Diet, metabolic polymorphisms and dna adducts: the EPIC-Italy cross-sectional study

Cruciferous Vegetable Intake and Bulky DNA Damage within Non-Smokers and Former Smokers in the Gen-Air Study (EPIC Cohort)

Epidemiologic studies have indicated that cruciferous vegetables can influence the cancer risk; therefore, we examined with a cross-sectional approach the correlation between the frequent consumption of the total cruciferous vegetables and the formation of bulky DNA damage, a biomarker of carcinogen exposure and cancer risk, in the Gen-Air study within the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort. DNA damage measurements were performed in the peripheral blood of 696 of those apparently healthy without cancer controls, including 379 never-smokers and 317 former smokers from seven European countries by the 32P-postlabeling assay. In the Gen-Air controls, the median intake of cruciferous vegetables was 6.16 (IQR 1.16−13.66) g/day, ranging from 0.37 (IQR 0−6.00) g/day in Spain to 11.34 (IQR 6.02−16.07) g/day in the UK. Based on this information, participants were grouped into: (a) high consumers (>20 g/day), (b) medium consumers (3−20 g/day) and (c) low consumers (<3.0 g/day). Overall, low cruciferous vegetable intake was correlated with a greater frequency of bulky DNA lesions, including benzo(a)pyrene, lactone and quinone-adducts and bulky oxidative lesions, in the adjusted models. Conversely, a high versus low intake of cruciferous vegetables was associated with a reduction in DNA damage (up to a 23% change, p = 0.032); this was particularly evident in former smokers (up to a 40% change, p = 0.008). The Generalized Linear Regression models indicated an overall Mean Ratio between the high and the low consumers of 0.78 (95% confidence interval, 0.64−0.97). The current study suggests that a higher intake of cruciferous vegetables is associated with a lower level of bulky DNA adducts and supports the potential for cancer prevention strategies through dietary habit changes aimed at increasing the consumption of cruciferous vegetables.

The Relationship Between GSTT1, GSTM1, GSTO1, GSTP1 and MTHFR Gene Polymorphisms and DNA Damage of BRCA1 and BRCA2 Genes in Arsenic-Exposed Workers

OBJECTIVE

To investigate the associations between genetic polymorphisms of GSTT1, GSTM1, GSTO1, GSTP1 and MTHFR genes and the DNA damage levels of BRCA1 and BRCA2 genes.

METHODS

Peripheral blood samples were used to measure DNA damage levels and genetic polymorphisms, and urine samples were collected to analyze arsenic metabolites in 79 arsenic-exposed workers and 24 non-arsenic-exposed workers.

RESULTS

The BRCA1 and BRCA2 damage levels in exposure group were significantly higher than that in control group. Significant associations were detected between GSTT1 and GSTO1 polymorphisms and DNA damage levels of BRCA1 and BRCA2 genes in subjects (P < 0.05).

CONCLUSIONS

Our findings suggest that the DNA damage levels of BRCA1 and BRCA2 genes may modulate by genetic variations of GSTT1 and GSTO1 when individuals are exposed to carcinogens, such as arsenic.

Genotoxic effect of meat consumption: A mini review

In 2015, the International Agency for Research on Cancer classified the consumption of processed meat as carcinogenic to humans (Group 1) and red meat as probably carcinogenic to humans (Group 2A) based on sufficient data from animal models and epidemiological studies. However, research characterising the mechanisms underlying this carcinogenic process in humans are limited, particularly with respect to measures of direct DNA damage. The current review sought to evaluate and summarize the recent literature, published since 2000, regarding the associations of meat consumption and three biomarkers of genotoxicity in humans: DNA strand breaks (measured using the comet assay), DNA adducts, and micronucleus formation. After screening 230 potential articles, 35 were included, and then were classified as experimental or observational in design, the latter of which were further categorized according to their dietary assessment approach. Among the 30 observational studies, 4 of which used two different assays, 3 of 5 comet assay studies, 13 of 20 DNA adduct studies, and 7 of 9 micronucleus studies reported a positive association between meat consumption and DNA damage. Among the 5 experimental studies, 1 of 1 using the comet assay, 3 of 3 measuring DNA adducts and 0 of 1 measuring micronuclei reported significant positive associations with meat consumption. Nevertheless, common limitations among the selected publications included small sample size, and poor methodological reporting of both exposure and outcome measures. Moreover, the vast majority of studies only measured DNA damage in one biological sample using a single assay and we cannot exclude the possibility of publication bias. Ultimately, our review of the literature, published since 2000, revealed a preponderance of studies that support mechanisms of genotoxicity in playing an important role in the meat-cancer association.

Genomics of aging: Genes, adducts, and telomeres

Genomics influences the aging process in many different ways. This 10-part series of articles describes what is known about genetics and aging, including genes, adducts, and telomeres, decreased immune defenses, oxidation and inefficient mitochondria, toxins and radiation, glycosylation, caloric intake and sirtuin production, neurotransmitter imbalance, hormone mechanisms, reduced nitric oxide, and stem cell slowdown. This first article explores gene adducts as an epigenetic "sludge," the influence of telomeres and other mutations that contribute to DNA dysfunction, cell stress, and premature aging. Factors that contribute to adduct formation and reduced telomere length are presented along with some changes in behavior, environmental exposure, food/supplement use, weight, sleep, and exercise that have been found to reduce damage, potentially increasing longevity. Adherence to a Mediterranean diet that contains fruits and whole grains along with fiber, antioxidants (e.g., beta-carotene, vitamins C and E), omega-3 fatty acids, and soy protein may reduce DNA adducts and protect telomeres. So providers may want to recommend these simple but key clinical and individual changes to enhance DNA health, wellness, and longevity.

Urinary 1-Hydroxypyrene and t, t-Muconic ACID as Biomarkers of Exposure to Environmental Pollutants in Two Areas in Italy (Epic-Florence and Ragusa)

Aims and background

Several chemical compounds included in the group of polycyclic aromatic hydrocarbons (PAH) and benzene are well-known human carcinogens present in the atmosphere of polluted urban areas. Major sources include vehicle traffic and industrial emissions, but also cigarette smoke. Genotoxic damage derived from exposure to PAHs can be measured in healthy adults by specific assays as PAH-DNA adducts. In the frame of EPIC-Italy, we recently carried out a cross-sectional study in different areas of the country (Palli et al., Int J Cancer, 87: 444-451, 2000) and showed that mean DNA adduct levels varied considerably among different centers, being highest in Florence (a large metropolitan area in Tuscany) and lowest in Ragusa (a small town in Sicily).

Methods

A subgroup of EPIC volunteers, representative of these two local cohorts, agreed to collect 24-h urine samples, and we measured the excretion of two potential biomarkers of exposure to environmental pollutants: t,t-muconic acid (MA), a metabolite of benzene, and 1-hydroxypyrene (1-OHP), a metabolite of pyrene. Overall, 69 24-h urine samples were available for analyses.

Results

The absolute amounts of 1-OHP and MA excreted in the 24-h urine samples were 169.6 ng and 33.8 μg, respectively. Urinary excretion of both metabolites did not vary according to age or area of residence. Strongly significant differences emerged when current smokers were compared to non-smokers for 1-OHP (P = 0.0001) and MA (P = 0.01), thus confirming that smokers are directly exposed to PAHs and benzene from tobacco smoke, with a dose-dependent effect particularly evident for MA. Multivariate analyses showed positive associations of 1-OHP excretion with male sex, low education and being overweight but not with residence in two areas with contrasting levels of urban pollution; MA excretion tended to be higher in Florence.

Conclusions

These two urinary metabolites are strongly related to tobacco smoke and do not appear to represent reliable biomarkers of exposure to environmental pollutants in the general population.

The Florence City Sample: Dietary and Life-Style Habits of a Representative Sample of Adult Residents. A Comparison with the Epic-Florence Volunteers

A representative sample of the general population residing in the city of Florence was invited to participate in the local section of the EPIC study with two major aims: i) to carry out a population-based survey on dietary and life-style habits in this urban area of Tuscany, Central Italy; ii) to compare these results with a large series of EPIC volunteers residing in the same municipality in order to evaluate the differences between the two groups. A random sample of 500 residents (250 women) aged 40-64 years, was invited to participate in the study; 362/500 (72.4%) accepted and followed the EPIC protocol. The distribution of selected individual characteristics (including measured weight and height) showed a high prevalence of being overweight in men (52.2%) and obesity in both sexes (17.4% in men and 12.5% in women). A dietary pattern characterized by a high consumption of red meat, processed meats, olive oil and wine emerged in both sexes; the consumption of vegetables and fresh fruit was approximately 200 and 300 g/day, respectively. The estimated mean intakes of macronutrients reflected this pattern, with a high mean intake of total fat and protein. The mean contribution to total caloric intake provided by fat was 30.9% and 33.6% in these randomly sampled men and women, respectively. The results were compared with those of 9,123 Florence residents aged 40-64 years and enrolled as EPIC volunteers. Current smokers and less educated subjects were less represented among male volunteers, who, in general, showed a healthier dietary pattern (more fresh fruit and less spirits). Female volunteers were taller and heavier and consumed more fresh fruit but also more beef and less carbohydrates. Other statistically significant differences emerged, but the absolute values of these differences were usually modest and the two groups appeared remarkably similar. Overall, our results suggest that the large EPIC-Florence cohort was not strictly selected and showed a total caloric intake and a range of dietary variability similar to that of the general population of the same area.

Physical Activity in the EPIC-Italy Centers

The European Prospective Investigation into Cancer and nutrition offers the opportunity to explore patterns of physical activity in a large series of healthy adults enrolled in the different local cohorts of the Italian section of the European EPIC project. Physical activity is considered one of the means by which chronic disease could be prevented. Subjects in the EPIC study completed a life-style questionnaire, with a section dedicated to the assessment of physical activity at work and during leisure time. Time spent in the various activities was transformed into an index of physical activity (physical activity level, PAL) and an activity index that includes intense activity (PAL; intense activity included). Quintiles of these indexes were computed in order to observe the distribution of subject characteristics according to levels of physical activity. In general, the population was characterized by low levels of physical activity at work, with more than 50% of the sample reporting sedentary occupations. During leisure time, only a small percentage of subjects compensated for the inactivity at work by engaging in energy-consuming activities. In particular, organized fitness activities were reported by a small percentage of people, whereas walking was the most common sort of physical activity. Specific types of activity seemed to characterize subjects in the different areas of the country, reflecting local traditions or specific living situations. Detailed information about physical activity habits, together with a description of other characteristics, could help in designing physical activity promotion programs in different Italian populations and age groups.

Bulky DNA Adducts, Tobacco Smoking, Genetic Susceptibility, and Lung Cancer Risk

The generation of bulky DNA adducts consists of conjugates formed between large reactive electrophiles and DNA-binding sites. The term "bulky DNA adducts" comes from early experiments that employed a ³²P-DNA postlabeling approach. This technique has long been used to elucidate the association between adducts and carcinogen exposure in tobacco smoke studies and assess the predictive value of adducts in cancer risk. Molecular data showed increased DNA adducts in respiratory tracts of smokers vs nonsmokers. Experimental studies and meta-analysis demonstrated that the relationship between adducts and carcinogens was linear at low doses, but reached steady state at high exposure, possibly due to metabolic and DNA repair pathway saturation and increased apoptosis. Polymorphisms of metabolic and DNA repair genes can increase the effects of environmental factors and confer greater likelihood of adduct formation. Nevertheless, the central question remains as to whether bulky adducts cause human cancer. If so, lowering them would reduce cancer incidence. Pooled and meta-analysis has shown that smokers with increased adducts have increased risk of lung cancer. Adduct excess in smokers, especially in prospective longitudinal studies, supports their use as biomarkers predictive of lung cancer.

Vehicular Traffic-Related Polycyclic Aromatic Hydrocarbon Exposure and Breast Cancer Incidence: The Long Island Breast Cancer Study Project (LIBCSP)

BACKGROUND

Polycyclic aromatic hydrocarbons (PAHs) are widespread environmental pollutants, known human lung carcinogens, and potent mammary carcinogens in laboratory animals. However, the association between PAHs and breast cancer in women is unclear. Vehicular traffic is a major ambient source of PAH exposure.

OBJECTIVES

Our study aim was to evaluate the association between residential exposure to vehicular traffic and breast cancer incidence.

METHODS

Residential histories of 1,508 participants with breast cancer (case participants) and 1,556 particpants with no breast cancer (control participants) were assessed in a population-based investigation conducted in 1996-1997. Traffic exposure estimates of benzo[a]pyrene (B[a]P), as a proxy for traffic-related PAHs, for the years 1960-1995 were reconstructed using a model previously shown to generate estimates consistent with measured soil PAHs, PAH-DNA adducts, and CO readings. Associations between vehicular traffic exposure estimates and breast cancer incidence were evaluated using unconditional logistic regression.

RESULTS

The odds ratio (95% CI) was modestly elevated by 1.44 (0.78, 2.68) for the association between breast cancer and long-term 1960-1990 vehicular traffic estimates in the top 5%, compared with below the median. The association with recent 1995 traffic exposure was elevated by 1.14 (0.80, 1.64) for the top 5%, compared with below the median, which was stronger among women with low fruit/vegetable intake [1.46 (0.89, 2.40)], but not among those with high fruit/vegetable intake [0.92 (0.53, 1.60)]. Among the subset of women with information regarding traffic exposure and tumor hormone receptor subtype, the traffic-breast cancer association was higher for those with estrogen/progesterone-negative tumors [1.67 (0.91, 3.05) relative to control participants], but lower among all other tumor subtypes [0.80 (0.50, 1.27) compared with control participants].

CONCLUSIONS

In our population-based study, we observed positive associations between vehicular traffic-related B[a]P exposure and breast cancer incidence among women with comparatively high long-term traffic B[a]P exposures, although effect estimates were imprecise.

CITATION

Mordukhovich I, Beyea J, Herring AH, Hatch M, Stellman SD, Teitelbaum SL, Richardson DB, Millikan RC, Engel LS, Shantakumar S, Steck SE, Neugut AI, Rossner P Jr., Santella RM, Gammon MD. 2016. Vehicular traffic-related polycyclic aromatic hydrocarbon exposure and breast cancer incidence: the Long Island Breast Cancer Study Project (LIBCSP). Environ Health Perspect 124:30-38; http://dx.doi.org/10.1289/ehp.1307736.

Gene-diet interactions in exposure to heterocyclic aromatic amines and bulky DNA adduct levels in blood leukocytes

Heterocyclic aromatic amines (HAAs), carcinogens produced in meat when cooked at high temperatures, are an emerging biologic explanation for the meat-colorectal cancer relationship. HAAs form DNA adducts; left unrepaired, adducts can induce mutations, which may initiate/promote carcinogenesis. The purpose of this research was to investigate the relationship between dietary HAAs, genetic susceptibility and bulky DNA adduct levels. Least squares regression was used to examine the relationship between dietary HAA exposure and bulky DNA adduct levels in blood measured using (32)P-postlabeling among 99 healthy volunteers. Gene-diet interactions between dietary HAAs and genetic factors relevant to the biotransformation of HAAs and DNA repair were also examined. No main effects of dietary HAAs on bulky DNA adduct levels was found. However, those with the putative NAT1 rapid acetylator phenotype had lower adduct levels than those with the slow acetylator phenotype (P = 0.02). Furthermore, having five or more 'at-risk' genotypes was associated with higher bulky DNA adduct levels (P = 0.03). Gene-diet interactions were observed between NAT1 polymorphisms and dietary HAAs (P < 0.05); among the slow acetylator phenotype, higher intakes of HAAs were associated with an increase in DNA adduct levels compared to lower intakes. This study provides evidence of a biologic relationship between dietary HAAs, genetic susceptibility and bulky DNA adduct formation. However, the lack of a strong main effect of HAAs suggests that dietary HAAs are not a large contributor to bulky DNA adducts in this population; future studies should consider relevant gene-diet interactions to clarify the role of HAAs in carcinogenesis.

Prenatal polycyclic aromatic hydrocarbon (PAH) exposure, antioxidant levels and behavioral development of children ages 6-9

PURPOSE

Prenatal polycyclic aromatic hydrocarbon (PAH) exposure has been shown to increase DNA adduct levels and to affect neurodevelopment. Micronutrients may modify the adverse effect of PAH on neurodevelopment. Thus, we examined if micronutrient concentrations modified the association between PAH exposure and neurodevelopmental outcomes.

METHODS

151 children from a birth cohort who had micronutrient concentrations measured in cord blood and completed the Child Behavioral Checklist (CBCL), between the ages of 6 and 9 years, were evaluated. Prenatal airborne PAH exposure was measured by personal air monitoring. The betas and 95% CI for the associations of antioxidant concentrations and PAH exposure with each of the outcomes of CBCL raw score and dichotomized standardized T-score (based on clinical cutpoints) were estimated, respectively, by multivariable poisson and logistic models.

RESULTS

Children below the median for alpha-tocopherol and gamma-tocopherol concentrations, compared to those above, were more likely to have thought problems, aggressive behavior and externalizing problems (p<0.05). Lower carotenoid concentration was associated with more thought problems (MVβ=0.60, p<0.001) and externalizing problems (MVβ=0.13, p<0.05) for the same contrast. No statistically significant associations were observed between retinol concentrations and neurodevelopmental symptoms. Overall, no consistent patterns were observed when we examined the interaction between antioxidants (e.g., alpha-tocopherol) and PAH in relation to CBCL symptoms (e.g., internalizing and externalizing problems, p<0.05).

CONCLUSIONS

Lower alpha-tocopherol, gamma-tocopherol and carotenoid levels may adversely affect healthy neurodevelopment, even after accounting for PAH exposure. Future research to confirm these findings are warranted given the importance of identifying modifiable factors for reducing harmful PAH effects.

Environmental, dietary, maternal, and fetal predictors of bulky DNA adducts in cord blood: a European mother-child study (NewGeneris)

BACKGROUND

Bulky DNA adducts reflect genotoxic exposures, have been associated with lower birth weight, and may predict cancer risk.

OBJECTIVE

We selected factors known or hypothesized to affect in utero adduct formation and repair and examined their associations with adduct levels in neonates.

METHODS

Pregnant women from Greece, Spain, England, Denmark, and Norway were recruited in 2006-2010. Cord blood bulky DNA adduct levels were measured by the 32P-postlabeling technique (n = 511). Diet and maternal characteristics were assessed via questionnaires. Modeled exposures to air pollutants and drinking-water disinfection by-products, mainly trihalomethanes (THMs), were available for a large proportion of the study population.

RESULTS

Greek and Spanish neonates had higher adduct levels than the northern European neonates [median, 12.1 (n = 179) vs. 6.8 (n = 332) adducts per 108 nucleotides, p < 0.001]. Residence in southern European countries, higher maternal body mass index, delivery by cesarean section, male infant sex, low maternal intake of fruits rich in vitamin C, high intake of dairy products, and low adherence to healthy diet score were statistically significantly associated with higher adduct levels in adjusted models. Exposure to fine particulate matter and nitrogen dioxide was associated with significantly higher adducts in the Danish subsample only. Overall, the pooled results for THMs in water show no evidence of association with adduct levels; however, there are country-specific differences in results with a suggestion of an association in England.

CONCLUSION

These findings suggest that a combination of factors, including unknown country-specific factors, influence the bulky DNA adduct levels in neonates.

Carcinogenicity of ambient air pollution: use of biomarkers, lessons learnt and future directions

The association between ambient air pollution (AAP) exposure and lung cancer risk has been investigated in prospective studies and the results are generally consistent, indicating that long-term exposure to air pollution can cause lung cancer. Biomarkers can enhance research on the health effects of air pollution by improving exposure assessment, increasing the understanding of mechanisms, and enabling the investigation of individual susceptibility. In this review, we assess DNA adducts as biomarkers of exposure to AAP and early biological effect, and DNA methylation as biomarker of early biological change and discuss critical issues arising from their incorporation in AAP health impact evaluations, such as confounding, individual susceptibilities, timing, intensity and duration of exposure, and investigated tissue. DNA adducts and DNA methylation are treated as paradigms. However, the lessons, learned from their use in the examination of AAP carcinogenicity, can be applied to investigations of other biomarkers involved in AAP carcinogenicity.

The GSTM1null (deletion) and MGMT84 rs12917 (Phe/Phe) haplotype are associated with bulky DNA adduct levels in human leukocytes

Tobacco smoke and air pollutants contain carcinogens, such as polycyclic aromatic hydrocarbons (PAHs) and tobacco specific nitrosamines (TSNA), that are substrates of metabolizing enzymes generating reactive metabolites that can bind to DNA. Variation in the activity of these enzymes may modify the extent to which these metabolites can interact with DNA. We compared the levels of bulky DNA adducts in blood leukocytes from 93 volunteers living in Mexico City with the presence of 13 single nucleotide polymorphisms (SNPs) in genes related to PAH and TSNA metabolism (AhR rs2044853, CYP1A1 rs1048943, CYP1A1 rs1048943, CYP1A1 rs1799814, EPHX1 rs1051740, EPHX1 rs2234922, GSTM1 null, GSTT1 null and GSTP1 rs947894), DNA repair (XRCC1 rs25487, ERCC2 rs13181 and MGMT rs12917) and cell cycle (TP53 rs1042522). (32)P-postlabeling analysis was used to quantify bulky DNA adduct formation. Genotyping was performed using PCR-RFLP. The mean levels of bulky DNA adducts were 8.51±3.66 adducts/10(8) nucleotides (nt) in smokers and 8.38±3.59 adducts/10(8) nt in non-smokers, being the difference not statistically significant. Without taking into account the smoking status, GSTM1 null individuals had a marginally significant lower adduct levels compared with GSTM1 volunteers (p=0.0433) and individuals heterozygous for MGMT Leu/Phe had a higher level of bulky adducts than those who were homozygous wild type (p=0.0170). A multiple regression analysis model showed a significant association between the GSTM1 (deletion) and MGMT rs12917 (Phe/Phe) haplotype and the formation of DNA adducts in smokers (R(2)=0.2401, p=0.0215). The presence of these variants conferred a greater risk for higher adduct levels in this Mexican population.

Spectrum of K ras mutations in Pakistani colorectal cancer patients

The incidence of colorectal cancer (CRC) is increasing daily worldwide. Although different aspects of CRC have been studied in other parts of the world, relatively little or almost no information is available in Pakistan about different aspects of this disease at the molecular level. The present study was aimed at determining the frequency and prevalence of K ras gene mutations in Pakistani CRC patients. Tissue and blood samples of 150 CRC patients (64% male and 36% female) were used for PCR amplification of K ras and detection of mutations by denaturing gradient gel electrophoresis, restriction fragment length polymorphism analysis, and nucleotide sequencing. The K ras mutation frequency was found to be 13%, and the most prevalent mutations were found at codons 12 and 13. A novel mutation was also found at codon 31. The dominant mutation observed was a G to A transition. Female patients were more susceptible to K ras mutations, and these mutations were predominant in patients with a nonmetastatic stage of CRC. No significant differences in the prevalence of K ras mutations were observed for patient age, gender, or tumor type. It can be inferred from this study that Pakistani CRC patients have a lower frequency of K ras mutations compared to those observed in other parts of the world, and that K ras mutations seemed to be significantly associated with female patients.

Dietary benzo(a)pyrene intake during pregnancy and birth weight: associations modified by vitamin C intakes in the Norwegian Mother and Child Cohort Study (MoBa)

BACKGROUND

Maternal exposure to polycyclic aromatic hydrocarbons (PAH) during pregnancy has been associated with reduced fetal growth. However, the role of diet, the main source of PAH exposure among non-smokers, remains uncertain.

OBJECTIVE

To assess associations between maternal exposure to dietary intake of the genotoxic PAH benzo(a)pyrene [B(a)P] during pregnancy and birth weight, exploring potential effect modification by dietary intakes of vitamins C, E and A, hypothesized to influence PAH metabolism.

METHODS

This study included 50,651 women in the Norwegian Mother and Child Cohort Study (MoBa). Dietary B(a)P and nutrient intakes were estimated based on total consumption obtained from a food frequency questionnaire (FFQ) and estimated based on food composition data. Data on infant birth weight were obtained from the Medical Birth Registry of Norway (MBRN). Multivariate regression was used to assess associations between dietary B(a)P and birth weight, evaluating potential interactions with candidate nutrients.

RESULTS

The multivariate-adjusted coefficient (95%CI) for birth weight associated with maternal energy-adjusted B(a)P intake was -20.5g (-31.1, -10.0) in women in the third compared with the first tertile of B(a)P intake. Results were similar after excluding smokers. Significant interactions were found between elevated intakes of vitamin C (>85mg/day) and dietary B(a)P during pregnancy for birth weight (P<0.05), but no interactions were found with other vitamins. The multivariate-adjusted coefficients (95%CI) for birth weight in women in the third compared with the first tertile of B(a)P intake were -44.4g (-76.5, -12.3) in the group with low vitamin C intakes vs. -17.6g (-29.0, -6.1) in the high vitamin C intake group.

CONCLUSION

The results suggest that higher prenatal exposure to dietary B(a)P may reduce birth weight. Lowering maternal intake of B(a)P and increasing dietary vitamin C intake during pregnancy may help to reduce any adverse effects of B(a)P on birth weight.

NRF2-ome: an integrated web resource to discover protein interaction and regulatory networks of NRF2

NRF2 is the master transcriptional regulator of oxidative and xenobiotic stress responses. NRF2 has important roles in carcinogenesis, inflammation, and neurodegenerative diseases. We developed an online resource, NRF2-ome, to provide an integrated and systems-level database for NRF2. The database contains manually curated and predicted interactions of NRF2 as well as data from external interaction databases. We integrated NRF2 interactome with NRF2 target genes, NRF2 regulating TFs, and miRNAs. We connected NRF2-ome to signaling pathways to allow mapping upstream NRF2 regulatory components that could directly or indirectly influence NRF2 activity totaling 35,967 protein-protein and signaling interactions. The user-friendly website allows researchers without computational background to search, browse, and download the database. The database can be downloaded in SQL, CSV, BioPAX, SBML, PSI-MI, and in a Cytoscape CYS file formats. We illustrated the applicability of the website by suggesting a posttranscriptional negative feedback of NRF2 by MAFG protein and raised the possibility of a connection between NRF2 and the JAK/STAT pathway through STAT1 and STAT3. NRF2-ome can also be used as an evaluation tool to help researchers and drug developers to understand the hidden regulatory mechanisms in the complex network of NRF2.

Dietary benzo(a)pyrene and fetal growth: effect modification by vitamin C intake and glutathione S-transferase P1 polymorphism

BACKGROUND

Previous studies have reported maternal exposure to airborne polycyclic aromatic hydrocarbons (PAH), as well as DNA adducts reflecting total PAH exposure, to be associated with reduced fetal growth. The role of diet, the main source of PAH exposure among non-smokers, remains uncertain.

OBJECTIVE

To assess associations between birth weight, length and small size for gestational age (SGA) with maternal intakes of the genotoxic PAH benzo(a)pyrene [B(a)P] during pregnancy, exploring potential effect modification by dietary intakes of vitamin C, vitamin E, alpha- and beta-carotene, as well as glutathione S-transferase P1 (GSTP1) polymorphisms, hypothesized to influence PAH metabolism.

METHODS

657 women in the INMA (Environment and Childhood) Project from Sabadell (Barcelona) were recruited during the first trimester of pregnancy. Dietary B(a)P and nutrient intakes were estimated from food consumption data. Genotyping was conducted for the Ile105Val variant of GSTP1. Multivariable models were used to assess associations between size at birth and dietary B(a)P, evaluating potential interactions with candidate nutrients and GSTP1 variants.

RESULTS

There were significant interactions between elevated intakes of vitamin C (above the mean of 189.41 mg/day) and dietary B(a)P during the first trimester of pregnancy in models for birth weight and length (P<0.05), but no interactions were found with other nutrients. B(a)P intakes were associated with significant reductions in birth weight and length (coefficient±SE for a 1-SD increase in B(a)P: -101.63±34.62 g and -0.38±0.16 cm, respectively) among women with low, but not high, vitamin C intakes. Elevated dietary B(a)P was also associated with increased risk of SGA births among women with low dietary vitamin C. Among these women, associations were strongest in those carrying the GSTP1 Val allele, associated with lower contaminant detoxification activity.

CONCLUSION

Results suggest that dietary B(a)P exposure may impair fetal growth, particularly in genetically susceptible populations, and that increasing maternal intakes of vitamin C may help to reduce any adverse effects.

The NRF2-related interactome and regulome contain multifunctional proteins and fine-tuned autoregulatory loops

NRF2 is a well-known, master transcription factor (TF) of oxidative and xenobiotic stress responses. Recent studies uncovered an even wider regulatory role of NRF2 influencing carcinogenesis, inflammation and neurodegeneration. Prompted by these advances here we present a systems-level resource for NRF2 interactome and regulome that includes 289 protein-protein, 7469 TF-DNA and 85 miRNA interactions. As systems-level examples of NRF2-related signaling we identified regulatory loops of NRF2 interacting proteins (e.g., JNK1 and CBP) and a fine-tuned regulatory system, where 35 TFs regulated by NRF2 influence 63 miRNAs that down-regulate NRF2. The presented network and the uncovered regulatory loops may facilitate the development of efficient, NRF2-based therapeutic agents.

Maternal diet and dioxin-like activity, bulky DNA adducts and micronuclei in mother-newborns

Maternal diet can contribute to carcinogenic exposures and also modify effects of environmental exposures on maternal and fetal genetic stability. In this study, associations between maternal diet and the levels of dioxin-like plasma activity, bulky DNA adducts in white blood cells and micronuclei (MN) in lymphocytes from mother to newborns were examined. From 98 pregnant women living in the greater area of Copenhagen, Denmark in 2006-2007, maternal peripheral blood and umbilical cord blood were collected, together with information on health, environmental exposure and lifestyle. Maternal diet was estimated on the basis of maternal food frequency questionnaire (FFQ) completed by the end of pregnancy. Biomarkers were detected in paired blood samples through the dioxin-responsive chemical-activated luciferase expression (CALUX)(®) bioassay, (32)P-postlabelling technique and cytokinesis-block MN assay. Maternal preference for meats with dark surface were significantly associated with higher bulky DNA adducts in both maternal (β 95%CI; 0.46 (0.08, 0.84)) and cord blood (β 95%CI; 0.46 (0.05, 0.86)) before and after adjustment for potential confounders. No other significant associations between the 18 dietary variables and the biomarkers measured in maternal and fetal samples were identified. The present study suggests that maternal intake of meats with dark surface contributes to the bulky DNA adduct levels in maternal and umbilical cord blood. Relationship between food preparation and bulky DNA adducts appear to be captured by a FFQ while potential associations for other biomarkers might be more complex or need larger sample size.

The importance of exposure rate on odds ratios by cigarette smoking and alcohol consumption for esophageal adenocarcinoma and squamous cell carcinoma in the Barrett's Esophagus and Esophageal Adenocarcinoma Consortium

BACKGROUND

Cigarette smoking is associated with esophageal adenocarcinoma (EAC), esophagogastric junctional adenocarcinoma (EGJA) and esophageal squamous cell carcinoma (ESCC), and alcohol consumption with ESCC. However, no analyses have examined how delivery rate modifies the strength of odds ratio (OR) trends with total exposure, i.e., the impact on the OR for a fixed total exposure of high exposure rate for short duration compared with low exposure rate for long duration.

METHODS

The authors pooled data from 12 case-control studies from the Barrett's Esophagus and Esophageal Adenocarcinoma Consortium (BEACON), including 1242 (EAC), 1263 (EGJA) and 954 (ESCC) cases and 7053 controls, modeled joint ORs for cumulative exposure and exposure rate for cigarette smoking and alcohol consumption, and evaluated effect modification by sex, body mass index (BMI), age and self-reported acid reflux.

RESULTS

For smoking, all sites exhibited inverse delivery rate effects, whereby ORs with pack-years increased, but trends weakened with increasing cigarettes/day. None of the examined factors modified associations, except for ESCC where younger ages at diagnosis enhanced smoking effects (P<0.01). For EAC and EGJA, ORs with drink-years exhibited inverse associations in <5 drinks/day consumers and no association in heavier consumers. For ESCC, ORs with drink-years increased, with trends strengthening with greater drinks/day. There was no significant effect modification, except for EAC and EGJA where acid reflux mitigated the inverse associations (P=0.02). For ESCC, younger ages at diagnosis enhanced drinking-related ORs (P<0.01).

CONCLUSIONS

Patterns of ORs by pack-years and drink-years, delivery rate effects and effect modifiers revealed common as well as distinct etiologic elements for these diseases.

Interaction of nitrate and folate on the risk of breast cancer among postmenopausal women

Ingested nitrate can be endogenously reduced to nitrite, which may form N-nitroso compounds, known potent carcinogens. However, some studies have reported no or inverse associations between dietary nitrate intake and cancer risk. These associations may be confounded by a protective effect of folate, which plays a vital role in DNA repair. We evaluated the interaction of dietary and water nitrate intake with total folate intake on breast cancer risk in the Iowa Women's Health Study. Dietary intake was assessed at study baseline. Nitrate intake from public water was assessed using a historical database on Iowa municipal water supplies. After baseline exclusions, 34,388 postmenopausal women and 2,875 incident breast cancers were included. Overall, neither dietary nor water nitrate was associated with breast cancer risk. Among those with folate intake ≥400 μg/day, breast cancer risk was significantly increased in public water users with the highest nitrate quintile (HR = 1.40, 95% CI = 1.05-1.87) and private well users (HR = 1.38, 95% CI = 1.05-1.82) compared to public water users with the lowest nitrate quintile; in contrast, there was no association among those with lower folate intake. Our findings do not support a previous report of increased risk of breast cancer among individuals with high dietary nitrate but low folate intake.

Body mass index and lung cancer risk: results from the ICARE study, a large, population-based case-control study

BACKGROUND

The association between body mass index (BMI) and lung cancer is still disputed because of possible residual confounding by smoking and preclinical weight loss in case-control studies. We examined this association using data from the multicenter ICARE study in France, a large, population-based case-control study.

METHODS

A total of 2,625 incident lung cancer cases and 3,381 controls were included. Weight was collected at interview, 2 years before the interview, and at age 30. Lifetime smoking exposure was calculated using the comprehensive smoking index (CSI). Adjusted odds ratios (aORs) and 95 % confidence intervals were estimated by unconditional logistic regression and controlled for age, area, education, CSI, occupational exposure, previous chronic bronchitis, and parental history of lung cancer. We also examined the role of weight change. Analyses were stratified by smoking status and sex.

RESULTS

When compared with that of men with normal BMI 2 years before the interview, lung cancer aORs (95 % CI) among men with BMIs of <18.5, 25-29.9, 30-32.4, and ≥32.5 kg/m(2) were 2.7 (95 % CI 1.2-6.2), 0.9 (95 % CI 0.7-1.1), 0.8 (95 % CI 0.6-1.1), and 0.8 (95 % CI 0.6-1.0), respectively (p(trend) = 0.02). Results were more pronounced among current smokers and were similar in men and women. Weight gain over time was associated with a significant decreased risk of lung cancer.

CONCLUSIONS

We found an inverse dose-dependent association between lung cancer risk and BMI 2 years prior to interview in current smokers. IMPACT STATEMENT: BMI might be an individual factor impacting the risk of lung cancer related to smoking's carcinogen-induced DNA damage.

Vitamin C for DNA damage prevention

The ability of vitamin C to affect genetic damage was reviewed in human studies that used molecular epidemiology methods, including analysis of DNA adducts, DNA strand breakage (using the Comet assay), oxidative damage measured as levels of 8-oxo-7,8-dihydroxy-2'-deoxyguanosine (8-oxodG), cytogenetic analysis of chromosomal aberrations and micronuclei, and the induction of DNA repair proteins. The protective effect of vitamin C was observed at plasma levels>50μmol/l. Vitamin C supplementation decreased the frequency of chromosomal aberrations in groups with insufficient dietary intake who were occupationally exposed to mutagens, and also decreased the sensitivity to mutagens as assessed using the bleomycin assay. High vitamin C levels in plasma decreased the frequency of genomic translocations in groups exposed to ionizing radiation or c-PAHs in polluted air. The frequency of micronuclei was decreased by vitamin C supplementation in smokers challenged with γ-irradiation, and higher vitamin C levels in plasma counteracted the damage induced by air pollution. The prevalence of DNA adducts inversely correlated with vitamin C levels in groups environmentally exposed to high concentrations of c-PAHs. Increased vitamin C levels decreased DNA strand breakage induced by air pollution. Oxidative damage (8-oxodG levels) was decreased by vitamin C supplementation in groups with plasma levels>50μmol/l exposed to PM2.5 and c-PAHs. Modulation of DNA repair by vitamin C supplementation was observed both in poorly nourished subjects and in groups with vitamin C plasma levels>50μmol/l exposed to higher concentrations of c-PAHs. It is possible that the impact of vitamin C on DNA damage depends both on background values of vitamin C in the individual as well as on the level of exposure to xenobiotics or oxidative stress.

Body mass index and risk of lung cancer among never, former, and current smokers

BACKGROUND

Although obesity has been directly linked to the development of many cancers, many epidemiological studies have found that body mass index (BMI)--a surrogate marker of obesity--is inversely associated with the risk of lung cancer. These studies are difficult to interpret because of potential confounding by cigarette smoking, a major risk factor for lung cancer that is associated with lower BMI.

METHODS

We prospectively examined the association between BMI and the risk of lung cancer among 448 732 men and women aged 50-71 years who were recruited during 1995-1996 for the National Institutes of Health-AARP Diet and Health Study. BMI was calculated based on the participant's self-reported height and weight on the baseline questionnaire. We identified 9437 incident lung carcinomas (including 415 in never smokers) during a mean follow-up of 9.7 years through 2006. Multivariable Cox proportional hazards regression models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) with adjustment for lung cancer risk factors, including smoking status. To address potential bias due to preexisting undiagnosed disease, we excluded potentially unhealthy participants in sensitivity analyses. All statistical tests were two-sided.

RESULTS

The crude incidence rate of lung cancer over the study follow-up period was 233 per 100 000 person-years among men and 192 per 100 000 person-years among women. BMI was inversely associated with the risk of lung cancer among both men and women (BMI ≥35 vs 22.5-24.99 kg/m(2): HR = 0.81, 95% CI = 0.70 to 0.94 and HR = 0.73, 95% CI = 0.61 to 0.87, respectively). The inverse association was restricted to current and former smokers and was stronger after adjustment for smoking. Among smokers, the inverse association persisted even after finely stratifying on smoking status, time since quitting smoking, and number of cigarettes smoked per day. Sensitivity analyses did not support the possibility that the inverse association was due to prevalent undiagnosed disease.

CONCLUSIONS

Our results suggest that a higher BMI is associated with a reduced risk of lung cancer in current and former smokers. Our inability to attribute the inverse association between BMI and the risk of lung cancer to residual confounding by smoking or to bias suggests the need for considering other explanations.

Protein intake and muscle strength in older persons: does inflammation matter?

OBJECTIVES

To examine whether protein intake is associated with change in muscle strength in older persons. Because systemic inflammation has been associated with protein catabolism, the study also evaluated whether a synergistic effect exists between protein intake and inflammatory markers on change in muscle strength.

DESIGN

Longitudinal.

SETTING

The Invecchiare in Chianti Study.

PARTICIPANTS

Five hundred and ninety-eight older adults.

MEASUREMENTS

Knee extension strength was measured at baseline (1998-2000) and during 3-year follow-up (2001-2003) using a handheld dynamometer. Protein intake was assessed using a detailed food frequency questionnaire. The inflammatory markers examined were C-reactive protein (CRP), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-α).

RESULTS

The main effect of protein intake on change in muscle strength was not significant. However, a significant interaction was found between protein intake and CRP (P = .003), IL-6 (P = .049), and TNF-α (P = .02), indicating that lower protein intake was associated with greater decline in muscle strength in persons with high levels of inflammatory markers.

CONCLUSION

Lower protein intake was associated with decline in muscle strength in persons with high levels of inflammatory markers. These results may help to understand the factors contributing to decline in muscle strength with aging and to identify the target population of older persons who may benefit from nutritional interventions aimed at preventing or reducing age-associated muscle impairments and its detrimental consequences.

MTHFR polymorphisms, folate intake and carcinogen DNA adducts in the lung

The methylenetetrahydrofolate reductase (MTHFR) genes and folate in one-carbon metabolism are essential for DNA methylation and synthesis. However, their role in carcinogen DNA damage in target lung tissue, a dosimeter for cancer risk, is not known. Our study aimed to investigate the association between genetic and nutritional one-carbon metabolism factors and DNA adducts in target lung. Data on 135 lung cancer cases from the Massachusetts General Hospital were studied. Genotyping was completed for MTHFR C677T (rs1801133) and A1298C (rs1801131). Information on dietary intake for one-carbon related micronutrients, folate and other B vitamin was derived from a validated food frequency questionnaire. DNA adducts in lung were measured by (32) P-postlabeling. After adjusting for potential confounders, DNA adduct levels in lung significantly increased by 69.2% [95% confidence interval (CI), 5.5% to 171.5%] for the MTHFR 1298AC+CC genotype. The high risk group, combining the A1298C (AC+CC) plus C677T (CT+TT) genotypes, had significantly enhanced levels of lung adducts by 210.7% (95% CI, 21.4% to 695.2%) in contrast to the A1298C (AA) plus C677T (CC) genotypes. Elevation of DNA adduct was pronounced-111.3% (95% CI, -3.0 to 360.5%) among 1298AC+CC patients, who consumed the lowest level of folate intake as compared to 1298AA individuals with highest tertile of intake. These results indicate that DNA adducts levels are influenced by MTHFR polymorphisms and low folate consumption, suggesting an important role of genetic and nutritional factors in protecting DNA damage from lung carcinogen in at-risk populations.

Fruit and vegetable and fried food consumption and 3-(2-deoxy-β-D-erythro-pentafuranosyl)pyrimido[1,2-α] purin-10(3H)-one deoxyguanosine adduct formation

Diet has been shown to modulate M(1)dG adduct, a biomarker of oxidative stress and lipid peroxidation. Thus, we analysed the association between diet and M(1)dG in 120 controls and 67 Map Ta Phut industrial estate workers in Rayong, Thailand, to evaluate the influence of fruit and vegetables, and fried and charcoal-grilled/barbecued food consumption on M(1)dG. M(1)dG was decreased in controls reporting to consume 14-17 servings/week of fruit and vegetables (mean ratio [MR]= 0.35, CI 0.18-0.69, p< 0.05). Conversely, a non-statistically significant M(1)dG increment was detected in controls consuming 9-18 servings/week of fried food (MR = 1.33, CI 0.88-2.00, p = 0.168). No effect of charcoal-grilled/barbecued food was found. No effect of diet was observed in workers. An association with smoking was observed in controls (MR = 1.88, CI 1.14-3.10, p < 0.05), but not in workers. M(1)dG can induce mutations and/or methylation changes within the promoter regions of cancer-related genes, thus promotion of healthy eating practices should be recommended.

Bulky DNA adducts and breast cancer risk in the prospective EPIC-Italy study

The role of environmental carcinogen exposure in breast cancer development has long been suspected, but no specific association has been identified so far. A few molecular epidemiology studies reported that DNA adducts detected by different methods are associated with a modest increase of breast cancer risk. We aimed to evaluate the association between bulky DNA adducts, detected by the (32)P-postlabelling method in peripheral leukocytes, and the risk of developing breast cancer in the female Italian cohorts of the EPIC (European Prospective Investigation into Cancer and nutrition) study. By using a nested case-control design, breast cancer cases identified in the follow-up of over 30,000 women of EPIC-Italy study have been matched to controls by specific criteria. We measured the levels of bulky DNA adducts by the (32)P-postlabelling method in peripheral leukocytes donated at enrolment. Conditional regression analyses adjusted for selected potential confounders were used. Results on DNA adduct levels were available for 292 cases and 292 matched controls. The mean DNA adduct levels were similar in both groups (P=0.62). Multivariate regression analyses failed to show any significant association between bulky DNA adducts and breast cancer. Our results do not support any association of breast cancer risk with exposure to environmental carcinogens as measured through the levels of bulky DNA adducts in pre-diagnostic white blood cells. Larger studies by using different methods and/or biomarkers are needed to better evaluate the role of specific environmental carcinogens in breast carcinogenesis.

Seasonal variations in the levels of PAH-DNA adducts in young adults living in Mexico City

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous components of polluted air. The Mexico City Metropolitan Area (MCMA), one of the most densely populated areas in the world, is 2240 m above sea level. At this altitude, less oxygen is available, making combustion less efficient and therefore producing more PAH pollutants. According to the Automatic Monitoring Network in Mexico City (RAMA, for its Spanish initials; http://www.sma.df.gob.mx/simat2/informaciontecnica/index.php?opcion=5&opciondifusion_bd=90), which performs environmental monitoring, the critical air pollutants in Mexico City are ozone and particulate matter (PM). PM emissions increase during the dry season (winter to spring) and decrease during the rainy season (summer to autumn). The bioactivation of some PAHs produces reactive metabolites that bind to DNA, and the presence of elevated levels of PAH-DNA adducts in tissues such as blood lymphocytes represents an elevated risk for the development of cancer. We have compared the levels of PAH-DNA adducts and the percentage of cells with chromosomal aberrations (CWAs) using a matched set of peripheral blood lymphocytes obtained on two separate occasions from young non-smoking inhabitants of the MCMA (n = 92) during the 2006 dry season and the following rainy season. PAH-DNA adducts were analysed using the r7, t8-dihydroxy-t-9, 10-oxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BPDE)-DNA chemiluminescence immunoassay (CIA). The percentages of CWA were determined in cultured lymphocytes from the same individuals. Both DNA adduct levels and chromosomal aberrations were tested for correlation with lifestyle and the polymorphisms of cytochromes P450 CYP1A1 and CYP1B1 as well as glutathione-S-transferases GSTM1 and GSTT1. The levels of PAH-DNA adducts were significantly higher (P < 0.001) in the dry season (10.66 ± 3.05 per 10(9) nt, n = 92) than during the rainy season (9.50 ± 2.85 per 10(9) nt, n = 92) and correlated with the seasonal levels of particulate matter with a diameter of ≤ 10 μm (PM(10)). The percentage of CWA was not seasonally related; however, significant associations between the number of risk alleles and adduct levels in the dry (R = 0.298, P = 0.048) and in the wet seasons (R = 0.473, P = 0.001) were observed.

NRF2, cancer and calorie restriction

The transcription factor NF-E2-related factor (NRF2) is a key regulator of several enzymatic pathways, including cytoprotective enzymes in highly metabolic organs. In this review, we summarize the ongoing research related to NRF2 activity in cancer development, focusing on in vivo studies using NRF2 knockout (KO) mice, which have helped in defining the crucial role of NRF2 in chemoprevention. The lower cancer protection observed in NRF2 KO mice under calorie restriction (CR) suggests that most of the beneficial effects of CR on the carcinogenesis process are likely mediated by NRF2. We propose that future interventions in cancer treatment would be carried out through the activation of NRF2 in somatic cells, which will lead to a delay or prevention of the onset of some forms of human cancers, and subsequently an extension of health- and lifespan.

Body mass index, cigarette smoking, and alcohol consumption and cancers of the oral cavity, pharynx, and larynx: modeling odds ratios in pooled case-control data

Odds ratios for head and neck cancer increase with greater cigarette and alcohol use and lower body mass index (BMI; weight (kg)/height(2) (m(2))). Using data from the International Head and Neck Cancer Epidemiology Consortium, the authors conducted a formal analysis of BMI as a modifier of smoking- and alcohol-related effects. Analysis of never and current smokers included 6,333 cases, while analysis of never drinkers and consumers of < or =10 drinks/day included 8,452 cases. There were 8,000 or more controls, depending on the analysis. Odds ratios for all sites increased with lower BMI, greater smoking, and greater drinking. In polytomous regression, odds ratios for BMI (P = 0.65), smoking (P = 0.52), and drinking (P = 0.73) were homogeneous for oral cavity and pharyngeal cancers. Odds ratios for BMI and drinking were greater for oral cavity/pharyngeal cancer (P < 0.01), while smoking odds ratios were greater for laryngeal cancer (P < 0.01). Lower BMI enhanced smoking- and drinking-related odds ratios for oral cavity/pharyngeal cancer (P < 0.01), while BMI did not modify smoking and drinking odds ratios for laryngeal cancer. The increased odds ratios for all sites with low BMI may suggest related carcinogenic mechanisms; however, BMI modification of smoking and drinking odds ratios for cancer of the oral cavity/pharynx but not larynx cancer suggests additional factors specific to oral cavity/pharynx cancer.

Pooled analysis of studies on DNA adducts and dietary vitamins

OBJECTIVES

There is some evidence that dietary components that are rich in antioxidant and vitamins are inversely associated with DNA adduct levels induced by environmental carcinogens such as polycyclic aromatic hydrocarbons, although the epidemiologic data are inconsistent. This study addresses the association between vitamins, DNA adducts and smoking.

METHODS

A combined analysis of individual data on the association between bulky DNA adducts and dietary vitamins was conducted. A Medline search was performed to identify studies on healthy subjects in which smoking and vitamins intake information were available, and bulky DNA adducts were measured in peripheral blood with 32P-postlabelling. Eight published studies met the eligibility criteria, and individual data from 7 data sets including 2758 subjects were obtained. GSTM1 and GSTT1 were also available on all the subjects.

RESULTS

Vitamin E was inversely significantly associated with DNA adducts after adjustment for possible confounding factors. Vitamins A and C were not independent predictors of DNA adducts. A stratified analysis showed that vitamin A had a significant inverse association with DNA adducts in ever smokers only.

CONCLUSIONS

This result is relevant to planning any future chemo-preventive interventions directed to high risk subgroups of the population, for cancer prevention.

Lifestyle, environmental, and genetic predictors of bulky DNA adducts in a study population nested within a prospective Danish cohort

Bulky DNA adducts are considered a potential biomarker of cancer risk. In this study, the association between various lifestyle, environmental, and genetic factors and the levels of bulky DNA adducts in peripheral leukocytes was examined in a study group nested within a population-based prospective Danish cohort. At enrollment, blood samples were collected and information on lifestyle, including dietary and smoking habits, obtained. Previously, bulky DNA adducts were measured in 245 individuals who developed lung cancer and 255 control members of the cohort. Of these 500 individuals, data on 375 individuals were included in this study, excluding 125 cases, which developed lung cancer within the first 3 yr after blood sampling. Bulky DNA adduct levels were measured by 32P-postlabeling technique and polymorphisms in carcinogen metabolism and DNA repair genes were determined. Potential predictors of bulky DNA adduct levels were analyzed by univariate and multivariate regression analyses. Women tended to have higher adduct levels than men. Living in central Copenhagen and surface darkness of fried meat and fish were associated with quantitative higher adduct levels. No significant associations were found between dietary factors or smoking and DNA adduct levels. Further, the results showed no prominent associations between any of 12 genetic polymorphisms and adduct levels. Overall, our study showed only few associations between dietary, environmental, and genetic factors and levels of bulky DNA adducts measured in peripheral leukocytes in a general Danish population.

Nrf2: friend or foe for chemoprevention?

Health reflects the ability of an organism to adapt to stress. Stresses--metabolic, proteotoxic, mitotic, oxidative and DNA-damage stresses--not only contribute to the etiology of cancer and other chronic degenerative diseases but are also hallmarks of the cancer phenotype. Activation of the Kelch-like ECH-associated protein 1 (KEAP1)-NF-E2-related factor 2 (NRF2)-signaling pathway is an adaptive response to environmental and endogenous stresses and serves to render animals resistant to chemical carcinogenesis and other forms of toxicity, whilst disruption of the pathway exacerbates these outcomes. This pathway can be induced by thiol-reactive small molecules that demonstrate protective efficacy in preclinical chemoprevention models and in clinical trials. However, mutations and epigenetic modifications affecting the regulation and fate of NRF2 can lead to constitutive dominant hyperactivation of signaling that preserves rather than attenuates cancer phenotypes by providing selective resistance to stresses. This review provides a synopsis of KEAP1-NRF2 signaling, compares the impact of genetic versus pharmacologic activation and considers both the attributes and concerns of targeting the pathway in chemoprevention.

Modulation of the effect of prenatal PAH exposure on PAH-DNA adducts in cord blood by plasma antioxidants

The fetus is more susceptible than the adult to the effects of certain carcinogens, such as polycyclic aromatic hydrocarbons (PAH). Nutritional factors, including antioxidants, have been shown to have a protective effect on carcinogen-DNA adducts and cancer risk in adults. We investigated whether the effect of prenatal airborne PAH exposure, measured by personal air monitoring during pregnancy, on the level of PAH-DNA adducts in a baby's cord blood is modified by the concentration of micronutrients in maternal and cord blood. The micronutrients examined were: retinol (vitamin A), alpha-tocopherol and gamma-tocopherol (vitamin E), and carotenoids. With the use of multiple linear regression, we found a significant interaction between prenatal PAH exposure and cord blood concentration of alpha-tocopherol and carotenoids in predicting the concentration of PAH adducts in cord blood. The association between PAH exposure and PAH adducts was much stronger among those with low alpha-tocopherol (beta = 0.15; P = 0.001) and among those with low carotenoids (beta = 0.16; P < 0.001) compared with babies with high levels of these micronutrients (among those with high alpha-tocopherol: beta = 0.05; P = 0.165; among those with high carotenoids: beta = 0.06; P = 0.111). These results suggest a protective effect of micronutrients on the DNA damage and potential cancer risk associated with prenatal PAH exposure.

Validation of biomarkers for the study of environmental carcinogens: a review

There is a need for validation of biomarkers. Our aim is to review published work on the validation of selected biomarkers: bulky DNA adducts, N-nitroso compounds, 1-hydroxypyrene, and oxidative damage to DNA. A systematic literature search in PubMed was performed. Information on the variability and reliability of the laboratory tests used for biomarkers measurements was collected. For the evaluation of the evidence on validation we referred to the ACCE criteria. Little is known about intraindividual variation of DNA adduct measurements, but measurements have a good repeatability irrespective of the technique used for their identification; reproducibility improved after the correction for a laboratory factor. A high-sensitivity method is available for the measurement of 1-hydroxypyrene in urine. There is consensus on validation of biomarkers of oxidative damage DNA based on the comet assay and chromatographic measurement in blood while urinary measurements by chromatographic assays are well validated, and ELISA-based assays appear to lack specificity. Immunoassays for the quantification of adducts of N-nitroso compounds are useful for large epidemiological studies, given their sensitivity, the small amount of DNA required and their potential for rapid and high-throughput analysis.

Body mass index and waist circumference in relation to lung cancer risk in the Women's Health Initiative

Investigators in several epidemiologic studies have observed an inverse association between body mass index (BMI) and lung cancer risk, while others have not. The authors used data from the Women's Health Initiative to study the association of anthropometric factors with lung cancer risk. Over 8 years of follow-up (1998-2006), 1,365 incident lung cancer cases were ascertained among 161,809 women. Cox proportional hazards models were used to estimate hazard ratios adjusted for covariates. Baseline BMI was inversely associated with lung cancer in current smokers (highest quintile vs. lowest: hazard ratio (HR) = 0.62, 95% confidence interval (CI): 0.42, 0.92). When BMI and waist circumference were mutually adjusted, BMI was inversely associated with lung cancer risk in both current smokers and former smokers (HR = 0.40 (95% CI: 0.22, 0.72) and HR = 0.61 (95% CI: 0.40, 0.94), respectively), and waist circumference was positively associated with risk (HR = 1.56 (95% CI: 0.91, 2.69) and HR = 1.50 (95% CI: 0.98, 2.31), respectively). In never smokers, height showed a borderline positive association with lung cancer. These findings suggest that in smokers, BMI is inversely associated with lung cancer risk and that waist circumference is positively associated with risk.

DNA adducts and cancer risk in prospective studies: a pooled analysis and a meta-analysis

Bulky DNA adducts are biomarkers of exposure to aromatic compounds and of the ability of the individual to metabolically activate carcinogens and to repair DNA damage. Their ability to predict cancer onset is uncertain. We have performed a pooled analysis of three prospective studies on cancer risk in which bulky DNA adducts have been measured in blood samples collected from healthy subjects (N = 1947; average follow-up 51-137 months). In addition, we have performed a meta-analysis by identifying all articles on the same subject published up to the end of 2006, including case-control studies. In the pooled analysis, a weakly statistically significant increase in the risk of lung cancer was apparent (14% per unit standard deviation change in adduct levels, 95% confidence interval 1-28%; using the weighted mean difference method, 0.15 SD, units higher adducts in cases than in controls). The association was evident only in current smokers and was absent in former smokers. Also the meta-analysis, which included both lung and bladder cancers, showed a statistically significant association in current smokers, whereas the results in never smokers were equivocal; in former smokers, no association was detected. The results of our pooled and meta-analyses suggest that bulky DNA adducts are associated with lung cancer arising in current smokers after a follow-up of several years.

Inhibition of cell cycle progression by hydroxytyrosol is associated with upregulation of cyclin-dependent protein kinase inhibitors p21(WAF1/Cip1) and p27(Kip1) and with induction of differentiation in HL60 cells

Recent evidence indicates that the cancer preventive activity of olive oil can be mediated by the presence of minor components, such as antioxidant phenolic compounds. However, their mechanisms of action remain largely unknown. In this study, we investigated the in vitro effects of one of the main olive oil phenols, hydroxytyrosol [3,4-dihydroxyphenylethanol (3,4-DHPEA)], on proliferation, cell cycle progression, apoptosis, and differentiation of HL60 human promyelocytic leukemia cells. 3,4-DHPEA showed a potent inhibitory activity on DNA synthesis, as evidenced by a 92% reduction of [3H]-thymidine incorporation at 100 micromol/L, and an induced apoptosis, as evidenced by the release of cytosolic nucleosomes and flow cytometry. This phenol, 3,4-DHPEA, was also able to inhibit the progression of the cell cycle in synchronized HL60 cells, which accumulated in the G0/G1 phase of the cell cycle after 25 h of treatment. Furthermore, 3,4-DHPEA induced differentiation on HL60 cells with a maximum effect (22% of cells) at 100 micromol/L after 72 h of treatment. Among the different proteins involved in the regulation of the cell cycle, 3,4-DHPEA reduced the level of cyclin-dependent kinase (CDK) 6 and increased that of cyclin D3. With regard to the CDK inhibitors, p15 was not altered by 3,4-DHPEA treatment, whereas the expression of p21(WAF1/Cip1) and p27(Kip1) was increased at both protein and mRNA levels. To our knowledge, these results provide the first evidence that 3,4-DHPEA may effect the expression of genes involved in the regulation of tumor cell proliferation and differentiation.

GSTM1 and GSTT1 polymorphism influences protection against induced oxidative DNA damage by quercetin and ascorbic acid in human lymphocytes in vitro

Antioxidants are of major importance in the protection against cellular oxidative damage caused by endogenous as well as exogenous free radicals. This study aims to establish the impact of genetic polymorphisms in GSTM1 and GSTT1, which encode for enzymatic antioxidative defence, on H(2)O(2)-induced oxidative DNA damage and on the effectiveness of quercetin and ascorbic acid in preventing this induced damage in human lymphocytes. Lymphocytes from 12 healthy volunteers were pre-incubated either with 10 microM of quercetin or with 10 microM of ascorbic acid, and exposed to 25 microM H(2)O(2) for 1h. The induction of oxidative DNA damage was quantified using the Comet assay. Genotyping of these 12 subjects showed that six individuals were GSTM1+ and six were GSTM1-; eight were GSTT1+ and four GSTT1-.

RESULTS

Baseline levels of oxidative DNA damage did not differ between GSTM1 or GSTT1 variants and their respective wild types. Also with respect to ex vivo induced levels of oxidative DNA damage, no significant difference was seen between variants and wild types of both genotypes. The protection against H(2)O(2)-induced oxidative DNA damage by quercetin was significantly higher in GSTT1 wild types than in GSTT1 variants (57% and 9% decrease, respectively; p=0.01); furthermore, GSTT1 wild types were protected against induced oxidative DNA damage by ascorbic acid pre-incubation while GSTT1 variants showed an increase of damage (16% decrease vs. 91% increase; p=0.01). For GSTM1 variants and wild types, observed differences in protective effects of quercetin or ascorbic acid were not statistically significant. Overall, quercetin proves to be better in protecting human lymphocytes in vitro against oxidative DNA damage upon H(2)O(2) challenge than ascorbic acid.

Polymorphisms in nucleotide excision repair genes, smoking and intake of fruit and vegetables in relation to lung cancer

Polymorphisms in nucleotide excision repair genes have been associated with risk for lung cancer. We examined gene-environment interactions in relation to lung cancer in 430 cases and 790 comparison persons identified within a prospective cohort of 57,053 persons. We included polymorphisms in the XPC, XPA and XPD genes involved in the nucleotide excision DNA repair pathway and analysed possible interactions with smoking and dietary intake of fruit and vegetables in relation to risk for lung cancer. We found that intake of fruit was associated with lower risk for lung cancer only among carriers of the XPA A23G variant genotype. The incidence rate ratio for lung cancer was 0.60 (95% confidence interval: 0.43-0.84; p=0.003) per 50% increase in fruit intake. No convincing interactions were detected between the polymorphisms and smoking.

Daily consumption of a high-phenol extra-virgin olive oil reduces oxidative DNA damage in postmenopausal women

Extra-virgin olive oils (EVOO), high in phenolic compounds with antioxidant properties, could be partly responsible for the lower mortality and incidence of cancer and CVD in the Mediterranean region. The present study aims to measure oxidative DNA damage in healthy human subjects consuming olive oils with different concentrations of natural phenols. A randomised cross-over trial of high-phenol EVOO (high-EVOO; 592mg total phenols/kg)Vlow-phenol EVOO (low-EVOO; 147mg/kg) was conducted in ten postmenopausal women in Florence. Subjects were asked to substitute all types of fat and oils habitually consumed with the study oil (50g/d) for 8 weeks in each period. Oxidative DNA damage was measured by the comet assay in peripheral blood lymphocytes, collected at each visit during the study period. Urine samples over 24h were collected to measure the excretion of the olive oil phenols. The average of the four measurements of oxidative DNA damage during treatment with high-EVOO was 30% lower than the average during the low-EVOO treatment (p=0·02). Urinary excretion of hydroxytyrosol and its metabolite homovanillyl alcohol were significantly increased in subjects consuming high-EVOO. Despite the small sample size, the present study showed a reduction of DNA damage by consumption of an EVOO rich in phenols, particularly hydroxytyrosol.

XPA A23G, XPC Lys939Gln, XPD Lys751Gln and XPD Asp312Asn polymorphisms, interactions with smoking, alcohol and dietary factors, and risk of colorectal cancer

Polymorphisms in the XPD and the XPC gene have been associated with a lower DNA repair capacity. We determined the risk of colorectal cancer in association with the four polymorphisms XPA A23G, XPC Lys939Gln, XPD Lys751Gln and XPD Asp312Asn, and interactions between the polymorphisms and the environmental factors: smoking intensity, intake of alcohol, red meat, processed meat, fish and poultry, fruits and vegetables and dietary fibres, in relation to development of colorectal cancer in a study population of 405 colorectal cancer cases and a comparison group of 810 persons, nested within the Danish prospective cohort, Diet, Cancer and Health, of 57053 cohort members. No association was found between the XPC Lys939Gln, XPA A23G, XPD Lys751Gln, and XPD Asp312Asn polymorphisms and risk of colorectal cancer. The association of the XPD Lys751Gln polymorphism was statistically significantly different between genders, with a lower risk of colorectal cancer among women carrying the variant allele. We observed a statistically significant interaction between the XPC Lys939Gln polymorphism and consumption of red meat, with a 3.7-fold increase in colorectal cancer risk per 100g red meat intake per day among carriers of the homozygous variant, but virtually no effect of red meat intake among carriers of the wild type allele. In the light of the multiple comparisons being made, this result may be a chance finding. The results showed no interaction between the XPD Lys751Gln, XPA A23G, and XPD Asp312Asn polymorphisms and the environmental factors for the development of colorectal cancer. Overall, the results of the present study indicate that the four polymorphisms are not of major importance in colorectal cancer carcinogenesis.

Seasonal variations in spontaneous levels of DNA damage; implication in the risk assessment of environmental chemicals

The alkaline comet assay was used to investigate DNA damage levels in white blood cells of 45 normal healthy subjects. Therefore blood was sampled at four different periods, namely in February, June, August and November of the same year. Higher DNA damage levels were found in summertime, as well as higher levels of 1-hydroxypyrene in urine in this period. This suggests a higher exposure to polycyclic hydrocarbons in the summer compared with other periods of the year. The observed seasonal variation in DNA damage levels is in agreement with some, but in contradiction with other data. Seasonal variations in DNA damage levels can easily be explained by the existence of different confounders that may influence the results of a biomonitoring study. Besides sunlight and environmental pollution, also diet, allergy and physical exercise, for example, were already identified as important influencing factors. The investigation confirms that the blood sampling period is crucial in the planning and interpretation of biomonitoring studies.

Determinants of anti-benzo[a]pyrene diol epoxide-DNA adduct formation in lymphomonocytes of the general population

We evaluated determinants of anti-benzo[a]pyrenediolepoxide-(B[a]PDE)-DNA adduct formation (adduct induced by the ultimate carcinogenic metabolite of B[a]P) in lymphomonocytes of subjects environmentally exposed to low doses of polycyclic aromatic hydrocarbons (PAHs) (B[a]P). Our study population consisted of 585 Caucasian subjects, all municipal workers living in North-East Italy and recruited during their periodic check-ups after informed consent. PAH (B[a]P) exposure was assessed by questionnaire. Anti-B[a]PDE-DNA levels were measured by HPLC fluorescence analysis. We found that cigarette smoking (smokers (22%) versus non-smokers, p<0.0001), dietary intake of PAH-rich meals (> or =52 (38%) versus <52 times/year, p<0.0001), and outdoor exposure (> or =4 (19%) versus <4h/day; p=0.0115) significantly influenced adduct levels. Indoor exposure significantly increased the frequency of positive subjects (> or =0.5 adducts/10(8) nucleotides; chi(2) for linear trend, p=0.051). In linear multiple regression analysis the major determinants of increased DNA adduct levels (ln values) were smoking (t=6.362, p<0.0001) and diet (t=4.035, p<0.0001). In this statistical analysis, indoor and outdoor exposure like other factors of PAH exposure had no influence. In non-smokers, the influence of diet (p<0.0001) and high indoor exposure (p=0.016) on anti-B[a]PDE-DNA adduct formation became more evident, but not that of outdoor exposure, as was confirmed by linear multiple regression analysis (diet, t=3.997, p<0.0001 and high indoor exposure, t=2.522, p=0.012). This study indicates that anti-B[a]PDE-DNA adducts can be detected in the general population and are modulated by PAH (B[a]P) exposure not only with smoking - information already known from studies with limited number of subjects - but also with dietary habits and high indoor exposure. In non-smokers, these two factors are the principal determinants of DNA adduct formation. The information provided here seems to be important, since DNA adduct formation in surrogate tissue is an index of genotoxic exposure also in target organs (e.g., lung) and their increase may also be predictive of higher risk for PAH-related cancers.

Trends in incidence rates of oesophagus and gastric cancer in Italy by subsite and histology, 1986-1997

OBJECTIVE

Population-based studies in Western countries suggest that the incidence of oesophageal adenocarcinoma (OA) and gastric cardia adenocarcinoma (GCA) is increasing, whereas the incidence of distal gastric carcinoma and oesophageal squamous cell carcinoma (OSCC) is declining. This is the first population-based study carried out in a southern European region to evaluate the time trends in incidence rates of oesophageal and gastric tumours according to subsite and histology over the period 1986-1997.

METHODS

Cancer cases were drawn from seven registries of the Italian Network of Cancer Registries, which covers approximately 9% of the Italian population (annual average 5 027 944). Time trends in age and sex-standardized incidence rates were reported. Estimated annual percentage changes (EAPC) and related 95% confidence intervals (CI) were estimated by modelling age, sex, subsite and morphology-specific incidence rates through Poisson log-linear regression, and whenever necessary negative-binomial regression. Overall, 25 895 gastric and 2497 oesophageal carcinomas were examined.

RESULTS

On the whole, an increasing trend was observed for OA plus GCA. The increase was statistically significant in younger women (<60 years: EAPC 3.7; 95% CI 0.2; 7.3) and in older men (>75 years: EAPC 4.0; 95% CI 1.2; 6.9). Similar trends were also observed in proximal gastric cancer (GCA plus fundus). A decline in the stomach subfundus incidence was observed in both sexes and in each age group. OSCC decreased significantly in men (EAPC-2.6; 95% CI-4.1;-0.9).

CONCLUSIONS

It is plausible that the different tendencies in oesophageal and proximal gastric cancer in men and women are attributable to heterogeneous distributions of risk factors by sex or age.