Isabelle Coupier

A SUMOylation-defective MITF germline mutation predisposes to melanoma and renal carcinoma

So far, no common environmental and/or phenotypic factor has been associated with melanoma and renal cell carcinoma (RCC). The known risk factors for melanoma include sun exposure, pigmentation and nevus phenotypes; risk factors associated with RCC include smoking, obesity and hypertension. A recent study of coexisting melanoma and RCC in the same patients supports a genetic predisposition underlying the association between these two cancers. The microphthalmia-associated transcription factor (MITF) has been proposed to act as a melanoma oncogene; it also stimulates the transcription of hypoxia inducible factor (HIF1A), the pathway of which is targeted by kidney cancer susceptibility genes. We therefore proposed that MITF might have a role in conferring a genetic predisposition to co-occurring melanoma and RCC. Here we identify a germline missense substitution in MITF (Mi-E318K) that occurred at a significantly higher frequency in genetically enriched patients affected with melanoma, RCC or both cancers, when compared with controls. Overall, Mi-E318K carriers had a higher than fivefold increased risk of developing melanoma, RCC or both cancers. Codon 318 is located in a small-ubiquitin-like modifier (SUMO) consensus site (ΨKXE) and Mi-E318K severely impaired SUMOylation of MITF. Mi-E318K enhanced MITF protein binding to the HIF1A promoter and increased its transcriptional activity compared to wild-type MITF. Further, we observed a global increase in Mi-E318K-occupied loci. In an RCC cell line, gene expression profiling identified a Mi-E318K signature related to cell growth, proliferation and inflammation. Lastly, the mutant protein enhanced melanocytic and renal cell clonogenicity, migration and invasion, consistent with a gain-of-function role in tumorigenesis. Our data provide insights into the link between SUMOylation, transcription and cancer.

The succinate dehydrogenase genetic testing in a large prospective series of patients with paragangliomas.

CONTEXT Germline mutations in SDHx genes cause hereditary paraganglioma. OBJECTIVE The aim of the study was to assess the indications for succinate dehydrogenase (SDH) genetic testing in a prospective study. DESIGN A total of 445 patients with head and neck and/or thoracic-abdominal or pelvic paragangliomas were recruited over 5 yr in 20 referral centers. In addition to classical direct sequencing of the SDHB, SDHC, and SDHD genes, two methods for detecting large genomic deletions or duplications were used, quantitative multiplex PCR of short fluorescent fragments (QMPSF) and multiplex ligation-dependent probe amplification (MLPA). RESULTS A large variety of SDH germline mutations were found by direct sequencing in 220 patients and by QMPSF and MLPA in 22 patients (9.1%): 130 in SDHD, 96 in SDHB, and 16 in SDHC. Mutation carriers were younger and more frequently had multiple or malignant paraganglioma than patients without mutations. A head and neck paraganglioma was present in 97.7% of the SDHD and 87.5% of the SDHC mutation carriers, but in only 42.7% of the SDHB carriers. A thoracic-abdominal or pelvic location was present in 63.5% of the SDHB, 16.1% of the SDHD, and in 12.5% of the SDHC mutation carriers. Multiple paragangliomas were diagnosed in 66.9% of the SDHD mutation carriers. A malignant paraganglioma was documented in 37.5% of the SDHB, 3.1% of the SDHD, and none of the SDHC mutation carriers. CONCLUSIONS SDH genetic testing, including tests for large genomic deletions, is indicated in all patients with head and neck and/or thoracic-abdominal or pelvic paraganglioma and can be targeted according to clinical criteria.

Significant contribution of large BRCA1 gene rearrangements in 120 French breast and ovarian cancer families.

Genetic linkage data have shown that alterations of the BRCA1 gene are responsible for the majority of hereditary breast-ovarian cancers. However, BRCA1 germline mutations are found much less frequently than expected, especially as standard PCR-based mutation detection approaches focus on point and small gene alterations. In order to estimate the contribution of large gene rearrangements to the BRCA1 mutation spectrum, we have extensively analysed a series of 120 French breast-ovarian cancer cases. Thirty-eight were previously found carrier of a BRCA1 point mutation, 14 of a BRCA2 point mutation and one case has previously been reported as carrier of a large BRCA1 deletion. The remaining 67 cases were studied using the BRCA1 bar code approach on combed DNA which allows a panoramic view of the BRCA1 region. Three additional rearrangements were detected: a recurrent 23.8 kb deletion of exons 8–13, a 17.2 kb duplication of exons 3–8 and a 8.6 kb duplication of exons 18–20. Thus, in our series, BRCA1 large rearrangements accounted for 3.3% (4/120) of breast-ovarian cancer cases and 9.5% (4/42) of the BRCA1 gene mutation spectrum, suggesting that their screening is an important step that should be now systematically included in genetic testing surveys.

Imaging Work-Up for Screening of Paraganglioma and Pheochromocytoma in SDHx Mutation Carriers: A Multicenter Prospective Study from the PGL.EVA Investigators

CONTEXT Recommendations have not been established concerning imaging to screen SDHx mutation carriers for paraganglioma and pheochromocytoma. OBJECTIVE Our objective was to compare the performance of gadolinium-enhanced magnetic resonance angiography, contrast-enhanced computed tomography, and [(123)I]metaiodo-benzylguanidine and somatostatin receptor scintigraphies for detecting head and neck and thoracic-abdominal-pelvic paragangliomas in SDHx mutation carriers. DESIGN AND SETTING We conducted a prospective, multicenter study from June 2005 to December 2009 at 23 French medical centers. PATIENTS A total of 238 index cases or relatives carrying mutations in SDHD, SDHB, or SDHC genes were included. INTERVENTION Images obtained by each technique were analyzed blind, without knowledge of results from other tests, first in each local center and then centrally. MAIN OUTCOME MEASURES We evaluated sensitivity, specificity, and likelihood ratios for individual and combinations of tests, the gold standard being the consensus of an expert committee. RESULTS Two hundred two tumors were diagnosed in 96 subjects. At local assessment, the sensitivity of anatomical imaging for detecting all tumors was higher (85.7%) than that of both scintigraphic techniques (42.7% for [(123)I]metaiodo-benzylguanidine and 69.5% for somatostatin receptor scintigraphy), except for thoracic localizations where somatostatin receptor scintigraphy was more sensitive (61.5 vs. 46.2% for anatomical imaging and 30.8% for [(123)I]metaiodo-benzylguanidine scintigraphy). The best diagnostic performance during local assessment was obtained by combining anatomical imaging tests and somatostatin receptor scintigraphy (sensitivity 91.7%). Central assessment significantly increased the sensitivity (98.6%) of tests in combination. CONCLUSIONS In routine practice, the imaging work-up for screening SDHx mutation carriers should include thoraco-abdomino-pelvic computed tomography, head and neck magnetic angiography, and somatostatin receptor scintigraphy. Expert centralized image assessment is recommended.

Novel FH mutations in families with hereditary leiomyomatosis and renal cell cancer (HLRCC) and patients with isolated type 2 papillary renal cell carcinoma

Background Hereditary leiomyomatosis and renal cell cancer (HLRCC) is an autosomal dominant disorder predisposing humans to cutaneous and uterine leiomyomas; in 20% of affected families, type 2 papillary renal cell cancers (PRCCII) also occur with aggressive course and poor prognosis. HLRCC results from heterozygous germline mutations in the tumour suppressor fumarate hydratase (FH) gene. Methods As part of the French National Cancer Institute (INCa) ‘Inherited predispositions to kidney cancer’ network, sequence analysis and a functional study of FH were preformed in 56 families with clinically proven or suspected HLRCC and in 23 patients with isolated PRCCII (5 familial and 18 sporadic). Results The study identified 32 different germline FH mutations (15 missense, 6 frameshifts, 4 nonsense, 1 deletion/insertion, 5 splice site, and 1 complete deletion) in 40/56 (71.4%) families with proven or suspected HLRCC and in 4/23 (17.4%) probands with PRCCII alone, including 2 sporadic cases. 21 of these were novel and all were demonstrated as deleterious by significant reduction of FH enzymatic activity. In addition, 5 asymptomatic parents in 3 families were confirmed as carrying disease-causing mutations. Conclusions This study identified and characterised 21 novel FH mutations and demonstrated that PRCCII can be the only one manifestation of HLRCC. Due to the incomplete penetrance of HLRCC, the authors propose to extend the FH mutation analysis to every patient with PRCCII occurring before 40 years of age or when renal tumour harbours characteristic histologic features, in order to discover previously ignored HLRCC affected families.

Bar code screening on combed DNA for large rearrangements of the BRCA1 and BRCA2 genes in French breast cancer families

Identification of the BRCA1 and BRCA2 genes was a major advance in the understanding of the familial forms of breast cancer, as alterations of these genes result in a high predisposition to breast cancer.1,2 To date, analysis of BRCA1 and BRCA2 coding sequences by mutation screening methods based on PCR sequencing protocols has allowed the identification of at least 900 different point or small disease causing germline alterations (Breast Cancer Information Core, BIC database). Furthermore, several large BRCA1 rearrangements have been reported, detected by Southern blotting, lymphocyte transcript analysis, or long range PCR.3–14 The majority of characterised rearrangements result from unequal recombination events between Alu sequences. We have estimated that the contribution of large rearrangements to the spectrum of BRCA1 mutations is close to 10% in French breast-ovarian cancer families.15 Only two rearrangements of the BRCA2 gene have been detected to date: a 5 kb deletion skipping exon 3 and a 6.2 kb deletion removing exons 12-13.16,17 However, few groups have systematically looked for BRCA2 rearrangements in defined series of breast cancer cases.17–19 In order to detect such rearrangements, we have developed a bar code on combed DNA for the BRCA2 gene, which leads to a panoramic view of this gene and its flanking regions, as previously described for BRCA1. 20,21 We have concurrently used BRCA1 and BRCA2 bar codes to analyse a series of 26 highly selected French patients with a family history of breast cancer only, who were previously found to be negative for point or small mutations in both BRCA1 and BRCA2 genes. From January 1991 to December 1999, women with breast cancer (index cases), ascertained in the Institut Curie cancer genetic clinic were referred to our laboratory for BRCA1 / 2 analysis. Familial criteria for genetic …

Fidelity of DNA double-strand break repair in heterozygous cell lines harbouring BRCA1 missense mutations.

Germ-line mutations of the BRCA1 and BRCA2 genes, when they lead to a truncated protein, confer a high risk of breast and ovarian cancer. However, the role of BRCA1 missense mutations in cancer predisposition is unclear. Functional assays may be very helpful to more clearly define the biological effect of these mutations, and could therefore be useful in clinical practice. A recent study using a Host Cell End-Joining assay showed that a truncating mutation results in impaired fidelity of DSB repair by DNA end-joining. In the present study, we examined the fidelity of DSB repair in four lymphoblastoid cell lines with BRCA1 missense mutations. The fidelity of DNA end-joining was impaired in the four cell lines studied compared to the normal control cell line. The fidelity of end-joining was similar to that of a truncated mutation control cell line for one cell line and slightly higher for the other cell lines.

Breast cancer risk in BRCA1 and BRCA2 mutation carriers and polyglutamine repeat length in the AIB1 gene.

Marked variation in phenotypic expression among BRCA1 and BRCA2 mutation carriers may be partly explained by modifier genes that influence mutation penetrance. Variation in CAG/CAA repeat lengths coding for stretches of glutamines in the C‐terminus of the AIB1 protein (amplified in breast cancer 1, a steroid receptor coactivator) has been proposed to modify the breast cancer risk in women carrying germline BRCA1 mutations. We genotyped the AIB1 repeat length polymorphism from the genomic DNA of a group of 851 BRCA1 and 324 BRCA2 female germline mutation carriers to estimate an association with breast cancer risk modification. Hazard ratios (HR) were calculated using a Cox proportional hazards model. For BRCA1 and BRCA2 mutation carriers, analyzed separately and together, we found that women who carried alleles with 28 or more polyglutamine repeats had no increased risk of breast cancer compared to those who carried alleles with fewer repeats (HR for BRCA1/2 carriers = 0.88, 95% CI [confidence interval] = 0.75–1.04). Analyzing average repeat lengths as a continuous variable showed no excess risk of breast cancer (BC) in BRCA1 or BRCA2 mutation carriers (HR for average repeat length in BRCA1/2 carriers = 1.01, 95% CI = 0.92–1.11). These results strongly suggest that contrary to previous studies, there is no significant effect of AIB1 genetic variation on BC risk in BRCA1 mutation carriers and provide an indication that there is also no strong risk modification in BRCA2 carriers.

Germline copy number variation of genes involved in chromatin remodelling in families suggestive of Li-Fraumeni syndrome with brain tumours.

Germline alterations of the tumour suppressor TP53 gene are detected approximately in 25% of the families suggestive of Li-Fraumeni syndrome (LFS), characterised by a genetic predisposition to a wide tumour spectrum, including soft-tissue sarcomas, osteosarcomas, premenopausal breast cancers, brain tumours, adrenocortical tumours, plexus choroid tumours, leukaemia and lung cancer. The aim of this study was to determine the contribution of germline copy number variations (CNVs) to LFS in families without detectable TP53 mutation. Using a custom-designed high-resolution array CGH, we evaluated the presence of rare germline CNVs in 64 patients fulfilling the Chompret criteria for LFS, but without any detectable TP53 alteration. In 15 unrelated patients, we detected 20 new CNVs absent in 600 controls. Remarkably, in four patients who had developed each brain tumour, the detected CNV overlap the KDM1A, MTA3, TRRAP or SIRT3 genes encoding p53 partners involved in histone methylation or acetylation. Focused analysis of SIRT3 showed that the CNV encompassing SIRT3 leads to SIRT3 overexpression, and that in vitro SIRT3 overexpression prevents apoptosis, increases G2/M and results in a hypermethylation of numerous genes. This study supports the causal role of germline alterations of genes involved in chromatin remodelling in genetic predisposition to cancer and, in particular, to brain tumours.

BRCA1/2 carriers: their childbearing plans and theoretical intentions about having preimplantation genetic diagnosis and prenatal diagnosis

Purpose:To assess the impact of BRCA1/2 test results on carriers’ reproductive decision-making and the factors determining their theoretical intentions about preimplantation genetic diagnosis (PGD) and prenatal diagnosis (PND).Methods:Unaffected BRCA1/2 mutation carriers of childbearing age (N = 605; 449 women; 151 men) were included at least 1 year after the disclosure of their test results in a cross-sectional survey nested in a national cohort. Multivariate adjustment was performed on the data obtained in self-administered questionnaires.Results:Response rate was 81.0%. Overall, 32.5% and 50% said that they would undergo PGD/PND, respectively, at a theoretical next pregnancy, whereas only 12.1% found termination of pregnancy (TOP) acceptable. Theoretical intentions toward PGD did not depend on gender/age, but were higher among those with no future childbearing plans (adjusted odds ratio (AOR) 95% confidence interval (CI): 3.5 (1.9–6.4)) and those having fewer relatives with cancer (AOR 1.5 95% CI (1.0–2.3)). Greater TOP acceptability was observed among males and those with lower educational levels; 85.4% of respondents agreed that information about PGD/PND should be systematically delivered with the test results.Conclusions:The closer to reproductive decision-making BRCA1/2 carriers are, i.e., when they are more likely to be making future reproductive plans, the less frequently they intend to have PGD. Carriers’ theoretical intentions toward PND are discussed further.Genet Med 2012:14(5):527–534