title: 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.affiliation: Thomas E. Starzl Transplantation Institute, Department of Surgery, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213, USA. wangz@pitt.edu
authors.forename: Ziqiu
authors.initials: Z
authors.lastname: Wang
authors.forename: Meifang
authors.initials: M
authors.lastname: Wang
authors.forename: Brian I
authors.initials: BI
authors.lastname: Carr
mesh_terms: D000818:Animals; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D018076:DNA, Complementary / Q000235:genetics / Q000494:pharmacology; D004354:Drug Screening Assays, Antitumor; D004357:Drug Synergism; D004791:Enzyme Inhibitors / Q000494:pharmacology / Q000627:therapeutic use; D048049:Extracellular Signal-Regulated MAP Kinases / Q000187:drug effects / Q000378:metabolism; D006131:Growth Inhibitors / Q000494:pharmacology*; D017228:Hepatocyte Growth Factor / Q000494:pharmacology* / Q000627:therapeutic use; D022781:Hepatocytes / Q000187:drug effects* / Q000201:enzymology; D006801:Humans; D008114:Liver Neoplasms, Experimental / Q000188:drug therapy* / Q000201:enzymology; D020935:MAP Kinase Signaling System / Q000187:drug effects* / Q000502:physiology; D009154:Mutation / Q000235:genetics; D010766:Phosphorylation / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D019908:Proto-Oncogene Proteins c-raf / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D011916:Rats, Inbred F344; D014407:Tumor Cells, Cultured; D014812:Vitamin K / Q000031:analogs & derivatives* / Q000494:pharmacology*; D020687:cdc25 Phosphatases / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: C446520:2-(2-hydroxyethylsulfanyl)-3-methyl-1,4-naphthoquinone; D018076:DNA, Complementary; D004791:Enzyme Inhibitors; D006131:Growth Inhibitors; D011518:Proto-Oncogene Proteins; D014812:Vitamin K; D017228:Hepatocyte Growth Factor; C494918:AKT1 protein, human; C494920:Akt1 protein, rat; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D019908:Proto-Oncogene Proteins c-raf; D048049:Extracellular Signal-Regulated MAP Kinases; C517004:CDC25A protein, human; C517007:Cdc25a protein, rat; D020687:cdc25 Phosphatases