Inhibition of mutant BRAF splice variant signaling by next-generation, selective RAF inhibitors

Pigment Cell Melanoma Res. 2014 May;27(3):479-84. doi: 10.1111/pcmr.12218. Epub 2014 Feb 10.


Vemurafenib and dabrafenib block MEK-ERK1/2 signaling and cause tumor regression in the majority of advanced-stage BRAF(V600E) melanoma patients; however, acquired resistance and paradoxical signaling have driven efforts for more potent and selective RAF inhibitors. Next-generation RAF inhibitors, such as PLX7904 (PB04), effectively inhibit RAF signaling in BRAF(V600E) melanoma cells without paradoxical effects in wild-type cells. Furthermore, PLX7904 blocks the growth of vemurafenib-resistant BRAF(V600E) cells that express mutant NRAS. Acquired resistance to vemurafenib and dabrafenib is also frequently driven by expression of mutation BRAF splice variants; thus, we tested the effects of PLX7904 and its clinical analog, PLX8394 (PB03), in BRAF(V600E) splice variant-mediated vemurafenib-resistant cells. We show that paradox-breaker RAF inhibitors potently block MEK-ERK1/2 signaling, G1/S cell cycle events, survival and growth of vemurafenib/PLX4720-resistant cells harboring distinct BRAF(V600E) splice variants. These data support the further investigation of paradox-breaker RAF inhibitors as a second-line treatment option for patients failing on vemurafenib or dabrafenib.

Keywords: BRAF; Paradox-breaker RAF inhibitor; splice variant; vemurafenib resistance.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Cycle / drug effects
  • Cell Line, Tumor
  • Drug Resistance, Neoplasm / drug effects
  • Enzyme Activation / drug effects
  • GTP Phosphohydrolases / antagonists & inhibitors
  • GTP Phosphohydrolases / genetics
  • Genes, ras
  • Humans
  • Imidazoles / pharmacology
  • Indoles / pharmacology
  • MAP Kinase Signaling System / drug effects
  • Melanoma / enzymology*
  • Melanoma / pathology
  • Membrane Proteins / antagonists & inhibitors
  • Membrane Proteins / genetics
  • Mutation, Missense
  • Neoplasm Proteins / antagonists & inhibitors*
  • Neoplasm Proteins / genetics
  • Oximes / pharmacology
  • Phosphorylation / drug effects
  • Protein Isoforms / antagonists & inhibitors
  • Protein Kinase Inhibitors / pharmacology*
  • Protein Processing, Post-Translational / drug effects
  • Proto-Oncogene Proteins B-raf / antagonists & inhibitors*
  • Proto-Oncogene Proteins B-raf / genetics
  • Signal Transduction / drug effects
  • Sulfonamides / pharmacology
  • Tumor Stem Cell Assay
  • Vemurafenib
  • raf Kinases / antagonists & inhibitors*


  • Imidazoles
  • Indoles
  • Membrane Proteins
  • Neoplasm Proteins
  • Oximes
  • Protein Isoforms
  • Protein Kinase Inhibitors
  • Sulfonamides
  • Vemurafenib
  • BRAF protein, human
  • Proto-Oncogene Proteins B-raf
  • raf Kinases
  • GTP Phosphohydrolases
  • NRAS protein, human
  • dabrafenib