Public release date: 16-Jul-2013 [ | E-mail | Share ]
Contact: John Rodgers pr@med.cornell.edu 646-317-7401 Weill Cornell Medical College
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 cells only express genes related to lung function, while brain cells express brain-specific genes. "Healthy cells are very tightly controlled. Normal cells have rules and only do certain things," says Dr. Crystal. "In cancer, that control is lost."
This loss of control allows cancerous cells to multiply without restraint and enables them to migrate to other organs because the genetic programming that keeps them on task is in disarray. The study found that smokers' cells were in the very early stages of losing this control.
"When you smoke a cigarette, some of the genetic programming of your lung cells is lost," says Dr. Crystal. "Your cells take on the appearance of a more primitive cell. It doesn't necessarily mean you will develop cancer, but that the soil is fertile to develop cancer."
Read the original post:
Even healthy-looking smokers have early cell damage which destroys necessary genetic programming