hormone shows promise for preventing breast cancer in
women, according to Philadelphia researchers.
In animal studies, human
chorionic gonadotropin (hCG) activated tumor suppressor
genes, stopped cancer cell growth, and induced other
genetic changes that indicate an anticancer effect, says
Irma H. Russo, MD, chief of molecular endocrinology at
Fox Chase Cancer Center.
"Our goal is to
eventually use this as a breast cancer preventive in
women, just like tamoxifen," she tells WebMD. But unlike
tamoxifen, "hCG is normally produced by the body and has
no toxic effects."
Tamoxifen, which has been
used to prevent breast cancer, has been associated with
an elevated risk of endometrial cancer and blood clots.
Cuts Breast Cancer Risk
Studies show that a woman
who becomes pregnant by age 20 cuts her risk of breast
cancer in half.
"Over the years, the link
between having children and breast cancer protection,
particularly if you have children when you're young,
became very solid," Russo says.
"What we found is that
rats that were given cancer-causing drugs when they're
young, virgin, and in puberty develop breast tumors,"
she says. "But if you give the same drug after
pregnancy, the animals do not develop tumors."
There's a risk period for
developing breast cancer during early puberty, when the
ovaries first start working and the breasts start
developing. "We wanted to try to manipulate [the risk
period] and eliminate it," Russo says.
"We knew pregnancy does
it," Russo says, "but the question is, can we do it with
Breast Cancer in Rats
In one set of
experiments, researchers gave rats that had just reached
puberty a cancer-causing drug to induce breast tumors.
They then gave the rats either two weeks of hCG
supplements or a combination of estrogen and progestin
hormones. The researchers compared the results with
virginal and pregnant rats.
The study was presented
by Russo and colleagues at the annual meeting of the
American Association for Cancer Research.
Breast tissue samples
taken before and after the animals took hCG showed that
the hormone reduced the number of cells that were
dividing. The treatment also stimulated the production
of tumor-suppressor genes and decreased the number of
cells that had estrogen receptors -- needed to help most
breast cancer cells grow. These are all signs that hCG
was working just like an anticancer drug, Russo says.
They checked to see which
genes were activated in breast tissue in the rats during
pregnancy and compared that data with the changes after
treatment with hCG.
Compared with the
untreated virgins, "we found a complete change in the
genetic signature of both the pregnant rats and the rats
treated with hCG," she says.
"An early pregnancy
modifies the genetic signature for life. And giving hCG
modifies the genetic signature for life."
There was no change in
the rats given estrogen and progestin.
Russo sees a day in the
future when women at high risk of breast cancer can take
hCG for a short time during puberty, thereby modifying
their genetic signature in such a way as to confer
protection for life.
Timothy Richard Rebbeck,
PhD, an expert in molecular epidemiology at the
University of Pennsylvania in Philadelphia, says the
studies "reflect the work of Russo's lab, which is
"The notion of taking a
very well-established risk factor like pregnancy that's
not really modifiable and taking it to the next step and
mimic it to prevent breast cancer is very innovative,"
he tells WebMD.
But further studies are
needed to determine other factors that may be working in
concert with hCG to exert an antitumor effect, he says.
Charlene Laino, reviewed by
SOURCES: 96th Annual
Meeting of the American Association for Cancer Research,
Anaheim, Calif., April 16-20, 2005.
Irma H. Russo, MD,
chief of molecular endocrinology, Fox Chase Cancer
Center, Philadelphia. Timothy Richard Rebbeck, PhD,
professor of epidemiology, University of Pennsylvania,