TY - JOUR
T1 - cFLIPL prevents TRAIL-induced apoptosis of hepatocellular carcinoma cells by inhibiting the lysosomal pathway of apoptosis
AU - Guicciardi, Maria Eugenia
AU - Bronk, Steven F.
AU - Werneburg, Nathan W.
AU - Gores, Gregory J.
PY - 2007/5
Y1 - 2007/5
N2 - Sensitivity to TNF-related apoptosis-inducing ligand (TRAIL)-mediated apoptosis and the lysosomal pathway of cell death are features of cancer cells. However, it is unknown if TRAIL cytotoxic signaling engages the lysosomal pathway of cell death. Our aim, therefore, was to ascertain if TRAIL killing involves lysosomal permeabilization. TRAIL-induced apoptosis of hepatocellular carcinoma cells (HuH-7, Hep3B) was associated with lysosomal permeabilization, as demonstrated by redistribution of the lysosomal protease cathepsin B into the cytosol. Pharmacological and short hairpin RNA-targeted inhibition of cathepsin B reduced apoptosis. Because cellular FLICE-inhibitory protein (cFLIP) inhibits TRAIL-induced cell death and is frequently overexpressed by human cancers, the ability of cFLIP to prevent lysosomal permeabilization during TRAIL treatment was examined. Enforced long-form cFLIP (cFLIPL) expression reduced release of cathepsin B from lysosomes and attenuated apoptosis. cFLIP L overexpression was also associated with robust p42/44 MAPK activation following exposure to TRAIL. In contrast, cFLIPL overexpression attenuated p38 MAPK activation and had no significant effect on JNK and NF-κB activation. Inhibition of p42/44 MAPK by PD98059 restored TRAIL-mediated lysosomal permeabilization and apoptosis in cFLIP-overexpressing cells. In conclusion, these results demonstrate that lysosomal permeabilization contributes to TRAIL-induced apoptosis of hepatocellular carcinoma cells and suggest that cFLIPL cytoprotection is, in part, due to p42/44 MAPK-dependent inhibition of lysosomal breakdown.
AB - Sensitivity to TNF-related apoptosis-inducing ligand (TRAIL)-mediated apoptosis and the lysosomal pathway of cell death are features of cancer cells. However, it is unknown if TRAIL cytotoxic signaling engages the lysosomal pathway of cell death. Our aim, therefore, was to ascertain if TRAIL killing involves lysosomal permeabilization. TRAIL-induced apoptosis of hepatocellular carcinoma cells (HuH-7, Hep3B) was associated with lysosomal permeabilization, as demonstrated by redistribution of the lysosomal protease cathepsin B into the cytosol. Pharmacological and short hairpin RNA-targeted inhibition of cathepsin B reduced apoptosis. Because cellular FLICE-inhibitory protein (cFLIP) inhibits TRAIL-induced cell death and is frequently overexpressed by human cancers, the ability of cFLIP to prevent lysosomal permeabilization during TRAIL treatment was examined. Enforced long-form cFLIP (cFLIPL) expression reduced release of cathepsin B from lysosomes and attenuated apoptosis. cFLIP L overexpression was also associated with robust p42/44 MAPK activation following exposure to TRAIL. In contrast, cFLIPL overexpression attenuated p38 MAPK activation and had no significant effect on JNK and NF-κB activation. Inhibition of p42/44 MAPK by PD98059 restored TRAIL-mediated lysosomal permeabilization and apoptosis in cFLIP-overexpressing cells. In conclusion, these results demonstrate that lysosomal permeabilization contributes to TRAIL-induced apoptosis of hepatocellular carcinoma cells and suggest that cFLIPL cytoprotection is, in part, due to p42/44 MAPK-dependent inhibition of lysosomal breakdown.
KW - Caspase-8
KW - Cathepsin B
KW - PD98059
KW - p42/44 mitogen-activated protein kinase
UR - http://www.scopus.com/inward/record.url?scp=34347392130&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=34347392130&partnerID=8YFLogxK
U2 - 10.1152/ajpgi.00497.2006
DO - 10.1152/ajpgi.00497.2006
M3 - Article
C2 - 17272514
AN - SCOPUS:34347392130
SN - 0193-1857
VL - 292
SP - G1337-G1346
JO - American Journal of Physiology - Gastrointestinal and Liver Physiology
JF - American Journal of Physiology - Gastrointestinal and Liver Physiology
IS - 5
ER -