Search PubMed⌕ Search

Biomedical subjects

G Lenoir

Publications and source records attributed to G Lenoir.

At least 55 records · Page 3Linked to original sources
PubMed1998

Multifactorial analysis of differences between sporadic breast cancers and cancers involving BRCA1 and BRCA2 mutations.

BACKGROUND: We have previously demonstrated that breast cancers associated with inherited BRCA1 and BRCA2 gene mutations differ from each other in their histopathologic appearances and that each of these types differs from breast cancers in patients unselected for family history (i.e., sporadic cancers). We have now conducted a more detailed examination of cytologic and architectural features of these tumors. METHODS: Specimens of tumor tissue (5-microm-thick sections) were examined independently by two pathologists, who were unaware of the case or control subject status, for the presence of cell mitosis, lymphocytic infiltration, continuous pushing margins, and solid sheets of cancer cells; cell nuclei, cell nucleoli, cell necrosis, and cell borders were also evaluated. The resulting data were combined with previously available information on tumor type and tumor grade and further evaluated by multifactorial analysis. All statistical tests are two-sided. RESULTS: Cancers associated with BRCA1 mutations exhibited higher mitotic counts (P = .001), a greater proportion of the tumor with a continuous pushing margin (P<.0001), and more lymphocytic infiltration (P = .002) than sporadic (i.e., control) cancers. Cancers associated with BRCA2 mutations exhibited a higher score for tubule formation (fewer tubules) (P = .0002), a higher proportion of the tumor perimeter with a continuous pushing margin (P<.0001), and a lower mitotic count (P = .003) than control cancers. CONCLUSIONS: Our study has identified key features of the histologic phenotypes of breast cancers in carriers of mutant BRCA1 and BRCA2 genes. This information may improve the classification of breast cancers in individuals with a family history of the disease and may ultimately aid in the clinical management of patients.

Adult↗
PubMed1998

Various mechanisms cause RET-mediated signaling defects in Hirschsprung's disease.

Hirschsprung's disease (HSCR) is a common congenital malformation characterized by the absence of intramural ganglion cells of the hindgut. Recently, mutations of the RET tyrosine kinase receptor have been identified in 50 and 15-20% of familial and sporadic HSCR, respectively. These mutations include deletion, insertion, frameshift, nonsense, and missense mutations dispersed throughout the RET coding sequence. To investigate their effects on RET function, seven HSCR missense mutations were introduced into either a 1114-amino acid wild-type RET isoform (RET51) or a constitutively activated form of RET51 (RET-MEN 2A). Here, we report that one mutation affecting the extracytoplasmic cadherin domain (R231H) and two mutations located in the tyrosine kinase domain (K907E, E921K) impaired the biological activity of RET-MEN 2A when tested in Rat1 fibroblasts and pheochromocytoma PC12 cells. However, the mechanisms resulting in RET inactivation differed since the receptor bearing R231H extracellular mutation resulted in an absent RET protein at the cell surface while the E921K mutation located within the catalytic domain abolished its enzymatic activity. In contrast, three mutations mapping into the intracytoplasmic domain neither modified the transforming capacity of RET-MEN 2A nor stimulated the catalytic activity of RET in our ligand-independent system (S767R, P1039L, M1064T). Finally, the C609W HSCR mutation exerts a dual effect on RET since it leads to a decrease of the receptor at the cell surface and converted RET51 into a constitutively activated kinase due to the formation of disulfide-linked homodimers. Taken together, our data show that allelic heterogeneity at the RET locus in HSCR is associated with various molecular mechanisms responsible for RET dysfunction.

3T3 Cells↗
PubMed1998

Host response to EBV infection in X-linked lymphoproliferative disease results from mutations in an SH2-domain encoding gene.

X-linked lymphoproliferative syndrome (XLP or Duncan disease) is characterized by extreme sensitivity to Epstein-Barr virus (EBV), resulting in a complex phenotype manifested by severe or fatal infectious mononucleosis, acquired hypogammaglobulinemia and malignant lymphoma. We have identified a gene, SH2D1A, that is mutated in XLP patients and encodes a novel protein composed of a single SH2 domain. SH2D1A is expressed in many tissues involved in the immune system. The identification of SH2D1A will allow the determination of its mechanism of action as a possible regulator of the EBV-induced immune response.

Antigens, CD↗
PubMed1998

Genetic heterogeneity and penetrance analysis of the BRCA1 and BRCA2 genes in breast cancer families. The Breast Cancer Linkage Consortium.

The contribution of BRCA1 and BRCA2 to inherited breast cancer was assessed by linkage and mutation analysis in 237 families, each with at least four cases of breast cancer, collected by the Breast Cancer Linkage Consortium. Families were included without regard to the occurrence of ovarian or other cancers. Overall, disease was linked to BRCA1 in an estimated 52% of families, to BRCA2 in 32% of families, and to neither gene in 16% (95% confidence interval [CI] 6%-28%), suggesting other predisposition genes. The majority (81%) of the breast-ovarian cancer families were due to BRCA1, with most others (14%) due to BRCA2. Conversely, the majority of families with male and female breast cancer were due to BRCA2 (76%). The largest proportion (67%) of families due to other genes was found in families with four or five cases of female breast cancer only. These estimates were not substantially affected either by changing the assumed penetrance model for BRCA1 or by including or excluding BRCA1 mutation data. Among those families with disease due to BRCA1 that were tested by one of the standard screening methods, mutations were detected in the coding sequence or splice sites in an estimated 63% (95% CI 51%-77%). The estimated sensitivity was identical for direct sequencing and other techniques. The penetrance of BRCA2 was estimated by maximizing the LOD score in BRCA2-mutation families, over all possible penetrance functions. The estimated cumulative risk of breast cancer reached 28% (95% CI 9%-44%) by age 50 years and 84% (95% CI 43%-95%) by age 70 years. The corresponding ovarian cancer risks were 0.4% (95% CI 0%-1%) by age 50 years and 27% (95% CI 0%-47%) by age 70 years. The lifetime risk of breast cancer appears similar to the risk in BRCA1 carriers, but there was some suggestion of a lower risk in BRCA2 carriers <50 years of age.

Adult↗
PubMed1998

Germ-line mutation analysis in patients with multiple endocrine neoplasia type 1 and related disorders.

Multiple endocrine neoplasia type 1 (MEN1) is an autosomal dominant syndrome predisposing to tumors of the parathyroid, endocrine pancreas, anterior pituitary, adrenal glands, and diffuse neuroendocrine tissues. The MEN1 gene has been assigned, by linkage analysis and loss of heterozygosity, to chromosome 11q13 and recently has been identified by positional cloning. In this study, a total of 84 families and/or isolated patients with either MEN1 or MEN1-related inherited endocrine tumors were screened for MEN1 germ-line mutations, by heteroduplex and sequence analysis of the MEN1 gene-coding region and untranslated exon 1. Germ-line MEN1 alterations were identified in 47/54 (87%) MEN1 families, in 9/11 (82%) isolated MEN1 patients, and in only 6/19 (31.5%) atypical MEN1-related inherited cases. We characterized 52 distinct mutations in a total of 62 MEN1 germ-line alterations. Thirty-five of the 52 mutations were frameshifts and nonsense mutations predicted to encode for a truncated MEN1 protein. We identified eight missense mutations and five in-frame deletions over the entire coding sequence. Six mutations were observed more than once in familial MEN1. Haplotype analysis in families with identical mutations indicate that these occurrences reflected mainly independent mutational events. No MEN1 germ-line mutations were found in 7/54 (13%) MEN1 families, in 2/11 (18%) isolated MEN1 cases, in 13/19 (68. 5%) MEN1-related cases, and in a kindred with familial isolated hyperparathyroidism. Two hundred twenty gene carriers (167 affected and 53 unaffected) were identified. No evidence of genotype-phenotype correlation was found. Age-related penetrance was estimated to be >95% at age >30 years. Our results add to the diversity of MEN1 germ-line mutations and provide new tools in genetic screening of MEN1 and clinically related cases.

Amino Acid Substitution↗
PubMed1998

NF2 gene in neurofibromatosis type 2 patients.

Neurofibromatosis type 2 (NF2) is an autosomal dominant disorder that predisposes to nervous system tumors. The schwannomin (also termed merlin) protein encoded by the NF2 gene shows a close relationship to the family of cytoskeleton-to-membrane proteins linkers ERM (ezrin-radixin-moesin proteins). Even though penetrance of the disease is >95% and no genetic heterogeneity has been described, point mutations in the NF2 gene have been observed in only 34-66% of the screened NF2 patients, depending on the series. In order to generate tools that would enable an exhaustive alteration screening for the NF2 gene, we have deduced its entire genomic sequence. This knowledge has provided the delineation of a mutation screening strategy which, when applied to a series of 19 NF2 patients, has revealed a high recurrence of large deletions in the gene and has raised the efficiency of mutation detection in NF2 patients to 84% of the cases in this series. The remaining three patients who express two functional NF2 alleles are all sporadic cases, an observation compatible with the presence of mosaicism for NF2 mutation.

Cells, Cultured↗
PubMed1997

Abundance of BRCA1 transcripts in human cancer and lymphoblastoid cell lines carrying BRCA1 germ-line alterations.

A competitive polymerase chain reaction has been developed for quantitation of BRCA1 mRNA. In human cancer cell lines, the amount of BRCA1 mRNA is relatively low, ranging from 6 to 38 copies per cell. The decay rate of these transcripts in actinomycin-treated cells indicates that the half-life of these molecules is about 4 hr, suggesting that the low concentration of BRCA1 messages is not due to molecular unstability. In human lymphoblastoid cell lines derived from patients carrying germ-line alterations of BRCA1, the amount of BRCA1 mRNA per cell is lowered only in cell lines exhibiting alterations leading to specific loss of transcripts from the mutated allele. These data indicate that the amount of BRCA1 available in these cells can be related directly to the number of "active" allele.

Breast Neoplasms↗
PubMed1997

Construction of a 1.2-Mb sequence-ready contig of chromosome 11q13 encompassing the multiple endocrine neoplasia type 1 (MEN1) gene. The European Consortium on MEN1.

Multiple endocrine neoplasia type 1 (MEN1) is an autosomal dominant familial cancer syndrome characterized by parathyroid, pancreatic, and anterior pituitary tumors. The MEN1 locus has been previously localized to chromosome 11q13, and a 2-Mb gene-rich region flanked by D11S1883 and D11S449 has been defined. We have pursued studies to facilitate identification of the MEN1 gene by narrowing this critical region to a 900-kb interval between the VRF and D11S1783 loci through melotic mapping. This was achieved by investigating 17 cosmids for microsatellite polymorphisms, which defined two novel polymorphisms at the VRF and A0138 loci, and utilizing these to characterize recombinants in MEN1 families. In addition, we have established a 1200-kb sequence-ready contig consisting of 26 cosmids, eight BACs, and eight PACs that encompass this region. The precise locations for 19 genes and three ESTs within this contig have been determined, and three gene clusters consisting of a centromeric group (VRF, FKBP2, PNG, and PLCB3), a middle group (PYGM, ZFM1, SCG1, SCG2 (which proved to be the MEN1 gene), and PPP2R5B), and a telomeric group (H4B, ANG3, ANG2, ANG1, FON, FAU, NOF, NON, and D11S2196E) were observed. These results represent a valuable transcriptional map of chromosome 11q13 that will help in the search for disease genes in this region.

Chromosome Mapping↗
PubMed1997

A descriptive study of BRCA1 testing and reactions to disclosure of test results.

BACKGROUND: The identification of the BRCA1 gene is a powerful tool for predicting a patient's lifetime risk for carcinoma of the breast and ovary when she has hereditary breast/ovarian carcinoma (HBOC) syndrome. The process of BRCA1 testing and genetic counseling and participants' reactions to test results, are described. METHODS: Education about the natural history of HBOC syndrome and the pros and cons of genetic testing was provided to 14 HBOC families comprised of 2549 bloodline relatives. Of these, 388 underwent DNA testing. After informed consent was given by participants, formal linkage analysis and gene mutation studies were performed on the families. Qualitative data on intentions and emotional reactions were collected by physicians/counselors during the genetic counseling sessions. RESULTS: Of those tested, 181 received their results after further genetic counseling. Seventy-eight of them were positive and 100 were negative for BRCA1 gene mutation. Three had ambiguous findings. The most common reasons given for seeking DNA testing were concern about risk to children and concern about surveillance and prevention. Prophylactic mastectomy was considered by 35% of women who tested positive, whereas prophylactic oophorectomy was considered an important option by 76%. Twenty-five percent of both BRCA1 positive and negative individuals were concerned about discrimination by insurance companies. Eighty percent of those who tested negative reported emotional relief, whereas over one-third of those who tested positive reported sadness, anger, or guilt. CONCLUSIONS: DNA testing of patients with HBOC syndrome must be performed in the context of genetic counseling. The authors' results demonstrate the many complex clinical and nonclinical issues that are important in this process.

Adult↗
PubMed1997

[Neurosarcoma associated with neurofibromatosis 1. Apropos of a case and review of the literature].

BACKGROUND: Type 1 neurofibromatosis considerably increases the risk of cancer development, particularly neurosarcoma. We report a case in a patient with chemosensitive metastatic neurosarcoma. CASE REPORT: A young female patient with familial type 1 neurofibromatosis developed pleural metastasis of a neurosarcoma located on the arm. This tumor was initially highly sensitive to chemotherapy, but relapse occurred. DISCUSSION: Follow-up in the order members of the family was particularly difficult to organize. One sister developed cerebral astrocytoma. Neurosarcomas develop earlier in patients with type 1 neurofibromatosis, worsening prognosis. We suggest a prospective and structured registration of such cases using a network of clinicians and pathologists in order to improve management schemes.

Adult↗
PubMed1997

Insight into cystic fibrosis by structural modelling of CFTR first nucleotide binding fold (NBF1).

Cystic fibrosis is a human monogenic genetic disease caused by mutations in the cystic fibrosis (CF) gene, which encodes a membrane protein which functions as a channel: the cystic fibrosis transmembrane conductance regulator (CFTR) protein. The most frequent mutation, a deletion of phenylalanine F508 (delta F508), is located in the first nucleotide binding domain of CFTR: NBF1. This mutation leads to a folding defect in NBF1, responsible for an incomplete maturation of CFTR. The absence of CFTR at the surface of epithelial cells causes the disease. Determination of the three-dimensional (3D) structure of NBF1 is a key step to understanding the alterations induced by the mutation. In the absence of any experimental data, we have chosen to build a 3D model for NBF1. This model was built by homology modelling starting from F1-ATPase, the only protein of known 3D structure in the ATP binding cassette (ABC) family. This new model defines the central and critical position of F508, predicted in the hydrophobic core of NBF1. F508 indeed could be involved in hydrophobic interactions to ensure a correct folding pathway. Moreover, this model enables the localization of the LSGGQ sequence (a highly conserved sequence in the ABC family) in a loop, at the surface of the protein. This reinforces the hypothesis of its role for mediation of domain-domain interactions of functional significance for the channel regulation. Finally, the model also allows redefinition of the ends of NBF1 within the CFTR sequence. These extremities are defined by the secondary structure elements that are involved in the NBF1 fold. They lead to reconsideration of the C-terminal limit which was initially defined by the end of exon 12.

Amino Acid Sequence↗
PubMed1997

Identification of the multiple endocrine neoplasia type 1 (MEN1) gene. The European Consortium on MEN1.

Multiple endocrine neoplasia type 1 (MEN1) is an autosomal dominant disorder characterised by tumours of the parathyroids, pancreas and anterior pituitary that represents one of the familial cancer syndromes. The MEN1 locus has been previously localised to chromosome 11q13, and a <300 kb gene-rich region flanked centromerically by PYGM and telomerically by D11S1783 defined by combined meiotic and tumour deletion mapping studies. Two candidate genes, ZFM1 and PPP2R5B, from this region have been previously excluded, and in order to identify additional candidate genes we used a BAC to isolate cDNAs from a bovine parathyroid cDNA library by direct selection. One of the novel genes that we identified, SCG2, proved to be identical to the recently published MEN1 gene, which is likely to be a tumour suppressor gene. The SCG2 transcript was 2.9 kb in all tissues with an additional 4.2 kb transcript also being present in the pancreas and thymus. Mutational analysis of SCG2 in 10 unrelated MEN1 families identified one polymorphism and nine different heterozygous mutations (one missense, four non-sense, one insertional and three deletional frameshifts) that segregated with the disease, hence providing an independent confirmation for the identification of the MEN1 gene.

Animals↗
PubMed1997

In vitro susceptibilities to amphotericin B, itraconazole, and miconazole of filamentous fungi isolated from patients with cystic fibrosis.

The antimicrobial activities of amphotericin B, itraconazole, and miconazole against 101 filamentous fungi from patients with cystic fibrosis were tested by a reproducible microdilution method. Itraconazole was very active against Aspergillus species and Scedosporium species (MIC at which 90% of the isolates were inhibited [MIC90], 0.06 to 0.5 mg/liter), whereas amphotericin B was less effective (MIC90, 0.5 to 8 mg/liter).

Amphotericin B↗
PubMed1997

A large multiple endocrine neoplasia type 1 family with clinical expression suggestive of anticipation.

We describe a large multigenerational multiple endocrine neoplasia Type 1 (MEN1) family with clinical expression suggestive of anticipation. In the second and third generations, two deceased obligate gene carriers died at the ages of 85 and 76 without the history of MEN1, whereas two other living gene carriers above the age of 65 have had no clinical evidence of MEN1 to date. In the fourth generation, eight members were affected, with four having severe MEN1-related and atypical malignancies: a case of metastatic endocrine pancreatic tumor, two cases of metastatic thymic carcinoids, and a case of spinal ependymoma. In the fifth generation, all five patients were below the age of 22 when the disease was detected. MEN1 was confirmed in the family by linkage analysis using MEN1-linked microsatellite markers and by identification of a nonsense mutation in the MEN1/menin gene. Alleotyping showed loss of heterozygosity (LOH) involving the wild-type alleles in seven tumors in the family including the ependymoma, which is the first MEN1-related case that shows genetic abnormality in chromosome 11q13, suggesting that MEN1 gene might be involved in the tumorigenesis of a subset of ependymomas. In relation to clinical anticipation, repeated expansion studies were carried out but failed to detect any expansion. We conclude that this is a unique MEN1 family and that an unknown genetic mechanism might be contributing to the anticipation phenomenon. We demonstrate in this family that all gene carriers, including the very young members, will need close and careful follow-up.

Adult↗
PubMed1997

[Severe colitis in mucoviscidosis].

We report the association of severe indeterminate colitis with cystic fibrosis in a 21 year old woman, with mild pulmonary involvement, and without digestive or pancreatic symptoms or pancreatic enzyme preparation. Ten cases of inflammatory bowel disease associated with a cystic fibrosis have been reported. Most fit with the diagnostic criteria of Crohn's disease. Although this case was compatible with this diagnosis, we have retained the diagnosis of "severe indeterminate colitis" because of the lack of specific histological features of Crohn's disease. The association between inflammatory bowel disease and cystic fibrosis is probably not fortuitous, although the pathophysiological link between the two diseases is unknown.

Adolescent↗
PubMed1997

[Endoscopic endonasal ethmoidectomy in severe sinusitis of cystic fibrosis. Mid-term results in 12 patients].

UNLABELLED: Sinusitis, with sometimes severe symptoms, are frequent in cystic fibrosis (CF). The aim of this mild-term retrospective study was to evaluate the functional and anatomical results of functional endoscopic ethmoidectomy (FEE) in 12 patients with CF. Nasal polyposis (9 cases) and medialization of the nasomaxillary wall (3 cases) were detected during endoscopic examination. Bilateral and multifocal opacities of the paranasal sinuses were present on the CT-scan images in all cases. A FEE was performed in 11 cases and in 1 case, only the anterior ethmoid was opened. Symptoms improved or disappeared in 9/12 cases between 1 and 3 years of follow-up and in 5/7 cases after 3 years of follow-up. A good or mild anatomical result was recorded in 6/12 cases between 1 and 3 years of follow-up and in 5/7 cases after 3 years of follow-up. During follow-up, a new surgical procedure (limited in 8 patients and complete in 3 patients) was often necessary. CONCLUSION: It is reasonable to propose FEE in CF patients with chronic sinusitis presenting severe symptoms with the aim of a substantial functional but not anatomical improvement.

Adolescent↗
PubMed1996

The relationship between specific RET proto-oncogene mutations and disease phenotype in multiple endocrine neoplasia type 2. International RET mutation consortium analysis.

OBJECTIVE: Multiple endocrine neoplasia type 2 (MEN 2) is an autosomal dominant disorder. The 3 recognized subtypes include MEN 2A, characterized by medullary thyroid carcinoma (MTC), pheochromocytoma (pheo), and hyperparathyroidism (HPT); MEN 2B, by MTC, pheo, and characteristic stigmata; and familial MTC (FMTC), by the presence of MTC only. The purpose of this study was to establish the relationship between specific mutations and the presence of certain disease features in MEN 2 which could help in clinical decision making. DESIGN: Correlative survey study of 477 MEN 2 families. SETTING: Eighteen tertiary referral centers worldwide. PATIENTS: A total of 477 independent MEN 2 families. MAIN OUTCOME MEASURES: Association between the position and type of germline mutation in the RET proto-oncogene and the presence or absence of MTC, pheo, HPT, and/or other features in a family. RESULTS: There is a statistically significant association between the presence of any mutation at a specific position (codon 634) and the presence of pheo and HPT. The presence of a specific mutation, CGC at codon 634, has yet to be associated with FMTC. Conversely, mutations at codons 768 and 804 are thus far seen only with FMTC, while codon 918 mutation is MEN 2B--specific. Rare families with both MEN 2 and Hirschsprung disease were found to have MEN 2-specific codon mutations. Patients with Hirschsprung disease presenting with such mutations should be monitored for the possible development of MEN 2 tumors. CONCLUSIONS: This consortium analysis suggests that genotype-phenotype correlations do exist and, if made reliably absolute, could prove useful in the future in clinical management with respect to screening, surveillance, and prophylaxis, as well as provide insight into the genetic effects of particular mutations.

Carcinoma, Medullary↗