Aspirin Chemoprevention of Some Colorectal Cancers Is Mediated by COX-2

In case-control studies, aspirin lowered risk for colorectal cancer by 30% to 50% in patients who took it regularly for 5 to 10 years. This benefit might be related to aspirin’s ability to regulate cyclooxygenase (COX) activity, because prostaglandins act as growth factors for some colorectal adenomas and cancers. However, aspirin also inhibits nuclear factor-κB, induces apoptosis, and promotes catabolism of polyamines, so the particular mechanism underlying its chemopreventive benefit in colorectal cancer is unclear.

Investigators used data and tissue samples from two large cohort studies — the Nurses’ Health Study (82,911 women) and the Health Professionals Follow-Up Study (47,363 men) — to determine the COX-2–expression status of 636 iden…