Why does cancer have multiple causes?

14 March 2012

Question

Why are there so many different causes for cancer? Most diseases only have one or two causes. Is it all down to damaged DNA?

Answer

As we heard from Professor Swanton earlier, at its heart cancer is a disease driven by faulty genes - either faults that lead to genes being switched on that drive cells to grow and spread, or that lead to protective genes being switched off. In fact, one of the most potent causes of gene damage is reactive oxygen molecules produced by our own cells as they make energy. We can also inherit gene faults that make our cells more likely to pick up damage or fail to repair it properly. Chemicals in tobacco, our diet and environment can also cause damage, as can UV light. And certain viruses - such as the human papillomavirus that causes cervical cancer - can also hijack the genetic programme of cells and make them grow out of control. Different cancer types often have different risk factors - for example, UV light from the sun or sunbeds damages DNA in skin cells and can lead to skin cancer, but it can't penetrate inside the body to cause cancer internally. So while the fundamental root of all cancers is the same - cells growing out of control - individual cancers may be caused by different factors, and usually by a combination of many different things that it may be impossible to separate out on an individual basis.

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