Novel mechanism of anti-apoptotic function of 78-kDa glucose-regulated protein (GRP78): endocrine resistance factor in breast cancer, through release of B-cell lymphoma 2 (BCL-2) from BCL-2-interacting killer (BIK)

Targeting PAK4 reverses cisplatin resistance in NSCLC by modulating ER stress

Chemoresistance poses a significant impediment to effective treatments for non-small-cell lung cancer (NSCLC). P21-activated kinase 4 (PAK4) has been implicated in NSCLC progression by invasion and migration. However, the involvement of PAK4 in cisplatin resistance is not clear. Here, we presented a comprehensive investigation into the involvement of PAK4 in cisplatin resistance within NSCLC. Our study revealed enhanced PAK4 expression in both cisplatin-resistant NSCLC tumors and cell lines. Notably, PAK4 silencing led to a remarkable enhancement in the chemosensitivity of cisplatin-resistant NSCLC cells. Cisplatin evoked endoplasmic reticulum stress in NSCLC. Furthermore, inhibition of PAK4 demonstrated the potential to sensitize resistant tumor cells through modulating endoplasmic reticulum stress. Mechanistically, we unveiled that the suppression of the MEK1-GRP78 signaling pathway results in the sensitization of NSCLC cells to cisplatin after PAK4 knockdown. Our findings establish PAK4 as a promising therapeutic target for addressing chemoresistance in NSCLC, potentially opening new avenues for enhancing treatment efficacy and patient outcomes.

GRP78 improves the therapeutic effect of mesenchymal stem cells on hemorrhagic shock-induced liver injury: Involvement of the NF-кB and HO-1/Nrf-2 pathways

Mesenchymal stem cells (MSCs) are a popular cell source for repairing the liver. Improving the survival rate and colonization time of MSCs may significantly improve the therapeutic outcomes of MSCs. Studies showed that 78-kDa glucose-regulated protein (GRP78) expression improves cell viability and migration. This study aims to examine whether GRP78 overexpression improves the efficacy of rat bone marrow-derived MSCs (rBMSCs) in HS-induced liver damage. Bone marrow was isolated from the femurs and tibias of rats. rBMSCs were transfected with a GFP-labeled GRP78 expression vector. Flow cytometry, transwell invasion assay, scratch assay immunoblotting, TUNEL assay, MTT assay, and ELISA were carried out. The results showed that GRP78 overexpression enhanced the migration and invasion of rBMSCs. Moreover, GRP78-overexpressing rBMSCs relieved liver damage, repressed liver oxidative stress, and inhibited apoptosis. We found that overexpression of GRP78 in rBMSCs inhibited activation of the NLRP3 inflammasome, significantly decreased the levels of inflammatory factors, and decreased the expression of CD68. Notably, GRP78 overexpression activated the Nrf-2/HO-1 pathway and inhibited the NF-κB pathway. High expression of GRP78 efficiently enhanced the effect of rBMSC therapy. GRP78 may be a potential target to improve the therapeutic efficacy of BMSCs.

TMEM215 Prevents Endothelial Cell Apoptosis in Vessel Regression by Blunting BIK-Regulated ER-to-Mitochondrial Ca Influx

BACKGROUND

In developmental and pathological tissues, nascent vessel networks generated by angiogenesis require further pruning/regression to delete nonfunctional endothelial cells (ECs) by apoptosis and migration. Mechanisms underlying EC apoptosis during vessel pruning remain elusive. TMEM215 (transmembrane protein 215) is an endoplasmic reticulum-located, 2-pass transmembrane protein. We have previously demonstrated that TMEM215 knockdown in ECs leads to cell death, but its physiological function and mechanism are unclear.

METHODS

We characterized the role and mechanism of TMEM215 in EC apoptosis using human umbilical vein endothelial cells by identifying its interacting proteins with immunoprecipitation-mass spectrometry. The physiological function of TMEM215 in ECs was assessed by establishing a conditional knockout mouse strain. The role of TMEM215 in pathological angiogenesis was evaluated by tumor and choroidal neovascularization models. We also tried to evaluate its translational value by delivering a Tmem215 small interfering RNA (siRNA) using nanoparticles in vivo.

RESULTS

TMEM215 knockdown in ECs induced apoptotic cell death. We identified the chaperone BiP as a binding partner of TMEM215, and TMEM215 forms a complex with and facilitates the interaction of BiP (binding immunoglobin protein) with the BH (BCL-2 [B-cell lymphoma 2] homology) 3-only proapoptotic protein BIK (BCL-2 interacting killer). TMEM215 knockdown triggered apoptosis in a BIK-dependent way and was abrogated by BCL-2. Notably, TMEM215 knockdown increased the number and diminished the distance of mitochondria-associated endoplasmic reticulum membranes and increased mitochondrial calcium influx. Inhibiting mitochondrial calcium influx by blocking the IP3R (inositol 1,4,5-trisphosphate receptor) or MCU (mitochondrial calcium uniporter) abrogated TMEM215 knockdown-induced apoptosis. TMEM215 expression in ECs was induced by physiological laminar shear stress via EZH2 downregulation. In EC-specific Tmem215 knockout mice, induced Tmem215 depletion impaired the regression of retinal vasculature characterized by reduced vessel density, increased empty basement membrane sleeves, and increased EC apoptosis. Moreover, EC-specific Tmem215 ablation inhibited tumor growth with disrupted vasculature. However, Tmem215 ablation in adult mice attenuated lung metastasis, consistent with reduced Vcam1 expression. Administration of nanoparticles carrying Tmem215 siRNA also inhibited tumor growth and choroidal neovascularization injury.

CONCLUSIONS

TMEM215, which is induced by blood flow-derived shear stress via downregulating EZH2, protects ECs from BIK-triggered mitochondrial apoptosis mediated by calcium influx through mitochondria-associated ER membranes during vessel pruning, thus providing a novel target for antiangiogenic therapy.

Introduction of a new recombinant vaccine based on GRP78 for breast cancer immunotherapy and evaluation in a mouse model

Introduction

Breast cancer is one of the most prevalent malignancies in women. Several treatment options are available today, including surgery, chemotherapy, and radiotherapy. Immunotherapy, as a highly specific therapy, involves adaptive immune responses and immunological memory. In our present research, we used the recombinant C-terminal domain of the GRP78 (glucose- regulated protein 78) protein to induce an immune response and investigate its therapeutic impact in the 4T1 breast cancer model.

Methods

BALB/c mice were immunized with the cGRP78 protein. The humoral immune response was assessed by ELISA. Then, BALB/c mice were injected subcutaneously with 1×106 4T1 tumor cells. Subsequently, tumor size and survival rate measurements, MTT, and cytokine assays were performed.

Results

The animals receiving the cGRP78 vaccine showed significantly more favorable survival and slower tumor growth rates compared with unvaccinated tumor-bearing mice as the negative control mice. Circulating levels of tumoricidal cytokines such as IFNγ were higher, whereas tolerogenic cytokines such as IL-2, 6, and 10 either did not increase or had a decreasing trend in mice receiving cGRP78.

Conclusion

cGRP78 vaccines generated potent immunotherapeutic effects in a breast cancer mouse model. This novel strategy of targeting the GRP78 protein can promote the development of cancer vaccines and immunotherapies for breast cancer malignancies.

The unfolded protein response (UPR) pathway: the unsung hero in breast cancer management

Tumor cells always have the need to produce an increased amount of proteins in the cells. This elevated amount of proteins increases the pressure on the organelles of the cell such as the endoplasmic reticulum and compels it to increase its protein folding efficiency. However, it is by a matter of fact, that the amount of proteins synthesized outweighs the protein folding capacity of the ER which in turn switches on the UPR pathway by activating the three major molecular sensors and other signaling cascades, which helps in cell survival instead of instant death. However, if this pathway is active for a prolonged period of time the tumor cells heads toward apoptosis. Again, interestingly this is not the same as in case of non- tumorogenic cells. This exhibit a straight natural pathway for tumor cells-specific destruction which has a great implication in today's world where hormone therapies and chemo-therapies are non-effective for various types of breast cancer, a major type being Triple Negative Breast Cancer. Thus a detailed elucidation of the molecular involvement of the UPR pathway in breast cancer may open new avenues for management and attract novel chemotherapeutic targets providing better hopes to patients worldwide.

Regulation of Bcl-2 Family Proteins in Estrogen Receptor-Positive Breast Cancer and Their Implications in Endocrine Therapy

Estrogen receptor (ER)-positive breast cancer accounts for around two-thirds of breast cancer occurrences, with endocrine therapy serving as first-line therapy in most cases. Targeting estrogen signaling pathways, which play a central role in regulating ER+ breast cell proliferation and survival, has proven to improve patient outcomes. However, despite the undeniable advantages of endocrine therapy, a subset of breast cancer patients develop acquired or intrinsic resistance to ER-targeting agents, limiting their efficacy. The activation of downstream ER signaling pathways upregulates pro-survival mechanisms that have been shown to influence the response of cells to endocrine therapy. The Bcl-2 family proteins play a central role in cell death regulation and have been shown to contribute to endocrine therapy resistance, supporting the survival of breast cancer cells and enhancing cell death evasion. Due to the overexpression of anti-apoptotic Bcl-2 proteins in ER-positive breast cancer, the role of these proteins as potential targets in hormone-responsive breast cancer is growing in interest. In particular, recent advances in the development of BH3 mimetics have enabled their evaluation in preclinical studies with ER+ breast cancer models, and BH3 mimetics have entered early ER+ breast cancer clinical trials. This review summarizes the molecular mechanisms underlying the regulation of Bcl-2 family proteins in ER+ breast cancer. Furthermore, an overview of recent advances in research regarding the efficacy of BH3 mimetics in ER+ breast cancer has been provided.

Down-regulating GRP78 reverses pirarubicin resistance of triple negative breast cancer by miR-495-3p mimics and involves the p-AKT/mTOR pathway

Due to the lack of known therapeutic targets for triple-negative breast cancer (TNBC), chemotherapy is the only available pharmacological treatment. Pirarubicin (tetrahydropyranyl Adriamycin, THP) is the most commonly used anthracycline chemotherapy agent. However, TNBC has a high recurrence rate after chemotherapy, and the mechanisms of chemoresistance and recurrence are not entirely understood. To study the chemoresistance mechanisms, we first screened compounds on a pirarubicin-resistant cell line (MDA-MB-231R) derived from MDA-MB-231. The drug resistance index of MDA-MB-231R cells was approximately five times higher than that of MDA-MB-231 cells. MDA-MB-231R cells have higher GRP78 and lower miR-495-3p expression levels than MDA-MB-231 cells. Transfecting MDA-MB-231R cells with a siGRP78 plasmid reduced GRP78 expression, which restored pirarubicin sensitivity. Besides, transfecting MDA-MB-231R cells with miR-495-3p mimics increased miR-495-3p expression, which also reversed pirarubicin chemoresistance. Cell counting kit-8 (CCK-8), EdU, wound healing, and Transwell assays showed that the miR-495-3p mimics also inhibited cell proliferation and migration. Based on our results, miR-495-3p mimics could down-regulate GRP78 expression via the p-AKT/mTOR signaling pathway in TNBC cells. Remarkably, chemo-resistant and chemo-sensitive TNBC tissues had opposite trends in GRP78 and miR-495-3p expressions. The lower the GRP78 and the higher the miR-495-3p expression, the better prognosis in TNBC patients. Therefore, the mechanism of pirarubicin resistance might involve the miR-495-3p/GRP78/Akt axis, which would provide a possible strategy for treating TNBC.

Proteomic Research on the Antitumor Properties of Medicinal Mushrooms

Medicinal mushrooms are increasingly being recognized as an important therapeutic modality in complementary oncology. Until now, more than 800 mushroom species have been known to possess significant pharmacological properties, of which antitumor and immunomodulatory properties have been the most researched. Besides a number of medicinal mushroom preparations being used as dietary supplements and nutraceuticals, several isolates from mushrooms have been used as official antitumor drugs in clinical settings for several decades. Various proteomic approaches allow for the identification of a large number of differentially regulated proteins serendipitously, thereby providing an important platform for a discovery of new potential therapeutic targets and approaches as well as biomarkers of malignant disease. This review is focused on the current state of proteomic research into antitumor mechanisms of some of the most researched medicinal mushroom species, including Phellinus linteus, Ganoderma lucidum, Auricularia auricula, Agrocybe aegerita, Grifola frondosa, and Lentinus edodes, as whole body extracts or various isolates, as well as of complex extract mixtures.

Endoplasmic Reticulum Chaperones in Viral Infection: Therapeutic Perspectives

Viruses are intracellular parasites that subvert the functions of their host cells to accomplish their infection cycle. The endoplasmic reticulum (ER)-residing chaperone proteins are central for the achievement of different steps of the viral cycle, from entry and replication to assembly and exit. The most abundant ER chaperones are GRP78 (78-kDa glucose-regulated protein), GRP94 (94-kDa glucose-regulated protein), the carbohydrate or lectin-like chaperones calnexin (CNX) and calreticulin (CRT), the protein disulfide isomerases (PDIs), and the DNAJ chaperones. This review will focus on the pleiotropic roles of ER chaperones during viral infection. We will cover their essential role in the folding and quality control of viral proteins, notably viral glycoproteins which play a major role in host cell infection. We will also describe how viruses co-opt ER chaperones at various steps of their infectious cycle but also in order to evade immune responses and avoid apoptosis. Finally, we will discuss the different molecules targeting these chaperones and the perspectives in the development of broad-spectrum antiviral drugs.

Apoptosis Deregulation and the Development of Cancer Multi-Drug Resistance

Simple Summary

Despite recent therapeutic advances against cancer, many patients do not respond well or respond poorly, to treatment and develop resistance to more than one anti-cancer drug, a term called multi-drug resistance (MDR). One of the main factors that contribute to MDR is the deregulation of apoptosis or programmed cell death. Herein, we describe the major apoptotic pathways and discuss how pro-apoptotic and anti-apoptotic proteins are modified in cancer cells to convey drug resistance. We also focus on our current understanding related to the interactions between survival and cell death pathways, as well as on mechanisms underlying the balance shift towards cancer cell growth and drug resistance. Moreover, we highlight the role of the tumor microenvironment components in blocking apoptosis in MDR tumors, and we discuss the significance and potential exploitation of epigenetic modifications for cancer treatment. Finally, we summarize the current and future therapeutic approaches for overcoming MDR.

Abstract

The ability of tumor cells to evade apoptosis is established as one of the hallmarks of cancer. The deregulation of apoptotic pathways conveys a survival advantage enabling cancer cells to develop multi-drug resistance (MDR), a complex tumor phenotype referring to concurrent resistance toward agents with different function and/or structure. Proteins implicated in the intrinsic pathway of apoptosis, including the Bcl-2 superfamily and Inhibitors of Apoptosis (IAP) family members, as well as their regulator, tumor suppressor p53, have been implicated in the development of MDR in many cancer types. The PI₃K/AKT pathway is pivotal in promoting survival and proliferation and is often overactive in MDR tumors. In addition, the tumor microenvironment, particularly factors secreted by cancer-associated fibroblasts, can inhibit apoptosis in cancer cells and reduce the effectiveness of different anti-cancer drugs. In this review, we describe the main alterations that occur in apoptosis-and related pathways to promote MDR. We also summarize the main therapeutic approaches against resistant tumors, including agents targeting Bcl-2 family members, small molecule inhibitors against IAPs or AKT and agents of natural origin that may be used as monotherapy or in combination with conventional therapeutics. Finally, we highlight the potential of therapeutic exploitation of epigenetic modifications to reverse the MDR phenotype.

Protein profile of MCF-7 breast cancer cell line treated with lectin delivered by CaCO3NPs revealed changes in molecular chaperones, cytoskeleton, and membrane-associated proteins

The second most predominant cancer in the world and the first among women is breast cancer. We aimed to study the protein abundance profiles induced by lectin purified from the Agaricus bisporus mushroom (ABL) and conjugated with CaCO₃NPs in the MCF-7 breast cancer cell line. Two-dimensional electrophoresis (2-DE) and orbitrap mass spectrometry techniques were used to reveal the protein abundance pattern induced by lectin. Flow cytometric analysis showed the accumulation of ABL-CaCO₃NPs treated cells in the G1 phase than the positive control. Thirteen proteins were found different in their abundance in breast cancer cells after 24 h exposure to lectin conjugated with CaCO₃NPs. Most of the identified proteins were showing a low abundance in ABL-CaCO₃NPs treated cells in comparison to the positive and negative controls, including V-set and immunoglobulin domain, serum albumin, actin cytoplasmic 1, triosephosphate isomerase, tropomyosin alpha-4 chain, and endoplasmic reticulum chaperone BiP. Hornerin, tropomyosin alpha-1 chain, annexin A2, and protein disulfide-isomerase were up-regulated in comparison to the positive. Bioinformatic analyses revealed the regulation changes of these proteins mainly affected the pathways of 'Bcl-2-associated athanogene 2 signalling pathway', 'Unfolded protein response', 'Caveolar-mediated endocytosis signalling', 'Clathrin-mediated endocytosis signalling', 'Calcium signalling' and 'Sucrose degradation V', which are associated with breast cancer. We concluded that lectin altered the abundance in molecular chaperones/heat shock proteins, cytoskeletal, and metabolic proteins. Additionally, lectin induced a low abundance of MCF-7 cancer cell proteins in comparison to the positive and negative controls, including; V-set and immunoglobulin domain, serum albumin, actin cytoplasmic 1, triosephosphate isomerase, tropomyosin alpha-4 chain, and endoplasmic reticulum chaperone BiP.

SOX2OT Long Noncoding RNA Is Regulated by the UPR in Oestrogen Receptor-Positive Breast Cancer

Endoplasmic reticulum (ENR) stress perturbs cell homeostasis and induces the unfolded protein response (UPR). In breast cancer, this process is activated by oestrogen deprivation and is associated with tamoxifen resistance. We present evidence that the transcription factor SOX2 and the long noncoding RNA SOX2 overlapping transcript (SOX2OT) are upregulated in oestrogen receptor-positive (ER+) breast cancer and in response to oestrogen deprivation. We examined the effect of the UPR on SOX2 and SOX2OT expression and the effect of SOX2OT on UPR pathways in breast cancer cell lines. The induction of the UPR by thapsigargin or glucose deprivation upregulates SOX2OT expression. This upregulation is also shown with the anti-oestrogen 4OH-tamoxifen and mTOR inhibitor everolimus in ER + breast cancer cells that are sensitive to oestrogen deprivation or everolimus treatment. SOX2OT overexpression decreased BiP and PERK expression. This effect of SOX2OT overexpression was confirmed on BiP and PERK pathway by q-PCR. Our results show that a long noncoding RNA regulates the UPR and evince a new function of SOX2OT as a participant of ENR stress reprogramming of breast cancer cells.

Altered glycolysis results in drug-resistant in clinical tumor therapy

Cancer cells undergo metabolic reprogramming, including increased glucose metabolism, fatty acid synthesis and glutamine metabolic rates. These enhancements to three major metabolic pathways are closely associated with glycolysis, which is considered the central component of cancer cell metabolism. Increasing evidence suggests that dysfunctional glycolysis is commonly associated with drug resistance in cancer treatment, and aberrant glycolysis plays a significant role in drug-resistant cancer cells. Studies on the development of drugs targeting these abnormalities have led to improvements in the efficacy of tumor treatment. The present review discusses the changes in glycolysis targets that cause drug resistance in cancer cells, including hexokinase, pyruvate kinase, pyruvate dehydrogenase complex, glucose transporters, and lactate, as well the underlying molecular mechanisms and corresponding novel therapeutic strategies. In addition, the association between increased oxidative phosphorylation and drug resistance is introduced, which is caused by metabolic plasticity. Given that aberrant glycolysis has been identified as a common metabolic feature of drug-resistant tumor cells, targeting glycolysis may be a novel strategy to develop new drugs to benefit patients with drug-resistance.

BIK and GRP78 protein expression as possible markers of response to preoperative chemotherapy and survival in breast cancer

OBJECTIVE

BIK and GRP78 have shown differential expression profiles in breast cancer (BC) tissue, in addition to its important participation in the pathophysiology of cancer. The purpose of this study was to evaluate the association of BIK and GRP78 protein expression with clinical and pathologic response to preoperative chemotherapy, recurrence, disease-free survival (DFS) and overall survival (OS), in patients with BC.

MATERIAL AND METHODS

Fifty-three patients who received preoperative chemotherapy where included in an observational, analytical and retrospective study to assess the BIK and GRP78 protein expression by immunohistochemistry in microarrays of BC tissue obtained before treatment. Associations between BIK and GRP78 expression with clinicopathological characteristics, clinical and pathologic response to preoperative chemotherapy, and recurrence were analyzed using Chi-square or Fisher's exact test. OS and postoperative DFS were assessed at 5-year follow-up by Kaplan-Meir curves, and the difference according to BIK and GRP78 expression was evaluated using the log-rank test. Bivariate analysis was performed using Cox risk proportion model. A p value < 0.05 was considered to be statistically significant.

RESULTS

BIK and GRP78 staining revealed positive expression in 37 (71.2%) and 35 patients (72.9%) respectively. Association between pathological complete response (pCR) and positive expression of BIK (p = 0.046), as well as between clinical complete response (cCR) and negative expression of GRP78 was observed (p = 0.048). Patients with expression of GRP78 had lower DFS (HR = 3.46; 95% CI 1.01-11.80; p = 0.047) and shorter OS (HR = 3.49; 95% CI 1.04 a 11.72; p = 0.043).

CONCLUSION

When finding association of GRP78 and BIK protein expression with the response (clinical and pathologic respectively) to preoperative chemotherapy, and GRP78 with DFS and OS, in patients with BC, our results suggest a potential prognostic value of both proteins; however, a larger sample size is required to confirm this.

Mining prognostic markers of Asian hepatocellular carcinoma patients based on the apoptosis-related genes

Background

Apoptosis-related genes(Args)play an essential role in the occurrence and progression of hepatocellular carcinoma(HCC). However, few studies have focused on the prognostic significance of Args in HCC. In the study, we aim to explore an efficient prognostic model of Asian HCC patients based on the Args.

Methods

We downloaded mRNA expression profiles and corresponding clinical data of Asian HCC patients from The Cancer Genome Atlas (TCGA) and International Cancer Genome Consortium (ICGC) databases. The Args were collected from Deathbase, a database related to cell death, combined with the research results of GeneCards、National Center for Biotechnology Information (NCBI) databases and a lot of literature. We used Wilcoxon-test and univariate Cox analysis to screen the differential expressed genes (DEGs) and the prognostic related genes (PRGs) of HCC. The intersection genes of DEGs and PGGs were seen as crucial Args of HCC. The prognostic model of Asian HCC patients was constructed by least absolute shrinkage and selection operator (lasso)- proportional hazards model (Cox) regression analysis. Kaplan-Meier curve, Principal Component Analysis (PCA) analysis, t-distributed Stochastic Neighbor Embedding (t-SNE) analysis, risk score curve, receiver operating characteristic (ROC) curve, and the HCC data of ICGC database and the data of Asian HCC patients of Kaplan-Meier plotter database were used to verify the model.

Results

A total of 20 of 56 Args were differentially expressed between HCC and adjacent normal tissues (p < 0.05). Univariate Cox regression analysis showed that 10 of 56 Args were associated with survival time and survival status of HCC patients (p < 0.05). There are seven overlapping genes of these 20 and 10 genes, including BAK1, BAX, BNIP3, CRADD, CSE1L, FAS, and SH3GLB1. Through Lasso-Cox analysis, an HCC prognostic model composed of BAK1, BNIP3, CSE1L, and FAS was constructed. Kaplan-Meier curve, PCA, t-SNE analysis, risk score curve, ROC curve, and secondary verification of ICGC database and Kaplan-Meier plotter database all support the reliability of the model.

Conclusions

Lasso-Cox regression analysis identified a 4-gene prognostic model, which integrates clinical and gene expression and has a good effect. The expression of Args is related to the prognosis of HCC patients, but the specific mechanism remains to be further verified.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-07886-6.

The role of MET in chemotherapy resistance

Chemotherapy remains the mainstay of treatment in the majority of solid and haematological malignancies. Resistance to cytotoxic chemotherapy is a major clinical problem and substantial research is ongoing into potential methods of overcoming this resistance. One major target, the receptor tyrosine kinase MET, has generated increasing interest with multiple clinical trials in progress. Overexpression of MET is frequently observed in a range of different cancers and is associated with poor prognosis. Studies have shown that MET promotes resistance to targeted therapies, including those targeting EGFR, BRAF and MEK. More recently, several reports suggest that MET also contributes to cytotoxic chemotherapy resistance. Here we review the preclinical evidence of MET's role in chemotherapy resistance, the mechanisms by which this resistance is mediated and the translational relevance of MET inhibitor therapy for patients with chemotherapy resistant disease.

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.

Glucose-regulated protein 78 (GRP78) as a potential novel biomarker and therapeutic target in multiple myeloma

INTRODUCTION

Glucose-regulated protein 78 (GRP78) is a stress-inducible molecular chaperone expressed within the endoplasmic reticulum where it acts as a master regulator of the unfolded protein response (UPR) pathway. At times of ER stress, activation of the UPR, a multimolecular pathway, limits proteotoxicity induced by misfolded proteins. In malignancies, including multiple myeloma which is characterized by an accumulation of misfolded immunoglobulins, GRP78 expression is increased, with notable translocation of GRP78 to the cell surface. Studies suggest cell-surface GRP78 (csGRP78) to be of prognostic significance with emerging evidence that it interacts with a myriad of co-ligands to activate signaling pathways promoting cell proliferation and survival or apoptosis.

AREAS COVERED

This review focuses on the role of ER and csGRP78 in physiology and oncogenesis in multiple myeloma, addressing factors that shift the balance in GRP78 signaling from survival to apoptosis. The role of GRP78 as a potential prognostic biomarker is explored and current therapeutics in development aimed at targeting csGRP78 are addressed. We conducted a PubMed literature search using the keywords 'GRP78,' 'multiple myeloma' reviewing studies prior to 2020.

EXPERT OPINION

Cell-surface GRP78 expression is a potential novel prognostic biomarker in myeloma and targeting of csGRP78 is promising and requires further investigation.

Atf6α impacts cell number by influencing survival, death and proliferation

Background

A growing body of literature suggests the cell–intrinsic activity of Atf6α during ER stress responses has implications for tissue cell number during growth and development, as well as in adult biology and tumorigenesis [1]. This concept is important, linking the cellular processes of secretory protein synthesis and endoplasmic reticulum stress response with functional tissue capacity and organ size. However, the field contains conflicting observations, especially notable in secretory cell types like the pancreatic beta cell.

Scope of review

Here we summarize current knowledge of the basic biology of Atf6α, along with the pleiotropic roles Atf6α plays in cell life and death decisions and possible explanations for conflicting observations. We include studies investigating the roles of Atf6α in cell survival, death and proliferation using well-controlled methodology and specific validated outcome measures, with a focus on endocrine and metabolic tissues when information was available.

Major conclusions

The net outcome of Atf6α on cell survival and cell death depends on cell type and growth conditions, the presence and degree of ER stress, and the duration and intensity of Atf6α activation. It is unquestioned that Atf6α activity influences the cell fate decision between survival and death, although opposite directions of this outcome are reported in different contexts. Atf6α can also trigger cell cycle activity to expand tissue cell number through proliferation. Much work remains to be done to clarify the many gaps in understanding in this important emerging field.

The Effect of Chinese Traditional Medicine Huaiqihuang (HQH) on the Protection of Nephropathy

Kidney disease is one of the common diseases with high morbidity and high mortality, which brings a huge burden to the society and the patient's family. The pathogenesis, treatment, and prognosis of kidney diseases are related to oxidative stress, inflammation, mitochondrial damage, and immune dysfunction. However, existing treatments always cause some damage to the kidneys. Kidney disease and immunosuppressant used together often lead to drug toxicity, patients with weakened immunity, organic rupture of the normal structure of the kidney, damage to the physiological function of the kidney, etc. Huaiqihuang is a kind of traditional Chinese medicine with a history of more than one thousand years. According to research, Robinia pseudoacacia can regulate the immune function by regulating oxidative stress, calcium inflow, and mitochondrial ATP. At the same time, it is also involved in regulating the ways of cell death, such as apoptosis, autophagy, ferroptosis, pyroptosis, and clockophagy, to reduce kidney damage, which has important clinical value. This article reviews the exact mechanism and clinical application of Huaiqihuang in different types of nephropathy. The aim is to provide new ideas for the treatment of clinical nephropathy.

BIK drives an aggressive breast cancer phenotype through sublethal apoptosis and predicts poor prognosis of ER-positive breast cancer

Apoptosis is fundamental to normal animal development and is the target for many anticancer therapies. Recent studies have explored the consequences of "failed apoptosis" where the apoptotic program is initiated but does not go to completion and does not cause cell death. Nevertheless, this failed apoptosis induces DNA double-strand breaks generating mutations that facilitate tumorigenesis. Whether failed apoptosis is relevant to clinical disease is unknown. BCL-2 interacting killer (BIK) is a stress-induced BH3-only protein that stimulates apoptosis in response to hormone and growth factor deprivation, hypoxia, and genomic stress. It was unclear whether BIK promotes or suppresses tumor survival within the context of breast cancer. We investigated this and show that BIK induces failed apoptosis with limited caspase activation and genomic damage in the absence of extensive cell death. Surviving cells acquire aggressive phenotypes characterized by enrichment of cancer stem-like cells, increased motility and increased clonogenic survival. Furthermore, by examining six independent cohorts of patients (total n = 969), we discovered that high BIK mRNA and protein levels predicted clinical relapse of Estrogen receptor (ER)-positive cancers, which account for almost 70% of all breast cancers diagnosed but had no predictive value for hormone receptor-negative (triple-negative) patients. Thus, this study identifies BIK as a biomarker for tumor recurrence of ER-positive patients and provides a potential mechanism whereby failed apoptosis contributes to cancer aggression.

Isolation and characterization of a novel nanobody for detection of GRP78 expressing cancer cells

Glucose-regulated protein 78 (GRP78) is an endoplasmic reticulum (ER) chaperone that has been shown that is overexpressed in cancer cells. Overexpression of GRP78 on cancer cells makes this molecule a suitable candidate for cancer detection and targeted therapy. VHH is the binding fragment of camelid heavy-chain antibodies also known as "nanobody." The aim of this study is to isolate and produce a new recombinant nanobody using phage display technique to detect cancer cells. Using the c-terminal domain of GRP78 (CGRP) as an antigen, four rounds of biopanning were performed, and high-affinity binders were selected by ELISA. Their affinity and functionality were characterized by surface plasmon resonance (SPR) cell ELISA and immunocytochemistry. A unique nanobody named V80 was purified. ELISA and SPR showed that this antibody had high specificity and affinity to the GRP78. Immunofluorescence analysis showed that V80 could specifically bind to the HepG2 and A549 cancer cell lines. This novel recombinant nanobody could bind to the cell surface of different cancer cells. After further evaluation, this nanobody can be used as a new tool for cancer detection and tumor therapy.

SOX2OT Long Noncoding RNA Is Regulated by the UPR in Oestrogen Receptor-Positive Breast Cancer

Endoplasmic reticulum (ER) stress perturbs cell homeostasis and induces the unfolded protein response (UPR). In breast cancer, this process is activated by oestrogen deprivation and is associated with tamoxifen resistance. We present evidence that the transcription factor SOX2 and the long noncoding RNA SOX2 overlapping transcript (SOX2OT) are up-regulated in oestrogen receptor-positive (ER+) breast cancer and in response to oestrogen deprivation. We examined the effect of the UPR on SOX2 and SOX2OT expression, and the effect of SOX2OT on UPR pathways in breast cancer cell lines. The induction of the UPR by thapsigargin or glucose deprivation up-regulates SOX2OT expression. This up-regulation is also shown with the anti-oestrogen 4OH-tamoxifen and mTOR inhibitor everolimus in ER + breast cancer cells that are sensitive to oestrogen deprivation or everolimus treatment. SOX2OT overexpression decreased BiP and PERK expression. This effect of SOX2OT overexpression was confirmed on BiP and PERK pathway by q-PCR. Our results show that a long noncoding RNA regulates the UPR and evince a new function of SOX2OT as a participant of ER stress reprogramming of breast cancer cells.

Alternative Mechanisms of p53 Action During the Unfolded Protein Response

The tumor suppressor protein p53 orchestrates cellular responses to a vast number of stresses, with DNA damage and oncogenic activation being some of the best described. The capacity of p53 to control cellular events such as cell cycle progression, DNA repair, and apoptosis, to mention some, has been mostly linked to its role as a transcription factor. However, how p53 integrates different signaling cascades to promote a particular pathway remains an open question. One way to broaden its capacity to respond to different stimuli is by the expression of isoforms that can modulate the activities of the full-length protein. One of these isoforms is p47 (p53/47, Δ40p53, p53ΔN40), an alternative translation initiation variant whose expression is specifically induced by the PERK kinase during the Unfolded Protein Response (UPR) following Endoplasmic Reticulum stress. Despite the increasing knowledge on the p53 pathway, its activity when the translation machinery is globally suppressed during the UPR remains poorly understood. Here, we focus on the expression of p47 and we propose that the alternative initiation of p53 mRNA translation offers a unique condition-dependent mechanism to differentiate p53 activity to control cell homeostasis during the UPR. We also discuss how the manipulation of these processes may influence cancer cell physiology in light of therapeutic approaches.

β-arrestin-2 enhances intestinal epithelial apoptosis in necrotizing enterocolitis

Apoptosis among intestinal epithelial cells contributes to necrotizing enterocolitis (NEC), a severe intestinal disease that particularly affects premature infants. β-arrestin-2, an important regulator of G-protein-coupled receptors, is expressed in intestinal epithelial cells, where its activation promotes apoptosis. We found that β-arrestin-2 was overexpressed in both human and murine NEC samples. β-arrestin-2-deficient mice were protected from endoplasmic reticulum stress and NEC development. The endoplasmic reticulum-resident chaperone BiP was found to promote intestinal epithelial cell survival. Pretreatment of intestinal epithelial cells or mice with the BiP inhibitor HA15 increased cell apoptosis and promoted NEC development. β-arrestin-2 bound to BiP and promoted its polyubiquitination and degradation, thereby facilitating the release of the pro-apoptotic molecule BIK from BiP. Silencing β-arrestin-2 downregulated apoptosis by increasing BiP levels, which suppressed endoplasmic reticulum stress. This study suggests that β-arrestin-2 induces NEC development by inhibiting BiP, thereby triggering apoptosis in response to endoplasmic reticulum stress. Thus, novel therapeutic strategies to inhibit β-arrestin-2 may enhance the treatment of NEC.

ER stress activation in the intestinal mucosa but not in mesenteric adipose tissue is associated with inflammation in Crohn's disease patients

Chronic/abnormal activation of endoplasmic reticulum (ER) stress is linked to the exacerbation of the inflammatory process and has been recently linked to Crohn’s disease (CD) pathophysiology. We investigated the intestinal mucosa and the mesenteric adipose tissue (MAT) collected from CD patients with active disease (CD group) and from non-IBD patients (CTR group) to study ER stress activation and to address tissue-specific modulation in CD. The intestinal mucosa of CD patients showed an upregulation in the expression of ER stress related genes, including ATF3, DNAJC3, STC2, DDIT3, CALR, HSPA5 and HSP90B1. Results showed that EIF2AK3 gene was upregulated, along with increased protein expression of p-eIF2α and p-eIF2α/eIF2α ratio. Additionally, ERN1 gene expression was upregulated, along with an increased spliced/activated form sXBP1 protein. Despite the upregulation of ATF6 gene expression in the intestinal mucosa of CD patients, no differences were found in ATF6 protein expression. Lastly, the analysis of MAT revealed unchanged levels of ER stress markers along with no differences in the activation of UPR. However, chaperone gene expression was modulated in the MAT of CD patients. To conclude, our results address tissue-specific differences in UPR activation in CD and point the ER stress as an important pro-inflammatory mechanism in CD, specifically in the intestinal mucosa.

Chemotherapy Resistance Explained through Endoplasmic Reticulum Stress-Dependent Signaling

Cancers cells have the ability to develop chemotherapy resistance, which is a persistent problem during cancer treatment. Chemotherapy resistance develops through different molecular mechanisms, which lead to modification of the cancer cells signals needed for cellular proliferation or for stimulating an immune response. The endoplasmic reticulum (ER) is an important organelle involved in protein quality control, by promoting the correct folding of protein and ER-mediated degradation of unfolded or misfolded protein, namely, ER-associated degradation. Disturbances of the normal ER functions causes an accumulation of unfolded or misfolded proteins in the ER lumen, resulting in a condition called “ER stress (ERS).” ERS triggers the unfolded protein response (UPR)—also called the ERS response (ERSR)—to restore homeostasis or activate cell death. Although the ERSR is one emerging potential target for chemotherapeutics to treat cancer, it is also critical for chemotherapeutics resistance, as well. However, the detailed molecular mechanism of the relationship between the ERSR and tumor survival or drug resistance remains to be fully understood. In this review, we aim to describe the most vital molecular mechanism of the relationship between the ERSR and chemotherapy resistance. Moreover, the review also discusses the molecular mechanism of ER stress-mediated apoptosis on cancer treatments.

The Interplay Between Pattern Recognition Receptors and Autophagy in Inflammation

Pattern recognition receptors (PRRs) are sensors of exogenous and endogenous "danger" signals from pathogen-associated molecular patterns (PAMPs), and damage associated molecular patterns (DAMPs), while autophagy can respond to these signals to control homeostasis. Almost all PRRs can induce autophagy directly or indirectly. Toll-like receptors (TLRs), Nod-like receptors (NLRs), retinoic acid-inducible gene-I-like receptors (RLRs), and cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS)-stimulator of interferon genes (STING) pathway can induce autophagy directly through Beclin-1 or LC3-dependent pathway, while the interactions with the receptor for advanced glycation end products (RAGE)/high mobility group box 1 (HMGB1), CD91/Calreticulin, and TLRs/HSPs are achieved by protein, Ca2⁺, and mitochondrial homeostasis. Autophagy presents antigens to PRRs and helps to clean the pathogens. In addition, the induced autophagy can form a negative feedback regulation of PRRs-mediated inflammation in cell/disease-specific manner to maintain homeostasis and prevent excessive inflammation. Understanding the interaction between PRRs and autophagy in a specific disease will promote drug development for immunotherapy. Here, we focus on the interactions between PRRs and autophagy and how they affect the inflammatory response.

ISG15 Promotes ERK1 ISGylation, CD8+ T Cell Activation and Suppresses Ovarian Cancer Progression

Increased number of tumor-infiltrating CD8+ lymphocytes is associated with improved survival in patients with advanced stage high grade serous ovarian cancer (HGSOC) but the underlying molecular mechanism has not been thoroughly explored. Using transcriptome profiling of microdissected HGSOC tissue with high and low CD8+ lymphocyte count and subsequent validation studies, we demonstrated that significantly increased ISG15 (Interferon-stimulated gene 15) expression in HGSOC was associated with high CD8+ lymphocyte count and with the improvement in median overall survival in both univariate and multivariate analyses. Further functional studies showed that endogenous and exogenous ISG15 suppressed ovarian cancer progression through ISGylation of ERK in HGSOC, and activation of NK cells and CD8+ T lymphocytes. These data suggest that the development of treatment strategies based on up-regulating ISG15 in ovarian cancer cells or increased circulating ISG15 in ovarian cancer patients is warranted.

Human Mesenchymal Stem Cell Secretome from Bone Marrow or Adipose-Derived Tissue Sources for Treatment of Hypoxia-Induced Pulmonary Epithelial Injury

Alveolar epithelial dysfunction induced by hypoxic stress plays a significant role in the pathological process of lung ischemia-reperfusion injury (IRI). Mesenchymal stem cell (MSC) therapies have demonstrated efficacy in exerting protective immunomodulatory effects, thereby reducing airway inflammation in several pulmonary diseases. Aim: This study assesses the protective effects of MSC secretome from different cell sources, human bone marrow (BMSC) and adipose tissue (ADSC), in attenuating hypoxia-induced cellular stress and inflammation in pulmonary epithelial cells. Methods: Pulmonary epithelial cells, primary rat alveolar epithelial cells (AEC) and A549 cell line were pre-treated with BMSC, or ADSC conditioned medium (CM) and subjected to hypoxia for 24 h. Results: Both MSC-CM improved cell viability, reduced secretion of pro-inflammatory mediators and enhanced IL-10 anti-inflammatory cytokine production in hypoxic injured primary rat AECs. ADSC-CM reduced hypoxic cellular injury by mechanisms which include: inhibition of p38 MAPK phosphorylation and nuclear translocation of subunits in primary AECs. Both MSC-CM enhanced translocation of Bcl-2 to the nucleus, expression of cytoprotective glucose-regulated proteins (GRP) and restored matrix metalloproteinases (MMP) function, thereby promoting repair and cellular homeostasis, whereas inhibition of GRP chaperones was detrimental to cell survival. Conclusions: Elucidation of the protective mechanisms exerted by the MSC secretome is an essential step for maximizing the therapeutic effects, in addition to developing therapeutic targets-specific strategies for various pulmonary syndromes.

Suppression of stress induction of the 78-kilodalton glucose regulated protein (GRP78) in cancer by IT-139, an anti-tumor ruthenium small molecule inhibitor

In many cancers, combination therapy regimens are successfully improving response and survival rates, but the challenges of toxicity remain. GRP78, the master regulator of the unfolded protein response, is emerging as a target that is upregulated in tumors, specifically following treatment, and one that impacts tumor cell survival and disease recurrence. Here, we show IT-139, an antitumor small molecule inhibitor, suppresses induction of GRP78 from different types of endoplasmic reticulum (ER) stress in a variety of cancer cell lines, including those that have acquired therapeutic resistance, but not in the non-cancer cells being tested. We further determined that IT-139 treatment exacerbates ER stress while at the same time suppresses GRP78 induction at the transcriptional level. Our studies revealed a differential effect of IT-139 on chaperone protein family expression at multiple levels in different cancer cell lines. In xenograft studies, IT-139 decreased BRAF inhibitor upregulation of GRP78 expression in the tumor, while having minimal effect on GRP78 expression in the adjacent normal cells. The preferential decrease in GRP78 levels in tumor cells over normal cells, supported by the manageable safety profile seen in the Phase 1 clinical trial, reinforce the value IT-139 brings to combination therapies as it continues its clinical development.

Endoplasmic Reticulum Chaperone GRP78 Protects Heart From Ischemia/Reperfusion Injury Through Akt Activation

RATIONALE

Restoration of coronary artery blood flow is the most effective means of ameliorating myocardial damage triggered by ischemic heart disease. However, coronary reperfusion elicits an increment of additional injury to the myocardium. Accumulating evidence indicates that the unfolded protein response (UPR) in cardiomyocytes is activated by ischemia/reperfusion (I/R) injury. Xbp1s (spliced X-box binding protein 1), the most highly conserved branch of the unfolded protein response, is protective in response to cardiac I/R injury. GRP78 (78 kDa glucose-regulated protein), a master regulator of the UPR and an Xbp1s target, is upregulated after I/R. However, its role in the protective response of Xbp1s during I/R remains largely undefined.

OBJECTIVE

To elucidate the role of GRP78 in the cardiomyocyte response to I/R using both in vitro and in vivo approaches.

METHODS AND RESULTS

Simulated I/R injury to cultured neonatal rat ventricular myocytes induced apoptotic cell death and strong activation of the UPR and GRP78. Overexpression of GRP78 in neonatal rat ventricular myocytes significantly protected myocytes from I/R-induced cell death. Furthermore, cardiomyocyte-specific overexpression of GRP78 ameliorated I/R damage to the heart in vivo. Exploration of underlying mechanisms revealed that GRP78 mitigates cellular damage by suppressing the accumulation of reactive oxygen species. We go on to show that the GRP78-mediated cytoprotective response involves plasma membrane translocation of GRP78 and interaction with PI3 kinase, culminating in stimulation of Akt. This response is required as inhibition of the Akt pathway significantly blunted the antioxidant activity and cardioprotective effects of GRP78.

CONCLUSIONS

I/R induction of GRP78 in cardiomyocytes stimulates Akt signaling and protects against oxidative stress, which together protect cells from I/R damage.

Proteomic evidences for microcystin-RR-induced toxicological alterations in mice liver

This study deals with the isolation and purification of an important variant of microcystins namely microcystin-RR (MCYST-RR) from Microcystis aeruginosa and reports its effects on mice liver protein profile and cellular functions. Protein profiling by 2-dimensional gel electrophoresis revealed changes in the number and accumulation of protein spots in liver of mice treated with different concentrations of MCYST-RR. Untreated (control) mice liver showed 368 protein spots while the number was 355, 348 and 332 in liver of mice treated with 200, 300 and 400 µg kg body wt⁻¹ of MCYST-RR respectively. Altogether 102, 97, and 92 spots were differentially up-accumulated and 93, 91, and 87 spots were down- accumulated respectively with the treatment of 200, 300, 400 µg kg body wt⁻¹. Eighteen differentially accumulated proteins present in all the four conditions were identified by MALDI-TOF MS. Of these eighteen proteins, 12 appeared to be involved in apoptosis/toxicological manifestations. Pathway analysis by Reactome and PANTHER database also mapped the identified proteins to programmed cell death/apoptosis clade. That MCYST-RR induces apoptosis in liver tissues was also confirmed by DNA fragmentation assay. Results of this study elucidate the proteomic basis for the hepatotoxicity of MCYST-RR which is otherwise poorly understood till date.

Intrinsic apoptotic pathway activation increases response to anti-estrogens in luminal breast cancers

Estrogen receptor-α positive (ERα+) breast cancer accounts for approximately 70–80% of the nearly 25,0000 new cases of breast cancer diagnosed in the US each year. Endocrine-targeted therapies (those that block ERα activity) serve as the first line of treatment in most cases. Despite the proven benefit of endocrine therapies, however, ERα+ breast tumors can develop resistance to endocrine therapy, causing disease progression or relapse, particularly in the metastatic setting. Anti-apoptotic Bcl-2 family proteins enhance breast tumor cell survival, often promoting resistance to targeted therapies, including endocrine therapies. Herein, we investigated whether blockade of anti-apoptotic Bcl-2 family proteins could sensitize luminal breast cancers to anti-estrogen treatment. We used long-term estrogen deprivation (LTED) of human ERα+ breast cancer cell lines, an established model of sustained treatment with and acquired resistance to aromatase inhibitors (AIs), in combination with Bcl-2/Bcl-xL inhibition (ABT-263), finding that ABT-263 induced only limited tumor cell killing in LTED-selected cells in culture and in vivo. Interestingly, expression and activity of the Bcl-2-related factor Mcl-1 was increased in LTED cells. Genetic Mcl-1 ablation induced apoptosis in LTED-selected cells, and potently increased their sensitivity to ABT-263. Increased expression and activity of Mcl-1 was similarly seen in clinical breast tumor specimens treated with AI + the selective estrogen receptor downregulator fulvestrant. Delivery of Mcl-1 siRNA loaded into polymeric nanoparticles (MCL1 si-NPs) decreased Mcl-1 expression in LTED-selected and fulvestrant-treated cells, increasing tumor cell death and blocking tumor cell growth. These findings suggest that Mcl-1 upregulation in response to anti-estrogen treatment enhances tumor cell survival, decreasing response to therapeutic treatments. Therefore, strategies blocking Mcl-1 expression or activity used in combination with endocrine therapies would enhance tumor cell death.

Structure-based design for binding peptides in anti-cancer therapy

The conventional anticancer therapeutics usually lack cancer specificity, leading to damage of normal tissues that patients find hard to tolerate. Ideally, anticancer therapeutics carrying payloads of drugs equipped with cancer targeting peptides can act like "guided missiles" with the capacity of targeted delivery toward many types of cancers. Peptides are amenable for conjugation to nano drugs for functionalization, thereby improving drug delivery and cellular uptake in cancer-targeting therapies. Peptide drugs are often more difficult to design through molecular docking and in silico analysis than small molecules, because peptide structures are more flexible, possess intricate molecular conformations, and undergo complex interactions. In this review, the development and application of strategies for structure-based design of cancer-targeting peptides against GRP78 are discussed. This Review also covers topics related to peptide pharmacokinetics and targeting delivery, including molecular docking studies, features that provide advantages for in vivo use, and properties that influence the cancer-targeting ability. Some advanced technologies and special peptides that can overcome the pharmacokinetic challenges have also been included.

Targeting protein quality control pathways in breast cancer

The efficient production, folding, and secretion of proteins is critical for cancer cell survival. However, cancer cells thrive under stress conditions that damage proteins, so many cancer cells overexpress molecular chaperones that facilitate protein folding and target misfolded proteins for degradation via the ubiquitin-proteasome or autophagy pathway. Stress response pathway induction is also important for cancer cell survival. Indeed, validated targets for anti-cancer treatments include molecular chaperones, components of the unfolded protein response, the ubiquitin-proteasome system, and autophagy. We will focus on links between breast cancer and these processes, as well as the development of drug resistance, relapse, and treatment.

Implications of aging and the endoplasmic reticulum unfolded protein response on the molecular modality of breast cancer

The endoplasmic reticulum (ER) is an important subcellular organelle that is involved in numerous activities required to achieve and maintain functional proteins in addition to its role in the biosynthesis of lipids and as a repository of intracellular Ca²⁺. The inability of the ER to cope with protein folding beyond its capacity causes disturbances that evoke ER stress. Cells possess molecular mechanisms aimed at clearing unwanted cargo from the ER lumen as an adaptive response, but failing to do so navigates the system towards cell death. This systemic approach is called the unfolded protein response. Aging insults cells through various perturbations in homeostasis that involve curtailing ER function by mitigating the expression of its resident chaperones and enzymes. Here the unfolded protein response (UPR) cannot protect the cell due to the weakening of its protective arm, which exacerbates imbalanced homeostasis. Aging predisposed breast malignancy activates the UPR, but tumor cells maneuver the mechanistic details of the UPR, favoring tumorigenesis and thereby eliciting a treacherous condition. Tumor cells exploit UPR pathways via crosstalk involving various signaling cascades that usher tumor cells to immortality. This review aims to present a collection of data that can delineate the missing links of molecular signatures between aging and breast cancer.

Inhibition of 17beta-hydroxysteroid dehydrogenase type 7 modulates breast cancer protein profile and enhances apoptosis by down-regulating GRP78

17beta-hydroxysteroid dehydrogenase type 7 (17β-HSD7) promotes breast cancer cell growth via dual-catalytic activity by modulating estradiol and DHT. Here, we clarified the expression pattern of 17β-HSD7 in postmenopausal luminal A type breast cancer with The Cancer Genome Atlas (TCGA) cohort. The impact of 17β-HSD7 inhibition on the proteome of MCF-7 cells was investigated and on cell apoptosis was revealed. MCF-7 cells were treated with an efficient inhibitor of 17β-HSD7 (INH7) or with vehicle, and a differential proteomics study was performed using two-dimensional (2D) gel electrophoresis followed by mass spectrometry and ingenuity pathway analysis (IPA). Cell apoptosis was analyzed by flow cytometry, followed by reverse transcription quantitative real-time PCR (RT-qPCR) and Western blot to investigate the expression of apoptosis-related genes. Our data showed 17β-HSD7 is amplified in primary and progressive breast cancer, inhibition of 17β-HSD7 in MCF-7 cells modulated 104 proteins primarily involved in cell death/survival, cell growth and DNA processing. The expression of 78kDa glucose-regulated protein (GRP78) and anti-apoptosis factor Bcl-2 were significantly suppressed via 17β-HSD7 inhibition with INH7, consequently induced MCF-7 cell apoptosis. However, INH7 treatment of T47D, another widely used epithelial ER+ breast cancer cell line, led to an up-regulation of GRP78 expression, resulting in a limited increase in apoptosis. These results suggest cell-specific effects of INH7 in the breast cancer, which is interesting for further study. An combinatory effect on apoptosis by INH7 and Letrozole (aromatase inhibitor) was further demonstrated in MCF-7. Down-regulation of GRP78 via 17β-HSD7 inhibition enhances cell apoptosis in response to Letrozole. This study highlights GRP78 as a key regulator related to 17β-HSD7 inhibition and effect. Taken together, results from the present study suggest a hypothesis that inhibition of 17β-HSD7 would be a complementary strategy to Letrozole by suppression of GRP78 in ER+ breast cancer. However, from a research perspective, further studies have to be carried out with more breast cancer cell lines as well as in vivo model to assess the efficacy of inhibitor combination.

Helicobacter pylori outer inflammatory protein A (OipA) suppresses apoptosis of AGS gastric cells in vitro

Outer inflammatory protein A (OipA) is an important virulence factor associated with gastric cancer and ulcer development; however, the results have not been well established and turned out to be controversial. This study aims to elucidate the role of OipA in Helicobacter pylori infection using clinical strains harbouring oipA "on" and "off" motifs. Proteomics analysis was performed on AGS cell pre-infection and postinfection with H. pylori oipA "on" and "off" strains, using liquid chromatography/mass spectrometry. AGS apoptosis and cell cycle assays were performed. Moreover, expression of vacuolating cytotoxin A (VacA) was screened using Western blotting. AGS proteins that have been suggested previously to play a role or associated with gastric disease were down-regulated postinfection with oipA "off" strains comparing to oipA "on" strains. Furthermore, oipA "off" and ΔoipA cause higher level of AGS cells apoptosis and G0/G1 cell-cycle arrest than oipA "on" strains. Interestingly, deletion of oipA increased bacterial VacA production. The capability of H. pylori to induce apoptosis and suppress expression of proteins having roles in human disease in the absence of oipA suggests that strains not expressing OipA may be less virulent or may even be protective against carcinogenesis compared those expressing OipA. This potentially explains the higher incidence of gastric cancer in East Asia where oipA "on" strains predominates.

LncRNA-TP53TG1 Participated in the Stress Response Under Glucose Deprivation in Glioma

Gliomas are the most common brain tumors of the center nervous system. And long non-coding RNAs (lncRNAs) are non-protein coding transcripts, which have been considered as one type of gene expression regulator for cancer development. In this study, we investigated the role of lncRNA-TP53TG1 in response to glucose deprivation in human gliomas. The expression levels of TP53TG1 in glioma tissues and cells were analyzed by qRT-PCR. In addition, the influence of TP53TG1 on glucose metabolism related genes at the mRNA level during both high and low glucose treatment was detected by qRT-PCR. MTT, clonogenicity assays, and flow cytometry were performed to detect the cell proliferation and cell apoptosis. Furthermore, the migration of glioma cells was examined by Transwell assays. The expression of TP53TG1 was significantly higher in human glioma tissues or cell lines compared with normal brain tissue or NHA. Moreover, TP53TG1 and some tumor glucose metabolism related genes, such as GRP78, LDHA, and IDH1 were up-regulated significantly in U87 and LN18 cells under glucose deprivation. In addition, knockdown of TP53TG1 decreased cell proliferation and migration and down-regulated GRP78 and IDH1 expression levels and up-regulated PKM2 levels in U87 cells under glucose deprivation. However, over-expression of TP53TG1 showed the opposite tendency. Moreover, the effects of TP53TG1 were more remarkable in low glucose than that in high glucose. Our data showed that TP53TG1 under glucose deprivation may promote cell proliferation and migration by influencing the expression of glucose metabolism related genes in glioma. J. Cell. Biochem. 118: 4897-4904, 2017. © 2017 Wiley Periodicals, Inc.

BIK is involved in BRAF/MEK inhibitor induced apoptosis in melanoma cell lines

In patients with BRAF-mutated melanoma specific inhibitors of BRAF^V600E and MEK1/2 frequently induce initial tumor reduction, frequently followed by relapse. As demonstrated previously, BRAF^V600E-inhibition induces apoptosis only in a fraction of treated cells, while the remaining arrest and survive providing a source or a niche for relapse. To identify factors contributing to the differential initial response towards BRAF/MEK inhibition, we established M14 melanoma cell line-derived single cell clones responding to treatment with BRAF inhibitor vemurafenib and MEK inhibitor trametinib predominantly with either cell cycle arrest (CCA-cells) or apoptosis (A-cells). Screening for differentially expressed apoptosis-related genes revealed loss of BCL2-Interacting Killer (BIK) mRNA in CCA-cells. Importantly, ectopic expression of BIK in CCA-cells resulted in increased apoptosis rates following vemurafenib/trametinib treatment, while knockdown/knockout of BIK in A-cells attenuated the apoptotic response. Furthermore, we demonstrate reversible epigenetic silencing of BIK mRNA expression in CCA-cells. Importantly, HDAC inhibitor treatment associated with re-expression of BIK augmented sensitivity of CCA-cells towards vemurafenib/trametinib treatment both in vitro and in vivo. In conclusion, our results suggest that BIK can be a critical mediator of melanoma cell fate determination in response to MAPK pathway inhibition.

Retrospective Proteomic Screening of 100 Breast Cancer Tissues

The present investigation has been conducted on one hundred tissue fragments of breast cancer, collected and immediately cryopreserved following the surgical resection. The specimens were selected from patients with invasive ductal carcinoma of the breast, the most frequent and potentially aggressive type of mammary cancer, with the objective to increase the knowledge of breast cancer molecular markers potentially useful for clinical applications. The proteomic screening; by 2D-IPG and mass spectrometry; allowed us to identify two main classes of protein clusters: proteins expressed ubiquitously at high levels in all patients; and proteins expressed sporadically among the same patients. Within the group of ubiquitous proteins, glycolytic enzymes and proteins with anti-apoptotic activity were predominant. Among the sporadic ones, proteins involved in cell motility, molecular chaperones and proteins involved in the detoxification appeared prevalent. The data of the present study indicates that the primary tumor growth is reasonably supported by concurrent events: the inhibition of apoptosis and stimulation of cellular proliferation, and the increased expression of glycolytic enzymes with multiple functions. The second phase of the evolution of the tumor can be prematurely scheduled by the occasional presence of proteins involved in cell motility and in the defenses of the oxidative stress. We suggest that this approach on large-scale 2D-IPG proteomics of breast cancer is currently a valid tool that offers the opportunity to evaluate on the same assay the presence and recurrence of individual proteins, their isoforms and short forms, to be proposed as prognostic indicators and susceptibility to metastasis in patients operated on for invasive ductal carcinoma of the breast.

17beta-hydroxysteroid dehydrogenase type 5 is negatively correlated to apoptosis inhibitor GRP78 and tumor-secreted protein PGK1, and modulates breast cancer cell viability and proliferation

17beta-hydroxysteroid dehydrogenase type 5 (17β-HSD5) is an important enzyme associated with sex steroid metabolism in hormone-dependent cancer. However, reports on its expression and its prognostic value in breast cancer are inconsistent. Here, we demonstrate the impact of 17β-HSD5 expression modulation on the proteome of estrogen receptor-positive (ER+) breast cancer cells. RNA interference technique (siRNA) was used to knock down 17β-HSD5 gene expression in the ER+ breast cancer cell line MCF-7 and the proteome of the 17β-HSD5-knockdown cells was compared to that of MCF-7 cells using two-dimensional (2-D) gel electrophoresis followed by mass spectrometry analysis. Ingenuity pathway analysis (IPA) was additionally used to assess functional enrichment analyses of the proteomic dataset, including protein network and canonical pathways. Our proteomic analysis revealed only four differentially expressed protein spots (fold change > 2, p<0.05) between the two cell lines. The four spots were up-regulated in 17β-HSD5-knockdown MCF-7 cells, and comprised 21 proteins involved in two networks and in functions that include apoptosis inhibition, regulation of cell growth and differentiation, signal transduction and tumor metastasis. Among the proteins are nucleoside diphosphate kinase A (NME1), 78kDa glucose-regulated protein (GRP78) and phosphoglycerate kinase 1 (PGK1). We also showed that expression of 17β-HSD5 and that of the apoptosis inhibitor GRP78 are strongly but negatively correlated. Consistent with their opposite regulation, GRP78 knockdown decreased MCF-7 cell viability whereas 17β-HSD5 knockdown or inhibition increased cell viability and proliferation. Besides, IPA analysis revealed that ubiquitination pathway is significantly affected by 17β-HSD5 knockdown. Furthermore, IPA predicted the proto-oncogene c-Myc as an upstream regulator linked to the tumor-secreted protein PGK1. The latter is over-expressed in invasive ductal breast carcinoma as compared with normal breast tissue and its expression increased following 17β-HSD5 knockdown. Our present results indicate a 17β-HSD5 role in down-regulating breast cancer development. We thus propose that 17β-HSD5 may not be a potent target for breast cancer treatment but its low expression could represent a poor prognosis factor.

p53-mediated suppression of BiP triggers BIK-induced apoptosis during prolonged endoplasmic reticulum stress

Physiological and pathological conditions that affect the folding capacity of the endoplasmic reticulum (ER) provoke ER stress and trigger the unfolded protein response (UPR). The UPR aims to either restore the balance between newly synthesized and misfolded proteins or if the damage is severe, to trigger cell death. However, the molecular events underlying the switch between repair and cell death are not well understood. The ER-resident chaperone BiP governs the UPR by sensing misfolded proteins and thereby releasing and activating the three mediators of the UPR: PERK, IRE1 and ATF6. PERK promotes G2 cell cycle arrest and cellular repair by inducing the alternative translated p53 isoform p53ΔN40 (p53/47), which activates 14-3-3σ via suppression of p21^CDKN1A. Here we show that prolonged ER stress promotes apoptosis via a p53-dependent inhibition of BiP expression. This leads to the release of the pro-apoptotic BH3-only BIK from BiP and activation of apoptosis. Suppression of bip mRNA translation is mediated via the specific binding of p53 to the first 346-nt of the bip mRNA and via a p53 trans-suppression domain located within the first seven N-terminal amino acids of p53ΔN40. This work shows how p53 targets BiP to promote apoptosis during severe ER stress and further illustrates how regulation of mRNA translation has a key role in p53-mediated regulation of gene expression during the UPR.

CAF-derived HGF promotes cell proliferation and drug resistance by up-regulating the c-Met/PI3K/Akt and GRP78 signalling in ovarian cancer cells

The tumour microenvironment is a highly heterogeneous entity that plays crucial roles in cancer progression. As the most prominent stromal cell types, cancer-associated fibroblasts (CAFs) produce a variety of factors into the tumour microenvironment. In the present study, we firstly isolated CAFs from tumour tissues of the patients with ovarian cancer and demonstrated that the hepatocyte growth factor (HGF) was highly expressed in the supernatants of CAFs. CAF-derived HGF or human recombinant HGF promoted cell proliferation in human ovarian cell lines SKOV3 and HO-8910 cells. Western blotting analysis also showed that CAF-derived HGF or recombinant HGF activated c-Met/phosphoinositide 3-kinase (PI3K)/Akt and glucose-regulated protein 78 (GRP78) signalling pathways in ovarian cancer cells, and these effects could be abrogated by anti-HGF and c-Met inhibitor INCB28060. Moreover, HGF in CAF matrix attenuated paclitaxel (PAC)-caused inhibition of cell proliferation and increase in cell apoptosis through activating c-Met/PI3K/Akt and GRP78 pathways in SKOV3 and HO-8910 cells. The results in vitro were further validated in nude mice. These findings suggest that CAF-derived HGF plays crucial roles in cell proliferation and drug resistance in ovarian cancer cells.

Targeting the unfolded protein response in cancer

Cancer cells are exposed to various intrinsic and extrinsic factors that disrupt protein homeostasis, producing endoplasmic reticulum (ER) stress. To cope with these situations, cancer cells evoke a highly conserved adaptive mechanism called the unfolded protein response (UPR) to restore the ER homeostasis. Recently, several pharmacological agents have been found to exhibit anti-tumor activity by targeting the UPR components. The development of potent and specific compounds that target the UPR components has not only shed light on the regulation of the UPR in cancer cells, but also brought the field closer to clinical drug candidates. Here we present an overview of the milestones in the field of UPR biology in cancer with a focus on new strategies for pharmacological inhibition.

The Endoplasmic Reticulum Chaperone GRP78/BiP Modulates Prion Propagation in vitro and in vivo

Prion diseases are fatal neurodegenerative disorders affecting several mammalian species, characterized by the accumulation of the misfolded form of the prion protein, which is followed by the induction of endoplasmic reticulum (ER) stress and the activation of the unfolded protein response (UPR). GRP78, also called BiP, is a master regulator of the UPR, reducing ER stress levels and apoptosis due to an enhancement of the cellular folding capacity. Here, we studied the role of GRP78 in prion diseases using several in vivo and in vitro approaches. Our results show that a reduction in the expression of this molecular chaperone accelerates prion pathogenesis in vivo. In addition, we observed that prion replication in cell culture was inversely related to the levels of expression of GRP78 and that both proteins interact in the cellular context. Finally, incubation of PrP^Sc with recombinant GRP78 led to the dose-dependent reduction of protease-resistant PrP^Scin vitro. Our results uncover a novel role of GRP78 in reducing prion pathogenesis, suggesting that modulating its levels/activity may offer a novel opportunity for designing therapeutic approaches for these diseases. These findings may also have implications for other diseases involving the accumulation of misfolded proteins.

Plumbagin sensitizes breast cancer cells to tamoxifen-induced cell death through GRP78 inhibition and Bik upregulation

The glucose regulated protein 78 (GRP78) is a major chaperone of the endoplasmic reticulum, and a prosurvival component of the unfolded protein response. GRP78 is upregulated in many types of cancers, including breast cancer. Research has suggested that GRP78 overexpression confers chemoresistance to anti-estrogen agents through a mechanism involving the inhibition of a pro-apoptotic BH3-only protein, Bik. In the present research the role of plumbagin, a naturally occurring naphthoquinone, in GRP78-associated cell death inhibition was examined. The results demonstrated that plumbagin inhibits GRP78 activity and GRP78 inhibition contributes to plumbagin-mediated cell death induction. Furthermore, Bik upregulation was associated with plumbagin-induced cell death and an increase in plumbagin-mediated Bik induction was observed upon GRP78 downregulation. Plumbagin sensitized estrogen-positive breast cancer cells to tamoxifen and the association of GRP78 inhibition and Bik upregulation in plumbagin-mediated cell sensitization was shown. Collectively, the results of this research suggest that plumbagin inhibits the antiapoptotic activity of GRP78 leading to Bik upregulation and apoptosis induction, which contributes to the sensitization of breast cancer cells to tamoxifen.