Overexpression of GRP78 and GRP94 are markers for aggressive behavior and poor prognosis in gastric carcinomas

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.

ER stress and the unfolded protein response in gastrointestinal stem cells and carcinogenesis

Endoplasmic reticulum (ER) stress and the adaptive response that follows, termed the unfolded protein response (UPR), are crucial molecular mechanisms to maintain cellular integrity by safeguarding proper protein synthesis. Next to being important in protein homeostasis, the UPR is intricate in cell fate decisions such as proliferation, differentiation, and stemness. In the intestine, stem cells are critical in governing epithelial homeostasis and they are the cell of origin of gastrointestinal malignancies. In this review, we will discuss the role of ER stress and the UPR in the gastrointestinal tract, focusing on stem cells and carcinogenesis. Insights in mechanisms that connect ER stress and UPR with stemness and carcinogenesis may broaden our understanding in the development of cancer throughout the gastrointestinal tract and how we can exploit these mechanisms to target these malignancies.

Targeting cell surface glucose-regulated protein 94 in gastric cancer with an anti-GRP94 human monoclonal antibody

Gastric cancer (GC), a leading cause of cancer-related mortality, remains a significant challenge despite recent therapeutic advancements. In this study, we explore the potential of targeting cell surface glucose-regulated protein 94 (GRP94) with antibodies as a novel therapeutic approach for GC. Our comprehensive analysis of GRP94 expression across various cancer types, with a specific focus on GC, revealed a substantial overexpression of GRP94, highlighting its potential as a promising target. Through in vitro and in vivo efficacy assessments, as well as toxicological analyses, we found that K101.1, a fully human monoclonal antibody designed to specifically target cell surface GRP94, effectively inhibits GC growth and angiogenesis without causing in vivo toxicity. Furthermore, our findings indicate that K101.1 promotes the internalization and concurrent downregulation of cell surface GRP94 on GC cells. In conclusion, our study suggests that cell surface GRP94 may be a potential therapeutic target in GC, and that antibody-based targeting of cell surface GRP94 may be an effective strategy for inhibiting GRP94-mediated GC growth and angiogenesis. [BMB Reports 2024; 57(4): 188-193].

Regulator of Ribosome Synthesis 1 (RRS1) Stabilizes GRP78 and Promotes Breast Cancer Progression

Regulator of ribosome synthesis 1 (RRS1), a crucial regulatory factor in ribosome biogenesis, exerts a remarkable impact on the progression of breast cancer (BC). However, the exact mechanisms and pathways have not yet been fully elucidated. To investigate the impact of RRS1 on BC growth and metastasis, along with its underlying mechanisms. We discovered that RRS1 is overexpressed in BC tissues and cell lines. This study aims to regulate the level of RRS1 through lentiviral transfection technology to explore its potential function in BC cells. Knockdown of RRS1 resulted in the inhibition of cell proliferation, invasion, and migration, whereas overexpression had the opposite effects. We firstly identified the interaction between RRS1 and Glucose-Regulated Protein 78 (GRP78) using Co-immunoprecipitation (Co-IP) combined with mass spectrometry analysis, providing evidences of co-localization and positive regulation between RRS1 and GRP78. We observed that RRS1 inhibited the degradation of GRP78 through the ubiquitin-proteasome pathway, resulting in the stabilization of GRP78. In addition, our findings suggested that RRS1 promoted BC progression by activating the GRP78-mediated phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) signaling pathway. In conclusion, this newly discovered RRS1/GRP78 signaling axis provides a molecular and theoretical basis for further exploring the mechanisms of breast cancer invasion and metastasis.

Expression of GRP78 and its copartners in HEK293 and pancreatic cancer cell lines (BxPC-3/PANC-1) exposed to MRI and CT contrast agents

Endoplasmic reticulum (ER) stress-associated chaperones trigger a defense mechanism called as unfolded protein response (UPR) which can manage apoptosis and be determinative in cell fate. Both anticancer drug effects and potential toxicity effects of magnetic resonance imaging (MRI) and computed tomography (CT) contrast agents were aimed to be evaluated. For this purpose, we investigated expression profiles of endoplasmic reticulum stress-associated chaperone molecules in human pancreatic tumor lines BxPC-3 and PANC-1 and control human embryonic kidney cells 293 (HEK293) induced with a variety of gadolinium and iohexol contrast agents. Protein expression levels of ER stress-associated chaperones (master regulator: GRP78/Bip and its copartners: Calnexin, Ero1, PDI, CHOP, IRE1α and PERK) were evaluated with Western blotting. Expression levels at mRNA level were also assessed for GRP78/Bip and CHOP with real-time PCR. Induction of cells was carried out with four different Gd-based contrast agents (GBCAs): (Dotarem, Optimark, Primovist and Gadovist) and two different iohexol agents (Omnipol, Omnipaque). CT contrast agents tested in the study did not result in significant ER stress in HEK293 cells. However, they do not seem to have theranostic potential in pancreas cancer through ER pathway. The potential efficiency of macrocyclic MRI contrast agents to provoke apoptosis via ER stress-associated chaperones in BxPC-3 cells lends credibility for their future theranostic use in pancreas cancer as long as undesired toxicity effects were carefully considered. ER stress markers and/or contrast agents seem to have promising potential to be translated into the clinical practice to manage pancreas cancer progression.

Possible New Histological Prognostic Index for Large B-Cell Lymphoma

We conducted a retrospective analysis of GRP94 immunohistochemical (IHC) staining, an ER stress protein, on large B-cell lymphoma (LBCL) cells, intracellular p53, and 15 factors involved in the metabolism of the CHOP regimen: AKR1C3 (HO metabolism), CYP3A4 (CHOP metabolism), and HO efflux pumps (MDR1 and MRP1). The study subjects were 42 patients with LBCL at our hospital. The IHC staining used antibodies against the 17 factors. The odds ratios by logistic regression analysis used a dichotomous variable of CR and non-CR/relapse were statistically significant for MDR1, MRP1, and AKR1C3. The overall survival (OS) after R-CHOP was compared by the log-rank test. The four groups showed that Very good (5-year OS, 100%) consisted of four patients who showed negative IHC staining for both GRP94 and CYP3A4. Very poor (1-year OS, 0%) consisted of three patients who showed positive results in IHC for both GRP94 and CYP3A4. The remaining 35 patients comprised two subgroups: Good (5-year OS 60-80%): 15 patients who showed negative staining for both MDR1 and AKR1C3 and Poor (5-year OS, 10-20%): 20 patients who showed positive staining for either MDR, AKR1C3, MRP1, or p53. The Histological Prognostic Index (HPI) (the four groups: Very poor, Poor, Good, and Very good) is a breakthrough method for stratifying patients based on the factors involved in the development of treatment resistance.

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

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

Protein Disulfide Isomerases Function as the Missing Link Between Diabetes and Cancer

Significance: Diabetes has long been recognized as an independent risk factor for cancer, but there is insufficient mechanistic understanding of biological mediators that bridge two disorders together. Understanding the pathogenic association between diabetes and cancer has become the focus of many studies, and findings are potentially valuable for the development of effective preventive or therapeutic strategies for both disorders. Recent Advances: A summary of literature reveals a possible connection between diabetes and cancer through the family of protein disulfide isomerase (PDI). Historical as well as the most recent findings on the structure, biochemistry, and biology of the PDI family were summarized in this review. Critical Issues: PDIs in general function as redox enzymes and protein chaperones to control the quality of proteins by correcting or otherwise eliminating misfolded proteins in conditions of oxidative stress and endoplasmic reticulum stress, respectively. However, individual members of the PDI family may contribute uniquely to the pathogenesis of diabetes and cancer. Studies of exemplary members such as protein disulfide isomerase-associated (PDIA) 1, PDIA6, and PDIA15 were reviewed to highlight their contributions in the pathogenesis of diabetes and cancer and how they can be potential links bridging the two disorders through the cross talk of signaling pathways. Future Directions: Apparently ubiquitous presence of the PDIs creates difficulties and challenges for scientific community to develop targeted therapeutics for the treatment of diabetes and cancer simultaneously. Understanding molecular contribution of individual PDI in the context of specific disease may provide some insights into the development of mechanism-based target-directed therapeutics. Antioxid. Redox Signal. 37, 1191-1205.

Live and let die: signaling AKTivation and UPRegulation dynamics in SARS-CoVs infection and cancer

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the pathogen responsible for the coronavirus disease 2019 (COVID-19) pandemic. Of particular interest for this topic are the signaling cascades that regulate cell survival and death, two opposite cell programs whose control is hijacked by viral infections. The AKT and the Unfolded Protein Response (UPR) pathways, which maintain cell homeostasis by regulating these two programs, have been shown to be deregulated during SARS-CoVs infection as well as in the development of cancer, one of the most important comorbidities in relation to COVID-19. Recent evidence revealed two way crosstalk mechanisms between the AKT and the UPR pathways, suggesting that they might constitute a unified homeostatic control system. Here, we review the role of the AKT and UPR pathways and their interaction in relation to SARS-CoV-2 infection as well as in tumor onset and progression. Feedback regulation between AKT and UPR pathways emerges as a master control mechanism of cell decision making in terms of survival or death and therefore represents a key potential target for developing treatments for both viral infection and cancer. In particular, drug repositioning, the investigation of existing drugs for new therapeutic purposes, could significantly reduce time and costs compared to de novo drug discovery.

A Pan-Cancer Analysis of Heat-Shock Protein 90 Beta1(HSP90B1) in Human Tumours

BACKGROUND

HSP90B1, a member of the heat-shock protein 90 family, plays a vital role as a molecular chaperone for oncogenes and stimulates tumour growth. However, its role in various cancers remains unexplored.

METHODS

Using the cancer genome atlas, gene expression omnibus the Human Protein Atlas databases and various other bioinformatic tools, this study investigated the involvement of HSP90B1 in 33 different tumour types.

RESULTS

The over-expression of HSP90B1 generally predicted poor overall survival and disease-free survival for patients with tumours, such as adrenocortical carcinoma, bladder urothelial carcinoma, kidney renal papillary cell carcinoma, and lung adenocarcinoma. In this study, HSP90B1 was highly expressed in the majority of tumours. A comparison was made between the phosphorylation of HSP90B1 in normal and primary tumour tissues, and putative functional mechanisms in HSP90B1-mediated oncogenesis were investigated. Additionally, the mutation burden of HSP90B1 in cancer was evaluated along with the survival rate of patients with cancer patients.

CONCLUSION

This first pan-cancer investigation reveals the oncogenic functions of HSP90B1 in various cancers.

Decoy receptor 2 mediates the apoptosis-resistant phenotype of senescent renal tubular cells and accelerates renal fibrosis in diabetic nephropathy

Apoptotic resistance leads to persistent accumulation of senescent cells and sustained expression of a senescence-associated secretory phenotype, playing an essential role in the progression of tissue fibrosis. However, whether senescent renal tubular epithelial cells (RTECs) exhibit an apoptosis-resistant phenotype, and the role of this phenotype in diabetic nephropathy (DN) remain unclear. Our previous study was the first to demonstrate that decoy receptor 2 (DcR2) is associated with apoptotic resistance in senescent RTECs and renal fibrosis. In this study, we aimed to further explore the mechanism of DcR2 in apoptosis-resistant RTECs and renal fibrosis in DN. DcR2 was co-localized with fibrotic markers (α-SMA, collagen IV, fibronectin), senescent marker p16, and antiapoptotic proteins FLIP and Bcl2 but rarely co-localized with caspase 3 or TUNEL. DcR2 overexpression promoted renal fibrosis in mice with streptozotocin (STZ)-induced DN, as evidenced by augmented Masson staining and upregulated expression of fibrotic markers. DcR2 overexpression also enhanced FLIP expression while reducing the expression of pro-apoptotic proteins (caspases 8 and 3) in senescent RTECs, resulting in apoptotic resistance. In contrast, DcR2 knockdown produced the opposite effects in vitro and in vivo. Moreover, quantitative proteomics and co-immunoprecipitation experiments demonstrated that DcR2 interacted with glucose-related protein 78 kDa (GRP78), which has been shown to promote apoptotic resistance in cancer. GRP78 exhibited co-localization with senescent and antiapoptotic markers but was rarely co-expressed with caspase 3 or TUNEL. Additionally, GRP78 knockdown decreased the apoptosis resistance of HG-induced senescent RTECs with upregulated cleaved caspase 3 and increased the percentage of apoptotic RTECs. Mechanistically, DcR2 mediated apoptotic resistance in senescent RTECs by enhancing GRP78-caspase 7 interactions and promoting Akt phosphorylation. Thus, DcR2 mediated the apoptotic resistance of senescent RTECs and renal fibrosis by interacting with GRP78, indicating that targeting the DcR2-GRP78 axis represents a promising therapeutic strategy for DN.

Sec62 promotes gastric cancer metastasis through mediating UPR-induced autophagy activation

BACKGROUND AND AIMS

Sec62 is a membrane protein of the endoplasmic reticulum that facilitates protein transport. Its role in cancer is increasingly recognised, but remains largely unknown. We investigated the functional role of Sec62 in gastric cancer (GC) and its underlying mechanism.

METHODS

Bioinformatics, tissue microarray, immunohistochemistry (IHC), western blotting (WB), quantitative polymerase chain reaction (qPCR), and immunofluorescence were used to examine the expression of target genes. Transwell, scratch healing assays, and xenograft models were used to evaluate cell migration and invasion. Transmission electron microscopy and mRFP-GFP-LC3 double-labeled adenoviruses were used to monitor autophagy. Co-immunoprecipitation (CO-IP) was performed to evaluate the binding activity between the proteins.

RESULTS

Sec62 expression was upregulated in GC, and Sec62 upregulation was an independent predictor of poor prognosis. Sec62 overexpression promoted GC cell migration and invasion both in vitro and in vivo. Sec62 promoted migration and invasion by affecting TIMP-1 and MMP2/9 balance. Moreover, Sec62 could activate autophagy by upregulating PERK/ATF4 expression and binding to LC3II with concomitant FIP200/Beclin-1/Atg5 activation. Furthermore, autophagy blockage impaired the promotive effects of Sec62 on GC cell migration and invasion, whereas autophagy activation rescued the inhibitory effect of Sec62 knockdown on GC metastasis. Notably, Sec62 inhibition combined with autophagy blockage exerted a synergetic anti-metastatic effect in vitro and in vivo.

CONCLUSION

Sec62 promotes GC metastasis by activating autophagy and subsequently regulating TIMP-1 and MMP2/9 balance. The activation of autophagy by Sec62 may involve the unfolded protein response (UPR)-related PERK/ATF4 pathway and binding of LC3II during UPR recovery involving FIP200/Beclin-1/Atg5 upregulation. Specifically, the dual inhibition of Sec62 and autophagy may provide a promising therapeutic strategy for GC metastasis.

Identification of immunization-related new prognostic biomarkers for papillary renal cell carcinoma by integrated bioinformatics analysis

Background

Despite papillary renal cell carcinoma (pRCC) being the second most common type of kidney cancer, the underlying molecular mechanism remains unclear. Targeted therapies in the past have not been successful because of the lack of a clear understanding of the molecular mechanism. Hence, exploring the underlying mechanisms and seeking novel biomarkers for pursuing a precise prognostic biomarker and appropriate therapies are critical.

Material and methods

In our research, the differentially expressed genes (DEGs) were screened from the TCGA and GEO databases, and a total of 149 upregulated and 285 downregulated genes were sorted. This was followed by construction of functional enrichment and protein–protein interaction (PPI) network, and then the top 15 DEGs were selected for further analysis. The P4HB gene was chosen as our target gene by repetitively validating multiple datasets, and higher levels of P4HB expression predicted lower overall survival (OS) in patients with pRCC.

Results

We found that P4HB not only connects with immune cell infiltration and co-expression with PD-1, PD-L2, and CTLA-4, but also has a strong connection with the newly discovered hot gene, TOX.

Conclusion

We speculate that P4HB is a novel gene involved in the progression of pRCC through immunomodulation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12920-021-01092-w.

GRP78 expression and prognostic significance in patients with pancreatic ductal adenocarcinoma treated with neoadjuvant therapy versus surgery first

BACKGROUND

Glucose-regulated protein 78 (GRP78) plays an essential role in protein folding, transportation, and degradation, thus regulates ER homeostasis and promotes cell survival, proliferation and invasion. GRP78 expression in PDAC patients who received neoadjuvant therapy has not been reported.

METHODS

This retrospective study of resected PDAC patients included 125 patients treated with neoadjuvant therapy (NAT) and 140 patients treated with surgery first (SF). The expression of GRP78 was evaluated by immunohistochemistry on tissue microarrays and the results were correlated with clinicopathologic parameters and survival.

RESULTS

GRP78 expression was higher in SF patients compared to NAT patients (P < 0.001). In SF cohort, the median disease-free survival (DFS) and overall survival (OS) for patients with GRP78-positive tumors were 11.2 months and 25.0 months, respectively, compared to DFS of 52.1 months (P = 0.008) and OS of 69.5 months (P = 0.02) for those with GRP78-negative tumors. GRP78 expression correlated with higher frequency of recurrent/metastasis (P = 0.045). In NAT cohort, GRP78 expression correlated with shorter OS (P = 0.03), but not DFS (P = 0.08). GRP78 expression was an independent prognosticator for both DFS (P = 0.02) and OS (P = 0.049) in SF cohort and was an independent prognosticator for OS (P = 0.03), but not for DFS (P = 0.06) in NAT cohort by multivariate analysis.

CONCLUSIONS

Our study showed that GRP78 expression in NAT cohort is lower than that in SF cohort. GRP78 expression correlated with shorter survival in both SF and NAT patients. Our findings suggest that targeting GRP78 may help to improve the prognosis in PDAC patients.

Activation of PERK-ATF4-CHOP pathway as a novel therapeutic approach for efficient elimination of HTLV-1-infected cells

Patients with adult T-cell leukemia (ATL) exhibit a poor prognosis and overall survival rate when treated with standard chemotherapy, highlighting the continued requirement for the development of novel safe and effective therapies for human T-cell leukemia virus type 1 (HTLV-1)-related diseases. In this study, we demonstrated that MK-2048, a second-generation HIV-1 integrase (IN) inhibitor, potently and selectively kills HTLV-1-infected cells. Differential transcriptome profiling revealed significantly elevated levels of gene expression of the unfolded protein response (UPR) PKR-like ER kinase (PERK) signaling pathway in ATL cell lines following MK-2048 treatment. We also identified a significant downregulation in glucose regulated protein 78 (GRP78), a master regulator of the UPR in the CD4+CADM1+ HTLV-1-infected cell population of primary HTLV-1 carrier peripheral blood mononuclear cells (PBMCs) (n = 9), suggesting that HTLV-1-infected cells are hypersensitive to endoplasmic reticulum (ER) stress-mediated apoptosis. MK-2048 efficiently reduced proviral loads in primary HTLV-1 carrier PBMCs (n = 4), but had no effect on the total numbers of these cells, indicating that MK-2048 does not affect the proliferation of HTLV-1-uninfected PBMCs. MK-2048 specifically activated the ER stress-related proapoptotic gene, DNA damage-inducible transcript 3 protein (DDIT3), also known as C/EBP homologous protein (CHOP), in HTLV-1-infected but not uninfected cells of HTLV-1-carrier PBMCs. Our findings demonstrated that MK-2048 selectively induces HTLV-1-infected cell apoptosis via the activation of the UPR. This novel regulatory mechanism of the HIV IN inhibitor MK-2048 in HTLV-1-infected cells provides a promising prophylactic and therapeutic target for HTLV-1-related diseases including ATL.

Molecular Chaperones and Thyroid Cancer

Thyroid cancers are the most common of the endocrine system malignancies and progress must be made in the areas of differential diagnosis and treatment to improve patient management. Advances in the understanding of carcinogenic mechanisms have occurred in various fronts, including studies of the chaperone system (CS). Components of the CS are found to be quantitatively increased or decreased, and some correlations have been established between the quantitative changes and tumor type, prognosis, and response to treatment. These correlations provide the basis for identifying distinctive patterns useful in differential diagnosis and for planning experiments aiming at elucidating the role of the CS in tumorigenesis. Here, we discuss studies of the CS components in various thyroid cancers (TC). The chaperones belonging to the families of the small heat-shock proteins Hsp70 and Hsp90 and the chaperonin of Group I, Hsp60, have been quantified mostly by immunohistochemistry and Western blot in tumor and normal control tissues and in extracellular vesicles. Distinctive differences were revealed between the various thyroid tumor types. The most frequent finding was an increase in the chaperones, which can be attributed to the augmented need for chaperones the tumor cells have because of their accelerated metabolism, growth, and division rate. Thus, chaperones help the tumor cell rather than protect the patient, exemplifying chaperonopathies by mistake or collaborationism. This highlights the need for research on chaperonotherapy, namely the development of means to eliminate/inhibit pathogenic chaperones.

Molecular Chaperone GRP94/GP96 in Cancers: Oncogenesis and Therapeutic Target

During tumor development and progression, intrinsic and extrinsic factors trigger endoplasmic reticulum (ER) stress and the unfolded protein response, resulting in the increased expression of molecular chaperones to cope with the stress and maintain tumor cell survival. Heat shock protein (HSP) GRP94, also known as GP96, is an ER paralog of HSP90 and has been shown to promote survival signaling during tumor-induced stress and modulate the immune response through its multiple clients, including TLRs, integrins, LRP6, GARP, IGF, and HER2. Clinically, elevated expression of GRP94 correlates with an aggressive phenotype and poor clinical outcome in a variety of cancers. Thus, GRP94 is a potential molecular marker and therapeutic target in malignancies. In this review, we will undergo deep molecular profiling of GRP94 in tumor development and summarize the individual roles of GRP94 in common cancers, including breast cancer, colon cancer, lung cancer, liver cancer, multiple myeloma, and others. Finally, we will briefly review the therapeutic potential of selectively targeting GRP94 for the treatment of cancers.

Cell Surface GRP94 as a Novel Emerging Therapeutic Target for Monoclonal Antibody Cancer Therapy

Glucose-regulated protein 94 (GRP94) is an endoplasmic reticulum (ER)-resident member of the heat shock protein 90 (HSP90) family. In physiological conditions, it plays a vital role in regulating biological functions, including chaperoning cellular proteins in the ER lumen, maintaining calcium homeostasis, and modulating immune system function. Recently, several reports have shown the functional role and clinical relevance of GRP94 overexpression in the progression and metastasis of several cancers. Therefore, the current review highlights GRP94’s physiological and pathophysiological roles in normal and cancer cells. Additionally, the unmet medical needs of small chemical inhibitors and the current development status of monoclonal antibodies specifically targeting GRP94 will be discussed to emphasize the importance of cell surface GRP94 as an emerging therapeutic target in monoclonal antibody therapy for cancer.

Current status of sorafenib nanoparticle delivery systems in the treatment of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the most common type of liver cancer and one of the leading causes of cancer-related death worldwide. Advanced HCC displays strong resistance to chemotherapy, and traditional chemotherapy drugs do not achieve satisfactory therapeutic efficacy. Sorafenib is an oral kinase inhibitor that inhibits tumor cell proliferation and angiogenesis and induces cancer cell apoptosis. It also improves the survival rates of patients with advanced liver cancer. However, due to its poor solubility, fast metabolism, and low bioavailability, clinical applications of sorafenib have been substantially restricted. In recent years, various studies have been conducted on the use of nanoparticles to improve drug targeting and therapeutic efficacy in HCC. Moreover, nanoparticles have been extensively explored to improve the therapeutic efficacy of sorafenib, and a variety of nanoparticles, such as polymer, lipid, silica, and metal nanoparticles, have been developed for treating liver cancer. All these new technologies have improved the targeted treatment of HCC by sorafenib and promoted nanomedicines as treatments for HCC. This review provides an overview of hot topics in tumor nanoscience and the latest status of treatments for HCC. It further introduces the current research status of nanoparticle drug delivery systems for treatment of HCC with sorafenib.

A review of fasting effects on the response of cancer to chemotherapy

BACKGROUND & AIMS

Studies suggest that fasting before or during chemotherapy may induce differential stress resistance, reducing the adverse effects of chemotherapy and enhancing the efficacy of drugs. In this article, we review the effects of fasting, including intermittent, periodic, water-only short-term fasting, and caloric restriction on the responsiveness of tumor cells to cytotoxic drugs, their protective effect on normal cells, and possible mechanisms of action.

METHODS

We could not perform a systematic review due to the wide variation in the study population, design, dependent measures, and outcomes (eg, type of cancer, treatment variation, experimental setting, etc.). However, a systematic approach to search and review literature was used. The electronic databases PubMed (MEDLINE), Scopus, and Embase were searched up to July 2020.

RESULTS

Fasting potentially improves the response of tumor cells to chemotherapy by (1) repairing DNA damage in normal tissues (but not tumor cells); (2) upregulating autophagy flux as a protection against damage to organelles and some cancer cells; (3) altering apoptosis and increasing tumor cells' sensitivity to the apoptotic stimuli, and preventing apoptosis-mediated damage to normal cells; (4) depleting regulatory T cells and improving the stimulation of CD8 cells; and (5) accumulating unfolded proteins and protecting cancer cells from immune surveillance. We also discuss how 'fasting-mimicking diet' as a modified form of fasting enables patients to eat a low calorie, low protein, and low sugar diet while achieving similar metabolic outcomes of fasting.

CONCLUSION

This review suggests the potential benefits of fasting in combination with chemotherapy to reduce tumor progression and increase the effectiveness of chemotherapy. However, with limited human trials, it is not possible to generalize the findings from animal and in vitro studies. More human studies with adequate sample size and follow-ups are required to confirm these findings.

A Triterpene Lactone from Callistemon citrinus Inhibits the PANC-1 Human Pancreatic Cancer Cells Viability through Suppression of Unfolded Protein Response

Human pancreatic tumor cells such as PANC-1 are known for their ability to tolerate nutrient starvation and thrive under the hypovascular tumor microenvironment, a phenomenon termed as 'austerity'. A search of agents that preferentially inhibit the cancer cell viability under the starvation condition without toxicity in the nutrient-rich condition is a promising approach in anticancer drug discovery. In this study, a triterpene lactone, 3β-hydroxy-13,28-epoxyurs-11-en-28-one (ursenolide), isolated from a Callistemon citrinus extract has shown strong preferential cytotoxicity against PANC-1 cells under nutrient starvation with PC₅₀ value of 0.4 μm. Ursenolide-induced rounding of PANC-1 cell morphology followed by rupture of the cell membrane leading to cell death. In a real-time cell migration study, ursenolide was found to inhibit PANC-1 cell migration significantly. Mechanistically, it inhibited GRP78 and GRP94 under the starvation condition suggesting inhibition of unfolded protein response (UPR), an adaptive process of cell survival during starvation. It also inhibited the phosphorylation of the key survival protein Akt and mTOR. Overall results suggested that ursenolide is a potential anticancer agent against pancreatic cancer.

Prognostic significance of glucose-related protein 94 in colorectal cancer

AIMS

The expression of glucose-related protein 94 (GRP94), a member of the heat shock protein 90 family, was correlated with a variety of clinicopathological factors and patient survival in a large colorectal cancer (CRC) cohort. We aimed to elucidate the role of GRP94 in the prognosis of CRC patients.

METHODS

Tissue microarray blocks were generated from 709 CRC samples and immunohistochemically stained for GRP94.

RESULTS

Of the 709 tumours, 164 (23.1%) and 545 (76.9%) were classified in the low and high expression groups, respectively. GRP94 expression was high in CRC cases with larger tumours (p =  0.005) and advanced pT stage (p =  0.021). GRP94 expression was higher in females than males (p =  0.024). In univariate and multivariate survival analyses, high GRP94 expression was unexpectedly associated with better overall survival in CRC patients younger than 65 years of age (p =  0.001) CONCLUSION: Our conflicting results indicate that GRP94 has the ability to switch between oncogenic and tumour-suppressive roles depending on the conditions and microenvironment of the tumour cells. Furthermore, GRP94 could be a candidate biomarker to predict better prognosis in CRC patients.

GALNT6 promotes invasion and metastasis of human lung adenocarcinoma cells through O-glycosylating chaperone protein GRP78

Lung adenocarcinoma remains a threat to human health due to its high rate of recurrence and distant metastasis. However, the molecular mechanism underlying lung adenocarcinoma metastasis remains yet incompletely understood. Here, we show that upregulated expression of polypeptide N-acetylgalactosaminyltransferase6 (GALNT6) in lung adenocarcinoma is associated with lymph node metastasis and poor prognosis. In lung adenocarcinoma cells, GALNT6 over-expression promoted epithelial-mesenchymal transition (EMT), wound healing, and invasion which could be significantly reversed by GALNT6 silencing. GALNT6 silencing also mitigated the metastasis of lung adenocarcinoma and prolonged the survival of xenograft tumor-bearing mice. Furthermore, GALNT6 directly interacted with, and O-glycosylated chaperone protein GRP78, which promoted EMT by enhancing the MEK1/2/ERK1/2 signaling in lung cancer cells. Therefore, GALNT6 is emerging as novel positive regulator for the malignancy of human lung adenocarcinoma. Targeting GALNT6-GRP78-MEK1/2/ERK1/2 may thus represent a new avenue to develop therapeutics against lung cancer metastasis.

FKBP9 promotes the malignant behavior of glioblastoma cells and confers resistance to endoplasmic reticulum stress inducers

Background

FK506-binding protein 9 (FKBP9) is amplified in high-grade gliomas (HGGs). However, the roles and mechanism(s) of FKBP9 in glioma are unknown.

Methods

The expression of FKBP9 in clinical glioma tissues was detected by immunohistochemistry (IHC). The correlation between FKBP9 expression levels and the clinical prognosis of glioma patients was examined by bioinformatic analysis. Glioblastoma (GBM) cell lines stably depleted of FKBP9 were established using lentiviruses expressing shRNAs against FKBP9. The effects of FKBP9 on GBM cells were determined by cell-based analyses, including anchorage-independent growth, spheroid formation, transwell invasion assay, confocal microscopy, immunoblot (IB) and coimmunoprecipitation assays. In vivo tumor growth was determined in both chick chorioallantoic membrane (CAM) and mouse xenograft models.

Results

High FKBP9 expression correlated with poor prognosis in glioma patients. Knockdown of FKBP9 markedly suppressed the malignant phenotype of GBM cells in vitro and inhibited tumor growth in vivo. Mechanistically, FKBP9 expression induced the activation of p38MAPK signaling via ASK1. Furthermore, ASK1-p38 signaling contributed to the FKBP9-mediated effects on GBM cell clonogenic growth. In addition, depletion of FKBP9 activated the IRE1α-XBP1 pathway, which played a role in the FKBP9-mediated oncogenic effects. Importantly, FKBP9 expression conferred GBM cell resistance to endoplasmic reticulum (ER) stress inducers that caused FKBP9 ubiquitination and degradation.

Conclusions

Our findings suggest an oncogenic role for FKBP9 in GBM and reveal FKBP9 as a novel mediator in the IRE1α-XBP1 pathway.

Polyalthia longifolia Extract Triggers ER Stress in Prostate Cancer Cells Concomitant with Induction of Apoptosis: Insights from In Vitro and In Vivo Studies

Plant-based therapies are being explored to prevent or treat several cancer types. The antioxidant properties of Polyalthia longifolia plant are well established. In our previous work, we demonstrated the presence of cytotoxic compounds in the methanol extract of Polyalthia longifolia (MEP) with potent activity against human leukemia cells. In the present study, we evaluated the efficacy of MEP against prostate cancer (PCa) and established the molecular basis of its effect in in vitro and in vivo models. We observed that MEP treatment resulted in a significant decrease in the growth and viability of PCa cells, associated with arrest in the G1/S phase of the cell cycle. Apoptosis was confirmed as the primary mode of MEP-induced cell death through activation of the intrinsic apoptotic machinery. Proteomic and biochemical studies identified BiP as an important target of MEP with the activation of the ER stress pathway, as a potential mechanism driving MEP-induced apoptosis. The extract exhibited strong efficacy in the PCa xenograft mouse model with significant inhibition of tumor growth and reduced tumor burden. Taken together, our findings indicate that MEP-induced apoptosis in PCa cells concomitant with the activation of the ER stress pathways results in the inhibition of tumor growth, in vitro and in vivo. Our studies provide initial evidence of the efficacy of MEP against PCa and advocate for in-depth studies in other preclinical models for its possible use in clinical settings.

Predicting the Lung Squamous Cell Carcinoma Diagnosis and Prognosis Markers by Unique DNA Methylation and Gene Expression Profiles

The early diagnosis of lung squamous cell carcinoma (LUSC) is difficult, causing an unsatisfactory prognosis. Therefore, the 5-year survival rate of LUSC is poor. This study aimed at screening the potential diagnostic and prognostic markers for LUSC. The data of LUSC gene expression profiles and DNA methylation were obtained from The Cancer Genome Atlas (TCGA) database; the differentially expressed genes (DEGs) and the differentially methylated genes (DMGs) were screened out by an independent t-test and Benjamini/Hochberg methods. Further, the classifiers of the gene expression and DNA methylation markers in LUSC were constructed. After that, diagnostic and prognostic markers in LUSC were analyzed by the protein-protein interaction (PPI) network. The DEGs and the DMGs from TCGA database of LUSC were screened out. After strict filtration, we identified three potential DMGs (POU domain, class 4, transcription factor 2 [POU4F2], EN1, single-minded homolog 1 [SIM1]) for early diagnosis and seven potential DEGs (G-protein coupled receptor 78 [GPR78], PCDHA5, myosin binding protein H [MYBPH], RTL3, KIAA0408, HSD3B2, PCDHA12) for prognosis of LUSC. The tumor-normal tissue classification model and prognosis model were validated in two independent datasets. In addition, the PPI network was constructed, including three DMGs and the five DEGs (GPR78, MYBPH, KIAA0408, HSD3B2, PCDHA12) of the seven DEGs. The potential DMGs (POU4F2, EN1, SIM1) and DEGs (GPR78, MYBPH, KIAA0408, HSD3B2, PCDHA12) for the diagnosis and prognosis of LUSC identified in this article are expected to be further applied in clinical practice of the treatment of LUSC.

Apoptotic effect of fluoxetine through the endoplasmic reticulum stress pathway in the human gastric cancer cell line AGS

Gastric cancer is the fourth most common cancer in the world. Fluoxetine (FLX), a selective serotonin reuptake inhibitor, can inhibit the growth of cancer cells by inducing apoptotic cell death through various signaling pathways. This study was aimed to determine the mechanism of apoptotic cell death induced by FLX in AGS cells. MTT assay for cell viability test and colony forming assay was performed for detection of cell proliferation. Western blot analysis was conducted for protein expression. Increased fluorescence intensity and chromatin condensation were observed using DAPI staining. Production of reactive oxygen species (ROS) was measured by DCFDA assay. AGS cell proliferation was remarkedly inhibited by FLX in a dose-dependent manner starting at a concentration of 20 μM. The expression of death receptors was increased, which resulted in elevated expression of activated caspases and cleaved PARP, leading to FLX-induced apoptosis. Moreover, FLX significantly increased production of ROS, and N-acetyl cysteine, which scavenges ROS, attenuated the cytotoxic effects of FLX. In addition, treatment with FLX increased the expression of the endoplasmic reticulum (ER) stress marker, CHOP. P53 protein expression in AGS cells also decreased significantly with FLX treatment. Inhibition of ER stress significantly decreased the expressions of death receptor 5 (DR5), cleaved caspase 3, and cleaved PARP, but not to control levels. FLX-induced apoptosis in AGS involved upregulation of death receptors, ROS generation, and activation of ER stress.

The clinical and prognostic evaluation of GRP94 immunoexpression in Caucasian patients with colorectal adenocarcinoma

Introduction

Colorectal cancer (CRC) is traditionally regarded as the most commonly diagnosed gastrointestinal malignant disease. Nevertheless, despite advances in diagnosis and novel therapeutic options, the clinical outcomes of patients are still unsatisfactory.

Aim

To investigate the clinicopathological and prognostic roles of GRP94 expression, the immunohistochemical investigation was performed on samples of CRC tumour tissues, adjacent non-pathological mucosa, and metastatic foci in regional lymph nodes in Caucasian patients.

Material and methods

Paraffin-embedded adenocarcinoma samples were assessed immunohistochemically for GRP94 protein and scored according to the percentage of cells with positive reaction combined with staining intensity. Connections between GRP94 immunoexpression and clinicopathological factors including the overall survival (OS) were evaluated.

Results

The level of the GRP94 immunohistochemical reactivity was correlated with the grade of the histological differentiation (H (2.92) = 25.906; p < 0.001), size of the primary tumour (Z = –4.010; p < 0.001), regional lymph node involvement (Z = –6.547; p < 0.001), and perineural invasion (Z = –6.235; p < 0.001). Kaplan-Meier survival analysis showed that the survival time for patients with a low expression of GRP94 was significantly longer than that for patients with a moderate or strong level of GRP94 immunoreactivity (p < 0.001).

Conclusions

An enhanced level of GRP94 immunoexpression was significantly associated with malignancy-related clinicopathological factors and reduced the 5-year overall survival in CRC patients. However, a multivariate analysis demonstrated that GRP94 was not revealed as an independent risk factor for CRC prognosis.

Endoplasmic reticulum proteostasis control and gastric cancer

The endoplasmic reticulum (ER) is the primary organelle responsible for the synthesis, modification, folding and secretion of proteins, especially in specialized secretory cells. It also contributes to the maintenance of cellular functions, such as Ca²⁺ storage, lipogenesis, gluconeogenesis, and organelle biogenesis. Cellular stress conditions, such as glucose deprivation, hypoxia and disturbance of Ca²⁺ homeostasis, may increase the risk of protein misfolding and perturb proteostasis. This activates ER stress and triggers the unfolded protein response (UPR), leading to either the restoration of homeostasis or cell death. ER stress and UPR have been shown to play crucial roles in the pathogenesis, progression and treatment response of various cancers. In gastric cancer (GC), one of the most aggressive cancer types, critical functions of ER stress signaling have also started to emerge. Herein, we summarize the current knowledge linking ER stress and UPR to GC; we also discuss the possible nodes of therapeutic intervention and propose directions of future research.

Hypoxia Induced ER Stress Response as an Adaptive Mechanism in Cancer

It is evident that regions within tumors are deprived of oxygen, which makes the microenvironment hypoxic. Cancer cells experiencing hypoxia undergo metabolic alterations and cytoprotective adaptive mechanisms to survive such stringent conditions. While such mechanisms provide potential therapeutic targets, the mechanisms by which hypoxia regulates adaptive responses-such as ER stress response, unfolded protein response (UPR), anti-oxidative responses, and autophagy-remain elusive. In this review, we summarize the complex interplay between hypoxia and the ER stress signaling pathways that are activated in the hypoxic microenvironment of the tumors.

Exosomes derived from siRNA against GRP78 modified bone-marrow-derived mesenchymal stem cells suppress Sorafenib resistance in hepatocellular carcinoma

BACKGROUND

Sorafenib is an effective clinical drug in therapy of hepatocellular carcinoma, having led to improved prognosis in hepatocellular carcinoma patients. However acquired resistance is still being encountered. So, it is urgently to develop alternative strategies to overcome drug resistance. Exosomes can be modified with a variety of molecules, thereby acting as a vehicle for the delivery of therapeutic agents. The GRP78 is overexpressed in Sorafenib resistant cancer cells compared to Sorafenib sensitive cancer cells and thus is able to act as a target for therapy of hepatocellular carcinoma.

RESULTS

In this study, we modified BM-MSCs to express the exosomal siGRP78. And we show that siGRP78 modified exosomes combined with Sorafenib is able to target GRP78 in hepatocellular carcinoma cells and inhibit the growth and invasion of the cancer cells in vitro. Further, siGRP78 modified exosomes combined with Sorafenib also inhibit the growth and metastasis of the cancer cells in vivo.

CONCLUSIONS

siGRP78 modified exosomes could sensitize Sorafenib resistant cancer cells to Sorafenib and reverse the drug resistance.

Effects of Beclin 1 overexpression on aggressive phenotypes of colon cancer cells

Beclin 1 is involved in autophagy, differentiation, apoptosis and cancer progression, and functions as a haploinsufficient tumor suppressor gene. The aim of the present study was to elucidate the function of Beclin 1 in colon cancer. A Beclin 1-expressing plasmid was transfected into HCT-15 and HCT-116 cells, and the phenotypes and associated molecules were determined. Beclin 1 transfectants were subcutaneously injected into nude mice to determine tumor growth, and proliferation and apoptosis levels using Ki-67 immunostaining and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL), respectively. Beclin 1 overexpression inhibited viability as determined using a Cell Counting Kit-8 assay, inhibited migration and invasion as determined using a wound healing assay or Transwell assay, and lamellipodia formation by filamentous actin staining, induced autophagy as determined using electron microscopy, and light chain 3B (LC-3B) expression, and apoptosis as determined using Annexin V staining in the two cell lines (P<0.05). Beclin 1 induced G₂ arrest of HCT-15 transfectants as determined using propidium iodide staining (P<0.05), whereas HCT-116 transfectants were arrested in G₁ phase (P<0.05). The two transfectants exhibited increased expression of c-Myc, cyclin D1, β-catenin, insulin-response element 1 and 78 kDa glucose-regulated protein compared with the control and mock cells as determined using the reverse transcription-quantitative polymerase chain reaction (P<0.05). Beclin 1 overexpression upregulated LC-3B and cyclin-dependent kinase 4 expression, but downregulated cyclin E expression of the cancer cell lines as determined using western blot analysis (P<0.05). Beclin 1 expression in vivo significantly suppressed the proliferation of colon cancer cells in xenograft models via inducing apoptosis by TUNEL, and inhibiting proliferation by Ki-67 expression (P<0.05). Beclin 1 overexpression may reverse aggressive phenotypes and suppress colon cancer tumor growth, and be employed as a target molecule for gene therapy of patients with colon cancer.

Tunicamycin-induced ER stress in breast cancer cells neither expresses GRP78 on the surface nor secretes it into the media

GRP78 (an Mr 78 kDa calcium dependent glucose binding protein) is located in ER lumen. It functions as ER chaperone and translocates proteins for glycosylation at the asparagine residue present in the sequon Asn-X-Ser/Thr. Paraffin sections from N-glycosylation inhibitor tunicamycin treated ER-/PR-/HER2+ (double negative) breast tumor in athymic nude mice exhibited reduced N-glycan but increased GRP78 expression. We have evaluated the effect of tunicamycin on cellular localization of GRP78 in metastatic human breast cancer cells MDA-MB-231 (ER-/PR-/HER2-). Tunicamycin inhibited cell proliferation in a time and dose-dependent manner. Nonmetastatic estrogen receptor positive (ER+) MCF-7 breast cancer cells were also equally effective. GRP78 expression (protein and mRNA) was higher in tunicamycin (1.0 μg/mL) treated MCF-7 and MDA-MB-231 cells. GRP78 is an ER stress marker, so we have followed its intracellular localization using immunofluorescence microscopy after subjecting the cancer cells to various stress conditions. Unfixed cells stained with either FITC-conjugated Concanavalin A (Con A) or Texas-red conjugated wheat germ agglutinin (WGA) exhibited surface expression of N-glycans but not GRP78. GRP78 became detectable only after a brief exposure of cells to ice-cold methanol. Western blotting did not detect GRP78 in conditioned media of cancer cells whereas it did for MMP-1. The conclusion, GRP78 is expressed neither on the outer-leaflet of the (ER-/PR-/HER2-) human breast cancer cells nor it is secreted into the culture media during tunicamycin-induced ER stress. Our study therefore suggests strongly that anti-tumorigenic action of tunicamycin can be modeled to develop next generation cancer therapy, i.e., glycotherapy for treating breast and other sold tumors.

Discovery of a Potent Grp94 Selective Inhibitor with Anti-Inflammatory Efficacy in a Mouse Model of Ulcerative Colitis

As the endoplasmic reticulum paralogue of Hsp90, Grp94 chaperones a small set of client proteins associated with some diseases, including cancer, primary open-angle glaucoma, and inflammatory disorders. Grp94-selective inhibition has been a potential therapeutic strategy for these diseases. In this study, inspired by the conclusion that ligand-induced "Phe199 shift" effect is the structural basis of Grp94-selective inhibition, a series of novel Grp94 selective inhibitors incorporating "benzamide" moiety were developed, among which compound 54 manifested the most potent Grp94 inhibitory activity with an IC₅₀ value of 2 nM and over 1000-fold selectivity to Grp94 against Hsp90α. In a DSS-induced mouse model of ulcerative colitis (UC), compound 54 exhibited significant anti-inflammatory efficacy. This work provides a potent Grp94 selective inhibitor as probe compound for the biological study of Grp94 and represents the first study that confirms the potential therapeutic efficacy of Grp94-selective inhibitors against UC.

Prognostic role of BiP/GRP78 expression as ER stress in patients with gastric adenocarcinoma

PURPOSE

The glucose-regulated protein 78 (GRP78), also referred to as immunoglobulin heavy chain binding protein (BiP) (BiP/GRP78), is a major molecular chaperone in the endoplasmic reticulum (ER) and is extensively expressed in human neoplasms. Although the enhanced expression of BiP/GRP78 has been described to be associated with poor prognosis in gastric cancer (GC), details regarding its prognostic significance remain unclear. The aim of this study was to elucidate the prognostic role of BiP/GRP78 in patients with GC.

METHODS

Study subjects included 328 patients who underwent surgical resection. Tumor specimens of primary tumors underwent immunohistochemical staining for BiP/GRP78.

RESULTS

BiP/GRP78 was highly expressed in 57% (188/328) of patients. High expression of BiP/GRP78 was significantly associated with older age, male, disease staging, T factor, lymph node metastases, differentiation, lymphatic permeation, and vascular invasion. According to univariate analysis, age, disease staging, T factor, N factor, lymphatic permeation, vascular invasion, and BiP/GRP78 expression were significant prognostic factors for OS. In particular, high BiP/GRP78 expression was proven to be a significant predictor of prognosis in patients with older age, female sex, early disease stage, T1-2 factor, well or moderately differentiated tumors, and negative vascular invasion.

CONCLUSION

BiP/GRP78 is significantly associated with tumor aggressiveness and progression. The increased expression of BiP/GRP78 was identified as an independent factor for predicting poor OS in patients with early stage of disease, especially T1-2 factor.

Structural and Functional Analysis of GRP94 in the Closed State Reveals an Essential Role for the Pre-N Domain and a Potential Client-Binding Site

Hsp90 chaperones undergo ATP-driven conformational changes during the maturation of client proteins, populating a closed state upon ATP binding in which the N-terminal domains of the homodimer form a second inter-protomer dimer interface. A structure of GRP94, the endoplasmic reticulum hsp90, in a closed conformation has not been described, and the determinants that regulate closure are not well understood. Here, we determined the 2.6-Å structure of AMPPNP-bound GRP94 in the closed dimer conformation. The structure includes the pre-N domain, a region preceding the N-terminal domain that is highly conserved in GRP94, but not in other hsp90s. We show that the GRP94 pre-N domain is essential for client maturation, and we identify the pre-N domain as an important regulator of ATPase rates and dimer closure. The structure also reveals a GRP94:polypeptide interaction that partially mimics a client-bound state. The results provide structural insight into the ATP-dependent client maturation process of GRP94.

Estrogen receptor-α36-mediated rapid estrogen signaling regulates 78 kDa glucose-regulated protein expression in gastric carcinoma cells

To determine whether estrogen receptor-α36 (ER-α36) -mediated rapid estrogen signaling is associated with 78 kDa glucose-regulated protein (GRP78) expression in gastric cancer, 86 samples of gastric tumor tissue with corresponding normal and tumor-adjacent tissues were used to examine expression patterns of GRP78 and ER-α36. Immunohistochemistry demonstrated that 55/86 (63.95%) patients with gastric carcinoma, and western blot analysis revealed that GRP78 was upregulated in 15/20 (75%) of tumor specimens. GRP78 expression was positively associated with ER-α36 expression, the male sex and lymph node metastasis (P<0.05). Estrogen treatment increased GRP78 and ER-α36 expression, as well as GSK-3β phosphorylation in established gastric cancer SGC-7901 cells. The steady-state level of GRP78 protein expression and the level of phosphorylated GSK-3β at Ser9 were decreased in SGC-7901 cells with ER-α36 knockdown. Forced expression of ER-α36 in SGC-7901 cells, however, led to an increase in GRP78 expression and GSK-3β phosphorylation. It may therefore be concluded that ER-α36-mediated rapid estrogen signaling positively regulates GRP78 expression, presumably via the GSK-3β pathway, which may be associated with gastric carcinogenesis.

Glucose-regulated protein of 94 kDa contributes to the development of an aggressive phenotype in breast cancer cells

Grp94 plays an essential role in protein assembly. We previously suggested that Grp94 overexpression is involved in tumor aggressiveness. However, the underlying mechanisms remain unknown. Since many tumors display high Grp94 levels, we investigated the effects of tumor microenvironment on the regulation of this chaperone expression. First, we found out that hypoxia did not change Grp94 expression in the human tumor cell lines MCF-7 (breast cancer) and HepG2 (liver cancer). Second, glucose deprivation significantly increased Grp94 protein levels. Subsequently, we focused in the putative role of Grp94 in the acquisition of an aggressive phenotype by cancer cells. Using a more aggressive cancer cell model (MDA-MB-231 breast tumor cells), we found out that Grp94 knockdown using siRNA decreased the invasive capacity of cancer cells. Moreover, cells with decreased Grp94 levels displayed an enhanced sensitivity of tumor cells to doxorubicin, a standard drug in the treatment of breast cancer. Taken together, our results suggest that the expression of Grp94 is linked to tumor aggressiveness. Therefore, targeting Grp94 could be an effective way to inhibit tumor growth improving chemotherapy outcome.

Quantitative proteomics and biochemical analyses reveal the role of endoplasmin in the regulation of the expression and secretion of A Disintegrin And Metalloproteinase 12

A Disintegrin And Metalloproteinase 12 (ADAM12) is highly expressed in multiple cancers such as breast and cervical cancers and its high expression reduces the overall patient survival rate. ADAM12 has two major splicing variants, the long membrane-anchored form ADAM12L and the short secreted form ADAM12S. However, how they are regulated and whether they are modulated similarly or differently in cells are not clear. Here, we use affinity purification and mass spectrometry to identify the ADAM12S-interacting proteins. Spectral counting and MaxQuant label-free quantification reveal that ADAM12S but not ADAM12L specifically interacts with a subset of endoplasmic reticulum proteins, such as endoplasmin (GRP94), 78 kDa glucose-regulated protein (GRP78), and UDP-glucose:glycoprotein glucosyltransferase I (UGGT1), that regulate the folding and processing of secreted proteins. Further biochemical experiments validate the interaction between ADAM12S and several of its interacting proteins. Computational docking analysis demonstrates that GRP94 preferentially interacts with ADAM12S over ADAM12L. The data also suggest that both the protein expression level and the secretion of ADAM12S are regulated by GRP94 expression and knockdown. Our results reveal a link between these two proteins that are highly expressed in cancer cells. Furthermore, our studies define a new ADAM12S-specific regulator that may contribute to the cancer development.

SIGNIFICANCE

A Disintegrin And Metalloproteinase 12 (ADAM12) is highly expressed in many cancers such as lung, breast, and cervical cancers. ADAM12 has two major splicing variants, the long membrane-anchored form ADAM12L and the short secreted form ADAM12S. However, how they are regulated and whether they are modulated similarly or differently are not completely understood. We use affinity purification and label-free quantitative proteomics to identify the ADAM12S-interacting proteins. Our results reveal that ADAM12S specifically interacts with a subset of endoplasmic reticulum proteins, including endoplasmin (GRP94), UDP-glucose:glycoprotein glucosyltransferase I (UGGT1), and neutral α-glucosidase AB (GANAB). Computer modeling reveals that ADAM12S interacts with the surface amino acids of GRP94 more strongly than ADAM12L. Biochemical experiments further reveal that GRP94 regulates both the protein level and the secretion of ADAM12S. Database mining finds that both GRP94 and ADAM12 are highly expressed in multiple cancers and their high expression is correlated with poor patient survival rate. Taken together, our work discovers a new upstream regulator for ADAM12S, which may contribute to its distinct functions in the regulation of the migration and invasion of cancer cells.

Autoantibodies against glucose-regulated protein 78 as serological biomarkers in metastatic and recurrent hepatocellular carcinoma

Purpose

To identify Heptocellular carcinoma (HCC) associated antigens by proteomics, and validate whether autoantibodies against tumor-associated antigens (TAAs) could be used for diagnosis and conditional monitoring.

RESULTS

The 78 kDa glucose regulated protein (GRP78) was selected as a candidate TAA. The titers of autoantibodies against 78 kDa glucose regulated protein (GRP78) from patients with HCC, liver cirrhosis (LC), and chronic hepatitis (CH) were significantly higher than that from normal controls (P<0.05, P<0.001, and P<0.01, respectively). The expression of autoantibodies against GRP78 was associated with clinical stage (P<0.01), portal vein invasion (P<0.05), and metastasis (P<0.05). The expression of anti-GRP78 antibodies was significantly higher 1 month after surgery in recurrent patients who had accepted hepatic resection 1 month after surgery compared to patients who had surgery before surgery or within 1 week after surgery (P<0.01 and P<0.001). Immunohistochemistry (IHC) showed higher expression of GRP78 in HCC compared to the non-HCC liver tissues (P <0.05).

Materials and Methods

HCC serum with high titer of autoantibodies against TAAs were screened and used for a proteome-based approach to identify HCC associated antigens. Indirect enzyme-linked immunoassay (ELISA) was used to detect the corresponding autoantibodies against TAAs.

Conclusion

GRP78 is an autoantigen that could stimulate autoimmune responses and serve as a potential marker for recurrent and metastatic progression in HCC.

Deficiency of protein-L-isoaspartate (D-aspartate) O-methyl-transferase expression under endoplasmic reticulum stress promotes epithelial mesenchymal transition in lung adenocarcinoma

A prognostic association between the novel chaperone protein-L-isoaspartate (D-aspartate) O-methyltransferase (PIMT) and lung adenocarcinoma has recently been reported. Here, we evaluated the functional roles of PIMT in the progression of lung adenocarcinoma. PIMT expression was detectable in 6 lung adenocarcinoma cell lines: A549, H441, H460, H1650, Calu 1, and Calu 6 cell lines. In A549 and H441 cells, knockdown by PIMT using silencing RNA of PIMT (si-PIMT) and/or small hairpin-RNA (sh-PIMT) induced a decrease in the expression of E-cadherin with an increase in vimentin expression, indicating that the epithelial to mesenchymal transition (EMT) was induced. Cell mobility, including migration and invasion capability, was increased in sh-PIMT A549 stable and si-PIMT H441 cells compared to in control cells. Endoplasmic reticulum (ER) stress, such as Thapsigargin (Tg) stress and hypoxia, induced EMT in A549 cells but not in other cell types, with an increase in GRP78 expression, whereas overexpression of PIMT reduced the EMT and cell invasion under stress conditions. The expression of hypoxia inducible factor-1 alpha (HIF1α) and Twist increased in sh-PIMT A549 and si-PIMT H441 cells, and Tg stress increased HIF1α expression levels in A549 cells in a dose-dependent manner. Moreover, LW6, an HIF1α inhibitor, reduced EMT, cancer invasion, and the levels of Twist in sh-PIMT A549 cells. Our results indicate that deficiency of supplemental PIMT expression under ER stress facilitates EMT and cell invasion in some cell types of lung adenocarcinoma.

Endoplasmic reticulum chaperone glucose-regulated protein 78 in gastric cancer: An emerging biomarker

The endoplasmic reticulum (ER) is the principal organelle responsible for the synthesis, initial post-translational modification, folding, export and secretion of proteins. It is also responsible for the maintenance of cellular homeostasis. In response to cellular stress conditions including glucose deprivation, hypoxia and changes in calcium homeostasis, ER stress machinery is activated and triggers the unfolded protein response, resulting in the restoration of homeostasis or activation of cell death. Glucose-regulated protein 78 (GRP78), a molecular chaperone, may be induced by ER stress at the transcriptional and translational level. A number of studies have demonstrated that GRP78 serves an important role in tumor cell proliferation, metastasis, angiogenesis and drug-resistance. The present review systematically describes the association between GRP78 expression and gastric cancer pathogenesis, and emphasizes that GRP78 is a novel diagnostic and therapeutic biomarker of gastric cancer.

Grp94 in complexes with IgG is a soluble diagnostic marker of gastrointestinal tumors and displays immune-stimulating activity on peripheral blood immune cells

Glucose-regulated protein94 (Grp94), the most represented endoplasmic reticulum (ER)-resident heat shock protein (HSP), is a tumor antigen shared by different types of solid and hematological tumors. The tumor-specific feature of Grp94 is its translocation from the ER to the cell surface where it displays pro-oncogenic functions. This un-physiological location has important implications for both the tumor pathology and anti-tumor therapy. We wanted to address the question of whether Grp94 could be measured as liquid marker in cancer patients in order to make predictions of diagnostic and therapeutic relevance for the tumor. To this aim, we performed an in-depth investigation on patients with primary tumors of the gastrointestinal (GI) tract, using different methodological approaches to detect Grp94 in tumor tissues, plasma and peripheral blood mononuclear cells (PBMCs). Results indicate that Grp94 is not only the antigen highly expressed in any tumor tissue and in cells of tumor infiltrates, mostly B lymphocytes, but it is also found in the circulation. However, the only form in which Grp94 was detected in the plasma of any patients and in B lymphocytes induced to proliferate, was that of stable complexes with Immunoglobulin (Ig)G. Using a specific immune-enzyme assay to measure plasma Grp94-IgG complexes, we showed that Grp94-IgG complexes were significantly increased in cancer patients compared to healthy control subjects, serving as diagnostic tumor biomarker. Results also demonstrate that the stimulation of patient PBMCs with Grp94-IgG complexes led to an increased secretion of inflammatory cytokines that might drive a potentially beneficial anti-tumor effect.

Glucose-regulated protein 94 mediates progression and metastasis of esophageal squamous cell carcinoma via mitochondrial function and the NF-kB/COX-2/VEGF axis

Esophageal cancer is a worldwide health problem with a very poor prognosis. Therefore, new diagnostic biomarkers or therapeutic strategies for identifying and managing esophageal squamous cell carcinoma (ESCC) are urgently needed. Glucose-regulated protein 94 (GRP94) is one of major endoplasmic reticulum-stress response proteins that plays a key role in cancer progression and therapeutic responses. However, the role of GRP94 in ESCC progression and metastasis remains unclear. The tissue array results indicated that higher GRP94 expression levels were associated with lower overall survival and higher lympho-node metastasis. Silencing GRP94 (GRP94-KD) reduced cell proliferation, migration and invasion in ESCC cells. In a xenotransplantation assay, silencing GRP94 reduced cell proliferation in the zebrafish embryo. Transmission electron microscopy revealed impaired mitochondria in GRP94-KD cells, which exhibited reduced basal respiration, spare respiratory capacity and ATP production and increased oxidative damage compared with scrambled control cells. Regarding the molecular mechanism underlying the effects of GRP94 knockdown, we found that silencing GRP94 may reduce the level of NF-kB, c-Jun, p38, IL-6, vascular endothelial growth factor (VEGF), and cyclooxygenase-2 (COX-2) as well as activation of AKT and ERK. In conclusion, our results indicate that silencing GRP94 in ESCC cells suppressed cancer growth and the metastatic potential via mitochondrial functions and NF-kB/COX-2/VEGF in ESCC cells.

Concomitant high expression of ERα36, GRP78 and GRP94 is associated with aggressive papillary thyroid cancer behavior

PURPOSE

Papillary thyroid cancer (PTC) is more common in women than in men. It has been suggested that estrogen may be involved in its development, as has previously been shown for breast, endometrial and ovarian cancer. The purpose of this study was to assess correlations between the expression of the estrogen receptor alpha36 (ERα36) and the glucose regulated proteins GRP78 and GRP94 (chaperones involved in glycoprotein folding) and various PTC clinicopathological features, as well as to evaluate the potential usefulness of these three potential oncogenic proteins in the prediction of aggressive PTC behavior.

METHODS

ERα36, GRP78 and GRP94 protein expression in 218 primary PTC tissues and PTC-derived BCPAP cells was examined using immunohistochemistry, Western blotting and immunocytochemistry. The proliferative, invasive and migrative capacities of BCPAP cells in which the respective genes were either exogenously over-expressed or silenced were assessed using BrdU incorporation and Transwell assays, respectively.

RESULTS

We found that ERα36, GRP78 and GRP94 protein expression was upregulated in the primary PTC tissues tested. We also found that ERα36, GRP78 and GRP94 expression modulation affected the proliferation, invasion and migration of PTC-derived BCPAP cells. A positive correlation and a positive feedback loop were noted between ERα36, GRP78 and GRP94 protein expression in the primary PTC tissues and in BCPAP cells, respectively. High ERα36 expression in combination with a high GRP78/ GRP94 expression was found to have a stronger correlation with extrathyroid extension (ETE), lymph node metastasis (LNM), distant metastasis (DM) and high TNM stage than high ERα36 expression in combination with either high GRP78 or high GRP94 expression (p = 0.028 for ETE, p = 0.002 for DM and p ≤ 0.001 for LNM and high TNM stage) or high ERα36 expression alone (p < 0.001 for ETE, LNM, DM and high TNM stage).

CONCLUSIONS

From our data we conclude that a concomitant high expression of ERα36, GRP78 and GRP94 is strongly associated with aggressive PTC behavior and may be used as a predictor for ETE, LNM, DM and high TNM stage.

Cancer-associated fibroblasts promote non-small cell lung cancer cell invasion by upregulation of glucose-regulated protein 78 (GRP78) expression in an integrated bionic microfluidic device

The tumor microenvironment is comprised of cancer cells and various stromal cells and their respective cellular components. Cancer-associated fibroblasts (CAFs), a major part of the stromal cells, are a key determinant in tumor progression, while glucose-regulated protein (GRP)78 is overexpressed in many human cancers and is involved in tumor invasion and metastasis. This study developed a microfluidic-based three dimension (3D) co-culture device to mimic an in vitro tumor microenvironment in order to investigate tumor cell invasion in real-time. This bionic chip provided significant information regarding the role of GRP78, which may be stimulated by CAFs, to promote non-small cell lung cancer cell invasion in vitro. The data showed that CAF induced migration of NSCLC A549 and SPCA-1 cells in this three-dimensional invasion microdevice, which is confirmed by using the traditional Transwell system. Furthermore, CAF induced GRP78 expression in A549 and SPCA-1 cells to facilitate NSCLC cell migration and invasion, whereas knockdown of GRP78 expression blocked A549 and SPCA-1 cell migration and invasion capacity. In conclusion, these data indicated that CAFs might promote NSCLC cell invasion by up-regulation of GRP78 expression and this bionic chip microdevice is a robust platform to assess the interaction of cancer and stromal cells in tumor environment study.

Regulation of tumor-stroma interactions by the unfolded protein response

The unfolded protein response (UPR) is a conserved adaptive pathway that helps cells cope with the protein misfolding burden within the endoplasmic reticulum (ER). Imbalance between protein folding demand and capacity in the ER leads to a situation called ER stress that is often observed in highly proliferative and secretory tumor cells. As such, activation of the UPR signaling has emerged as a key adaptive mechanism promoting cancer progression. It is becoming widely acknowledged that, in addition to its intrinsic effect on tumor biology, the UPR can also regulate tumor microenvironment. In this review, we discuss how the UPR coordinates the crosstalk between tumor and stromal cells, such as endothelial cells, normal parenchymal cells, and immune cells. In addition, we further describe the involvement of ER stress signaling in the response to current treatments as well as its impact on antitumor immunity mainly driven by immunogenic cell death. Finally, in this context, we discuss the relevance of targeting ER stress/UPR signaling as a potential anticancer approach.

Genetic host factors in Helicobacter pylori-induced carcinogenesis: Emerging new paradigms

Helicobacter Pylori is a gram negative rod shaped microaerophilic bacterium that colonizes the stomach of approximately half the world's population. Infection with c may cause chronic gastritis which via a quite well described process known as Correas cascade can progress through sequential development of atrophic gastritis, intestinal metaplasia and dysplasia to gastric cancer. H. pylori is currently the only bacterium that is classified as a class 1 carcinogen by the WHO, although the exact mechanisms by which this bacterium contributes to gastric carcinogenesis are still poorly understood. Only a minority of H. pylori-infected patients will eventually develop gastric cancer, suggesting that host factors may be important in determining the outcome of H. pylori infection. This is supported by a growing body of evidence suggesting that the host genetic background contributes to risk of H. pylori infection and gastric carcinogenesis. In particular single nucleotide polymorphisms in genes that influence bacterial handling via pattern recognition receptors appear to be involved, further strengthening the link between host risk factors, H. pylori incidence and cancer. Many of these genes influence cellular pathways leading to inflammatory signaling, inflammasome formation and autophagy. In this review we summarize known carcinogenic effects of H. pylori, and discuss recent findings that implicate host genetic pattern recognition pathways in the development of gastric cancer and their relation with H. pylori.