Mechanistic study on growth suppression and apoptosis induction by targeting hepatoma-derived growth factor in human hepatocellular carcinoma HepG2 cells.
Hepatoma-derived growth factor (HDGF) is frequently overexpressed in human cancer. The growth factor was previously demonstrated to be a survival factor as knock-down of HDGF suppresses the growth and induces apoptosis in human cancer cells through the Bad-mediated intrinsic apoptotic pathway. However, inactivation of Bad cannot completely repress the apoptosis induced upon HDGF knock-down, indicating the presence of other unidentified pathways. In the present study, HDGF knock-down was shown to trigger the Fas-mediated extrinsic apoptotic pathway in human hepatocellular carcinoma HepG2 cells through NF-kappaB signaling pathway. Increases in Fas expression and fas promoter activity were detected upon HDGF knock-down by Western blot analysis and luciferase reporter assay. Knock-down of fas inhibited HDGF knock-down effect on apoptosis induction and growth suppression as revealed by annexin V binding assay and soft agar assay. Down-regulation of IkappaBalpha was also observed upon HDGF knock-down. Overexpression of IkappaBalpha by transient transfection or inhibition of NF-kappaB by BAY11-7082 suppressed HDGF knock-down effect on fas promoter activation, Fas up-regulation, apoptosis induction and growth suppression. Furthermore, the interaction of Fas-mediated extrinsic and Bad-mediated intrinsic apoptotic pathways was demonstrated as a stronger inhibition on apoptosis induction and growth suppression upon HDGF knock-down was observed when both pathways were inactivated. The results therefore suggested that, through both intrinsic and extrinsic apoptotic pathways, HDGF may function as a survival factor and be a potential target for cancer therapy.
Tsang
Tsun Yee
TY
Department of Biochemistry, The Chinese University of Hong Kong, Shatin, Hong Kong SAR, China.
Tang
Wan Yee
WY
Tsang
Wing Pui
WP
Co
Ngai Na
NN
Kong
Siu Kai
SK
Kwok
Tim Tak
TT
D017304:Annexin A5 / Q000032:analysis / Q000378:metabolism; D017209:Apoptosis; D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D045744:Cell Line, Tumor; D053938:DNA Fragmentation / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D017930:Genes, Reporter; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics*; D008113:Liver Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D049410:Luciferases, Renilla / Q000378:metabolism; D008954:Models, Biological; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism; D009570:Nitriles / Q000494:pharmacology; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D034741:RNA, Small Interfering / Q000378:metabolism; D015398:Signal Transduction; D013450:Sulfones / Q000494:pharmacology; D014162:Transfection; D051025:bcl-Associated Death Protein / Q000378:metabolism; D019014:fas Receptor / Q000096:biosynthesis
C434003:3-(4-methylphenylsulfonyl)-2-propenenitrile; D017304:Annexin A5; D036341:Intercellular Signaling Peptides and Proteins; D016328:NF-kappa B; D009570:Nitriles; D016376:Oligonucleotides, Antisense; D034741:RNA, Small Interfering; D013450:Sulfones; D051025:bcl-Associated Death Protein; D019014:fas Receptor; C051610:hepatoma-derived growth factor; D049410:Luciferases, Renilla