The endoplasmic reticulum stress marker CHOP predicts survival in malignant mesothelioma

Disturbance of Fetal Growth by Azithromycin Through Induction of ER Stress in the Placenta

Aim: Azithromycin (AZM) is widely used to treat mycoplasma infection in pregnancy. However, there is no adequate evaluation of its side effect on the placenta. In this study, using human placental syncytiotrophoblasts and a mouse model, we investigated whether AZM use in pregnancy might adversely affect placental function and pregnancy outcome. Results: Transcriptomic analysis of AZM-treated human placental syncytiotrophoblasts showed increased expression of endoplasmic reticulum (ER) stress-related genes and decreased expression of genes for hormone production and growth factor processing. Verification studies showed that AZM increased the abundance of ER stress mediators (phosphorylated eIF2α, activating transcription factor 4 [ATF4], and C/EBP Homologous Protein [CHOP]) and decreased the abundance of enzymes involved in progesterone and estradiol synthesis (STS, CYP11A1, and CYP19A1) and insulin-like growth factor binding protein (IGFBP) cleavage (PAPPA and ADAM12) in human placental syncytiotrophoblasts. Inhibition of ER stress blocked AZM-induced decreases in the expression of CYP19A1, CYP11A1, PAPPA, and ADAM12, suggesting that the inhibition of AZM on those genes' expression was secondary to AZM-induced ER stress. Further mechanism study showed that increased ATF4 in ER stress might repressively interact with C/EBPα to suppress the expression of those genes, including CEBPA itself. Mouse studies showed that AZM administration decreased fetal weights along with increased ER stress mediators and decreased levels of insulin-like growth factor, estrogen, and progesterone in the maternal blood, which could be alleviated by inhibition of ER stress. Innovation and Conclusion: These findings first support the fact that AZM, often used during pregnancy, may affect fetal growth by inhibiting crucial enzymes for estrogen and progesterone synthesis and disrupting crucial proteases for IGFBP cleavage via inducing ER stress in placental syncytiotrophoblasts.

Integrated multi-omic analysis and experiment reveals the role of endoplasmic reticulum stress in lung adenocarcinoma

BACKGROUND

Lung cancer is a highly prevalent malignancy worldwide and is associated with high mortality rates. While the involvement of endoplasmic reticulum (ER) stress in the development of lung adenocarcinoma (LUAD) has been established, the underlying mechanism remains unclear.

METHODS

In this study, we utilized data from The Cancer Genome Atlas (TCGA) to identify differentially expressed endoplasmic reticulum stress-related genes (ERSRGs) between LUAD and normal tissues. We performed various bioinformatics analyses to investigate the biological functions of these ERSRGs. Using LASSO analysis and multivariate stepwise regression, we constructed a novel prognostic model based on the ERSRGs. We further validated the performance of the model using two independent datasets from the Gene Expression Omnibus (GEO). Additionally, we conducted functional enrichment analysis, immune checkpoint analysis, and immune infiltration analysis and drug sensitivity analysis of LUAD patients to explore the potential biological function of the model. Furthermore, we conducted a battery of experiments to verify the expression of ERSRGs in a real-world cohort.

RESULTS

We identified 106 ERSRGs associated with LUAD, which allowed us to classify LUAD patients into two subtypes based on gene expression differences. Using six prognostic genes (NUPR1, RHBDD2, VCP, BAK1, EIF2AK3, MBTPS2), we constructed a prognostic model that exhibited excellent predictive performance in the training dataset and was successfully validated in two independent external datasets. The risk score derived from this model emerged as an independent prognostic factor for LUAD. Confirmation of the linkage between this risk model and immune infiltration was affirmed through the utilization of Gene Set Enrichment Analysis (GSEA), Gene Ontology (GO), and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses. The q-PCR results verified significant differences in the expression of prognostic genes between cancer and paracancer tissues. Notably, the protein expression of NUPR1, as determined by immunohistochemistry (IHC), exhibited an opposite pattern compared to the mRNA expression patterns.

CONCLUSION

This study establishes a novel prognostic model for LUAD based on six ER stress-related genes, facilitating the prediction of LUAD prognosis. Additionally, NUPR1 was identified as a potential regulator of stress in LUAD.

Antitumoral effects of Bortezomib in malignant mesothelioma: evidence of mild endoplasmic reticulum stress in vitro and activation of T cell response in vivo

BACKGROUND

Malignant mesothelioma (MM) is a rare tumor with a dismal prognosis. The low efficacy of current treatment options highlights the urge to identify more effective therapies aimed at improving MM patients' survival. Bortezomib (Bor) is a specific and reversible inhibitor of the chymotrypsin-like activity of the 20S core of the proteasome, currently approved for the treatment of multiple myeloma and mantle cell lymphoma. On the other hand, Bor appears to have limited clinical effects on solid tumors, because of its low penetration and accumulation into tumor tissues following intravenous administration. These limitations could be overcome in MM through intracavitary delivery, with the advantage of increasing local drug concentration and decreasing systemic toxicity.

METHODS

In this study, we investigated the effects of Bor on cell survival, cell cycle distribution and modulation of apoptotic and pro-survival pathways in human MM cell lines of different histotypes cultured in vitro. Further, using a mouse MM cell line that reproducibly forms ascites when intraperitoneally injected in syngeneic C57BL/6 mice, we investigated the effects of intraperitoneal Bor administration in vivo on both tumor growth and the modulation of the tumor immune microenvironment.

RESULTS

We demonstrate that Bor inhibited MM cell growth and induced apoptosis. Further, Bor activated the Unfolded Protein Response, which however appeared to participate in lowering cells' sensitivity to the drug's cytotoxic effects. Bor also affected the expression of EGFR and ErbB2 and the activation of downstream pro-survival signaling effectors, including ERK1/2 and AKT. In vivo, Bor was able to suppress MM growth and extend mice survival. The Bor-mediated delay of tumor progression was sustained by increased activation of T lymphocytes recruited to the tumor microenvironment.

CONCLUSIONS

The results presented herein support the use of Bor in MM and advocate future studies aimed at defining the therapeutic potential of Bor and Bor-based combination regimens for this treatment-resistant, aggressive tumor.

Is GRP78 (Glucose-regulated protein 78) a prognostic biomarker in differents types of cancer? A systematic review and meta-analysis

GRP78 is a chaperone with anti-apoptotic function associated with aggressive tumors. This systematic review aimed to evaluate GRP78 expression in cancer and its relation to prognosis outcomes. This review was conducted in different databases searching for human cancer studies assessing GRP78 immunohistochemical levels on tissue samples. A total of 98 manuscripts were included. In 62% of the studies, GRP78 was associated with a worse prognosis. A meta-analysis included 29 studies that detected a significantly higher expression of GRP78 in cancer tissues (RR= 2.35, 95% CI 1.75-3.15) compared to control. A meta-analysis of 3 and 5-years Overall Survival revealed an increased risk of death for tumors with high expression of GRP78 (RR=1.36, 95%CI 1.16-1,59, I² = 57%) and (RR=1.65, 95%CI 1.22-2.21, I² =64%), respectively. GRP78 is an important prognostic biomarker for different types of cancer and a promising therapeutic target.

The Evolving Therapeutic Landscape for Malignant Pleural Mesothelioma

PURPOSE OF REVIEW

For patients with malignant pleural mesothelioma, prognosis is poor with extremely low 5-year survival rates and limited therapeutic options. Here, we review the current treatment landscape for mesothelioma and highlight promising future therapeutic directions.

RECENT FINDINGS

Evolving frontline therapeutic options for mesothelioma include VEGF inhibition in combination with chemotherapy and dual immune checkpoint inhibition, with synergisms between the therapies and response prediction via biomarkers also being explored. Evolving experimental treatments for mesothelioma include PARP and ALK inhibitors, dendritic and CAR T-cell therapies, anti-mesothelin vaccines, and oncolytic viral therapies, representing timely advances in the field. The therapeutic landscape for malignant pleural mesothelioma is evolving and preferred treatment in the frontline and later settings will likely evolve with it. However, this does not preclude the evidence for including multi-modal therapies spanning angiogenesis and immune checkpoint inhibitors, and biomarker utilization, in current clinical trials and management.

Prognosis and immune infiltration analysis of endoplasmic reticulum stress-related genes in bladder urothelial carcinoma

Background: Abnormal activation of endoplasmic reticulum (ER) stress sensors and their downstream signalling pathways is a key regulator of tumour growth, tumour metastasis and the response to chemotherapy, targeted therapy and immunotherapy. However, the study of ER stress on the immune microenvironment of bladder urothelial carcinoma (BLCA) is still insufficient.

Methods: Firstly, 23 ER stress genes were selected to analyse their expression differences and prognostic value in BLCA based on the existing BLCA genome atlas data. According to the expression level of ER stress-related genes in BLCA, two independent clusters were identified using consensus cluster analysis. Subsequently, the correlation between these two clusters in terms of the immune microenvironment and their prognostic value was analysed. Finally, we analysed the prognostic value of the key ER stress gene HSP90B1 in BLCA and its corresponding mechanism that affects the immune microenvironment.

Results: Consensus clustering showed a worse prognosis and higher expression of immunoassay site-related genes (HAVCR2, PDCD1, CTLA4, CD274, LAG3, TIGIT and PDCD1LG2) in cluster 1 compared with cluster 2. Additionally, both TIMER and CIBERSORT algorithms showed that the expression of immune infiltrating cells in cluster 1 was significantly higher than that in cluster 2. Subsequently, HSP90B1 was identified as a key ER stress gene in BLCA, and its high expression indicated poor prognosis and was closely related to PD1. We also analysed the correlation between HSP90B1 expression and immune-infiltrating cell related biomarkers, which showed positive results. Finally, we verified the prognostic value of HSP90B1 in BLCA using an immunohistochemical assay in a tissue microarray of 100 patients with BLCA, validating the potential of HSP90B1 as a prognostic biomarker in patients with BLCA.

Conclusion: Our work reveals that ER stress genes play a crucial role in the BLCA immunological milieu, and HSP90B1 is a potential prognostic biomarker and therapeutic target for cancer immunotherapy.

ER Stress Response and Induction of Apoptosis in Malignant Pleural Mesothelioma: The Achilles Heel Targeted by the Anticancer Ruthenium Drug BOLD-100

Simple Summary

Malignant mesothelioma is a rare cancer arising from the serosal surfaces of the body, mainly from the pleural layer. This cancer, strongly linked to asbestos exposure, shows a very inauspicious prognosis. In fact, there is no efficient therapeutic treatment for malignant pleural mesothelioma (MPM). Thus, there is an urgent need to develop novel therapeutic approaches to treat this form of cancer. Our previous study showed the importance of GRP78 in MPM survival. BOLD-100 is a specific modulator of GRP78 and we have observed that it shows cytotoxicity against MPM cells. In particular, we describe that BOLD-100 increases oxidative stress and deregulates the calcium homeostasis leading to cell stress and, ultimately, to cell death. Our in vitro data strongly suggest that BOLD-100 inhibits the growth of MPM cell lines, proposing the application as a single agent, or in combination with other standard-of-care drugs, to treat MPM.

Abstract

Malignant mesothelioma is a rare cancer arising from the serosal surfaces of the body, mainly from the pleural layer. This cancer is strongly related to asbestos exposure and shows a very inauspicious prognosis, because there are scarce therapeutic options for this rare disease. Thus, there is an urgent need to develop novel therapeutic approaches to treat this form of cancer. To explore the biology of malignant pleural mesothelioma (MPM), we previously observed that MPM cell lines show high expression of the GRP78 protein, which is a chaperone protein and the master regulator of the unfolded protein response (UPR) that resides in the endoplasmic reticulum (ER). Based on our previous studies showing the importance of GRP78 in MPM, we observed that BOLD-100, a specific modulator of GRP78 and the UPR, shows cytotoxicity against MPM cells. Our studies demonstrated that BOLD-100 increases ROS production and Ca²⁺ release from the ER, leading to ER stress activation and, ultimately, to cell death. Our in vitro data strongly suggest that BOLD-100 inhibits the growth of MPM cell lines, proposing the application as a single agent, or in combination with other standard-of-care drugs, to treat MPM.

Regulation of endoplasmic reticulum stress by hesperetin: Focus on antitumor and cytoprotective effects

BACKGROUND

Cancer is still an all-times issue due to a large and even increasing number of deaths. Impaired genes regulating cell proliferation and apoptosis are targets for the development of novel cancer treatments.

HYPOTHESIS

Increased transcription of NADPH oxidase activator (NOXA), Bcl2-like11 (BIM), BH3-only proteins and p53 unregulated apoptosis modulator (PUMA) is caused by the imbalance between pro- and anti-apoptotic Bcl-2 proteins due to endoplasmic reticulum (ER) stress. The membranous network of ER is present in all eukaryotic cells. ER stress facilitates the interaction between Bax and PUMA, triggering the release of cytochrome C. As a main intracellular organelle, ER is responsible for translocation as well as post-translation modification and protein folding.

RESULTS

Hesperetin is a cytoprotective flavonone, which acts against ER stress and protects from cell damage induced by reactive oxygen species (ROS) and reactive nitrogen species (RNS). Hesperetin inhibits lipid peroxidation induced by Fe²⁺ and l-ascorbic acid in rat brain homogenates.

CONCLUSION

This review deals with the anticancer effects of hesperetin regarding the regulation of ER stress as a principal mechanism in the pathogenesis of tumors.

Roles and Clinical Significances of ATF6, EMC6, and APAF1 in Prognosis of Pancreatic Cancer

Background: Pancreatic cancer (PC) is prevalent among malignant tumors with poor prognosis and lacks efficient therapeutic strategies. Endoplasmic reticulum (ER) stress and apoptosis are associated with chronic inflammation and cancer progression. However, the prognostic value of ER stress-related, and apoptosis-related genes in PC remains to be further elucidated. Our study aimed at confirming the prognostic values of the ER stress-related genes, ATF6, EMC6, XBP1, and CHOP, and the apoptosis-related gene, APAF1, in PC patients.

Methods: Gene Expression Profiling Interactive Analysis 2 (GEPIA2) was used to evaluate prognosis value of ATF6, EMC6, XBP1, CHOP, and APAF1 in PC. Clinical data from 69 PC patients were retrospectively analyzed. Immunohistochemistry, Western blotting, and qRT-PCR were used for the assessment of gene or protein expression. The cell counting kit-8 (CCK-8) and the Transwell invasion assays were, respectively, used for the assessment of the proliferative and invasive abilities of PC cells. The prognostic values of ATF6, XBP1, CHOP, EMC6, and APAF1 in PC patients were evaluated using Kaplan–Meier and Cox regression analyses.

Results: XBP1 and CHOP expressions were not associated with PC recurrence-free survival (RFS), overall survival (OS) and disease-specific survival (DSS). ATF6 upregulation and EMC6 and APAF1 downregulations significantly correlated with the poor RFS, OS, and DSS of PC patients. ATF6 promoted PC cell proliferation and invasion, while EMC6 and APAF1 inhibited these events.

Conclusion: ATF6 upregulation and EMC6 and APAF1 downregulations may be valid indicators of poor prognosis of PC patients. Moreover, ATF6, EMC6, and APAF1 may constitute potential therapeutic targets in PC patients.

Sensitization of the UPR by loss of PPP1R15A promotes fibrosis and senescence in IPF

The unfolded protein response (UPR) is a direct consequence of cellular endoplasmic reticulum (ER) stress and a key disease driving mechanism in IPF. The resolution of the UPR is directed by PPP1R15A (GADD34) and leads to the restoration of normal ribosomal activity. While the role of PPP1R15A has been explored in lung epithelial cells, the role of this UPR resolving factor has yet to be explored in lung mesenchymal cells. The objective of the current study was to determine the expression and role of PPP1R15A in IPF fibroblasts and in a bleomycin-induced lung fibrosis model. A survey of IPF lung tissue revealed that PPP1R15A expression was markedly reduced. Targeting PPP1R15A in primary fibroblasts modulated TGF-β-induced fibroblast to myofibroblast differentiation and exacerbated pulmonary fibrosis in bleomycin-challenged mice. Interestingly, the loss of PPP1R15A appeared to promote lung fibroblast senescence. Taken together, our findings demonstrate the major role of PPP1R15A in the regulation of lung mesenchymal cells, and regulation of PPP1R15A may represent a novel therapeutic strategy in IPF.

Biological basis for novel mesothelioma therapies

Mesothelioma is an aggressive cancer that is associated with exposure to asbestos. Although asbestos is banned in several countries, including the UK, an epidemic of mesothelioma is predicted to affect middle-income countries during this century owing to their heavy consumption of asbestos. The prognosis for patients with mesothelioma is poor, reflecting a failure of conventional chemotherapy that has ultimately resulted from an inadequate understanding of its biology. However, recent work has revolutionised the study of mesothelioma, identifying genetic and pathophysiological vulnerabilities, including the loss of tumour suppressors, epigenetic dysregulation and susceptibility to nutrient stress. We discuss how this knowledge, combined with advances in immunotherapy, is enabling the development of novel targeted therapies.

Combination of Niraparib, Cisplatin and Twist Knockdown in Cisplatin-Resistant Ovarian Cancer Cells Potentially Enhances Synthetic Lethality through ER-Stress Mediated Mitochondrial Apoptosis Pathway

Poly (ADP-ribose) polymerase 1 inhibitors (PARPi) are used to treat recurrent ovarian cancer (OC) patients due to greater survival benefits and minimal side effects, especially in those patients with complete or partial response to platinum-based chemotherapy. However, acquired resistance of platinum-based chemotherapy leads to the limited efficacy of PARPi monotherapy in most patients. Twist is recognized as a possible oncogene and contributes to acquired cisplatin resistance in OC cells. In this study, we show how Twist knockdown cisplatin-resistant (CisR) OC cells blocked DNA damage response (DDR) to sensitize these cells to a concurrent treatment of cisplatin as a platinum-based chemotherapy agent and niraparib as a PARPi on in vitro two-dimensional (2D) and three-dimensional (3D) cell culture. To investigate the lethality of PARPi and cisplatin on Twist knockdown CisR OC cells, two CisR cell lines (OV90 and SKOV3) were established using step-wise dose escalation method. In addition, in vitro 3D spheroidal cell model was generated using modified hanging drop and hydrogel scaffolds techniques on poly-2-hydroxylethly methacrylate (poly-HEMA) coated plates. Twist expression was strongly correlated with the expression of DDR proteins, PARP1 and XRCC1 and overexpression of both proteins was associated with cisplatin resistance in OC cells. Moreover, combination of cisplatin (Cis) and niraparib (Nira) produced lethality on Twist-knockdown CisR OC cells, according to combination index (CI). We found that Cis alone, Nira alone, or a combination of Cis+Nira therapy increased cell death by suppressing DDR proteins in 2D monolayer cell culture. Notably, the combination of Nira and Cis was considerably effective against 3D-cultures of Twist knockdown CisR OC cells in which Endoplasmic reticulum (ER) stress is upregulated, leading to initiation of mitochondrial-mediated cell death. In addition, immunohistochemically, Cis alone, Nira alone or Cis+Nira showed lower ki-67 (cell proliferative marker) expression and higher cleaved caspase-3 (apoptotic marker) immuno-reactivity. Hence, lethality of PARPi with the combination of Cis on Twist knockdown CisR OC cells may provide an effective way to expand the therapeutic potential to overcome platinum-based chemotherapy resistance and PARPi cross resistance in OC.

Role of unfolded proteins in lung disease

The lungs are exposed to a range of environmental toxins (including cigarette smoke, air pollution, asbestos) and pathogens (bacterial, viral and fungal), and most respiratory diseases are associated with local or systemic hypoxia. All of these adverse factors can trigger endoplasmic reticulum (ER) stress. The ER is a key intracellular site for synthesis of secretory and membrane proteins, regulating their folding, assembly into complexes, transport and degradation. Accumulation of misfolded proteins within the lumen results in ER stress, which activates the unfolded protein response (UPR). Effectors of the UPR temporarily reduce protein synthesis, while enhancing degradation of misfolded proteins and increasing the folding capacity of the ER. If successful, homeostasis is restored and protein synthesis resumes, but if ER stress persists, cell death pathways are activated. ER stress and the resulting UPR occur in a range of pulmonary insults and the outcome plays an important role in many respiratory diseases. The UPR is triggered in the airway of patients with several respiratory diseases and in corresponding experimental models. ER stress has been implicated in the initiation and progression of pulmonary fibrosis, and evidence is accumulating suggesting that ER stress occurs in obstructive lung diseases (particularly in asthma), in pulmonary infections (some viral infections and in the setting of the cystic fibrosis airway) and in lung cancer. While a number of small molecule inhibitors have been used to interrogate the role of the UPR in disease models, many of these tools have complex and off-target effects, hence additional evidence (eg, from genetic manipulation) may be required to support conclusions based on the impact of such pharmacological agents. Aberrant activation of the UPR may be linked to disease pathogenesis and progression, but at present, our understanding of the context-specific and disease-specific mechanisms linking these processes is incomplete. Despite this, the ability of the UPR to defend against ER stress and influence a range of respiratory diseases is becoming increasingly evident, and the UPR is therefore attracting attention as a prospective target for therapeutic intervention strategies.

The integrated stress response in pulmonary disease

The respiratory tract and its resident immune cells face daily exposure to stress, both from without and from within. Inhaled pathogens, including severe acute respiratory syndrome coronavirus 2, and toxins from pollution trigger a cellular defence system that reduces protein synthesis to minimise viral replication or the accumulation of misfolded proteins. Simultaneously, a gene expression programme enhances antioxidant and protein folding machineries in the lung. Four kinases (PERK, PKR, GCN2 and HRI) sense a diverse range of stresses to trigger this “integrated stress response”. Here we review recent advances identifying the integrated stress response as a critical pathway in the pathogenesis of pulmonary diseases, including pneumonias, thoracic malignancy, pulmonary fibrosis and pulmonary hypertension. Understanding the integrated stress response provides novel targets for the development of therapies.

Therapeutic Landscape of Malignant Pleural Mesothelioma: Collateral Vulnerabilities and Evolutionary Dependencies in the Spotlight

Malignant pleural mesothelioma (MPM) is the epitome of a recalcitrant cancer driven by pharmacologically intractable tumor suppressor proteins. A significant but largely unmet challenge in the field is the translation of genetic information on alterations in tumor suppressor genes (TSGs) into effective cancer-specific therapies. The notion that abnormal tumor genome subverts physiological cellular processes, which creates collateral vulnerabilities contextually related to specific genetic alterations, offers a promising strategy to target TSG-driven MPM. Moreover, emerging evidence has increasingly appreciated the therapeutic potential of genetic and pharmacological dependencies acquired en route to cancer development and drug resistance. Here, we review the most recent progress on vulnerabilities co-selected by functional loss of major TSGs and dependencies evolving out of cancer development and resistance to cisplatin based chemotherapy, the only first-line regimen approved by the US Food and Drug Administration (FDA). Finally, we highlight CRISPR-based functional genomics that has emerged as a powerful platform for cancer drug discovery in MPM. The repertoire of MPM-specific “Achilles heel” rises on the horizon, which holds the promise to elucidate therapeutic landscape and may promote precision oncology for MPM.

Tissue expression of lactate transporters (MCT1 and MCT4) and prognosis of malignant pleural mesothelioma (brief report)

BACKGROUND

Malignant pleural mesothelioma (MPM) is an aggressive neoplasm of the pleura, mainly related to asbestos exposure. As in other solid tumors, malignant cells exhibit high glucose uptake and glycolytic rates with increased lactic acid efflux into the interstitial space. Lactate transport into and out of cells, crucial to maintaining intracellular pH homeostasis and glycolysis, is carried out by monocarboxylate transporters (MCTs) and the chaperone basigin (CD147). We set out to examine the clinical significance of basigin, MCT1 and MCT4 in the context of MPM and to evaluate their expression in relation to the evolution of the disease.

METHODS

We used immunohistochemistry to measure the expression of basigin, MCT1 and MCT4 in a cohort of 135 individuals with MPM compared to a series of 15 non-MPM pleura specimens. Moreover, by Kaplan-Meier and Cox analyses we evaluated whether an expression over the average of these markers could be associated with the patients' overall survival (OS).

RESULTS

We detected positive staining of basigin, MCT1, and MCT4 in most MPM specimens. In particular, MCT4 was always positive in malignant tissues but undetectable in the 4 normal pleural specimens incorporated within the tissue microarray. This was confirmed in the additional series of 15 normal pleural samples. Moreover, MCT4 expression was significantly associated with reduced OS.

CONCLUSION

In this study, the tissue expression of basigin did not prove to be exploitable as a diagnostic or prognostic marker for MPM patients. The expression of MCT1 was not informative either, being tightly correlated with that of basigin. However, the expression of MCT4 showed promise as a diagnostic/therapeutic and prognostic biomarker.

Licochalcone H Synthesized by Modifying Structure of Licochalcone C Extracted from Glycyrrhiza inflata Induces Apoptosis of Esophageal Squamous Cell Carcinoma Cells

Esophageal cancer is one of the malignant cancers with a low 5-year survival rate. Licochalcone (LC) H, a chemically synthesized substance, is a regioisomer of LCC extracted from licorice. The purpose of this study was to determine whether LCH might have anticancer effect on human esophageal squamous cell carcinoma (ESCC) cell lines via apoptosis signaling pathway. After 48 h of treatment, IC₅₀ of LCH in KYSE 30, KYSE 70, KYSE 410, KYSE 450, and KYSE 510 cells were 15, 14, 18, 15, and 16 μM, respectively. This study demonstrated that LCH potently suppressed proliferation of ESCC cells in a concentration- and time-dependent manner. LCH triggered G2/M-phase arrest by modulating expression levels of cdc2, cyclin B1, p21, and p27. LCH also induced apoptosis of ESCC cells through reactive oxygen species-mediated endoplasmic reticulum (ER) stress via JNK/p38 activation pathways. The anticancer effect of LCH was associated with ER stress and mitochondrial dysfunction. It also affected protein levels of Mcl-1, tBid, Bax, Bcl-2, cytochrome c, Apaf-1, PARP, cleaved-PARP, and ER stress-related proteins (GRP78 and CHOP). Our findings provide the first demonstration that LCH has anticancer effect on ESCC. Thus, LCH might have potential for preventing and/or treating human ESCC.

ER stress-induced mediator C/EBP homologous protein thwarts effector T cell activity in tumors through T-bet repression

Understanding the intrinsic mediators that render CD8⁺ T cells dysfunctional in the tumor microenvironment is a requirement to develop more effective cancer immunotherapies. Here, we report that C/EBP homologous protein (Chop), a downstream sensor of severe endoplasmic reticulum (ER) stress, is a major negative regulator of the effector function of tumor-reactive CD8⁺ T cells. Chop expression is increased in tumor-infiltrating CD8⁺ T cells, which correlates with poor clinical outcome in ovarian cancer patients. Deletion of Chop in T cells improves spontaneous antitumor CD8⁺ T cell immunity and boosts the efficacy of T cell-based immunotherapy. Mechanistically, Chop in CD8⁺ T cells is elevated primarily through the ER stress-associated kinase Perk and a subsequent induction of Atf4; and directly represses the expression of T-bet, a master regulator of effector T cell function. These findings demonstrate the primary role of Chop in tumor-induced CD8⁺ T cell dysfunction and the therapeutic potential of blocking Chop or ER stress to unleash T cell-mediated antitumor immunity.

Targeting the functional interplay between endoplasmic reticulum oxidoreductin-1α and protein disulfide isomerase suppresses the progression of cervical cancer

Background

Endoplasmic reticulum (ER) oxidoreductin-1α (Ero1α) and protein disulfide isomerase (PDI) constitute the pivotal pathway of oxidative protein folding, and are highly expressed in many cancers. However, whether targeting the functional interplay between Ero1α and PDI could be a new approach for cancer therapy remains unknown.

Methods

We performed wound healing assays, transwell migration and invasion assays and xenograft assays to assess cell migration, invasion and tumorigenesis; gel filtration chromatography, oxygen consumption assay and in cells folding assays were used to detect Ero1α-PDI interaction and Ero1α oxidase activity.

Findings

Here, we report that elevated expression of Ero1α is correlated with poor prognosis in human cervical cancer. Knockout of ERO1A decreases the growth, migration and tumorigenesis of cervical cancer cells, through downregulation of the H₂O₂-correlated epithelial-mesenchymal transition. We identify that the conserved valine (Val) 101 of Ero1α is critical for Ero1α-PDI complex formation and Ero1α oxidase activity. Val101 of Ero1α is specifically involved in the recognition of PDI catalytic domain. Mutation of Val101 results in a reduced ER, retarded oxidative protein folding and decreased H₂O₂ levels in the ER of cervical cancer cells and further impairs cell migration, invasion, and tumor growth.

Interpretation

Our study identifies the critical residue of Ero1α for recognizing PDI, which underlines the molecular mechanism of oxidative protein folding for tumorigenesis and provides a proof-of-concept for cancer therapy by targeting Ero1α-PDI interaction.

Fund

This work was supported by National Key R&D Program of China, National Natural Science Foundation of China, and Youth Innovation Promotion Association, CAS.

Measuring the effects of α1 -antitrypsin polymerisation on the structure and biophysical properties of the endoplasmic reticulum

An important function of the endoplasmic reticulum (ER) is to serve as a site of secretory protein folding. When the accumulation of misfolded proteins threatens to disturb luminal homoeostasis, the cell is said to experience ER stress. By contrast, the accumulation of well-folded proteins inside the ER leads to a distinct form of strain called ER overload. The serpins comprise a large family of proteins whose folding has been studied in great detail. Some mutant serpins misfold to cause ER stress, whereas others fold but then polymerise to cause ER overload. We discuss recent advances in the use of dynamic fluorescence imaging to study these phenomena. We also discuss a new technique that we recently published, rotor-based organelle viscosity imaging (ROVI), which promises to shed more light on the biophysical features of ER stress and ER overload.

Clinicopathological and prognostic significance of C/EBP homologous protein (CHOP) in advanced gastric cancer

BACKGROUND

Few studies have reported the clinical and prognostic significance of C/EBP homologous protein (CHOP) in advanced gastric cancer (GC). Therefore, the present study investigated the expression of CHOP in advanced GC patients to determine its potential prognostic role.

METHODS

The levels of CHOP in 95 patients with advanced GC and adjacent non-cancerous tissues were evaluated by qRT-PCR, western blot and immunohistochemistry. Furthermore, the association of CHOP expression with clinicopathological parameters and prognosis of advanced GC patients was analyzed.

RESULTS

The levels of CHOP were down-regulated in advanced GC compared with non-cancerous tissues (P<0.01). In addition, high CHOP expression more frequently occurred in advanced GC tissues with depth of invasion of T_1-2 (P < 0.01), lower clinical stage (TNM Ⅰ-Ⅱ stage) (P<0.05) and without lymph node metastasis (P<0.05). No significant difference was observed between the expression of CHOP and age, gender, tumor size, lesion site and differentiation (P>0.05). The Kaplan-Meier survival analyses showed that the overall survival rate of advanced GC patients with positive CHOP expression was significantly higher than that of patients with negative CHOP expression (P<0.01). Univariate and multivariate Cox proportional hazards models revealed that low CHOP expression (OR = 0.314, 95%CI: 0.176～0.794, P = 0.003) was an independent factor for poor overall survival in advanced GC patients.

CONCLUSION

Low expression of CHOP predicts the poor prognosis of advanced GC patients, and CHOP may be a prognostic biomarker for patients with advanced GC.

(-)- Epigallocatechin-3-gallate induces GRP78 accumulation in the ER and shifts mesothelioma constitutive UPR into proapoptotic ER stress

GRP78 is a molecular chaperone of the endoplasmic reticulum (ER) that aids proper folding of nascent polypeptides. When unfolded proteins accumulate, GRP78 triggers unfolded protein response (UPR), involving activation of transcription factors like XBP1 and CHOP that may restore cell homeostasis. Increased expression of GRP78 and mild UPR can be constitutive in cancer cells, hindering apoptosis, and promoting cell survival, for example, by GRP78 relocation to the plasma membrane that activates MAPK and PI3 K/AKT pathways. These processes are thought to favor the insurgence of chemoresistance and worsen patient outcome. We have previously shown that (-)-epigallocatechin-3-gallate (EGCG) enhances ROS production and alters Ca²⁺ homeostasis in cell lines deriving from therapy-recalcitrant malignant mesothelioma (MMe). We consider here the EGCG impact on GRP78 and downstream factors by using qRT-PCR, Western blot, immunofluorescence, caspase assays, GRP78 siRNA silencing, and cell surface ELISA. MMe cells were found to display mild constitutive UPR, as shown by increased levels of GRP78, and presence of the protein at the cell surface, linked to AKT activation. Exposure to EGCG further increased GRP78 in the ER, and induced ATF4, spliced XBP1, CHOP, and EDEM expressions, combined with a reduction of cell surface GRP78 and a rise in caspase 3 and 8 activities. We propose that GRP78 accumulation in the ER, caused by EGCG, converts constitutive UPR of MMe cells into proapoptotic ER stress. This argues for a possible therapeutic use of EGCG in the treatment of MMe as a co-drug able to abolish chemoresistance to conventional drugs at tolerable doses.

Inhibition of breast cancer cell growth by methyl pyropheophenylchlorin photodynamic therapy is mediated though endoplasmic reticulum stress-induced autophagy in vitro and vivo

Autophagy and ER stress participated in the inhibition of MPPa‐PDT on tumor growth, but the molecular links between them remain undefined. We just explore the molecular mechanism between them in vitro and vivo. CCK‐8 assay and flow cytometer were used to detect the cytotoxicity and mode of cell death after MPPa‐PDT. Furthermore, the role of autophagy was verified in MPPa‐PDT. Confocal microscopy was used to show the intracellular distribution of MPPa. ER stress markers and PERK signaling pathway were detected by western blot. While in vivo, tumor histology and immunohistochemistry were performed to show the effect of MPPa‐PDT in mice. After MPPa‐PDT, cells viability decreased in dose‐dependent manner. Besides, the cell apoptosis increased along with the increasing of Beclin‐1and LC3B II but declining of P62. When pretreated with 3‐MA, LC3B II formation and the cytotoxicity declined. MPPa‐PDT caused increasing of ER stress markers (GRP78, CHOP) as MPPa accumulated in ER. However, pretreatment with ER stress inhibitor 4PBA, the expression of GRP78 and LC3B II was blocked but the PERK signaling pathway activated and the expression of P62 increased. In vivo, the tumor growth was significantly inhibited by MPPa‐PDT. Besides, the appearance of ER stress and autophagy was further demonstrated by immunohistochemistry. Our findings demonstrate that autophagy mediated by MPPa‐PDT was regulated by ER stress, via PERK signaling pathway, to kill MDA‐MB‐231 cells in vitro and vivo.

Lnc-chop Promotes Immunosuppressive Function of Myeloid-Derived Suppressor Cells in Tumor and Inflammatory Environments

Myeloid-derived suppressor cells (MDSCs) are major regulators of immune responses in cancer. Both C/EBP homologous protein (CHOP) and C/EBPβ play a critical role in regulating immunosuppressive function of MDSCs. In this study, we identified a novel long noncoding RNA termed as lnc-chop in MDSCs, which may interact with CHOP and the C/EBPβ isoform liver-enriched inhibitory protein. The binding of lnc-chop with both CHOP and the C/EBPβ isoform liver-enriched inhibitory protein promoted the activation of C/EBPβ and upregulated the expression of arginase-1, NO synthase 2, NADPH oxidase 2, and cyclooxygenase-2, which are related to the immunosuppressive function of MDSCs in inflammatory and tumor environments. Additionally, lnc-chop also promoted the enrichment of H3K4me3 on the promoter region of arginase-1, NO synthase 2, NADPH oxidase 2, and cyclooxygenase-2. These findings suggest an important role of lnc-chop in controlling immunosuppressive function of MDSCs in the tumor environment.

Interplay between P-Glycoprotein Expression and Resistance to Endoplasmic Reticulum Stressors

Multidrug resistance (MDR) is a phenotype of cancer cells with reduced sensitivity to a wide range of unrelated drugs. P-glycoprotein (P-gp)—a drug efflux pump (ABCB1 member of the ABC transporter gene family)—is frequently observed to be a molecular cause of MDR. The drug-efflux activity of P-gp is considered as the underlying mechanism of drug resistance against P-gp substrates and results in failure of cancer chemotherapy. Several pathological impulses such as shortages of oxygen and glucose supply, alterations of calcium storage mechanisms and/or processes of protein N-glycosylation in the endoplasmic reticulum (ER) leads to ER stress (ERS), characterized by elevation of unfolded protein cell content and activation of the unfolded protein response (UPR). UPR is responsible for modification of protein folding pathways, removal of misfolded proteins by ER associated protein degradation (ERAD) and inhibition of proteosynthesis. However, sustained ERS may result in UPR-mediated cell death. Neoplastic cells could escape from the death pathway induced by ERS by switching UPR into pro survival mechanisms instead of apoptosis. Here, we aimed to present state of the art information about consequences of P-gp expression on mechanisms associated with ERS development and regulation of the ERAD system, particularly focused on advances in ERS-associated therapy of drug resistant malignancies.

Both nitric oxide and nitrite prevent homocysteine-induced endoplasmic reticulum stress and subsequent apoptosis via cGMP-dependent pathway in neuronal cells

Growing evidence indicates that endoplasmic reticulum (ER) stress and/or ER stress-mediated apoptosis may play a role in the pathogenesis of neurodegenerative diseases such as Alzheimer's disease. The present study investigated the effects of non-cytotoxic concentrations of nitric oxide (NO) and nitrite, a metabolite of NO, on ER stress and ER stress-mediated apoptosis in Neuro-2a cells exposed to homocysteine (Hcy), an endogenous ER stress inducer. Hcy induced ER stress, as confirmed by inositol-requiring enzyme 1α (IRE1α) phosphorylation and X-box-binding protein-1 (Xbp1) mRNA splicing as well as C/EBP homologous protein (CHOP) expression, and apoptosis, as verified by Annexin V-positive cells. Surprisingly, non-cytotoxic NO (S-nitrosoglutathione) and nitrite markedly reduced Hcy-induced IRE1α phosphorylation, Xbp1 mRNA splicing, CHOP expression, and Annexin V-positive cells, indicating the cytoprotection of NO and nitrite against Hcy-induced ER stress and apoptosis. Moreover, inhibition of sGC/cGMP pathway abolished the cytoprotective effects of NO and nitrite, whereas cellular elevation of cGMP levels mimicked the cytoprotective actions of NO and nitrite. These findings provide the first evidence showing that both NO and nitrite can reduce ER stress and subsequent apoptosis via NO-sGC-cGMP pathway in neuronal cells and suggesting that NO and/or nitrite may have therapeutic value in the treatment of ER stress-associated neurodegenerative diseases.

Dendritic cell rehab: new strategies to unleash therapeutic immunity in ovarian cancer

Immune-based therapies that induce remarkable and durable responses against melanoma and lung cancer have unfortunately demonstrated limited success in ovarian cancer patients. This is likely due to the exceptional immunoregulatory nature of ovarian tumors, which employ numerous strategies to effectively suppress anti-tumor immunity. Here, we summarize a decade of research indicating that ovarian cancers possess an exquisite capacity to subvert the activity of host dendritic cells (DCs) as a key mechanism to impede the development and maintenance of protective T cell-based immune responses. Identifying, understanding, and disabling the precise mechanisms promoting DC dysfunction in ovarian cancer are, therefore, fundamental requirements for devising the next generation of successful immunotherapies against this devastating malignancy.

Role of the unfolded protein response in tumor cell characteristics and cancer outcome

PURPOSE OF REVIEW

In the present review, we discuss the possible role of the unfolded protein response (UPR) in the acquisition of tumor cell characteristics and in the prognosis of cancer outcome, which could assist and contribute to the development of more promising therapeutic strategies.

RECENT FINDINGS

Accumulating evidence supports the idea that alteration of endoplasmic reticulum proteostasis is a key player in cancer development and aggressiveness. Some UPR components were reported as independent prognostic biomarker. Recent evidence supports a relationship between the UPR activation status and prognosis of tumors. This may represent an interesting avenue for better characterization of carcinogenesis and tumor type.

SUMMARY

The contribution of the UPR to the characteristics of malignant tumors is complex and dependent on both intrinsic (e.g. oncogene addiction) and extrinsic (e.g. hypoxia) contexts. Through adaptation to severe microenvironmental conditions, UPR branches are generally a survival strategy for cancer cells, which are able to cope with this challenging context. We address the question of whether the activation status of the UPR is related to tumor properties and discuss the role of the UPR in the clinical context.

Physiological/pathological ramifications of transcription factors in the unfolded protein response

Numerous environmental, physiological, and pathological insults disrupt protein-folding homeostasis in the endoplasmic reticulum (ER), referred to as ER stress. Eukaryotic cells evolved a set of intracellular signaling pathways, collectively termed the unfolded protein response (UPR), to maintain a productive ER protein-folding environment through reprogramming gene transcription and mRNA translation. The UPR is largely dependent on transcription factors (TFs) that modulate expression of genes involved in many physiological and pathological conditions, including development, metabolism, inflammation, neurodegenerative diseases, and cancer. Here we summarize the current knowledge about these mechanisms, their impact on physiological/pathological processes, and potential therapeutic applications.

Endoplasmic reticulum stress in lung disease

Exposure to inhaled pollutants, including fine particulates and cigarette smoke is a major cause of lung disease in Europe. While it is established that inhaled pollutants have devastating effects on the genome, it is now recognised that additional effects on protein folding also drive the development of lung disease. Protein misfolding in the endoplasmic reticulum affects the pathogenesis of many diseases, ranging from pulmonary fibrosis to cancer. It is therefore important to understand how cells respond to endoplasmic reticulum stress and how this affects pulmonary tissues in disease. These insights may offer opportunities to manipulate such endoplasmic reticulum stress pathways and thereby cure lung disease.

Tumorigenic and Immunosuppressive Effects of Endoplasmic Reticulum Stress in Cancer

Malignant cells utilize diverse strategies that enable them to thrive under adverse conditions while simultaneously inhibiting the development of anti-tumor immune responses. Hostile microenvironmental conditions within tumor masses, such as nutrient deprivation, oxygen limitation, high metabolic demand, and oxidative stress, disturb the protein-folding capacity of the endoplasmic reticulum (ER), thereby provoking a cellular state of "ER stress." Sustained activation of ER stress sensors endows malignant cells with greater tumorigenic, metastatic, and drug-resistant capacity. Additionally, recent studies have uncovered that ER stress responses further impede the development of protective anti-cancer immunity by manipulating the function of myeloid cells in the tumor microenvironment. Here, we discuss the tumorigenic and immunoregulatory effects of ER stress in cancer, and we explore the concept of targeting ER stress responses to enhance the efficacy of standard chemotherapies and evolving cancer immunotherapies in the clinic.

Unfolding anti-tumor immunity: ER stress responses sculpt tolerogenic myeloid cells in cancer

Established tumors build a stressful and hostile microenvironment that blocks the development of protective innate and adaptive immune responses. Different subsets of immunoregulatory myeloid populations, including dendritic cells, myeloid-derived suppressor cells (MDSCs) and macrophages, accumulate in the stressed tumor milieu and represent a major impediment to the success of various forms of cancer immunotherapy. Specific conditions and factors within tumor masses, including hypoxia, nutrient starvation, low pH, and increased levels of free radicals, provoke a state of “endoplasmic reticulum (ER) stress” in both malignant cells and infiltrating myeloid cells. In order to cope with ER stress, cancer cells and tumor-associated myeloid cells activate an integrated signaling pathway known as the Unfolded Protein Response (UPR), which promotes cell survival and adaptation under adverse environmental conditions. However, the UPR can also induce cell death under unresolved levels of ER stress. Three branches of the UPR have been described, including the activation of the inositol-requiring enzyme 1 (IRE1), the pancreatic ER kinase (PKR)-like ER kinase (PERK), and the activating transcription factor 6 (ATF6). In this minireview, we briefly discuss the role of ER stress and specific UPR mediators in tumor development, growth and metastasis. In addition, we describe how sustained ER stress responses operate as key mediators of chronic inflammation and immune suppression within tumors. Finally, we discuss multiple pharmacological approaches that overcome the immunosuppressive effect of the UPR in tumors, and that could potentially enhance the efficacy of cancer immunotherapies by reprogramming the function of tumor-infiltrating myeloid cells.

Thapsigargin sensitizes human esophageal cancer to TRAIL-induced apoptosis via AMPK activation

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a promising anticancer agent for esophageal squamous cell carcinoma (ESCC). Forced expression of CHOP, one of the key downstream transcription factors during endoplasmic reticulum (ER) stress, upregulates the death receptor 5 (DR5) levels and promotes oxidative stress and cell death. In this study, we show that ER stress mediated by thapsigargin promoted CHOP and DR5 synthesis thus sensitizing TRAIL treatment, which induced ESCC cells apoptosis. These effects were reversed by DR5 siRNA in vitro and CHOP siRNA both in vitro and in vivo. Besides, chemically inhibition of AMPK by Compound C and AMPK siRNA weakened the anti-cancer effect of thapsigargin and TRAIL co-treatment. Therefore, our findings suggest ER stress effectively sensitizes human ESCC to TRAIL-mediated apoptosis via the TRAIL-DR5-AMPK signaling pathway, and that activation of ER stress may be beneficial for improving the efficacy of TRAIL-based anti-cancer therapy.

Novel CHOP activator LGH00168 induces necroptosis in A549 human lung cancer cells via ROS-mediated ER stress and NF-κB inhibition

AIM

C/EBP homologous protein (CHOP) is a transcription factor that is activated at multiple levels during ER stress and plays an important role in ER stress-induced apoptosis. In this study we identified a novel CHOP activator, and further investigated its potential to be a therapeutic agent for human lung cancer.

METHODS

HEK293-CHOP-luc reporter cells were used in high-throughput screening (HTS) to identify CHOP activators. The cytotoxicity against cancer cells in vitro was measured with MTT assay. The anticancer effects were further examined in A549 human non-small cell lung cancer xenograft mice. The mechanisms underlying CHOP activation were analyzed using luciferase assays, and the anticancer mechanisms were elucidated in A549 cells.

RESULTS

From chemical libraries of 50 000 compounds, LGH00168 was identified as a CHOP activator, which showed cytotoxic activities against a panel of 9 cancer cell lines with an average IC₅₀ value of 3.26 μmol/L. Moreover, administration of LGH00168 significantly suppressed tumor growth in A549 xenograft bearing mice. LGH00168 activated CHOP promoter via AARE1 and AP1 elements, increased DR5 expression, decreased Bcl-2 expression, and inhibited the NF-κB pathway. Treatment of A549 cells with LGH00168 (10 μmol/L) did not induce apoptosis, but lead to RIP1-dependent necroptosis, accompanied by cell swelling, plasma membrane rupture, lysosomal membrane permeabilization, MMP collapse and caspase 8 inhibition. Furthermore, LGH00168 (10 and 20 μmol/L) dose-dependently induced mito-ROS production in A549 cells, which was reversed by the ROS scavenger N-acetyl-L-cysteine (NAC, 10 mmol/L). Moreover, NAC significantly diminished LGH00168-induced CHOP activation, NF-κB inhibition and necroptosis in A549 cells.

CONCLUSION

LGH00168 is a CHOP activator that inhibits A549 cell growth in vitro and lung tumor growth in vivo.

Endoplasmic reticulum stress, unfolded protein response and development of colon adenocarcinoma

When misfolded proteins accumulate in the endoplasmic reticulum (ER), the cell is said to experience ER stress. This triggers an unfolded protein response (UPR) to restore the balance between misfolded proteins and ER chaperones such as BiP. UPR signalling is required for the growth of many solid cancers. In chronic ER stress, factors including CHOP have been shown to mediate cell death. Colorectal adenocarcinoma arises due to progressive changes within pre-malignant lesions. Our aim was to test the hypothesis that the expression of BiP and CHOP correlates with the progression of those pre-malignant lesions.Eighty-one patients with colon neoplasms treated at Rouen University Hospital between January 1, 2003 and January 1, 2013 were randomly selected. The expression of BiP and CHOP was estimated by immunohistochemical staining of a tissue microarray generated from colon cores: normal tissue, low-grade and high-grade adenoma, invasive colon adenocarcinoma and lymph node metastasis of colon adenocarcinoma. In parallel, nine cases comprising areas from normal epithelium to dyplasia to invasive carcinoma and included in the TMA were analysed on whole sections.As colon epithelium shows increasing evidence of pre-malignant and then malignant changes, BiP expression significantly increases (p for trend < 0.001), whereas CHOP expression is attenuated (p for trend < 0.001).We identified a positive relationship between BiP expression and colon carcinogenesis, and a negative correlation for CHOP expression. These findings are consistent with a model in which ER stress accompanies oncogenesis and in which loss of proteins that mediate the toxicity of ER stress, such as CHOP, may facilitate tumorigenesis. This raises the exciting possibility that restoration of the negative feedback loop of UPR, if achievable, might antagonise the malignant process.

A STAT3-NFkB/DDIT3/CEBPβ axis modulates ALDH1A3 expression in chemoresistant cell subpopulations

Here we studied the relevance and modulation of aldehyde dehydrogenase (ALDH) expression in malignant pleural mesothelioma (MPM) chemoresistant cell subpopulations (ALDH^bright cells), which survive pemetrexed + cisplatin treatment in vitro and in vivo. Expression of the ALDH1A3 isoform was invariably enriched in purified ALDH^bright cells from multiple MPM cell lines and accounted for the enzymatic activity of those cells. RNAi mediated downregulation of ALDH1A3 reduced the survival of the ALDH^bright cells at steady state and, much more, after pemetrexed + cisplatin treatment. We demonstrated, for the first time, that a pSTAT3(tyr705)-NFkB(p65) complex is required for the repression of DDIT3 mRNA and this ensures high levels of CEBPβ-dependent ALDH1A3 promoter activity. Inhibition of STAT3-NFkB activity allowed high levels of DDIT3 expression with increased formation of a DDIT3-CEBPβ complex. This reduced the occupancy of the ALDH1A3 promoter by CEBPβ, thus largely reducing the ALDH1A3 expression. Consequently, survival of ALDH^bright cells in pemetrexed + cisplatin-treated cultures was impaired, following increased apoptosis. We show that such a mechanism is relevant in vivo and underlies the action of butein, a dual STAT3-NFkB inhibitor capable of abating the chemoresistance of mesothelioma cells in vivo. The possible broad translational relevance of the described mechanism is discussed.

2-Deoxy-d-Glucose Sensitizes Human Ovarian Cancer Cells to Cisplatin by Increasing ER Stress and Decreasing ATP Stores in Acidic Vesicles

Cisplatin is a commonly used chemotherapeutic agent; however, the development of acquired resistance limits its application. Here, we demonstrate that 2-deoxy-d-glucose (2-DG) enhanced the antitumor effects of cisplatin in SKOV3 cells, which include inhibition of proliferation and promotion of apoptosis. Additionally, either cisplatin or 2-DG alone could upregulate the endoplasmic reticulum (ER) stress-associated protein glucose-regulated protein-78 (GRP78). Moreover, exposure to 2-DG increased the expression of GRP78 induced by cisplatin. Cisplatin also upregulated ER stress-associated apoptotic protein 153/C/EBP homology protein (CHOP) in SKOV3 cells. While treatment with 2-DG alone could not upregulate the CHOP expression, a combination of both 2-DG and cisplatin increased the protein levels of CHOP above those induced by Cisplatin alone. Finally, cisplatin mediated an increase in ATP stores within acidic vesicles, whereas 2-DG decreased this effect. These data demonstrate that 2-DG sensitizes SKOV3 cells to cisplatin by increasing ER stress and decreasing ATP stores in acidic vesicles.

Down-regulation of C/EBP homologous protein (CHOP) expression in gastric cardia adenocarcinoma: Their relationship with clinicopathological parameters and prognostic significance

OBJECTIVE

C/EBP homologous protein (CHOP) is a multi-functional protein involved in the apoptosis pathway of endoplasmic reticulum stress (ERS) and is related to cancer progression. The purpose of this study was to assess CHOP expression as a prognostic biomarker in gastric cardia adenocarcinoma (GCA).

METHODS

The levels of CHOP mRNA and protein in GCA and matched adjacent non-cancerous tissues were evaluated by quantitative real-time-polymerase chain reaction (qRT-PCR) and western blot. Furthermore, the CHOP protein expression and localization were examined by immunohistochemistry in GCA and corresponding adjacent non-cancerous tissues, gastritis and normal cardiac tissues. The association of CHOP expression with clinical pathological parameters and prognosis of GCA patients was statistically analyzed.

RESULTS

Compared with adjacent non-cancerous tissues, the CHOP was down-regulated at mRNA and protein levels in GCA (P<0.01). In addition, immunohistochemistry analysis showed that CHOP positivity was lower in GCA than that in paired adjacent non-cancerous tissues, gastritis and normal tissues (P<0.01). CHOP expression rate gradually decreased with an increase in clinical stage, tumor differentiation and lymph node metastasis of GCA (P<0.05). Kaplan-Meier survival analysis revealed that low expression of CHOP correlated with poor prognosis of GCA patients. Moreover, univariate and multivariate analyses showed that CHOP was an independent prognostic marker for overall survival of GCA patients.

CONCLUSIONS

Our results suggest that low CHOP expression predicts poor prognosis of GCA patients, and CHOP may be potentially a prognostic biomarker for GCA.

The stress-response sensor chop regulates the function and accumulation of myeloid-derived suppressor cells in tumors

Adaptation of malignant cells to the hostile milieu present in tumors is an important determinant of their survival and growth. However, the interaction between tumor-linked stress and antitumor immunity remains poorly characterized. Here, we show the critical role of the cellular stress sensor C/EBP-homologous protein (Chop) in the accumulation and immune inhibitory activity of tumor-infiltrating myeloid-derived suppressor cells (MDSCs). MDSCs lacking Chop had decreased immune-regulatory functions and showed the ability to prime T cell function and induce antitumor responses. Chop expression in MDSCs was induced by tumor-linked reactive oxygen and nitrogen species and regulated by the activating-transcription factor-4. Chop-deficient MDSCs displayed reduced signaling through CCAAT/enhancer-binding protein-β, leading to a decreased production of interleukin-6 (IL-6) and low expression of phospho-STAT3. IL-6 overexpression restored immune-suppressive activity of Chop-deficient MDSCs. These findings suggest the role of Chop in tumor-induced tolerance and the therapeutic potential of targeting Chop in MDSCs for cancer immunotherapy.

The toxicity mechanisms of action of Aβ25-35 in isolated rat cardiac myocytes

β-Amyloid (Aβ) is deposited in neurons and vascular cells of the brain and is characterized as a pathologic feature of Alzheimer's disease (AD). Recently studies have reported that there is an association between cardiovascular risk factors and AD, however the mechanism of this association is still uncertain. In this study we observed Aβ had an effect on cardiovascular cells. We represent as a major discovery that Aβ25-35 had toxicity on isolated rat cardiac myocytes by impacting the cytoskeleton assembly and causing ER stress, ultimately contributing to the apoptosis of the myocytes. Importantly, the activation of ER stress and subsequent cellular dysfunction and apoptosis by Aβ25-35 was regulated by the MAPK pathway, which could be prevented by inhibition of p38 via pharmacological inhibitors. It was noteworthy that Aβ25-35 played a critical role in cardiac myocytes, suggesting that Alzheimer's disease (AD) had a relation with the heart and understanding of these associations in future will help search for effective treatment strategies.

The integrated stress response in lung disease

Lungs are repeatedly exposed to inhaled toxic insults, such as smoke, diesel exhaust, and microbes, which elicit cellular stress responses. The phosphorylation of eukaryotic translation initiation factor 2α by one of four stress-sensing kinases triggers a pathway called the integrated stress response that helps protect cellular reserves of nutrients and prevents the accumulation of toxic proteins. In this review, we discuss how activation of the integrated stress response has been shown to play an important role in pulmonary pathology, and how its study may help in the development of novel therapies for diverse conditions, from hypoxia to cancer.

Endoplasmic reticulum stress and cancer

The endoplasmic reticulum (ER) is the principal organelle responsible for multiple cellular functions including protein folding and maturation and the maintenance of cellular homeostasis. ER stress is activated by a variety of factors and triggers the unfolded protein response (UPR), which restores homeostasis or activates cell death. Multiple studies have clarified the link between ER stress and cancer, and particularly the involvement of the UPR. The UPR seems to adjust the paradoxical microenvironment of cancer and, as such, is one of resistance mechanisms against cancer therapy. This review describes the activity of different UPRs involved in tumorigenesis and resistance to cancer therapy.

Endoplasmic reticulum stress in malignancy

The combination of relative nutrient deprivation and dysregulation of protein synthesis make malignant cells especially prone to protein misfolding. Endoplasmic reticulum stress, which results from protein misfolding within the secretory pathway, has a profound effect on cancer cell proliferation and survival. In this review, we examine the evidence implicating endoplasmic reticulum dysfunction in the pathology of cancer and discuss how recent findings may help to identify novel therapeutic targets.

The endoplasmic reticulum stress markers GRP78 and CHOP predict disease-free survival and responsiveness to chemotherapy in breast cancer

Glucose-regulated protein (GRP) 78 and C/-EBP homologous protein (CHOP) are commonly used as markers of endoplasmic reticulum (ER) stress. As an ER chaperone, GRP78 functions as a potent anti-apoptotic factor and confers drug resistance, whereas CHOP is a key initiating factor of ER stress-related cell death. We aimed at investigating the predictive values of GRP78 and CHOP in breast cancer patients who underwent adjuvant chemotherapy. An immunohistochemistry screen for GRP78 and CHOP was performed using a tissue microarray containing 250 tumors from female patients diagnosed with invasive ductal breast carcinoma at the Fudan University Shanghai Cancer Center. The staining results were scored semi-quantitatively, and a prediction model was constructed to verify the hypothesis. In this retrospective cohort study, CHOP correlated with prolonged disease-free survival (HR = 0.385, 95 % CI 0.215-0.688; P = 0.001), whereas GRP78 showed an opposite association (HR = 4.573; 95 % CI 2.291-9.128; P < 0.001). Moreover, in a GRP78-positive subset, CHOP overexpression correlated with a lower risk of recurrence. In the receiver operating characteristic analysis, the prediction capability of the predictive model combining the above two markers surpassed that of the traditional model (P = 0.0085 for the area under the curve comparison). Within the anthracycline-treatment subgroup, the combined GRP78 and CHOP exhibited similar predictive significance. Cumulatively, our findings suggest a tight association between ER stress markers and clinical outcomes for patients with breast cancer.

Zebrafish transgenic line huORFZ is an effective living bioindicator for detecting environmental toxicants

Reliable animal models are invaluable for monitoring the extent of pollution in the aquatic environment. In this study, we demonstrated the potential of huORFZ, a novel transgenic zebrafish line that harbors a human upstream open reading frame of the chop gene fused with GFP reporter, as an animal model for monitoring environmental pollutants and stress-related cellular processes. When huORFZ embryos were kept under normal condition, no leaked GFP signal could be detected. When treated with hazardous chemicals, including heavy metals and endocrine-disrupting chemicals near their sublethal concentrations (LC50), huORFZ embryos exhibited different tissue-specific GFP expression patterns. For further analysis, copper (Cu²⁺), cadmium (Cd²⁺) and Chlorpyrifos were applied. Cu²⁺ triggered GFP responses in skin and muscle, whereas Cd²⁺ treatment triggered GFP responses in skin, olfactory epithelium and pronephric ducts. Moreover, fluorescence intensity, as exhibited by huORFZ embryos, was dose-dependent. After surviving treated embryos were returned to normal condition, survival rates, as well as TUNEL signals, returned to pretreatment levels with no significant morphological defects observed. Such results indicated the reversibility of treatment conditions used in this study, as long as embryos survived such conditions. Notably, GFP signals decreased along with recovery, suggesting that GFP signaling of huORFZ embryos likely reflected the overall physiological condition of the individual. To examine the performance of the huORFZ line under real-world conditions, we placed huORFZ embryos in different river water samples. We found that the huORFZ embryos correctly detected the presence of various kinds of pollutants. Based on these findings, we concluded that such uORF^chop-based system can be integrated into a first-line water alarm system monitoring the discharge of hazardous pollutants.

The stress-regulated transcription factor CHOP promotes hepatic inflammatory gene expression, fibrosis, and oncogenesis

Viral hepatitis, obesity, and alcoholism all represent major risk factors for hepatocellular carcinoma (HCC). Although these conditions also lead to integrated stress response (ISR) or unfolded protein response (UPR) activation, the extent to which these stress pathways influence the pathogenesis of HCC has not been tested. Here we provide multiple lines of evidence demonstrating that the ISR-regulated transcription factor CHOP promotes liver cancer. We show that CHOP expression is up-regulated in liver tumors in human HCC and two mouse models thereof. Chop-null mice are resistant to chemical hepatocarcinogenesis, and these mice exhibit attenuation of both apoptosis and cellular proliferation. Chop-null mice are also resistant to fibrosis, which is a key risk factor for HCC. Global gene expression profiling suggests that deletion of CHOP reduces the levels of basal inflammatory signaling in the liver. Our results are consistent with a model whereby CHOP contributes to hepatic carcinogenesis by promoting inflammation, fibrosis, cell death, and compensatory proliferation. They implicate CHOP as a common contributing factor in the development of HCC in a variety of chronic liver diseases.

Liver cancer is the third most common cause of cancer death worldwide. It is most commonly caused by viral hepatitis, alcoholism, or obesity, all of which activate cellular stress responses in the liver. However, the contribution of these responses to disease pathogenesis was unknown. We found that expression of the stress-regulated transcription factor CHOP—widely thought to be anti-oncogenic because of its cell death-promoting properties—was associated with both human liver cancer and two mouse models thereof. In response to challenge with a tumor-causing agent, mice lacking CHOP developed fewer tumors, exhibited less cell death, compensatory cellular proliferation, and liver scarring (fibrosis), and showed lower expression of immune and inflammatory genes. These findings establish CHOP as a biomarker for liver cancer and demonstrate its importance in promoting liver tumor formation. They raise the possibility that promotion of tumorigenesis by CHOP is a common feature of liver cancer caused by viral infection, alcoholism, and obesity.