A single treatment to cure all cancers? Scientists may be one step closer. In a recent study, scientists reported that they successfully tested an antibody treatment that shrank human breast, ovary, colon, bladder, brain, liver and prostate tumors transplanted into mice. The antibody blocks a protein called CD47, which normally sits on the cell surface and issues a don't eat me" signal that prevents the body's immune system from attacking it. About a decade ago, scientists at Stanford University School of Medicine, led by professor of pathology Irving Weissman, discovered that using an antibody to block CD47 cured some cases of leukemia and lymphoma in mice by allowing macrophages to seek and destroy the cancerous cells. In the new study, Weissman's Stanford team showed that the CD47-blocking antibodies may also work against a number of other cancers. The researchers found that CD47 existed on nearly every cell, which suggests that the protein may be common to all cancers. Cancer cells expressed about three times more CD47 than healthy cells. "If the tumor was highly aggressive, the antibody also blocked metastasis. It's becoming very clear that, in order for a cancer to survive in the body, it has to find some way to evade the cells of the innate immune system," said Weissman in a statement. The antibody treatment didn't work in all cases. Some mice injected with breast cancer cells from a human patient showed no changes after treatment. Yet in five mice with breast cancer, the antibody treatment cured them, with no signs of recurrence four months after treatment.