Familial breast cancer and DNA repair genes: Insights into known and novel susceptibility genes from the GENESIS study, and implications for multigene panel testing

Pathogenic variants in BRCA1 and BRCA2 only explain the underlying genetic cause of about 10% of hereditary breast and ovarian cancer families. Because of cost‐effectiveness, multigene panel testing is often performed even if the clinical utility of testing most of the genes remains questionable. The purpose of our study was to assess the contribution of rare, deleterious‐predicted variants in DNA repair genes in familial breast cancer (BC) in a well‐characterized and homogeneous population. We analyzed 113 DNA repair genes selected from either an exome sequencing or a candidate gene approach in the GENESIS study, which includes familial BC cases with no BRCA1 or BRCA2 mutation and having a sister with BC (N = 1,207), and general population controls (N = 1,199). Sequencing data were filtered for rare loss‐of‐function variants (LoF) and likely deleterious missense variants (MV). We confirmed associations between LoF and MV in PALB2, ATM and CHEK2 and BC occurrence. We also identified for the first time associations between FANCI, MAST1, POLH and RTEL1 and BC susceptibility. Unlike other associated genes, carriers of an ATM LoF had a significantly higher risk of developing BC than carriers of an ATM MV (OR_LoF = 17.4 vs. OR_MV = 1.6; p_Het = 0.002). Hence, our approach allowed us to specify BC relative risks associated with deleterious‐predicted variants in PALB2, ATM and CHEK2 and to add MAST1, POLH, RTEL1 and FANCI to the list of DNA repair genes possibly involved in BC susceptibility. We also highlight that different types of variants within the same gene can lead to different risk estimates.

What's new?

Pathogenic variants in BRCA1 and BRCA2 only explain the genetic cause of about 10% of hereditary breast and ovarian cancer families, and the clinical usefulness of testing other genes following the recent introduction of cost‐effective multigene panel sequencing in diagnostics laboratories remains questionable. This large case‐control study describes genetic variation in 113 DNA repair genes and specifies breast cancer relative risks associated with rare deleterious‐predicted variants in PALB2, ATM, and CHEK2. Importantly, different types of variants within the same gene can lead to different risk estimates. The results may help improve risk prediction models and define gene‐specific consensus management guidelines.

Telomere length, ATM mutation status and cancer risk in Ataxia-Telangiectasia families

Recent studies have linked constitutive telomere length (TL) to aging-related diseases including cancer at different sites. ATM participates in the signaling of telomere erosion, and inherited mutations in ATM have been associated with increased risk of cancer, particularly breast cancer. The goal of this study was to investigate whether carriage of an ATM mutation and TL interplay to modify cancer risk in ataxia-telangiectasia (A-T) families.The study population consisted of 284 heterozygous ATM mutation carriers (HetAT) and 174 non-carriers (non-HetAT) from 103 A-T families. Forty-eight HetAT and 14 non-HetAT individuals had cancer, among them 25 HetAT and 6 non-HetAT were diagnosed after blood sample collection. We measured mean TL using a quantitative PCR assay and genotyped seven single-nucleotide polymorphisms (SNPs) recurrently associated with TL in large population-based studies.HetAT individuals were at increased risk of cancer (OR = 2.3, 95%CI = 1.2-4.4, P = 0.01), and particularly of breast cancer for women (OR = 2.9, 95%CI = 1.2-7.1, P = 0.02), in comparison to their non-HetAT relatives. HetAT individuals had longer telomeres than non-HetAT individuals (P = 0.0008) but TL was not associated with cancer risk, and no significant interaction was observed between ATM mutation status and TL. Furthermore, rs9257445 (ZNF311) was associated with TL in HetAT subjects and rs6060627 (BCL2L1) modified cancer risk in HetAT and non-HetAT women.Our findings suggest that carriage of an ATM mutation impacts on the age-related TL shortening and that TL per se is not related to cancer risk in ATM carriers. TL measurement alone is not a good marker for predicting cancer risk in A-T families.

GENESIS: a French national resource to study the missing heritability of breast cancer

Background

Less than 20 % of familial breast cancer patients who undergo genetic testing for BRCA1 and BRCA2 carry a pathogenic mutation in one of these two genes. The GENESIS (GENE SISter) study was designed to identify new breast cancer susceptibility genes in women attending cancer genetics clinics and with no BRCA1/2 mutation.

Methods

The study involved the French national network of family cancer clinics. It was based on enrichment in genetic factors of the recruited population through case selection relying on familial criteria, but also on the consideration of environmental factors and endophenotypes like mammary density or tumor characteristics to assess potential genetic heterogeneity. One of the initial aims of GENESIS was to recruit affected sibpairs. Siblings were eligible when index cases and at least one affected sister were diagnosed with infiltrating mammary or ductal adenocarcinoma, with no BRCA1/2 mutation. In addition, unrelated controls and unaffected sisters were recruited. The enrolment of patients, their relatives and their controls, the collection of the clinical, epidemiological, familial and biological data were centralized by a coordinating center.

Results

Inclusion of participants started in February 2007 and ended in December 2013. A total of 1721 index cases, 826 affected sisters, 599 unaffected sisters and 1419 controls were included. 98 % of participants completed the epidemiological questionnaire, 97 % provided a blood sample, and 76 % were able to provide mammograms. Index cases were on average 59 years old at inclusion, were born in 1950, and were 49.7 years of age at breast cancer diagnosis. The mean age at diagnosis of affected sisters was slightly higher (51.4 years). The representativeness of the control group was verified.

Conclusions

The size of the study, the availability of biological specimens and the clinical data collection together with the detailed and complete epidemiological questionnaire make this a unique national resource for investigation of the missing heritability of breast cancer, by taking into account environmental and life style factors and stratifying data on endophenotypes to decrease genetic heterogeneity.

Social sharing of genetic information in the family: a study on hereditary breast and ovarian cancers

The present study assessed how preventive medical information about hereditary breast and ovarian cancer is spread within the family before actual genetic test results. Forty-two women (19 had a breast or ovarian tumor and 23 did not) were asked to fill out a questionnaire about: (1) the spread within the family of the medical information received during the consultation; and (2) the reasons for sharing this information. Results indicate that all of the women socially shared medical information with an immediate family member for preventive purposes, and generally not for seeking emotional or informative social support.

Familial transmission of information dealing with BRCA1/2 mutations in hereditary breast and ovarian cancer

Abstract #1104

Background: A mutation of the BRCA1/2 genes is implicated in 5 to 10% of the breast and ovarian cancer cases. In France, when such a genetic mutation is discovered in a family, the consulting persons are expected to transmit themselves this medical information to their relatives. Indeed, for legal reasons, physicians are not allowed to contact them personally. An important gap has been observed however between the number of persons who are potentially concerned by this genetic information and the number of persons actually consulting. We then wondered about (1) the actual transmission of genetic information to relatives, (2) possible reasons for the non-transmission of this information, (3) the rate of concerned consulting relatives and (4) presumed reasons for not consulting when informed.
 Methods: This sample includes 31 target consultants (index cases) of mutated families who received the result of the genetic test between January 2003 and June 2005. Data were gathered in two successive steps: some were first referring to consultants' medical files, then we called these target consultants asking them standardized questions about their relatives. Final analyses concern 264 relatives complying with our selection criteria.
 Results: According to information gathered thanks to medical files and calls to target consultants, most of the relatives (73.1 %) are informed that a deleterious mutation is present in the family. Women are more often informed (80.7 %) than men (63.2 %). The non-informational motives are on the one hand mainly social and emotional distance and, on the other hand, the stressful content of this information. It would be disclosed through family by the women who are alive and carry the mutation. Moreover, a minority of the presumed informed women (39.7 %) have attended the oncogenetic consultation. This rate represents 32 % of all concerned women. Almost no man has consulted. We can just assume the motives for short-term absence of consultation. They seem to be especially linked to relatives' disinterest towards genetic information. The studied characteristics just allow us to point out the closeness with a mutated relative as a determinant factor of consultation.
 Discussion: This study brings two main results linked to relatives' information and consultation when a breast and ovarian cancer genetic risk has been identified in the family. On the first hand, it confirms that familial transmission of the medical information is pretty good. On the other hand, despite the good communication among family members, the rate of consultation remains low in informed women. According to these findings, efforts have to be made to give better explanations about the goals of oncogenetic consultation as well as enhancing the quality of information transmission in mutated families. These improvements could raise consultation rates and then increase the efficiency of screening and preventive measures.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 1104.

Patients' characteristics and rate of Internet use to obtain cancer information

The aim of this study was to present baseline data on the access to Internet by French breast cancer patients attending genetic clinics and to examine factors affecting Internet health-related use. Twenty-four percent of participants used Internet to obtain information about the disease. This rate was higher among patients with health occupations [adjusted odds ratio (adjOR) 2.6; 95% confidence interval (CI) 1.3-5.1], the most highly educated (adjOR 2.1; 95% CI 1.1-4.0) and those under 41 years of age (adjOR 7.3; 95% CI 2.1-26.2). Almost one of every three women was dissatisfied of this source of information.

Impact of an information booklet on satisfaction and decision-making about BRCA genetic testing

The aim of this study was to assess the impact of a standardized patient information booklet on decisions women make about genetic testing. This French national multi-centre survey included all women with cancer to whom genetic testing for BRCA1/2 mutation had been proposed. The control group was surveyed before the booklet became available (n = 263), and the experimental group, after being given it personally (n = 297). After multivariate adjustment, the booklet had a positive impact on satisfaction with the information provided (Odds ratio (OR) = 2.9; 99% confidence interval (CI) = 1.7-5.0; P = 0.001), decreased the decisional conflicts due to lack of information (OR = 1.9; 99% CI = 1.1-3.3; P = 0.002), and had a marginal impact on knowledge (R2-gain = 3%; P = 0.001). The women in the experimental group decided more frequently to undergo testing (99% vs. 95%; P = 0.009). In addition to a consultation providing more tailored information, a standardized written document improved the decision-making process involved in giving informed consent to genetic testing.

Large-cell medulloblastoma with arrestin-like protein expression

We report a case of a cerebellar large-cell medulloblastoma in a 12-year-old patient. Despite a gross-total resection followed by a radiation therapy and then a chemotherapy, the death occurred 6 months later. The cyogenetic analysis showed an isochromosome 17q. Immunoreactivity for synaptophysin, neurofilaments, chromogranin and arrestin-like proteins was detected, whereas rhodopsin, vimentin, EMA and PAX-6 were negative. In this study, we demonstrate that large-cell medulloblastoma with translocation in chromosome 17q is a neuronal differentiated medulloblastoma with non-photoreceptor characterization. By reverse transcription and polymerase chain reaction (RT-PCR) method, using primers for beta1, beta2 and visual arrestin, we demonstrate corresponding mRNA for beta1, beta2 arrestin but not for visual arrestin. These results suggest that arrestin immunoreactivity in this tumor corresponds to non-visual arrestin. This case corresponds to a new entity of large-cell medulloblastoma. The potential role of a new marker linked to a beta2 adrenergic receptor needs further molecular characterization to be useful.

Nonrandom 4p13 rearrangements of the RhoH/TTF gene, encoding a GTP-binding protein, in non-Hodgkin's lymphoma and multiple myeloma

We recently isolated the RhoH/TTF gene by its fusion to the LAZ3/BCL6 gene, in a non-Hodgkin's lymphoma (NHL) cell line, which bore a t(3;4)(q27;p11-13) translocation. This gene encodes a novel Rho GTP-binding protein and is specifically expressed in hematopoietic tissues. We made its precise mapping at band 4p13, and described its partial genomic structure. Using fluorescence in situ hybridization and molecular analyses, we report here on the rearrangement of the RhoH/TTF gene, at band 4p13, in four cases of NHL with t(3;4)(q27;p13) translocation and its fusion to the LAZ3/BCL6 gene at band 3q27, in three of these cases. RT-PCR analysis of two cases allowed the detection of variable fusion transcripts emerging from the rearranged alleles, and in one case, a deregulated expression of both RhoH/TTF and LAZ3/BCL6 genes, by promoter substitution, was observed. We also show here another rearrangement of the RhoH/TTF gene in a patient with multiple myeloma and t(4;14)(p13;q32) translocation, with breakage within the IGH gene. It is the first report which describes the recurrent chromosomal alteration of a GTP-binding protein encoding gene, in patients with hematopoietic malignancies.

Germline BRCA1 mutations in patients from 84 families with breast and/or ovarian cancers in northern France

The BRCA1 gene modification is responsible for an autosomal dominant syndrome of inherited early onset breast and/or ovarian cancer. This gene is estimated to account for almost half of inherited breast cancers and three quarters of inherited breast/ovarian cancers. This suggests that about 1 in every 500 women may carry the BRCA1 mutation. The BRCA1 was isolated by positional cloning in 1994. More than 100 different mutations have been found in the germline of affected individuals. Using systematic sequencing, we looked at BRCA1 germline mutations in 84 patients treated at the Centre Oscar Lambret for breast and/or ovarian cancer who belonged to high-risk families. We found 39 mutations: 22 true mutations inducing modifications of the BRCA1 protein (BRCA1+), six mutations with unknown consequences on the BRCA1 protein, and eleven mutations corresponding to polymorphisms that had been described previously. All the BRCA1+ cases had a HPG3 tumour. The median age of discovery and the receptor positivity percentage are lower in hereditary breast cancer than in the standard population of the breast cancers treated in our centre. Conversely, most of the BRCA1+ patients are without node involvement. This shows that BRCA1 mutations are not always related to parameters thought to indicate a bad prognosis.

Evaluation and use of the white blood cell differential provided by the Coulter STKS in a children's hospital

The Coulter STKS was evaluated in a children's hospital, in order to (a) compare the WBC differential given by the instrument to a 400 cell visual differential (reference method); (b) evaluate the sensitivity and specificity of the alarm system, and (c) provide data concerning the use and interpretation of results in children. 653 blood samples were collected. The Coulter STKS results were studied in 523 patients having no morphological abnormalities in the blood smears, separated into subgroups according to the presence of STKS alarms and according to age. The results were found accurate both in STKS negative and STKS positive patients (i.e., those with alarms: 'Blasts', Imm Gran 2, Variant Lymph, NRBC, review slide). Negative STKS results had the same accuracy in all age groups, except in neonates where slide review must be systematically performed. The instrument exhibited a good sensitivity of the suspect flags studied (91.4%), with a lower specificity (72%) reflecting the number of false positive results found in our group, probably due to the cytological features particular to children. However, it was shown that the numerical results given by the Coulter STKS in positive patients could be taken into account, provided that a scan of the blood smear was negative for morphological WBC abnormalities.