The aim of this study is to clarify the relationship between COX expressions and radioresistance in cervical cancer.

Patients with cervical cancer treated by primary radiotherapy were selected from the tumor registry of our institution. According to the response to radiotherapy during and after a month of radiation, poor responder and good responder was defined. Immunohistochemical staining was performed by the ABC method using formalin-fixed, paraffin-embedded tissue sections and monoclonal anti-COX-1,2 antibodies. Correlation of COX expression and response to radiation was analyzed. Cell lines derived from human cervical tumors were used: HeLa, HT3, and C33A. Using western blot, COX-1,2 expressions were identified in each cell line. The sensitivity of the cervix cancer cells to radiation was measured using a clonogenic assay.

COX-1 and COX-2 expressions were higher in poor responders than good responders. The difference of COX-1 expression between two groups had marginal statistical significance (p=0.099, Fisher's exact test) and COX-2 expression was significantly higher in poor responders (p=0.034, Fisher's exact test). In the clonogenic assay, survival fraction of HeLa and HT-3 cell lines, which have COX-1 and COX-2 activity, was significantly higher than C33A cell line which has no COX activity (p<0.001).

Our results suggest that the expression of COX in cervical cancer might be deeply associated with the effect of radiation therapy.