Potentiation of tumor response to radiation or chemoradiation by selective cyclooxygenase-2 enzyme inhibitors

Int J Radiat Oncol Biol Phys. 2004 Feb 1;58(2):369-75. doi: 10.1016/j.ijrobp.2003.09.061.


Cyclooxygenase-2 (COX-2) is an enzyme expressed primarily in pathologic states, such as inflammatory disorders and cancer, where it mediates prostaglandin production. Its overexpression is associated with more aggressive biologic tumor behavior and adverse patient outcome. Increasing evidence shows that agents that selectively inhibit COX-2 enhance tumor response to radiation or chemotherapeutic agents. This article gives an overview of some of this evidence. In addition, we describe new results showing that celecoxib, a selective COX-2 inhibitor, enhanced response of A431 human tumor xenografts in nude mice to radiation by an enhancement factor (EF) of 1.43 and to the chemotherapeutic agent docetaxel by an EF of 2.07. Celecoxib also enhanced tumor response when added to the combined docetaxel plus radiation treatment (EF = 2.13). Further experiments showed that selective COX-2 inhibitors enhanced tumor cell sensitivity to ionizing radiation, involving inhibition of cellular repair from radiation damage and cell cycle redistribution as mechanisms for some cell types. The results show that selective COX-2 inhibitors have the potential to improve tumor radiotherapy or radiochemotherapy, and this therapeutic strategy is currently under clinical testing.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Celecoxib
  • Combined Modality Therapy
  • Cyclooxygenase 2
  • Cyclooxygenase 2 Inhibitors
  • Cyclooxygenase Inhibitors / therapeutic use*
  • Drug Interactions
  • Humans
  • Isoenzymes / antagonists & inhibitors*
  • Isoenzymes / metabolism
  • Membrane Proteins
  • Mice
  • Mice, Inbred C3H
  • Mice, Nude
  • Neoplasm Proteins / antagonists & inhibitors*
  • Neoplasm Proteins / metabolism
  • Neoplasms / drug therapy*
  • Neoplasms / radiotherapy*
  • Prostaglandin-Endoperoxide Synthases / metabolism
  • Pyrazoles / therapeutic use*
  • Radiation Tolerance
  • Radiation-Sensitizing Agents / therapeutic use*
  • Sulfonamides / therapeutic use*


  • 4-(5-(4-chlorophenyl)-3-(trifluoromethyl)-1H-pyrazol-1-yl)benzenesulfonamide
  • Cyclooxygenase 2 Inhibitors
  • Cyclooxygenase Inhibitors
  • Isoenzymes
  • Membrane Proteins
  • Neoplasm Proteins
  • Pyrazoles
  • Radiation-Sensitizing Agents
  • Sulfonamides
  • Cyclooxygenase 2
  • PTGS2 protein, human
  • Prostaglandin-Endoperoxide Synthases
  • Celecoxib