Hepatocyte growth factor enhances protein phosphatase Cdc25A inhibitor compound 5-induced hepatoma cell growth inhibition via Akt-mediated MAPK pathway

J Cell Physiol. 2005 Jun;203(3):510-9. doi: 10.1002/jcp.20243.

Abstract

We have previously shown that Compound 5 (Cpd 5), an inhibitor of protein phosphatase Cdc25A, inhibits Hep3B human hepatoma cell growth. We now show that hepatocyte growth factor (HGF), a hepatocyte growth stimulant, can strongly enhance Cpd 5-induced growth inhibition in Hep3B cells, and this enhancement in cell growth inhibition is correlated with a much stronger ERK phosphorylation when compared to cells treated with Cpd 5 or HGF separately. We found that HGF/Cpd 5-induced ERK phosphorylation and cell growth inhibition were mediated by Akt (protein kinase B) pathway, since combination HGF/Cpd 5 treatment of Hep3B cells inhibited Akt phosphorylation at Ser-473 and its kinase activity, which led to the suppression of Raf-1 phosphorylation at Ser-259. The suppression of Raf-1 Ser-259 phosphorylation caused the induction of Raf-1 kinase activity, as well as hyper-ERK phosphorylation. Transient transfection of Hep3B cells with dominant negative Akt c-DNA further enhanced both Cpd 5- and HGF/Cpd 5-induced ERK phosphorylation, while over-expression of wild-type Akt c-DNA diminished their effects. In contrast, HGF antagonized the growth inhibitory actions of Cpd 5 on normal rat hepatocytes, thus showing a selective effect on tumor cells compared to normal cells. Our data suggest that Akt kinase negatively regulates MAPK activity at the Akt-Raf level. Suppression of Akt activity by either combination HGF/Cpd 5 treatment or by dominant negative Akt c-DNA transfection antagonizes the Akt inhibitory effect on Raf-1, resulting in an enhancement of Cpd 5-induced MAPK activation and cell growth inhibition.

Publication types

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

MeSH terms

  • Animals
  • Antineoplastic Combined Chemotherapy Protocols / pharmacology
  • Cell Proliferation / drug effects
  • Cells, Cultured
  • DNA, Complementary / genetics
  • DNA, Complementary / pharmacology
  • Drug Screening Assays, Antitumor
  • Drug Synergism
  • Enzyme Inhibitors / pharmacology
  • Enzyme Inhibitors / therapeutic use
  • Extracellular Signal-Regulated MAP Kinases / drug effects
  • Extracellular Signal-Regulated MAP Kinases / metabolism
  • Growth Inhibitors / pharmacology*
  • Hepatocyte Growth Factor / pharmacology*
  • Hepatocyte Growth Factor / therapeutic use
  • Hepatocytes / drug effects*
  • Hepatocytes / enzymology
  • Humans
  • Liver Neoplasms, Experimental / drug therapy*
  • Liver Neoplasms, Experimental / enzymology
  • MAP Kinase Signaling System / drug effects*
  • MAP Kinase Signaling System / physiology
  • Mutation / genetics
  • Phosphorylation / drug effects
  • Protein Serine-Threonine Kinases / drug effects
  • Protein Serine-Threonine Kinases / genetics
  • Protein Serine-Threonine Kinases / metabolism*
  • Proto-Oncogene Proteins / drug effects
  • Proto-Oncogene Proteins / genetics
  • Proto-Oncogene Proteins / metabolism*
  • Proto-Oncogene Proteins c-akt
  • Proto-Oncogene Proteins c-raf / drug effects
  • Proto-Oncogene Proteins c-raf / metabolism
  • Rats
  • Rats, Inbred F344
  • Tumor Cells, Cultured
  • Vitamin K / analogs & derivatives*
  • Vitamin K / pharmacology*
  • cdc25 Phosphatases / antagonists & inhibitors
  • cdc25 Phosphatases / metabolism

Substances

  • 2-(2-hydroxyethylsulfanyl)-3-methyl-1,4-naphthoquinone
  • DNA, Complementary
  • Enzyme Inhibitors
  • Growth Inhibitors
  • Proto-Oncogene Proteins
  • Vitamin K
  • Hepatocyte Growth Factor
  • AKT1 protein, human
  • Akt1 protein, rat
  • Protein Serine-Threonine Kinases
  • Proto-Oncogene Proteins c-akt
  • Proto-Oncogene Proteins c-raf
  • Extracellular Signal-Regulated MAP Kinases
  • CDC25A protein, human
  • Cdc25a protein, rat
  • cdc25 Phosphatases