Genetic factors important in survival after breast cancer, study shows

A UK study has revealed that breast cancer patients who have the POLQ gene are eight times more likely to suffer from recurrence after treatment compared to patients who do not carry the gene.

A lack of the gene DNA polymerase theta (POLQ) has previously been shown to make tumour cells more sensitive to radiotherapy.

Scientists based at the Cancer Research UK/MRC Gray Institute for Radiation Oncology and Biology at Oxford University investigated whether 279 women with breast cancer who over-expressed POLQ had worse outcomes than women who did not. The team reported that excessive POLQ was associated with an 8.1 times higher risk of poor survival, which was independent of other clinical features of the women's cancer including how big their tumours were and how old they were.

'This is important research which provides evidence that POLQ may be a very appealing target for drug development', said Professor Gillies McKenna, director of the Institute.

'As POLQ is not switched on by most healthy tissues it is possible that if drugs could be developed to block this gene, they would make tumours more responsive to treatments such as radiotherapy and chemotherapy, but not increase the side effects caused to healthy cells'.

The researchers are unsure as to why POLQ is linked to poor survival, but they suggest that it could cause tumour cells to be resistant to treatments including radiotherapy, which are frequently used to treat breast cancer patients with early stage disease. POLQ could also induce tumour cells to behave more aggressively than cancers that do not express the gene.

'Drugs that block POLQ may be able to reverse the very poor survival associated with over production of this gene', added Professor McKenna.

In 2007, almost 45,700 women in the UK were diagnosed with breast cancer, according to figures from Cancer Research UK.

Dr Lesley Walker, science information director at the charity said: ‘Fundamental scientific research like this to examine the genetic causes for breast cancer provides us with the foundations to develop new exciting drugs to beat the disease and increase survival in the future'.