Melanomas Acquire Resistance to B-RAF(V600E) Inhibition by RTK or N-RAS Upregulation

Nature. 2010 Dec 16;468(7326):973-7. doi: 10.1038/nature09626. Epub 2010 Nov 24.

Abstract

Activating B-RAF(V600E) (also known as BRAF) kinase mutations occur in ∼7% of human malignancies and ∼60% of melanomas. Early clinical experience with a novel class I RAF-selective inhibitor, PLX4032, demonstrated an unprecedented 80% anti-tumour response rate among patients with B-RAF(V600E)-positive melanomas, but acquired drug resistance frequently develops after initial responses. Hypotheses for mechanisms of acquired resistance to B-RAF inhibition include secondary mutations in B-RAF(V600E), MAPK reactivation, and activation of alternative survival pathways. Here we show that acquired resistance to PLX4032 develops by mutually exclusive PDGFRβ (also known as PDGFRB) upregulation or N-RAS (also known as NRAS) mutations but not through secondary mutations in B-RAF(V600E). We used PLX4032-resistant sub-lines artificially derived from B-RAF(V600E)-positive melanoma cell lines and validated key findings in PLX4032-resistant tumours and tumour-matched, short-term cultures from clinical trial patients. Induction of PDGFRβ RNA, protein and tyrosine phosphorylation emerged as a dominant feature of acquired PLX4032 resistance in a subset of melanoma sub-lines, patient-derived biopsies and short-term cultures. PDGFRβ-upregulated tumour cells have low activated RAS levels and, when treated with PLX4032, do not reactivate the MAPK pathway significantly. In another subset, high levels of activated N-RAS resulting from mutations lead to significant MAPK pathway reactivation upon PLX4032 treatment. Knockdown of PDGFRβ or N-RAS reduced growth of the respective PLX4032-resistant subsets. Overexpression of PDGFRβ or N-RAS(Q61K) conferred PLX4032 resistance to PLX4032-sensitive parental cell lines. Importantly, MAPK reactivation predicts MEK inhibitor sensitivity. Thus, melanomas escape B-RAF(V600E) targeting not through secondary B-RAF(V600E) mutations but via receptor tyrosine kinase (RTK)-mediated activation of alternative survival pathway(s) or activated RAS-mediated reactivation of the MAPK pathway, suggesting additional therapeutic strategies.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Base Sequence
  • Cell Line, Tumor
  • Drug Resistance, Neoplasm* / drug effects
  • Enzyme Activation / drug effects
  • Gene Expression Regulation, Neoplastic* / drug effects
  • Genes, ras / genetics*
  • Humans
  • Indoles / pharmacology
  • Indoles / therapeutic use
  • MAP Kinase Signaling System / drug effects
  • Melanoma / drug therapy*
  • Melanoma / enzymology*
  • Melanoma / genetics
  • Melanoma / pathology
  • Mitogen-Activated Protein Kinase Kinases / antagonists & inhibitors
  • Mutation / genetics
  • Oligonucleotide Array Sequence Analysis
  • Protein Kinase Inhibitors / pharmacology
  • Protein Kinase Inhibitors / therapeutic use
  • Proto-Oncogene Proteins B-raf / antagonists & inhibitors*
  • Proto-Oncogene Proteins B-raf / chemistry
  • Proto-Oncogene Proteins B-raf / genetics
  • Proto-Oncogene Proteins B-raf / metabolism
  • Receptor Protein-Tyrosine Kinases / metabolism*
  • Receptor, Platelet-Derived Growth Factor beta / biosynthesis
  • Receptor, Platelet-Derived Growth Factor beta / genetics
  • Sulfonamides / pharmacology
  • Sulfonamides / therapeutic use
  • Up-Regulation / drug effects
  • Vemurafenib

Substances

  • Indoles
  • Protein Kinase Inhibitors
  • Sulfonamides
  • Vemurafenib
  • Receptor Protein-Tyrosine Kinases
  • Receptor, Platelet-Derived Growth Factor beta
  • BRAF protein, human
  • Proto-Oncogene Proteins B-raf
  • Mitogen-Activated Protein Kinase Kinases

Associated data

  • GEO/GSE24862
  • GEO/GSE24890