December 20, 2005
Courtesy the University of Washington
and World Science staff
An extract of the sweet wormwood plant used for centuries to fight malaria, and shown to target and kill cancer cells, may help prevent breast cancer, researchers have found.
The two bioengineers with the University of Washington in Seattle, Wash., found that the substance, artemisinin, seemed to prevent breast cancer in rats that had swallowed a cancer-causing chemical. The study appears in the latest issue of the research journal Cancer Letters.
“Based on earlier studies, artemisinin is selectively toxic to cancer cells and is effective orally,” said bioengineer Henry Lai. “With the results of this study, it’s an attractive candidate for cancer prevention.”
The properties that make artemisinin an effective antimalarial agent also appear responsible for its anti-cancer clout, the researchers said.
When artemisinin makes contact with iron, a chemical reaction ensues that spawns free radicals – unstable chemicals that attack a cell’s protective membrane and other structures, killing the cell. The malaria parasite can’t eliminate iron in the blood cells it eats, and stores it. Artemisinin makes that iron toxic to the parasite.
The same seems to be true for cancer, according to the researchers.
Because they multiply so rapidly, most cancer cells take up iron rapidly, they explained. The cell surfaces have large numbers of molecules called receptors that draw iron into the cells. The artemisinin apparently can selectively target and kill the cells based on their higher iron content, the researchers found.
They fed rats a dose of a substance known to induce breast tumors, 7,12-dimethylbenz[a]anthracene. Half of the rats then were fed regular food, while the other half got food with 0.02 percent artemisinin. For 40 weeks, researchers monitored each group for the formation of breast tumors.
Among the rats that didn’t get artemisinin, 96 percent got tumors, they reported, while 57 percent of the artemisinin-fed rats got tumors. And tumors in the artemisinin-fed rats were “significantly fewer and smaller,” the researchers said.
The reason for artemisinin’s apparent preventive effect may be twofold, the researchers said. The substance may kill precancerous cells, which also tend to use more iron than ordinary cells, before those cells become a tumor. Artemisinin also may block angiogenesis, or a tumor’s ability to grow networks of blood vessels that allow it to enlarge.
Because artemisinin is widely used in Asia and Africa as an anti-malarial, it has a track record of being relatively safe, Lai said. The results “indicate that it may be a potent cancer-chemoprevention agent... additional studies are needed to investigate whether the breast cancer prevention property of artemisinin can be generalized to other types of cancer.”