Smoking may turn on some genes in the body in a permanent and
harmful way, scientists said in a recent study that may help
explain why the risk of cancer remains high even after smokers
quit.
They found many genetic changes that stop when a smoker quits,
but found several genes that stay turned on for years, including
several not previously linked with tobacco use.
"These irreversible changes may account for the persistent lung
cancer risk despite smoking cessation," the researchers wrote in
their report, published in BioMed Central journal BMC Genomics.
In any cell, only about one-fifth of the genes are switched on
at any given time.
Raj Chari of the British Columbia Cancer Research Centre in
Vancouver and colleagues took tissue samples from 20 smokers and
former smokers and compared their gene activity to one another and
to the genes of four people who had never smoked.
They found some DNA repair genes were turned off in smokers and
stayed off in the former smokers. Damage to the DNA is one of the
main causes of cancer.
One gene that was switched on in smokers and former smokers was
CABYR, a gene involved in helping sperm to swim.
"Fifty percent of newly diagnosed lung cancer patients are
former smokers. It is therefore important to understand the effects
of tobacco smoking on the (airways) in both active and former
smokers," the researchers wrote.
(China Daily via agencies October 1, 2007)