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Query: UMLS:C0006142 (breast cancer)
 160,383 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In a study of nine families with "site-specific" ovarian cancer (criterion: three or more cases of epithelial ovarian cancer and no cases of breast cancer diagnosed at age < 50 years) we have obtained evidence of linkage to the breast-ovarian cancer susceptibility gene, BRCA1 on 17q12-21. If the risk of cancer in these families is assumed to be restricted to the ovary, the best estimate of the proportion of families linked to BRCA1 is .78 (95% confidence interval .32-1.0). If predisposition to both breast and ovarian cancer is assumed, the proportion linked is 1.0 (95% confidence interval .46-1.0). The linkage of familial site-specific ovarian cancer to BRCA1 indicates the possibility of predictive testing in such families; however, this is only appropriate in families where the evidence for linkage to BRCA1 is conclusive.
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PMID:Familial site-specific ovarian cancer is linked to BRCA1 on 17q12-21. 797 46

We report a family with the Li-Fraumeni syndrome (LFS) in whom we have been unable to detect a mutation in the coding sequence of the p53 gene. Analysis of linkage to three polymorphic markers within p53 enabled direct involvement of p53 to be excluded. This is the first example of a LFS family in whom exclusion of p53 has been possible. Four affected members of the family with sarcoma or premenopausal breast cancer showed increased expression of p53 protein in their normal tissues as detected by immunohistochemistry. It therefore appears that the LFS phenotype has been conferred by an aberrant gene, showing a dominant pattern of inheritance, which may be acting to compromise normal p53 function rather than by a mutation in p53 itself. In order to try to determine the chromosomal location of this putative gene, we have carried out studies of linkage to candidate loci. By these means we have excluded involvement of Rb1 and BRCA1 on chromosomes 13q and 17q respectively. The MDM2 oncogene on chromosome 12q was considered to be the prime candidate as MDM2 is amplified in sarcomas and the MDM2 product binds to p53. Furthermore, p53 mutation and amplification of MDM2 have been shown to be mutually exclusive events in tumour development. Linkage analysis to two polymorphic markers within MDM2 yielded a three-point LOD score of -5.4 at a recombination fraction theta equal to zero. Therefore MDM2 could be excluded. It is possible that the gene which is responsible for cancer susceptibility in this family, possibly via interaction with p53, will be important in the histogenesis of breast cancer in general. We are now carrying out further studies to locate and identify this gene.
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PMID:Linkage studies in a Li-Fraumeni family with increased expression of p53 protein but no germline mutation in p53. 798 Oct 72

Studies of familial breast and ovarian cancer have traditionally been directed towards a single type of cancer, but recent evidence leads us to consider these two types of cancer together. The original evidence for a common hereditary basis for breast and ovarian cancer comes from the observation of large families with several cases of both types. The number of cancers in these families was too great to be explained by chance and none of the known environmental risk factors are sufficient to account for the clustering. Statistical analysis performed on a number of breast-ovary cancer families identified by Dr Henry Lynch and his colleagues led them to conclude that the clustering could be explained by the effect of a single dominant gene. Women with breast cancer are at increased risk of developing a second primary cancer of the ovary; and relatives of women with breast or ovarian cancer are at roughly double the risk for either tumour. The most convincing evidence, however, for a common predisposition for breast and ovarian cancer comes from genetic linkage studies. In a linkage study cancer susceptibility in a family is shown to be transmitted with a particular allele of genetic marker of known chromosomal location. A gene from chromosome region 17q12-q21, designated BRCA1, identified in 1990 by Dr Mary-Claire King and colleagues, predisposes to both cancer of the breast and the ovary.
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PMID:Genetics of breast and ovarian cancer. 798 46

BRCA1, a gene predisposing to breast and ovarian cancer, was mapped to chromosome 17q21 by linkage analysis. Loss of heterozygosity in breast and ovarian tumors from BRCA1-linked patients always involved loss of wild-type alleles from chromosome 17q21, suggesting that BRCA1 acts as a tumor suppressor gene. Meiotic recombination in linked families constrained the BRCA1 region to an estimated physical size of 650 kilobases. Twenty-two candidate genes were isolated by screening complementary DNA libraries with yeast artificial chromosomes and cosmids from the critical region. Of these, 8 were known human genes, 7 were homologues of genes identified in other species, and 7 encoded novel transcripts. Each gene were sequenced and analyzed for variation, revealing 44 variants, including two missense mutations in two genes which segregated with breast cancer and were not found in controls. However, no frame-shift, nonsense, or regulatory mutations were found.
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PMID:The search for BRCA1. 798 31

A small proportion of breast cancer (perhaps about 5%) and a higher proportion of early onset cases are due to the inheritance of mutations in dominant susceptibility genes which confer a high lifetime risk of the disease. This would equate to about 1250 cases per year in the U.K. and 9000 in the U.S.A. Even within these cases, there is genetic heterogeneity, i.e. there are several genes involved, each giving rise to different patterns of other cancers associated with the familial breast cancer. One such gene (p53) has been identified and a second (BRCA1) has been precisely mapped in the human genome, but further breast cancer predisposition genes remain to be identified. In addition, there are other genes which confer a lower risk of the disease, but may account for a larger proportion of cases, the most important example to date being ataxia telangiectasia. The identification of these genes will enable the entity of familial breast cancer to be more precisely defined and has implications for management of gene carriers with breast cancer and their relatives who are at risk. A major consideration in this new area of cancer genetics is that the identification of gene carriers may become possible on a large scale and this raises ethical and social issues.
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PMID:The genetics of familial breast cancer and their practical implications. 799 29

The pathology of early-age onset breast cancer is considered here from three perspectives: 1) benign proliferative disease, 2) the cancers themselves, and 3) familial and hereditary breast cancer. Hereditary breast cancer, a subset of familial breast cancer featuring a strong autosomal dominant pedigree pattern and multiple primary cancers, has a strong predilection for younger women, accounting for about one half of breast cancers under age 30. With respect to benign proliferative disease, the increased relative risk of breast cancer associated with proliferative disease with atypia, about fourfold to fivefold for all ages, is doubled by the presence of a family history of breast cancer and amplified by young age. With respect to the carcinomas, the relative incidences of medullary carcinoma and ductal carcinoma in situ are increased in young women, while lobular and tubular carcinomas are decreased. Invasive breast cancer is higher grade and more proliferative in younger women, as measured by thymidine-labeling index, DNA flow cytometric S-phase fraction, and proliferation-associated proteins. The increased fraction of ductal carcinoma in situ and higher grade invasive cancers may help to account, respectively, for increased recurrence rates with conservative therapy, and more aggressive natural history in younger women. Familial breast cancers show trends for increased medullary type, but the effect is not independent of age. Weak associations of family history with tubular carcinoma have been reported, but data for associations with lobular carcinoma in situ and invasive lobular carcinoma are conflicting. Hereditary breast cancer as a class has higher tumor proliferation rates, an effect independent of age. Knowledge of the pathology and biomarker characteristics of BRCA1 gene-linked hereditary breast cancers, which account for a substantial fraction of breast cancers in younger women, should shed light on the nature of the responsible gene(s) and guide approaches to therapy and prophylaxis.
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PMID:Pathology and heredity of breast cancer in younger women. 799 66

Clinical observations suggest that breast cancer is occasionally inherited as an autosomal dominant disease in families. Epidemiologic studies consistently have shown that a history of breast cancer in a first-degree relative increases a woman's risk of breast cancer when compared with the general population. The risk is similar if a mother or sister is affected and is increased further if both are affected. The difficulty with such an observation is that in itself it does not clarify the nature of the true underlying risk factors which could be genetic or due to the aggregation of environmental risk factors in families. Complex segregation analysis of breast cancer aggregation in families suggests that breast cancer susceptibility is due to an autosomal dominant inheritance of one or more rare genes in a few families in which carriers have a high probability of developing the disease perhaps as great as 100 percent. Close linkage of a breast-cancer-susceptibility gene (BRCA1), between markers of the chromosomal region 17q12-q21 on the long arm of chromosome 17, with breast cancer recently has been reported. Families linked to BRCA1 were more likely to have early onset of breast cancer or have breast and ovarian cancer in the family. It is likely that other genes play a role in the unlinked breast-cancer families. Both the epidemiologic and genetic data suggest that breast cancer is a heterogeneous disease.
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PMID:Familial risk and genetic susceptibility for breast cancer. 799 68

Perturbations of oncogenes in breast carcinoma include amplifications of the HER-2/neu and PRAD1 genes, as well as p53 mutations. Some of these lesions frequently appear in early cancers such as ductal carcinoma in situ and are stable as the tumors become invasive and metastasize. Thus these findings suggest that oncogene mutations may define a point of origin for a given breast cancer, and are fixed lesions during tumor progression. Such germline abnormalities may occur at the BRCA1, H-RAS VNTR, and p53 loci. The rational use of genetics may be to identify women at high risk for the development of breast cancer so that they may be enrolled in future chemoprevention trials.
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PMID:Oncogenes, breast cancer, and chemoprevention. 800 94

Four genes are now known to be responsible for inherited susceptibility to breast cancer: the BRCA1 gene on chromosome 17q21, the ataxia-telangiectasia (AT) gene (11q22-q23), the TP53 gene (17p13.1) and the androgen receptor (AR) (Xq11.2-q12). These genes, however, differ dramatically in terms of the risk of breast cancer that they confer, the proportion of breast cancer incidence that they account for and the other cancers and other phenotypes with which they are associated. Genetic linkage studies have shown that some high risk breast cancer families, particularly those where breast cancer occurs in association with ovarian cancer, are due to a gene on chromosome 17q known as BRCA1. The BRCA1 gene is estimated to confer a breast cancer risk of about 70% by age 70, and may account for about 2% of overall breast cancer incidence, although a higher proportion of younger cases. Germline mutations in the TP53 gene are responsible for a high proportion of LI-Fraumeni families, in which breast cancer occurs in association with childhood sarcomas and other cancers. In such families, the risk of breast cancer is over 50% by age 50, and the risk of all cancers is nearly 100%; germline TP53 mutations are, however, probably responsible for much less than 1% of all breast cancer. By contrast, heterozygotes for the AT gene carry a much more moderate risk of breast cancer. This gene, however, is much more common in the population and may account for 7% or more of breast cancer incidence. Finally, germline mutations in the androgen receptor are known to cause male breast cancer, but this has only been demonstrated in two families. Evidence from linkage and population based studies suggests that these genes may account for about one half of the observed familial clustering of breast cancer; other breast cancer susceptibility genes therefore remain to be identified.
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PMID:Inherited susceptibility to breast cancer. 801 3

BRCA1, the susceptibility gene for hereditary breast-ovarian cancer, is located on chromosome 17q12-21 but has not yet been identified. Two tandem oestradiol 17 beta hydroxysteroid dehydrogenase genes (17HSD) are assigned to this region. The active 17HSDII gene encodes the normal enzyme which regulates local synthesis of oestrogens, whereas 17HSDI is considered to be a pseudogene. We used reverse transcription coupled to polymerase chain reaction (RT-PCR) and found that the 17HSDI gene was also transcribed in half of the human cell lines and most of the biopsies studied, suggesting that 17HSDI could modulate normal 17HSDII activity in oestrogen target cells. We hypothesize that altered 17HSDI gene expression could lead to both hereditary and/or sporadic breast cancer by increasing local oestrogen concentration and that it is still a potential candidate for BRCA1.
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PMID:17 beta Hydroxysteroid dehydrogenase 1 "pseudogene" is differentially transcribed: still a candidate for the breast-ovarian cancer susceptibility gene (BRCA1). 802 76


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