MG132, a proteasome inhibitor, induces apoptosis in tumor cells

Guo, Na; Peng, Zhilan

doi:10.1111/j.1743-7563.2012.01535.x

Cited by 154 publications

(102 citation statements)

References 28 publications

(29 reference statements)

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“…In order to measure the autophagic ratio, the EC9706 cells were plated into 24-cell plates at a density of 1x10 5 cells. Subsequent to a 24-h incubation with the different drugs, the cell pellets were suspended with 0.05 mM MDC for 60 min at 37˚C, washed with PBS three times, fixed with 4% paraformaldehyde for 15 min at 4˚C and then collected in 10 mM Tris-HCl (pH 8.0) containing 0.1% Triton X-100.…”

Section: Measurement Of Cell Viability and Apoptosismentioning

confidence: 99%

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Inhibition of autophagy promotes cell apoptosis induced by the proteasome inhibitor MG-132 in human esophageal squamous cell carcinoma EC9706 cells

Gao

Yang

et al. 2015

Oncology Letters

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Abstract. Lysosome-dependent macroautophagy, also termed autophagy, and the ubiquitin-proteasome system and are the primary intracellular pathways involved in protein degradation. Previous studies have demonstrated that proteasome inhibitors are able to inhibit tumor growth and activate autophagy. The present study investigated the effect of the proteasome inhibitor MG-132 on cellular proliferation using a cell counting kit 8 assay, and the effect of the agent on apoptosis and autophagy was assessed using flow cytometry and monodansylcadaverine, respectively. Western blot analysis was used to investigate protein changes during the course of treatment. It was revealed that MG-132 inhibited cell proliferation, activated autophagy and induced cell death in EC9706 cells. Autophagy was activated through the class III PI3K pathway, and the expression of the Beclin-1 protein was determined to be significantly upregulated. However, the autophagy inhibitor 3-methyladenine (3-MA) inhibited the expression of the autophagy-associated protein Beclin-1 and reduced the accumulation of autophagic vacuoles induced by MG-132. MG-132-induced apoptosis was enhanced by the autophagy inhibitor 3-MA, which may be a result of caspase-3 activation in the EC9706 cells. These findings suggest that inhibition of the proteasome can induce autophagy in human ESCC cells, and also increase cell death. This indicates that proteasome inhibitors may be potential novel anti-cancer agents for the adjuvant treatment of esophageal squamous cell carcinoma. IntroductionThe ubiquitin-proteasome system (UPS) and lysosome-dependent macroautophagy, also termed autophagy, are the primary conserved intracellular pathways involved in protein degradation. These pathways work together in order to maintain homeostasis in eukaryotic cells (1). UPS-mediated proteolysis affects several different proteins through proteasome-mediated degradation, which is involved in the regulation of the cell cycle, apoptosis and cellular differentiation (2). Therefore, targeting this pathway using proteasome inhibitors may represent a novel approach for the treatment of cancer (3). A number of previous studies have demonstrated that proteasome inhibitors can induce tumor cell death via inhibiting proteasome activity (4,5).Autophagy is an evolutionarily conserved intracellular mechanism that degrades long-lived, misfolded proteins and damaged organelles in order to maintain cellular homeostasis by providing substrates and recycling amino acids and nucleotides (6). Although autophagy can be activated in a number of various cancer cells, including esophageal cancer, by different approaches, such as chemoradiotherapy (7), the exact role of autophagy in cancer cells is complex. In certain circumstances, autophagy demonstrates a protective role in cancer cells, whereas in others, it is involved in type II programmed cell death, termed autophagic cell death (8). One previous study reported that when UPS is inhibited, autophagy is upregulated (9). This suggests that the UPS and autophagy m...

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Section: Measurement Of Cell Viability and Apoptosismentioning

confidence: 99%

“…Therefore, targeting this pathway using proteasome inhibitors may represent a novel approach for the treatment of cancer (3). A number of previous studies have demonstrated that proteasome inhibitors can induce tumor cell death via inhibiting proteasome activity (4,5).…”

Section: Introductionmentioning

confidence: 99%

Inhibition of autophagy promotes cell apoptosis induced by the proteasome inhibitor MG-132 in human esophageal squamous cell carcinoma EC9706 cells

Gao

Yang

et al. 2015

Oncology Letters

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“…MG132 is a specific, potent, reversible and cell-permeable proteasome inhibitor that reduces the degradation of ubiquitin-conjugated proteins in mammalian cells. 27 Silencing of Ku70, USP9X or both in H1299 cells resulted in decreased levels of Mcl-1, which could be reversed by MG132 (Figure 2a (Figure 3b). To further test the effect of Ku70 on Mcl-1 stability, the half-life of Mcl-1 was measured using cycloheximide-blocking methods as described.…”

Section: Resultsmentioning

confidence: 92%

Role of Ku70 in deubiquitination of Mcl-1 and suppression of apoptosis

Wang

Xie

et al. 2014

Cell Death Differ

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Mcl-1 is a unique antiapoptotic Bcl2 family member with a short half-life due to its rapid turnover through ubiquitination. We discovered that Ku70, a DNA double-strand break repair protein, functions as a deubiquitinase to stabilize Mcl-1. Ku70 knockout in mouse embryonic fibroblast (MEF) Mcl-1 is an antiapoptotic molecule that is overexpressed in various types of cancers, including lung cancer, 1 leukemia, 2 lymphoma, 3 hepatocellular carcinoma 4 and so on. In addition to its antiapoptotic function, Mcl-1 is also an oncoprotein that promotes the development of cancer. 5 In contrast to other Bcl2 family members such as Bcl2 and Bcl-XL, Mcl-1 is unique in its short half-life (30 min-3 h) and short-term prosurvival function, which probably relates to the presence of a long proline-, glutamic acid-, serine-and threonine-rich (PEST) region upstream of the Bcl2 homology (BH) domain. 1 The mechanism(s) that stabilizes the Mcl-1 protein are critical for its long-term survival function. Mcl-1 protein can be phosphorylated at multiple sites that distinctly regulate Mcl-1 protein turnover. For example, extracellular signal-regulated kinase 1/2-mediated T163 site phosphorylation enhances the half-life and antiapoptotic function of Mcl-1. 1,6 In contrast, S159 phosphorylation by GSK-3b facilitates Mcl-1 ubiquitination and degradation to reduce its survival activity. 7 Ubiquitination and deubiquitination are two reversible processes that can control protein stability. E3 ligases and deubiquitinases (deubiquitinating enzymes (DUBs)) are two groups of regulatory enzymes that orchestrate the ubiquitination levels of target proteins in eukaryotic cells. 8 Recently, Mule and FBW7 have been identified as Mcl-1 ubiquitin E3 ligases that can directly induce polyubiquitination and degradation of Mcl-1. 9,10 Inversely, USP9X has been demonstrated as the Mcl-1 deubiquitinase that removes the Lys 48-linked polyubiquitin chains that normally mark Mcl-1 for proteasomal degradation, leading to stabilization of Mcl-1. 3 Therefore, the stability of Mcl-1 in cells is tightly regulated by its E3 ligases and deubiquitinase, which is dependent on Mcl-1 phosphorylation status. 3,11 Ku70 is a protein that binds to DNA double-strand break (DSB) ends and is required for the non-homologous endjoining pathway of DSB repair. 12-15 The Ku70 protein consists of three structural domains, including the N-terminal, central (that is, DNA binding) and C-terminal domains. 16,17 Ku70 usually heterodimerizes with Ku86, which forms a functional complex for DSB repair. By forming a bridge between the broken DNA ends, the Ku70/Ku86 heterodimer acts to structurally support and align the DNA ends, to protect them from degradation and to prevent promiscuous binding to unbroken DNA. Ku70/Ku86 effectively aligns the DNA, while still allowing access of polymerases, nucleases and ligases to the broken DNA ends to promote end joining. 18 In some cases, a fourth domain is present at the C terminus of Ku86, which binds to the DNA-dependent protein kinase catalytic subunit...

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“…It is well known that the ubiquitin–proteasome pathway is involved in regulating multiple intracellular proteolysis 31. MG132, a peptide aldehyde that efficiently inhibits the proteolytic activity of the 26S proteasome, has been used as a selective proteasome inhibitor to elucidate the actions of the ubiquitin–proteasome pathway in various cellular processes 26, 31, 32. Hu et al .…”

Section: Discussionmentioning

confidence: 99%

Pannexin3 inhibits TNF‐α‐induced inflammatory response by suppressing NF‐κB signalling pathway in human dental pulp cells

Song

Sun

Wang

et al. 2016

J Cellular Molecular Medi

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Human dental pulp cells (HDPCs) play a crucial role in dental pulp inflammation. Pannexin 3 (Panx3), a member of Panxs (Pannexins), has been recently found to be involved in inflammation. However, the mechanism of Panx3 in human dental pulp inflammation remains unclear. In this study, the role of Panx3 in inflammatory response was firstly explored, and its potential mechanism was proposed. Immunohistochemical staining showed that Panx3 levels were diminished in inflamed human and rat dental pulp tissues. In vitro, Panx3 expression was significantly down‐regulated in HDPCs following a TNF‐α challenge in a concentration‐dependent way, which reached the lowest level at 10 ng/ml of TNF‐α. Such decrease could be reversed by MG132, a proteasome inhibitor. Unlike MG132, BAY 11‐7082, a NF‐κB inhibitor, even reinforced the inhibitory effect of TNF‐α. Quantitative real‐time PCR (qRT‐PCR) and enzyme‐linked immunosorbent assay (ELISA) were used to investigate the role of Panx3 in inflammatory response of HDPCs. TNF‐α‐induced pro‐inflammatory cytokines, interleukin (IL)‐1β and IL‐6, were significantly lessened when Panx3 was overexpressed in HDPCs. Conversely, Panx3 knockdown exacerbated the expression of pro‐inflammatory cytokines. Moreover, Western blot, dual‐luciferase reporter assay, immunofluorescence staining, qRT‐PCR and ELISA results showed that Panx3 participated in dental pulp inflammation in a NF‐κB‐dependent manner. These findings suggested that Panx3 has a defensive role in dental pulp inflammation, serving as a potential target to be exploited for the intervention of human dental pulp inflammation.

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MG132, a proteasome inhibitor, induces apoptosis in tumor cells

Cited by 154 publications

References 28 publications

Inhibition of autophagy promotes cell apoptosis induced by the proteasome inhibitor MG-132 in human esophageal squamous cell carcinoma EC9706 cells

Inhibition of autophagy promotes cell apoptosis induced by the proteasome inhibitor MG-132 in human esophageal squamous cell carcinoma EC9706 cells

Role of Ku70 in deubiquitination of Mcl-1 and suppression of apoptosis

Pannexin3 inhibits TNF‐α‐induced inflammatory response by suppressing NF‐κB signalling pathway in human dental pulp cells

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