ScienceDaily (Apr. 6, 2011) — Numerous studies show that non-steroidal anti-inflammatory drugs (NSAIDs) reduce the risk of colon cancer. However, animal studies testing the NSAID naproxen or its derivative, NO-naproxen, have focused primarily on chemically-induced tumor formation. Now, researchers at Fox Chase Cancer Center find that naproxen and NO-naproxen reduce tumor formation in a strain of mutant mice that spontaneously develop colon tumors. The data also suggest that naproxen blocks a gatekeeper step that initiates tumor formation.