HGF-mediated apoptosis via p53/bax-independent pathway activating JNK1.
Current studies have indicated both positive and negative roles for the hepatocyte growth factor (HGF)/c-met receptor signaling system in tumor development. Recently, we have shown that HGF has the capacity to induce both growth inhibition and programmed cell death in aflatoxin-transformed (AFLB8) rat liver epithelial cells. Using the same cell line, we have now investigated a potential mechanism for HGF-induced apoptosis. Immunoblot analysis of bcl-2 gene family member (bax, bcl-2, bclX-s/l) expression showed no correlation with HGF treatment, suggesting that HGF-mediated apoptosis is bax independent. Following HGF treatment retinoblastoma protein (pRB) was present in the hypophosphorylated state. HGF treatment increased cyclin A, cyclin G1 and nuclear transcriptional factor (NFkappaB) protein expression. However, electrophoretic mobility shift analysis showed that NFkappaB activity decreased with HGF treatment. Under these apoptotic conditions, c-Jun N-terminal kinase (JNK1) and extracellular signal-regulated kinase (ERK2) were activated with lower level activation of ERK2, while no involvement of phosphatidylinositol-3 kinase was observed. Epidermal growth factor (EGF) was not protective, and actually induced cells to undergo apoptosis to a level similar to that of HGF alone or EGF/HGF in combination. These results suggest the possibility of cross-talk between HGF/c-met and EGF/EGFR signaling pathways, and the involvement of JNK1 induction in HGF-mediated apoptotic cell death.
Conner
E A
EA
Laboratory of Experimental Carcinogenesis, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
Teramoto
T
T
Wirth
P J
PJ
Kiss
A
A
Garfield
S
S
Thorgeirsson
S S
SS
D000348:Aflatoxins / Q000633:toxicity; D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism / Q000502:physiology*; D002461:Cell Line, Transformed / Q000187:drug effects; D016213:Cyclins / Q000096:biosynthesis / Q000235:genetics; D004789:Enzyme Activation / Q000187:drug effects; D004815:Epidermal Growth Factor / Q000494:pharmacology; D066246:ErbB Receptors / Q000502:physiology; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D019254:Genes, bcl-2; D017228:Hepatocyte Growth Factor / Q000494:pharmacology*; D048031:JNK Mitogen-Activated Protein Kinases; D008099:Liver / Q000166:cytology / Q000187:drug effects*; D019950:Mitogen-Activated Protein Kinase 1; D020928:Mitogen-Activated Protein Kinases; D016328:NF-kappa B / Q000096:biosynthesis / Q000235:genetics; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D011518:Proto-Oncogene Proteins / Q000502:physiology*; D019253:Proto-Oncogene Proteins c-bcl-2; D051381:Rats; D011994:Recombinant Proteins / Q000494:pharmacology; D016160:Retinoblastoma Protein / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D016159:Tumor Suppressor Protein p53 / Q000502:physiology*; D051028:bcl-2-Associated X Protein
D000348:Aflatoxins; C494828:Bax protein, rat; D016213:Cyclins; D016328:NF-kappa B; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D011994:Recombinant Proteins; D016160:Retinoblastoma Protein; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein; D004815:Epidermal Growth Factor; D017228:Hepatocyte Growth Factor; D019869:Phosphatidylinositol 3-Kinases; D066246:ErbB Receptors; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D020928:Mitogen-Activated Protein Kinases