Radiation induces upregulation of cyclooxygenase-2 (COX-2) protein in PC-3 cells

Purpose: To investigate the impact of gamma-irradiation on cyclooxygenase-2 (COX-2) expression and its enzymatic activity in PC-3 cells. Cell cycle redistribution, viability, and apoptosis were quantitated in control and irradiated cells with or without the COX-2 inhibitor NS-398. Methods and Materials: Western blot analysis was used to assess COX-2 protein expression, Prostaglandin (PGE,) was measured after addition of arachidonic acid (AA) using a Monoclonal Immunoassay Kit. Cell cycle and apoptosis were assessed using flow cytometry. Results: We observed a dose-dependent increase in COX-2 of 37.0%, 79.7%, and 97.5% following irradiation with 5,10, and 15 Gy, respectively. The PGE(2) level of irradiated cells was higher than in controls (1512 +/- 157.5 vs. 973.7 +/- 54.2 rho g PGE(2)/mL; p < 0.005, n = 4) while cells irradiated in the presence of NS-398 had reduced PGE(2) levels (218.8 +/- 80.1 rho g PGE(2)/mL; p < 0.005; n = 4), We found no differences in cell cycle distribution or apoptosis between cells irradiated in the presence or absence of NS-398, Conclusions: COX-2 protein is upregulated and enzymatically active after irradiation, resulting in elevated levels of PGE(2). This effect can be suppressed by NS-398, which has clinical implications for therapies combining COX-2 inhibitors with radiation therapy. (C) 2000 Elsevier Science Inc.