Researchers at the University of Washington have blended the past with the present in the fight against cancer, synthesizing a promising new compound from an ancient Chinese remedy. The substance, artemisinin, is derived from the wormwood plant and has been used in China since ancient times to treat malaria. Earlier work by Henry Lai and Narendra Singh indicated that artemisinin alone could selectively kill cancer cells while leaving normal cells unharmed. The new compound appears to vastly improve that deadly selectivity.

“By itself, artemisinin is about 100 times more selective in killing cancer cells as opposed to normal cells,” Lai said. “In this study, the new artemisinin compound was 34,000 times more potent in killing the cancer cells as opposed to their normal cousins.”

Because they multiply so rapidly, most cancer cells need more iron than normal cells to replicate DNA. To facilitate that, cancer cells have inlets on their surface, known as transferrin receptors, in greater numbers than other cells. Those receptors allow quick transport into the cell of transferrin, an iron-carrying protein found in blood.

In creating the compound, researchers bound artemisinin to transferrin at the molecular level. The combination of the two ingredients appears to fool the cancer cell.

“We call it a Trojan horse because the cancer cell recognizes transferrin as a natural, harmless protein,” Lai said. “So the cell picks up the compound without knowing that a bomb – artemisinin – is hidden inside.”

Once inside the cell, the artemisinin reacts with the iron, spawning highly reactive chemicals called “free radicals.” The free radicals attack other molecules and the cell membrane, breaking it apart and killing the cell.

University of Washington, Feb 8, 2005