title: RIG-I inhibits the MAPK-dependent proliferation of BRAF mutant melanoma cells via MKP-1.
abstract: BACKGROUND
  BRAF-mutant melanoma is characterized by aggressive metastatic potential and therapeutic resistance. The innate immune receptor RIG-I has emerged as a potential target in melanoma therapies but the contributing pathways involved in anti-cancer activity are poorly characterized.
  
  
  METHODS
  Baseline and ATRA-induced expression of RIG-I in nine (3 wild type and 6 BRAF-mutant) melanoma cell lines was measured with Q-PCR and Western blot. Ligand-specific stimulation of RIG-I was detected by Q-PCR and ELISA. Activation of the RIG-I-coupled IRF3, NF-κB and MAPK pathways was tested with protein array and Western blot. Cell proliferation and apoptosis was monitored by flow cytometry and cell counting. Down modulation of MKP-1 expression in melanoma cells was performed by specific siRNA.
  
  
  RESULTS
  Short-term ATRA pre-treatment increases the expression of RIG-I in BRAF-mutant melanoma cells. Specific activation of RIG-I by 5'ppp-dsRNA leads to increased activity of the IRF3-IFNβ pathway but does not influence NF-κB signaling. RIG-I mediates the targeted dephosphorylation of several MAPKs (p38, RSK1, GSK-3α/β, HSP27) via the endogenous regulator MKP-1 resulting in decreased melanoma cell proliferation.
  
  
  CONCLUSIONS
  RIG-I has the potential to exert anticancer activity in BRAF-mutant melanoma via controlling IFNβ production and MAPK signaling. This is the first study showing that RIG-I activation results in MKP-1-mediated inhibition of cell proliferation via controlling the p38-HSP27, c-Jun and rpS6 pathways thus identifying RIG-I and MKP-1 as novel and promising therapeutical targets.
authors.affiliation: Department of Immunology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary; Sapientia Hungarian University of Transylvania, Department of Bioengineering, Miercurea-Ciuc, Romania. Electronic address: szattila@med.unideb.hu.
authors.forename: Attila
authors.initials: A
authors.lastname: Szabo
authors.affiliation: Department of Immunology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary.
authors.forename: Tunde
authors.initials: T
authors.lastname: Fekete
authors.affiliation: Department of Immunology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary; Sapientia Hungarian University of Transylvania, Department of Bioengineering, Miercurea-Ciuc, Romania.
authors.forename: Gabor
authors.initials: G
authors.lastname: Koncz
authors.affiliation: Department of Immunology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary.
authors.forename: Brahma V
authors.initials: BV
authors.lastname: Kumar
authors.affiliation: Department of Immunology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary.
authors.forename: Kitti
authors.initials: K
authors.lastname: Pazmandi
authors.affiliation: Department of Immunology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary.
authors.forename: Zsofia
authors.initials: Z
authors.lastname: Foldvari
authors.affiliation: 2nd Institute of Pathology, Semmelweis University, Budapest, Hungary; MTA-SE Molecular Oncology Research Group, Hungarian Academy of Sciences, Budapest, Hungary.
authors.forename: Balazs
authors.initials: B
authors.lastname: Hegedus
authors.affiliation: 2nd Institute of Pathology, Semmelweis University, Budapest, Hungary; MTA-SE Molecular Oncology Research Group, Hungarian Academy of Sciences, Budapest, Hungary.
authors.forename: Tamas
authors.initials: T
authors.lastname: Garay
authors.affiliation: Department of Immunology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary; Sapientia Hungarian University of Transylvania, Department of Bioengineering, Miercurea-Ciuc, Romania.
authors.forename: Attila
authors.initials: A
authors.lastname: Bacsi
authors.affiliation: Department of Immunology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary; Sapientia Hungarian University of Transylvania, Department of Bioengineering, Miercurea-Ciuc, Romania.
authors.forename: Eva
authors.initials: E
authors.lastname: Rajnavolgyi
authors.affiliation: Department of Immunology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary; Sapientia Hungarian University of Transylvania, Department of Bioengineering, Miercurea-Ciuc, Romania.
authors.forename: Arpad
authors.initials: A
authors.lastname: Lanyi
mesh_terms: D045744:Cell Line, Tumor; D049109:Cell Proliferation; D016207:Cytokines / Q000378:metabolism; D000071457:DEAD Box Protein 58 / Q000378:metabolism*; D054638:Dual Specificity Phosphatase 1 / Q000378:metabolism*; D006801:Humans; D050838:Interferon Regulatory Factor-3 / Q000378:metabolism; D020935:MAP Kinase Signaling System; D008545:Melanoma / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics*; D011971:Receptors, Immunologic; D014212:Tretinoin / Q000494:pharmacology
chemical_list: D016207:Cytokines; C494232:IRF3 protein, human; D050838:Interferon Regulatory Factor-3; D016328:NF-kappa B; D011971:Receptors, Immunologic; D014212:Tretinoin; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf; D020928:Mitogen-Activated Protein Kinases; C517019:DUSP1 protein, human; D054638:Dual Specificity Phosphatase 1; C452820:RIGI protein, human; D000071457:DEAD Box Protein 58
keywords: BRAF; MAPK; MKP-1/DUSP1; Melanoma; Proliferation; RIG-I