In mice with acute myeloid leukaemia (AML), drugs called PARP inhibitors reduced leukaemia growth by around 90%, doubling survival times. Similar effects on cell growth were seen in leukaemia patients’ cells studied in the laboratory.
The results were so promising that the researchers believe PARP inhibition may represent a new approach to targeting this type of leukaemia. It is diagnosed in around 2,400 people each year in the UK and currently only one in five survive past five years.
The research was funded by the blood cancer charity Bloodwise with additional funding from Cancer Research UK.
PARP inhibitors can shrink tumours in cancer patients who have a faulty version of either the BRCA1 or BRCA2 gene. Faulty BRCA proteins cannot repair DNA damage in cells as they normally would, potentially leading to cancer. These cancer cells rely on poly ADP-ribose polymerase (PARP) proteins to ‘patch up’ just enough critical DNA so that they can survive and continue to multiply. When PARP is also blocked, the cancer cells become so damaged that they are forced to self-destruct.
In a report published in the journal Nature Medicine, scientists at King’s College London have shown that the PARP inhibitor olaparib can also selectively kill certain AML cells, despite the absence of BRCA errors. The researchers think this works because when the faulty proteins AML1-ETO and PML-RARα drive AML growth, they also suppress key DNA damage repair processes.
When the researchers also looked at mice with mixed lineage leukaemia (MLL), a traditionally chemotherapy-resistant subtype of AML, they found that they were resistant to PARP inhibitors. This is because DNA repair is not suppressed in this cancer. Another protein, Hoxa9, activates other DNA damage repair pathways in these leukaemia cells, keeping them alive. But when the scientists used a drug to block Hoxa9, as well as a PARP inhibitor, DNA repair was wiped out and the leukaemia cells then self-destructed.
When subjected to PARP inhibitors, the leukaemia cells became so genetically damaged that they entered a process of programmed cell death, just like in cancers with faulty BRCA. Unlike traditional chemotherapy, PARP inhibitors specifically target the cancer cells without damaging healthy tissue.
Professor Eric So, who led the research at King’s College London, said: “PARP inhibitors could potentially offer a completely different approach to specifically target certain subtypes of acute myeloid leukaemia. New treatments are desperately needed for this aggressive type of leukaemia, which has very poor survival rates – especially in older patients where intensive chemotherapy is often not possible.”
Dr Matt Kaiser, Head of Research at Bloodwise, said: “PARP inhibitors are exciting as they appear to target just the cancer cells, which could spare patients from the gruelling side-effects of traditional treatments. But until this study, their potential was thought to be limited mostly to cancers where BRCA faults play a role.
“While this approach seems promising from these laboratory studies, it is still very early days. We need to see how real patients respond to these drugs and how effective they are. PARP inhibitors such as olaparib are already being used to treat patients with other cancers and have been shown to be safe. This should speed up the time it takes for this potentially effective new treatment to enter clinical trials.”
Professor Steve Jackson, Cancer Research UK expert at the University of Cambridge Gurdon Institute, said: “PARP inhibitors are designed to target a weakness in cancer cells by stopping DNA being effectively repaired. It’s fantastic to see how PARP inhibitors such as olaparib – the world’s first PARP inhibitor which was developed through Cancer Research UK-funded work could treat a wider range of cancers than first thought.”
For further information, please contact Henry Winter at the Bloodwise Press Office on 020 7269 9019, press mobile 07824 375880, or email: [email protected]
Notes to Editors
The findings will be published online in Nature Medicine on 23 November 2015 under the title ‘Synthetic lethal targeting of oncogenic transcription factors in acute leukemia by PARP inhibitors’. Corresponding author: Professor Eric So, Department of Haematological Medicine, King’s College London
Bloodwise is the UK’s biggest blood cancer charity dedicated to improving the lives of patients. The charity, which was formed in 1960, changed its name from Leukaemia & Lymphoma Research in September 2015. Its life-saving work is focused on stopping people from dying of blood cancer, improving the quality of life for patients and their families, and where possible, stopping people getting blood cancer in the first place.
The charity’s research is targeted at understanding more about blood cancer, finding causes, improving diagnosis and treatments, and running groundbreaking clinical trials for patients. The charity champions patients’ needs by influencing relevant decision makers and influencers, and seeking to raise awareness of the issues faced by patients. Their patient services provide information, support and assistance to patients at every stage of their journey.
Around 38,000 people of all ages, from children to adults, are diagnosed with blood cancers and related disorders every year in the UK. It is a complex disease area made up of 137 individual diseases. Some affect thousands of people, such as common forms of leukaemia, lymphoma and myeloma. Others affect only a handful. But together, blood cancers are the fifth most common form of cancer.
For more information visit www.bloodwise.org.uk.
About Cancer Research UK
Cancer Research UK is the world’s leading cancer charity dedicated to saving lives through research.
Cancer Research UK’s pioneering work into the prevention, diagnosis and treatment of cancer has helped save millions of lives.
Cancer Research UK receives no government funding for its life-saving research. Every step it makes towards beating cancer relies on every pound donated.
Cancer Research UK has been at the heart of the progress that has already seen survival in the UK double in the last forty years.
Today, 2 in 4 people survive their cancer for at least 10 years. Cancer Research UK’s ambition is to accelerate progress so that 3 in 4 people will survive their cancer for at least 10 years within the next 20 years.
Cancer Research UK supports research into all aspects of cancer through the work of over 4,000 scientists, doctors and nurses.
Together with its partners and supporters, Cancer Research UK’s vision is to bring forward the day when all cancers are cured.
For further information about Cancer Research UK’s work or to find out how to support the charity, please call 0300 123 1022 or visit www.cancerresearchuk.org. Follow us on Twitter and Facebook.
About King’s College London
King’s College London is one of the top 20 universities in the world (2015/16 QS World University Rankings) and among the oldest in England. King’s has more than 26,500 students (of whom nearly 10,400 are graduate students) from some 150 countries worldwide, and nearly 6,900 staff. The university is in the second phase of a £1 billion redevelopment programme which is transforming its estate.
For more information, please visit King’s in Brief (www.kcl.ac.uk/newsevents/About-Kings.aspx).
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