Endoplasmic Reticulum Stress Signaling in Cancer Cells

Identification of endoplasmic reticulum stress-related genes as prognostic markers in colon cancer

Endoplasmic reticulum stress (ERS) has been implicated in the pathogenesis of various cancers, including colon cancer, by regulating tumor cell survival, growth, and immune response. However, the specific genes involved in ERS that could serve as prognostic markers in colon cancer remain underexplored. This study aims to identify and validate endoplasmic reticulum stress related genes (ERSRGs) in colon cancer that correlate with patient prognosis, thereby enhancing the understanding of ERS in oncological outcomes and potential therapeutic targeting. We utilized bioinformatics analyses to identify ERSRGs from publicly available colon cancer datasets. Differential expression analysis and survival analysis were performed to assess the prognostic significance of these genes. Validation was conducted through quantitative real-time PCR (RT-qPCR) on selected colon cancer cell lines. Our study identified nine ERS related genes (ASNS, ATF4, ATF6B, BOK, CLU, DDIT3, MANF, SLC39A14, TRAF2) involved in critical pathways including IL-12, PI3K-AKT, IL-7, and IL-23 signaling, and linked to 1-, 3-, and 5-year survival of patients with colon cancer. A multivariate Cox model based on these ERS related genes demonstrated significant prognostic power. Further, TRAF2 strong correlated with immune cells infiltration, suggesting its potential roles in modulating immune responses in the tumor microenvironment. The RT-qPCR validation confirmed the differential expression of these genes in human colon cancer cell lines versus human normal colonic epithelial cell line. The identified ERSRGs could serve as valuable prognostic markers and may offer new insights into the therapeutic targeting of ERS in colon cancer.

Developments in the connection between epithelial‑mesenchymal transition and endoplasmic reticulum stress (Review)

Endoplasmic reticulum stress (ERS) and epithelial‑mesenchymal transition (EMT) have important roles in fibrosis and tumour development. Moderate ERS activates cellular defence mechanisms in response to noxious stimuli; however, sustained or overly strong ERS induces apoptosis. In this disease process, EMT induces epithelial cells to acquire the ability to migrate and invade. Reportedly, ERS directly or indirectly regulates EMT processes through multiple mechanisms (such as key transcription factors, signalling pathways, ferroptosis, autophagy and oxidative stress), and both processes form a complex network of interactions. Given the critical roles of ERS and EMT in disease, targeted intervention of these two processes has emerged as a potential therapeutic strategy. In the present study, the molecular interaction mechanism of ERS and EMT was systematically explored, research progress in fibrotic and neoplastic diseases was reviewed and the potential application prospects of related targeted therapies were examined, which may provide new ideas for the development of drugs to reverse fibrosis and treat tumours.

Molecular and therapeutic insight into ER stress signalling in NSCLC

Endoplasmic Reticulum (ER) stress is intricately involved in cancer development, progression and response to chemotherapy. ER stress related genes might play an important role in predicting the prognosis in lung adenocarcinoma patients and may be manipulated to improve the treatment outcome and overall survival rate. In this review, we analysed the contribution of the three major ER stress pathways-IRE1, ATF6, and PERK-in lung cancer pathogenesis via modulation of tumour microenvironment (TME) and processes as metastasis, angiogenesis, apoptosis and N-glycosylation. Furthermore, we discuss the regulatory role of microRNAs in fine-tuning ER stress pathways in Non-Small Cell Lung Cancer (NSCLC). Our review also highlights various promising strategies to overcome chemoresistance by targeting ER stress pathways, offering new therapeutic opportunities.

Therapeutic Effect of V8 Affecting Mitophagy and Endoplasmic Reticulum Stress in Acute Myeloid Leukemia Mediated by ROS and CHOP Signaling

Acute myeloid leukemia (AML) is characterized by the malignant proliferation of abnormally or poorly differentiated myeloid cells in the hematopoietic system. However, there is a lack of effective drugs for treating non-M3 AML. V8, a newly synthesized derivative of the natural flavonoid wogonin, which is a potential anticancer drug, has demonstrated significant antitumor activity both in vitro and in vivo. Here, we investigated the effects of V8 on AML cell lines and primary AML cells as well as its underlying mechanisms. Our results showed that V8 exerted significant concentration-dependent growth inhibition and apoptosis induction in AML cells, accompanied by characteristic pathological features including lysosomal functions suppression, mitochondrial dysfunction, and endoplasmic reticulum stress (ERS) activation. Mechanistic investigations revealed that V8 induced mitochondrial membrane potential collapse through elevation of intracellular reactive oxygen species (ROS) levels, while concurrently blocking mitophagy via lysosomal functional inhibition. Furthermore, V8 selectively activated the PERK/p-eIF2α/ATF4 and IRE1α/XBP1 signaling axes of ERS, ultimately triggering CHOP-mediated apoptosis through the ERS-specific pathway. In vivo studies confirmed that V8 treatment significantly prolonged survival duration in NOD/SCID mice bearing primary AML xenografts and suppressed tumor progression in BALB/c nude mice with U937 cell xenografts, with antitumor efficacy closely associated with CHOP-dependent ERS pathway modulation. These findings not only elucidate the multi-targeted mechanism of V8 against AML through coordinated regulation of the ROS-mitochondria-lysosome-ERS signaling network, but also provide critical theoretical foundations for developing natural product-based therapeutics for AML. The multi-pathway synergistic characteristics exhibited by V8 underscore its considerable potential as a clinically translatable candidate drug.

Glycoproteomics of Gastrointestinal Cancers and Its Use in Clinical Diagnostics

Cancer is a leading cause of death worldwide, resulting in substantial economic costs. Because cancer is a complex, heterogeneous group of diseases affecting a variety of cells, its detection may sometimes be difficult. Herein we review a large group of the gastrointestinal cancers (oral, esophageal, stomach, pancreatic, liver, and bowel cancers) and the possibility of using glycans conjugated to protein backbones for less-invasive diagnoses than the commonly used endoscopic approaches. The reality of bacterial N-glycosylation and the effect of epithelial mucosa on gut microbiota are discussed. Current advantages, barriers, and advantages in the prospective use of selected glycomic approaches in clinical practice are also detailed.

Endoplasmic Reticulum Stress in Tuberculosis: Molecular Bases and Pathophysiological Implications in the Immunopathogenesis of the Disease

Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb), is a severe pulmonary disease with high mortality, particularly in low-income countries. Early diagnosis and timely treatment, including both intensive and maintenance phases, are critical for controlling the disease and preventing its transmission. In Brazil, where TB incidence remains high, thousands of new cases are reported annually. Transmission occurs primarily through airborne droplets expelled by infected individuals. The immune response involves various cell types, such as lymphocytes and macrophages, which form granulomas to limit the spread of the bacillus. Upon entering the lungs, Mtb is phagocytosed by immune cells, where it evades destruction by blocking phagolysosome formation and inhibiting phagosome acidification. In response, the immune system forms granulomas that contain the infection, although these can become reactivated if immune function deteriorates. Mtb also interferes with host cellular organelles, particularly the endoplasmic reticulum (ER) and mitochondria, inducing cellular stress and apoptosis, which aids in its survival. Key Mtb-secreted proteins, such as BAG2 and CdhM, modulate autophagy and apoptosis pathways, influencing pathogen survival within immune cells. A deeper understanding of these molecular mechanisms, particularly the role of ER stress and its impact on immune responses, is essential for developing novel therapeutic strategies for TB prevention and treatment.

COL5A2-mediated endoplasmic reticulum stress promotes macrophage M2 polarization in lung adenocarcinoma

Collagen is a major component of the extracellular matrix. Type V collagen α2 (COL5A2), a common collagen subtype, plays a crucial role in immune regulation, angiogenesis, and tumor metastasis. It is highly expressed in various malignancies, but its mechanistic role in lung adenocarcinoma (LUAD) remains unclear. Therefore, this study aims to investigate the regulatory mechanism of COL5A2 in mediating macrophage M2 polarization in LUAD. We analyzed COL5A2 expression in LUAD samples from the TCGA-LUAD database. Using GSEA, we sought to identify the signaling pathways influenced by COL5A2 expression. mRNA levels of COL5A2, TGF-β, and IL-10 were quantified via qPCR analysis, and protein levels of COL5A2, PD-L1, and endoplasmic reticulum (ER) stress-related proteins (GRP78 and CHOP) were assessed using western blot. Immunofluorescence assay detected the fluorescence signal of CD206 in M2 macrophages, while flow cytometry assessed the M2 macrophage marker CD206, flow cytometry determined the positive rates for CD68 and CD206. Exosome uptake by macrophages was examined using confocal microscopy, and cell viability was measured with cell counting kit-8. KI-67 protein expression was analyzed by immunohistochemistry, and in vivo assays in animals verified our findings. The results showed that elevated COL5A2 levels in LUAD were found to correlate with a shift toward M2 macrophage polarization. Specifically, the overexpression of COL5A2 amplified ER stress, which led to an increase in PD-L1 exosome release and macrophage uptake of PD-L1, thus driving the M2 phenotype. In conclusion, COL5A2 in LUAD induces ER stress, which is associated with elevated PD-L1 exosome secretion and macrophage PD-L1 uptake, ramping up M2 polarization in macrophages.

The Role of ER Stress and the Unfolded Protein Response in Cancer

Dysregulation of protein synthesis, folding, and secretion leads to endoplasmic reticulum (ER) stress, triggering the unfolded protein response (UPR). While the UPR is essential for cell survival under stress, its chronic activation in cancer cells supports tumorigenesis, metastasis, and chemoresistance by enabling cellular adaptation to hypoxia, nutrient deprivation, and oxidative stress. This review provides a comprehensive overview of the roles of key UPR mediators - binding immunoglobulin protein (BiP), protein kinase R (PKR)-like endoplasmic reticulum kinase (PERK), inositol-requiring enzyme 1α (IRE1α), and activating transcription factor 6 (ATF6) - in cancer progression and therapy resistance. Furthermore, it discusses strategies to target UPR pathways, including small molecule inhibitors, gene therapies, natural compounds, and combination therapies, while it evaluates their preclinical and clinical relevance. Finally, it explores how modulating UPR signaling can overcome therapeutic resistance, improve immunotherapy outcomes, and reshape the tumor microenvironment. This review emphasizes the promise of UPR-targeted approaches in enhancing the efficacy of current cancer treatments and achieving better patient outcomes.

TRAF3IP3 Induces ER Stress-Mediated Apoptosis with Protective Autophagy to Inhibit Lung Adenocarcinoma Proliferation

TNF receptor-associated factor 3 interacting protein 3 (TRAF3IP3/T3JAM) exhibits dual roles in cancer progression. While upregulated in most malignancies and critical for immune regulation. However, the specific effects and molecular mechanisms of TRAF3IP3 on the progression of lung adenocarcinoma (LUAD) remains poorly understood. This study reveals TRAF3IP3 is upregulated in several tumor tissues but exclusively decreased in LUAD and Lung squamous cell carcinoma (LUSC) tissues, consequential in a favorable overall survival (OS) in LUAD rather than LUSC. Herein, it is reported that TRAF3IP3 can suppress cell proliferation and promote the apoptosis rate of LUAD cells by inducing excessive ER stress-related apoptosis. Importantly, TRAF3IP3 triggers ER stress via the PERK/ATF4/CHOP pathway, accompanied by stimulated ER stress-induced cytoprotective autophagy in LUAD cells. Through IP-MS analysis, STRN3 is identified as a direct downstream interactor with TRAF3IP3 and corroborated to regulate ER stress positively. Mechanistically, TRAF3IP3 facilitates the recruitment of STRN3 to the ER lumen through its transmembrane domain and fulfills its functional role in ER stress in an STRN3-dependent manner in LUAD cells. Given its dual role in orchestrating ER stress-associated apoptosis and autophagy in LUAD cell fate determination, the importance of TRAF3IP3 is highlighted as novel therapeutic target for LUAD treatment.

Targeting polyunsaturated fatty acids desaturase FADS1 inhibits renal cancer growth via ATF3-mediated ER stress response

OBJECTIVE

Fatty Acid Desaturase 1 (FADS1) is a rate-limiting enzyme controlling the bioproduction of long-chain polyunsaturated fatty acids (PUFAs). Increasing studies suggest that FADS1 is a potential cancer target. Our previous research has demonstrated the significant role of FADS1 in cancer biology and patient survival, especially in kidney cancers. We aim to explore the underlying mechanism in this study.

METHOD AND RESULTS

We found that pharmacological inhibition or knockdown of the expression of FADS1 significantly reduced the intracellular conversion of long-chain PUFAs, effectively inhibits renal cancer cell proliferation, and induces cell cycle arrest. The stable knockdown of FADS1 also significantly inhibits tumor formation in vivo. Mechanistically, we showed that while FADS1 inhibition induces endoplasmic reticulum (ER) stress, FADS1 expression is augmented by ER-stress inducer, suggesting a necessary role of PUFA production in response to ER stress. FADS1-inhibition sensitized cellular response to ER stress inducers, leading to cell apoptosis. Also, FADS1 inhibition-induced ER stress leads to activation of the PERK/eIF2α/ATF4/ATF3 pathway. Inhibiting PERK or knockdown of ATF3 rescued FADS1 inhibition-induced ER stress and cell growth suppression, while ATF3-overexpression aggravates the FADS1 inhibition-induced cell growth suppression and leads to cell death. Metabolomic analysis revealed that FADS1 inhibition results in decreased level of UPD-N-Acetylglucosamine, a critical mediator of the unfolded protein response, as well as impaired biosynthesis of nucleotides, possibly accounting for the cell cycle arrest.

CONCLUSION

Our findings suggest that PUFA desaturation is crucial for rescuing cancer cells from persistent ER stress, supporting FADS1 as a new therapeutic target.

Endoplasmic reticulum stress in non-small cell lung cancer

The Endoplasmic reticulum (ER), an organelle present in various eukaryotic cells, is responsible for protein synthesis, modification, folding, and transport, as well as for the regulation of lipid metabolism and Ca2+ homeostasis. ER stress plays a pivotal role in the pathogenesis and therapeutic response of non-small cell lung cancer (NSCLC), significantly influencing cellular fate decisions through its unique sensing and regulatory mechanisms. This review aims to elucidate the key role of ER stress sensors and to explore how they mediate cell autophagy, apoptosis, and non-apoptotic modes of cell death in the context of drug-treated NSCLC. This investigation lays a solid foundation for optimizing future treatment strategies for NSCLC.

Development and validation of a novel endoplasmic reticulum stress-related lncRNA signature in laryngeal squamous cell carcinoma

Endoplasmic reticulum stress (ERS) is an intracellular process in which improperly folded proteins lead to a cellular stress response. How endoplasmic reticulum stress contributes to the onset and progression of laryngeal squamous cell carcinoma remains unclear. Our research aimed to find an ERS signature to forecast the prognosis of laryngeal squamous cell carcinoma and to investigate its potential biological functions. LSCC sample data obtained from The Cancer Genome Atlas (TCGA) database were co-expressed with ERS- related genes, and then a prognostic signature on the basis of endoplasmic reticulum stress- related lncRNAs (ERS-related lncRNAs) was constructed by differential analysis and Cox regression analysis. Survival analysis, TMB, consensus cluster analysis, drug sensitivity analysis, immune analysis and clinical drug prediction were carried out on the model. Finally, the function of LHX1-DT was verified by in vitro experiments. From the TCGA-LSCC cohort, 35 significantly different ERS-related lncRNAs were identified. A prognostic signature consisting of three lncRNAs (AC110611.2, LHX1-DT, and AL157373.2) was identified. Kaplan-Meier analysis demonstrated the predictive ability of the model for overall survival. Calibration curves and receiver operating characteristic curves were validated and showed high predictive accuracy. Ultimately, the experimental results verified the expression of LHX1-DT in LSCC.

Cytosolic and endoplasmic reticulum chaperones inhibit wt-p53 to increase cancer cells' survival by refluxing ER-proteins to the cytosol

The endoplasmic reticulum (ER) is an essential sensing organelle responsible for the folding and secretion of almost one-third of eukaryotic cells' total proteins. However, environmental, chemical, and genetic insults often lead to protein misfolding in the ER, accumulating misfolded proteins, and causing ER stress. To solve this, several mechanisms were reported to relieve ER stress by decreasing the ER protein load. Recently, we reported a novel ER surveillance mechanism by which proteins from the secretory pathway are refluxed to the cytosol to relieve the ER of its content. The refluxed proteins gain new prosurvival functions in cancer cells, thereby increasing cancer cell fitness. We termed this phenomenon ER to CYtosol Signaling (or 'ERCYS'). Here, we found that in mammalian cells, ERCYS is regulated by DNAJB12, DNAJB14, and the HSC70 cochaperone SGTA. Mechanistically, DNAJB12 and DNAJB14 bind HSC70 and SGTA - through their cytosolically localized J-domains to facilitate ER-protein reflux. DNAJB12 is necessary and sufficient to drive this phenomenon to increase AGR2 reflux and inhibit wt-p53 during ER stress. Mutations in DNAJB12/14 J-domain prevent the inhibitory interaction between AGR2-wt-p53. Thus, targeting the DNAJB12/14-HSC70/SGTA axis is a promising strategy to inhibit ERCYS and impair cancer cell fitness.

ALKBH5 Inhibits YTHDF2-m6A-Mediated Degradation of RCN1 mRNA to Promote Keloid Formation by Activating IRE1α-XBP1-Mediated ER Stress

BACKGROUND

Reticulocalbin 1 (RCN1) was reported to be upregulated in keloid, but its molecular mechanism remains unclear. The aim of this study is to investigate the role of RCN1 in keloid.

METHODS

The expression of RCN1 was detected in keloid tissues. Keloid fibroblasts were transfected with RCN1 overexpression vector. Cell viability, collagen production, apoptosis, and cell invasion were measured. Then, the m6A modification level of RCN1 mRNA was detected by methylated RNA immunoprecipitation (MeRIP), and the effect of overexpression of ALKB homolog5 (ALKBH5) on the m6A modification level of RCN1 mRNA was evaluated. Subsequently, the relationship between RCN1 and XBP1 was verified by co-immunoprecipitation (Co-IP) assay. pcDNA-RCN1 and XBP1 shRNA were transfected into keloid fibroblasts to for reversal experiments, and changes in the endoplasmic reticulum (ER) structure of keloid fibroblasts were observed by transmission electron microscopy (TEM). Finally, we established a mouse keloid model and injected mice with the RCN1 shRNA lentiviral vectors to monitor the keloid formation in mice.

RESULTS

RCN1 was highly expressed in keloid tissues and keloid fibroblasts. Overexpression of RCN1 significantly increased keloid fibroblast viability, collagen production, and invasion, but inhibited cell apoptosis. ALKBH5 upregulated RCN1 expression by reducing m6A-YTHDF2-mediated degradation of RCN1 mRNA, and RCN1 knockdown reversed the promoting effect of ALKBH5 overexpression on cell viability collagen production and invasion, and the inhibitory effect of ALKBH5 overexpression on apoptosis in keloid fibroblasts. Moreover, overexpression of RCN1 significantly upregulated the protein levels of XBP1, GRP78, and IRE1α, and promoted ER stress in keloid fibroblasts, but this change was eliminated by sh-XBP1 intervention. In vivo experiments showed that knockdown of RCN1 significantly inhibited keloid formation by alleviating cell apoptosis and ER stress in mice.

CONCLUSION

Our data revealed that RCN1 was upregulated by ALKBH5 to promote keloid formation by activating IRE1α-XBP1-mediated ER stress, RCN1 may be a potential biomarker for treatment of keloid.

Endoplasmic reticulum stress-related signatures: a game-changer in prognostic stratification for hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) has limited therapeutic options and a poor prognosis. The endoplasmic reticulum (ER) plays a crucial role in tumor progression and response to stress, making it a promising target for HCC stratification. This study aimed to develop a risk stratification model using ER stress-related signatures.

METHODS

We utilized transcriptome data from The Cancer Genome Atlas and Gene Expression Omnibus, which encompass whole-genome expression profiles and clinical annotations. Machine learning algorithms, including the least absolute shrinkage and selection operator, random forest, and support vector machine recursive feature elimination, were applied to the key genes associated with HCC prognosis. A prognostic system was developed using univariate Cox hazard analysis and least absolute shrinkage and selection operator Cox regression, followed by validation using Kaplan-Meier analysis and receiver operating characteristic curves. Tumor immune dysfunction and exclusion tools were used to predict immunotherapy responsiveness.

RESULTS

Two distinct clusters associated with ER stress were identified in HCC, each exhibiting unique clinical and biological features. Using a computational approach, a prognostic risk model, namely the ER stress-related signature, was formulated, demonstrating enhanced predictive accuracy compared with that of existing prognostic models. An effective clinical nomogram was established by integrating the risk model with clinicopathological factors. Patients with lower risk scores exhibited improved responsiveness to various chemotherapeutic, targeted, and immunotherapeutic agents.

CONCLUSION

The critical role of ER stress in HCC is highlighted. The ER stress-related signature developed in this study is a powerful tool to assess the risk and clinical treatment of HCC.

The relationship between serum levels of GRP78, GRP94, calnexin, and calreticulin and prognosis in patients with lung cancer

BackgroundTo determine the serum levels of endoplasmic reticulum (ER) chaperones, glucose-regulated protein 78 (GRP78), glucose-regulated protein 94 (GRP94), calnexin, and calreticulin in patients with lung cancer and in the control group and to evaluate the relationship between chaperone levels and clinical data and patient survival.MethodsGRP78, GRP94, calnexin and calreticulin were measured in serum by ELISA. The serum chaperone levels of patients with lung cancer and the control group were compared. The relationship between serum chaperone levels and clinical data and patient prognosis was evaluated. The median survival time was calculated using the Kaplan-Meier method. Cox regression analysis was performed to determine the hazard ratio of ER chaperones considering prognostic factors.ResultsThe serum levels of all ER chaperones GRP78, GRP94, calnexin, and calreticulin were higher in patients with lung cancer than in the control group and correlated with each other. Serum calreticulin levels were not affected by demographic and clinical characteristics. Serum levels of GRP78, GRP94, and calnexin were not associated with survival. However, median survival ± SE (95%CI) was 16.00 ± 1.72 (12.62-19.38) months in patients with serum calreticulin levels of 250.52 ng/ml and above, while it was 8.00 ± 1.38 (5.29-10.71) months in patients with calreticulin levels below the cut-off value (log-rank = 6.919; p = 0.009). Calreticulin impacted survival, even after adjustment for sex, histologic subtype, stage, treatment, and response to chemotherapy, which impacted survival [HR (95%CI): 0.656 (0.433-0.995); p = 0.047].ConclusionCalreticulin is promising for delineating risk groups in lung cancer screening studies, guiding treatment and monitoring outcomes.

Sphingosine-1-Phosphate-Cathelicidin Axis Plays a Pivotal Role in the Development of Cutaneous Squamous Cell Carcinoma

Cutaneous squamous cell carcinoma (cSCC) is a common skin cancer caused by mutagenesis resulting from excess UVR or other types of oxidative stress. These stressors also upregulate the production of a cutaneous innate immune element, cathelicidin antimicrobial peptide (CAMP), through endoplasmic reticulum stress-initiated, sphingosine-1-phosphate (S1P) signaling pathway. Although CAMP has beneficial antimicrobial activities, it also can be proinflammatory and procarcinogenic. We addressed whether and how S1P-induced CAMP production leads to cSCC development. Our study demonstrated that (i) CAMP expression is increased in cSCC cells and skin from patients with cSCC; (ii) S1P levels are elevated in cSCC cells, whereas inhibition of S1P production attenuates CAMP-stimulated cSCC growth; (iii) exogenous CAMP stimulates cSCC but not normal human keratinocyte growth; (iv) blockade of FPRL1 protein, a CAMP receptor, attenuates cSCC growth as well as the growth and invasion of cSCC cells mediated by CAMP into an extracellular matrix-containing fibroblast substrate; (v) FOXP3+ regulatory T-cell (which decreases antitumor immunity) levels increase in cSCC skin; and (vi) CAMP induces endoplasmic reticulum stress in cSCC cells. Together, the endoplasmic reticulum stress-S1P-CAMP axis forms a vicious circle, creating a favorable environment for cSCC development, that is, cSCC growth and invasion impede anticancer immunity.

Trichostatin A augments cell migration and epithelial-mesenchymal transition in esophageal squamous cell carcinoma through BRD4/c-Myc endoplasmic reticulum-stress pathway

BACKGROUND

The causes of death in patients with advanced esophageal cancer are multifactorial, with tumor metastasis being one of the important factors. Histone acetylation promotes the migration of esophageal squamous cell carcinoma (ESCC) cells, while the histone deacetylase inhibitor (HDACi) shows complex effects on tumor functions.

AIM

To comprehensively elucidate the impact and molecular mechanisms of trichostatin A (TSA), an HDACi, on cell migration in ESCC through bromodomain-containing protein (BRD4)/cellular myelocytomatosis oncogene (c-Myc)/endoplasmic reticulum (ER)-stress.

METHODS

The effects of TSA on ESCC cell lines Eca109 and EC9706 migration were evaluated using Transwell assays, with small interfering transfection and pathway-specific inhibitors to elucidate underlying mechanisms. The mRNA levels involved were examined by quantitative real-time polymerase chain reaction. Protein levels of acetylated histones H3 (acH3) and acetylated histones H4, BRD4, c-Myc, as well as markers of ER stress and epithelial-mesenchymal transition (EMT), were analyzed using western blot. Additionally, this method was also used to examine acH3 levels in esophageal cancer tissues and adjacent tissues. Patient outcomes were subsequently tracked to identify prognostic indicators using Log-Rank tests and Cox multivariate analysis.

RESULTS

TSA promoted the migration of ESCC cells by stimulating the EMT process. TSA-mediated histone acetylation facilitated the recruitment of BRD4, a bromodomain-containing protein, triggering the expression of c-Myc. This cascade induced ER stress and enhanced EMT in ESCC cells. To further elucidate the underlying mechanism, we employed various interventions including the ER stress inhibitor 4-phenylbutyric acid, knockdown of c-Myc and BRD4 expression, and utilization of the BRD4 inhibitor carboxylic acid as well as the inhibitor of TSA 1. Mechanistically, these studies revealed that TSA-mediated histone acetylation facilitated the recruitment of BRD4, which in turn triggered the expression of c-Myc. This sequential activation induced ER stress and subsequently enhanced EMT, thereby promoting the migration of ESCC cells. Additionally, we examined histone acetylation levels in specimens from 43 patients with ESCC, including both tumor tissues and paired adjacent tissues. Statistical analysis unveiled a negative correlation between the level of histone acetylation and the long-term prognosis of patients with ESCC.

CONCLUSION

TSA promoted ESCC cell migration through the BRD4/c-Myc/ER stress pathway. Moreover, elevated histone acetylation in ESCC tissues correlated with poor ESCC prognosis. These findings enhance our understanding of ESCC migration and HDACi therapy.

Homeostasis control in health and disease by the unfolded protein response

Cells rely on the endoplasmic reticulum (ER) to fold and assemble newly synthesized transmembrane and secretory proteins - essential for cellular structure-function and for both intracellular and intercellular communication. To ensure the operative fidelity of the ER, eukaryotic cells leverage the unfolded protein response (UPR) - a stress-sensing and signalling network that maintains homeostasis by rebalancing the biosynthetic capacity of the ER according to need. The metazoan UPR can also redirect signalling from cytoprotective adaptation to programmed cell death if homeostasis restoration fails. As such, the UPR benefits multicellular organisms by preserving optimally functioning cells while removing damaged ones. Nevertheless, dysregulation of the UPR can be harmful. In this Review, we discuss the UPR and its regulatory processes as a paradigm in health and disease. We highlight important recent advances in molecular and mechanistic understanding of the UPR that enable greater precision in designing and developing innovative strategies to harness its potential for therapeutic gain. We underscore the rheostatic character of the UPR, its contextual nature and critical open questions for its further elucidation.

Integrated analysis of single-cell and bulk transcriptomics reveals cellular subtypes and molecular features associated with osteosarcoma prognosis

BACKGROUND

Osteosarcoma (OS) is the most common primary bone malignancy with variable molecular biology and prognosis. However, our understanding of the association between cell types and OS progression remains poor.

METHODS

We generated a human OS cell atlas by integrating over 110,000 single cells from 17 samples. Multiple machine learning algorithms were applied to develop tumor purity prediction models based on transcriptomic profile of OS. The Scissor algorithm and gene enrichment analyses were conducted to delve into cell-intrinsic molecular characteristics linked to OS prognosis. Moreover, the study investigated the impact of ATF6α in OS aggressiveness through genetic and pharmacological loss of function analyses. Lastly, the CellChat algorithm was employed to investigate cell-cell communications.

RESULTS

Utilizing the high-quality human OS cell atlas, we identified tumor purity as a prognostic indicator and developed a robust tumor purity prediction model. We respectively delineated cancer cell- and immune cell-intrinsic molecular characteristics associated with OS prognosis at single-cell resolution. Interestingly, tumor cells with activated unfolded protein response (UPR) pathway were significantly associated with disease aggressiveness. Notably, ATF6α emerged as the top-activated transcription factor for this tumor subcluster. Subsequently, we confirmed that ATF6α was markedly associated with OS progression, while both genetic and pharmacological inhibition of ATF6α impaired the survival of HOS cells. Lastly, we depicted the landscape of signal crosstalk between the UPR-related subcluster and other cell types within the tumor microenvironment.

CONCLUSION

In summary, our work provides novel insights into the molecular biology of OS, and offers valuable resource for OS biomarker discovery and treatment strategy development.

An unfolded protein response (UPR)-signature regulated by the NFKB-miR-29b/c axis fosters tumor aggressiveness and poor survival in bladder cancer

Background

Bladder cancer continues to pose a substantial global health challenge, marked by a high mortality rate despite advances in treatment options. Therefore, in-depth understanding of molecular mechanisms related to disease onset, progression, and patient survival is of utmost importance in bladder cancer research. Here, we aimed to investigate the underlying mechanisms using a stringent differential expression and survival analyses-based pipeline.

Methods

Gene and miRNA expression data from TCGA and NCBI GEO databases were analyzed. Differentially expressed genes between normal vs tumor, among tumor aggressiveness groups and between early vs advanced stage were identified using Student's t-test and ANOVA. Kaplan-Meier survival analyses were conducted using R. Functional annotation, miRNA target and transcription factor prediction, network construction, random walk analysis and gene set enrichment analyses were performed using DAVID, miRDIP, TransmiR, Cytoscape, Java and GSEA respectively.

Results

We identified elevated endoplasmic reticulum (ER) stress response as key culprit, as an eight-gene unfolded protein response (UPR)-related gene signature (UPR-GS) drives aggressive disease and poor survival in bladder cancer patients. This elevated UPR-GS is linked to the downregulation of two miRNAs from the miR-29 family (miR-29b-2-5p and miR-29c-5p), which can limit UPR-driven tumor aggressiveness and improve patient survival. At further upstream, the inflammation-related NFKB transcription factor inhibits miR-29b/c expression, driving UPR-related tumor progression and determining poor survival in bladder cancer patients.

Conclusion

These findings highlight that the aberrantly activated UPR, regulated by the NFKB-miR-29b/c axis, plays a crucial role in tumor aggressiveness and disease progression in bladder cancer, highlighting potential targets for therapeutic interventions and prognostic markers in bladder cancer management.

Dynamic Modulation of IRE1α-XBP1 Signaling by Adenovirus

The abundant production of foreign proteins and nucleic acids during viral infection elicits a variety of stress responses in host cells. Viral proteins that accumulate in the endoplasmic reticulum (ER) can trigger the unfolded protein response (UPR), a coordinated signaling program that culminates in the expression of downstream genes that collectively restore protein homeostasis. The model pathogen adenovirus serotype 5 (HAdV5) activates the UPR via the signaling axis formed by inositol-requiring enzyme type 1 (IRE1α) and the X-box binding protein 1 (XBP1), a transcription factor required for immune function. Recent studies have suggested that IRE1α-XBP1 activity supports adenovirus replication. Here, we show that HAdV5 exerted opposing effects on IRE1α and XBP1. IRE1α was activated in response to HAdV5, but the production of the XBP1 isoform, XBP1s, was post-transcriptionally blocked. The tumor suppressor p53, which is eliminated by HAdV5 after infection, inhibited IRE1α activation. The de-repression of IRE1α following the degradation of p53 conceivably reflects a novel antiviral mechanism, which HAdV5 ultimately evades by co-opting IRE1α and suppressing XBP1s. Our findings illustrate the opposing mechanisms used by adenoviruses and their host cells to exert control over the UPR, a critical determinant of cell fate.

TROP2 regulates cisplatin sensitivity of triple-negative breast cancer cells by regulating endoplasmic reticulum stress

Triple-negative breast cancer (TNBC) is a kind of breast cancer with a high metastasis rate and poor prognosis. As a transmembrane glycoprotein, tumor-associated calcium signal transducer 2 (TROP2) plays a certain role in the cancers. This study aimed to explore the potential mechanism of TROP2 affecting cisplatin (CDDP) resistance in TNBC from endoplasmic reticulum stress (ERS). MDA-MB-231 and CDDP-resistant cell lines MDA-MB-231/CDDP were used in this study, and the expression of TROP2 was detected by western blotting. After transfecting with the interference sequence of siRNA targeting TROP2, cell proliferation and apoptosis were detected by the cell counting kit-8, colony formation, and flow cytometry, and the expression of ERS-marker proteins was detected by western blotting. Furthermore, the effects of ERS in TROP2 on drug resistance of TNBC cells were explored by using ERS inhibitor 4-phenylbutyric acid (4-PBA). Results found that TROP2 expression in MDA-MB-231/CDDP was significantly upregulated compared with MDA-MB-231. The expression of TROP2 in MDA-MB-231/CDDP was significantly decreased after transfection with siRNA-TROP2, and the proliferation of MDA-MB-231 and MDA-MB-231/CDDP cells was significantly decreased after further induction with CDDP. TROP2 significantly affected TNBC cell cloning, apoptosis, and the expression of ERS-related marker proteins, while 4-PBA reversed the promoting effects of siRNA-TROP2 on apoptosis and ERS, as well as the inhibitory effects on cell proliferation, suggesting that TROP2 affected the resistance of TNBC cells to CDDP through ERS. In conclusion, TROP2 inhibited apoptosis of TNBC cells, improved the cell cloning ability, and regulated the sensitivity of TNBC cells to CDDP through ERS.

ECD co-operates with ERBB2 to promote tumorigenesis through upregulation of unfolded protein response and glycolysis

The ecdysoneless (ECD) mRNA and protein are overexpressed in breast cancer (BC), and its overexpression correlates with poor prognosis and short patient survival, particularly in ERBB2/HER2-positive BC. This study investigates the co-operative oncogenic mechanism of ECD and ERBB2 by deriving transgenic mice overexpressing ECD and/or ERBB2 (huHER2) in mammary epithelium under MMTV promoter, as well as human mammary immortal epithelial cell lines (hMECs) overexpressing ECD and/or ERBB2. While huHER2 Tg mice developed more homogenous solid nodular carcinomas, double transgenic mice ( ECD;huHER2 Tg) developed heterogenous and histologically aggressive mammary tumors with basal-like phenotype and epithelial mesenchymal transition (EMT) features, like ECD Tg tumors, resembling more to patient tumors. Importantly, transcriptomic profile of ECD;huHER2 Tg tumors revealed upregulation of two major oncogenic pathways, unfolded protein response (UPR) and glycolysis. Similarly, hMECs expressing both ECD and ERBB2 as compared to single gene expressing cells showed increase in oncogenic traits, and RNA-seq analysis showed a significant upregulation of glycolysis and UPR pathways. ECD is an RNA binding protein, and directly associates with three key glycolytic enzymes ( LDHA , PKM2 and HK2 ) and mRNA of a major UPR regulated gene GRP78, that results in increased mRNA stability. Lastly, we show an increase in glucose uptake and enhanced glycolytic rate in ECD+ERBB2-overexpressing cells as compared to ECD- or ERBB2-overexpressing hMECs. Taken together, our findings support a co-operative role of ECD and ERBB2 in oncogenesis by enhancing two major oncogenic pathways, UPR and glycolysis.

Significance

This study provides mechanistic insights that overexpression of ECD in ERBB2+ breast cancer patients correlates with shorter patient survival, by identifying direct ECD binding to mRNAs for UPR and glycolysis pathways.

Inhibition of Endoplasmic Reticulum Stress Cooperates with SLC7A11 to Promote Disulfidptosis and Suppress Tumor Growth upon Glucose Limitation

Disulfidptosis is a newly discovered type of regulated cell death triggered by disulfide bond accumulation and NADPH (nicotinamide adenine dinucleotide phosphate) depletion due to glucose deprivation. However, the regulatory mechanisms involving additional cellular circuits remain unclear. Excessive disulfide bond accumulation can impair endoplasmic reticulum (ER) homeostasis and activate the ER stress response. In this study, we found that SLC7A11-mediated disulfidptosis upon glucose deprivation is accompanied by ER stress induction. Pharmacological inhibition of SLC7A11-mediated cystine uptake or cystine withdrawal not only blocks disulfidptosis under glucose starvation but also suppresses the ER stress response, indicating a close link between these processes. Moreover, inhibitors targeting the ER stress response promote disulfidptosis, while ER stress inducers suppress glucose starvation-induced disulfidptosis in SLC7A11-high-expressing cells, suggesting a protective role for ER stress during disulfidptosis. Similar effects are observed in cells treated with glucose transporter inhibitors (GLUTi). Finally, combined treatment with ER stress inhibitors and GLUTi significantly suppresses tumor growth both in vitro and in vivo by inducing disulfide stress and subsequent disulfidptosis. In summary, these findings reveal a novel role for ER stress in regulating disulfidptosis and provide theoretical insights into the potential application of GLUTi and ER stress inhibitors in cancer therapy.

Proteomic Analysis of Breast Cancer Subtypes Identifies Stromal Contributions that Dictate Aggressive Malignant Behavior

Breast cancer manifests as multiple subtypes with distinct patient outcomes and treatment strategies. Here, we optimized proteomic analysis of Formalin-Fixed Paraffin-Embedded (FFPE) specimens from patients diagnosed with five breast cancer subtypes, luminal A, luminal B, Her2, triple negative (TNBC) and metaplastic breast cancers (MBC), and from disease-free individuals undergoing reduction mammoplasty (RM). We identified and quantified ∼6,000 protein groups (with >2 peptides per protein) with significant changes in over 26% of proteins comparing each cancer subtype with control RM. Stringent statistical filters allowed us to deeply mine 576 significant conserved protein changes shared by all subtypes and protein changes unique to each subtype. The most aggressive subtype, MBC, revealed exacerbated stromal stress responses, as illustrated by a collagenolytic extracellular matrix (ECM) and immune participation biased towards neutrophils and eosinophils. Immunostaining of breast tissue sections confirmed differences across subtypes, in particular, a dramatic upregulation of SERPINH1, neutrophil-specific myeloperoxidase and eosinophil cationic protein in MBC. In summary, deep proteomic, digitalized protein abundance profiles, generated from FFPE breast cancer tissues, revealed significant changes in ECM and cellular proteins providing insight into clinically relevant states.

The endoplasmic reticulum degradation-enhancing α-mannosidase-like protein 3 attenuates the unfolded protein response and has pro-survival and pro-viral roles in hepatoma cells and hepatocellular carcinoma patients

BACKGROUND

Chronic hepatitis B virus (HBV) infection is a major risk for development of hepatocellular carcinoma (HCC), a frequent malignancy with a poor survival rate. HBV infection results in significant endoplasmic reticulum (ER) stress and activation of the unfolded protein response (UPR) signaling, a contributing factor to carcinogenesis. As part of the UPR, the ER-associated degradation (ERAD) pathway is responsible for removing the burden of misfolded secretory proteins, to re-establish cellular homeostasis. Emerging evidence indicates consistent upregulation of ERAD factors, including members of the ER degradation-enhancing alpha-mannosidase-like protein (EDEM) family in infection and various tumor types. However, the significance of this gene expression pattern in HBV-driven pathology is just beginning to be deciphered.

METHODS

In this study we quantified the expression of the ERAD factor EDEM3, in a cohort of HCC patients with and without HBV infection, and validated our results by analysis of publically available transcriptomic and microarray data sets. We performed mechanistic studies in HepaRG cells with modulated EDEM3 expression to address UPR, ERAD, autophagy and apoptosis signaling, and their consequences on HBV infection.

RESULTS

Our work revealed significantly elevated EDEM3 expression in HCC tissues irrespective of HBV infection, while the highest levels were observed in tissues from HBV-infected patients. Investigation of published transcriptomic data sets confirmed EDEM3 upregulation in independent HCC patient cohorts, associated with tumor progression, poor survival prognosis and resistance to therapy. EDEM3-overexpressing hepatic cells exhibited attenuated UPR and activated secretory autophagy, which promoted HBV production. Conversely, cell depletion of EDEM3 resulted in significant ER stress inducing pro-apoptotic mechanisms and cell death.

CONCLUSIONS

We provide evidence of major implications of the ERAD pathway in HBV infection and HCC development and progression. Our results suggest that ERAD activation in HBV-infected cells is a protective mechanism against prolonged ER stress, potentially contributing to establishment of chronic HBV infection and promoting tumorigenesis. Developing specific inhibitors for ERAD factors may be an attractive approach to improve efficiency of current antiviral and anticancer therapies.

The effect of chemotherapeutic agents on epidermal neural crest stem cells

Human Epidermal Neural Crest Stem Cells (hEPI-NCSCs), as a transient population of multipotent migratory stem cells can differentiate into multiple types of neural and non-neural cells and tissues in the body. Here, we tried to determine the role of chemo agents in mediating the stress induced pathways like autophagy and unfolded protein responses (UPR), as well as the migratory potential of NCSCs. hEPI-NCSCs were treated with chemo agents including Dithiothreitol [(DTT) 10µM)], Salinomycin (9mM), Ebselen (10mM), 5-Fluorouracil [(5-FU) 8µM] and Cisplatin (6mM) for 72 hours. The reverse transcription-quantitative polymerase chain reaction (RT- qPCR) and scratch wound healing assays were used to assess the effect of chemo agents on NCSCs function. After treatment with DTT, hEPI-NCSCs upregulated the expression of genes related to autophagy and UPR pathways including LC3, P62 and CHOP. These genes were also overexpressed when NCSCs were treated with Salinomycin. Reverse results were verified by 5-FU, Ebselen and Cisplatin treatment. Salinomycin and Cisplatin upregulated the expression of XBP-1, which down regulated with DTT, 5-FU and Ebselen. Inhibition in migratory capacity of NCSCs was detected following treatment by Salinomycin, 5-FU, Ebselen and Cisplatin. DTT and 5-FU promoted the expression of BDNF, while Salinomycin, Cisplatin and Ebselen treatment reduced its expression. During exposition to DTT, the autophagy pathway was activated, implying that autophagy functions as a survival mechanism for deactivating the inhibitory effects of DTT on the migratory capacity of NCSCs. Chemotherapeutic agents like 5-FU and cisplatin exert cytotoxic effects on NCSCs by suppressing autophagy, UPR pathways, and the migratory potential of NCSCs.

Endoplasmic reticulum stress induced autophagy in cancer and its potential interactions with apoptosis and ferroptosis

The endoplasmic reticulum (ER) is a dynamic organelle that is a site of the synthesis of proteins and lipids, contributing to the regulation of proteostasis, lipid metabolism, redox balance, and calcium storage/-dependent signaling events. The disruption of ER homeostasis due to the accumulation of misfolded proteins in the ER causes ER stress which activates the unfolded protein response (UPR) system through the activation of IRE1, PERK, and ATF6. Activation of UPR is observed in various cancers and therefore, its association with process of carcinogenesis has been of importance. Tumor cells effectively utilize the UPR system to overcome ER stress. Moreover, ER stress and autophagy are the stress response mechanisms operating together to maintain cellular homeostasis. In human cancers, ER stress-driven autophagy can function as either pro-survival or pro-death in a context-dependent manner. ER stress-mediated autophagy can have crosstalk with other types of cell death pathways including apoptosis and ferroptosis. In this connection, the present review has evaluated the role of ER stress in the regulation of autophagy-mediated tumorigenesis and its interactions with other cell death mechanisms such as apoptosis and ferroptosis. We have also comprehensively discussed the effect of ER stress-mediated autophagy on cancer progression and chemotherapeutic resistance.

Impacts and potential mechanisms of fine particulate matter (PM2.5) on male testosterone biosynthesis disruption

Exposure to PM2.5 is the most significant air pollutant for health risk. The testosterone level in male is vulnerable to environmental toxicants. In the past, researchers focused more attention on the impacts of PM2.5 on respiratory system, cardiovascular system, and nervous system, and few researchers focused attention on the reproductive system. Recent studies have reported that PM2.5 involved in male testosterone biosynthesis disruption, which is closely associated with male reproductive health. However, the underlying mechanisms by which PM2.5 causes testosterone biosynthesis disruption are still not clear. To better understand its potential mechanisms, we based on the existing scientific publications to critically and comprehensively reviewed the role and potential mechanisms of PM2.5 that are participated in testosterone biosynthesis in male. In this review, we summarized the potential mechanisms of PM2.5 triggering the change of testosterone level in male, which involve in oxidative stress, inflammatory response, ferroptosis, pyroptosis, autophagy and mitophagy, microRNAs (miRNAs), endoplasmic reticulum (ER) stress, and N6-methyladenosine (m6A) modification. It will provide new suggestions and ideas for prevention and treatment of testosterone biosynthesis disruption caused by PM2.5 for future research.

Endoplasmic reticulum stress in acute lung injury and pulmonary fibrosis

Pulmonary fibrosis (PF) is a progressive and irreversible lung disease that leads to diminished lung function, respiratory failure, and ultimately death and typically has a poor prognosis, with an average survival time of 2 to 5 years. Related articles suggested that endoplasmic reticulum (ER) stress played a critical role in the occurrence and progression of PF. The ER is responsible for maintaining protein homeostasis. However, factors such as aging, hypoxia, oxidative stress, or inflammation can disrupt this balance, promoting the accumulation of misfolded proteins in the ER and triggering ER stress. To cope with this situation, cells activate the unfolded protein response (UPR). Since acute lung injury (ALI) is one of the key onset events of PF, in this review, we will discuss the role of ER stress in ALI and PF by activating multiple signaling pathways and molecular mechanisms that affect the function and behavior of different cell types, with a focus on epithelial cells, fibroblasts, and macrophages. Linking ER stress to these cell types may broaden our understanding of the mechanisms underlying lung fibrosis and help us target these cells through these mechanisms. The relationship between ER stress and PF is still evolving, and future research will explore new strategies to regulate UPR pathways, providing novel therapeutic targets.

Dynamic modulation of IRE1α-XBP1 signaling by adenovirus

The abundant production of foreign proteins and nucleic acids during viral infection elicits a variety of stress responses in host cells. Viral proteins that accumulate in the endoplasmic reticulum (ER) can trigger the unfolded protein response (UPR), a coordinated signaling program that culminates in the expression of downstream genes that collectively restore protein homeostasis. The model pathogen adenovirus serotype 5 (HAdV5) activates the UPR via the signaling axis formed by inositol-requiring enzyme type 1 (IRE1α) and the X-box binding protein 1 (XBP1), a transcription factor required for immune function. Recent studies have suggested that IRE1α-XBP1 activity supports adenovirus replication. Here, we show that HAdV5 exerted opposing effects on IRE1α and XBP1. IRE1α was activated in response to HAdV5 but the production of the XBP1 isoform, XBP1s, was post-transcriptionally blocked. The tumor suppressor p53, which is eliminated by HAdV5 after infection, inhibited IRE1α activation. The de-repression of IRE1α following the degradation of p53 conceivably reflects a novel antiviral mechanism, which HAdV5 ultimately evades by suppressing XBP1s. Our findings highlight the defective antiviral defenses in cancer cells and further illustrate the opposing mechanisms used by adenoviruses and their host cells to exert control over the UPR, a critical determinant of cell fate.

An endoplasmic reticulum stress related signature for clinically predicting prognosis of breast cancer patients

BACKGROUND

Endoplasmic Reticulum Stress (ER stress) was an important event in the development of breast cancer. We aimed to predict prognosis based on ER stress related key genes.

METHODS

Data of the RNA-seq and clinical information of breast cancer cases were downloaded from the TCGA database. A total of 4 genes related with ER stress was identified by the univariate Cox regression and Least Absolute Shrinkage and Selection Operator (LASSO)-penalized Cox proportional hazards regression analysis. The predictive ability of the ER stress model was evaluated by utilizing Kaplan-Meier curves and time-dependent receiver operating characteristic (ROC) curves. Moreover, we verified 4 genes expression and its relationship with clinical breast cancer cases in real-world.

RESULTS

4 genes including RNF186, BCAP31, SERPINA1, TAPBP were identified as a prognostic risk score model. Based on that, we found patients of breast cancer had a better survival with low-risk score. And also, ER stress model showed a good diagnostic efficacy with AUC curve. The risk score was significantly associated with patients' age, T stage and clinical stage. A nomogram was constructed to estimate individual survival. Further GO and KEGG analysis showed our model was related with immune infiltration. Patients of breast cancer with high-risk scores were usually accompanied with poor immune infiltration. It was predicted that high risk group was more sensitive to Vinorelbine, Docetaxel and Cisplatin. At last, we verified the expression of four signature genes using qRT-PCR and immunohistochemistry.

CONCLUSION

Our ER stress model performed a valuable prediction on breast cancer patients.

Qing Hua Chang Yin ameliorates chronic colitis in mice by inhibiting PERK-ATF4-CHOP pathway of ER stress and the NF-κB signalling pathway

CONTEXT

Ulcerative colitis has been clinically treated with Qing Hua Chang Yin (QHCY), a traditional Chinese medicine formula. However, its precise mechanisms in mitigating chronic colitis are largely uncharted.

OBJECTIVE

To elucidate the therapeutic efficiency of QHCY on chronic colitis and explore its underlying molecular mechanisms.

MATERIALS AND METHODS

A total ion chromatogram fingerprint of QHCY was analysed. Chronic colitis was induced in male C57BL/6 mice using 2% dextran sodium sulphate (DSS) over 49 days. Mice were divided into control, DSS, DSS + QHCY (0.8, 1.6 and 3.2 g/kg/d dose, respectively) and DSS + mesalazine (0.2 g/kg/d) groups (n = 6). Mice were intragastrically administered QHCY or mesalazine for 49 days. The changes of disease activity index (DAI), colon length, colon histomorphology and serum pro-inflammatory factors in mice were observed. RNA sequencing was utilized to identify the differentially expressed transcripts (DETs) in colonic tissues and the associated signalling pathways. The expression of endoplasmic reticulum (ER) stress-related protein and NF-κB signalling pathway-related proteins in colonic tissues was detected by immunohistochemistry staining.

RESULTS

Forty-seven compounds were identified in QHCY. Compared with the DSS group, QHCY significantly improved symptoms of chronic colitis like DAI increase, weight loss, colon shortening and histological damage. It notably reduced serum levels of IL-6, IL-1β and TNF-α. QHCY suppressed the activation of PERK-ATF4-CHOP pathway of ER stress and NF-κB signalling pathways in colonic tissues.

DISCUSSION AND CONCLUSIONS

The findings in this study provide novel insights into the potential of QHCY in treating chronic colitis patients.

The role of microRNAs regulation of endoplasmic reticulum stress in ischemia-reperfusion injury: A review

The endoplasmic reticulum (ER) is an important organelle in eukaryotic cells, responsible for a range of biological functions such as the secretion, modification and folding of proteins, maintaining Ca2+ homeostasis and the synthesis of steroids/lipids, secreted proteins and membrane proteins. When cells are affected by internal or external factors, including abnormal energy metabolism, disrupted Ca2+ balance, altered glycosylation, drug toxicity, and so on, the unfolded or misfolded proteins accumulate in the ER, leading to the unfolded protein response (UPR) and ER stress. The abnormal ER stress has been reported to be involved in various pathological processes. MicroRNAs (miRNAs) are non-coding RNAs with the length of approximately 19-25 nucleotides. They control the expression of multiple genes through posttranscriptional gene silencing in eukaryotes or some viruses. Increasing evidence indicates that miRNAs are involved in various cellular functions and biological processes, such as cell proliferation and differentiation, growth and development, and metabolic homeostasis. Hence, miRNAs participate in multiple pathological processes. Recently, many studies have shown that miRNAs play an important role by regulating ER stress in ischemia-reperfusion (I/R) injury, but the relevant mechanisms are not fully understood. In this review, we reviewed the current understanding of ER stress, as well as the biogenesis and function of miRNAs, and focused on the role of miRNAs regulation of ER stress in I/R injury, with the aim of providing new targets for the treatment of I/R injury.

The Integrated Stress Response in Pancreatic Development, Tissue Homeostasis, and Cancer

Present in all eukaryotic cells, the integrated stress response (ISR) is a highly coordinated signaling network that controls cellular behavior, metabolism, and survival in response to diverse stresses. The ISR is initiated when any 1 of 4 stress-sensing kinases (protein kinase R-like endoplasmic reticulum kinase [PERK], general control non-derepressible 2 [GCN2], double-stranded RNA-dependent protein kinase [PKR], heme-regulated eukaryotic translation initiation factor 2α kinase [HRI]) becomes activated to phosphorylate the protein translation initiation factor eukaryotic translation initiation factor 2α (eIF2α), shifting gene expression toward a comprehensive rewiring of cellular machinery to promote adaptation. Although the ISR has been shown to play an important role in the homeostasis of multiple tissues, evidence suggests that it is particularly crucial for the development and ongoing health of the pancreas. Among the most synthetically dynamic tissues in the body, the exocrine and endocrine pancreas relies heavily on the ISR to rapidly adjust cell function to meet the metabolic demands of the organism. The hardwiring of the ISR into normal pancreatic functions and adaptation to stress may explain why it is a commonly used pro-oncogenic and therapy-resistance mechanism in pancreatic ductal adenocarcinoma and pancreatic neuroendocrine tumors. Here, we review what is known about the key roles that the ISR plays in the development, homeostasis, and neoplasia of the pancreas.

The UPRising connection between endoplasmic reticulum stress and the tumor microenvironment

The tumor microenvironment (TME) represents a dynamic network of cancer cells, stromal cells, immune mediators, and extracellular matrix components, crucial for cancer progression. Stress conditions such as oncogene activation, nutrient deprivation, and hypoxia disrupt the endoplasmic reticulum (ER), activating the unfolded protein response (UPR), the main adaptive mechanism to restore ER function. The UPR regulates cancer progression by engaging cell-autonomous and cell-non-autonomous mechanisms, reprogramming the stroma and promoting immune evasion, angiogenesis, and invasion. This review explores the role of UPR beyond cancer cells, focusing on how ER stress signaling reshapes the TME, supporting tumor growth. The therapeutic potential of targeting the UPR is also discussed.

Modulating Endoplasmic Reticulum Stress in Gastrointestinal Cancers: Insights from Traditional Chinese Medicine

Endoplasmic reticulum (ER) stress and the unfolded protein response (UPR) play critical roles in tumorigenesis, cancer progression, and drug resistance. Persistent activation of the ER stress system enhances the survival capacities of malignant tumor cells, including increased proliferation, invasion, and resistance to treatment. Dysregulation of ER function and the resultant stress is a common cellular response to cancer therapies and may lead to cancer cell death. Currently, growing evidence suggests that Traditional Chinese medicine (TCM), either as a monotherapy or in combination with other treatments, offers significant advantages in preventing cancer, inhibiting tumor growth, reducing surgical complications, improving drug sensitivity, and mitigating drug-induced damage. Some of these natural products have even entered clinical trials as primary or complementary anticancer agents. In this review, we summarize the anticancer effects of TCM monomers/natural products on the gastrointestinal (GI) tumors and explore their mechanisms through ER stress modulation. We believe that ongoing laboratory research and the clinical development of TCM-based cancer therapies hold considerable potential for advancing future cancer treatments.

Tongguanteng injection exerts anti-osteosarcoma effects through the ER stress-associated IRE1/CHOP pathway

BACKGROUND

In China, Tongguanteng injection (TGT) is widely used in the treatment or adjuvant treatment of various types of cancer. However, the effect and mechanism of TGT in osteosarcoma is not clear.

METHODS

The 143B and MG-63 cells were treated with different concentrations of TGT. Cell proliferation, migration, invasion and apoptosis were detected using CCK8 assay, transwell assay and flow cytometry. Differentially expressed genes (DEGs) were screened using RNA sequencing (RNA-seq). The identified mRNA and protein expression associated with the IRE1/CHOP pathway was validated by RT-PCR and western blot assay. To explore the underlying mechanisms, 4-phenylbutyric acid (4-PBA) was selected as a specific endoplasmic reticulum (ER) stress inhibitor. Small interfering RNA (siRNA) or pEX-3-ERN1 plasmid was transfected into 143B cells to silence or overexpress IRE1, respectively. The potential downstream proteins, including CHOP, and apoptosis associated proteins, caspase-3 and PARP1 were determined. Furthermore, the effect of TGT was demonstrated in 143B cell tumor-bearing mice in vivo. H&E staining, TUNEL staining and immunohistochemistry were conducted in tumor tissues obtained from the xenograft mouse model.

RESULTS

TGT was shown to dramatically suppress the proliferation, migration and invasion, and induce apoptosis of osteosarcoma 143B and MG-63 cells in vitro. The identified DEGs included HSPA5 (encoding BiP) and ERN1 (encoding the IRE1 protein), as well as apoptosis-associated gene DDIT3 (encoding the CHOP protein). The term "IRE1-mediated unfolded protein response" was screened to be the most enriched biological process GO term. The expression of ER stress-associated proteins including ATF6, BiP, p-IRE1, XBP1s and CHOP, as well as apoptosis-associated cleaved caspase-3 and cleaved PARP1 proteins, was significantly upregulated by TGT treatment in osteosarcoma 143B cells, suggesting that TGT might promote the apoptosis of osteosarcoma 143B cells through the IRE1/CHOP pathway. Furthermore, knocking down IRE1 with si-IRE1 or inhibiting of ER stress with 4-PBA suppressed the expression of ATF6, BiP, XBP1s and CHOP induced by TGT, as well as the expression of cleaved caspase-3 and cleaved PARP1. On the contrary, overexpressing IRE1 promoted CHOP expression and induced osteosarcoma cell apoptosis. Consistent with in vitro results, TGT dramatically inhibited the tumor growth and promoted the expression of p-IRE1 and CHOP in tumor-bearing mice.

CONCLUSION

The findings suggest that TGT exerts an anti-osteosarcoma effect in vitro and in vivo. The underlying mechanism might be associated with the activation of IRE1/CHOP pathway in ER stress. Our findings suggest that targeting IRE1/CHOP pathway might be a potential novel approach for osteosarcoma treatment.

Connections Between Endoplasmic Reticulum Stress and Prognosis of Hepatocarcinoma

Endoplasmic reticulum (ER) stress is a state in which misfolded or unfolded proteins accumulate in the lumen of the ER as a result of some exogenous or endogenous factors. It plays a crucial role in the pathogenesis of malignancies, affecting cell survival, proliferation, and metastasis in cancer. ER stress genes could provide new ideas for potential therapeutic targets in cancer. In our study, we aimed to construct an ER stress-related genes (ERGs) model for hepatocellular carcinoma (HCC). ERGs with differential expression and significant survival were screened to construct a prognostic model. The effectiveness of the model was successfully validated by external datasets. High and low-risk groups were classified based on risk scores. Functional analysis showed risk groups involved in the unfolded protein response, DNA repair, and other differential pathways. When compared to patients with low risk, the prognosis for HCC patients in the high-risk group might be worsened by disruptions in these pathways. Importantly, we considered genomic druggability and predicted drugs. Sorafenib-induced autophagy in HCC cells through an ES stress mechanism. Sorafenib was more sensitive for high-risk patients. In brief, our model predicted the prognosis of HCC and provided novel treatment strategies for the study of other cancers.

Lactate activates ER stress to promote alveolar epithelial cells apoptosis in pulmonary fibrosis

Pulmonary fibrosis (PF) is a chronic, progressive lung disease characterized by fibroblast proliferation, extensive extracellular matrix and collagen deposition, accompanied by inflammatory damage, ultimately leading to death due to respiratory failure. Endoplasmic reticulum (ER) stress in pulmonary fibrotic tissue is indeed recognized as a significant factor exacerbating PF development. Emerging evidences indicated a potential association between ER stress induced by lactate and cellular apoptosis in PF. However, the mechanisms in this process need further elucidation. In this paper, pulmonary fibrosis model was induced by bleomycin (BLM) intratracheally in mice. In the cellular model, type II epithelial cells were treated by lactate and TGF-β to detect ER stress and apoptosis markers. Lactate could promote ER stress response and apoptosis. Mechanically, lactate activated Caspase-12 via ATF4-Chop axis to induce cell apoptosis and promote fibrosis. ER stress inhibitor could effectively suppress alveolar epithelial cells apoptosis and pulmonary fibrosis. We concluded that pro-fibrotic properties of lactate are associated with alveolar epithelial cells apoptosis by causing ER stress and thus provide new potential therapeutic targets for pulmonary fibrosis.

Targeting PERK and GRP78 in colorectal cancer: Genetic insights and novel therapeutic approaches

Colorectal cancer (CRC) ranks among the leading causes of cancer-related deaths worldwide. Enhancing CRC diagnosis and prognosis requires the development of improved biomarkers and therapeutic targets. Emerging evidence suggests that the unfolded protein response (UPR) plays a pivotal role in CRC progression, presenting new opportunities for diagnosis, treatment, and prevention. This study hypothesizes that genetic variants in endoplasmic reticulum (ER) stress response genes influence CRC susceptibility. We examined the frequencies of SNPs in PERK (rs13045) and GRP78/BiP (rs430397) within a South Iranian cohort. We mapped the cellular and molecular features of PERK and GRP78 genes in colorectal cancer, observing their differential expressions in tumor and metastatic tissues. We constructed co-expression and protein-protein interaction networks and performed gene set enrichment analysis, highlighting autophagy as a significant pathway through KEGG. Furthermore, the study included 64 CRC patients and 60 control subjects. DNA extraction and genotyping were conducted using high-resolution melting (HRM) analysis. Significant differences in PERK and GRP78 expressions were observed between CRC tissues and controls. Variations in PERK and GRP78 genotypes were significantly correlated with CRC risk. Utilizing a Multi-Target Directed Ligands approach, a dual PERK/GRP78 inhibitor was designed and subjected to molecular modeling studies. Docking experiments indicated high-affinity binding between the proposed inhibitor and both genes, PERK and GRP78, suggesting a novel therapy for CRC. These findings highlight the importance of understanding genetic backgrounds in different populations to assess CRC risk. Polymorphisms in UPR signaling pathway elements may serve as potential markers for predicting CRC susceptibility, paving the way for personalized therapeutic strategies.

Exploring paraptosis as a therapeutic approach in cancer treatment

A variety of cell death pathways play critical roles in the onset and progression of multiple diseases. Paraptosis, a unique form of programmed cell death, has gained significant attention in recent years. Unlike apoptosis and necrosis, paraptosis is characterized by cytoplasmic vacuolization, swelling of the endoplasmic reticulum and mitochondria, and the absence of caspase activation. Numerous natural products, synthetic compounds, and newly launched nanomedicines have been demonstrated to prime cell death through the paraptotic program and may offer novel therapeutic strategies for cancer treatment. This review summarizes recent findings, delineates the intricate network of signaling pathways underlying paraptosis, and discusses the potential therapeutic implications of targeting paraptosis in cancer treatment. The aim of this review is to expand our understanding of this unique cell death process and explore the potential therapeutic implications of targeting paraptosis in cancer treatment.

Analysis of Unfolded Protein Response Activation in Colon Adenocarcinoma Epithelial Cells: A Proteomic Study

PURPOSE

High throughput technologies have identified molecular patterns in colorectal cancer (CRC) cells, aiding in modeling responses to anti-cancer treatments. The different responses observed depend on the type of cancer, the tumour grade and the functional programme of the cancer cells. Recent studies suggest that the unfolded protein response (UPR), autophagy and apoptosis could be involved in treatment resistance mechanisms by interacting with the tumour microenvironment (TME).

EXPERIMENTAL DESIGN

We analysed by LC-MS/MS the proteome of two representative colon adenocarcinoma epithelial cell lines from different tumour grades (CCL-233 and CCL-221) at the basal state or after the UPR induction.

RESULTS

Cell lines expressed a different proteome on about 10% of their total proteins identified, especially on UPR, autophagy and apoptosis pathways proteins at basal state. After UPR induction, the proteome of the cells was modified with a greater adaptive response to cellular stress in CCL-221 cells where the UPR was strongly activated at the basal state.

CONCLUSIONS AND CLINICAL RELEVANCE

CRC cell lines at different tumour grades expressed different functional programmes at the proteomic level and were characterised by different responses to the UPR induction. This study suggests that baseline cancer cell stress status could have an impact on the efficiency of cancer therapies.

Prophylactic supplementation with selenium nanoparticles protects against foodborne toxin zearalenone-induced intestinal barrier dysfunction

Selenium nanoparticles (SeNPs) have been used as a potential alternative to other forms of selenium in nutritional supplements for the treatment and prevention of inflammatory and oxidative stress-related diseases. Zearalenone (ZEA) is a foodborne mycotoxin present in grains that poses a health threat. Here, we investigated the adverse impacts of ZEA on intestinal homeostasis and explored the protective effects of probiotic-synthesized SeNPs against its damage. Results showed that ZEA reduced mucin and tight junction proteins expression in jejunum, induced inflammatory process and oxidative stress which in turn increased intestinal permeability in mice. ZEA-induced intestinal toxicity was further verified in vitro. Intracellular redox imbalance triggered endoplasmic reticulum (ER) stress in intestinal epithelial cells, which caused structural damage to the ER. Remarkably, SeNPs exhibited a counteractive effect by inducing a decrease in intracellular levels of Inositol 1,4,5-trisphosphate (IP3) and Ca2+, along with a reduction in the expression level of IP3 receptor. SeNPs effectively mitigated ZEA-induced ER stress was related to the increased activity of selenium-dependent antioxidant enzymes and the expression of ER-resident selenoproteins. Furthermore, SeNPs significantly inhibited the activation of PERK/eIF2α/ATF4/CHOP pathway in vitro and in vivo. In addition, SeNPs effectively reversed ZEA-induced gut microbiota dysbiosis and increased the abundance of short-chain fatty acid-producing beneficial bacteria (Alloprevotella and Muribaculaceae). The Spearman correlation analysis suggested that the structure of gut microbiota was closely related to the SeNPs attenuation of ZEA-induced intestinal toxicity. This study provides new insights into ZEA-induced intestinal toxicity and identifies a novel potential nutrient SeNPs to overcome adverse effects.

Hypoxic Upregulation of IER2 Increases Paracrine GMFG Signaling of Endoplasmic Reticulum Stress-CAF to Promote Chordoma Progression via Targeting ITGB1

Currently, the oncogenic mechanism of endoplasmic reticulum stress-CAF (ERS-CAF) subpopulation in chordoma remains unknown. Here, single-cell RNA sequencing, spatial transcriptomics, GeoMx Digital Spatial Profiler, data-independent acquisition proteomics, bulk RNA-seq, and multiplexed quantitative immunofluorescence are used to unveil the precise molecular mechanism of how ERS-CAF affected chordoma progression. Results show that hypoxic microenvironment reprograms CAFs into ERS-CAF subtype. Mechanistically, this occurrs via hypoxia-mediated transcriptional upregulation of IER2. Overexpression of IER2 in CAFs promotes chordoma progression, which can be impeded by IER2 knockdown or use of ERS inhibitors. IER2 also induces expression of ERS-CAF marker genes and results in production of a pro-tumorigenic paracrine GMFG signaling, which exert its biological function via directly binding to ITGB1 on tumor cells. ITGB1 inhibition attenuates tumor malignant progression, which can be partially reversed by exogenous GMFG intervention. Further analyses reveal a positive correlation between ITGB1high tumor cell counts and SPP1+ macrophage density, as well as the spatial proximity of these two cell types. Clinically, a significant correlation of high IER2/ITGB1 expression with tumor aggressive phenotype and poor patient survival is observed. Collectively, the findings suggest that ERS-CAF regulates SPP1+ macrophage to aggravate chordoma progression via the IER2/GMFG/ITGB1 axis, which may be targeted therapeutically in future.

ERP29 regulates the proliferation of endometrial carcinoma via M6A modification

AIMS

Endoplasmic reticulum protein 29 (ERP29) is crucial for endoplasmic reticulum stress (ERS). M6A plays an important role in the progression of endometrial cancer (EC). The study investigated the role of ERS-related gene (ERP29) and m6A in EC.

MATERIALS AND METHODS

We screened ERS-related genes based on the GEO dataset, GSEA dataset and TCGA-UCEC database using WGCNA and two machine learning algorithms. The m6A-related GEO dataset was employed to identify the ERS-related hub genes with m6A. Expression of hub genes in different cell types were visualize through scRNA-seq data analyzing. Using qPCR, Western blot, and Immunohistochemical assays to detect the expression of ERP29, the effect of ERP29 on cancer cell proliferation was investigated through CCK8, EdU and clone formation experiments. M6A modifications were studied using m6A Dot blot and MeRIP-qPCR. Finally, we conducted rescue experiments.

KEY FINDINGS

Ten ERS-related hub genes with m6A were identified. ERP29 is highly expressed in EC. ERP29 knockdown inhibits EC cell proliferation. METTL3 overexpression increases the ERP29 mRNA m6A and decreases the expression of ERP29. Cycloleucine (Cyc), a nucleic acid methylation inhibitor, treatment reduces ERP29 mRNA m6A and increases the expression of ERP29. Cyc rescue the low expression of ERP29 caused by overexpression of METTL3 through m6A. ERP29 knockdown rescued the increased proliferation of EC cells caused by low m6A.

SIGNIFICANCE

ERP29 is highly expressed in EC. m6A regulates ERP29 expression and affects the proliferation of endometrial cancer cells. This represents the premise for applying ERP29 and m6A modifications in diagnosing and treating EC.

Endoplasmic reticulum stress in abdominal aortic aneurysm

Abdominal aortic aneurysms (AAAs) are characterized by permanent dilatation of the abdominal aorta, which is accompanied by inflammation, degradation of the extracellular matrix (ECM) and disruption of vascular smooth muscle cell (VSMC) homeostasis. Endoplasmic reticulum (ER) stress is involved in the regulation of inflammation, oxidative stress and VSMC apoptosis, all of which are critical factors in AAA development. Although several studies have revealed the occurrence of ER stress in AAA development, the specific biological functions of ER stress in AAA development remain largely unknown. Given that targeting ER stress is a promising strategy for treating AAAs, further investigation of the physiological and pathological roles of ER stress in AAA development is warranted.

A novel gene signature based on endoplasmic reticulum stress for predicting prognosis in hepatocellular carcinoma

Background

Hepatocellular carcinoma (HCC) remains one of the most common human cancers, the death cases induced by HCC are increasing these years. Endoplasmic reticulum stress (ERS) occurs when misfolded proteins cannot be disposed of properly. It is reported that ERS plays a crucial role in the pathogenesis of human malignant tumors. The aim of this study is to construct a novel gene signature based on ERS for predicting prognosis in HCC.

Methods

The data of HCC patients were downloaded from public databases. The Cox regression analysis and least absolute shrinkage and selection operator (LASSO) regression analysis were performed to construct ERS-related gene signature. The cases were divided into high- and low-risk groups based on the ERS-related gene signature in The Cancer Genome Atlas (TCGA) cohort. Subsequently, the differences in messenger ribonucleic acid (mRNA) expression patterns, immune status, tumor mutation burden (TMB) and copy number variants (CNV) were investigated between high- and low-risk groups. Then, a predictive nomogram according to the ERS-related gene signature and clinicopathological variables was established. At last, we explored the biological functions of TMX1 which had the biggest coefficient and we investigated the effect of BRSK2 on apoptosis in HCC.

Results

In our study, a 9-gene ERS-related gene signature was constructed. The results showed that patients in the low-risk group had a better prognosis than the high-risk group patients. The results of receiver operating characteristic (ROC) curves revealed that the area under the curve (AUC) was 0.784 at 1 year, 0.780 at 2 years, 0.793 at 3 years in the training set. While in validation cohort, this index was 0.694 at 1 year, 0.622 at 2 years, 0.613 at 3 years respectively. The analysis of immune status revealed an immunosuppressive microenvironment in the high-risk group. The analysis of TMB and CNV revealed that the high-risk group patients had a higher genomic mutation frequency. In Univariate Cox regression analysis, the hazard ratio of RiskScore was 2.718 [95% confidence interval (CI): 2.173-3.399]. In Multivariate Cox regression analysis, the hazard ratio of RiskScore was 2.422 (95% CI: 1.805-3.25). Then, we established a nomogram according to the RiskScore and Eastern Cooperative Oncology Group performance status. The AUCs of the nomogram were 0.851 at 1 year, 0.860 at 2 years, and 0.866 at 3 years. At last, we found that TMX1 knockdown can inhibit the proliferation and migration of Huh7 and HepG2 cells. In addition, BRSK2 knockdown could promote the apoptosis induced by ERS.

Conclusions

In our study, a novel ERS-related gene signature was constructed to predict the prognosis of HCC patients. In addition, TMX1 and BRSK2 could promote the progression of HCC. This study may provide a new understanding for HCC.

The Proteostasis Network is a Therapeutic Target in Acute Myeloid Leukemia

Oncogenic growth places great strain and dependence on the proteostasis network. This has made proteostasis pathways attractive therapeutic targets in cancer, but efforts to drug these pathways have yielded disappointing clinical outcomes. One exception is proteasome inhibitors, which are approved for frontline treatment of multiple myeloma. However, proteasome inhibitors are largely ineffective for treatment of other cancers, including acute myeloid leukemia (AML), although reasons for these differences are unknown. Here, we determined that proteasome inhibitors are ineffective in AML due to inability to disrupt proteostasis. In response to proteasome inhibition, AML cells activated HSF1 and autophagy, two key stem cell proteostasis pathways, to prevent unfolded protein accumulation. Inactivation of HSF1 sensitized human AML cells to proteasome inhibition, marked by unfolded protein accumulation, activation of the PERK-mediated integrated stress response, severe reductions in protein synthesis, proliferation and cell survival, and significant slowing of disease progression and extension of survival in vivo . Similarly, combined autophagy and proteasome inhibition suppressed proliferation, synergistically killed AML cells, and significantly reduced AML burden and extended survival in vivo . Furthermore, autophagy and proteasome inhibition preferentially suppressed protein synthesis and induced apoptosis in primary patient AML cells, including AML stem/progenitor cells, without severely affecting normal hematopoietic stem/progenitor cells. Combined autophagy and proteasome inhibition also activated the integrated stress response, but surprisingly this occurred in a PKR-dependent manner. These studies unravel how proteostasis pathways are co-opted to promote AML growth, progression and drug resistance, and reveal that disabling the proteostasis network is a promising strategy to therapeutically target AML.