Soy Compound Has Anti-Cancer Effect

This section is compiled by Frank M. Painter, D.C.
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March 9, 1998

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NEW YORK (Reuters) - A high consumption of soy- based food such as tofu is thought to protect against cancer, and now California researchers suggest a reason why: a compound found in soy, called genistein, suppresses the production of stress proteins in cells - proteins that otherwise help cancer cells survive destruction by the immune system.

Such proteins, including heat shock proteins (HSP) and glucose-related proteins (GRPs), can also protect a cell in stressful, high temperature conditions by allowing the cell to avoid apoptosis, the natural cell suicide mechanism that helps to eliminate defective cells.

Cancer cells are known to produce high levels of such proteins, allowing them to survive an attack by the immune system, chemotherapy, and radiation therapy. Genistein, by inhibiting the process, may make precancerous or cancer cells more vulnerable to destruction, according to senior investigator Dr. Amy S. Lee, a professor of biochemistry and molecular biology at the University of Southern California in Los Angeles.

"Genistein is a natural component of the diet of Chinese and Japanese who are at low risk for breast, colon, and prostate cancers," reported Lee and co-author Yanhong Zhou. "The anti-cancer effects of genistein may be related to its ability to reduce the expression of stress response-related genes," they wrote.

The researchers treated cultured hamster and mouse cells with azetidine, a chemical that elicits a stress response in cells, including the production of certain types of HSP and GRP. Treating the cells with genistein in laboratory dishes suppressed the production of the HSPs and GRPs by interfering with a transcription factor, an enzyme that translates genetic material into proteins.

However, more study is needed to determine if genistein alone can help prevent cancer in the body. Soy may contain compounds that "complement genistein in regulating gene expression and contribute to its putative chemopreventive effect," the researchers wrote.

"The effectiveness of genistein as an anticancer agent in humans awaits further preclinical, clinical, and epidemiologic testing," they concluded.

SOURCE: Journal of the National Cancer Institute 1998; 90: 381-388

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