• Question: Could you tell me how smoking mutates cells in the lungs to cause cancer?

    Asked by naughtybear124 to Dr D, Alexis on 17 Jun 2013.
    • Photo: Andrew Devitt

      Andrew Devitt answered on 17 Jun 2013:

      That’s a big question and not all the answers are known. But there is an awful lot more than lung cancer that can be caused by smoking. Other cancers and cardiovascular disease….all pretty grim. And the biggest risk comes from starting smoking young, smoking a lot every day and smoking for a long time.

      The thing about cigarettes is that the smoke contains lots and lots of chemicals and some of these are known cancer-causing chemicals. One effect of some of these chemicals is that they affect a protein known as p53. This is a normal protein in our cells and it protects our cells. When damage (mutation) to our DNA is detected, p53 levels in the cell rise and it stops the cells dividing (you don’t want cells with mutations to divide because then you’d have two cells with mutations). It turns on other genes involved in repairing the damage and if the damage is too great, it can instruct the cell to die. It’s really important and efficient. But when p53 is inactivated, we lose the protection and mutations can persist and cancer can form.

      Chemicals in smoke can damage p53 so it doesn’t work. And p53 has been called the ‘guardian of the genome’…..so having it damaged isn’t great.

      So how important is this? Well over 50% of human cancers have a damaged p53

    • Photo: Alexis Barr

      Alexis Barr answered on 17 Jun 2013:

      Cigarette smoke contains approximately 20 “carcinogens” – which basically means cancer causing chemicals. These carcinogens are activated in your body and can bind to DNA in cells. Usually, the cell can repair this damage and the DNA goes back to normal. However, sometimes the damage isn’t or can’t be repaired. This causes a permanent mutation in the DNA which, in addition to other mutations, could lead to cancer.
      Smoking is particularly bad because cigarettes contain Nicotine which is addictive so once people have started smoking, it becomes very difficult to stop.

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