benzyloxycarbonylleucyl-leucyl-leucine-aldehyde and Liver-Neoplasms

Sonodynamic therapy (SDT) is a promising and significant measure for the treatment of tumors. However, the internal situation of hepatocellular carcinoma (HCC) is complex, separate SDT treatment is difficult to play a good therapeutic effect. Here, we used SDT combined with MG-132 to mediate apoptosis and autophagy of HCC cells to achieve the purpose of treatment of cancer.. To determine the generated reactive oxygen species (ROS) and the change of mitochondrial membrane potential (ΔΨm), HepG2 cells were stained by 2,7-dichlorodihydrofluorescein diacetate (DCFH-DA) and 5,5',6,6'-Tetrachloro-1,1',3,3'-tetraethyl-imidacarbocyanine iodide (JC-1) staining to determine the IR-820@NBs-mediated SDT to achieve HCC therapy through the mitochondrial pathway. Cell counting kit 8 (CCK-8) assay and flow cytometry were used to detect cell viability and apoptosis rate of HepG2 cells. Autophagy was detected by mCherry-GFP-LC3B fluorescence labeling. Chloroquine (Cq) pretreatment was used to explore the relationship between autophagy and apoptosis. To detect the ability of HepG2 cells migration and invasion, cell scratch assay and transwell assay were used.. The successfully prepared IR-820@NBs could effectively overcome the shortcomings of IR-820 and induce lethal levels of ROS by ultrasound irradiation. As a dual agonist of apoptosis and autophagy, MG-132 could effectively enhance the efficacy of SDT in the process of treating HCC. After pre-treatment with Cq, the cell activity increased and the level of apoptosis decreased, which proved that apoptosis and autophagy were induced by combined therapy, autophagy, and apoptosis have the synergistic anti-tumor effect, and part of apoptosis was autophagy-dependent. After combined therapy, the activity and invasive ability of HCC cells decreased significantly.. SDT combined with MG-132 in the process of treating liver cancer could effectively induce apoptosis and autophagy anti-tumor therapy, which is helpful to the research of new methods to treat liver cancer.

Topics: Apoptosis; Autophagy; Carcinoma, Hepatocellular; Cell Line, Tumor; Humans; Liver Neoplasms; Reactive Oxygen Species; Ultrasonic Therapy

How Wnt signaling is orchestrated in liver regeneration and tumorigenesis remains elusive. Recently, we identified transmembrane protein 9 (TMEM9) as a Wnt signaling amplifier.. TMEM9 facilitates v-ATPase assembly for vesicular acidification and lysosomal protein degradation. TMEM9 is highly expressed in regenerating liver and hepatocellular carcinoma (HCC) cells. TMEM9 expression is enriched in the hepatocytes around the central vein and acutely induced by injury. In mice, Tmem9 knockout impairs hepatic regeneration with aberrantly increased adenomatosis polyposis coli (Apc) and reduced Wnt signaling. Mechanistically, TMEM9 down-regulates APC through lysosomal protein degradation through v-ATPase. In HCC, TMEM9 is overexpressed and necessary to maintain β-catenin hyperactivation. TMEM9-up-regulated APC binds to and inhibits nuclear translocation of β-catenin, independent of HCC-associated β-catenin mutations. Pharmacological blockade of TMEM9-v-ATPase or lysosomal degradation suppresses Wnt/β-catenin through APC stabilization and β-catenin cytosolic retention.. Our results reveal that TMEM9 hyperactivates Wnt signaling for liver regeneration and tumorigenesis through lysosomal degradation of APC.

Topics: Adenomatous Polyposis Coli Protein; Animals; beta Catenin; Carbon Tetrachloride; Carcinogenesis; Carcinoma, Hepatocellular; Cell Nucleus; Chemical and Drug Induced Liver Injury; Disease Models, Animal; Gene Knockout Techniques; HEK293 Cells; Hep G2 Cells; Humans; Leupeptins; Liver Neoplasms; Liver Regeneration; Lysosomes; Male; Membrane Proteins; Mice; Mice, Knockout; Proteolysis; Vacuolar Proton-Translocating ATPases; Wnt Signaling Pathway; Xenograft Model Antitumor Assays

Hepatocellular carcinoma (HCC) is one of the most lethal and prevalent cancers worldwide. CD147 (EMMPRIN or basigin) is a leading gene relating to hepatocarcinogenesis and metastasis, and is detected in transmembrane, exosome or circulating forms in HCC patients. The endosome recycling of CD147 further enhances the function of this oncoprotein from a dynamic perspective. However, previous studies about CD147 mainly focused on one separate form, and little attention has been paid to how the different forms of tumor-derived CD147 changes. Moreover, uncovering the roles of the residual C-terminal portion of CD147 after shedding is inevitable to fully understand CD147 promoting tumor progression. In this study, we discovered that under low-cholesterol condition, CD147 endocytosis is inhibited but its shedding mediated by ADAM10 is enhanced. Further procession of residual CD147 in the lysosome produces nuclear-localized CD147-ICD (intracellular domain of CD147), which contributes to autophagy through NF-κB-TRAIL-caspase8-ATG3 axis. As autophagy endows cancer cells with increased adaptability to chemotherapy, and HAb 18 (a specific antibody targeting CD147) inhibits CD147 shedding and sequential CD147-ICD enhances autophagy, we found the combination of HAb 18 and cisplatin exhibited marked antitumor efficiency.

Topics: ADAM10 Protein; ADP-Ribosylation Factor 6; ADP-Ribosylation Factors; Amyloid Precursor Protein Secretases; Animals; Antibodies, Monoclonal; Antineoplastic Agents; Autophagy; Basigin; Beclin-1; beta-Cyclodextrins; Carcinoma, Hepatocellular; Cell Line, Tumor; Cisplatin; Drug Resistance, Neoplasm; Female; Humans; Leupeptins; Liver Neoplasms; Membrane Proteins; Mice; Mice, Nude; Proteolysis; Simvastatin

Metastasis associated 1 protein (MTA1) is one of the prime facilitators of metastatic progression in all solid tumors including hepatocellular carcinoma (HCC). However, the underlying regulatory mechanism of MTA1 expression in HCC is not clear. In this study, we evaluated MTA1 transcript and protein expression in HCC and normal hepatic cell lines. The results revealed that MTA1 protein expression had a significantly increase in HCC cell line, HuH6, compared with that in normal hepatic cell line, THLE-2. Determination of protein half-life using cycloheximide (CHX) treatment did not reveal any statistically significant difference in protein turn-over rates between THLE-2 (3.3 ± 0.25 h) and HuH6 (3.6 ± 0.15 h) cell lines. MTA1 protein level was stabilized in THLE-2 cells after treatment with MG-132 to levels similar to those observed in HuH6 cells. Mass spectrometric analysis of FLAG immunoprecipitates of FLAG-MTA1 transfected THLE-2 cells after MG-132 treated revealed candidate ubiquitin ligases that were interacting with MTA1. RNAi-mediated silencing of each prospective ubiquitin ligase in THLE-2 cells indicated that knockdown of TRIM25 resulted in stabilization of MTA1 protein, indicating TRIM25 as a putative E3 ligase for MTA1. Coimmunoprecipitation of FLAG-tagged MTA1, but not IgG, in MG-132 treated and untreated THLE-2 cells cotransfected with either FLAG-MTA1 or Myc-TRIM25 revealed robust polyubiquitinated MTA1, confirming that the TRIM25 is the ubiquitin ligase for MTA1 degradation. Overexpression of TRIM25 in HuH6 and RNAi mediated silencing of TRIM25 in THLE-2 cells inhibited and increased the cell migration and invasion, respectively. Analysis of The Cancer Genome Atlas data for assessment of TRIM25 transcript level and MTA1 protein expression in 25 HCC patients confirmed an inverse correlation between the expression of TRIM25 and MTA1. Cumulatively, our data reveal a novel mechanism of post-translational to regulate MTA1 expression in normal hepatic cells, which is repressed in HCC. © 2017 IUBMB Life, 69(10):795-801, 2017.

Topics: Atlases as Topic; Carcinoma, Hepatocellular; Cell Line; Cell Line, Tumor; Cell Movement; Cycloheximide; Disease Progression; Gene Expression Regulation, Neoplastic; Half-Life; Hepatocytes; Histone Deacetylases; Humans; Leupeptins; Liver Neoplasms; Protein Binding; Protein Stability; Proteolysis; Repressor Proteins; RNA, Small Interfering; Signal Transduction; Trans-Activators; Transcription Factors; Tripartite Motif Proteins; Ubiquitin-Protein Ligases; Ubiquitination

Tumour metastasis, the spread of cancer cells from the original tumour site followed by growth of secondary tumours at distant organs, is the primary cause of cancer-related deaths and remains poorly understood. Here we demonstrate that inhibition of CDK4/6 blocks breast tumour metastasis in the triple-negative breast cancer model, without affecting tumour growth. Mechanistically, we identify a deubiquitinase, DUB3, as a target of CDK4/6; CDK4/6-mediated activation of DUB3 is essential to deubiquitinate and stabilize SNAIL1, a key factor promoting epithelial-mesenchymal transition and breast cancer metastasis. Overall, our study establishes the CDK4/6-DUB3 axis as an important regulatory mechanism of breast cancer metastasis and provides a rationale for potential therapeutic interventions in the treatment of breast cancer metastasis.

Topics: Animals; Antineoplastic Agents; Cell Line, Tumor; Cell Movement; Cyclin-Dependent Kinase 4; Cyclin-Dependent Kinase 6; Disease Models, Animal; Endopeptidases; Female; Gene Expression Regulation, Neoplastic; Humans; Leupeptins; Liver Neoplasms; Lung Neoplasms; MCF-7 Cells; Mice; Ovarian Neoplasms; Piperazines; Pyridines; RNA, Small Interfering; Signal Transduction; Snail Family Transcription Factors; Triple Negative Breast Neoplasms; Xenograft Model Antitumor Assays

Suppressor of cytokine signaling 1 (SOCS1) is considered as a tumor suppressor protein in hepatocellular carcinoma (HCC), but the underlying mechanisms remain unclear. Previously, we have shown that SOCS1-deficient hepatocytes displayed increased responsiveness to hepatocyte growth factor (HGF) due to enhanced signaling via the MET receptor tyrosine kinase. As aberrant MET activation occurs in many tumors including HCC, here we elucidated the mechanisms of SOCS1-mediated regulation. SOCS1 attenuated HGF-induced proliferation of human and mouse HCC cell lines and their growth as tumors in NOD.scid.gamma mice. Tumors formed by SOCS1 expressing HCC cells showed significantly reduced MET expression, indicating that SOCS1 not only attenuates MET signaling but also regulates MET expression. Mechanistically, SOCS1 interacted with MET via the Src homology 2 domain and this interaction was promoted by MET tyrosine kinase activity. The SOCS1-mediated reduction in MET expression does not require the juxtamembrane Y1003 residue implicated in Cbl-mediated downmodulation. Moreover, the proteasome inhibitor MG-132, but not the inhibitors of lysosomal degradation bafilomycin and chloroquine, reversed the SOCS1-mediated reduction in MET expression, indicating that this process is distinct from Cbl-mediated downmodulation. Accordingly, SOCS1 promoted polyubiquitination of MET via K48-dependent but not K63-mediated ubiquitin chain elongation. Furthermore, siRNA-mediated downmodulation of Cbl did not abolish SOCS1-mediated reduction in MET expression in HCC cells. SOCS1-dependent ubiquitination of endogenous MET receptor occurred rapidly following HGF stimulation in HCC cells, leading to proteasomal degradation of phosphorylated MET receptor. These findings indicate that SOCS1 mediates its tumor suppressor functions, at least partly, by binding to MET and interfering with downstream signaling pathways as well as by promoting the turnover of the activated MET receptor. We propose that loss of this control mechanism due to epigenetic repression of SOCS1 could contribute to oncogenic MET signaling in HCC and other cancers, and that MET inhibitors might be useful in treating these patients.

Topics: Animals; Carcinoma, Hepatocellular; Cell Line, Tumor; Cell Proliferation; Chlorocebus aethiops; Chloroquine; COS Cells; Gene Expression Regulation, Neoplastic; HEK293 Cells; Hep G2 Cells; Humans; Leupeptins; Liver Neoplasms; Mice; Proto-Oncogene Proteins c-cbl; Proto-Oncogene Proteins c-met; Signal Transduction; Suppressor of Cytokine Signaling 1 Protein; Suppressor of Cytokine Signaling Proteins

Identification of substances with specific toxicity for carcinoma cells promises to facilitate the development of cancer chemotherapeutics that cause minimal side effects. Here, we show that knockdown of the farnesoid X receptor (FXR) effectively suppresses the proliferation of human hepatocellular carcinoma cell lines HepG2 and HLE accompanied by elevated expression of cyclin-dependent kinase (CDK) inhibitor p16/INK4a and p21/Cip1 proteins. On the other hand, the growth of the primary human hepatocyte-derived cell line Fa2N-4 is not affected by the treatment with FXR siRNA irrespective of marked increases in the mRNAs of p16/INK4a and p21/Cip1. Surprisingly, the expression levels of p16/INK and p21/Cip1 proteins are left unchanged in Fa2N-4 cells that are subjected to the FXR siRNA treatment. Since the expression levels of these CDK inhibitor proteins in FXR-knockdown Fa2N-4 cells were elevated in the presence of proteasomal inhibitor MG132, these CDK inhibitors may be subjected to the proteasomal degradation, thereby counteracting the increased expression of their cognate mRNAs, therefore similar levels of p16 and p21 proteins were observed in control and FXR-knockdown Fa2N-4 cells. These results suggest that FXR-knockdown is effective for inhibiting the proliferation of hepatocellular carcinoma cells, not interfering with the regulatory mechanism of normal hepatocyte growth.

Topics: Carcinoma, Hepatocellular; Cell Proliferation; Cyclin-Dependent Kinase Inhibitor p16; Cyclin-Dependent Kinase Inhibitor p21; Gene Expression; Gene Knockdown Techniques; Hep G2 Cells; Hepatocytes; Humans; Leupeptins; Liver Neoplasms; Proteasome Endopeptidase Complex; Receptors, Cytoplasmic and Nuclear; RNA, Messenger; RNA, Small Interfering

Cellular senescence evasion caused by the inactivation of tumor suppressive programs is implicated in tumor initiation and therapeutic resistance. Our previous study has shown that the downregulation of growth arrest and DNA damage 45G (GADD45G) contributes to senescence bypass in hepatocellular carcinoma (HCC). Here, we report that the Smad-interacting protein-1 (SIP1) is transcriptionally activated and functions critically in the GADD45G-induced tumor cell senescence. Knockdown of SIP1 significantly abrogates the suppressive effects of GADD45G on the growth of xenografted liver tumor in vivo. The essential role of SIP1 in GADD45G activities is further validated in the model of the proteasome inhibitor MG132-induced cell senescence. We further show that JNK but not p38 MAPK activation is involved in the GADD45G-mediated SIP1 upregulation, and that JNK inhibition counteracts the GADD45G-induced cellular senescence. More importantly, we show that GADD45G and SIP1 expression are coincidently downregulated in primary human HCC tissues. Together, our results establish that the dowregulation of GADD45G-SIP1 axis may contribute to cellular senescence evasion and HCC development.

Topics: Animals; Antineoplastic Agents; Carcinoma, Hepatocellular; Cell Growth Processes; Cell Line, Tumor; Cellular Senescence; Cysteine Proteinase Inhibitors; GADD45 Proteins; HEK293 Cells; Homeodomain Proteins; Humans; Intracellular Signaling Peptides and Proteins; Leupeptins; Liver Neoplasms; MAP Kinase Kinase 4; Mice; Mice, Nude; Repressor Proteins; Xenograft Model Antitumor Assays; Zinc Finger E-box Binding Homeobox 2

Liver cancer in men is the fifth most frequently diagnosed cancer worldwide. Programmed cell death 5 (PDCD5) is an apoptosis related gene and plays an important role in the pathogenesis and development of cancer. In this study, we confirmed that the levels of PDCD5 mRNA and protein were lower in hepatocellular carcinoma (HCC) tissue compared to normal tissue. PDCD5 expression was significantly associated with HBV infection, tumor number, lymph node metastasis and the survival time of the patients with HCC. In addition, the serum levels of PDCD5 and AFP in the patients were significantly positively correlated. We also confirmed that upregulation of PDCD5 was able to inhibit cell proliferation and mobility, induce apoptosis and G1 arrest. Interestingly, PDCD5 also inhibited proteasome activity similarly to the proteosome inhibitor MG132. PDCD5 could be considered as a reliable marker of favorable prognosis of HCC patients.

Topics: Aged; alpha-Fetoproteins; Apoptosis; Apoptosis Regulatory Proteins; Biomarkers, Tumor; Carcinoma, Hepatocellular; Cell Proliferation; Female; Gene Expression Regulation, Neoplastic; Hep G2 Cells; Humans; Leupeptins; Liver Neoplasms; Lymphatic Metastasis; Male; Middle Aged; Neoplasm Proteins; Prognosis; Treatment Outcome

Despite the antitumour effect of ursolic acid observed in several cancers, the underlying mechanism remains unclear. Thus, in the present study, the roles of AMP-activated protein kinase (AMPK) and glycogen synthase kinase 3 beta (GSK3β) were examined in ursolic acid induced apoptosis in HepG2 hepatocellular carcinoma cells. Ursolic acid significantly exerted cytotoxicity, increased the sub-G1 population and the number of ethidium homodimer and terminal deoxynucleotidyl transferase(TdT) mediated dUTP nick end labeling positive cells in HepG2 cells. Also, ursolic acid enhanced the cleavages of poly-ADP-ribose polymerase (PARP) and caspase3, attenuated the expression of astrocyte elevated gene (AEG1) and survivin in HepG2 cells. Interestingly, ursolic acid increased the phosphorylation of AMPK and coenzyme A carboxylase and also enhanced phosphorylation of GSK3β at inactive form serine 9, whereas ursolic acid attenuated the phosphorylation of AKT and mTOR in HepG2 cells. Conversely, AMPK inhibitor compound C or GSK3β inhibitor SB216763 blocked the cleavages of PARP and caspase 3 induced by ursolic acid in HepG2 cells. Furthermore, proteosomal inhibitor MG132 suppressed AMPK activation, GSK3β phosphorylation, cleaved PARP and deceased AEG-1 induced by ursolic acid in HepG2 cells. Overall, our findings suggest that ursolic acid induced apoptosis in HepG2 cells via AMPK activation and GSK3β phosphorylation as a potent chemopreventive agent.

Topics: AMP-Activated Protein Kinases; Apoptosis; Carcinoma, Hepatocellular; Caspase 3; Cell Adhesion Molecules; Glycogen Synthase Kinase 3; Glycogen Synthase Kinase 3 beta; Hep G2 Cells; Humans; Indoles; Leupeptins; Liver Neoplasms; Maleimides; Membrane Proteins; Phosphorylation; Poly(ADP-ribose) Polymerases; Protein Kinase Inhibitors; Proto-Oncogene Proteins c-akt; RNA-Binding Proteins; TOR Serine-Threonine Kinases; Triterpenes; Ubiquitination; Ursolic Acid

The activating receptor natural killer group 2, member D (NKG2D) and its ligands play a crucial role in immune response to tumors. NKG2D ligand expression in tumors has been shown to be associated with tumor eradication and superior patient survival, but the involvement of NKG2D ligands in the immune response against hepatocellular carcinoma (HCC) still remains to be elucidated.. We investigated the expression of NKG2D ligands in HCC tissues collected from 54 patients and HCC cell lines. We also examined the proteasome expression and the effect of inhibition of proteasome activity on NKG2D ligand expression in HCC tissues and cell lines.. In dysplastic nodules (DN), well-differentiated (well-HCC), and moderately-differentiated HCCs (mod-HCC), UL16-binding protein (ULBP) 1 was expressed predominantly in tumor cells, but not in poorly-differentiated HCCs (poor-HCC). Remarkably, recurrence-free survival of patients with ULBP1-negative HCC was significantly shorter than that of patients with ULBP1-positive HCC (p=0.006). Cox regression analysis revealed that loss of ULBP1 expression was an independent predictor of early recurrence (p=0.008). We confirmed that ULBP1 was expressed in the well- and mod-HCC cell lines, but not in the poor-HCC cell line KYN-2. However, inhibition of proteasome activity resulted in significant up-regulation of ULBP1 expression in KYN-2. Moreover, we found that 20S proteasome expression was more abundant in KYN-2 than that in the well- and mod-HCC cell lines.. ULBP1 is prevalently expressed in DN to mod-HCC, but loss of its expression correlates with tumor progression and early recurrence.

Topics: Aged; Carcinoma, Hepatocellular; Cell Differentiation; Cell Line, Tumor; Cysteine Proteinase Inhibitors; Disease-Free Survival; Female; Gene Expression; GPI-Linked Proteins; Humans; Intracellular Signaling Peptides and Proteins; Killer Cells, Natural; Leupeptins; Ligands; Liver Neoplasms; Male; Middle Aged; Neoplasm Recurrence, Local; NK Cell Lectin-Like Receptor Subfamily K; Proteasome Endopeptidase Complex; RNA, Messenger; RNA, Neoplasm

Geranylgeranoic acid (GGA) and its derivatives are currently under development as chemopreventive agents against second primary hepatoma in Japan. We aimed to evaluate chemoprevention targets of GGA and a surrogate marker of chemopreventive response to clarify the molecular mechanism of hepatoma chemoprevention with GGA. Human hepatoma-derived cell lines such as HuH-7, PLC/PRF/5, and HepG-2, were treated with GGA and its derivatives. Cellular dynamics of several cell-cycle-related proteins were assessed by either immunoblotting or immunofluorescence method. The cellular expression of cyclin D1 protein was suppressed immediately after GGA treatment. This reduction was partially blocked by pretreatment with 26S proteasome inhibitor MG-132, indicating that proteasomal degradation was involved in GGA-induced disappearance of cyclin D1. A phosphorylation of retinoblastoma protein (RB) at serine 780, a target site of cyclin D1-dependent kinase 4, was rapidly decreased in GGA-treated HuH-7 cells. Furthermore, subcellular fractionation, Western blotting, and immunofluorescence revealed GGA-induced nuclear accumulation of RB. These results strongly suggest that cyclin D1 may be a target of chemopreventive GGA in human hepatoma cells. GGA-induced rapid repression of cyclin D1, and a consequent dephosphorylation and nuclear translocation of RB, may influence cell cycle progression and may be relevant to GGA-induced cell death mechanisms.

Topics: Cell Cycle; Cell Line, Tumor; Cyclin D1; Diterpenes; Down-Regulation; E2F1 Transcription Factor; Gene Expression Regulation, Neoplastic; Hep G2 Cells; Humans; Leupeptins; Liver Neoplasms; Phosphorylation; Proteasome Endopeptidase Complex; Retinoblastoma Protein; Reverse Transcriptase Polymerase Chain Reaction

Abstract Raf-1 kinase inhibitor protein (RKIP) is a tumor and metastasis suppressor that promotes drug-induced apoptosis in cancer cells. It is frequently downregulated, both at the mRNA and protein level, in hepatocellular carcinoma (HCC), but the mechanisms leading to this reduction are obscure. We sequenced the whole RKIP gene in three human HCC cell lines (HA22T/VGH, HepG2, and Hep3B), and in five clinical HCC samples, but could not find any gene variant that might account for their low RKIP levels. We also examined whether gene methylation may be responsible for the altered RKIP expression. No methylation of the RKIP gene was found in the tumor samples, while among the cell lines only Hep3B showed methylation of the gene, which was reduced by treatment with 5-aza-2'-deoxycytidine (5-AZA). The same treatment caused upregulation of RKIP at the mRNA, but not at the protein level, indicating that gene methylation is not a principal mechanism of the decrease in RKIP in the Hep3B cells. Furthermore, different elements consistently suggested that RKIP may be a target repressed by miR-224, a miRNA that is frequently and specifically upregulated in HCC, but our results excluded that this occurs, at least in the HCC cell lines. Factors like Snail, EZH2, and HDAC, have been implicated in the RKIP downregulation present in breast and prostate tumors, though some of our results from the cell lines do not support that they play such a role in HCC; however, this aspect is worthy of further study. However, recent results of ours and others suggest a significant involvement of proteosomal degradation and of its pharmacological inhibition. In conclusion, the causes of RKIP downregulation in HCC remain incompletely understood. However, we think that the present observations will be useful to generate further research, with the ultimate possible goal of devising specific approaches to restore the relevant antitumor function of the factor.

Topics: Antineoplastic Agents; Azacitidine; Carcinoma, Hepatocellular; Cell Line, Tumor; DNA Methylation; Gene Expression Regulation, Neoplastic; Hep G2 Cells; Humans; Leupeptins; Liver Neoplasms; MicroRNAs; Mutation; Phosphatidylethanolamine Binding Protein; Promoter Regions, Genetic; RNA Interference

The hepatoma upregulated protein (HURP) represents a putative oncogene that is overexpressed in many human cancers, especially hepatocellular carcinoma (HCC). HURP plays an important role during mitotic spindle formation, a process that is targeted by various anti-cancer drugs like taxol. However, the role of HURP during the establishment of taxol chemoresistance in HCC remains unclear. In this study, we observed that high HURP protein level correlates with taxol resistance in HCC cells. Following HURP knockdown, HCC cells show a more sensitive response to taxol treatment. Notably, sorafenib, a tyrosine kinase inhibitor approved for the treatment of HCC, inhibits HURP expression primarily at the transcriptional level and sensitizes HCC cells to sub-lethal doses of taxol. By using real-time PCR and chromatin immunoprecipitation assays, we observed that the NF-κB family member c-Rel represents a putative transcription factor that activates HURP gene expression. In addition, the inhibitory effect of sorafenib on HURP expression was attributed to a reduced translation and nuclear translocation of c-Rel. Accordingly, downregulation of c-Rel using short-hairpin RNA was shown to reduce HURP protein level and enhance taxol-induced cell death. Taken together, our results indicate that HURP acts as a novel survival protein that protects HCC cells against taxol-induced cell death. In addition, the regulation of HURP gene expression by NF-κB signaling appears to be critical for the response of HCC cells to taxol.

Topics: Apoptosis; Benzenesulfonates; Carcinoma, Hepatocellular; Cell Line, Tumor; Eukaryotic Initiation Factor-4E; Humans; Leupeptins; Liver Neoplasms; Neoplasm Proteins; NF-kappa B; Niacinamide; Paclitaxel; Phenylurea Compounds; Protein Kinase Inhibitors; Proto-Oncogene Proteins c-rel; Pyridines; Sorafenib

Melanoma antigen (MAGE)-A4 is processed to generate a C-terminal fragment with proapoptotic activity. Here we demonstrate that Adriamycin promotes generation of the processed MAGE-A4 by activating the proteasome. The proteasome is known to prevent accumulation of toxic proteins to maintain cellular homeostasis.. Treatment of hepatoma cells expressing MAGE-A4 with a sublethal dose of Adriamycin increased the MAGE-A4 processing and sensitized the cells to Adriamycin-induced apoptosis. The processing of MAGE-A4 was inhibited by the proteasome inhibitors MG115, MG132, lactacystin and epoxamicin. MAGE-A4 was coimmunoprecipitated with the S6 proteasomal ATPase, and present in the fractions containing the proteasome during glycerol gradient centrifugation. Consistent with the notion that the proteasome cleaves MAGE-A4, the 26S proteasome, ubiquitin, and cell lysates were necessary for efficient in vitrocleavage of MAGE-A4.. The present study suggests that a low dose of Adriamycin increases the proteasome activity, which either maintains cellular homeostasis or leads to apoptosis depending, at least under the present conditions, on the expression of MAGE-A4.

Topics: Acetylcysteine; Animals; Antigens, Neoplasm; Antineoplastic Agents; Apoptosis; Carcinoma, Hepatocellular; Cell Line, Tumor; Chlorocebus aethiops; COS Cells; Doxorubicin; HEK293 Cells; Humans; Leupeptins; Liver Neoplasms; Neoplasm Proteins; Proteasome Endopeptidase Complex; Ubiquitin

The nonstructural 5A (NS5A) protein of hepatitis C virus (HCV) plays a critical role in HCV replication and is an attractive target for the therapy of HCV infection. So far, little is known about the posttranslational regulation of NS5A protein and its precise role in HCV RNA replication. Our objectives were to elucidate the down-regulation of NS5A protein and HCV RNA replication by zinc mesoporphyrin (ZnMP) and the mechanism by which this process occurs.. Human hepatoma cells expressing HCV proteins were used to investigate the posttranslational regulation of ZnMP on NS5A protein by Western blots and immunoprecipitation. Real-time quantitative reverse transcription polymerase chain reaction was used to determine the effects of ZnMP on HCV RNA replication.. ZnMP selectively and markedly down-regulated NS5A protein levels by increasing degradation of NS5A protein (half-life fell from 18.7 hours to 2.7 hours). The proteasome inhibitors epoxomicin and MG132 significantly abrogated degradation of NS5A protein by ZnMP without affecting levels of NS5A in the absence of ZnMP. Analysis of immunoprecipitates with an antiubiquitin antibody revealed polyubiquitination of NS5A, suggesting that ZnMP induces ubiquitination of NS5A protein. In addition, 10 micromol/L of ZnMP reduced HCV replication by approximately 63% in the Con1 replicon cells, approximately 70% in J6/Japanese fulminant hepatitis 1 HCV-transfected cells, and approximately 90% in J6/Japanese fulminant hepatitis 1 HCV-infected cells without affecting cell viability.. ZnMP produces a rapid and profound down-regulation of the NS5A protein by enhancing its polyubiquitination and proteasome-dependent catabolism. ZnMP may hold promise as a novel agent to treat HCV infection.

Topics: Antiviral Agents; Carcinoma, Hepatocellular; Cell Line, Tumor; Cysteine Proteinase Inhibitors; Dose-Response Relationship, Drug; Down-Regulation; Half-Life; Hepacivirus; Humans; Leupeptins; Liver Neoplasms; Metalloporphyrins; Oligopeptides; Proteasome Endopeptidase Complex; Protein Processing, Post-Translational; Protein Stability; RNA, Viral; Time Factors; Transfection; Ubiquitination; Viral Nonstructural Proteins; Virus Replication

Pigment epithelium-derived factor (PEDF) has several biological actions on tumor cells, but its effects are cell-type dependent. The aim of this study was to examine the pathophysiological role of PEDF in hepatocellular carcinoma (HCC). PEDF expression was examined in various hepatoma cell lines and human HCC tissues, and was seen in various hepatoma cell lines including HepG2 cells. In human HCC tissues, PEDF expression was higher than in adjacent non-HCC tissues. In addition, serum PEDF levels were higher in HCC patients than in non-HCC patients, and curative treatment of HCC caused significant reductions in serum PEDF levels compared with pretreatment levels. In vitro experiments, camptothecin (CPT) was used to induce apoptosis and the effect of PEDF was investigated by knockdown of the PEDF gene in CPT-treated HepG2 cells. Knockdown of the PEDF gene enhanced CPT-induced apoptosis, simultaneously down-regulating Bcl-xL expression in HepG2 cells. Expression of apoptosis-related molecules and effects of bafilomycin A1 on CPT-induced apoptosis were also examined in PEDF gene knockdown HepG2 cells. Treatment with bafilomycin A1 suppressed CPT-induced decreases in Bcl-xL expression and increases in apoptosis in PEDF gene knockdown HepG2 cells. PEDF may, therefore, exert anti-apoptotic effects through inhibition of lysosomal degradation of Bcl-xL in CPT-treated HepG2 cells.

Topics: Apoptosis; bcl-X Protein; Camptothecin; Carcinoma, Hepatocellular; Cell Cycle; Cyclophilins; Densitometry; Eye Proteins; Gene Expression Regulation, Neoplastic; Gene Knockdown Techniques; Hep G2 Cells; Humans; Leupeptins; Liver; Liver Neoplasms; Lysosomes; Macrolides; Nerve Growth Factors; Protein Processing, Post-Translational; Recombinant Proteins; RNA, Messenger; Serpins

Hypoxia-inducible factor-1alpha (HIF-1alpha) is destabilized via the ubiquitin-proteasome system. Thus HIF-1alpha expression is robustly upregulated by proteasome inhibition, but paradoxically its activity is reduced. In the present study, we investigated the mechanism underlying the paradoxical response of HIF-1alpha to proteasome inhibition. In both Hep3B and HEK293 cells, a proteasome inhibitor MG132 noticeably attenuated hypoxic induction of erythropoietin and VEGF mRNAs. MG132 inactivated HIF-1alpha C-terminal transactivation domain (CAD), independently of factor inhibiting HIF-1 (FIH) and inhibited p300 recruitment by HIF-1alpha. We next tested the possibility that CITED2 is involved in the HIF-1 inactivation. CITED2 was found to be degraded via the ubiquitin-proteasome system and thus was stabilized by proteasome inhibition. Both the activity and the p300 binding of HIF-1alpha were inhibited by CITED2 expression and recovered by CITED2 siRNA in the presence of MG132. These results suggest that CITED2 is stabilized by proteasome inhibition and inactivates HIF-1 by interfering with the HIF-1alpha-p300 interaction. This may be an important mode-of-action for proteasome inhibition-based cancer therapy.

Topics: Carcinoma, Hepatocellular; Cell Hypoxia; Cells, Cultured; Cysteine Proteinase Inhibitors; DNA-Binding Proteins; E1A-Associated p300 Protein; Erythropoietin; Humans; Hypoxia-Inducible Factor 1, alpha Subunit; Immunoprecipitation; Kidney; Leupeptins; Liver Neoplasms; Mixed Function Oxygenases; Proteasome Endopeptidase Complex; Proteasome Inhibitors; Repressor Proteins; RNA, Messenger; Trans-Activators; Transcription Factors; Ubiquitin; Vascular Endothelial Growth Factor A

Down-regulation of interleukin (IL)-6-type cytokine signaling has been shown to occur, among other mechanisms, via induction of the feedback inhibitor SOCS3 (suppressor of cytokine signaling 3). Binding of SOCS3 to the phosphorylated Tyr(759) in the cytoplasmic region of gp130, the common signal transducing receptor chain of all IL-6-type cytokines, is necessary for inhibition of Janus kinase-mediated signaling. In the present study, we analyzed the effect of SOCS3 on signal transduction by the proinflammatory cytokine oncostatin M (OSM), which signals through a receptor complex of gp130 and the OSM receptor (OSMR). OSM leads to a much stronger and prolonged induction of SOCS3 in HepG2 hepatoma cells and murine embryonal fibroblasts (MEF) compared with IL-6. A negative effect of SOCS3 on OSM signaling was confirmed using MEF cells lacking SOCS3. We can show that the OSMR-mediated signaling is inhibited by SOCS3 to a similar extent as previously described for gp130. However, the inhibition occurs independent of tyrosine motifs within the OSMR. Instead, SOCS3 interacts directly with JAK1 in a stimulation-dependent manner, a mechanism so far only known for SOCS1.

Topics: Animals; Antineoplastic Agents; Blotting, Western; Carcinoma, Hepatocellular; Cell Line, Transformed; Cell Line, Tumor; Cell Transformation, Viral; Cytokine Receptor gp130; Cytokines; Fibroblasts; Gene Expression Regulation; Genes, Reporter; Humans; Interleukin-6; Janus Kinase 1; Leupeptins; Liver Neoplasms; Luciferases; Mice; Oncostatin M; Precipitin Tests; Protein Binding; Protein-Tyrosine Kinases; Receptors, Amino Acid; Receptors, Cytokine; Receptors, Oncostatin M; Signal Transduction; Suppressor of Cytokine Signaling 3 Protein; Suppressor of Cytokine Signaling Proteins

High NaCl activates the transcription factor tonicity-responsive enhancer/osmotic response element binding protein (TonEBP/OREBP) by increasing its abundance and transactivation, the latter signaled by a variety of protein kinases. In addition, high NaCl causes TonEBP/OREBP to translocate into the nucleus, but little is known about the signals directing this translocation. The result is increased transcription of protective genes, including those involved in accumulation of organic osmolytes. High NaCl also damages DNA, and DNA damage activates ataxia telangiectasia-mutated (ATM) kinase through autophosphorylation on serine 1981. We previously found that ATM is involved in the high NaCl-induced increase in TonEBP/OREBP transactivation. The purpose of the present studies was to test whether ATM is also involved in high NaCl-induced TonEBP/OREBP nuclear translocation. We quantified TonEBP/OREBP in nuclear and cytoplasmic extracts from cultured cells by Western blot analysis. In COS-7 cells, wortmannin, an inhibitor of ATM, reduces high NaCl-induced nuclear translocation of TonEBP/OREBP. We used AT cells (in which ATM is inactive) to test the specificity of this effect. Nuclear translocation of native TonEBP/OREBP and of its recombinant NH2-terminal rel homology domain, which contains the nuclear localization signal, is reduced in AT cells and is restored when the cells are reconstituted with functional ATM. In conclusion, activation of ATM contributes to high NaCl-induced nuclear translocation of TonEBP/OREBP.

Topics: Androstadienes; Animals; Ataxia Telangiectasia Mutated Proteins; Carcinoma, Hepatocellular; Cell Cycle Proteins; Cell Line, Tumor; Cell Nucleus; Chlorocebus aethiops; COS Cells; Cysteine Proteinase Inhibitors; DNA Damage; DNA-Binding Proteins; Humans; Leupeptins; Liver Neoplasms; NFATC Transcription Factors; Osmotic Pressure; Protein Kinase Inhibitors; Protein Serine-Threonine Kinases; Recombinant Proteins; Signal Transduction; Sodium Chloride; Transcription Factors; Transfection; Tumor Suppressor Proteins; Water-Electrolyte Balance; Wortmannin

Chronic ethanol consumption causes increased oxidative damage in the liver. Induction of CYP2E1 is one pathway involved in how ethanol produces oxidative stress. Ethanol can cause protein accumulation, decreased proteolysis, and decreased proteasome activity. The objective of this study was to investigate the effect of inhibition of the proteasome activity on CYP2E1-dependent toxicity. HepG2 cells over-expressing CYP2E1 (E47 cells) were treated with arachidonic acid (AA) plus iron, agents important in development of alcoholic liver injury and which are toxic to E47 cells by a mechanism dependent on CYP2E1, oxidative stress, and lipid peroxidation. Addition of various proteasome inhibitors was associated with significant potentiation of the loss of cell viability caused by AA plus iron. Potentiation of toxicity was associated with increased oxidative damage as reflected by an increase in lipid peroxidation and accumulation of oxidized and nitrated proteins in E47 cells and an enhanced decline in mitochondrial membrane potential. Antioxidants prevented the loss of viability and the potentiation of this loss of viability by proteasome inhibition. CYP2E1 levels were elevated about 3-fold by the proteasome inhibitors. Inhibition of proteasome activity also potentiated toxicity of AA alone and toxicity after treatment to remove glutathione (GSH). Similar results were found in hepatocytes from pyrazole-treated rats with high levels of CYP2E1. In conclusion, proteasome activity plays an important role in modulating CYP2E1-mediated toxicity in HepG2 cells by regulating CYP2E1 levels and by removal of oxidized proteins. Such interactions may be important in CYP2E1-catalyzed toxicity of hepatotoxins and in alcohol-induced liver injury.

Topics: Antioxidants; Arachidonic Acid; Buthionine Sulfoximine; Carcinoma, Hepatocellular; Cysteine Endopeptidases; Cytochrome P-450 CYP2E1; Drug Synergism; Endopeptidases; Humans; Iron; Leupeptins; Lipid Peroxides; Liver Neoplasms; Lysosomes; Membrane Potentials; Mitochondria, Liver; Multienzyme Complexes; Proteasome Endopeptidase Complex; Tumor Cells, Cultured; Tyrosine

This report is focused on the apoptotic effect induced by MG132, an inhibitor of 26S proteasome, in human hepatoma HepG2 cells. The results were compared with those obtained with non-transformed human Chang liver cells. MG132 reduced the viability of HepG2 cells in a time- and dose-dependent manner. The effect was in tight connection with the induction of apoptosis, as indicated by fluorescence microscopy and cytometric analysis, and was accompanied by a remarkable increase in the production of H2O2 and a reduction in mitochondrial transmembrane potential (Deltapsim). In addition cell death was prevented by antioxidants such as GSH, N-acetylcysteine or catalase. Western blot analysis showed that HepG2 cells contain a very low level of Bcl-2 and a much higher level of Bcl-XL, another antiapoptotic factor of the same family. When the cells were exposed to MG132 the level of Bcl-XL diminished, while a new band, corresponding to the expression of the proapoptotic protein Bcl-XS was detected. MG132 also caused the release of cytochrome c from mitochondria and the activation of caspase-3 with the consequent degradation of poly-ADP ribose polymerase (PARP). The observation that the broad spectrum caspase inhibitor z-VAD markedly reduced the apoptotic effect of the drug clearly demonstrated that caspases play an important role in MG132-induced apoptosis. MG132 exerted a modest effect on the viability of Chang liver cells which primarily depended on the G2/M arrest of cell cycle while only a small percentage of apoptotic cells was found. The remarkable differences in the effects induced by MG132 in Chang liver cells and HepG2 cells made us hypothesise the potential use of proteasome inhibitors in hepatocarcinoma therapy.

Topics: Antineoplastic Agents; Apoptosis; bcl-X Protein; Blotting, Western; Caspase 3; Caspases; Cell Cycle; Cell Survival; Cysteine Endopeptidases; Cytosol; Enzyme Activation; Flow Cytometry; G2 Phase; Hepatoblastoma; Humans; Hydrogen Peroxide; Leupeptins; Liver Neoplasms; Membrane Potentials; Mitochondria; Mitosis; Multienzyme Complexes; Oxidative Stress; Proteasome Endopeptidase Complex; Proto-Oncogene Proteins c-bcl-2; Time Factors; Tumor Cells, Cultured