Abstract: To investigate the inhibitory effect of indomethacin combined with radiation on proliferation of HL-60 cells and to provide  basis for study on antitumor therapy.
Methods The HL-60 cells were exposed to indometnacin at 0,20,40,60,80,and 100  μmol·L^-1 together with 3 Gy X-rays radiation and cultivated for 24 h.MTT and Trypan blue exclusion experiments were used to detect the inhibitory rate of cell proliferation and viability respectively.Real-time PCR was used to detect the changes of cell proliferation and apoptosis-related gene PCNA and Caspase-3 mRNA expressions.Results  Compared with control group,the inhibitory rates of proliferation of HL-60 cells in different doses of indomethacin groups were increased significantly（P<0.01）,especially in 80  μmol·L^-1 indomethacin group.Compared with control,indomethacin (80  μmol·L^-1) and 3 Gy X-rays radiation groups,the inhibitory rate of cell viability of HL-60 cells in 80  μmol·L^-1 indomethacin combined with radiation group was  increased significantly（P<0.01）.Compared with control,indomethacin (80 μmol·L^-1) and 3 Gy X-rays radiation groups,the expression of PCNA mRNA in 80 μmol·L^-1 indomethacin combined with radiation group  was decreased and the expression of Caspase-3 mRNA was increased significantly （P<0.01）.Conclusion Indomethacin can enhance the inhibitory effect of radiation on roliferatio
n of HL-60 cells.

Key words: indomethacin, radiation, HL-60 cells, cell proliferation, apoptosis