Thursday, 27 July 2017

Leukaemia & Lymphoma Published Research

You may have noticed over the past couple of months that we have had a number of posts on social media relating to new publications from the Blood Cancer research group in the Centre for Cancer Research and Cell Biology at Queen’s University Belfast.

The main way that research is disseminated to the wider world, scientific, academic and the public, is by publication in peer reviewed journals.   A point that I discussed in a previous LLNI blog, in March 2016, about the media storm over the use of immunotherapy in acute lymphoblastic leukaemia (ALL).  The media interest arose from a presentation at a conference and had not been through the peer review process – a process in which scientists will comment on the paper and question the results, not always in a constructive manner – a process that has its critics and flaws but one that scientists have used for years and is accepted.   Our recent publications have been through this process and have required one or two rounds of revision prior to being deemed suitable for publication.  

It is perhaps unusual for a number of papers to be published in a short period of time, but from the start of the idea of the research project, undertaking the research, analysing the data, writing the manuscript and getting it accepted for publication takes many years – and in one case that has been nearly 10 years!     All the studies have benefitted from some research support from Leukaemia and Lymphoma NI with other partners including the NI Assembly Department of Employment and Learning (DEL) students – now rebranded as the Department for the Economy (DfE). 

So what do our four papers actually mean!   Well they represent three different but related areas of research.  

One of the papers is very bioinformatics – that is a computer based - analysis of different type of cell lines we use in the laboratory.  Cell lines have been developed around the world from donated leukaemia samples from patients and have been grown in the laboratory in a safe sterile environment for our research.   However, there is always concern that they have changed or evolved do not represent the original type of leukaemia.   This study with a colleague, Dr Jaine Blayney, has mapped the patterns of RNA in the cell lines back to a large data set representing 18 different types or sub-types of leukaemia in over 2000 patients; in which I was a co-author in 2010.   The recent study has shown that the cell lines do reflect the original sub-types of leukaemia and can be used as a model of the disease for laboratory studies.

The second paper is focused on paediatric leukaemia, and one sub-type in particular, acute lymphoblastic leukaemia (ALL) with a chromosome abnormality in which part of chromosome 12 is switched with a part of chromosome 21.  This is called a translocation and noted as t(12;21)(p12;q22), the latter part indicating the location on the chromosomes where the breaks occur.   This gave rise to a fusion protein called ETV6/RUNX1, which is only found in this sub-type of leukaemia.   In this study, Drs Marie Gaine and Danny Sharpe led an examination of the role of  GATA2, a gene that regulates other genes, on the erythropoietin receptor (EPOR) gene, whose protein is usually associated with red cells, but is very high in patients with t(12;21) ALL.   We showed that indeed GATA2 did regulate EPOR in these patients and this was done at several levels:  at an epigenetic level (which we mention again later), at the level of RNA production and also after RNA production by microRNAs (miRNA).  However, more studies are required to see how this can be developed in possible therapeutic options of children with this type of leukaemia.    Dr Marie Gaine is now working at the University of Iowa Carver College of Medicine in Iowa, USA and Dr Danny Sharpe is working in ‎Exploristics Ltd in Belfast. 

The last two papers are related in that they have identified possible novel combinations of therapies.   Elderly patients with acute myeloid leukaemia (AML) are often unable to tolerate the intensive therapies required to treat the disease.   In these cases, lower intensive treatments are used and these are often “epigenetic” therapies.   Epigenetics is a molecular process which is “above the genome” by which genes are switched on and off as required depending on the tissues or stage of aging.    It is a natural process but in cancer, the normal pattern of genes is disrupted resulting in mis-programmed cells.    Epigenetic therapies can reverse the abnormal patterns allowing genes to be expressed if required; but which genes are expressed and which are important was not known.   We undertook an investigation of what happens when cells are “epi-sensitised” – that is the consequence of the epigenetic therapies.    Our studies monitored the cascade of genes activated following exposure to different epigenetic therapies allowing us to identify molecular targets for combination therapies – a rational choice of therapeutic partners.  

One of the epigenetic drugs used was Vorinostat, which is called a histone deactylase inhibitor or HDACi.   DNA is wrapped around a complex of histones, the tails of the histone proteins can be modified by the addition of chemical acetyl group.   If the acetyl group is present, it opens up the DNA to allow the production of RNA and subsequently proteins.   If the in case of cancer cells, the acetyl group is not present, the DNA is tightly wrapped and the RNA and proteins cannot be made.    Vorinostat blocks the activity of proteins that removal of the acetyl groups allowing the DNA to be opened.    Dr Jodie Hay, who is now working in leukaemia research in the University of Glasgow, showed through an integrated laboratory and computer analysis that one of the consequences of Vorinostat treatment was the activation of sonic hedgehog (SHH) signalling pathway.  The SHH pathway is usually inactive in adult human tissues but can promote cancer cells to grow – definitely not the result you want!   Jodie then exposed the Vorinostat treated cells with an inhibitor of SHH and showed that more of the leukaemia cells could be killed – which you do want!

Dr Christine Young, who now working in the University of Edinburgh, also looked at the concept of epi-sensitising cells for combination therapies.  She took another epigenetic drug, Decitabine, which remove methyl groups from the DNA.   One effect of DNA methylation is that it switches off DNA.  As an analogy, open DNA or chromatin is like the kitchen utensils you use daily, readily accessible, DNA in which histones are not acetylated represents the kitchen stuff you use occasionally in a cupboard, but want at hand, like blenders or pasta makers!  Methylated DNA, usually with deacetylated histones is all the other stuff that you have but are never going to use and are in boxes under the stairs or in the attic!   Christine’s concept was to use Decitabine to open the chromatin followed by Vorinostat (which Jodie showed can activated some genes) to mimic clinical trial situations which already use this combination.    The recently published study has shown that amongst the cascade of genes activated, one gene was highly expressed following the double combination and not with either of the single agents.   This gene was AXL; this is acts in the cell by damping down the immune response allowing the cells to survive.   The addition of an AXL specific inhibitor BGB324, from BerGenBio in Norway, after the double combination of Decitabine then Vorinostat had a dramatic on increasing cell death.    BGB324 has been used in a clinical trial as a single agent and only when patients had measurable levels of AXL; our study has suggested that it could be used on more patients by inducing AXL expression although further studies would be needed to confirm that. 

It is only by understanding the way that blood cancer are abnormal and the way that they respond to drugs that we can hope to develop new  or combinations of therapies that are more effective and less toxic for patients.   These studies are not the whole answer but contribute towards this aim.

These studies have all benefited from research funding from the Leukaemia and Lymphoma NI and demonstrate that local research can have global impact.