title: Potential role of Notch signalling in CD34+ chronic myeloid leukaemia cells: cross-talk between Notch and BCR-ABL.
abstract: Notch signalling is critical for haemopoietic stem cell (HSC) self-renewal and survival. The role of Notch signalling has been reported recently in chronic myeloid leukaemia (CML) - a stem cell disease characterized by BCR-ABL tyrosine kinase activation. Therefore, we studied the relationship between BCR-ABL and Notch signalling and assessed the expression patterns of Notch and its downstream target Hes1 in CD34+ stem and progenitor cells from chronic-phase CML patients and bone marrow (BM) from normal subjects (NBM). We found significant upregulation (p<0.05) of Notch1, Notch2 and Hes1 on the most primitive CD34+Thy+ subset of CML CD34+ cells suggesting that active Notch signalling in CML primitive progenitors. In addition, Notch1 was also expressed in distinct lymphoid and myeloid progenitors within the CD34+ population of primary CML cells. To further delineate the possible role and interactions of Notch with BCR-ABL in CD34+ primary cells from chronic-phase CML, we used P-crkl detection as a surrogate assay of BCR-ABL tyrosine kinase activity. Our data revealed that Imatinib (IM) induced BCR-ABL inhibition results in significant (p<0.05) upregulation of Notch activity, assessed by Hes1 expression. Similarly, inhibition of Notch leads to hyperactivation of BCR-ABL. This antagonistic relationship between Notch and BCR-ABL signalling was confirmed in K562 and ALL-SIL cell lines. In K562, we further validated this antagonistic relationship by inhibiting histone deacetylase (HDAC) - an effector pathway of Hes1, using valproic acid (VPA) - a HDAC inhibitor. Finally, we also confirmed the potential antagonism between Notch and BCR/ABL in In Vivo, using publically available GSE-database, by analysing gene expression profile of paired samples from chronic-phase CML patients pre- and post-Imatinib therapy. Thus, we have demonstrated an antagonistic relationship between Notch and BCR-ABL in CML. A combined inhibition of Notch and BCR-ABL may therefore provide superior clinical response over tyrosine-kinase inhibitor monotherapy by targeting both quiescent leukaemic stem cells and differentiated leukaemic cells and hence must be explored.
authors: Faculty of Life Sciences, Manchester Institute of Biotechnology (MIB), University of Manchester, Manchester, United Kingdom.
authors: Abdullah
authors: A
authors: Aljedai
authors: Faculty of Life Sciences, Manchester Institute of Biotechnology (MIB), University of Manchester, Manchester, United Kingdom.
authors: Anne-Marie
authors: AM
authors: Buckle
authors: Department of Paediatric Haematology, Great Ormond Street Hospital (GOSH), London, United Kingdom.
authors: Prashant
authors: P
authors: Hiwarkar
authors: Faculty of Life Sciences, Manchester Institute of Biotechnology (MIB), University of Manchester, Manchester, United Kingdom; Institute of Inflammation and Repair, Manchester Institute of Biotechnology (MIB), University of Manchester, Manchester, United Kingdom.
authors: Farhatullah
authors: F
authors: Syed
mesh_terms: D018952:Antigens, CD34 / Q000378:metabolism*; D017209:Apoptosis / Q000187:drug effects; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism*; D015153:Blotting, Western; D002453:Cell Cycle / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D016044:Fusion Proteins, bcr-abl / Q000235:genetics / Q000378:metabolism*; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D000068877:Imatinib Mesylate / Q000627:therapeutic use; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism*; D014411:Neoplastic Stem Cells / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000627:therapeutic use; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D051881:Receptor, Notch1 / Q000235:genetics / Q000378:metabolism*; D051883:Receptor, Notch2 / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000072056:Transcription Factor HES-1; D014407:Tumor Cells, Cultured
chemical_list: D018952:Antigens, CD34; D051792:Basic Helix-Loop-Helix Proteins; D016044:Fusion Proteins, bcr-abl; D018398:Homeodomain Proteins; D000068877:Imatinib Mesylate; D047428:Protein Kinase Inhibitors; D012333:RNA, Messenger; D051881:Receptor, Notch1; D051883:Receptor, Notch2; D000072056:Transcription Factor HES-1; C497761:NOTCH1 protein, human; C497764:NOTCH2 protein, human; C078493:HES1 protein, human