Stem cell treatment to prevent leukemia returning is a step closer, say scientists

Researchers at King's College London have identified a way of eliminating leukaemic stem cells, which could lead to new treatments that may enable complete remission for leukaemia patients. An early study in mice has shown that leukaemic stem cells can be abolished by suppressing two proteins found in the body.

Leukaemic stem cells sustain the disease and are likely to be responsible for relapse, so elimination of these cells is believed to be key for achieving complete remission. These encouraging findings highlight the two proteins as potential therapeutic targets to prevent the most aggressive forms of leukaemia returning. The study, funded by Cancer Research UK and Leukaemia Lymphoma Research, is to be published in the journal Cell Stem Cell.

King's scientists looked at leukaemic stem cells found in a type of leukaemia that involves mutations of the MLL gene. This accounts for around 70 per cent of infant leukaemias and 10 per cent of adult acute leukaemias. The prognosis for MLL in children is not good – only 50 per cent survive past two years after receiving standard treatment.

The protein Bmi1 was already known to play a key role in the survival and proliferation of various cancer stem cells. But this study has for the first time shown that, although the protein is needed for survival of various Acute Myeloid Leukaemia (AML) cells, in MLL leukaemia the cancer stem cells actually survive independently of Bmi1. This shows that for these MLL patients, targeting Bmi1 alone would not have a major impact on eradicating leukaemic stem cells, as was previously thought.

However, the team also found high levels of another protein called Hoxa9 in the MLL mice and human patients. Similar to Bmi1, a major role of this protein is to ensure leukaemia cells divide and grow by allowing their escape from the inherent surveillance system, which will otherwise cause cell death. They found that in mice with MLL leukaemic stem cells (that can proliferate without Bmi1), suppression of both Bmi1 and Hoxa9 completely abolishes the ability of MLL mutation to induce leukaemia.

These findings provide evidence for the different pathways involved in the development of different types of leukaemic stem cells, and highlight the importance of targeting Bmi1 and Hoxa9 together to abolish MLL leukaemic stem cells in particular.

Professor Eric So, Head of the Leukaemia and Stem Cell Biology group at King's, said: 'These findings take us a step forward in our understanding of how this devastating disease can return in patients after they have received the standard treatment.

'Now we know that leukaemic stem cells in certain types of leukaemia, such as MLL, can survive and proliferate independently of the Bmi1 protein, we need to consider more carefully the future of stem cell therapy to treat the disease. It's not as easy as people originally thought it might be.

'But these findings provide us with vital information that will help us look at alternative ways of combating different forms of the disease, which will ultimately allow patients to achieve long-term complete remission.

'What we need to do now is to find out exactly how Bmi1 and Hoxa9 proteins sustains the growth of cancer cells in order to develop an effective treatment to stop the disease returning.'

Professor Peter Johnson, Cancer Research UK's chief clinician, said: 'This study builds on previous Cancer Research UK-funded work trying to pinpoint the molecules responsible for driving the development of MLL-related leukaemia stem cells.

'Cancer stem cells appear to be more resistant to radiotherapy and chemotherapy than the other leukaemia cells, so understanding how they originate – and how we can kill them – will be a major step in being able to help even more people survive leukaemia in future.'

CONTACT
Katherine Barnes
International Press Officer
King's College London
Tel: +44 (0) 207 848 3076
Email: katherine.barnes@kcl.ac.uk

A copy of the Cell Stem Cell paper is available on request

King's College London is one of the top 25 universities in the world (2010 QS international world rankings), The Sunday Times 'University of the Year 2010/11' and the fourth oldest in England. A research-led university based in the heart of London, King's has nearly 23,500 students (of whom more than 9,000 are graduate students) from nearly 140 countries, and some 6,000 employees. King's is in the second phase of a £1 billion redevelopment programme which is transforming its estate.

King's has an outstanding reputation for providing world-class teaching and cutting-edge research. In the 2008 Research Assessment Exercise for British universities, 23 departments were ranked in the top quartile of British universities; over half of our academic staff work in departments that are in the top 10 per cent in the UK in their field and can thus be classed as world leading. The College is in the top seven UK universities for research earnings and has an overall annual income of nearly £450 million.

King's has a particularly distinguished reputation in the humanities, law, the sciences (including a wide range of health areas such as psychiatry, medicine, nursing and dentistry) and social sciences including international affairs. It has played a major role in many of the advances that have shaped modern life, such as the discovery of the structure of DNA and research that led to the development of radio, television, mobile phones and radar. It is the largest centre for the education of healthcare professionals in Europe; no university has more Medical Research Council Centres.

King's College London and Guy's and St Thomas', King's College Hospital and South London and Maudsley NHS Foundation Trusts are part of King's Health Partners. King's Health Partners Academic Health Sciences Centre (AHSC) is a pioneering global collaboration between one of the world's leading research-led universities and three of London's most successful NHS Foundation Trusts, including leading teaching hospitals and comprehensive mental health services. For more information, visit: www.kingshealthpartners.org.

Cancer Research UK is the world's leading cancer charity dedicated to saving lives through research

The charity's groundbreaking work into the prevention, diagnosis and treatment of cancer has helped save millions of lives. This work is funded entirely by the public.

Cancer Research UK has been at the heart of the progress that has already seen survival rates double in the last forty 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 beat cancer. For further information about Cancer Research UK's work or to find out how to support the charity, please call +44 (0) 20 7121 6699 or visit www.cancerresearchuk.org

Leukaemia & Lymphoma Research is the only UK charity solely dedicated to research into blood cancers, including leukaemia, lymphoma and myeloma. These cancers are diagnosed in around 28,500 children, teenagers and adults in the UK every year. As it receives no government funding and relies entirely on voluntary support, it needs to raise £120 million in the next five years to continue this lifesaving research. Further information, including patient information booklets, is available from www.beatbloodcancers.org or on 020 7405 0101.