Activation of caspase-8 during N-(4-hydroxyphenyl)retinamide-induced apoptosis in Fas-defective hepatoma cells.
We observed that N-(4-hydroxyphenyl)retinamide (4HPR), a chemopreventive and chemotherapeutic agent, effectively induced apoptosis in hepatoma cells. Interestingly, Fas-negative (Hep 3B and PLC/PRF/5) hepatoma cells were shown to be more susceptible to apoptosis induced by 4HPR than were Fas-positive (Hep G2 and SK-HEP-1) hepatoma cells. Thus, we explored the mechanisms underlying 4HPR-induced apoptosis in Fas-defective hepatoma cells. Hep 3B cells stably expressing the dominant-negative Fas-associated death domain (dnFADD) showed no alteration in 4HPR drug susceptibility, but when stably expressing E1B19K, Crm A, or dominant-negative FLICE (dnFLICE), Hep 3B cells were resistant, suggesting that 4HPR-induced apoptosis was mediated by caspase-8 activation. Furthermore, apoptosis could be completely blocked by Z-VAD-FMK (a general caspase inhibitor) or by IETD-CHO (a caspase-8 inhibitor), but was only partially blocked by Ac-DEVD-CMK (a caspase-3 inhibitor), by N-acetyl-L-cysteine (NAC) (an antioxidant), by N-acetyl-leucyl-leucyl-norleucinal (ALLN) (a calpain inhibitor I), or by Z-LEHD-FMK (a caspase-9 inhibitor). Time-sequence analysis of the induction of apoptosis by 4HPR revealed that an initial caspase-8 activation was followed by late mitochondrial cytochrome c release and minor caspase-9 activation, which suggested that caspase-8 activation is the primary upstream regulatory point. Activation of Bid or induction of proapoptotic Bax was not observed during apoptosis. In contrast, Bcl-xL expression was decreased during 4HPR-induced apoptosis. Taken together, these results indicate that 4HPR may be a potential chemotherapeutic drug, which is able to induce apoptosis in Fas-defective hepatoma cells through caspase-8 activation.
You
K R
KR
Division of GI and Hepatology, Department of Internal Medicine, Research Institute of Clinical Medicine, Chonbuk National University Medical School and Hospital, Chonju, Republic of Korea.
Shin
M N
MN
Park
R K
RK
Lee
S O
SO
Kim
D G
DG
D048868:Adaptor Proteins, Signal Transducing; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000502:physiology*; D051023:BH3 Interacting Domain Death Agonist Protein; D006528:Carcinoma, Hepatocellular / Q000473:pathology / Q000503:physiopathology*; D002352:Carrier Proteins / Q000378:metabolism / Q000502:physiology; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism*; D004789:Enzyme Activation; D053200:Fas-Associated Death Domain Protein; D017313:Fenretinide / Q000494:pharmacology*; D006801:Humans; D008113:Liver Neoplasms / Q000473:pathology / Q000503:physiopathology*; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D014407:Tumor Cells, Cultured; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein; D019014:fas Receptor / Q000502:physiology*
D048868:Adaptor Proteins, Signal Transducing; D000970:Antineoplastic Agents; C494826:BAX protein, human; C494811:BCL2L1 protein, human; D051023:BH3 Interacting Domain Death Agonist Protein; C494814:BID protein, human; D002352:Carrier Proteins; C505533:FADD protein, human; D053200:Fas-Associated Death Domain Protein; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein; D019014:fas Receptor; D017313:Fenretinide; C505530:CASP8 protein, human; C506433:CASP9 protein, human; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases