Enlarge Image Survivor. When mice with human tumors received doses of anti-CD47, which sets the immune system against tumor cells, the cancers shrank and disappeared. Credit: Fotosearch A single drug can shrink or cure human breast, ovary, colon, bladder, brain, liver, and prostate tumors that have been transplanted into mice, researchers have found. The treatment, an antibody that blocks a "do not eat" signal normally displayed on tumor cells, coaxes the immune system to destroy the cancer cells. A decade ago, biologist Irving Weissman of the Stanford University School of Medicine in Palo Alto, California, discovered that leukemia cells...