Soy Compound May Halt Spread Of Prostate Cancer

[Guest guest]

I don't consume any now but may begin adding small amount of soy to my

diet.

Soy Compound May Halt Spread Of Prostate Cancer

ScienceDaily (Mar. 14, 2008) — 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, C. Bergan, MD, director of

experimental therapeutics for the 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.

A Veterans Administration Merit Award supported the study.

Adapted from materials provided by American Association for Cancer

Research.