• Salvage of oxidized guanine derivatives in the (2'-deoxy)ribonucleotide pool as source of mutations in DNA.

      Henderson, Paul T.; Evans, Mark D.; Cooke, Marcus S. (2010-11-28)
      Recent evidence suggests that salvage of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) and 8-oxo-7,8-dihydro-guanine (8-oxoGua) can contribute substantially to levels of 8-oxoGua in DNA and RNA. However, it remains to be determined if this mechanism contributes to mutagenesis and disease. This review covers the predominant methods for detecting 8-oxoGua and its derivatives, summarizes some of the relevant recent DNA repair studies and discusses the mechanisms for metabolism of oxidized guanine derivatives in the (2'-deoxy)ribonucleoside and (2'-deoxy)ribonucleotide pools.
    • Selection of influential genetic markers among a large number of candidates based on effect estimation rather than hypothesis testing: an approach for genome-wide association studies.

      Stromberg, Ulf; Bjork, Jonas; Broberg, Karin; Mertens, Fredrik; Vineis, Paolo (2008-03)
      In epidemiologic studies on direct genetic associations, hypothesis testing is primarily considered for evaluating the effects of each candidate genetic marker, eg, single nucleotide polymorphisms. To help investigators protect themselves from over-interpreting statistically significant findings that are not likely to signify a true effect-a problem connected to multiple comparisons-consideration of the false-positive report probability has been proposed. There have also been arguments advocating estimation of effect size rather than hypothesis testing (P value). Here, we propose an estimation-based approach that offers an attractive alternative to the test-based false-positive report probability, when the task is to select promising genetic markers for further analyses. We discuss the potential of this estimation-based approach for genome-wide association studies.
    • Selenium and cancer: biomarkers of selenium status and molecular action of selenium supplements.

      Gromadzinska, Jolanta; Reszka, Edyta; Bruzelius, Katharina; Wasowicz, Wojciech; Akesson, Bjorn (2008-05)
      BACKGROUND: The relationship between selenium and cancer involves many different aspects. These include the forms of selenium present in the diet and in the body, their functions and mechanisms of action, and methods employed in assessing an individual's selenium nutritional status-both in general, and in epidemiological studies of the risk of cancer in relation to diet, as well as in connection with long-term trials for investigating the disease-preventive potential of selenium supplementation. AIM OF THE REVIEW: To review different aspects on selenium metabolism, the occurrence of different selenoproteins and their use as biomarkers of selenium status, the results of intervention trials of the cancer-preventive effects of selenium supplementation, the mechanisms of action involved, together with epidemiological findings on relations between the selenium status in the body and risk of cancer. RESULTS AND CONCLUSIONS: The rapid advance in the knowledge of different selenoproteins and their biological functions has opened up new possibilities for the understanding of the biological effects of selenium supplementation. A wide variety of effects of different forms and doses of selenium has been observed in a number of experimental systems, and it is at present difficult to pinpoint the mechanism that may explain the positive preventive effects of selenium supplementation observed in some human long-term trials. Moreover, additional such trials are needed to define the benefits and risks of different types and doses of selenium supplements which in the future may be implemented for public health reasons. Another necessary focus for future research is a better understanding of the mechanisms by which selenium interferes with the carcinogenesis process.
    • Selenoproteins and selenium speciation in food.

      Hoac, T.; Lundh, T.; Onning, G.; Akesson, B. (Zhejiang University Press : Springer, 2012)
      Different forms of selenium may have varying bioavailability and may also have different effects on body physiology. For these reasons we have studied the occurrence of different forms of selenium in some foods. The pattern of soluble selenium compounds in different species of fish varied markedly as studied by size-exclusion chromatography coupled to ICP-MS or GFAAS. Most flatfish contained mainly low-molecular-weight selenium compounds while other fish species contained more protein-bound selenium. Studies of muscle from seven meat animal species showed four major selenium peaks as found by size-exclusion chromatography. The second and third peaks probably corresponded to glutathione peroxidase (GPx) and selenoprotein W, respectively, and they contained 85% –100% of the recovered selenium. The distribution among the four peaks of soluble selenium varied considerably among muscles from different species. In other experiments, several factors were found to affect the activity of GPx in tissues such as species differences, tissue specificity and heating. In bovine milk, another selenium-rich food, GPx3 is the only identified selenoprotein so far. Bovine whey was found to contain most of the selenium in β-lactoglobulin, α-lactalbumin and selenomethionine. Supplementation of the cow’s feed by yeast selenium increased the proportion of selenium in the former two fractions. It can be concluded that different animal foods contain a variety of selenium compounds and that the selenium profiles of fish, meat and milk differ markedly and also show species differences. The role of this diversity for the bioavailability of selenium from different foods and the effects of different forms of selenium on the organism need to be explored.
    • Sensitivity and specificity of techniques for the identification of biomarkers.

      Farmer, Peter B.; Phillips, David; Moller, Lennart; Singh, Raj; van Schooten, Frederik-Jan; Godschalk, Roger; Mateuca, Raluca; Kirsch-Volders, Micheline (The Nofer Institute of Occupational Medicine, 2006)
      The approaches described for the determination of DNA adducts mostly reach sensitivity limits in the range of 1 adduct/107–109 nucleotides and are thus applicable for studies of environmental exposure to genotoxins. Availability of DNA may be a limiting feature and the kind of sample required will determine how a method is used in human biomonitoring studies. Protein adducts are generally stable and are therefore very suitable for use as biomarkers of exposure. The sensitivity of the mass spectral approaches for these assays has been shown to be sufficient for detection of adducts at low pmol/g protein levels. However, there is a lack of a screening method for characterisation of exposures to complex mixtures and no really high throughput analytical methods,preferable for large-scale human molecular epidemiological studies, exist. Structural chromosomal aberrations in peripheral blood lymphocytes have been widely used in occupational and environmental settings as a biomarker of early effects of geno-toxic carcinogens. The predictivity of chromosomal aberrations as a biomarker for increased cancer risk may depend on the composition of the cohorts included in the study. The use of micronuclei as a measure of chromosomal damage has become a standard assay in both genetic toxicology testing and human biomonitoring studies. Analysis of re-sults from European cohorts indicated that subjects with cancer had a significant increase in frequency of micronuclei.
    • Sensitivity of the association between increased lung cancer risk and bitumen fume exposure to the assumptions in the assessment of exposure.

      de Vocht, Frank; Burstyn, Igor; Ferro, Gilles; Olsson, Ann; Hashibe, Mia; Kromhout, Hans; Boffetta, Paolo (2009-05)
      PURPOSE: A multi-centre IARC-coordinated European cohort study provided evidence of an association between lung cancer risk and bitumen fume exposure. Sensitivity analyses were conducted to assess whether these associations were robust to assumptions in the exposure assessment for which support could not be obtained due to lack of either measurements or direct observations. METHODS: New exposure estimates were generated by changing assumptions on exposure levels, specific tasks, lags, and coal tar use. Subsequently, Poisson regression models estimated relative risks (RRs); change in fit of models was evaluated. RESULTS: The influence of these assumptions was minimal, with log-likelihood deviations between -5.0 and 4.7% and similar patterns in dose-dependent increases of lung cancer risk. In the highest exposure categories, point estimates of RRs ranged 2.07-2.83 for average, and 1.22-2.23 for cumulative exposure. CONCLUSIONS: The small increase in lung cancer risk associated with bitumen fume exposure depends only to a limited extent on the subjective judgments made in the exposure assessment for this cohort.
    • Separation of selenium, zinc, and copper compounds in bovine whey using size exclusion chromatography linked to inductively coupled plasma mass spectrometry.

      Hoac, Tien; Lundh, Thomas; Purup, Stig; Onning, Gunilla; Sejrsen, Kristen; Akesson, Bjorn (2007-05-16)
      To study the role of trace elements for the quality and nutritional value of bovine milk, the distribution of selenium, zinc, and copper in whey was investigated using a method linking size exclusion chromatography to inductively coupled plasma mass spectrometry (SEC-ICP-MS). Three major peaks were detected for selenium, two peaks for zinc, and five peaks for copper. More than 65% of the selenium was found in protein fractions, mainly in fractions coinciding with the major whey proteins beta-lactoglobulin and alpha-lactalbumin. All zinc was associated with low molecular weight compounds (<5 kDa) and one of these compounds was probably citrate. More than 60% of the copper eluted in protein fractions and two of the five major peaks probably contained metallothionein and citrate. This method was used to compare milk and whey produced by organic and conventional feeding procedures. The selenium content in whey and desalted milk produced using organic regimens was significantly lower than that in conventional samples. Moreover, the proportion of selenium in protein fractions of organic whey was significantly smaller than that in conventional whey, but the distributions of zinc and copper did not differ. This study showed that with the SEC-ICP-MS technique the distribution profiles of several trace elements in whey could be studied in the same run and that the selenium profile differed in whey produced by organic and conventional procedures.
    • A sequence variant at 4p16.3 confers susceptibility to urinary bladder cancer.

      Kiemeney, Lambertus A.; Sulem, Patrick; Besenbacher, Soren; Vermeulen, Sita H.; Sigurdsson, Asgeir; Thorleifsson, Gudmar; Gudbjartsson, Daniel F.; Stacey, Simon N.; Gudmundsson, Julius; Zanon, Carlo; et al. (2010-05)
      Previously, we reported germline DNA variants associated with risk of urinary bladder cancer (UBC) in Dutch and Icelandic subjects. Here we expanded the Icelandic sample set and tested the top 20 markers from the combined analysis in several European case-control sample sets, with a total of 4,739 cases and 45,549 controls. The T allele of rs798766 on 4p16.3 was found to associate with UBC (odds ratio = 1.24, P = 9.9 x 10(-12)). rs798766 is located in an intron of TACC3, 70 kb from FGFR3, which often harbors activating somatic mutations in low-grade, noninvasive UBC. Notably, rs798766[T] shows stronger association with low-grade and low-stage UBC than with more aggressive forms of the disease and is associated with higher risk of recurrence in low-grade stage Ta tumors. The frequency of rs798766[T] is higher in Ta tumors that carry an activating mutation in FGFR3 than in Ta tumors with wild-type FGFR3. Our results show a link between germline variants, somatic mutations of FGFR3 and risk of UBC.
    • Sequence variant on 8q24 confers susceptibility to urinary bladder cancer.

      Kiemeney, Lambertus A.; Thorlacius, Steinunn; Sulem, Patrick; Geller, Frank; Aben, Katja K.H.; Stacey, Simon N.; Gudmundsson, Julius; Jakobsdottir, Margret; Bergthorsson, Jon T..; Sigurdsson, Asgeir; et al. (2008-11)
      We conducted a genome-wide SNP association study on 1,803 urinary bladder cancer (UBC) cases and 34,336 controls from Iceland and The Netherlands and follow up studies in seven additional case-control groups (2,165 cases and 3,800 controls). The strongest association was observed with allele T of rs9642880 on chromosome 8q24, 30 kb upstream of MYC (allele-specific odds ratio (OR) = 1.22; P = 9.34 x 10(-12)). Approximately 20% of individuals of European ancestry are homozygous for rs9642880[T], and their estimated risk of developing UBC is 1.49 times that of noncarriers. No association was observed between UBC and the four 8q24 variants previously associated with prostate, colorectal and breast cancers, nor did rs9642880 associate with any of these three cancers. A weaker signal, but nonetheless of genome-wide significance, was captured by rs710521[A] located near TP63 on chromosome 3q28 (allele-specific OR = 1.19; P = 1. 15 x 10(-7)).
    • Sequence variants at the TERT-CLPTM1L locus associate with many cancer types.

      Rafnar, Thorunn; Sulem, Patrick; Stacey, Simon N.; Geller, Frank; Gudmundsson, Julius; Sigurdsson, Asgeir; Jakobsdottir, Margret; Helgadottir, Hafdis; Thorlacius, Steinunn; Aben, Katja K.H.; et al. (2009-02)
      The common sequence variants that have recently been associated with cancer risk are particular to a single cancer type or at most two. Following up on our genome-wide scan of basal cell carcinoma, we found that rs401681[C] on chromosome 5p15.33 satisfied our threshold for genome-wide significance (OR = 1.25, P = 3.7 x 10(-12)). We tested rs401681 for association with 16 additional cancer types in over 30,000 cancer cases and 45,000 controls and found association with lung cancer (OR = 1.15, P = 7.2 x 10(-8)) and urinary bladder, prostate and cervix cancer (ORs = 1.07-1.31, all P < 4 x 10(-4)). However, rs401681[C] seems to confer protection against cutaneous melanoma (OR = 0.88, P = 8.0 x 10(-4)). Notably, most of these cancer types have a strong environmental component to their risk. Investigation of the region led us to rs2736098[A], which showed stronger association with some cancer types. However, neither variant could fully account for the association of the other. rs2736098 corresponds to A305A in the telomerase reverse transcriptase (TERT) protein and rs401681 is in an intron of the CLPTM1L gene.
    • Serum levels of organochlorine pesticides in healthy adults from five regions of Spain.

      Jakszyn, Paula; Goni, Fernando; Etxeandia, Arsenio; Vives, Asuncion; Millan, Esmeralda; Lopez, Raul; Amiano, Pilar; Ardanaz, Eva; Barricarte, Aurelio; Chirlaque, M. Dolores; et al. (2009-09)
      The aim of this study was to measure of serum levels of p,p'-dichlorodiphenyl trichloroethane (p,p'-DDT), p,p'-dichlorodiphenyl dichlorethylene (p,p'-DDE), beta-hexachlorocyclohexane (beta-HCH), and hexachlorobenzene (HCB) in healthy adults in Spain. Furthermore, we also analyzed these levels according to dietary, other lifestyle factors and anthropometric characteristics. We measured the concentrations of such organochlorine pesticides (OCPs) in serum samples collected during 1992-1996 from 953 subjects aged 35-64 years, they were residents of five Spanish regions, they were randomly selected from the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort. OCPs were determined by means of gas chromatography with electron-capture detection (GC-ECD). The most frequent compound found in serum was p,p'-DDE, present in 98% of the samples, followed by HCB and beta-HCH, found in 89% and 77% of samples, respectively, while p,p'-DDT could be measured only in 26% of subjects. The geometric means of serum concentrations (ng/g lipid) were 822 for p,p'-DDE, 167 for beta-HCH, and 379 for HCB. The concentrations of all OCPs were positively associated with age and body mass index, and decreased along the period of blood collection. No association was found between OCPs levels and dietary factors. The concentrations of p,p'-DDE and beta-HCB were higher in Murcia, one of southern regions, most likely associated with intensive past use of pesticides related to agricultural practices, while higher levels of HCB were found in Navarra, located in the north, maybe due to industrial use rather than agricultural application.
    • Serum undercarboxylated osteocalcin as biomarker of vitamin K intake and risk of prostate cancer: a nested case-control study in the Heidelberg cohort of the European prospective investigation into cancer and nutrition.

      Nimptsch, Katharina; Rohrmann, Sabine; Nieters, Alexandra; Linseisen, Jakob (2009-01)
      From cell studies, Vitamin K is known to exert anticancer effects on a variety of cancer cell lines, including prostate cancer cells. Recently, we reported an inverse association between dietary intake of menaquinones (vitamin K(2)), but not phylloquinone (vitamin K(1)), and risk of prostate cancer. In this nested case-control study including 250 prostate cancer cases and 494 matched controls, we aimed to confirm this cancer-protective effect using serum undercarboxylated osteocalcin (ucOC), a biomarker of vitamin K status inversely associated with vitamin K intake. In addition, effect modification by a functionally relevant polymorphism in the vitamin K epoxide reductase gene (VKORC1) was assessed. Serum ucOC and intact total osteocalcin (iOC) were analyzed with the use of ELISA tests. Serum ucOC was expressed relative to iOC (i.e., as ucOC/iOC ratio). Conditional logistic regression was used to calculate multivariate adjusted odds ratios (OR) and 95% confidence intervals (95% CI). Serum ucOC/iOC ratio was positively associated with advanced-stage (OR per 0.1 increment, 1.38; 95% CI, 1.03-1.86) and high-grade prostate cancer (OR, 1.21; 95% CI, 1.00-1.46) but not with total prostate cancer. The significant association with advanced-stage prostate cancer was confirmed when serum ucOC/iOC ratio was jointly modeled with menaquinone intake data. There was indication of a lower prostate cancer risk in carriers of the A allele (compared with GG carriers) of the +2255 VKORC1 polymorphism with increasing menaquinone intake (P(interaction) = 0.14) whereas no distinct effect modification was observed for the ucOC/iOC ratio (P(interaction) = 0.37). The increased risks of advanced-stage and high-grade prostate cancer with higher serum ucOC/iOC ratio strengthen the findings for dietary menaquinone intake.
    • Short-term effects of selenium supplementation of cows' feed on the content and distribution of selenium, copper and zinc in bovine milk, whey and blood plasma.

      Hoac, Tien; Stagsted, Jan; Lundh, Thomas; Nielsen, Jacob H.; Akesson, Bjorn (2008-08)
      The effect of selenium supplementation of feed on the Se content in bovine milk, whey and plasma, and on the distribution of Se, Zn and Cu in whey and plasma was investigated. In a cross-over study two groups of cows were given a basal feed with 0.16 ppm selenite (approx. 3 mg Se/d) with or without 25 mg yeast Se/d for 2 weeks. In the supplemented group the Se content increased 10-fold in milk, 10-fold in whey and 2-fold in plasma, and after the cessation of the supplementation, selenium in milk decreased with a calculated half-life of 3.5 d. In another experiment, two groups of cows were given either 100 mg yeast Se/d for 1 week or only the basal feed. The increase in Se content in both whole and defatted milk was 40-50-fold, and in whey it was approx. 20-fold. Size-exclusion chromatography of whey using inductively coupled plasma mass spectrometry for detection showed that supplementation increased the proportion of Se in the beta-lactoglobulin-alpha-lactalbumin fraction. Distribution of Cu and Zn was essentially unaffected. In plasma, supplementation increased the Se content in all major Se fractions like selenoprotein P, albumin and low-molecular-weight compounds, but the distribution profiles of Zn and Cu underwent no major changes. The study showed for the first time the rapid kinetics of the Se increase and decrease in milk after the initiation and cessation of supplementation, respectively, and the preferential appearance of Se in the beta-lactoglobulin-alpha-lactalbumin fraction of whey. Milk highly enriched in selenium will be a useful tool for different research purposes.
    • A short-term intervention trial with selenate, selenium-enriched yeast and selenium-enriched milk: effects on oxidative defence regulation.

      Ravn-Haren, Gitte; Bugel, Susanne; Krath, Britta N.; Hoac, Tien; Stagsted, Jan; Jorgensen, Karina; Bresson, June R.; Larsen, Erik H.; Dragsted, Lars O. (2008-04)
      Increased Se intakes have been associated with decreased risk of cancer and CVD. Several mechanisms have been proposed, including antioxidant effects through selenoproteins, induction of carcinogen metabolism and effects on the blood lipid profile. In a 4 x 1 week randomised, double-blind cross-over study, healthy young men supplemented their usual diet with selenate, Se-enriched yeast, Se-enriched milk or placebo (Se dose was 300 microg/d for selenate and Se-enriched yeast, and about 480 microg/d for Se-enriched milk) followed by 8-week washout periods. All Se sources increased serum Se levels after supplementation for 1 week. The effect of the organic forms did not differ significantly and both increased serum Se more than selenate. Conversely, thrombocyte glutathione peroxidase (GPX) was increased in the periods where subjects were supplemented with selenate but not in those where they were given Se-enriched yeast or Se-enriched milk. We found no effect on plasma lipid resistance to oxidation, total cholesterol, TAG, HDL- and LDL-cholesterol, GPX, glutathione reductase (GR) and glutathione S-transferase (GST) activities measured in erythrocytes, GPX and GR activities determined in plasma, or GR and GST activities in thrombocytes. Leucocyte expression of genes encoding selenoproteins (GPX1, TrR1 and SelP), and of electrophile response element-regulated genes (GCLC, Fra1 and NQO1) were likewise unaffected at all time points following intervention. We conclude that thrombocyte GPX is specifically increased by short-term selenate supplementation, but not by short-term supplementation with organic Se. Short-term Se supplementation does not seem to affect blood lipid markers or expression and activity of selected enzymes and a transcription factor involved in glutathione-mediated detoxification and antioxidation.
    • Simultaneous genotyping of GSTT1 and GSTM1 null polymorphisms by melting curve analysis in presence of SYBR Green I.

      Marin, Fatima; Garcia, Nadia; Munoz, Xavier; Capella, Gabriel; Gonzalez, Carlos A.; Agudo, Antonio; Sala, Nuria (2010-05)
      Due to their ability to metabolize xenobiotics, glutathione S-transferases (GSTs) play an important role in cellular protection. GST family members mu (GSTM1) and theta (GSTT1) exhibit a common polymorphism that results in the complete deletion of the gene (null allele). Homozygous deletions, which result in the absence of the enzyme, are considered a risk factor for several diseases, including cancer. We report a simple, low cost, and high throughput assay for the simultaneous analysis of the GSTM1 and GSTT1 null polymorphisms in a single step. The assay is based on multiplex real-time PCR in the presence of SYBR Green I and genotype discrimination by melting curve analysis in a LightCycler. We have genotyped 792 samples to compare this new approach with conventional PCR followed by gel electrophoresis. Comparison of the methods gave a good agreement, with kappa values of 0.88 for GSTM1 and 0.64 for GSTT1. Reanalysis of discrepant samples indicated that absence of amplification of the larger GSTT1 fragment by conventional PCR accounted for most of the discrepancies. Moreover, the improved amplification efficiency of the real-time PCR results in a significant reduction of missing values. Due to its simplicity and low cost, this assay is well suited for the rapid analysis of GST-null genotypes in studies that involve large number of samples.
    • Size distribution and total number concentration of ultrafine and accumulation mode particles and hospital admissions in children and the elderly in Copenhagen, Denmark.

      Andersen, Z.J.; Wahlin, P.; Raaschou-Nielsen, O.; Ketzel, M.; Scheike, T.; Loft, S. (2008-07)
      OBJECTIVES: To study the association between short-term exposure to ultrafine particles and morbidity in Copenhagen, Denmark. METHODS: We studied the association between urban background levels of the total number concentration of particles (NC(tot), 6-700 nm in diameter) measured at a single site (15 May 2001 to 31 December 2004) and hospital admissions due to cardiovascular (CVD) and respiratory disease (RD) in the elderly (age >or=65 years), and due to asthma in children (age 5-18 years). We examined these associations in the presence of PM(10), PM(2.5) (particulate matter <10 and 2.5 microm in diameter, respectively) and ambient gasses. We utilised data on size distribution to calculate NC(tot) for four modes with median diameters 12, 23, 57 and 212 nm, and NC(100) (number concentration of particles <100 nm in diameter) and examined their associations with health outcomes. We used a time series Poisson generalised additive model adjusted for overdispersion, season, day of the week, public holidays, school holidays, influenza, pollen and meteorology, with up to 5 days' lagged exposure. RESULTS AND CONCLUSIONS: The adverse health effects of particulate matter on CVD and RD hospital admissions in the elderly were mainly mediated by PM(10) and accumulation mode particles with lack of effects for NC(100). For paediatric asthma, accumulation mode particles, NC(100) and nitrogen oxides (mainly from traffic related sources) were relevant, whereas PM(10) appeared to have little effect. Our results suggest that particle volume/mass from long-range transported air pollution is relevant for CVD and RD admissions in the elderly, and possibly particle numbers from traffic sources for paediatric asthma.
    • Size-dependent toxicity of metal oxide particles--a comparison between nano- and micrometer size.

      Karlsson, Hanna L.; Gustafsson, Johanna; Cronholm, Pontus; Moller, Lennart (2009-07-24)
      Toxicological studies have shown increased toxicity of nanoparticles (<100 nm) compared to micrometer particles of the same composition, which has raised concern about the impact on human health from nanoparticles. However, if this is true for a wide range of particles with different chemical composition is not clear. The aim of this study was to compare the toxicity of nano- and micrometer particles of some metal oxides (Fe(2)O(3), Fe(3)O(4), TiO(2) and CuO). The ability of the particles to cause cell death, mitochondrial damage, DNA damage and oxidative DNA lesions were evaluated after exposure of the human cell line A549. This study showed that nanoparticles of CuO were much more toxic compared to CuO micrometer particles. One key mechanism may be the ability of CuO to damage the mitochondria. In contrast, the micrometer particles of TiO(2) caused more DNA damage compared to the nanoparticles, which is likely explained by the crystal structures. The iron oxides showed low toxicity and no clear difference between the different particle sizes. In conclusion, nanoparticles are not always more toxic than micrometer particles, but the high toxicity of CuO nanoparticles shows that the nanolevel gives rise to specific concern.
    • Small field radiotherapy of head and neck cancer patients is responsible for oxidatively damaged DNA/oxidative stress on the level of a whole organism.

      Roszkowski, Krzysztof; Gackowski, Daniel; Rozalski, Rafal; Dziaman, Tomasz; Siomek, Agnieszka; Guz, Jolanta; Szpila, Anna; Foksinski, Marek; Olinski, Ryszard (2008-10-15)
      It is possible that oxidatively damaged DNA which arises as a result of radiotherapy may be involved in the therapeutic effect of the ionizing radiation and in the side effects. Therefore, for the first time, the broad spectrum of oxidatively damaged DNA biomarkers: urinary excretion of 8-oxodG (8-oxo-7,8-dihydro-2'-deoxyguanosine), 8-oxoGua (8-oxo-7,8-dihydroguanine) as well as the level of oxidatively damaged DNA in leukocytes, was analyzed in head and neck cancer patients (n = 27) undergoing fractionated radiotherapy using methodologies which involve HPLC (high-performance liquid chromatography) prepurification followed by gas chromatography with isotope dilution mass spectrometry detection and HPLC/EC. Of all the analyzed parameters in the majority of patients, only urinary excretion of the modified nucleoside significantly increased over the initial level in the samples collected 24 hr after the last fraction. However, for the distinct subpopulation of 10 patients, a significant increase in the level of 8-oxodG in cellular DNA and a simultaneous drop in urinary 8-oxoGua (the repair product of oxidative DNA damage) were detected after completion of the therapy. Because 8-oxoGua is a repair product of the DNA damage, there is a possibility that, at least in the case of some patients with the lowest activity of OGG1 (8-oxo-7,8-dihydroguanine glycosylase), the combination of lower OGG1 repair efficacy and irradiation was associated with increased background level of 8-oxoGua in cellular DNA. Apparently reduced DNA repair is unable to cope with the radiation-induced, and the extra amount of 8-oxoGua leading to an increase of potentially mutagenic/carcinogenic lesions.
    • Smoking-related O4-ethylthymidine formation in human lung tissue and comparisons with bulky DNA adducts.

      Anna, Livia; Kovacs, Katalin; Gyorffy, Erika; Schoket, Bernadette; Nair, Jagadeesan (2011-07)
      Tobacco smoke contains many alkylating agents that can react with DNA to produce O(4)-ethylthymidine (O(4)-etT) and several other types of promutagenic base modifications. Our aims were (i) to confirm results of a pilot study (Godschalk, R., Nair, J., Schooten, F. J., Risch, A., Drings, P., Kayser, K., Dienemann, H. and Bartsch, H. (2002) Comparison of multiple DNA adduct types in tumor adjacent human lung tissue: effect of cigarette smoking. Carcinogenesis, 23, 2081-2086) on the formation of O(4)-etT in smokers' lung; (ii) to explore associations between levels of O(4)-etT and smoking status and (iii) to investigate whether a correlation exists between levels of O(4)-etT and bulky (polycyclic aromatic hydrocarbons-derived) DNA adducts. Archived DNA samples originated from histologically normal peripheral lung tissues of 64 Hungarian lung cancer patients, who underwent lung resection. O(4)-etT was determined by an immunoenriched (32)P-postlabelling-high-performance liquid chromatography method. Levels of bulky DNA adducts were determined by the nuclease P1 adduct-enriched (32)P-postlabelling. O(4)-etT levels ranged from 0.01 to 3.91 adducts/10(8) thymidines. In the combined group of subjects who smoked until surgery or gave up smoking at most 1 year before it, the mean level of O(4)-etT was 1.7-fold (P = 0.015) and of bulky DNA adducts 2.2-fold (P < 0.0001) higher than in long-term ex-smokers (LES) and never-smokers (NS) combined. We found no significant correlation between the individual levels of the two DNA adduct types. No dose-response was detected between O(4)-etT formation and smoking dose. In one-third of LES, O(4)-etT levels were above the 2.0-fold mean level of adducts found in NS, indicating its high persistence. Our results confirm the smoking-related formation of O(4)-etT in human lung DNA that should be explored as biomarker. Its long persistence in target tissue implicates a role of this potentially miscoding lesion in tobacco smoking-associated cancers.
    • Sources of extracellular, oxidatively-modified DNA lesions: implications for their measurement in urine.

      Cooke, Marcus S.; Henderson, Paul T.; Evans, Mark D. (2009-11)
      There is a robust mechanistic basis for the role of oxidation damage to DNA in the aetiology of various major diseases (cardiovascular, neurodegenerative, cancer). Robust, validated biomarkers are needed to measure oxidative damage in the context of molecular epidemiology, to clarify risks associated with oxidative stress, to improve our understanding of its role in health and disease and to test intervention strategies to ameliorate it. Of the urinary biomarkers for DNA oxidation, 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) is the most studied. However, there are a number of factors which hamper our complete understanding of what meausrement of this lesion in urine actually represents. DNA repair is thought to be a major contributor to urinary 8-oxodG levels, although the precise pathway(s) has not been proven, plus possible contribution from cell turnover and diet are possible confounders. Most recently, evidence has arisen which suggests that nucleotide salvage of 8-oxodG and 8-oxoGua can contribute substantially to 8-oxoG levels in DNA and RNA, at least in rapidly dividing cells. This new observation may add an further confounder to the conclusion that 8-oxoGua or 8-oxodG, and its nucleobase equivalent 8-oxoguanine, concentrations in urine are simply a consequence of DNA repair. Further studies are required to define the relative contributions of metabolism, disease and diet to oxidised nucleic acids and their metabolites in urine in order to develop urinalyis as a better tool for understanding human disease.