Biomedical subjects

Gilles Thomas

Publications and source records attributed to Gilles Thomas.

At least 19 recordsLinked to original sources

PubMed2006

Genetic and clinical implications of the Val617Phe JAK2 mutation in 72 families with myeloproliferative disorders.

To study the prevalence of the Val617Phe JAK2 mutation in familial cases of myeloproliferative disorder (MPD) and its possible implication as a predisposing genetic factor, we analyzed 72 families including 174 patients (81 polycythemia vera [PV], 68 essential thrombocythemia [ET], 11 myelofibrosis with myeloid metaplasia [MMM], 12 chronic myeloid leukemia), 1 systemic mastocytosis, and 1 chronic myelomonocytic leukemia (CMML). The JAK2 mutation was found in three quarters of patients with PV and MMM and in half of patients with ET. Among 46 families with at least 2 cases of PV, ET, or MMM, the JAK2 mutation was absent in 6 families, heterogeneously distributed in 18, and present in all MPD patients in 22. Among these 22 families, the absence of the JAK2 mutation both in purified T and B cells in 13 unrelated patients and the observation of variable ratios of the JAK2 mutant allele in patient leucocytes indicated that the Val617Phe JAK2 mutation was acquired in familial MPDs. The JAK2 mutation was present in natural killer cells in two thirds of tested patients (27 of 40), suggesting its occurrence in a multipotent hematopoietic progenitor cell. The analysis of the hematologic profile showed that the homozygous JAK2 mutation confers a proliferative advantage and is associated with the progression of the hematologic disease.

Cohort Studies↗

PubMed2006

Haplotype analysis of the HSD17B1 gene and risk of breast cancer: a comprehensive approach to multicenter analyses of prospective cohort studies.

The 17beta-hydroxysteroid dehydrogenase 1 gene (HSD17B1) encodes 17HSD1, which catalyzes the final step of estradiol biosynthesis. Despite the important role of HSD17B1 in hormone metabolism, few epidemiologic studies of HSD17B1 and breast cancer have been conducted. This study includes 5,370 breast cancer cases and 7,480 matched controls from five large cohorts in the Breast and Prostate Cancer Cohort Consortium. We characterized variation in HSD17B1 by resequencing and dense genotyping a multiethnic sample and identified haplotype-tagging single nucleotide polymorphisms (htSNP) that capture common variation within a 33.3-kb region around HSD17B1. Four htSNPs, including the previously studied SNP rs605059 (S312G), were genotyped to tag five common haplotypes in all cases and controls. Conditional logistic regression was used to estimate odds ratios (OR) for disease. We found no evidence of association between common HSD17B1 haplotypes or htSNPs and overall risk of breast cancer. The OR for each haplotype relative to the most common haplotype ranged from 0.98 to 1.07 (omnibus test for association: X2 = 3.77, P = 0.58, 5 degrees of freedom). When cases were subdivided by estrogen receptor (ER) status, two common haplotypes were associated with ER-negative tumors (test for trend, Ps = 0.0009 and 0.0076; n = 353 cases). HSD17B1 variants that are common in Caucasians are not associated with overall risk of breast cancer; however, there was an association among the subset of ER-negative tumors. Although the probability that these ER-negative findings are false-positive results is high, these findings were consistent across each cohort examined and warrant further study.

17-Hydroxysteroid Dehydrogenases↗

PubMed2006

Allele-specific relative telomere lengths are inherited.

Previous studies have indicated that single relative telomere lengths are defined in the zygote. In order to explore the possibility that single telomere lengths segregate in families, we compared relative telomere lengths obtained from allelic chromosome extremities transmitted from parent to child, representing a total of 31 independent meiotic events. We find a significant positive correlation of 0.65 (P=0.0004) between these telomere lengths, whereas the correlation between the non-transmitted parental homologue and the transmitted homologue in the child is not statistically significant (r=0.16; P=0.195). This study indicates that, even though there is a telomerase-mediated maintenance/elongation of telomeres in germ cells, allele-specific relative telomere lengths are preserved in the next generation.

Alleles↗

PubMed2006

Retention of chromosome arm 5q in stage II colon cancers identifies 83% of liver metastasis occurrences.

The decision to use chemotherapy in the treatment of colon cancer patients depends on the risk of developing metastases, as estimated by clinicopathological staging combining body imaging and pathological findings. The aim of this study was to identify all chromosome arms that, when allelotyped, correlate with the metastatic process, add prognostic information to pathology, and are of relevance for predicting metachronous metastases. A 5-year follow-up survey enrolled 401 MSS (microsatellite stable) colon cancer patients who were divided into three groups. Staging was performed with and without imaging data (called tumor and patient staging, respectively). The first 192 patients were used to construct a model prognosticating metastases. The subsequent 146 patients were used to validate this model. The third group evaluated its consistency by comparing the status of the relevant chromosome arms in 63 liver metastases and primary tumors that did or did not metastasize. The first group identified three factors: tumor staging (P < 0.0001), 5q status (P = 0.003), and gender (P = 0.02). The second group confirmed 5q as a marker of metastasis occurrence (P = 0.004). Merged data predicted that, when both 5q arms are retained, metastatic risk increases 4.3-fold in stage II patients. The third group corroborated these findings, with a 5q retention rate in metastases comparable to that of primary tumors that metastasize, but significantly higher than that observed in nonmetastatic tumors (one-tail, P = 0.0005). Long arm of chromosome 5 allelotyping detects high-risk stage II tumors. This simple, easily implemented, and inexpensive test increases the power of randomized studies that evaluate chemotherapy.

Aged↗

PubMed2005

Genetic variation in the HSD17B1 gene and risk of prostate cancer.

Steroid hormones are believed to play an important role in prostate carcinogenesis, but epidemiological evidence linking prostate cancer and steroid hormone genes has been inconclusive, in part due to small sample sizes or incomplete characterization of genetic variation at the locus of interest. Here we report on the results of a comprehensive study of the association between HSD17B1 and prostate cancer by the Breast and Prostate Cancer Cohort Consortium, a large collaborative study. HSD17B1 encodes 17beta-hydroxysteroid dehydrogenase 1, an enzyme that converts dihydroepiandrosterone to the testosterone precursor Delta5-androsterone-3beta,17beta-diol and converts estrone to estradiol. The Breast and Prostate Cancer Cohort Consortium researchers systematically characterized variation in HSD17B1 by targeted resequencing and dense genotyping; selected haplotype-tagging single nucleotide polymorphisms (htSNPs) that efficiently predict common variants in U.S. and European whites, Latinos, Japanese Americans, and Native Hawaiians; and genotyped these htSNPs in 8,290 prostate cancer cases and 9,367 study-, age-, and ethnicity-matched controls. We found no evidence that HSD17B1 htSNPs (including the nonsynonymous coding SNP S312G) or htSNP haplotypes were associated with risk of prostate cancer or tumor stage in the pooled multiethnic sample or in U.S. and European whites. Analyses stratified by age, body mass index, and family history of disease found no subgroup-specific associations between these HSD17B1 htSNPs and prostate cancer. We found significant evidence of heterogeneity in associations between HSD17B1 haplotypes and prostate cancer across ethnicity: one haplotype had a significant (p < 0.002) inverse association with risk of prostate cancer in Latinos and Japanese Americans but showed no evidence of association in African Americans, Native Hawaiians, or whites. However, the smaller numbers of Latinos and Japanese Americans in this study makes these subgroup analyses less reliable. These results suggest that the germline variants in HSD17B1 characterized by these htSNPs do not substantially influence the risk of prostate cancer in U.S. and European whites.

17-Hydroxysteroid Dehydrogenases↗

PubMed2005

Vessels' morphology in SMAD4 and BMPR1A-related juvenile polyposis.

Juvenile polyposis syndrome is a hamartomatous intestinal polyposis associated with malignant changes in 20% of patients at an early age. Germline mutations mostly involve two genes, SMAD4 and BMPR1, with no strong evidence of phenotype-genotype correlation, which could be predictive of the specific long-term evolution. In contrast, PTEN mutations are more commonly associated with Cowden and related diseases. Forty-two unrelated patients affected by juvenile polyposis syndrome were analyzed for germline alterations in the BMPR1A and SMAD4 genes, and for clinical and histological features. Deleterious mutations were found in 14/42 (33%) patients: 5 in BMPR1A and 9 in SMAD4. Low-grade adenomas were present in both SMAD4 and BMPR1A mutation carriers; only patients with SMAD4 mutations harbored carcinoma lesions (5/9). Malformative vessels were present in all SMAD4 related polyps when the mutation involved codons prior to position 423. No gastric polyps were observed in BMPR1A mutation carriers. SMAD4 germline mutations are responsible for a more aggressive digestive phenotype in patients with juvenile polyposis. The presence of malformative vessels within the stromal component might be a useful tool to drive the subsequent genetic and clinical management.

Adolescent↗

PubMed2005

Differential nonsense mediated decay of mutated mRNAs in mismatch repair deficient colorectal cancers.

The nonsense-mediated decay (NMD) system normally targets mRNAs with premature termination codons (PTCs) for rapid degradation. We investigated for a putative role of NMD in cancers with microsatellite instability (MSI-H cancers), because numerous mutant mRNAs containing PTC are generated in these tumors as a consequence of their mismatch repair deficiency. Using a quantitative RT-PCR approach in a large series of colorectal cancer cell lines, we demonstrate a significantly increased rate of degradation of mutant mRNAs containing a PTC compared with wild-type. A specific siRNA strategy was used to inhibit RENT-1 and/or RENT-2 activity, two major genes in the NMD system. This allowed us to show that increased degradation of PTC-containing mRNAs in MSI-H tumors was partly dependent upon NMD activity. The efficiency of NMD for the degradation of mutant mRNAs from target genes was highly variable in these cancers. NMD degraded some of them (TGFssRII, MSH3, GRK4), although allowing the persistent expression of others (BAX, TCF-4). This is of particular interest within the context of a proposed conservation of biological activity for the corresponding mutated proteins. We thus propose that NMD might play an important role in the selection of target gene mutations with a functional role in MSI-H carcinogenesis.

Codon, Nonsense↗

PubMed2004

Synergy of Nf2 and p53 mutations in development of malignant tumours of neural crest origin.

Previously, we have mimicked human neurofibromatosis type 2 (NF2) in conditional Nf2 mutant (P0Cre;Nf2flox2/flox2) mice. Schwannomas, characteristic for NF2, were found at low frequency in older mice. Here, we report that these mice, upon additional hemizygosity for p53, rapidly develop multiple tumours showing features consistent with malignant peripheral nerve sheath tumours. Thus, p53 hemizygosity promotes tumorigenesis of mutant Nf2 peripheral nerve cells. In contrast, young P0Cre;Nf2flox2/+;p53+/- cis mice mainly succumb to Nf2/p53-related osteogenic tumours. Therefore, Cre-mediated early biallelic loss of Nf2 function in neural crest-derived cells hemizygous for p53 results in resistance to osteogenic tumours and increased susceptibility to peripheral nerve sheath tumours.

Animals↗

PubMed2004

Significant linkage to spondyloarthropathy on 9q31-34.

Spondyloarthropathy (SpA) is a frequent rheumatologic disorder with a prevalence of 0.3% in Caucasian populations from western Europe. It commonly presents as chronic axial and/or peripheral arthritis with potential disabling outcome. SpA is also variably associated with extra-articular manifestations. The pathogenesis of SpA is considered as complex, with a strong genetic component. Human leukocyte antigen B27 has been identified as a predisposing factor for SpA, but family and twin studies suggest that additional genetic risk factors exist outside the major histocompatibility complex (MHC). To map SpA susceptibility loci, 120 multiplex SpA families were included in a genome-wide scan. Linkage analyses performed on the first 65 families allowed us to identify four candidate non-MHC regions on chromosomes 5q, 9q, 13q and 17q, which were further explored in the remaining 55 multiplex families (extension study). Non-parametric multipoint linkage analyses of the whole data set yielded evidence of significant linkage to 9q31-34, in the vicinity of marker D9S1776 (NPL=4.87, LOD=5.15, P=0.00002). This result provides evidence for the presence of a non-MHC susceptibility locus for SpA mapping to 9q31-34.

Chromosome Mapping↗

PubMed2004

The relative lengths of individual telomeres are defined in the zygote and strictly maintained during life.

Previous studies have indicated that average telomere length is partly inherited (Slagboom et al., 1994; Rufer et al., 1999) and that there is an inherited telomere pattern in each cell (Graakjaer et al., 2003); (Londoño-Vallejo et al., 2001). In this study, we quantify the importance of the initially inherited telomere lengths within cells, in relation to other factors that influence telomere length during life. We have estimated the inheritance by measuring telomere length in monozygotic (MZ) twins using Q-FISH with a telomere specific peptide nucleic acid (PNA)-probe. Homologous chromosomes were identified using subtelomeric polymorphic markers. We found that identical homologous telomeres from two aged MZ twins show significantly less differences in relative telomere length than when comparing the two homologues within one individual. This result means that towards the end of life, individual telomeres retain the characteristic relative length they had at the outset of life and that any length alteration during the lifespan impacts equally on genetically identical homologues. As the result applies across independent individuals, we conclude that, at least in lymphocytes, epigenetic/environmental effects on relative telomere length are relatively minor during life.

Age Factors↗

PubMed2004

[Identification and management of HNPCC syndrome (hereditary non polyposis colon cancer), hereditary predisposition to colorectal and endometrial adenocarcinomas].

BACKGROUND: The HNPCC syndrome (hereditary non polyposis colon cancer) is an inherited condition defined by clinical and genealogical information, known as Amsterdam criteria. In about 70% of cases, HNPCC syndrome is caused by germline mutations in MMR genes, leading to microsatellite instability of tumor DNA (MSI phenotype). Patients affected by the disease are at high risk for colorectal and endometrial carcinomas, but also for small intestine, urothelial, ovary, stomach and biliary tract carcinomas. HNPCC syndrome is responsible for 5% of colorectal cancers. Identification and management of this disease are part of a multidisciplinary procedure. METHODS: 12 experts have been mandated by the French Health Ministry to analyze and synthesize their consensus position, and the resulting document has been reviewed by an additional group of 4 independent experts. MAIN RECOMMENDATIONS: The lack of sensitivity of Amsterdam criteria in recognizing patients carrying a MMR germline mutation led to an enlargement of these criteria for the recruitment of possible HNPCC patients, and to a 2-steps strategy, asking first for a tumor characterization according to MSI phenotype, especially in case of early-onset sporadic cases. The identification of germline MMR mutations has no major consequence on the cancer treatments, but influences markedly the long-term follow-up and the management of at-risk relatives. Gene carriers will enter a follow-up program regarding their colorectal and endometrial cancer risks, but other organs being at low lifetime risk, no specific surveillance will be proposed.

Adenocarcinoma↗

PubMed2003

Haplotype-based identification of a microsomal transfer protein marker associated with the human lifespan.

We previously reported a genomewide linkage study for human longevity using 308 long-lived individuals (LLI) (centenarians or near-centenarians) in 137 sibships and identified statistically significant linkage within chromosome 4 near microsatellite D4S1564. This interval spans 12 million bp and contains approximately 50 putative genes. To identify the specific gene and gene variants impacting lifespan, we performed a haplotype-based fine-mapping study of the interval. The resulting genetic association study identified a haplotype marker within microsomal transfer protein as a modifier of human lifespan. This same variant was tested in a second cohort of LLI from France, and although the association was not replicated, there was evidence for statistical distortion in the form of Hardy-Weinberg disequilibrium. Microsomal transfer protein has been identified as the rate-limiting step in lipoprotein synthesis and may affect longevity by subtly modulating this pathway. This study provides proof of concept for the feasibility of using the genomes of LLI to identify genes impacting longevity.

Adolescent↗

PubMed2003

Intrinsic susceptibility to radiation-induced apoptosis of human lymphocyte subpopulations.

PURPOSE: With the aim to evaluate intrinsic radiosensitivity, the susceptibility of lymphocyte subpopulations to radiation-induced apoptosis was determined. The investigated parameters included measurement reliability, phenotypic variance, intra- and inter-individual variability, and correlations between radiation-induced and spontaneous apoptosis. METHODS AND MATERIALS: Quiescent lymphocytes of 63 healthy volunteers, sampled up to four times over a 1-year period were gamma-irradiated in vitro. Subsequent apoptosis (annexin V) was measured for T4-, T8-, and B-lymphocyte subpopulations using 6-color flow cytometry. Spontaneous apoptosis was measured and radiosensitivity was quantified from the dose-effect curves. RESULTS: After thawing and short-term culture, both spontaneous apoptosis as well as radiation-induced apoptosis (radiosensitivity) differed among the three lymphocyte subpopulations, with T4 being most resistant, and B most sensitive. Spontaneous and radiation-induced apoptosis were correlated in all cell types, and variance between individuals was considerably higher than variance within individuals for both. A small but highly significant increase of both spontaneous and radiation-induced apoptosis was observed with age for T8, but not for T4 and B. Radiosensitivity of T8 and B proved to be sex-independent, whereas female T4 lymphocytes were less radiosensitive than those from males. T4 and T8 radiosensitivities were loosely correlated, and neither of them was related to B radiosensitivity. CONCLUSION: Tendency to spontaneous and radiation-induced apoptosis of lymphocyte subpopulations differs among individuals. In addition, depending on the cell types, age and sex are factors influencing these parameters.

Apoptosis↗

PubMed2003

Gene-environment interaction modulated by allelic heterogeneity in inflammatory diseases.

CARD15 is a major susceptibility gene for a frequent multifactorial chronic inflammatory bowel disorder, Crohn disease (CD). By using NF-kappaB activation assays, the cytosolic CARD15 was shown to efficiently detect bacterial peptidoglycan (PGN), reminiscent of the PGN recognition protein surveillance mechanism in Drosophila. The 3 CD-associated variants and 13 additional variants carried by CD patients demonstrated impaired PGN-dependent response revealing null, hypomorphic, or dominant-negative properties. Quantitative parametrization of this response, computed from the patients' CARD15 genotypes, was predictive of several variable CD manifestations. In contrast, CARD15 alleles associated with Blau's syndrome promoted PGN-independent NF-kappaB activation, an observation that accounts for the minimal microbial input in the etiology of this dominant, monogenic inflammatory disorder affecting solely aseptic sites.

Alleles↗

PubMed2003

Nod2 is a general sensor of peptidoglycan through muramyl dipeptide (MDP) detection.

Nod2 activates the NF-kappaB pathway following intracellular stimulation by bacterial products. Recently, mutations in Nod2 have been shown to be associated with Crohn's disease, suggesting a role for bacteria-host interactions in the etiology of this disorder. We show here that Nod2 is a general sensor of peptidoglycan through the recognition of muramyl dipeptide (MDP), the minimal bioactive peptidoglycan motif common to all bacteria. Moreover, the 3020insC frameshift mutation, the most frequent Nod2 variant associated with Crohn's disease patients, fully abrogates Nod2-dependent detection of peptidoglycan and MDP. Together, these results impact on the understanding of Crohn's disease development. Additionally, the characterization of Nod2 as the first pathogen-recognition molecule that detects MDP will help to unravel the well known biological activities of this immunomodulatory compound.

Acetylmuramyl-Alanyl-Isoglutamine↗

PubMed2003

Clustering of Crohn's disease within affected sibships.

Crohn's disease (CD) is a complex genetic disorder for which aetiology is unknown. Recently, genetic factors for susceptibility have been described. Several genetic loci have been mapped and partially explain the familial aggregations of the disease. However, environmental factors may also contribute to these aggregations. We considered that if the role of non-genetic factors was negligible, CD patients would be randomly distributed in sibships with multiple affected siblings. On the other hand if there was a significant environmental contribution, the siblings would be affected non-randomly over exposure status. In order to test this hypothesis, we studied 102 sibships with two or more affected siblings. A statistical test, named Cluster of Affected Sibling Test or CAST, was developed, based on the exact calculation of the probability of observing a given number of clusters of affected siblings in multiplex families. The null hypothesis of a random distribution of affected siblings was rejected (P=0.005). The observed excess of affected sibling clusters indicates that birth order influences the disease status. Considering that an adjacent order of birth is a global estimate of environmental sharing, this observation strongly suggests that environmental factors contribute to the observed familial aggregations of the disease. This observation provides evidence that familial CD is a relevant tool for further studies of environmental factors and gene-environment interaction. More generally, the CAST statistics may be widely applicable to estimate the involvement of environmental factors in the aetiology of other binary traits which may be observed in multiple members of the same sibship.

Adult↗

PubMed2002

Prognostic value of P53 mutations in rectal carcinoma.

The influence of p53 mutations on the response to ionizing radiation and survival was retrospectively evaluated in patients treated with preoperative radiotherapy for rectal carcinoma. From 1989 to 1991, 86 rectal cancer patients treated by preoperative radiotherapy were included in this series. For all patients, endorectal sonography (to define ultrasonography TNM [uTNM]) was performed before treatment; 19 patients were classified as stage 1, 27 as stage 2 and 40 as stage 3. Response to radiotherapy (39 Gy in 13 fractions delivered in 17 days) was assessed by comparing the uT and the T obtained by histologic examination of the resected specimen (TNM classification). A rectal cancer biopsy was performed before treatment and enabled the search for p53 mutations by denaturing gradient gel electrophoresis (DGGE) and sequencing. The status of the p53 gene was correlated with the response to radiotherapy and survival. Forty-nine percent of the tumors presented abnormal DGGE profiles. The prevalence of p53 mutations was significantly higher in patients who did not respond to radiotherapy (63%) than in those who did respond (34%) (p < 0.01). Presence of a p53 mutation was associated with significantly shorter 5-year survival compared to patients without mutations (p < 0.02). In a multivariate analysis, p53 mutation status remained a prognostic factor independent of tumor posttreatment staging (p < 0.05). p53 status is an independent prognostic factor of response to radiotherapy and survival in rectal carcinoma.

Adenocarcinoma↗

PubMed2002

Nf2 gene inactivation in arachnoidal cells is rate-limiting for meningioma development in the mouse.

Biallelic NF2 gene inactivation is common in sporadic and in neurofibromatosis type 2 (NF2)-related meningiomas. We show that, beginning at four months of age, thirty percent of mice with arachnoidal cell Cre-mediated excision of Nf2 exon 2 developed a range of meningioma subtypes histologically similar to the human tumors. Additional hemizygosity for p53 did not modify meningioma frequency or progression suggesting that Nf2 and p53 mutations do not synergize in meningeal tumorigenesis. This first mouse model initiated with a genetic lesion found in human meningiomas provides a powerful tool for investigating tumor progression and for the preclinical evaluation of therapeutic interventions.

Adenoviridae↗