Nitric oxide (NO) is an important signaling molecule in mammals. The compound has both beneficial and harmful influences on these organisms. Nitric oxide is suspected to be produced by the immune system in response to bacterial infections. Scientists from MIT’s Division of Comparative Medicine and Department of Biological Engineering, led by James Fox, director of the Division of Comparative Medicine (DCM), have recently discovered that nitric oxide, produced by inflammatory cells in the course of a bacterial infection, can cause colon cells to become cancerous. These findings suggest that chemically blocking the chemical may help treat or prevent colon cancer.