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 685,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Despite nearly six decades of epidemiological studies, meta-analyses, and reviews, there is still considerable controversy in the literature about the question, does postmenopausal estrogen administration increase the risk of breast cancer? In an effort to resolve the controversy, a number of animal, biochemical, and clinical investigative studies in this field have been reviewed. The following summary formulation is proposed: 1. Administration of estrogen is inherently capable of promoting the growth of breast cancer, and therefore of increasing the incidence of clinical breast cancer. 2. Human response to estrogen is like that of the low-cancer-incidence strains of mice studied by Lacassagne, in that large doses and prolonged administration are required to induce clinical breast cancer. 3. The blood levels of estradiol produced by the usual doses of postmenopausal estrogen are relatively low, equivalent to those of the follicular phase of the menstrual cycle. These levels may be near the threshold for producing breast-cancer-promoting effects; therefore, the tumor response will vary greatly in different populations, depending on genetic susceptibility factors: a. The prevalence of a family history of premenopausal breast cancer in a first-degree relative. b. The prevalence of abnormal BRCA1, BRCA2, and p53 genes. c. The prevalence of increased 16 alpha-hydroxylation of estradiol. d. The prevalence of smokers who are slow acetylators. 4. Consumption of alcohol (5 grams or more daily) along with the postmenopausal estrogen administration results in elevation of blood estradiol levels to values equivalent to those of the periovulatory peak of the menstrual cycle, which may be well above the threshold for producing breast-cancer-promoting effects in all women. The risk for cancer will therefore be uniformly increased in women who use alcohol and take estrogen. 5. Increased risk of breast cancer from postmenopausal estrogen administration can be eliminated by taking two synergistic steps: a. Eliminating alcohol consumption, or at least keeping it well below an average of 5 grams daily (equivalent to 2/3 ounce of whiskey or 3 ounces of wine). b. Diminishing the capacity to 16 alpha-hydroxylate estradiol, either through pharmacological agents such as indole-3-carbinol or through increased consumption of cruciferous vegetables. It is concluded that despite the inherent ability of postmenopausal estrogen therapy to increase the risk of breast cancer in theory, the increased risk can be eliminated in practice by minimizing or eliminating consumption of alcohol and ingesting pharmacological or dietary agents that reduce the 16 alpha-hydroxylation of estradiol.
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PMID:Does postmenopausal estrogen administration increase the risk of breast cancer? Contributions of animal, biochemical, and clinical investigative studies to a resolution of the controversy. 942 Dec 4

Germline alterations of BRCA1 result in susceptibility to breast and ovarian cancer. The protein encoded by BRCA1 interacts in vivo with the BRCA1-associated RING domain (BARD1) protein. Accordingly, BARD1 is likely to be a critical factor in BRCA1-mediated tumor suppression and may also serve as a target for tumorigenic lesions in some human cancers. We have now determined the genomic structure of BARD1 and performed a mutational analysis of 58 ovarian tumors, 50 breast tumors and 60 uterine tumors. Seven polymorphisms were detected within the 2.34 kb coding sequence of BARD1 . Somatically acquired missense mutations were observed in one breast carcinoma and one endometrial tumor; in at least one of these cases, tumor formation was accompanied by loss of the wild-type BARD1 allele, following the paradigm for known tumor suppressor genes. In addition, a germline alteration of BARD1 was identified in a clear cell ovarian tumor (Gln564His); again, loss of the wild-type BARD1 allele was observed in the malignant cells of this patient. The Gln564His patient was also diagnosed with two other primary cancers: a synchronous lobular breast carcinoma and a stage IA clear cell endometrioid cancer confined to an endometrial polyp 6 years earlier. These findings suggest an occasional role for BARD1 mutations in the development of sporadic and hereditary tumors.
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PMID:Mutations in the BRCA1-associated RING domain (BARD1) gene in primary breast, ovarian and uterine cancers. 942 26

The RNA polymerase II (Pol II) holoenzyme in yeast is an essential transcriptional regulatory complex which has been defined by genetic and biochemical approaches. The mammalian counterpart to this complex, however, is less well defined. Experiments herein demonstrate that, along with Pol II and SRB proteins, proteins associated with transcriptional regulation as cofactors are associated with the Pol II holoenzyme. Earlier experiments have demonstrated that the breast cancer-associated tumor suppressor BRCA1 and the CREB binding protein (CBP) were associated with the holoenzyme complex. The protein related to CBP, the E1A-associated p300 protein, is shown in these experiments to be associated with the holoenzyme complex as well as the BRG1 subunit of the chromatin remodeling SWI/SNF complex. Importantly, the Pol II holoenzyme complex does not contain some factors previously reported as stoichiometric components of the holoenzyme complex, most notably the proteins which function in repair of damaged DNA, such as PCNA, RFC and RPA. The presence of the p300 coactivator and the chromatin-modifying BRG1 protein support a role for the Pol II holoenzyme as a key target for regulation by enhancer binding proteins.
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PMID:Factors associated with the mammalian RNA polymerase II holoenzyme. 944 79

During the last years, homologues of E coli RecA have been cloned in numerous species including man. These Rad51 proteins share sequence as well as functional homologies with the bacterial protein. Human Rad51 (HsRad51) is able to catalyze strand exchange in vitro between homologous DNAs, but with a lower efficiency compared to that of RecA. This suggests the requirement of additional factors. A very interesting feature of Rad51 is its essential role in mouse which could mean that it has gained an essential function in cell growth. The interaction of HsRad51 with several tumor suppressor genes namely p53, BRCA1 and BRCA2 implies possible role(s) of this protein in tumorigenesis. Thus, the continued study of Rad51 should bring important insights not only into homologous recombination mechanisms but also into cell proliferation regulation.
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PMID:Mammalian Rad51 protein: a RecA homologue with pleiotropic functions. 946 96

Recent studies have suggested that BRCA1-associated hereditary breast cancer may be a more aggressive form of disease than sporadic breast cancer. BRCA1-associated breast cancer has been reported to be significantly associated with grade 3 disease. Because grade 3 disease indicates a poor prognosis, this implies that women with a germ-line mutation in BRCA1 who develop breast cancer may have a poorer prognosis than those with sporadic disease. However, little is known about the association of BRCA1 expression with biological markers of prognosis. The present study examined the expression of BRCA1 in a total of 40 archival breast tumor specimens from three patient cohorts (sporadic, familial, and early onset breast cancer) to determine localization of the protein. Furthermore, BRCA1 staining was compared with expression of markers of tumor biology. We found that BRCA1 is generally located in the nucleus and the cytoplasm of normal and malignant breast tissue. Nuclear staining for BRCA1 was observed in most sporadic tumors, but nuclear BRCA1 was reduced or absent in the majority of familial and early onset breast tumors. Although no correlation was found between nuclear BRCA1 expression and estrogen and progesterone status, a significant inverse correlation was found between nuclear BRCA1 and expression of the proliferation marker Ki-67 (P = 0.01). Our findings suggest that tumors associated with a germ-line mutation in one of the breast cancer genes may be highly proliferative and support the view that loss of BRCA1 expression in breast tumors may lead to a more aggressive tumor phenotype.
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PMID:Loss of nuclear BRCA1 expression in breast cancers is associated with a highly proliferative tumor phenotype. 949 11

Inheritance is believed to play a major role in 5-10% of breast cancer. The breast cancer susceptibility genes BRCA1 and BRCA2 are estimated to account for more than half of these cases. Recent studies have suggested that breast cancers associated with BRCA1 germline mutations are of higher grade than sporadic cases. The purpose of this investigation was to determine if there are significant pathologic and biologic differences between hereditary BRCA2 related breast carcinomas and non-hereditary breast cancers. Forty cases of hereditary breast cancer from families associated with a specific 999del5 BRCA2 mutation were compared with regard to histologic and biologic factors to an age matched control group. Thirty-four patients (85%) had ductal carcinoma, two had lobular carcinoma, and one patient had medullary carcinoma. Compared to the control group, the BRCA2 tumors had less tubule formation (p = 0.02), more nuclear pleomorphism (p = 0.02), and higher mitotic rates (p = 0.002), and were thus of higher histologic grade (p = 0.003). By flow cytometry the BRCA2 tumors also had significantly higher S-phase fractions than the control tumors (p = 0.02). Significant differences in axillary lymph-node involvement or ploidy status were not detected. According to the results of this study, hereditary breast cancers associated with the 999del5 BRCA2 mutation are high grade tumors with a rapid proliferation rate. Other or additional factors than the defining BRCA2 mutation are involved in determining the tumor type.
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PMID:Inherited BRCA2 mutation associated with high grade breast cancer. 949

In situ duct carcinoma (DCIS) is a heterogeneous group of lesions which has recently been subdivided into three types: well-differentiated (type I), intermediately differentiated (type II) and poorly differentiated (type III) DCIS. Fourteen cases of DCIS and 11 of DCIS with minimal invasion were analysed for mRNA levels of beta-actin, EGFR, c-cerbB2, MTS1, k-ras, RB, BRCA1, cyclin E, and c-myc genes. A microdissection technique was used on paraffin-embedded tissue. A statistically significantly higher expression of cyclin E oncogene and MTS1 tumor suppressor gene was seen in type III DCIS than in the other types, while no significant differences in the mRNA expression patterns of the other genes were observed. These data are consistent with the fact that poorly differentiated DCIS is a readily recognizable class of tumours that have a particularly aggressive behaviour and probably unique histogenesis.
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PMID:Molecular characterization of intraductal breast carcinomas. 950 54

Genetic predisposition is responsible for 5-10% of all breast cancer, and a much larger percent of early-onset disease. Within the past few years, a number of genes associated with a high risk of breast cancer have been identified, including BRCA1, BRCA2, p53, and the Cowden disease gene PTEN/MMAC1. These genes appear to function as tumor suppressors, and although their mutation frequency in the general population is low, certain populations have a carrier frequency of up to 1% for particular BRCA1 and BRCA2 mutations. The isolation of these genes is likely to provide important insight into the pathogenesis of human cancer. The clinical application of these molecular discoveries raises controversial issues regarding presymptomatic testing for patients suspected of harboring cancer predisposing mutations.
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PMID:Hereditary breast cancer. 950 73

We analyzed the clinical features of 25 ovarian cancer patients who were associated with germ-line mutations of BRCA1 from four site-specific ovarian cancer families and seven breast-ovarian cancer families in Japan. The average age at diagnosis was 51.1 years (range, 38-77 years). Histological examination revealed 24 serous cyst adenocarcinomas in 25 patients. In 23 patients with clear clinical records, 3 patients had stage I disease, 17 had stage III disease, and 3 had stage IV disease. Thirteen patients with stage III disease who were treated with cisplatin-containing chemotherapy following tumor reduction surgery showed more favorable outcomes in both the survival rate and disease-free intervals, compared with age- and treatment course-matched controls (5-year survival rate, 0.786 versus 0.303; median disease-free interval, 91.43 versus 40.92 months; P < 0.05 for both, by logarithmic rank test). Our statistical model for the inheritance of susceptibility to ovarian cancer was derived from the analysis of 26 patients and 19 healthy carriers of 12 families. The expected lifetime risk of ovarian cancer is about 80% for women with mutations of BRCA1. These results suggest that the clinical outcome of ovarian cancer with germ-line mutations of BRCA1 appears to be more favorable than that with sporadic cases and that the disease penetrance among pedigrees with germ-line mutations of the BRCA1 gene is substantially high.
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PMID:Clinical features of ovarian cancer in Japanese women with germ-line mutations of BRCA1. 951 77

The breast and ovarian cancer tumor suppressor gene, BRCA1, encodes for a Zn2+-binding RING finger motif located near the protein NH2 terminus. The RING finger motif is characterized by eight conserved Cys and His residues which form two Zn2+-binding sites termed Site I and Site II. We used limited proteolysis in conjunction with matrix-assisted laser desorption ionization time-of-flight mass spectroscopy to investigate the metal binding properties and to probe the solution structures of wild-type and mutant BRCA1 constructs that include the RING finger. Our results show that the RING finger motif is part of a larger proteolysis-resistant structural domain which encompasses the first 110 residues of BRCA1. Analytical gel-filtration chromatography and chemical cross-linking experiments demonstrate that the BRCA1 NH2-terminal domain readily homodimerizes in solution. The cancer-predisposing C61G mutation, which alters a conserved Zn2+-binding residue, abolishes metal binding to Site II of the RING finger motif, while Site I remains intact and functional. The C61G mutation also results in increased proteolytic susceptibility of the COOH-terminal portion of the NH2-terminal domain and perturbs the oligomerization properties of BRCA1.
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PMID:The cancer-predisposing mutation C61G disrupts homodimer formation in the NH2-terminal BRCA1 RING finger domain. 952 70


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