| Certain tobacco chemicals
trigger cellular genetic damage. Damaged cells are supposed to commit suicide; if they do
not, the damage eventually accumulates enough to turn cancerous. Nicotine activates an enzyme reaction that inhibits
cellular suicide, says new research by scientists at the National Cancer Institute.
Nicotine starts activating that enzyme,
called Akt, within minutes, while cancer-causing genetic damage takes hours to begin, NCI
researchers report in Thursday’s Journal of Clinical Investigation. That suggests
nicotine — along with other chemicals that also block cell suicide — may make
cells more vulnerable to the cancer-causers.
“Nicotine is not a carcinogen and
we’re not trying to make that argument,” said the study leader, Dr. Phillip
Dennis. But “it may have a permissive effect” for cancer formation.
Scientists first discovered nicotine may
block cell suicide 10 years ago, said nicotine expert Dr. Neal Benowitz of the University
of California, San Francisco. But the new research uncovers the actual enzyme involved.
That enzyme pathway could prove important
in developing cancer-preventing drugs, Dennis said. The immediate question is whether the
effect matters for people using nicotine in gum or patches in an effort to kick the habit.
“It’s clearly better for
people to stop smoking and use a patch than to continue smoking,” Dennis said. But
the study reinforces that anti-smoking medicines are for short-term use because
“there may be biologic consequences” of using patches for months or years, he
added.
But Benowitz said the NCI study used cells in
laboratory dishes, while previous studies of snuff users — who do not absorb nearly
as many carcinogens as smokers — suggest there is little cancer risk from nicotine.
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