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Miracles happen:
Samoa's mamala tree could lead to AIDS cure
by David Pescovitz
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Last August, Keasling presented his research to an audience of Samoans. One month later, he signed a landmark agreement between UC Berkeley and the Samoan government offering village elders half the profits from production of the anti-AIDS drug prostratin, which he hopes to synthesize from Samoa's Homalanthus nutans, or mamala tree. Samoans call the tree their "gift to the world."
STEPHEN KING PHOTO |
Last fall, Keasling visited Samoa, home of the mamala tree that harbors a gene for a promising anti-AIDS drug. Samoan healers use the bark of the tree to treat hepatitis, but scientists discovered that the compound derived from the tree, prostratin, also activates dormant HIV cells in patients so that they can be targeted by current anti-AIDS drugs. Clinical trials are encouraging, but the drug supply is limited to the small amount that can be extracted from the tree. If it works as well as researchers hope, there will be an immediate shortage.
That’s where Keasling can help. Last September, UC Berkeley signed a landmark agreement with the Samoan government and village elders to return to them half the profits from production of an anti-AIDS drug Keasling hopes to produce.
The first step, he explains, is to identify the enzymes that build the prostratin molecule. Then, the aim is to clone the appropriate genes and slip them into the E. coli-based microbial factory where biology will bulk manufacture the valuable substance. A similar technique, says Keasling, could also supply Taxol, an expensive yet effective chemotherapy used to treat breast, ovarian, and lung cancers.
“Taxol is produced in minute quantities in the bark of the Pacific yew tree to kill beetles and fungi that attack the tree,” he says. “That means, if you want to use it as a therapeutic, you have to cut down a lot of trees or collect a ton of pine needles. Or you could engineer a bacterium to produce it.”
Eventually, Keasling adds, synthetic biologists might even synthesize a biological drug delivery system for Taxol. A bacterium designed to detect tumors could produce Taxol when triggered to do so and release it into the body. Once it reaches the tumor, the bacteria would go into kamikaze mode, secreting the toxin to kill itself and the cancer cells.
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