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Genomic Integrity (genomic + integrity)
Selected AbstractsPolymorphisms in the thymidylate synthase promoter and the DNA repair genes XRCC1 and XPD in a Brazilian populationENVIRONMENTAL AND MOLECULAR MUTAGENESIS, Issue 9 2006Renata Canalle Abstract Polymorphisms in genes responsible for maintaining genomic integrity are potential modifiers of disease risk. Since considerable interindividual and interethnic variation in DNA repair capacity has been associated with polymorphic alleles, we evaluated the frequency of the 2R/3R variants in the TS promoter, Arg194Trp and Arg399Gln in the XRCC1 gene, and Asp312Asn and Lys751Gln in the XPD gene in 364 healthy individuals from a Brazilian population separated by ethnicity (European ancestry and African ancestry). The genotypes were determined by PCR (TS) or by PCR-RFLP (XRCC1 and XPD). The frequency of the TS 3R allele was 0.56 for whites and 0.51 for nonwhites. In the case of the XRCC1 MspI polymorphism, the allele frequencies were 0.09 for 194Trp in both nonwhites and whites and 0.27 and 0.28 for 399Gln in nonwhites and whites, respectively. For the XPD 312Asn allele, we found a frequency of 0.25 in white individuals, which was significantly different (P = 0.025) from that seen in nonwhites (0.15). Similarly, the 751Gln polymorphic allele of the XPD gene was significantly more frequent (P < 0.002) in whites (0.30) than in nonwhites (0.20). The genotype frequencies were within Hardy,Weinberg equilibrium. We concluded that the genotype and allele frequencies of XPD gene polymorphism differed between white and nonwhite Brazilians, and that the frequencies of the XPD 312Asn and XRCC1 399Gln alleles in this Brazilian population showed ethnic variability when compared with those observed in other populations. Environ. Mol. Mutagen., 2006. © 2006 Wiley-Liss, Inc. [source] Cell-cycle deregulation in BALB/c 3T3 cells transformed by 1,2-dibromoethane and folpet pesticidesENVIRONMENTAL AND MOLECULAR MUTAGENESIS, Issue 5 2003Maria Alessandra Santucci Abstract The cell-transforming potential of 1,2-dibromoethane and folpet, two widely used agricultural pesticides that are potential sources of environmental pollution, has been previously ascribed to their promoting activity. In this study, we investigated whether BALB/c 3T3 transformation by these chemicals was associated with the deregulation of signals involved in cell-cycle progression and in cell-cycle checkpoint induction. We found that two BALB/c 3T3 cell clones transformed by in vitro medium-term (8-week) exposure to the carcinogens had a constitutive acceleration of cell transition from G1 to S phase and an abrogation of the radiation-induced G1/S checkpoint. These events involved multiple signals; in particular, the inhibitors of cyclin/cyclin-dependent kinase complexes p21 and p27 were significantly down-modulated and the positive regulators of cell-cycle progression cyclin D3 and E were up-modulated. As anticipated for cells where the G1/S checkpoint was abrogated, the transformed cells exhibited a significant reinforcement of the radiation-induced G2/M checkpoint, the only checkpoint remaining to protect genomic integrity. However, cyclin A1 and B1 coexpression and cyclin A1 overexpression were found despite the G2 arrest in irradiated cells and these signals likely attenuate the G2/M checkpoint. These alterations to normal cell cycling may promote the emergence of both numerical and structural chromosomal abnormalities and their tolerance. Such a condition could play a key role in neoplastic transformation and be crucial in tumor progression. Furthermore, cyclin A1 overexpression may play an autonomous role in the neoplastic transformation of BALB/c 3T3 cells, as it does in other cell types of mesenchymal origin. Environ. Mol. Mutagen. 41:315,321, 2003. © 2003 Wiley-Liss, Inc. [source] Dermal benzene and trichloroethylene induce aneuploidy in immature hematopoietic subpopulations in vivoENVIRONMENTAL AND MOLECULAR MUTAGENESIS, Issue 3 2001Cynthia R. Giver Abstract Accumulation of genetic damage in long-lived cell populations with proliferative capacity is implicated in tumorigenesis. Hematopoietic stem cells (hsc) maintain lifetime hematopoiesis, and recent studies demonstrate that hsc in leukemic patients are cytogenetically aberrant. We postulated that exposure to agents associated with increased leukemia risk would induce genomic changes in cells in the hsc compartment. Aneusomy involving chromosomes 2 and 11 in sorted hsc (Lin,c-kit+Sca-1+) and maturing lymphoid and myeloid cells from mice that received topical doses of benzene (bz) or trichloroethylene (TCE) was quantified using fluorescence in situ hybridization. Six days after bz or TCE exposure, aneuploid cells in the hsc compartment increase four- to eightfold in a dose- and schedule-independent manner. Aneuploid lymphoid and myeloid cells from bz- and TCE-treated mice approximate controls, except after repeated benzene exposures. Aneuploid cells are more frequent in the hsc compartment than in mature hematopoietic subpopulations. Hematotoxicity was also quantified in bz- and TCE-exposed hematopoietic subpopulations using two colony-forming assays: CFU-GM (colony-forming units/granulocyte-macrophage progenitors) and CAFC (cobblestone area,forming cells). Data indicate that bz is transiently cytotoxic (,1 week) to hsc subpopulations, and induces more persistent toxicity (>2 weeks) in maturing, committed progenitor subpopulations. TCE is not hematotoxic at the doses applied. In conclusion, we provide direct evidence for induction of aneuploidy in cells in the hsc compartment by topical exposure to bz and TCE. Disruption of genomic integrity and/or toxicity in hsc subpopulations may be one step in leukemic progression. Environ. Mol. Mutagen. 37:185,194, 2001. © 2001 Wiley-Liss, Inc. [source] The molecular determinants of sunburn cell formationEXPERIMENTAL DERMATOLOGY, Issue 3 2001G. Murphy Abstract: Sunburn cell (SBC) formation in the epidermis is a characteristic consequence of ultraviolet radiation (UVR) exposure at doses around or above the minimum erythema dose. SBC have been identified morphologically and biologically as keratinocytes undergoing apoptosis. There is evidence that SBC formation is a protective mechanism to eliminate cells at risk of malignant transformation. The level of DNA photodamage is a major determinant of SBC induction by a process controlled by the tumor suppressor gene p53. However, extra-nuclear events also contribute to SBC formation, such as the activation of death receptors including CD95/Fas. UVR triggers death receptors either by direct activation of these surface molecules or by inducing the release of their ligands such as CD95 ligand or tumor necrosis factor. Oxidative stress also appears to be involved, probably via mitochondrial pathways, resulting in the release of cytochrome C. Pathways which modify SBC formation are now extensively studied given the importance of apoptosis in eliminating irreparably damaged cells. A greater understanding of the mechanisms that induce and prevent UVR-induced apoptosis will contribute to our understanding of mechanisms relevant in genomic integrity. [source] Age-related alterations of gene expression patterns in human CD8+ T cellsAGING CELL, Issue 1 2010Jia-Ning Cao Summary Aging is associated with progressive T-cell deficiency and increased incidence of infections, cancer and autoimmunity. In this comprehensive study, we have compared the gene expression profiles in CD8+ T cells from aged and young healthy subjects using Affymetrix microarray Human Genome U133A-2 GeneChips. A total of 5.2% (754) of the genes analyzed had known functions and displayed statistically significant age-associated expression changes. These genes were involved in a broad array of complex biological processes, mainly in nucleic acid and protein metabolism. Functional groups, in which down-regulated genes were overrepresented, were the following: RNA transcription regulation, RNA and DNA metabolism, intracellular (Golgi, endoplasmic reticulum and nuclear) transportation, signaling transduction pathways (T-cell receptor, Ras/MAPK, JNK/Stat, PI3/AKT, Wnt, TGF,, insulin-like growth factor and insulin), and the ubiquitin cycle. In contrast, the following functional groups contained more up-regulated genes than expected: response to oxidative stress and cytokines, apoptosis, and the MAPKK signaling cascade. These age-associated gene expression changes may be responsible for impaired DNA replication, RNA transcription, and signal transduction, possibly resulting in instability of cellular and genomic integrity, and alterations of growth, differentiation, apoptosis and anergy in human aged CD8+ T cells. [source] Oxygen accelerates the accumulation of mutations during the senescence and immortalization of murine cells in cultureAGING CELL, Issue 6 2003Rita A. Busuttil Summary Oxidative damage is a causal factor in aging and cancer, but it is still not clear how DNA damage, the cellular responses to such damage and its conversion to mutations by misrepair or misreplication contribute to these processes. Using transgenic mice carrying a lacZ mutation reporter, we have previously shown that mutations increase with age in most organs and tissues in vivo. It has also been previously shown that mouse cells respond to oxidative stress, typical of standard culture conditions, by undergoing cellular senescence. To understand better the consequences of oxidative stress, we cultured mouse embryo fibroblasts (MEFs) from lacZ mice under physiological oxygen tension (3%) or the high oxygen tension (20%) associated with standard culture, and determined the frequency and spectrum of mutations. Upon primary culture, the mutation frequency was found to increase approximately three-fold relative to the embryo. The majority of mutations were genome rearrangements. Subsequent culture in 20% oxygen resulted in senescence, followed by spontaneous immortalization. Immortalization was accompanied by an additional three-fold increase in mutations, most of which were G:C to T:A transversions, a signature mutation of oxidative DNA damage. In 3% oxygen, by contrast, MEFs did not senesce and the mutation frequency and spectrum remained similar to primary cultures. These findings demonstrate for the first time the impact of oxidative stress on the genomic integrity of murine cells during senescence and immortalization. [source] Cisplatin resistance conferred by the RAD51D (E233G) genetic variant is dependent upon p53 status in human breast carcinoma cell linesMOLECULAR CARCINOGENESIS, Issue 7 2009Aditi Nadkarni Abstract RAD51D, a paralog of the mammalian RAD51 gene, contributes towards maintaining genomic integrity by homologous recombination DNA repair and telomere maintenance. A RAD51D variant, E233G, was initially identified as a potential susceptibility allele in high-risk, site-specific, familial breast cancer. We describe in this report that the Rad51d (E233G) genetic variant confers increased cisplatin resistance and cell growth phenotypes in human breast carcinoma cell lines with a mutant p53 gene (BT20 and T47D) but not with a wild-type p53 gene (MCF-7). Treatment with a p53 specific inhibitor, pifithrin ,, restored this resistant phenotype in the MCF-7 cell line. Additionally, Rad51d (E233G) conferred increased cisplatin resistance of an MCF7 cell line in which p53 expression was stably knocked down by shRNAp53, indicating that the effect of this variant is dependent upon p53 status. Further study of Rad51d (E233G) will provide mechanistic insight towards the role of RAD51D in cellular response to anticancer agents and as a potential target for cancer therapy. © 2009 Wiley-Liss, Inc. [source] Association of ERCC1 polymorphisms and susceptibility to nasopharyngeal carcinomaMOLECULAR CARCINOGENESIS, Issue 3 2009Zhi-Hui Yang Abstract The normal function of excision repair cross complementing group 1 (ERCC1) is essential for maintaining genomic integrity and preventing cellular neoplastic transformation, and multiple studies have reported an association between ERCC1 polymorphisms and increased risk of cancers. To test whether the genetic variants of ERCC1 gene modify the risk of nasopharyngeal carcinoma (NPC), we compared the 8092 C,>,A and 19007 C,>,T single nucleotide polymorphisms (SNPs) and the haplotypes of ERCC1 between 267 patients with NPC and 304 healthy controls. Linkage disequilibrium was observed between the two SNPs loci (D,,=,0.861). Significant differences of allele frequencies were found for ERCC1 8092C,>,A between the cases and controls. Individuals with 8092 C allele showed 1.411-fold (OR,=,1.411, 95% CI, 1.076,1.850, P,=,0.014) increased risk of developing NPC, and the CC haplotype was associated with a significantly increased risk of NPC (OR,=,1.712; 95% CI, 1.211,2.421; P,=,0.013). No interactions were found between 8092C,>,A polymorphism and genders, smoking status and alcohol consumption. These results suggested that the polymorphism of ERCC1 8092 C,>,A might be a contributing factor in the development of NPC in Chinese population. © 2008 Wiley-Liss, Inc. [source] On the Way to Selective PARP-2 Inhibitors.CHEMMEDCHEM, Issue 6 2008Design, Preliminary Evaluation of a Series of Isoquinolinone Derivatives, Synthesis Abstract PARP-1 and PARP-2 are members of the family of poly(ADP-ribose)polymerases, which are involved in the maintenance of genomic integrity under conditions of genotoxic stimuli. The different roles of the two isoforms under pathophysiological conditions have not yet been fully clarified, and this is partially due to the lack of selective inhibitors. We report herein the synthesis and preliminary pharmacological evaluation of a large series of isoquinolinone derivatives as PARP-1/PARP-2 inhibitors. Among them, we identified the 5-benzoyloxyisoquinolin-1(2,H)-one derivative as the most selective PARP-2 inhibitor reported so far, with a PARP-2/PARP-1 selectivity index greater than 60. [source] | |||||||||||||