Cytokinetically quiescent (G0/G1) human multiple myeloma cells are susceptible to simultaneous inhibition of Chk1 and MEK1/2

Blood. 2011 Nov 10;118(19):5189-200. doi: 10.1182/blood-2011-02-339432. Epub 2011 Sep 12.


Effects of Chk1 and MEK1/2 inhibition were investigated in cytokinetically quiescent multiple myeloma (MM) and primary CD138(+) cells. Coexposure to the Chk1 and MEK1/2 inhibitors AZD7762 and selumetinib (AZD6244) robustly induced apoptosis in various MM cells and CD138(+) primary samples, but spared normal CD138(-) and CD34(+) cells. Furthermore, Chk1/MEK1/2 inhibitor treatment of asynchronized cells induced G(0)/G(1) arrest and increased apoptosis in all cell-cycle phases, including G(0)/G(1). To determine whether this regimen is active against quiescent G(0)/G(1) MM cells, cells were cultured in low-serum medium to enrich the G(0)/G(1) population. G(0)/G(1)-enriched cells exhibited diminished sensitivity to conventional agents (eg, Taxol and VP-16) but significantly increased susceptibility to Chk1 ± MEK1/2 inhibitors or Chk1 shRNA knock-down. These events were associated with increased γH2A.X expression/foci formation and Bim up-regulation, whereas Bim shRNA knock-down markedly attenuated lethality. Immunofluorescent analysis of G(0)/G(1)-enriched or primary MM cells demonstrated colocalization of activated caspase-3 and the quiescent (G(0)) marker statin, a nuclear envelope protein. Finally, Chk1/MEK1/2 inhibition increased cell death in the Hoechst-positive (Hst(+)), low pyronin Y (PY)-staining (2N Hst(+)/PY(-)) G(0) population and in sorted small side-population (SSP) MM cells. These findings provide evidence that cytokinetically quiescent MM cells are highly susceptible to simultaneous Chk1 and MEK1/2 inhibition.

Publication types

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

MeSH terms

  • Apoptosis / drug effects
  • Benzimidazoles / administration & dosage
  • Benzimidazoles / therapeutic use
  • Cell Line, Tumor
  • Checkpoint Kinase 1
  • DNA Damage
  • G1 Phase
  • Humans
  • Interleukin-6 / metabolism
  • MAP Kinase Kinase 1 / antagonists & inhibitors*
  • MAP Kinase Kinase 2 / antagonists & inhibitors*
  • Multiple Myeloma / drug therapy*
  • Multiple Myeloma / metabolism*
  • Multiple Myeloma / pathology
  • Protein Kinase Inhibitors / administration & dosage
  • Protein Kinase Inhibitors / therapeutic use*
  • Protein Kinases / metabolism*
  • Resting Phase, Cell Cycle
  • Syndecan-1 / metabolism
  • Thiophenes / administration & dosage
  • Thiophenes / therapeutic use
  • Urea / administration & dosage
  • Urea / analogs & derivatives
  • Urea / therapeutic use


  • 3-(carbamoylamino)-5-(3-fluorophenyl)-N-(3-piperidyl)thiophene-2-carboxamide
  • AZD 6244
  • Benzimidazoles
  • IL6 protein, human
  • Interleukin-6
  • Protein Kinase Inhibitors
  • SDC1 protein, human
  • Syndecan-1
  • Thiophenes
  • Urea
  • Protein Kinases
  • MAP2K2 protein, human
  • CHEK1 protein, human
  • Checkpoint Kinase 1
  • MAP Kinase Kinase 1
  • MAP Kinase Kinase 2
  • MAP2K1 protein, human