Another reason to eat your tofu: UC Berkeley researchers discover soybean protein has anti-cancer properties

By Kathleen Scalise, Public Affairs

BERKELEY--Whether it's tofu, soy protein powder or soy drinks, health food advocates have long touted soy as an anti-cancer preventative. Now, University of California, Berkeley, researchers have discovered a gene from soybeans that, when inserted into cancer cells, can have an effect similar to the anti-cancer drug taxol.

The researchers report their finding in the May issue of the journal "Nature Biotechnology."

They say the soybean gene they discovered produces a protein called lunasin that stops mitosis, the process by which cells replicate. One reason the researchers are pleased with their finding is because they believe lunasin works in a different way than the common antimitotic chemotherapeutic agents - taxol and its semisynthetic analog, docetaxel - therefore potentially providing yet another tool to someday fight disease.

Associate Professor Benito de Lumen and postdoctoral researcher Alfredo Galvez, both of UC Berkeley's Division of Nutritional Sciences and Toxicology, came upon their discovery serendipitously while working to improve the nutritional quality of soy protein.

Galvez, de Lumen and former UC Berkeley graduate student Jay Revilleza cloned the lunasin gene from soybean seed. When Galvez implanted and expressed the gene in mammalian cells, including human cells, he discovered lunasin not only stops cell division but also causes the cell to become dysfunctional and eventually to self-destruct.

Galvez and de Lumen went on to show that lunasin prevents the attachment of microtubules - structures that move and properly arrange chromosomes during mitosis - to the correct chromosome region. Taxol, in contrast, disrupts the microtubules themselves, making them too stable to function and assemble correctly.

Lunasin was shown to affect both normal and cancerous cells, including human breast cancer cells, said Galvez.

In nature, lunasin may play a functional role during seed development, de Lumen said. He believes it may stop seed storage cells from dividing so cells instead can grow larger and fill with nutrients needed by the young plant during germination and growth.

While the researchers believe lunasin might one day be found useful as a therapeutic agent, for this to happen it would need to be delivered specifically to cancer cells, de Lumen said. Many cancer researchers are working on such delivery systems, he said, but at present none are very effective.

Should delivery become possible, proteins such as lunasin might prove valuable, said Galvez, since the tools of biotechnology are making proteins easy to tailor and change to reduce side effects in pharmaceuticals. Taxol, on the other hand, is not a protein. It is a complicated chemical extracted from plants, and even its synthetic derivative is tricky to change while retaining its function.

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