Abstract: OBJECTIVE: To investigate the changes of COX II gene expression in lymphoblastoid cells induced by ionizing radiation，in order to provide scientific evidence for gene expression as a biomarker in radiobiodosimetry. METHODS：Lymphoblastoid cells were irradiated by 60Co γ-rays at doses of 0-15 Gy，and then cultured for different periods of 0-72 h. The levels of COX II gene expression were measured by real-time PCR and Western blot. RESULTS：Real-time PCR results showed there were no significant changes in COX II gene expression at the transcriptional level after irradiation by 0-15 Gy 60Co γ-rays (P>0.05). While，at the translation level，COX II gene expression levels were significantly increased 24-72 h after being irradiated by 60Co γ-rays (P﹤0.05). In particular at two post-irradiation time-points，48 h and 72 h，COX II gene expression level correlated with radiation dose. The radiation-induced changes of COX II gene expression between the mRNA and protein levels in human lymphoblastoid cells were not identical. CONCLUSION：At the translation level，radiation could significantly increase COX II gene expression 24-72 h after irradiation in human lymphocytes，and showed good dose- response relationships at 48 h and 72 h. COX II has the potential of becoming a sensitive biomarker and biodosimeter for radiation damage.

Key words: 60Co γ-rays, lymphoblastoid cells, COX II gene, biomarker