title: Gliotoxin is a potent NOTCH2 transactivation inhibitor and efficiently induces apoptosis in chronic lymphocytic leukaemia (CLL) cells.
abstract: Chronic lymphocytic leukaemia (CLL) cells express constitutively activated NOTCH2 in a protein kinase C (PKC)- dependent manner. The transcriptional activity of NOTCH2 correlates not only with the expression of its target gene FCER2 (CD23) but is also functionally linked with CLL cell viability. In the majority of CLL cases, DNA-bound NOTCH2 complexes are less sensitive to the γ-secretase inhibitor (GSI) DAPT. Therefore, we searched for compounds that interfere with NOTCH2 signalling at the transcription factor level. Using electrophoretic mobility shift assays (EMSA), we identified the Aspergillum-derived secondary metabolite gliotoxin as a potent NOTCH2 transactivation inhibitor. Gliotoxin completely blocked the formation of DNA-bound NOTCH2 complexes in CLL cells independent of their sensitivity to DAPT. The inhibition of NOTCH2 signalling by gliotoxin was associated with down regulation of CD23 (FCER) expression and induction of apoptosis. Short time exposure of CLL cells indicated that the early apoptotic effect of gliotoxin is independent of proteasome regulated nuclear factor κB activity, and is associated with up regulation of NOTCH3 and NR4A1 expression. Gliotoxin could overcome the supportive effect of primary bone marrow stromal cells in an ex vivo CLL microenvironment model. In conclusion, we identified gliotoxin as a potent NOTCH2 inhibitor with a promising therapeutic potential in CLL.
authors.affiliation: Clinic of Internal Medicine I, Division of Haematology and Haemostaseology, Comprehensive Cancer Centre Vienna, Drug and Target Screening Unit DTSU, Medical University of Vienna, Vienna, Austria.
authors.forename: Rainer
authors.initials: R
authors.lastname: Hubmann
authors.forename: Martin
authors.initials: M
authors.lastname: Hilgarth
authors.forename: Susanne
authors.initials: S
authors.lastname: Schnabl
authors.forename: Elena
authors.initials: E
authors.lastname: Ponath
authors.forename: Marlies
authors.initials: M
authors.lastname: Reiter
authors.forename: Dita
authors.initials: D
authors.lastname: Demirtas
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Sieghart
authors.forename: Peter
authors.initials: P
authors.lastname: Valent
authors.forename: Christoph
authors.initials: C
authors.lastname: Zielinski
authors.forename: Ulrich
authors.initials: U
authors.lastname: Jäger
authors.forename: Medhat
authors.initials: M
authors.lastname: Shehata
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D017209:Apoptosis / Q000187:drug effects*; D045744:Cell Line, Tumor / Q000187:drug effects / Q000473:pathology; D018920:Coculture Techniques; D004252:DNA Mutational Analysis; D003864:Depression, Chemical; D005260:Female; D015973:Gene Expression Regulation, Leukemic / Q000187:drug effects*; D005912:Gliotoxin / Q000494:pharmacology*; D006801:Humans; D007143:Immunoglobulin Heavy Chains / Q000235:genetics; D020128:Inhibitory Concentration 50; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000097:blood / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D016328:NF-kappa B / Q000378:metabolism; D009363:Neoplasm Proteins / Q000037:antagonists & inhibitors* / Q000096:biosynthesis / Q000235:genetics; D057105:Nuclear Receptor Subfamily 4, Group A, Member 1 / Q000096:biosynthesis / Q000235:genetics; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D051883:Receptor, Notch2 / Q000037:antagonists & inhibitors*; D000071656:Receptor, Notch3; D051880:Receptors, Notch / Q000096:biosynthesis / Q000235:genetics; D017154:Stromal Cells / Q000502:physiology; D014157:Transcription Factors / Q000502:physiology; D015533:Transcriptional Activation / Q000187:drug effects*; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000473:pathology
chemical_list: D007143:Immunoglobulin Heavy Chains; D016328:NF-kappa B; C497764:NOTCH2 protein, human; C499374:NOTCH3 protein, human; C539821:NR4A1 protein, human; D009363:Neoplasm Proteins; D057105:Nuclear Receptor Subfamily 4, Group A, Member 1; D051883:Receptor, Notch2; D000071656:Receptor, Notch3; D051880:Receptors, Notch; D014157:Transcription Factors; D005912:Gliotoxin; D046988:Proteasome Endopeptidase Complex