Selective inhibition of cyclooxygenase-2 enhances mitomycin-C-induced apoptosis

Chung Tsen Hsueh, Chang Fang Chiu, David P. Kelsen, Gary K. Schwartz

Research output: Contribution to journalArticlepeer-review

63 Scopus citations

Abstract

Purpose: Cyclooxygenase-2 (COX-2) is involved in antiapoptosis signaling, and its induction may require activation of protein kinase C (PKC). Safingol (SAF), a PKC inhibitor, has been shown to enhance apoptosis induced by mitomycin-C (MMC) in human gastric cancer MKN-74 cells. The aim of this study was to identify the role of COX-2 in MMC-induced apoptosis in MKN- 74 cells. Methods: Protein expression of COX-2 and Bcl-2 and activation of PKCα were examined by Western blot analysis. Apoptosis induction was examined by staining with bisbenzimide trihydrochloride (Hoechst-33258) of condensed chromatin, which characterizes the cells undergoing apoptosis. COX- 2 mRNA levels were examined by Northern blot analysis. Results: After exposure for 1-2 h to 1 μg/ml MMC, upregulation of COX-2 and Bcl-2 protein expression was noted. The activation of PKCα occurred within 1 h of MMC exposure, and temporally preceded the induction of COX-2. Similar results were observed in cells exposed to the PKC activator, 3-phorbol 12-myristate 13-acetate. Cotreatment with SAF and MMC abolished the induction of COX-2 by MMC. Furthermore, NS-398, a selective COX-2 inhibitor, significantly enhanced MMC-induced apoptosis by fivefold from 4 ± 2% (MMC alone) to 20 ± 2% (MMC plus NS-398). There was no discernible change in COX-2 mRNA levels after a 2- h exposure to MMC but a twofold increase after a 24-h exposure. Conclusions: MMC upregulates COX-2 expression, which appears to be an antiapoptotic signal downstream of PKC. Selective inhibition of COX-2 can therefore provide a novel way to enhance MMC-induced apoptosis independent of inhibiting PKC.

Original languageEnglish
Pages (from-to)389-396
Number of pages8
JournalCancer Chemotherapy and Pharmacology
Volume45
Issue number5
DOIs
StatePublished - 2000
Externally publishedYes

Keywords

  • Bcl-2
  • Gene expression
  • Phorbol esters
  • Protein kinase C
  • Safingol

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