title: NOTCH2 links protein kinase C delta to the expression of CD23 in chronic lymphocytic leukaemia (CLL) cells.
abstract: One characteristic of chronic lymphocytic leukaemia (CLL) lymphocytes is high expression of CD23, which has previously been identified as a downstream target for NOTCH2 signalling. The mechanisms regulating NOTCH2-dependent CD23 expression, however, are largely unknown. This study showed that peripheral CLL cells overexpressed transcriptionally active NOTCH2 (N2(IC)), irrespective of their prognostic marker profile. When placed in culture, NOTCH2 activity was spontaneously decreased in 25 out of 31 CLL cases (81%) within 24 h. DNA-bound N2(IC) complexes could be maintained by the protein kinase C (PKC) activator phorbol 12-myristate 13-acetate (PMA) or by gamma-interferon (IFN-gamma), two CLL characteristic inducers of CD23 expression. Inhibition of PKC-delta by RNA interference or by rottlerin antagonised PMA-induced NOTCH2 activation and also suppressed NOTCH2 activity in CLL cases with constitutively activated NOTCH2 signalling. In 23 out of 29 CLL cases tested (79%), DNA-bound N2(IC) complexes were found to be resistant to the gamma-secretase inhibitor (GSI) DAPT, suggesting that GSIs will be only effective in a subset of CLL cases. These data suggest that deregulation of NOTCH2 signalling is critically involved in maintaining the malignant phenotype of CLL lymphocytes and point to a link between PKC-delta and NOTCH2 signalling in the leukemic cells.
authors.affiliation: Clinic of Internal Medicine I, Department of Haematology and Haemostaseology, Medical University of Vienna, Waehringer Guertel 18-20, Vienna, Austria.
authors.forename: Rainer
authors.initials: R
authors.lastname: Hubmann
authors.forename: Markus
authors.initials: M
authors.lastname: Düchler
authors.forename: Susanne
authors.initials: S
authors.lastname: Schnabl
authors.forename: Martin
authors.initials: M
authors.lastname: Hilgarth
authors.forename: Dita
authors.initials: D
authors.lastname: Demirtas
authors.forename: Dieter
authors.initials: D
authors.lastname: Mitteregger
authors.forename: Andrea
authors.initials: A
authors.lastname: Hölbl
authors.forename: Katrina
authors.initials: K
authors.lastname: Vanura
authors.forename: Trang
authors.initials: T
authors.lastname: Le
authors.forename: Thomas
authors.initials: T
authors.lastname: Look
authors.forename: Josef D
authors.initials: JD
authors.lastname: Schwarzmeier
authors.forename: Peter
authors.initials: P
authors.lastname: Valent
authors.forename: Ulrich
authors.initials: U
authors.lastname: Jäger
authors.forename: Medhat
authors.initials: M
authors.lastname: Shehata
mesh_terms: D000951:Antigens, Neoplasm / Q000378:metabolism; D014408:Biomarkers, Tumor / Q000378:metabolism; D006801:Humans; D007371:Interferon-gamma / Q000276:immunology; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000235:genetics / Q000276:immunology*; D009363:Neoplasm Proteins / Q000378:metabolism*; D011379:Prognosis; D051745:Protein Kinase C-delta / Q000037:antagonists & inhibitors / Q000378:metabolism*; D034622:RNA Interference; D051883:Receptor, Notch2 / Q000235:genetics / Q000378:metabolism*; D017455:Receptors, IgE / Q000378:metabolism*; D015398:Signal Transduction; D013755:Tetradecanoylphorbol Acetate / Q000276:immunology; D014407:Tumor Cells, Cultured
chemical_list: D000951:Antigens, Neoplasm; D014408:Biomarkers, Tumor; C497764:NOTCH2 protein, human; D009363:Neoplasm Proteins; D051883:Receptor, Notch2; D017455:Receptors, IgE; D007371:Interferon-gamma; D051745:Protein Kinase C-delta; D013755:Tetradecanoylphorbol Acetate