Smoking may kill off the Y chromosome in men’s blood cells

Smoking may kill off the Y chromosome in men’s blood cells



New research suggests the Y chromosome—a repository of genes that only males have—may help explain why men live less long than women, and are more susceptible to smoking-related cancers.

With advancing age, some cells can lose their Y chromosome. Two new studies suggest this loss may increase cancer risk—and that smoking may exacerbate the chromosome loss. Both projects came from the same group of researchers, and while they did not prove cause-and-effect relationships, they found associations between the events in question.

The earlier study, published in the research journal Nature Genetics online April 28, “demonstrated an association between loss of the Y chromosome in blood and greater risk for cancer,” said Lars Forsberg of Uppsala University in Sweden, one of the investigators.

For the second project, published in the Dec. 4 issue of the research journal Science, he added that the group tested “if there were any lifestyle- or clinical factors that could be linked to loss of the Y chromosome.”

The result: “Out of a large number of factors that were studied, such as age, blood pressure, diabetes, alcohol intake and smoking, we found that loss of the Y chromosome in a fraction of the blood cells was more common in smokers than in non-smokers.”

Y chromosome loss is “the most common human mutation” to begin with, added Jan Dumanski, a co-researcher at Uppsala. The new work “may in part explain why men in general have a shorter life span than women, and why smoking is more dangerous for men.”

Smoking is a risk factor for various diseases, not only lung cancer, the researchers noted; male smokers have shown a greater risk of developing non-respiratory-tract cancers than female smokers.

The investigators found the association between smoking and Y chromosome loss to be “dose dependent”—heavy smokers had more widespread losses. But ex-smokers who had quit showed normal levels of Y chromosome loss. So “this process might be reversible,” which “could be very persuasive for motivating smokers to quit,” said Forsberg.

How the smoking-induced Y chromosome loss in blood cells is linked to cancer remains unclear. Perhaps immune cells in blood, bereft of Y chromosomes, are less able to fight cancer cells, the scientists speculated.

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