When mice with human tumors received doses of anti-CD47, which sets the immune system against tumor cells, the cancers shrank and disappeared. 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 produce higher levels of a protein called CD47 than do healthy cells.
CD47, he and other scientists found, is also displayed on healthy blood cells; it’s a marker that blocks the immune system from destroying them as they circulate. Cancers take advantage of this flag to trick the immune system into ignoring them.
In the past few years, Weissman’s lab showed that blocking CD47 with an antibody cured some cases of lymphomas and leukemias in mice by stimulating the immune system to recognize the cancer cells as invaders. Now, he and colleagues have shown that the CD47-blocking antibody may have a far wider impact than just blood cancers.