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Existing breast cancer drug offers new targeted treatment for triple negative breast cancer

Breast Cancer Now-funded researchers at The Institute of Cancer Research, London, have identified a specific defect in some triple negative breast cancers that is linked to poorer outcomes for patients, and a drug that could help to treat the disease.

The study suggests that the drug palbociclib, which is currently used to treat other breast cancers that have spread to a different part of the body (known as secondary or metastatic), has the potential to also be used to treat about a fifth of people living with triple negative breast cancer.

This discovery could provide a much-needed targeted treatment for women who are more likely to see their cancer spread sooner, becoming incurable and often resistant to traditional chemo.

Triple negative breast cancer refers to a diverse group of breast cancers that lack the three molecules which are normally used to classify the disease: the oestrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2).

While these molecules have successfully been used to develop a variety of targeted treatments for other types of breast cancer, the absence of these molecules in triple negative breast cancer means there is a lack of variety in treatment options for this group of breast cancers.

And as a result, triple negative breast cancer is usually treated with a combination of surgery, chemo, and radiotherapy.

Around 55,000 women are diagnosed with breast cancer in the UK every year.

And around one in five of these women (over 8,000 cases a year in the UK) will be triple negative. This type of breast cancer tends to be more aggressive and disproportionately affects younger women and black women.

This new research, led by Dr Rachael Natrajan, at the Breast Cancer Now Toby Robins Research Centre at The Institute of Cancer Research (ICR), has discovered a way to identify triple negative breast tumours that could be more likely to respond to a class of drugs called CDK4/6 inhibitors, including palbociclib.

The team screened 200 of the most frequently-altered genes in breast cancer to investigate how changes in these genes affect cancer’s ability to grow.

Using ‘mini-tumours’ grown in the lab that mimic the tumour growth in a human body, researchers found that triple negative breast cancer cells with alterations that caused a decrease in the levels of a protein called CREBBP, could grow faster and more aggressively.

The team then used two large patient databases to further investigate what happens when CREBBP levels in the tumour are low, and found this to be linked to poorer survival rates for patients with triple negative breast cancer.

Furthermore, low levels of this protein occur in a variety of other cancers including uterine, ovarian, and some lung and bladder cancers, suggesting it plays a vital role in tumour development or growth. 

They found that when CREBBP levels are low, tumour cells switch to a different way of multiplying relying on proteins called CDK4 and CDK6. These proteins can be blocked with a group of drugs known as CDK4/6 inhibitors, which stops the cancer from growing.

Palbociclib is a CDK4/6 inhibitor that is currently used in the UK to treat some secondary (or metastatic) breast cancers.

The researchers tested the effectiveness of palbociclib on cancer cells with CREBBP alterations in the lab and in mice.

The drug was effective even when tested on standard chemo-resistant triple negative breast cancer cells, that lacked CREBBP, donated by a patient.

Overall, this study shows that palbociclib successfully stops the growth of triple negative cancer cells when they have low CREBBP levels, suggesting this could be a successful new treatment for this type of breast cancer. 

While not all triple negative breast cancer tumours have low CREBBP levels, it is the case in about a fifth of patients.

This means that measuring CREBBP protein levels in tumours could help to identify thousands of patients that could benefit from a treatment that is already approved for use in the UK.

Being an already licenced drug, already proven to be safe, means palbociclib can be quickly progressed into clinical trials for triple negative breast cancer and potentially benefit patients sooner.

This study provides a strong case for a clinical trial into the use of palbociclib for triple negative breast cancer tumours with low CREBBP levels.

Dr Rachael Natrajan, Team Leader in Functional Genomics at The Institute of Cancer Research, London, said:

“Our study shows what drives the growth of some triple negative breast cancers and suggests the exciting possibility that an already-approved breast cancer drug could be used to help women with this type of disease. 

“Our findings were only possible because we used an innovative model, involving the growth of 3D ‘mini tumours’ in the lab, to more closely reflect how tumours develop in the body.”

Dr Simon Vincent, Director of Research, Support and Influencing at Breast Cancer Now, said:

“It’s hugely exciting that this research has uncovered a new possible use for palbociclib as a targeted treatment for some women living with triple negative breast cancer.

“Each year, around 8,000 UK women are diagnosed with this aggressive form of breast cancer and we desperately need new, effective ways to treat them and stop them dying from this devastating disease.

"We hope that if clinical trials confirm that palbociclib is beneficial for some of these women, it will be advanced through the approval process and made available for those who need it as quickly as possible. 

“Despite this exciting discovery, Breast Cancer Now’s world-class research has been devastatingly affected by the COVID pandemic. We are now less able to fund new research that could transform the lives of people affected by breast cancer.

"This is why now, more than ever, we need your support so that we can continue to give hope for the future through our research.

"For more information and to donate visit:”

Anyone seeking information and support can speak to Breast Cancer Now’s expert nurses by calling the charity's free Helpline on 0808 800 6000.

Breast Cancer Now thanks Art For Cure for their generous support of Dr Natrajan’s research.


For more information or to arrange an interview, please contact the Breast Cancer Now press office at or on 07436 107914.

Notes to Editors

About Breast Cancer Now:

  • Breast Cancer Now is the UK’s first comprehensive breast cancer charity, combining world-class research and life-changing care.
  • Breast Cancer Now’s ambition is that, by 2050, everyone who develops breast cancer will live and be supported to live well.
  • Breast Cancer Now, the research and care charity, launched in October 2019, created by the merger of specialist support and information charity Breast Cancer Care and leading research charity Breast Cancer Now.
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  • Anyone looking for support or information can call Breast Cancer Now’s free Helpline on 0808 800 6000.

The Institute of Cancer Research, London, is one of the world's most influential cancer research organisations.

Scientists and clinicians at The Institute of Cancer Research (ICR) are working every day to make a real impact on cancer patients' lives.

Through its unique partnership with The Royal Marsden NHS Foundation Trust and 'bench-to-bedside' approach, the ICR is able to create and deliver results in a way that other institutions cannot.

Together, the two organisations are rated in the top-four centres for cancer research and treatment globally.

The ICR has an outstanding record of achievement dating back more than 100 years. It provided the first convincing evidence that DNA damage is the basic cause of cancer, laying the foundation for the now universally accepted idea that cancer is a genetic disease.

Today it is a world leader at identifying cancer-related genes and discovering new targeted drugs for personalised cancer treatment.

A college of the University of London, the ICR is the UK’s top-ranked academic institution for research quality, and provides postgraduate higher education of international distinction.

It has charitable status and relies on support from partner organisations, charities and the general public.

The ICR's mission is to make the discoveries that defeat cancer.

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