Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0006142 (breast cancer)
 160,383 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

It has been suggested that increased fragile site expression in lymphocyte cultures can be used as a marker for genetic predisposition to cancer. We wished to determine whether aphidicolin (APC), an inhibitor of the DNA repair enzyme DNA polymerase alpha, could be used as a reliable biomarker in identification of DNA repair capacity in unaffected individuals at high risk from breast cancer families. PHA-stimulated lymphocyte cultures, with and without APC, were set up in 65 individuals, of whom 14 were breast cancer patients, 26 were unaffected individuals from breast cancer families, and 25 were controls. A significant proportion of breast cancer patients and unaffected individuals from familial breast cancer (FBC) families exhibited premature separation of centromeres (PSC) and aneuploidy in the untreated cultures. In the APC treated cultures, almost all such individuals exhibited a marked depression of mitotic index and increased aneuploidy, as compared to controls. Our results indicate that these individuals have defective DNA repair capacity. Such individuals could thus have a much higher risk of cancer as compared to persons exhibiting PSC and aneuploidy or DNA repair defects alone. We propose that APC may be a valuable biomarker in identifying individuals with genetic predisposition to cancer from FBC families.
 ...
PMID:Reduced DNA repair capacity in breast cancer patients and unaffected individuals from breast cancer families. 953 Mar 43

We examined expression of N-methylpurine-DNA glycosylase (MPG), a DNA repair enzyme that removes N-alkylpurine damage, in normal, malignant, and immortalized breast epithelial cells, and breast cancer cell lines (MDA-MB-231, MCF7, T47D). Northern analysis showed increased expression in cancer versus normal breast epithelial cells (2-24-fold). Southern blots revealed no gene amplification or polymorphisms. Immunofluorescence, immunohistochemistry, and Western blot analysis demonstrated increased MPG protein expression in the tumor cells that correlated with elevated glycosylase activity. Since MPG overexpression has been shown to be paradoxically associated with increased susceptibility to DNA damage, up-regulation of this gene may suggest a functional role in breast carcinogenesis.
 ...
PMID:Altered expression of the DNA repair protein, N-methylpurine-DNA glycosylase (MPG) in breast cancer. 968 56

The covalent rejoining of DNA ends at single-stranded or double-stranded DNA breaks is catalyzed by DNA ligases. Four DNA ligase activities (I-IV) have been identified in mammalian cells [1]. It has recently been demonstrated that DNA ligase IV interacts with and is catalytically stimulated by the XRCC4 protein [2,3], which is essential for DNA double-strand break repair and the genomic rearrangement process of V(D)J recombination [4]. Together with the finding that the yeast DNA ligase IV homologue is essential for nonhomologous DNA end joining [5-7], this has led to the hypothesis that mammalian DNA ligase IV catalyzes ligation steps in both of these processes [8]. DNA ligase IV is characterized by a unique carboxy-terminal tail comprising two BRCT (BRCA1 carboxyl terminus) domains. BRCT domains were initially identified in the breast cancer susceptibility protein BRCA1 [9], but are also found in other DNA repair proteins [10]. It has been suggested that DNA ligase IV associates with XRCC4 via its tandem BRCT domains and that this may be a general model for protein-protein interactions between DNA repair proteins [3]. We have performed a detailed deletional analysis of DNA ligase IV to define its XRCC4-binding domain and to characterize regions essential for its catalytic activity. We find that a region in the carboxy-terminal tail of DNA ligase IV located between rather than within BRCT domains is necessary and sufficient to confer binding to XRCC4. The catalytic activity of DNA ligase IV is affected by mutations within the first two-thirds of the protein including a 67 amino-acid amino-terminal region that was previously thought not to be present in human DNA ligase IV [11].
 ...
PMID:DNA ligase IV binds to XRCC4 via a motif located between rather than within its BRCT domains. 970 34

The DNA repair enzyme, N-methylpurine DNA glyclosylase (MPG), is overexpressed in breast cancer as compared with its expression in normal breast epithelial cells. In an effort to determine the mechanism responsible for this difference in expression, we studied rates and regulation of transcription of the MPG gene in normal (HMEC), spontaneously immortalized (MCF10A), and malignant (T47D) mammary epithelial cells. Steady state levels of MPG mRNA are 3-4-fold greater in T47D cells than in MCF10A cells. Nuclear "run-off" transcription measurements revealed MPG transcription rates to be approximately 3-fold greater in the tumor cells than in normal cells. Characterization of the MPG promoter by deletion analysis and transient transfection experiments revealed that all basal promoter activity resided between nucleotides -227 and -81 upstream from the ATG translation start site. Constructs containing this region were expressed at 4-fold greater levels when transfected into malignant T47D cells (56 x baseline) than in MCF10A cells (14 x baseline). Computer database analysis of the region of nucleotides -227 to -81 revealed multiple overlapping Sp1 consensus binding sites and two overlapping consensus AP-2 binding sites located between bases -181 and -169. Electrophoretic mobility shift assays indicated that while Sp1 bound this region of the promoter, nuclear extracts from both cell types contained equal Sp1 binding activity. In contrast, AP-2 binding activity was significantly greater in T47D cells, and Western blots confirmed increased AP-2 protein levels in these cells. Cotransfection into MCF10A cells of the MPG promoter construct and an AP-2 expression plasmid increased MPG promoter activity 2.1-fold. Cotransfection of a dominant negative mutant of AP-2 into T47D cells reduced the extent of MPG promoter-driven transcription by 50%. To investigate the functional significance of the two overlapping AP-2 consensus binding sites, each site was mutated separately. Mutation of the upstream site decreased promoter activity by 15%, but mutation of the downstream site decreased promoter activity by 45% and abolished AP-2 binding to the promoter sequence. These data suggest that AP-2 is important in regulating MPG expression in breast cancer cells, and that the increased amount of AP-2 in these cells plays a major role in directing the increased expression of MPG.
 ...
PMID:Regulation of expression of N-methylpurine DNA glycosylase in human mammary epithelial cells: role of transcription factor AP-2. 1056 36

The breast cancer predisposing genes BRCA1 and BRCA2 appear to be involved in DNA repair. In particular, the sensitivity of BRCA2-deficient mouse embryonic fibroblasts to ionizing radiation and the demonstrated interaction of the BRCA2 protein with Rad51, a major factor in recombinational repair, indicate that BRCA2 is important for double strand break repair. The human BRCA2-deficient human cell line Capan-1, whilst being sensitive to ionizing radiation, is also sensitive to the alkylating agent methymethanesulfonate. The major lesions induced by this agent are methylated bases which are removed primarily by the base excision repair (BER) pathway. We have investigated the efficiency of BER in Capan-1 cells by an in vitro assay in which plasmid substrates containing a single lesion are repaired by mammalian cell extracts. In comparison to the control cell lines BxPC-3, T24 and MCF7, Capan-1 cells exhibited a reduced rate of DNA ligation during both the single-nucleotide insertion and PCNA-dependent pathways of BER. The reduced rate of DNA ligation exhibited by Capan-1 cell extracts was complemented by addition of bacteriophage T4 DNA ligase or human DNA ligase III. BRCA2-mutant Capan-1 cells may possess reduced DNA ligase activity during BER.
 ...
PMID:Reduced ligation during DNA base excision repair supported by BRCA2 mutant cells. 1112 65

An important determinant of cellular resistance to chemotherapeutic O6-alkylating agents, which comprise methylating and chloroethylating agents, is the ability of cells to repair alkylation damage at the O6-position of guanine in DNA. This is achieved by a specific DNA repair enzyme O6-alkylguanine DNA-alkyltransferase. In this study O6-alkylguanine DNA-alkyltransferase expression was measured in human breast tumours using both biochemical and immunohistochemical techniques. O6-alkylguanine DNA-alkyltransferase activity was then compared with known clinical prognostic indices to assess the potential role of O6-alkylguanine DNA-alkyltransferase in predicting the behaviour of this common malignancy. The application of both biochemical and immunohistochemical techniques was feasible and practical. Most breast tumours expressed high levels of O6-alkylguanine DNA-alkyltransferase. Immunohistochemical analysis showed marked variation in expression not only between individuals but also within individual tumours, and in the same patient, between metastases and between primary tumour and metastatic site. O6-alkylguanine DNA-alkyltransferase activity in tissue extracts significantly correlated not only with immunohistochemical staining intensity determined by subjective quantitation, but also with measures of protein levels using a computerised image analysis system including mean grey (P<0.001), percentage of cells positive for O6-alkylguanine DNA-alkyltransferase (P<0.001), and integrated optical density (P<0.001). O6-alkylguanine DNA-alkyltransferase expression did not correlate with any of the established clinical prognostic indicators for current treatment regimens. However, immunohistochemical offers a rapid and convenient method for assessing potential utility of O6-alkylating agents or O6-alkylguanine DNA-alkyltransferase inactivating agents in future studies of breast cancer treatment.
 ...
PMID:Heterogeneity of O6-alkylguanine DNA-alkyltransferase expression in human breast tumours. 1208 69

We present findings on the associations between DNA adduct levels in breast tissue, risk of breast cancer, and polymorphisms in the DNA repair enzyme XPD. Breast cancer cases, benign breast disease (BBD) controls, and healthy controls were enrolled. Polycyclic aromatic hydrocarbons (PAH)-DNA adduct levels were measured by immunohistochemistry in breast tissue samples from cases and BBD controls. XPD polymorphisms at codons 312 and 751 was determined by polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) analysis using white blood cell DNA. Neither of the polymorphisms were associated with case-control status, both in comparisons of cases and BBD controls, and cases and healthy controls. XPD polymorphisms at codons 312 and 751 were associated with higher levels of PAH-DNA in tumor tissue from breast cancer cases. Subjects with an Asp/Asn or Asn/Asn polymorphic genotype in codon 312 of XPD had elevated levels of PAH-DNA adducts compared to subjects with the Asp/Asp genotype (0.55 optical density (OD) v.s. 0.33 OD, p < 0.01). PAH-DNA adducts were associated with increasing copy number of the Gln allele for the codon 751 polymorphism (p for trend <0.01). Among subjects with the Asp/Asn or Asn/Asn genotype at codon 312, adduct levels were higher in tumor tissue compared to tissue from BBD controls (0.55 OD v.s. 0.36 OD, p = 0.003). Among subjects with the Gln/Gln genotype at codon 751 adduct levels were higher in tumor tissue compared to tissue from BBD controls (0.68 OD v.s. 0.40 OD, p = 0.01). The trend of increasing PAH-DNA adduct levels with either the Asn/Asn or Gln/Gln genotype was greater in tumor tissue than the trend in BBD control tissue.
Breast Cancer Res Treat 2002 Sep
PMID:Polymorphisms in the DNA repair enzyme XPD are associated with increased levels of PAH-DNA adducts in a case-control study of breast cancer. 1224 8

The project focuses on cancer types with outstanding publich health importance (breast-, colorectalhead and neck cancers and childhood tumors). Epidemiological studies revealed significant regional differences in the mobidity/mortality of these cancer types in Hungary. Molecular epidemiological studies revealed characteristic BRCA1 mutation patterns of familiar breast cancer and DNA repair enzyme polymorphism in head and neck cancer. New methods have been developed for the screening (lactoferrin), prognostication (c-met expression) or the prediction of therapeutic sensitivity (TS expression) of colorectal cancer. In the pediatric oncology program alternative way of MRD monitoring (WT1 expression) and a potential new therapeutic modality (IFN-alpha) of ALL was developed. Experimental studies demonstrated that the tumoral matrix significantly influences the effects of the classic chemotherapeutic agents. We have identified several genes the expression of which could serve efficiently as markers or targets for therapy of the progression of melanoma (alphaIIbbeta3 integrin, CD44v3 and decorin proteoglycans, AMF receptor).
 ...
PMID:[Report on the first year of the activity of the National Oncological RD Consortium]. 1256 51

Recent studies have shown that the antiestrogens tamoxifen and raloxifene may protect against breast cancer, presumably because of a blockade of estrogen receptor (ER)-mediated transcription. Another possible explanation is that antiestrogen-liganded ER transcriptionally induces genes that are protective against cancer. We previously reported that antiestrogen-liganded ERbeta transcriptionally activates the major detoxifying enzyme quinone reductase (QR) [NAD(P)H:quinone oxidoreductase]. It has been established that metabolites of estrogen, termed catecholestrogens, can form DNA adducts and cause oxidative DNA damage. We hypothesize that QR inhibits estrogen-induced DNA damage by detoxification of reactive catecholestrogens. We report here that physiological concentrations of 17beta-estradiol cause oxidative DNA damage, as measured by levels of 8- hydroxydeoxyguanine, in ER-positive MCF7 breast cancer cells, MDA-MB-231 breast cancer cells (ERalpha negative/ERbeta positive) and nontumorigenic MCF10A breast epithelial cells (very low ER), which is dependent on estrogen metabolism. Estrogen-induced 8-hydroxydeoxyguanine was inversely correlated to QR and ERbeta levels and was followed by downstream induction of the DNA repair enzyme XPA. Trans-hydroxytamoxifen, raloxifene, and the pure antiestrogen ICI-182,780 protected against estradiol-mediated damage in breast cancer cells containing ERbeta. This is most likely due to the ability of these antiestrogens to activate expression of QR via ERbeta. We conclude that up-regulation of QR, either by overexpression or induction by tamoxifen, can protect breast cells against oxidative DNA damage caused by estrogen metabolites, representing a possible novel mechanism of tamoxifen prevention against breast cancer.
 ...
PMID:Functional implications of antiestrogen induction of quinone reductase: inhibition of estrogen-induced deoxyribonucleic acid damage. 1271 3

A new rapid assay method for DNA ligases has been developed, which allows direct quantification of enzyme activity without using the traditional polyacrylamide gel electrophoretic technique. In this method, the 5'-biotinylated nicked duplex was used as a substrate for the ligase reaction, in which the 5'-end of the first oligonucleotide (19-mer) on the nicked strand is biotinylated and the second oligonucleotide (20-mer) on the same strand is labeled with radioactive 32P at the 5'-end. After ligation of the biotinylated 19-mer oligonucleotide into the second oligonucleotide with the reaction of DNA ligases, the biotinylated 19-mer oligonucleotide is converted into the radioactive 39-mer oligonucleotide. The ligase reaction products were heat-denatured to release both ligated and unligated biotinylated oligonucleotides. The biotinylated oligonucleotides were then captured on a streptavidin-coated microtiter plate and counted. The results obtained using this method correlated very well with those from the standard assay method using electrophoresis. Using this assay method, we were able to screen a chemical library and identify new DNA ligase inhibitors structurally related to resorcinol, which has growth inhibitory effects on the human breast cancer cell, MCF-7. The method described here is anticipated to be very useful for screening DNA ligase inhibitors from chemical libraries.
 ...
PMID:Development of non-electrophoretic assay method for DNA ligases and its application to screening of chemical inhibitors of DNA ligase I. 1513 6


1 2 3 Next >>