Soy compund may halt spread of prostate cancer
- From: Old Tom <rascal_51@xxxxxxxxxxx>
- Date: Sat, 15 Mar 2008 17:20:48 -0700 (PDT)
Soy compound may halt spread of prostate cancer
http://www.physorg.com/news124695930.html
A compound found in soybeans almost completely prevented the spread of
human prostate cancer in mice, according to a study published in the
March 15 issue of Cancer Research, a journal of the American
Association for Cancer Research.
Researchers say that the amount of the chemical, an antioxidant known
as genistein, used in the experiments was no higher than what a human
would eat in a soybean-rich diet.
Investigators from Northwestern University found that genistein
decreased metastasis of prostate cancer to the lungs by 96 percent
compared with mice that did not eat the compound in their chow -
making the study the first to demonstrate genistein can stop prostate
cancer metastasis in a living organism.
"These impressive results give us hope that genistein might show some
effect in preventing the spread of prostate cancer in patients," said
the study's senior investigator, Raymond C. Bergan, MD, director of
experimental therapeutics for the Robert H. Lurie Comprehensive Cancer
Center of Northwestern University.
"Diet can affect cancer and it doesn't do it by magic," Bergan said.
"Certain chemicals have beneficial effects and now we have all the
preclinical studies we need to suggest genistein might be a very
promising chemopreventive drug."
Bergan and his team have previously demonstrated in prostate cancer
cell cultures that genistein inhibits detachment of cancer cells from
a primary prostate tumor and represses cell invasion. It does this by
blocking activation of p38 MAP kinases, molecules which regulate
pathways that activate proteins that loosen cancer cells from their
tight hold within a tumor, pushing them to migrate. "In culture, you
can actually see that when genistein is introduced, cells flatten
themselves in order to spread out and stick strongly to nearby cells,"
he said.
In this study, investigators fed genistein to several groups of mice
before implanting them with an aggressive form of prostate cancer .The
amount of genistein in the blood of the animals was comparable to
human blood concentrations after consumption of soy foods, Bergan
said.
The researchers found that while genistein didn't reduce the size of
tumors that developed within the prostate, it stopped lung metastasis
almost completely. They repeated the experiment and found the same
result.
They then examined tissue in the animals, measuring the size of tumor
cells' nuclei to determine if the cells had flattened out in order to
spread. "Within a tumor, it is hard to tell where the borders of cells
stop, so one way to measure adherence is to look at the size of the
nuclei in cells and see if they are wider due to cell spread," Bergan
said. "And that is what we found, demonstrating that the drug is
having a primary effect on metastasis."
He said that the study also found that mice fed genistein expressed
higher levels of genes that are involved in cancer cell migration
which, Bergan says, at first might not make sense in light of the
study's conclusion that genistein almost completely blocked
metastasis.
"What we think is happening here is that the cells we put in the mice
normally like to move. When genistein restricted their ability to do
so, they tried to compensate by producing more protein involved in
migration. But genistein prevented those proteins from being
activated," he said. "This is really a lesson for researchers who
depend on biomarker studies to test whether a treatment is working.
They need to be aware that those biomarkers might be telling only half
of the story."
Bergan cautioned that much is unknown about use of genistein in
preventing cancer spread. For example, it may be that the effects of
the compound in people who have eaten soy all their lives is stronger
than benefit seen in patients who have only started to use genistein.
"The problem we have faced is that epidemiology studies that found men
who eat soy are at reduced risk of prostate cancer death are all
associative. They don't prove anything," he said. "The only way we
will find out how promising genistein is will be from conducting
clinical trials."
Human observational studies have found that while the spread of
prostate cancer is reduced in men who eat soy-rich foods, findings
have been mixed as to whether prostate cancer incidence is markedly
different. Results of some laboratory studies of genistein have also
been mixed, but most have shown favorable results, Bergan said,
demonstrating that genistein can inhibit a variety of cell molecules
including tyrosine kinases, which activate proteins by attaching them
to phosphate chemicals.
Source: American Association for Cancer Research
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