March 9, 1998
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
"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
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