title: Destabilization of CARP mRNAs by aloe-emodin contributes to caspase-8-mediated p53-independent apoptosis of human carcinoma cells.
abstract: Using short hairpin RNA against p53, transient ectopic expression of wild-type p53 or mutant p53 (R248W or R175H), and a p53- and p21-dependent luciferase reporter assay, we demonstrated that growth arrest and apoptosis of FaDu (human pharyngeal squamous cell carcinoma), Hep3B (hepatoma), and MG-63 (osteosarcoma) cells induced by aloe-emodin (AE) are p53-independent. Co-immunoprecipitation and small interfering RNA (siRNA) studies demonstrated that AE caused S-phase cell cycle arrest by inducing the formation of cyclin A-Cdk2-p21 complexes through extracellular signal-regulated kinase (ERK) activation. Ectopic expression of Bcl-X(L) and siRNA-mediated Bax attenuation significantly inhibited apoptosis induced by AE. Cyclosporin A or the caspase-8 inhibitor Z-IETD-FMK blocked AE-induced loss of mitochondrial membrane potential and prevented increases in reactive oxygen species and Ca(++). Z-IETD-FMK inhibited AE-induced apoptosis, Bax expression, Bid cleavage, translocation of tBid to mitochondria, ERK phosphorylation, caspase-9 activation, and the release of cytochrome c, apoptosis-inducing factor (AIF), and endonuclease G from mitochondria. The stability of the mRNAs encoding caspase-8 and -10-associated RING proteins (CARPs) 1 and 2 was affected by AE, whereas CARP1 or 2 overexpression inhibited caspase-8 activation and apoptosis induced by AE. Collectively, our data indicate AE induces caspase-8-mediated activation of mitochondrial death pathways by decreasing the stability of CARP mRNAs in a p53-independent manner.
authors.affiliation: Department of Medical Laboratory Science and Biotechnology, China Medical University, Taichung, Taiwan.
authors.forename: Meng-Liang
authors.initials: ML
authors.lastname: Lin
authors.forename: Yao-Cheng
authors.initials: YC
authors.lastname: Lu
authors.forename: Hong-Lin
authors.initials: HL
authors.lastname: Su
authors.forename: Hsin-Ting
authors.initials: HT
authors.lastname: Lin
authors.forename: Chuan-Chun
authors.initials: CC
authors.lastname: Lee
authors.forename: Shang-En
authors.initials: SE
authors.lastname: Kang
authors.forename: Tan-Chen
authors.initials: TC
authors.lastname: Lai
authors.forename: Jing-Gung
authors.initials: JG
authors.lastname: Chung
authors.forename: Shih-Shun
authors.initials: SS
authors.lastname: Chen
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D051017:Apoptosis Regulatory Proteins; D015153:Blotting, Western; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D053181:Caspase 8 / Q000235:genetics / Q000378:metabolism*; D002453:Cell Cycle / Q000187:drug effects; D018797:Cell Cycle Proteins; D002460:Cell Line; D045744:Cell Line, Tumor; D019925:Cyclin A / Q000235:genetics / Q000378:metabolism; D051357:Cyclin-Dependent Kinase 2 / Q000235:genetics / Q000378:metabolism; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics / Q000378:metabolism; D004642:Emodin / Q000494:pharmacology*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D009369:Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011485:Protein Binding / Q000187:drug effects; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D034622:RNA Interference; D020871:RNA Stability / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*
chemical_list: D051017:Apoptosis Regulatory Proteins; C512817:CA11 protein, human; C477529:CCAR1 protein, human; C493956:CDKN1A protein, human; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D019925:Cyclin A; D050759:Cyclin-Dependent Kinase Inhibitor p21; D009419:Nerve Tissue Proteins; D047428:Protein Kinase Inhibitors; D012333:RNA, Messenger; D016159:Tumor Suppressor Protein p53; D051357:Cyclin-Dependent Kinase 2; D048049:Extracellular Signal-Regulated MAP Kinases; D053181:Caspase 8; D004642:Emodin