Inhibitors of MEK1/2 interact with UCN-01 to induce apoptosis and reduce colony formation in mammary and prostate carcinoma cells

Cancer Biol Ther. 2002 May-Jun;1(3):243-53. doi: 10.4161/cbt.75.


Recent studies have suggested that inhibition of the mitogen activated protein kinase (MAPK) pathway as well as abrogation of cell cycle check-point control can potentiate the lethal actions of chemotherapeutic drugs and radiation. We therefore investigated the impact of combined exposure to the check-point abrogator (UCN-01) in conjunction with MEK1/2 inhibitors upon survival of breast and prostate carcinoma cells. Treatment of cells with UCN-01 alone resulted in prolonged activation of the MAPK pathway. Inhibition of MEK1/2 caused modest reductions in basal MAPK activity and transiently suppressed UCN-01-stimulated MAPK activity below that of MEK1/2 inhibitor alone. Significantly, combined, but not individual, exposure of cells to UCN-01 and MEK1/2 inhibitors enhanced BAX association with mitochondria and triggered release of cytochrome c into the cytosol, accompanied by activation of effector pro-caspases, resulting in a greater than additive potentiation of apoptosis within 1 8-24h. Radiation exposure of drug treated cells did not further enhance apoptosis. Treatment of cells with both caspase 9 and caspase 8 inhibitors was required to completely inhibit apoptosis in carcinoma cells. Overexpression of Bcl-(xL) blocked cytochrome c release and cell killing induced by the drug combination. Colony forming assays demonstrated that cells exposed to both agents exhibited a substantial reduction in clonogenic survival compared to either drug alone; moreover, radiation further reduced clonogenic survival despite failing to promote additional apoptosis. Collectively, these data demonstrate that combined exposure of carcinoma cells to UCN-01 and MEK1/2 inhibitors induces apoptosis and interacts with radiation to further reduce clonogenic survival.

Publication types

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

MeSH terms

  • Alkaloids / pharmacology*
  • Apoptosis / drug effects*
  • Apoptosis / radiation effects
  • Breast Neoplasms / enzymology
  • Breast Neoplasms / pathology*
  • Caspases / metabolism
  • Cell Cycle / drug effects
  • Cell Cycle / radiation effects
  • Cell Division / drug effects
  • Cell Division / radiation effects
  • Colony-Forming Units Assay
  • Cytochrome c Group / metabolism
  • Drug Synergism
  • Enzyme Activation
  • Enzyme Inhibitors / pharmacology*
  • Female
  • Flavonoids / pharmacology
  • Humans
  • In Situ Nick-End Labeling
  • MAP Kinase Kinase 1
  • MAP Kinase Kinase 2
  • MAP Kinase Signaling System / drug effects
  • MAP Kinase Signaling System / radiation effects
  • Male
  • Membrane Potentials / drug effects
  • Membrane Potentials / radiation effects
  • Mitochondria / drug effects
  • Mitochondria / physiology
  • Mitochondria / radiation effects
  • Mitogen-Activated Protein Kinase Kinases / antagonists & inhibitors*
  • Mitogen-Activated Protein Kinase Kinases / metabolism
  • Prostatic Neoplasms / enzymology
  • Prostatic Neoplasms / pathology*
  • Protein Serine-Threonine Kinases / antagonists & inhibitors*
  • Protein-Tyrosine Kinases / antagonists & inhibitors*
  • Staurosporine / analogs & derivatives
  • Stem Cells / drug effects
  • Stem Cells / metabolism
  • Stem Cells / radiation effects
  • Tumor Cells, Cultured


  • Alkaloids
  • Cytochrome c Group
  • Enzyme Inhibitors
  • Flavonoids
  • 7-hydroxystaurosporine
  • MAP2K2 protein, human
  • Protein-Tyrosine Kinases
  • Protein Serine-Threonine Kinases
  • MAP Kinase Kinase 1
  • MAP Kinase Kinase 2
  • MAP2K1 protein, human
  • Mitogen-Activated Protein Kinase Kinases
  • Caspases
  • Staurosporine
  • 2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one