Intrinsic resistance to selumetinib, a selective inhibitor of MEK1/2, by cAMP-dependent protein kinase A activation in human lung and colorectal cancer cells

Br J Cancer. 2012 May 8;106(10):1648-59. doi: 10.1038/bjc.2012.129.


Background: MEK is activated in ∼40% colorectal cancer (CRC) and 20-30% non-small cell lung cancer (NSCLC). Selumetinib is a selective inhibitor of MEK1/2, which is currently in clinical development.

Methods: We evaluated the effects of selumetinib in vitro and in vivo in CRC and NSCLC cell lines to identify cancer cell characteristics correlating with sensitivity to MEK inhibition.

Results: Five NSCLC and six CRC cell lines were treated with selumetinib and classified according to the median inhibitory concentration (IC(50)) values as sensitive (≤1 μM) or resistant (>1 μM). In selumetinib-sensitive cancer cell lines, selumetinib treatment induced G1 cell-cycle arrest and apoptosis and suppression of tumour growth as xenografts in immunodeficient mice. Evaluation of intracellular effector proteins and analysis of gene mutations showed no correlation with selumetinib sensitivity. Microarray gene expression profiles revealed that the activation of cAMP-dependent protein kinase A (PKA) was associated with MEK inhibitor resistance. Combined targeting of both MEK and PKA resulted in cancer cell growth inhibition of MEK inhibitor-resistant cancer cell lines in vitro and in vivo.

Conclusion: This study provides molecular insights to explain resistance to an MEK inhibitor in human cancer cell lines.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Apoptosis / drug effects
  • Benzimidazoles / pharmacology*
  • Cell Cycle / drug effects
  • Cell Line, Tumor
  • Cell Proliferation
  • Colorectal Neoplasms / drug therapy*
  • Colorectal Neoplasms / pathology
  • Cyclic AMP-Dependent Protein Kinases / physiology*
  • Drug Resistance, Neoplasm
  • Enzyme Activation / drug effects
  • Gene Expression Profiling
  • Humans
  • Lung Neoplasms / drug therapy*
  • Lung Neoplasms / pathology
  • Mitogen-Activated Protein Kinase Kinases / antagonists & inhibitors*
  • Mutation
  • Xenograft Model Antitumor Assays


  • AZD 6244
  • Benzimidazoles
  • Cyclic AMP-Dependent Protein Kinases
  • Mitogen-Activated Protein Kinase Kinases