RAD51C germline mutations found in Spanish site-specific breast cancer and breast-ovarian cancer families

BRCA1 and BRCA2 are the most well-known breast and ovarian cancer susceptibility genes. Additional genes involved in DNA repair have been identified as predisposing to breast cancer. Recently, RAD51C, a new Fanconi Anemia gene, essential for homologous recombination repair, has been reported to be a rare hereditary breast and ovarian cancer susceptibility gene. Indeed, several pathogenic mutations have been identified in BRCA1/BRCA2-negative hereditary breast and ovarian cancer families. Here, we present the results of the screening of RAD51C mutations in a large series of 516 BRCA1/BRCA2-negative Spanish patients from breast and/or ovarian cancer families, and the evaluation of these results in the context of all RAD51C carriers. RAD51C mutation screening was performed by DNA analysis for all index cases. All the genetic variants identified were analyzed in silico for splicing and protein predictions. cDNA analysis was performed for three selected variants. All previous RAD51C mutation studies on breast and/or ovarian cancer were reviewed. We identified three inactivating RAD51C mutations. Two mutations were found in breast and ovarian cancer families and one mutation in a site-specific breast cancer family. Based on the mean age of ovarian cancer diagnosis in RAD51C carriers, we would recommend prophylactic bilateral salpingo-ophorectomy in premenopausal RAD51C mutation carriers. Our results support that RAD51C is a rare breast and ovarian cancer susceptibility gene and may contribute to a small fraction of families including breast and ovarian cancer cases and families with only breast cancer. Thus, RAD51C testing should be offered to hereditary breast and/or ovarian cancer families without selecting for specific cancer origin.     

RAD51C: a novel cancer susceptibility gene is linked to Fanconi anemia and breast cancer

Germline mutations in many of the genes that are involved in homologous recombination (HR)-mediated DNA double-strand break repair (DSBR) are associated with various human genetic disorders and cancer. RAD51 and RAD51 paralogs are important for HR and in the maintenance of genome stability. Despite the identification of five RAD51 paralogs over a decade ago, the molecular mechanism(s) by which RAD51 paralogs regulate HR and genome maintenance remains obscure. In addition to the known roles of RAD51C in early and late stages of HR, it also contributes to activation of the checkpoint kinase CHK2. One recent study identifies biallelic mutation in RAD51C leading to Fanconi anemia-like disorder. Whereas a second study reports monoallelic mutation in RAD51C associated with increased risk of breast and ovarian cancer. These reports show RAD51C is a cancer susceptibility gene. In this review, we focus on describing the functions of RAD51C in HR, DNA damage signaling and as a tumor suppressor with an emphasis on the new roles of RAD51C unveiled by these reports.     

The RAD51 gene family, genetic instability and cancer

Prostate cancer (CaP) is the most commonly diagnosed nonskin cancer and the second leading cause of cancer death in American men. Its etiology is not fully understood. Ethnicity/race and family history are associated with it, and incidence increases with age. As with other solid tumors, accumulation of mutations and decline in DNA repair during aging may lead to CaP. However, we believe that conducting a large population screening for every cancer susceptibility gene (e.g. DNA repair) is only meaningful, if we can predict to what extent genetic variants contribute to DNA-repair functional phenotype and CaP risk. This review focuses on the association between CaP and nucleotide excision repair (NER), because some of the DNA adducts generated by CaP-related carcinogens are removed by the NER pathway, and our previous data showed a significant association between lower NER capacity (NERC) and CaP risk. Many laboratories, including ours, have employed a variety of approaches to evaluate the functional significance of DNA-repair single-nucleotide polymorphisms (SNPs) in human cancer risk assessment. Genetic profiling and computational modeling that can predict NERC may have great potential for CaP-risk assessment, because the current NERC assay is quite labor intensive, costly, and therefore not suitable for population-based screening.     

Further evidence for the contribution of the RAD51C gene in hereditary breast and ovarian cancer susceptibility

RAD51C, a RAD51 paralogue involved in homologous recombination, is a recently established Fanconi anemia and breast cancer predisposing factor. In the initial report, RAD51C mutations were shown to confer a high risk for both breast and ovarian tumors, but most of the replication studies published so far have failed to identify any additional susceptibility alleles. Here, we report a full mutation screening of the RAD51C gene in 147 Finnish familial breast cancer cases and in 232 unselected ovarian cancer cases originating from Finland and Sweden. In addition, in order to resolve whether common RAD51C SNPs are risk factors for breast cancer, we genotyped five tagging single nucleotide polymorphisms, rs12946522, rs304270, rs304283, rs17222691, and rs28363312, all located within the gene, from 993 Finnish breast cancer cases and 871 controls for cancer associated variants. Whereas, none of the studied common SNPs associated with breast cancer susceptibility, mutation analysis revealed two clearly pathogenic alterations. RAD51C c.-13_14del27 was observed in one familial breast cancer case and c.774delT in one unselected ovarian cancer case, thus confirming that RAD51C mutations are implicated in breast and ovarian cancer predisposition, although their overall frequency seems to be low. Independent identification of the very recently reported RAD51C c.774delT mutation in yet another patient originating from Sweden suggests that it might be a recurrent mutation in that population and should be studied further. The reliable estimation of the clinical implications of carrying a defective RAD51C allele still requires the identification of additional mutation positive families.     

BRIP1, PALB2, and RAD51C mutation analysis reveals their relative importance as genetic susceptibility factors for breast cancer

Mutations in the recognized breast cancer susceptibility genes BRCA1, BRCA2, TP53, ATM, and CHEK2 account for approximately 20% of hereditary breast cancer. This raises the possibility that mutations in other biologically relevant genes may be involved in genetic predisposition to breast cancer. In this study, BRIP1, PALB2, and RAD51C were sequenced for mutations as a result of previously being associated with breast cancer risk due to their role in the double-strand break repair pathway and their close association with BRCA1 and BRCA2. Two truncating mutations in PALB2 (Q66X and W1038X), one of which is has not been reported before, were detected in an independent Australian cohort of 70 individuals with breast or ovarian cancer, and have strong family histories of breast or breast/ovarian cancer. In addition, six missense variants predicted to be causative were detected, one in BRIP1 and five in PALB2. No causative variants were identified in RAD51C. This study supports recent observations that although rare, PALB2 mutations are present in a small but substantial proportion of inherited breast cancer cases, and indicates that RAD51C at a population level does not account for a substantial number of familial breast cancer cases.     

RAD51 135G>C polymorphism contributes to breast cancer susceptibility: a meta-analysis involving 26,444 subjects

RAD51 plays a key role in homologous recombination repair of double-stranded DNA breaks which may cause chromosomal breaks and genomic instability. We performed a meta-analysis of 9 epidemiological studies involving 13,241 cases and 13,203 controls that examined the association between RAD51 135G>C polymorphism and breast cancer. No significant association of RAD51 135G>C polymorphism with breast cancer was found in overall and European populations. However, after the studies which did not fulfill Hardy–Weinberg equilibrium were excluded, we observed an overall significant increased breast cancer risk (for the recessive model CC vs. GG/CG: OR = 1.35, 95% CI = 1.05–1.74, P _{heterogeneity} = 0.06). In summary, our meta-analysis suggested the RAD51 135G>C polymorphism may contribute to breast cancer susceptibility.     

Risk communication in genetic testing for cancer susceptibility

Risk communication is an integral part of genetic counseling and testing for cancer susceptibility. This paper reviews the emerging literature on this topic. Three relevant aspects of risk communication are addressed: communication of individual risk, communication of the risks inherent in genetic testing, and family communications related to risk. These studies suggest that (a) most individuals with some family history of cancer, including those at low to moderate risk, overestimate their personal cancer risk; (b) awareness of the risks of genetic testing is limited; (c) decision making about genetic testing is influenced strongly by exaggerated perceptions of personal cancer risk and less so by perceptions of the risks of genetic testing; (d) perceptions of personal risk of cancer are resistant to standard education and counseling approaches; (e) psychologic distress and coping processes influence the processing of risk information and subsequent decision making in genetic testing; and (f) family influences play an important role in risk awareness, genetic testing decisions, and outcomes. To study these issues further, new theoretical models and measures of risk perceptions need to be developed. Both observational and experimental methods should be used to examine both the content and process of risk communication in cancer genetic counseling and testing. Emotional, familial, and sociocultural influences on the risk communication process require special attention.     

RAD51 G135C polymorphism is associated with breast cancer susceptibility: a meta-analysis involving 22,399 subjects

Several studies have investigated the associations between RAD51 G135C polymorphism and the susceptibility to breast cancer, but results have been inconclusive. In order to derive a more precise estimation of the relationship, a meta-analysis was performed. A total of 17 case control studies, including 12,153 cases and 10,245 controls, were selected. Overall, significant decreased risk was found for the additive model (OR = 0.995, 95% CI = 0.991–0.998) and dominant model (OR = 0.994, 95% CI = 0.991–0.998). In the subgroup analysis by ethnicity, statistically significantly decreased risk was found in Asians (additive model: OR = 0.977, 95% CI = 0.954–1.000 and dominant model: OR = 0.981, 95% CI = 0.963–1.000). In conclusion, this meta-analysis suggests that the RAD51 G135C polymorphism is a low-penetrant risk factor for developing breast cancer.     

Variation in the RAD51 gene and familial breast cancer

Introduction  

Human RAD51 is a homologue of the Escherichia coli RecA protein and is known to function in recombinational repair of double-stranded DNA breaks. Mutations in the lower eukaryotic homologues of RAD51 result in a deficiency in the repair of double-stranded DNA breaks. Loss of RAD51 function would therefore be expected to result in an elevated mutation rate, leading to accumulation of DNA damage and, hence, to increased cancer risk. RAD51 interacts directly or indirectly with a number of proteins implicated in breast cancer, such as BRCA1 and BRCA2. Similar to BRCA1 mice, RAD51 ^-/- mice are embryonic lethal. The RAD51 gene region has been shown to exhibit loss of heterozygosity in breast tumours, and deregulated RAD51 expression in breast cancer patients has also been reported. Few studies have investigated the role of coding region variation in the RAD51 gene in familial breast cancer, with only one coding region variant – exon 6 c.449G>A (p.R150Q) – reported to date.     

Evaluation of nurses and genetic counselors as providers of education about breast cancer susceptibility testing

PURPOSE/OBJECTIVES: To compare outcomes of pretest education about breast cancer susceptibility testing provided by nurses and genetic counselors. DESIGN: Two-group, post-test only evaluation of an educational intervention. SETTING: A tertiary care hospital. SAMPLE: 87 women who had a first-degree relative with premenopausal breast cancer; six specially-trained providers (four genetic counselors and two nurses). METHODS: Self-administered questionnaire completed immediately following education sessions. MAIN RESEARCH VARIABLES: Subjects' understanding of the limitations of testing, perceived autonomy in decision making, and satisfaction; partnership as perceived by subjects and providers. FINDINGS: After the sessions, 62% of subjects understood the limitations of testing, 98% reported a high degree of perceived autonomy in decision making, 81% were highly satisfied with the session, and 91% reported forming a partnership with their providers. Lower perceived partnership reported by genetic counselors was the only significant difference by provider type. CONCLUSIONS: With training and supervision, nurses and genetic counselors can be equally effective in providing education about genetic testing for breast cancer susceptibility in research settings. Additional research is needed to determine the outcomes of education provided in clinical settings. IMPLICATIONS FOR NURSING PRACTICE: As the demand for education about genetic testing for cancer susceptibility increases, nurses need to be educated and trained to provide this service.     

Primary care physicians'' knowledge and attitudes towards genetic testing for breast-ovarian cancer predisposition.

Background:Primary health care providers are expected to bedirectly involved in the genetic testing for cancer susceptibility. This studyassessed physicians' knowledge, attitude and perception of their role towardstesting for hereditary breast–ovarian cancer. Design:A mail-in survey was sent to all general practitioners,internists, obstetrician-gynecologists and oncologists in private practice inGeneva county, Switzerland. Questions included socio-demographic variables,knowledge about hereditary breast–ovarian cancer, attitude towardstesting and assessment of their role in the pre- and post-test procedure. Results:Two hundred fifty-nine (65%) of four hundredquestionnaires were returned of which two hundred forty-three (61%)were analysed. Response rates were similar between specialties; women answeredmore frequently. The majority of the respondents (87%) approved ofgenetic susceptibility testing. The most common objection to testing was theabsence of approved strategies for the prevention and detection of earlybreast cancer. Most physicians felt they had an active part to play in thepre-test procedure, the disclosure of results, and especially the consultants'long-term care and support (99%). Physicians correctly answered a third(32%) of the knowledge questions. The abstention rate for individualitems ranged from 13% to 60%. Scores varied by specialty.Oncologists were more knowledgeable than gynecologists, internists and generalpractitioners. Conclusions:The majority of the primary care physicians in thisstudy have a favourable attitude and are ready to play a prominent role ingenetic counseling and testing for breast–ovarian cancer predisposition.Defective knowledge scores, however, underline the need for targetededucational programs.     

Current status of genetic testing for colorectal cancer susceptibility

Over 130,000 new cases of colon cancer are diagnosed annually. Approximately 20% to 30% of these are attributable to familial risk, and 3% to 5% belong to a hereditary colorectal cancer predisposition syndrome. Recent discoveries of the genes responsiblefor the inherited colorectal cancer conditions have expanded the field of commercial genetic testing. Health-care providers who use genetic testing in clinical practice are aware of the benefits that genetic testing can confer on screening, prevention, and treatment options for patients with a personal and/or family history of colon cancer. When genetic test results are correctly interpreted, the information they provide can offer medical guidance for the entire family. The psychological impact, however, of presymptomatic testing can be multifaceted. There are unprecedented benefits but also complex issues surrounding genetic testing. For these reasons, the practice of offering genetic testing to individuals at high risk for colon cancer is heavily fortified with guidelines and recommendations. This review covers the current availability and limitations of genetic testing for inherited colorectal cancer syndromes and focuses on guidelines that address the psychological, ethical, and social concerns stemming from genetic testing.     

Genetic variants of BLM interact with RAD51 to increase breast cancer susceptibility

The role of the familial breast cancer susceptibility genes,BRCA1 and BRCA2, in the homologous recombination (HR) pathwayfor DNA double-strand break (DSB) repair suggests that the mechanismsinvolved in HR and DNA DSB repair are of etiological importanceduring breast tumorigenesis. Bloom (BLM) helicase directly interactswith RAD51 recombinase, which is involved in regulating HR,and it is thus of particular interest to examine whether thisinteraction is associated with breast cancer susceptibility.This single-nucleotide polymorphism (SNP)-based case–controlstudy was performed to examine this hypothesis using specimensfrom 933 patients with breast cancer and 1539 healthy controls.The results showed that one SNP (rs2380165) in BLM and two (rs2412546and rs4417527) in RAD51 were associated with breast cancer risk.Furthermore, haplotype and diplotype analyses based on combinationsof five SNPs in RAD51 revealed a strong association betweenRAD51 polymorphisms and breast cancer risk (P < 0.05). Supportfor the interaction between BLM and RAD51 in determining breastcancer risk came from the finding that the association betweencancer risk and at-risk genotypes/haplotype pairs of RAD51 wasstronger and more significant in women harboring homozygousvariant alleles of BLM (P for interaction < 0.05). Interestingly,not only the intronic SNP located within the region encodingthe helicase domain of BLM but also those within the RAD51-interactiondomain-encoding region showed an interaction with RAD51 polymorphismsin determining breast cancer susceptibility. Our results suggesta contribution of BLM and RAD51 to breast cancer developmentand provide support for the tumorigenic significance of thefunctional interaction between these two HR proteins. Abbreviations: BLM, Bloom; DSB, double-strand break; HR, homologous recombination; LD, linkage disequilibrium; SNP, single-nucleotide polymorphism Received July 1, 2008; revised September 9, 2008; accepted September 30, 2008.     

Germline mutations in RAD51C in Jewish high cancer risk families

Germline mutations in BRCA1 and BRCA2 account for ~30 % of inherited breast cancer. RAD51C was reported as an additional breast/ovarian cancer susceptibility gene in some populations. There is a paucity of data on the putative contribution of this gene to inherited breast/ovarian cancer in Jewish high risk families. High risk Jewish women, none of whom was a carrier of the predominant Jewish mutations in BRCA1 or BRCA2, were screened for RAD51C germline mutations by direct sequencing of exons and flanking intronic sequences. Overall, 206 high risk women, 79 (38.3 %) of Ashkenazi origin, were genotyped for RAD51C mutations: 190 (92.3 %) with uni- or bilateral breast cancer (mean age at diagnosis 51.3 ± 11.1 years), 14 with ovarian cancer (mean age at diagnosis 55.6 ± 8.7 years), and two with both breast and ovarian cancer. No truncating mutations were noted, and two previously described missense mutations were detected: p.Ile144Thr and p.Thr287Ala in Iraqi and mixed ethnicity Balkan-North African participants, respectively. These missense mutations were evolutionarily conserved, possibly pathogenic, based on some prediction algorithms, and were not detected in any of healthy Iraqi (n = 60) and mixed ethnicity (n = 140), cancer free controls, respectively. Germline mutations in RAD51C contribute marginally to breast and ovarian cancer susceptibility in ethnically diverse, Jewish high risk families. The p.Thr287Ala missense mutation may be a recurring, pathogenic RAD51C mutation in ethnically diverse populations.     

Cancer genetic testing panels for inherited cancer susceptibility: the clinical experience of a large adult genetics practice

Next-generation sequencing genetic testing panels for cancer susceptibility (cancer panels) have recently become clinically available. At present, clinical utility is unknown and there are no set criteria or guidelines established for whom to offer such testing. Although it may be a cost-effective method to test multiple cancer susceptibility genes concurrently, the rate of finding variants of unknown significance (VUS) may be high and testing may yield mutations in genes with no established management recommendations. We describe our Center’s experience over a 14-month period (April 2012–June 2013) for patient interest and uptake in cancer panel testing and whether there were predictors of pursuing testing or identifying mutations. Using a clinical ranking system, patients’ family histories were ranked from 0 to 3 (low likelihood to high likelihood for underlying genetic susceptibility). The clinical ranking system was assessed to determine its predictability of finding mutations. Of the 689 patients who met inclusion criteria, the option of pursuing a cancer panel was discussed with 357 patients; 63 (17.6 %) patients pursued testing. Those who pursued testing were more likely to be older, male, affected with cancer, affected with multiple primary cancers, and had a higher clinical rank than non-pursuers. There were no significant predictors of finding a mutation on panel testing. Of the 61 patients who have received results, there was a 6.6 % mutation rate and 19.7 % VUS rate. The yield of cancer panels in clinical practice is low and the strength of family history alone may not predict likelihood of finding a mutation.