XRCC5 and lung cancer: In this study, we used biotin-streptavidin pulldown assay to look for and identify the unknown and essential transcriptional regulators for COX-2 and found that Ku80 specifically bound to the COX-2 promoter and activated COX-2 transcription, and then increased COX-2 expression and the production of its downstream molecule PGE2. We also studied the clinical association between Ku80 and COX-2 in lung cancer tissue samples.