Search

The rate of genetic diagnosis of French patients with familial pancreatic ductal adenocarcinoma (PDAC) is not known. We report germline genetic testing data from 133 index cases meeting criteria for familial pancreatic cancer (FPC) as well as 87 'FPC‐like' index cases who did not fulfilled strict FPC definition but were evocative for a PDAC predisposition. The overall rate of genetic diagnosis (in BRCA1, BRCA2, CDKN2A, and ATM genes) was 8.3% in FPC patients and 4.6% in FPC‐like patients, consistent with the literature in other populations. Genetic variants were also identified in FANCA and BAP1 genes, as well as in the CDKN2A p12 transcript. This pancreas‐specific transcript is a known key player in driving pancreatic oncogenesis. This might be the first described case of a PDAC genetic predisposition due to a variant in this specific transcript. [ABSTRACT FROM AUTHOR]

Germline BRCA2 mutations are the first known cause of inherited (familial) pancreatic ductal adenocarcinoma (PDAC). This tumor is the third most frequent cancer in carriers of germline BRCA2 mutations, as it occurs in around 10% of BRCA2 families. PDAC is known as one of the most highly lethal cancers, mainly because of its chemoresistance and frequently late diagnosis. Based on recent developments in molecular biology, a subgroup of BRCA2-associated PDAC has been created, allowing screening, early surgical treatment and personalized systemic treatment. BRCA2 germline mutation carriers who have ≥1 first-degree relative, or ≥2 blood relatives with PDAC, should undergo screening and regular follow-up based on magnetic resonance imaging and endoscopic ultrasound. The goal of screening is to detect early invasive PDAC and advanced precancerous lesions suitable for a stepwise surgical complete (R0) resection. Increasing evidence on the molecular role of the BRCA2 protein in the homologous recombination of DNA damages suggest that BRCA2-related PDAC are sensitive to agents causing DNA cross-linking damage, such as platinum salts, and treatments targeting rescue DNA repair pathways, such as poly(ADP-ribose) polymerase inhibitors that are currently under investigation. [ABSTRACT FROM AUTHOR]

Background. The MC1R gene implicated in melanogenesis and skin pigmentation is highly polymorphic. Several alleles are associated with red hair and fair skin phenotypes and contribute to melanoma risk. Objective. This work aims to assess the effect of different classes of MC1R variants, notably rare variants, on melanoma risk. Methods. MC1R coding region was sequenced in 1131 melanoma patients and 869 healthy controls. MC1R variants were classified as RHC (R) and non-RHC (r). Rare variants (frequency < 1%) were subdivided into two subgroups, predicted to be damaging (D) or not (nD). Results. Both R and r alleles were associated with melanoma (OR = 2.66 [2.20-3.23] and 1.51 [1.32-1.73]) and had similar population attributable risks (15.8% and 16.6%).We also identified 69 rare variants, of which 25 were novel. D variants were strongly associated with melanoma (OR = 2.38 [1.38-4.15]) and clustered in the same MC1R domains as R alleles (intracellular 2, transmembrane 2 and 7). Conclusion. This work confirms the role of R and r alleles in melanoma risk in the French population and proposes a novel class of rare D variants as important melanoma risk factors. These findings may improve the definition of high-risk subjects that could be targeted for melanoma prevention and screening. [ABSTRACT FROM AUTHOR]

Background & Aims: Recent studies reported a role for more than 70 genes or loci in the susceptibility to Crohn's disease (CD). However, the impact of these associations in clinical practice remains to be defined. The aim of the study was to analyse the relationship between genotypes and phenotypes for the main 53 CD-associated polymorphisms. Method: A cohort of 798 CD patients with a median follow up of 7 years was recruited by tertiary adult and paediatric gastroenterological centres. A detailed phenotypic description of the disease was recorded, including clinical presentation, response to treatments and complications. The participants were genotyped for 53 CD-associated variants previously reported in the literature and correlations with clinical sub-phenotypes were searched for. A replication cohort consisting of 722 CD patients was used to further explore the putative associations. Results: The NOD2 rare variants were associated with an earlier age at diagnosis (p = 0.0001) and an ileal involvement (OR = 2.25[1.49-3.41] and 2.77 [1.71-4.50] for rs2066844 and rs2066847, respectively). Colonic lesions were positively associated with the risk alleles of IL23R rs11209026 (OR = 2.25 [1.13-4.51]) and 6q21 rs7746082 (OR = 1.60 [1.10-2.34] and negatively associated with the risk alleles of IRGM rs13361189 (OR = 0.29 [0.11-0.74]) and DEFB1 rs11362 (OR = 0.50 [0.30- 0.80]). The ATG16L1 and IRGM variants were associated with a non-inflammatory behaviour (OR = 1.75 [1.22-2.53] and OR = 1.50 [1.04-2.16] respectively). However, these associations lost significance after multiple testing corrections. The protective effect of the IRGM risk allele on colonic lesions was the only association replicated in the second cohort (p = 0.03). Conclusions: It is not recommended to genotype the studied polymorphisms in routine practice. [ABSTRACT FROM AUTHOR]

Xeroderma pigmentosum (XP) is a rare autosomal recessive disorder that is associated with an inherited defect of the nucleotide excision repair pathway (NER). In this study, we investigated the involvement of XP genes in 86 XP patients belonging to 66 unrelated families, most of them consanguineous and originating from Maghreb. Sequencing analysis was performed either directly (44 probands) or after having previously characterized the involved XP gene by complementation assay (22 families). XPC and XPA mutations were respectively present in 56/66 and 8/66 probands. Strikingly, we identified the same homozygous frameshift mutation c.1643_1644delTG (p.Val548AlafsX25) in 87% of XP-C patients. Haplotype analysis showed a common founder effect for this mutation in the Mediterranean region, with an estimated age of 50 generations or 1,250 years. Among 7/8 XP-A patients, we found the previously reported nonsense homozygous XPA mutation (p.Arg228X). Six mutations—to our knowledge previously unreported—(five in XPC, one in XPA) were also identified. In conclusion, XPC appears to be the major disease-causing gene concerning xeroderma pigmentosum in North Africa. As the (p.Val548AlafsX25) XPC mutation is responsible for a huge proportion of XP cases, our data imply an obvious simplification of XP molecular diagnosis, at least in North Africa. [ABSTRACT FROM AUTHOR]

Background: Altered tumor suppressor p53 and/or CDKN2A as well as Ras genes are frequently found in primary and metastatic melanomas. These alterations were found to be responsible for acquisition of invasive and metastatic potential through their defective regulatory control of metalloproteinases and urokinase genes. Methodology/Principal Findings: Using primary human melanoma M10 cells with altered p53, CDKN2A and N-Ras genes, we found that inhibition of the proprotein convertases (PCs), enzymes involved in the proteolytic activation of various cancer-related protein precursors resulted in significantly reduced invasiveness. Analysis of M10 cells and their gastric and lymph node derived metastatic cells revealed the presence of all the PCs found in the secretory pathway. Expression of the general PCs inhibitor α1-PDX in these cells in a stable manner (M10/PDX) had no effect on the mRNA expression levels of these PCs. Whereas, in vitro digestion assays and cell transfection experiments, revealed that M10/PDX cells display reduced PCs activity and are unable to process the PCs substrates proIGF-1R and proPDGF-A. These cells showed reduced migration and invasion that paralleled decreased gelatinase MMP-2 activity and increased expression and secretion of tissue inhibitor of metalloproteinase-1 (TIMP-1) and TIMP-2. Furthermore, these cells showed decreased levels of urokinase-type plasminogen activator receptor (uPAR) and increased levels of plasminogen activator inhibitor-1 (PAI-1). Conclusions: Taken together, these data suggest that inhibition of PCs activity results in decreased invasiveness of primary human melanoma cells despite their altered p53, CDKN2A and N-Ras genes, suggesting that PCs may serve as novel therapeutic targets in melanoma. [ABSTRACT FROM AUTHOR]

The occuloalbinism 2 (OCA2) gene, localized at 15q11, encodes a melanosomal transmembrane protein that is involved in the most common form of human occulo-cutaneous albinism, a human genetic disorder characterized by fair pigmentation and susceptibility to skin cancer. We wondered whether allele variations at this locus could influence susceptibility to malignant melanoma (MM). In all, 10 intragenic single-nucleotide polymorphisms (SNPs) were genotyped in 113 patients with melanomas and in 105 Caucasian control subjects with no personal or family history of skin cancer. By comparing allelic distribution between cases and controls, we show that MM and OCA2 are associated (p value=0.030 after correction for multiple testing). Then, a recently developed strategy, the ‘combination test’ enabled us to show that a combination formed by two SNPs was most strongly associated to MM, suggesting a possible interaction between intragenic SNPs. In addition, the role of OCA2 on MM risk was also detected using a logistic model taking into account the presence of variants of the melanocortin 1 receptor gene (MC1R, a key pigmentation gene) and all pigmentation characteristics as melanoma risk factors. Our data demonstrate that a second pigmentation gene, in addition to MC1R, is involved in genetic susceptibility to melanoma.European Journal of Human Genetics (2005) 13, 913–920. doi:10.1038/sj.ejhg.5201415; published online 27 April 2005 [ABSTRACT FROM AUTHOR]

Background: The INK4a-ARF locus encodes two tumor suppressor proteins, p16(INK4a) and p14(ARF), that act through the Rb-CDK4 and p53 pathways, respectively. Data from murine models and sporadic human skin carcinomas implicate p16(INK4a) and p14(ARF) in the development of skin carcinomas. We examined the frequency of INK4a-ARF, p53, and CDK4 mutations in skin carcinomas from patients with xeroderma pigmentosum (XP), a rare autosomal disease that is associated with a defect in DNA repair and that predisposes patients to skin cancer.Methods: DNA from skin cancers of 28 unrelated XP patients was screened for mutations in p53, INK4a-ARF, and CDK4 coding exons by single-strand conformation polymorphism analysis and automated sequencing. Data were evaluated with the use of the exact unconditional test derived from Fisher's test. All statistical tests were two-sided.Results: Eight of 28 XP-associated tumors had mutations in the INK4a-ARF locus. Three XP-associated tumors had multiple mutations at this locus. In all, 13 mutations in the INK4a-ARF locus were detected in XP-associated tumors, of which seven (54%) were signature UV radiation-induced mutations, i.e., tandem CC : GG-->TT : AA transitions. p53 mutations, mostly of the type induced by UV radiation, were present in 12 tumors (43%). Statistically significant positive associations were found between the frequency of mutations in p53 and in p16(INK4a) (P =.008) and between the frequency of mutations in p53 and in p14(ARF) (P<.001). No mutations were detected within the CDK4 gene.Conclusions: We have demonstrated for the first time the occurrence of UV radiation-induced mutations in INK4a-ARF in XP-associated skin carcinomas. The simultaneous inactivation of p53 and INK4a-ARF may be linked to the genetic instability caused by XP and could be advantageous for tumor progression. [ABSTRACT FROM AUTHOR]

Germline mutations in the p16 and CDK4 genes have been reported in a subset of melanoma pedigrees, but their prevalence is not well known. We searched for such germline mutations in 48 French melanoma-prone families selected according to two major criteria: families with at least three affected members (n = 20) or families with two affected members, one of them affected before the age of 50 (n = 28), and one additional minor criterion. Sixteen different p16 germline mutations were found in 21 families, while one germline mutation, Arg24His, was detected in the CDK4 gene. The frequency of p16 gene mutation in our sample (44%) is among the highest rates yet reported and the CDK4 mutation is the second mutation detected in this gene worldwide. In summary, our results show frequent involvement of the p16 gene in familial melanoma and confirm the role of the CDK4 gene as a melanoma-predisposing gene. [ABSTRACT FROM AUTHOR]

Abstract: We report here a three generations family with nevoid basal cell carcinoma syndrome (NBCCS) in which the diagnosis was made only after a second trimester of pregnancy ultrasonography revealing fetal cranio-cerebral malformations. A mutation was subsequently characterized in the aborted fetus, as well as in the mother, sister and grand-mother as an 18bp deletion in exon 15 of the patched homologue 1 (PTCH1) gene. MC1R gene sequencing identified in two NBCCS patients affected by multiple basal cell carcinomas a functional MC1R variant, D294H, previously shown to be associated with skin cancer risk. This variant was absent in the NBCCS patient that did not develop basal cell carcinomas, suggesting that this variant could have favored the development of skin cancers, in patients carrying the PTCH1 mutation. [Copyright &y& Elsevier]