PAH-DNA Adduct Levels Research Articles

Attenuation of Polycyclic Aromatic Hydrocarbon (PAH)-Induced Carcinogenesis and Tumorigenesis by Omega-3 Fatty Acids in Mice In Vivo.

Lung cancer is the leading cause of cancer death worldwide. Polycyclic aromatic hydrocarbons (PAHs) are metabolized by the cytochrome P450 (CYP)1A and 1B1 to DNA-reactive metabolites, which could lead to mutations in critical genes, eventually resulting in cancer. Omega-3 fatty acids, such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are beneficial against cancers. In this investigation, we elucidated the mechanisms by which omega-3 fatty acids EPA and DHA will attenuate PAH-DNA adducts and lung carcinogenesis and tumorigenesis mediated by the PAHs BP and MC. Adult wild-type (WT) (A/J) mice, Cyp1a1-null, Cyp1a2-null, or Cyp1b1-null mice were exposed to PAHs benzo[a]pyrene (BP) or 3-methylcholanthrene (MC), and the effects of omega-3 fatty acid on PAH-mediated lung carcinogenesis and tumorigenesis were studied. The major findings were as follows: (i) omega-3 fatty acids significantly decreased PAH-DNA adducts in the lungs of each of the genotypes studied; (ii) decreases in PAH-DNA adduct levels by EPA/DHA was in part due to inhibition of CYP1B1; (iii) inhibition of soluble epoxide hydrolase (sEH) enhanced the EPA/DHA-mediated prevention of pulmonary carcinogenesis; and (iv) EPA/DHA attenuated PAH-mediated carcinogenesis in part by epigenetic mechanisms. Taken together, our results suggest that omega-3 fatty acids have the potential to be developed as cancer chemo-preventive agents in people.

Interaction of polycyclic aromatic hydrocarbon DNA adducts and telomere length on missed abortion

Objective: To analyze the contribution and interaction of polycyclic aromatic hydrocarbons (PAH)-DNA adducts and changes of telomere length (TL) on missed abortion. Methods: From March to December 2019, patients with missed abortion in the First Hospital of Shanxi Medical University and pregnant women with normal pregnancy but voluntary abortion in the same department during the same period were selected and divided into a case group and a control group. Questionnaire was used to investigate the general situation and the pregnancy situation of the subjects. The abortion villi were collected and the content of PAH-DNA adducts and TL was detected. Logistic regression model was used to analyze the associated factors of missed abortion. R epiR package and Mediation package were used to analyze the effect and relationship between PAH-DNA adducts and TL on missed abortion. Results: The age of the subjects was(29.92±5.69)years old. The M(Q1,Q3)of PAH-DNA adducts was 453.75(404.61, 504.72) pg/ml. The M(Q1,Q3)of TL was 1.21(0.77, 1.72). The content of PAH-DNA adducts in the case group was higher than that in the control group (Z=-2.10, P=0.036), while the TL was lower than that in the control group (Z=-4.05, P<0.001). Multivariate logistic regression showed that low, medium and high levels of PAH-DNA adducts (OR=3.17,95%CI:1.41-7.14;OR=2.85,95%CI:1.25-6.52;OR=2.46,95%CI:1.07-5.64), and long, medium and short levels of TL (OR=2.50,95%CI:1.11-5.63;OR=3.32,95%CI:1.45-7.56;OR=3.22,95%CI:1.42-7.26) were all risk factors for missed abortion. The medium level of PAH-DNA adducts had a 2.76-fold higher risk of shortened TL than those with the lowest level, and no mediating role of TL was found. The stratified analysis showed that when the TL level was longer (>1.21), the low and high levels of PAH-DNA adducts were associated with missed abortion (all P<0.05); when the TL level was shorter (<1.21), the medium level of PAH-DNA adducts was associated with abortion (P=0.025). At lower levels of PAH-DNA adducts, no effect of TL on missed abortion was observed, while, at higher levels, TL was strongly associated with missed abortion (OR=7.50,95%CI:1.95-28.82;OR=6.04,95%CI:1.54-23.65;OR=9.05,95%CI:2.34-35.04). The interaction analysis found that the AP was 0.72 (95%CI: 0.46-0.99), and the SI was 5.21 (95%CI: 2.30-11.77). Conclusion: The high level of PAH-DNA adducts and shortened TL may increase the risk of missed abortion, and there may be a positive additive interaction between the two factors on missed abortion.

The effect of different tobacco tar levels on DNA damage in cigarette smoking subjects

To explore the genetic damage caused by different tar levels in the human body. The subjects were divided into high, medium and low (12mg, 8mg, 5mg) tar groups according to the tar levels. Nonsmoking populations served as a control group. 2ml of peripheral blood was collected on the 10th day after morning fasting. Oxidative and genetic toxicological damage indicators were analysed with enzyme-linked immunosorbent assay, cytokinesis-block micronucleus assay in human lymphocyte and single cell gel electrophoresis. The distribution of hOGG1 concentration was significantly different within all groups, P<0.01. The concentrations of cotinine, 8-OHdG and Rap-2b were significantly differences between control and medium tar group, control and high tar group, low and medium tar group and low and high tar group, respectively, P<0.05. The level of PAH-DNA adducts was not significantly changed in the middle tar group and high tar group, P>0.05. The level of CRP was significantly changed between control and high tar group, low and high tar group and medium and high tar group, respectively, P<0.0001. The rate of comet tailing was significantly different between all groups. The rate of micronucleus cells was not significantly different between all groups. The increase of tar content could increase the DNA damage to a certain extent, so the intake of tar content should be monitored.

Intestinal polycyclic aromatic hydrocarbon-DNA adducts in a population of beluga whales with high levels of gastrointestinal cancers.

Carcinogenic polycyclic aromatic hydrocarbons (PAHs) were disposed directly into the Saguenay River of the St. Lawrence Estuary (SLE) by local aluminum smelters (Quebec, Canada) for 50 years (1926-1976). PAHs in the river sediments are likely etiologically related to gastrointestinal epithelial cancers observed in 7% of 156 mature (>19-year old) adult beluga found dead along the shorelines. Because DNA adduct formation provides a critical link between exposure and cancer induction, and because PAH-DNA adducts are chemically stable, we hypothesized that SLE beluga intestine would contain PAH-DNA adducts. Using an antiserum specific for DNA modified with several carcinogenic PAHs, we stained sections of paraffin-embedded intestine from 51 SLE beluga (0-63 years), 4 Cook Inlet (CI) Alaska beluga (0-26 years), and 20 beluga (0-46 years) living in Arctic areas (Eastern Beaufort Sea, Eastern Chukchi Sea, Point Lay Alaska) and aquaria, all with low PAH contamination. Stained sections showed nuclear light-to-dark pink color indicating the presence of PAH-DNA adducts concentrated in intestinal crypt epithelial lining cells. Scoring of whole tissue sections revealed higher values for the 51 SLE beluga, compared with the 20 Arctic and aquarium beluga (P = 0.003). The H-scoring system, applied to coded individual photomicrographs, confirmed that SLE beluga and CI beluga had levels of intestinal PAH-DNA adducts significantly higher than Arctic and aquarium beluga (P = 0.003 and 0.02, respectively). Furthermore, high levels of intestinal PAH-DNA adducts in four SLE beluga with gastrointestinal cancers, considered as a group, support a link of causality between PAH exposure and intestinal cancer in SLE beluga. Environ. Mol. Mutagen. 60:29-41, 2019. Published 2018. This article is a U.S. Government work and is in the public domain in the USA.

Shorter telomere length in cord blood associated with prenatal air pollution exposure: Benefits of intervention

BackgroundTo examine the molecular benefits of the government action to close the local coal burning power plant in Tongliang County, Chongqing Municipality, we compared biologic markers and health outcomes in two successive birth cohorts enrolled before and after the plant was shut down. In this city, polycyclic aromatic hydrocarbons (PAH) were primarily emitted by the coal burning facility. We previously reported that cord blood levels of PAH-DNA adducts (a biomarker of exposure) and various adverse health outcomes were reduced in the second cohort, whereas levels of brain-derived neurotrophic factor/BDNF (a protein involved in neuronal growth) were increased. Here we assessed telomere length (TL), which has been associated with risk of certain chronic diseases, early mortality, aging and cognitive decline in adults. ObjectivesThe goals of the present study were to determine whether TL differed between the two cohorts and whether prenatal PAH exposure, estimated by PAH-DNA adducts in cord white blood cells of newborns in China, were predictive of shorter TL in cord blood, suggesting the potential accrual of risk of certain chronic diseases during the prenatal period. We explored relationships of TL with BDNF and neurodevelopmental outcomes, each previously associated with PAH-DNA adducts in these cohorts, as well as the potential mediating role of TL in the associations between adducts and neurodevelopmental outcomes. MethodsWe analyzed TL in cord blood of 255 newborns who also had data on PAH-DNA adducts, BDNF, and relevant covariates. Multiple regression analysis was carried out to test associations between adducts and TL and between TL and BDNF, adjusting for relevant covariates. In the subset with developmental quotient (DQ) scores from Gesell testing at age 2 (N = 210), we explored whether TL was a mediator of the relationship between PAH-DNA adducts and DQ scores by first examining the associations between cord adducts and DQ, cord adducts and TL, and TL and DQ, adjusting for the same covariates. ResultsAs hypothesized, the mean TL was significantly higher in the second cohort compared to the first cohort. Overall, PAH-DNA cord adducts were significantly and inversely correlated with TL. Multiple regression analysis showed a significant association between adducts and TL, after adjusting for key covariates: β (effect size per standard deviation adducts) = −0.019, p = .003. The regression coefficient of TL on (Ln) BDNF was also significant (β = 0.167, p < .001). Exploratory analysis, regressing TL on Gesell developmental scores, showed generally inverse, but not significant associations. TL was not, therefore, deemed to be a potential mediator of the association between adducts and developmental scores at age two. ConclusionThis study provides the first evidence that prenatal PAH exposure from coal burning may adversely affect TL, with potential implications for future risk of chronic diseases including cardiovascular disease. The improvement in TL in the second cohort and the observed correlation between increased TL and higher levels of BDNF indicate direct benefits to the health and development of children resulting from the government's closure of the power plant.

Prenatal airborne polycyclic aromatic hydrocarbon exposure, LINE1 methylation and child development in a Chinese cohort

BackgroundPolycyclic aromatic hydrocarbons (PAH) are carcinogenic, neurotoxic environmental pollutants generated during incomplete combustion of fossil fuel and other organic material. PAH exposure has been associated with adverse fetal development and epigenetic alterations in cord blood. Several molecular epidemiology studies have established PAH-DNA adducts as biomarkers of PAH exposure. ObjectivesWe investigated the relationship between LINE1 DNA methylation and PAH-DNA adduct levels in cord blood, and with neurodevelopmental outcomes. MethodsIn Tongliang County, China, the current study enrolled two population-based cohorts of nonsmoking pregnant women before (2002) and after (2005) the closure of a local coal-fired power plant in May 2004. We analyzed cord blood samples collected from mothers in the two cohorts (n=110 from 2002 cohort and n=107 from 2005 cohort) for PAH-DNA adducts and genomic LINE1 DNA methylation. Neurodevelopmental data on children were collected using the Gesell Developmental Scales (GDS) at age 2 and using the Wechsler Intelligence Scale for Children (WISC) at age 5. ResultsA significant inverse relationship was observed between PAH-DNA adducts and LINE1 DNA methylation (β=−0.010, p<0.038). A significant, positive association between LINE1 methylation and scores on WISC full scale and verbal (β=85.31, p<0.005; β=94.36, p<0.003) but not on the GDS. Mediation analysis did not find LINE1 to be a direct mediator between PAH-DNA adducts and IQ score. ConclusionLINE1 methylation in cord blood DNA was a positive predictor of IQ at age 5 and was decreased at higher levels of prenatal PAH exposure measured by PAH-DNA adducts in cord blood. However, the adverse effects of prenatal exposure to PAH on IQ scores did not appear to be directly mediated by altered LINE1 methylation.

Institutes in the Lead: Identifying Environmental Factors in Breast Cancer.

Institutes in the Lead: Identifying Environmental Factors in Breast Cancer.

Abstract 1214: TP53 affects SOX2 copy number alterations and expression in non-small cell lung cancer

Abstract Background: Amplifications of the transcription factor, SRY (sex determining region Y)-box 2 (SOX2), are common in non-small cell lung cancer (NSCLC). SOX2-signaling is important in maintaining the stem cell-like phenotype of cancer cells and contributes to the pathogenesis of lung cancer. TP53 is recognized as a critical regulator of stem cell pluripotency, and it is known that TP53 represses many stem cell associated genes following DNA damage. We hypothesized that SOX2 copy number alterations in lung tumors could be correlated to mutational status of TP53 gene in tumors and that TP53 played a role in regulation of SOX2 gene expression. Material and Methods: Early-stage lung cancer cases (n = 258) of Norwegian Caucasians origin were recruited when admitted to Haukeland University Hospital in Bergen, Norway between 1986 and 1994. Samples of adjacent histologically non-tumorous lung tissue were collected in the lobectomi specimens at the time of surgery. Tumor histology was confirmed by an experienced pathologist and samples containing &amp;gt;80% of tumor cells were analyzed in this study. After resection tumor and non-tumorous tissues were snap-frozen in liquid nitrogen and kept at -80oC until further processing. All subjects gave written consent, and the study was approved by the regional ethical committee in accordance with the Helsinki Declaration. SOX2 copy number alterations were evaluated by quantitative RT- PCR using SYBR Green I Technology. The TP53 and SOX2 expression levels were assessed by q-PCR in the tumors where mRNA was available. Furthermore, to understand mechanisms, TP53 and SOX2 genes were knocked down by siRNA in the A427 human lung adenocarcinoma cell line. Additionally, some miRNAs were also analyzed by q-PCR. TP53 mutations in tumors were analyzed by sequencing and PAH-DNA adduct levels were determined in non-tumorous lung tissue by 382P-postlabelling. Results: SOX2 copy number alterations were more frequent in tumor tissues (34%) than in the adjacent non-tumorous tissues (3%) and TP53 mutations were associated with an increased risk of acquiring a SOX2 copy number alteration (OR = 2.08, 95% CI: 1.14-3.79, p = 0.017). SOX2 and TP53 expressions were strongly correlated in lung tumors and reduction in TP53 decreased SOX2 expression in lung adenocarcinoma cells. TP53 knockdown also reduced the miRNA hsa-miR-145, which has previously been shown to regulate SOX2 expression. We propose that SOX2 may be an important target of TP53 signaling in lung cancer and that hsa-miR-145-5p may be one potential driver miRNA involved in this regulation requiring further studies on the mechanisms behind the TP53-induced regulation of SOX2 expression and the possible importance of hsa-miR-145 in lung cancer. Citation Format: Johanna Samulin-Erdem, Vidar Skaug, Per Bakke, Amund Gulsvik, Aage Haugen, Shanbeh Zienolddiny. TP53 affects SOX2 copy number alterations and expression in non-small cell lung cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1214. doi:10.1158/1538-7445.AM2015-1214

Relationship of GSTT1 and GSTM1 Gene Polymorphisms and PAH-DNA Adducts with Pathogenesis of Multiple Myeloma

To explore the relationship of GSTT1, GSTM1 gene polymorphisms and PAH-DNA adduct with pathogenesis of multiple myeloma. The bone marrow samples from 37 newly-diagnosed MM patients and 52 healthy peoples as controls were collected; the PCR-based restriction fragment length polymorphism (PCR-RFLP) method was used to detecte the polymorphism of GSTT1 and GSTM1, and to analysis their relationship with clinical characters of MM patients; the engyme linked immunosorbent assay (ELISA) was performed to detect the concentration of PAH-DNA adducts. GSTT1 null and GSTM1 null genotypes increased the risk of multiple myeloma with OR 2.57 (P=0.035) and 1.37 (P>0.05) respectively. In MM patients group, GSTT1 null genotype in stage III was significantly higher than that in stages I, II (P=0.038). However, no statistically significant association was found between GSTT1 gene polymorphism and clinical characters, such as age, type, hemoglobin, β2-MG, albumin. Compared with Hb≥85 g/L of the newly-diagnosed MM patients, MM patients with Hb<85 g/L had significantly higher incidence of GSTM1 null genetype (P<0.05). The level of PAH-DNA adducts in MM patients was higher than that in controls (2358±1182 pg/ml vs 1853±996 pg/ml) (P<0.05). GSTT1 null genotype with PAH-DNA level≥2100 pg/ml showed a risk index of MM (OR=4.500, P<0.05). GSTT1 gene may have a critical function in the development of MM, and correlates with staging of MM. GSTM1 gene polymorphism correlates with hemoglobin levels of patients with MM. The content of PAH-DNA adducts may play an important role in the pathogenesis of multiple myeloma.

Mechanistic relationships between hepatic genotoxicity and carcinogenicity in male B6C3F1 mice treated with polycyclic aromatic hydrocarbon mixtures.

The genotoxicity of a complex mixture [neutral fraction (NF)] from a wood preserving waste and reconstituted mixture (RM) mimicking the NF with seven major polycyclic aromatic hydrocarbons (PAHs) and benzo(a)pyrene (BaP) was investigated by determining DNA adducts and tumor incidence in male B6C3F1 mice exposed to three different doses of the chemical mixtures. The peak values of DNA adducts were observed after 24 h, and the highest levels of PAH-DNA adducts were exhibited in mice administered NF + BaP, and the highest tumor incidence and mortality were also observed in this group. DNA adduct levels after 1, 7, or 21 days were significantly correlated with animal mortality and incidence of total tumors including liver, lung, and forestomach. However, only hepatic DNA adducts after 7 days significantly correlated with liver tumor incidence. Most proteins involved in DNA repair including ATM, pATR, Chk1, pChk1, DNA PKcs, XRCC1, FANCD2, Ku80, Mre11, and Brca2 were significantly lower in liver tumor tissue compared to non-tumor tissue. Expressions of proteins involved in apoptosis and cell cycle regulation were also significantly different in tumor versus non-tumor tissues, and it is possible that PAH-induced changes in these gene products are important for tumor development and growth.

Molecular and Neurodevelopmental Benefits to Children of Closure of a Coal Burning Power Plant in China

Polycyclic aromatic hydrocarbons (PAH) are major toxic air pollutants released during incomplete combustion of coal. PAH emissions are especially problematic in China because of their reliance on coal-powered energy. The prenatal period is a window of susceptibility to neurotoxicants. To determine the health benefits of reducing air pollution related to coal-burning, we compared molecular biomarkers of exposure and preclinical effects in umbilical cord blood to neurodevelopmental outcomes from two successive birth cohorts enrolled before and after a highly polluting, coal-fired power plant in Tongliang County, China had ceased operation. Women and their newborns in the two successive cohorts were enrolled at the time of delivery. We measured PAH-DNA adducts, a biomarker of PAH-exposure and DNA damage, and brain-derived neurotrophic factor (BDNF), a protein involved in neuronal growth, in umbilical cord blood. At age two, children were tested using the Gesell Developmental Schedules (GDS). The two cohorts were compared with respect to levels of both biomarkers in cord blood as well as developmental quotient (DQ) scores across 5 domains. Lower levels of PAH-DNA adducts, higher concentrations of the mature BDNF protein (mBDNF) and higher DQ scores were seen in the 2005 cohort enrolled after closure of the power plant. In the two cohorts combined, PAH-DNA adducts were inversely associated with mBDNF as well as scores for motor (p = 0.05), adaptive (p = 0.022), and average (p = 0.014) DQ. BDNF levels were positively associated with motor (p = 0.018), social (p = 0.001), and average (p = 0.017) DQ scores. The findings indicate that the closure of a coal-burning plant resulted in the reduction of PAH-DNA adducts in newborns and increased mBDNF levels that in turn, were positively associated with neurocognitive development. They provide further evidence of the direct benefits to children's health as a result of the coal plant shut down, supporting clean energy and environmental policies in China and elsewhere.

Levels of PAHs and PAH-DNA Adducts in Placental Tissue and the Risk of Fetal Neural Tube Defects

Levels of PAHs and PAH-DNA Adducts in Placental Tissue and the Risk of Fetal Neural Tube Defects

Influence of genetic polymorphisms on biomarkers of exposure and effects in children living in Upper Silesia

This article is a follow-up to our previous molecular epidemiology studies on the DNA damage in children from the Upper Silesia region of Poland. It is expected that metabolic and DNA repair gene polymorphisms may modulate individual susceptibility to environmental exposure. In this study, we investigate the association between polymorphisms of metabolising (CYP2D, EPHX1, GSTM1, GSTP1, GSTT1, NAT2) and DNA repair (XPD, XRCC1, XRCC3) genes and selected biomarkers of exposure and effect such as levels of 1-hydroxypyrene (1-OHP) and urinary mutagenicity, aromatic DNA adducts, sister chromatid exchange (SCE) and micronuclei (MN) in 74 children. Both 1-OHP concentration and urinary mutagenicity tested by TA98+S9 were significantly higher in individuals with EPHX1 (exon 4) Arg/Arg genotype than in individuals with other genotype. The EPHX1 (exon 3) significantly affected urinary mutagenicity tested with strain YG1024+S9. The urinary mutagenicity in individuals with Tyr/Tyr homozygotes was lower than in individuals with Tyr/His and His/His (1057±685 vs. 1432±1003 revertants/mol creatinine). XRCC3 Met/Met genotype was associated with significantly higher levels of 1-OHP in urine compared with only The/Met genotype. The PAH-DNA adduct levels in the subgroup with GSTM1 null genotype was 2-fold higher than in individuals with GSTM1 active (7.06±5.12 vs. 13.14±9.81 adduct/10(8) nucleotides). The mean level of aromatic DNA adducts in children with deletion of the GSTT1 gene was significantly higher compared with individuals with that gene present (8.03±6.23 vs. 14.66±10.70 adduct/10(8) nucleotides). Also the carriers of the XPD Lys/Lys genotype showed higher levels of DNA adducts than heterozygotes (13.16±9.70 vs. 6.81±5.86 adducts/10(8) nucleotides). Children carrying the XRCC3-241 Met/Met genotype exhibited a higher number of SCE in peripheral blood lymphocytes than carriers of Thr/Met allele (8.15±0.86 vs. 7.62±0.79 SCE/cell). It was also observed that children with the GSTP1 slow conjugator had significantly elevated MN in peripheral blood lymphocytes compared with fast conjugator (4.23±3.49 vs. 6.56±5.00 MN/1000 cells).

Abstract 4177: Detection of mir-449 and mir-let-7g expression in Taiwan paired hepatocellular carcinoma.

Abstract Hepatocellular carcinoma (HCC) is one of the most common and rapidly fatal human malignancies. In recent decades, it has been increasing in Western, developed countries such as the United States. MicroRNAs (miR) regulate genes involved in diverse biological functions and alterations in miR expression have been linked to the pathogenesis of many malignancies. Some previous studies have reported that miR-449 and miR-let-7g have tumor suppressor functions, but other studies indicate that miR-449 may have more variable functions. In the present study, miR-449 and miR-let-7g expression were measured in 36 Taiwanese paired HCC tumor/adjacent tissues using formalin fixed paraffin embedded samples with real-time RT-PCR. The mean log levels of miR-449 expression in tumor and adjacent non-tumor tissues are -1.14 and -2.65, respectively (p=0.02); for miR-let-7g, the mean log levels of tumor and adjacent non-tumor expression are 5.40 and 5.49 respectively (p=0.87). The relationship between exposure to chemical carcinogens as indicated by levels of polycyclic aromatic hydrocarbon (PAH)-DNA adducts and miR expression was also investigated. The mean log levels of miR449 in tumor tissues with high, moderate and low PAH-DNA adduct levels are -2.27, -2.22 and -0.43, respectively (p=0.02). The log levels of miR449 in tumors with and without cirrhosis are 0.02 and -1.42, respectively (p=0.02). These findings suggest that chemical carcinogen exposure and cirrhosis status may affect miR449 expression in HCC. Larger sample sizes and studies on the underlying mechanisms of miR449 and mir-let-7g expression in HCC are needed. Citation Format: Yu-Jing Zhang, Hui-Chen Wu, Jing Shen, Ming-Whei Yu, Regina M. Santella. Detection of mir-449 and mir-let-7g expression in Taiwan paired hepatocellular carcinoma. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4177. doi:10.1158/1538-7445.AM2013-4177

Levels of PAH–DNA adducts in placental tissue and the risk of fetal neural tube defects in a Chinese population

We examined the relationship between PAH–DNA adduct levels in the placental tissue, measured by a highly sensitive 32P-postlabeling assay, and the risk of fetal neural tube defects (NTDs). We further explored the interaction between PAH–DNA adducts and placental PAHs with respect to NTD risk. Placental tissues from 80 NTD-affected pregnancies and 50 uncomplicated normal pregnancies were included in this case-control study. Levels of PAH–DNA adducts were lower in the NTD group (8.12 per 108 nucleotides) compared to controls (9.92 per 108 nucleotides). PAH–DNA adduct concentrations below the median was associated with a 3-fold increased NTD risk. Women with a low PAH–DNA adduct level in concert with a high placental PAH level resulted in a 10-fold elevated risk of having an NTD-complicated pregnancy. A low level of placental PAH–DNA adducts was associated with an increased risk of NTDs; this risk increased dramatically when a low adduct level was coupled with a high placental PAH concentration.

Elevated polycyclic aromatic hydrocarbon-DNA adducts in benign prostate and risk of prostate cancer in African Americans.

Carcinogen-DNA adducts, a marker of DNA damage, are capable of inducing mutations in oncogenes and tumor suppressor genes, resulting in carcinogenesis. We have shown previously that polycyclic aromatic hydrocarbon (PAH)-DNA adduct levels in prostate cancer cases vary by cellular histology and that higher adduct levels are associated with biochemical recurrence. A nested case-control study was conducted in a historical cohort of 6692 men with histopathologically benign prostate specimens. PAH-DNA adduct levels were determined by immunohistochemistry in benign prostate specimens from 536 prostate cancer case-control pairs (59% White and 41% African American). We estimated the overall and race-stratified risk of subsequent prostate cancer associated with higher adduct levels. Prostate cancer risk for men with elevated adduct levels (defined as greater than control group median) was slightly increased [odds ratio (OR) = 1.28, 95% confidence interval (CI) = 0.98-1.67, P = 0.07]. After race stratification, elevated adduct levels were significantly associated with increased risk in African American men (OR = 1.56, CI = 1.00-2.44, *P = 0.05) but not White men (OR = 1.14, CI = 0.82-1.59, P = 0.45). Elevated PAH-DNA adduct levels were significantly associated with 60% increased risk of prostate cancer among cases diagnosed 1-4 years after cohort entry (OR = 1.60, CI = 1.07-2.41) with a greater risk observed in African Americans within the first 4 years of follow-up (OR = 4.71, CI = 1.97-11.26, ***P = 0.0005). Analyses stratified by age or tumor grade revealed no additional significant heterogeneity in risk. Increased prostate cancer risk associated with high PAH-DNA adduct levels in benign prostate was found only in African Americans; risk was greatest within 4 years of follow-up, possibly reflecting a carcinogenic process not yet histologically detectable.

Benzo[a]pyrene (BP) DNA adduct formation in DNA repair-deficient p53 haploinsufficient [Xpa(-/-)p53(+/-)] and wild-type mice fed BP and BP plus chlorophyllin for 28 days

We have evaluated DNA damage (DNA adduct formation) after feeding benzo[a]pyrene (BP) to wild-type (WT) and cancer-susceptible Xpa(-/-)p53(+/-) mice deficient in nucleotide excision repair and haploinsufficient for the tumor suppressor p53. DNA damage was evaluated by high-performance liquid chromatography/electrospray ionization tandem mass spectrometry (HPLC/ES-MS/MS), which measures r7,t8,t9-trihydroxy-c-10-(N (2)-deoxyguanosyl)-7,8,9,10-tetrahydrobenzo[a]pyrene (BPdG), and a chemiluminescence immunoassay (CIA), using anti-r7,t8-dihydroxy-t-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BPDE)-DNA antiserum, which measures both BPdG and the other stable BP-DNA adducts. When mice were fed 100 ppm BP for 28 days, BP-induced DNA damage measured in esophagus, liver and lung was typically higher in Xpa(-/-)p53(+/-) mice, compared with WT mice. This result is consistent with the previously observed tumor susceptibility of Xpa(-/-)p53(+/-) mice. BPdG, the major DNA adduct associated with tumorigenicity, was the primary DNA adduct formed in esophagus (a target tissue in the mouse), whereas total BP-DNA adducts predominated in higher levels in the liver (a non-target tissue in the mouse). In an attempt to lower BP-induced DNA damage, we fed the WT and Xpa(-/-)p53(+/-) mice 0.3% chlorophyllin (CHL) in the BP-containing diet for 28 days. The addition of CHL resulted in an increase of BP-DNA adducts in esophagus, liver and lung of WT mice, a lowering of BPdG in esophagi of WT mice and livers of Xpa(-/-)p53(+/-) mice and an increase of BPdG in livers of WT mice. Therefore, the addition of CHL to a BP-containing diet showed a lack of consistent chemoprotective effect, indicating that oral CHL administration may not reduce PAH-DNA adduct levels consistently in human organs.

Contributions of Aryl Hydrocarbon Receptor Genetic Variants to the Risk of Glioma and PAH-DNA Adducts

The aryl hydrocarbon receptor (AHR) gene is involved in the response to polycyclic aromatic hydrocarbon (PAH) exposure. To investigate the hypothesis that the genetic variants in the AHR gene might be a causal genetic susceptibility to PAH-DNA adduct formation and glioma risk, we conducted a case-control study of 384 glioma cases and 384 cancer-free controls to explore the association between six common single-nucleotide polymorphisms of the AHR gene and glioma risk. Using PAH-DNA adducts as biomarkers, we then evaluated the association between PAH-DNA adduct levels and glioma risk based on a tissue microarray including 11 controls and 77 glioma patients. We further explored the contributions of the glioma risk-associated AHR polymorphisms to the levels of PAH-DNA adducts in glioma tissues based on 77 glioma patients. We found that PAH-DNA adduct staining existed in normal brain tissues and grades I-IV gliomas, and the staining intensity was significantly associated with the glioma grade. Two AHR polymorphisms (rs2066853 and rs2158041) demonstrated significant association with glioma risk. Intriguingly, we also found statistically significant associations between these two variants and PAH-DNA adduct levels in glioma tissue. These data suggest the contributions of AHR rs2066853 and rs2158041 to glioma risk and the PAH-DNA adduct levels, which shed new light on gene-environment interactions in the etiology of glioma. Further studies with a larger sample size and ethnically diverse populations are required to elucidate the potential biological mechanism for, as well as the impact of, the susceptibility to glioma due to genetic variants of AHR.

Abstract 2646: Genetic determinants of PAH-DNA adduct level and nucleotide excision repair among non-smokers in a high risk area for esophageal squamous cell carcinoma

Abstract Background: Polycyclic aromatic hydrocarbons (PAHs) play a role in esophageal squamous cell carcinoma in high risk areas where even non-smokers are highly exposed to these compounds. Their early biological effect is the formation of DNA adducts, mediated by phase 1 and 2 pathways and nucleotide excision repair (NER). We aimed at finding a genetic model to explain inter-individual variations in PAH-DNA adduct level among people with similar exposures. Methods: In 111 randomly-selected female non-smokers from the Golestan Cohort Study in Iran, 21 SNPs in 14 genes related to xenobiotic metabolism and 13 SNPs in 9 DNA repair genes were studied (Table). NER capacity was evaluated by a comet assay, and DNA adduct level was measured by 32p-postlabelling. Multivariate regression was used to assess the effects of the number of risk alleles, NER capacity, and environmental exposures on the log-transformed PAH-DNA adduct levels. Models were compared by Akaike's information criterion (AIC). Results: Mean PAH-DNA adduct level was 5.76+3.13 per 108 nucleotides (range: 1.71 - 18.57). The level of PAH-DNA adducts was significantly lower in homozygotes for N-acetyltransferase 2 (NAT2) slow alleles and excision repair cross-complementing (ERCC)-5 T/T genotype, and higher in individuals with myeloperoxidase (MPO) G/G genotype. The sum of risk alleles in these genes had a significant correlation with the log-adduct level (r=0.4, p&amp;lt;0.001). The table shows gene level coefficients for multivariate analysis. The model including environmental exposures, phase 1 SNPs and NER capacity had the best fit (AIC=93.7). NER capacity itself was affected by a polymorphism in the methylenetetrahydrofolate reductase gene. Conclusion: We observed a high level of PAH-DNA adducts with great inter-individual variation, which could be best explained by a combination of environmental factors, number of polymorphisms in phase 1 genes and DNA repair capacity. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2646. doi:1538-7445.AM2012-2646

Neighborhood socioeconomic status modifies the association between individual smoking status and PAH‐DNA adduct levels in prostate tissue

Interactions between smoking and neighborhood-level socioeconomic status (SES) as risk factors for higher polycyclic aromatic hydrocarbon (PAH) DNA adduct levels in prostate tissue were investigated. PAH-DNA adducts were measured by immunohistochemistry with staining intensity measured in optical density units by semiquantitative absorbance image analysis in tumor adjacent tissue from 400 prostatectomy specimens from the Henry Ford Health System in Detroit. For each subject, their U.S. Census tract of residence was classified as being of higher or lower SES using the median value of the distribution of the proportion of tract residents with a high-school education. Generalized estimating equation models were used to assess interactions between neighborhood-level SES and smoking status, adjusting for race, age, education level, tumor volume, primary Gleason grade and prostate specific antigen (PSA) at diagnosis. There was a statistical interaction (P = 0.004) between tract-level SES and smoking status. In lower SES tracts smoking status was not associated with adduct staining, but in higher SES tracts adduct staining intensity was 13% (P = 0.01) higher in ever-smokers as compared to never-smokers. Among never-smokers, living in a lower SES tract was associated with a 25% higher mean staining intensity (P < 0.001). Neighborhood SES modifies the association between individual smoking status and PAH-DNA adduct levels in prostate tissue.