title: Combination of pan-RAF and MEK inhibitors in NRAS mutant melanoma.
abstract: BACKGROUND
  Approximately 20% of melanomas contain a mutation in NRAS. However no direct inhibitor of NRAS is available. One of the main signaling pathways downstream of NRAS is the MAPK pathway. In this study we investigated the possibility of blocking oncogenic signaling of NRAS by inhibiting two signaling points in the MAPK pathway.
  
  
  METHODS
  Fourteen NRAS mutated human melanoma cell lines were treated with a pan-RAF inhibitor (PRi, Amgen Compd A), a MEK inhibitor (MEKi, trametinib) or their combination and the effects on proliferation, cell cycle progression, apoptosis, transcription profile and signaling of the cells were investigated.
  
  
  RESULTS
  The majority of the cell lines showed a significant growth inhibition, with high levels of synergism of the PRi and MEKi combination. Sensitive cell lines showed induction of apoptosis by the combination treatment and there was a correlation between p-MEK levels and synergistic effect of the combination treatment. Proliferation of sensitive cell lines was blocked by the inhibition of the MAPK pathway, which also blocked expression of cyclin D1. However, in resistant cell lines, proliferation was blocked by combined inhibition of the MAPK pathway and cyclin D3, which is not regulated by the MAPK pathway. Resistant cell lines also showed higher levels of p-GSK3β and less perturbation of the apoptotic profile upon the treatment in comparison with the sensitive cell lines.
  
  
  CONCLUSIONS
  The combination of PRi + MEKi can be an effective regimen for blocking proliferation of NRAS mutant melanomas when there is higher activity of the MAPK pathway and dependence of proliferation and survival on this pathway.
authors: Department of Medicine, Division of Hematology-Oncology, University of California Los Angeles (UCLA), Los Angeles, CA, USA. matefi@ucla.edu.
authors: Mohammad
authors: M
authors: Atefi
authors: Department of Molecular and Medical Pharmacology, University of California Los Angeles (UCLA), Los Angeles, CA, USA. bjoern.r.titz@googlemail.com.
authors: Bjoern
authors: B
authors: Titz
authors: Department of Medicine, Division of Hematology-Oncology, University of California Los Angeles (UCLA), Los Angeles, CA, USA. eavramis@gmail.com.
authors: Earl
authors: E
authors: Avramis
authors: New York University, New York, USA. Charles.Ng@med.nyu.edu.
authors: Charles
authors: C
authors: Ng
authors: Department of Medicine, Division of Hematology-Oncology, University of California Los Angeles (UCLA), Los Angeles, CA, USA. DeWong@mednet.ucla.edu.
authors: Deborah J L
authors: DJ
authors: Wong
authors: Department of Medicine, Division of Hematology-Oncology, University of California Los Angeles (UCLA), Los Angeles, CA, USA. amandalassen@hotmail.com.
authors: Amanda
authors: A
authors: Lassen
authors: Department of Medicine, Division of Hematology-Oncology, University of California Los Angeles (UCLA), Los Angeles, CA, USA. cerni.michael@gmail.com.
authors: Michael
authors: M
authors: Cerniglia
authors: Department of Medicine, Division of Hematology-Oncology, University of California Los Angeles (UCLA), Los Angeles, CA, USA. helena.escuin@gmail.com.
authors: Helena
authors: H
authors: Escuin-Ordinas
authors: Department of Medicine, Division of Hematology-Oncology, University of California Los Angeles (UCLA), Los Angeles, CA, USA. DFoulad@mednet.ucla.edu.
authors: David
authors: D
authors: Foulad
authors: Department of Surgery, Division of Surgical-Oncology, University of California Los Angeles (UCLA), Los Angeles, CA, USA. BComin@mednet.ucla.edu.|Jonsson Comprehensive Cancer Center at UCLA, Los Angeles, CA, USA. BComin@mednet.ucla.edu.
authors: Begonya
authors: B
authors: Comin-Anduix
authors: Department of Molecular and Medical Pharmacology, University of California Los Angeles (UCLA), Los Angeles, CA, USA. TGraeber@mednet.ucla.edu.|Jonsson Comprehensive Cancer Center at UCLA, Los Angeles, CA, USA. TGraeber@mednet.ucla.edu.
authors: Thomas G
authors: TG
authors: Graeber
authors: Department of Medicine, Division of Hematology-Oncology, University of California Los Angeles (UCLA), Los Angeles, CA, USA. aribas@mednet.ucla.edu.|Department of Molecular and Medical Pharmacology, University of California Los Angeles (UCLA), Los Angeles, CA, USA. aribas@mednet.ucla.edu.|Department of Surgery, Division of Surgical-Oncology, University of California Los Angeles (UCLA), Los Angeles, CA, USA. aribas@mednet.ucla.edu.|Jonsson Comprehensive Cancer Center at UCLA, Los Angeles, CA, USA. aribas@mednet.ucla.edu.|Department of Medicine, Division of Hematology-Oncology, Jonsson Comprehensive Cancer Center, University of California Los Angeles (UCLA), 11-934 Factor Building, 10833 Le Conte Avenue, Los Angeles, CA, 90095-1782, USA. aribas@mednet.ucla.edu.
authors: Antoni
authors: A
authors: Ribas
mesh_terms: D017209:Apoptosis / Q000235:genetics; D002453:Cell Cycle / Q000235:genetics; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000235:genetics; D019938:Cyclin D1 / Q000235:genetics; D056743:Cyclin D3 / Q000235:genetics; D020558:GTP Phosphohydrolases / Q000235:genetics*; D038362:Glycogen Synthase Kinase 3 / Q000235:genetics; D000071679:Glycogen Synthase Kinase 3 beta; D006801:Humans; D020935:MAP Kinase Signaling System / Q000235:genetics*; D008545:Melanoma / Q000235:genetics*; D008565:Membrane Proteins / Q000235:genetics*; D009154:Mutation / Q000235:genetics*; D015398:Signal Transduction / Q000235:genetics; D014158:Transcription, Genetic / Q000235:genetics; D048490:raf Kinases / Q000235:genetics*
chemical_list: C530104:CCND1 protein, human; C534696:CCND3 protein, human; D056743:Cyclin D3; D008565:Membrane Proteins; D019938:Cyclin D1; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; D048490:raf Kinases; D038362:Glycogen Synthase Kinase 3; D020558:GTP Phosphohydrolases; C579846:NRAS protein, human
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