• The aryl hydrocarbon receptor-dependent deregulation of cell cycle control induced by polycyclic aromatic hydrocarbons in rat liver epithelial cells.

      Andrysik, Zdenek; Vondracek, Jan; Machala, Miroslav; Krcmar, Pavel; Svihalkova-Sindlerova, Lenka; Kranz, Anne; Weiss, Carsten; Faust, Dagmar; Kozubík, Alois; Dietrich, Cornelia (2007-02-03)
      Disruption of cell proliferation control by polycyclic aromatic hydrocarbons (PAHs) may contribute to their carcinogenicity. We investigated role of the aryl hydrocarbon receptor (AhR) in disruption of contact inhibition in rat liver epithelial WB-F344 'stem-like' cells, induced by the weakly mutagenic benz[a]anthracene (BaA), benzo[b]fluoranthene (BbF) and by the strongly mutagenic benzo[a]pyrene (BaP). There were significant differences between the effects of BaA and BbF, and those of the strongly genotoxic BaP. Both BaA and BbF increased percentage of cells entering S-phase and cell numbers, associated with an increased expression of Cyclin A and Cyclin A/cdk2 complex activity. Their effects were significantly reduced in cells expressing a dominant-negative AhR mutant (dnAhR). Roscovitine, a chemical inhibitor of cdk2, abolished the induction of cell proliferation by BbF. However, neither BaA nor BbF modulated expression of the principal cdk inhibitor involved in maintenance of contact inhibition, p27(Kip1), or pRb phosphorylation. The strongly mutagenic BaP induced apoptosis, a decrease in total cell numbers and significantly higher percentage of cells entering S-phase than either BaA or BbF. Given that BaP induced high levels of Cyclin A/cdk2 activity, downregulation of p27(Kip1) and hyperphosphorylation of pRb, the accumulation of cells in S-phase was probably due to cell proliferation, although S-phase arrest due to blocked replication forks can not be excluded. Both types of effects of BaP were significantly attenuated in dnAhR cells. Transfection of WB-F344 cells with siRNA targeted against AhR decreased induction of Cyclin A induced by BbF or BaP, further supporting the role of AhR in proliferative effects of PAHs. This suggest that activation of AhR plays a significant role both in disruption of contact inhibition by weakly mutagenic PAHs and in genotoxic effects of BaP possibly leading to enhanced cell proliferation. Thus, PAHs may increase proliferative rate and the likelihood of fixation of mutations.
    • Assessment and reduction of comet assay variation in relation to DNA damage: studies from the European Comet Assay Validation Group.

      Moller, Peter; Moller, Lennart; Godschalk, Roger W. L.; Jones, George D. D. (2010-03)
      The alkaline single cell gel electrophoresis (comet) assay has become a widely used method for the detection of DNA damage and repair in cells and tissues. Still, it has been difficult to compare results from different investigators because of differences in assay conditions and because the data are reported in different units. The European Comet Assay Validation Group (ECVAG) was established for the purpose of validation of the comet assay with respect to measures of DNA damage formation and its repair. The results from this inter-laboratory validation trail showed a large variation in measured level of DNA damage and formamidopyrimidine DNA glycosylase-sensitive sites but the laboratories could detect concentration-dependent relationships in coded samples. Standardization of the results with reference standards decreased the inter-laboratory variation. The ECVAG trail indicates substantial reliability for the measurement of DNA damage by the comet assay but there is still a need for further validation to reduce both assay and inter-laboratory variation.
    • Assessment of cumulative evidence on genetic associations: interim guidelines.

      Ioannidis, John P.A; Boffetta, Paolo; Little, Julian; O'Brien, Thomas R.; Uitterlinden, Andre G.; Vineis, Paolo; Balding, David J.; Chokkalingam, Anand; Dolan, Siobhan M.; Flanders, W Dana; et al. (Oxford University Press, 2008-02)
      Established guidelines for causal inference in epidemiological studies may be inappropriate for genetic associations. A consensus process was used to develop guidance criteria for assessing cumulative epidemiologic evidence in genetic associations. A proposed semi-quantitative index assigns three levels for the amount of evidence, extent of replication, and protection from bias, and also generates a composite assessment of 'strong', 'moderate' or 'weak' epidemiological credibility. In addition, we discuss how additional input and guidance can be derived from biological data. Future empirical research and consensus development are needed to develop an integrated model for combining epidemiological and biological evidence in the rapidly evolving field of investigation of genetic factors.
    • Association between 8-oxo-7,8-dihydro-2'-deoxyguanosine Excretion and Risk of Postmenopausal Breast Cancer: Nested Case-Control Study.

      Loft, Steffen; Olsen, Anja; Møller, Peter; Poulsen, Henrik E.; Tjønneland, Anne (2013-07)
      Oxidative stress may be important in carcinogenesis and a possible risk factor for breast cancer. The urinary excretion of oxidatively generated biomolecules, such as 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG), represents biomarkers of oxidative stress, reflecting the rate of global damage to DNA in steady state.
    • Association between GPx1 Pro198Leu polymorphism, GPx1 activity and plasma selenium concentration in humans.

      Jablonska, Ewa; Gromadzinska, J.; Reszka, Edyta; Wasowicz, Wojciech; Sobala, Wojciech; Szeszenia-Dabrowska, Neonila; Boffetta, P. (2009-09)
      BACKGROUND: Glutathione peroxidase 1 (GPx1) is an antioxidant selenoenzyme that protects the cells against reactive oxygen species. Its activity depends on the concentration of selenium (Se) which is present in the active centre of the enzyme. The genetic polymorphism of GPx1 encoding gene (GPx1) associated with the proline (Pro) to leucine (Leu) change at codon 198 is supposed to be functional. An in vitro study performed on human breast carcinoma cell line showed that GPx1Leu allele was associated with a lower responsiveness of the enzyme to Se added to the culture medium. Some authors observed a decrease in GPx1 activity associated with GPx1 Leu allele in humans; however, there were no findings on how GPx1 activity changes with Se concentration in individuals with different GPx1 genotypes. AIM OF THE STUDY: To assess whether GPx1 activity that depends on the Se status may be influenced by GPx1 polymorphism through studying this relationship in the blood of healthy individuals. METHODS: The association between the Se status, GPx1 activity and GPx1 genotype was assessed in 405 individuals of Polish origin. GPx1 activity in red blood cells was measured by the spectrophotometric method by Paglia and Valentine, using t-butylhydroperoxide as the substrate. Plasma Se concentration was measured using graphite furnace atomic absorption spectrometry. GPx1 Pro198Leu polymorphism was determined with the Molecular Beacon Real-Time PCR assay. RESULTS: In the subjects examined, the mean plasma Se concentration was 54.4 +/- 14.2 mcg/L. The mean GPx1 activity was 15.1 +/- 4.7 U/g Hb. No difference regarding both the parameters was found between individuals with different GPx1 genotype. However, the association between GPx1 activity and Se concentration, analyzed separately for each genotype group, was not the same. The correlation coefficients amounted to r = 0.44 (p < 0.001) for Pro/Pro, r = 0.35 (p < 0.001) for Pro/Leu and r = 0.25 (p = 0.45) for Leu/Leu group, which indicates that the correlation strength was as follows: Pro/Pro > Pro/Leu > Leu/Leu. Notably, statistically significant difference in this relationship (analyzed as difference between correlation coefficients for linear trends) was found between genotypes Pro/Pro and Leu/Leu (p = 0.034). CONCLUSIONS: The findings of the present study provide evidence for the hypothesis based on in vitro studies which assumes that GPx1 Pro198Leu polymorphism has a functional significance for the human organism and that this functionality is associated with a different response of GPx1 activity to Se. They also point to the importance of the genetic background in the assessment of the Se status with the use of selenoprotein biomarkers such as GPx1 activity.
    • Association between total number of deaths, diabetes mellitus, incident cancers, and haplotypes in chromosomal region 8q24 in a prospective study.

      Guarrera, Simonetta; Ricceri, Fulvio; Polidoro, Silvia; Sacerdote, Carlotta; Allione, Alessandra; Rosa, Fabio; Voglino, Floriana; Critelli, Rossana; Russo, Alessia; Vineis, Paolo; et al. (2012-03-15)
      The 8q24 region is a gene desert, although chromosomal aberrations and somatic amplification involving this region, including translocations involving the protooncogene c-MYC, have been frequently reported in people with cancer. To investigate the role of variants in 8q24 region, the authors analyzed data from a prospective study (n = 10,372 participants who were followed for 11 years) in which a large number of health events (>1,500) occurred (1993-1998). They genotyped all subjects for 5 candidate single nucleotide polymorphisms (rs672888, rs1447295, rs9642880, rs16901979, and rs6983267) that were identified in previous genome-wide scans. Although significant associations with individual single nucleotide polymorphisms were small in magnitude, the authors observed higher increases in the risks of different types of cancer with specific haplotypes, particularly when subjects were homozygous for the haplotype: for breast cancer and homozygotes for haplotype CAGCT, hazard ratio = 3.40, 95% confidence interval: 1.24, 9.21; for prostate cancer and grouped rare haplotypes, hazard ratio = 7.43, 95% confidence interval: 3.00, 18.37; and for brain cancer and homozygotes for haplotype CGGCT, hazard ratio = 13.48, 95% confidence interval: 3.00, 59.53. Significant associations were also observed between haplotypes and deaths from cardiovascular diseases and cerebrovascular diseases; the most stable association was between homozygotes for haplotypes CGTCG and CAGCT and total deaths in men (hazard ratio = 3.5, 95% confidence interval: 1.8, 6.9, and hazard ratio = 2.8, 95% confidence interval: 1.3, 6.4, respectively). In conclusion, the authors have observed a strong pleiotropic effect of the 8q24 region in a large prospective study. This observation can shed light on the mechanisms underlying reported associations between 8q24 variants and disparate chronic diseases.
    • Association between transcriptional activity, local chromatin structure, and the efficiencies of both subpathways of nucleotide excision repair of melphalan adducts.

      Episkopou, Hara; Kyrtopoulos, Soterios A.; Sfikakis, Petros P.; Fousteri, Maria; Dimopoulos, Meletios A.; Mullenders, Leon H. F.; Souliotis, Vassilis L. (2009-05-15)
      The repair of melphalan-induced N-alkylpurine monoadducts and interstrand cross-links was examined in different repair backgrounds, focusing on four genes (beta-actin, p53, N-ras, and delta-globin) with dissimilar transcription activities. Adducts were found to be substrates for both global genome repair (GGR) and transcription-coupled repair (TCR), with TCR being less efficient than GGR. In nucleotide excision repair-deficient cells, adducts accumulated to similar levels in all four genes. The repair efficiency in different gene loci varied in a qualitatively and quantitatively similar way in both GGR-deficient and TCR-deficient backgrounds and correlated with transcriptional activity and local chromatin condensation. No strand-specific repair was found in GGR(+)/TCR(+) cells, implying that GGR dominated. Adducts were lost over two sharply demarcated phases: a rapid phase resulting in the removal within 1 hour of up to approximately 80% of the adducts, and a subsequent phase with t(1/2) approximately 36 to 48 hours. Following pretreatment of cells with alpha-amanitin, the rate of transcription, the state of chromatin condensation, and the repair efficiencies (both TCR and GGR) of the transcribed beta-actin, p53, and N-ras genes became similar to those of the nontranscribed delta-globin gene. In conclusion, a continuous, parallel variation of the state of transcription and local chromatin condensation, on one hand, and the rates of both GGR and TCR, on the other hand, have been shown.
    • The association of gastric cancer risk with plasma folate, cobalamin, and methylenetetrahydrofolate reductase polymorphisms in the European Prospective Investigation into Cancer and Nutrition.

      Vollset, Stein Emil; Igland, Jannicke; Jenab, Mazda; Fredriksen, Ase; Meyer, Klaus; Eussen, Simone; Gjessing, Hakon K.; Ueland, Per Magne; Pera, Guillem; Sala, Nuria; et al. (2007-11)
      Previous studies have shown inconsistent associations of folate intake and polymorphisms of the methylenetetrahydrofolate reductase (MTHFR) gene with gastric cancer risk. Our nested case-control study within the European Prospective Investigation into Cancer and Nutrition cohort is the first prospective study of blood folate levels and gastric cancer. Gastric cancer cases (n=247) and controls (n=631) were matched for study center, age, sex, and time of blood donation. Two common single nucleotide polymorphisms of the MTHFR gene were determined, as were plasma concentrations of folate, cobalamin (vitamin B12), total homocysteine, and methylmalonic acid (cobalamin deficiency marker) in prediagnostic plasma. Risk measures were calculated with conditional logistic regression. Although no relations were observed between plasma folate or total homocysteine concentrations and gastric cancer, we observed a trend toward lower risk of gastric cancer with increasing cobalamin concentrations (odds ratio, 0.79 per SD increase in cobalamin; P=0.01). Further analyses showed that the inverse association between cobalamin and gastric cancer was confined to cancer cases with low pepsinogen A levels (marker of severe chronic atrophic gastritis) at the time of blood sampling. The 677 C-->T MTHFR polymorphism was not associated with gastric cancer, but we observed an increased risk with the variant genotype of the 1298 A-->C polymorphism (odds ratio, 1.47 for CC versus AA; P=0.04). In conclusion, we found no evidence of a role of folate in gastric cancer etiology. However, we observed increased gastric cancer risk at low cobalamin levels that was most likely due to compromised cobalamin status in atrophic gastritis preceding gastric cancer.
    • Beta-carotene metabolites enhance inflammation-induced oxidative DNA damage in lung epithelial cells.

      van Helden, Yvonne G.J.; Keijer, Jaap; Knaapen, Ad M.; Heil, Sandra G.; Briede, Jacob J.; Van Schooten, Frederik J.; Godschalk, Roger W.L. (2009-01-15)
      beta-Carotene (BC) intake has been shown to enhance lung cancer risk in smokers and asbestos-exposed subjects (according to the ATBC and CARET studies), but the mechanism behind this procarcinogenic effect of BC is unclear. Both smoking and asbestos exposure induce an influx of inflammatory neutrophils into the airways, which results in an increased production of reactive oxygen species and formation of promutagenic DNA lesions. Therefore, the aim of our study was to investigate the effects of BC and its metabolites (BCM) on neutrophil-induced genotoxicity. We observed that the BCM vitamin A (Vit A) and retinoic acid (RA) inhibited the H(2)O(2)-utilizing enzyme myeloperoxidase (MPO), which is released by neutrophils, thereby reducing H(2)O(2) conversion. Moreover, BC and BCM were able to increase (.)OH formation from H(2)O(2) in the Fenton reaction (determined by electron spin resonance spectroscopy). Addition of Vit A and RA to lung epithelial cells that were co-incubated with activated neutrophils resulted in a significant increase in the level of oxidized purines assessed by the formamidopyrimidine DNA glycosylase-modified comet assay. These data indicate that BCM can enhance neutrophil-induced genotoxicity by inhibition of MPO in combination with subsequent increased formation of hydroxyl radicals.
    • Biologically relevant oxidants and terminology, classification and nomenclature of oxidatively generated damage to nucleobases and 2-deoxyribose in nucleic acids.

      Cadet, Jean; Loft, Steffen; Olinski, Ryszard; Evans, Mark D.; Bialkowski, Karol; Richard Wagner, J.; Dedon, Peter C.; Moller, Peter; Greenberg, Marc M.; Cooke, Marcus S. (2012-04)
      A broad scientific community is involved in investigations aimed at delineating the mechanisms of formation and cellular processing of oxidatively generated damage to nucleic acids. Perhaps as a consequence of this breadth of research expertise, there are nomenclature problems for several of the oxidized bases including 8-oxo-7,8-dihydroguanine (8-oxoGua), a ubiquitous marker of almost every type of oxidative stress in cells. Efforts to standardize the nomenclature and abbreviations of the main DNA degradation products that arise from oxidative pathways are reported. Information is also provided on the main oxidative radicals, non-radical oxygen species, one-electron agents and enzymes involved in DNA degradation pathways as well in their targets and reactivity. A brief classification of oxidatively generated damage to DNA that may involve single modifications, tandem base modifications, intrastrand and interstrand cross-links together with DNA-protein cross-links and base adducts arising from the addition of lipid peroxides breakdown products is also included.
    • Biomarkers of dietary intake of flavonoids and phenolic acids for studying diet-cancer relationship in humans.

      Linseisen, Jakob; Rohrmann, Sabine (2008-05)
      BACKGROUND: For many polyphenolic compounds found in plant-derived food, biological effects possibly relevant for cancer prevention have been shown. Since dietary intake estimates suffer from imprecision, the measurement of these compounds (or metabolites of) in biological specimens collected in epidemiological studies is expected to improve accuracy of exposure estimation. AIM OF THE STUDY: The current use of biomarkers in etiologic studies on polyphenolics and cancer risk is evaluated. In addition, available analytical methods are discussed with respect to the requirements for their integration in epidemiological studies, putting specific emphasis on the epidemiological validation of such markers. METHODS: The scientific literature was screened for epidemiologic studies on the relationship of flavonoid and phenolic acid concentrations in human specimens (i.e. blood, urine) and cancer risk. In addition, original data on intra- and inter-subject variability of several flavonoids and phenolic acids are presented. RESULTS: Although several techniques are used in bioavailability or short-term intervention studies, their integration in epidemiological studies is very limited. An exception are phytoestrogens where validated immunoassays allow the rapid measurement of large sample numbers with small sample volume. For several polyphenols, the data on the epidemiologic validity encourages for their use in epidemiological studies. CONCLUSIONS: There are valid possibilities for additional biomarkers of flavonoid and phenolic acid intake that are best applied in prospective studies with more than one biological sample per subject. Currently, a combination of a single biomarker measurement with long-term dietary intake estimates will probably be the most valuable choice to decrease measurement error in exposure data.
    • Biomarkers of exposure to vitamins A, C, and E and their relation to lipid and protein oxidation markers.

      Dragsted, Lars O. (2008-05)
      Since antioxidant vitamins may affect an organism's capacity for defence against reactive oxygen species, biological markers of the dietary exposure to these vitamins is of importance. There is also a need of effect biomarkers for determining the ability of these and other antioxidants to increase the overall antioxidant capacity and decrease the oxidative damage occurring in biological samples. This review is concerned with exposure markers and markers of lipid- or protein damage following intervention with vitamins A, C and E. While there are several high quality exposure markers available it is not possible to identify functional markers of lipid or protein oxidation, which respond reliably to human dietary intervention with vitamins A, C or E.
    • Biomarkers of oxidative damage to DNA and repair.

      Loft, Steffen; Hogh Danielsen, Pernille; Mikkelsen, Lone; Risom, Lotte; Forchhammer, Lykke; Moller, Peter (2008-10)
      Oxidative-stress-induced damage to DNA includes a multitude of lesions, many of which are mutagenic and have multiple roles in cancer and aging. Many lesions have been characterized by MS-based methods after extraction and digestion of DNA. These preparation steps may cause spurious base oxidation, which is less likely to occur with methods such as the comet assay, which are based on nicking of the DNA strand at modified bases, but offer less specificity. The European Standards Committee on Oxidative DNA Damage has concluded that the true levels of the most widely studied lesion, 8-oxodG (8-oxo-7,8-dihydro-2'-deoxyguanosine), in cellular DNA is between 0.5 and 5 lesions per 10(6) dG bases. Base excision repair of oxidative damage to DNA can be assessed by nicking assays based on oligonucleotides with lesions or the comet assay, by mRNA expression levels or, in the case of, e.g., OGG1 (8-oxoguanine DNA glycosylase 1), responsible for repair of 8-oxodG, by genotyping. Products of repair in DNA or the nucleotide pool, such as 8-oxodG, excreted into the urine can be assessed by MS-based methods and generally reflects the rate of damage. Experimental and population-based studies indicate that many environmental factors, including particulate air pollution, cause oxidative damage to DNA, whereas diets rich in fruit and vegetables or antioxidant supplements may reduce the levels and enhance repair. Urinary excretion of 8-oxodG, genotype and expression of OGG1 have been associated with risk of cancer in cohort settings, whereas altered levels of damage, repair or urinary excretion in case-control settings may be a consequence rather than the cause of the disease.
    • Biosynthesis of selenoproteins in cultured bovine mammary cells.

      Bruzelius, Katharina; Purup, Stig; James, Peter; Onning, Gunilla; Akesson, Bjorn (2008)
      The biosynthesis of selenoproteins was studied in relation to milk formation and mammary cell biology by incubating the bovine mammary cell line MAC-T with ((75)Se)selenite. Intracellular proteins and proteins secreted into the cell culture medium were separated by 2D electrophoresis, the selenoproteins were detected by autoradiography, and the proteins were identified by MALDI-TOF. Approximately 35 (75)Se-containing spots were found in the cell proteins from MAC-T cells. Among them, one-third showed high intensity. The strongest spot was identified as glutathione peroxidase 1. About 20 spots were observed in protein precipitated from cell culture medium, one-third of them being distinctly visible. In an attempt to study a perturbation of the system, the effect of retinoic acid (RA) on the formation of selenoproteins was investigated. The concentration of (75)Se in total cell protein was reduced by about 35% in cells cultured with RA compared with control cells, while the opposite effect was observed in protein precipitated from cell culture medium, which contained 60% more (75)Se in RA-treated samples than in controls. There were also indications that RA might affect different selenoproteins in different ways. The methods described provide a promising approach for further studies of the regulation of selenoprotein formation in the mammary gland.
    • Both replication bypass fidelity and repair efficiency influence the yield of mutations per target dose in intact mammalian cells induced by benzo[a]pyrene-diol-epoxide and dibenzo[a,l]pyrene-diol-epoxide.

      Lagerqvist, Anne; Hakansson, Daniel; Prochazka, Gabriela; Lundin, Cecilia; Dreij, Kristian; Segerback, Dan; Jernstrom, Bengt; Tornqvist, Margareta; Seidel, Albrecht; Erixon, Klaus; et al. (2008-08-02)
      Mutations induced by polycyclic aromatic hydrocarbons (PAH) are expected to be produced when error-prone DNA replication occurs across unrepaired DNA lesions formed by reactive PAH metabolites such as diol epoxides. The mutagenicity of the two PAH-diol epoxides (+)-anti-7,8-dihydroxy-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BPDE) and (+/-)-anti-11,12-dihydroxy-13,14-epoxy-11,12,13,14-tetrahydrodibenzo[a,l]pyrene (DBPDE) was compared in nucleotide excision repair (NER) proficient and deficient hamster cell lines. We applied the (32)P-postlabelling assay to analyze adduct levels and the hprt gene mutation assay for monitoring mutations. It was found that the mutagenicity per target dose was 4 times higher for DBPDE compared to BPDE in NER proficient cells while in NER deficient cells, the mutagenicity per target dose was 1.4 times higher for BPDE. In order to investigate to what extent the mutagenicity of the different adducts in NER proficient cells was influenced by repair or replication bypass, we measured the overall NER incision rate, the rate of adduct removal, the rate of replication bypass and the frequency of induced recombination in the hprt gene. The results suggest that NER of BPDE lesions are 5 times more efficient than for DBPDE lesions, in NER proficient cells. However, DBPDE adducts block replication more efficiently and also induce 6 times more recombination events in the hprt gene than adducts of BPDE, suggesting that DBPDE adducts are, to a larger extent, bypassed by homologous recombination. The results obtained here indicate that the mutagenicity of PAH is influenced not only by NER, but also by replication bypass fidelity. This has been postulated earlier based on results using in vitro enzyme assays, but is now also being recognized in terms of forward mutations in intact mammalian cells.
    • Bulky DNA adduct formation and risk of bladder cancer.

      Castano-Vinyals, Gemma; Talaska, Glenn; Rothman, Nathaniel; Alguacil, Juan; Garcia-Closas, Montserrat; Dosemeci, Mustafa; Cantor, Kenneth P.; Malats, Nuria; Real, Francisco X.; Silverman, Debra; et al. (2007-10)
      Exposure to polycyclic aromatic hydrocarbons (PAHs) has been associated with risk of bladder cancer and with increased bulky DNA adduct levels in several studies, mainly in smokers. We investigated the relation between bulky PAH-DNA adducts in peripheral blood mononuclear cells and bladder cancer in nonsmoking subjects from a large hospital-based case-control study in Spain. Additionally, we examined the association between DNA adduct formation and several air pollution proxies. The study comprised 76 nonsmoking cases and 76 individually matched controls by sex, region of residence, age, and smoking status (never, former). To maximize the relevance of the DNA adduct measurement as a proxy of PAH exposure, subjects selected had not changed residence, occupation, and major lifestyle factors during the last 10 years. Bulky DNA adducts were measured using the (32)P-postlabeling technique, nuclease P1 treatment. The percentage of detectable adducts was higher in controls (41%) than in cases (32%) with an odds ratio of 0.75 (95% confidence interval, 0.36-1.58). In an analysis limited to controls, a higher percentage of DNA adducts was found among those whose last residence was in a big city (50%) compared with those living in villages (19%; P = 0.04). No consistent associations were found for other markers of air pollution. In this study, among nonsmokers with stable environmental and lifestyle factors, bulky DNA adducts were not associated with bladder cancer risk. Results do not support an association of bladder cancer risk with low-level exposure to PAHs as measured through the formation of bulky DNA adducts in peripheral mononuclear cells.
    • Bulky DNA adducts in white blood cells: a pooled analysis of 3,600 subjects.

      Ricceri, Fulvio; Godschalk, Roger W.; Peluso, Marco; Phillips, David H.; Agudo, Antonio; Georgiadis, Panagiotis; Loft, Steffen; Tjonneland, Anne; Raaschou-Nielsen, Ole; Palli, Domenico; et al. (2010-12)
      Bulky DNA adducts are markers of exposure to genotoxic aromatic compounds, which reflect the ability of an individual to metabolically activate carcinogens and to repair DNA damage. Polycyclic aromatic hydrocarbons (PAHs) represent a major class of carcinogens that are capable of forming such adducts. Factors that have been reported to be related to DNA adduct levels include smoking, diet, body mass index (BMI), genetic polymorphisms, the season of collection of biologic material, and air pollutants.
    • The cancer chemopreventive actions of phytochemicals derived from glucosinolates.

      Hayes, John D.; Kelleher, Michael O.; Eggleston, Ian M. (2008-05)
      This article reviews the mechanisms by which glucosinolate breakdown products are thought to inhibit carcinogenesis. It describes how isothiocyanates, thiocyanates, nitriles, cyano-epithioalkanes and indoles are produced from glucosinolates through the actions of myrosinase, epithiospecifier protein and epithiospecifier modifier protein released from cruciferous vegetables during injury to the plant. The various biological activities displayed by these phytochemicals are described. In particular, their abilities to induce cytoprotective genes, mediated by the Nrf2 (NF-E2 related factor 2) and AhR (arylhydrocarbon receptor) transcription factors, and their abilities to repress NF-kappaB (nuclear factor-kappaB) activity, inhibit histone deacetylase, and inhibit cytochrome P450 are outlined. Isothiocyanates appear to alter gene expression through modification of critical thiols in regulatory proteins such as Keap1 (Kelch-like ECH-associated protein 1) or IKK (IkappaB kinase), causing activation of Nrf2 and inactivation of NF-kappaB, respectively. Certain indoles act as ligands for AhR. Isothiocyanates and indoles are also capable of affecting cell cycle arrest and stimulating apoptosis. The mechanisms responsible for these anti-proliferative responses are discussed.
    • Cereal fiber intake may reduce risk of gastric adenocarcinomas: the EPIC-EURGAST study.

      Mendez, Michelle A.; Pera, Guillem; Agudo, Antonio; Bueno-de-Mesquita, H. Bas; Palli, Domenico; Boeing, Heiner; Carneiro, Fatima; Berrino, Franco; Sacerdote, Carlotta; Tumino, Rosario; et al. (2007-10-01)
      Numerous case-control studies suggest dietary fiber may reduce risk of gastric cancer, but this has not been confirmed prospectively. A previous case-control study reported reduced risk of gastric cardia adenocarcinomas associated with cereal fiber, but not with fruit or vegetable fiber. To date, different food sources of fiber have not been examined with respect to noncardia tumors or diverse histologic sub-types. This study prospectively examines associations between fiber from different food sources and incident gastric adenocarcinomas (GC) among more than 435,000 subjects from 10 countries participating in the European Prospective Investigation into Cancer and Nutrition study. Subjects aged 25-70 years completed dietary questionnaires in 1992-98, and were followed up for a median of 6.7 years. About 312 incident GCs were observed. The relative risk of GC was estimated based on cohort-wide sex-specific fiber intake quartiles using proportional hazards models to estimate hazards ratios (HRs) and 95% confidence intervals (CIs). Intakes of cereal fiber, but not total, fruit or vegetable fiber, were associated with reduced GC risk [adjusted HR for the highest vs. lowest quartile of cereal fiber 0.69, 0.48-0.99]. There was a strong inverse association for diffuse [HR 0.43, 0.22-0.86], but not intestinal type [HR 0.98, 0.54-1.80] tumors. Associations for cardia vs. noncardia tumors were similar to those for overall GC, although cardia associations did not reach significance. Cereal fiber consumption may help to reduce risk of GC, particularly diffuse type tumors. Further study on different food sources of fiber in relation to GC risk is warranted to confirm these relationships.
    • Chromosomal changes: induction, detection methods and applicability in human biomonitoring.

      Mateuca, R.; Lombaert, N.; Aka, P.V.; Decordier, I.; Kirsch-Volders, M. (2006-11)
      The objective of this state of the art paper is to review the mechanisms of induction, the fate, the methodology, the sensitivity/specificity and predictivity of two major cytogenetic endpoints applied for genotoxicity studies and biomonitoring purposes: chromosome aberrations and micronuclei. Chromosomal aberrations (CAs) are changes in normal chromosome structure or number that can occur spontaneously or as a result of chemical/radiation treatment. Structural CAs in peripheral blood lymphocytes (PBLs), as assessed by the chromosome aberration (CA) assay, have been used for over 30 years in occupational and environmental settings as a biomarker of early effects of genotoxic carcinogens. A high frequency of structural CAs in lymphocytes (reporter tissue) is predictive of increased cancer risk, irrespective of the cause of the initial CA increase. Micronuclei (MN) are small, extranuclear bodies that arise in dividing cells from acentric chromosome/chromatid fragments or whole chromosomes/chromatids that lag behind in anaphase and are not included in the daughter nuclei in telophase. The cytokinesis-block micronucleus (CBMN) assay is the most extensively used method for measuring MN in human lymphocytes, and can be considered as a "cytome" assay covering cell proliferation, cell death and chromosomal changes. The key advantages of the CBMN assay lie in its ability to detect both clastogenic and aneugenic events and to identify cells which divided once in culture. Evaluation of the mechanistic origin of individual MN by centromere and kinetochore identification contributes to the high sensitivity of the method. A number of findings support the hypothesis of a predictive association between the frequency of MN in cytokinesis-blocked lymphocytes and cancer development. Recent advances in fluorescence in situ hybridization (FISH) and microarray technologies are modifying the nature of cytogenetics, allowing chromosome and gene identification on metaphase as well as in interphase. Automated scoring by flow cytometry and/or image analysis will enhance their applicability.