title: Signal transducers and activators of transcription 3 pathway activation in drug-resistant ovarian cancer.
abstract: OBJECTIVE
  One of the major obstacles in the treatment of ovarian cancer is the development of multidrug resistance. Recent evidence shows that high-grade ovarian cancer often shows activation of the signal transducers and activators of transcription 3 (Stat3) pathway with subsequent transcription of genes that support tumor growth and survival. Less studied is the role of the Stat3 pathway in acquired drug resistance. There is no information on Stat3 expression in chemotherapy naïve ovarian cancer as compared with tumors collected later in the natural history of the disease. To further clarify the significance of Stat3 activation in ovarian cancer, here we investigated the Stat3 expression and activation in ovarian cancer and ovarian cancer multidrug resistance cell lines.
  
  
  METHODS
  Western blotting, electrophoretic mobility shift assay, luciferase assays, ELISA assay, and real-time reverse transcription-PCR determined interleukin-6 and Stat3 pathway expression and activation in cell lines. Stat3 expression in ovarian cancer tissue microarray was evaluated by immunohistochemistry.
  
  
  RESULTS
  Activated (phosphorylated) Stat3 is overexpressed in most paclitaxel-resistant ovarian cancer cells. Inhibition of Stat3 activation results in significant decreases in paclitaxel resistance and enhanced apoptosis. Drug-resistant recurrent tumors have significantly greater phosphorylated Stat3 (pStat3) expression as compared with matched primary tumors. Tumors with associated inflammatory cell infiltrates also have a higher proportion of cells staining intensely for nuclear phosphorylated Stat3 as compared with tumors without inflammatory infiltrates, consistent with paracrine activation of the Stat3 pathway by immune-mediated cytokines.
  
  
  CONCLUSIONS
  These data support the hypothesis that interruption of Stat3 signaling could reverse resistance to paclitaxel and perhaps other chemotherapy agents in human cancer.
authors.affiliation: Division of Hematology/Oncology, Department of Pathology, and Biostatistics Center, Massachusetts General Hospital, Boston, Massachusetts 02114, USA. zduan@partners.org
authors.forename: Zhenfeng
authors.initials: Z
authors.lastname: Duan
authors.forename: Rosemary
authors.initials: R
authors.lastname: Foster
authors.forename: Debra A
authors.initials: DA
authors.lastname: Bell
authors.forename: Jennifer
authors.initials: J
authors.lastname: Mahoney
authors.forename: Kathryn
authors.initials: K
authors.lastname: Wolak
authors.forename: Ami
authors.initials: A
authors.lastname: Vaidya
authors.forename: Constanze
authors.initials: C
authors.lastname: Hampel
authors.forename: Hang
authors.initials: H
authors.lastname: Lee
authors.forename: Michael V
authors.initials: MV
authors.lastname: Seiden
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B / Q000032:analysis; D017209:Apoptosis / Q000187:drug effects; D045744:Cell Line, Tumor; D019008:Drug Resistance, Neoplasm; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics; D006801:Humans; D007150:Immunohistochemistry; D015850:Interleukin-6 / Q000032:analysis / Q000378:metabolism; D010051:Ovarian Neoplasms / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D017239:Paclitaxel / Q000494:pharmacology / Q000627:therapeutic use; D010766:Phosphorylation; D034741:RNA, Small Interfering / Q000494:pharmacology; D050796:STAT3 Transcription Factor / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000235:genetics*; D046888:Tissue Array Analysis / Q000379:methods; D015854:Up-Regulation; D000097202:ATP-Binding Cassette Sub-Family B Member 4
chemical_list: D018435:ATP Binding Cassette Transporter, Subfamily B; D015850:Interleukin-6; D017239:Paclitaxel; D034741:RNA, Small Interfering; D050796:STAT3 Transcription Factor; D000097202:ATP-Binding Cassette Sub-Family B Member 4; C494086:STAT3 protein, human