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Biomedical subjects

B Ponder

Publications and source records attributed to B Ponder.

At least 19 recordsLinked to original sources
PubMed2006

A prospective study of neurofibromatosis type 1 cancer incidence in the UK.

Neurofibromatosis type 1 (NF1) is an autosomal dominant condition affecting around one in 3000 live births. The manifestations of this condition are extremely variable, even within families, and genetic counselling is consequently difficult with regard to prognosis. Individuals with NF1 are acknowledged to be at increased risk of malignancy. Several studies have previously attempted to quantify this risk, but have involved relatively small study populations. We present prospective data from 448 individuals with NF1 with a total of 5705 years of patient follow-up. These data have been collected via the UK NF1 association for patients. Demographic information on the affected individuals was cross-referenced with UK cancer registry data by the UK Office of National Statistics. The overall risk of cancer was 2.7 times higher in this cohort of NF1 patients than in the general population (95% confidence interval (CI) 1.9-3.7). The cumulative risk of a malignancy by age 50 years was 20% (95% CI 14-29%); beyond this age, the risk of cancer was not significantly elevated (P=0.27). The most frequent types of cancer were connective tissue (14% risk by age 70, 95% CI 7.8-24%) and brain tumours (7.9, 95% CI 3.9-16%). There was no statistically significant excess of cancers at other sites (P=0.22).

Adolescent↗
PubMed1999

High frequency of germ-line BRCA2 mutations among Hungarian male breast cancer patients without family history.

To determine the contribution of BRCA1 and BRCA2 mutations to the pathogenesis of male breast cancer in Hungary, the country with the highest male breast cancer mortality rates in continental Europe, a series of 18 male breast cancer patients and three patients with gynecomastia was analyzed for germ-line mutations in both BRCA1 and BRCA2. Although no germ-line BRCA1 mutation was observed, 6 of the 18 male breast cancer cases (33%) carried truncating mutations in the BRCA2 gene. Unexpectedly, none of them reported a family history for breast/ovarian cancer. Four of six truncating mutations were novel, and two mutations were recurrent. Four patients (22%) had a family history of breast/ovarian cancer in at least one first- or second-degree relative; however, no BRCA2 mutation was identified among them. No mutation was identified in either of the genes in the gynecomastias. These results provide evidence for a strong genetic component of male breast cancer in Hungary.

Adenocarcinoma↗
PubMed1999

National Confidential Enquiry into counselling for genetic disorders by non-geneticists: general recommendations and specific standards for improving care.

OBJECTIVES: To assess genetic counselling by non-geneticists and to improve clinical practice. DESIGN: National retrospective review of casenotes. SETTING: Antenatal, paediatric, medical, and surgical units. SAMPLE: 1293 genetic events were identified, involving potentially avoidable cases of Down's syndrome, neural tube defect, cystic fibrosis, beta thalassaemia major and late onset medullary carcinoma of the thyroid (multiple endocrine neoplasia). Notes were available for review in 888 (69%) of these cases. OUTCOMES: Documented counselling, offers of relevant genetic screening and prenatal diagnosis. RESULTS: Clinical audit was frustrated by poor quality hospital records lacking evidence of counselling. Non-geneticist clinicians concentrate on the management of disease, and may overlook the need for counselling and recording data which patients will later need for decisions about reproduction or disease prevention. Counselling, screening and prenatal diagnosis were sometimes impossible because of late booking in pregnancy, or because of delayed diagnosis of an earlier affected child with cystic fibrosis. There are marked regional inequalities of access to genetic services, particularly for minority ethnic groups with increased risks of thalassaemia. Although patients were selected for this enquiry because they had known high risks of genetic disorders, on average less than half were referred to medical geneticists. General recommendations relevant for improvement of care for patients and families with medical genetic needs and those specific for each disorder are given. CONCLUSIONS: Assessment of the quality of genetic care becomes increasingly important as genetic counselling spreads beyond the narrow confines of specialist genetic services. Even though the events studied in this enquiry largely occurred between 1991 and 1995, there is little reason to believe that clinicians in general have become markedly better trained in medical genetics. The General Medical Council and Medical Royal Colleges should urgently consider the need for a national policy for improving undergraduate and postgraduate medical, nursing and midwifery education in genetics. Commissioners of clinical services should require that genetic management be at least as well-documented as surgical operations, drug records and informed consent, perhaps by using a nationally agreed pro-forma for prenatal diagnosis. Regular audit of counselling provided by non-geneticists is necessary to confirm that clinical improvements are occurring and standards are being met. The Confidential Enquiry provides data for a systematic approach to clinical governance of genetics in all specialities. This sets the scene for multi-speciality NHS genetic services capable of giving patients greater consistency both in access and in quality.

Clinical Competence↗
PubMed1998

Consortium study on 1280 breast carcinomas: allelic loss on chromosome 17 targets subregions associated with family history and clinical parameters.

The pattern of loss of heterozygosity (LOH) on chromosome 17 in human breast cancer is complicated and shows many different regions of loss. In an attempt to narrow down the relevant regions of LOH on chromosome 17, we have studied the deletion pattern and its association with clinical parameters in 1280 breast carcinoma-venous blood lymphocyte pairs. In total, 42 different chromosome 17 loci were investigated, and between 25 and 625 cases were analyzed at each locus. The frequency of LOH observed on the p arm was much higher than that observed on the q arm. The opposite effect was observed in 52 ovarian cancer cases investigated, with less LOH on 17p than on 17q. Patterns of loss consistent with interstitial and terminal deletions, as well as loss of either the p or q arm or monosomy 17 were observed. To determine whether loss at particular loci may be associated with biological features of breast tumors, clinical data including age of onset, family history of breast cancer, tumor histopathology, tumor size, estrogen receptor (ER) status, and occurrence of lymph node or distant metastases were collected for each case. Overall, large-sized, ER-negative, lymph node-positive ductal tumors showed the highest frequencies of LOH, with ER-negative and ductal tumors showing LOH for markers along the majority of the chromosome. Eight regions of chromosome 17 appear to be associated with human breast cancer, two on 17p and six on 17q. These regions were not necessarily in the areas exhibiting the highest frequencies of LOH but were defined by interstitial and terminal deletions in multiple independent cases. Seven of these regions showed statistically significant differences in LOH associated with clinical parameters. These data strongly suggest that loci on chromosome 17 may determine aspects of tumor presentation and disease behavior in human breast cancer and pinpoint candidate tumor suppressor gene loci.

Adult↗
PubMed1997

Genetic testing for cancer risk.

Genetic testing for cancer susceptibility is already part of the clinical management of families with some of the well-defined (but uncommon) inherited cancer syndromes. In cases where the risks associated with a predisposing mutation are less certain, or where there is no clearly effective intervention to offer those with a positive result, its use is more controversial. Careful evaluation of costs and benefits, and of the efficacy of interventions in those found to be at risk, is essential and is only just beginning. An immediate challenge is to ensure that both health professionals and the public understand clearly the issues involved.

Confidentiality↗
PubMed1996

GDNF signalling through the Ret receptor tyrosine kinase.

Mutational analysis in humans and mice has demonstrated that the Ret, the product of the c-ret proto-oncogene, a member of the receptor tyrosine kinase (RTK) superfamily, is essential for development of the enteric nervous system and kidney. Despite the established role of Ret in mammalian embryogenesis, its cognate ligand(s) is currently unknown. Here we demonstrate, by using a Xenopus embryo bioassay, that glial-cell-line-derived neurotrophic factor (GDNF), a distant member of the transforming growth factor (TGF)-beta superfamily, signals through the Ret RTK. Furthermore, using explant cultures from wild-type and Ret-deficient mouse embryos, we show that normal c-ret function is necessary for GDNF signalling in the peripheral nervous system. Our data strongly suggest that Ret is a functional receptor for GDNF, and that GDNF, in addition to its potential role in the differentiation and survival of central nervous system neurons, has profound effects on kidney organogenesis and the development of the peripheral nervous system.

Animals↗
PubMed1996

Allele loss from large regions of chromosome 17 is common only in certain histological subtypes of ovarian carcinomas.

Using a panel of ten polymorphic markers, we examined the frequency of loss of heterozygosity (LOH) on chromosome 17 in 55 sporadic ovarian tumours. LOH on 17p and 17q was observed to be 50% and 62% respectively. LOH at D17S5 was detected in 24/36 (67%) of malignant cases and in 19/43 (44%) at TP53; the marker D17S855 intragenic to the BRCA1 gene showed allele loss in 50% (20/40) cases. The data presented here suggest that loss of the whole chromosome 17 is a relatively frequent event (30%) in ovarian carcinomas and this observation is especially frequent for serous, transitional cell and anaplastic histological subtypes. Mucinous and endometrioid ovarian tumours showed only short interstitial deletions (4/11, 36%). The overall frequency of the short deletions was relatively low (7/43, 16%) in our panel of carcinomas. Amplification of c-erbB-2/neu oncogene was detected in 32% (11/34) of the carcinomas tested; the gene was amplified only in those histological subtypes in which high incidence of LOH on chromosome 17 was observed, and was associated with advanced stages of the disease. We conclude that different histological types of tumour may have different aetiological mechanisms, and tumour-suppressor genes on chromosome 17 might be associated specifically with serous and transitional cell ovarian carcinomas.

Alleles↗
PubMed1996

Haplotype and phenotype analysis of six recurrent BRCA1 mutations in 61 families: results of an international study.

Several BRCA1 mutations have now been found to occur in geographically diverse breast and ovarian cancer families. To investigate mutation origin and mutation-specific phenotypes due to BRCA1, we constructed a haplotype of nine polymorphic markers within or immediately flanking the BRCA1 locus in a set of 61 breast/ovarian cancer families selected for having one of six recurrent BRCA1 mutations. Tests of both mutations and family-specific differences in age at diagnosis were not significant. A comparison of the six mutations in the relative proportions of cases of breast and ovarian cancer was suggestive of an effect (P = .069), with 57% of women presumed affected because of the 1294 del 40 BRCA1 mutation having ovarian cancer, compared with 14% of affected women with the splice-site mutation in intron 5 of BRCA1. For the BRCA1 mutations studied here, the individual mutations are estimated to have arisen 9-170 generations ago. In general, a high degree of haplotype conservation across the region was observed, with haplotype differences most often due to mutations in the short-tandem-repeat markers, although some likely instances of recombination also were observed. For several of the instances, there was evidence for multiple, independent, BRCA1 mutational events.

Alleles↗
PubMed1995

A matched control study of familial epithelial ovarian cancer: patient characteristics, response to chemotherapy and outcome.

BACKGROUND: Many of the characteristics of patients with familial epithelial ovarian cancer (EOC) are not yet well defined. This report describes some of the characteristics of patients with EOC in particular response rates to chemotherapy and 5-year survival, and compares them with matched controls with sporadic EOC. PATIENTS AND METHODS: There were 28 cases of familial epithelial ovarian cancer (EOC) presenting to the Royal Marsden Hospital from January 1983 to September 1993. The incidence of familial EOC over this time period was 2.2% (28/1268). For each case of familial EOC, 3 controls were selected and matched for age, FIGO stage, volume of residual disease after initial surgery and type of chemotherapy; the matched controls were compared to the familial EOC cases for differences in histological subtype, response to chemotherapy and 5-year survival. There was a statistically significant difference in histological subtype, 83% of patients with familial EOC had serous cystadenocarcinoma compared to 49% in the matched control group (p = 0.0025) providing evidence that familial EOC has a genetic basis. However there were no differences in median age or FIGO stage between patients with familial EOC and the sporadic cases and no difference in overall response to chemotherapy or 5-year survival. CONCLUSIONS: Our results imply that familial and sporadic EOC are biologically very similar and therefore molecular studies on the pathogenesis of and cellular mechanisms involved in EOC may have an important impact on therapeutic strategies for the much commoner sporadic form of the disease. In addition, our data suggest that all patients should be closely questioned with regard to family history not just those who present at a young age.

Adolescent↗
PubMed1992

Molecular analysis of neurofibromatosis type 1 mutations.

We have examined a panel of 115 unrelated NF1 individuals for mutation in the 3' region of the NF1 gene, using Southern blotting and polymerase chain reaction amplification of exons followed by single-strand conformation polymorphism (SSCP) analysis. We found only 2 unequivocal mutations: a 571 bp deletion which removed exon 6 and resulted in a frameshift in exon 7, and a 2 bp deletion in exon 1. A third sequence variation detected by SSCP was predicted to cause a lysine-arginine substitution in exon 6. This is a conservative change, and since the affected individual is a new mutation whose parents are not available, we cannot be sure of its biological significance. We detected mutations in at most 3% of individuals, from an analysis which covered 17% of the coding sequence by SSCP and a larger region by Southern blotting. This relative failure to detect mutations accords with the experience of others. Even allowing for the incomplete sensitivity of the methods used, the results suggest that the majority of NF1 mutations lie elsewhere in the coding sequence or outside it.

Base Sequence↗
PubMed1992

Linkage mapping of human chromosome 10 microsatellite polymorphisms.

Ten microsatellite DNA polymorphisms located on human chromosome 10 were regionally mapped using subchromosomal somatic cell hybrids and linkage analysis. The resulting order of the markers from pter-qter was [D10S89, D10S111], D10S107, D10S109, [D10S91, D10S110, D10S108, D10S88, D10S168], and D10S169. Order of the markers within brackets was uncertain, although the order given was most likely. The microsatellites were distributed along the chromosome from the proximal p arm to near qter, with an unlinked gap between D10S168 and D10S169.

Alleles↗