Modified Anthrax Kills Cancer

<P>Engineered Form of the Toxin Targets Tumors</P>

From the WebMD Archives

Jan. 13, 2003 -- A genetically altered form of anthrax may be able to target and kill cancer cells with fewer side effects than conventional treatments. A new study shows the engineered version of the anthrax protein effectively zapped tumors in mice, without damaging surrounding areas.

The results of early tests of the experimental treatment appear in the Jan. 13 early edition of Proceedings of the National Academy of Sciences

Anthrax is a highly contagious agent that has recently been in the spotlight due to its potential for use in a bioterrorist attack. In this study, researchers harnessed the infectious nature of the anthrax toxin and manipulated it to zero in on cancerous tumors.

Using a disabled strain of anthrax, researchers took proteins from anthrax and genetically altered and programmed them to attach to cells that actively secrete a certain type of protein found in cancer cells called urokinase. Researchers say nearly all forms of cancer produce high levels of this particular protein, which helps cancer cells invade tissue and spread. Once attached to the cancer cells another anthrax protein called lethal factor destroys the cancer cells. The urokinase secreted from cancer cells makes it an effective target for a variety of anti-cancer treatments.

In tests on mice with human forms of cancer, the study found the modified version of the anthrax protein reduced tumor size by 65% to 92% after just one treatment. Two treatments completely eliminated 88% of fibrosarcomas (a rare form of cancer that affects connective tissues) and 17% of melanomas (a hard-to-treat and deadly form of skin cancer).

Researcher Thomas H. Bugge, PhD, of the National Institute of Dental and Craniofacial Research (part of the National Institutes of Health), and colleagues say the tumor cells began to die within 12 hours of treatment. But the anthrax toxin did not damage skin or hair follicles around the tumor, which suggests that this form of treatment may produce fewer severe side effects than those caused by current forms of chemotherapy.

Although these initial results are promising, the researchers say they are only in the very early stages of understanding how proteins like urokinase circulate in the body and more research is needed to see if the altered version of anthrax has the same beneficial anti-cancer effects in humans.

SOURCE: Proceedings of the National Academy of Sciences, Jan. 13, 2003.