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Query: UMLS:C0596263 (carcinogenesis)
 64,820 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We provide an overview of the functional interrelationship between genes and proteins related to DNA repair by homologous recombination and cell cycle regulation in relation to the progression and therapy resistance of human tumours. To ensure the high-fidelity transmission of genetic information from one generation to the next, cells have evolved mechanisms to monitor genome integrity. Upon DNA damage, cells initiate complex response pathways including cell cycle arrest, activation of genes and gene products involved in DNA repair, and under some circumstances, the triggering of programmed cell death. Deregulation of this co-ordinated response leads to genetic instability and is fundamental to the aetiology of human cancer. Homologous recombination involved in DNA repair is induced by environmental damage as well as misreplication during the normal cell cycle. However, when not regulated properly, it can result in the loss of heterozygocity or genetic rearrangements, central to the process of carcinogenesis. The central step of homologous recombination is the DNA strand exchange reaction catalysed by the eukaryotic Rad51 protein. Here, we describe the recent progress in our understanding of how Rad51 is involved in the signalling and repair of DNA damage and how tumour suppressors, such as p53, ATM, BRCA1, BRCA2, BLM and FANCD2 are linked to Rad51-dependent pathways. An increased knowledge of the role of Rad51 in DNA repair by homologous recombination and its effects on cell cycle progression, tumour development and tumour resistance may provide opportunities for identifying improved diagnostic markers and developing more effective treatments for cancer.
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PMID:Homologous recombination and cell cycle checkpoints: Rad51 in tumour progression and therapy resistance. 1459 70

Ovarian cancer is the most common cause of death from gynecological cancers in the Western world. There are many genetic and environmental factors which can influence a woman's risk of getting ovarian cancer. A strong family history of breast or ovarian cancer is definitely one of the most important and best-defined epidemiological risk factors. This review evaluates current knowledge of hereditary ovarian cancer. Histologic, cytologic and molecular studies on the ovarian surface epithelium (OSE), which is the origin of ovarian epithelial carcinomas, from women with a strong family history for ovarian carcinomas or with a mutation in one of the two known cancer susceptibility genes - BRCA1 and BRCA2, provide a background to facilitate understanding of the early changes in ovarian carcinogenesis. This overview is followed by a discussion of recent hypotheses and research on two questions. First, is there a mutational hotspot of BRCA mutation for ovarian cancer? Second, why do mutations in BRCA1 and BRCA2, which are ubiquitously expressed genes that participate in general cellular activities, lead preferentially to breast and ovarian cancer?
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PMID:Ovarian surface epithelium: family history and early events in ovarian cancer. 1460 32

Prepubertal exposure to soy or its biologically active component genistein reduces later breast cancer risk in both animal models and human populations. We investigated whether that might be due to reported estrogenic properties of genistein. Our study indicated that daily prepubertal exposures between postnatal days 7 and 20 to 10 microg 17beta-estradiol (E2) reduced later risk of developing 7,12-dimethylbenz[a]anthracene (DMBA)-induced mammary tumors. Assessment of mammary gland morphology revealed that both prepubertal E2 and genistein (50 microg daily) exposures reduced the size of mammary epithelial area and number of terminal end buds (TEBs) and increased the density of lobulo-alveolar structures, suggesting that these exposures induced elimination of targets for malignant transformation by differentiation. Next, the mechanisms mediating the protective effects of E2 and genistein were investigated. E2 is shown to up-regulate BRCA1, a tumor suppressor gene that participates in DNA damage repair processes and cell differentiation and that down-regulates the activity of estrogen receptor (ER)-alpha. The expression of BRCA1 mRNA was up-regulated in the mammary glands of rats exposed to E2 or genistein during prepuberty, when determined at the ages of 3, 8 and 16 weeks. Prepubertal E2 exposure reduced ER-alpha levels in the mammary gland, while prepubertal genistein exposure had an opposite effect. Our results suggest that prepubertal estrogenic exposures may reduce later breast cancer risk by inducing a persistent up-regulation of BRCA1 in the mammary gland.
Carcinogenesis 2004 May
PMID:Prepubertal estradiol and genistein exposures up-regulate BRCA1 mRNA and reduce mammary tumorigenesis. 1472 90

In response to DNA damage, the cell cycle checkpoint kinase 2 (CHEK2) may phosphorylate p53, Cdc25A and Cdc25C, and regulate BRCA1 function, leading to cell cycle arrest and DNA repair. The truncating germline mutation CHEK2(*)1100delC abrogates kinase activity and confers low-penetrance susceptibility to breast cancer. We found CHEK2(*)1100delC in 0.5% of 190 oesophageal squamous cell carcinomas and in 1.5% of 196 oesophageal adenocarcinomas. In addition, we observed the mutation in 3.0% of 99 Barrett's metaplasias and 1.5% of 66 dysplastic Barrett's epithelia, both known precursor lesions of oesophageal adenocarcinoma. Since CHEK2(*)1100delC mutation frequencies did not significantly differ among oesophageal squamous cell carcinomas, adenocarcinomas and (dysplastic) Barrett's epithelia, as compared to healthy individuals, we conclude that the CHEK2(*)1100delC mutation has no major contribution in oesophageal carcinogenesis.
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PMID:The CHEK2(*)1100delC mutation has no major contribution in oesophageal carcinogenesis. 1497 Aug 69

The regulation of protein stability by the ubiquitin-proteasome pathway is a critical issue central to the comprehension of the molecular basis of carcinogenesis. However, ubiquitin modification of target substrates signals many cellular processes other than proteolysis that are also important for the development of cancer. It is noteworthy that many proteins studied by clinical breast cancer researchers are involved in these ubiquitin pathways. This review summarizes recent works on such proteins including cyclins, CDK inhibitors, and the SCF in cell cycle control; the breast and ovarian cancer suppressor BRCA1-BARD1; ErbB2/HER2/Neu and its ubiquitin ligase c-Cbl or CHIP; and the estrogen receptor and its downstream target Efp. Understanding these pathways may provide some hints toward developing diagnostic tools and treatments for breast cancer patients.
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PMID:Ubiquitin and breast cancer. 1502 95

Long-term exposure to synthetic and endogenous estrogens has been associated with the development of cancer in several tissues. One potential mechanism of estrogen carcinogenesis involves catechol formation and these catechols are further oxidized to electrophilic/redox active o-quinones, which have the potential to both initiate and promote the carcinogenic process. Previously we showed that 4-hydroxyequilenin (4-OHEN) autoxidized to an o-quinone and caused a variety of damage to DNA. Since these deleterious effects could contribute to gene mutations, we investigated the Chinese hamster V79 cells to ascertain the relative ability of estradiol, 4-hydroxyestradiol, 17beta-hydroxyequilenin, 4,17beta-hydroxyequilenin, estrone, 4-hydroxyestrone, equilenin, and 4-hydroxyequilenin to induce the mutation of the hypoxanthine-guanine phosphoribosyltransferase (hprt) gene. All the 4-hydroxylated catechols induced significantly more colony formations in V79 cells as compared to the parent phenols at 100nM, suggesting that the catechol estrogen metabolites are more mutagenic towards the hprt gene than estrogens. Since 4-OHEN induced the highest mutation frequency, we examined a biomarker for transformation potential of this compound in MCF-10A cells using an anchorage-independent growth assay. Although 4-OHEN induced anchorage-independent growth of these cells, the isolated clones were not able to grow as tumors in vivo when injected into nude mice. These cells were assayed for genetic changes using cDNA microarrays. Real time RT-PCR confirmation of some of the differentially expressed genes showed down-regulation of metallothionein 2A, p53, BRCA1, and c-myc. Moreover, we showed the involvement of other genes important in cell transformation and oxidative stress, strengthening the hypothesis that this mechanism plays a considerable role in 4-OHEN-induced anchorage-independent growth.
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PMID:Equine estrogen metabolite 4-hydroxyequilenin induces anchorage-independent growth of human mammary epithelial MCF-10A cells: differential gene expression. 1513 45

The identification of an interaction between BRCA1 and acetyl-CoA carboxylase alpha (ACCalpha), a key enzyme in lipid synthesis, led us to investigate the role of ACCalpha in breast cancer development, where it might contribute to the energy-sensing mechanisms of malignant transformation. In order to investigate if certain ACCalpha alleles may be high-risk breast cancer susceptibility alleles, 37 extended breast and breast/ovarian cancer families negative for BRCA1 and BRCA2 mutations were exhaustively screened for sequence variations in the entire coding sequence, intron-exon junctions, 5'UTR, 3'UTR (untranslated regions) and the promoter regions of the ACCalpha gene. Two possibly disease-associated ACCalpha variants were each identified in a single family and were not present in 137 controls. Multiple polymorphisms were detected in breast cancer families, including 12 single nucleotide polymorphisms where the frequency of the rare allele estimated in controls was >0.10. The observed lack of variation in the ACCalpha coding region along with the presence of extended areas of linkage disequilibrium and low haplotype diversity indicates an overall high preservation of this gene. The prevalence of the ACCalpha haplotypes composed of common polymorphisms was determined in 453 breast cancer cases and 469 female controls. One haplotype was found to be associated with a substantial and highly significant increase in breast cancer risk (odds ratio = 3.10, 95% confidence interval 1.87-5.14, P < 0.0001), whereas three other haplotypes were found to have a protective effect. Our results indicate that mutations in the ACCalpha gene are unlikely to be a major cause of high-risk breast cancer susceptibility; however, certain common ACCalpha alleles may influence breast cancer risk. This study provides the first insight into the involvement of the ACCalpha gene in breast cancer predisposition and calls for further, large-scale studies that will be needed to understand the role of ACCalpha in tumour susceptibility and development.
Carcinogenesis 2004 Dec
PMID:Acetyl-CoA carboxylase alpha gene and breast cancer susceptibility. 1533 68

Cancer is a genetic disease. Breast cancer tumorigenesis can be described as a multi-step process in which each step is thought to correlate with one or more distinct mutations in major regulatory genes. The question addressed is how far a multi-step progression model for sporadic breast cancer would differ from that for hereditary breast cancer. Hereditary breast cancer is characterized by an inherited susceptibility to breast cancer on basis of an identified germline mutation in one allele of a high penetrance susceptibility gene (such as BRCA1, BRCA2, CHEK 2, TP53 or PTEN). Inactivation of the second allele of these tumour suppressor genes would be an early event in this oncogenic pathway (Knudson's "two-hit" model). Sporadic breast cancers result from a serial stepwise accumulation of acquired and uncorrected mutations in somatic genes, without any germline mutation playing a role. Mutational activation of oncogenes, often coupled with non-mutational inactivation of tumour suppressor genes, is probably an early event in sporadic tumours, followed by more, independent mutations in at least four or five other genes, the chronological order of which is likely less important. Oncogenes that have been reported to play an early role in sporadic breast cancer are MYC, CCND1 (Cyclin D1) and ERBB2 (HER2/neu). In sporadic breast cancer, mutational inactivation of BRCA1/2 is rare, as inactivation requires both gene copies to be mutated or totally deleted. However, non-mutational functional suppression could result from various mechanisms, such as hypermethylation of the BRCA1 promoter or binding of BRCA2 by EMSY. In sporadic breast tumorigenesis, at least three different pathway-specific mechanisms of tumour progression are recognizable, with breast carcinogenesis being different in ductal versus lobular carcinoma, and in well differentiated versus poorly differentiated ductal cancers. Thus, different breast cancer pathways emerge early in the process of carcinogenesis, ultimately leading to clinically different tumour types. As mutations acquired early during tumorigenesis will be present in all later stages, large-scale gene expression profiling using DNA microarray analysis techniques can help to classify breast cancers into clinically relevant subtypes.
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PMID:Oncogenic pathways in hereditary and sporadic breast cancer. 1943 86

Breast and ovarian cancers, like other cancers, occur due to genetic damage. Research aimed to determine the specific genes involved in the development of breast and ovarian cancers will help to understand how normal breast and ovarian epithelial cells escape regulation of proliferation, apoptosis and senescence. It was determined that approximately 10% of ovarian cancers and 20-30% of breast cancers arise in women who have inherited mutations in cancer susceptibility genes such as BRCA1, BRCA2 and other DNA repair genes. The ability to perform genetic testing permits the identification of women at increased risk who can then be offered preventive strategies. The vast majority of ovarian and breast cancers are sporadic, presumably resulting from the accumulation of genetic damage over lifetime. Several genes involved in breast and ovarian carcinogenesis have been identified, most notably the p53 tumor suppressor. The recent availability of expression microarrays has facilitated the simultaneous screening of thousands of genes and this will extend further the understanding of molecular events involved in the dynamic development of ovarian and breast cancers. Then, all this knowledge could be translated into effective screening, surveillance, prevention, and treatment strategies in the future.
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PMID:Mutational spectrum of p53 mutations in primary breast and ovarian tumors. 1550 Oct 75

BRCA1 (BReast-CAncer susceptibility gene 1) and BRCA2 are tumor suppressor genes, the mutant phenotypes of which predispose to breast and ovarian cancers. Intensive research has shown that BRCA proteins are involved in a multitude of pivotal cellular processes. In particular, both genes contribute to DNA repair and transcriptional regulation in response to DNA damage. Recent studies suggest that BRCA proteins are required for maintenance of chromosomal stability, thereby protecting the genome from damage. New data also show that BRCAs transcriptionally regulate some genes involved in DNA repair, the cell cycle, and apoptosis. Many of these functions are mediated by a large number of cellular proteins that interact with BRCAs. The functions of BRCA proteins are also linked to distinct and specific phosphorylation events; however, the extent to which phosphorylation-activated molecular pathways contribute to tumor suppressor activity remains unclear. Finally, the reasons why mutations in BRCA genes lead to the development of breast and ovarian cancers are not clearly understood. Elucidation of the precise molecular functions of BRCAs is expected to improve our understanding of hereditary as well as sporadic mammary carcinogenesis.
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PMID:Role of BRCA1 and BRCA2 as regulators of DNA repair, transcription, and cell cycle in response to DNA damage. 1554 3


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