The identification of hundreds of genes involved in the formation and spread of cancer is leading to promising new methods for diagnosis, prevention, and treatment. In the case of colon cancer, researchers are developing genetic tests for detecting the cancer-causing mutations. Researchers are also investigating anticancer therapies that take advantage of the molecular differences between cancer cells and the normal cells surrounding them. Gleevec, for example, is a compound designed to disable a protein that spurs the growth of certain types of leukemia. In Dr. Vogelstein's lab, scientists are deploying specialized microbes to penetrate tumors, proliferate rapidly, and kill the cancer cells.