A protein found in high levels in breast cancer patients which helps keep tumour cells alive could be targeted with a drug that is already being trialled.

Scientists in Glasgow say the 'exciting' research breakthrough could have implications for other cancers including leukaemia, those affecting the lung and Glioblastoma, the most aggressive type of cancer that begins in the brain.

The study has shown definitively that a protein called MCL-1 helps breast cancer cells survive and replicate by hindering cells’ natural ability to die through a process called apoptosis, and proves that tumours rely on it to help them grow more aggressively, by blocking this natural cellular self-destruct function.

Apoptosis can also play a key role in preventing cancer; however, cancer cells will often evolve to avoid this process.

A new type of drug called BH3 mimetics, which target the MCL-1 protein and is already being trialled for some blood cancers could be used to ‘kick-start’ apoptosis in breast cancer cells to slow the growth of tumours.

The study also discovered that breast cancer stem cells, which are thought to be responsible for the disease spreading and becoming resistant to treatments, are especially dependent on MCL-1 for growth and survival.

Scientists said it is likely the inhibitor would be used in conjunction with conventional treatments including chemotherapy and hopefully at an early stage when patients receive surgery to remove tumours.

The study was led by Professor Stephen Tait and Dr Kirsteen Campbell, of the Institute of Cancer Sciences at the University of Glasgow and Professor Karen Blyth from the Beatson Institute for Cancer Research.

Prof Tait said: "I work in the areas of cancer cell death and there a lot of excitment in this protein. It may be important in a lot of different cancer types.

"We are currently working in gioblastoma as well. We found MCL-1 is very important in actually allowing the tumour to develop there as well. 

"We are quite hopeful that it may be quite a broadly important protein.

""Our main findings is that we have definitively shown it's role in keeping cells alive, which is it's main function in breast cancer.

Glasgow Times:

"Usually these drugs are trialled on late stage patients who have gone through other types of therapy but it would be used, I would imagine, earlier on at the point when a patient gets surgery for breast cancer.

""We have drugs that are going through clinical trial just now for use in multiple myeloma a type of leukemia, which is known to be dependend on MCL-1 but the great thing about that is, if they go through those trials effectively, then they can be used in other cancer types as well."

The research was jointly led by Dr Kirsteen Campbell at the Institute of Cancer Sciences at the University of Glasgow and Professor Karen Blyth from the Beatson Institute for Cancer Research.

"The other finding that was interesting is this stem cell theory in cancer that even if you get rid of the vast majority of cells, you will still have some stem cells left, which re-populate and bring the tumour back. Kirsteen shows  quite nicely that MCL-1 seems to be quite important in helping those stem cells survive."

While this study involved mice, previous research suggests it would result in a similar outcome in human particpants.  Dr Kirsteen Campbell looked at samples from patients with Triple-Negative breast cancer, the most deadly form, over a long period of time. Her research  found that high expressions of MCL-1 correlated with a worse prognosis for patients.

Prof Tait said: " We think based on this that it would be applicable in humans. Until you start going into trials, you don't know for sure but this is what we think.

"I know that Kirsteen is keen to look at Triple-Negative as that is the worst kind of breast cancer. 

"There is quite a lot of interest in looking at this in lung cancer too."

Dr Simon Vincent, Director of Research, Support and Influencing at Breast Cancer Now, which funded the study, said: “With around 55,000 women being diagnosed with breast cancer every year in the UK, we urgently need to find new ways to treat people and prevent deaths from this devastating disease.

"As such, while further research is needed, we hope this study leads to new and effective treatments being available for people affected by breast cancer.

“We’re hugely proud to have funded this exciting discovery, especially at a time when we are all too aware of the profound effects the COVID-19 pandemic has already had on our world-class research."

For information and support call Breast Cancer Now’s free Helpline on 0808 800 6000.