Researchers at the University of Washington have updated a traditional Chinese medicine to create a compound that is more than 1,200 times more specific in killing certain kinds of cancer cells than currently available drugs,

The new compound is derived from the sweet wormwood plant (Artemisia annua L). Sweet wormwood has been used in herbal Chinese medicine for at least 2,000 years, and is eaten in salads in some Asian countries.

The research holds the promise of more effective cancer treatments with minimal side effects. For the study, scientists used rats ande attached a chemical homing device to artemisinin that targets the drug selectively to cancer cells, sparing healthy cells. The results are published in the journal Cancer Letters.

“The compound is like a special agent planting a bomb inside the cell,” said Tomikazu Sasaki, chemistry professor at UW and senior author of the study.

In the study, the UW researchers tested their artemisinin-based compound on human leukemia cells. It was highly selective at killing the cancer cells. The researchers also have preliminary results showing that the compound is similarly selective and effective for human breast and prostate cancer cells, and that it effectively and safely kills breast cancer in rats, Sasaki said.

“Side effects are a major limitation to current chemotherapies,” Sasaki said. “Some patients even die from them.”

The compound Sasaki and his colleagues developed kills 12,000 cancer cells for every healthy cell, meaning it could be turned into a drug with minimal side effects. A cancer drug with low side effects would be more effective than currently available drugs, since it could be safely taken in higher amounts.

The artemisinin compound takes advantage of cancer cell’s high iron levels. Artemisinin is highly toxic in the presence of iron, but harmless otherwise. Cancer cells need a lot of iron to maintain the rapid division necessary for tumor growth. The compound is so selective for cancer cells partly due to their rapid multiplication, which requires high amounts of iron, and partly because cancer cells are not as good as healthy cells at cleaning up free-floating iron.

Artemisinin alone is fairly effective at killing cancer cells. It kills approximately 100 cancer cells for every healthy cell, about ten times better than current chemotherapies. To improve those odds, the researchers added a small chemical tag to artemisinin that sticks to the “iron needed here” signal from cells. The cancer cell, unaware of the toxic compound lurking on its surface, engulfs everything — including the iron and the toxic compound.

Once inside the cell, the iron reacts with artemisinin to release poisonous molecules called free radicals. When enough of these free radicals accumulate, the cell dies.

“The compound is like a little bomb-carrying monkey riding on the back of a Trojan horse,” said Henry Lai, UW bioengineering professor and co-author of the study.

Source
University of Washington