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Investigating the molecular implications of smoking

Around the world, visual health warnings on cigarettes intentionally provide a disturbing picture of the damage smoking can cause to the human body.

It has been acknowledged for several decades that tobacco use is dangerous. However, it is only recently that scientists have discovered the extent to which cigarettes can cause harm on the molecular level.

A recent study into the DNA mutations caused by smoking compared the cancer cells of 2,500 smokers and 1,000 non-smokers. The researchers found that smokers had a greater number of mutations overall, and found that smoking one pack a day can cause an additional 150 mutations per lung cell. Furthermore, smoking was discovered to cause mutations in other, more distal organs as well, including: 97 for each cell in the larynx, 18 for each bladder cell, and six mutations per liver cell.

Mutations are simply a change to DNA, but most of the time the change has a detrimental effect. The DNA in our cells regulates cell multiplication. Cancer occurs when the cells in an organ start multiplying uncontrollably; this can go on to form a tumour and spread to other parts of the body if not treated. In theory, all mutations have the potential to cause cancer, however it depends on which genes in the DNA are affected. If the gene mutated is one that protects against or stimulates cancer, the person affected may go on to develop the disease.

There are 70 carcinogens, chemicals which cause cancer, in tobacco. At present, there are 17 cancers known to be associated with smoking. The researchers believe their findings will help them to discover the root of cancer: “Before now, we had a large body of epidemiological evidence linking smoking with cancer, but now we can actually observe and quantify the molecular changes in the DNA due to cigarette smoking,” Ludmil Alexandrov, lead author of the study, has stated.

The discovery of mutations in the kidneys, liver, and bladder were particularly interesting because these organs are not directly exposed to tobacco smoke. Instead, researchers found, the chemicals from the tobacco make their way to these organs, leading to mutations.

Currently Alexandrov is researching the likelihood of a single smoking-related mutation to cause cancer, and which types of mutations are most likely to be cancerous. However, he is clear about one thing:  The more you smoke the more at risk you are to developing cancer.

“Smoking is like playing Russian roulette” Alexandrov says: “The more you play, the higher the chance the mutations will hit the right genes and you will develop cancer”.

Image: Guilia Ciappa (User on Wikipedia)

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