Nuclear proteins extracted from human colon cancer cell lines (RKO, LoVo, DLD-1 and SW480) were incubated with biotin-labeled COX-2 promoter probes, and streptavidin-agarose beads were utilized to pull down nuclear proteins bound at COX-2 promoter region. The gene discussed is PTGS2; the disease is malignant colon neoplasm.