Statins could be prescribed to breast cancer survivors after researchers discovered the cholesterol-lowering drugs may prevent the disease from returning.
Scientists have known for years that the hormone oestrogen fuels cancer and causes it to spread.
Up to 80% of breast cancer cases are 'ER-positive', meaning that they have more oestrogen receptors (ER) than normal breast cells and are particularly sensitive to oestrogen. It is estimated that up to 40,000 women are diagnosed with ER-positive breast cancer each year.
But in some cases, patients do not respond effectively to standard hormone-blocking therapy, which is designed to target oestrogen production.
But in a new study, researchers discovered that certain types of breast cancer use cholesterol to produce a molecule, called 25-HC, which is having the same impact as oestrogen and may explain the cancer's resistance to therapy.
For these patients, taking statins to lower cholesterol was found to halve their chance of the disease returning in 10 years.
“During the course of treatment, ER-positive breast cancers, that are ‘fed’ by oestrogen, often become resistant to standard hormone therapy. Our research has demonstrated that these cancer cells can use a cholesterol molecule to mimic oestrogen so that they continue to grow without it," lead researcher Dr Lesley-Ann Martin explained.
"This is hugely significant. Testing the patient’s tumour for 25-HC or the enzymes that make it may allow us to predict which patients are likely to develop resistance hormone therapy, and tailor their treatment accordingly.
"Our study also demonstrates that statins could be a valuable addition to breast cancer treatment, and that this warrants investigation in clinical trials."
According to the researchers, cholesterol is an important molecule that allows the body to build and maintain cell membranes and produce a number of hormones.
As well as obtaining cholesterol from food, the body produces its own cholesterol in a process called the cholesterol biosynthesis pathway.
Using breast cancer cells grown in the lab, a team of scientists led by Dr Martin investigated the processes that cause women with ER-positive breast cancer to relapse while taking aromatase inhibitors (AIs), generally taken for five years after surgery.
The researchers grew ER-positive cells in the absence of oestrogen, mimicking the cells found in tumours being treated with AIs.
They found that the cholesterol biosynthesis pathway was enabling the cells to make their own fuel by producing 25-HC, allowing them to continue growing despite a lack of oestrogen.
Using these models, the team found that blocking the production of parts of this cholesterol-production mechanism slowed down the proliferation of the cancer cells by 30-50%.
Baroness Delyth Morgan, chief executive at Breast Cancer Now, said this is a "really crucial discovery".
"Far too many women have to deal with the potentially devastating consequences of their breast cancer coming back and this research presents an important opportunity to improve the effectiveness of today’s most commonly used treatments," she added.
"This study breaks new ground in uncovering how some breast cancers continue to survive without oestrogen and suggests that women could benefit from adding statins to standard anti-hormone treatments.
“But this is early research and greater clinical evidence is now needed to understand the potential risks and benefits of this approach."
The research was completed by scientists working with the Breast Cancer Now Toby Robins Research Centre at The Institute of Cancer Research and is published in full in the journal Breast Cancer Research.