Adaptive resistance of melanoma cells to RAF inhibition via reversible induction of a slowly dividing de-differentiated state

Mol Syst Biol. 2017 Jan 9;13(1):905. doi: 10.15252/msb.20166796.


Treatment of BRAF-mutant melanomas with MAP kinase pathway inhibitors is paradigmatic of the promise of precision cancer therapy but also highlights problems with drug resistance that limit patient benefit. We use live-cell imaging, single-cell analysis, and molecular profiling to show that exposure of tumor cells to RAF/MEK inhibitors elicits a heterogeneous response in which some cells die, some arrest, and the remainder adapt to drug. Drug-adapted cells up-regulate markers of the neural crest (e.g., NGFR), a melanocyte precursor, and grow slowly. This phenotype is transiently stable, reverting to the drug-naïve state within 9 days of drug withdrawal. Transcriptional profiling of cell lines and human tumors implicates a c-Jun/ECM/FAK/Src cascade in de-differentiation in about one-third of cell lines studied; drug-induced changes in c-Jun and NGFR levels are also observed in xenograft and human tumors. Drugs targeting the c-Jun/ECM/FAK/Src cascade as well as BET bromodomain inhibitors increase the maximum effect (Emax) of RAF/MEK kinase inhibitors by promoting cell killing. Thus, analysis of reversible drug resistance at a single-cell level identifies signaling pathways and inhibitory drugs missed by assays that focus on cell populations.

Keywords: BRAFV600E melanomas; RAF and MEK inhibitors; adaptive and reversible drug resistance; de‐differentiated NGFRHigh state.

MeSH terms

  • Animals
  • Cell Differentiation / drug effects
  • Cell Line, Tumor
  • Cell Proliferation / drug effects
  • Cell Survival / drug effects
  • Drug Resistance, Neoplasm / drug effects
  • Gene Expression Profiling / methods
  • Gene Expression Regulation, Neoplastic / drug effects
  • Humans
  • Indoles / administration & dosage*
  • Indoles / pharmacology
  • MAP Kinase Signaling System / drug effects*
  • Melanoma / drug therapy
  • Melanoma / genetics*
  • Mice
  • Mutation
  • Nerve Tissue Proteins / genetics*
  • Proto-Oncogene Proteins B-raf / genetics*
  • Receptors, Nerve Growth Factor / genetics*
  • Single-Cell Analysis
  • Sulfonamides / administration & dosage*
  • Sulfonamides / pharmacology
  • Vemurafenib
  • Xenograft Model Antitumor Assays


  • Indoles
  • NGFR protein, human
  • Nerve Tissue Proteins
  • Receptors, Nerve Growth Factor
  • Sulfonamides
  • Vemurafenib
  • BRAF protein, human
  • Proto-Oncogene Proteins B-raf