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  • 1
    In: Cancer Research, American Association for Cancer Research (AACR), Vol. 75, No. 15 ( 2015-08-01), p. 3108-3117
    Abstract: O6-Methylguanine-DNA methyltransferase (MGMT) is a DNA repair enzyme that protects cells from carcinogenic effects of alkylating agents; however, MGMT is silenced by promoter hypermethylation during carcinogenesis. A single-nucleotide polymorphism (SNP) in an enhancer in the MGMT promoter was previously identified to be highly significantly associated with risk for MGMT methylation in lung cancer and sputum from smokers. To further genetic investigations, a genome-wide association and replication study was conducted in two smoker cohorts to identify novel loci for MGMT methylation in sputum that were independent of the MGMT enhancer polymorphism. Two novel trans-acting loci (15q15.2 and 17q24.3) that were identified acted together with the enhancer SNP to empower risk prediction for MGMT methylation. We found that the predisposition to MGMT methylation arising from the 15q15.2 locus involved regulation of the ubiquitin protein ligase E3 component UBR1. UBR1 attenuation reduced turnover of MGMT protein and increased repair of O6-methylguanine in nitrosomethylurea-treated human bronchial epithelial cells, while also reducing MGMT promoter activity and abolishing MGMT induction. Overall, our results substantiate reduced gene transcription as a major mechanism for predisposition to MGMT methylation in the lungs of smokers, and support the importance of UBR1 in regulating MGMT homeostasis and DNA repair of alkylated DNA adducts in cells. Cancer Res; 75(15); 3108–17. ©2015 AACR.
    Type of Medium: Online Resource
    ISSN: 0008-5472 , 1538-7445
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    Language: English
    Publisher: American Association for Cancer Research (AACR)
    Publication Date: 2015
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  • 2
    In: The American Journal of Pathology, Elsevier BV, Vol. 177, No. 4 ( 2010-10), p. 1936-1945
    Type of Medium: Online Resource
    ISSN: 0002-9440
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    Language: English
    Publisher: Elsevier BV
    Publication Date: 2010
    detail.hit.zdb_id: 1480207-7
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  • 3
    Online Resource
    Online Resource
    Oxford University Press (OUP) ; 1975
    In:  JNCI: Journal of the National Cancer Institute Vol. 55, No. 1 ( 1975-7), p. 147-152
    In: JNCI: Journal of the National Cancer Institute, Oxford University Press (OUP), Vol. 55, No. 1 ( 1975-7), p. 147-152
    Type of Medium: Online Resource
    ISSN: 1460-2105 , 0027-8874
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    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 1975
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    detail.hit.zdb_id: 1465951-7
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  • 4
    In: Cancer Research, American Association for Cancer Research (AACR), Vol. 64, No. 3 ( 2004-02-01), p. 1050-1057
    Abstract: Oxidative stress to DNA is recognized as one of the mechanisms for the carcinogenic effects of some environmental agents. Numerous studies have been conducted in an attempt to document the fact that chemical carcinogens that are thought to induce production of oxidants also cause the formation of oxidative DNA lesions. Although many DNA adducts continue to be useful biomarkers of dose/effect, changes in gene expression have been proposed to be a practical novel tool for studying the role of chemically induced oxidative DNA damage. Here, we hypothesized that expression of base excision DNA repair genes is a sensitive biomarker for in vivo detection of chemically induced chronic oxidative stress. To test this hypothesis, mice were treated with a known rodent carcinogen and peroxisome proliferator, WY-14,643 (500 ppm, 1 month). A number of end points that are commonly used to assess oxidative DNA damage were considered. Our data demonstrate that no difference in 8-oxoguanine, the number of abasic sites, or single strand breaks can be detected in genomic DNA from livers of control or WY-treated animals. However, a concordant marked induction of genes specific for the long-patch base excision DNA repair, a predominant pathway that removes oxidized DNA lesions in vivo, was observed in livers of WY-treated mice. Kupffer cell NADPH oxidase, and peroxisomes in parenchymal cells have been proposed as the potential sources of peroxisome proliferator-induced oxidants. The analysis of expression of base excision DNA repair genes was used to assess whether this biomarker of oxidative stress can be used to determine the source of oxidants. The data suggest that DNA-damaging oxidants are generated by enzymes that are induced after activation of peroxisome proliferator activator receptor α, such as those involved in lipid metabolism in peroxisomes, and are not the result of activation of NADPH oxidase in Kupffer cells. We conclude that expression of base excision DNA repair genes is a sensitive in vivo biomarker for chemically induced oxidative stress to DNA that can be successfully used for the identification of the molecular source of radicals responsible for DNA damage in vivo.
    Type of Medium: Online Resource
    ISSN: 0008-5472 , 1538-7445
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    Language: English
    Publisher: American Association for Cancer Research (AACR)
    Publication Date: 2004
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  • 5
    Online Resource
    Online Resource
    American Association for Cancer Research (AACR) ; 2012
    In:  Cancer Research Vol. 72, No. 8_Supplement ( 2012-04-15), p. 4473-4473
    In: Cancer Research, American Association for Cancer Research (AACR), Vol. 72, No. 8_Supplement ( 2012-04-15), p. 4473-4473
    Abstract: 1,3-butadiene (BD) is one of the most potent and abundant carcinogens present in cigarette smoke. BD is metabolically activated to 3,4-epoxy-1-butene (EB), 1,2,3,4-diepoxy butane (DEB), hydroxymethylvinylketone (HMVK), and 3,4-epoxy-1,2-butanediol (EBD), which can react with DNA nucleobases and proteins to form promutagenic adducts. Alternatively, these electrophilic metabolites can be detoxified via hydrolysis or conjugation with glutathione. The glutathione conjugates of these metabolites are ultimately excreted in urine as 1-hydroxy 2-(N-acetylcysteinyl)-3-butene (MHBMA), 1,4-bis-(N-acetylcysteinyl)butane-2,3-diol (bis-BDMA), 1,2-dihydroxy-4-(N-acetylcysteinyl)-butane (DHBMA), and 1,2,3-trihydroxy-4-(N-acetylcysteinyl)-butane (THBMA), respectively. Since epoxide metabolites of BD are thought to be responsible for its adverse health effects, it is important to develop specific biomarkers of their formation in vivo to be used in molecular epidemiology studies. While MHBMA, DHBMA, THBMA have been previously detected in smoker's urine, bis-BDMA has not been reported. In the present study, novel stable isotope dilution HPLC-ESI-MS/MS methods for accurate and precise quantification of MHBMA, DHBMA, THBMA, and bis-BDMA in urine have been developed. Dose dependent formation of all BD-mercapturic acids including bis-BDMA was observed in urine samples from male and female F344 rats exposed to 0, 62.5 and 200 ppm of BD for 2 weeks by inhalation. The relative amounts of MHBMA, DHBMA, THBMA, and bis-BDMA in rat urine were 20:50:50:1. Furthermore, MHBMA, DHBMA, and THBMA were detected in urine samples from known smokers and non-smokers, with significantly higher concentrations observed in smokers. The mean levels of these BD-mercapturic acids in smokers were 3, 340, and 27 ng/mg creatinine, respectively. In contrast, bis-BDMA could not be detected in human urine samples, probably a result of the inefficient DEB formation in humans. These methods are now being applied to a multi-ethnic cohort study to identify any differences in metabolism that contribute to ethnic and inter-individual differences in lung cancer incidence. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4473. doi:1538-7445.AM2012-4473
    Type of Medium: Online Resource
    ISSN: 0008-5472 , 1538-7445
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    Language: English
    Publisher: American Association for Cancer Research (AACR)
    Publication Date: 2012
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    detail.hit.zdb_id: 1432-1
    detail.hit.zdb_id: 410466-3
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  • 6
    Online Resource
    Online Resource
    American Association for Cancer Research (AACR) ; 2006
    In:  Cancer Research Vol. 66, No. 5 ( 2006-03-01), p. 2860-2868
    In: Cancer Research, American Association for Cancer Research (AACR), Vol. 66, No. 5 ( 2006-03-01), p. 2860-2868
    Abstract: Tobacco smoke produces oxidative and alkylative DNA damage that necessitates repair by base excision repair coordinated by X-ray cross-complementing gene 1 (XRCC1). We investigated whether polymorphisms in XRCC1 alter DNA repair capacity and modify breast cancer risk associated with smoking. To show the functionality of the 280His variant, we evaluated single-strand break (SSB) repair capacity of isogenic Chinese hamster ovary cells expressing human forms of XRCC1 after exposure to hydrogen peroxide (H2O2), methyl methanesulfonate (MMS), or camptothecin by monitoring NAD(P)H. We used data from the Carolina Breast Cancer Study (CBCS), a population-based, case-control study that included 2,077 cases (786 African Americans and 1,281 Whites) and 1,818 controls (681 African Americans and 1,137 Whites), to examine associations among XRCC1 codon 194, 280, and 399 genotypes, breast cancer, and smoking. Odds ratios and 95% confidence intervals (95% CI) were calculated by unconditional logistic regression. Only cells expressing the 280His protein accumulated SSB, indicated by NAD(P)H depletion, from both H2O2 and MMS exposures. In the CBCS, positive associations were observed between breast cancer and smoking dose for participants with XRCC1 codon 194 Arg/Arg (Ptrend = 0.046), 399 Arg/Arg (Ptrend = 0.012), and 280 His/His or His/Arg (Ptrend = 0.047) genotypes. The 280His allele was in strong linkage disequilibrium with 194Arg (Lewontin's D′ = 1.0) and 399Arg (D′ = 1.0). These data suggest that less common, functional polymorphisms may lie within common haplotypes and drive gene-environment interactions. (Cancer Res 2006; 66(5): 2860-8)
    Type of Medium: Online Resource
    ISSN: 0008-5472 , 1538-7445
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    Language: English
    Publisher: American Association for Cancer Research (AACR)
    Publication Date: 2006
    detail.hit.zdb_id: 2036785-5
    detail.hit.zdb_id: 1432-1
    detail.hit.zdb_id: 410466-3
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  • 7
    Online Resource
    Online Resource
    Oxford University Press (OUP) ; 1970
    In:  Journal of Neuropathology and Experimental Neurology Vol. 29, No. 1 ( 1970-01), p. 128-
    In: Journal of Neuropathology and Experimental Neurology, Oxford University Press (OUP), Vol. 29, No. 1 ( 1970-01), p. 128-
    Type of Medium: Online Resource
    ISSN: 0022-3069
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    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 1970
    detail.hit.zdb_id: 2033048-0
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  • 8
    Online Resource
    Online Resource
    Oxford University Press (OUP) ; 1984
    In:  JNCI: Journal of the National Cancer Institute Vol. 72, No. 1 ( 1984-01-01), p. 151-160
    In: JNCI: Journal of the National Cancer Institute, Oxford University Press (OUP), Vol. 72, No. 1 ( 1984-01-01), p. 151-160
    Type of Medium: Online Resource
    ISSN: 0027-8874 , 1460-2105
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    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 1984
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    detail.hit.zdb_id: 1465951-7
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  • 9
    Online Resource
    Online Resource
    American Association for Cancer Research (AACR) ; 2012
    In:  Cancer Research Vol. 72, No. 8_Supplement ( 2012-04-15), p. 2552-2552
    In: Cancer Research, American Association for Cancer Research (AACR), Vol. 72, No. 8_Supplement ( 2012-04-15), p. 2552-2552
    Abstract: A DNA damage response analysis makes use of the chicken DT40 isogenic cell line and its dozens of available mutants knocked out in various DNA repair and cell cycle pathways. While this DT40 cell system is valuable for understanding the DNA damage response to genotoxic agents, no convenient mutation assay for mutagens currently exists for this reverse-genetic system. Here we establish a proaerolysin (PA) selection-based mutation assay in DT40 cells to identify glycosylphosphatidylinositol (GPI)-anchor deficient cells. Using PA, we detected an increase in the number of PA-resistant DT40 cells exposed to MMS for 24 hours followed by a 5-day period of phenotype expression. GPI anchor synthesis is catalyzed by a series of phosphatidylinositol glycan complementation groups (PIGs). The PIG-O gene is on the sex chromosome (Chromosome Z) in chicken cells and is critical for GPI anchor synthesis at the intermediate step. We identified that all PA-resistant DT40 cells analyzed have mutations in the PIG-O gene. This novel assay for DT40 cells provides a valuable tool to investigate the mode of action of mutations caused by reactive agents using a series of isogenic mutant DT40 cells. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2552. doi:1538-7445.AM2012-2552
    Type of Medium: Online Resource
    ISSN: 0008-5472 , 1538-7445
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    Language: English
    Publisher: American Association for Cancer Research (AACR)
    Publication Date: 2012
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    detail.hit.zdb_id: 1432-1
    detail.hit.zdb_id: 410466-3
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  • 10
    Online Resource
    Online Resource
    American Association for Cancer Research (AACR) ; 2009
    In:  Cancer Research Vol. 69, No. 6 ( 2009-03-15), p. 2479-2486
    In: Cancer Research, American Association for Cancer Research (AACR), Vol. 69, No. 6 ( 2009-03-15), p. 2479-2486
    Abstract: 1,3-Butadiene (BD) is an important industrial and environmental chemical classified as a human carcinogen based on epidemiologic studies in occupationally exposed workers and animal studies in laboratory rats and mice. BD is metabolically activated to three epoxides that can react with nucleophilic sites in biomolecules. Among these, 1,2,3,4-diepoxybutane (DEB) is considered the ultimate carcinogen due to its high genotoxicity and mutagenicity attributed to its ability to form DNA-DNA cross-links. Our laboratory has developed quantitative high-performance liquid chromatography–μESI+–tandem mass spectrometry methods for two DEB-specific DNA-DNA cross-links, 1,4-bis-(guan-7-yl)-2,3-butanediol (bis-N7G-BD) and 1-(guan-7-yl)-4-(aden-1-yl)-2,3-butanediol (N7G-N1A-BD). This report describes molecular dosimetry analysis of these adducts in tissues of B6C3F1 mice and F344 rats exposed to a range of BD concentrations (0–625 ppm). Much higher (4- to 10-fold) levels of DEB-DNA cross-links were observed in mice compared with rats exposed to the same BD concentrations. In both species, bis-N7G-BD levels were 1.5- to 4-fold higher in the liver than in other tissues examined. Interestingly, tissues of female animals exposed to BD contained higher concentrations of bis-N7G-BD adducts than tissues of male animals, which is in accord with previously reported differences in tumor incidence. The molecular dosimetry data presented herein suggest that species and gender differences observed in BD-induced cancer are directly related to differences in the extent of BD metabolism to DEB. Furthermore, a rat model of sensitivity to BD may be more appropriate than a mouse model for assessing human risk associated with BD exposure, because rats and humans seem to be similar with respect to DEB formation. [Cancer Res 2009;69(6):2479–8]
    Type of Medium: Online Resource
    ISSN: 0008-5472 , 1538-7445
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    Language: English
    Publisher: American Association for Cancer Research (AACR)
    Publication Date: 2009
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    detail.hit.zdb_id: 410466-3
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