title: [Effects of siltuximab on the interleukin-6/Stat3 signaling pathway in ovarian cancer].
abstract: OBJECTIVE
  To study the effects of siltuximab on the interleukin-6 (IL-6)/signal transducer and activator of transcription 3 (Stat3) signaling pathway in ovarian epithelial carcinoma.
  
  
  METHODS
  (1) Expressions of IL-6 in ovarian cancer patient specimens were assessed by immunohistochemistry. (2) Expression of phosphorylation Stat3 (pStat3) protein in siltuximab and IL-6 treated SKOV3 cell lines was determined by western blot, and expression levels of Stat3-induced bcl-XL, MCL-1, survivin, in siltuximab treated SKOV3/TR and CAOV3/TR cells lines were also determined by western blot. (3) Real-time image analysis was used to study the nuclear translocation of pEGFP-Stat3 fusion protein in ovarian cancer cell line SKOV3-pEGFP-Stat3 treated with siltuximab and IL-6. (4) Paclitaxel sensitivity in siltuximab treated SKOV3/TR and CAOV3/TR cell lines were assessed using the methyl thiazolyl tetrazolium (MTT). The 50% inhibiting concentration (IC(50)) was defined as the paclitaxel concentration required to decrease the A(490) value to 50%.
  
  
  RESULTS
  (1) There were significantly difference in IL-6 staining density and the positive rate of IL-6 protein stained among the metastatic, and drug-resistant recurrent tumors, and matched primary tumors [69% (18/26)] vs. 77% (20/26) vs. 23% (6/26), P < 0.05]. (2)A clear increase in Stat3 phosphorylation levels was observed in the IL-6-treated SKOV3 cell lines as compared to the SKOV3 cell lines. When the IL-6-treated SKOV3 cells were incubated with siltuximab with a range of concentrations of 0.001, 0.01, 0.1, 1.0 and 10 µg/ml, there were trends toward reduced pStat3 expression in the treated cell lines. Compared without treatment with siltuximab, the expression of the anti-apoptotic proteins MCL-1, bcl-XL and survivin in SKOV3/TR and CAOV3/TR cell lines were significantly decreased after treated with siltuximab. (3) In resting cells, the majority of pEGFP-Stat3 was cytoplasmic until the addition of human IL-6, which promptly induced the translocation of fluorescent Stat3 molecules to the nucleus. Exposure of cells to siltuximab with a range of concentrations of 0.001, 0.01, 0.1, 1.0 and 10 µg/ml, followed by an incubation in IL-6 significantly reduced pEGFP-Stat3 nucleocytoplasmic translocation. (4) MTT cytotoxicity assay demonstrated that siltuximab increased paclitaxel-induced cell death and partially overcame paclitaxel resistance. Treated with siltuximab (1 and 10 µg/ml), the paclitaxel IC(50) value of siltuximab in SKOV3/TR (0.49, 0.19 µg/ml) and CAOV3/TR (0.0010, 0.0008 µg/ml) cells were significantly lower than those in untreated cells (0.71, 0.0021 µg/ml; all P < 0.05).
  
  
  CONCLUSIONS
  These results demonstrated that siltuximab effectively block the IL-6 signaling pathways, which. Blockage of IL-6 signaling may provide benefits for the treatment of ovarian cancer.
authors.affiliation: Department of Obstetrics and Gynecology, Zhengzhou University, Zhengzhou 450052, China.
authors.forename: Yu-qi
authors.initials: YQ
authors.lastname: Guo
authors.forename: Ping
authors.initials: P
authors.lastname: Lu
authors.forename: Zhen-feng
authors.initials: ZF
authors.lastname: Duan
authors.forename: Zhan
authors.initials: Z
authors.lastname: Zhang
mesh_terms: D000911:Antibodies, Monoclonal / Q000494:pharmacology*; D015153:Blotting, Western; D045744:Cell Line, Tumor; D019008:Drug Resistance, Neoplasm; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D015850:Interleukin-6 / Q000378:metabolism* / Q000494:pharmacology; D010051:Ovarian Neoplasms / Q000378:metabolism / Q000473:pathology*; D017239:Paclitaxel / Q000494:pharmacology; D010766:Phosphorylation; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D050796:STAT3 Transcription Factor / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects*; D051020:bcl-X Protein / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; C508600:IL6 protein, human; D015850:Interleukin-6; D019253:Proto-Oncogene Proteins c-bcl-2; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D051020:bcl-X Protein; D017239:Paclitaxel; C504234:siltuximab