A case-control study of smoking and bladder cancer risk: emergent patterns over time

BACKGROUND

Cigarette smoking is a well-established risk factor for bladder cancer. The effects of smoking duration, intensity (cigarettes per day), and total exposure (pack-years); smoking cessation; exposure to environmental tobacco smoke; and changes in the composition of tobacco and cigarette design over time on risk of bladder cancer are unclear.

METHODS

We examined bladder cancer risk in relation to smoking practices based on interview data from a large, population-based case-control study conducted in Maine, New Hampshire, and Vermont from 2001 to 2004 (N = 1170 urothelial carcinoma case patients and 1413 control subjects). We calculated odds ratios (ORs) and 95% confidence intervals (CIs) using unconditional logistic regression. To examine changes in smoking-induced bladder cancer risk over time, we compared odds ratios from New Hampshire residents in this study (305 case patients and 335 control subjects) with those from two case-control studies conducted in New Hampshire in 1994-1998 and in 1998-2001 (843 case patients and 1183 control subjects).

RESULTS

Regular and current cigarette smokers had higher risks of bladder cancer than never-smokers (for regular smokers, OR = 3.0, 95% CI = 2.4 to 3.6; for current smokers, OR = 5.2, 95% CI = 4.0 to 6.6). In New Hampshire, there was a statistically significant increasing trend in smoking-related bladder cancer risk over three consecutive periods (1994-1998, 1998-2001, and 2002-2004) among former smokers (OR = 1.4, 95% CI = 1.0 to 2.0; OR = 2.0, 95% CI = 1.4 to 2.9; and OR = 2.6, 95% CI = 1.7 to 4.0, respectively) and current smokers (OR = 2.9, 95% CI = 2.0 to 4.2; OR = 4.2, 95% CI = 2.8 to 6.3; OR = 5.5, 95% CI = 3.5 to 8.9, respectively) (P for homogeneity of trends over time periods = .04). We also observed that within categories of intensity, odds ratios increased approximately linearly with increasing pack-years smoked, but the slope of the increasing trend declined with increasing intensity.

CONCLUSIONS

Smoking-related risks of bladder cancer appear to have increased in New Hampshire since the mid-1990s. Based on our modeling of pack-years and intensity, smoking fewer cigarettes over a long time appears more harmful than smoking more cigarettes over a shorter time, for equal total pack-years of cigarettes smoked.

Lung cancer in a U.S. population with low to moderate arsenic exposure

BACKGROUND

Little is known about the carcinogenic potential of arsenic in areas with low to moderate concentrations of arsenic (< 100 microg/L) in drinking water.

OBJECTIVES

We examined associations between arsenic and lung cancer.

METHODS

A population-based case-control study of primary incident lung cancer was conducted in 10 counties in two U.S. states, New Hampshire and Vermont. The study included 223 lung cancer cases and 238 controls, each of whom provided toenail clippings for arsenic exposure measurement by inductively coupled-plasma mass spectrometry. We estimated odds ratios (ORs) of the association between arsenic exposure and lung cancer using unconditional logistic regression with adjustment for potential confounders (age, sex, race/ethnicity, smoking pack-years, education, body mass index, fish servings per week, and toenail selenium level).

RESULTS

Arsenic exposure was associated with small-cell and squamous-cell carcinoma of the lung [OR = 2.75; 95% confidence interval (CI), 1.00-7.57] for toenail arsenic concentration > or = 0.114 microg/g, versus < 0.05 microg/g. A history of lung disease (bronchitis, chronic obstructive pulmonary disease, or fibrosis) was positively associated with lung cancer (OR = 2.86; 95% CI, 1.39-5.91). We also observed an elevated risk of lung cancer among participants with a history of lung disease and toenail arsenic > or = 0.05 microg/g (OR = 4.78; 95% CI, 1.87-12.2) than among individuals with low toenail arsenic and no history of lung disease.

CONCLUSION

Although this study supports the possibility of an increased risk of specific lung cancer histologic types at lower levels of arsenic exposure, we recommend large-scale population-based studies.

Polymorphisms in DNA repair genes, smoking, and bladder cancer risk: findings from the international consortium of bladder cancer

Tobacco smoking is the most important and well-established bladder cancer risk factor and a rich source of chemical carcinogens and reactive oxygen species that can induce damage to DNA in urothelial cells. Therefore, common variation in DNA repair genes might modify bladder cancer risk. In this study, we present results from meta-analyses and pooled analyses conducted as part of the International Consortium of Bladder Cancer. We included data on 10 single nucleotide polymorphisms corresponding to seven DNA repair genes from 13 studies. Pooled analyses and meta-analyses included 5,282 cases and 5,954 controls of non-Latino white origin. We found evidence for weak but consistent associations with ERCC2 D312N [rs1799793; per-allele odds ratio (OR), 1.10; 95% confidence interval (95% CI), 1.01-1.19; P = 0.021], NBN E185Q (rs1805794; per-allele OR, 1.09; 95% CI, 1.01-1.18; P = 0.028), and XPC A499V (rs2228000; per-allele OR, 1.10; 95% CI, 1.00-1.21; P = 0.044). The association with NBN E185Q was limited to ever smokers (interaction P = 0.002) and was strongest for the highest levels of smoking dose and smoking duration. Overall, our study provides the strongest evidence to date for a role of common variants in DNA repair genes in bladder carcinogenesis.

A computationally efficient hypothesis testing method for epistasis analysis using multifactor dimensionality reduction

Multifactor dimensionality reduction (MDR) was developed as a nonparametric and model-free data mining method for detecting, characterizing, and interpreting epistasis in the absence of significant main effects in genetic and epidemiologic studies of complex traits such as disease susceptibility. The goal of MDR is to change the representation of the data using a constructive induction algorithm to make nonadditive interactions easier to detect using any classification method such as naïve Bayes or logistic regression. Traditionally, MDR constructed variables have been evaluated with a naïve Bayes classifier that is combined with 10-fold cross validation to obtain an estimate of predictive accuracy or generalizability of epistasis models. Traditionally, we have used permutation testing to statistically evaluate the significance of models obtained through MDR. The advantage of permutation testing is that it controls for false positives due to multiple testing. The disadvantage is that permutation testing is computationally expensive. This is an important issue that arises in the context of detecting epistasis on a genome-wide scale. The goal of the present study was to develop and evaluate several alternatives to large-scale permutation testing for assessing the statistical significance of MDR models. Using data simulated from 70 different epistasis models, we compared the power and type I error rate of MDR using a 1,000-fold permutation test with hypothesis testing using an extreme value distribution (EVD). We find that this new hypothesis testing method provides a reasonable alternative to the computationally expensive 1,000-fold permutation test and is 50 times faster. We then demonstrate this new method by applying it to a genetic epidemiology study of bladder cancer susceptibility that was previously analyzed using MDR and assessed using a 1,000-fold permutation test.

Ecogeographic genetic epidemiology

Complex diseases such as cancer and heart disease result from interactions between an individual's genetics and environment, i.e. their human ecology. Rates of complex diseases have consistently demonstrated geographic patterns of incidence, or spatial "clusters" of increased incidence relative to the general population. Likewise, genetic subpopulations and environmental influences are not evenly distributed across space. Merging appropriate methods from genetic epidemiology, ecology and geography will provide a more complete understanding of the spatial interactions between genetics and environment that result in spatial patterning of disease rates. Geographic information systems (GIS), which are tools designed specifically for dealing with geographic data and performing spatial analyses to determine their relationship, are key to this kind of data integration. Here the authors introduce a new interdisciplinary paradigm, ecogeographic genetic epidemiology, which uses GIS and spatial statistical analyses to layer genetic subpopulation and environmental data with disease rates and thereby discern the complex gene-environment interactions which result in spatial patterns of incidence.

Arsenic activates EGFR pathway signaling in the lung

Arsenic is an established lung carcinogen, however, the carcinogenic mechanisms are currently under investigation. Phosphorylation of the epidermal growth factor receptor (EGFR) has been reported with arsenic exposure in bladder cells. EGFR is a tyrosine kinase transmembrane receptor that regulates important processes in carcinogenesis, including cell survival, cell cycle progression, tumor invasion, and angiogenesis. We investigated the mechanisms of EGFR pathway activation by levels of arsenic relevant to human exposure scenarios both in vitro using cultured lung epithelial cells, and in lung tumors samples from New England Lung Cancer Study participants. Toenail arsenic levels were used as an internal biomarker of arsenic exposure. Our in vitro data suggest that arsenic increases levels of the EGFR ligand, heparin binding-EGF, and activate EGFR phosphorylation in the lung. Downstream of EGFR, arsenic exposure increased pERK and cyclin D1 levels. These effects were inhibited by treatment of cultured cells with the EGFR tyrosine kinase inhibitor, Tarceva (erlotinib). In a consecutive series of human lung tumor specimens, pEGFR protein levels were higher in subjects with elevated toenail arsenic levels compared to those with low exposure (odds ratio adjusted for other factors, OR 4.1 (95% confidence interval 1.1-15.6) (p = 0.04). These data suggest that arsenic exposure may stimulate EGFR pathway activation in the lung. Moreover, the tumors that arise in arsenic-exposed individuals also exhibit signs of EGFR pathway dysregulation. Further work is needed to assess the clinical utility of targeting the EGFR pathway in subgroups of lung cancer patients who have been exposed to elevated levels of arsenic.

DNA repair genotype interacts with arsenic exposure to increase bladder cancer risk

Drinking water arsenic exposure has been associated with increased bladder cancer susceptibility. Epidemiologic and experimental data suggest a co-carcinogenic effect of arsenic with exposure to DNA damaging agents, such as cigarette smoke. Recent evidence further supports the hypothesis that genetic variation in DNA repair genes can modify the arsenic-cancer relationship, possibly because arsenic impairs DNA repair capacity. We tested this hypothesis in a population-based study of bladder cancer with XRCC3, ERCC2 genotype/haplotype and arsenic exposure data on 549 controls and 342 cases. Individual exposure to arsenic was determined in toenail samples by neutron activation. Gene-environment interaction with arsenic exposure was observed in relation to bladder cancer risk for a variant allele of the double-strand break repair gene XRCC3 T241M (adjusted OR 2.8 (1.1-7.3)) comparing to homozygous wild type among those in the top arsenic exposure decile (interaction p-value 0.01). Haplotype analysis confirmed the association of the XRCC3 241. Thus, double-strand break repair genotype may enhance arsenic associated bladder cancer susceptibility in the U.S. population.

EGFR pathway polymorphisms and bladder cancer susceptibility and prognosis

The epidermal growth factor receptor (EGFR) pathway has recently been appreciated as a central mediator of tumorigenesis and an important drug target; however, the influence of genetic variation in this pathway on bladder cancer is not understood. Pathway activation leads to cell proliferation, angiogenesis and is antiapoptotic. We sought to test the hypothesis that bladder cancer susceptibility and survival are modified by inherited variations in the sequence of the EGFR and its pathway members. We tested associations using a population-based study of 857 bladder cancer cases and 1191 controls from New Hampshire. Multifactor dimensionality reduction software was used to predict gene-gene interactions. We detected an increased risk of bladder cancer associated with variant genotypes for the single nucleotide polymorphisms EGFR_03 [adjusted odds ratio (OR) 1.7 (95% confidence interval (CI) 1.0-2.8)] and EGFR_05 [adjusted OR 1.5 (95% CI 1.0-2.1)] compared with wild-type. EGFR variants experienced longer survival than those with wild-type alleles [e.g. adjusted hazard ratio EGFR_1808 0.3 (95% CI 0.1-0.9)]. In contrast, the variant form of the ligand, EGF_04, had worse survival [adjusted hazard ratio 1.5 (95% CI 1.0-2.3)] compared with wild-type. Our findings suggest modified bladder cancer risk and survival associated with genetic variation in the EGFR pathway. Understanding these genetic influences on increased bladder cancer susceptibility and survival may help in cancer prevention, drug development and choice of therapeutic regimen.

Selenium and risk of bladder cancer: a population-based case-control study

Emerging evidence indicates a potential role of selenium in the prevention of several types of cancer, including bladder cancer. We investigated the association between toenail selenium concentrations and bladder cancer risk in a population-based case-control study in New Hampshire. We analyzed data from 857 incidence cases diagnosed between July 1, 1994 and June 30, 2001 and 1,191 general population controls. Newly diagnosed cases of bladder cancer were identified from the New Hampshire State Cancer Registry, which operates a rapid reporting system. Controls were selected from population lists (driver's license and Medicare enrollment). We used logistic regression analyses to generate odds ratios (OR) and 95% confidence intervals (95% CI), controlling for age, sex, and pack-years of smoking and conducted separate analyses according to the intensity of p53 immunohistochemical staining of the tumor. Overall, toenail selenium concentrations were not significantly related to bladder cancer [OR Q4 versus Q1, 0.90 (95% CI, 0.68-1.19); P(trend) = 0.15]. However, within specific subgroups there were inverse associations, i.e., among moderate smokers [OR, 0.61 (95% CI, 0.39-0.96); P(trend) = 0.004], women [OR, 0.66 (95% CI, 0.40-1.10); P(trend) = 0.11], and those with p53-positive cancers [OR Q4 versus Q1, 0.57 (95% CI, 0.34-0.94); P(trend) = 0.01]. Our results indicate that selenium is not inversely related to risk of bladder cancer overall; however, they raise the possibility that selenium may be preventive in certain molecular phenotypes of tumors (e.g., p53 positive) or within certain subsets of a population (e.g., women or moderate smokers).

International Lung Cancer Consortium: pooled analysis of sequence variants in DNA repair and cell cycle pathways

BACKGROUND

The International Lung Cancer Consortium was established in 2004. To clarify the role of DNA repair genes in lung cancer susceptibility, we conducted a pooled analysis of genetic variants in DNA repair pathways, whose associations have been investigated by at least 3 individual studies.

METHODS

Data from 14 studies were pooled for 18 sequence variants in 12 DNA repair genes, including APEX1, OGG1, XRCC1, XRCC2, XRCC3, ERCC1, XPD, XPF, XPG, XPA, MGMT, and TP53. The total number of subjects included in the analysis for each variant ranged from 2,073 to 13,955 subjects.

RESULTS

Four of the variants were found to be weakly associated with lung cancer risk with borderline significance: these were XRCC3 T241M [heterozygote odds ratio (OR), 0.89; 95% confidence interval (95% CI), 0.79-0.99 and homozygote OR, 0.84; 95% CI, 0.71-1.00] based on 3,467 cases and 5,021 controls from 8 studies, XPD K751Q (heterozygote OR, 0.99; 95% CI, 0.89-1.10 and homozygote OR, 1.19; 95% CI, 1.02-1.39) based on 6,463 cases and 6,603 controls from 9 studies, and TP53 R72P (heterozygote OR, 1.14; 95% CI, 1.00-1.29 and homozygote OR, 1.20; 95% CI, 1.02-1.42) based on 3,610 cases and 5,293 controls from 6 studies. OGG1 S326C homozygote was suggested to be associated with lung cancer risk in Caucasians (homozygote OR, 1.34; 95% CI, 1.01-1.79) based on 2,569 cases and 4,178 controls from 4 studies but not in Asians. The other 14 variants did not exhibit main effects on lung cancer risk.

DISCUSSION

In addition to data pooling, future priorities of International Lung Cancer Consortium include coordinated genotyping and multistage validation for ongoing genome-wide association studies.

Arsenic-induced decreases in the vascular matrix

Chronic ingestion of arsenic is associated with increased incidence of respiratory and cardiovascular diseases. To investigate the role of arsenic in early events in vascular pathology, C57BL/6 mice ingested drinking water with or without 50 ppb sodium arsenite (AsIII) for four, five, or eight weeks. At five and eight weeks, RNA from the lungs of control and AsIII-exposed animals was processed for microarray. Sixty-five genes were significantly and differentially expressed. Differential expression of extracellular matrix (ECM) gene transcripts was particularly compelling, as 91% of genes in this category, including elastin and collagen, were significantly decreased. In additional experiments, real-time RT-PCR showed an AsIII-induced decrease in many of these ECM gene transcripts in the heart and NIH3T3 fibroblast cells. Histological stains for collagen and elastin show a distinct disruption in the ECM surrounding small arteries in the heart and lung of AsIII-exposed mice. Immunohistochemical detection of alpha-smooth muscle actin in blood vessel walls was decreased in the AsIII-exposed animals. These data reveal a functional link between AsIII exposure and disruption in the vascular ECM. These AsIII-induced early pathological events may predispose humans to respiratory and cardiovascular diseases linked to chronic low-dose AsIII exposure.

Histological classification and stage of newly diagnosed bladder cancer in a population-based study from the Northeastern United States

OBJECTIVE

There are limited data on the distribution of bladder cancers in the general population, classified by World Health Organization (WHO)/International Society of Urological Pathology (ISUP) criteria. This study evaluated the classification and stage of bladder cancers as part of a population-based epidemiological study of bladder cancer in the Northeastern United States.

MATERIAL AND METHODS

All New Hampshire residents with bladder cancer newly diagnosed from 1998 to 2000 were identified through the state cancer registry. All slides were reviewed by a single pathologist. Tumors were classified by two sets of standard criteria.

RESULTS

The retrieval rate for cases was over 90%. Of 342 cases reviewed, 15 were excluded for technical reasons or because malignancy was not definitively diagnosed. According to WHO/ISUP criteria, 25.7% of tumors were papillary urothelial neoplasms of low malignant potential (PUNLMP), 34.3% low-grade papillary carcinomas, 22.6% high-grade papillary carcinomas, 10.1% non-papillary urothelial carcinomas and 5.5% carcinoma in situ. By WHO (1973) criteria, 52.5% of tumors were grade 1, 21.4% grade 2 and 26.1% grade 3. Two-thirds of all tumors were stage Ta, 20.8% stage T1 and 7.6% stage >or=T2. 100% of PUNLMPs were non-invasive, 6.3% of low-grade carcinomas were invasive and 64.9% of high-grade carcinomas were invasive.

CONCLUSIONS

Compared to clinic or hospital referral-based series, this study documents a higher percentage of non-invasive tumors and a lower percentage of muscle-invasive tumors. There was also a higher percentage of PUNLMP tumors and fewer high-grade papillary carcinomas than in other series. These results may more accurately reflect prevalence data for bladder cancer grade and stage, although geographic variability may exist.

Drinking-water arsenic exposure modulates gene expression in human lymphocytes from a U.S. population

BACKGROUND

Arsenic exposure impairs development and can lead to cancer, cardiovascular disease, and diabetes. The mechanism underlying these effects remains unknown. Primarily because of geologic sources of contamination, drinking-water arsenic levels are above the current recommended maximum contaminant level of 10 microg/L in the northeastern, western, and north central regions of the United States.

OBJECTIVES

We investigated the effects of arsenic exposure, defined by internal biomarkers at levels relevant to the United States and similarly exposed populations, on gene expression.

METHODS

We conducted separate Affymetrix microarray-based genomewide analyses of expression patterns. Peripheral blood lymphocyte samples from 21 controls interviewed (1999-2002) as part of a case-control study in New Hampshire were selected based on high- versus low-level arsenic exposure levels.

RESULTS

The biologic functions of the transcripts that showed statistically significant abundance differences between high- and low-arsenic exposure groups included an overrepresentation of genes involved in defense response, immune function, cell growth, apoptosis, regulation of cell cycle, T-cell receptor signaling pathway, and diabetes. Notably, the high-arsenic exposure group exhibited higher levels of several killer cell immunoglobulin-like receptors that inhibit natural killer cell activity.

CONCLUSIONS

These findings define biologic changes that occur with chronic arsenic exposure in humans and provide leads and potential targets for understanding and monitoring the pathogenesis of arsenic-induced diseases.

Survival Following the Diagnosis of Noninvasive Bladder Cancer: WHO/International Society of Urological Pathology Versus WHO Classification Systems

PURPOSE

The WHO/International Society of Urological Pathology classification of bladder cancer, introduced in 1998, differs from the traditional 1973 WHO classification. Few studies have reported survival data based on the WHO/International Society of Urological Pathology classification and none has demonstrated clear superiority compared to the 1973 WHO system. In a large, nonselected population of patients with bladder cancer we rated all incident tumors using each system and compared long-term patient survival.

MATERIALS AND METHODS

New Hampshire residents with bladder cancer diagnosed between 1994 and 2000 were identified through the State Cancer Registry. Slides were retrieved from more than 90% of cases and reviewed by a single pathologist. Tumors were classified according to WHO and WHO/International Society of Urological Pathology criteria. Overall patient survival was determined for the cohort of 504 patients after an average of 7 years using a national mortality database.

RESULTS

For both grading systems there was a gradient of progressively lower survival times from the lowest grade to the highest grade tumors. Hazard ratios and 95% confidence intervals for the WHO/International Society of Urological Pathology system were 1.9 (1.0-3.4) for low grade papillary urothelial carcinoma and 3.0 (1.5-6.0) for high grade papillary urothelial carcinoma, compared to papillary urothelial neoplasms of low malignant potential. For the WHO (1973) system compared to grade 1 tumors the hazard ratio for grade 2 tumors was 1.8 (1.1-3.1) and for grade 3 was 2.4 (1.2-4.7).

CONCLUSIONS

Advantages of the WHO/International Society of Urological Pathology bladder tumor classification include more detailed diagnostic criteria, the ability to define a lesion with minimal malignant potential and the ability to identify a larger group of patients needing closer surveillance. However, we found that the WHO/International Society of Urological Pathology tumor categories did not detect a clear overall survival advantage compared to the WHO (1973) classification system.

DNA repair polymorphisms modify bladder cancer risk: a multi-factor analytic strategy

OBJECTIVES

A number of common non-synonymous single nucleotide polymorphisms (SNPs) in DNA repair genes have been reported to modify bladder cancer risk. These include: APE1-Asn148Gln, XRCC1-Arg399Gln and XRCC1-Arg194Trp in the BER pathway, XPD-Gln751Lys in the NER pathway and XRCC3-Thr241Met in the DSB repair pathway.

METHODS

To examine the independent and interacting effects of these SNPs in a large study group, we analyzed these genotypes in 1,029 cases and 1,281 controls enrolled in two case-control studies of incident bladder cancer, one conducted in New Hampshire, USA and the other in Turin, Italy.

RESULTS

The odds ratio among current smokers with the variant XRCC3-241 (TT) genotype was 1.7 (95% CI 1.0-2.7) compared to wild-type. We evaluated gene-environment and gene-gene interactions using four analytic approaches: logistic regression, Multifactor Dimensionality Reduction (MDR), hierarchical interaction graphs, classification and regression trees (CART), and logic regression analyses. All five methods supported a gene-gene interaction between XRCC1-399/XRCC3-241 (p = 0.001) (adjusted OR for XRCC1-399 GG, XRCC3-241 TT vs. wild-type 2.0 (95% CI 1.4-3.0)). Three methods predicted an interaction between XRCC1-399/XPD-751 (p = 0.008) (adjusted OR for XRCC1-399 GA or AA, XRCC3-241 AA vs. wild-type 1.4 (95% CI 1.1-2.0)).

CONCLUSIONS

These results support the hypothesis that common polymorphisms in DNA repair genes modify bladder cancer risk and highlight the value of using multiple complementary analytic approaches to identify multi-factor interactions.

Analgesic and anti-inflammatory drug use and risk of bladder cancer: a population based case control study

Background

Use of phenacetin and other analgesic and non-steroidal anti-inflammatory drugs (NSAIDs) potentially influences bladder cancer incidence, but epidemiologic evidence is limited.

Methods

We analyzed data from 376 incident bladder cancer cases and 463 controls from a population-based case-control study in New Hampshire on whom regular use of analgesic drugs and NSAIDs was obtained. Odds ratios and 95% confidence intervals were computed using logistic regression with adjustment for potentially confounding factors. Separate models by tumor stage, grade and TP53 status were conducted.

Results

We found an elevated odds ratio (OR) associated with reported use of phenacetin-containing medications, especially with longer duration of use (OR _{>8 years} = 3.00, 95% confidence interval (CI) = 1.4–6.5). In contrast, use of paracetamol did not relate overall to risk of bladder cancer. We also found that regular use of any NSAID was associated with a statistically significant decrease in bladder cancer risk (OR = 0.6, 95% CI = 0.4–0.9), and specifically use of aspirin. Further, the association with NSAID use was largely among invasive, high grade and TP53 positive tumors.

Conclusion

While these agents have been investigated in several studies, a number of questions remain regarding the effects of analgesic and NSAID use on risk of bladder cancer.

Exposure to Arsenic at Levels Found in U.S. Drinking Water Modifies Expression in the Mouse Lung

The mechanisms of action of drinking water arsenic in the lung and the threshold for biologic effects remain controversial. Our study utilizes Affymetrix 22,690 transcript oligonucleotide microarrays to assess the long-term effects of increasing doses of drinking water arsenic on expression levels in the mouse lung. Mice were exposed at levels commonly found in contaminated drinking water wells in the United States (0, 0.1, 1 ppb), as well as the 50 ppb former maximum contaminant level, for 5 weeks. The expression profiles revealed modification of a number of important signaling pathways, many with corroborating evidence of arsenic responsiveness. We observed statistically significant expression changes for transcripts involved in angiogenesis, lipid metabolism, oxygen transport, apoptosis, cell cycle, and immune response. Validation by reverse transcription-PCR and immunoblot assays confirmed expression changes for a subset of transcripts. These data identify arsenic-modified signaling pathways that will help guide investigations into mechanisms of arsenic's health effects and clarify the threshold for biologic effects and potential disease risk.

Measures of cumulative exposure from a standardized sun exposure history questionnaire: a comparison with histologic assessment of solar skin damage

Ultraviolet radiation exposure is the dominant environmental determinant of all major forms of skin cancer; however, the nature of the association is incompletely understood. Existing instruments to capture sun exposure history tend to yield reproducible results, but the validity of these responses is unknown. To address this question, the authors examined the relation between responses to a standardized sun exposure instrument and histologic evidence of actinic damage in a population-based study of keratinocyte cancers from New Hampshire diagnosed from July 1, 1997, through March 31, 2000. A single study dermatopathologist histologically reviewed the adjacent skin of 925 skin cancer biopsies for the presence of solar keratoses and the extent of solar elastosis. The authors compared these measures with responses to a personal interview on history of sunburns, sunbathing, and time spent outdoors. Focusing on site-specific exposure, they found variables that estimated cumulative exposure related to histologic evidence of actinic damage. In contrast, measures of acute/intermittent exposure were generally unrelated to solar damage histologically. Findings suggest that cumulative, but not intermittent, measures of sun exposure derived from a personal interview appear to reflect a person's exposure history based on histologic evidence.

Arsenic exposure is associated with decreased DNA repair in vitro and in individuals exposed to drinking water arsenic

The mechanism(s) by which arsenic exposure contributes to human cancer risk is unknown ; however, several indirect cocarcinogenesis mechanisms have been proposed. Many studies support the role of As in altering one or more DNA repair processes. In the present study we used individual-level exposure data and biologic samples to investigate the effects of As exposure on nucleotide excision repair in two study populations, focusing on the excision repair cross-complement 1 (ERCC1) component. We measured drinking water, urinary, or toenail As levels and obtained cryopreserved lymphocytes of a subset of individuals enrolled in epidemiologic studies in New Hampshire (USA) and Sonora (Mexico). Additionally, in corroborative laboratory studies, we examined the effects of As on DNA repair in a cultured human cell model. Arsenic exposure was associated with decreased expression of ERCC1 in isolated lymphocytes at the mRNA and protein levels. In addition, lymphocytes from As-exposed individuals showed higher levels of DNA damage, as measured by a comet assay, both at baseline and after a 2-acetoxyacetylaminofluorene (2-AAAF) challenge. In support of the in vivo data, As exposure decreased ERCC1 mRNA expression and enhanced levels of DNA damage after a 2-AAAF challenge in cell culture. These data provide further evidence to support the ability of As to inhibit the DNA repair machinery, which is likely to enhance the genotoxicity and mutagenicity of other directly genotoxic compounds, as part of a cocarcinogenic mechanism of action.

Concordance of multiple analytical approaches demonstrates a complex relationship between DNA repair gene SNPs, smoking and bladder cancer susceptibility

Study results of single nucleotide polymorphisms (SNPs) and cancer susceptibility are often conflicting, possibly because of the analytic challenges of testing for multiple genetic and environmental risk factors using traditional analytic tools. We investigated the relationship between DNA repair gene SNPs, smoking, and bladder cancer susceptibility in 355 cases and 559 controls enrolled in a population-based study of bladder cancer in the US. Our multifaceted analytical approach included logistic regression, multifactor dimensionality reduction, and hierarchical interaction graphs for the analysis of gene-gene and gene-environment interactions followed by linkage disequilibrium and haplotype analysis. Overall, we did not find an association between any single DNA repair gene SNP and bladder cancer risk. We did find a marginally significant elevated risk of the XPD codon 751 homozygote variant among never smokers [adjusted odds ratio (OR) 2.5, 95% confidence interval (CI) 1.0-6.2]. In addition, the XRCC1 194 variant allele was associated with a reduced bladder cancer risk among heavy smokers [adjusted OR 0.4, 95% CI 0.2-0.9)]. The best predictors of bladder cancer included the XPD codon 751 and 312 SNPs along with smoking. Interpretation of this multifactor model revealed that the relationship between the XPD SNPs and bladder cancer is mostly non-additive while the effect of smoking is mostly additive. Since the two XPD SNPs are in significant linkage disequilibrium (D' = 0.52, P = 0.0001), we estimated XPD haplotypes. Individuals with variant XPD haplotypes were more susceptible to bladder cancer [e.g. adjusted OR 2.5, 95% CI 1.7-3.6] and the effect was magnified when smoking was considered. These results support the hypothesis that common polymorphisms in DNA repair genes modify bladder cancer risk and emphasize the need for a multifaceted statistical approach to identify gene-gene and gene-environment interactions.

Methylenetetrahydrofolate reductase (MTHFR) variants and bladder cancer: A population-based case-control study

Functional variants in the methylenetetrahydrofolate reductase (MTHFR) gene, including the 677C>T and 1298A>C polymorphisms, have been associated with a moderately reduced risk of several cancers, including colorectal cancers. While recent studies have investigated the role of these polymorphisms on bladder cancer susceptibility, results have been mixed. To clarify the role of MTHFR polymorphisms on bladder cancer risk, we genotyped MTHFR 677C > T and MTHFR 1298A > C in a population-based study of bladder cancer of 352 patients and 551 controls from New Hampshire, USA. The allelic frequency was 35.6% for MTHFR 677C>T and 40.4% for MTHFR 1298A > C among controls. We found no evidence of a main gene effect for either polymorphism (adjusted OR for MTHFR 677C>T variants versus the reference genotype = 1.1; 95% CI, 0.8-1.4 and adjusted OR for MTHFR 1298A>C variants versus the reference genotype = 1.0; 95% CI, 0.7-1.4). Odds ratios did not appear to differ by smoking status or gender. We observed differences in the risk estimates for the MTHFR polymorphisms by arsenic exposure, but they were not statistically significant (P = 0.67 for MTHFR 677C > T and P = 0.12 for MTHFR 1298A>C). Thus, our findings do not support the presence of a main gene effect. The possibility that MTHFR polymorphism affects susceptibility to environmental exposures warrants further consideration.

Bladder cancer risk and personal hair dye use

Several cohort and case-control studies have found an increased risk of bladder cancer among hairdressers and barbers who are occupationally exposed to hair dyes. However, the carcinogenic risk associated with personal use of hair dyes remains uncertain since several large case-control and cohort studies did not find an association between personal hair dye use and bladder cancer. To address this question, the authors used data collected on 459 bladder cancer cases and 665 controls who were interviewed as part of a case-control study conducted in New Hampshire between 1994 and 1998. Participants underwent a structured personal interview with regard to history of hair dye use and bladder cancer risk factors. Unconditional logistic regression analysis was used to compute odds ratios that were associated with hair dye use, while controlling for potential confounding factors. A history of any hair dye use was inversely associated with bladder cancer incidence in men [adjusted odds ratio (OR) = 0.5; 95% confidence interval (CI)=0.3-0.8], although risk reductions were not statistically significant for individual dye types. In women, use of permanent (adjusted OR = 1.5; 95%CI = 0.8-2.7) and rinse-type hair dye (adjusted OR = 1.7; 95%CI = 0.8-3.6) were associated with a modestly elevated risk of bladder cancer but with limited statistical precision; no association was found with use of semi-permanent dyes (adjusted OR = 0.7; 95%CI = 0.3-1.4). For permanent hair dye use, odds ratios were most pronounced for younger age at first use, higher frequency and prolonged time since first use; however there were no clear trends in risk by these factors. In light of the prevalence of hair dye use, further studies are needed that address the effects of specific colors and types of hair dyes along with the possible role of individual susceptibility.

Genomic and proteomic profiling of responses to toxic metals in human lung cells

Examining global effects of toxic metals on gene expression can be useful for elucidating patterns of biological response, discovering underlying mechanisms of toxicity, and identifying candidate metal-specific genetic markers of exposure and response. Using a 1,200 gene nylon array, we examined changes in gene expression following low-dose, acute exposures of cadmium, chromium, arsenic, nickel, or mitomycin C (MMC) in BEAS-2B human bronchial epithelial cells. Total RNA was isolated from cells exposed to 3 M Cd(II) (as cadmium chloride), 10 M Cr(VI) (as sodium dichromate), 3 g/cm2 Ni(II) (as nickel subsulfide), 5 M or 50 M As(III) (as sodium arsenite), or 1 M MMC for 4 hr. Expression changes were verified at the protein level for several genes. Only a small subset of genes was differentially expressed in response to each agent: Cd, Cr, Ni, As (5 M), As (50 M), and MMC each differentially altered the expression of 25, 44, 31, 110, 65, and 16 individual genes, respectively. Few genes were commonly expressed among the various treatments. Only one gene was altered in response to all four metals (hsp90), and no gene overlapped among all five treatments. We also compared low-dose (5 M, noncytotoxic) and high-dose (50 M, cytotoxic) arsenic treatments, which surprisingly, affected expression of almost completely nonoverlapping subsets of genes, suggesting a threshold switch from a survival-based biological response at low doses to a death response at high doses.

Decreased DNA repair gene expression among individuals exposed to arsenic in United States drinking water

Arsenic is well established as a human carcinogen, but its precise mechanism of action remains unknown. Arsenic does not directly damage DNA, but may act as a carcinogen through inhibition of DNA repair mechanisms, leading indirectly to increased mutations from other DNA damaging agents. The molecular mechanism underlying arsenic inhibition of nucleotide excision repair after UV irradiation (Hartwig et al., Carcinogenesis 1997;18:399-405) is unknown, but could be due to decreased expression of critical genes involved in nucleotide excision repair of damaged DNA. This hypothesis was tested by analyzing expression of repair genes and arsenic exposure in a subset of 16 individuals enrolled in a population based case-control study investigating arsenic exposure and cancer risk in New Hampshire. Toenail arsenic levels were inversely correlated with expression of critical members of the nucleotide excision repair complex, ERCC1 (r(2) = 0.82, p < 0.0001), XPF (r(2) = 0.56, p < 0.002), and XPB (r(2) = 0.75, p < 0.0001). The internal dose marker, toenail arsenic level, was more strongly associated with changes in expression of these genes than drinking water arsenic concentration. Our findings, based on human exposure to arsenic in a US population, show an association between biomarkers of arsenic exposure and expression of DNA repair genes. Although our findings need verification in a larger study group, they are consistent with the hypothesis that inhibition of DNA repair capacity is a potential mechanism for the co-carcinogenic activity of arsenic.

A novel pathway for nickel-induced interleukin-8 expression

Inhalation of particulate nickel subsulfide (Ni3S2) causes chronic active inflammation and fibrosis of the lungs. However, the mechanisms for these effects are not well understood. Therefore, cell culture experiments with BEAS-2B human airway epithelial cells were conducted to test the hypothesis that exposure to non-cytotoxic levels of Ni3S2 induces expression of inflammatory cytokines such as interleukin-8 (IL-8). Exposure to Ni3S2 for 48 h was required to significantly increase IL-8 protein levels. Transcriptional stimulation of IL-8 mRNA levels preceded the increase in protein. Transient exposure to soluble nickel sulfate failed to increase IL-8 mRNA. Transfection with truncated IL-8 promoter constructs linked to the luciferase gene demonstrated that nickel-induced IL-8 transcription required -272 bp of the promoter relative to the transcriptional start site. A -133-bp construct, containing cytokine and hypoxia-sensitive AP-1, NF-IL6, and NF-kappaB sites, was insufficient for induction by nickel. Transfection with a dominant negative AP-1 construct or mutation of the AP-1, GATA, or C/EBP sites in the -272-bp IL-8 promoter construct blocked induction by nickel. Inhibiting ERK, phosphatidylinositol 3-kinase, but not p38 kinase, diacylglycerol kinase, or hypoxia-inducible factor-1alpha, attenuated nickel induction of IL-8. These studies indicate that nickel induced IL-8 transcription through a novel pathway that requires both AP-1 and non-traditional transcription factors.

Nickel requires hypoxia-inducible factor-1 alpha, not redox signaling, to induce plasminogen activator inhibitor-1

Human epidemiological and animal studies have associated inhalation of nickel dusts with an increased incidence of pulmonary fibrosis. At the cellular level, particulate nickel subsulfide inhibits fibrinolysis by transcriptionally inducing expression of plasminogen activator inhibitor (PAI)-1, an inhibitor of the urokinase-type plasminogen activator. Because nickel is known to mimic hypoxia, the present study examined whether nickel transcriptionally activates PAI-1 through the hypoxia-inducible factor (HIF)-1 alpha signaling pathway. The involvement of the NADPH oxidase complex, reactive oxygen species, and kinases in mediating nickel-induced HIF-1 alpha signaling was also investigated. Addition of nickel to BEAS-2B human airway epithelial cells increased HIF-1 alpha protein levels and elevated PAI-1 mRNA levels. Pretreatment of cells with the extracellular signal-regulated kinase inhibitor U-0126 partially blocked HIF-1 alpha protein and PAI-1 mRNA levels induced by nickel, whereas antioxidants and NADPH oxidase inhibitors had no effect. Pretreating cells with antisense, but not sense, oligonucleotides to HIF-1 alpha mRNA abolished nickel-stimulated increases in PAI-1 mRNA. These data indicate that signaling through extracellular signal-regulated kinase and HIF-1 alpha is required for nickel-induced transcriptional activation of PAI-1.

AP-1-dependent induction of plasminogen activator inhibitor-1 by nickel does not require reactive oxygen

Inhalation of nickel dust has been associated with an increased incidence of pulmonary fibrosis. Nickel may promote fibrosis by transcriptionally activating plasminogen activator inhibitor (PAI)-1 and inhibiting fibrinolysis. The current studies examined whether nickel stimulated the PAI-1 promoter though an oxidant-sensitive activator protein (AP)-1 signaling pathway. Addition of nickel to BEAS-2B human airway epithelial cells stimulated intracellular oxidation, induced c-Jun and c-Fos mRNA levels, increased phospho- and total c-Jun protein levels, and elevated PAI-1 mRNA levels over a 24-h time course. Pretreatment of the cells with antioxidants did not affect increased c-Jun protein or PAI-1 mRNA levels. Expression of the dominant negative inhibitor of AP-1, TAM67, prevented nickel-stimulated AP-1 DNA binding, AP-1-luciferase reporter construct activity, and PAI-1 mRNA levels. Overexpression of c-Jun, however, failed to induce the AP-1 luciferase reporter construct or PAI-1 mRNA levels. These data indicated that nickel activated AP-1 through an oxidant-independent pathway and that basal AP-1 is necessary for nickel-induced expression of PAI-1.

Osmium isotope constraints on ore metal recycling in subduction zones

Veined peridotite xenoliths from the mantle beneath the giant Ladolam gold deposit on Lihir Island, Papua New Guinea, are 2 to 800 times more enriched in copper, gold, platinum, and palladium than surrounding depleted arc mantle. Gold ores have osmium isotope compositions similar to those of the underlying subduction-modified mantle peridotite source region, indicating that the primary origin of the metals was the mantle. Because the mantle is relatively depleted in gold, copper, and palladium, tectonic processes that enhance the advective transport and concentration of these fluid soluble metals may be a prerequisite for generating porphyry-epithermal copper-gold deposits.

Effect of arsenite on induction of CYP1A, CYP2B, and CYP3A in primary cultures of rat hepatocytes

In earlier studies, sodium arsenite treatment was shown to decrease induction of enzymatic activities associated with hepatic CYPs in rats. Here we investigated the effect of sodium arsenite on induction of CYP2B, CYP1A, and CYP3A in primary cultures of rat hepatocytes. Arsenite decreased the induction of all three families of CYP, as measured enzymatically and immunochemically. These decreases in CYPs occurred at concentrations of arsenite (2.5-10 microM) at which no toxicity was observed; however, toxicity was observed at 25 microM arsenite. With 3-methylcholanthrene as inducer, 5 microM arsenite caused a 55% decrease in CYP1A1 immunoreactive protein and enzyme activity, but only a 25% decrease in CYP1A1 mRNA. With phenobarbital (PB) as the inducer, 2.5 microM arsenite decreased CYP2B enzyme activity and immunoreactive protein 50%, with only a 25% decrease in CYP2B1 mRNA. 5 microM Arsenite decreased CYP2B enzyme activity and immunoreactive protein 80%, but decreased CYP2B1 mRNA only 50%, while CYP3A protein was decreased greater than 75% with no decrease in CYP3A23 mRNA. With dexamethasone (DEX) as inducer, 5 microM sodium arsenite caused a 50% decrease in immunoreactive CYP3A and a 30% decrease in CYP3A23 mRNA. Although arsenite-mediated increases in heme oxygenase (HO) inversely correlated with decreases in CYP2B or CYP1A activity, inclusion of heme in cultures treated with inducers of CYP1A or CYP2B did not prevent the arsenite-mediated decreases in these CYPs. Even though added heme induced HO to similar levels with and without arsenite, decreases in CYPs were only observed in the presence of arsenite. These results suggest that, in rat hepatocytes, elevated levels of HO alone are not responsible for arsenite-mediated decreases in CYP.