ECNIS Repository

Revised assignment of absolute configuration of the cis- and trans-N6-deoxyadenosine adducts at C14 of (+/-)-11beta,12alpha-dihydroxy-13alpha,14alpha-epoxy-11,12,13,14-tetrahydrodibenzo[a,l]pyrene by stereoselective synthesis.

Fri, 28 Nov 2008 22:58:59 GMT

Title: Revised assignment of absolute configuration of the cis- and trans-N6-deoxyadenosine adducts at C14 of (+/-)-11beta,12alpha-dihydroxy-13alpha,14alpha-epoxy-11,12,13,14-tetrahydrodibenzo[a,l]pyrene by stereoselective synthesis.

Authors: Yagi, Haruhiko; Frank, Heinrich; Seidel, Albrecht; Jerina, Donald M.

Abstract: We have reassigned relative and absolute configurations by unambiguous stereoselective syntheses of the cis- (13s and 13R) and trans-N6-deoxyadenosine (dAdo) adduct diastereomers (14S and 14R) derived from (+/-)-11beta,12alpha-dihydroxy-13alpha,14alpha-epoxy-11,12,13,14-tetrahydrodibenzo[a,l]pyrene (DB[a,l]P DE-2), previously reported by Li et al. [(1999) Chem. Res. Toxicol. 12, 758-767]. Two stereoselective methods, asymmetric aminohydroxylation of the (+/-)-trans-11,12-dihydrodiol (3) with 3',5'-di-O-(tert -butyldimethylsilyl)-2'-deoxyadenosine (4) and the highly stereoselective cis addition of 4 to (+/-)-DB[a,l]P DE-2 in hexafluoropropan-2-ol (HFP), were employed. Both afforded a 1:1 mixture of the cis-N6-dAdo adduct diastereomers, which were separated as triacetates (5S and 5R) in comparable yields (approximately 80%). The corresponding trans adduct diastereomers (10S and 10R) were obtained by coupling the aminotriol derived from trans opening of (+/-)-DB[a,l]P DE-2 with 6-fluoro-(2'-deoxy-3,5-di-tert-butyldimethylsilyloxy-beta-D-erythro-pentafuranosyl)purine (9) and subsequent acetylation in approximately 70% yield. The cis-5S and -5R and trans-10S and -10R were separately treated with 7% HF-pyridine followed by ammonolysis in NH3-saturated MeOH to give the dAdo adducts with all hydroxyl groups free (13S, 13R, 14S, and 14R). Comparison of the 1H NMR and CD spectra of these presently synthesized dAdo adducts with spectra of the previously reported compounds revealed that the interpretation of the 1H NMR and CD spectra and assignment of the relative stereochemistry (cis/trans) and absolute configuration made by Li et al. were at variance with our results. The above highly stereoselective syntheses of (+/-)-DB[a,l]P DE-2 adducted dAdo derivatives enabled efficient preparation of each of the four possible stereoisomeric 5'-dimethoxytrityl-3'-phosphoramidites for use in oligonucleotide synthesis.

A technical mixture of 2,2',4,4'-tetrabromo diphenyl ether (BDE47) and brominated furans triggers aryl hydrocarbon receptor (AhR) mediated gene expression and toxicity.

Fri, 29 Aug 2008 22:58:59 GMT

Title: A technical mixture of 2,2',4,4'-tetrabromo diphenyl ether (BDE47) and brominated furans triggers aryl hydrocarbon receptor (AhR) mediated gene expression and toxicity.

Authors: Wahl, M.; Lahni, B.; Guenther, R.; Kuch, B.; Yang, L.; Straehle, U.; Strack, S.; Weiss, C.

Abstract: Polybrominated diphenyl ethers (PBDE) are found as ubiquitous contaminants in the environment, e.g., in sediments and biota as well as in human blood samples and mother's milk. PBDEs are neuro- and developmental toxins, disturb the endocrine system and some are even carcinogenic. Structural similarities of PBDEs with dioxin-like compounds, e.g., 2,3,7,8-tetrachloro-dibenzodioxin (TCDD), have raised concern about a possible "dioxin-like" action of PBDEs. TCDD exerts its toxicity via binding to and activation of the aryl hydrocarbon receptor (AhR). AhR ligands are in contrast to PBDEs usually coplanar compounds. Thus, PBDEs are not likely to be strong AhR agonists. The aim of this study was to analyze the effects of the most abundant PBDE congener, 2,2',4,4'-tetrabromo diphenyl ether (BDE47), on AhR activity and signaling. Initially, we measured cytochrome P450 1A1 (Cyp1A1) induction as a readout for AhR activation by BDE47. Low grade purified BDE47 increased CYP1A1 levels in transformed and primary rat hepatocytes and human hepatoma cells. Chemical analysis of the BDE47 sample identified trace contaminations with brominated furans such as 2,3,7,8-tetrabromo dibenzodioxin (TBDF), which most likely were responsible for the observed activation of AhR. Subsequently, the BDE47 mixture was studied for its effect on AhR mediated toxicity and global gene expression. Indeed, in rat hepatoma cells and in zebrafish embryos the BDE47 mixture provoked changes in gene expression and toxicity similar to known AhR agonists. In addition to the dioxin-like actions, the BDE47 sample enhanced Cyp2B and Cyp3A expression suggesting that commercial PBDE mixtures, which also often contain brominated furans, may disturb cellular homeostasis at multiple levels.

Guidelines to evaluate human observational studies for quantitative risk assessment.

Fri, 28 Nov 2008 22:58:59 GMT

Title: Guidelines to evaluate human observational studies for quantitative risk assessment.

Authors: Vlaanderen, Jelle; Vermeulen, Roel; Heederik, Dick; Kromhout, Hans

Abstract: BACKGROUND: Careful evaluation of the quality of human observational studies (HOS) is required to assess the suitability of HOS for quantitative risk assessment (QRA). In particular, the quality of quantitative exposure assessment is a crucial aspect of HOS to be considered for QRA. OBJECTIVE: We aimed to develop guidelines for the evaluation of HOS for QRA and to apply these guidelines to case-control and cohort studies on the relation between exposure to benzene and acute myeloid leukemia (AML). METHODS: We developed a three-tiered framework specific for the evaluation of HOS for QRA and used it to evaluate HOS on the relation between exposure to benzene and AML. RESULTS: The developed framework consists of 20 evaluation criteria. A specific focus of the framework was on the quality of exposure assessment applied in HOS. Seven HOS on the relation of benzene and AML were eligible for evaluation. Of these studies, five were suitable for QRA and were ranked based on the quality of the study design, conduct, and reporting on the study. CONCLUSION: The developed guidelines facilitate a structured evaluation that is transparent in its application and harmonizes the evaluation of HOS for QRA. With the application of the guidelines, it was possible to identify studies suitable for QRA of benzene and AML and rank these studies based on their quality. Application of the guidelines in QRA will be a valuable addition to the assessment of the weight of evidence of HOS for QRA.

A field synopsis on low-penetrance variants in DNA repair genes and cancer susceptibility.

Tue, 06 Jan 2009 22:58:59 GMT

Title: A field synopsis on low-penetrance variants in DNA repair genes and cancer susceptibility.

Authors: Vineis, Paolo; Manuguerra, Maurizio; Kavvoura, Fotini K.; Guarrera, Simonetta; Allione, Alessandra; Rosa, Fabio; Di Gregorio, Alessandra; Polidoro, Silvia; Saletta, Federica; Ioannidis, John P.A; Matullo, Giuseppe

Abstract: BACKGROUND: Several genes encoding for DNA repair molecules implicated in maintaining genomic integrity have been proposed as cancer-susceptibility genes. Although efforts have been made to create synopses for specific fields that summarize the data from genetic association studies, such an overview is not available for genes involved in DNA repair. METHODS: We have created a regularly updated database of studies addressing associations between DNA repair gene variants (excluding highly penetrant mutations) and different types of cancer. Using 1087 datasets and publicly available data from genome-wide association platforms, meta-analyses using dominant and recessive models were performed on 241 associations between individual variants and specific cancer types that had been tested in two or more independent studies. The epidemiological strength of each association was graded with Venice criteria that assess amount of evidence, replication, and protection from bias. All statistical tests were two-sided. RESULTS: Thirty-one nominally statistically significant (ie, P < .05 without adjustment for multiple comparisons) associations were recorded for 16 genes in dominant and/or recessive model analyses (BRCA2, CCND1, ERCC1, ERCC2, ERCC4, ERCC5, MGMT, NBN, PARP1, POLI, TP53, XPA, XRCC1, XRCC2, XRCC3, and XRCC4). XRCC1, XRCC2, TP53, and ERCC2 variants were each nominally associated with several types of cancer. Three associations were graded as having "strong" credibility, another four had modest credibility, and 24 had weak credibility based on Venice criteria. Requiring more stringent P values to account for multiplicity of comparisons, only the associations of ERCC2 codon 751 (recessive model) and of XRCC1 -77 T>C (dominant model) with lung cancer had P

Expectations and challenges stemming from genome-wide association studies.

Wed, 29 Oct 2008 22:58:59 GMT

Title: Expectations and challenges stemming from genome-wide association studies.

Authors: Vineis, Paolo; Brennan, Paul; Canzian, Federico; Ioannidis, John P.A; Matullo, Giuseppe; Ritchie, Marylyn; Stromberg, Ulf; Taioli, Emanuela; Thompson, John

Abstract: There are considerable expectations about the ability of genome-wide association (GWA) studies to make exciting discoveries about the role of genes in common diseases. GWA studies may allow researchers to identify causal pathways that have not been unveiled before, thus opening new avenues to disease understanding, prevention and therapy. However, there are still many open challenges. One is how to analyse these studies. The problem of false positives and false negatives provides an interesting methodological stimulus to find optimal solutions. Once main genetic effects have been concretely documented, the next question is how to proceed with the investigation of gene-gene and gene-environment interactions. It is possible that what really counts is not the main effect of genes but complex interactions. Finding and interpreting such interactions is not straightforward. Finally, continuous updated integration of all evidence, from both old studies, current GWA investigations and future replication studies, and careful interpretation of the strength of the evidence are crucial to maximize transparency and lead to informative selection of the next steps of research in this field. The present Commentary is a report of an Environmental Cancer Risk, Nutrition and Individual Susceptibility network Workshop held in Venice in October 2007 and discusses some of the problems outlined above, with examples.

Beta-carotene metabolites enhance inflammation-induced oxidative DNA damage in lung epithelial cells.

Wed, 14 Jan 2009 22:58:59 GMT

Title: Beta-carotene metabolites enhance inflammation-induced oxidative DNA damage in lung epithelial cells.

Authors: van Helden, Yvonne G.J.; Keijer, Jaap; Knaapen, Ad M.; Heil, Sandra G.; Briede, Jacob J.; Van Schooten, Frederik J.; Godschalk, Roger W.L.

Abstract: beta-Carotene (BC) intake has been shown to enhance lung cancer risk in smokers and asbestos-exposed subjects (according to the ATBC and CARET studies), but the mechanism behind this procarcinogenic effect of BC is unclear. Both smoking and asbestos exposure induce an influx of inflammatory neutrophils into the airways, which results in an increased production of reactive oxygen species and formation of promutagenic DNA lesions. Therefore, the aim of our study was to investigate the effects of BC and its metabolites (BCM) on neutrophil-induced genotoxicity. We observed that the BCM vitamin A (Vit A) and retinoic acid (RA) inhibited the H(2)O(2)-utilizing enzyme myeloperoxidase (MPO), which is released by neutrophils, thereby reducing H(2)O(2) conversion. Moreover, BC and BCM were able to increase (.)OH formation from H(2)O(2) in the Fenton reaction (determined by electron spin resonance spectroscopy). Addition of Vit A and RA to lung epithelial cells that were co-incubated with activated neutrophils resulted in a significant increase in the level of oxidized purines assessed by the formamidopyrimidine DNA glycosylase-modified comet assay. These data indicate that BCM can enhance neutrophil-induced genotoxicity by inhibition of MPO in combination with subsequent increased formation of hydroxyl radicals.

Determination of 8-oxo-2'-deoxyguanosine and creatinine in murine and human urine by liquid chromatography/tandem mass spectrometry: application to chemoprevention studies.

Mon, 29 Dec 2008 22:58:59 GMT

Title: Determination of 8-oxo-2'-deoxyguanosine and creatinine in murine and human urine by liquid chromatography/tandem mass spectrometry: application to chemoprevention studies.

Authors: Teichert, Friederike; Verschoyle, Richard D.; Greaves, Peter; Thorpe, James F.; Mellon, J. Kilian; Steward, William P.; Farmer, Peter B.; Gescher, Andreas J.; Singh, Rajinder

Abstract: Urinary 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) represents a non-invasive biomarker for oxidative stress and may be useful for monitoring chemotherapeutic and chemopreventive interventions associated with cancer-related alterations in oxidative stress. We describe the development and validation of two separate liquid chromatography/tandem mass spectrometry (LC/MS/MS) selected reaction monitoring (SRM) methods for the determination of 8-oxodG and creatinine in both murine and human urine using stable isotope labelled internal standards. Levels of 8-oxodG were normalised to creatinine. The LC/MS/MS methods were applied to two chemoprevention studies utilising tea polyphenols in humans and TRAMP (TRansgenic Adenocarcinoma of the Mouse Prostate) mice. Patients with benign prostatic hyperplasia received 1 g/day of green tea polyphenols (GTP), 1 g/day of black tea theaflavins (BTT) or no treatment for 4 weeks. TRAMP mice received GTP (0.05% in drinking water) for 4 or 25 weeks. Prostate pathology in TRAMP mice was not affected by GTP. Levels of 8-oxodG were not altered by tea polyphenols in either mice or humans. In TRAMP mice, urinary 8-oxodG levels were elevated with increasing age (p < 0.0001) but not changed by the presence of prostate tumours. In conclusion, the LC/MS/MS SRM methods described here are ideally suited for the accurate determination of 8-oxodG and creatinine in urine samples from both clinical and pre-clinical studies.

Anticarcinogenic compounds of olive oil and related biomarkers.

Mon, 28 Apr 2008 22:58:59 GMT

Title: Anticarcinogenic compounds of olive oil and related biomarkers.

Authors: Sotiroudis, Theodore G.; Kyrtopoulos, Soterios A.

Abstract: Olive oil, one of the oldest vegetable oils consumed without any refining, is associated with a reduced risk of a number of common cancers. Minor constituents of virgin olive oil have been suggested to be among the major chemopreventive components. A brief overview is presented of recent findings concerning the bioavailability of certain important olive oil minor components including efficient antioxidant polyphenols, the triterpene hydrocarbon squalene and beta-sitosterol, considered as putative nutritional biomarkers, in relation to the incidence of cancer.

Cytotoxicity and gene expression profiling of two hydroxylated polybrominated diphenyl ethers in human H295R adrenocortical carcinoma cells.

Tue, 24 Feb 2009 22:58:59 GMT

Title: Cytotoxicity and gene expression profiling of two hydroxylated polybrominated diphenyl ethers in human H295R adrenocortical carcinoma cells.

Authors: Song, Renfang; Duarte, Tiago L.; Almeida, Gabriela M.; Farmer, Peter B.; Cooke, Marcus S.; Zhang, Wenbing; Sheng, Guoying; Fu, Jiamo; Jones, George D.D.

Abstract: Polybrominated diphenyl ethers (PBDEs) are commonly used as flame retardants in a variety of commercial and household products. They have been detected in the environment and accumulate in mammalian tissues and fluids. PBDE toxicity is thought to be associated with endocrine disruption, developmental neurotoxicity and changes in fetal development. Although humans are exposed to PBDEs, our knowledge of the effects of PBDE metabolites on human cells with respect to health risk is insufficient. Two hydroxylated PBDEs (OH-PBDEs), 2-OH-BDE47 and 2-OH-BDE85, were investigated for their effects on cell viability/proliferation, DNA damage, cell cycle distribution and gene expression profiling in H295R adrenocortical carcinoma cells. We show that the two agents are cytotoxic in a dose-dependent manner only at micromolar concentrations, with 2-OH-BDE85 being more toxic than 2-OH-BDE47. However, no DNA damage was observed for either chemical, suggesting that the biological effects of OH-PBDEs occur primarily via non-genotoxic routes. Furthermore, no evidence of aryl hydrocarbon receptor (AHR)-mediated, dioxin-like toxicity was observed. Instead, we report that a micromolar concentration of OH-PBDEs induces transcriptional changes associated with endoplasmic reticulum stress and the unfolded protein response. We discuss whether OH-PBDE bioaccumulation could result in impairment of the adrenocortical secretory function.

Repair of UV dimers in skin DNA of patients with basal cell carcinoma.

Fri, 29 Aug 2008 22:58:59 GMT

Title: Repair of UV dimers in skin DNA of patients with basal cell carcinoma.

Authors: Segerback, Dan; Strozyk, Malgorzata; Snellman, Erna; Hemminki, Kari

Abstract: Epidemiologic studies suggest that exposure to sunlight is the primary etiologic agent for basal cell carcinoma. Formation of UV-induced DNA damage is believed to be a crucial event in the process leading to skin cancer. In this study, repair of photoproducts in DNA was followed in the skin of patients with basal cell carcinoma and control subjects. The subjects were exposed to 800 J/m(2) Commission Internationale de 1'Eclairag of solar-simulating radiation on buttock skin. Biopsies were taken at 0 hour, 24 hours, and 3 weeks after the exposure. Two cyclobutane pyrimidine dimers, TT=C and TT=T, were measured using a sensitive (32)P-postlabeling assay. Initial levels of both TT=C and TT=T differed between individuals in both groups. The levels of TT=T in patients with basal cell carcinoma and controls were similar (9.9 +/- 4.0 and 9.2 +/- 2.9 products per 10(6) normal nucleotides), whereas the level of TT=C was significantly lower in controls than in patients with basal cell carcinoma (6.2 +/- 3.1 versus 10.9 +/- 4.5 products per 10(6) normal nucleotides). The fractions of TT=T remaining after 24 hours and 3 weeks were significantly higher in patients with basal cell carcinoma (72% and 11%) compared with controls (48% and 5%). A slower removal in patients with basal cell carcinoma than in controls was indicated also for TT=C (52% versus 42% remaining at 24 hours); however, the difference between groups was not significant. When including data from our previously reported small-scale study, the fraction of dimers remaining at 24 hours was significantly higher in patients with basal cell carcinoma for both TT=C and TT=T. The data suggest that patients with basal cell carcinoma have a reduced capacity to repair UV-induced DNA lesions.