title: Inhibition of both BRAF and MEK in BRAF(V600E) mutant melanoma restores compromised dendritic cell (DC) function while having differential direct effects on DC properties.
abstract: OBJECTIVE
  Dendritic cells (DCs) can induce strong tumor-specific T-cell immune responses. Constitutive upregulation of the mitogen-activated protein kinase (MAPK) pathway by a BRAF(V600) mutation, which is present in about 50 % of metastatic melanomas, may be linked to compromised function of DCs in the tumor microenvironment. Targeting both MEK and BRAF has shown efficacy in BRAF(V600) mutant melanoma.
  
  
  METHODS
  We co-cultured monocyte-derived human DCs with melanoma cell lines pretreated with the MEK inhibitor U0126 or the BRAF inhibitor vemurafenib. Cytokine production (IL-12 and TNF-α) and surface marker expression (CD80, CD83, and CD86) in DCs matured with the Toll-like receptor 3/Melanoma Differentiation-Associated protein 5 agonist polyI:C was examined. Additionally, DC function, viability, and T-cell priming capacity were assessed upon direct exposure to U0126 and vemurafenib.
  
  
  RESULTS
  Cytokine production and co-stimulation marker expression were suppressed in polyI:C-matured DCs exposed to melanoma cells in co-cultures. This suppression was reversed by MAPK blockade with U0126 and/or vemurafenib only in melanoma cell lines carrying a BRAF(V600E) mutation. Furthermore, when testing the effect of U0126 directly on DCs, marked inhibition of function, viability, and DC priming capacity was observed. In contrast, vemurafenib had no effect on DC function across a wide range of dose concentrations.
  
  
  CONCLUSIONS
  BRAF(V600E) mutant melanoma cells modulate DC through the MAPK pathway as its blockade can reverse suppression of DC function. MEK inhibition negatively impacts DC function and viability if applied directly. In contrast, vemurafenib does not have detrimental effects on important functions of DCs and may therefore be a superior candidate for combination immunotherapy approaches in melanoma patients.
authors.affiliation: New York University Cancer Institute, New York University School of Medicine, 522 First Avenue, SRB 1303, New York, NY, 10016, USA. patrick_ott@dfci.harvard.edu
authors.forename: Patrick A
authors.initials: PA
authors.lastname: Ott
authors.forename: Trevor
authors.initials: T
authors.lastname: Henry
authors.forename: Sonja Jimenez
authors.initials: SJ
authors.lastname: Baranda
authors.forename: Davor
authors.initials: D
authors.lastname: Frleta
authors.forename: Olivier
authors.initials: O
authors.lastname: Manches
authors.forename: Dusan
authors.initials: D
authors.lastname: Bogunovic
authors.forename: Nina
authors.initials: N
authors.lastname: Bhardwaj
mesh_terms: D015703:Antigens, CD / Q000096:biosynthesis / Q000276:immunology; D018122:B7-1 Antigen / Q000096:biosynthesis / Q000276:immunology; D002070:Butadienes / Q000494:pharmacology; D019013:CD40 Antigens / Q000096:biosynthesis / Q000276:immunology; D045744:Cell Line, Tumor; D018920:Coculture Techniques; D016207:Cytokines / Q000096:biosynthesis / Q000276:immunology; D003713:Dendritic Cells / Q000276:immunology*; D006801:Humans; D007136:Immunoglobulins / Q000096:biosynthesis / Q000276:immunology; D007211:Indoles / Q000494:pharmacology; D020930:MAP Kinase Kinase Kinases / Q000037:antagonists & inhibitors* / Q000276:immunology; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000276:immunology; D008545:Melanoma / Q000201:enzymology* / Q000235:genetics / Q000276:immunology*; D008562:Membrane Glycoproteins / Q000096:biosynthesis / Q000276:immunology; D009154:Mutation; D009570:Nitriles / Q000494:pharmacology; D011070:Poly I-C / Q000276:immunology; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D048493:Proto-Oncogene Proteins B-raf / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000276:immunology; D013449:Sulfonamides / Q000494:pharmacology; D013601:T-Lymphocytes / Q000276:immunology; D000077484:Vemurafenib; D000097802:CD83 Antigen
chemical_list: D015703:Antigens, CD; D018122:B7-1 Antigen; D002070:Butadienes; D019013:CD40 Antigens; D016207:Cytokines; D007136:Immunoglobulins; D007211:Indoles; D020930:MAP Kinase Kinase Kinases; D008562:Membrane Glycoproteins; D009570:Nitriles; D011070:Poly I-C; D047428:Protein Kinase Inhibitors; D048493:Proto-Oncogene Proteins B-raf; D013449:Sulfonamides; D000077484:Vemurafenib; D000097802:CD83 Antigen; C113580:U 0126; C482119:BRAF protein, human