NEW YORK, Nov 21, 2000 (Reuters Health) - Nicotine from cigarettes or from patches
or gum can be converted by the body into chemicals that have been shown to cause
lung cancer, results of a study suggest.
Dr. Stephen Hecht and colleagues from the University of Minnesota Cancer
Center in Minneapolis, identified two nicotine forms in urine that suggested a
particular pathway the body might use to break down the addictive agent.
This pathway leads to the production of a chemical called aminoketone that
contributes directly to the formation of NNK, a tobacco-specific cause of lung
cancer, according to the report in the October 24th issue of the Proceedings of
the National Academy of Sciences.
The investigators confirmed this possibility by showing, in a variety of
test-tube experiments, that human enzymes could be used in the laboratory to
produce aminoketone from nicotine.
Moreover, extracts from human liver cells could convert nicotine to
aminoketone, which was then broken down into one of the products the
investigators had identified in human urine.
The researchers report that they did not actually identify NNK during these
laboratory experiments but that aminoketone should be readily converted to NNK
in the body.
"These considerations lead to the realistic possibility that NNK could be
formed...in people who use tobacco products, resulting in exposure to this
carcinogen above and beyond the amounts already present in these products," the
authors conclude.
"It is also possible that NNK could be formed...during nicotine replacement
therapy, particularly under conditions of long-term therapy," they add.
Still, these findings should not cause people to stop using nicotine
replacement therapy, Hecht told Reuters Health. "Nicotine replacement therapy is
far better than smoking," he said, "even if some NNK is formed. As for long-term
nicotine replacement therapy, we really don't know. There may be some risks
involved, but it is impossible at this point to say how much, if any."
SOURCE: Proceedings of the National Academy of Sciences 2000;97:12493-12497.
