Carcinogenic Etheno DNA Adducts in Alcoholic Liver Disease: Correlation with Cytochrome P-4502E1 and Fibrosis.

BACKGROUND: One mechanism by which alcoholic liver disease (ALD) progresses is oxidative stress and the generation of reactive oxygen species, among others due to the induction of cytochrome P-4502E1 (CYP2E1). Experimental data underline the key role of CYP2E1 because ALD could be partially prevented in rats by the administration of the specific CYP2E1 inhibitor chlormethiazole. As CYP2E1 is linked to the formation of carcinogenic etheno DNA adducts in ALD patients, a causal role of alcohol-induced CYP2E1 in hepatocarcinogenesis is implicated. The purpose of this study was to investigate CYP2E1 induction in ALD, and its correlation with oxidative DNA lesions and with hepatic histology. METHODS: Hepatic biopsies from 97 patients diagnosed with ALD were histologically scored for steatosis, inflammation, and fibrosis. CYP2E1 and the exocyclic etheno DNA adduct 1,N6 -etheno-2'deoxyadenosine (εdA) were determined immunohistochemically. In addition, in 42 patients, 8-hydroxydeoxyguanosine (8-OHdG) was also evaluated using immunohistochemistry. RESULTS: A significant positive correlation was found between CYP2E1 and εdA (p < 0.0001) as well as between CYP2E1 and 8-OHdG (p = 0.039). Both CYP2E1 (p = 0.0094) and ɛdA (p < 0.0001) also correlated significantly with the stage of hepatic fibrosis. Furthermore, a significant correlation between the fibrosis stage and the grade of lobular inflammation (p < 0.0001) was observed. However, the amount of alcohol consumed did not correlate with any of the parameters determined. CONCLUSIONS: These data suggest an important role of CYP2E1 in the generation of εdA, in the fibrotic progression of ALD, and thus in alcohol-mediated hepatocarcinogenesis. CYP2E1 may be a target in the treatment of ALD and a potential prognostic marker for disease progression.

Chronic Ethanol Consumption and Generation of Etheno-DNA Adducts in Cancer-Prone Tissues.

Chronic ethanol consumption is a risk factor for several human cancers. A variety of mechanisms may contribute to this carcinogenic effect of alcohol including oxidative stress with the generation of reactive oxygen species (ROS), formed via inflammatory pathways or as byproducts of ethanol oxidation through cytochrome P4502E1 (CYP2E1). ROS may lead to lipidperoxidation (LPO) resulting in LPO-products such as 4-hydoxynonenal (4-HNE) or malondialdehyde. These compounds can react with DNA bases forming mutagenic and carcinogenic etheno-DNA adducts. Etheno-DNA adducts are generated in the liver (HepG2) cells over-expressing CYP2E1 when incubated with ethanol;and are inhibited by chlormethiazole. In liver biopsies etheno-DNA adducts correlated significantly with CYP2E1. Such a correlation was also found in the esophageal- and colorectal mucosa of alcoholics. Etheno-DNA adducts also increased in liver biopsies from patients with non alcoholic steatohepatitis (NASH). In various animal models with fatty liver either induced by high fat diets or genetically modified such as in the obese Zucker rat, CYP2E1 is induced and paralleled by high levels of etheno DNA-adducts which may be modified by additional alcohol administration. As elevation of adduct levels in NASH children were already detected at a young age, these lesions may contribute to hepatocellular cancer development later in life. Together these data strongly implicate CYP2E1 as an important mediator for etheno-DNA adduct formation, and this detrimental DNA damage may act as a driving force for malignant disease progression.

Possible Mechanisms of Ethanol-Mediated Colorectal Carcinogenesis: The Role of Cytochrome P4502E1, Etheno-DNA Adducts, and the Anti-Apoptotic Protein Mcl-1.

BACKGROUND: Chronic alcohol consumption is a risk factor for colorectal cancer. The mechanisms by which ethanol (EtOH) exerts its carcinogenic effect on the colorectal mucosa are not clear and may include oxidative stress with the action of reactive oxygen species (ROS) generated through EtOH metabolism via cytochrome P4502E1 (CYP2E1) leading to carcinogenic etheno-DNA adducts. ROS may also induce apoptosis. However, the effect of chronic EtOH consumption on CYP2E1, etheno-DNA adducts as well as anti-apoptotic proteins in the colorectal mucosa of heavy drinkers without colorectal inflammation is still not known. METHODS: Rectal biopsies from 32 alcoholics (>60 g EtOH/d) and from 12 controls (<20 g EtOH/d) were histologically examined, and immunohistochemistry for CYP2E1 and etheno-DNA adducts was performed. Apoptosis (cleaved PARP) as well as anti-apoptotic proteins including Bcl-xL , Bcl-2, and Mcl-1 were immunohistochemically determined. RESULTS: No significant difference in mucosal CYP2E1 or etheno-DNA adducts was observed between alcoholics and control patients. However, CYP2E1 and etheno-DNA adducts correlated significantly when both groups were combined (p < 0.001). In addition, although apoptosis was found not to be significantly affected by EtOH, the anti-apoptotic protein Mcl-1, but neither Bcl-xL nor Bcl-2, was found to be significantly increased in heavy drinkers as compared to controls (p = 0.014). CONCLUSIONS: Although colorectal CYP2E1 was not found to be significantly increased in alcoholics, CYP2E1 correlated overall with the level of etheno-DNA adducts in the colorectal mucosa, which identifies CYP2E1 as an important factor in colorectal carcinogenesis. Most importantly, however, is the up-regulation of the anti-apoptotic protein Mcl-1 in heavy drinkers counteracting apoptosis and possibly stimulating cancer development.

Lipid peroxidation and DNA adduct formation in lymphocytes of premenopausal women: Role of estrogen metabolites and fatty acid intake.

A diet high in linoleic acid (an ω-6 PUFA) increased the formation of miscoding etheno (ε)--DNA adducts in WBC-DNA of women, but not in men (Nair et al., Cancer Epidemiol Biomark Prev 1997;6:597-601). This gender specificity could result from an interaction between ω-6 PUFA intake and estrogen catabolism, via redox-cycling of 4-hydroxyestradiol (4-OH-E(2) ) and subsequent lipid peroxidation (LPO). In this study, we investigated whether in premenopausal women LPO-derived adducts in WBC-DNA are affected by serum concentration of 2- and 4-hydroxyestradiol metabolites and by fatty acid intake. DNA extracted from buffy coat and plasma samples, both blindly coded from healthy women (N = 124, median age 40 year) participating in the EPIC-Heidelberg cohort study were analyzed. Three LPO-derived exocyclic DNA adducts, εdA, εdC and M(1) dG were quantified by immuno-enriched (32) P-postlabelling and estradiol metabolites by ultra-sensitive GC-mass spectrometry. Mean M(1) dG levels in WBC-DNA were distinctly higher than those of εdA and εdC, and all were positively and significantly interrelated. Serum levels of 4-OH-E(2) , but not of 2-OH-E(2) , metabolites were positively related to etheno DNA adduct formation. Positive correlations existed between M(1) dG levels and linoleic acid intake or the ratios of dietary linoleic acid/oleic acid and PUFA/MUFA. Aerobic incubation of 4-OH-E(2) , arachidonic acid and calf thymus DNA yielded two to threefold higher etheno DNA adduct levels when compared with assays containing 2-OH-E(2) instead. In conclusion, this study is the first to compare M(1) dG and etheno-DNA adducts and serum estradiol metabolites in human samples in the same subjects. Our results support a novel mechanistic link between estradiol catabolism, dietary ω-6 fatty acid intake and LPO-induced DNA damage supported by an in vitro model. Similar studies in human breast epithelial tissue and on amplification of DNA-damage in breast cancer patients are in progress.

Identification of 3,N(4)-etheno-5-methyl-2'-deoxycytidine in human DNA: a new modified nucleoside which may perturb genome methylation.

Methylation of cytidine at dCpdG sequences regulates gene expression and is altered in many chronic inflammatory diseases. Inflammation generates lipid peroxidation (LPO) products which can react with deoxycytidine, deoxyadenosine, and deoxyguanosine in DNA to form pro-mutagenic exocyclic etheno-nucleoside residues. Since 5-methyl-2'-deoxycytidine (5mdC) residues exhibit increased nucleophilicity at N3, they should be even better targets for LPO products. We synthesized and characterized 3,N(4)-etheno-5-methyl-2'-deoxycytidine-3'-phosphate and showed that LPO products can indeed form the corresponding etheno-5mdC (ε5mdC) lesion in DNA in vitro. Our newly developed (32)P-postlabeling method was subsequently used to detect ε5mdC lesions in DNA from human white blood cells, lung, and liver at concentrations 4-10 times higher than that observed for etheno adducts on nonmethylated cytidine. Our new detection method can now be used to explore the hypothesis that this DNA lesion perturbs the DNA methylation status.

Ethanol-mediated carcinogenesis in the human esophagus implicates CYP2E1 induction and the generation of carcinogenic DNA-lesions.

Chronic alcohol consumption is a major risk factor for esophageal cancer. Various mechanisms may mediate carcinogenesis including the genotoxic effect of acetaldehyde and oxidative stress. Ethanol exerts its carcinogenic effect in the liver among others via the induction of cytochrome P450 2E1 (CYP2E1) and the generation of carcinogenic etheno-DNA adducts. Here we investigated if such effects can also be observed in the human esophagus. We studied nontumorous esophageal biopsies of 37 patients with upper aerodigestive tract cancer and alcohol consumption of 102.3 ± 131.4 g/day (range: 15-600 g) as well as 16 controls without tumors (12 teetotalers and 4 subjects with a maximum of 25 g ethanol/day). CYP2E1, etheno-DNA adducts and Ki67 as a marker for cell proliferation were determined immunohistologically. Chronic alcohol ingestion resulted in a significant induction of CYP2E1 (p = 0.015) which correlated with the amount of alcohol consumed (r = 0.6, p < 0.001). Furthermore, a significant correlation between CYP2E1 and the generation of the carcinogenic exocyclic etheno-DNA adducts 1,N(6)-ethenodeoxyadenosine (r = 0.93, p < 0.001) and 3,N(4)-ethenodeoxycytidine (r = 0.92, p < 0.001) was observed. Etheno-DNA adducts also correlated significantly with cell proliferation (p < 0.01), which was especially enhanced in patients who both drank and smoked (p < 0.001). Nonsmokers and nondrinkers had the lowest rate of cell proliferation, CYP2E1 expression and DNA lesions. Our data demonstrate for the first time an induction of CYP2E1 in the esophageal mucosa by ethanol in a dose dependent manner in man and may explain, at least in part, the generation of carcinogenic DNA lesions in this target organ.

Biomarkers for hazard identification in humans.

BACKGROUND: Oxidative stress enhances lipid peroxidation (LPO), which both are implicated in the promotion and progression stages of carcinogenesis, in particular under conditions of chronic inflammation and infections. Exocyclic etheno-DNA adducts, which are formed by LPO-products such as 4-hydroxy -2-nonenal, are strongly pro-mutagenic DNA lesions. METHODS: The development of ultra-sensitive detection methods for etheno-adducts in human tissues, white blood cells( WBC) and urine has provided evidence that these adducts are elevated in affected organs of cancer-prone patients, probably acting as a driving force to malignancy. RESULTS: Two recent studies that yielded some new insights into disease causation are briefly reviewed: DNA-damage in WBC of mother-newborn child pairs, and lipid peroxidation derived DNA damage in patients with cancer-prone liver diseases. Our results indicate that biomonitoring of etheno-DNA adducts in humans are promising tools (i) to better understand disease aetiopathogenesis, allowing hazard identification(ii) to monitor disease progression and (iii) to verify the efficacy of chemopreventive and therapeutic interventions. Such clinical trials are warranted.

Genetic polymorphisms of MPO, GSTT1, GSTM1, GSTP1, EPHX1 and NQO1 as risk factors of early-onset lung cancer.

Early-onset lung cancer diagnosed up to the age of 50 is a very rare disease, with an increasing incidence rate. Differences in aetiology, characteristics and epidemiology of early and older onset lung cancer have been described previously, suggesting the importance of genetic factors in early-onset lung cancer aetiology. A case-control study was conducted to investigate the effects of genetic polymorphisms in the MPO, EPHX1, GSTT1, GSTM1, GSTP1 and NQO1 genes on the risk of early-onset lung cancer development. Six hundred thirty-eight Caucasian patients under the age of 51 with confirmed primary lung cancer and 1,300 cancer free control individuals, matched by age and sex, were included in this analysis. Seventeen single nucleotide polymorphisms and two deletion polymorphisms were genotyped. No significant association was found for any of the analyzed polymorphisms and overall lung cancer risk. Nonsignificantly decreased risk of lung cancer was observed for carriers of 1 or 2 copies of GSTM1. Subgroup analysis revealed gender- and/or smoking-specific effects of EPHX1 rs2854455 (IV-1464C > T) and rs2234922 (His139Arg), GSTT1 deletion, GSTP1 rs1695 (Ile105Val), rs947895 (+991C > A) and rs4891 (Ser185Ser) and NQO1 rs1800566 (Pro187Ser) polymorphisms. However, none of the observed effects were confirmed by interaction tests nor were they significant after Bonferroni correction for multiple testing. In summary, our study suggested a modifying effect of polymorphisms in EPHX1, GSTP1, GSTT1, GSTM1 and NQO1 genes on the risk of early-onset lung cancer. To confirm these observations and to eliminate possible bias in our analyses, larger studies are warranted.

Ethanol-induced cytochrome P4502E1 causes carcinogenic etheno-DNA lesions in alcoholic liver disease.

UNLABELLED: Oxidative stress is thought to play a major role in the pathogenesis of hepatocellular cancer (HCC), a frequent complication of alcoholic liver disease (ALD). However, the underlying mechanisms are poorly understood. In hepatocytes of ALD patients, we recently detected by immunohistochemistry significantly increased levels of carcinogenic etheno-DNA adducts that are formed by the reaction of the major lipid peroxidation product, 4-hydroxynonenal (4-HNE) with nucleobases. In the current study, we show that protein-bound 4-HNE and etheno-DNA adducts both strongly correlate with cytochrome P450 2E1 (CYP2E1) expression in patients with ALD (r = 0.9, P < 0.01). Increased levels of etheno-DNA adducts were also detected in the liver of alcohol-fed lean (Fa/?) and obese (fa/fa) Zucker rats. The number of nuclei in hepatocytes stained positively for etheno-DNA adducts correlated significantly with CYP2E1 expression (r = 0.6, P = 0.03). To further assess the role of CYP2E1 in the formation of etheno-DNA adducts, HepG2 cells stably transfected with human CYP2E1 were exposed to ethanol with or without chlormethiazole (CMZ), a specific CYP2E1 inhibitor. Ethanol increased etheno-DNA adducts in the nuclei of CYP2E1-transfected HepG2 cells in a concentration-dependent and time-dependent manner, but not in vector mock-transfected control cells. CMZ blocked the generation of etheno-DNA adducts by 70%-90% (P < 0.01). CONCLUSION: Our data support the assumption that ethanol-mediated induction of hepatic CYP2E1 leading inter alia to highly miscoding lipid peroxidation-derived DNA lesions may play a central role in hepatocarcinogenesis in patients with ALD.

Accumulation of miscoding etheno-DNA adducts and highly expressed DNA repair during liver fluke-induced cholangiocarcinogenesis in hamsters.

Infection by Opisthorchis viverrini, a risk factor for cholangiocarcinoma (CCA) may act through chronic inflammation, oxidative stress and lipid peroxidation (LPO)-related damage and growth stimuli. 1,N6-etheno-2'-deoxyadenosine (epsilondA), and 3,N4-etheno-2'-deoxycytidine (epsilondC), markers for LPO-derived DNA damage were highly increased in white blood cell and urine of O. viverrini-infected Thai patients. In order to investigate tissue specificity etheno adducts were measured in a cholangiocarcinogenesis model, in O. viverrini-infected hamsters that had received N-nitrosodimethylamine (NDMA, 12.5 ppm in dw) for 2 months. epsilondA- and epsilondC-levels were analyzed in paraffin-embedded liver sections by a novel immunohistochemical method, from 21 up to 180 days post-O. viverrini-infection. In inflamed areas of the liver, etheno adducts were localized in the nuclei of inflammatory cells and in the epithelial lining of the bile duct. Semi-quantitative image analysis showed higher adduct levels in the liver of O. viverrini-infected hamsters, treated with or w/o NDMA when compared with untreated controls. Levels were found highest in the liver of O. viverrini-infected plus NDMA-treated hamsters. Adducts increased in an age-dependent manner from O. viverrini-infection until CCA development. Increased adduct formation paralleled histopathological changes in plasma alkaline phosphatase (ALP) activity, bile duct hyperplasia, dysplasia, precancerous lesions, and CCA appearance. Also elevated expression of alkyladenine DNA glycosylase (AAG), which excises 1,N6-ethenoadenine (epsilonA) was linked to higher adduct formation, suggesting imbalanced repair. Our results implicate accumulation of inflammation-related, promutagenic DNA damage in target tissue and possibly imbalanced repair in the onset of cholangiocarcinogenesis.

High urinary excretion of lipid peroxidation-derived DNA damage in patients with cancer-prone liver diseases.

Chronic inflammatory processes induce oxidative and nitrative stress that trigger lipid peroxidation (LPO), whereby DNA-reactive aldehydes such as trans-4-hydroxy-2-nonenal (HNE) are generated. Miscoding etheno-modified DNA adducts including 1,N(6)-etheno-2'-deoxyadenosine (epsilondA) are formed by reaction of HNE with DNA-bases which are excreted in urine, following elimination from tissue DNA. An ultrasensitive and specific immunoprecipitation/HPLC-fluorescence detection method was developed for quantifying epsilondA excreted in urine. Levels in urine of Thai and European liver disease-free subjects were in the range of 3-6 fmol epsilondA/micromol creatinine. Subjects with inflammatory cancer-prone liver diseases caused by viral infection or alcohol abuse excreted massively increased and highly variable epsilondA-levels. Groups of Thai subjects (N=21) with chronic hepatitis, liver cirrhosis, or hepatocellular carcinoma (HCC) due to HBV infection had 20, 73 and 39 times higher urinary epsilondA levels, respectively when compared to asymptomatic HBsAg carriers. In over two thirds of European patients (N=38) with HBV-, HCV- and alcohol-related liver disease, urinary epsilondA levels were increased 7-10-fold compared to healthy controls. Based on this pilot study we conclude: (i) high urinary epsilondA-levels, reflecting massive LPO-derived DNA damage in vivo may contribute to the development of HCC; (ii) epsilondA-measurements in urine and target tissues should thus be further explored as a putative risk marker to follow malignant progression of inflammatory liver diseases in affected patients; (iii) etheno adducts may serve as biomarkers to assess the efficacy of (chemo-)preventive and therapeutic interventions.

CYP450 polymorphisms as risk factors for early-onset lung cancer: gender-specific differences.

Cytochrome P450 (CYP) enzymes, involved in metabolism of tobacco carcinogens, are also involved in estrogen metabolism and many are regulated by estrogens. These genes may thus be of relevance to gender-specific differences in lung cancer risk, particularly in early-onset lung cancer, where a high proportion of women is observed. We conducted a case-control study to investigate genetic polymorphisms in cytochromes that might modify the risk of developing early-onset lung cancer. In total, 638 Caucasian patients under the age of 51 with primary lung cancer and 1300 cancer-free control individuals, matched by age and sex, were included in this analysis. Thirteen polymorphisms in the CYP1A1, CYP1B1, CYP2A13, CYP3A4 and CYP3A5 genes were analyzed. No significant association was found for any of the analyzed polymorphisms and lung cancer risk overall. However, among women, a significantly increased risk of early-onset lung cancer was observed for carriers of the minor allele of CYP1B1 SNP rs1056836 [odds ratio (OR) 1.97; 95% confidence interval (CI) 1.32-2.94; P < 0.001]. Also, a non-significant increase in lung cancer risk was observed in the group of women carriers of the minor allele of CYP2A13 SNP rs1709084 (OR 1.64; 95% CI 1.00-2.70; P = 0.05). The effect of these two polymorphisms was shown to be modified by smoking. Haplotype analysis was performed for CYP1B1 and CYP2A13. No differences between cases and controls were observed for both genes (P = 0.63 and P = 0.42 for CYP1B1 and CYP2A13, respectively). Our results suggest that the CYP1B1 and the CYP2A13 genotypes may contribute to individual susceptibility to early-onset lung cancer in women.

Accumulation of lipid peroxidation-derived DNA lesions in iron-overloaded thalassemic mouse livers: comparison with levels in the lymphocytes of thalassemia patients.

In thalassemia patients, iron overload can stimulate lipid peroxidation (LPO), thereby generating miscoding DNA adducts. Adducted DNA was measured in the lymphocytes of beta-Thal/Hb E patients and healthy controls and in the organs of thalassemic mice. epsilondA, epsilondC and M(1)dG residues were quantified by (32)P-postlabeling-TLC/HPLC. M(1)dG levels in lymphocyte DNA from patients were 4 times as high as in controls, while the increase in epsilondA and epsilondC was not significant. Adducted DNA accumulated in the liver of thalassemic mice having >2.7 mg Fe/g tissue dry weight; DNA adducts and iron were highly correlated. epsilondA was not specifically generated in certain mouse liver cell types as revealed by immunohistochemical staining. We found elevated LPO-induced DNA damage in the liver of thalassemic mouse and in lymphocytes, implicating that massive DNA damage occurs in the liver of thalassemia patients. We conclude that promutagenic LPO-derived DNA lesions are involved in the onset of hepatocellular carcinoma in these patients.

Polymorphisms in ABCG2, ABCC3 and CNT1 genes and their possible impact on chemotherapy outcome of lung cancer patients.

The prognosis of lung cancer patients treated with chemotherapy is poor, motivating the search for predictive factors. Single nucleotide polymorphisms (SNPs) in membrane transporter genes could influence the pharmacokinetics of cytostatic drugs and therefore affect treatment outcome. We examined 6 SNPs with known or suspected phenotypic effect: ABCG2 G34A, C421A; ABCC3 C-211T, G3890A, C3942T and CNT1 G565A. For 349 Caucasian patients with primary lung cancer [161 small cell lung cancer (SCLC), 187 nonsmall cell lung cancer (NSCLC) and 1 mixed] receiving first-line chemotherapy 3 different endpoints were analyzed: response after the 2nd cycle (R), progression-free survival (PFS) and overall survival (OS). The prognostic value of the SNPs was analyzed using multivariable logistic regression, calculating odds ratios (ORs) when comparing genotype frequencies in responders and nonresponders after the 2nd cycle. Hazard ratios (HRs) for PFS and for OS were calculated using Cox regression methods. In all lung cancer patients, none of the investigated polymorphisms modified response statistically significant. The only significant result in the histological subpopulations was in SCLC patients carrying the ABCC3 -211T allele who showed significantly worsened PFS (HR: 1.79; 95% confidence interval (CI) 1.13-2.82). In an exploratory subgroup analysis significantly worse OS was seen for carriers of the ABCG2 421A-allele treated with platinum-based drugs (HR: 1.60; 95% CI 1.04-2.47; n = 256). In conclusion, this study prioritizes ABCC3 C-211T and ABCG2 C421A as candidate transporter SNPs to be further investigated as possible predictors of the clinical outcome of chemotherapy in lung cancer patients.

A distinct ERCC1 haplotype is associated with mRNA expression levels in prostate cancer patients.

Both genetic variants and messenger RNA (mRNA) expression of DNA repair and tumor suppressor genes have been investigated as molecular markers for therapy outcome. However, the phenotypic impact of genetic variants often remained unclear, thus the rationale of their use in risk prediction may be limited. We therefore analyzed genetic variants together with anthropometric and lifestyle factors to see how these affect mRNA levels of ERCC1, MDM2 and TP53 in primary blood lymphocytes. mRNA expression was measured in 376 prostate cancer patients by quantitative real-time polymerase chain reaction after reverse transcription, and ERCC1 rs11615 T>C, ERCC1 rs3212986 C>A, MDM2 rs2279744 T>G and TP53 rs17878362 (p53PIN3) polymorphisms were determined. Considerable interindividual differences in mRNA expression were found (coefficients of variation: ERCC1, 45%; MDM2, 43% and TP53, 35%). ERCC1 expression was positively correlated with plasma levels of beta-carotene (P = 0.03) and negatively correlated with canthaxanthin (P = 0.02) and lutein (P = 0.02). Overall, the polymorphisms affected mRNA expression only weakly. Carriers of a distinct ERCC1 haplotype (CC) showed, however, significantly lower expression values than non-carriers (P = 0.001). Applying logistic regression, we found that CC haplotype carriers had a 1.69-fold increased odds ratio (95% confidence interval: 1.06-2.71) for reduced ERCC1 mRNA levels. This low ERCC1 expression might be associated with reduced DNA repair and better therapy response. In summary, the association we have found between ERCC1 genotype and mRNA expression supports recent clinical observations that genetic variation in ERCC1 can affect treatment outcome and prognosis. Our study further revealed a modulating effect by nutritional factors.

Increased urinary 1,N6-ethenodeoxyadenosine and 3,N4-ethenodeoxycytidine excretion in thalassemia patients: markers for lipid peroxidation-induced DNA damage.

Thalassemic diseases including homozygous beta-thalassemia and beta-thalassemia/Hb E (beta-Thal/Hb E) are prevalent in Southeast Asia. Iron overload is a common complication in beta-thalassemia patients which induces intracellular oxidative stress and lipid peroxidation (LPO). LPO end products generate miscoding etheno adducts in DNA which after their repair are excreted in urine. We investigated whether urinary levels of 1,N6-ethenodeoxyadenosine (epsilondA) and 3,N4-ethenodeoxycytidine (epsilondC) can serve as putative cancer risk markers in beta-Thal/Hb E patients. epsilondA and epsilondC levels were assayed in collected urine samples by immunoprecipitation-HPLC-fluorescence and 32P-postlabeling TLC, respectively. Mean epsilondA (fmol/micromol creatinine) levels in urine of beta-Thal/Hb E patients ranged from 4.8 to 120.4 (33.8+/-3.9; n=37) and were 8.7 times higher compared to asymptomatic controls (1.4-13.8; 3.9+/-0.8; n=20). The respective epsilondC levels ranged from 0.15 to 32.5 (5.2+/-1.3; n=37) and were increased some 13 times over controls (0.04-1.2; 0.4+/-0.7; n=20). epsilondC levels were correlated positively with NTBI (r=0.517; P=0.002), whereas epsilondA showed only a trend (r=0.257; P=0.124). We conclude that the strongly increased urinary excretion of etheno adducts indicates elevated LPO-induced DNA damage in internal organs such as the liver. These highly promutagenic lesions may contribute to the increased risk of thalassemia patients to develop hepatocellular carcinoma.

High excretion of etheno adducts in liver fluke-infected patients: protection by praziquantel against DNA damage.

Chronic infection by Opisthorchis viverrini (OV) is a strong risk factor for developing cholangiocarcinoma (CCA). To clarify the involvement of oxidative stress and lipid peroxidation (LPO)-derived DNA damage, the excretion of LPO-derived etheno DNA adducts was measured in urine samples collected from healthy volunteers and OV-infected Thai subjects. 1,N(6)-etheno-2'-deoxyadenosine (epsilondA) and 3,N(4)-etheno-2'-deoxycytidine (epsilondC) levels were quantified by immunoprecipitation/high-performance liquid chromatography/fluorescence detection and (32)P-postlabeling TLC. Excreted etheno adduct levels were related to indicators of inflammatory conditions [malondialdehyde (MDA) and nitrate/nitrite levels in urine and plasma alkaline phosphatase (ALP) activity]. Mean epsilondA and epsilondC levels were 3 to 4 times higher in urine of OV-infected patients; MDA, nitrate/nitrite, and ALP were also increased up to 2-fold. MDA and ALP were positively related to epsilondA excretion. Two months after a single dose of the antiparasitic drug Praziquantel, epsilondA and epsilondC concentrations in urine of OV-infected subjects were decreased; MDA, nitrate/nitrite, and ALP were concomitantly lowered. We conclude that chronic OV infection through oxidative/nitrative stress leads to increased urinary excretion of the etheno-bridged deoxyribonucleosides, reflecting high LPO-derived DNA damage in vivo. These promutagenic DNA etheno adducts in bile duct epithelial cells may increase the risk of OV-infected patients to later develop CCA. Urinary epsilondA and epsilondC levels should be explored (a) as noninvasive risk markers for developing opisthorchiasis-related CCA and (b) as promising biomarkers to assess the efficacy of preventive and therapeutic interventions.

In vitro radiation-induced expression of XPC mRNA as a possible biomarker for developing adverse reactions during radiotherapy.

Repair of radiation-induced DNA damage is believed to play a critical role in developing adverse reactions during radiotherapy. Ionizing radiation induces transcription of several DNA repair genes including XPC as a part of the p53-transmitted stress response. XPC gene induction was measured to analyze whether it predicts occurrence of therapy-related acute side effects. Prostate cancer patients (n = 406) receiving radiotherapy were monitored for development of acute adverse effects using common toxicity criteria. For gene induction analysis, lymphocytes from 99 patients were selected according to their observed grade of clinical side effects. Cells were irradiated in vitro with 5 Gy and analyzed after 4 hr for XPC gene induction using reverse transcription and quantitative real-time PCR. Analysis of modulation of XPC induction by personal, clinical or lifestyle factors was included. Inter-individual induction of XPC expression by ionizing radiation varied up to 20-fold (0.29-5.77) and was significantly higher in current or exsmokers than in never-smokers (p value: 0.008). Patients with XPC induction above the 90th percentile compared to those with lower induction levels were at increased risk of suffering from adverse reactions during radiotherapy (odds ratio 5.3, 95% confidence interval 1.2-24.5; adjusted for smoking). In summary, XPC mRNA levels induced by ionizing radiation were shown for the first time to be strongly affected by smoking and to be associated with an approximately 5-fold increased risk for developing acute side effects of radiotherapy. The predictive value of DNA damage-induced XPC levels as a possible biomarker for radiosensitivity has to be further investigated.

Lipid peroxidation-induced DNA damage in cancer-prone inflammatory diseases: a review of published adduct types and levels in humans.

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