Activation of caspase-8 in transforming growth factor-beta-induced apoptosis of human hepatoma cells.
Transforming growth factor-beta1 (TGF-beta1) has been shown to induce apoptosis in normal or transformed hepatocytes. To elucidate the biochemical pathways leading to apoptosis induced by TGF-beta1 in human hepatoma cells (HuH-7), we examined the expression of Bcl-2-related proteins and X-chromosome-linked inhibitor of apoptosis (XIAP), and activation of the caspase cascade following TGF-beta1 treatment. Bcl-xL expression began to decline at 12 hours after TGF-beta1 treatment and progressively decreased to very low levels in a time-dependent manner. Bax expression showed a little change throughout the experiment. On the other hand, activation of caspase-8 was clearly observed at 36 hours after TGF-beta1 treatment, followed by activation of caspase-9, and caspase-3 was activated at 48 hours after treatment at which time apoptosis of HuH-7 cells was observed. TGF-beta1 significantly decreased XIAP expression in HuH-7 cells. Addition of an inhibitor of caspase-8 or caspase-3 (IETD-FMK or DEVD-CHO) markedly inhibited TGF-beta1-induced apoptosis of HuH-7 cells. Fas/Fas ligand (FasL) interactions in HuH-7 cells were not involved in the apoptotic process. Furthermore, epidermal growth factor (EGF) also completely inhibited TGF-beta1-induced apoptosis of HuH-7 cells by inhibiting activation of the caspase cascade. Our results suggested that activation of caspase-3 initiated through caspase-8 activation is involved in the apoptotic process induced by TGF-beta1 in HuH-7 cells. Our results also showed that down-regulation of the expression of Bcl-xL and XIAP by TGF-beta1 may facilitate activation of caspase-3 in these cells.
Shima
Y
Y
Department of Clinical Pharmacology, Nagasaki University School of Medicine, Nagasaki, Japan.
Nakao
K
K
Nakashima
T
T
Kawakami
A
A
Nakata
K
K
Hamasaki
K
K
Kato
Y
Y
Eguchi
K
K
Ishii
N
N
D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D006528:Carcinoma, Hepatocellular; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism*; D002455:Cell Division / Q000187:drug effects*; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D004815:Epidermal Growth Factor / Q000494:pharmacology; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D020287:In Situ Nick-End Labeling; D007700:Kinetics; D008113:Liver Neoplasms; D009842:Oligopeptides / Q000494:pharmacology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics; D013997:Time Factors; D016212:Transforming Growth Factor beta / Q000633:toxicity*; D014407:Tumor Cells, Cultured; D051020:bcl-X Protein; D019014:fas Receptor / Q000502:physiology
C494811:BCL2L1 protein, human; D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors; D009842:Oligopeptides; D019253:Proto-Oncogene Proteins c-bcl-2; D016212:Transforming Growth Factor beta; C108637:aspartyl-glutamyl-valyl-aspartal; D051020:bcl-X Protein; D019014:fas Receptor; D004815:Epidermal Growth Factor; C505407:CASP3 protein, human; C505530:CASP8 protein, human; C506433:CASP9 protein, human; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases