title: Regulation of cell cycle and cyclins by 16alpha-hydroxyestrone in MCF-7 breast cancer cells.
abstract: It has been suggested that alterations in estradiol (E(2)) metabolism, resulting in increased production of 16alpha-hydroxyestrone (16alpha-OHE(1)), is associated with an increased risk of breast cancer. In the present study, we examined the effects of 16alpha-OHE(1)on DNA synthesis, cell cycle progression, and the expression of cell cycle regulatory genes in MCF-7 breast cancer cells. G(1) synchronized cells were treated with 1 to 25 nM 16alpha-OHE(1) for 24 and 48 h. [(3)H]Thymidine incorporation assay showed that 16alpha-OHE(1) caused an 8-fold increase in DNA synthesis compared with that of control cells, whereas E(2) caused a 4-fold increase. Flow cytometric analysis of cell cycle progression also demonstrated the potency of 16alpha-OHE(1) in stimulating cell growth. When G(1) synchronized cells were treated with 10 nM 16alpha-OHE(1) for 24 h, 62+/-3% of cells were in S phase compared with 14+/-3% and 52+/-2% of cells in the control and E(2)-treated groups respectively. In order to explore the role of 16alpha-OHE(1) in cell cycle regulation, we examined its effects on cyclins (D1, E, A, B1), cyclin dependent kinases (Cdk4, Cdk2), and retinoblastoma protein (pRB) using Western and Northern blot analysis. Treatment of cells with 10 nM 16alpha-OHE(1) resulted in 4- and 3-fold increases in cyclin D1 and cyclin A, respectively, at the protein level. There was also a significant increase in pRB phosphorylation and Cdk2 activation. In addition, transient transfection assay using an estrogen response element-driven luciferase reporter vector showed a 15-fold increase in estrogen receptor-mediated transactivation compared with control. These results show that 16alpha-OHE(1) is a potent estrogen capable of accelerating cell cycle kinetics and stimulating the expression of cell cycle regulatory proteins.
authors.affiliation: Department of Medicine, University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School, 125 Paterson Street, New Brunswick, NJ 08903, USA.
authors.forename: J S
authors.initials: JS
authors.lastname: Lewis
authors.forename: T J
authors.initials: TJ
authors.lastname: Thomas
authors.forename: C M
authors.initials: CM
authors.lastname: Klinge
authors.forename: M A
authors.initials: MA
authors.lastname: Gallo
authors.forename: T
authors.initials: T
authors.lastname: Thomas
mesh_terms: D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D042846:CDC2-CDC28 Kinases; D002453:Cell Cycle / Q000187:drug effects*; D002455:Cell Division / Q000187:drug effects; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases / Q000378:metabolism; D016213:Cyclins / Q000235:genetics / Q000378:metabolism*; D004273:DNA, Neoplasm / Q000096:biosynthesis; D004958:Estradiol / Q000378:metabolism; D005260:Female; D017930:Genes, Reporter; D006801:Humans; D006894:Hydroxyestrones / Q000494:pharmacology*; D008156:Luciferases / Q000235:genetics; D009376:Neoplasms, Hormone-Dependent / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D011960:Receptors, Estrogen / Q000235:genetics; D016160:Retinoblastoma Protein / Q000378:metabolism; D015533:Transcriptional Activation / Q000187:drug effects; D014407:Tumor Cells, Cultured
chemical_list: D016213:Cyclins; D004273:DNA, Neoplasm; D006894:Hydroxyestrones; D012333:RNA, Messenger; D011960:Receptors, Estrogen; D016160:Retinoblastoma Protein; C026702:16-hydroxyestrone; D004958:Estradiol; D008156:Luciferases; D017346:Protein Serine-Threonine Kinases; D042846:CDC2-CDC28 Kinases; C495894:CDK2 protein, human; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases