Analysis of RAD51C germline mutations in high-risk breast and ovarian cancer families and ovarian cancer patients

There is strong evidence that overtly inactivating mutations in RAD51C predispose to hereditary breast and ovarian cancer but the prevalence of such mutations, and whether they are associated with a particular clinical phenotype, remains unclear. Resolving these questions has important implications for the implementation of RAD51C into routine clinical genetic testing. Consequently, we have performed a large RAD51C mutation screen of hereditary breast and ovarian cancer families, and the first study of unselected patients diagnosed with ovarian cancer. Our data confirm a consistent but low frequency (2/335 families) of inactivating RAD51C mutations among families with a history of both breast and ovarian cancer and an absence of mutations among breast cancer only families (0/1,053 families). Our data also provide support for the designation of the missense variant p.Gly264Ser as a moderate penetrance allele.     

Genetic testing for RAD51C mutations: in the clinic and community

Much of the observed familial clustering of breast and ovarian cancer cannot be explained by mutations in BRCA1 and BRCA2. Several other cancer susceptibility genes have been identified, but their value in routine clinical genetic testing is still unclear. Germline mutations in RAD51C have been identified in about 1% of hereditary breast and ovarian cancer families. RAD51C mutations are predominantly found in families with a history of ovarian cancer and are rare in families with a history of breast cancer alone. RAD51C is primarily an ovarian cancer susceptibility gene. A mutation is present in approximately 1% of unselected ovarian cancers. Among mutation carriers, the lifetime risk of ovarian cancer is approximately 9%. The average age at onset is approximately 60 years; this suggests that preventive oophorectomy can be delayed until after natural menopause. Under current guidelines, genetic testing for RAD51C is expected to have a limited impact on ovarian cancer incidence at a population level. This is because the penetrance is 9% to age 80; the great majority of families with mutations would be represented by a single case of ovarian cancer, these are potentially preventable through population screening but not through screening of established ovarian cancer families.     

Germline RAD51C mutations in ovarian cancer susceptibility

Several genes might explain BRCA1/2 negative breast and ovarian family cases. Deleterious mutations in few genes involved in the Fanconi complex are responsible for Fanconi anemia at the homozygous state and breast cancer (BC) susceptibility at the heterozygous state (BRCA2, PALB2, BRIP1). RAD51C plays an important role in the double‐strand break repair pathway and a biallelic missense mutation in the RAD51C gene was found in a Fanconi anemia‐like disorder. Subsequently, six monoallelic pathogenic mutations were identified after screening 480 BRCA1/2 negative breast and ovarian cancer (BC/OC) pedigrees. Several reports were unsuccessful to replicate these results. To investigate whether germline mutations in RAD51C are associated with an increased risk of developing BC/OC, we screened, by Sanger sequencing of the coding sequence, 117 index cases of breast and ovarian families from French or European origin, and negative for BRCA1/2 mutations. In our study, we found 3 pathogenic mutations among 117 families screened which corresponds to a 2.6% frequency. Our results confirm that RAD51C is a susceptibility gene for ovarian and BC and that this gene should be screened for mutations in families with multiple BC/OC.     

Mutational analysis of RAD51C and RAD51D genes in hereditary breast and ovarian cancer families from Murcia (southeastern Spain)

RAD51C and RAD51D have been defined as susceptibility genes for hereditary breast and ovarian cancer syndrome in several studies. In the present study, a mutation analysis of these genes was performed on non BRCA1/2 families. RAD51C and RAD51D genes were analyzed in 141 and 77 families, respectively. The analysis included direct sequencing and multiple ligation probe analysis. The RAD51C pathogenic variant c.404G?>?A was identified in a breast and ovarian cancer family (0.7%), while the RAD51D pathogenic variant c.694C?>?T was described in an ovarian cancer family (1.3%). Moreover, three unknown clinical significance variants were detected: c.307T?>?G in RAD51C, and c.413A?>?G and c.715C?>?T in RAD51D. No large genomic rearrangements (LGRs) were found. RAD51D carriers suffered from premenopausal ovarian tumors. These results increase our knowledge about the RAD51C and RAD51D mutation spectrum and support the notion that these genes should be included in the gene panel testing performed on patients with hereditary breast and ovarian cancer syndrome.     

Dinucleotide repeat polymorphisms of RAD51, BRCA1, BRCA2 gene regions in breast cancer

Recent studies suggest that genetic polymorphisms of the DNA repair genes have been implicated in breast cancer risk. BRCA1 and BRCA2 , two breast cancer susceptibility genes, are essential to maintain chromosomal integrity. This is mediated via regulation of RAD51 during homologous recombination. Dinucleotide polymorphism repeats in the 15q14–21, 17q21 and 13q12–13 regions, where the RAD51 , BRCA1 and BRCA2 genes are located, respectively, have been evaluated. The polymorphism was determined using the following microsatellite markers: D15S118, D15S214, D15S1006, D17S855, D17S1323, D13S260 and D13S290. Genotypes containing the (CA)₁₇ or (CA)₁₉ alleles in the RAD51 region were found to be associated with a decreased breast cancer risk. Genotype containing the (CA)₁₇ allele in the 13q12–13 region was found to be associated with an increased breast cancer risk. The results indicate that dinucleotide CA repeat polymorphism at RAD51 and BRCA2 gene regions might be associated with genetic susceptibility to breast cancer.     

RAD51基因135G/C多态与人群发生肺癌的易感性研究

目的 探讨DNA双链断裂修复基因RAD51的5'-UTR区135G/C多态与我国人群肺癌发病的关联.方法 采用PCR-RFLP技术,检测300对肺癌病例与正常对照RAD51基因135FG/C多态位点的基因型.用SAD9.13软件进行非条件Logistic回归,校正混杂因素的影响,分析该位点变异与肺癌发病的关联.结果 病例及对照组中,皆未检测出135CC基因型.病例组135GC基因型频率显著低于对照组(26.7%比34.7%,P=0.0336).以携带GG野生基因型个体为参照,携带GC基因型能显著减少个体发生肺癌的危险性(调整优势比=0.72;95%置信区间=0.49～0.98;P=0.042).结论 RAD51的5'-UTR区135G/C多态与我国人群肺癌发病存在显著性关联,135C可能是我国人群肺癌发生的一个遗传保护因素.     

Hereditary cancer predispositions: Comparison of multigene panel sequencing on fresh-frozen breast/ovarian tumor versus blood

In breast or ovarian cancer (BC/OC) patients with evocative personal and/or family history, multigene panel sequencing is performed on blood to diagnose hereditary predispositions. Additionally, BRCA1/BRCA2 testing can be performed on tumor sample for therapeutic purpose. The accuracy of multigene panel tumor analysis on BC/OC to detect predisposing germline pathogenic variants (gPV) has not been precisely assessed. By comparing sequencing data from blood and fresh-frozen tumor we show that tumor genomic instability causes pitfalls to consider when performing tumor testing to detect gPV. Even if loss of heterozygosity increases germline signal in most cases, somatic copy number variants (CNV) can mask germline CNV and collapse point gPV variant allele frequency (VAF). Moreover, VAF does not allow an accurate distinction between germline and somatic pathogenic variants.     

RAD51基因G135C单核苷酸多态性及p53突变在肺癌中的意义

目的探讨RAD51基因G135C多态性与肺癌发病风险、病理特点及p53基因突变的相关性。方法选择80例肺癌患者为病例组,40例非肿瘤肺疾病患者为对照组。以PCR-RFLP技术检测病例组和对照组的RAD51基因型,比较不同基因型与肺癌危险性以及肺癌病理特点的关系;并采用免疫组化法对病例组进行p53突变的检测。结果 (1)RAD51基因型G/G、G/C和C/C在病例组的分布频率分别为77.5%、15.0%和1.3%,在对照组的分布频率分别为92.5%、7.5%和0。与携带G/G的个体相比,携带RAD51变异基因型(G/C和C/C)的个体具有更高的患癌风险(P<0.05);(2)RAD51基因型与肺癌的病理学类型及组织学分级无相关性;(3)RAD51 G135C基因型在不同p53基因突变状态肺癌中的分布频率差异无显著性(P>0.05)。结论 RAD51基因多态性与肺癌发病风险有关,携带RAD51变异基因型(G/C和C/C)的个体易患肺癌。     

Screening for ESR mutations in breast and ovarian cancer patients

In the present study, leukocyte DNA from 143 patients with familial clustering of breast and/or ovarian cancer and tumour DNA from 96 breast carcinomas were screened for base mutations in the estrogen receptor gene (ESR). Three patients with a family history of cancer were carrying a Gly160Cys germline substitution. This alteration was also detected in eight (four females and four males) of 729 controls (366 female, 363 males), indicating that the substitution probably represents a polymorphism. However, in the 229 female controls in whom family history of cancer was known, one of two who had a sister with breast cancer was carrying the variant allele. Hence, a possible clinical significance of the glycine into cysteine cannot be completely ruled out and should be further investigated. Somatic mutations were not detected in any of the tumours studied, and the present data do not provide support for somatic ESR base mutations as an important mechanism for hormonal therapy resistance in estrogen receptor-positive breast carcinomas. Hum. Mutat. 9:531–536, 1997. © 1997 Wiley-Liss, Inc.     

High frequency and allele‐specific differences of BRCA1 founder mutations in breast cancer and ovarian cancer patients from Belarus

Bogdanova NV, Antonenkova NN, Rogov YI, Karstens JH, Hillemanns P, Dörk T. High frequency and allele‐specific differences of BRCA1 founder mutations in breast cancer and ovarian cancer patients from Belarus. Breast cancer and ovarian cancer are common malignancies in Belarus accounting for about 3500 and 800 new cases per year, respectively. For breast cancer, the rates and age of onset appear to vary significantly in regions differentially affected by the Chernobyl accident. We assessed the frequency and distribution of three BRCA1 founder mutations 5382insC, 4153delA and Cys61Gly in two hospital‐based series of 1945 unselected breast cancer patients and of 201 unselected ovarian cancer patients from Belarus as well as in 1019 healthy control females from the same population. Any of these mutations were identified in 4.4% of the breast cancer patients, 26.4% of the ovarian cancer patients and 0.5% of the controls. In the breast cancer patients, BRCA1 mutations were strongly associated with earlier age at diagnosis, with oestrogen receptor (ER) negative tumours and with a first‐degree family history of breast cancer, although only 35% of the identified BRCA1 mutation carriers had such a family history. There were no marked differences in the regional distribution of BRCA1 mutations, so that the significant differences in age at diagnosis and family history of breast cancer patients from areas afflicted by the Chernobyl accident could not be explained by BRCA1. We next observed a higher impact and a shifted mutational spectrum of BRCA1 in the series of Byelorussian ovarian cancer patients where the three founder mutations accounted for 26.4% (53/201). While the Cys61Gly mutation appeared underrepresented in ovarian cancer as compared with breast cancer cases from the same population (p = 0.01), the 4153delA mutation made a higher contribution to ovarian cancer than to breast cancer (p < 0.01). BRCA1 mutations were significantly enriched among ovarian cancer cases with a first‐degree family history of breast or ovarian cancer, whereas the median age at ovarian cancer diagnosis was not different between mutation carriers and non‐carriers. Taken together, these results identify three BRCA1 founder mutations as key components of inherited breast and ovarian cancer susceptibility in Belarus and might have implications for cancer prevention, treatment and genetic counselling in this population.     

Identification of Rad51 alteration in patients with bilateral breast cancer

The human Rad51 gene, HsRAD51, is a homolog of RecA of Escherichia coli and functions in recombination and DNA repair. BRCA1 and BRCA2 proteins form a complex with Rad51, and these genes are thought to participate in a common DNA damage response path-way associated with the activation of homologous recombination and double-strand break repair. Additionally, we have shown that the pattern of northern blot analysis of the Rad51 gene is closely similar to those of the BRCA1 and BRCA2 genes. It is therefore possible that alterations of the Rad51 gene may be involved in the development of hereditary breast cancer. To investigate this possibility, we screened Japanese patients with hereditary breast cancer for Rad51 mutations and found a single alteration in exon 6. This was determined to be present in the germline in two patients with bilateral breast cancer, one with synchronous bilateral breast cancer and the other with synchronous bilateral multiple breast cancer. In both patients, blood DNAs showed a G-to-A transition in the second nucleotide of codon 150, which results in the substitution of glutamine for arginine. As this alteration was not present in any patients with breast or colon cancer examined, we assume that this missense alteration is likely to be a disease-causing mutation. Received: November 9, 1999 / Accepted: December 16, 1999     

Identification of germline alterations in breast cancer predisposition genes among Malaysian breast cancer patients using panel testing

Although an association between protein‐truncating variants and breast cancer risk has been established for 11 genes, only alterations in BRCA1, BRCA2, TP53 and PALB2 have been reported in Asian populations. Given that the age of onset of breast cancer is lower in Asians, it is estimated that inherited predisposition to breast cancer may be more significant. To determine the potential utility of panel testing, we investigated the prevalence of germline alterations in 11 established and 4 likely breast cancer genes in a cross‐sectional hospital‐based cohort of 108 moderate to high‐risk breast cancer patients using targeted next generation sequencing. Twenty patients (19%) were identified to carry deleterious mutations, of whom 13 (12%) were in the BRCA1 or BRCA2, 6 (6%) were in five other known breast cancer predisposition genes and 1 patient had a mutation in both BRCA2 and BARD1. Our study shows that BRCA1 and BRCA2 account for the majority of genetic predisposition to breast cancer in our cohort of Asian women. Although mutations in other known breast cancer genes are found, the functional significance and breast cancer risk have not yet been determined, thus limiting the clinical utility of panel testing in Asian populations.     

Pre‐test genetic counseling services for hereditary breast and ovarian cancer delivered by non‐genetics professionals in the state of Florida

Genetic counseling and testing for hereditary breast and ovarian cancer now includes practitioners from multiple healthcare professions, specialties, and settings. This study examined whether non‐genetics professionals (NGPs) perform guideline‐based patient intake and informed consent before genetic testing. NGPs offering BRCA testing services in Florida (n = 386) were surveyed about clinical practices. Among 81 respondents (response rate = 22%), approximately half reported: sometimes scheduling a separate session for pre‐test counseling lasting 11–30 min prior to testing, discussing familial implications of testing, benefits and limitations of risk management options, and discussing the potential psychological impact and insurance‐related issues. Few constructed a three‐generation pedigree, discussed alternative hereditary cancer syndromes, or the meaning of a variant result. This lack of adherence to guideline‐based practice may result in direct harm to patients and their family members. NGPs who are unable to deliver guideline adherent cancer genetics services should focus on identification and referral of at‐risk patients to in person or telephone services provided by genetics professionals.     

BRCA1 and BRCA2 mutations in breast/ovarian cancer patients from central Italy

We report on the screening of the entire BRCA1/BRCA2 coding sequence by SSCP, PTT, and direct sequencing in 68 Italian families with recurrent breast or ovarian cancer. For each investigated proband, the probability of being carrier of a BRCA1/BRCA2 mutation was evaluated using the BRCAPRO software. We detected BRCA1/BRCA2 mutations in 8 patients (11.7%). However, if considering only patients with a carrier probability >10%, the detection rate was 36.8%, confirming the usefulness of the BRCAPRO software. One change (BRCA1 4172insT) was a novel mutation not reported in BIC database.     

Comparing family members' motivations and attitudes towards genetic testing for hereditary breast and ovarian cancer: a qualitative analysis

Genetic testing for hereditary breast and ovarian cancer reveals significant risk information regarding one''s chances of developing cancer that has potential implications for patients and their families. This study reports on the motivations and attitudes of index patients and their relatives towards genetic testing for hereditary breast and ovarian cancer. In total, 10 female index patients and 20 of their relatives were interviewed regarding their experiences of communicating genetic information within their families, and their motivations and attitudes towards genetic testing. The analysis found two types of ‘family groups'': groups strongly committed to genetic testing and groups uncertain about testing. Within committed family groups, index patients and their relatives felt obliged to be tested for others, leading some relatives to be tested without having fully thought through their decision or the implications of knowing their mutation status. These family groups also described considerations in relation to the value of testing for themselves. In family groups uncertain about testing, relatives had not attended for predictive testing, had postponed decision making until some point in the future or had expressed ambivalence about the value of testing for themselves. Results suggest the value of explicitly acknowledging motivations for genetic testing within the context of family obligations, relationships and communication, and the possible value of involving family members in genetic counselling and decision making from a family''s first contact with genetic services.