The use of cyclooxygenase-2 inhibitors for improvement of efficacy of radiotherapy in cancers

• COX-2 is overexpressed in tumour cells and is involved in cell proliferation and progression and angiogenesis.
• COX-2 inhibitors can block various signalling pathways, proteins and processes involved in tumour progression.
• COX-2 inhibitors have synergistic effects with ionising radiation on cytotoxic effects on cancer cells.
• COX-2 inhibitors can protect normal cells against proinflammatory processes induced by ionising radiation.
• COX-2 inhibitors increase therapeutic index by protecting normal cells and sensitising tumour cells to radiotherapy.

Cyclooxygenase-2 (COX-2) is overexpressed in cancer cells and is associated with carcinogenesis and maintenance of progressive tumour growth as well as resistance of cancer cells to ionising radiation (IR). COX-2 inhibitors can attenuate tumour growth and expression of markers of cell proliferation as well as induce apoptosis in tumour cells. These agents can have a synergistic effect with IR in the killing of cancer cells. In this review, we discuss the rational basis and molecular mechanisms regarding the usefulness of COX-2 inhibitors in cancer therapy, and also their potential role in increasing the therapeutic index of chemoradiation by protecting normal cells and sensitising tumour cells to radiotherapy.