Contribution of transcription factor, SP1, to the promotion of HB-EGF expression in defense mechanism against the treatment of irinotecan in ovarian clear cell carcinoma

Cancer Med. 2014 Oct;3(5):1159-69. doi: 10.1002/cam4.301. Epub 2014 Jul 24.


Ovarian clear cell carcinoma (OCCC) is a worst histological subtype than other ovarian malignant tumor. Heparin-binding epidermal growth factor-like growth factor (HB-EGF) is a promising target for ovarian cancer therapy. The aims of this study were to validate the efficacy of HB-EGF-targeted therapy for OCCC and to identify the transcription factor that contributed to the induction of HB-EGF by SN38 treatment in OCCC cells. HB-EGF was highly expressed in OCCC cells, and an increase of HB-EGF was induced by SN38 which had only antitumor effect among conventional anticancer agents on OCCC. A specific inhibitor of HB-EGF, a cross-reacting material 197 (CRM197), led to a synergistic increase in the number of apoptotic OCCC cells with the treatment of SN38. The luciferase assay with 5'-deletion promoter constructs identified a GC-rich element between -125 and -178 (the distal transcription start site was denoted +1) as a cis-regulatory region, and the treatment of SN38 induced luciferase activity in this region. An in silico and chromatin immunoprecipitation analysis estimated that SP1 bound to the cis-regulatory region of HB-EGF in OCCC cells. Real-time PCR and cell viability assays showed that the transfection of a small interfering RNA targeting SP1 suppressed the expression of HB-EGF induced by SN38, resulting in the enhanced sensitivity of SN38. Taken together, these results indicate that induction of HB-EGF expression contributed to defense mechanism against treatment of SN38 through the transcriptional activity of SP1 in OCCC cells.

Keywords: Chemotherapy; HB-EGF; gene transcriptional regulation; ovarian cancer.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenocarcinoma, Clear Cell / genetics*
  • Adenocarcinoma, Clear Cell / metabolism*
  • Antineoplastic Agents, Phytogenic / pharmacology
  • Apoptosis / drug effects
  • Camptothecin / analogs & derivatives*
  • Camptothecin / pharmacology
  • Cell Line, Tumor
  • Cell Survival / drug effects
  • Drug Resistance, Neoplasm
  • Female
  • Gene Expression Regulation, Neoplastic / drug effects*
  • Heparin-binding EGF-like Growth Factor / genetics*
  • Heparin-binding EGF-like Growth Factor / metabolism
  • Humans
  • Irinotecan
  • Ovarian Neoplasms / genetics*
  • Ovarian Neoplasms / metabolism*
  • Promoter Regions, Genetic
  • Protein Binding
  • Sp1 Transcription Factor / metabolism*


  • Antineoplastic Agents, Phytogenic
  • Heparin-binding EGF-like Growth Factor
  • Sp1 Transcription Factor
  • Irinotecan
  • Camptothecin