title: A high nuclear basal level of ERK2 phosphorylation contributes to the resistance of cisplatin-resistant human ovarian cancer cells.
abstract: OBJECTIVE
  The aim of this study was to elucidate the role of ERK1/2 on cisplatin resistance in human ovarian cancer cells.
  
  
  METHODS
  The relationship between nuclear levels of ERK2 and cisplatin-induced apoptosis in human ovarian carcinoma cell line, OVCAR-3, and in cells of the cisplatin-resistant subclone, OVCAR-3/CDDP, was examined using immunoblotting and immunocytochemistry.
  
  
  RESULTS
  Cisplatin treatment resulted in the activation of ERK2, both in OVCAR-3 and OVCAR-3/CDDP cells. However, considerable levels of activated ERK2 existed in the nuclei of OVCAR-3/CDDP cells during serum starvation and in the early period (1-3 h) after cisplatin treatment. Conversely, phospho-ERK2 was marginally detected in the nuclei of OVCAR-3 cells prior to cisplatin treatment. These phenomena were confirmed by immunofluorescence staining of the phosphorylated ERK2 in the nuclei of both cells. High basal phospho-ERK2 in the nuclei of OVCAR-3/CDDP cells contributed to cisplatin resistance, and was supported by several observations; (1) treatment of U0126, an inhibitor of MEK/ERK signaling pathway, partially sensitized OVCAR-3/CDDP cells to cisplatin; (2) pretreatment of OVCAR-3 cells with phorbol 12-myristate 13-acetate (PMA), an activator of ERK, induced nuclear translocation of activated ERK2, which led to the suppression of cisplatin-induced apoptosis.
  
  
  CONCLUSIONS
  These results collectively indicate that prelocalization of activated ERK2 in the nuclei contribute to cisplatin resistance in OVCAR-3/CDDP cells.
authors.affiliation: Bioanalysis and Biotechnology Research Center, Korea Institute of Science and Technology, Seoul 136-791, South Korea.
authors.forename: Sooyong
authors.initials: S
authors.lastname: Lee
authors.forename: Seunghee
authors.initials: S
authors.lastname: Yoon
authors.forename: Dong-Hyun
authors.initials: DH
authors.lastname: Kim
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D002070:Butadienes / Q000494:pharmacology; D053148:Caspase 3 / Q000378:metabolism; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000201:enzymology; D002945:Cisplatin / Q000494:pharmacology*; D019008:Drug Resistance, Neoplasm; D004357:Drug Synergism; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D006801:Humans; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D009570:Nitriles / Q000494:pharmacology; D010051:Ovarian Neoplasms / Q000188:drug therapy* / Q000201:enzymology* / Q000473:pathology; D010766:Phosphorylation; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D000970:Antineoplastic Agents; D002070:Butadienes; D004791:Enzyme Inhibitors; D009570:Nitriles; C113580:U 0126; D019950:Mitogen-Activated Protein Kinase 1; D053148:Caspase 3; D013755:Tetradecanoylphorbol Acetate; D002945:Cisplatin