Women with a faulty copy of a DNA repair gene called RAD51D have a 1 in 11 risk of developing ovarian cancer compared to 1 in 70 in the general population, according to a landmark Cancer Research UK-funded study led by Professor Nazneen Rahman at The Institute of Cancer Research (ICR) published in the 7 August online issue of Nature Genetics. There is hope that personalized treatment will be available sooner than usual because a class of drugs already developed showed promise in targeting affected cells.

Rahman, who is Professor of Human Genetics and Section Chair of Cancer Genetics at ICR told the press the study represents a significant step forward in our understanding of how faulty genes contribute to the development of some cases of ovarian cancer, and there is “real hope on the horizon that drugs specifically targeted to the gene will be available”.

RAD51D repairs damaged DNA. When the gene is faulty, an important repair pathway fails, leaving damaged DNA to build up in cells, which increases the risk they will become cancerous.

For their study, Rahman and colleagues examined DNA from women in 911 families with ovarian and breast cancer and compared it to the DNA from a control group of 1,060 people in the general population (the controls).

They found eight inactivating RAD51D mutations in unrelated women with cancer, compared with only one in the controls.

The association was principally with ovarian cancer, with three mutations found in 59 of the families with three or more individuals with ovarian cancer.

The researchers also found cells deficient in RAD51D were sensitive to treatment with a relatively new class of cancer drug known as a PARP inhibitor, “suggesting a possible therapeutic approach for cancers arising in RAD51D mutation carriers”, they write.

PARP inhibitors are a group of drugs that inhibit the action of the enzyme Poly ADP ribose polymerase (PARP), a protein that plays a role in many cell processes that involve DNA repair and programmed cell death.

PARP inhibitors are already showing promising results in clinical trials for the treatment of breast and ovarian cancers with mutations in BRCA1 and BRCA2 genes, which are also involved in repairing damaged DNA.

Ovarian cancer is the fifth most common cancer in women. In the UK every year about 6,500 women are diagnosed with the disease. However, often develops without any clear symptoms, so unfortunately many women only find out they have it once it has spread to other parts of the body, by which time the chances of survival are much worse.

The researchers estimate that the RAD51D mutations they discovered are present in just under 1% of women with ovarian cancer, affecting around 50 individuals in the UK every year.

Rahman said:

“Women with a fault in RAD51D gene have a one in 11 chance of developing ovarian cancer. At this level of risk, women may wish to consider having their ovaries removed after having children, to prevent ovarian cancer occurring.”

Professor Nic Jones, chief scientists at Cancer Research UK, said it was “incredibly exciting to discover this high risk gene for ovarian cancer”.

“It’s further evidence that a range of different high risk genes are causing the development of breast and ovarian cancer and we hope there are more waiting to be discovered in different cancers,” said Jones, adding that they believe “the results of this research will help inform personalised treatment approaches and give doctors better information about risks of cancer to tell patients”.

Harpal Kumar, chief executive of Cancer Research UK said:

“All of our research is generously funded by the public. This support has allowed us to invest heavily in the identification of DNA changes which paint a picture of which parts of a person’s gene set are linked to cancer. This life-changing discovery exemplifies the importance of this research and the importance of ongoing public support.”

Last year, Cancer Research UK spent more than £12 million of publicly donated funds on tackling ovarian cancer. The charity is the largest single funder of research into the disease in the UK.

Written by Catharine Paddock, PhD