title: Inhibition of glycogen synthase kinase-3 increases NKG2D ligand MICA expression and sensitivity to NK cell-mediated cytotoxicity in multiple myeloma cells: role of STAT3.
abstract: Engagement of NKG2D and DNAX accessory molecule-1 (DNAM-1) receptors on lymphocytes plays an important role for anticancer response and represents an interesting therapeutic target for pharmacological modulation. In this study, we investigated the effect of inhibitors targeting the glycogen synthase kinase-3 (GSK3) on the expression of NKG2D and DNAM-1 ligands in multiple myeloma (MM) cells. GSK3 is a pleiotropic serine-threonine kinase point of convergence of numerous cell-signaling pathways, able to regulate the proliferation and survival of cancer cells, including MM. We found that inhibition of GSK3 upregulates both MICA protein surface and mRNA expression in MM cells, with little or no effects on the basal expression of the MICB and DNAM-1 ligand poliovirus receptor/CD155. Moreover, exposure to GSK3 inhibitors renders myeloma cells more efficient to activate NK cell degranulation and to enhance the ability of myeloma cells to trigger NK cell-mediated cytotoxicity. We could exclude that increased expression of β-catenin or activation of the heat shock factor-1 (transcription factors inhibited by active GSK3) is involved in the upregulation of MICA expression, by using RNA interference or viral transduction of constitutive active forms. On the contrary, inhibition of GSK3 correlated with a downregulation of STAT3 activation, a negative regulator of MICA transcription. Both Tyr(705) phosphorylation and binding of STAT3 on MICA promoter are reduced by GSK3 inhibitors; in addition, overexpression of a constitutively active form of STAT3 significantly inhibits MICA upregulation. Thus, we provide evidence that regulation of the NKG2D-ligand MICA expression may represent an additional immune-mediated mechanism supporting the antimyeloma activity of GSK3 inhibitors.
authors.affiliation: Department of Molecular Medicine, Cenci Bolognetti Foundation-Pasteur Institute, Sapienza University of Rome, 00161 Rome, Italy.
authors.forename: Cinzia
authors.initials: C
authors.lastname: Fionda
authors.forename: Giulia
authors.initials: G
authors.lastname: Malgarini
authors.forename: Alessandra
authors.initials: A
authors.lastname: Soriani
authors.forename: Alessandra
authors.initials: A
authors.lastname: Zingoni
authors.forename: Francesca
authors.initials: F
authors.lastname: Cecere
authors.forename: Maria Luisa
authors.initials: ML
authors.lastname: Iannitto
authors.forename: Maria Rosaria
authors.initials: MR
authors.lastname: Ricciardi
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Federico
authors.forename: Maria Teresa
authors.initials: MT
authors.lastname: Petrucci
authors.forename: Angela
authors.initials: A
authors.lastname: Santoni
authors.forename: Marco
authors.initials: M
authors.lastname: Cippitelli
mesh_terms: D015153:Blotting, Western; D045744:Cell Line, Tumor; D047369:Chromatin Immunoprecipitation; D003602:Cytotoxicity, Immunologic / Q000276:immunology; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D038362:Glycogen Synthase Kinase 3 / Q000037:antagonists & inhibitors / Q000276:immunology*; D015395:Histocompatibility Antigens Class I / Q000276:immunology* / Q000378:metabolism; D006801:Humans; D007694:Killer Cells, Natural / Q000276:immunology* / Q000378:metabolism; D008213:Lymphocyte Activation / Q000276:immunology; D009101:Multiple Myeloma / Q000276:immunology* / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D050796:STAT3 Transcription Factor / Q000276:immunology* / Q000378:metabolism; D014161:Transduction, Genetic; D014162:Transfection
chemical_list: D015395:Histocompatibility Antigens Class I; C099187:MHC class I-related chain A; D050796:STAT3 Transcription Factor; D038362:Glycogen Synthase Kinase 3