(Ivanhoe Newswire) – There may now be an explanation for why some tumors seem to suddenly stop growing and go into a long period of dormancy.

A multinational team of researchers has found the immune system can stop the growth of a cancerous tumor without actually killing it. They say when the cancer cannot be killed with immune attacks it may be possible to find a way to use the immune system to contain it.

The study calls the cancer-immune system stalemate equilibrium. During this state the immune system decreases the cancer’s drive to replicate and also kills some of the cancerous cells, but doesn’t do it quickly enough to eliminate or shrink the tumor.
 

“We may one day be able to use immunotherapy to artificially induce equilibrium and convert cancer into a chronic but controllable disease,” co-author Mark J. Smyth, Ph.D., Peter McCallum Cancer Centre, Melbourne, Australia, was quoted as saying. “Proper immune function is now appreciated as another important factor in preventing the development of some cancers. Further research and clinical validation of this process may also turn established cancers into a chronic condition, similar to other serious diseases that are controlled long-term by taking a medicine.”

To observe dormant tumors in mice, researchers injected them with small doses of a chemical carcinogen. Some of the mice had small, stable masses at the injection site. When certain components of their immune systems were disabled, the small growths turned into full-blown cancers - this suggests the immune system was previously holding the tumors in check.

Researchers now want to what happens in tumors and the immune system during equilibrium at the molecular level. And they want to see if their results are applicable in humans and in different types of cancers.

SOURCE: Nature published online Nov. 2007