Abstract
Diethylstilbestrol (DES) is a carcinogen in humans and rodents which has eluded mechanistic clarification of its carcinogenic action. In vitro and in vivo, binding of DES to DNA has been found previously, but covalent DNA adducts could not be identified. In this study, the nature of binding was investigated by 32P-postlabeling, a rapid and highly sensitive assay for covalent DNA damage, to distinguish between a genotoxic or epigenetic mechanism of carcinogenesis by DES. A unique and distinct DNA adduct pattern was observed in kidney, liver, uterus (or testes) of female (or male, respectively) Syrian hamsters treated with a single injection of DES (200 mg/kg body weight). This set of DNA adducts closely matched patterns generated in vitro by reaction of diethylstilbestrol-4',4''-quinone with DNA or 2'-deoxyguanosine 3'-monophosphate. The major and several minor DES-DNA adducts in vivo had identical chromatographic mobilities in 11 different solvent systems with corresponding adducts obtained in vitro. The major adduct spot, generated in vitro by reaction of diethylstilbestrol-4',4''-quinone and DNA, was chemically unstable (half-life at 37 degrees C: 4-5 days). The persistence in vivo of these DNA modifications was low (biological half-life: 14 h) presumably because of chemical instability in concert with DNA repair. After injection of identical dosages of DES, adduct concentrations were 4-6-fold higher in females than in males. These results demonstrate that DES is capable of covalently modifying DNA. Moreover, diethylstilbestrol-4',4"-quinone is the major reactive metabolic intermediate responsible for the genotoxic activity of DES. Tumors are expected to arise only in rapidly dividing cells due to the short biological lifetimes of DES-DNA adducts.
Highlights
Diethylstilbestrol ((DES)is a carcinogen in humans difficulties experienced in defining the nature of DES-DNA and rodentswhich has eluded mechanistic clarification interaction were partially explained by the instability of DNA of its carcinogenic action.In vitro and in vivo,binding binding of DES Q, a metabolic intermediate of DES, in vitro of DES to DNA has been found previouslyb,ut covalent [7] and of DES in rats andhamsters i n vivo [6]
Was low presumably because DNA adducts were detected inhamster liver, kidney, and of chemical instability in concert with DNA repair. uterus after a single injection of DES
It was thought that hormonal imbalance or an uncontrolled hormonal stimulation of cell proliferation was the dominantaspect of carcinogenesis by this stilbene estropatterns induced by a variety of estrogens, including DES, inthehamster kidney as published previously
Summary
From the De,oartmentof Pharmacologyand Toxicology, University of Texas MedicalBranch, Galueston, Texas 77550-2774. A unique and distinct DNA adduct pattern waosbserved in kidney, liver, uterus (otrestes) of female (or male, respectively) Syrian hamst’ers treated wiathsingle injection of DES (200 mg/kg body weight). This set ofDNA adducts closely matched patterns generatedin vitroby reaction of diethylsti.lbestrol-4’,4”-quinonewith DNA or 2’-deoxyguanosine 3’-monophosphate. In contrast,a number of biological and biochemical effects of DES were noted which depended on metabolic activation of the stilbene and are commonly associated with genotoxic activity (reviewed by Metzler [9]) These include: induction of sister chromatid exchange [10,11], of unscheduled DNA synthesis [12], and of aneuploidy in Syrian hamster embryo cells [13].TheseDES-induced genetic alterations, usually indicative of a genotoxic agent, as well as the covalent interaction of the metabolic intermediate DES Q with peptides and proteins [7] suggested a renewed study of the nature of binding of DES toDNA by 32P-postlabelinganalysis, a more vitro.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
