The proposed studies will evaluate the mechanisms by which dehydroepiandrosterone (DHEA) and its reduced metabolite (5-ene-androstene- 3beta,17beta-diol or ADIOL) alter the metabolic activation and early steps in the promotion phase of chemical carcinogenesis and toxicity. Since feeding of these compounds blocks chemical carcinogenesis and a number of deleterious pathophysiological states, we will evaluate the effect of these androgens on induction of enzymes commonly involved in the metabolic activation or detoxification of chemical carcinogens and toxicants to establish whether they either directly inhibit the action of these enzymes or affect induction of detoxification enzymes to ameliorate their effects. 1. The goal of aim 1 is to characterize the enzymes involved in carcinogen and drug metabolism and the biochemical mechanism by which they are induced or suppressed by these steroid chemopreventive agents. After we identify and characterize the form(s) of xenobiotic metabolizing enzymes induced by DHEA, we will study of the mechanism(s) of induction (transcription, translation, stabilization) of these proteins. The structure-function relationship of induction of these enzymes will be established to elucidate its putative receptor. 2. The goal of Aim 2 is to establish whether there are alterations of other processes involved in subsequent phases of chemical carcinogenesis or toxicity with DHEA-feeding. Activities of key processes in carcinogenesis will be monitored to establish any effect of DHEA and ADIOL administration. Since chemical carcinogenesis by PAH is thought to involve the induction of cytochrome P450IA1, we will establish whether DHEA or ADIOL inhibit the induction of PAH-inducible enzymes. Any role of DHEA or ADIOL in altering normal hormone-mediated expression of a limited number of P450s (IIB1, IIIA1, IIC11) will be studied and the modulating effect of other hormones on the expression of proteins (P450IVA1, NADPH-cytochrome P450 oxidoreductase, malic enzyme) with DHEA will be tested. 3. The goal of Aim 3 is to establish whether these chemopreventive agents simultaneously cause increases in hydrogen peroxide production and decreases in carcinogen metabolism in isolated rodent hepatocytes. The effects of DHEA and ADIOL on the enzyme activities associated with carcinogen activation or detoxification in cultured rat hepatocytes will be studied to elucidate any direct or indirect inhibitory actions of these androgens.
