NEW YORK (July 16, 2013) -- Smokers who've received a clean bill of health from their doctor may believe cigarettes haven't harmed their lungs. However, researchers at Weill Cornell Medical College have found that even smokers who seem healthy have damaged airway cells, with characteristics similar to cells found in aggressive lung cancer.
The study, published today in the journal Stem Cell, compared cells that line the airway from healthy nonsmokers with those from smokers with no detectable lung disease. The smokers' cells showed early signs of impairment, similar to that found in lung cancer -- providing evidence that smoking causes harm, even when there is no clinical evidence that anything is wrong.
"The study doesn't say these people have cancer, but that the cells are already starting to lose control and become disordered," says the study's senior investigator, Dr. Ronald G. Crystal, chairman and professor of genetic medicine at Weill Cornell Medical College. "The smoker thinks they are normal, and their doctor's exam is normal, but we know at the biologic level that all cigarette smokers' lungs are abnormal to some degree."
The researchers found that in the cells lining the airways of the smokers's lungs, human embryonic stem cell genes had been turned on. These are genes that are normally expressed in developing embryos -- soon after eggs are fertilized -- before cells are programmed with their specific assignment. This gene is also "on" in the most aggressive, hard-to-treat lung cancers.
"We were surprised to see that the smokers were expressing these very primitive human embryonic stem cell genes," Dr. Crystal says. "These genes are not normally functioning in the healthy lung."
Healthy lung cells, like all of the body's cells, have very specific assignments. Although all of the body's cells contain the same genes, genes are only "turned on" for each cell's defined task. Therefore, healthy lung c
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Weill Cornell Medical College