Inherited Breast Cancer Susceptibility Research Articles

Genetic Testing in Metastatic Breast Cancer in the USA: A Podcast.

This podcast highlights the importance of genetic testing in patients with metastatic breast cancer, with a specific focus on germline or inherited breast cancer susceptibility gene (BRCA) mutations. In the USA, national guidelines recommend that all patients with recurrent or metastatic breast cancer should be offered genetic testing for germline breast cancer susceptibility gene 1 or 2 (BRCA1 or 2) mutations to identify patients potentially suitable for treatment with a poly(ADP-ribose) polymerase inhibitor. However, a retrospective study indicated that only 43% of patients with hormone receptor-positive/human epidermal growth factor receptor 2-negative advanced breast cancer who may be eligible for genetic testing have undergone germline BRCA1 or 2 testing. Therefore, a large national effort is required to offer genetic testing to more patients with recurrent or metastatic breast cancer. The aim of this podcast is to provide physicians with information to support the early engagement of patients in discussions about genetic testing, and guidance on how to manage patient concerns about the potential implications of testing. Here, a healthcare professional discusses germline genetic testing with a patient advocate and answers questions regarding the importance of testing in patients with metastatic breast cancer. Furthermore, the authors discuss what it means to receive a positive or negative result for a germline BRCA mutation and the impact this may have on the patient and their family members. Overall, the authors emphasize the importance of healthcare professionals providing every patient with metastatic breast cancer with the relevant information about genetic testing so that patients can make informed decisions. Podcast Audio and Infographic available for this article.Podcast Audio and Infographic available for this article.

Exome sequencing identified rare recurrent copy number variants and hereditary breast cancer susceptibility.

Copy number variants (CNVs) are a major source of genetic variation and can disrupt genes or affect gene dosage. They are known to be causal or underlie predisposition to various diseases. However, the role of CNVs in inherited breast cancer susceptibility has not been thoroughly investigated. To address this, we performed whole-exome sequencing based analysis of rare CNVs in 98 high-risk Northern Finnish breast cancer cases. After filtering, selected candidate alleles were validated and characterized with a combination of orthogonal methods, including PCR-based approaches, optical genome mapping and long-read sequencing. This revealed three recurrent alterations: a 31 kb deletion co-occurring with a retrotransposon insertion (delins) in RAD52, a 13.4 kb deletion in HSD17B14 and a 64 kb partial duplication of RAD51C. Notably, all these genes encode proteins involved in pathways previously identified as essential for breast cancer development. Variants were genotyped in geographically matched cases and controls (altogether 278 hereditary and 1983 unselected breast cancer cases, and 1229 controls). The RAD52 delins and HSD17B14 deletion both showed significant enrichment among cases with indications of hereditary disease susceptibility. RAD52 delins was identified in 7/278 cases (2.5%, P = 0.034, OR = 2.86, 95% CI = 1.10-7.45) and HSD17B14 deletion in 8/278 cases (2.9%, P = 0.014, OR = 3.28, 95% CI = 1.31-8.23), the frequency of both variants in the controls being 11/1229 (0.9%). This suggests a role for RAD52 and HSD17B14 in hereditary breast cancer susceptibility. The RAD51C duplication was very rare, identified only in 2/278 of hereditary cases and 2/1229 controls (P = 0.157, OR = 4.45, 95% CI = 0.62-31.70). The identification of recurrent CNVs in these genes, and especially the relatively high frequency of RAD52 and HSD17B14 alterations in the Finnish population, highlights the importance of studying CNVs alongside single nucleotide variants when searching for genetic factors underlying hereditary disease predisposition.

CEACAM Gene Family Mutations Associated With Inherited Breast Cancer Risk – A Comparative Oncology Approach to Discovery

IntroductionRecent studies comparing canine mammary tumors (CMTs) and human breast cancers have revealed remarkable tumor similarities, identifying shared expression profiles and acquired mutations. CMTs can also provide a model of inherited breast cancer susceptibility in humans; thus, we investigated breed-specific whole genome sequencing (WGS) data in search for novel CMT risk factors that could subsequently explain inherited breast cancer risk in humans.MethodsWGS was carried out on five CMT-affected Gold Retrievers from a large pedigree of 18 CMT-affected dogs. Protein truncating variants (PTVs) detected in all five samples (within human orthlogs) were validated and then genotyped in the 13 remaining CMT-affected Golden Retrievers. Allele frequencies were compared to canine controls. Subsequently, human blood-derived exomes from The Cancer Genome Atlas breast cancer cases were analyzed and allele frequencies were compared to Exome Variant Server ethnic-matched controls.ResultsCarcinoembryonic Antigen-related Cell Adhesion Molecule 24 (CEACAM24) c.247dupG;p.(Val83Glyfs∗48) was the only validated variant and had a frequency of 66.7% amongst the 18 Golden Retrievers with CMT. This was significant compared to the European Variation Archive (p-value 1.52 × 10–8) and non-Golden Retriever American Kennel Club breeds (p-value 2.48 × 10–5). With no direct ortholog of CEACAM24 in humans but high homology to all CEACAM gene family proteins, all human CEACAM genes were investigated for PTVs. A total of six and sixteen rare PTVs were identified in African and European American breast cancer cases, respectively. Single variant assessment revealed five PTVs associated with breast cancer risk. Gene-based aggregation analyses revealed that rare PTVs in CEACAM6, CEACAM7, and CEACAM8 are associated with European American breast cancer risk, and rare PTVs in CEACAM7 are associated with breast cancer risk in African Americans. Ultimately, rare PTVs in the entire CEACAM gene family are associated with breast cancer risk in both European and African Americans with respective p-values of 1.75 × 10–13 and 1.87 × 10–04.ConclusionThis study reports the first association of inherited CEACAM mutations and breast cancer risk, and potentially implicates the whole gene family in genetic risk. Precisely how these mutations contribute to breast cancer needs to be determined; especially considering our current knowledge on the role that the CEACAM gene family plays in tumor development, progression, and metastasis.

The contemporary landscape of genetic testing and breast cancer: Emerging issues

The landscape of genetic testing for breast cancer susceptibility has transformed dramatically over the last decade and a half. Traditionally, the process of genetic testing resided fully within a medical infrastructure, from identification of appropriate testing candidates to gene selection to risk mitigation recommendations. More recently, decreasing costs, advancing technology, and a growing understanding of therapeutic implications of certain genetic test results have led to more widespread uptake of testing that increasingly involves broad multigene panels. Germline genetic testing for breast cancer susceptibility can now be obtained through one of three approaches: through clinical care; a direct-to-consumer (DTC) approach that is entirely consumer-driven; or a hybrid, patient-initiated, provider-mediated model. Increased access to testing has led to extensive dialogue about the best way to conduct testing and act on results. Points of discussion include: selection of appropriate candidates for genetic testing; optimal composition of genes on panels; informed consent; safe return of results; privacy; and legal protections for those found to have relevant pathogenic or likely pathogenic variants. As more individuals undergo genetic testing, a growing population of individuals with inherited breast cancer predisposition informs optimal management of cancer risk and also highlights unanswered questions. This article aims to review the current state of genetic testing for inherited breast cancer susceptibility including testing approaches, the legal, ethical and social landscape, and selected contemporary management issues.

Abstract 2545: Identification of germline pathogenic alleles in 143 cancer predisposing genes in Mexican patients with hereditary breast cancer by massive parallel sequencing

Abstract Breast cancer is the neoplastic disease with the highest incidence and mortality worldwide and nearly 10% of the cases are due to inherited pathogenic alleles in cancer predisposing genes such as BRCA1 and BRCA2. However, the spectrum of inherited breast cancer susceptibility not caused by BRCA1/2 pathogenic alleles has not been explored in the Mexican population. In this work we evaluated the presence of germline pathogenic alleles in the coding sequence and splice sites of 143 cancer susceptibility genes in 69 Mexican female patients with cancer that were selected for family cancer history. Inclusion criteria followed the guidelines of the National Comprehensive Cancer Network for Genetic/Familial High-Risk Assessment of Breast and Ovarian Cancer. Data from international databases of normal populations and cancer patients, as well as annotation information and technical parameters were used to define pathogenic variants. The genes with the highest frequency of pathogenic alleles (stopgain/loss, frameshift indels) were BRCA1 (8.7%, 6/69), BRCA2 (2.9%, 2/69), FANCC (2.9%), MSR1 (2.9%), FANCL (1.4%, 1/69), SDHB (1.4%) and TSC2 (1.4%). New or rare missense variants with unknown clinical significance (VUS), but defined as pathogenic in ClinVar or by algorithms assessing evolutionary conservation and deleterious structural changes at protein level, were found in single patients in the genes AIP, ANTXR1, APC, ATR, CD96, CYP21A2, ERCC3, ERCC6, FANCA, FANCB, FANCE, LIG4, LYST, MSH6, MSR1, MTAP, PDE11A, PDGFRA, PMS2, POLE, PTCH1, RAD50, RHBDF2, RUNX1 and WRN. These patients did not have pathogenic alleles, suggesting a potential contribution of these VUS to disease susceptibility. This work contributes to identify new susceptibility alleles that can predispose to hereditary breast cancer in the Mexican population. Further studies need to be conducted to define the clinical impact of the VUS identified here, which together with international efforts will better define genetic susceptibility to breast cancer. This work was supported by the National Autonomous University of Mexico, PAPIIT (IA204215). Citation Format: Felipe Vaca-Paniagua, Rosalía Quezada-Urban, Clara Estela Díaz-Velásquez, Rina Gitler, María Patricia Rojo-Castillo, Max Sirota-Toporek, Andrea Figueroa-Morales, Oscar Moreno-García, Fernando Mainero-Ratchelous, Lizzette Sabrina De Hoyos-Arévalo, Ivan Delgado-Enciso, Victor Hugo Garzón-Barrientos, Luis Ignacio Terrazas. Identification of germline pathogenic alleles in 143 cancer predisposing genes in Mexican patients with hereditary breast cancer by massive parallel sequencing. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2545.

Abstract P3-07-01: Family history of breast cancer in a population-based breast cancer cohort: No association with PAM50 intrinsic subtype or prognosis

Abstract Basal-like intrinsic subtype and poor prognosis are characteristic of breast cancers in BRCA1 families, but other genes also confer inherited predisposition to breast cancer, and subtype associations may differ. The objective of this study was to examine whether family history of breast cancer is associated with basal-like subtype and/or poor prognosis in a population-based sample of women with breast cancer. METHODS: The study population was the Life After Cancer Epidemiology (LACE) cohort, diagnosed with breast cancer in 1996-2000, and the Pathways cohort, diagnosed with breast cancer in 2006-2008. History of breast cancer among first-degree relatives was obtained by self-report at study enrollment, and women were followed for breast cancer recurrence and mortality. Primary breast cancer tissue was obtained for a case-cohort sample. Intrinsic subtypes were classified based on RT-PCR assay of 50 genes (PAM50). Sample-weighted subtype distributions were compared by family history. Hazard ratios (HR) for recurrence and mortality were estimated from Cox proportional hazards models. RESULTS: From 4,256 women in the parent cohorts who responded to the family history question, 20.5% reported a first-degree family history of breast cancer. Among women with family history, 80.6% were diagnosed at ages 50 and older, compared with 76.3% of women without family history, p = 0.007. Among cases with family history, 79.2% were non-Hispanic whites, compared with 72.3% of cases without family history, p < 0.001. Within the subcohort with PAM50 results (n = 1,319), cases with and without family history had 8.5% and 10.2% prevalence of basal-like tumors, respectively, p = 0.27. For cases diagnosed before age 50, the prevalences of basal-like subtype for women with and without family history were 18.6% and 15.9%, respectively, p = 0.62. Women with family history had similar recurrence risk to those without, HR 0.82 (95% CI 0.61, 1.11; age- and race-adjusted). Women with family history had a suggestive reduced risk of death from all causes, HR 0.75 (95% 0.55, 1.02). Family history was not significantly associated with recurrence or survival within any intrinsic subtype group. DISCUSSION: Although BRCA1 is known to predispose to basal-like subtype, we found no association between family history of breast cancer and basal-like subtype or worse prognosis in this population-based cohort. Mutation status for BRCA1 and other cancer susceptibility genes are unknown for cohort members. First-degree family history of breast cancer may represent the presence of one of the several inherited breast cancer susceptibility genes, or chance aggregation of sporadic cases. Particularly for a woman diagnosed at an older age, her mother and sisters would also have reached ages when sporadic breast cancer incidence is high. Among women diagnosed before age 50, family history was associated with a small and non-significant excess of basal-like tumors. Implications of this study are that for women from the general population diagnosed with breast cancer, a first-degree family history of breast cancer indicates neither a higher probability of a basal-like tumor nor worse prognosis. Support: NIH CA129059 and CA105274. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P3-07-01.

Intergenerational communication about inherited breast cancer susceptibility between mothers and their children

5 ISSN 1758-1923 10.2217/BMT.13.70 © 2014 Future Medicine Ltd Breast Cancer Manage. (2014) 3(1), 5–8 Family communication about high-risk hereditary breast cancer genetic testing (e.g., genetic testing for BRCA1/2 mutations) and maternal disclosure of cancer genetic test results to minor children is a complex decision and raises a number of parenting challenges. Genetic counseling can help mitigate some of these challenges by providing patients with educational resources. The development of family communication decision-support tools can further augment patients’ genetic counseling experience by creating a more shared and informed framework for understanding communication choices and outcomes. Given the field’s growing propensity to genetically test multiple generations of relatives within the same family over time, adequately meeting the needs of patients seeking to engage in intergenerational cancer risk communication with children is an important and emerging area of behavioral oncology research. The advent of BRCA1/2 genetic testing for hereditary breast cancer risk in the mid1990s was ushered in by rapid advances in genome science and biotechnology, making it possible to provide both men and women with tangible information about cancer risks and for them to be better informed about subsequent risk-reduction options. These test results could, in turn, be disseminated by patients to their relatives to share information about their potential risk for developing cancer as well. Today, decades later, familial genetic testing has cascaded into second and third generations within some families, as children and even grandchildren of the ‘genetic testing pioneers’ begin presenting for genetic testing themselves. Additionally, the absolute number of probands, or first family member to be tested, has increased as BRCA1/2 genetic testing has become a routine aspect of practice [101]. More recently, a household-name celebrity’s announcement of her choice to undergo prophylactic mastectomy based on a positive BRCA test result brought a surge of awareness to cancer genetic testing and its potentially life-changing implications for patients and their relatives [1]. Concurrently, expanded policy recommendations

Abstract CN05-02: Targeting the Fanconi anemia/BRCA pathway.

Abstract Cancer cells have genomic instability resulting from acquired defects in DNA repair. One DNA repair pathway, the Fanconi Anemia/BRCA homologous recombination pathway (Kennedy and D'Andrea, Genes & Development 19:2925, 2005), is defective in many human cancers, including breast, ovarian, pancreatic, and lung neoplasms. Disruption of the FA/BRCA Pathway results in the characteristic chromosome instability and radiation/crosslinker hypersensitivity of these tumors. In general, loss of one DNA repair pathway often leads to hyperdependence on another pathway for tumor cell survival. This hyperdependence offers a unique opportunity for the development of anticancer therapeutics. For instance, FA/BRCA pathway deficient tumors are hyperdependent on base excision repair (BER) and, accordingly, these tumors are hypersensitive to single agent treatment with PARP1 inhibitors which block BER. Our laboratory efforts are focused on profiling the FA/BRCA pathway and the other five major DNA repair pathways in tumor cells (Kennedy and D'Andrea, JCO 24: 3799, 2006). Each DNA repair pathway has a characteristic protein biomarker and repairs a specific type of DNA lesion. By profiling these pathways in primary tumor samples with activation-specific antibodies to DNA repair proteins, we are developing methods to: 1) predict the sensitivity of tumors to conventional chemotherapy and radiation (Personalized Medicine); 2) to subset tumors for their sensitivity to novel classes of DNA repair inhibitors (i.e., PARP1, Chk1, and ATM inhibitors); and 3) to screen for new small molecule inhibitors of other DNA repair pathways. This combination of novel DNA repair inhibitors, conventional DNA damaging agents, and DNA repair biomarkers offers new opportunities for developing more effective anticancer therapy. The FA/BRCA pathway was elucidated through the systematic study of the rare inherited chromosome breakage disorder, Fanconi Anemia (Moldovan and D'Andrea, Ann Rev Genet 43:223, 2009). FA is an autosomal recessive disease characterized by bone marrow failure, congenital malformations, and cellular sensitivity to cisplatin, mitomycin C, and other DNA interstrand crosslinking agents. Patients with FA develop hematopoietic malignancies and squamous cell carcinomas. Based on somatic cell fusion studies, there are sixteen FA complementation groups (A, B, C, D1, D2, E, F, G, I, J, L, M, N, O, P, Q), and the corresponding gene for each of these complementation groups has been identified. Interestingly, the sixteen FA proteins cooperate in a common cellular pathway in normal human cells, referred to as the Fanconi Anemia/BRCA pathway. Eight of the FA proteins (A, B, C, E, F, G, L, M) are assembled in a core complex (the FA core complex) which is an active ubiquitin E3 ligase. In response to DNA damage, the FA core complex modifies (monoubiquitinates) the downstream FANCD2 protein. Monoubiquitinated FANCD2 translocates to nuclear foci where it interacts with the FANCD1/BRCA2 protein and participates in the process of homologous recombination DNA repair. Additional FA proteins (namely, FANCJ/BRIP1 and FANCN/PALB2) function downstream of FANCD2 monoubiquitination. At least three of the FA genes (FANCD1, FANCJ, and FANCN) are inherited breast cancer susceptibility genes. Disruption of any step in the FA/BRCA pathway results in the common clinical and cellular phenotype of FA patients. Human tumor cells, derived from cancer patients from the general (non-FA) population, often exhibit genomic instability. Genomic instability of tumors has important clinical consequences. On the one hand, genomic instability gives the tumor the ability to break and fuse chromosomes, inactivate tumor suppressor genes, form novel oncogene fusions, and amplify drug resistance genes. Thus, the tumor with genomic instability may become more malignant and drug resistant over time. On the other hand, in order to achieve a state of genomic instability, a tumor cell must inactivate one of its major DNA repair pathways. This inactivation appears to account, at least in part, for the selective hypersensitivity of cancer cells to the cytotoxic effects of conventional anticancer radiation and chemotherapy. Recent studies indicate that some human tumors inactivate the FA/BRCA pathway. Pathway inactivation may result from somatic mutation of genes in the FA/BRCA pathway or by epigenetic silencing. For instance, methylation of one of the FA genes, FANCF, has been implicated as a mechanism for genomic instability in a wide variety of cancers, including ovarian, breast, lung, cervical, and head and neck squamous cell carcinomas. Somatic inactivation of the FA/BRCA pathway appears to account for the genomic instability and the cisplatin hypersensitivity of many of these cancers. In my presentation, I will review the features of the FA/BRCA pathway in human cells, and how knowledge of this pathway in cancers can lead to the prediction of drug response. Citation Information: Mol Cancer Ther 2013;12(11 Suppl):CN05-02. Citation Format: Alan D. D'Andrea. Targeting the Fanconi anemia/BRCA pathway. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr CN05-02.

Abstract SY11-01: Targeting the Fanconi anemia/BRCA pathway in cancer therapy

Abstract SY11-01: Targeting the Fanconi anemia/BRCA pathway in cancer therapy

Abstract CN05-02: Targeting the Fanconi anemia/BRCA pathway in cancer therapy.

Abstract CN05-02: Targeting the Fanconi anemia/BRCA pathway in cancer therapy.

Abstract IA9: Targeting the Fanconi anemia/BRCA pathway in cancer therapy

Abstract IA9: Targeting the Fanconi anemia/BRCA pathway in cancer therapy

Abstract SY28-01: Targeting DNA repair pathways in cancer therapy

Abstract SY28-01: Targeting DNA repair pathways in cancer therapy

Mutation screening of breast cancer susceptibility genes in Chinese high-risk families: the results will develop the genetic testing strategy in China

Inactivating mutations in 10 different genes in pathways critical to genomic integrity have been confirmed to be associated with inherited breast cancer in different ethnic groups [1]. We conducted a large-scale and systemic mutation analysis of BRCA1, BRCA2, p53, BRIP1, PALB2 and CHEK2 c.1100delC among 591 patients with early-onset (B35 years) breast cancer or affected relatives in China within 4 years, and the results contributed to the development of the genetic testing strategy in Chinese high-risk breast cancer families. All the included individuals were collected from six different medical centers located in southern and northern China, and were genetically independent ethnic Han Chinese. A total of 550 unrelated patients were analyzed for BRCA1 and BRCA2 mutations. The mutation frequency of BRCA1/2 in Chinese population was 9.45%, with 7.5% in early-onset and 13.4% in familial patients. When those patients with both early-onset breast cancer and affected relatives were concerned, the mutation frequency was up to 22.8%. We also observed that in patients with a family history of ovarian or gastric cancer, the incidence of BRCA1/2 mutation was about twice or more as that in patients without reporting the family history of these malignancies. The two recurrent BRCA1 mutations identified in our study, 1100delAT and 5589del8, accounted for 33.3% (8/24) of the deleterious mutations identified in BRCA1 gene, and haplotype analysis indicated that there might be some degree of shared ancestry for the two mutations in Chinese [2]. Among 240 non-BRCA1/2 patients without the phenotype of Li-Fraumeni syndrome (LFS) or Li-Fraumeni-like syndrome (LFL), we detected two novel germ line mutations (563T[C and 643_660del18) of p53, neither of which appeared in 768 normal controls. Functional assays revealed that they should be associated with the increasing risk of breast cancer [3]. PALB2 and BRIP1 have been recently identified as breast cancer susceptibility genes, which can colocalize with BRCA2 and BRCA1, respectively, at sites of DNA damage, and then contribute to their DNA repair function [1]. In our analysis, two truncating mutations of PALB2, 751C[T and 1050_1051delAAinsTCT, were identified in three independent patients with wild-type sequences at BRCA1 and BRCA2 (1% of the series), and that 751C[T was a recurrent mutation. We found that exon 4 accounted for 44.1% (15/34) of the person-times carrying any variant in PALB2 gene [4]. In BRIP1, we did not detect any protein-truncated mutation except a novel recurrent nonsynonymous variant (2971C[G, resulting in Q944E) [5]. Truncating allele 1100delC of CHEK2 has a frequency of 0.002-0.005 in northern Europe populations, but our results did not demonstrate the presence of CHEK2 c.1100delC among 114 studied patients [6]. At present, in view that much associated evidence in terms of the implications for breast cancer management in BRCA mutation carriers, current genetic testing still limits to BRCA genes, and there is growing evidence that BRCA mutation status may influence treatment recommendations [7]. Genetic testing for inherited breast cancer susceptibility has become a standard of care option for appropriately selected patients in the developed countries [8], while in China, little has been recognized. Recent trends show that A-Y. Cao Z. Hu Z.-M. Shao (&) Breast Cancer Institute, Cancer Hospital/Cancer Institute, Department of Oncology, Shanghai Medical College, Fudan University, 270 Dong’an Road, 200032 Shanghai, People’s Republic of China e-mail: zhimingshao@yahoo.com

Genomics and breast cancer: the different levels of inherited susceptibility

Our understanding of inherited breast cancer susceptibility has changed dramatically over the last 5 years, with the discovery of many genes in which mutations influence the risk of developing breast cancer. These fall into three main groups: genes in which mutations confer a high risk of developing cancer, but where such mutations are rare; uncommon mutations in genes conferring a moderate increase in risk (odds ratios of approximately 2–4), and common polymorphic variants which each confer only slight risk alterations (odds ratios rarely above 1.2 for variants conferring increased risk). The discovery of these genes and loci was predicated on linkage analysis (for high-risk genes), screening for mutations in candidate genes selected because they were involved in functional pathways related to BRCA1 and BRCA2 function (moderate risk), and genome-wide association studies (low penetrance polymorphisms). However, with this increased knowledge comes the difficulty of knowing how this information may best be utilized in clinical practice. The review by Ripperger et al1 in this edition of the Journal examines the current knowledge of newly identified moderate and low risk susceptibility genes, classifying the genes involved in inherited breast cancer susceptibility into the categories described above. The tables and diagrams are helpful in indicating the relative frequency and penetrance for breast cancer of genetic variants in these different categories, and give some indication of the proportion of the disease burden associated with mutations in each gene. The discovery of lower penetrance genes2 indicates that inherited breast cancer susceptibility is due to a number of genetic factors, and it may well be that the familial clusters of breast cancer not due to mutations in BRCA1 and BRCA2, originally attributed to BRCA3, are in fact due to a combination of the effects of lower penetrance gene mutations and environmental factors. Healthcare providers will have the dilemma of deciding whether it will be cost-effective to introduce population screening of variants of these low penetrance genes and what level of risk would justify medical intervention. Inheritance of one low penetrance risk-conferring polymorphic allele may only confer a very minor increase in risk of developing cancer, but individuals who have inherited several high-risk polymorphic variants may be at significantly increased risk. It has recently been argued, for instance,3 that individuals who have, say, six ‘high'-risk alleles, may have a sufficiently increased risk to justify initiating mammographic surveillance 10 years before the generally recommended age for women in the general population, and women with six low risk alleles could start screening at a later age.

Nijmegen Breakage Syndrome mutations and risk of breast cancer

Mutations in the NBS1 gene have been identified as disease-causing mutations in patients with Nijmegen Breakage Syndrome (NBS), but their clinical impact on breast cancer susceptibility has remained uncertain. We determined the frequency of 2 NBS mutations, 657del5 and R215W, in two large series of breast cancer cases and controls from Northern Germany and from the Republic of Belarus. The 5-bp-deletion 657del5 was identified in 15/1,588 cases (0.9%) from Belarus and in 1/1,076 cases (0.1%) from Germany but in only 1/1,014 population controls from Belarus and 0/1017 German controls (p < 0.01). The missense substitution R215W was observed in 9/1,588 Byelorussian and 9/1,076 German patients (0.6% and 0.8%, respectively) but was also present in 5/1,014 Byelorussian and 2/1,017 German control individuals (adjusted OR = 1.9, 95%CI 0.8-4.6, p = 0.18). Studies of lymphoblastoid cell lines revealed that NBS1/p95 protein levels were reduced to 70% in cells from a heterozygous breast cancer patient carrying R215W and to 15% in cells from a NBS patient compound heterozygous for 657del5/R215W suggesting that the R215W substitution may be associated with protein instability. Levels of radiation-induced phosphorylation of Nbs1/p95(Ser343) were reduced to 60% and 35% of wildtype, respectively. Neither age at diagnosis nor family history of breast cancer differed significantly between carriers and noncarriers of NBS mutations. The combined data are in line with an about 3-fold increase in breast cancer risk for female NBS heterozygotes (OR 3.1; 95%CI 1.4-6.6) and indicate that the 657del5 deletion and perhaps the R215W substitution contribute to inherited breast cancer susceptibility in Central and Eastern Europe.

The CHEK2 gene and inherited breast cancer susceptibility

Checkpoint kinase 2 (CHEK2, Chk2) emerges as an important signal transducer of cellular responses to DNA damage and a candidate tumor suppressor whose defects contribute to molecular pathogenesis of diverse types of human malignancies, both sporadic and hereditary. Here, we briefly outline the molecular properties, regulation and physiological role of CHEK2, and review in more detail its defects that predispose to tumors, with particular emphasis on familial breast cancer. The frequency, penetrance and epidemiological as well as clinical significance of the two most studied breast cancer-predisposing variants of the CHEK2 gene, 1100delC and I157T, are highlighted in more depth, and additional CHEK2 mutations and their cancer relevance are discussed as well. These recent findings are considered also from a broader perspective of CHEK2 as the integral component of the ataxia telangiectasia-mutated-CHEK2-p53 pathway within the genome integrity maintenance system and a barrier against tumor progression. Finally, the potential value of information about the CHEK2 status in family counseling and optimizition of individualized cancer treatment is discussed.

Association of two mutations in the CHEK2 gene with breast cancer

The 1100delC mutation of the cell cycle checkpoint kinase 2 (CHEK2) gene confers an increased risk for breast cancer, but the clinical impact of other CHEK2 gene variants remains unclear. We determined the frequency of two functionally relevant CHEK2 gene mutations, I157T and IVS2+1G > A, in two large series of breast cancer cases and controls from two independent populations. Our first series consisted of a hospital-based cohort of 996 German breast cancer cases and 486 population controls, and the second series consisted of 424 breast cancer patients and 307 population controls from the Republic of Belarus. The missense substitution I157T was identified in 22/996 cases (2.2%) vs. 3/486 controls (0.6%; OR = 3.6, 95% CI 1.1-12.2, p = 0.044) in the German population and in 24/424 cases (5.7%) vs. 4/307 controls (1.3%; OR = 4.5, 95% CI 1.6-13.2, p = 0.005) in the Byelorussian cohorts. The splicing mutation IVS2+1G > A was infrequent in both populations, being observed in 3/996 German and 4/424 Byelorussian patients (0.3% and 0.9%, respectively) and in 1/486 German controls (0.2%; adjusted OR = 4.0, 95% CI 0.5-30.8, p = 0.273). Heterozygous CHEK2 mutation carriers tended to be diagnosed at an earlier age in both populations, but these differences did not reach statistical significance. Family history of breast cancer did not differ between carriers and noncarriers. Our data indicate that the I157T allele, and possibly the IVS2+1G > A allele, of the CHEK2 gene contribute to inherited breast cancer susceptibility.

Family history and treatment outcome in young women after breast-conserving surgery and radiation therapy for early-stage breast cancer.

To evaluate the safety and efficacy of breast-conserving therapy for young women with a family history (FH) suggestive of inherited breast cancer susceptibility. A total of 201 patients aged 36 or younger at diagnosis treated with breast-conserving surgery and radiation therapy (> or = 60 Gy) for early-stage breast cancer were categorized by FH. FH was considered positive in 29 patients who, at the time of diagnosis, had a mother or sister previously diagnosed with breast cancer before age 50 or ovarian cancer at any age. Clinical, pathologic, and demographic variables; sites of first failure; disease-free survival; and overall survival (OS) were compared between FH-positive and -negative groups. Median follow-up time was 11 years. Patient and tumor features were similar between those with and without an FH. Regression analysis of sites of first failure at 5 years demonstrated a risk ratio (RR) of 5.7 for opposite breast cancer for FH-positive patients. Rates of local, regional, and distant failure and disease-free survival or OS did not differ between FH-positive and -negative patients. Age at diagnosis and Ashkenazi heritage were not significantly predictors of patterns of failure. Breast-conserving surgery combined with radiation therapy is not associated with a higher rate of local recurrence, distant failure, or second (non-breast) cancers in young women with an FH suggestive of inherited breast cancer susceptibility compared with young women without an FH. However, their increased risk of opposite breast cancer should be taken into account when considering breast conservation as a treatment option.

Cloning, chromosomal mapping and expression pattern of the mouse Brca2 gene.

A proportion of human breast cancers result from an inherited predisposition to the disease. Mutations in the BRCA2 gene confer a high risk of breast cancer and are responsible for almost half of these cases. The recent cloning of the human BRCA2 gene has revealed that it encodes a large protein having little significant homology to known proteins. Here we describe the mouse Brca2 gene. The gene maps to mouse chromosome 5, consistent with its location on human chromosome 13q12. We have sequenced cDNA for the entire 3329 amino acid Brca2 protein and this has revealed that, like Brca1, Brca2 is relatively poorly conserved between humans and mice. Brca2 is transcribed in a diverse range of mouse tissues, and the pattern of expression is strikingly similar to that of Brca1. Taken together, our data highlight some intriguing similarities between two genes involved in inherited breast cancer susceptibility.