title: Activation of cyclin D1 by estradiol and spermine in MCF-7 breast cancer cells: a mechanism involving the p38 MAP kinase and phosphorylation of ATF-2.
abstract: Estradiol (E2) and the naturally occurring polyamines (putrescine, spermidine, and spermine) play important roles in breast cancer cell growth and differentiation. We examined the effects of E2 and spermine on the phosphorylation and DNA binding of activating transcription factor-2 (ATF-2) in MCF-7 breast cancer cells. ATF-2 is a transcription factor involved in estrogenic regulation of cyclin D1 gene, and thereby cell cycle progression. DNA affinity immunoblot assays showed a six- to eightfold increase in the binding of ATF-2 to a 74-mer ATF/CRE oligonucleotide (ODN1) from cyclin D1 promoter in the presence of 4 nM E2 and 0.5 mM spermine, compared to untreated control. Individual treatments with E2 or spermine caused a twofold or lower increase in ATF-2 binding to ODN1. Immunoblotting with phospho-ATF-2 antibody showed that increased DNA binding of ATF-2 was associated with its phosphorylation. A p38 MAP kinase inhibitor, PD169316, inhibited ATF-2 phosphorylation. In contrast, the MEK-ERK1/2 inhibitor, PD98059, or the JNK inhibitor, SP600125, had no significant effect on DNA binding of ATF-2. Cyclin D1 promoter (-1745CD1) activity increased by approximately 12-fold (above control) in the presence of E2 and spermine, compared to a sixfold increase in the presence of E2 alone and a twofold increase with spermine. Cells transfected with a dominant negative mutant of ATF-2 showed decreased transactivation of cyclin D1 promoter in response to E2 and spermine. These results indicate that spermine can enhance E2-induced cell signaling and cyclin D1 transcription by activation of the p38 MAP kinase and phosphorylation of ATF-2, contributing to breast cancer cell proliferation.
authors.affiliation: Department of Medicine, University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School, New Brunswick, New Jersey, NJ 08903, USA.
authors.forename: Joan S
authors.initials: JS
authors.lastname: Lewis
authors.forename: Veena
authors.initials: V
authors.lastname: Vijayanathan
authors.forename: T J
authors.initials: TJ
authors.lastname: Thomas
authors.forename: Richard G
authors.initials: RG
authors.lastname: Pestell
authors.forename: Chris
authors.initials: C
authors.lastname: Albanese
authors.forename: Michael A
authors.initials: MA
authors.lastname: Gallo
authors.forename: Thresia
authors.initials: T
authors.lastname: Thomas
mesh_terms: D051698:Activating Transcription Factor 2; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000201:enzymology / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002851:Chromatography, High Pressure Liquid; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism*; D019938:Cyclin D1 / Q000235:genetics*; D004357:Drug Synergism; D004958:Estradiol / Q000494:pharmacology*; D006801:Humans; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D013096:Spermine / Q000494:pharmacology*; D014157:Transcription Factors / Q000378:metabolism*; D015533:Transcriptional Activation / Q000187:drug effects; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
chemical_list: C497105:ATF2 protein, human; D051698:Activating Transcription Factor 2; D017362:Cyclic AMP Response Element-Binding Protein; D014157:Transcription Factors; D019938:Cyclin D1; D013096:Spermine; D004958:Estradiol; D048051:p38 Mitogen-Activated Protein Kinases