Study explains cancer vaccines might fail

Baltimore -- U.S. scientists have identified an "escape route" that cancers use to evade the body's immune system, allowing the cancer to spread.

Researchers, including Johns Hopkins University scientists, said such escape hatches explain why anticancer vaccines mostly fail. In the latest research, investigators describe how myeloid-derived suppressor cells, which normally keep the immune system in check and prevent it from attacking otherwise healthy tissue, can suppress the anti-tumor response to cancer.

The suppressor cells block other immune system cells, CD8 "killer" T cells, from binding with proteins that identify the foreign antigens on the surface of unhealthy cancer cells, marking them for destruction, the team reported.

The researchers said their experiments also suggest the chain reactions in T-cell tolerance are reversible, raising the possibility of vaccine and drug therapies that break through the blocked immune system.

The study -- conducted at Johns Hopkins, the University of South Florida, and the University of Nebraska -- was reported in the July 1 issue of the journal Nature Medicine.

Copyright 2007 by United Press International.