[Show abstract][Hide abstract] ABSTRACT: The genetic basis underlying the majority of hereditary pancreatic adenocarcinoma (PC) is unknown. Since DNA repair genes are widely implicated in gastrointestinal malignancies, including PC, we hypothesized that there are novel DNA repair PC susceptibility genes. As germline DNA repair gene mutations may lead to PC subtypes with selective therapeutic responses, we also hypothesized that there is an overall survival (OS) difference in mutation carriers versus non-carriers. We therefore interrogated the germline exomes of 109 high-risk PC cases for rare protein-truncating variants (PTVs) in 513 putative DNA repair genes. We identified PTVs in 41 novel genes among 36 kindred. Additional genetic evidence for causality was obtained for 17 genes, with FAN1, NEK1 and RHNO1 emerging as the strongest candidates. An OS difference was observed for carriers versus non-carriers of PTVs with early stage (≤IIB) disease. This adverse survival trend in carriers with early stage disease was also observed in an independent series of 130 PC cases. We identified candidate DNA repair PC susceptibility genes and suggest that carriers of a germline PTV in a DNA repair gene with early stage disease have worse survival.
Cancer Letters 01/2016; 370(2):302-312. DOI:10.1016/j.canlet.2015.10.030 · 5.62 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Specific germline mutations in the hereditary breast-ovarian cancer susceptibility (HBC/HBOC) genes, BRCA1, BRCA2 and PALB2, have been shown to recur in French Canadians of Quebec, Canada, and this has been attributed to common ancestors. Germline TP53 mutation carriers are known to segregate in Li-Fraumeni syndrome families, which feature young age of onset breast cancer. We have reported rare TP53 mutation carriers in French Canadian HBC families, though none recurred possibly due to the limited number of cancer families investigated. Here we describe TP53 germline mutations found in French Canadian cancer families provided from hereditary cancer clinics; investigate 37 new BRCA1 and BRCA2 mutation-negative HBC/HBOC families for the TP53 mutations; and assess the frequency of TP53 mutations in a 1235 French Canadian breast cancer cases not selected for family history of cancer.
TP53 mutation-positive pedigrees from French Canadian cancer families were provided from local hereditary cancer clinics. Bidirectional Sanger sequencing of all protein encoding exons of TP53 was performed using peripheral blood lymphocyte DNA from breast/ovarian cancer probands from 37 HBC/HBOC families of French Canadian descent. Targeted bidirectional Sanger sequencing assay of regions containing the identified TP53 mutations was performed on 1235 French Canadian breast cancer cases not selected for family history cancer.
Five new TP53 mutations were identified in six pedigrees from hereditary cancer clinics. No deleterious mutations were identified in cancer probands from 37 HBC/HBOC families. A targeted mutation screen of the 1235 breast cancer cases identified a c.844C>T [p.Arg282Trp] mutation carrier. This mutation was also found among the six mutation-positive cancer families provided by the local hereditary cancer clinics. The targeted screen also uncovered a new TP53 mutation, c.685T>C [p.Cys229Arg] that was found in two breast cancer cases. All TP53 mutation carriers were among the 656 women with breast cancer diagnosed less than 50 years of age.
In all six new TP53 mutations were identified in French Canadians, where two each occurred in independently ascertained cases/families. Although all newly identified breast cancer mutation carriers reported a family history of cancer, none were consistent with features of Li-Fraumeni syndrome families.
BMC Medical Genetics 12/2015; 16(1):24. DOI:10.1186/s12881-015-0169-y · 2.08 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: DICER1 is an endoribonuclease which catalyzes the generation of mature 5p and 3p miRNAs. We present the detailed molecular characterization of three DICER1 mutations occurring in a child with multinodular goitre (MNG) and an ovarian sex cord-stromal tumor (OSCST), conditions associated with the DICER1 syndrome (OMIM 601200). We identified three DICER1 mutations affecting the RNase IIIb domain in the child: a novel germ-line DICER1 mutation (c.5441C>T) which does not affect the metal ion binding residues of RNase IIIb, and two different somatic mutations (5425G>T in the MNG and c.5125G>A in the OSCST), both situated at these metal ion binding residues. In vitro functional studies of the germ-line DICER1 (c.5441C>T) mutation showed that both 5p and 3p miRNAs were decreased, whereas the somatic mutation occurring in the MNG, c. 5425G>T, is predicted to function either as a missense (p.D1810Y) or a cryptic splice site (p.K1844fsX17). When the latter, no miRNAs are made. We also identified the previously studied c.5125G>A (p.D1709N) mutation in the OSCST. Following identification of the c.5125G>A, review of the original diagnosis of the OSCST (adult granulosa cell tumour) was revised to Sertoli-Leydig cell tumour, illustrating how molecular analysis can assist in the diagnosis of uncommon ovarian neoplasms. We also report the first instance of biallelic DICER1 mutations in a MNG. The three single base pair substitutions in DICER1 all affect the RNase IIIb domain, but have different effects on miRNA generation. This study demonstrates that detailed functional characterisation of DICER1 missense mutations may be required to determine pathogenicity.
Endocrine Related Cancer 11/2015; DOI:10.1530/ERC-15-0460 · 4.81 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Purpose:
Most women from BRCA1/2 mutation-positive families who did not inherit the familial mutation have breast and ovarian cancer risks similar to those of women of the same age in the general population. However, recent studies suggest that some of these noncarriers may exhibit screening practices that may be considered as excessive compared to general population screening guidelines. Reasons for such tendencies remain largely unknown. This study aims to better understand how the implications of a noncarrier status are explained to these women and how their own realization of this status affects their screening behaviors.
A qualitative study was conducted with five focus groups (n = 28) in Quebec City and Montreal, Canada.
Thematic analysis of the discussions highlighted four major themes: (i) acquiring a noncarrier identity takes place progressively; (ii) noncarriers show a range of opinions about screening; (iii) noncarriers have mixed feelings about the follow-up by their physicians and gynecologists; and (iv) noncarriers need more information in a context where genetics progresses ever more rapidly.
Our results provide novel insights regarding the physician-patient interaction and the organizational aspects of the health-care system that may significantly impact the cancer screening practices of BRCA1/2 noncarriers.Genet Med advance online publication 05 November 2015Genetics in Medicine (2015); doi:10.1038/gim.2015.135.
Genetics in medicine: official journal of the American College of Medical Genetics 11/2015; DOI:10.1038/gim.2015.135 · 7.33 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Background:
Caspase recruitment domain-containing protein 9 (CARD9) deficiency is an autosomal recessive primary immunodeficiency conferring human susceptibility to invasive fungal disease, including spontaneous central nervous system candidiasis (sCNSc). However, clinical characterization of sCNSc is variable, hindering its recognition. Furthermore, an in-depth understanding of the bases for this susceptibility has remained elusive.
We sought to comprehensively characterize sCNSc and to dissect the mechanisms by which a hypomorphic CARD9 mutation causes susceptibility to Candida species.
We describe the clinical and radiologic findings of sCNSc caused by CARD9 deficiency in a French-Canadian cohort. We performed genetic, cellular, and molecular analyses to further decipher its pathophysiology.
In our French-Canadian series (n = 4) sCNSc had onset in adulthood (median, 38 years) and was often misinterpreted radiologically as brain malignancies; 1 patient had additional novel features (eg, endophthalmitis and osteomyelitis). CARD9 deficiency resulted from a hypomorphic p.Y91H mutation and allelic imbalance established in this population through founder effects. We demonstrate a consistent cellular phenotype of impaired GM-CSF responses. The ability of CARD9 to complex with B-cell CLL/lymphoma 10 (BCL10) and mucosa-associated lymphoid tissue lymphoma translocation protein 1 (MALT1) is intact in our series, arguing against its involvement in susceptibility to fungi. Instead, we show that the p.Y91H mutation impairs the ability of CARD9 to complex with Ras protein-specific guanine nucleotide-releasing factor 1 (RASGRF1), leading to impaired activation of nuclear factor κB and extracellular signal-regulated kinase (ERK) in monocytes and subsequent GM-CSF responses. Successful treatment of a second patient with adjunctive GM-CSF bolsters the clinical relevance of these findings.
Hypomorphic CARD9 deficiency caused by p.Y91H results in adult-onset disease with variable penetrance and expressivity. Our findings establish the CARD9/RASGRF1/ERK/GM-CSF axis as critical to the pathophysiology of sCNSc.
The Journal of allergy and clinical immunology 11/2015; DOI:10.1016/j.jaci.2015.09.016 · 11.48 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The current standard model for identifying carriers of high-risk mutations in cancer-susceptibility genes (CSGs) generally involves a process that is not amenable to population-based testing: access to genetic tests is typically regulated by health-care providers on the basis of a labour-intensive assessment of an individual's personal and family history of cancer, with face-to-face genetic counselling performed before mutation testing. Several studies have shown that application of these selection criteria results in a substantial proportion of mutation carriers being missed. Population-based genetic testing has been proposed as an alternative approach to determining cancer susceptibility, and aims for a more-comprehensive detection of mutation carriers. Herein, we review the existing data on population-based genetic testing, and consider some of the barriers, pitfalls, and challenges related to the possible expansion of this approach. We consider mechanisms by which population-based genetic testing for cancer susceptibility could be delivered, and suggest how such genetic testing might be integrated into existing and emerging health-care structures. The existing models of genetic testing (including issues relating to informed consent) will very likely require considerable alteration if the potential benefits of population-based genetic testing are to be fully realized.
[Show abstract][Hide abstract] ABSTRACT: Background:
Somatic mosaicism is being increasingly recognised as an important cause of non-Mendelian presentations of hereditary syndromes. A previous whole-exome sequencing study using DNA derived from peripheral blood identified mosaic mutations in DICER1 in two children with overgrowth and developmental delay as well as more typical phenotypes of germline DICER1 mutation. However, very-low-frequency mosaicism is difficult to detect, and thus, causal mutations can go unnoticed. Highly sensitive, cost-effective approaches are needed to molecularly diagnose these persons. We studied four children with multiple primary tumours known to be associated with the DICER1 syndrome, but in whom germline DICER1 mutations were not detected by conventional mutation detection techniques.
Methods and results:
We observed the same missense mutation within the DICER1 RNase IIIb domain in multiple tumours from different sites in each patient, raising suspicion of somatic mosaicism. We implemented three different targeted-capture technologies, including the novel HaloPlex(HS) (Agilent Technologies), followed by deep sequencing, and confirmed that the identified mutations are mosaic in origin in three patients, detectable in 0.24-31% of sequencing reads in constitutional DNA. The mosaic origin of patient 4's mutation remains to be unequivocally established. We also discovered likely pathogenic second somatic mutations or loss of heterozygosity (LOH) in tumours from all four patients.
Mosaic DICER1 mutations are an important cause of the DICER1 syndrome in patients with severe phenotypes and often appear to be accompanied by second somatic truncating mutations or LOH in the associated tumours. Furthermore, the molecular barcode-containing HaloPlex(HS) provides the sensitivity required for detection of such low-level mosaic mutations and could have general applicability.
Journal of Medical Genetics 10/2015; DOI:10.1136/jmedgenet-2015-103428 · 6.34 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The purpose of this study is to estimate the age-specific annual risks of breast cancer in a woman with a germline BRCA mutation and an affected first-degree relative according to the age of breast cancer diagnosis in the relative. Women with BRCA mutations with no previous diagnosis of breast cancer and with one first-degree relative with breast cancer were followed for breast cancers for a mean of 5.9 years (minimum 2 years). Age-specific annual breast cancer risks were calculated, according to the age of breast cancer diagnosis in the proband and the first-degree relative. 1114 cancer-free women with a BRCA mutation with a single first-degree relative with breast cancer were eligible for the study. 122 women (11.0 %) were diagnosed with incident breast cancer. The annual risk of breast cancer was 2.0 % for women with BRCA1 mutations and was 1.6 % for women with BRCA2 mutations. The age of breast cancer diagnosis in the first-degree relative did not affect the annual breast cancer risks for BRCA1 mutation carriers. For BRCA2 mutation carriers, the annual breast cancer risk was 4.5 % for women with a first-degree relative diagnosed with breast cancer under the age of 30 years and was 0.7 % for women with a relative diagnosed over the age of 60. Among women with BRCA2 mutations, a family history of early-onset breast cancer is a risk factor for developing breast cancer. Risk assessment for healthy BRCA2 mutation carriers should consider the ages of breast cancers diagnosed in first-degree relatives.
Breast Cancer Research and Treatment 10/2015; 154(1). DOI:10.1007/s10549-015-3596-8 · 3.94 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To measure weight gain among unaffected women with a BRCA1 or BRCA2 mutation after undergoing an oophorectomy.
We compared the bodyweight of women with (n = 405) and without an oophorectomy (n = 741) at baseline as well as the rate of weight change prior to and following surgery among 1454 BRCA mutation carriers who had an oophorectomy.
There was a small and non-significant difference in bodyweight between BRCA mutation carriers who had an oophorectomy compared with those women who did not (151.5 vs 149.1 pounds; p = 0.26). There was an increase in bodyweight with increasing age, but this relationship did not differ prior to and following surgery (p comparing the slope parameters = 0.78).
Oophorectomy is not associated with significant weight gain in high-risk women.
Women s Health 08/2015; 11(4):1-7. DOI:10.2217/WHE.15.4
[Show abstract][Hide abstract] ABSTRACT: Over the past decade, chromatin remodelling disorders have emerged as one of the most important causes of both abnormal development and cancer. Although much has been written about one or another of the complexes, no recent concise summary of the chromatin remodelling families as a whole is available. In this short review, we introduce the family members, briefly summarize their role in developmental abnormalities and neoplasia and outline the different ways in which these families remodel chromatin.
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The Journal of Pathology 07/2015; DOI:10.1002/path.4585 · 7.43 Impact Factor