• Inter-laboratory variation in DNA damage using a standard comet assay protocol.

      Forchhammer, Lykke; Ersson, Clara; Loft, Steffen; Moller, Lennart; Godschalk, Roger W. L.; van Schooten, Frederik J.; Jones, George D. D.; Higgins, Jennifer A.; Cooke, Marcus; Mistry, Vilas; et al. (2012-07-27)
      There are substantial inter-laboratory variations in the levels of DNA damage measured by the comet assay. The aim of this study was to investigate whether adherence to a standard comet assay protocol would reduce inter-laboratory variation in reported values of DNA damage. Fourteen laboratories determined the baseline level of DNA strand breaks (SBs)/alkaline labile sites and formamidopyrimidine DNA glycosylase (FPG)-sensitive sites in coded samples of mononuclear blood cells (MNBCs) from healthy volunteers. There were technical problems in seven laboratories in adopting the standard protocol, which were not related to the level of experience. Therefore, the inter-laboratory variation in DNA damage was only analysed using the results from laboratories that had obtained complete data with the standard comet assay protocol. This analysis showed that the differences between reported levels of DNA SBs/alkaline labile sites in MNBCs were not reduced by applying the standard assay protocol as compared with the laboratory's own protocol. There was large inter-laboratory variation in FPG-sensitive sites by the laboratory-specific protocol and the variation was reduced when the samples were analysed by the standard protocol. The SBs and FPG-sensitive sites were measured in the same experiment, indicating that the large spread in the latter lesions was the main reason for the reduced inter-laboratory variation. However, it remains worrying that half of the participating laboratories obtained poor results using the standard procedure. This study indicates that future comet assay validation trials should take steps to evaluate the implementation of standard procedures in participating laboratories.
    • Interlaboratory and Interplatform Comparison of Microarray Gene Expression Analysis of HepG2 Cells Exposed to Benzo(a)pyrene.

      Hockley, Sarah L.; Mathijs, Karen; Staal, Yvonne C.M.; Brewer, Daniel; Giddings, Ian; van Delft, Joost H.M.; Phillips, David H. (2009-04)
      Abstract Microarray technology is being used increasingly to study gene expression of biological systems on a large scale. Both interlaboratory and interplatform differences are known to contribute to variability in microarray data. In this study we have investigated data from different platforms and laboratories on the transcriptomic profile of HepG2 cells exposed to benzo(a)pyrene (BaP). RNA samples generated in two different laboratories were analyzed using both Agilent oligonucleotide microarrays and Cancer Research UK (CR-UK) cDNA microarrays. Comparability of the expression profiles was assessed at various levels including correlation and overlap between the data, clustering of the data and affected biological processes. Overlap and correlation occurred, but it was not possible to deduce whether choice of platform or interlaboratory differences contributed more to the data variation. Principal component analysis (PCA) and hierarchical clustering of the expression profiles indicated that the data were most clearly defined by duration of exposure to BaP, suggesting that laboratory and platform variability does not mask the biological effects. Real-time quantitative PCR was used to validate the two array platforms and indicated that false negatives, rather than false positives, are obtained with both systems. All together these results suggest that data from similar biological experiments analyzed on different microarray platforms can be combined to give a more complete transcriptomic profile. Each platform gives a slight variation in the BaP-gene expression response and, although it cannot be stated which is more correct, combining the two data sets is more informative than considering them individually.
    • Interlaboratory comparison of methodologies for the measurement of urinary 8-oxo-7,8-dihydro-2'-deoxyguanosine.

      Cooke, Marcus S.; Barregard, Lars; Mistry, Vilas; Potdar, Neelam; Rozalski, Rafal; Gackowski, Daniel; Siomek, Agnieszka; Foksinski, Marek; Svoboda, Peter; Kasai, Hiroshi; et al. (2009-03)
      Urinary 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo) is widely used as a marker of oxidative stress. Here we report the comparison of two, distinct chromatographic assays with an enzyme-linked immunosorbent assay (ELISA). The chromatographic assays displayed good agreement (r =:0.89, p < 0.0001), whereas there was markedly worse, albeit still significant, agreement with the ELISA (high-pressure liquid chromatography followed by gas chromatography (HPLC-GC/MS), r = 0.43; HPLC with electrochemical detection (HPLC-EC), r = 0.56; p < 0.0001). Mean values differed significantly between the chromatographic assays and the ELISA (HPLC-GC/MS 3.86, HPLC-EC 4.20, ELISA 18.70 ng mg(-1) creatinine; p < 0.0001). While it is reassuring to note good agreement between chromatographic assays, this study reveals significant short-comings in the ELISA, which brings into question its continued use in its present form.
    • International Validation of the Comet Assay and a Human Intervention Study.

      Ersson, Clara (Karolinska Institutet, 2011, 2011)
      The comet assay is an established, sensitive method extensively used in biomonitoring studies. The methods' advantages include; a) only a small cell sample is required, b) possibility to measure damage in practically any cell type, c) ability to measure heterogeneity in response within a cell population, d) relatively fast and economical procedure, and e) various applications of the method, which allow measurement of a range of different DNA lesions as well as DNA repair. Several guidelines for the comet assay have been published, but no standardised protocol exists as yet. There are considerable differences between the protocols used by different research groups, which negatively affect inter-laboratory comparisons of results. Several experts in the field have highlighted the need for multi-laboratory, international validation studies, to assess intra- and inter-laboratory reproducibility and to investigate sources of variability in the results. The papers in this thesis can be divided into two parts; one part that deals with international inter-laboratory validation studies and methodological aspects of the comet assay (paper I-III), and the other part covers a human intervention study with antioxidant capsules consisting of many different antioxidants in low doses for which the comet assay has been applied (paper IV-V). The inter-laboratory validation trials in papers I-II indicate that the participants can detect dose-responses of both DNA breaks and oxidatively damaged DNA in coded cells, but that there is a large inter-laboratory variation in the reported values. This variation can in part be explained by differences in comet assay protocols and in image analysis. The inter-laboratory variation was decreased, but not completely removed, by calibration with ionising radiation. In paper III we verified that several protocol steps significantly affected the outcome of the comet assay, including a) density of the agarose gel, b) extent of enzymatic incubation, c) duration of alkaline treatment, and d) time of electrophoresis, as well as the strength of the electric field applied. In a parallel placebo-controlled, double-blind intervention study, overweight middle-aged men were supplemented for six weeks with a multivitamin supplement consisting of a range of antioxidants in doses resembling those achieved by a healthy diet (paper IV-V). In spite of elevated levels of seven out of eight measured antioxidants in the blood, the intervention did not affect the level of oxidation of lipids or DNA. Many intervention studies with good design report similar null findings. It is preferred to consume antioxidants through a healthy diet, and dietary supplements are not recommended for cancer prevention.
    • Introducing a true internal standard for the Comet assay to minimize intra- and inter-experiment variability in measures of DNA damage and repair.

      Zainol, Murizal; Stoute, Julia; Almeida, Gabriela M.; Rapp, Alexander; Bowman, Karen J.; Jones, George D. D. (2009-12)
      The Comet assay (CA) is a sensitive/simple measure of genotoxicity. However, many features of CA contribute variability. To minimize these, we have introduced internal standard materials consisting of 'reference' cells which have their DNA substituted with BrdU. Using a fluorescent anti-BrdU antibody, plus an additional barrier filter, comets derived from these cells could be readily distinguished from the 'test'-cell comets, present in the same gel. In experiments to evaluate the reference cell comets as external and internal standards, the reference and test cells were present in separate gels on the same slide or mixed together in the same gel, respectively, before their co-exposure to X-irradiation. Using the reference cell comets as internal standards led to substantial reductions in the coefficient of variation (CoV) for intra- and inter-experimental measures of comet formation and DNA damage repair; only minor reductions in CoV were noted when the reference and test cell comets were in separate gels. These studies indicate that differences between individual gels appreciably contribute to CA variation. Further studies using the reference cells as internal standards allowed greater significance to be obtained between groups of replicate samples. Ultimately, we anticipate that development will deliver robust quality assurance materials for CA.
    • Introduction.

      Akesson, Bjorn (The Nofer Institute of Occupational Medicine, 2007-04)
    • Introduction.

      Kyrtopoulos, Soterios (The Nofer Institute of Occupational Medicine, 2007)
    • Introduction. Compounds in food.

      Akesson, B.; Kyrtopoulos, S.A. (2008-05)
    • Investigation of the associations of smoking-related DNA damages with biomarkers in a human lung cancer population.

      Anna, Livia (2012)
      The aim of my PhD research was to further explore the associations among smoking status, two different DNA adduct types, the O4-etT and bulky DNA adduct, the TP53 tumour suppressor gene mutations and lung cancer in a molecular epidemiological study in a Hungarian lung cancer study population. The levels of O4-etT and bulky DNA adducts were significantly higher in the combined group of subjects who smoked until surgery or gave up smoking at most one year before surgery than in the combined group of those subjects who gave up smoking more than one year before the surgery or never smoked. O4-etT appeared to be a highly persistent DNA damage. There was no statistically significant correlation between the individual levels of O4-etT and of bulky DNA adducts. The TP53 mutation frequency and the variety of mutation types were higher in the present study population as compared to the IARC database. 45% of the samples carried TP53 mutation. The mutation frequency was significantly higher in squamous cell carcinoma than in adenocarcinoma, and in the cases with more than 20 years of smoking history. The most common mutations were G→A (19%), G→T (19%) and G→C (16%) base changes. The mutation pattern was influenced by the smoking status. G→T transversion was detected exclusively in smokers, and most carriers of the G→T transversions had also high level of bulky DNA adducts. My results confirm that O4-etT level is increased by smoking in the lung. O4-etT is persistent in human lung, and the activation and elimination pathways of O4-etT and bulky DNA adducts are not closely linked. I consider O4-etT a suitable biomarker of smoking exposure for comparison of exposure groups in molecular epidemiological studies. For the first time at international level, I demonstrated strong association between G→T mutation of TP53 and high level of bulky DNA adducts in a human study, which is a significant scientific progress from the in vitro studies in the exploration of the causal relationship between a carcinogen-DNA adduct and a gene mutation.
    • Involvement of MRE11A and XPA gene polymorphisms in the modulation of DNA double-strand break repair activity: a genotype-phenotype correlation study.

      Ricceri, Fulvio; Porcedda, Paola; Allione, Alessandra; Turinetto, Valentina; Polidoro, Silvia; Guarrera, Simonetta; Rosa, Fabio; Voglino, Floriana; Pezzotti, Annamaria; Minieri, Valentina; et al. (2011-10-10)
      DNA double-strand breaks (DSB) are the most lethal form of ionizing radiation-induced DNA damage, and failure to repair them results in cell death. In order to see if any associations exist between DNA repair gene polymorphisms and phenotypic profiles of DSB repair (DSBR) we performed a genotype-phenotype correlation study in 118 young healthy subjects (mean age 25.8±6.7years). Subjects were genotyped for 768 single nucleotide polymorphisms (SNPs) with a custom Illumina Golden Gate Assay, and an H2AX histone phosphorylation assay was done to test DSBR capacity. We found that H2AX phosphorylation at 1h was significantly lower in subjects heterozygous (no variant homozygotes were observed) for the XPA gene SNP rs3176683 (p-value=0.005), while dephosphorylation was significantly higher in subjects carrying the variant allele in three MRE11A gene SNPs: rs1014666, rs476137 and rs2508784 (p-value=0.003, 0.003 and 0.008, respectively). An additive effect of low-activity DNA repair alleles was associated with altered DSBR activity, as demonstrated by both H2AX phosphorylation at 1 h (p-trend <0.0001) and γH2AX dephosphorylation at 3h (p-trend <0.0001). Our study revealed that in addition to SNPs of genes that are well-established players in DSBR, non-DSBR genes, such as the XPA gene that is mainly involved in the nucleotide excision repair pathway, can also influence DSBR in healthy subjects. This suggests that successful DSBR may require both DSBR and non-DSBR mechanisms.
    • LC-QTOF/MS metabolomic profiles in human plasma after a 5-week high dietary fiber intake.

      Johansson-Persson, Anna; Barri, Thaer; Ulmius, Matilda; Onning, Gunilla; Dragsted, Lars Ove (2013-05)
      The objective was to investigate the alterations of plasma metabolome profiles to identify exposure and effect markers of dietary fiber intake. Subjects (n = 25) aged 58.6 (1.1) years (mean and SD) with a body mass index of 26.6 (0.5) kg/m(2) were given a high fiber (HF) and a low fiber (LF) diet, in a 5-week randomized controlled crossover intervention. The HF diet consisted of oat bran, rye bran, and sugar beet fiber incorporated into test food products, whereas the LF diet was made of equivalent food products to the HF diet, but without adding fibers. Blood plasma samples were collected at the start and end of each intervention period and analyzed by LC-QTOF/MS. In total, 6 features in positive mode and 14 features in negative mode were significantly different between the HF and the LF diet (p < 0.01, q < 0.05). Two markers, 2,6-dihydroxybenzoic acid and 2-aminophenol sulfate, were increased after HF diet, along with a tentatively identified saponin derived from oat avenacosides. The untargeted metabolomics approach enabled the identification of two new markers of dietary fiber intake in human plasma. Further studies will be needed to verify if these markers could serve as compliance markers of fiber intake.
    • Lipid peroxidation-induced DNA damage in cancer-prone inflammatory diseases: a review of published adduct types and levels in humans.

      Nair, Urmila; Bartsch, Helmut; Nair, Jagadeesan (2007-10-15)
      Persistent oxidative stress and excess lipid peroxidation (LPO), induced by inflammatory processes, impaired metal storage, and/or dietary imbalance, cause accumulations and massive DNA damage. This massive DNA damage, along with deregulation of cell homeostasis, leads to malignant diseases. Reactive aldehydes produced by LPO, such as 4-hydroxy-2-nonenal, malondialdehyde, acrolein, and crotonaldehyde, react directly with DNA bases or generate bifunctional intermediates which form exocyclic DNA adducts. Modification of DNA bases by these electrophiles, yielding promutagenic exocyclic adducts, is thought to contribute to the mutagenic and carcinogenic effects associated with oxidative stress-induced LPO. Ultrasensitive detection methods have facilitated studies of the concentrations of promutagenic DNA adducts in human tissues, white blood cells, and urine, where they are excreted as modified nucleosides and bases. Thus, immunoaffinity-(32)P-postlabeling, high-performance liquid chromatography-electrochemical detection, gas chromatography-mass spectrometry, liquid chromatography-tandem mass spectrometry, immunoslotblot assay, and immunohistochemistry have made it possible to detect background concentrations of adducts arising from endogenous LPO products in vivo and studies of their role in carcinogenesis. These background adduct levels in asymptomatic human tissues occur in the order of 1 adduct/10(8) and in organs affected by cancer-prone inflammatory diseases these can be 1 or 2 orders of magnitude higher. In this review, we critically discuss the accuracy of the available methods and their validation and summarize studies in which measurement of exocyclic adducts suggested new mechanisms of cancer causation, providing potential biomarkers for cancer risk assessment in humans with cancer-prone diseases.
    • Lung cancer risk associated with selenium status is modified in smoking individuals by Sep15 polymorphism.

      Jablonska, Ewa; Gromadzinska, Jolanta; Sobala, Wojciech; Reszka, Edyta; Wasowicz, Wojciech (2008-02)
      BACKGROUND: Selenium (Se) is a trace element suggested to act chemopreventive in lung cancer. The mechanism by which Se suppresses tumour development may be associated with some of the functions of selenoproteins, including 15 kDa selenoprotein (Sep15). This protein exhibits antioxidant properties and thus may be involved in the process of carcinogenesis. Recently, it has been shown that the genetic polymorphism of Sep15, resulting in different response of the protein to Se, is associated with the risk of breast and head and neck cancers. AIM OF THE STUDY: The aim of the study was to investigate the possible association between lung cancer risk and Sep15 polymorphism in combination with Se status in the Polish population. METHODS: The study concerned 325 cases and 287 controls. All the participants were smokers. Plasma Se concentration was determined using graphite furnace atomic absorption spectrometry, and Sep15 polymorphism (1125 G/A transition within 3'-untranslated region) was detected with polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay. RESULTS: The adjusted odds ratios (ORs) for lung cancer cases, compared to individuals with Sep15 wild type variant (GG), were: 0.91 (95% CI: 0.64-1.32) for the heterozygous variant (GA) and 0.80 (95% CI: 0.39-1.65) for the homozygous variant (AA). Although plasma Se concentration was statistically lower in lung cancer cases (49.4 +/- 17.4 ng/ml) compared to controls (53.3 +/- 14.0 ng/ml, p < 0.002), the analysis of the joint effect of Sep15 polymorphism and Se status for lung cancer development revealed that lung cancer risk differed between the Se15 genotype groups. An increasing Se concentration was associated with a decreased risk in all individuals; however, at Se concentration above 80 ng/ml, the risk started to increase in individuals possessing the Sep15 1125 GG or GA genotype. CONCLUSIONS: It appears that among smoking individuals, those with the Sep15 1125 AA genotype may benefit most from a higher Se intake, whereas in those with the GG or GA genotype, a higher Se status may increase the risk for lung cancer.
    • Lung cancers attributable to environmental tobacco smoke and air pollution in non-smokers in different European countries: a prospective study.

      Vineis, Paolo; Hoek, Gerard; Krzyzanowski, Michal; Vigna-Taglianti, Federica; Veglia, Fabrizio; Airoldi, Luisa; Overvad, Kim; Raaschou-Nielsen, Ole; Clavel-Chapelon, Francoise; Linseisen, Jacob; et al. (2007)
      BACKGROUND: Several countries are discussing new legislation on the ban of smoking in public places, and on the acceptable levels of traffic-related air pollutants. It is therefore useful to estimate the burden of disease associated with indoor and outdoor air pollution. METHODS: We have estimated exposure to Environmental Tobacco Smoke (ETS) and to air pollution in never smokers and ex-smokers in a large prospective study in 10 European countries (European Prospective Investigation into Cancer and Nutrition)(N = 520,000). We report estimates of the proportion of lung cancers attributable to ETS and air pollution in this population. RESULTS: The proportion of lung cancers in never- and ex-smokers attributable to ETS was estimated as between 16 and 24%, mainly due to the contribution of work-related exposure. We have also estimated that 5-7% of lung cancers in European never smokers and ex-smokers are attributable to high levels of air pollution, as expressed by NO2 or proximity to heavy traffic roads. NO2 is the expression of a mixture of combustion (traffic-related) particles and gases, and is also related to power plants and waste incinerator emissions. DISCUSSION: We have estimated risks of lung cancer attributable to ETS and traffic-related air pollution in a large prospective study in Europe. Information bias can be ruled out due to the prospective design, and we have thoroughly controlled for potential confounders, including restriction to never smokers and long-term ex-smokers. Concerning traffic-related air pollution, the thresholds for indicators of exposure we have used are rather strict, i.e. they correspond to the high levels of exposure that characterize mainly Southern European countries (levels of NO2 in Denmark and Sweden are closer to 10-20 ug/m3, whereas levels in Italy are around 30 or 40, or higher).Therefore, further reduction in exposure levels below 30 ug/m3 would correspond to additional lung cancer cases prevented, and our estimate of 5-7% is likely to be an underestimate. Overall, our prospective study draws attention to the need for strict legislation concerning the quality of air in Europe.
    • Lymphoma; Pre-diagnostic Blood Markers and Occupational and Environmental Exposures.

      Saberi Hosnijeh, Fatemeh (Utrecht University, 2012, 2012)
      The overall aim of this thesis is to study the possible perturbations of the immune system by occupational and environmental risk factors of Non-Hodgkin lymphoma (NHL) and to study these changes in relation to NHL risk in prospective cohorts. In the first section, we validated the application of single blood cytokine measurements as a biomarker of immune status in prospective epidemiological studies. Potential utility of stored blood samples of a prospective cohort was evaluated by the effect of different blood sample types and freeze-thaw cycles on cytokine levels. This study showed strong correlations between different sample types. Moreover, freeze-thaw cycles did not markedly change cytokine levels. The intra-individual variance in cytokine levels was much smaller than the inter-individual variance which supports the notion that a single cytokine measurement can be used to characterize an individual's immune profile prospectively. Subsequently, we assessed the levels of these cytokines in pre-diagnostic blood samples of participants of a case–control study nested into the Italian European Prospective Investigation into Cancer and Nutrition cohort (EPIC) and determined their association with the risk of developing NHL. The results suggest a possible association between increased/decreased plasma levels of interleukin (IL)2, inter-cellular adhesion molecule, interferon gamma (IFN-γ), and tumor necrosis factor alpha with NHL risk. In the second section, we studied the possible immunological effects of two possibly lymphomagens: an occupational exposure (i.e. 2,3,7,8- tetrachlorodibenzo-p-dioxin (TCDD)) and an environmental risk factor (i.e. obesity). We assessed a broad range of immunologic parameters directed towards detecting abnormalities in the humoral and cellular arms of the immune system among workers exposed to chlorophenoxy herbicides, chlorophenols and dioxins in particular TCDD. These studies showed that plasma TCDD levels were not associated with markers of humoral immunity with the possible exception of a decrease in complement factor 4 levels. Most lymphocyte subsets, in particular the B cell compartment, showed a decrease in cell counts with increasing levels of TCDD. Moreover, blood levels of most cytokines, chemokines and growth factors had a negative association with TCDD levels with a formal statistical significance for fractalkine, transforming growth factor alpha and fibroblast growth factor 2. These changes were independent from the changes in blood cell counts. Our findings support the notion that dioxin exposure can have an adverse impact on the immune system and likely suppresses the immune system. To identify immunologic hallmarks of obesity, we measured plasma levels of cytokines in pre-diagnostic blood samples of participants of a case-control study nested in the Italian EPIC cohort. IL8, IL10, IFN-γ, and interferon-induced protein 10 (IP10) were related to obesity. However, the set of obesity predictors (IL8, IL10, IFN-γ, IP10) were not associated with future NHL risk. Our studies support that subtle perturbations in the immune system may precede lymphoma development and suggest that B cell activation, chronic inflammation and/or an unbalance in Th1/Th2-responses are likely important phenomena in lymphomagenesis. Although, possible occupational and environmental risk factors of NHL influence the immune system they did not pertubate immune markers shown to be associated with future NHL risk.
    • Measurement and meaning of oxidatively modified DNA lesions in urine.

      Cooke, Marcus S.; Olinski, Ryszard; Loft, Steffen (2008-01)
      BACKGROUND: Oxidatively generated damage to DNA has been implicated in the pathogenesis of a wide variety of diseases. The noninvasive assessment of such damage, i.e., in urine, and application to large-scale human studies are vital to understanding this role and devising intervention strategies. METHODS: We have reviewed the literature to establish the status quo with regard to the methods and meaning of measuring DNA oxidation products in urine. RESULTS: Most of the literature focus upon 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG), and whereas a large number of these reports concern clinical conditions, there remains (a) lack of consensus between methods, (b) possible contribution from diet and/or cell death, (c) no definitive DNA repair source of urinary 2'-deoxyribonucleoside lesions, and (d) no reference ranges for healthy or diseased individuals. CONCLUSIONS: The origin of 8-oxodG is not identified; however, recent cell culture studies suggest that the action of Nudix hydrolase(s) on oxidative modification of the nucleotide pool is a likely candidate for the 8-oxodG found in urine and, potentially, of other oxidized 2'-deoxyribonucleoside lesions. Literature reports suggest that diet and cell death have minimal, if any, influence upon urinary levels of 8-oxodG and 8-oxo-7,8-dihydroguanine, although this should be assessed on a lesion-by-lesion basis. Broadly speaking, there is consensus between chromatographic techniques; however, ELISA approaches continue to overestimate 8-oxodG levels and is not sufficiently specific for accurate quantification. With increasing numbers of lesions being studied, it is vital that these fundamental issues are addressed. We report the formation of the European Standards Committee on Urinary (DNA) Lesion Analysis whose primary goal is to achieve consensus between methods and establish reference ranges in health and disease.
    • Mechanisms of combined action of different chemopreventive dietary compounds: a review.

      de Kok, Theo M.; van Breda, Simone G.; Manson, Margaret M. (2008-05)
      Consumption of fruits and vegetables has generally been associated with a decrease in cancer incidence and cardiovascular disease. Over the years, numerous bioactive compounds have been identified that contribute to these beneficial health effects. More recently, evidence is emerging that specific combinations of phytochemicals may be far more effective in protecting against cancer than isolated compounds. Combinatorial effects have been observed where any one of the single agents is inactive. Apart from interactions among dietary micronutrients, drug-phytochemical interactions have also been observed, indicating possibilities for improved cancer therapeutic strategies. Our understanding of the molecular mechanisms underlying such synergistic effects is still limited, but it appears that different combinations of complementary modes of actions are involved. In this review, we discuss the molecular mechanisms that are likely to be involved in cancer chemoprevention and summarize the most important findings of those studies that report synergistic chemopreventive effects of dietary compounds.
    • Mechanisms related to the genotoxicity of particles in the subway and from other sources.

      Karlsson, Hanna L.; Holgersson, Asa; Moller, Lennart (2008-03)
      Negative health effects of airborne particles have clearly been shown in epidemiological studies. People get exposed to particles from various sources such as the combustion of, for example, diesel and wood and also from particles arising from tire-road wear. Another source of importance for certain populations is exposure to particles in subway systems. We recently reported that these particles were more genotoxic when compared to that of several other particle types. The aim of this study was to further investigate and compare the toxicity of subway particles and particles from other sources as well as investigate some mechanisms behind the genotoxicity of subway particles. This was done by comparing the ability of subway particles and particles from a street, pure tire-road wear particles, and particles from wood and diesel combustion to cause mitochondrial depolarization and to form intracellular reactive oxygen species (ROS). Furthermore, the genotoxicity and ability to cause oxidative stress was compared to magnetite particles since this is a main component in subway particles. It was concluded that the subway particles and also street particles and particles from wood and diesel combustion caused mitochondrial depolarization. The ability to damage the mitochondria is thus not the only explanation for the high genotoxicity of subway particles. Subway particles also formed intracellular ROS. This effect may be part of the explanation as to why subway particles show such high genotoxicity when compared to that of other particles. Genotoxicity can, however, not be explained by the main component, magnetite, by water-soluble metals, or by intracellular mobilized iron. The genotoxicity is most likely caused by highly reactive surfaces giving rise to oxidative stress.
    • Melphalan-induced DNA damage in vitro as a predictor for clinical outcome in multiple myeloma.

      Dimopoulos, Meletios A.; Souliotis, Vassilis L.; Anagnostopoulos, Athanasios; Bamia, Christina; Pouli, Anastasia; Baltadakis, Ioannis; Terpos, Evangelos; Kyrtopoulos, Soterios A.; Sfikakis, Petros P. (2007-11)
      BACKGROUND AND OBJECTIVES: As new therapeutic options for multiple myeloma (MM) emerge, identification of biological markers which could predict clinical response to standard treatment with high-dose melphalan (HDM) supported by autologous stem cell transplantation (ASCT) becomes more important. DESIGN AND METHODS: Melphalan-induced damage formation and repair of monoadducts and interstrand cross-links in the p53 gene were studied in peripheral blood mononuclear cells obtained from 32 patients prior to therapy. The same studies were performed in the peripheral blood cells of these patients immediately after subsequent HDM administration. Clinical response and time to progression were correlated with molecular endpoints obtained in vitro. RESULTS: Values for all molecular end-points examined in vitro were highly correlated with the respective in vivo results within individual patients. All in vitro end-points indicative of increased DNA damage and slower repair capacity were predictive of a favorable response to HDM; the area under the curve of total adducts (AUC-TA) had the highest predictive ability. Using the cut-off value of 736 adducts/10(6) nucleotides x h for the AUC-TA, the positive predictive value for clinical response to HDM was 100%. Moreover, patients with an AUC-TA equal to or higher than this cut-off value had significantly longer times to progression than had patients with an AUC-TA lower than the cut-off value (hazard ratio 0.19; 95% confidence intervals 0.06 to 0.60). INTERPRETATION AND CONCLUSIONS: An in vitro assay to quantify melphalan-induced p53-specific damage formation/repair can be used to select those patients with MM who are more likely to benefit from HDM supported by ASCT.