and 1/566 (0.2%) sporadic BC cases versus 1/1025 (0.1%) controls. Additional carriers were identified in 6/605 (0.9%) OC cases. Tumour DNA from ERCC5, NEIL1 and NTHL1 variant carriers exhibited loss of the wild-type allele. Carriers of various candidate variants in these genes were identified in 31/937 (3.3%) OC cases of diverse ancestries versus 0-0.004% in cancer-free controls. The strategy of applying a candidate gene approach in a population exhibiting genetic drift identified new candidate OC predisposition variants in DNA repair pathway genes.

Abstract 2056: The genomic landscape of carriers of rare variants in FANCI, a new candidate ovarian cancer predisposing gene

Abstract The potentially pathogenic variant (PPV), FANCI c.1813C>T; p.L605F, in a new candidate ovarian cancer (OC) predisposing gene was discovered by whole exome sequencing (WES) of familial OC cases from the founder French Canadian (FC) population for discovering new OC predisposing genes. Modeling this variant in cellulo suggested this variant encodes an unstable protein. FANCI is an essential member upstream of the homologous recombination DNA repair pathway and intersects BRCA1 and BRCA2 function, proteins encoded by genes involved in hereditary OC. Investigating the FC founder population facilitates the discovery of PPVs as they are more likely to harbor recurrent variants due to common ancestors, increasing the likelihood of identifying candidate genes in cancer families. To further support the candidacy of FANCI as a new OC predisposing gene, we investigated the germline landscape of c.1813C>T carrier FC OC cases for co-occurring PPVs in known or proposed new (emerging) OC predisposing genes or other genes involved in similar pathways (DNA repair). Using WES of peripheral blood lymphocyte DNA, the genomic landscape of 10 FANCI carriers were investigated for heterozygous PPVs in 276 DNA repair pathways genes, which included known (BRCA1, BRCA2, MSH2, MLH1, MSH6, PMS2) and emerging (BRIP1, RAD51C, RAD51D) OC predisposing genes. Top ranking candidate variants (minor allele frequency <1%) were identified using 11 different in silico tools that assessed amino acid conversation or potential pathogenicity. Pathogenicity of known and emerging OC predisposing genes was assessed using BRCAExchange (www.brcaexchange.org) and ClinVar (www.ncbi.nlm.nih.gov/clinvar/). A similar analysis was done with WES data from 13 FC OC cases harboring pathogenic BRCA1/BRCA2 variants. We identified 31 variants in 27 genes in FANCI c.1813C>T carriers. A previously known carrier of a pathogenic BRCA1 variant (c.2836_2837del; p.Ile946GlnfsTer5) was also identified in a familial case. No carriers of other pathogenic variants in known or emerging OC predisposing genes were found. However, FANCI carriers were found to carry at least one other PPV in a DNA repair pathway gene (range 2-9; average=4.1). There were no other carriers of variants in common among all OC cases, though at least 2 cases carried a variant in the same gene. FC OC cases harboring BRCA1/BRCA2 variants carried at least one other PPV in a DNA repair pathway gene (range 2-7; average 4). It is possible that the identified variants influence or modify risk in conjunction with FANCI, though no PPV was identified in all carriers. As new cancer predisposing genes are identified it will become increasingly important to characterize the genetic context in which variants are identified. This will allow for further insight to clinical translatability once penetrance has been established. Citation Format: Caitlin Fierheller, Wejdan M Alenezi, Corinne Serruya, Timothée Revil, Javad Nadaf, Anne-Marie Mes-Masson, Diane Provencher, William D Foulkes, Zaki El Haffaf, Celia M T Greenwood, Jean-Yves Masson, Jiannis Ragoussis, Patricia N Tonin. The genomic landscape of carriers of rare variants in FANCI, a new candidate ovarian cancer predisposing gene [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2056.

Peripheral blood BRCA1 methylation profiling to predict familial ovarian cancer.

ObjectiveFamilial cancer appears at a young age and its incidence is increasing. About 12% of familial ovarian cancer cases are associated with BRCA1/2 mutations (BRCAm). In this study, we investigated BRCA1 methylation may predict ovarian cancer in those with a family history of cancer (FHC) but without BRCA1/2 mutations (BRCAwt).MethodsUsing peripheral blood DNA from 55 subjects without a history of cancer [cancer(−)] and 52 ovarian cancer patients, we examined BRCA1 promoter methylation through bisulfite sequencing of the promoter and expressed the results as the cumulative methylation index. Then, we evaluated the BRCA1 promoter methylation according to BRCA1/2 germline mutations.ResultsBRCA1 methylation was more prevalent in the BRCAm cancer(−) group than in the BRCAwt cancer(−) group and ovarian cancer patients (p=0.031 and p=0.019, respectively). In the BRCAwt cancer(−) group, BRCA1 methylation was more prevalent in those with an FHC than in those without one and in the BRCAm cancer(−) group with an FHC (p=0.001 and p<0.001, respectively).ConclusionOur data suggest a predictive role of BRCA1 methylation profile for ovarian cancer in those without a history of cancer but with an FHC. BRCA1 methylation has important implications for diagnostic and predictive testing of those with BRCAwt cancer(−) status with FHC.

Variants in the Signaling Protein TSAd are Associated with Susceptibility to Ovarian Cancer in BRCA1/2 Negative High Risk Families

A substantial fraction of familial ovarian cancer cases cannot be attributed to specific genetic factors. The discovery of additional susceptibility genes will permit a more accurate assessment of hereditary cancer risk and allow for monitoring of predisposed women in order to intervene at the earliest possible stage. We focused on a population with elevated familial breast and ovarian cancer risk. In this study, we identified a SNP rs926103 whose minor allele is associated with predisposition to ovarian but not breast cancer in a Caucasian high-risk population without BRCA1/BRCA2 mutations. We have found that the allelic variation of rs926103, which alters amino acid 52 of the encoded protein SH2D2A/TSAd, results in differences in the activity of this protein involved in multiple signal transduction pathways, including regulation of immune response, tumor vascularization, cell growth, and differentiation. Our observation provides a novel candidate genetic biomarker of elevated ovarian cancer risk in members of high-risk families without BRCA1/2 mutations, as well as a potential therapeutic target, TSAd.

Mutational analysis of the estrogen receptor‐α gene in familial ovarian cancer

The genetic region of 6q25 containing the estrogen receptor-alpha (ER-alpha) gene is lost in a significant number of ovarian tumors. The aim of this study was to identify how inherited variation in the ER-alpha gene contributes to susceptibility to familial ovarian cancer. DNA obtained from 18 cases of familial ovarian cancer without mutation of the BRCA1 and BRCA2 genes, 20 cases with BRCA1 mutation, 20 cases of sporadic ovarian cancer, and 19 controls were screened for mutations in the coding region of the ER-alpha gene using direct sequencing. Two germline missense variants at codons 307 [GCC(Ala)-->TCC(Ser)] and 347 [ACC(Thr)-->TCC(Ser)] were detected in two unrelated cases with BRCA1 mutation, but not in all other cases tested. Three polymorphisms in codon 10 [TCT-->TCC(Ser)], codon 325 [CCC-->CCG(Pro)], and codon 594 [ACA-->ACG(Thr)] were identified in this series, and a higher frequency of the allele TCC at codon 10 and a lower frequency of the allele CCG at codon 325 were observed in familial cases without BRCA1 mutation, compared with those in familial cases with BRCA1 mutation, in both the sporadic cases and in the controls. We could not detect pathogenic mutations of the ER-alpha gene in ovarian cancer cases without BRCA1 mutation. However, association analyses of two polymorphisms suggest that the ER-alpha gene or a gene located close to the ER-alpha locus might be related to susceptibility of familial ovarian cancer without BRCA1 mutation.

Infrequent mutations of Archipelago ( hAGO, hCDC4, Fbw7) in primary ovarian cancer

Objective. Archipelago (AGO, also known as hCdc4, Fbw7, or Sel-10) is an F-box containing component of the SCF complex implicated in the ubiquitination and proteolysis of cyclin E and c-Myc, and found to be mutated in 16% of endometrial carcinomas. We have previously reported somatic mutations in AGO in 3/10 ovarian cancer cell lines, but the frequency of such mutations in primary ovarian cancer is unknown. Methods. The coding sequence of AGO was analyzed in 95 primary sporadic ovarian tumors and 16 cases of familial ovarian cancer, and correlated with levels of cyclin E and c-Myc protein expression. Constructs encoding mutations in AGO were transfected into an AGO-null cell line to directly test their ability to regulate cyclin E and c-Myc levels. Results. Mutations were present in only 2 of 95 sporadic cases: a premature stop within the WD domain (471 Ter) and a missense change near the F-box (S245T). Both primary tumor specimens containing these mutations showed high levels of cyclin E and c-Myc, but reconstitution of an AGO-null cell line with constructs encoding these mutations showed 471 Ter to be inactive in regulating endogenous cyclin E and c-Myc levels, while the S245T mutant was indistinguishable from wild-type. No germ-line mutations were found in familial cases of ovarian cancer. Conclusion. Somatic AGO mutations are infrequent in primary ovarian cancers and are unlikely to contribute to familial ovarian cancer. Reconstitution experiments, rather than measuring tumor levels of cyclin E and c-Myc, provide an effective approach to determine the functional significance of AGO mutations identified in human cancers.

Survival analysis in familial ovarian cancer, a case control study

Objective: familial ovarian cancer patients have been found to differ from sporadic cases, clinically as well as in the molecular make-up of the tumour. Here, a case control study is performed to analyse potential differences in survival. Study design: 31 families with a strong history of ovarian and/or breast cancer presenting to a family cancer clinic 44 ovarian cancer patients were included. Each patient was matched for age and stage with controls from a cancer registry. Survival rates and the effect of several prognostic factors were analysed. Results: median survival in the study group differed significantly from controls. A survival benefit for familial cases was maintained up to 5 years after diagnosis. Long-term survival was equally poor in both groups. Conclusion: the difference in survival between familial ovarian cancer cases and matched controls may reflect differences in biological behaviour. This may have important implications for the management and prevention of familial ovarian cancer.

Classification of IVS1-10T →C as a Polymorphism of BRCA1

Mutations inactivating the tumor suppressor gene BRCA1 may be responsible for disease for up to 80% of familial ovarian cancer cases. In this syndrome, tumorigenesis classically initiates from an inherited mutation in one allele followed by somatic deletion of the normal allele. Sequencing of BRCA1 amplified from genomic DNA of lymphocytes and microdissected ovarian tumor cells of a familial ovarian cancer patient revealed three, rare heterozygous DNA variations (2418delA, 233G→A, and IVS1-10T→C) in both tumor and constitutional (lymphocyte) DNA. Thus, both copies of BRCA1 were retained in tumor. Haplotype analysis of the patient and four siblings assigned 2418delA to one copy of BRCA1 and 233G→A and IVS1-10T→C to the other. The DNA change, 2418delA, is considered a mutation that inactivated one BRCA1 allele because it caused a frameshift and generation of a premature stop codon, resulting in synthesis of a truncated peptide as evidenced by an in vitro protein truncation test. The DNA variation, 233G→A, does not result in an amino acid change, and is considered a benign polymorphism. IVS1-10T→C is a unique BRCA1 change that occurs in the last nucleotide of a consensus sequence for a branch site critical for RNA splicing. Therefore, we investigated whether IVS1-10T→C deleteriously affected BRCA1 splicing or expression, and thereby inactivated the other BRCA1 allele. Using the technique of reverse transcription-polymerase chain reaction (PCR) with RNA isolated from lymphoid cell lines of the patient and of controls, no evidence was found that IVS1-10TC abnormally disrupted mRNA splicing or caused the absence of BRCA1 mRNA. Thus, IVS1-10T→C is not harmful to BRCA1 function, and is classified a benign polymorphism. Retention of the normal BRCA1 allele in the tumor with the heterozygous germline BRCA1 mutation, 2418delA, indicated that mutational inactivation of both BRCA1 alleles was not required for tumorigenesis. It is possible that the normal allele may be functionally inactivated by a nonmutational mechanism.

Prophylactic Oophorectomy: Reducing the U.S. Death Rate from Epithelial Ovarian Cancer. A Continuing Debate

The Oncologist 1996;1:326-330 Correspondence: M. Steven Piver, M.D., Department of Gynecologic Oncology, Gilda Radner Familial Ovarian Cancer Registry, Roswell Park Cancer Institute, Elm and Carlton Streets, Buffalo, NY 14263, USA. Telephone: 716-845-3110; Fax: 716-845-7608. Received August 1, 1996; accepted for publication August 27, 1996. ©AlphaMed Press 1083-7159/96/$5.00/0 If instead of the title “Prophylactic Oophorectomy: Reducing the U.S. Death Rate from Epithelial Ovarian Cancer,” the title were “Drug X Reducing the U.S. Death Rate from Epithelial Ovarian Cancer,” there would be great media and medical attention worldwide to such a report. Correctly so. Regrettably, there probably is no new Drug X in the foreseeable future that will significantly reduce the death rate from ovarian cancer, be it Taxol®, taxotere, topotecan, gemcitabine, or liposomal doxorubicin—although each may result in significant responses and some prolongation of median survival. Epithelial ovarian cancer is a much more complex disease than anyone envisioned, when it was believed that extensive debulking surgery and the newest cytotoxic chemotherapy would radically reduce the death rate from ovarian cancer in the United States. Over 20 years after the first patient was treated with cisplatin for epithelial ovarian cancer, the annual death rate from ovarian cancer continued to increase. Just in the past decade, the number of women in the United States dying from ovarian cancer has increased 18% (Fig. 1) [1]. Although ovarian cancer is estimated to account for 26,700 cases and 14,800 deaths in 1996, it is a low-prevalence disease in comparison with breast cancer, which in 1996 is estimated to account for 185,700 cases and 44,560 deaths. Inexplicably, similar to breast cancer, the lifetime risk for ovarian cancer in the United States continues to increase. The most recent Surveillance, Epidemiology and End Results (SEER) calculations of lifetime risk for ovarian cancer are that 1 in 55 women will develop ovarian cancer over their lifetime, or 1.8%, up from the 1970 figures of 1 in 70, or 1.4% [2]. The 1.8% baseline lifetime risk for the general population is used to estimate the lifetime risk of known ovarian cancer risk factors (Table 1). Even utilizing what are now believed to be two of the most effective cytotoxic drugs against stage III and IV epithelial ovarian cancer, Taxol® and cisplatin, researchers reported that this resulted in an increase in the median disease-free survival of only five months, as compared with those women allocated to receive cisplatin and cyclophosphamide (median diseasefree survival of 18 and 12.9 months, respectively), felt then to be the standard therapy [3]. Patients treated with Taxol® and cisplatin survived a median of 14 months longer than those

Evidence for a unifocal origin in familial ovarian cancer

OBJECTIVE: The purpose of this investigation was to determine the pattern of loss of heterozygosity in multiple tumor sites from familial ovarian cancer cases. If ovarian cancer arises focally in one ovary and then metastasizes to other sites, a similar pattern should be seen in all tumor sites. However, if ovarian cancer arises multifocally throughout the peritoneal cavity, a different pattern of loss would be expected among the different sites. STUDY DESIGN: The presence or absence of loss of specific alleles for 9 loci on chromosomes 1, 6, 11, 13, 16, and 17 was determined in multiple tumor sites from 12 familial ovarian cancer cases. RESULTS: The frequency of loss of heterozygosity was as follows: chromosome 17 (100%), chromosome 13 (82%), chromosome 6 (80%), chromosome 16 (73%), chromosome 1 (57%), and chromosome 11 (22%). In every case an identical pattern was present for at least one locus. In four cases loss of the same allele was present in tumor from the ovary and all metastatic sites for all informative loci. In the remaining eight cases loss of the same allele for one to five (mean three) loci was detected. CONCLUSIONS: The pattern of loss of heterozygosity in the 12 familial ovarian cancers included in this investigation favors a unifocal origin of disease. A dual primary origin could not be absolutely excluded in 3 cases. High frequencies on chromosomes 17q and 13 suggest that loss of whole or part of these chromosomes is important in ovarian carcinogenesis. (A M J O BSTET G YNECOL 1996;174:1102-8.)