title: Preclinical exploration of combining plasmacytoid and myeloid dendritic cell vaccination with BRAF inhibition.
abstract: BACKGROUND
  Melanoma is the most lethal type of skin cancer and its incidence is progressively increasing. The introductions of immunotherapy and targeted therapies have tremendously improved the treatment of melanoma. Selective inhibition of BRAF by vemurafenib results in objective clinical responses in around 50 % of patients suffering from BRAFV600 mutated melanoma. However, drug resistance often results in hampering long-term tumor control. Alternatively, immunotherapy by vaccination with natural dendritic cells (nDCs) demonstrated long-term tumor control in a proportion of patients. We postulate that the rapid tumor debulking by vemurafenib can synergize the long-term tumor control of nDC vaccination to result in an effective treatment modality in a large proportion of patients. Here, we investigated the feasibility of this combination by analyzing the effect of vemurafenib on the functionality of nDCs.
  
  
  METHODS
  Plasmacytoid DCs (pDCs) and myeloid DCs (mDCs) were isolated from PBMCs obtained from buffy coats from healthy volunteers or vemurafenib-treated melanoma patients. Maturation of pDCs, mDCs and immature monocyte-derived DCs was induced by R848 in the presence or absence of vemurafenib and analyzed by FACS. Cytokine production and T cell proliferation induced by mature DCs were analyzed.
  
  
  RESULTS
  Vemurafenib inhibited maturation and cytokine production of highly purified nDCs of healthy volunteers resulting in diminished allogeneic T cell proliferation. This deleterious effect of vemurafenib on nDC functionality was absent when total PBMCs were exposed to vemurafenib. In patients receiving vemurafenib, nDC functionality and T cell allostimulatory capacity were unaffected.
  
  
  CONCLUSIONS
  Although vemurafenib inhibited the functionality of purified nDC of healthy volunteers, this effect was not observed when nDCs were matured in the complete PBMC fraction. This might have been caused by increased vemurafenib uptake in absence of other cell types. In accordance, nDCs isolated from patients on active vemurafenib treatment showed no negative effects. In conclusion, our results pave the way for a combinatorial treatment strategy and, we propose that combining vemurafenib with nDC vaccination represent a powerful opportunity that deserves more investigation in the clinic.
authors.affiliation: Department of Tumor Immunology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, 6500 HB, Nijmegen, The Netherlands.
authors.forename: Jurjen
authors.initials: J
authors.lastname: Tel
authors.affiliation: Department of Medical Oncology, Radboud University Medical Center, Nijmegen, The Netherlands.
authors.forename: Rutger
authors.initials: R
authors.lastname: Koornstra
authors.affiliation: Department of Tumor Immunology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, 6500 HB, Nijmegen, The Netherlands.
authors.forename: Nienke
authors.initials: N
authors.lastname: de Haas
authors.affiliation: Department of Tumor Immunology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, 6500 HB, Nijmegen, The Netherlands.
authors.forename: Vincent
authors.initials: V
authors.lastname: van Deutekom
authors.affiliation: Department of Tumor Immunology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, 6500 HB, Nijmegen, The Netherlands.|Department of Medical Oncology, Radboud University Medical Center, Nijmegen, The Netherlands.
authors.forename: Harm
authors.initials: H
authors.lastname: Westdorp
authors.affiliation: Department of Tumor Immunology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, 6500 HB, Nijmegen, The Netherlands.|Department of Medical Oncology, Radboud University Medical Center, Nijmegen, The Netherlands.
authors.forename: Steve
authors.initials: S
authors.lastname: Boudewijns
authors.affiliation: Department of Pharmacy, Radboud University Medical Center, Nijmegen, The Netherlands.
authors.forename: Nielka
authors.initials: N
authors.lastname: van Erp
authors.affiliation: Department of Tumor Immunology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, 6500 HB, Nijmegen, The Netherlands.
authors.forename: Stefania
authors.initials: S
authors.lastname: Di Blasio
authors.affiliation: Department of Medical Oncology, Radboud University Medical Center, Nijmegen, The Netherlands.
authors.forename: Winald
authors.initials: W
authors.lastname: Gerritsen
authors.affiliation: Department of Tumor Immunology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, 6500 HB, Nijmegen, The Netherlands.
authors.forename: Carl G
authors.initials: CG
authors.lastname: Figdor
authors.affiliation: Department of Tumor Immunology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, 6500 HB, Nijmegen, The Netherlands. jolanda.devries@radboudumc.nl.
authors.forename: I Jolanda M
authors.initials: IJ
authors.lastname: de Vries
authors.affiliation: Department of Tumor Immunology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, 6500 HB, Nijmegen, The Netherlands.
authors.forename: Stanleyson V
authors.initials: SV
authors.lastname: Hato
mesh_terms: D017951:Antigen Presentation / Q000187:drug effects; D000951:Antigens, Neoplasm / Q000276:immunology; D001682:Biological Availability; D002454:Cell Differentiation / Q000187:drug effects; D002469:Cell Separation; D016207:Cytokines / Q000378:metabolism; D003713:Dendritic Cells / Q000187:drug effects / Q000276:immunology*; D015536:Down-Regulation / Q000187:drug effects; D006801:Humans; D007211:Indoles / Q000097:blood / Q000494:pharmacology; D008213:Lymphocyte Activation / Q000187:drug effects; D008545:Melanoma / Q000097:blood / Q000473:pathology; D022423:Myeloid Cells / Q000187:drug effects / Q000276:immunology*; D048493:Proto-Oncogene Proteins B-raf / Q000037:antagonists & inhibitors* / Q000378:metabolism; D011728:Pyridones / Q000494:pharmacology; D011744:Pyrimidinones / Q000494:pharmacology; D013449:Sulfonamides / Q000097:blood / Q000494:pharmacology; D014611:Vaccination; D000077484:Vemurafenib
chemical_list: D000951:Antigens, Neoplasm; D016207:Cytokines; D007211:Indoles; D011728:Pyridones; D011744:Pyrimidinones; D013449:Sulfonamides; D000077484:Vemurafenib; C560077:trametinib; D048493:Proto-Oncogene Proteins B-raf
keywords: BDCA1 + myeloid DCs; DC vaccination; Plasmacytoid DCs; Vemurafenib