How can faulty genes lead to cancer?
Every cell in our body contains thousands of genes - the instructions that tell a cell when to divide, what to do, and even when to die.
We pick up faults, or mutations, in our genes throughout our lives. These are caused by the natural processes in our cells, and by things such as ultraviolet radiation from the sun or the chemicals in tobacco smoke. And sometimes people inherit certain faulty genes from their parents.
Mutations in important genes mean that the cell no longer understand its instructions, and it may start to multiply out of control. This can lead to cancer.
There are four main types of gene involved in cell division. Most tumours have faulty copies of more than one of these types.
Genes involved in cancer
Oncogenes are genes that, under normal circumstances, play a role in telling cells to start dividing. We can think of them as being a bit like the accelerator pedal in a car.
When oncogenes are activated, they speed up a cell's growth rate. When one of them becomes damaged, causing cancer, it is like the accelerator becoming stuck down - the cell, and all its daughter cells, are permanently instructed to divide.
These genes make proteins whose normal function is the opposite of oncogenes. Tumour suppressors stop a cell from dividing, and must be switched off by other proteins before a cell can grow. They are a bit like a car's handbrake, which must be taken off before the car can move.
One of the most important tumour suppressor genes is called p53. This gene was co-discovered in 1979 by Cancer Research UK scientist Professor Sir David Lane. You can find out more about his discovery on our Science Update blog.
Apoptosis, or cell suicide, is a highly complex and hugely important process. Cells are usually able to commit suicide whenever something goes wrong, to prevent damage to their neighbours.
There are many different genes (and therefore proteins) involved. If these 'suicide genes' become damaged, then a faulty cell can keep dividing and become cancerous.
The DNA in every cell in your body is under constant assault from a variety of directions. But cells contain many different proteins whose job is to repair damaged DNA. Thanks to these, scientists think that the vast majority of DNA damage is repaired immediately, with no ill effects.
But if the DNA damage occurs to a gene that makes a DNA repair protein, a cell's ability to repair itself will be reduced, so errors to accumulate in other genes over time. This can cause cancer, and it explains why cancer is mainly a disease of older people.
Cancer Research UK is at the forefront of the search for genes that cause cancer when they're damaged. Find out more about our research into cancer genes in our Research Highlights section.
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