Novel mechanisms of carboplatin resistance in epithelial ovarian cancer and their therapeutic potential

  • Author / Creator
    Barghout, Samir H
  • Ovarian cancer is the fifth leading cause of cancer-related mortality in women. Epithelial ovarian cancer (EOC) constitutes approximately 90% of all ovarian malignancies. Platinum-based compounds have been used to treat EOC, with carboplatin currently being used as a first-line therapeutic agent in combination with paclitaxel. Despite the initial positive response to carboplatin, relapse occurs in most advanced EOC patients and resistance eventually develops, with a 5-year survival rate of only 30%. Accordingly, there is an urgent need to identify the molecular mechanisms underlying chemoresistance in EOC in order to develop more effective therapeutic strategies. To address this objective, the gene expression profiles of the EOC cell line A2780s (cisplatin-sensitive) and its derivative A2780cp (cisplatin-resistant) were compared by conducting DNA microarray and ingenuity pathway analysis (IPA). A number of genes were found to be differentially expressed between these two cell lines including RUNX3 and genes encoding several components of the Wnt/β-catenin signaling pathway. These genes were selected for further analysis as they have not been previously studied in the context of chemoresistance in EOC. RUNX3 is a member of the RUNX family of transcription factors that act as developmental regulators and have an oncogenic role in EOC. Consistent with DNA microarray data, subsequent validation by Western blotting showed that RUNX3 expression was higher in A2780cp cells compared to A2780s cells. Further gain- and loss-of-function studies in A2780 cells confirmed the role of RUNX3 in EOC resistance to carboplatin-induced cytotoxicity. Interestingly, the results demonstrate that RUNX3 upregulates the expression of cellular inhibitor of apoptosis 2 (cIAP2), suggesting a potential mechanism by which RUNX3 confers resistance to carboplatin. In addition, DNA microarray analysis and subsequent validation by qRT-PCR suggested that the Wnt/β-catenin signaling pathway is more active in A2780cp cells compared to A2780s cells. Consistent with this finding, further analysis showed increased nuclear localization of β-catenin and higher β-catenin transcriptional activity in A2780cp cells compared to A2780s cells. Interestingly, chemical inhibition of Wnt/β-catenin signaling by CCT036477 sensitized A2780cp cells to carboplatin, especially at high concentrations. Further investigation of the effect of other Wnt/β-catenin signaling inhibitors is warranted. Two Wnt negative regulators, dickkopf-related protein 1 (DKK1) and secreted frizzled-related protein 1 (SFRP1), were among the down-regulated proteins in A2780cp cells. Gain- and loss-of-function approaches are planned to investigate their specific roles in chemoresistance in EOC. In conclusion, our data suggest that RUNX3 contributes to carboplatin resistance of EOC cells and therefore it could be a potential therapeutic target. In addition, the Wnt/β-catenin signaling pathway is more active in resistant EOC cells, suggesting its potential contribution to chemoresistance in EOC.

  • Subjects / Keywords
  • Graduation date
  • Type of Item
  • Degree
    Master of Science
  • DOI
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.
  • Language
  • Institution
    University of Alberta
  • Degree level
  • Department
    • Medical Sciences-Obstetrics and Gynecology
  • Supervisor / co-supervisor and their department(s)
    • YangXin Fu/Oncology and Obstetrics and Gynecology
  • Examining committee members and their departments
    • Denise G. Hemmings/Obstetrics and Gynecology
    • Roseline Godbout/Oncology
    • Lynne-Marie Postovit/Oncology and Obstetrics and Gynecology
    • Michael Weinfeld/Oncology