Biomedical subjects

S A Gayther

Publications and source records attributed to S A Gayther.

At least 19 recordsLinked to original sources

PubMed2001

Apparent human BRCA1 knockout caused by mispriming during polymerase chain reaction: implications for genetic testing.

We report an apparent BRCA1 homozygous knockout that, on further analysis, was found to be an artefact of the polymerase chain reaction. This finding has two important implications. First, it challenges results of a previous study that reported a homozygous knockout associated with the same BRCA1 mutation. Second, our findings suggest that mispriming caused by mismatched primers at the site of single-nucleotide polymorphisms, leading to preferential amplification of one allele, may represent a significant proportion of instances of mutation-detection insensitivity. This may have major implications for the sensitivity of all polymerase chain reaction-based mutation-detection methods in clinical genetic testing laboratories.

Artifacts↗

PubMed2000

The frequency of germ-line mutations in the breast cancer predisposition genes BRCA1 and BRCA2 in familial prostate cancer. The Cancer Research Campaign/British Prostate Group United Kingdom Familial Prostate Cancer Study Collaborators.

Predisposition to prostate cancer has a genetic component, and there are reports of familial clustering of breast and prostate cancer. Two highly penetrant genes that predispose individuals to breast cancer (BRCA1 and BRCA2) are known to confer an increased risk of prostate cancer of about 3-fold and 7-fold, respectively, in breast cancer families. Blood DNA from affected individuals in 38 prostate cancer clusters was analyzed for germ-line mutations in BRCA1 and BRCA2 to assess the contribution of each of these genes to familial prostate cancer. Seventeen DNA samples were each from an affected individual in families with three or more cases of prostate cancer at any age; 20 samples were from one of affected sibling pairs where one was < or = 67 years at diagnosis. No germ-line mutations were found in BRCA1. Two germ-line mutations in BRCA2 were found, and both were seen in individuals whose age at diagnosis was very young (< or = 56 years) and who were members of an affected sibling pair. One is a 4-bp deletion at base 6710 (exon 11) in a man who had prostate cancer at 54 years, and the other is a 2-bp deletion at base 5531 (exon 11) in a man who had prostate cancer at 56 years. In both cases, the wild-type allele was lost in the patient's prostate tumor at the BRCA2 locus. However, intriguingly, in neither case did the affected brother also carry the mutation. Germ-line mutations in BRCA2 may therefore account for about 5% of prostate cancer in familial clusters.

Adult↗

PubMed2000

Frequent loss of BRCA1 mRNA and protein expression in sporadic ovarian cancers.

Germline mutations in the BRCA1 gene cause inherited susceptibility to breast and ovarian cancers. However, somatic mutations of BRCA1 are rare in sporadic breast and ovarian tumours. To establish whether BRCA1 is altered during the development of sporadic ovarian cancer by mechanisms other than somatic mutation, we have analysed 57 sporadic epithelial ovarian tumours for BRCA1 protein and RNA expression. Reduced or absent protein expression was observed in 90% of tumours. Decreased protein expression was significantly associated with a reduction in the levels of RNA expression. Somatic mutations of BRCA1 and LOH at the BRCA1 locus were detected in 3.5% and 44% of informative tumours, respectively; there was no significant correlation between the levels of protein and RNA expression and the DNA mutation and/or LOH status. Together, these data suggest that expression of BRCA1 is down-regulated at the level of transcription during the development of sporadic ovarian cancers.

BRCA1 Protein↗

PubMed2000

Risk models for familial ovarian and breast cancer.

We investigated risk models for the inherited susceptibility of breast and ovarian cancer, using data from both high-risk families and a population based series of ovarian cancer. The first data set consisted of 112 families containing two or more relatives with epithelial ovarian cancer. BRCA1 and BRCA2 germline mutations were detected in 50% of these families. The second study involved 374 ovarian cancer cases, unselected for family history, who had DNA samples analyzed for BRCA1 mutations. Twelve women were found to be carriers. We constructed genetic models for ovarian and breast cancer using the computer program MENDEL. In the first study, we modeled the effects of BRCA1 and BRCA2 simultaneously and allowed for a third gene predisposing to ovarian cancer. None of the models fitted gave significant evidence for a third gene. Population frequencies of BRCA1 and BRCA2 mutations were estimated to be 0. 00128 and 0.00172, respectively. Our results suggest that BRCA1 and BRCA2 may be sufficient to explain the majority of familial ovarian cancer and that families without mutations can be explained by sensitivity of mutation testing and chance clusters of sporadic cases. Using data on the families of the 12 mutation carriers in the second study, we estimated age-specific ovarian and breast cancer risks for BRCA1 mutation carriers. Under the best-fitting model, the cumulative ovarian cancer risk was 66% by age 70, and the corresponding breast cancer risk was 45%. The high penetrance estimate for ovarian cancer, compared with other studies, suggests that modifying genetic or environmental factors may be important determinants of risk.

Breast Neoplasms↗

PubMed2000

Idiopathic slow-transit constipation is not associated with mutations of the RET proto-oncogene or GDNF.

PURPOSE: Idiopathic slow-transit constipation is a severe disorder of unknown cause. The onset in early childhood and history of constipation or Hirschsprung's disease in close family relatives suggest that slow-transit constipation could have a genetic basis. Several germline mutations have been described in Hirschsprung's disease, including mutations of RET and the gene encoding its ligand glial cell-derived neurotrophic factor. The aim of this study was to screen a panel of 16 cases of familial idiopathic slow-transit constipation, including 4 families in which there were relatives with Hirschsprung's disease, for RET and glial cell-derived neurotrophic factor mutations previously identified in Hirschsprung's disease. METHODS: Genomic DNA from 16 patients with slow-transit constipation and four relatives with Hirschsprung's disease was analyzed using single strand and heteroduplex conformation polymorphism analysis at two conditions and by direct DNA sequencing using the fluorescent dideoxy terminator method. RESULTS: Although common sequence polymorphisms were demonstrated with a frequency comparable with published data, no published or new mutation was seen in any of the exons of RET or glial cell-derived neurotrophic factor. CONCLUSIONS: Mutation of RET or glial cell-derived neurotrophic factor is not a frequent cause of idiopathic slow-transit constipation.

Adult↗

PubMed2000

Mutations truncating the EP300 acetylase in human cancers.

The EP300 protein is a histone acetyltransferase that regulates transcription via chromatin remodelling and is important in the processes of cell proliferation and differentiation. EP300 acetylation of TP53 in response to DNA damage regulates its DNA-binding and transcription functions. A role for EP300 in cancer has been implied by the fact that it is targeted by viral oncoproteins, it is fused to MLL in Leukaemia and two missense sequence alterations in EP300 were identified in epithelial malignancies. Nevertheless, direct demonstration of the role of EP300 in tumorigenesis by inactivating mutations in human cancers has been lacking. Here we describe EP300 mutations, which predict a truncated protein, in 6(3%) of 193 epithelial cancers analysed. Of these six mutations, two were in primary tumours (a colorectal cancer and a breast cancer) and four were in cancer cell lines (colorectal, breast and pancreatic). In addition, we identified a somatic in-frame insertion in a primary breast cancer and missense alterations in a primary colorectal cancer and two cell lines (breast and pancreatic). Inactivation of the second allele was demonstrated in five of six cases with truncating mutations and in two other cases. Our data show that EP300 is mutated in epithelial cancers and provide the first evidence that it behaves as a classical tumour-suppressor gene.

Acetyltransferases↗

PubMed1999

Increased frequency of TP53 mutations in BRCA1 and BRCA2 ovarian tumours.

We screened 81 ovarian tumours (30 BRCA1 associated, 18 BRCA2 associated, and 33 sporadic) for somatic TP53 mutations using both DNA analysis and immunostaining. TP53 mutations were significantly more frequent in tumours with mutations in BRCA1 (70% by immunostaining and 60% by DNA analysis) and BRCA2 (67% and 50%) compared to sporadic controls (39% and 30%) (P = 0.009). A higher proportion of tumours with BRCA1 and BRCA2 mutations were poorly differentiated, and TP53 mutant tumours in all categories were also more likely to be poorly differentiated. The poor differentiation of tumours with BRCA1 and BRCA2 mutations may be directly related to the role of these genes in DNA repair, and the need to overcome cell cycle checkpoints, often through loss of TP53. These results are consistent with the model of BRCA-induced tumorigenesis in which loss of checkpoint control is necessary for tumour development.

Alleles↗

PubMed1999

The contribution of germline BRCA1 and BRCA2 mutations to familial ovarian cancer: no evidence for other ovarian cancer-susceptibility genes.

To establish the contribution of germline BRCA1 and BRCA2 mutations to familial ovarian cancer, we have analyzed both genes in DNA samples obtained from an affected individual in each of 112 families containing at least two cases of epithelial ovarian cancer. Germline mutations were found in 43% of the families; BRCA1 mutations were approximately four times more common than BRCA2 mutations. The extent of family history of ovarian and breast cancers was strongly predictive of BRCA1-mutation status. Segregation analysis suggests that a combination of chance clustering of sporadic cases and insensitivity of mutation detection may account for the remaining families; however, the contribution of other genes cannot be excluded. We discuss the implications for genetic testing and clinical management of familial ovarian cancer arising from the data presented in these studies.

BRCA2 Protein↗

PubMed1999

Familial gastric cancer: overview and guidelines for management.

Families with autosomal dominant inherited predisposition to gastric cancer have been described. More recently, germline E-cadherin/CDH1 mutations have been identified in hereditary diffuse gastric cancer kindred. The need to have protocols to manage and counsel these families in the clinic led a group of geneticists, gastroenterologists, surgeons, oncologists, pathologists, and molecular biologists to convene a workshop to produce consensus statements and guidelines for familial gastric cancer. Review of the available cancer pathology from people belonging to families with documented germline E-cadherin/CDH1 mutations confirmed that the gastric cancers were all of the diffuse type. Criteria to define the different types of familial gastric cancer syndromes were agreed. Foremost among these criteria was that review of histopathology should be part of the evaluation of any family with aggregation of gastric cancer cases. Guidelines for genetic testing and counselling in hereditary diffuse gastric cancer were produced. Finally, a proposed strategy for clinical management in families with high penetrance autosomal dominant predisposition to gastric cancer was defined.

Cadherins↗

PubMed1998

Identification of germ-line E-cadherin mutations in gastric cancer families of European origin.

E-cadherin germ-line mutations have recently been described as a molecular basis for early-onset familial gastric cancer in Maori kindred. We screened 18 gastric cancer families of European origin for germ-line mutations to determine the proportion in which E-cadherin mutations occur and the clinical characteristics of the affected families. Truncating mutations were identified in three kindred with familial diffuse gastric cancer. In these families, the age of onset of gastric cancer was variable, the penetrance was incomplete, and one kindred contained individuals with cancers at other sites. Here, we show that a proportion of diffuse gastric cancer families of European origin have germ-line E-cadherin mutations; however, these mutations are absent in intestinal gastric cancer families.

Adult↗

PubMed1998

The genetics of inherited breast cancer.

The isolation of BRCA1 and BRCA2 has greatly increased our understanding of the genetics of inherited breast and ovarian cancer although the functions of these genes are not yet fully understood. We will discuss the current state of knowledge about the function of BRCA1 and BRCA2 and summarize the cancer risks in women carrying a BRCA1 or BRCA2 mutation. We review the evidence for gene-gene and gene-environment interaction in modifying that risk, and discuss the contribution of BRCA1 and BRCA2 and other high penetrance genes to both inherited and sporadic breast cancer.

BRCA1 Protein↗

PubMed1998

Mutation analysis of the c-mos proto-oncogene in human ovarian teratomas.

Female transgenic mice lacking a functional c-mos proto-oncogene develop ovarian teratomas, indicating that c-mos may behave as a tumour-suppressor gene for this type of tumour. We have analysed the entire coding region of the c-MOS gene in a series of human ovarian teratomas to determine whether there are any cancer-causing alterations. DNA from twenty teratomas was analysed by single-strand conformational analysis (SSCA) and heteroduplex analysis (HA) to screen for somatic and germline mutations. In nine of these tumours the entire gene was also sequenced. A previously reported polymorphism and a single new sequence variant were identified, neither of which we would predict to be disease-causing alterations. These results suggest that mutations in the coding region of the c-MOS gene do not play a significant role in the genesis of human ovarian teratomas.

DNA Mutational Analysis↗

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

Clues to the function of the tumour susceptibility gene BRCA2.

The breast cancer susceptibility gene BRCA2 was isolated in 1995. BRCA2 is a large gene comprising 10,254 nucleotides and 26 coding exons. Neither the nucleotide nor the predicted protein sequences (comprising 3,418 amino acids) have provided substantial clues about its function. As a result, researchers have been trying to elucidate the function using a combination of cell biological and biochemical methods and the construction of animal models using gene targeting in mice. Recent data suggest that BRCA2 may participate in pathways associated with recombination or double-strand DNA break repair and may act by either sensing or responding to DNA damage. In addition, there is evidence to suggest that BRCA2 functions in a manner similar to the previously isolated breast cancer susceptibility gene BRCA1.

Animals↗

PubMed1997

Aberrant splicing of the TSG101 and FHIT genes occurs frequently in multiple malignancies and in normal tissues and mimics alterations previously described in tumours.

Intragenic deletions of TSG101, the human homolog of a mouse gene (tsg101) that acts to suppress malignant cell growth, were reported in human breast tumours. We screened TSG101 for somatic mutations in DNA and RNA samples isolated from a variety of common human malignancies, EBV-immortalised B-cells, and normal lung parenchyma. Intragenic TSG101 deletions in RNA transcripts were frequently found in all types of samples. Analysis of DNA failed to show genomic rearrangements corresponding to transcripts containing deletions in the same samples. The breakpoints of most transcript deletions coincide with genuine or cryptic splice site sequences, suggesting that they result from alternative or aberrant splicing. A similar spectrum of transcript deletions has previously been described in the putative tumour suppressor gene FHIT. We analysed FHIT in the same series of RNA samples and detected truncated FHIT transcripts frequently in both tumour and normal tissues. In addition, transcripts from TSG101, FHIT and seven other genes were analysed in RNA isolated from normal peripheral blood lymphocytes. Large TSG101 and FHIT intragenic transcript deletions were detected and these appeared to be the predominant transcript in 'aged' lymphocytes. Similar alterations were not detected in transcripts of the other genes which were analysed. Our findings demonstrate that truncated TSG101 and FHIT transcripts are commonly detected in both normal and malignant tissues and that a significant fraction of these are likely to be the result of aberrant splicing. While we cannot exclude that alterations in TSG101 and FHIT occur during cancer development, our data indicate that in this context the commonly observed transcript abnormalities are misleading.

Acid Anhydride Hydrolases↗

PubMed1997

Contribution of BRCA1 mutations to ovarian cancer.

BACKGROUND: Inherited mutations in the BRCA1 gene confer a high risk of breast and ovarian cancer in some families. To determine the contribution of BRCA1 mutations to ovarian cancer in the general population, we analyzed DNA samples from a consecutive series of women with ovarian cancer seen at one center. METHODS: We studied 374 women who received a diagnosis of epithelial ovarian cancer before the age of 70 years and were treated at the Royal Marsden Hospital between July 1993 and September 1995. Genomic DNA was analyzed by multiplex heteroduplex analysis. Variants were further identified by sequencing. RESULTS: Probable germ-line BRCA1 mutations were identified in 13 of the 374 women (3 percent; 95 percent confidence interval, 2 to 6 percent). Six of the variants have not been described previously. Of the 13 mutations, 12 are predicted to result in a truncated protein product. An additional variant results in an in-frame deletion just outside the putative zinc-finger domain. Nine of the 12 women with truncating mutations had family histories of breast or ovarian cancer or both. CONCLUSIONS: Assuming that our method has a sensitivity of 70 percent, mutations in BRCA1 occur in approximately 5 percent (95 percent confidence interval, 3 to 8 percent) of women in whom ovarian cancer is diagnosed before the age of 70 years.

Adenocarcinoma, Clear Cell↗

PubMed1997

Mutations of the BRCA1 and BRCA2 genes and the possibilities for predictive testing.

Two cancer susceptibility genes, BRCA1 on chromosome 17q12-21 and BRCA2 on chromosome 13q12-13, are thought to be responsible for approximately 80% of families containing multiple cases of early-onset female breast cancer. Germline mutations of BRCA1 are also associated with ovarian cancer and mutations of BRCA2 are associated with an increased risk of male breast cancer, ovarian cancer, prostate cancer and pancreatic cancer. The recent isolation of both genes should make possible the identification of the genetic defect that predisposes affected individuals to breast and ovarian cancer and might lead to the use of genetic information for predictive testing.

BRCA2 Protein↗

PubMed1997

Variation of risks of breast and ovarian cancer associated with different germline mutations of the BRCA2 gene.

The breast cancer susceptibility gene BRCA2 on chromosome 13q12-13 has recently been identified. Germline mutations of BRCA2 are predicted to account for approximately 35% of families with multiple case, early onset female breast cancer, and they are also associated with an increased risk of male breast cancer, ovarian cancer, prostate cancer and pancreatic cancer. Germline mutations of a second cancer susceptibility gene BRCA1 (ref. 5), are associated with a strong predisposition to ovarian cancer as well as female breast cancer. Recent studies have suggested that the phenotype in BRCA1 families with respect to the ratio of breast to ovarian cancer varies with the location of the BRCA1 mutation. To determine whether germline mutations in BRCA2 are associated with a similar variation in phenotypic risk, we have analysed the distribution of mutations in 25 families with multiple cases of breast and/or ovarian cancer ascertained in the United Kingdom and Eire. These mutations all lead to premature truncation of BRCA2 as a result of frameshift deletions/insertions or nonsense mutations. Analysis of the mutation distribution along the length of the gene indicates a significant genotype-phenotype correlation. Truncating mutations in families with the highest risk of ovarian cancer relative to breast cancer are clustered in a region of approximately 3.3 kb in exon 11 (P = 0.0004). Published data on mutations in 45 other BRCA2-linked families provide support for this correlation.

BRCA2 Protein↗