ARSENIC BIOMARKER EPIDEMIOLOGY

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We propose to conduct a biomarker case-control study of bladder cancer to investigate the effects of arsenic in drinking water in the province of Cordoba, Argentina. Preliminary studies have shown increased bladder cancer mortality in two counties in Cordoba with an overall relateive risk estimate of 2.5. Based on studies in Taiwan, this increased mortality is most likely due to drinking water containing high levels of arsenic (between 100 and 1000 mug/L) in a number of localities in the two counties. Thr proposed research project will involve 150 cases of bladder cancer and will include collection of bladder tumor biopsy specimens. Tumor DNA will be analyzed for genetic alterations using a three-tiered approach, with screening of the entire genome for gains and loses using comparative genomic hybridization (CGH), specific analyses of chromosomes 9 and 17p for loss of heterozygosity using restriction fragment length polymorphism (RFLP), and analysis of the p53 gene for mutations using polymerase chain reaction-single-strand conformation polymorphism analysis (PCR-SSCP). Controls residing in the same two counties as the cases will be selected from voter registration lists matched to each case by sex and date of birth. Cases and controls will be interviewed to obtain lifetime residential histories and information concerning consumption of water, smoking, diet, and other variables. Arsenic measurements will be obtained for water sources used by each case and control. Dose-response analyses will be conducted investigating the relationship between bladder cancer risk and exposure to arsenic. The frequency and pattern of genetic alterations in bladder tumors of arsenic exposed and unexposed cases will be compared, along with assessment of the potential synergistic action of arsenic on genotoxic effects of cigarette smoking. In addition, susceptibility differences between cases and controls will be investigated by identifying the presence or presence or absence of the glutathione S- transferases GSTMI null genotypes in buccal cells and by comparing urinary arsenic methylation patterns. One strength of the study is that it will be possible to explore genetic biomarkers in bladder tumors and link these to risk status related to arsenic and smoking. These findings will be confirmed in years 4 and 5 using bladder tumor biopsies from a high arsenic exposure population in northern Chile (over 400 mug/L) and a lower exposure population in the U.S. (around 100 mug/L). A second strength of the proposal study is that it has potential to provide the definitive evidence concerning the probable causal association between arsenic ingestion and bladder cancer, and to establish the dose-response relationship for use in risk assessment.