University of Bonn researchers have created a "designer molecule" that helps the body's own immune system better target the tumor, while also confusing the cancer into committing cellular suicide.

The research team designed their system using small RNA molecules to target and turn off certain genes within the cancer cell - a Nobel prize winning effect known as RNA interference. "We used this method in order to drive the tumor cells to suicide," the Bonn dermatology researcher Professor Thomas Tüting explains. Every single body cell is equipped with a corresponding suicide program. It is activated, for example, if the cell becomes malignant. It dies before it can do any more harm. "But in tumors a gene is active that suppresses this suicide program," Professor Tüting, who is head of the Experimental Dermatology Laboratory, explains. "We have pinpointed this gene and switched it off by using RNA interference."

The researchers also knocked the legs out from under the cancer cells by taking advantage of the natural immune response of the body towards viruses - thus waging an attack on the cancer from two sides. "We basically 'disguised' our RNA," Professor Gunther Hartmann, director of the Institute of Clinical Chemistry and Pharmacology says. "That is why the immune system took it for the genetic makeup of a virus." Many viruses use RNA to store information - so if the body discovers RNA fragments which it takes to be the genetic makeup of a virus, it mounts an attack on them. By means of this trick the body's defenses were prompted to tackle the tumor cells far more aggressively than normal.

RNA is also present in the body's own cells. For a long time it was not known how the immune system distinguishes between "harmful" and "harmless" RNA. Only two years ago, Professor Hartmann was able to shed light on the problem in a sensational article in the journal Science. The scientists used this knowledge in order to modify the RNA substance in such a way that it was able to alert the immune system.

"The beauty of this method is that we can attack the cancer with one designer molecule along two completely different routes," Professor Hartmann says. "This way the tumor is deprived of opportunities of sidestepping the attack that make successful therapy so difficult in other cases." Initial experiments in mouse models have shown that growth of metastases in the lungs is inhibited significantly by the new molecule. The therapy even led to the secondary tumors becoming smaller or even disappearing entirely.

Despite this, the research team warns against excessive optimism: "What works in mice does not necessarily prove successful in humans as well," Professor Tüting warns. "Apart from that, many issues need to be addressed before a trial with cancer patients can even be thought of." Still, the approach appears very promising, especially as the therapeutic RNA molecule can be easily customized to suit different kinds of cancer.

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