Study gives new insight into genetic risk of breast, prostate and ovarian cancers
More than 80 regions of the genome that can increase an individual's risk of breast, prostate and ovarian cancers have been found in the largest ever study of its kind.
The research, led by scientists at the University of Cambridge and The Institute of Cancer Research, London, funded by Cancer Research UK and the Wellcome Trust, is part of the Collaborative Oncological Gene-environment Study (COGS). The findings could lead to new treatments, targeted screening and a greater understanding of how these diseases develop.
The scientists were looking for genetic variations – called single nucleotide polymorphisms (SNPs) – linked to an increased risk of developing cancer. By studying the DNA make-up of more than 100,000 people with cancer and 100,000 people from the general population, they found alterations that were more common in people with prostate, breast or ovarian cancers.
Each alteration raises the risk of cancer by a small amount, but the one per cent of people who have lots of these alterations could see their risk of developing prostate cancer increase to nearly 50 per cent and their risk of developing breast cancer increase to around 30 per cent.
Study author Professor Doug Easton, a Cancer Research UK scientist at the University of Cambridge, said: "We're on the verge of being able to use our knowledge of these genetic variations to develop tests that could complement breast cancer screening and take us a step closer to having an effective prostate cancer screening programme.
"By looking for people who carry most of these variations, we will be able to identify those who are at the greatest risk of getting these cancers and then targeting screening tests to these individuals."
Many of the SNPs found in the studies were near to areas of the genome that control how certain genes behave. Alterations to these control areas can lead to the 'brakes' that stop cells growing out of control being lifted. They can also help cancers to spread throughout the body or help cells grow rapidly out of control. Understanding how these areas of the genome are involved in cancer could provide new understanding of how cancers develop and how to treat them.
In prostate cancer, 23 new genetic variations were found, taking the total to 78. Importantly, 16 of these are associated with the more aggressive and life-threatening forms of the disease.
Professor Ros Eeles, professor of oncogenetics at The Institute of Cancer Research (ICR), said: "These results are the single biggest leap forward in finding the genetic causes of prostate cancer yet made. They allow us, for the first time, to identify men who have a very high risk of developing prostate cancer during their lifetime through inheritance of multiple risk genetic variants.
"If we can show from further studies that such men benefit from regular screening, we could have a big impact on the number of people dying from the disease, which is still far too high."
For breast cancer the researchers found 49 SNPs, more than doubling the number previously identified. Some of these were found in regions that have been linked to other cancers, suggesting that they are disrupting the same underlying mechanisms that can cause the disease.
In ovarian cancer, far less is understood about the genetic regions that might affect the risk of disease. The research identified three new cancer risk regions and confirmed a further two that had previously been suspected as being regions linked to increased risk. This takes the total to 12.
As well as looking for the variations that raise the risk of these cancers, the researchers also looked for the SNPs that may influence how different breast cancers behave and regions that influence the cancer risk of people with faults in the BRCA genes. Carriers of BRCA gene faults are known to be at a greater risk of developing breast and ovarian cancers, but it's not clear which women will go onto develop cancer.
The researchers found that the five per cent of women who have a BRCA1 fault and carry most of the genetic variants linked to BRCA1 have a more than 80 per cent chance of developing breast cancer by the age of 80. Women with few of these variants and a BRCA1 fault have a 50 per cent risk of developing the disease.
In a series of accompanying papers, the researchers looked for the changes that affect how different types of breast cancer behave. They found a series of SNPs that are only associated with a more aggressive form of breast cancer – called oestrogen receptor negative – suggesting it develops in a unique way, which could open the door to new treatments.
The findings are published in a series of papers published today in 'Nature Genetics', 'Nature Communications', 'PLOS Genetics', the 'American Journal of Human Genetics' and 'Human Molecular Genetics'. The papers and accompanying editorial essays are available in a special Focus from 'Nature Genetics'.