Occupational exposure to arylamines used in the manufacturing of industrial dyes was the first known cause of human bladder cancer. These carcinogenic arylamines, specifically, 4-aminobiphenyl (4-ABP), beta-naphthylamine, and benzidine, are also contained in tobacco smoke, and are the most likely causative agents responsible for the raised rates of bladder cancer in smokers. Oxidation of arylamines is recognized as a critical first step in turning these chemical species into their carcinogenic metabolites capable of causing DNA damage to urothelial cells. Hair dyes represent another substantial source of arylamines in humans, and we recently showed that sustained use of permanent hair dyes in women is a risk factor for bladder cancer, especially among those deficient in arylamine detoxifying enzymes. Subsequently, 4-ABP was detected in bottles of commercial hair dyes bought in a US store. Then, using hemoglobin adducts of 4-ABP as a biomarker of exposure, we showed that other, presumably diffuse, sources of 4-ABP exposure may be related to bladder cancer in nonsmokers. Thus, the latest evidence indicates arylamine exposure as the primary cause of bladder cancer in the United States. Ten years ago, we reported that a reason for the 3-fold increased risk of bladder cancer in US white versus Chinese men despite their comparable smoking habits may be the higher prevalence in the former population of individuals with deficient arylamine-detoxifying enzymes, which are under genetic control. We capitalized on this finding and launched a population-based case-control study involving both a Los Angeles and a Shanghai, China component to explore genetic factors that play a major role in determining bladder cancer risk in arylamine-exposed individuals. This already completed database consists of roughly 1300 cases of incident bladder cancer (750 cases in Los Angeles, 550 cases in Shanghai) and about an equal number of control subjects. Our initial goals were to investigate the roles of selected polymorphic, arylarnine-metabolizing genotypes/phenotypes in bladder cancer, and in the Los Angeles component, to use hemoglobin adducts as biomarkers of exposure to arylamines in examining nonsmoking-related bladder cancer. In this application, we aim for a more comprehensive understanding of the arylamine-bladder cancer etiologic link through the following extensions on our Los Angeles/Shanghai database: (1) Completion of arylamine hemoglobin adduct measurements on Shanghai subjects in order to compare the respective effects of these adducts on risk between Los Angles and Shanghai study subjects;(2) Addition of genotypes involved in arylamine metabolism, in cellular response to oxidative stress and in DNA repair;and (3) Development of a Bayesian hierarchical statistical model to allow for an efficient, pathway-driven examination of multiple gene-arylamine interactions in bladder cancer. The ultimate goal of this research is to assess individual bladder cancer risk for the purpose of preventive interventions.
Showing the most recent 10 out of 16 publications
