title: The oncogenic BRAF kinase inhibitor PLX4032/RG7204 does not affect the viability or function of human lymphocytes across a wide range of concentrations.
abstract: OBJECTIVE
  PLX4032 (RG7204), an oncogenic BRAF kinase inhibitor undergoing clinical evaluation, has high response rates in early clinical trials in patients with advanced BRAF(V600E) mutant melanoma. Combining PLX4032 with immunotherapy may allow expanding the durability of responses. The effects of PLX4032 on immune cells were studied to explore the feasibility of future combinatorial approaches with immunotherapy for melanoma.
  
  
  METHODS
  Peripheral blood mononuclear cells (PBMC) and BRAF(V600E) mutant melanoma cells were exposed to increasing concentrations of PLX4032 and the cell viability, proliferation, cell cycle, apoptosis, and phosphorylation of signaling proteins were analyzed. Effects of PLX4032 on antigen-specific T-cell function were analyzed by specific cytokine release and cytotoxicity activity.
  
  
  RESULTS
  The 50% inhibition concentration (IC(50)) of PLX4032 for resting human PBMC was between 50 and 150 μmol/L compared with an IC(50) below 1 μmol/L for sensitive BRAF(V600E) mutant melanoma cell lines. Activated lymphocytes were even more resistant with no growth inhibition up to concentrations of 250 μmol/L. PLX4032 had a marginal effect on cell-cycle arrest, apoptotic cell changes or alteration of phosphorylated signaling molecules in lymphocytes. Functional analysis of specific antigen recognition showed preserved T-cell function up to 10-μmol/L concentration of PLX4032, whereas the cytotoxic activity of PLX4032 was maintained up to high concentrations of 50 μmol/L.
  
  
  CONCLUSIONS
  The preserved viability and function of lymphocytes exposed to high concentrations of PLX4032 suggest that this agent could be a potential candidate for combining with immunotherapy strategies for the treatment of patients with BRAF(V600)(E) mutant melanoma.
authors.affiliation: Department of Surgery, Division of Surgical Oncology, Jonsson Comprehensive Cancer Center, University of California Los Angeles, Los Angeles, California 90095-1782, USA.
authors.forename: Begoña
authors.initials: B
authors.lastname: Comin-Anduix
authors.forename: Thinle
authors.initials: T
authors.lastname: Chodon
authors.forename: Hooman
authors.initials: H
authors.lastname: Sazegar
authors.forename: Douglas
authors.initials: D
authors.lastname: Matsunaga
authors.forename: Stephen
authors.initials: S
authors.lastname: Mock
authors.forename: Jason
authors.initials: J
authors.lastname: Jalil
authors.forename: Helena
authors.initials: H
authors.lastname: Escuin-Ordinas
authors.forename: Bartosz
authors.initials: B
authors.lastname: Chmielowski
authors.forename: Richard C
authors.initials: RC
authors.lastname: Koya
authors.forename: Antoni
authors.initials: A
authors.lastname: Ribas
mesh_terms: D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004353:Drug Evaluation, Preclinical; D006801:Humans; D007167:Immunotherapy / Q000379:methods; D007211:Indoles / Q000494:pharmacology*; D020128:Inhibitory Concentration 50; D020014:K562 Cells; D018655:Lymphocyte Count; D008214:Lymphocytes / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D008545:Melanoma / Q000188:drug therapy / Q000473:pathology; D009994:Osmolar Concentration; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D048493:Proto-Oncogene Proteins B-raf / Q000037:antagonists & inhibitors*; D013449:Sulfonamides / Q000494:pharmacology*; D000077484:Vemurafenib
chemical_list: D007211:Indoles; D047428:Protein Kinase Inhibitors; D013449:Sulfonamides; D000077484:Vemurafenib; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf