4-hydroxyestradiol and Kidney-Neoplasms

Long-term exposure to estrogen and its metabolites may play an important role in renal cell carcinogenesis. Catechol-O-methyltransferase (COMT) participates in the estrogen metabolism pathway by neutralizing toxic substances. Although reduced COMT activity has been suggested to be a risk factor for estrogen-associated cancers, no studies have investigated the biological significance of COMT in the pathogenesis of human renal cell cancers (RCCs). We initially found that COMT levels are significantly decreased in human RCC tissues and cells suggesting it plays a suppressive role in tumor development. However, transient overexpression of COMT has no functional effect on RCC cell lines. In contrast, when cells overexpressing COMT are treated with its substrate 4-hydroxyestradiol (4-OHE(2)), growth is inhibited by apoptotic cell death. We also found that COMT overexpression combined with 4-OHE(2) induces upregulation of growth arrest- and DNA damage-inducible protein α (GADD45α). We further show that downregulation of GADD45α by a small interfering RNA-mediated approach inhibits cell death, indicating the essential role of GADD45α in the underlying mechanism of COMT action in response to 4-OHE(2). Finally, 4-methoxyestradiol fully reproduces the antiproliferative function of COMT with 4-OHE(2) by promoting GADD45α induction. Together, these findings show that COMT in the presence of 4-OHE(2) prevents RCC cell proliferation by enhancing apoptosis and that GADD45α plays a critical role in the COMT-mediated inhibition of RCC.

Topics: Apoptosis; Carcinoma, Renal Cell; Catechol O-Methyltransferase; Cell Cycle Proteins; Cell Death; Cell Growth Processes; Cell Line; Cell Line, Tumor; Down-Regulation; Estradiol; Estrogens, Catechol; Humans; Kidney Neoplasms; Nuclear Proteins; RNA, Messenger; Up-Regulation

Catecholestrogens have been postulated to mediate the induction of kidney tumors by estradiol in male Syrian hamsters. In this study, we examined the mechanism of inhibition by quercetin of the catechol O-methyltransferase-catalyzed O-methylation of catecholestrogens as a basis for the previously reported enhancement of estradiol-induced tumorigenesis by this flavonoid. In hamsters treated with 50 micrograms of [6,7-3H]estradiol, quercetin increased concentrations of 2- and 4-hydroxyestradiol in kidney by 80 and 59%, respectively. In animals treated with two 10-mg estradiol implants, quercetin also decreased by 63-65% the urinary excretion of 2- and 4-hydroxyestradiol monomethyl ethers. Taken together, these results demonstrate the in vivo inhibition of the O-methylation of catecholestrogens by quercetin. S-Adenosyl-L-homocysteine, produced by the methylation of catecholestrogens, noncompetitively inhibited the O-methylation of 2- and 4-hydroxyestradiol by hamster kidney cytosolic catechol O-methyltransferase (IC50 approximately 10-14 microM). Due to the rapid O-methylation of quercetin itself, quercetin decreased renal concentrations of S-adenosyl-L-methionine by approximately 25% in control or estradiol-treated hamsters and increased concentrations of S-adenosyl-L-homocysteine by 5-15 nmol/g of wet tissue, which was estimated to cause a 30-70% inhibition of the enzymatic O-methylation of catecholestrogens. Quercetin or fisetin (a structural analog) inhibited the O-methylation of 2- and 4-hydroxyestradiol by a competitive plus noncompetitive mechanism (IC50 approximately 2-5 microM). These results suggest that the in vivo O-methylation of catecholestrogens is inhibited more by S-adenosyl-L-homocysteine than by quercetin. The accumulation of 2- and 4-hydroxyestradiol during co-administration of estradiol and quercetin may enhance metabolic redox cycling of catecholestrogens and thus estradiol-induced kidney tumorigenesis.

Topics: Animals; Catechol O-Methyltransferase Inhibitors; Cricetinae; Enzyme Inhibitors; Estradiol; Estrogens, Catechol; Flavonoids; Flavonols; Hesperidin; Kidney; Kidney Neoplasms; Kinetics; Male; Mesocricetus; Methylation; Oxidation-Reduction; Quercetin; S-Adenosylhomocysteine

The chronic administration of estradiol by subcutaneous (s.c.) implantation into male Syrian hamsters induces kidney tumors. Free radicals generated by redox cycling between catecholestrogens and their quinones have been proposed to damage DNA and to thus mediate renal hormone-induced carcinogenesis. As part of an examination of this postulate, we assayed by a filter elution technique DNA single-strand breaks in livers and kidneys of male hamsters treated with estrogen by single intraperitoneal (i.p.) injection, by s.c. implant or by continuous infusion and compared values to those in untreated controls. The DNAs of hamster liver and kidney were not affected by one i.p. injection of 5, 15 or 150 mg/kg estradiol. However, treatment of hamsters with one 25 mg estradiol implant/animal for 2 weeks elevated by 10% the levels of DNA single-strand breaks in kidney, but only to a minor extent in liver, which is not a target of estrogen-induced carcinogenesis. An infusion of 250 micrograms/day/animal of estradiol or 4-hydroxyestradiol for one week by osmotic pumps into hamsters resulted in a comparable increase of single-strand breaks in kidney DNA, whereas 2-hydroxyestradiol under these conditions had a negligible effect. It is concluded that the induction of DNA single-strand breakage by either estradiol or 4-hydroxyestradiol in hamster kidney supports a mechanism of estrogen-induced carcinogenesis by free radical generation via redox cycling between 4-hydroxyestradiol and its corresponding quinone.

Topics: Animals; Cricetinae; DNA; DNA Damage; DNA, Single-Stranded; Dose-Response Relationship, Drug; Estradiol; Estrogens; Estrogens, Catechol; Free Radicals; Kidney; Kidney Neoplasms; Male; Mesocricetus

Estradiol and other estrogens induce renal carcinoma in male Syrian hamsters. The mechanism of carcinogenesis still remains unclear. Activation of estrogens to catechol metabolites has in the past been postulated to play a role in estrogen-induced carcinogenesis. Therefore, the carcinogenic activity of catechol estrogens was investigated. After 175 days of treatment, 4-hydroxyestradiol was found to be as carcinogenic as estradiol in male Syrian hamsters (4/5 and 4/5 animals with kidney tumors, respectively). Animals treated with 2-hydroxyestradiol (0/5) or 2-methoxyestradiol (0/6) did not develop renal carcinoma. The catechol estrogens failed to be mutagenic in the Ames test (reversions of his- S. typhimurium to histidine prototrophy in the TA 100 strain). The lack of carcinogenic activity of 2-hydroxyestradiol was not due to a failure to stimulate estrogen-dependent tumor growth. Growth of H-301 cells, an estrogen-dependent hamster kidney tumor cell line, was supported in vivo by estrogens in the following order: estradiol greater than 4-hydroxyestradiol greater than 2-hydroxyestradiol. Stimulation of tumor growth by 2-methoxyestradiol was not detected. It was concluded that the carcinogenic activity of 4-hydroxyestradiol was consistent with a role of catechol metabolites in estrogen-induced carcinogenesis. However, the intrinsic carcinogenic or hormonal activity of 2-hydroxyestradiol probably can not be assessed accurately in vivo because of its rapid methylation and metabolic clearance.

Topics: Animals; Carcinoma, Renal Cell; Cricetinae; Estradiol; Estrogens, Catechol; Kidney Neoplasms; Male; Mesocricetus; Mutagenicity Tests; Mutagens; Neoplasms, Hormone-Dependent; Salmonella typhimurium