Abstract
The proteasome inhibitor bortezomib is an efficacious inducer of apoptosis in the hepatoma HepG2 cell line. This study shows that bortezomib increased in these cells the level of the survival factor Hsp72 in a time- and dose-dependent manner. In a first phase of treatment, Hsp72 rapidly increased so that at 24 h of incubation with 50 nM bortezomib its level was approximately five-fold higher than the control. In this phase Hsp72 seemed to play a role in preventing HepG2 cell death, since it interacted with and sequestered the pro-apoptotic factors p53, AIF, Bax and Apaf-1. During a second day of treatment, although the nuclear levels of Hsp72, p53 and AIF increased, the interaction of Hsp72 with these factors diminished. In addition, bortezomib induced the activation of caspases, which stimulated Hsp72 degradation. In conclusion, in the second day of treatment with bortezomib the protective ability of Hsp72 decreased thus favouring the appearance of apoptosis.
MeSH terms
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Amino Acid Chloromethyl Ketones / pharmacology
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Apoptosis / drug effects*
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Apoptosis / physiology
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Apoptosis Inducing Factor / genetics
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Apoptosis Inducing Factor / metabolism
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Apoptosis Regulatory Proteins / genetics
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Apoptosis Regulatory Proteins / metabolism*
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Apoptotic Protease-Activating Factor 1 / genetics
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Apoptotic Protease-Activating Factor 1 / metabolism
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Blotting, Western
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Boronic Acids / pharmacology*
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Bortezomib
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Carcinoma, Hepatocellular / genetics
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Carcinoma, Hepatocellular / metabolism
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Carcinoma, Hepatocellular / pathology
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Cell Line, Tumor
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HSP72 Heat-Shock Proteins / genetics
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HSP72 Heat-Shock Proteins / metabolism*
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HSP72 Heat-Shock Proteins / physiology
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Humans
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Immunoprecipitation
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Liver Neoplasms / genetics
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Liver Neoplasms / metabolism
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Liver Neoplasms / pathology
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Protease Inhibitors / pharmacology
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Protein Binding
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Pyrazines / pharmacology*
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Reverse Transcriptase Polymerase Chain Reaction
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Time Factors
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Tumor Suppressor Protein p53 / genetics
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Tumor Suppressor Protein p53 / metabolism
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bcl-2-Associated X Protein / genetics
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bcl-2-Associated X Protein / metabolism
Substances
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AIFM1 protein, human
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APAF1 protein, human
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Amino Acid Chloromethyl Ketones
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Apoptosis Inducing Factor
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Apoptosis Regulatory Proteins
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Apoptotic Protease-Activating Factor 1
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BAX protein, human
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Boronic Acids
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HSP72 Heat-Shock Proteins
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Protease Inhibitors
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Pyrazines
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Tumor Suppressor Protein p53
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bcl-2-Associated X Protein
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benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone
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Bortezomib