Multiple-case Breast Cancer Families Research Articles

Exome sequencing identifies RASSF1 and KLK3 germline variants in an Iranian multiple-case breast cancer family

Breast cancer is the most frequent malignancy among women in both developed and developing countries. Although several genes have been identified to harbor germline variants contributing to breast cancer risk, much of the heritability for breast cancer is yet undefined. In the present study, we have performed exome sequencing to detect susceptibility genes in an Iranian family with five first-degree family members affected with breast cancer. We identified novel candidate variants with predicted pathogenicity in RASSF1, KLK3 and FAM81B. The RASSF1 and KLK3 variants, but not the FAM81B variant, partially co-segregated with disease in the investigated pedigree and were not found in additional screenings outside the specific family. RASSF1 p.S135F is a missense substitution abolishing the ATM phosphorylation site, and KLK3 variant p.M1? is a deletion at the initiation codon that is predicted to abolish translation to the functional kallikrein protease, PSA. Our study suggests germline variation in RASSF1 and KLK3 as potential candidate contributors to familial breast cancer predisposition and illustrates the difficulties to determine the causal genetic risk factor among novel variants restricted to a single family.

Current gene panels account for nearly all homologous recombination repair-associated multiple-case breast cancer families

It was hypothesized that variants in underexplored homologous recombination repair (HR) genes could explain unsolved multiple-case breast cancer (BC) families. We investigated HR deficiency (HRD)-associated mutational signatures and second hits in tumor DNA from familial BC cases. No candidates genes were associated with HRD in 38 probands previously tested negative with gene panels. We conclude it is unlikely that unknown HRD-associated genes explain a large fraction of unsolved familial BC.

VTRNA2-1: Genetic Variation, Heritable Methylation and Disease Association.

VTRNA2-1 is a metastable epiallele with accumulating evidence that methylation at this region is heritable, modifiable and associated with disease including risk and progression of cancer. This study investigated the influence of genetic variation and other factors such as age and adult lifestyle on blood DNA methylation in this region. We first sequenced the VTRNA2-1 gene region in multiple-case breast cancer families in which VTRNA2-1 methylation was identified as heritable and associated with breast cancer risk. Methylation quantitative trait loci (mQTL) were investigated using a prospective cohort study (4500 participants with genotyping and methylation data). The cis-mQTL analysis (334 variants ± 50 kb of the most heritable CpG site) identified 43 variants associated with VTRNA2-1 methylation (p < 1.5 × 10−4); however, these explained little of the methylation variation (R2 < 0.5% for each of these variants). No genetic variants elsewhere in the genome were found to strongly influence VTRNA2-1 methylation. SNP-based heritability estimates were consistent with the mQTL findings (h2 = 0, 95%CI: −0.14 to 0.14). We found no evidence that age, sex, country of birth, smoking, body mass index, alcohol consumption or diet influenced blood DNA methylation at VTRNA2-1. Genetic factors and adult lifestyle play a minimal role in explaining methylation variability at the heritable VTRNA2-1 cluster.

Abstract 3314: Heritable methylation marks associated with prostate and breast cancer risk

Abstract While most epigenetic marks are reprogrammed during early embryogenesis, some studies have reported Mendelian-like inheritance of germline DNA methylation in particular in cancer susceptibility genes. For instance, individuals with MLH1 silenced throughout the soma fit the clinical criteria for hereditary nonpolyposis colorectal cancer that is indistinguishable from the syndrome resulting from germline mutations in MLH1. Research using multiple-case breast cancer families has shown that LINE-1 and Sat2 DNA methylation levels are lower in individuals with a strong family history. Family clustering of cancer could therefore be due to epigenetic as well as genetic and shared environmental factors. We have recently identified heritable methylation marks associated with breast and/or prostate cancer susceptibility by conducting a study involving 45 Australian multi-generational families with multiple cases of breast or prostate cancer who are not known to carry genetic mutations in cancer susceptibility genes. We developed and applied a new statistical method to identify heritable methylation marks based on complex segregation analysis and identified 24 and 41 methylation marks significantly associated with breast and prostate cancer risk respectively. Several marks across VTRNA2-1, a gene located in a differentially methylated region that is involved in imprinting and shows allele-specific methylation, were associated with heritable risk of both cancer types. A proportion of all identified marks were found to be associated with cancer risk in independent nested case-control studies (ie outside of the multiple-case family setting). We are expanding these successful studies to include additional families and to estimate HRs and age-specific cumulative risks of cancer associated with these marks to enable the incorporation of this information into clinical tools for risk prediction. Citation Format: Melissa C. Southey, Jihoon E. Joo, James G. Dowty, Roger L. Milne, EE Ming Wong, Pierre-Antoine Dugué, Dallas English, John L. Hopper, David E. Goldgar, Graham G. Giles. Heritable methylation marks associated with prostate and breast cancer risk [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3314.

Heritable DNA methylation marks associated with susceptibility to breast cancer

Mendelian-like inheritance of germline DNA methylation in cancer susceptibility genes has been previously reported. We aimed to scan the genome for heritable methylation marks associated with breast cancer susceptibility by studying 25 Australian multiple-case breast cancer families. Here we report genome-wide DNA methylation measured in 210 peripheral blood DNA samples provided by family members using the Infinium HumanMethylation450. We develop and apply a new statistical method to identify heritable methylation marks based on complex segregation analysis. We estimate carrier probabilities for the 1000 most heritable methylation marks based on family structure, and we use Cox proportional hazards survival analysis to identify 24 methylation marks with corresponding carrier probabilities significantly associated with breast cancer. We replicate an association with breast cancer risk for four of the 24 marks using an independent nested case–control study. Here, we report a novel approach for identifying heritable DNA methylation marks associated with breast cancer risk.

Targeted massively parallel sequencing of a panel of putative breast cancer susceptibility genes in a large cohort of multiple-case breast and ovarian cancer families

IntroductionGene panel testing for breast cancer susceptibility has become relatively cheap and accessible. However, the breast cancer risks associated with mutations in many genes included in these panels are unknown.MethodsWe...

Rare mutations in RINT1 predispose carriers to breast and Lynch syndrome-spectrum cancers.

Approximately half of the familial aggregation of breast cancer remains unexplained. A multiple-case breast cancer family exome-sequencing study identified three likely pathogenic mutations in RINT1 (NM_021930.4) not present in public sequencing databases: RINT1 c.343C>T (p.Q115X), c.1132_1134del (p.M378del), and c.1207G>T (p.D403Y). On the basis of this finding, a population-based case-control mutation-screening study was conducted that identified 29 carriers of rare (minor allele frequency < 0.5%), likely pathogenic variants: 23 in 1,313 early-onset breast cancer cases and six in 1,123 frequency-matched controls [OR, 3.24; 95% confidence interval (CI), 1.29-8.17; P = 0.013]. RINT1 mutation screening of probands from 798 multiple-case breast cancer families identified four additional carriers of rare genetic variants. Analysis of the incidence of first primary cancers in families of women carrying RINT1 mutations estimated that carriers were at increased risk of Lynch syndrome-spectrum cancers [standardized incidence ratio (SIR), 3.35; 95% CI, 1.7-6.0; P = 0.005], particularly for relatives diagnosed with cancer under the age of 60 years (SIR, 10.9; 95% CI, 4.7-21; P = 0.0003). The work described in this study adds RINT1 to the growing list of genes in which rare sequence variants are associated with intermediate levels of breast cancer risk. Given that RINT1 is also associated with a spectrum of cancers with mismatch repair defects, these findings have clinical applications and raise interesting biological questions.

Molecular Characterization and Cancer Risk Associated with BRCA1 and BRCA2 Splice Site Variants Identified in Multiple-Case Breast Cancer Families

The original article to which this Erratum refers was published in Human Mutation 26:495 (DOI 10.1002/humu.9379). The authors discovered an error in their interpretation of one of the BRCA1 c.5277+1G>A (IVS20+1G>A) variant transcripts in their published article, in that they originally reported this variant to result in an out of frame inclusion of 85 bp of intron 20 leading to a premature stop codon. However, they were recently alerted to the fact that this is a miss count of the bps involved in the inclusion; the inclusion is actually 87 bp and the inclusion is inframe. The authors regret this error.

Preventing breast and ovarian cancers in high‐risk BRCA1 and BRCA2 mutation carriers

To estimate the prevalence of the use of cancer risk-reducing measures among Australian BRCA1 and BRCA2 mutation carriers. Prospective follow-up of female carriers of BRCA1 or BRCA2 mutations who had no personal history of cancer and were enrolled in a multiple-case breast cancer family cohort study (kConFab). Data, including cancer events and uptake of risk-reducing surgery and medication were collected by self-report at cohort entry and 3 yearly thereafter. Surgery was confirmed from pathology and medical records. Women were followed up from enrolment until cancer diagnosis, date of last follow-up, or death. Data were collected from 3 November 1997 to 21 May 2012. Uptake of risk-reducing surgery and/or medication. Of 175 BRCA1 and 150 BRCA2 mutation carriers (median age, 37 years at cohort enrolment), 69 (21%) underwent risk-reducing mastectomy, 125 (38%) underwent risk-reducing bilateral salpingo-oophorectomy and nine (3%) participated in a clinical trial of risk-reducing medication, during 2447 person-years of follow-up (median follow-up, 9 years). Sixty-eight women (21%) reported incident cancers, including 52 breast cancers and nine ovarian cancers (defined in this article as high-grade serous cancers of the ovary, fallopian tube or peritoneum). There is considerable scope to increase the uptake of cancer risk-reducing measures in Australian BRCA1 and BRCA2 mutation carriers. These findings should drive (i) future research into the factors contributing to low uptake in Australia and (ii) changes to policy and practice to help better translate genetic knowledge into reductions in cancer incidence.

Prevalence of PALB2 mutations in Australasian multiple-case breast cancer families

IntroductionPopulation-based studies of breast cancer have estimated that some PALB2 mutations confer a breast cancer risk (penetrance) comparable to the average pathogenic mutation in BRCA2. As this risk is of clinical relevance, we sought to identify mono-allelic PALB2 mutations and determine their frequencies in multiple-case breast cancer families attending Familial Cancer Clinics in Australia and New Zealand.MethodsThe youngest affected woman, not known to carry a mutation in BRCA1 or BRCA2, from 747 multiple-case breast cancer families participating in kConFab were selected for PALB2 mutation screening. The coding and flanking intronic regions of PALB2 in DNA extracted from blood were screened using high-resolution melt curve analysis with Sanger sequencing confirmation. Where possible, relatives of women found to carry PALB2 mutations were genotyped for the family-specific mutation, mutant transcripts were characterised and breast tumours arising in mutation carriers were recalled and reviewed. Missense mutations were assessed for potential to disrupt protein function via SIFT, Align GVGD and Polyphen-2.ResultsThe mutation screen identified two nonsense mutations (PALB2 c.3113G>A in eight women and PALB2 c.196C>T in one woman), two frameshift mutations (PALB2 c.1947_1948insA and PALB2 c.2982_2983insT each in one woman), 10 missense variants, eight synonymous variants and four variants in intronic regions. Of the four PALB2 mutations identified that were predicted to produce truncated protein products, only PALB2 c.1947_1948insA had not previously been reported. PALB2 c.3113G>A and PALB2 c.196C>T were previously identified in the Australian population whereas PALB2 c.2982_2983insT was previously reported in the UK population. Transcripts derived from three of these mutant PALB2 alleles were vulnerable to nonsense-mediated decay. One missense mutation (PALB2 c.2993G>A) was predicted to disrupt protein function via the three in silico assessment methods applied. The majority of breast cancers arising in carriers that were available for review were high-grade invasive ductal carcinomas. Conclusions: About 1.5% (95% CI 0.6to 2.4) of Australasian multiple-case breast cancer families attending clinics are segregating protein-truncating mutations in PALB2, most being PALB2 c.3113G>A, p.Trp1038*. Given the prevalence, breast cancer risk, and tumour grade associated with this mutation, consideration of clinical PALB2 testing is warranted.

Low prevalence of SLX4 loss-of-function mutations in non-BRCA1/2 breast and/or ovarian cancer families

Fanconi anemia is a genetically heterogeneous autosomal recessive disorder characterized by development abnormalities, bone marrow failure, and childhood cancers. Compelling evidence indicates a common genetic basis for FA and breast/ovarian cancer susceptibility. Recently, biallelic germ-line mutations in SLX4 have been demonstrated to cause a previously unknown FA subtype (FA-P). We address the role of SLX4/FANCP in breast/ovarian cancer susceptibility by conducting a comprehensive mutation scanning in 486 index cases from non-BRCA1/BRCA2 multiple-case breast and/or ovarian cancer families (non-BRCA1/2 families) from Spain. We detected one unequivocal loss-of-function mutation (p.Glu1517X). In addition, one missense change (p.Arg372Trp) predicted to be pathogenic by in silico analysis co-segregates with disease in one family. Overall, the study indicates that SLX4 mutation screening will have a very low impact (if any) in the genetic counseling of non-BRCA1/2 families.

Psychosocial factors and uptake of risk-reducing salpingo-oophorectomy in women at high risk for ovarian cancer

Bilateral risk-reducing salpingo-oophorectomy (RRSO) has been shown to significantly reduce the risk of ovarian cancer. This study assessed factors predicting uptake of RRSO. Women participating in a large multiple-case breast cancer family cohort study who were at increased risk for ovarian and fallopian tube cancer (i.e. BRCA1 or BRCA2 mutation carrier or family history including at least one first- or second-degree relative with ovarian or fallopian tube cancer), with no personal history of cancer and with at least one ovary in situ at cohort enrolment, were eligible for this study. Women who knew they did not carry the BRCA1 or BRCA2 mutation segregating in their family (true negatives) were excluded. Sociodemographic, biological and psychosocial factors, including cancer-specific anxiety, perceived ovarian cancer risk, optimism and social support, were assessed using self-administered questionnaires and interviews at cohort enrolment. RRSO uptake was self-reported every three years during systematic follow-up. Of 2,859 women, 571 were eligible. Mean age was 43.3 years; 62 women (10.9 %) had RRSO a median of two years after cohort entry. Factors predicting RRSO were: being parous (OR 3.3, p = 0.015); knowing one's mutation positive status (OR 2.9, p < 0.001) and having a mother and/or sister who died from ovarian cancer (OR 2.5, p = 0.013). Psychological variables measured at cohort entry were not associated with RRSO. These results suggest that women at high risk for ovarian cancer make decisions about RRSO based on risk and individual socio-demographic characteristics, rather than in response to psychological factors such as anxiety.

Abstract LB-441: Mutation in SLX4 gen in a multiple case breast cancer family

Abstract Fanconi Anemia (FA) is a genetically heterogeneous, rare autosomal recessive disorder characterized by development abnormalities, bone marrow failure, and childhood cancers. Over the past few years, a common genetic basis for FA and breast and/or ovarian cancer susceptibility has been uncovered. In particular, BRCA2 (FANCD1), BRIP1 (also known as BACH1 and FANCJ), PALB2 (FANCN), and RAD51C germ-line mutations have been found to lead both to FA (when biallelic) and to increased breast and/or ovarian cancer risk (when monoallelic). Recently, two studies demonstrated that biallelic germ-line mutations in SLX4, which encodes an endonuclease, cause a previously unknown FA subtype (FA-P). Therefore, SLX4 should be considered a bona fide candidate gene for breast cancer susceptibility, as suggested in both studies. We have screened 347 non-BRCA1/BRCA2 index cases from multiple case breast and/or ovarian cancer families for point mutations in the SLX4 gene. The whole coding sequence and flanking intronic regions were analyzed using High Resolution Melting (HRM) analysis followed by direct sequencing of abnormal melting curve samples. An SLX4 missense change in c.1114C&amp;gt;T (p.Arg372Trp) was detected in a family with four cases of breast cancer in two generations. This mutation segregates with disease within the family and is not present in the dbSNP (build 34). Polyphen-2 and SIFT in silico analysis tools predict a deleterious effect on protein structure and multiple alignment within orthologous proteins suggests a high degree of conservation. Previous studies in FA patients have identified two different splicing mutations (c.1163+2T&amp;gt;A and c.1163+3dupT) that cause in frame exon 5 skipping. The resulting protein (p.Arg317_Phe387del) lacks two repeated UBZ4 domains known to interact with other endonucleases, mismatch repair proteins, and ubiquitin. It has been suggested that UBZ4 may be involved in targeting SLX4 to sites of DNA damage by binding to ubiquitinated proteins. The missense change we have found introduces a highly hydrophobic amino acid within the same region, which could affect the folding of the UBZ4 domain or disrupt a specific protein-protein interaction. Our study supports a role for SLX4 in breast cancer susceptibility. Further studies performed in larger cohorts will be necessary to determine the prevalence of SLX4 mutations among breast cancer risk factors. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr LB-441. doi:1538-7445.AM2012-LB-441

Expanded genetic analysis of a PALB2 c.3113G&gt;A mutation carrying multiple-case breast cancer family via exome sequencing

PALB2 is a breast cancer (BC) susceptibility gene. Its product is the binding partner of BRCA1 and BRCA2 and is involved in DNA repair. Studies of multiple-case BC families have reported that truncating mono-allelic PALB2 mutations, on average, increase BC risk two to six fold. Our recent population-based study estimated that carriers of PALB2 c.3113G>A had a cumulative BC risk of carrying PALB2 c.3113G>A to be 91% (95%CI=41-100) by age 70, comparable to 65% (95%CI=44-78) and 45% (95%CI=31-56) average risk estimates for BRCA1 and BRCA2 mutation carriers respectively. One of these pedigrees used for the above estimation, extensively screened but not found to carry a BRCA1 or BRCA2 mutation, exhibited ten diagnoses of BC, including five under 50 years of age, and a pedigree structure that does not allow for all cases to be explained by a single genetic factor. In view of such a high risk estimate and the observations of BC in non-PALB2 mutation carriers in this and other pedigrees, we hypothesise that there may be other genetic risk factors segregating through this family. Several genetic modifiers of BC risk have been verified in BRCA1 and BRCA2 mutation carriers. Although these genetic modifiers are associated with small changes in risk individually, collectively they may account for considerable risk modification for some women. Other moderate to highly penetrant genetic factors could also influence risk in BRCA1 and BRCA2 mutation carriers and non-carriers in BC families harbouring such genetic variants. Similarly, the presence of other genetic factors in the subject PALB2 c.3113G>A pedigree of this study, could alter the risk for mutation carriers and/or convey BC risk to non-PALB2 mutation carriers. Such additional factors could further explain the multiple cases of early onset BC and the high estimated risk of PALB2 c.3113G>A in this family. Whole exome capture followed by massively parallel sequencing was performed on four strategically selected affected females of this family. We have shortlisted 15 variants in this family predicted to be protein damaging by SIFT in genes with plausible relevance to cancer aetiology. Eight such variants are predicted to result in protein truncation or are variants predicted to have strong effects on splicing efficiency, one of which have been observed in key DNA repair genes. Six of the genes have roles in DNA repair, three in cell cycle checkpoint regulation, one controls telomerase activity and another has been reported to be a prostate cancer predisposition gene. Further analyses of these candidate BC predisposition genes will be presented.

Searching for BRCA3 by exome sequencing

The current paradigm suggests that some non-BRCA1/2 multiple case breast cancer families are caused by rare mutations in high-risk genes. We are using exome sequencing to identify putative ‘BRCA3’ genes in a small number of kConFab families. We selected five non-BRCA1/2 families containing 5-9 breast cancer cases (of which 0-4 per family were affected under the age of 40) who have had extensive analysis of BRCA1 and BRCA2, and for which germline DNA was available from two distant relatives (at least 4th degree) affected with breast cancer between 30 and 56 years of age. In first stage we isolated the exomes of two pairs of affected individuals (4th and 5th degree relatives, from two families) diagnosed with breast cancer between the age of 30 and 39, using the SeqCap EZ exome capture kit (NimbleGen) and then sequenced the libraries on the GAIIx and HiSeq (Illumina) platforms with a paired-end protocol. The sequences were aligned to the human genome with BWA and we then compared several pipelines for processing the sequences and calling variants. The best results were obtained with the Picard/GATK pipeline after local re-alignment and re-calibration of the base quality. The samples from the remaining three families will be sequenced by Axeq Inc. and the results of the analysis will be presented.

Identification of new breast cancer predisposition genes via whole exome sequencing

The application of massively parallel sequencing (MPS) platforms has begun to revolutionize our understanding of the immense variation in the human genome and the complexity that can underlie genetic susceptibility to disease. The utility of exome capture MPS through the identification of genes for rare Mendelian disorders based on analysis of only a few individuals has been eloquently demonstrated. Common diseases such as breast cancer present substantially increased complexity in terms of locus, allelic and phenotypic heterogeneity, as well as complex relationships between genotype and phenotype (reduced penetrance, phenocopies etc.). With careful consideration of study design [1], thoughtful selection of families from our international resources (whole exome sequencing of two highly selected affected members of multiple-case breast cancer families), and a well-developed strategy (analytical pipeline) for distinguishing the few true breast cancer susceptibility genes from the many genes that have rare genetic variants that could plausibly alter protein function, we are advancing a large program of work aimed at identifying the majority of the “missing heritability” of breast cancer. Our early findings demonstrate that: 1) despite very plausible biological roles, some genetic variants in some genes predicted to be damaging by SIFT and Polyphen2 do not appear to be associated with breast cancer risk [2]. 2) application of our strategy can identify new breast cancer susceptibility genes. During the early conduct of this program, we identified a family with a protein truncating mutation in a gene involved in DNA repair. Follow-up has included mutation screening of: a) youngest affected members of 250 multiple-case breast cancer families, b) cases and controls participating in Australian population-based studies of breast cancer (ABCFS and MCCS) c) cases and controls in an international population-based case-control-family resource (BCFR) To date, these analyses have identified 6 families with frameshift or evolutionarily unlikely missense mutations in this gene. Features of these families include multiple-cases of early-onset female breast cancer with some potentially other interesting features such as early-onset male breast cancer and pancreatic cancer. These mutations have not been found in approximately 3000 unaffected population-based controls without a family history of breast cancer. We are continuing to expand our dataset to include the exome sequences of further families and coordinating the follow-up of candidate genes using appropriate MPS platforms and as founding partners of a newly formed international consortium of breast cancer exome sequencing researchers.

Early exploration of two candidate breast cancer susceptibility genes identified by whole-exome sequencing

Breast cancer (BC) is the most frequently diagnosed cancer in women around the world, and an estimated15-20% of BC cases present with a family history of disease. Genetic variants in known susceptibility genes explain a relatively small proportion of the heritable risk for BC. Genetic variants have been broadly classified into three categories with different levels of risk and prevalence: rare mutations in high-risk genes (e.g. BRCA1, BRCA2); rare mutations in intermediate-risk genes (e.g. CHEK2); and common very modest-risk genetic variants (identified throughout the genome). These categories currently account for 20%, 5% and ~15% of the familial risk, respectively, leaving about 60% of the familial BC risk to be determined. We have conducted whole-exome capture followed by massive parallel sequencing (XC-MPS)-based analysis on greater than third degree affected relatives from highly selected multiple-case BC families (at least four cases of invasive breast cancer diagnosed before 50 years) which had previously been screened and found not to carry identifiable BRCA1 or BRCA2 mutations. In this presentation, we focus on two candidate BC susceptibility genes identified by this analysis, each playing a key-role in DNA repair. In both cases, one individual from the pair of cousins was found to carry a predicted protein damaging genetic variant at a consensus splice site. The variants were confirmed and extended analysis within the respective pedigrees performed by Sanger sequencing, subject to DNA sample availability. Further characterization of these variants is being pursued by much larger scale case-control genotyping using the TaqMan platform. Our work further illustrates the complexities of human genetic variation and the technical and analytical challenges of identifying variation that is associated with inherited predisposition to complex diseases such as breast cancer.

Mutation analysis of RAD51L1 (RAD51B/REC2) in multiple-case, non-BRCA1/2 breast cancer families

Although a significant proportion of familial aggregation of breast cancer remains unexplained, many of the currently known breast cancer susceptibility genes, including BRCA1, BRCA2 and TP53, play a role in maintaining genome integrity by engaging in DNA repair. RAD51L1 is one of the five RAD51 paralogs involved in homologous recombination (HR) repair of DNA double-strand breaks (DSBs); it also interacts directly with p53. Deleterious mutations have been found in one RAD51 paralog, RAD51C (RAD51L2), in non-BRCA1/2 breast and ovarian cancer families, which suggests that all five paralogs are strong candidate breast cancer susceptibility genes. A genome-wide association study (GWAS) has already identified a single nucleotide polymorphism (SNP) deep within intron 10 of RAD51L1 as a risk locus for breast cancer. Based on its biological functions and association with RAD51C, there is reason to suggest that RAD51L1 (RAD51B/REC2) may also contain high risk mutations in the gene that give rise to multiple-case breast cancer families. In order to investigate this hypothesis, we have used high resolution melt (HRM) analysis to screen RAD51L1 for germline mutations in 188 non-BRCA1/2 multiple-case breast cancer families and 190 controls. We identified a total of seven variants: one synonymous, three intronic, and three previously identified SNPs, but no truncating or nonsense changes. Therefore, our results suggest that RAD51L1 is unlikely to represent a high-penetrance breast cancer susceptibility gene.

Familial concordance of breast cancer pathology as an indicator of genotype in multiple-case families

The heterogeneity of multiple case breast cancer families that do not carry mutations in BRCA1 or BRCA2 (non-BRCA1/2 families) poses a challenge to the identification of breast cancer susceptibility genes. The aim of this study was to determine whether intrafamilial concordance in breast cancer pathology could identify subgroups of non-BRCA1/2 families with consistent genotypic features. Invasive breast cancers were reviewed from 84 individuals belonging to 30 multiple-case families; BRCA1 (n = 9), BRCA2 (n = 10), and non-BRCA1/2 (n = 11). Hierarchical cluster analysis based on histopathology and age at first diagnosis was then used to specify three subgroups designated Clusters 1-3. The genomic features of non-BRCA1/2 families were examined by genome wide linkage and FGFR2 SNP genotyping, according to whether they showed cluster-concordant or cluster-mixed familial pathology. The majority of pathogenic BRCA1 mutation carriers (80%) fell into a single cluster. In contrast pathogenic BRCA2 mutation carriers were distributed across all three clusters and within families, cluster groups were also generally mixed. Most non-BRCA1/2 mutation carriers belonged to Cluster 3 (71%). Genome wide linkage data from five non-BRCA1/2 Cluster 3-concordant families were compared with four mixed cluster non-BRCA1/2 families. This revealed a number of distinct linkage peaks, including some regions previously associated with breast cancer susceptibility. The distribution of low risk alleles in FGFR2 was not different between these two subgroups (P = 0.237). The pattern of breast cancer pathology concordance amongst family members may assist the investigation of breast cancer susceptibility in multiple case families.

Predictors of breast cancer screening behavior in women with a strong family history of the disease

This study applied the self-regulation model to examine cognitive and emotional predictors of screening in unaffected women with a strong family history of breast cancer. 748 unaffected female members of an Australian registry of multiple-case breast cancer families formed the sample. Participants completed a baseline psychosocial questionnaire and a screening questionnaire 3 years later. Multinomial logistic regression was employed to determine predictors of under- and over-screening according to national guidelines. At follow-up 16% of women under-screened and 10% over-screened with mammography; 55% under-screened with clinical breast examination (CBE); and 9% over-screened with breast self-examination (BSE). Of the women found screening according to guidelines for mammography 72% reported ever having received specific recommendations for mammography screening from a health professional. Compared to appropriate screeners, under-screeners on mammography were less likely to have received a screening recommendation (as were under-screeners on CBE), were younger and reported lower perceived breast cancer risk, but were at higher relative risk (RR) of breast cancer and were more likely to report elevated depression. Over-screeners on mammography were more likely to be younger and have a lower RR of breast cancer. Over-screeners on BSE reported elevated cancer-specific anxiety, were less likely to be university educated and more likely to have received a recommendation for BSE. Under- and over-screening is common in women with a strong family history of breast cancer. Evaluation of interventions targeting perceived risk of breast cancer, anxiety and depression are needed to ensure women obtain accurate advice from relevant specialists and enact screening recommendations.