UW scientists report success in herb enhanced to fight cancerDrug now used against malaria
Last updated October 13, 2008
By TOM PAULSON
P-I REPORTER
Seattle scientists have developed a new technique for improving a common Chinese herb's ability to attack cancer cells that they say appears, in laboratory tests at least, to be much more precise and less likely to cause the kind of toxic side effects accompanying most standard chemotherapy drugs today.The herb, artemisinin, or sweet wormwood, is an ancient Chinese medicinal herb already commonly used to treat malaria worldwide. Because its effect in the body is relatively brief, it is often used in a pharmaceutical combination with other routine anti-malarial drugs -- an approach known as ACT, artemisinin-based combination therapy. "It's quite effective against cancer cells as well," said Tomikazu Sasaki, a chemistry professor at the University of Washington and lead author of a report on this in the current online issue of Cancer Letters.
Sasaki said his co-authors, UW bioengineers Henry Lai and Narendra Singh, began looking into the possibility of using this herb as an anti-cancer drug in the mid-1990s. Since then, he said, others have done studies on artemisinin's ability in laboratory cell cultures to kill cancer cells. But there wasn't much understanding exactly how this happened or how to improve upon the herb's ability to target cancer and avoid healthy cells.
"The connection here is iron," explained Sasaki.
Artemisinin is good at killing malaria parasites because it reacts and becomes highly toxic in the presence of iron, he said. Malaria parasites cause illness in humans by consuming red blood cells, which contain iron in the hemoglobin protein that carries oxygen in the blood. Similarly, cancer cells use lots of iron as they proliferate in tumors.
Recognizing this connection, Lai and Singh in the 1990s began exploring the possibility of using this Chinese herb as a cancer drug. They continued to publish about it, and the UW patented the idea. Sasaki joined the team in 2000, and the scientists formed a local company, Artemisia Biomedical Inc., to explore how to turn this into a commercial drug therapy.
In the report published this month, the UW trio describe how they have created their own kind of artemisinin compound to enhance the herb's cancer-killing abilities. Basically, the scientists manipulated the herb's protein surface and boosted it with iron. When the cancer cells consume the compound, it releases toxic chemicals that kill the cells.
"The compound is like a little bomb-carrying monkey riding on the back of a Trojan horse," Lai said in a statement accompanying the report. Lai, who is perhaps best known publicly for his controversial studies linking cancer and cell phone use, is not afraid to mix humor with science, let alone metaphors.
Most chemotherapy drugs today have serious side effects, Sasaki said, because they generally kill one healthy cell for every 10 cancer cells. The UW's artemisinin compound used in cell cultures and in rats with breast cancer showed much better targeting and less collateral damage -- killing about 12,000 cancer cells for every healthy cell killed. Even regular artemisinin, without the UW alteration, only kills one good cell for every 100 cancer cells, he said.
"Normal cells don't use iron very often," Sasaki said. "When we deliver this artemisinin-iron package to cancer cells, we have much higher selectivity and much less toxic side effects."
Given that the herb is in wide use and readily available for only a few dollars a dose, why wouldn't someone with cancer just go out and take the drug?
"We see patients doing all kind of things based on findings in animal tests," said Dr. Daniel Labriola, a naturopathic physician in Ballard who is also medical director for naturopathic care at the Swedish Cancer Institute and Seattle Children's hospital. "There are a lot of people using this already."
That's risky business at this point, Labriola warned, because there is still no solid evidence this is either effective or safe. Given that cancer cells love iron, he noted, delivering an herbal package full of iron could actually cause harm and make the cancer worse. Many cancer patients used to take anti-oxidants such as vitamin C to supplement their drugs, Labriola noted, until scientific studies showed the supplements actually counteracted the chemo.
"We have to do a lot more studies on efficacy and toxicity before testing in humans," agreed Sasaki. Given artemisinin's wide use as an anti-malarial drug, he said, it is likely to be safe for most uses. Sasaki said he also was aware of local doctors prescribing artemisinin to cancer patients, some of them reporting great success in individual cases.
But more study is required to show scientifically that this approach can work and not cause harm, Sasaki said. "This is very exciting, but it will be many years before we can get this into regular medical practice," he said.
P-I reporter Tom Paulson can be reached at 206-448-8318 or tompaulson@seattlepi.com.
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