title: 2-methoxyestradiol blocks cell-cycle progression at G(2)/M phase and inhibits growth of human prostate cancer cells.
abstract: 2-Methoxyestradiol (2-ME), an endogenous metabolite of 17beta-estradiol, is present in human blood and urine. Here we show for the first time that 2-ME significantly inhibited the growth of normal prostate epithelial cells and androgen-dependent LNCaP and androgen-independent DU145 prostate cancer cells. This growth inhibition was accompanied by a twofold increase in the G(2)/M population, with a concomitant decrease in the G(1) population, as shown by cell-cycle analysis. 2-ME treatment affected the cell-cycle progression of prostate cancer cells specifically by blocking cells in the G(2) phase. Immunoblot analysis of the key cell-cycle regulatory proteins in the G(2)/M phase showed a 14-fold increase in the expression of p21 and an eightfold increase in the expression of p34 cell division cycle 2 (cdc2). We also found an accumulation of phosphorylated cdc2 after 2-ME treatment. Furthermore, Wee 1 kinase was detectable after 2-ME treatment. 2-ME treatment also led to an increase in the activity of caspase-3, followed by apoptosis, as shown by terminal deoxynucleotidyl transferase-mediated deoxyuridine 5-triphosphate-biotin nick end-labeling and fluorescein isothiocyanate-poly(ADP-ribose) polymerase assay. Estrogen receptor levels did not change after treatment with 2-ME. Examination of the signaling pathways that mediate 2-ME-induced apoptosis showed reduction in the level of p53 expression and its DNA-binding activity. Given the fact that p53 mutations are common in patients with metastatic prostate cancer, our finding that 2-ME-mediated growth inhibition of human prostate cancer cells occurred in a p53-independent manner has considerable clinical significance. These findings, combined with the limited toxicity of 2-ME, may have significant implications for alternative treatment of advanced prostate cancer.
authors.affiliation: Center for Cancer Causation and Prevention, AMC Cancer Research Center and University of Colorado Comprehensive Cancer Center, Denver, Colorado 80214, USA.
authors.forename: A P
authors.initials: AP
authors.lastname: Kumar
authors.forename: G E
authors.initials: GE
authors.lastname: Garcia
authors.forename: T J
authors.initials: TJ
authors.lastname: Slaga
mesh_terms: D000077584:2-Methoxyestradiol; D016588:Anticarcinogenic Agents / Q000494:pharmacology*; D017209:Apoptosis; D015153:Blotting, Western; D016203:CDC2 Protein Kinase / Q000096:biosynthesis; D053148:Caspase 3; D020169:Caspases / Q000096:biosynthesis; D002453:Cell Cycle / Q000187:drug effects*; D018797:Cell Cycle Proteins; D002455:Cell Division / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004958:Estradiol / Q000031:analogs & derivatives / Q000494:pharmacology*; D005434:Flow Cytometry; D016193:G1 Phase / Q000187:drug effects; D016195:G2 Phase / Q000187:drug effects; D016158:Genes, p53 / Q000235:genetics; D006801:Humans; D020287:In Situ Nick-End Labeling; D008297:Male; D008938:Mitosis / Q000187:drug effects; D009154:Mutation; D009687:Nuclear Proteins; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D011471:Prostatic Neoplasms / Q000188:drug therapy* / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000096:biosynthesis; D016283:Proto-Oncogene Proteins p21(ras) / Q000096:biosynthesis; D011960:Receptors, Estrogen / Q000378:metabolism; D013997:Time Factors; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism
chemical_list: D016588:Anticarcinogenic Agents; D018797:Cell Cycle Proteins; D009687:Nuclear Proteins; D011960:Receptors, Estrogen; D016159:Tumor Suppressor Protein p53; D004958:Estradiol; D000077584:2-Methoxyestradiol; D011065:Poly(ADP-ribose) Polymerases; D011505:Protein-Tyrosine Kinases; C499349:WEE1 protein, human; D016203:CDC2 Protein Kinase; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; C501009:HRAS protein, human; D016283:Proto-Oncogene Proteins p21(ras)