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

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.

• Authors: Ziqiu Wang, Meifang Wang, Brian I Carr
• Journal: Journal of cellular physiology (J Cell Physiol) Vol. 203 Issue 3 Pg. 510-9 (Jun 2005) ISSN: 0021-9541 [Print] United States
• PMID: 15534860 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, U.S. Gov't, P.H.S.)
• Copyright: Copyright 2004 Wiley-Liss, Inc.

Chemical References

• 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

Topics

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