Cancer and genes

Researchers are working hard to understand more about how genes work inside the body and why things sometimes go wrong. Recently, cancer research has focused on understanding how a normal cell, through a series of genetic changes, turns into a cancerous cell. A number of genes have been identified that play a part in the development of some cancers. If a person is born with a gene change (mutation) that makes them more likely to develop cancer, we say that they have inherited a cancer gene. This mutation may then also be passed on to their children.

There are two types of genetic changes or mutations:

• those that are passed down from generation to generation (germline mutations)
• those that happen during the lifetime of a person and are not passed on to the next generation (somatic mutations).

Germline mutations are inherited at the moment of conception (the fertilisation of your mother's egg with your father's sperm). Because all the cells of your body develop from this one fertilised egg, all the cells in your body will contain the genetic change. You get half your genes from your father and half from your mother. If either of your parents has a genetic change that increases their risk of getting cancer (a cancer gene), you have a 50/50 (1 in 2) chance of inheriting it.

The other type of genetic mutation, somatic gene changes, only happens later on in life. Scientists are not sure what causes these genetic changes, but factors such as radiation or the exposure to dangerous chemicals (for example, through smoking) can play a part. You might have read that certain tumours show genetic changes, which help doctors choose the best treatment for a particular cancer. These genetic changes are usually somatic (develop during the person's lifetime), and are usually not passed on to the next generation.

The most common cancers that may, in some cases, be due to an inherited mutation are breast|, ovarian|, bowel| and womb (endometrial) cancer. Genetic tests can identify some of the genes responsible for these cancers. In some cases, other cancers such as prostate, pancreatic and testicular cancer may be caused by an inherited mutation. However, although genes thought to be linked with these cancers have been identified, genetic tests for these cancers have not yet been developed.

Some very rare genetic disorders can increase a person's risk of getting several different types of cancer at a young age, for example:

• Li-Fraumeni syndrome
• multiple endocrine neoplasia type 1 (MEN1)
• von Lippel-Hindau disease
• neurofibromatosis
• retinoblastoma.

If you or a member of your family is affected by one of these rare conditions, you might want to get in touch with the Genetic Interest Group. Our cancer support specialists| can also give you information about rare cancers.