SECOND-HAND SMOKE MAY HARM FETUS

Cancer-causing mutations are more likely

Pregnant women who are exposed to other people's cigarette smoke might be
raising their fetuses' risk of developing cancer in childhood.

A study found that babies born to exposed mothers showed higher rates of a
kind of genetic mutation in blood cells. This kind of mutation is caused by
a particular enzyme, and it is often found in childhood leukemia and
lymphoma.

Experts say it is the first time scientists have linked second-hand smoke to
genetic mutations in a fetus. Prior research found elevated mutation rates
in fetuses from women who themselves smoked during pregnancy.

The study doesn't show a direct link to cancer. In fact, the specific gene
mutations it monitored are harmless because they occurred in a gene
unrelated to cancer.

The findings suggest only that if a pregnant woman is exposed to cigarette
smoke, the mutation-making enzyme might become more active in her fetus,
raising the risk of hazardous mutations in cancer-related genes.

The study couldn't define how big a risk second-hand smoke might pose, but
it's rare for children to get leukemia or lymphoma at all. Only about 3,000
new cases, mostly leukemia, are expected in the United States this year in
children up to age 14.

The work was presented in the October issue of the journal Nature Medicine
by Dr. Barry Finette, Dr. Richard Albertini and colleagues at the University
of Vermont in Burlington.

It's an important finding that requires follow-up study, says Frederica
Perera, director of Columbia University's Centre for Children's
Environmental Health. A fetus is "exquisitely sensitive" to exposure to many
toxins, including those in tobacco smoke, because the defence systems
present in adults are still developing, she says.

The study involved 24 newborns from non-smoking mothers. Half were born to
women who said they had been exposed to other people's smoke at home, at
work or in both places. The other half were born to women who reported no
such exposure.

The researchers inspected white cells in blood from the placenta. They
looked for mutations in a gene called HPRT. This gene has nothing to do with
cancer, but researchers used it as an indicator of how often particular
kinds of mutations had occurred generally in the newborn.

The key finding pertained to a kind of genetic splicing carried out by an
enzyme called V(D)J recombinase.

Normally, the enzyme helps the immune system prepare to fight a variety of
germs. But when the enzyme makes a mistake, it can set the stage for cancer.

The study found that HPRT mutations produced by the enzyme appeared at a
higher rate in the smoke-exposed group, at 34 per cent of all mutations
counted versus 20 per cent.

When researchers counted only mutations that deleted large chunks of genetic
material, the difference was 67 per cent versus 37 per cent.

Finette says he suspects substances in cigarette smoke make fetal DNA more
vulnerable to mutations by the enzyme.

Checked-by: Rolf Ernst