Smoking may cause loss of Y chromosome

Smoking can cause loss of the Y chromosome in blood cells, which may put male smokers at a greater risk of cancer, a new study has found.
Researchers at Uppsala University in Sweden found an association between smoking and loss of the Y chromosome in blood cells. Loss of the Y chromosome was more common in heavy smokers compared to moderate smokers, the study found.
Since only men have the Y chromosome, these results might explain why smoking is a greater risk factor for cancer among men and, in the broader perspective, also why men in general have a shorter life expectancy, researchers said.

"We have previously in 2014 demonstrated an association between loss of the Y chromosome in blood and greater risk for cancer," said Lars Forsberg, researcher at the Department of Immunology, Genetics and Pathology, Uppsala University.
"We now tested if there were any lifestyle or clinical factors that could be linked to loss of the Y chromosome.
"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," Forsberg said.

The association between smoking and loss of the Y chromosome was only valid for men who were current smokers. Men who had been smoking previously, but quit, showed the same frequency of cells with loss of the Y chromosome, as men who had never smoked.

"These results indicate that smoking can cause loss of the Y chromosome and that this process might be reversible," said Forsberg.
"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. This discovery could be very persuasive for motivating smokers to quit," said Forsberg.

It is not clear how loss of the Y chromosome in blood cells, induced by smoking, is connected with the development of cancer throughout the body.
One possibility is that immune cells in blood, that have lost their Y chromosome, have a reduced capacity to fight cancer cells, researchers said.
The study was published in the journal Science.