The interaction between SPARC and GRP78 interferes with ER stress signaling and potentiates apoptosis via PERK/eIF2α and IRE1α/XBP-1 in colorectal cancer

Phelligridimer A enhances the expression of mitofusin 2 and protects against cerebral ischemia/reperfusion injury

Mitochondrial dysfunction and endoplasmic reticulum (ER) stress play pivotal roles in the pathology of cerebral ischemia. In this study, we investigated whether phelligridimer A (PA), an active compound isolated from the medicinal and edible fungus Phellinus igniarius, ameliorates ischemic cerebral injury by restoring mitochondrial function and restricting ER stress. An in vitro cellular model of ischemic stroke-induced neuronal damage was established by exposing HT-22 neuronal cells to oxygen-glucose deprivation/reoxygenation (OGD/R). An in vivo animal model was established in rats subjected to middle cerebral artery occlusion/reperfusion (MCAO/R). The results showed that PA (1-10 μM) dose-dependently increased HT-22 cell viability, reduced OGD/R-induced lactate dehydrogenase release, and reversed OGD/R-induced apoptosis. PA reduced OGD/R-induced accumulation of reactive oxygen species, restored mitochondrial membrane potential, and increased ATP levels. Additionally, PA reduced the expression of the 78-kDa glucose-regulated protein (GRP78) and the phosphorylation of inositol-requiring enzyme-1α (p-IRE1α) and eukaryotic translation-initiation factor 2α (p-eIF2α). PA also inhibited the activation of the mitogen-activated protein kinase (MAPK) pathway in the OGD/R model. Moreover, treatment with PA restored the expression of mitofusin 2 (Mfn-2), a protein linking mitochondria and ER. The silencing of Mfn-2 abolished the protective effects of PA. The results from the animal study showed that PA (3-10 mg/kg) significantly reduced the volume of cerebral infarction and neurological deficits, which were accompanied by an increased level of Mfn-2, and decreased activation of the ER stress in the penumbra of the ipsilateral side after MCAO/R in rats. Taken together, these results indicate that PA counteracts cerebral ischemia-induced injury by restoring mitochondrial function and reducing ER stress. Therefore, PA might be a novel protective agent to prevent ischemia stroke-induced neuronal injury.

Mechanisms Underlying the Rarity of Skeletal Muscle Cancers

Skeletal muscle (SKM), despite comprising ~40% of body mass, rarely manifests cancer. This review explores the mechanisms that help to explain this rarity, including unique SKM architecture and function, which prohibits the development of new cancer as well as negates potential metastasis to SKM. SKM also presents a unique immune environment that may magnify the anti-tumorigenic effect. Moreover, the SKM microenvironment manifests characteristics such as decreased extracellular matrix stiffness and altered lactic acid, pH, and oxygen levels that may interfere with tumor development. SKM also secretes anti-tumorigenic myokines and other molecules. Collectively, these mechanisms help account for the rarity of SKM cancer.

Benefits and Pitfalls of a Glycosylation Inhibitor Tunicamycin in the Therapeutic Implication of Cancers

The aberrant glycosylation is a hallmark of cancer progression and chemoresistance. It is also an immune therapeutic target for various cancers. Tunicamycin (TM) is one of the potent nucleoside antibiotics and an inhibitor of aberrant glycosylation in various cancer cells, including breast cancer, gastric cancer, and pancreatic cancer, parallel with the inhibition of cancer cell growth and progression of tumors. Like chemotherapies such as doxorubicin (DOX), 5'fluorouracil, etoposide, and cisplatin, TM induces the unfolded protein response (UPR) by blocking aberrant glycosylation. Consequently, stress is induced in the endoplasmic reticulum (ER) that promotes apoptosis. TM can thus be considered a potent antitumor drug in various cancers and may promote chemosensitivity. However, its lack of cell-type-specific cytotoxicity impedes its anticancer efficacy. In this review, we focus on recent advances in our understanding of the benefits and pitfalls of TM therapies in various cancers, including breast, colon, and pancreatic cancers, and discuss the mechanisms identified by which TM functions. Finally, we discuss the potential use of nano-based drug delivery systems to overcome non-specific toxicity and enhance the therapeutic efficacy of TM as a targeted therapy.

Endoplasmic reticulum stress and the unfolded protein response: emerging regulators in progression of traumatic brain injury

Traumatic brain injury (TBI) is a common trauma with high mortality and disability rates worldwide. However, the current management of this disease is still unsatisfactory. Therefore, it is necessary to investigate the pathophysiological mechanisms of TBI in depth to improve the treatment options. In recent decades, abundant evidence has highlighted the significance of endoplasmic reticulum stress (ERS) in advancing central nervous system (CNS) disorders, including TBI. ERS following TBI leads to the accumulation of unfolded proteins, initiating the unfolded protein response (UPR). Protein kinase RNA-like ER kinase (PERK), inositol-requiring protein 1 (IRE1), and activating transcription factor 6 (ATF6) are the three major pathways of UPR initiation that determine whether a cell survives or dies. This review focuses on the dual effects of ERS on TBI and discusses the underlying mechanisms. It is suggested that ERS may crosstalk with a series of molecular cascade responses, such as mitochondrial dysfunction, oxidative stress, neuroinflammation, autophagy, and cell death, and is thus involved in the progression of secondary injury after TBI. Hence, ERS is a promising candidate for the management of TBI.

Paeoniflorin Induces ER Stress-Mediated Apoptotic Cell Death by Generating Nox4-Derived ROS under Radiation in Gastric Cancer

Gastric cancer is one of the most prevalent cancer types worldwide, and its resistance to cancer therapies, such as chemotherapy and radiotherapy, has made treating it a major challenge. Paeoniflorin (PF) is one potential pharmacological treatment derived from paeony root. However, in cancer, the molecular mechanisms and biological functions of PF are still unclear. In the present study, we found that PF exerts anti-tumor effects in vivo and in vitro and induces apoptotic cell death through ER stress, calcium (Ca2+), and reactive oxygen species (ROS) release in gastric cancer cells. However, ROS inhibition by DPI and NAC blocks cell death and the PERK signaling pathway via the reduction of Nox4. Moreover, PF triggers a synergistic inhibitory effect of the epithelial-mesenchymal transition (EMT) process under radiation exposure in radiation-resistant gastric cancer cells. These findings indicate that PF-induced Ca2+ and ROS release overcomes radioresistance via ER stress and induces cell death under radiation in gastric cancer cells. Therefore, PF, in combination with radiation, may be a powerful strategy for gastric cancer therapy.

Cholesterol induction in CD8+ T cell exhaustion in colorectal cancer via the regulation of endoplasmic reticulum-mitochondria contact sites

BACKGROUND

Hypercholesterolemia is one of the risk factors for colorectal cancer (CRC). Cholesterol can participate in the regulation of human T cell function and affect the occurrence and development of CRC.

OBJECTIVE

To elucidate the pathogenesis of CRC immune escape mediated by CD8+ T cell exhaustion induced by cholesterol.

METHODS

CRC samples (n = 217) and healthy individuals (n = 98) were recruited to analyze the relationship between peripheral blood cholesterol levels and the clinical features of CRC. An animal model of CRC with hypercholesterolemia was established. Intraperitoneal intervention with endoplasmic reticulum stress (ERS) inhibitors in hypercholesterolemic CRC mice was performed. CD69, PD1, TIM-3, and CTLA-4 on CD8+ T cells of spleens from C57BL/6 J mice were detected by flow cytometry. CD8+ T cells were cocultured with MC38 cells (mouse colon cancer cell line). The proliferation, apoptosis, migration and invasive ability of MC38 cells were detected by CCK-8 assay, Annexin-V APC/7-AAD double staining, scratch assay and transwell assay, respectively. Transmission electron microscopy was used to observe the ER structure of CD8+ T cells. Western blotting was used to detect the expression of ERS and mitophagy-related proteins. Mitochondrial function and energy metabolism were measured. Immunoprecipitation was used to detect the interaction of endoplasmic reticulum-mitochondria contact site (ERMC) proteins. Immunofluorescence colocalization was used to detect the expression and intracellular localization of ERMC-related molecules.

RESULTS

Peripheral blood cholesterol-related indices, including Tc, low density lipoproteins (LDL) and Apo(a), were all increased, and high density lipoprotein (HDL) was decreased in CRCs. The proliferation, migration and invasion abilities of MC38 cells were enhanced, and the proportion of tumor cell apoptosis was decreased in the high cholesterol group. The expression of IL-2 and TNF-α was decreased, while IFN-γ was increased in the high cholesterol group. It indicated high cholesterol could induce exhaustion of CD8+ T cells, leading to CRC immune escape. Hypercholesterolemia damaged the ER structure of CD8+ T cells and increased the expression of ER stress molecules (CHOP and GRP78), lead to CD8+ T cell exhaustion. The expression of mitophagy-related proteins (BNIP3, PINK and Parkin) in exhausted CD8+ T cells increased at high cholesterol levels, causing mitochondrial energy disturbance. High cholesterol enhanced the colocalization of Fis1/Bap31, MFN2/cox4/HSP90B1, VAPB/PTPIP51, VDAC1/IPR3/GRP75 in ERMCs, indicated that high cholesterol promoted the intermolecular interaction between ER and mitochondrial membranes in CD8+ T cells.

CONCLUSION

High cholesterol regulated the ERS-ERMC-mitophagy axis to induce the exhaustion of CD8+ T cells in CRC.

Unveiling the dark side of glucose-regulated protein 78 (GRP78) in cancers and other human pathology: a systematic review

Glucose-Regulated Protein 78 (GRP78) is a chaperone protein that is predominantly expressed in the lumen of the endoplasmic reticulum. GRP78 plays a crucial role in protein folding by assisting in the assembly of misfolded proteins. Under cellular stress conditions, GRP78 can translocate to the cell surface (csGRP78) were it interacts with different ligands to initiate various intracellular pathways. The expression of csGRP78 has been associated with tumor initiation and progression of multiple cancer types. This review provides a comprehensive analysis of the existing evidence on the roles of GRP78 in various types of cancer and other human pathology. Additionally, the review discusses the current understanding of the mechanisms underlying GRP78's involvement in tumorigenesis and cancer advancement. Furthermore, we highlight recent innovative approaches employed in downregulating GRP78 expression in cancers as a potential therapeutic target.

Oridonin promotes endoplasmic reticulum stress via TP53-repressed TCF4 transactivation in colorectal cancer

BACKGROUND

The incidence of colorectal cancer and cancer death rate are increasing every year, and the affected population is becoming younger. Traditional Chinese medicine therapy has a unique effect in prolonging survival time and improving the prognosis of patients with colorectal cancer. Oridonin has been reported to have anti-cancer effects in a variety of tumors, but the exact mechanism remains to be investigated.

METHODS

Cell Counting Kit-8 assay (CCK8) and 5-Ethynyl-2'-deoxyuridine (EdU) staining assay, Tranwell, and Wound healing assays were performed to measure cell proliferation, invasion, and migration capacities, respectively. The protein and mRNA expression levels of various molecules were reflected by Western blot and Reverse Transcription quantitative Polymerase Chain Reaction (qRT-PCR). Transcription Factor 4 (TCF4) and its target genes were analyzed by Position Weight Matrices (PWMs) software and the Gene Expression Omnibus (GEO) database. Immunofluorescence (IF) was performed to visualize the expression and position of Endoplasmic Reticulum (ER) stress biomarkers. The morphology of the ER was demonstrated by the ER tracker-red. Reactive Oxygen Species (ROS) levels were measured using a flow cytometer (FCM) or fluorescent staining. Calcium ion (Ca²⁺) concentration was quantified by Fluo-3 AM staining. Athymic nude mice were modeled with subcutaneous xenografts.

RESULTS

Oridonin inhibited the proliferation, invasion, and migration of colorectal cancer, and this effect was weakened in a concentration-dependent manner by ER stress inhibitors. In addition, oridonin-induced colorectal tumor cells showed increased expression of ER stress biomarkers, loose morphology of ER, increased vesicles, and irregular shape. TCF4 was identified as a regulator of ER stress by PWMs software and GEO survival analysis. In vitro and in vivo experiments confirmed that TCF4 inhibited ER stress, reduced ROS production, and maintained Ca²⁺ homeostasis. In addition, oridonin also activated TP53 and inhibited TCF4 transactivation, further exacerbating the elevated ROS levels and calcium ion release in tumor cells and inhibiting tumorigenesis in colorectal cancer cells in vivo.

CONCLUSIONS

Oridonin upregulated TP53, inhibited TCF4 transactivation, and induced ER stress dysregulation in tumor cells, promoting colorectal cancer cell death. Therefore, TCF4 may be one of the important nodes for tumor cells to regulate ER stress and maintain protein synthesis homeostasis. And the inhibition of the TP53/TCF4 axis plays a key role in the anti-cancer effects of oridonin.

Mitochondria associated ER membrane and cerebral ischemia: molecular mechanisms and therapeutic strategies

Endoplasmic reticulum (ER) and mitochondria are two important organelles that are highly dynamic in mammalian cells. The physical connection between them is mitochondria associated ER membranes (MAM). In recent years, studies on endoplasmic reticulum and mitochondria have shifted from independent division to association and comparison, especially MAM has gradually become a research hotspot. MAM connects the two organelles, not only to maintain their independent structure and function, but also to promote metabolism and signal transduction between them. This paper reviews the morphological structure and protein localization of MAM, and briefly analyzes the functions of MAM in regulating Ca²⁺ transport, lipid synthesis, mitochondrial fusion and fission, endoplasmic reticulum stress and oxidative stress, autophagy and inflammation. Since ER stress and mitochondrial dysfunction are important pathological events in neurological diseases including ischemic stroke, MAM is likely to play an important role in cerebral ischemia by regulating the signaling of the two organelles and the crosstalk of the two pathological events.

COLEC10 Induces Endoplasmic Reticulum Stress by Occupying GRP78 and Inhibiting Hepatocellular Carcinoma

Collectin subfamily member 10 (COLEC10), a C-type lectin mainly expressed in the liver, is involved in the development of hepatocellular carcinoma (HCC). However, its underlying molecular mechanism in HCC progression remains unknown. In this study, reduced COLEC10 expression in tumor tissues was validated by various HCC cohorts and was associated with poor patient prognosis. COLEC10 overexpression attenuated HCC cell growth and migration abilities in vitro and in vivo. We identified that COLEC10 was a novel interactor of GRP78, a master modulator of the unfolded protein response (UPR) in the endoplasmic reticulum (ER). COLEC10 overexpression potentiated ER stress in HCC cells, as demonstrated by elevated expression levels of p-PERK, p-IRE1α, ATF4, CHOP, and XBP-1s. The ER in COLEC10 overexpressing cells also showed a dilated and fragmented pattern. Mechanistically, COLEC10 overexpression increases GRP78 occupancy through direct binding by C-terminal CRD in the ER, which released and activated the ER stress transducers PERK and IRE1α, triggering the UPR activity. COLEC10 overexpressing HCC cells generated a relatively high ROS level and switched to apoptotic cell death under sorafenib-treated conditions. Our study provides the first novel view that COLEC10 inhibits HCC progression by regulating GRP78-mediated ER stress signaling and may serve as a promising therapeutic and prognostic biomarker.

Novel anthraquinone derivatives trigger endoplasmic reticulum stress response and induce apoptosis

Background: Endoplasmic reticulum (ER) stress is a therapeutic target in cancer given its regulation of bioenergetics and cell death. Methodology & results: We synthesized 14 ER stress-triggered anthraquinone derivatives by introducing an amino group at the 3-position side chain of the lead compound obtained previously. Most of the anthraquinone derivatives exhibited good antitumor activity due to their ability to induce ER damage through cytoplasmic vacuoles. The mechanisms of ER stress caused by compound KA-4c were related to increasing the expression levels of the ATF6 and Bip proteins and upregulating CHOP and cleaved PARP. Conclusion: Compound KA-4c triggers ER stress response and induces apoptosis via the ATF6-CHOP signaling pathway.

The progress of protein synthesis factors eIFs, eEFs and eRFs in inflammatory bowel disease and colorectal cancer pathogenesis

Colorectal diseases are threatening human health, especially inflammatory bowel disease (IBD) and colorectal cancer (CRC). IBD is a group of chronic, recurrent and incurable disease, which may affect the entire gastrointestinal tract, increasing the risk of CRC. Eukaryotic gene expression is a complicated process, which is mainly regulated at the level of gene transcription and mRNA translation. Protein translation in tissue is associated with a sequence of steps, including initiation, elongation, termination and recycling. Abnormal regulation of gene expression is the key to the pathogenesis of CRC. In the early stages of cancer, it is vital to identify new diagnostic and therapeutic targets and biomarkers. This review presented current knowledge on aberrant expression of eIFs, eEFs and eRFs in colorectal diseases. The current findings of protein synthesis on colorectal pathogenesis showed that eIFs, eEFs and eRFs may be potential targets for CRC treatment.

Mitochondria-associated endoplasmic reticulum membranes and cardiac hypertrophy: Molecular mechanisms and therapeutic targets

Cardiac hypertrophy has been shown to compensate for cardiac performance and improve ventricular wall tension as well as oxygen consumption. This compensatory response results in several heart diseases, which include ischemia disease, hypertension, heart failure, and valvular disease. Although the pathogenesis of cardiac hypertrophy remains complicated, previous data show that dysfunction of the mitochondria and endoplasmic reticulum (ER) mediates the progression of cardiac hypertrophy. The interaction between the mitochondria and ER is mediated by mitochondria-associated ER membranes (MAMs), which play an important role in the pathology of cardiac hypertrophy. The function of MAMs has mainly been associated with calcium transfer, lipid synthesis, autophagy, and reactive oxygen species (ROS). In this review, we discuss key MAMs-associated proteins and their functions in cardiovascular system and define their roles in the progression of cardiac hypertrophy. In addition, we demonstrate that MAMs is a potential therapeutic target in the treatment of cardiac hypertrophy.

Gas plasma-oxidized sodium chloride acts via hydrogen peroxide in a model of peritoneal carcinomatosis

Gas plasma technology generates reactive oxygen and nitrogen species (ROS/RNS), inducing lethal oxidative damage in tumor cells. The transfer of gas plasma-derived ROS/RNS into liquids has been proposed as an innovative anti-cancer strategy targeting peritoneal carcinomatosis (PC). However, the mechanism of action is under debate. To this end, we compared gas plasma-oxidized medical-grade sodium chloride (oxNaCl) with a concentration-matched control (cmc) of NaCl enriched with equivalent concentrations of H₂O₂ and NO₃^- in several cell lines and models of PC. Strikingly, oxNaCl and cmc performed equally well in oxidation and cytotoxic activity in tumor cells in two-dimensional cultures, three-dimensional (3D) tumor spheroids, vascularized 3D tumors grown on chicken-embryo chorioallantoic membranes, and a syngeneic PC mouse model in vivo. Given the importance of immunotherapies in oncology today, we focused on immunological consequences of the treatment. Again, to a similar extent, oxNaCl and cmc increased tumor cell immunogenicity and enhanced uptake by and maturation of peripheral blood monocyte-derived dendritic cells together with an inflammatory secretion profile. Furthermore, NanoString gene expression profiling revealed immune system processes and unfolded protein response-related pathways as being linked to the observed anti-tumor effects for both oxNaCl and cmc. In conclusion, gas plasma-generated oxNaCl and cmc showed equal therapeutic efficacy in our PC-related models. In light of the many promising anti-cancer studies of gas plasma-oxidized liquids and the convenient production of corresponding cmcs in large quantities as needed in clinics, our findings may spur research lines based on low-dose oxidants in peritoneal cancer therapy.

Pro-Survival Factor EDEM3 Confers Therapy Resistance in Prostate Cancer

Prostate cancer is the most common cancer in men, and it is primarily driven by androgen steroid hormones. The glycosylation enzyme EDEM3 is controlled by androgen signalling and is important for prostate cancer viability. EDEM3 is a mannosidase that trims mannose from mis-folded glycoproteins, tagging them for degradation through endoplasmic reticulum-associated degradation. Here, we find that EDEM3 is upregulated in prostate cancer, and this is linked to poorer disease-free survival. Depletion of EDEM3 from prostate cancer cells induces an ER stress transcriptomic signature, and EDEM3 overexpression is cyto-protective against ER stressors. EDEM3 expression also positively correlates with genes involved in the unfolded protein response in prostate cancer patients, and its expression can be induced through exposure to radiation. Importantly, the overexpression of EDEM3 promotes radio-resistance in prostate cancer cells and radio-resistance can be reduced through depletion of EDEM3. Our data thus implicate increased levels of EDEM3 with a role in prostate cancer pathology and reveal a new therapeutic opportunity to sensitise prostate tumours to radiotherapy.

Muscle-to-tumor crosstalk: The effect of exercise-induced myokine on cancer progression

Physical exercise has gradually become a focus in cancer treatment due to its pronounced role in reducing cancer risk, enhancing therapeutic efficacy, and improving prognosis. In recent decades, skeletal muscles have been considered endocrine organs, exerting their biological functions via the endocrine, autocrine, and paracrine systems by secreting various types of myokines. The amount of myokines secreted varies depending on the intensity, type, and duration of exercise. Recent studies have shown that muscle-derived myokines are highly involved the effects of exercise on cancer. Multiple myokines, such as interleukin-6 (IL-6), oncostatin M (OSM), secreted protein acidic and rich in cysteine (SPARC), and irisin, directly mediate cancer progression by influencing the proliferation, apoptosis, stemness, drug resistance, metabolic reprogramming, and epithelial-mesenchymal transformation (EMT) of cancer cells. In addition, IL-6, interleukin-8 (IL-8), interleukin-15 (IL-15), brain-derived neurotrophic factor (BDNF), and irisin can improve obesity-induced inflammation by stimulating lipolysis of adipose tissues, promoting glucose uptake, and accelerating the browning of white fat. Furthermore, some myokines could regulate the tumor microenvironment, such as angiogenesis and the immune microenvironment. Cancer cachexia occurs in up to 80% of cancer patients and is responsible for 22%-30% of patient deaths. It is characterized by systemic inflammation and decreased muscle mass. Exercise-induced myokine production is important in regulating cancer cachexia. This review summarizes the roles and underlying mechanisms of myokines, such as IL-6, myostatin, IL-15, irisin, fibroblast growth factor 21 (FGF21) and musclin, in cancer cachexia. Through comprehensive analysis, we conclude that myokines are potential targets for inhibiting cancer progression and the associated cachexia.

Effects of SPARC and Possible Receptors on Colon Cancer Cell Line

Objective: The aim of this study was to observe the apoptotic/cytotoxic effects of exogenous SPARC on colon cancer cell line HT-29, then to investigate the function of stabilin-1 and integrin αvβ3, which are possible receptors for SPARC in colon cancer cells and to determine the quantitation of their receptor numbers. Methods: Appropriate doses of exogenous SPARC and it’s inhibitor, cilengitide added to HT-29 cell line were determined by xCELLigence Real-Time Cell Analysis system, SPARC-mediated caspase 3 expressions were measured. Using the RT-PCR system, gene expression levels of SPARC, stabilin-1 and integrin αvβ3 receptors (silenced/nonsilenced with cilengitide) were detected then the numbers of receptors per cell were quantitated by flow cytometry. Results: IC50 value of SPARC was determined as 4.57 μg/mL and IC50 value of cilengitide was determined as 50 nM. 5 μg/mL exogenous SPARC caused increased apoptosis in the HT-29 line. Significant increase in gene expression of integrin αvβ3 receptor was observed in the group incubated with 5 μg/mL SPARC, contrarily, the addition of cilengitide decreased gene expressions. The integrin αvβ3 receptor numbers increased approximately 2-fold with SPARC compared to the control. No significant changes were observed in the gene expression and receptor numbers of stabilin-1. Conclusion: Exogenous SPARC was shown to reduce proliferation and induce apoptosis in colon cancer cells. Integrin αvβ3 is thought to be the possible receptor mediating SPARC in colon cancer cells. Quantification of surface receptors per cell, which we think we have done first, can be considered as a marker in the follow-up of anticancer treatments.

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.

Calcium-Related Gene Signatures May Predict Prognosis and Level of Immunosuppression in Gliomas

Gliomas are the most common primary brain cancer. While it has been known that calcium-related genes correlate with gliomagenesis, the relationship between calcium-related genes and glioma prognosis remains unclear. We assessed TCGA datasets of mRNA expressions with differentially expressed genes (DEGs) and enrichment analysis to specifically screen for genes that regulate or are affected by calcium levels. We then correlated the identified calcium-related genes with unsupervised/supervised learning to classify glioma patients into 2 risk groups. We also correlated our identified genes with immune signatures. As a result, we discovered 460 calcium genes and 35 calcium key genes that were associated with OS. There were 13 DEGs between Clusters 1 and 2 with different OS. At the same time, 10 calcium hub genes (CHGs) signature model were constructed using supervised learning, and the prognostic risk scores of the 3 cohorts of samples were calculated. The risk score was confirmed as an independent predictor of prognosis. Immune enrichment analysis revealed an immunosuppressive tumor microenvironment with upregulation of checkpoint markers in the high-risk group. Finally, a nomogram was generated with risk scores and other clinical prognostic independent indicators to quantify prognosis. Our findings suggest that calcium-related gene expression patterns could be applicable to predict prognosis and predict levels of immunosuppression.

Role of endoplasmic reticulum stress in apoptosis induced by HK2 inhibitor and its potential as a new drug combination strategy

Compared with normal cells, tumor cells mainly obtain energy through aerobic glycolysis. Hexokinase 2 (HK2) plays a key role in the regulation of tumor cell aerobic glycolysis, and targeting HK2 has become a new strategy for cancer treatment. However, little is known about the role of HK2 in colon cancer and the regulation of its targeted inhibitors. In this study, we found that the expression of HK2 in colorectal cancer tissues was significantly higher than that in adjacent tissues, and the expression level of HK2 in metastatic colorectal cancer was further increased. Meanwhile, the expression level of HK2 was closely related to clinical TNM stage and outcome of colorectal cancer patients. We provide here evidence that HK2 inhibitor 3-Bromopyruvate acid (3-BP) can significantly inhibit the survival and proliferation of colon cancer cells, and induce apoptosis through mitochondrial apoptosis signaling pathway. In addition, we found that 3-BP can also induce endoplasmic reticulum stress in colon cancer cells, the mechanism may be through the increase of intracellular calcium concentration. In vitro and in vivo experiments showed that inhibition of endoplasmic reticulum stress could further increase the proliferation inhibition and apoptosis induced by 3-BP. Collectively, our results show that HK2 is highly expressed in colorectal cancer. 3-BP, an inhibitor of HK2, can induce apoptosis and endoplasmic reticulum stress in colon cancer cells. Endoplasmic reticulum stress plays a protective role in cell death induced by 3-BP. This result suggested that targeting HK2 and endoplasmic reticulum stress may be a valuable strategy in targeted and combination therapy of colon cancer.

Self-Reinforced Cancer Targeting (SRCT) Depending on Reciprocally Enhancing Feedback between Targeting and Therapy

Conventional cancer targeting methodology needs to be reformed to overcome the intrinsic barriers responsible for poor targeting efficiency. This study describes a concept of self-reinforced cancer targeting (SRCT) by correlating targeting with therapy in a reciprocally enhancing manner. SRCT is achieved on the basis of two prerequisites: (1) target molecules have to be expressed on cancer cell membranes but not on normal cells, and (2) notably, their expression on cancer cells must be actively upregulated in response to cellular attack by cancer treatments. As a proof-of-concept, a GRP78-targeting nanovehicle for chemotherapy was designed. Resultant data showed that chemotherapeutic drugs could effectively elevate GRP78 expression on the plasma membranes of cancer cells while having minimal influence on normal cells. DOX pretreatment of cancer cells and tumor tissues can greatly increase the targeting efficacy and therapeutic performance of the prepared GRP78-targeting nanomedicine while somewhat disfavoring the nontargeting counterpart. In vivo and in vitro results demonstrated that this GRP78-targeting nanomedicine could accurately target cancer cells to not only implement chemotherapy but also induce GRP78 upregulation on cancer cells, eventually benefiting continuous cancer-cell-targeted attack by the nanomedicines remaining in the blood circulation or administered in the next dose. The GRP78-targeting nanomedicine displays much better antitumor performance compared with the nontargeting counterpart. SRCT is expected to advance cancer-targeted therapy based on the positive dependency between targeting and therapeutic modalities.

The effect and apoptosis mechanism of 6-methoxyflavone in HeLa cells

INTRODUCTION

Tumor cell apoptosis is a crucial indicator for judging the antiproliferative effects of anti-cancer drugs. The detection of optical and macromolecular biomarkers is the most common method for assessing the level of apoptosis. We aimed to explore the anti-tumor mechanisms of 6-methoxyflavone.

MATERIAL AND METHODS

Three optical methods, including the percentage of apoptotic cells, cell morphology, and subcellular ultrastructure changes, were obtained using flow cytometry, inverted fluorescence microscopy, and transmission electron microscope imaging. The mRNA or protein expression of macromolecular biomarkers related to common apoptotic pathways was determined via polymerase chain reactions or western blot assays. The functional role of the core gene biomarker was investigated through overexpression, knockdown, and phosphorylation inhibitor (GSK2656157).

RESULTS

Transcriptome sequencing and the optical biomarkers assays demonstrated that 6-methoxyflavone could induce apoptosis in HeLa cells. The expression of macromolecular biomarkers indicated that 6-methoxyflavone induced apoptosis through the PERK/EIF2α/ATF4/CHOP pathway. Phosphorylated PERK was identified as the core biomarker of this pathway. Both overexpression and GSK2656157 significantly altered the expression level of phosphorylated PERK in 6-methoxyflavone-treated HeLa cells.

DISCUSSION AND CONCLUSION

Macromolecular biomarkers such as phosphorylated PERK and phosphorylated EIF2α are of great significance for assessing the therapeutic effects of 6-methoxyflavone.

Agonists Specific for κ-Opioid Receptor Induces Apoptosis of HCC Cells Through Enhanced Endoplasmic Reticulum Stress

Cancer pain is an important factor affecting life quality of patients especially in the advanced stage and relieving pain is one of fundamental strategies for cancer treatment. Opioids such as morphine are the most widely used in clinics. However, they have been reported to be associated with the occurrence and development of several types of cancer. Thus, search for an opioid that has analgesic effect and can retard cancer progress simultaneously is critical for cancer management. In this study, we first examined the expression of μ and κ (MOR and KOR) in cell lines and tumor tissues of hepatocellular carcinoma (HCC), a malignant tumor with high mortality, and then compared the effects of opioid receptors-specific agonists on malignant phenotypes of HCC cells in vitro and tumor growth in an HCC xenograft mouse model. KOR and MOR were found to be highly expressed in HCC cell lines and HCC tissues. The KOR-specific agonist U50488h, oxycodone (agonist for both KOR and MOR) and the MOR-specific agonist morphine inhibited HCC cell proliferation, while only U50488h and oxycodone suppressed colony formation and migration of HCC cells. U50488h and oxycodone, but not morphine, induced HCC apoptosis. Further detection of PERK, GRP78 and CHOP revealed that PERK signaling was upregulated by treatment with U50488h, while treatment with the PERK inhibitor GSK2656157 partially reversed the promotion of apoptosis and inhibition of cell proliferation by U50488h, indicating that endoplasmic reticulum stress is associated with its suppressing effect on HCC malignant phenotypes. Similar to the in vitro results, HCC growth was significantly reduced by administration of U50488h and oxycodone, but not by morphine, in the HCC xenograft mouse model. PERK and caspase-3 in the HCC tissues were up-regulated by U50488h treatment as detected by immunohistochemistry and western blotting. Taken together, our results revealed that activation of KOR by U50488h inhibited malignant phenotypes of HCC both in vitro and in vivo, while activation of MOR by morphine did not have such effect. Because of their dual roles in the relief of pain and in the suppression of malignant phenotypes, opioids such as U50488h that act on KOR should be considered as the first choice for HCC management.

The multifaceted role of Matricellular Proteins in health and cancer, as biomarkers and therapeutic targets

The extracellular matrix (ECM) is composed of a mesh of proteins, proteoglycans, growth factors, and other secretory components. It constitutes the tumor microenvironment along with the endothelial cells, cancer-associated fibroblasts, adipocytes, and immune cells. The proteins of ECM can be functionally classified as adhesive proteins and matricellular proteins (MCP). In the tumor milieu, the ECM plays a major role in tumorigenesis and therapeutic resistance. The current review encompasses thrombospondins, osteonectin, osteopontin, tenascin C, periostin, the CCN family, laminin, biglycan, decorin, mimecan, and galectins. The matrix metalloproteinases (MMPs) are also discussed as they are an integral part of the ECM with versatile functions in the tumor stroma. In this review, the role of these proteins in tumor initiation, growth, invasion and metastasis have been highlighted, with emphasis on their contribution to tumor therapeutic resistance. Further, their potential as biomarkers and therapeutic targets based on existing evidence are discussed. Owing to the recent advancements in protein targeting, the possibility of agents to modulate MCPs in cancer as therapeutic options are discussed.

Taurine attenuates ER stress‑associated apoptosis and catabolism in nucleus pulposus cells

Nucleus pulposus (NP) apoptosis and subsequent excessive degradation of the extracellular matrix (ECM) are key pathological characteristics of intervertebral disc degeneration (IDD). The present study aims to examine the signaling processes underlying the effects of taurine on IDD, with specific focus on endoplasmic reticulum (ER) stress-mediated apoptosis and ECM degradation, in NP cells. To clarify the role of taurine in IDD, NP cells were treated with various concentrations of taurine and IL-1β or thapsigargin (TG). Cell Counting Kit-8, western blotting, TUNEL, immunofluorescence assays and reverse transcription-quantitative PCR were applied to measure cell viability, the expression of ER stress-associated proteins (GRP78, CHOP and caspase-12), apoptosis and the levels of metabolic factors associated with ECM (MMP-1, 3, 9, ADAMTS-4, 5 and collagen II), respectively. Taurine was found to attenuate ER stress and prevent apoptosis in NP cells induced by IL-1β treatment. Additionally, taurine significantly decreased the expression of ER stress-activated glucose regulatory protein 78, C/EBP homologous protein and caspase-12. TUNEL results revealed that taurine decreased the number of apoptotic TG-treated NP cells. TG-treated NP cells also exhibited characteristics of increased ECM degradation, supported by observations of increased MMP-1, MMP-3, MMP-9 and A disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS)-4 and ADAMTS-5 expression in addition to decreased collagen-II expression. However, taurine treatment significantly reversed all indicators of excessive ECM catabolism aforementioned. These data suggest that taurine can mediate protection against apoptosis and ECM degradation in NP cells by inhibiting ER stress, implicating therapeutic potential for the treatment of IDD.

A novel small-molecule activator of unfolded protein response suppresses castration-resistant prostate cancer growth

Androgen receptor-targeted therapy improves survival in castration-resistant prostate cancer (CRPC). However, almost all patients with CRPC eventually develop secondary resistance to these drugs. Therefore, alternative therapeutic approaches for incurable metastatic CRPC are urgently needed. Unfolded protein response (UPR) is regarded as a cytoprotective mechanism that removes misfolded proteins in rapidly proliferating tumor cells. However, acute activation of the UPR directly leads to tumor cell death. This study has shown that WJ-644A, a novel small molecule activator of UPR, potently inhibited the proliferation of prostate cancer cells and caused tumor regression with a good safety profile in multiple animal models. Mechanistically, we have identified that WJ-644A induced cell methuosis and autophagy upon UPR activation. Our study not only identifies the UPR as an actionable target for CRPC treatment, but also establishes WJ-644A as a novel UPR activator that has potential therapeutic value for CRPC.

Legacy effect of high glucose on promoting survival of HCT116 colorectal cancer cells by reducing endoplasmic reticulum stress response

Patients with diabetes have increased risk of cancer and poor response to anti-cancer treatment. Increased protein synthesis is associated with endoplasmic reticulum (ER) stress which can trigger the unfolded protein response (UPR) to restore homeostasis, failure of which can lead to dysregulated cellular growth. We hypothesize that hyperglycemia may have legacy effect in promoting survival of cancer cells through dysregulation of UPR. Using HCT116 colorectal cancer cells as a model, we demonstrated the effects of high glucose (25 mM) on promoting cell growth which persisted despite return to normal glucose medium (5.6 mM). Using the Affymetrix gene expression microarray in HCT116 cells programmed by high glucose, we observed activation of genes related to cell proliferation and cell cycle progression and suppression of genes implicated in UPR including BiP and CHOP. These gene expression changes were validated in HCT116 cancer cells using quantitative real-time PCR and Western blot analysis. We further examined the effects of thapsigargin, an anti-cancer prodrug, which utilized ER stress pathway to induce apoptosis. High glucose attenuated thapsigargin-induced UPR and growth inhibition in HCT116 cells, which persisted despite return to normal glucose medium. Western blot analysis showed activation of caspase-3 in thapsigargin-treated cells in both normal and high glucose medium, albeit with lower levels of cleaved caspase-3 in cells exposed to high glucose, suggesting reduced apoptosis. Flow cytometry analysis confirmed fewer apoptotic cells under thapsigargin treatment in cells exposed to high glucose. Our results suggested that hyperglycemia altered gene expression involved in UPR with increased cell proliferation and facilitated survival of HCT116 cells under thapsigargin-induced ER stress by reducing the apoptotic response.

Downregulation of DEAD-box helicase 21 (DDX21) inhibits proliferation, cell cycle, and tumor growth in colorectal cancer via targeting cell division cycle 5-like (CDC5L)

Identification of novel anti-tumor target is crucial for cancer diagnosis, prognosis, and therapeutic strategy. The study aimed to explore the roles and interaction of DEAD-box helicase 21 (DDX21) and cell division cycle 5-like (CDC5L) in colorectal cancer (CRC) progression. Levels of DDX21 and CDC5L were detected in colorectal cancer cell lines by RT-qPCR and Western blot assay. The role of DDX21 and CDC5L on the cell proliferation, cell cycle and tumor growth were evaluated both in vitro and in vivo. The interaction of DDX21 and CDC5L was predicted by The STRING publicly available data and verified by immunoprecipitation. The results showed that DDX21 was dramatically upregulated in colorectal cancer cells. In vivo and in vitro experiments revealed that downregulation of DDX21 suppressed colorectal cancer cell proliferation, colony formation, cell cycle development, and tumor growth, while overexpression of CDC5L reversed the suppressive effects of DDX21 silencing. Furthermore, DDX21 interacted with CDC5L to exert the tumor-promoting effects in CRC. In summary, the data indicate a novel role for DDX21/CDC5L in the development of CRC, which enrich the therapeutic strategy for CRC.

TMAO promotes apoptosis and oxidative stress of pancreatic acinar cells by mediating IRE1α-XBP-1 pathway

BACKGROUND

Acute pancreatitis caused by hyperlipidemia is a severe life-threatening condition. Therefore, it is urgent to develop new therapeutic methods to treat this disease.

METHODS

Cell viability was determined by the Cell Counting Kit-8 (CCK-8) assay. Western blotting (WB) was used to detect the expression levels of apoptotic and endoribonuclease inositol-requiring enzyme 1α (IRE1α)/X-box binding protein 1 (XBP-1) pathway-associated proteins. The induction of cell apoptosis was determined using flow cytometry. The expression levels of the oxidative stress indicators were measured by an enzyme-linked immunosorbent assay.

RESULTS

WB analysis and the CCK-8 assay demonstrated that trimethylamine-N-oxide (TMAO) decreased cell viability and facilitated apoptosis of MPC-83 cells in a dose-dependent manner. Furthermore, the induction of oxidative stress was assessed by evaluating the levels of specific markers, including hydrogen peroxide, reactive oxygen species, nitric oxide, and superoxide dismutase. The levels of the aforementioned markers were increased in the TMAO-treated group. Subsequently, the IRE1α/XBP-1 pathway-associated proteins were analyzed by WB analysis and the data demonstrated that the regulatory effects of TMAO on MPC-83 cells were meditated by the IRE1α/XBP-1 signaling pathway. Subsequently, rescue experiments were performed to further assess the effects of TMAO.

CONCLUSION

The present study provides evidence on the application of TMAO as a potential diagnostic and therapeutic strategy for the therapeutic intervention of hyperlipidemic acute pancreatitis.

Interaction between PSMD10 and GRP78 accelerates endoplasmic reticulum stress-mediated hepatic apoptosis induced by homocysteine

Background

The liver plays an important role in production and metabolism of homocysteine (Hcy), which has been reported to be involved in liver injury. In our previous work, we confirm that Hcy can induce liver injury by activating endoplasmic reticulum (ER) stress. However, the underlying mechanisms remain largely unknown.

Results

In present study, we established the Hcy-induced liver injury model by feeding cbs^+/− mice with high methionine diet, and found that a considerable mass of disordered arrangement of hepatocytes and enlarged space between hepatocytes were frequently occurred in the liver of cbs^+/− mice, accompanied with elevated expression levels of apoptosis-related proteins. In addition, Hcy could activate ER stress both in cbs^+/− mice and hepatocytes. Mechanistically, Hcy promoted the expression levels of proteasome 26S subunit non-ATPase 10 (PSMD10) in hepatocytes; and the expression of ER stress indicators and apoptosis-associated proteins were significantly suppressed when PSMD10 was silenced in hepatocytes under Hcy treatment. Moreover, bioinformatics analysis and luciferase reporter assay demonstrated that PSMD10 was a target gene of miR-212-5p. Consistently, miR-212-5p overexpression could inhibit ER stress-mediated apoptosis of hepatocytes under Hcy treatment. With the help of co-immunoprecipitation assay, we identified that the interaction between PSMD10 and GRP78 accelerated ER stress-mediated hepatic apoptosis induced by Hcy.

Conclusions

Our findings indicate that miR-212-5p directly targets PSMD10 and subsequently activates ER stress to promote Hcy-induced apoptosis of hepatocytes. We propose that endogenous PSMD10 physically interacts with GRP78 to regulate ER stress. Our study may provide the therapeutic target for the liver injury induced by Hcy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13099-021-00455-z.

Tonsil-derived mesenchymal stem cells incorporated in reactive oxygen species-releasing hydrogel promote bone formation by increasing the translocation of cell surface GRP78

Controlling the senescence of mesenchymal stem cells (MSCs) is essential for improving the efficacy of MSC-based therapies. Here, a model of MSC senescence was established by replicative subculture in tonsil-derived MSCs (TMSCs) using senescence-associated β-galactosidase, telomere-length related genes, stemness, and mitochondrial metabolism. Using transcriptomic and proteomic analyses, we identified glucose-regulated protein 78 (GRP78) as a unique MSC senescence marker. With increasing cell passage number, GRP78 gradually translocated from the cell surface and cytosol to the (peri)nuclear region of TMSCs. A gelatin-based hydrogel releasing a sustained, low level of reactive oxygen species (ROS-hydrogel) was used to improve TMSC quiescence and self-renewal. TMSCs expressing cell surface-specific GRP78 (csGRP78+), collected by magnetic sorting, showed better stem cell function and higher mitochondrial metabolism than unsorted cells. Implantation of csGRP78+ cells embedded in ROS-hydrogel in rats with calvarial defects resulted in increased bone regeneration. Thus, csGRP78 is a promising biomarker of senescent TMSCs, and the combined use of csGRP78+ cells and ROS-hydrogel improved the regenerative capacity of TMSCs by regulating GRP78 translocation.

CTRP1 Attenuates Cerebral Ischemia/Reperfusion Injury via the PERK Signaling Pathway

Cerebral ischemic stroke is one of the leading causes of death worldwide. Previous studies have shown that circulating levels of CTRP1 are upregulated in patients with acute ischemic stroke. However, the function of CTRP1 in neurons remains unclear. The purpose of this study was to explore the role of CTRP1 in cerebral ischemia reperfusion injury (CIRI) and to elucidate the underlying mechanism. Middle cerebral artery occlusion/reperfusion (MCAO/R) and oxygen-glucose deprivation/reoxygenation (OGD/R) models were used to simulate cerebral ischemic stroke in vivo and in vitro, respectively. CTRP1 overexpression lentivirus and CTRP1 siRNA were used to observe the effect of CTRP1 expression, and the PERK selective activator CCT020312 was used to activate the PERK signaling pathway. We found the decreased expression of CTRP1 in the cortex of MCAO/R-treated rats and OGD/R-treated primary cortical neurons. CTRP1 overexpression attenuated CIRI, accompanied by the reduction of apoptosis and suppression of the PERK signaling pathway. Interference with CTRP1 expression in vitro aggravated apoptotic activity and increased the expression of proteins involved in the PERK signaling pathway. Moreover, activating the PERK signaling pathway abolished the protective effects of CTRP1 on neuron injury induced by CIRI in vivo and in vitro. In conclusion, CTRP1 protects against CIRI by reducing apoptosis and endoplasmic reticulum stress (ERS) through inhibiting the PERK-dependent signaling pathway, suggesting that CTRP1 plays a crucial role in the pathogenesis of CIRI.

Castration-Induced Downregulation of SPARC in Stromal Cells Drives Neuroendocrine Differentiation of Prostate Cancer

Fatal neuroendocrine differentiation (NED) of castration-resistant prostate cancer is a recurrent mechanism of resistance to androgen deprivation therapies (ADT) and antiandrogen receptor pathway inhibitors (ARPI) in patients. The design of effective therapies for neuroendocrine prostate cancer (NEPC) is complicated by limited knowledge of the molecular mechanisms governing NED. The paucity of acquired genomic alterations and the deregulation of epigenetic and transcription factors suggest a potential contribution from the microenvironment. In this context, whether ADT/ARPI induces stromal cells to release NED-promoting molecules and the underlying molecular networks are unestablished. Here, we utilized transgenic and transplantable mouse models and coculture experiments to unveil a novel tumor-stroma cross-talk that is able to induce NED under the pressure of androgen deprivation. Castration induced upregulation of GRP78 in tumor cells, which triggers miR29-b-mediated downregulation of the matricellular protein SPARC in the nearby stroma. SPARC downregulation enabled stromal cells to release IL6, a known inducer of NED. A drug that targets GRP78 blocked NED in castrated mice. A public, human NEPC gene expression dataset showed that Hspa5 (encoding for GRP78) positively correlates with hallmarks of NED. Finally, prostate cancer specimens from patients developing local NED after ADT showed GRP78 upregulation in tumor cells and SPARC downregulation in the stroma. These results point to GRP78 as a potential therapeutic target and to SPARC downregulation in stromal cells as a potential early biomarker of tumors undergoing NED. SIGNIFICANCE: Tumor-stroma cross-talk promotes neuroendocrine differentiation in prostate cancer in response to hormone therapy via a GRP78/SPARC/IL6 axis, providing potential therapeutic targets and biomarkers for neuroendocrine prostate cancer.

Structure and Function of Mitochondria-Associated Endoplasmic Reticulum Membranes (MAMs) and Their Role in Cardiovascular Diseases

Abnormal function of suborganelles such as mitochondria and endoplasmic reticulum often leads to abnormal function of cardiomyocytes or vascular endothelial cells and cardiovascular disease (CVD). Mitochondria-associated membrane (MAM) is involved in several important cellular functions. Increasing evidence shows that MAM is involved in the pathogenesis of CVD. MAM mediates multiple cellular processes, including calcium homeostasis regulation, lipid metabolism, unfolded protein response, ROS, mitochondrial dynamics, autophagy, apoptosis, and inflammation, which are key risk factors for CVD. In this review, we discuss the structure of MAM and MAM-associated proteins, their role in CVD progression, and the potential use of MAM as the therapeutic targets for CVD treatment.

SPARC inhibition accelerates NAFLD-associated hepatocellular carcinoma development by dysregulating hepatic lipid metabolism

BACKGROUND AND AIMS

Non-alcoholic fatty liver (NAFLD) and its more serious form non-alcoholic steatohepatitis increase risk of hepatocellular carcinoma (HCC). Lipid metabolic alterations and its role in HCC development remain unclear. SPARC (Secreted Protein, Acidic and Rich in Cysteine) is involved in lipid metabolism, NAFLD and diabetes, but the effects on hepatic lipid metabolism and HCC development is unknown. The aim of this study was to evaluate the role of SPARC in HCC development in the context of NAFLD.

METHODS

Primary hepatocyte cultures from knockout (SPARC^-/- ) or wild-type (SPARC^+/+ ) mice, and HepG2 cells were used to assess the effects of free fatty acids on lipid accumulation, expression of lipogenic genes and de novo triglyceride (TG) synthesis. A NAFLD-HCC model was stabilized on SPARC^-/- or SPARC^+/+ mice. Correlations among SPARC, lipid metabolism-related gene expression patterns and clinical prognosis were studied using HCC gene expression dataset.

RESULTS

SPARC^-/- mice increases hepatic lipid deposits over time. Hepatocytes from SPARC^-/- mice or inhibition of SPARC by an antisense adenovirus in HepG2 cells resulted in increased TG deposit, expression of lipid-related genes and nuclear translocation of SREBP1c. Human HCC database analysis revealed that SPARC negatively correlated with genes involved in lipid metabolism, and with poor survival. In NAFLD-HCC murine model, the absence of SPARC accelerates HCC development. RNA-seq study revealed that pathways related to lipid metabolism, cellular detoxification and proliferation were upregulated in SPARC^-/- tumour-bearing mice.

CONCLUSIONS

The absence of SPARC is associated with an altered hepatic lipid metabolism, and an accelerated NAFLD-related HCC development.

lncRNA NEAT1 regulates gastric carcinoma cell proliferation, invasion and apoptosis via the miR‑500a‑3p/XBP‑1 axis

Gastric cancer is a serious malignant tumor. Despite progression in gastric cancer research in recent years, the specific molecular mechanism underlying the pathogenesis of the disease is not completely understood. Long non-coding RNA (lncRNA) nuclear paraspeckle assembly transcript 1 (NEAT1) affects the proliferation and metastasis of multiple types of tumor cells in colorectal cancer and breast cancer but its specific role in gastric cancer requires further investigation. The aim of the present study was to analyze the role of NEAT1 in gastric cancer. The expression of endoplasmic reticulum stress marker proteins and apoptosis-related proteins in gastric cancer tissue and cell lines was analyzed using western blotting. The targeting relationship of NEAT1 and miR-500a-3p was analyzed using dual-luciferase reporter assay. Cell proliferation was analyzed using CCK8 assay and colony formation assay while cell invasion was detected using Transwell assay. Cell apoptosis was analyzed using TUNEL staining and LC3 expression through immunofluorescent staining (IF). The results showed that lncRNA NEAT1-overexpression gastric cancer cells were established to determine its effects on cell proliferation, invasion, apoptosis, autophagy and endoplasmic reticulum stress. Subsequently, microRNA (miR)-500a was overexpressed in lncRNA NEAT1-overexpression cells. Compared with the vector group, lncRNA NEAT1 overexpression significantly inhibited gastric cancer cell proliferation and invasion, but significantly promoted cell apoptosis. Furthermore, the results indicated that lncRNA NEAT1 targeted and downregulated the expression of miR-500a-3p, and miR-500a-3p targeted X-box binding protein-1 (XBP-1) mRNA. lncRNA NEAT1 overexpression-mediated inhibition of gastric cancer cell proliferation and invasion was significantly reversed by miR-500a-3p overexpression. Furthermore, compared with the vector group, the expression levels of endoplasmic reticulum stress-related proteins (XBP-1S/XBP-1U ratio and 78-kDa glucose-regulated protein) and apoptosis-related proteins (Bax and cleaved-caspase-3) were significantly upregulated by lncRNA NEAT1 overexpression; however, miR-500a-3p overexpression reversed lncRNA NEAT1 overexpression-mediated effects on protein expression. The present study demonstrated that lncRNA NEAT1 inhibited gastric cancer cell proliferation and invasion, and promoted apoptosis by regulating the miR-500a-3p/XBP-1 axis.

SPARC Knockdown Reduces Glutamate-Induced HT22 Hippocampal Nerve Cell Damage by Regulating Autophagy

Secreted protein acidic and rich in cysteine (SPARC) is a matricellular protein involved in the extracellular matrix and interactions between cells during neural development of the central nervous system (CNS). Oxidative glutamate toxicity is involved in CNS diseases, including epilepsy, Alzheimer’s disease, and ischemic stroke. However, the molecular mechanism of nerve injury is not fully understood in CNS diseases. Herein, the glutamate-induced nerve damage model was used to explore the molecular mechanisms affecting nerve damage. The levels of SPARC and autophagy were increased in glutamate-induced HT22 hippocampal nerve injury. In summary, the current study confirmed that SPARC regulates autophagy in HT22 hippocampal nerve cells, and its knockdown reduces the glutamate-induced HT22 hippocampal nerve injury by inhibiting autophagy. These findings suggested that SPARC plays a crucial role in nerve injury of CNS diseases.

Membrane Interactome of a Recombinant Fragment of Human Surfactant Protein D Reveals GRP78 as a Novel Binding Partner in PC3, a Metastatic Prostate Cancer Cell Line

Surfactant protein-D (SP-D), a member of the collectin family has been shown to induce apoptosis in cancer cells. SP-D is composed of an N-terminal collagen-like domain and a calcium-dependent carbohydrate recognition domain (CRD). Recently, we reported that a recombinant fragment of human SP-D (rfhSP-D), composed of homotrimeric CRD region, induced intrinsic apoptotic pathway in prostate cancer cells. Here, we analyzed the membrane interactome of rfhSP-D in an androgen-independent prostate cancer cell line, PC3, by high resolution mass spectrometry and identified 347 proteins. Computational analysis of PPI network of this interactome in the context of prostate cancer metastasis and apoptosis revealed Glucose Regulated Protein of 78 kDa (GRP78) as an important binding partner of rfhSP-D. Docking studies suggested that rfhSP-D (CRD) bound to the substrate-binding domain of glycosylated GRP78. This was further supported by the observations that human recombinant GRP78 interfered with the binding of rfhSP-D to anti-SP-D polyclonal antibodies; GRP78 also significantly inhibited the binding of recombinant full-length human SP-D with a monoclonal antibody specific to the CRD in a dose-dependent manner. We conclude that the interaction with rfhSP-D is likely to interfere with the pro-survival signaling of GRP78.

Sappanone A Protects Against Inflammation, Oxidative Stress and Apoptosis in Cerebral Ischemia-Reperfusion Injury by Alleviating Endoplasmic Reticulum Stress

Endoplasmic reticulum stress is an important contributor to the cerebral ischemic injury. Sappanone A (SA), a kind of natural homoisoflavanone extracted from Caesalpinia sappan L, has been evidenced to exhibit anti-inflammatory and antioxidative properties. The present study aimed to investigate the potential neuroprotective effects of SA in cerebral ischemia-reperfusion injury. The potential neuroprotective effect of SA was tested in a rat model of middle cerebral artery occlusion (MCAO) allowing reperfusion and PC12 cell model of oxygen-glucose deprivation and reperfusion (OGD/R). Post-ischemic neuronal injury was evaluated by 2, 3, 5-triphenyltetrazolium chloride (TTC) and hematoxylin-eosin (H&E) staining. The levels of inflammatory factors and oxidative stress-related markers were detected using corresponding kits. Cell apoptosis was evaluated by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) or flow cytometry, and the expression of apoptosis-associated proteins was determined using western blot analysis. Subsequently, endoplasmic reticulum stress-related proteins were detected through western blot analysis, and CCAAT/enhancer binding protein (C/EBP) homologous protein (CHOP) was overexpressed to confirm the contribution of endoplasmic reticulum stress inhibition by SA to the neuroprotective effects post OGD/R. Results revealed that SA was effective in ameliorating cerebral infarction and pathological injuries post-reperfusion following MCAO, which is associated with reduced inflammation, oxidative stress, and cell apoptosis by SA in the brain. Consistently, these neuroprotective effects of SA post ischemia-reperfusion were also observed in a PC12 cell model of OGD/R. Importantly, endoplasmic reticulum stressors, including the CHOP, the 78 kDa glucose-regulated protein 78 (GRP78), and phosphorylated eukaryotic initiation factors 2α (EIF-2α), were significantly downregulated by SA, while CHOP overexpression attenuated the beneficial effects of SA on inflammation, oxidative stress, and apoptosis in OGD/R-induced PC12 cells. These results demonstrated that SA alleviates endoplasmic reticulum stress, ameliorating inflammation, oxidative stress, and apoptosis, and thereby serves as therapeutic potential for protection against cerebral ischemia-reperfusion injury in ischemic stroke.

Translation initiation and its relevance in colorectal cancer

Protein synthesis is one of the most essential processes in every kingdom of life, and its dysregulation is a known driving force in cancer development. Multiple signaling pathways converge on the translation initiation machinery, and this plays a crucial role in regulating differential gene expression. In colorectal cancer, dysregulation of initiation results in translational reprogramming, which promotes the selective translation of mRNAs required for many oncogenic processes. The majority of upstream mutations found in colorectal cancer, including alterations in the WNT, MAPK, and PI3K\AKT pathways, have been demonstrated to play a significant role in translational reprogramming. Many translation initiation factors are also known to be dysregulated, resulting in translational reprogramming during tumor initiation and/or maintenance. In this review, we outline the role of translational reprogramming that occurs during colorectal cancer development and progression and highlight some of the most critical factors affecting the etiology of this disease.

Plecstatin-1 induces an immunogenic cell death signature in colorectal tumour spheroids

Organometallic metal(arene) anticancer agents were believed to confer low selectivity for potential cellular targets. However, the ruthenium(arene) pyridinecarbothioamide (plecstatin-1) showed target selectivity for plectin, a scaffold protein and cytolinker. We employed a three-dimensional cancer spheroid model and showed that plecstatin-1 limited spheroid growth, induced changes in the morphology and in the architecture of tumour spheroids by disrupting the cytoskeletal organization. Additionally, we demonstrated that plecstatin-1 induced oxidative stress, followed by the induction of an immunogenic cell death signature through phosphorylation of eIF2α, exposure of calreticulin, HSP90 and HSP70 on the cell membrane and secretion of ATP followed by release of high mobility group box-1.

Adaptive response of resistant cancer cells to chemotherapy

Despite advances in cancer therapeutics and the integration of personalized medicine, the development of chemoresistance in many patients remains a significant contributing factor to cancer mortality. Upon treatment with chemotherapeutics, the disruption of homeostasis in cancer cells triggers the adaptive response which has emerged as a key resistance mechanism. In this review, we summarize the mechanistic studies investigating the three major components of the adaptive response, autophagy, endoplasmic reticulum (ER) stress signaling, and senescence, in response to cancer chemotherapy. We will discuss the development of potential cancer therapeutic strategies in the context of these adaptive resistance mechanisms, with the goal of stimulating research that may facilitate the development of effective cancer therapy.

Copper Induces Apoptosis Through Endoplasmic Reticulum Stress in Skeletal Muscle of Broilers

The purpose of this research was to investigate whether copper (Cu) exposure could induce apoptosis via endoplasmic reticulum stress (ERS) in skeletal muscle of broilers. A total of 240 one-day-old chickens were randomly divided into four groups by free access; the diets are as follows: control diet (Cu 11 mg/kg, control group) and high level of Cu diets (Cu 110 mg/kg, group I; Cu 220 mg/kg, group II; Cu 330 mg/kg, group III). The skeletal muscle tissues were collected on day 49 for further examination. The content of Cu, histopathology, and the expression levels of the genes and proteins related to ERS and apoptosis were detected. Results showed that the Cu levels in skeletal muscle were increased in a dose-dependent manner. Meanwhile, the spaces between the muscle fibers were wider with the increase of Cu content, and the myolysis was observed in group III. Besides, the mRNA expression levels of GRP78, GRP94, eIF2α, ATF6, XBP1, CHOP, Caspase-12, and Caspase3 were markedly increased in treated groups compared with control group, and the protein expression levels of GRP78, Caspase3, Active-Caspase3 and JNK were significantly elevated with the increase of dietary Cu. In summary, these findings suggested that Cu could induce apoptosis through ERS in skeletal muscle of broilers.

Extracellular vesicles from hydroxycamptothecin primed umbilical cord stem cells enhance anti-adhesion potential for treatment of tendon injury

BACKGROUND

Peritendinous fibrosis represents a fibrotic healing process that usually occurs after tendon injury or surgery. This worldwide challenge hampers the functional rehabilitation and the mobility of extremities. However, effective treatment is still lacking at present. The aim of our study was to explore the effect of extracellular vesicles derived from hydroxycamptothecin primed human umbilical cord stem cells (HCPT-EVs) on post-traumatic tendon adhesion.

METHODS

Extracellular vesicles derived from unprimed human umbilical cord mesenchymal stem cells (Unprimed EVs) or HCPT-EVs were isolated and characterized. A rat model of Achilles tendon injury was used to confirm the anti-adhesion effect of HCPT-EVs and compared with that of Unprimed EVs in vivo. In vitro, the inhibitory effects of HCPT-EVs on fibroblast proliferation, viability, and myofibroblast differentiation upon TGF-β1 stimulation were compared with the effects of Unprimed EVs. For mechanistic analysis, the expression of endoplasmic reticulum stress (ERS)-associated proteins was examined among the effector cargos of HCPT-EVs and Unprimed EVs. The ERS antagonist salubrinal was used to determine the ERS dependence of the anti-adhesion effects of HCPT-EVs.

RESULTS

There were no obvious differences between Unprimed EVs and HCPT-EVs in terms of morphology, particle size, characteristic protein expression, and cellular uptake. HCPT-EVs exhibited a fortified anti-adhesion effect after Achilles tendon injury compared with Unprimed EVs. Fibroblast proliferation and viability and myofibroblast differentiation were all inhibited by HCPT-EVs. These properties were superior for HCPT-EVs relative to Unprimed EVs. Mechanistically, HCPT-EVs contained more ERS-associated protein than Unprimed EVs and activated the ERS pathway in fibroblast to counteract myofibroblast differentiation.

CONCLUSION

This study demonstrates that HCPT-EVs show high anti-adhesion potential for the treatment of tendon injury by provoking ERS in fibroblasts. HCPT-EVs represent a promising strategy for clinical use in treating adhesion-related diseases.

Low Levels of SPARC are Associated with Tumor Progression and Poor Prognosis in Human Endometrial Carcinoma

Background

SPARC (secreted protein acidic and rich in cysteine), also known as osteonectin, BM-40, and 43 K protein, is a matricellular protein associated with various tumor progressions. The aim of this research was to investigate the prognostic value of SPARC in endometrial carcinoma (EC) and its function in cancer cell invasion and metastasis.

Methods

From both mRNA and protein levels, SPARC expression in normal endometrial tissue and EC tissue, normal endometrial cells and 4 EC cell lines (KLE, HEC-1A, HEC-1B, Ishikawa) were evaluated by immunohistochemistry (IHC) or immunocytochemistry (ICC), quantitative real-time PCR (qRT-PCR) and Western blotting. RNA interference mediated by lentivirus was performed to get the stable SPARC down-expressing cells. The functional analysis techniques in vitro and in vivo were used to detect the effects of SPARC knockdown on EC cell proliferation, apoptosis, invasion and metastasis.

Results

The expressions of SPARC in EC tissues and cells were much lower than those in normal endometrial cells and tissues; meanwhile, its low expression was closely related to the malignant clinicopathological characteristics of EC. SPARC knockdown could inhibit apoptosis, promote the process of EMT and improve the proliferation and invasion capacities of EC cells in vitro and in vivo.

Conclusion

The low expression of SPARC was detected in EC tissues and cells, which was positively correlated with the poor prognosis of EC patients. SPARC acted as a tumor suppressor gene that hindered EC progression, which proposed a new therapeutic strategy for EC treatment.

Calreticulin promotes EMT in pancreatic cancer via mediating Ca2+ dependent acute and chronic endoplasmic reticulum stress

Background

Our previous study showed that calreticulin (CRT) promoted EGF-induced epithelial-mesenchymal transition (EMT) in pancreatic cancer (PC) via Integrin/EGFR-ERK/MAPK signaling. We next investigated the novel signal pathway and molecular mechanism involving the oncogenic role of CRT in PC.

Methods

We investigated the potential role and mechanism of CRT in regulating intracellular free Ca²⁺ dependent acute and chronic endoplasmic reticulum stress (ERS)-induced EMT in PC in vitro and vivo.

Results

Thapsigargin (TG) induced acute ERS via increasing intracellular free Ca²⁺ in PC cells, which was reversed by CRT silencing. Additionally, CRT silencing inhibited TG-induced EMT in vitro by reversing TG-induced changes of the key proteins in EMT signaling (ZO-1, E-cadherin and Slug) and ERK/MAPK signaling (pERK). TG-promoted cell invasion and migration was also rescued by CRT silencing but enhanced by IRE1α silencing (one of the key stressors in unfolded protein response). Meanwhile, CRT was co-immunoprecipitated and co-localized with IRE1α in vitro and its silencing led to the chronic ERS via upregulating IRE1α independent of IRE1-XBP1 axis. Moreover, CRT silencing inhibited IRE1α silencing-promoted EMT, including inhibiting the activation of EMT and ERK/MAPK signaling and the promotion of cell mobility. In vivo, CRT silencing decreased subcutaneous tumor size and distant liver metastasis following with the increase of IRE1α expression. A negative relationship between CRT and IRE1α was also observed in clinical PC samples, which coordinately promoted the advanced clinical stages and poor prognosis of PC patients.

Conclusions

CRT promotes EMT in PC via mediating intracellular free Ca²⁺ dependent TG-induced acute ERS and IRE1α-mediated chronic ERS via Slug and ERK/MAPK signaling.

Use of Small-molecule Inhibitory Compound of PERK-dependent Signaling Pathway as a Promising Target-based Therapy for Colorectal Cancer

BACKGROUND

Colorectal cancer constitutes one of the most common cancer with a high mortality rate. The newest data has reported that activation of the pro-apoptotic PERK-dependent unfolded protein response signaling pathway by small-molecule inhibitors may constitute an innovative anti-cancer treatment strategy.

OBJECTIVE

In the presented study, we evaluated the effectiveness of the PERK-dependent unfolded protein response signaling pathway small-molecule inhibitor 42215 both on HT-29 human colon adenocarcinoma and CCD 841 CoN normal human colon epithelial cell lines.

METHODS

Cytotoxicity of the PERK inhibitor was evaluated by the resazurin-based and lactate dehydrogenase (LDH) tests. Apoptotic cell death was measured by flow cytometry using the FITCconjugated Annexin V to indicate apoptosis and propidium iodide to indicate necrosis as well as by colorimetric caspase-3 assay. The effect of tested PERK inhibitor on cell cycle progression was measured by flow cytometry using the propidium iodide staining. The level of the phosphorylated form of the eukaryotic initiation factor 2 alpha was detected by the Western blot technique.

RESULTS

Obtained results showed that investigated PERK inhibitor is selective only toward cancer cells, since inhibited their viability in a dose- and time-dependent manner and induced their apoptosis and G2/M cell cycle arrest. Furthermore, 42215 PERK inhibitor evoked significant inhibition of eIF2α phosphorylation within HT-29 cancer cells.

CONCLUSION

Highly-selective PERK inhibitors may provide a ground-breaking, anti-cancer treatment strategy via activation of the pro-apoptotic branch of the PERK-dependent unfolded protein response signaling pathway.

Targeting the GRP78 Pathway for Cancer Therapy

The 78-kDa glucose-regulated protein (GRP78) plays an important part in maintaining protein stability, regulating protein folding, and inducing apoptosis autophagy, which is considered as a powerful protein. Meanwhile, it also plays a role in ensuring the normal function of organs. In recent years, more and more researches have been carried out on the targeted therapy of GRP78, mainly focusing on its relevant role in tumor and its role as a major modulator and modulator of subordinate pathways. The ability of GRP78 to respond to endoplasmic reticulum stress (ERS) determines whether tumor cells survive and whether the changes in expression level of GRP78 regulated by endoplasmic reticulum (ER) caused by various factors will directly or indirectly affect cell proliferation, apoptosis, and injury, or reduce the body's defense ability, or have protective effects on various organs.

SPARC-p53: The double agents of cancer

Cancer is a complex disease with high incidence and mortality rates. The important role played by the tumor microenvironment in regulating oncogenesis, tumor growth, and metastasis is by now well accepted in the scientific community. SPARC is known to participate in tumor-stromal interactions and impact cancer growth in ambiguous ways, which either enhance or suppress cancer aggressiveness, in a context-dependent manner. p53 transcription factor, a well-established tumor suppressor, has been reported to promote tumor growth in certain situations, such as hypoxia, thus displaying a duality in its action. Although both proteins are being tested in clinical trials, the synergistic relation between them is yet to be explored in clinical practice. In this review, we address the controversial roles of SPARC and p53 as double agents in cancer, briefly summarizing the interaction found between these two molecules and its importance in cancer.