Source: Reuter

Study suggests smoking damage may be longlasting

PITTSBURGH (Reuter) People who smoked for many years may face a
permanently increased risk of lung cancer, even after giving up the
habit, research at the University of Pittsburgh indicates. Longterm
smoking may throw a a biological ``switch'' that drives the growth of
lung cells and could lead to cancer, according to Dr. Jill Siegfried,
director of basic science at the University of Pittsburgh Cancer
Institute's Lung Cancer Center. Research directed by Siegfried, who
is also an associate professor of pharmacology at the university's
School of Medicine, was published in this month's issue of the
Journal of Respiratory and Critical Care Medicine. ``We believe this
switch is an indicator of lung cancer risk, because we see it
activated in most people with a long history of smoking, regardless
of whether they already have developed cancer,'' Siegfried said.
``Once this switch is turned on, it appears to be permanent,'' she
said. ``(That) may explain in part why longterm exsmokers who have
not had a cigarette in over 25 years are still at high risk for
getting lung cancer.'' Dr. Michael Tuhn, director of analytic
epidemiology at the American Cancer Society, said the research should
not discourage smokers from kicking the habit because they think it
means they will develop cancer whether they quit or not. ``The
benefits to quitting are huge,'' he said. ``The benefits are very
well established, as in reducing the risk of heart attack, lung
cancer and stroke. ``It's reasonable to assume that (some) adverse
effects are not repaired,'' he said, referring to Siegfried's study.
``But insofar as the person on the street goes, the risks of dying
(from smokingrelated diseases) fall dramatically when one quits, and
the earlier you quit the better.'' The ``switch'' in Siegfried's
research is a gastrinreleasing peptide receptor, a protein found on
the surface of lung cells in people with a history of smoking one or
more packs of cigarettes a day for at least 25 years. That receptor
captures nearby circulating hormones, which in turn spur lung cells
to divide. As cells divide and new clusters form, cancer can
eventually occur, Siegfried said. Her study looked at cells lining
the lungs of 37 subjects. Some of them were nonsmokers, some had
smoked less than 25 years, and others had smoked 25 years or longer.
Only 14.7 percent of those who smoked less than 25 years showed the
receptor, but 77 percent of those who smoked more than 25 years
showed it, even if they had quit some time ago. ``This shows that the
duration of smoking, not just whether someone smoked, is critical to
expressing the receptor,'' Siegfried said. She said a largescale
study to confirm the research was being conducted on both smokers and
nonsmokers. ^REUTER@