Genes Permanently Turned On by Smoking

Those who smoke tobacco should know that this habit is not considered to be sexy anymore. However, smoking can turn on permanently some of the genes. A study, which was published in BMC Genomics, an on-line open-access journal, was able to explain why those people who used to smoke still have a higher risk for lung cancer development than those who never had the bad habit.

Wan L Lam and Stephen Lam, who work at the BC Cancer Agency, together with a team of Canadian researchers, examined the lungs of former smokers, those who still cannot get rid of smoking and people who never for it. Researchers took lung samples from all of the three categories of people and then used them for making libraries. They used a special technique called serial analysis of gene expression. This technique serves for identifying patterns of gene activity.

It turned out that, at any given time, only about 1/5 of the genes in a cell are switched on, but such environmental changes like smoking can cause some changes in the activity of genes. Scientists discovered that there were some irreversible changes and changes that were reversed because the person stopped smoking.

Those genes that were reversible were involved in the so-called xenofobic functions, nucleotide metabolism and mucus secretion. Smoking damages some DNA repair genes that cannot be reversed. In addition smoking is able to switch off those genes that are meant to protect against cancer growth. Some genes, that scientists previously thought of not having any connection with smoking, are switched on in people who are still enjoying their favorite cigarettes. One of such genes is CABYR. It is meant to help sperm swim and it is linked with brain tumours.

Scientists continued their study by investigating the changes in genes that were involved in airway repair and regeneration. Thus, from this group they identified genes that they arranged into 3 categories, following cessation of smoking. The first group is called reversible, the second partially reversible and finally irreversible.

"Those genes and functions which do not revert to normal levels upon smoking cessation may provide insight into why former smokers still maintain a risk of developing lung cancer," mentioned Raj Chari, one of the authors of the study.

It is worth mentioning that tobacco smoking is linked to about 85 percent of lung cancers. Those who used to smoke account for half of smokers newly diagnosed with the lung cancer.