THE ease with which breast tissue absorbs carcinogens could explain many
of the 500 000 new cases of breast cancer recorded around the world each year,
say British researchers.
David Phillips and his colleagues at the Institute of Cancer Research in
London took samples of healthy breast tissue from 40 women who were undergoing
breast reduction surgery. Laboratory tests revealed that the tissue鈥攐r
chemicals contained in it鈥攃aused DNA damage and mutation in bacterial and
human cells. The researchers argue that the fatty tissue that makes up 80 per
cent of a woman鈥檚 breasts soaks up carcinogens鈥攚hich tend to be
fat-soluble organic molecules. This would make cells in the breast more likely
to form tumours.
鈥淲e know that cancer is caused by damage to DNA and that many compounds which
are capable of causing this damage are fat soluble,鈥� says Phillips. 鈥淥ur
research shows for the first time that human breast fat can act as a reservoir
for these carcinogens.鈥�
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Despite the excitement surrounding the discovery of the 鈥渂reast cancer
genes鈥�, BRCA1 and BRCA2, the causes of breast cancer are still
unknown in over 90 per cent of cases. Phillips and his colleagues hope that
their discovery, reported in this month鈥檚 Cancer Research, will lead to
new insights.
Phillips now intends to track down the chemicals responsible for the effects
his team has observed. He suspects certain foods may be a major source of the
mystery chemicals, although the researchers have not ruled out the possibility
that some of the carcinogens are airborne, or are by-products of metabolism.
However, Doug Easton, a cancer epidemiologist at the Institute of Public
Health in Cambridge, fears that even if the carcinogens are identified, it could
be hard to reduce women鈥檚 exposure to many of them. 鈥淚t could be that almost
unavoidable levels of carcinogens are behind some cases of sporadic breast
cancer,鈥� he says.
But Easton agrees with Phillips that the big variations in breast cancer
rates between countries suggest that some risk reduction is possible. When women
from Japan, which has a very low rate of breast cancer, move to the US, for
example, their risk of developing the disease rises dramatically.