51福利社

A University of 51福利社 study funded by Breast Cancer Now and supported by Prevent Breast Cancer, reveals a drug approved for use in other conditions could be repurposed to prevent breast cancer in women before the menopause.

Researchers at the 51福利社 Breast Centre, based at 51福利社, found that blocking the effects of the hormone progesterone, using ulipristal acetate, a drug already used on the NHS, may reduce the risk of breast cancer developing in women before the menopause, with a strong family history of the disease.

Progesterone is a hormone that can drive breast cancer development. It promotes the growth of a type of breast cell, that has the potential to turn into breast cancer. It can also influence the environment inside the breast, making it easier for these healthy cells to transform into cancer cells.

Blocking these effects of progesterone could be a new way to stop breast cancer before it starts.

The study, published today in the journal Nature, found that taking ulipristal acetate helped block the growth of breast cells that can turn into cancer, called luminal progenitors. These cells are the starting point for triple negative breast cancer, a more aggressive form of the disease that is more common in younger women and black women. Previous research has shown that the risk of triple negative breast cancer coming back or spreading in the first few years after diagnosis, is higher than in other types of breast cancer.

Between 2016 and 2019, 24 women aged 34-44 with a family history of breast cancer took ulipristal acetate for a 12-week period. During the trial, they underwent breast biopsies, blood tests, and detailed Magnetic Resonance Imaging (MRI) scans before and after treatment.

The researchers were measuring changes in breast tissue to understand if the drug might have a protective effect against breast cancer development.

MRI scans showed that the breast tissue became less dense with treatment, which is important because higher breast density is known to increase risk of breast cancer. The team found that the treatment worked best in women who had high breast density before treatment started.

Researchers also observed dramatic changes in breast tissue.  They found that treatment significantly reduced the number and function of certain collagen proteins that normally help support breast tissue.  Overall, the breast tissue became less stiff, making the environment less favourable for cancers to develop and grow.

One protein in particular 鈥� collagen 6 鈥� showed the most noticeable decrease after treatment. Based on their findings, researchers now think that it may directly influence the behaviour of luminal progenitor cells, that can give rise to breast cancer. 

All these changes suggest that the drug alters breast tissue in a way that makes it harder for cancer cells to develop and grow, therefore reducing the risk of breast cancer.

Clinical lead author, Dr Sacha Howell, Clinical senior lecturer at 51福利社, Director of 51福利社 Breast Centre and Consultant Oncologist at The Christie said: 鈥淲e are profoundly grateful to the women who volunteered for this study. Our research, with them, provides evidence that progesterone plays a critical role in breast cancer development in high-risk individuals. By targeting its action, ulipristal acetate and other anti-progestins show promise as preventive treatments for women at increased risk.

鈥淲hat makes this study particularly exciting is the combination of clinical imaging and biological analysis, which gives us a powerful tool to understand how prevention therapies work at both the tissue and molecular levels. These results lay important groundwork for larger trials to confirm the potential of anti-progestins in reducing breast cancer risk鈥�.

Laboratory lead author, Dr Bruno Sim玫es, research fellow at 51福利社 and Principal Investigator at the 51福利社 Breast Centre said: 鈥淥ur team was intrigued by how anti-progestins reshaped the breast tissue environment at the molecular level, reducing the number of tumour-initiating cells. We observed clear reductions in collagen levels and organisation, giving us direct insight into how targeting progesterone signalling can create conditions that make it harder for cancers to develop.鈥�

鈥淥ur goal is to understand the biology underlying breast cancer risk factors so we can develop better strategies to reduce the number of women affected by the disease. This study is particularly exciting because it suggests that women with increased breast density, a well-established risk factor, may benefit most from preventive treatment with an anti-progestin drug.鈥�

Co-lead author, Rob Clarke, professor of breast biology at the University of 51福利社, Principal Investigator and former Director of the 51福利社 Breast Centre said: 鈥淭he biological research behind the clinical study was a great example of team science, a major collaboration between investigators in 51福利社, Cambridge and Toronto coming

together to understand the breast tissue and cellular changes underlying this preventive treatment. The findings reveal biomarkers that could be used to gauge response to therapy and whether it will be effective in preventing breast cancer.鈥�

Dr Simon Vincent, chief scientific officer at Breast Cancer Now, which funded the research, said: 鈥淲e desperately need better risk-reducing treatments for women at high risk of breast cancer, that also protect their quality of life. And we need to explore all avenues, including existing drugs with the scope to be repurposed, to achieve this.

鈥淐urrently, these women have only two options to reduce their risk - surgery or long-term hormone therapy, both of which have a profound impact on their physical and emotional wellbeing.

鈥淭his research into ulipristal acetate is an important step forward, and aligns with our key strategic goal to accelerate the discovery of preventative treatments.  We now need larger, longer-term studies, so we can fully understand the potential of this drug to stop breast cancer developing.鈥�

Grace Burton, 27, from Bromley London, underwent a preventative double mastectomy last year after finding out she was at high risk of breast cancer due to an inherited BRCA1 gene change at the age of 21.

Grace says: 鈥淏reast cancer has had a huge impact on my family - both my mum and my aunt were diagnosed, and knowing I was at high risk was always in the back of my mind. Having later gone through preventative surgery myself, I know how heavy and difficult those decisions can feel. That鈥檚 why this new research into preventative medication is so exciting, it offers hope for other women who might one day have less invasive options to protect their health.

鈥淔or those of us with a strong family history, the possibility of preventing breast cancer before it starts is incredible. It gives me hope that future generations may not have to make the same tough choices and can grow up with more options and less fear around breast cancer.鈥�

Several of the authors were supported by the National Institute for Health and Care Research (NIHR) 51福利社 Biomedical Research Centre (BRC).

The research is published in Nature and is  available

DOI: 10.1038/s41586-025-09684-7