Radiosensitization of human glioma cells by cyclooxygenase-2 (COX-2) inhibition: independent on COX-2 expression and dependent on the COX-2 inhibitor and sequence of administration

Gitta K Kuipers, Ben J Slotman, Laurine E Wedekind, T Rianne Stoter, Jaap van den Berg, Peter Sminia, M Vincent M Lafleur

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PURPOSE: Patients with a malignant glioma have a very poor prognosis. Cyclooxygenase-2 (COX-2) protein is regularly upregulated in gliomas and might be a potential therapeutic target. The effects of three selective COX-2 inhibitors were studied on three human glioma cell lines.

MATERIALS AND METHODS: The selective COX-2 inhibitors NS-398, Celecoxib and Meloxicam and three human glioma cell lines (D384, U251 and U87) were used. Cell growth was assessed by a proliferation assay, the interaction with radiation (0 - 6 Gy) was studied using the clonogenic assay and cell cycle distribution was determined by FACS (fluorescence-activated cell sorting) analysis.

RESULTS: All COX-2 inhibitors reduced proliferation of the glioma cell lines irrespective of their COX-2 expression level. Incubation with 200 microM NS-398 24 h before radiation enhanced radiation-induced cell death of D384 cells and 750 microM Meloxicam resulted in radiosensitization of D384 and U87 cells. No radiosensitization was observed with COX-2 inhibitor administration after radiotherapy. Treatment of D384 with NS-398 (200 microM) or Celecoxib (50 microM) and U87 with NS-398 (200 microM) after radiation resulted even in radioprotection.

CONCLUSIONS: Effectiveness of COX-2 inhibitors on cell proliferation and radio-enhancement was independent of COX-2 protein expression. The sequence of COX-2 inhibitor addition and irradiation is very important.

Original languageEnglish
Pages (from-to)677-85
Number of pages9
JournalInternational journal of radiation biology
Issue number10
Publication statusPublished - Oct 2007


  • Celecoxib
  • Cell Line, Tumor/drug effects
  • Cell Proliferation/drug effects
  • Cyclooxygenase 2 Inhibitors/pharmacology
  • Cyclooxygenase 2/genetics
  • Dose-Response Relationship, Radiation
  • Flow Cytometry/methods
  • Gene Expression Regulation, Neoplastic
  • Glioma/pathology
  • Humans
  • Neoplasms/drug therapy
  • Nitrobenzenes/pharmacology
  • Pyrazoles/pharmacology
  • Radiation-Protective Agents/pharmacology
  • Sulfonamides/pharmacology
  • Thiazines/pharmacology
  • Thiazoles/pharmacology

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