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

Cancer Immunol Immunother. 2013 Apr;62(4):811-22. doi: 10.1007/s00262-012-1389-z. Epub 2013 Jan 10.


Purpose: 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.

MeSH terms

  • Antigens, CD / biosynthesis
  • Antigens, CD / immunology
  • B7-1 Antigen / biosynthesis
  • B7-1 Antigen / immunology
  • Butadienes / pharmacology
  • CD40 Antigens / biosynthesis
  • CD40 Antigens / immunology
  • Cell Line, Tumor
  • Coculture Techniques
  • Cytokines / biosynthesis
  • Cytokines / immunology
  • Dendritic Cells / immunology*
  • Humans
  • Immunoglobulins / biosynthesis
  • Immunoglobulins / immunology
  • Indoles / pharmacology
  • MAP Kinase Kinase Kinases / antagonists & inhibitors*
  • MAP Kinase Kinase Kinases / immunology
  • MAP Kinase Signaling System / drug effects
  • MAP Kinase Signaling System / immunology
  • Melanoma / enzymology*
  • Melanoma / genetics
  • Melanoma / immunology*
  • Membrane Glycoproteins / biosynthesis
  • Membrane Glycoproteins / immunology
  • Mutation
  • Nitriles / pharmacology
  • Poly I-C / immunology
  • Protein Kinase Inhibitors / pharmacology
  • Proto-Oncogene Proteins B-raf / antagonists & inhibitors*
  • Proto-Oncogene Proteins B-raf / genetics
  • Proto-Oncogene Proteins B-raf / immunology
  • Sulfonamides / pharmacology
  • T-Lymphocytes / immunology
  • Vemurafenib


  • Antigens, CD
  • B7-1 Antigen
  • Butadienes
  • CD40 Antigens
  • CD83 antigen
  • Cytokines
  • Immunoglobulins
  • Indoles
  • Membrane Glycoproteins
  • Nitriles
  • Protein Kinase Inhibitors
  • Sulfonamides
  • U 0126
  • Vemurafenib
  • BRAF protein, human
  • Proto-Oncogene Proteins B-raf
  • MAP Kinase Kinase Kinases
  • Poly I-C