A Functional Landscape of Resistance to MEK1/2 and CDK4/6 Inhibition in NRAS-Mutant Melanoma

Cancer Res. 2019 May 1;79(9):2352-2366. doi: 10.1158/0008-5472.CAN-18-2711. Epub 2019 Feb 28.


Combinatorial inhibition of MEK1/2 and CDK4/6 is currently undergoing clinical investigation in NRAS-mutant melanoma. To prospectively map the landscape of resistance to this investigational regimen, we utilized a series of gain- and loss-of-function forward genetic screens to identify modulators of resistance to clinical inhibitors of MEK1/2 and CDK4/6 alone and in combination. First, we identified NRAS-mutant melanoma cell lines that were dependent on NRAS for proliferation and sensitive to MEK1/2 and CDK4/6 combination treatment. We then used a genome-scale ORF overexpression screen and a CRISPR knockout screen to identify modulators of resistance to each inhibitor alone or in combination. These orthogonal screening approaches revealed concordant means of achieving resistance to this therapeutic modality, including tyrosine kinases, RAF, RAS, AKT, and PI3K signaling. Activated KRAS was sufficient to cause resistance to combined MEK/CDK inhibition and to replace genetic depletion of oncogenic NRAS. In summary, our comprehensive functional genetic screening approach revealed modulation of resistance to the inhibition of MEK1/2, CDK4/6, or their combination in NRAS-mutant melanoma. SIGNIFICANCE: These findings reveal that NRAS-mutant melanomas can acquire resistance to genetic ablation of NRAS or combination MEK1/2 and CDK4/6 inhibition by upregulating activity of the RTK-RAS-RAF and RTK-PI3K-AKT signaling cascade.

Publication types

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

MeSH terms

  • Antineoplastic Agents / pharmacology
  • Apoptosis
  • Cell Cycle Checkpoints
  • Cell Proliferation
  • Cyclin-Dependent Kinase 4 / antagonists & inhibitors*
  • Cyclin-Dependent Kinase 6 / antagonists & inhibitors*
  • Drug Resistance, Neoplasm / genetics*
  • GTP Phosphohydrolases / genetics*
  • Humans
  • MAP Kinase Kinase 1 / antagonists & inhibitors*
  • MAP Kinase Kinase 2 / antagonists & inhibitors*
  • Melanoma / drug therapy*
  • Melanoma / genetics
  • Melanoma / pathology
  • Membrane Proteins / genetics*
  • Mutation*
  • Phosphorylation
  • Signal Transduction / drug effects
  • Tumor Cells, Cultured


  • Antineoplastic Agents
  • Membrane Proteins
  • MAP2K2 protein, human
  • CDK4 protein, human
  • CDK6 protein, human
  • Cyclin-Dependent Kinase 4
  • Cyclin-Dependent Kinase 6
  • MAP Kinase Kinase 1
  • MAP Kinase Kinase 2
  • MAP2K1 protein, human
  • GTP Phosphohydrolases
  • NRAS protein, human