A, chemical structures of sulindac sulfide (SS) and SBA. B, tumor cell growth inhibitory activity of SS and SBA as measured by luciferase-based ATP assay after 72 hours of treatment. C, COX-1 and COX-2 inhibitory activity of SS, but not SBA. D, inhibition of PGE2 production by SS, but not SBA in LPS-stimulated U937 promonocytic cells. E, COX-2 protein expression in human HT-29, HCT 116, and SW480 colon cancer cells. GAPDH, glyceraldehyde-3-phosphate dehydrogenase.