New research being described as the largest ever study to sequence the whole genomes of breast cancers has given scientists the clearest understanding yet of what factors influence tumour development, with researchers identifying a number of mutation patterns in people's DNA that can make breast cancer more likely.
The discovery – hailed by some as providing a "complete view of breast cancer" – could lead to a range of treatment options for breast cancer patients depending on their particular genetic makeup. Basically, we're talking more effective, personalised cancer care.
An international team of researchers led by the Wellcome Trust Sanger Institute in the UK analysed 560 breast cancer genomes in total – 556 from women and four from men – sourced from patients in the US, Europe, Asia, and elsewhere around the globe.
They were looking for patterns in the patients' DNA mutations – called mutational signatures – that characterise how the DNA in our cells changes as we get older, both from exposure to things in the environment, and the normal ageing process.
The researchers found 13 mutational signatures that influence tumour development, giving rise to 93 protein-coding cancer genes that act like sets of instructions to turn normal tissue into cancerous tissue.
"There are about 20,000 genes in the human genome," Sir Mike Stratton, the director of the Sanger Institute, told James Gallagher at the BBC. "It turns out, now we have this complete view of breast cancer – there are 93 of those [genes] that if mutated will convert a normal breast cell into a breast cancer cell. That is an important piece of information."
"We hand that list over to the universities, the pharmaceuticals, the biotech companies to start developing new drugs because those mutated genes and their proteins are targets for new therapeutics," he added. "There are now many drugs that have been developed over the last 15 years against such targets which we know work."
In their analysis, the team found that women who carry the BRCA1 or BRCA2 genes – giving them an increased risk of breast and ovarian cancer – had whole cancer genome profiles that were highly distinctive. The scientists suggest this uniqueness could lead to new methods of classifying patients for treatments, depending on their personal level of risk.
"In the future, we'd like to be able to profile individual cancer genomes so that we can identify the treatment most likely to be successful for a woman or man diagnosed with breast cancer," said one of the team, Serena Nik-Zainal from the Sanger Institute, in a press release. "It is a step closer to personalised healthcare for cancer."
It's unknown to what extent we might be able to alter or impact the mutation patterns in the future, so that we could potentially stop cancers from developing in the first place , but now that we know about them, we can at least help identify patients who may be at a higher risk.
"This study brings us closer to getting a complete picture of the genetic changes at the heart of breast cancer and throws up intriguing clues about the key biological processes that go wrong in cells and drive the disease," researcher Emma Smith from Cancer Research UK, who was not involved with the study, told the BBC. "Understanding these underlying processes has already led to more effective treatments for patients, so genetic studies on this scale could be an important stepping stone towards developing new drugs and boosting the number of people who survive cancer."
The findings are published in Nature and Nature Communications.