BPA exposure linked to prostate cancer
By Brian Bienkowski, Environmental Health News
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| Bisphenol A is used to make polycarbonate plastic and is found in the linings of some food and drink cans and thermal paper receipts |
Exposure to low levels
of bisphenol A during development may make men more susceptible to prostate
cancer later in life, according to a new study published on January 7.
The study, which uses a
new model of implanting human stem cells into mice, is the first to link
early-life BPA exposure to human prostate cancer. It adds to a growing body of
research that suggests exposure to low doses of the chemical alters cells and
can lead to diseases later in life.
“Overall I think this is
some of the strongest and most convincing evidence to date linking early-life
BPA exposure and cancer,” said Heather Patisaul, a researcher at North Carolina
State University who was not involved in the study. “They were careful to make
the exposures human relevant, used cells derived from healthy humans and
replicated physiological conditions seen in aging men.”
Prostate cancer is the
second leading cause of cancer-related death in U.S. men. About 15 percent of
men will be diagnosed with prostate cancer in their lifetime, according to the
National Cancer Institute.
BPA is used to make
polycarbonate plastics and is found in in some paper receipts, liners of some
food cans and dental sealants. More than 90 percent of Americans have traces in
their bodies and previous studies suggest there is "universal
fetal exposure."
Researchers led by a
team from the University of Illinois at Chicago implanted prostate stem cells
from deceased young men into mice. When the mice were fed BPA by mouth for the
first two weeks of life, 33 percent of the stem cells had cancerous or
precancerous lesions later in life.
Forty-five percent of the cells that were
exposed to BPA before and after mice implantation developed precancerous or
cancerous lesions later. In comparison, only 12 percent of the mice not exposed
to BPA during development had cancer or precancerous lesions later in life.
BPA acts as an estrogen
and previous research has linked elevated estrogen levels during pregnancy to
increased risk of prostate cancer in males.
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| Researchers implanted mice with human prostate stem cells |
“We know that stem cells
help replenish our organs throughout life. We propose that if there is exposure
early in life to an estrogenic compound – such as BPA – it reprograms our stem
cells," said Gail Prins, a University of Illinois at Chicago researcher
and lead author of the study, which was published in the journal Endocrinology.
Although the cells were
from deceased adults, by using regenerative stem cells that produce prostate
tissues, the researchers said they were able to simulate developmental
exposure. It is the latest addition to a growing body of research – called
epigenetics – that has linked some chemicals to altered DNA sequencing in
fetuses that can lead to diseases later in life.
Patisaul said the new
model cannot “perfectly replicate human physiology,” but is advantageous
because they’re exploring “the impact of BPA ... on human cells in a whole
animal instead of a dish.”
However, a
representative of the chemical industry said that the model of implanting the
stem cells into mice has not been established to be valid. The study has “very
limited relevance to real-life human exposures to BPA,” Steve Hentges, a
representative of the American Chemistry Council, said in a prepared statement.
"The [BPA] levels
tested are more than 1,000 times higher than typical human exposures," he
said.
Prins said “that’s just
not true."
“Twenty minutes after
exposure the levels of BPA measured in the blood of the animals that were the
hosts bearing the transplants were exactly what we’re seeing measured in the
umbilical cord fluid of women,” Prins said, citing a 2013
study on California women.
In addition to the BPA,
all the mice were given an estrogen to simulate human male aging. As men age
their estrogen levels rise.
Men's rising levels of
estrogen are at least partly responsible for prostate cancer. Prins said the
early-life exposure to BPA is sensitizing the prostate stem cells to estrogen,
and the stem cells pass along this estrogen sensitivity to prostate tissues
later in life.
Prins’ earlier work found that rats exposed to BPA
at human-relevant doses had adult prostates that were more sensitive to
developing cancer.
Also, developmental BPA
exposure was linked to breast cancer in rats last year by Tufts
University researchers, but the data did not reach statistical significance,
said Nicole Acevedo, a postdoctoral researcher at Tufts University and lead
author of the study. Some rats exposed to low doses of BPA developed malignant
tumors while none of the non-exposed did.
