BLADDER CANCER: METABOLISM OF CARCINOGENS & PREVENTION

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We propose to continue defining specific mechanisms involved in initiation of chemically-induced bladder cancer. The N-[4-(5-nitro-2-furyl)-2-thiazolyl] formamide (FANFT) model was chosen because of flexibility in experimental design permitted by a high incidence of the desired lesion. Hypotheses forming the basis of our proposal are: 1) Certain specific physiologic and metabolic functions are responsible for the delivery of high concentrations of the more proximate deformylated carcinogen, ANFT, to urothelium. 2) Metabolic activation occurs in urothelial cells with oxidation of ANFT by prostaglandin H synthase (PHS) a likely mechanism of activation. Other pathways may also be involved. 3) Agents which decrease the amount of ANFT accessible to bladder epithelium, prevent activation in bladder and/or prevent activated intermediates from binding DNA will reduce the incidence of FANFT-induced bladder cancer. FANFT-ANFT metabolism and disposition will be assessed by intact rat and guinea pig, species susceptible and resistant, respectively, to FANFT-induced bladder cancer. Target tissue metabolism will be assessed with urothelial cells from rat, human and guinea pig. Tissue distribution, covalent binding and chromatographically separable metabolite determiantions will be facilitated by the use of 14C- and 35S-labeled FANFT-ANFT. Renal FANFT deformylase purified from rat will be characterized. Urothelial cell synthesis of eicosanoid substrates of PHS will also be assessed. Biologic assessment will include cell transformation and urothelial cell toxicity evaluation of ANFT and its metabolites. The in vivo method will use the two-stage FANFT model to evaluate effects of dietary factors on physiologic (urine pH) and metabolic (activation) parameters of FANFT initiation. Each set of experiments will continuously test our hypotheses by the selection of agents which alter metabolism and disposition and ameliorate pathogenic processes. Data obtained from this renewal will have a profound impact on theoretical and practical aspects of bladder cancer. Theoretic signfiicance relates to determiation of pathways involved in initiation while practical significance relates to development of therapeutic strategies of prevention.