What is the “cancer gene”?

Jolie has ovaries and fallopian tubes removed 2 years after double mastectomy. (Photo taken by Remy Steinegger, via Wikimedia commons)

You have probably seen in the news that Angelina Jolie has undergone surgery to remove her ovaries and fallopian tubes. She does so 2 years after having a double mastectomy – surgical removal of both of her breasts. It was reported this morning that TV star Kelly Osbourne will also undergo the same preventative surgery, as she too carries the “cancer gene”.

But just what is this high risk gene? Can one gene really affect your likelihood of getting cancer? This post will explore these questions, as well as give some background information on what genes actually are.

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What is a gene, and what does it do?

A gene is basically an instruction book, containing the instructions the body needs to make a protein. The words of this instruction book are in the form of DNA, which itself is made of four different “letters”. A string of DNA comes together, and can be read by an enzyme (see previous post for explanation of what an enzyme is) which assembles a protein from the instructions given by the gene.

A gene is a string of DNA that codes for a protein. Different proteins have different roles, and can be involved in things such as cancer.

For a more detailed explanation about how DNA and genes drive the production of proteins, and the role of proteins in the body, I found this explanation particularly helpful.

What is the “cancer gene”?

The name of the gene Angelina Jolie and Kelly Osbourne are talking about is the BRCA1 gene (from BReast CAncer 1). This gene is actually found in ALL humans in breast tissue (and other tissues), so just having this gene doesn’t put you at risk of cancer. What does put you at risk however, is having a copy of this gene that contains a mutation – a slight change – in its DNA sequence.

Why do we have a copy of this gene if it can be harmful?

The normal, healthy copy of this gene (with no mutation) codes for a protein that performs some pretty helpful functions in the body – it repairs DNA damage, and if the damage cannot be repaired it destroys that cell.

However, if there is a mutation in this gene (like there is for Angelina Jolie and Kelly Osbourne), the protein it produces doesn’t function properly – meaning the DNA is not repaired and cells are not destroyed. This allows DNA damage to build up, which can cause mutations in other nearby genes. All of these mutations can accumulate and allow cells to divide uncontrollably – forming a mass of cells, which is the basis of how a tumour is formed. It is important to know that it is the mutation in the BRCA1 gene that dramatically increases your risk of breast cancer, not just the presence of the gene.

How risky is this mutation?

Women with a mutation in the BRCA1 gene can have up to an 80% chance of developing breast cancer, as well as about a 55% chance of developing ovarian cancer. (However, these mutations can be identified by simple genetic tests, so if breast cancer or ovarian cancer runs in your family, it may be worth consulting your GP.)

Hopefully now you understand a little but more about the infamous “cancer gene”, but if anything is unclear feel free to leave a comment!