12 new genes linked to ovarian cancer identified

Scientists have identified 12 new genetic variants that increase risk of developing ovarian cancer, after analysing the DNA of almost 100,000 people.
The analysis, that included data from 17,000 patients with the most common type of ovarian cancer, also confirmed the association of 18 of the previously published variants.
According to Cancer Research UK, there were 7,378 new cases of ovarian cancer in the UK in 2014. Around nine out of ten of these cases was epithelial ovarian cancer. The peak rate of cases is among women aged 75-79 years old.
"We know that a woman's genetic make-up accounts for about one third of her risk of developing ovarian cancer. This is the inherited component of disease risk," said Paul Pharoah from the University of Cambridge in the UK.

"We're less certain of environmental factors that increase our risk, but we do know that several factors reduce the risk of ovarian cancer, including taking oral contraceptive pills, having your tubes tied and having children," said Pharoah.
Inherited faults in genes such as BRCA1 and BRCA2 account for about 40 per cent of the inherited component.

These faults are rare (carried by about one in 300 people) and are associated with high lifetime risks of ovarian cancer - about 50 per cent for BRCA1 and 16 per cent for BRCA2 on average - as well as a high risk of breast cancer.

Variants that are common in the population (carried by more than one in 100 people) are believed to account for most of the rest of the inherited component of risk.
Previously, researchers had identified 27 common variants across the genome associated with ovarian cancer risk. However, some of these are associated only with rare subtypes of ovarian cancer.
The magnitude of the associated risk however is modest: together, the variants account for only about 4 per cent of the inherited component of disease.
The new study analysed the genomes of over 25,000 people with epithelial ovarian cancer and compared them to almost 41,000 healthy controls.

They then analysed results from a further 31,000 BRCA1 and BRCA2 mutation carriers, which included almost 4,000 epithelial ovarian cancer patients.
This enabled them to identify a further 12 variants associated with risk and confirm the association of 18 of the previously published variants; some of the other variants failed to replicate.
There are now known to be 30 risk variants, accounting for 6.5 per cent of the inherited component of risk.
"Ovarian cancer is clearly a very complex disease - even the 30 risk variants that we now know increase risk of developing the disease account for just a small fraction of the inherited component," said Catherine Phelan from the Moffitt Cancer Centre in the US.

"We believe that there will likely be many more genetic variants involved, each with extremely small effects," said Phelan.
The research appears in the journal Nature Genetics.