Ginkgo biloba extract may inhibit breast cancer

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Ginkgo biloba extract: More than just for memory?

Washington, DC -- Researchers at town University Medical Center

say they now have a clearer picture of how an extract from the leaves

of the Ginkgo biloba tree reduces the risk of aggressive cancer in

animal experiments.

In the January-February issue of the journal Anticancer Research, the

investigators reported that treating mice with an extract of leaves of

Ginkgo biloba both before and after implanting human breast or brain

(glioma) tumors decreased expression of a cell receptor associated

with invasive cancer. This decreased expression slowed the growth of

the breast tumors by 80 percent as long as the extract was used,

compared to untreated mice, and also reduced the size of the brain

tumors, but temporarily, and to a lesser extent.

Ginkgo biloba extract is a popular supplement that comes from the

leaves of the Gingko tree, which is indigenous to Japan, Korea and

China but can be found all over the world. Many believe it enhances

memory, and is being currently being tested as a treatment for

Alzheimer's disease.

" It is very encouraging that Ginkgo biloba appeared to reduce the

aggressiveness of these cancers, because it suggests that the leaves

could be useful in some early stage diseases to prevent them from

becoming invasive, or spreading, " said the study's senior author,

Vassilios Papadopoulos, DPharm, PhD, Director, Biomedical Graduate

Research Organization and Associate Vice President of town

University Medical Center.

" But I must stress that this is a study in mice, and so we cannot say

what anticancer effects, if any, Gingko biloba might offer humans, " he

said.

Papadopoulos and his research team became interested in Gingko biloba

because their research suggested that it might interact with the

peripheral-type benzodiazepine receptor (PBR), a molecule they have

been studying for the last 20 years. For example, they have determined

that this protein (discovered by accident when researchers looked at

how the anti-anxiety drug diazepam, better known as Valium®, worked)

is involved in bringing cholesterol into a cell's mitochondria.

In some cells the mitochondria uses cholesterol to produce steroids,

which are regulatory hormones that, among other functions, help a cell

grow, Papadopoulos said. " In fact, we have found that most life forms,

including plants, insects, and animals, have receptors like these that

help regulate growth. "

So they looked at whether cancer cells -- with their need to

proliferate -- produce more of these cholesterol-bearing receptors,

and found that some highly invasive cancers do, indeed, over-express

PBR. " Accelerated growth requires production of new cell membranes,

and one of the main components of membranes is cholesterol, "

Papadopoulos said.

The researchers also knew that steroids help regulate brain function,

and they found over-expression of PBR is also associated with a

variety of neurological disorders. Because the leaf of Ginkgo biloba

is an ancient Chinese treatment for dementia that is still widely used

-- and which is now being tested in the U.S. to treat Alzheimer's

disease patients -- Papadopoulos decided to look at the effect of

Ginkgo biloba on PBR production.

He selected breast cancer cells that over-expressed PBR, implanted

them in mice, and treated the mice with a standardized extract of

Ginkgo biloba leaves. After 30 days, tumor size was reduced by 35

percent, compared to untreated mice. That research was published in 2000.

One aim of this new study, then, was to find whether other cancer cell

lines also over-express PBR. They found that, in addition to one form

of aggressive breast cancer (invasive estrogen-receptor negative),

certain brain, colon, and prostate cancers also show higher than

normal levels of PBR.

The other part of the research was to see if Ginkgo biloba would show

any anticancer effects on these cancer cell lines, and concluded that

the extract did nothing to cancers that were not invasive, but

significantly slowed the growth of aggressive cancer cells.

Papadopoulos and his team then studied whether a non-commercial

injectable form of a standardized extract of Ginkgo biloba leaves

might have any preventive effects, and selected the aggressive breast

cancer and brain glioma to study in mice. The researchers pretreated

the animals with this pharmaceutical preparation of Ginkgo biloba,

then implanted the tumors. The Ginkgo biloba extract inhibited growth

of the breast tumors by more than 80 percent, but glioma tumors did

not respond as strongly, and the benefit was maintained for only 50

days despite continuous treatment. Tumors implanted in mice that did

not over-express PBR did not respond to the extract.

Papadopoulos now plans to examine the notion that a cancer diagnosis

might increase production of stress steroids such as corticosteroids

through PBR over-expression, and it is this stress that, in effect,

pushes a tumor to become invasive. " Ginkgo biloba could possibly

reduce this stress by tamping down PBR, " he said.

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The study was funded by the National Center for Complementary and

Alternative Medicine (NCCAM), National Institutes of Health and the

Institut Henri Beaufour-IPSEN, France. Co-authors from town

University Medical Center are first author Ewald Pretner, MD, Hakima

Amri, PhD, Wenping Li, MD, PhD, Brown, PhD, Chin-Shoou Lin, MS,

and i Makariou, MD. Also contributing to the research were Francis

Defeudis, PhD, from the Institute for Bioscience, in Westborough, MA.,

and Katy Drieu, DPharm, from the Institut Henri Beaufour-IPSEN, in Paris.

About town University Medical Center

town University Medical Center is an internationally recognized

academic medical center with a three-part mission of research,

teaching and patient care (through our partnership with MedStar

Health). Our mission is carried out with a strong emphasis on public

service and a dedication to the Catholic, Jesuit principle of cura

personalis -- or " care of the whole person. " The Medical Center

includes the School of Medicine and the School of Nursing and Health

Studies, both nationally ranked, the world-renowned Lombardi

Comprehensive Cancer Center and the Biomedical Graduate Research

Organization (BGRO).