BRCA1 breast cancer gene finding 'is an important piece of science'

In collaboration with the Press Association

Researchers from the US and Sweden have shed light on how faults in the BRCA1 gene increase the risk of breast cancer, in a finding hailed as significant by Cancer Research UK.

The charity said the finding could lay the groundwork for the development of new breast cancer treatments.

Between 80 and 85 per cent of women who inherit a faulty version of the BRCA1 gene develop a highly aggressive form of breast cancer called 'basal-like' breast cancer at some stage in their lives, but researchers have been unable to understand exactly how mutations in the gene cause cancer.

'Basal-like' breast cancer also account for 10-20 per cent of all non-inherited breast cancer. It is known as 'triple-negative' breast cancer as tumours usually lack oestrogen, progesterone, and HER2 receptors, which are needed for most breast cancer treatments to be effective.

Since BRCA1 faults were first linked to inherited breast cancers in the early 90s, several laboratories have uncovered evidence that the BRCA1's 'normal' role is to repair damaged DNA.

Now, a team from Columbia University and Sweden's Lund University have discovered that damage to BRCA1 leads to yet more gene damage - crucially, in a powerful 'tumour suppressor' gene called PTEN - which normally acts as a 'brake' on cell multiplication.

This in turn allows a strong growth-promoting signal to be sent inside tumour cells, giving them a growth advantage over their neighbouring cells and leading to the development of cancer.

The findings are published in Nature Genetics.

Researchers hope that by shutting down one of the proteins in the pathway, they may be able to halt the growth of cancer, and Phase I clinical trials are currently underway to investigate potential therapies.

Ramon Parsons, professor of medicine and pathology at Columbia University College of Physicians and Surgeons, said: "These findings are exciting because ever since the link was established between BRCA1 and breast cancer more than ten years ago, we have been frustrated by our lack of understanding about how mutations in this gene cause breast cancer.

"Now that we know that PTEN is involved, we finally have a target for therapy for these cancers."

The experts suggest that around 50 per cent of BRCA1 inherited breast cancers may have mutated versions of PTEN and Dr Lao Saal, the study's first author, said that the results point to PTEN as a major player in breast cancer.

Dr Lesley Walker, director of cancer information at Cancer Research UK, said: "We urgently need to find new treatments for people with breast cancer who don't respond well to the current treatments available. This is an important piece of science.

"As well as discovering genes that lead to cancer, it's crucial that we find out how these genes actually work, as this then gives scientists the insights they need to discover new treatments."

Dr Walker pointed out that the discovery may lead to the development of targeted therapies for breast cancer in the future.

"This is important work and the authors' suggestion that similar gene changes might also have been missed in other cancers will lead to further discoveries," Dr Walker added.

Breast cancers caused by inherited faulty BRCA1 genes account for between two and five percent of all cases.