How Aspirin Reduces Colon Cancer Risk

A variety of studies have suggested that taking aspirin can decrease the risk of colon cancer. But the mechanism by which the common painkiller exerts its protective effect has eluded researchers. A team led by Andrew T. Chan of Massachusetts General Hospital and Sanford D. Markowitz of Case Western Reserve University now reports that aspirin’s colon cancer protection is linked to levels of an enzyme called 15-PGDH (Sci. Transl. Med. 2014, DOI: 10.1126/scitransl​med.3008481). The researchers note that the enzyme plays a role in the degradation of prostaglandins, which are important lipid messenger molecules that can also be involved in certain colon cancers. Aspirin appears to reduce prostaglandin levels by inhibiting the activity of another enzyme involved in prostaglandin synthesis. The researchers examined tissue samples from 270 cases of colon cancer stemming from two studies that tracked aspirin use of 128,000 people for three decades. They found that people who consumed at least two 325-mg aspirin tablets per week lowered their risk of colon cancer by 50%—but only if their 15-PGDH levels were higher than average. The finding could help identify people who can reduce their colon cancer risk with aspirin. Likewise, identifying individuals who won’t benefit from aspirin’s protection could help them avoid the drug’s side effects, which include gastrointestinal bleeding and ulcers.