TOXICS
INFORMATION PROJECT (TIP)
Liberty
Goodwin, Director
P.O. Box 40572, Providence, RI 02940
Tel. 401-351-9193, E-Mail:
TIP@toxicsinfo.org
Website: www.toxicsinfo.org
(Lighting
the Way to Less Toxic Living)
Jose
Russo, M.D., Fox Chase Cancer
Center in Philadelphia Senior Member, Director
Breast Cancer Research Laboratory;, Director of the Environment Breast Cancer
Research Center, Director of the Medical Outreach and Minority Affairs Program;
Adjunct Professor of Pathology and Cell Biology, Thomas Jefferson College of
Medicine
BREAST CANCER MAY
BE LINKED TO MOTHER’S CHILDHOOD
Chemical
exposure in past generations could affect present ones, scientists say
By Douglas
Fischer, Oakland Tribune November 3, 2006
OAKLAND - New thinking on the causes of breast cancer suggests
the disease's origins may be found not in anything a woman has done, but in
what her mother - and possibly her grandmother - did before her. The findings further suggest that tiny exposure to
hormone-like industrial chemicals early in life can have profound effects not
just later in adulthood, but in future generations as well.
Taken as a whole, said
scientists gathered today for a conference on early environmental exposures and
their link to breast cancer, the research simultaneously offers hope and
despair: It points the way to potential new cures while highlighting how little
we understand of a pollution pervasive in our bodies and environment. "We are
inducing certain genetic sequences that later on make the animal more susceptible
to cancer," said Dr. Jose Russo, director of the Fox Chase Cancer Center
in Philadelphia, where some of this research is being done. "This is not a humongous dose where you
kill the animal. These are levels found in the environment, but are enough to
change the (genetic) _expression," he said.
The current thinking on breast cancer is fairly straightforward:
The earlier a girl hits puberty, the greater her odds of getting breast cancer
later in life. Scientists generally agree that diet, obesity, lack of exercise
and other factors play key roles in the increasingly earlier onset of menarche
in girls - sometimes at 8 years or younger, particularly in First World economies. This new information does not change what is commonly
accepted about breast cancer. Rather, it suggests that diet, hormone-like
chemicals, and genetic susceptibility interact in ways regulators and
scientists do not fully grasp. Much of the science is a result of an ambitious
seven-year, $35 million effort to map the environmental causes of breast
cancer. The project is in its fourth year.
Two results in particular are startling. The first is the notion
that these hormone-like chemicals - known as endocrine disruptors and found in
everything from shampoo and cosmetics to canned tomato sauce and baby toys -
muck with our genes. They do so not
by altering the genes themselves, said Thea Tlsty a pathology professor at
University of California, San Francisco, but by influencing the tightly
choreographed sequences controlling when genes flip on or off.
It's akin to taking a computer that crunches numbers and
reprogramming it to only play music.
The computer - the gene, in this case - hasn't changed, but its output
has. That, Tlsty said, is what
endocrine disruptors do: They alter not the genome, but the epigenome - the
program.
Take a crucial protein, HOXA9, known to fight breast cancer
cells. In almost all women with breast cancer, Tlsty said, there is no HOXA9
activity, or _expression. But almost half
those women have the protein, Tlsty found. It just never flipped on. So what
would keep it off? Any of a number of common contaminants, Tlsty said. What's
more, the effect was translated across generations, she said.
Turn the gene controlling HOXA9 off in a mouse, and that mouse's
offspring never express it, either. It's as if the
protein disappeared. Except that, in the United States, if a chemical altered
the gene, it would most likely be banned. There is no standard for chemicals
altering the epigene, or program.
The other startling finding concerns timing:
A dose of any given pollutant considered inconsequential to an adult - the
basis for most regulatory standards - may in fact have considerable
consequences when given at or before birth or during adolescence.
At
the Cox Center in Philadelphia, Russo's team is feeding laboratory mice small
amounts of various common chemicals - dioxins, phthalates, bisphenol-A - at
various life stages, including before birth, via the mother. And while Russo's research deals only with
rodents, it suggests there may be factors at play influencing puberty and young
girls' development that we do not fully grasp.
"If
we can study these things that affect the variability impacting the onset of
puberty, we could have a better sense of the factors contributing to
breast cancer," said Dr. Frank Biro, a professor of pediatrics at the
Cincinnati Children's Hospital.
"We're casting a fairly broad net to try and understand these
environmental influences," he said.