Antoine de Pauw

Germline BAP1 Mutations Predispose to Renal Cell Carcinomas

The genetic cause of some familial nonsyndromic renal cell carcinomas (RCC) defined by at least two affected first-degree relatives is unknown. By combining whole-exome sequencing and tumor profiling in a family prone to cases of RCC, we identified a germline BAP1 mutation c.277A>G (p.Thr93Ala) as the probable genetic basis of RCC predisposition. This mutation segregated with all four RCC-affected relatives. Furthermore, BAP1 was found to be inactivated in RCC-affected individuals from this family. No BAP1 mutations were identified in 32 familial cases presenting with only RCC. We then screened for germline BAP1 deleterious mutations in familial aggregations of cancers within the spectrum of the recently described BAP1-associated tumor predisposition syndrome, including uveal melanoma, malignant pleural mesothelioma, and cutaneous melanoma. Among the 11 families that included individuals identified as carrying germline deleterious BAP1 mutations, 6 families presented with 9 RCC-affected individuals, demonstrating a significantly increased risk for RCC. This strongly argues that RCC belongs to the BAP1 syndrome and that BAP1 is a RCC-predisposition gene.

CDH1 germline mutations and the hereditary diffuse gastric and lobular breast cancer syndrome: a multicentre study

Introduction CDH1 predisposes primarily to diffuse gastric cancer (DGC). Multiple DGC cases in a family, DGC at a young age in an individual or the combination of DGC andlobular breast cancer (LBC) in an individual or a family define the hereditary DGC syndrome (HDGC), and testing for germline CDH1 mutations is warranted in HDGC. Methods and results We report all index cases from Ile-de-France in which a germline CDH1 mutation has been identified. Out of 18 cases, 7 do not fulfil the HDGC-defining criteria. Three of them are women who presented initially with bilateral LBC below age 50, without personal or family history of DGC, and who subsequently developed symptomatic DGC. Discussion Our series of CDH1 mutation carriers is the largest to date and demonstrates that LBC might be the first manifestation of HDGC. A personal or family history of multiple LBCs at a young age, even without DGC, should prompt CDH1 mutation screening. It is paramount to identify mutation carriers early, so that they can benefit from prophylactic gastrectomy before they develop symptomatic, highly lethal DGC. We recommend a revision of the HDGC-defining criteria and propose for consideration the name ‘Hereditary Diffuse Gastric and Lobular Breast Cancer’ instead of HDGC.

EMMA, a cost- and time-effective diagnostic method for simultaneous detection of point mutations and large-scale genomic rearrangements: application to BRCA1 and BRCA2 in 1,525 patients†

The detection of unknown mutations remains a serious challenge and, despite the expected benefits for the patients health, a large number of genes are not screened on a routine basis. We present the diagnostic application of EMMA (Enhanced Mismatch Mutation Analysis®, Fluigent, Paris, France), a novel method based on heteroduplex analysis by capillary electrophoresis using innovative matrices. BRCA1 and BRCA2 were screened for point mutations and large rearrangements in 1,525 unrelated patients (372 for the validation step and 1,153 in routine diagnosis) using a single analytical condition. Seven working days were needed for complete BRCA1/2 screening in 30 patients by one technician (excluding DNA extraction and sequencing). A total of 137 mutations were found, including a BRCA2 duplication of exons 19 and 20, previously missed by Comprehensive BRACAnalysis®. The mutation detection rate was 11.9%, which is consistent with patient inclusions. This study therefore suggests that EMMA represents a valuable short‐term and midterm option for many diagnostic laboratories looking for an easy, reliable, and affordable strategy, enabling fast and sensitive analysis for a large number of genes. Hum Mutat 32:1–10, 2011.

Impact of BRCA1 and BRCA2 variants on splicing: clues from an allelic imbalance study

Nearly one-half of BRCA1 and BRCA2 sequence variations are variants of uncertain significance (VUSs) and are candidates for splice alterations for example, by disrupting/creating splice sites. As out-of-frame splicing defects lead to a marked reduction of the level of the mutant mRNA cleared through nonsense-mediated mRNA decay, a cDNA-based test was developed to show the resulting allelic imbalance (AI). Fifty-four VUSs identified in 53 hereditary breast/ovarian cancer (HBOC) patients without BRCA1/2 mutation were included in the study. Two frequent exonic single-nucleotide polymorphisms on both BRCA1 and BRCA2 were investigated by using a semiquantitative single-nucleotide primer extension approach and the cDNA allelic ratios obtained were corrected using genomic DNA ratios from the same sample. A total of five samples showed AI. Subsequent transcript analyses ruled out the implication of VUS on AI and identified a deletion encompassing BRCA2 exons 12 and 13 in one sample. No sequence abnormality was found in the remaining four samples, suggesting implication of cis- or trans-acting factors in allelic expression regulation that might be disease causative in these HBOC patients. Overall, this study showed that AI screening is a simple way to detect deleterious splicing defects and that a major role for VUSs and deep intronic mutations in splicing anomalies is unlikely in BRCA1/2 genes. Methods to analyze gene expression and identify regulatory elements in BRCA1/2 are now needed to complement standard approaches to mutational analysis.

Clinicopathologic Characteristics of Endometrial Cancer in Lynch Syndrome: A French Multicenter Study

Background Limited data exist on Lynch syndrome (LS)–related endometrial cancer (EC) features. Amsterdam criteria II, commonly used, have poor sensitivity for detection of LS, which is underdiagnosed. Aim The aim of this study was to describe the clinical and pathological features of LS-related EC among mutation-proven patients. Methods We conducted a retrospective study from 1977 to 2013 in 5 hospitals. The inclusion criteria were patients who had a primary EC associated to LS proven by a germline mutation. We analyzed the clinical data and the pathology of the tumors. The patient management and the survival data were also collected. Results Forty-nine patients (15 MLH1, 20 MSH2, 13 MSH6, 1 PMS2) were included. The mean age at diagnosis was 49.7 (SD, 10.5) years. The median body mass index was 22.6 kg/m2. In 81.4% of cases, EC was the first cancer of the LS spectrum to occur. Endometrioid adenocarcinoma accounted for 89.2% of the EC, the lower uterine segment was involved in 25% of cases, and a synchronous ovarian cancer was present in 21.6% of patients. The tumors were grade 3 in 19.3% of cases and FIGO (International Federation of Gynecology and Obstetrics) stage I in 66.6% of cases. With a median follow-up of 58 months, 3 patients with conservative management developed a recurrence, and no patient died of EC. Conclusions The LS-associated EC is characterized by a young age at onset, a high prevalence of lower uterine segment involvement, and synchronous ovarian cancers. The prognosis of these cancers does not appear different from sporadic tumors.

Supporting disclosure of genetic information to family members: professional practice and timelines in cancer genetics

Disclosure of genetic information within families is one of the longstanding questions under scrutiny in the field of genetics. Most of the probands entrusted with family disclosure succeed in this task, but there are still many problematic cases where it proves difficult. How can professionals help probands disclose this information? What levers can they activate to foster the diffusion of genetic information within families? In the context of a new legal framework concerning this question in France, this paper offers a comprehensive view of the process of genetic counselling in a cancer genetics department. Based on an ethnographic study, it focuses on the interactions between professionals and probands during each step of the testing procedures in order to identify key times when the issue can be addressed. The results show that the question of family disclosure needs to be addressed before, during and after the test. Greater awareness of this continuum among professionals could help them foster family disclosure by supporting the probands at each stage of the testing procedure

Hereditary diffuse gastric cancer syndrome: improved performances of the 2015 testing criteria for the identification of probands with a CDH1 germline mutation

The international, consensus testing criteria for CDH1 germline mutations were recently revised in order to increase their performances, particularly their sensitivity. It is paramount to identify a high proportion of actual mutation carriers, as finding a mutation in a proband and subsequently in some of his relatives allows for risk-reducing recommendations regarding diffuse gastric cancer (DGC) and lobular breast cancer (LBC). We collected data on all French probands tested for CDH1 in a retrospective study on the hereditary DGC syndrome (HDGC). Out of 627 probands, 52 were carriers. We compared the new, 2015 version of these criteria to the 2010 version, and showed that both the sensitivity and the Youden index ( J ), an index that estimates the criteria discriminating power, increased. CDH1 is a tumour suppressor gene located on chromosome 16q22. It codes for the E-cadherin adhesion protein. Monoallelic germline mutations in CDH1 cause HDGC, in which carriers have a high lifetime risk of DGC (also called signet ring cell gastric cancer), and LBC (reviewed in ref. 1). In clinical practice, mutations are first identified in a proband with a personal history of DGC and/or LBC, and adult relatives are subsequently tested to see whether they also carry the mutation. Asymptomatic carriers are then advised to undergo risk-reducing gastrectomy, and for women annual breast cancer screening using MRI. The International Gastric Cancer Linkage Consortium defined clinical criteria warranting CDH1 germline testing in a proband. The criteria were first published in 1999 and then updated in 2010.2 ,3 A new 2015 version is being published in this issue of the Journal of Medical Genetics …

Les formes héréditaires des cancers de l’ovaire

Approximately 5 to 10 % of all ovarian cancers arise in the setting of a major genetic predisposition. The two main hereditary forms of ovarian adenocarcinomas are the hereditary breast/ovarian cancers associated with a BRCA1 or BRCA2 gene mutation and the Lynch syndrome associated with a MLH1, MSH2, MSH6 or PMS2 gene mutation. Their identification and the characterization of a causative germline mutation are crucial and have a major impact for affected women and their relatives in terms of medical management. The aim of this review is to indicate cancer risks associated with these two entities, to evaluate their contribution in the pathogenesis of ovarian cancers and to indicate the clinical data suggestive of these diagnoses, the validated indications for genetic analyses and the current management guidelines. We will also illustrate the diagnostic strategy by reporting a clinical observation.

Sporadic endometrial adenocarcinoma with MMR deficiency due to biallelic MSH2 somatic mutations

The invalidation of the Mismatch Repair (MMR) system is responsible for a so-called “deficient MMR” phenotype (dMMR) characterized by microsatellite instability and abnormal pattern of expression of MMR proteins in tumor tissue. This phenotype occurs in at least 20% of sporadic endometrial adenocarcinomas by epigenetic silencing of MLH1 gene. It is also observed in virtually all tumors occurring in patients with Lynch syndrome by monoallelic germline mutation in one of the MMR genes. The determination of this phenotype (dMMR vs. proficient MMR—pMMR) has therefore a pivotal place in the diagnosis algorithm for Lynch syndrome by monoallelic germline mutation in one of the MMR genes. The determination of this phenotype (dMMR vs. proficient MMR—pMMR) has therefore a pivotal place in the diagnosis algorithm for Lynch syndrome. We report the case of a woman with an early-onset endometrial adenocarcinoma who was suspected to be affected with Lynch syndrome based on tumor dMMR phenotype (MSI associated with loss of expression of MSH2 and MSH6 proteins). After complete germline and somatic evaluations, this phenotype was eventually explained by two MSH2 somatic mutations and the diagnosis of Lynch-like syndrome due to an unidentified MSH2 germline mutation was ruled out. Somatic mosaicism at low mutation rate was unlikely as no mutation was detected by DNA analysis from various tissue samples. Nevertheless, the three patient’s children were tested for the two mutations and these tests were negative. Biallelic somatic mutations of one MMR gene is a mechanism of invalidation of the MMR system in sporadic cases. Clinicians have to be aware of this mechanism because of the great clinical implication for the patients and their relatives.

Contribution of germline deleterious variants in the RAD51 paralogs to breast and ovarian cancers

RAD51 paralogs (RAD51B, RAD51C, RAD51D, XRCC2, and XRCC3) have recently been involved in breast and ovarian cancer predisposition: RAD51B, RAD51C, and RAD51D in ovarian cancer, RAD51B and XRCC2 in breast cancer. The aim of this study was to estimate the contribution of deleterious variants in the five RAD51 paralogs to breast and ovarian cancers. The five RAD51 paralog genes were analyzed by next-generation sequencing technologies in germline DNA from 2649 consecutive patients diagnosed with breast and/or ovarian cancer. Twenty-one different deleterious variants were identified in the RAD51 paralogs in 30 patients: RAD51B (n = 4), RAD51C (n = 12), RAD51D (n = 7), XRCC2 (n = 2), and XRCC3 (n = 5). The overall deleterious variant rate was 1.13% (95% confidence interval (CI): 0.72–1.55%) (30/2649), including 15 variants in breast cancer only cases (15/2063; 0.73% (95% CI: 0.34–1.11%)) and 15 variants in cases with at least one ovarian cancer (15/570; 2.63% (95% CI: 1.24–4.02%)). This study is the first evaluation of the five RAD51 paralogs in breast and ovarian cancer predisposition and it demonstrates that deleterious variants can be present in breast cancer only cases. Moreover, this is the first time that XRCC3 deleterious variants have been identified in breast and ovarian cancer cases.