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Gene
Discovery Links
Smoking and Colorectal Cancer
NEW
YORK (Reuters Health) - People who have a genetic mutation previously
linked to emphysema are three times more likely to develop a certain
type of colorectal cancer than those without the defect, study
results suggest. And smokers with the defect may be 20 times more
likely to develop the cancer, researchers warn.
``There has
been a lot of controversy surrounding whether smoking and colorectal
cancer are related,'' Dr. Ping Yang told Reuters Health. ``This
study confirms a strong relationship between the two in a group
of colorectal cancers.'' Yang is a clinical epidemiologist at
the Mayo Clinic in Rochester, Minnesota.
The mutation
is in the gene for alpha-1 antitrypsin, a substance that neutralizes
protein-destroying enzymes. People who have the gene mutation
are more likely to develop emphysema--particularly if they smoke--and
are at greater risk of liver and bladder cancer.
In the new
study, Yang and colleagues looked at alpha-1 antitrypsin genes
in 161 patients with cancers of the colon or rectum and 191 people
the same age who were cancer-free.
The investigators
found that 22% of the colorectal cancer patients with a specific
type of tumor had mutations in the alpha-1 antitrypsin gene, compared
with just 9% of the other colorectal cancer patients and 9% of
those who were cancer-free, according to the report in the December
issue of Molecular Genetics and Metabolism.
``We believe
almost 30% of all cases of colorectal cancer may be associated
with a lack of alpha-1 antitrypsin,'' Yang said. Smokers with
a mutation in the alpha-1 antitrypsin gene were 20 times as likely
to develop the subtype of colorectal cancer compared with nonsmokers
who did not have the gene mutation, the report indicates.
Lack of alpha-1
antitrypsin may encourage the development of colorectal cancer
by allowing chronic tissue damage to accumulate. Over time, such
tissue damage may result in the formation of cancers. Cigarette
smoking may promote the process, the researchers suggest.
``One thing
people can do right away to reduce their risk of colorectal cancer
is not smoke, and quit if they do,'' Yang said. ``Smokers should
be aware that their risk of lung cancer and heart disease is elevated,
and so is their risk of colorectal cancer.''
SOURCE:
Molecular Genetics and Metabolism 2000;71:639-645.
Reference
Source 89
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