Clusterin protects hepatocellular carcinoma cells from endoplasmic reticulum stress induced apoptosis through GRP78

Early monitoring values of oncogenic signalling molecules for hepatocellular carcinoma

The prevention and early diagnosis of liver cancer remains a global medical challenge. During the malignant transformation of hepatocytes, a variety of oncogenic cellular signalling molecules, such as novel high mobility group-Box 3, angiopoietin-2, Golgi protein 73, glypican-3, Wnt3a (a signalling molecule in the Wnt/β-catenin pathway), and secretory clusterin, can be expressed and secreted into the blood. These signalling molecules are derived from different signalling pathways and may not only participate in the malignant transformation of hepatocytes but also become early diagnostic indicators of hepatocarcinogenesis or specific targeted molecules for hepatocellular carcinoma therapy. This article reviews recent progress in the study of several signalling molecules as sensitive biomarkers for monitoring hepatocarcinogenesis.

Early monitoring values of oncogenic signalling molecules for hepatocellular carcinoma

The prevention and early diagnosis of liver cancer remains a global medical challenge. During the malignant transformation of hepatocytes, a variety of oncogenic cellular signalling molecules, such as novel high mobility group-Box 3, angiopoietin-2, Golgi protein 73, glypican-3, Wnt3a (a signalling molecule in the Wnt/β-catenin pathway), and secretory clusterin, can be expressed and secreted into the blood. These signalling molecules are derived from different signalling pathways and may not only participate in the malignant transformation of hepatocytes but also become early diagnostic indicators of hepatocarcinogenesis or specific targeted molecules for hepatocellular carcinoma therapy. This article reviews recent progress in the study of several signalling molecules as sensitive biomarkers for monitoring hepatocarcinogenesis.

CLU (clusterin) and PPARGC1A/PGC1α coordinately control mitophagy and mitochondrial biogenesis for oral cancer cell survival

Mitophagy involves the selective elimination of defective mitochondria during chemotherapeutic stress to maintain mitochondrial homeostasis and sustain cancer growth. Here, we showed that CLU (clusterin) is localized to mitochondria to induce mitophagy controlling mitochondrial damage in oral cancer cells. Moreover, overexpression and knockdown of CLU establish its mitophagy-specific role, where CLU acts as an adaptor protein that coordinately interacts with BAX and LC3 recruiting autophagic machinery around damaged mitochondria in response to cisplatin treatment. Interestingly, CLU triggers class III phosphatidylinositol 3-kinase (PtdIns3K) activity around damaged mitochondria, and inhibition of mitophagic flux causes the accumulation of excessive mitophagosomes resulting in reactive oxygen species (ROS)-dependent apoptosis during cisplatin treatment in oral cancer cells. In parallel, we determined that PPARGC1A/PGC1α (PPARG coactivator 1 alpha) activates mitochondrial biogenesis during CLU-induced mitophagy to maintain the mitochondrial pool. Intriguingly, PPARGC1A inhibition through small interfering RNA (siPPARGC1A) and pharmacological inhibitor (SR-18292) treatment counteracts CLU-dependent cytoprotection leading to mitophagy-associated cell death. Furthermore, co-treatment of SR-18292 with cisplatin synergistically suppresses tumor growth in oral cancer xenograft models. In conclusion, CLU and PPARGC1A are essential for sustained cancer cell growth by activating mitophagy and mitochondrial biogenesis, respectively, and their inhibition could provide better therapeutic benefits against oral cancer.

Enhancing precision medicine: Bispecific antibody-mediated targeted delivery of lipid nanoparticles for potential cancer therapy

The precise delivery of therapeutic agents to specific cell populations, including cancer cells, remains a target in modern medicine, to enhance treatment efficacy, while minimizing unintended side effects. This study presents a strategy utilizing bispecific antibodies for the targeted delivery of nucleic acid drugs to the surface of glucose-regulated protein 78 (GRP78)-overexpressing cancer cells. Strong binding affinity of the bispecific antibodies to GRP78-overexpressing cancer cells, including HEPG2 cells, confirmed the tumor-targeting potential of this platform. Functional analyses demonstrated the role of the bispecific antibodies in enhancing lipid nanoparticle (LNP) uptake, causing increased gene expression levels of nucleic acid drugs loaded within LNPs. In vivo imaging confirmed the potency of the bispecific-antibody-modified LNPs in delivering nucleic acid drugs to tumors and sustaining therapeutic expression levels. In vivo therapy results indicated that the bispecific antibodies improved the antitumor activity of PE38-loaded LNPs in tumors overexpressing surface GRP78. This study pioneered a bispecific-antibody-centered platform for the targeted delivery of nucleic acid drugs. The robust antigen-antibody binding affinity, tumor-selective interactions, enhanced cellular uptake, and proficient gene expression promise to advance precision therapeutics in oncology. Continued refinement and translation of this drug delivery strategy are important to unlock its full clinical potential.

The role and function of CLU in cancer biology and therapy

Clusterin (CLU) is a highly evolutionary conserved glycoprotein with multiple isoform-specific functions and is widely distributed in different species. Accumulated evidence has shown the prominent role of CLU in regulating several essential physiological processes, including programmed cell death, metastasis, invasion, proliferation and cell growth via regulating diverse signaling pathways to mediate cancer progression in various cancers, such as prostate, breast, lung, liver, colon, bladder and pancreatic cancer. Several studies have revealed the potential benefit of inhibiting CLU in CLU inhibition-based targeted cancer therapies in vitro, in vivo or in human, suggesting CLU is a promising therapeutic target. This review discusses the multiple functions and mechanisms of CLU in regulating tumor progression of various cancers and summarizes the inhibitors of CLU used in CLU inhibition-based targeted cancer therapies.

The Ins and Outs of Clusterin: Its Role in Cancer, Eye Diseases and Wound Healing

Clusterin (CLU) is a glycoprotein originally discovered in 1983 in ram testis fluid. Rapidly observed in other tissues, it was initially given various names based on its function in different tissues. In 1992, it was finally named CLU by consensus. Nearly omnipresent in human tissues, CLU is strongly expressed at fluid-tissue interfaces, including in the eye and in particular the cornea. Recent research has identified different forms of CLU, with the most prominent being a 75-80 kDa heterodimeric protein that is secreted. Another truncated version of CLU (55 kDa) is localized to the nucleus and exerts pro-apoptotic activities. CLU has been reported to be involved in various physiological processes such as sperm maturation, lipid transportation, complement inhibition and chaperone activity. CLU was also reported to exert important functions in tissue remodeling, cell-cell adhesion, cell-substratum interaction, cytoprotection, apoptotic cell death, cell proliferation and migration. Hence, this protein is sparking interest in tissue wound healing. Moreover, CLU gene expression is finely regulated by cytokines, growth factors and stress-inducing agents, leading to abnormally elevated levels of CLU in many states of cellular disturbance, including cancer and neurodegenerative conditions. In the eye, CLU expression has been reported as being severely increased in several pathologies, such as age-related macular degeneration and Fuch's corneal dystrophy, while it is depleted in others, such as pathologic keratinization. Nevertheless, the precise role of CLU in the development of ocular pathologies has yet to be deciphered. The question of whether CLU expression is influenced by these disorders or contributes to them remains open. In this article, we review the actual knowledge about CLU at both the protein and gene expression level in wound healing, and explore the possibility that CLU is a key factor in cancer and eye diseases. Understanding the expression and regulation of CLU could lead to the development of novel therapeutics for promoting wound healing.

The clusterin connectome: Emerging players in chondrocyte biology and putative exploratory biomarkers of osteoarthritis

Introduction

Clusterin is amoonlighting protein that hasmany functions. It is amultifunctional Q6 holdase chaperone glycoprotein that is present intracellularly and extracellularly in almost all bodily fluids. Clusterin is involved in lipid transport, cell differentiation, regulation of apoptosis, and clearance of cellular debris, and plays a protective role in ensuring cellular survival. However, the possible involvement of clusterin in arthritic disease remains unclear. Given the significant potential of clusterin as a biomarker of osteoarthritis (OA), a more detailed analysis of its complex network in an inflammatory environment, specifically in the context of OA, is required. Based on the molecular network of clusterin, this study aimed to identify interacting partners that could be developed into biomarker panels for OA.

Methods

The STRING database and Cytoscape were used to map and visualize the clusterin connectome. The Qiagen Ingenuity Pathway Analysis (IPA) software was used to analyze and study clusterinassociated signaling networks in OA. We also analyzed transcription factors known to modulate clusterin expression, which may be altered in OA.

Results

The top hits in the clusterin network were intracellular chaperones, aggregate-forming proteins, apoptosis regulators and complement proteins. Using a text-mining approach in Cytoscape, we identified additional interacting partners, including serum proteins, apolipoproteins, and heat shock proteins.

Discussion

Based on known interactions with proteins, we predicted potential novel components of the clusterin connectome in OA, including selenoprotein R, semaphorins, and meprins, which may be important for designing new prognostic or diagnostic biomarker panels.

The Influence of Clusterin Glycosylation Variability on Selected Pathophysiological Processes in the Human Body

The present review gathers together the most important information about variability in clusterin molecular structure, its profile, and the degree of glycosylation occurring in human tissues and body fluids in the context of the utility of these characteristics as potential diagnostic biomarkers of selected pathophysiological conditions. The carbohydrate part of clusterin plays a crucial role in many biological processes such as endocytosis and apoptosis. Many pathologies associated with neurodegeneration, carcinogenesis, metabolic diseases, and civilizational diseases (e.g., cardiovascular incidents and male infertility) have been described as causes of homeostasis disturbance, in which the glycan part of clusterin plays a very important role. The results of the discussed studies suggest that glycoproteomic analysis of clusterin may help differentiate the severity of hippocampal atrophy, detect the causes of infertility with an immune background, and monitor the development of cancer. Understanding the mechanism of clusterin (CLU) action and its binding epitopes may enable to indicate new therapeutic goals. The carbohydrate part of clusterin is considered necessary to maintain its proper molecular conformation, structural stability, and proper systemic and/or local biological activity. Taking into account the wide spectrum of CLU action and its participation in many processes in the human body, further studies on clusterin glycosylation variability are needed to better understand the molecular mechanisms of many pathophysiological conditions. They can also provide the opportunity to find new biomarkers and enrich the panel of diagnostic parameters for diseases that still pose a challenge for modern medicine.

Thymoquinone Potentiated the Anticancer Effect of Cisplatin on Hepatic Tumorigenesis by Modulating Tissue Oxidative Stress and Endoplasmic GRP78/CHOP Signaling

Thymoquinone (TQ) combined with Cisplatin may augment its anticancer effect on hepatocellular carcinoma (HCC), through oxidative stress mitigation and endoplasmic reticulum (ER) protein modulation. Fifty adult male Wistar albino rats were assigned into five equal experimental groups (n = 10); 1) Control, 2) diethylnitrosamine/carbon tetrachloride-induced liver tumorigenesis model (HCC), 3) Cisplatin (2 mg.kg^-1ip) treated rats, 4) Thymoquinone treated group (20 mg.kg^-1oral), and 5) group treated with both drugs as in Groups 3 and 4. Treatment regimens started following model confirmation and continued for 4 weeks. In the HCC model, we detected elevated ER chaperone glucose-regulated protein-78 (GRP78) and reduced C/EBP-homologous protein (CHOP)-mediated apoptosis that was accompanied by the elevated alpha-fetoprotein (AFP) marker and deteriorated liver functions. Our original results indicated that Thymoquinone potentiated the pro-apoptotic effect of cisplatin by modulating GRP78/CHOP signaling. Cisplatin/TQ reduced the elevated GRP78 and induced CHOP-mediated apoptosis in the diseased liver tissues compared to the HCC and Cisplatin treated groups. Cisplatin/TQ combination normalized AFP levels and improved liver functions compared to both HCC and cisplatin groups alone. In conclusion, Thymoquinone enhanced the efficacy of Cisplatin in HCC treatment by modulating the GRP78/CHOP/caspase-3 pathway. Thymoquinone is recommended to achieve greater therapeutic benefits and reduce the cisplatin hepatotoxicity in HCC management.

Comprehensive Identification of Potential Crucial Genes and miRNA-mRNA Regulatory Networks in Papillary Thyroid Cancer

Background

Thyroid cancer is the most common endocrine malignancy, with a recent global increase of 20% in age-related incidence. Ultrasonography and ultrasonography-guided fine-needle aspiration biopsy (FNAB) are the most widely used diagnostic tests for thyroid nodules; however, it is estimated that up to 25% of thyroid biopsies are cytologically inconclusive. Molecular markers can help guide patient-oriented and targeted treatment of thyroid nodules and thyroid cancer.

Methods

Datasets related to papillary thyroid cancer (PTC) or thyroid carcinoma (GSE129562, GSE3678, GSE54958, GSE138042, and GSE124653) were downloaded from the GEO database and analysed using the Limma package of R software. For functional enrichment analysis, the Kyoto Encyclopedia of Genes and Genomes pathway analysis and Gene Ontology were applied to differentially expressed genes (DEGs) using the Metascape website. A protein-protein interaction (PPI) network was built from the STRING database. Gene expression, protein expression, immunohistochemistry, and potential functional gene survival were analysed using the GEPIA website, the Human Protein Atlas website, and the UALCAN website. Potential target miRNAs were predicted using the miRDB and Starbase datasets.

Results

We found 219 upregulated and 310 downregulated DEGs, with a cut-off of p < 0.01 and ∣log FC | >1.5. The DEGs in papillary thyroid cancer were mainly enriched in extracellular structural organisation. At the intersection of the PPI network and Metascape MCODEs, the hub genes in common were identified as FN1, APOE, CLU, and SDC2. In the targeted regulation network of miRNA-mRNA, the hsa-miR-424-5p was found to synchronously modulate two hub genes. Survival analysis showed that patients with high expression of CLU and APOE had better prognosis.

Conclusions

CLU and APOE are involved in the molecular mechanism of papillary thyroid cancer. The hsa-miR-424-5p might have the potential to reverse the processes of papillary thyroid cancer by modulating the hub genes. These are potential targets for the treatment of patients with papillary thyroid cancer.

Clusterin Protects Lipotoxicity-Induced Apoptosis via Upregulation of Autophagy in Insulin-Secreting Cells

BACKGROUND

There is a great need to discover factors that could protect pancreatic β-cells from apoptosis and thus prevent diabetes mellitus. Clusterin (CLU), a chaperone protein, plays an important role in cell protection in numerous cells and is involved in various cellular mechanisms, including autophagy. In the present study, we investigated the protective role of CLU through autophagy regulation in pancreatic β-cells.

METHODS

To identify the protective role of CLU, mouse insulinoma 6 (MIN6) cells were incubated with CLU and/or free fatty acid (FFA) palmitate, and cellular apoptosis and autophagy were examined.

RESULTS

Treatment with CLU remarkably upregulated microtubule-associated protein 1-light chain 3 (LC3)-II conversion in a doseand time-dependent manner with a significant increase in the autophagy-related 3 (Atg3) gene expression level, which is a mediator of LC3-II conversion. Moreover, co-immunoprecipitation and fluorescence microscopy experiments showed that the molecular interaction of LC3 with Atg3 and p62 was markedly increased by CLU. Stimulation of LC3-II conversion by CLU persisted in lipotoxic conditions, and FFA-induced apoptosis and dysfunction were simultaneously improved by CLU treatment. Finally, inhibition of LC3-II conversion by Atg3 gene knockdown markedly attenuated the cytoprotective effect of CLU.

CONCLUSION

Taken together, these findings suggest that CLU protects pancreatic β-cells against lipotoxicity-induced apoptosis via autophagy stimulation mediated by facilitating LC3-II conversion. Thus, CLU has therapeutic effects on FFA-induced pancreatic β-cell dysfunction.

Increased expression and retention of the secretory chaperone proSAAS following cell stress

The secretory pathway of neurons and endocrine cells contains a variety of mechanisms designed to combat cellular stress. These include not only the unfolded protein response pathways but also diverse chaperone proteins that collectively work to ensure proteostatic control of secreted and membrane-bound molecules. One of the least studied of these chaperones is the neural- and endocrine-specific molecule known as proSAAS. This small chaperone protein acts as a potent anti-aggregant both in vitro and in cellulo and also represents a cerebrospinal fluid biomarker in Alzheimer's disease. In the present study, we have examined the idea that proSAAS, like other secretory chaperones, might represent a stress-responsive protein. We find that exposure of neural and endocrine cells to the cell stressors tunicamycin and thapsigargin increases cellular proSAAS mRNA and protein in Neuro2A cells. Paradoxically, proSAAS secretion is inhibited by these same drugs. Exposure of Neuro2A cells to low concentrations of the hypoxic stress inducer cobalt chloride, or to sodium arsenite, an oxidative stressor, also increases cellular proSAAS content and reduces its secretion. We conclude that the cellular levels of the small secretory chaperone proSAAS are positively modulated by cell stress.

Astragalin alleviates ischemia/reperfusion‑induced brain injury via suppression of endoplasmic reticulum stress

Excessive apoptosis and neuronal dysfunction are pathological features of ischemic stroke. Previous studies have demonstrated that astragalin (AST) exerted both anti‑​apoptotic and anti‑inflammatory effects in several types of disease, although its potential effect in ischemic stroke remains unclear. The purpose of the present study was to investigate the effects of AST on cerebral ischemia/reperfusion (I/R)‑induced brain injury and the underlying mechanisms. Brain injury was assessed in an experimental rat model using measurement of neurological scores and inflammatory factors. To assess the role of AST in I/R‑induced brain injury and the potential mechanism of action, SH5Y were treated with thapsigargin and AST. Apoptotic rate and ER stress levels were measured by western blotting, reverse transcription‑quantitative PCR and immunofluorescence staining. It was discovered that AST significantly improved long‑term neurological outcomes in rats following cerebral I/R injury, through the attenuation of the expression levels of apoptotic proteins (Bax and cleaved‑caspase‑3) and the release of inflammatory cytokines, as well as upregulating the expression levels of the anti‑apoptotic protein Bcl‑2. Furthermore, AST attenuated the expression levels of the endoplasmic reticulum (ER) stress‑related protein, glucose‑regulated protein, 78 kDa, as well as its downstream apoptotic mediators (CHOP and caspase‑12). Thapsigargin‑induced ER stress activation and apoptosis were also attenuated by AST in an in vitro neuronal cell culture model. In conclusion, these results suggested that AST may protect against I/R‑induced brain injury, thus, highlighting its therapeutic potential in patients with ischemic stroke.

Secretory Clusterin as a Novel Molecular-targeted Therapy for Inhibiting Hepatocellular Carcinoma Growth

BACKGROUND

Although secretory clusterin (sCLU) plays a crucial role in Hepatocellular Carcinoma (HCC) cells proliferation, Multiple Drug Resistance (MDR), metastasis and so on, its targeted effects and exact mechanism are still unknown. This review summarizes some new progress in sCLU as a molecular-targeted therapy in the treatment of HCC.

METHODS

A systematic review of the published English-language literature about sCLU and HCC has been performed using the PubMed and bibliographic databases. Some valuable studies on sCLU in HCC progression were searched for relevant articles with the keywords: HCC, diagnosis, MDR, as molecular-targeted in treatment, and so on.

RESULTS

The incidence of the positive rate of sCLU was significantly higher in HCC tissues as compared to the surrounding tissues at mRNA or protein level, gradually increasing with tumor-nodemetastasis staging (P<0.05). Also, the abnormal level of sCLU was related to poor differentiation degree, and considered as a useful marker for HCC diagnosis or independent prognosis for patients. Hepatic sCLU could be silenced at mRNA level by specific sCLU-shRNA or by OGX-011 to inhibit cancer cell proliferation with an increase in apoptosis, cell cycle arrest, reversal MDR, alteration of cell migration or invasion behaviors, and a decrease in GSK-3β or AKT phosphorylation in vitro, as well as significant suppression of the xenograft growth by down-regulating β-catenin, p-GSK3β, and cyclinD1 expression in vivo.

CONCLUSION

Abnormal hepatic sCLU expression should not only be a new diagnostic biomarker but also a novel promising target for inhibiting HCC growth.

Aspirin inhibits hepatocellular carcinoma cell proliferation in vitro and in vivo via inducing cell cycle arrest and apoptosis

Aspirin, a nonsteroidal anti‑inflammatory drug (NSAID), is known to inhibit cell proliferation in a variety of cancers. However, the underlying mechanism of this inhibition remains unknown. We investigated the effects of aspirin on hepatocellular carcinoma (HCC) cells using in vitro and in vivo models. Six HCC cell lines and a liver cancer cell line including Huh‑7 were used in assays that evaluated cell proliferation, cell cycle, and apoptosis. Flow cytometry, enzyme‑linked immunosorbent assay (ELISA), western blot analysis, and phosphorylated receptor tyrosine kinase array were used to evaluate the effects of aspirin on the cells, and microRNAs (miRNAs) were analyzed by a miRNA array chip. The results were validated in vivo using a nude mouse model of Huh‑7‑xenografted tumors. Our results showed that aspirin exhibited an antiproliferative effect on all cell lines. Moreover, aspirin induced G0/G1 cell cycle arrest and modulated the levels of cell cycle‑related molecules such as cyclin E, cyclin D1, and cyclin‑dependent kinase 2 (Cdk2). In addition, aspirin upregulated the levels of caspase‑cleaved cytokeratin 18, increased the proportion of early apoptotic cells, decreased the levels of clusterin and heat shock protein 70 (HSP 70), upregulated the levels of miRNA‑137 and inhibited epidermal growth factor receptor (EGFR) activation. In addition, we observed that aspirin suppressed cell proliferation partially through the miRNA‑137/EGFR pathway. Our in vivo results showed that aspirin reduced the growth of xenograft tumors in nude mice. In conclusion, aspirin was able to inhibit the growth of HCC cells by cell cycle arrest, apoptosis, and alteration of miRNA levels in in vitro and in vivo models.

Identification of Candidate Biomarkers for HCV Leading to Hepatocellular Carcinoma Differential Stages From Serum Samples

Background:

Hepatocellular carcinoma (HCC) is one of the most deadly liver malignancy found and Hepatitis C virus (HCV) is a prominent risk factor for this disease. Prognosis of HCC is poor; initiate the need of markers to discover therapeutic targets in HCC.

Introduction:

Clinical staging systems of HCC composed of tumor characteristics along with liver function test are important in prognosis but they are not precise. Molecular profiling can lead to a better understanding of the physiopathology of HCC and can help in the development of novel therapeutic approaches.

Methods:

64 HCC serum samples (shifted from HCV) were graded into stage I- IV; along with +ive (3 Hepatitis C) and -ive control (2 healthy persons). Proteins were separated by sodium dodecyl sulfatepolyacrylamide gel electrophoresis (SDS-PAGE) and differential mRNA expression from serum samples of different HCC stages was confirmed by Real Time Polymerase Chain Reaction (qPCR).

Results:

HCC serum proteins displayed differential expression of glutathione s-transferase (GST), glypican-3 (GPC3), vitronectin (VTN), and clusterin (CLU) by SDS-PAGE. GST was expressed in -ive control, while GPC3 was found in both -ive and +ive control. The qPCR analysis, display more than 0.07 fold decrease in GST in I-IV HCC stages. The highest increase in HCC stages was observed by GPC3; about 4 fold increase in I-IV stages. VTN show 1.7-3.4 fold; while CLU show 2-3.5 fold increase in four stages of HCC.

Conclusion:

GPC3, VTN and CLU in combination can be good potential markers for differentiating stages (I-IV) of HCC.

Tracking acute phase protein response during acute and chronic Toxoplasma gondii infection

Toxoplasmosis is a disease caused by the protozoan Toxoplasma gondii, which occurs worldwide in mammals and birds. Brain is the primary target organ because Toxoplasma gondii is a ubiquitous intracellular parasite that causes most frequently life-threatening encephalitis in immunocompromised patients. Relation of tissue cysts number, histopathology score and acute phase proteins were investigated. In this study, 36 mice are infected with Me49 strain of Toxoplasma gondii. The control group has 6 healthy mice. After inoculation of Toxoplasma gondii, at 10., 15., 20., 30., 45., 60. days, 6 each mice euthanized after collection of blood samples. Hemopexin, haptoglobulin, macroglobulin, serum amyloid A and clusterin levels are determined by ELISA. Then, brain tissues were investigated histopathologically and lesions were scored. The average cyst numbers were determined by counting three samples (25 μl each) of each brain homogenate under light microscopy. Inflammatory reaction was observed on day 10 days after inoculation (d.a.i.) The lesions were characterized by perivascular mononuclear cell infiltration, focal mononuclear cell infiltration in the meninges, and glial proliferation. Tissue cysts were observed in all Toxoplasma gondii-infected groups. The highest lesion score was observed at 60 d.a.i. And the most tissue cyst number were on day 30. d.a.i. Serum levels of hemopexin, haptoglobulin, macroglobulin, serum amyloid A and clusterin were significantly higher than the control group on day 10-20., 10., 10-30., 10.,10-45 d.a.i., respectively. High level of acute phase proteins in mice on certain days infected with Toxoplasma gondii was exhibited a relationship between brain lesions and tissue cysts.

The role of Clusterin in cancer metastasis

Clusterin is a conserved glycoprotein that has been characterized from almost all human tissues and fluids and plays a key role in cellular stress response and survival. Recently, research efforts have been contributed to explore the function of Clusterin in cancer metastasis, which is particularly important to design the strategies for treating metastatic patients. Evidence collected has demonstrated that Clusterin is overexpressed in tumor metastatic patients and experimental metastasis models. Specifically, Clusterin has been shown to have the role in anti-apoptotic capacities, development of therapy resistance and induction of epithelial–mesenchymal transition, all associated with cancer metastasis. Inhibition of Clusterin is known to increase the cytotoxic effects of chemotherapeutic agents and improves advanced cancer patients survival in clinical trials. Our unpublished data have demonstrated that Clusterin is overexpressed in bladder cancer and metformin, a well-known metabolism modulator specifically targets Clusterin by inhibiting migration of bladder cancer cells. In this review, we provide a general view of how Clusterin modulates cancer metastasis and update current understanding of detailed molecular mechanisms underlying of Clusterin for developing cancer management in future.

Clusterin in Alzheimer's Disease: Mechanisms, Genetics, and Lessons From Other Pathologies

Clusterin (CLU) or APOJ is a multifunctional glycoprotein that has been implicated in several physiological and pathological states, including Alzheimer's disease (AD). With a prominent extracellular chaperone function, additional roles have been discussed for clusterin, including lipid transport and immune modulation, and it is involved in pathways common to several diseases such as cell death and survival, oxidative stress, and proteotoxic stress. Although clusterin is normally a secreted protein, it has also been found intracellularly under certain stress conditions. Multiple hypotheses have been proposed regarding the origin of intracellular clusterin, including specific biogenic processes leading to alternative transcripts and protein isoforms, but these lines of research are incomplete and contradictory. Current consensus is that intracellular clusterin is most likely to have exited the secretory pathway at some point or to have re-entered the cell after secretion. Clusterin's relationship with amyloid beta (Aβ) has been of great interest to the AD field, including clusterin's apparent role in altering Aβ aggregation and/or clearance. Additionally, clusterin has been more recently identified as a mediator of Aβ toxicity, as evidenced by the neuroprotective effect of CLU knockdown and knockout in rodent and human iPSC-derived neurons. CLU is also the third most significant genetic risk factor for late onset AD and several variants have been identified in CLU. Although the exact contribution of these variants to altered AD risk is unclear, some have been linked to altered CLU expression at both mRNA and protein levels, altered cognitive and memory function, and altered brain structure. The apparent complexity of clusterin's biogenesis, the lack of clarity over the origin of the intracellular clusterin species, and the number of pathophysiological functions attributed to clusterin have all contributed to the challenge of understanding the role of clusterin in AD pathophysiology. Here, we highlight clusterin's relevance to AD by discussing the evidence linking clusterin to AD, as well as drawing parallels on how the role of clusterin in other diseases and pathways may help us understand its biological function(s) in association with AD.

Clusterin increases mitochondrial respiratory chain complex I activity and protects against hexavalent chromium-induced cytotoxicity in L-02 hepatocytes

Previous evidence revealed significant elevated liver cancer mortality in the areas where water was contaminated with hexavalent chromium [Cr(vi)], which highlighted that we should pay more attention to Cr(vi)-induced cytotoxicity in hepatocytes. We found that Clusterin (CLU) was up-regulated in Cr(vi)-exposed L-02 hepatocytes, but the role CLU played in Cr(vi)-induced cytotoxicity has never been explored. In the present study, we demonstrate Cr(vi) targeted mitochondrial respiratory chain complex I (MRCC I) activity and induced reactive oxygen species (ROS) accumulation, which caused mitochondrial damage that was characterized by the increase of permeability transition pore (PTP) open rate, the collapse of mitochondrial membrane potential (MMP), and the release of apoptosis-inducing factor (AIF) and Cytochrome C (Cyt C) from mitochondria to cytoplasm, which then induced cell viability loss and increased aspartate transaminase (AST)/alanine transaminase (ALT) leakage. We reveal that Cr(vi) may regulate CLU expression through the ROS-ataxia telangiectasia mutant (ATM)-insulin-like growth factor 1 (IGF-1) axis, and CLU expression was positively correlated to MRCC I activity. We further confirmed that CLU may regulate MRCC I activity via modulating its subunit nicotinamide adenine dinucleotide dehydrogenase (ubiquinone) Fe-S protein 3 (NDUFS3) expression. By the establishment of CLU over-expression cells, we found that over-expression of CLU alleviated Cr(vi)-induced MRCC I inhibition and further rescued cell viability loss and reduced AST and ALT leakage. Thus, we reached the conclusion that the CLU-induced increase of MRCC I activity protected against Cr(vi)-induced cytotoxicity. The present research will provide new experimental evidence for thoroughly clarifying the cytotoxicity and the carcinogenic mechanism of Cr(vi).

Role of secretory clusterin in hepatocarcinogenesis

Secretory clusterin (sCLU) is a small stress-induced cytoprotective chaperone protein. Its biological functions are similar to those of a heat-shock protein. The sCLU plays a crucial role in cell proliferation, multiple drug resistance, metastasis, and tumor progression. Abnormal sCLU expression in tumor tissues or sera of patients with primary hepatic cancer has been considered a useful biomarker for diagnosis and surveillance. However, the exact relationship between sCLU overexpression and malignant transformation of hepatocytes is still unknown. The present review examines some novel advances of the knowledge about the oncogenic role of sCLU in hepatocarcinogenesis.

Secretory Clusterin Mediates Oxaliplatin Resistance via the Gadd45a/PI3K/Akt Signaling Pathway in Hepatocellular Carcinoma

Purpose: Systemic therapy has often been used for patients with advanced hepatocellular carcinoma (HCC). However, due to drug resistance, the use of cytotoxic chemotherapy in the treatment of patients with advanced HCC has typically demonstrated low response rates. Secretory clusterin (sCLU) is expressed in aggressive late-stage tumors and associated with resistance to chemotherapy, including that in HCC cases. The present research aimed to investigate the biological role of sCLU in HCC.

Methods: sCLU expression in HCC and normal tissues was examined using immunohistochemical staining, followed by analysis of the correlation between sCLU expression and clinical indicators. In addition, the role and internal mechanism of sCLU in cell proliferation and apoptosis were investigated in HCC cells.

Results: sCLU expression was significantly upregulated in HCC tissues; and was associated with histological grade and poor overall survival. The levels of sCLU were significantly increased in Bel7402, SMMC7721 and resistant HCC cells (Bel7404-OR). Inhibiting the activity of sCLU enhanced the chemosensitivity of Bel7402 and SMMC7721 cells. Downregulation of sCLU could increase the expression of Gadd45a in HCC cells. Overexpression of sCLU contributed to drug resistance in Bel7402, SMMC7721 and Bel7404-OR cells; whereas, overexpression of Gadd45a alone overcame drug resistance in the cells above. No significant expression changes of sCLU and Gadd45a were observed in HCC cells after the interference of a selective inhibitor of the PI3K/Akt signaling pathway. However, regulation of the expression of Gadd45a could influence the phosphorylation level of Akt; and further regulate the expression of Bcl-2 and Bax proteins involved in the mitochondrial apoptosis pathways.

Conclusions: The results demonstrate that sCLU/Gadd45a/PI3K/Akt signaling represents a novel pathway that could regulate drug resistance in a one-way manner in HCC cells.

GP73 level determines chemotherapeutic resistance in human hepatocellular carcinoma cells

Objective GP73 is a new hepatocellular carcinoma (HCC) marker, which is highly expressed in hepatocellular carcinoma and closely relates to prognosis. This study was to investigate the effects of GP73 on cellular proliferation, apoptosis, oxaliplatin (OXA) resistance and secretory clusterin (sCLU) of HCC cells. Materials and Methods Western blot and immunofluorescence was used to detect the expression of GP73 in 8 types of commonly used HCC cell lines. Drug resistance was induced by increasing concentration gradient method. The drug-resistant human HCC cell lines underwent GP73 overexpression or inhibition. Flow cytometry were used to detect the proliferation and apoptosis of HCC cell lines. The changes of sCLU were detected by enzyme-linked immunosorbent assay (ELISA). Results The expression of GP73 in MHC-97H cells was the highest and in Hep3B cells the lowest. The expression of GP73 was found further elevated in OXA-resistant MHC-97H cells. After the knockdown of GP73 in OXA-resistant 97H cells, the IC₅₀ of OXA decreased and the ability of cell proliferation decreased significantly. After over-expression of GP73 in OXA-resistant Hep3B cells, the IC₅₀ of OXA increased and the cell proliferation ability increased, showing that GP73 is critical for OXA resistant in HCC cell lines; No significant change of sCLU level in GP73 overexpressed Hep3B and GP73 blocked MHCC-97H were identified. Conclusion The expression level of GP73 is critical for the resistance of OXA in HCC cell lines.

l-Glutamine Attenuates Apoptosis Induced by Endoplasmic Reticulum Stress by Activating the IRE1α-XBP1 Axis in IPEC-J2: A Novel Mechanism of l-Glutamine in Promoting Intestinal Health

Intestinal absorption and barrier malfunctions are associated with endoplasmic reticulum stress (ERS) in the intestine. We induced ERS by exposing the intestinal porcine epithelial cell line J2 (IPEC-J2) to tunicamycin (TUNI) to explore the potential of l-glutamine to reduce ERS-induced apoptosis. Our experiments demonstrated that exposing cells to TUNI results in spontaneous ERS and encourages the upregulation of glucose-regulated protein 78 (GRP78). Prolonged TUNI-induced ERS was found to increase apoptosis mediated by C/enhancer binding protein homologous protein (CHOP), accompanied by GRP78 downregulation. Treatment with l-glutamine was found to promote cell proliferation within the growth medium but to have little effect in basic Dulbecco’s modified Eagle medium. Finally, in the milieu of TUNI-induced ERS, l-glutamine was found to maintain a high level of GRP78, alleviate CHOP-mediated apoptosis and activate the inositol requiring enzyme 1α (IRE1α)-X-box binding protein 1 (XBP1) axis. A specific inhibitor of the IRE1α-XBP1 axis reversed the protective effect of l-glutamine by blocking the expression of IRE1α/XBP1s. We propose that the functional effect of l-glutamine on intestinal health may be partly due to its modulation of ERS and CHOP-mediated apoptosis.

Clusterin inhibition mediates sensitivity to chemotherapy and radiotherapy in human cancer

Since its discovery in 1983, the protein clusterin (CLU) has been isolated from almost all human tissues and fluids and linked to the development of different physiopathological processes, including carcinogenesis and tumor progression. During the last few years, several studies have shown the cytoprotective role of secretory CLU in tumor cells, inhibiting their apoptosis and enhancing their resistance to conventional treatments including hormone depletion, chemotherapy, and radiotherapy. In an effort to determine the therapeutic potential that the inhibition of this protein could have on the development of new strategies for cancer treatment, numerous studies have been carried out in this field, with results, in most cases, satisfactory but sometimes contradictory. In this document, we summarize for the first time the current knowledge of the effects that CLU inhibition has on sensitizing tumor cells to conventional cancer treatments and discuss its importance in the development of new strategies against cancer.

Reduced glutathione alleviates tunicamycin-induced endoplasmic reticulum stress in mouse preimplantation embryos

Endoplasmic reticulum (ER) stress, a dysfunction in protein-folding capacity, is involved in many pathological and physiological responses, including embryonic development. This study aims to determine the developmental competence, apoptosis, and stress-induced gene expression in mouse preimplantation embryos grown in an in vitro culture medium supplemented with different concentrations of the ER stress inducer tunicamycin (TM) and the antioxidant glutathione (GSH). Treatment of zygotes with 0.5 µg/ml TM significantly decreased (P < 0.05) the rate of blastocyst formation, whereas 1 mM GSH supplementation improved the developmental rate of blastocysts. Furthermore, TM treatment significantly increased (P < 0.05) the apoptotic index and reduced the total number of cells, whereas GSH significantly increased the total number of cells and decreased the apoptotic index. The expression levels of ER chaperones, including immunoglobulin-binding protein, activating transcription factor 6, double-stranded activated protein kinase-like ER kinase, activating transcription factor 4, and C/EBP homologous protein were significantly increased (P < 0.05) by TM, but significantly decreased (P < 0.05) by GSH treatment. A similar pattern was observed in the case of the pro-apoptotic gene, B cell lymphoma-associated X protein. The expression level of the anti-apoptotic gene B cell lymphoma 2, was decreased by TM, but significantly increased after co-treatment with GSH. In conclusion, GSH improves the developmental potential of mouse embryos and significantly alleviates ER stress.

Screening and Characterization of Drugs That Protect Corneal Endothelial Cells Against Unfolded Protein Response and Oxidative Stress

Purpose

To screen for and characterize compounds that protect corneal endothelial cells against unfolded protein response (UPR) and oxidative stress.

Methods

Bovine corneal endothelial cells (BCECs) were treated for 48 hours with 640 compounds from a Food and Drug Administration (FDA)-approved drug library and then challenged with thapsigargin or H₂O₂ to induce UPR or oxidative stress, respectively. Cell viability was measured using the CellTiter-Glo survival assay. Selected “hits” were subjected to further dose-response testing, and their ability to modulate expression of UPR and oxidative stress markers was assessed by RT-PCR, Western blot, and measurement of protein carbonyl and 8-hydroxydeoxyguanosine (8-OHdG) adducts in immortalized human corneal endothelial cells (iHCECs).

Results

Forty-one drugs at 20 μM and 55 drugs at 100 μM increased survival of H₂O₂-challenged cells, and 8 drugs at 20 μM and 2 drugs at 100 μM increased survival of thapsigargin-challenged cells, compared with untreated control cells. Nicergoline, ergothioneine, nimesulide, oxotremorine, and mefenamic acid increased survival of both H₂O₂- and thapsigargin-challenged cells. Oxotremorine altered DNA damage inducible 3 (CHOP) gene expression, glucose-regulated protein 78 kDa (GRP78) and activating transcription factor 4 (ATF4) protein expression, and protein carbonyl and 8-OHdG levels. Mefenamic acid altered GRP78 protein expression and protein carbonyl and 8-OHdG levels.

Conclusions

Oxotremorine and mefenamic acid are potential survival factors for corneal endothelial cells under UPR and oxidative stress. The described assay can be further expanded to screen additional drugs for potential therapeutic effect in corneal endothelial diseases such as Fuchs' endothelial corneal dystrophy.

Melittin inhibits tumor growth and decreases resistance to gemcitabine by downregulating cholesterol pathway gene CLU in pancreatic ductal adenocarcinoma

Melittin is a Chinese traditional medicine for treating chronic inflammation, immunological diseases and cancers, however, the efficacy of melittin and its mechanism for treating pancreatic ductal adenocarcinoma (PDAC) are still unknown. Here we investigated the anti-cancer activity of melittin and its regulated mechanism(s) in the PDAC models. Melittin was found to suppress tumor growth by promoting cell apoptosis and cell-cycle arrest. Interestingly, the microarray analyses demonstrated that melittin significantly regulated cholesterol biosynthesis pathway during treatment. For instance, the cholesterol pathway gene clusterin (CLU) was highly downregulated by melittin which also enhanced gemcitabine sensitivity in PDAC cells by inhibiting CLU expression. In contrast, overexpression of CLU significantly diminished melittin mediated tumor suppression and gemcitabine sensitization, suggesting that CLU is the target of melittin. Furthermore, in the xenograft mouse model, the combination therapy of melittin and gemcitabine is more efficacious for inhibiting PDAC tumor growth than either single regimen. Taken together, our study has indicated that melittin is capable of suppressing tumor growth and promoting gemcitabine sensitivity in PDAC by downregulating cholesterol pathway.

Oncogenic secretory clusterin in hepatocellular carcinoma: Expression at early staging and emerging molecular target

Secretory clusterin (sCLU) is associated with hepatocellular carcinoma (HCC) progression by contributing to angiogenesis, chemoresistance, cell survival, and metastasis. However, the sCLU expression at early stage of HCC progression remains to be clarified. In this study, the alteration of sCLU oncogenicity was firstly evaluated in HCC- and their para-cancerous- tissues. The incidence of sCLU expression in HCC was significantly higher than that in their non-tumorous tissues at message RNA (mRNA) or protein level, gradually increasing with tumor-node-metastasis (TNM) staging. Abnormal sCLU expression was associated with the poor differentiation, TNM stage, and considered as an independent prognostic factor for HCC patients. Furthermore, silencing sCLU gene transcription inhibited the colony formation and proliferation of HCC cells, with decreasing phosphorylation level of AKT and GSK-3β in HCCLM3 cells in vitro and significantly suppressed the HCC xenograft growth in vivo, suggesting that sCLU with oncogenicity should be not only an early indicator but also novel potential molecular-targeted therapy for HCC.

Relationship of clusterin with renal inflammation and fibrosis after the recovery phase of ischemia-reperfusion injury

Background

Long-term outcomes after acute kidney injury (AKI) include incremental loss of function and progression towards chronic kidney disease (CKD); however, the pathogenesis of AKI to CKD remains largely unknown. Clusterin (CLU) is a chaperone-like protein that reduces ischemia-reperfusion injury (IRI) and enhances tissue repair after IRI in the kidney. This study investigated the role of CLU in the transition of IRI to renal fibrosis.

Methods

IRI was induced in the left kidneys of wild type (WT) C57BL/6J (B6) versus CLU knockout (KO) B6 mice by clamping the renal pedicles for 28 min at the body temperature of 32 °C. Tissue damage was examined by histology, infiltrate phenotypes by flow cytometry analysis, and fibrosis-related gene expression by PCR array.

Results

Reduction of kidney weight was induced by IRI, but was not affected by CLU KO. Both WT and KO kidneys had similar function with minimal cellular infiltration and fibrosis at day 14 of reperfusion. After 30 days, KO kidneys had greater loss in function than WT, indicated by the higher levels of both serum creatinine and BUN in KO mice, and exhibited more cellular infiltration (CD8 cells and macrophages), more tubular damage and more severe tissue fibrosis (glomerulopathy, interstitial fibrosis and vascular fibrosis). PCR array showed the association of CLU deficiency with up-regulation of CCL12, Col3a1, MMP9 and TIMP1 and down-regulation of EGF in these kidneys.

Conclusion

Our data suggest that CLU deficiency worsens renal inflammation and tissue fibrosis after IRI in the kidney, which may be mediated through multiple pathways.

Electronic supplementary material

The online version of this article (doi:10.1186/s12882-016-0348-x) contains supplementary material, which is available to authorized users.

Transcriptome-Based Analysis of Molecular Pathways for Clusterin Functions in Kidney Cells

Clusterin (CLU) is a chaperone-like protein and plays a protective role against renal ischemia-reperfusion injury (IRI); however, the molecular pathways for its functions in the kidney are not fully understood. This study was designed to investigate CLU-mediating pathways in kidney cells by using bioinformatics analysis. CLU null renal tubular epithelial cells (TECs) expressing human CLU cDNA (TEC-CLU(hCLU) ) or empty vector (TEC-CLU(-/-) ) were exposed to normoxia or hypoxia (1% O2 ). Transcriptome profiling with a significant twofold change was performed using SurePrint G3 Mouse Gene Expression 8 × 60 K microarray, and the signaling pathways was ranked by using Ingenuity pathway analysis. Here, we showed that compared to CLU null controls, ectopic expression of human CLU in CLU null kidney cells promoted cell growth but inhibited migration in normoxia, and enhanced cell survival in hypoxia. CLU expression affected expression of 3864 transcripts (1893 up-regulated) in normoxia and 3670 transcripts (1925 up-regulated) in hypoxia. CLU functions in normoxia were associated mostly with AKT2/PPP2R2B-dependent PI3K/AKT, PTEN, VEGF, and ERK/MAPK signaling and as well with GSK3B-mediated cell cycle progression. In addition to unfolded protein response (UPR) and/or endoplasmic reticulum (ER) stress, CLU-enhanced cell survival in hypoxia was also associated with PIK3CD/MAPK1-dependent PI3K/AKT, HIF-α, PTEN, VEGF, and ERK/MAPK signaling. In conclusion, our data showed that CLU functions in kidney cells were mainly mediated in a cascade manner by PI3K/AKT, PTEN, VEGF, and ERK/MAPK signaling, and specifically by activation of UPR/ER stress in hypoxia, providing new insights into the protective role of CLU in the kidney. J. Cell. Physiol. 231: 2628-2638, 2016. © 2016 Wiley Periodicals, Inc.

A Targetable Molecular Chaperone Hsp27 Confers Aggressiveness in Hepatocellular Carcinoma

Heat shock protein 27 (Hsp27) is an ATP-independent molecular chaperone and confers survival advantages and resistance to cancer cells under stress conditions. The effects and molecular mechanisms of Hsp27 in HCC invasion and metastasis are still unclear. In this study, hepatocellular carcinoma (HCC) tissue array (n = 167) was used to investigate the expression and prognostic relevance of Hsp27 in HCC patients. HCC patients with high expression of Hsp27 exhibited poor prognosis. Overexpression of Hsp27 led to the forced invasion of HCC cells, whereas silencing Hsp27 attenuated invasion and metastasis of HCC cells in vitro and in vivo. We revealed that Hsp27 activated Akt signaling, which in turn promoted MMP2 and ITGA7 expression and HCC metastasis. We further observed that targeting Hsp27 using OGX-427 obviously suppressed HCC metastasis in two metastatic models. These findings indicate that Hsp27 is a useful predictive factor for prognosis of HCC and it facilitates HCC metastasis through Akt signaling. Targeting Hsp27 with OGX-427 may represent an attractive therapeutic option for suppressing HCC metastasis.

Inhibition of mitogen-activated protein kinase signaling pathway sensitizes breast cancer cells to endoplasmic reticulum stress-induced apoptosis

Accumulation of unfolded proteins in the endoplasmic reticulum (ER) induces ER stress which is observed in many human diseases, including breast cancer. Cellular adaptation to ER stress is mediated by the unfolded protein response (UPR), which aims at restoring ER homeostasis. Higher levels of GRP78 expression indicates constitutive activation of the UPR in breast cancer leading to breast cancer cells that are relatively resistant to ER stress-induced apoptosis. Tunicamycin (TM), an ER stress inducer, constitutively activates the mitogen-activated protein kinase (MAPK)/extracellular signal regulated kinase (ERK), and (MEK)/ERK pathway which plays a role in upregulation of GRP78 by ER stress in that inhibition of MEK by U0126 reduces the levels of GRP78 and blocks its upregulation by TM. Inhibition of the MEK/ERK pathway by U0126 sensitizes breast cancer cells to TM-induced apoptosis. Inhibition of GRP78 by siRNA knockdown enhances TM- and U0126-induced apoptosis in breast cancer cells. This sensitization of breast cancer cells to TM-induced apoptosis by inhibition of MEK/ERK and GRP78 is caspase-dependent, at least in part, by activation of caspase-4. These results seem to indicate that GRP78 has potential as a chemotherapeutical target and have important implications for new treatment strategies in breast cancer by combination with agents that induce ER stress with inhibitors of the MEK/ERK pathway.

Requirement of clusterin expression for prosurvival autophagy in hypoxic kidney tubular epithelial cells

Cellular autophagy is a prosurvival mechanism in the kidney against ischemia-reperfusion injury (IRI), but the molecular pathways that activate the autophagy in ischemic kidneys are not fully understood. Clusterin (CLU) is a chaperone-like protein, and its expression is associated with kidney resistance to IRI. The present study investigated the role of CLU in prosurvival autophagy in the kidney. Renal IRI was induced in mice by clamping renal pedicles at 32°C for 45 min. Hypoxia in renal tubular epithelial cell (TEC) cultures was induced by exposure to a 1% O2 atmosphere. Autophagy was determined by either light chain 3-BII expression with Western blot analysis or light chain 3-green fluorescent protein aggregation with confocal microscopy. Cell apoptosis was determined by flow cytometric analysis. The unfolded protein response was determined by PCR array. Here, we showed that autophagy was significantly activated by IRI in wild-type (WT) but not CLU-deficient kidneys. Similarly, autophagy was activated by hypoxia in human proximal TECs (HKC-8) and WT mouse primary TECs but was impaired in CLU-null TECs. Hypoxia-activated autophagy was CLU dependent and positively correlated with cell survival, and inhibition of autophagy significantly promoted cell death in both HKC-8 and mouse WT/CLU-expressing TECs but not in CLU-null TECs. Further experiments showed that CLU-dependent prosurvival autophagy was associated with activation of the unfolded protein response in hypoxic kidney cells. In conclusion, these data suggest that activation of prosurvival autophagy by hypoxia in kidney cells requires CLU expression and may be a key cytoprotective mechanism of CLU in the protection of the kidney from hypoxia/ischemia-mediated injury.

Clusterin facilitates metastasis by EIF3I/Akt/MMP13 signaling in hepatocellular carcinoma

Clusterin (CLU) is a stress-induced chaperone that confers proliferative and survival advantages to cancer cells. However, effects and molecular mechanisms of CLU in hepatocellular carcinoma (HCC) metastasis are still unknown. In this study, HCC tissue array (n = 198) was utilized to investigate correlation between CLU expression and clinicopathological features. Overexpression of CLU in HCC tissues was correlated with shorter overall survival and higher tumor recurrence. In vitro and in vivo assays demonstrated that silencing CLU attenuated the invasion and metastasis of HCC cells, whereas ectopic overexpression of CLU resulted in the forced metastasis of HCC cells. We also revealed that CLU activated Akt signaling through complexing with eukaryotic translation initiation factor 3 subunit I (EIF3I), which in turn promoted matrix metalloproteinase 13 (MMP13) expression and HCC metastasis. Positive correlations between CLU and MMP13, p-Akt, or EIF3I were found in HCC tissues. We further observed that CLU knockdown using the CLU inhibitor OGX-011 significantly suppressed HCC metastasis in two metastatic models through inhibiting EIF3I/Akt/MMP13 signaling. These findings indicate that CLU is an independent predictive factor for prognosis of HCC and it facilitates metastasis through EIF3I/Akt/MMP13 signaling. CLU suppression using OGX-011 may represent a promising therapeutic option for suppressing HCC metastasis.

Heat shock proteins in hepatocellular carcinoma: Molecular mechanism and therapeutic potential

Heat shock proteins (HSPs) are highly conserved proteins, which are expressed at low levels under normal conditions, but significantly induced in response to cellular stresses. As molecular chaperones, HSPs play crucial roles in protein homeostasis, apoptosis, invasion and cellular signaling transduction. The induction of HSPs is an important part of heat shock response, which could help cancer cells to adapt to stress conditions. Because of the constant stress condition in tumor microenvironment, HSPs overexpression is widely reported in many human cancers. In light of the significance of HSPs for cancer cells to survive and obtain invasive phenotype under stress condition, HSPs are often associated with poor prognosis and treatment resistance in many types of human cancers. It has been described that upregulation of HSPs may serve as diagnostic and prognostic markers in hepatocellular carcinoma (HCC). Targeting HSPs with specific inhibitor alone or in combination with chemotherapy regimens holds promise for the improvement of outcomes for HCC patients. In this review, we summarize the expression profiles, functions and molecular mechanisms of HSPs (HSP27, HSP70 and HSP90) as well as a HSP-like protein (clusterin) in HCC. In addition, we address progression and challenges in targeting these HSPs as novel therapeutic strategies in HCC.

Silencing clusterin gene transcription on effects of multidrug resistance reversing of human hepatoma HepG2/ADM cells

Abnormal clusterin (CLU) expression is associated with multidrug resistance (MDR) of hepatocellular carcinoma (HCC). In the present study, the CLU expression was analyzed in human hepatoma cells and chemoresistant counterpart HepG2/ADM cells. Compared with L02 cells, the overexpression of cellular CLU was identified in HepG2, HepG2/ADM, SMMC7721, Hep3B ,and PLC cells and relatively lower expression in Bel-7404, SNU-739, and MHCC97H cells. Specific short hairpin RNAs (shRNAs) to silence CLU gene transcription were designed, and the most effective sequences were screened. After the HepG2/ADM cells transfected with shRNA-1, the inhibition of CLU expression was 73.68 % at messenger RNA (mRNA) level by real-time quantitative RT-PCR with obvious enhancement in cell chemosensitivity, increasing apoptosis induced by doxorubicin using fluorescence kit, and Rh-123 retention qualified with flow cytometry. Knockdown CLU also significantly decreased the drug efflux pump activity through the depression of MDR1/P-glycoprotein (q = 11.739, P < 0.001). Moreover, silencing CLU led to downregulation of β-catenin (q = 13.544, P = 0.001), suggesting that downregulation of CLU might be a key point to reverse multidrug resistance of HepG2/ADM cells.

Modulation of the unfolded protein response impedes tumor cell adaptation to proteotoxic stress: a PERK for hepatocellular carcinoma therapy

Background

Functional disturbances of the endoplasmic reticulum (ER) lead to activation of the unfolded protein response (UPR), which is involved in the consecutive steps of carcinogenesis. In human hepatocellular carcinoma (HCC), the UPR is shown to be activated; however, little is known about the UPR kinetics and effects of UPR modulation in HCC.

Methods

We sequentially monitored the UPR over time in an orthotopic mouse model for HCC and explored the effects of UPR modulation on cell viability and proliferation in vitro and in the mouse model.

Results

The expression of ER-resident chaperones peaked during tumor initiation and increased further during tumor progression, predominantly within the nodules. A peak in Ire1 signaling was observed during tumor initiation. The Perk pathway was activated during tumor progression, and the proapoptotic target Chop was upregulated from week 5 and continued to rise, especially in the tumors. The Atf6 pathway was modestly activated only after tumor initiation. Consistent with the UPR activation, electron microscopy demonstrated ER expansion and reorganization in HCC cells in vivo. Strikingly, under ER stress or hypoxia, the Perk inhibitor and not the Ire1 inhibitor reduced cell viability and proliferation via escalating proteotoxic stress in vitro. Notably, the Perk inhibitor significantly decreased tumor burden in the mouse model.

Conclusion

We provide the first evaluation of the UPR dynamics in a long-term cancer model and identified a small molecule inhibitor of Perk as a promising strategy for HCC therapy.

Electronic supplementary material

The online version of this article (doi:10.1007/s12072-014-9582-0) contains supplementary material, which is available to authorized users.

Endoplasmic reticulum oxidoreductin 1α mediates hepatic endoplasmic reticulum stress in homocysteine-induced atherosclerosis

Endoplasmic reticulum (ER) stress is emerging as an important modulator of different pathological process and as a mechanism contributing to homocysteine (Hcy)-induced hepar injury. However, the molecular event that Hcy-induced ER stress in the hepar under the atherosclerosis background is currently unknown. Endoplasmic reticulum oxidoreductin 1α (ERO1α) plays a crucial role in maintaining ER stress function. In this study, we determined the expression of ERO1α in the hepar in hyperhomocysteinemia and the effect of ERO1α in hepacytes ER stress in the presence of Hcy. HHcy model was established by feeding the methionine diet in apolipoprotein-E-deficient (ApoE-/-) mice, and the hepatocytes were incubated with folate and different concentrations of Hcy. Our results showed that Hcy triggered ER stress characterized by an increased contents of glucose-regulated protein 78 (GRP78), protein kinase RNA-like ER kinase (PERK), activating transcription factor (ATF) 6 and X-box binding protein-1 (XBP-1). The ERO1α expressions in HHcy mice and Hcy-treated hepatocytes were decreased compared with those in ApoE-/- group and control hepacytes (P < 0.05), respectively. Knocking-down the expression of ERO1α with small-interfering RNA significantly augmented Hcy-induced ER stress. Meanwhile, the expressions of ER stress-related factor including GRP78, PERK, ATF6 and XBP-1, were significantly decreased when the ERO1α gene was over-expressed in hepacytes. Our results suggested that ERO1α may be involved in Hcy-induced hepar ER stress, and the inhibition of ERO1α expression can accelerate this process.

Overexpression of fibrinogen-like protein 2 induces epithelial-to-mesenchymal transition and promotes tumor progression in colorectal carcinoma

The main cause of death in colorectal carcinoma (CRC) patients is tumor metastasis; however, the underlying molecular mechanisms are largely unknown. In the present study, a novel metastasis-related gene, fibrinogen-like protein 2 (FGL2), was characterized for its role in CRC metastasis and underlying molecular mechanisms. The clinical significance of FGL2 was investigated using tissue microarray analysis of samples from 82 patients with CRC. The molecular effects of FGL2 in CRC cells were determined using RNA interference and ectopic expression of FGL2. The overexpression of FGL2 was examined by immunohistochemistry in 82 CRC patients, and it was determined to be an independent predictor of overall survival (P < 0.05). The depletion of FGL2 expression inhibited tumor progression and epithelial-to-mesenchymal transition (EMT) in vitro and in vivo, while ectopic overexpression of FGL2 enhanced cell invasion and induced EMT in vitro. Our results suggest that FGL2 plays an important oncogenic role in CRC aggressiveness by inducing EMT, and FGL2 could be employed as a novel prognostic marker and effective therapeutic target for CRC.

Cab45S inhibits the ER stress-induced IRE1-JNK pathway and apoptosis via GRP78/BiP

Disturbance of endoplasmic reticulum (ER) homeostasis causes ER stress and leads to activation of the unfolded protein response, which reduces the stress and promotes cell survival at the early stage of stress, or triggers cell death and apoptosis when homeostasis is not restored under prolonged ER stress. Here, we report that Cab45S, a member of the CREC family, inhibits ER stress-induced apoptosis. Depletion of Cab45S increases inositol-requiring kinase 1 (IRE1) activity, thus producing more spliced forms of X-box-binding protein 1 mRNA at the early stage of stress and leads to phosphorylation of c-Jun N-terminal kinase, which finally induces apoptosis. Furthermore, we find that Cab45S specifically interacts with 78-kDa glucose-regulated protein/immunoglobulin heavy chain binding protein (GRP78/BiP) on its nucleotide-binding domain. Cab45S enhances GRP78/BiP protein level and stabilizes the interaction of GRP78/BiP with IRE1 to inhibit ER stress-induced IRE1 activation and apoptosis. Together, Cab45S, a novel regulator of GRP78/BiP, suppresses ER stress-induced IRE1 activation and apoptosis by binding to and elevating GRP78/BiP, and has a role in the inhibition of ER stress-induced apoptosis.

The chaperone protein clusterin may serve as a cerebrospinal fluid biomarker for chronic spinal cord disorders in the dog

Chronic spinal cord dysfunction occurs in dogs as a consequence of diverse aetiologies, including long-standing spinal cord compression and insidious neurodegenerative conditions. One such neurodegenerative condition is canine degenerative myelopathy (DM), which clinically is a challenge to differentiate from other chronic spinal cord conditions. Although the clinical diagnosis of DM can be strengthened by the identification of the Sod1 mutations that are observed in affected dogs, genetic analysis alone is insufficient to provide a definitive diagnosis. There is a requirement to identify biomarkers that can differentiate conditions with a similar clinical presentation, thus facilitating patient diagnostic and management strategies. A comparison of the cerebrospinal fluid (CSF) protein gel electrophoresis profile between idiopathic epilepsy (IE) and DM identified a protein band that was more prominent in DM. This band was subsequently found to contain a multifunctional protein clusterin (apolipoprotein J) that is protective against endoplasmic reticulum (ER) stress-mediated apoptosis, oxidative stress, and also serves as an extracellular chaperone influencing protein aggregation. Western blot analysis of CSF clusterin confirmed elevated levels in DM compared to IE (p < 0.05). Analysis of spinal cord tissue from DM and control material found that clusterin expression was evident in neurons and that the clusterin mRNA levels from tissue extracts were elevated in DM compared to the control. The plasma clusterin levels was comparable between these groups. However, a comparison of clusterin CSF levels in a number of neurological conditions found that clusterin was elevated in both DM and chronic intervertebral disc disease (cIVDD) but not in meningoencephalitis and IE. These findings indicate that clusterin may potentially serve as a marker for chronic spinal cord disease in the dog; however, additional markers are required to differentiate DM from a concurrent condition such as cIVDD.