Contribution of transcription factor, SP 1, to the promotion of HB ‐ EGF expression in defense mechanism against the treatment of irinotecan in ovarian clear cell carcinoma

• Published in: Cancer medicine (Malden, MA) Vol. 3; no. 5; pp. 1159 - 1169
• Main Authors: Miyata, Kohei, Yotsumoto, Fusanori, Nam, Sung Ouk, Odawara, Takashi, Manabe, Sadao, Ishikawa, Toyokazu, Itamochi, Hiroaki, Kigawa, Junzo, Takada, Shuji, Asahara, Hiroshi, Kuroki, Masahide, Miyamoto, Shingo
• Format: Journal Article
• Language: English
• Published: Bognor Regis John Wiley & Sons, Inc 01.10.2014
• Subjects: Antitumor activity; Antitumor agents; Apoptosis; Arsenic; Cancer therapies; Cell viability; Chemotherapy; Chromatin; Clonal deletion; Defense mechanisms; Epidermal growth factor; Gastric cancer; Gene deletion; Heparin; Immunoprecipitation; Irinotecan; Lung cancer; Medical prognosis; Ovarian cancer; R&D; Research & development; siRNA; Transcription factors; Transfection; Japan
• ISSN: 2045-7634; 2045-7634
• DOI: 10.1002/cam4.301

Abstract 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 SN 38 treatment in OCCC cells. HB ‐ EGF was highly expressed in OCCC cells, and an increase of HB ‐ EGF was induced by SN 38 which had only antitumor effect among conventional anticancer agents on OCCC . A specific inhibitor of HB ‐ EGF , a cross‐reacting material 197 ( CRM 197), led to a synergistic increase in the number of apoptotic OCCC cells with the treatment of SN 38. 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 SN 38 induced luciferase activity in this region. An in silico and chromatin immunoprecipitation analysis estimated that SP 1 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 SP 1 suppressed the expression of HB ‐ EGF induced by SN 38, resulting in the enhanced sensitivity of SN 38. Taken together, these results indicate that induction of HB ‐ EGF expression contributed to defense mechanism against treatment of SN 38 through the transcriptional activity of SP 1 in OCCC cells.