Hepatocyte growth factor enhances death receptor-induced apoptosis by up-regulating DR5.
BACKGROUND
Hepatocyte growth factor (HGF) and its receptor c-MET are commonly expressed in malignant gliomas and embryonic neuroectodermal tumors including medulloblastoma and appear to play an important role in the growth and dissemination of these malignancies. Dependent on cell context and the involvement of specific downstream effectors, both pro- and anti-apoptotic effects of HGF have been reported.


METHODS
Human medulloblastoma cells were treated with HGF for 24-72 hours followed by death receptor ligand TRAIL (Tumor necrosis factor-related apoptosis-inducing ligand) for 24 hours. Cell death was measured by MTT and Annexin-V/PI flow cytometric analysis. Changes in expression levels of targets of interest were measured by Northern blot analysis, quantitative reverse transcription-PCR, Western blot analysis as well as immunoprecipitation.


RESULTS
In this study, we show that HGF promotes medulloblastoma cell death induced by TRAIL. TRAIL alone triggered apoptosis in DAOY cells and death was enhanced by pre-treating the cells with HGF for 24-72 h prior to the addition of TRAIL. HGF (100 ng/ml) enhanced TRAIL (10 ng/ml) induced cell death by 36% (P<0.001). No cell death was associated with HGF alone. Treating cells with PHA-665752, a specific c-Met receptor tyrosine kinase inhibitor, significantly abrogated the enhancement of TRAIL-induced cell death by HGF, indicating that its death promoting effect requires activation of its canonical receptor tyrosine kinase. Cell death induced by TRAIL+HGF was predominately apoptotic involving both extrinsic and intrinsic pathways as evidenced by the increased activation of caspase-3, 8, 9. Promotion of apoptosis by HGF occurred via the increased expression of the death receptor DR5 and enhanced formation of death-inducing signal complexes (DISC).


CONCLUSIONS
Taken together, these and previous findings indicate that HGF:c-Met pathway either promotes or inhibits medulloblastoma cell death via pathway and context specific mechanisms.
Li
Yang
Y
Hugo W, Moser Research Institute at Kennedy Krieger, Baltimore, MD, USA. yli44@jhu.edu
Fan
Xing
X
Goodwin
C Rory
CR
Laterra
John
J
Xia
Shuli
S
D017209:Apoptosis / Q000187:drug effects / Q000235:genetics*; D045744:Cell Line, Tumor; D053418:Death Domain Receptor Signaling Adaptor Proteins / Q000096:biosynthesis / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic; D017228:Hepatocyte Growth Factor / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D008527:Medulloblastoma / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D009373:Neoplasms, Germ Cell and Embryonal / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D019859:Proto-Oncogene Proteins c-met / Q000235:genetics / Q000378:metabolism; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics*; D011994:Recombinant Proteins / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D013450:Sulfones / Q000494:pharmacology; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000378:metabolism
C480541:5-((2,6-dichlorobenzyl)sulfonyl)-3-((3,5-dimethyl-4-((2-(pyrrolidin-1-ylmethyl)pyrrolidin-1-yl)carbonyl)-1H-pyrrol-2-yl)methylene)-1,3-dihydro-2H-indol-2-one; D053418:Death Domain Receptor Signaling Adaptor Proteins; D007211:Indoles; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D011994:Recombinant Proteins; D013450:Sulfones; D053221:TNF-Related Apoptosis-Inducing Ligand; D017228:Hepatocyte Growth Factor; D019859:Proto-Oncogene Proteins c-met