P53 Information sheet

We already know smoking causes lung cancer. Finally, we have the first direct proof of exactly how it does. It all comes about because of a fascinating and important gene known as p53.

The p53 gene, which is found in the nucleus of every cell in the human body, is known as "the guardian of the genome". The genome is the technical name of genetic information: DNA. Every day, DNA in many of our cells copies itself, and every day a few errors are made in this process. The new cells created by these mistakes have the potential to become cancerous. One of p53's main roles is to clean up those changes and errors within the cell. Obviously, a p53 gene which does not work properly would leave a cell, and ultimately a human body, highly susceptible to cancer. (1)

A damaged p53 gene is found in at least half of all cancers.(2,3) p53 is damaged in a very specific way in about 60% of people who smoke and develop lung cancer.(4) Some components of cigarette smoke react chemically with DNA. If such damaged DNA is not repaired, mistakes are introduced when the damaged DNA replicates during cell division. In this way, a modified cell population which is not responsive to normal growth control may develop and ultimately evolve into cancer.

Scientists from California and Texas made the direct genetic link between smoking and lung cancer in 1996 when they proved that a carcinogen, benzopyrene which is found in high concentrations in cigarette smoke, directly damages p53.(4) They showed that cigarette smoke leaves its distinctive signature on p53. There is no doubt at all that smoking damages p53, and this allows lung cancer to develop.

There is no simple test to see what condition somebody's p53 genes may be in.

Diagram of how P53 gene is damaged

Text version of the diagram above:

Most of the time the p53 tumor supressor gene stops mutating cells becoming cancer; but when p53 is damaged, mutations accumulate more rapidly leading to cancer.

  • Image of human lungs exposure to tobacco smoke - p53 is damaged by cigarette smoke
  • Image of chemicals in smoke reacting with DNA in cells DNA mutates and is damaged permanently
  • Image of cell with damaged p53
  • Image of cell accumulating mutations
  • Image of cell with damaged DNA divides and forms cancer cells
  • Image of cancer cell growing
  • Image of Lung cancer disease
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Questions and answers about P53

What is p53 ?

p53 is a gene which codes for a protein found in the nucleus of every cell in the human body and many other species.

What does it do?

The p53 protein's main role is to prevent cancer cells evolving.

How does it suppress cancer?

p53 both stops damaged cells dividing and may encourage such cells to suicide.

What happens if my p53 is damaged?

If your p53 is damaged, it may be repaired. Otherwise the risk of long term change in particular tissues is increased.

How do you know this?

Recent medical research has shown that p53 is damaged in a very specific way in about 60% of people who smoke and develop lung cancer. A chemical in cigarette smoke damages p53. (4) That has been proven beyond doubt.

Is there a simple test for damaged p53 ?

No, not yet.

What can I do to protect myself?

Quit smoking.

Sources:
1. Nature 1992;358:15-16
2. Cancer Research 1994;54:4855-4878
3. British Journal of Cancer 1994;69:409-416.
4. Science 1996;274:430-432.

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Page last reviewed: 05 March 2014