Research links smoking to loss of male chromosome

Researchers in Sweden say they have linked the loss of the male Y chromosome with smoking in men, which, they say, explains a greater incidence of smoking-related cancers in men than women.

The new study, published in the journal Science, looked at the blood cells of men who smoke. The researchers found that blood cells showed a definite loss of the Y chromosome, the chromosome that determines a person’s sex. Men have both Y and X chromosomes, while women have two X chromosomes.

Past studies have shown that men who smoke are at a greater risk of developing various cancers—not just lung cancer—than their female counterparts. Dr. Lars Forsberg of Uppsala University, Uppsala, Sweden, study co-author, says this loss of the Y chromosome may help explain that increased threat.

The study results, which were gathered from data on more than 6,000 men, participating in three different ongoing Swedish studies on epidemiology, show that the more a man smoked, the greater the loss of the Y chromosome in the blood samples. The older the men, the greater the loss, the study shows. Among men 70 to 80 years old, 15.6 percent showed the Y chromosome loss, as compared to 4.1 percent of men younger than 70. Comparing smokers to non-smokers, those who smoke had a 2.4 to 4.3 time’s greater risk of the genetic loss.

How loss of the Y chromosome in blood cells is connected with the possible development of cancer is still unclear. Dr. Frosberg says one possibility is that a man’s immune cells in blood, having lost the Y chromosome, have a reduced capacity to fight cancer cells.

However, Dr. Forsberg says the loss may be reversible.

“We found that the frequency of cells with loss of the Y chromosome was not different among ex-smokers compared to men who had never smoked,” he says in a statement. “This discovery could be very persuasive for motivating smokers to quit.”

And this study only covers the increased risk of cancer. There’s no mention, yet, on how this could affect the host of other conditions identified earlier this year by the U.S. Surgeon General connected to smoking—including diabetes and erectile dysfunction.

“This study is food for thought,” says Dr. Sangeetha Nimmagadda, oncologist with Advocate Illinois Masonic Medical Center in Chicago. “The greater message here is to stop smoking. Smoking is a modifiable behavior that is a risk factor not only for various cancers, but for heart disease, stroke and aneurysm.”

Dr. Nimmagadda says that, though the study establishes a somewhat tenuous relationship between cancer and the loss of the Y chromosome, it does begin to build upon already long-held knowledge that cancer is caused by genetic mutation.

“The more we work on genetically profiling cancers—learning the exact genetic mutations that cause them—the more we can tailor treatment,” she says. “We’ll be able to better target our treatment with the appropriate drug for the appropriate cancer by identifying the genomic profile of the cancer.”