- To determine whether celecoxib downregulates GATA-6 expression to upregulate 15-LOX-1 expression and induce apoptosis in human rectal tumors, researchers will measure GATA-6 and 15-LOX-1 expression, 13-S-HODE levels, and apoptosis rates in normal and colorectal polyp epithelial tissues before and after 6 months of celecoxib treatment of patients with familial adenomatous polyposis (FAP).