Scientists at Johns Hopkins and elsewhere say they have mapped out an escape route that cancers use to evade the bodys immune system, allowing the disease to spread unchecked.

In a report published in the July 1 issue of the journal Nature Medicine, the Hopkins team, along with researchers from Florida and Nebraska, describe how myeloid-derived suppressor cells (MDSCs), which normally keep the immune system in check and prevent it from attacking otherwise healthy tissue, can suppress the anti-tumor response to cancer.

These 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 reports.

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

Previous research had confirmed that MDSCs, produced in the bone marrow, were attracted to tumors, but until now, scientists had not identified exactly how the cells inhibit the immune systems ability to mount an attack.

By explaining some of the precise biological workings of MDSCs in cancer the teams findings suggest why experimental cancer vaccines have to date been plagued by T-cell tolerance, a weakened rather than strengthened immune response, says Jonathan Schneck, M.D., Ph.D., one of the studys authors.

Our findings also open up a new door in drug and vaccine development that we never knew existed and provide another opportunity for drug development into autoimmune diseases, where the immune system is in overdrive and needs to be slowed down, says Schneck, a professor of medicine, pathology and oncology at The Johns Hopkins University School of Medicine and its Kimmel Cancer Center.

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Contact: David March
dmarch1@jhmi.edu
410-955-1534
Johns Hopkins Medical Institutions
16-Jul-2007