Decitabine-Vorinostat combination treatment in acute myeloid leukemia activates pathways with potential for novel triple therapy

// Christine S. Young 1, 2 , Kathryn M. Clarke 1, 3 , Laura M. Kettyle 1, 4 , Alexander Thompson 1, 5 and Ken I. Mills 1 1 Blood Cancer Research Group, Centre for Cancer Research and Cell Biology, Queen’s University, Belfast, United Kingdom 2 MRC Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Western General Hospital, Edinburgh, United Kingdom 3 Department of Haematology, Addenbrooke’s Hospital, Cambridge, United Kingdom 4 Haematopoietic Stem Cell Biology Laboratory, MRC Molecular Haematology Unit, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, Oxford, United Kingdom 5 Division of Cancer and Stem Cells, Centre for Biomolecular Sciences, University of Nottingham, Nottingham, United Kingdom Correspondence to: Christine S. Young, email: Christine.Young@igmm.ed.ac.uk Ken I. Mills, email: k.mills@qub.ac.uk Keywords: epigenetic combination therapies, AXL receptor tyrosine kinase, acute myeloid leukemia, HDAC inhibitors, DNMT inhibitors Received: October 25, 2016      Accepted: May 07, 2017      Published: May 19, 2017 ABSTRACT Despite advancements in cancer therapeutics, acute myeloid leukemia patients over 60 years old have a 5-year survival rate of less than 8%. In an attempt to improve this, epigenetic modifying agents have been combined as therapies in clinical studies. In particular combinations with Decitabine and Vorinostat have had varying degrees of efficacy. This study therefore aimed to understand the underlying molecular mechanisms of these agents to identify potential rational epi-sensitized combinations. Combined Decitabine-Vorinostat treatment synergistically decreased cell proliferation, induced apoptosis, enhanced acetylation of histones and further decreased DNMT1 protein with HL-60 cells showing a greater sensitivity to the combined treatment than OCI-AML3. Combination therapy led to reprogramming of unique target genes including AXL , a receptor tyrosine kinase associated with cell survival and a poor prognosis in AML, which was significantly upregulated following treatment. Therefore targeting AXL following epi-sensitization with Decitabine and Vorinostat may be a suitable triple combination. To test this, cells were treated with a novel triple combination therapy including BGB324, an AXL specific inhibitor. Triple combination increased the sensitivity of OCI-AML3 cells to Decitabine and Vorinostat as shown through viability assays and significantly extended the survival of mice transplanted with pretreated OCI-AML3 cells, while bioluminescence imaging showed the decrease in disease burden following triple combination treatment. Further investigation is required to optimize this triple combination, however, these results suggest that AXL is a potential marker of response to Decitabine-Vorinostat combination treatment and offers a new avenue of epigenetic combination therapies for acute myeloid leukemia.