Metabolic activation and formation of DNA adducts of hexestrol, a synthetic nonsteroidal carcinogenic estrogen.
Hexestrol (HES), a synthetic nonsteroidal estrogen, is carcinogenic in Syrian golden hamsters. The major metabolite of HES is its catechol, 3'-OH-HES, which can be metabolically converted to the electrophilic catechol quinone, HES-3',4'-Q, by peroxidases and cytochrome P450. Standard adducts were synthesized by reacting HES-3',4'-Q with dG and dA to produce the adducts 3'-OH-HES-6'(alpha, beta)-N7Gua and HES-3',4'-Q-6'-N6dA, respectively. When HES-3',4'-Q was reacted with calf thymus DNA, 3'-OH-HES-6'(alpha,beta)-N7Gua was identified by HPLC and tandem mass spectrometry as the depurinating adduct, with minor amounts of stable adducts. 3'-OH-HES was bound to DNA after activation by horseradish peroxidase, lactoperoxidase, or rat liver microsomes. The depurinating adduct 3'-OH-HES-6'(alpha, beta)-N7Gua was identified in these systems at levels of 65, 41, and 11 micromol/mol of DNA-P, respectively. Unidentified stable adducts were observed in much lower amounts and were quantified by the 32P-postlabeling method. Similarly to 3'-OH-HES, the catechol metabolites of the natural steroidal estrogens estrone (E1) and estradiol (E2), namely, 2-OHE1, 4-OHE1, 2-OHE2, and 4-OHE2, can be oxidized to their corresponding quinones by peroxidases and cytochrome P450. The quinones of the carcinogenic 4-OHE1 and 4-OHE2 have chemical and biochemical properties similar to those of HES-3',4'-Q. The results suggest that formation of HES-3',4'-Q may be a critical event in tumor initiation by HES and that HES is an excellent model compound to corroborate the hypothesis that estrogen-3,4-quinones are ultimate carcinogenic metabolites of the natural steroidal estrogens E1 and E2.
Jan
S T
ST
Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, 600 South 42nd Street, Omaha, Nebraska 68198-6805, USA.
Devanesan
P D
PD
Stack
D E
DE
Ramanathan
R
R
Byun
J
J
Gross
M L
ML
Rogan
E G
EG
Cavalieri
E L
EL
D000818:Animals; D001711:Biotransformation; D002273:Carcinogens / Q000378:metabolism* / Q000633:toxicity; D002851:Chromatography, High Pressure Liquid; D006224:Cricetinae; D018736:DNA Adducts / Q000378:metabolism*; D004968:Estrogens, Non-Steroidal / Q000378:metabolism* / Q000633:toxicity; D006589:Hexestrol / Q000378:metabolism* / Q000633:toxicity; D066298:In Vitro Techniques; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D011809:Quinones / Q000737:chemistry / Q000378:metabolism; D051381:Rats; D016339:Spectrometry, Mass, Fast Atom Bombardment
D002273:Carcinogens; D018736:DNA Adducts; D004968:Estrogens, Non-Steroidal; D011809:Quinones; D006589:Hexestrol