Mapping the breast cancer landscape

Do you remember the last time you were lost? Maybe you were on holiday in a new city, or you were just trying to get to a housewarming party at your friend’s new place. How did you find your way?

You might have used a map – whether it was on your smartphone, a sat-nav, displays on the street, or even a good-old-fashioned printed version, maps help us to navigate the environment and show where the big landmarks are.

In the news today were the results of the largest effort to date to create a detailed map of the genetic landscape of breast cancer.

The breast cancer map

Inside almost all of our cells is our DNA, the instructions that tell our cells what to do. However, if faults or mutations in the DNA occur, then cells can misbehave, multiplying wildly out of control and not responding to the normal cues that usually keep them in line. This is what we know as cancer.

But there are so many different mutations which could help breast cancer develop, we know about some of them but not all. Without a detailed picture of the DNA landscape in breast tumours we wouldn’t have a clue what turns normal cells into cancer.

That’s why mapping out the DNA of breast cancer is so vital. In the same way that you might look at a map of where you’re going on holiday to help plan what you’re going to do, having a map of the genetic landscape of breast cancer will help scientists to work out how they can treat breast cancer better – and perhaps find ways to prevent the disease in the first place.

Milestone research

An international team of researchers, led by Professor Sir Mike Stratton at the Sanger Institute in Cambridge, studied the entire DNA code of hundreds of breast tumours donated by patients to draft the most detailed map of the breast cancer genome to date. This involved reading every single one of the 3 billion letters found in the DNA code (about a thousand times the length of the Bible) of 560 individual tumours – even using the latest high-tech equipment and computers, this was painstaking work. This team included Breast Cancer Now-funded researcher at King’s College London Professor Andrew Tutt, who is also the director of the Breast Cancer Now Toby Robins Research Centre at the Institute of Cancer Research in London.

Although people can inherit genetic mutations from their parents, what the team were looking at were the mutations that accumulated over time in cancer cells. These faults in the DNA instructions reveal what’s gone wrong inside normal cells to turn them cancerous.

Though the map they created provides more detail than ever before, as you might expect, a lot of what was found we already knew about – all the famous landmarks were there, like mutations in genes called TP53, PIK3CA, and MYC, which the researchers were already familiar with. But a handful of new breast cancer genes were found which reveal new ways that the disease develops. All in all, mutations in 93 genes were discovered, which the researchers reckon is probably the definitive list of all genes that go wrong in breast cancer.

Another important confirmation was which genes are the most common locations for mutations that turn good cells bad. Of the 1,600 different mutations discovered across the 93 genes, nearly two-thirds of all the faults occurred in just 10 genes. This points to common roads that the development of breast cancer follows, and so potential drugs which block these paths. But the sheer number of different mutations and genes also shows how diverse breast cancer can be and how many routes it has available.

The long road ahead

So, the map of mutations that occur in breast cancer is pretty much complete – now it’s back over to the scientists to figure out what to do with it. The identities of the different genes involved is much clearer, and will help design new drugs which can be used to counteract mutations which cause breast cancer. For example, Breast Cancer Now was involved in developing drugs called PARP inhibitors which could be used to treat breast cancer patients with mutations faults in their BRCA2 gene – this study reveals a lot more potential targets for new drugs.

The research has also reminded us that the breast cancer landscape is incredibly complex, and that no two breast tumours are alike. However, the ultimate hope for breast cancer is that we can respond in an equally sophisticated way, by developing new drugs and tailoring treatments to individual patients to counteract their cancer’s unique collection of mutations. Like research has mapped out the breast cancer landscape, its research that will help us find a way through it.