Cancers May Use Decoys as Defense

Some cancers may use decoys to avoid being killed by the body’s immune system, a study suggests. If so, drugs that block that strategy might help fight the disease.

Cancers use several tricks to evade the immune system, and the new study provides indirect evidence that the newfound decoys are one of the strategies.

Some immune system cells display a protein structure called the Fas ligand to kill other cells. The ligand fits into a receptor on the target cell, which makes that cell commit suicide.

In the new work, scientists discovered a previously unknown gene they called DcR3. It lets cells produce a chemical decoy that binds to the death-dealing ligand and keeps it from working.

To look for evidence of a possible role in cancer, researchers examined 35 lung and colon tumors. About half showed extra copies of the DcR3 gene, which suggests the gene offers some tumors a survival advantage.

The work is presented in the Dec. 17 issue of the journal Nature by Avi Ashkenazi and colleagues at Genentech Inc. of South San Francisco. In a telephone interview, Ashkenazi said a drug that neutralizes the decoys might prove useful in fighting cancer.