Effect on tumor cells of blocking survival response to glucose deprivation

2-Deoxy-D-Glucose Downregulates Fatty Acid Synthase Gene Expression Via an Endoplasmic Reticulum Stress-Dependent Pathway in HeLa Cells

Fatty acid synthase (FASN) catalyzes the rate-limiting step of cellular lipogenesis. FASN expression is upregulated in various types of cancer cells, implying that FASN is a potential target for cancer therapy. 2-Deoxy-D-glucose (2-DG) specifically targets cancer cells by inhibiting glycolysis and glucose metabolism, resulting in multiple anticancer effects. However, whether the effects of 2-DG involve lipogenic metabolism remains to be elucidated. We investigated the effect of 2-DG administration on FASN expression in HeLa human cervical cancer cells. 2-DG treatment for 24 h decreased FASN mRNA and protein levels and suppressed the activity of an exogenous rat Fasn promoter. The use of a chemical activator or inhibitors or of a mammalian expression plasmid showed that neither AMPK nor the Sp1 transcription factor is responsible for the inhibitory effect of 2-DG on FASN expression. Administration of thapsigargin, an endoplasmic reticulum (ER) stress inducer, or 4-(2-aminoethyl) benzenesulfonyl fluoride (AEBSF), a site 1 protease inhibitor, mimicked the inhibitory effect of 2-DG on FASN expression. 2-DG did not further decrease FASN expression in the presence of thapsigargin or AEBSF. Site 1 protease mediates activation of ATF6, an ER stress mediator, as well as sterol regulatory element-binding protein 1 (SREBP1), a robust transcription factor for FASN. Administration of 2-DG or thapsigargin for 24 h suppressed activation of ATF6 and SREBP1, as did AEBSF. We speculated that these effects of 2-DG or thapsigargin are due to feedback inhibition via increased GRP78 expression following ER stress. Supporting this, exogenous overexpression of GRP78 in HeLa cells suppressed SREBP1 activation and Fasn promoter activity. These results suggest that 2-DG suppresses FASN expression via an ER stress-dependent pathway, providing new insight into the molecular basis of FASN regulation in cancer.

Glucose deprivation triggers DCAF1-mediated inactivation of Rheb-mTORC1 and promotes cancer cell survival

Low glucose is a common microenvironment for rapidly growing solid tumors, which has developed multiple approaches to survive under glucose deprivation. However, the specific regulatory mechanism remains largely elusive. In this study, we demonstrate that glucose deprivation, while not amino acid or serum starvation, transactivates the expression of DCAF1. This enhances the K48-linked polyubiquitination and proteasome-dependent degradation of Rheb, inhibits mTORC1 activity, induces autophagy, and facilitates cancer cell survival under glucose deprivation conditions. This study identified DCAF1 as a new cellular glucose sensor and uncovered new insights into mechanism of DCAF1-mediated inactivation of Rheb-mTORC1 pathway for promoting cancer cell survival in response to glucose deprivation.

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.

Induction of stearoyl-CoA desaturase confers cell density-dependent ferroptosis resistance in melanoma

Ferroptosis is a form of regulated cell death that is induced by inhibiting glutathione peroxidase 4 (GPX4), which eliminates lipid peroxidation. Ferroptosis induction is influenced by the cell environment. However, the cellular states altering ferroptosis susceptibility remain largely unknown. We found that melanoma cell lines became resistant to ferroptosis as cell density increased. Comparative transcriptome and metabolome analyses revealed that cell density-dependent ferroptosis resistance was coupled with a shift toward a lipogenic phenotype accompanied by strong induction of stearoyl-CoA desaturase (SCD). Database analysis of gene dependency across hundreds of cancer cell lines uncovered a negative correlation between GPX4 and SCD dependency. Importantly, SCD inhibition, either pharmacologically or through genetic knockout, sensitized melanoma cells to GPX4 inhibition, thereby attenuating ferroptosis resistance in cells at high density. Our findings indicate that transition to an SCD-inducing, lipogenic cell state produces density-dependent resistance to ferroptosis, which may provide a therapeutic strategy against melanoma.

Endoplasmic Reticulum Stress and Cancer: Could Unfolded Protein Response Be a Druggable Target for Cancer Therapy?

Unfolded protein response (UPR) is an adaptive response which is used for re-establishing protein homeostasis, and it is triggered by endoplasmic reticulum (ER) stress. Specific ER proteins mediate UPR activation, after dissociation from chaperone Glucose-Regulated Protein 78 (GRP78). UPR can decrease ER stress, producing an ER adaptive response, block UPR if ER homeostasis is restored, or regulate apoptosis. Some tumour types are linked to ER protein folding machinery disturbance, highlighting how UPR plays a pivotal role in cancer cells to keep malignancy and drug resistance. In this review, we focus on some molecules that have been revealed to target ER stress demonstrating as UPR could be a new target in cancer treatment.

Nutrient deprivation and hypoxia alter T cell immune checkpoint expression: potential impact for immunotherapy

Aim

Use of immune checkpoint blockade to enhance T cell-mediated immunity within the hostile tumour microenvironment (TME) is an attractive approach in oesophageal adenocarcinoma (OAC). This study explored the effects of the hostile TME, including nutrient deprivation and hypoxia, on immune checkpoint (IC) expression and T cell phenotypes, and the potential use of nivolumab to enhance T cell function under such conditions.

Methods and Results

ICs were upregulated on stromal immune cells within the tumour including PD-L2, CTLA-4 and TIGIT. OAC patient-derived PBMCs co-cultured with OE33 OAC cells upregulated LAG-3 and downregulated the co-stimulatory marker CD27 on T cells, highlighting the direct immunosuppressive effects of tumour cells on T cells. Hypoxia and nutrient deprivation altered the secretome of OAC patient-derived PBMCs, which induced upregulation of PD-L1 and PD-L2 on OE33 OAC cells thus enhancing an immune-resistant phenotype. Importantly, culturing OAC patient-derived PBMCs under dual hypoxia and glucose deprivation, reflective of the conditions within the hostile TME, upregulated an array of ICs on the surface of T cells including PD-1, CTLA-4, A2aR, PD-L1 and PD-L2 and decreased expression of IFN-γ by T cells. Addition of nivolumab under these hostile conditions decreased the production of pro-tumorigenic cytokine IL-10.

Conclusion

Collectively, these findings highlight the immunosuppressive crosstalk between tumour cells and T cells within the OAC TME. The ability of nivolumab to suppress pro-tumorigenic T cell phenotypes within the hostile TME supports a rationale for the use of immune checkpoint blockade to promote anti-tumour immunity in OAC.

Graphical abstract

Study schematic: (A) IC expression profiles were assessed on CD45+ cells in peripheral whole blood and infiltrating tumour tissue from OAC patients in the treatment-naïve setting. (B) PBMCs were isolated from OAC patients and expanded ex vivo for 5 days using anti-CD3/28 + IL-2 T cell activation protocol and then co-cultured for 48 h with OE33 cells. T cell phenotypes were then assessed by flow cytometry. (C) PBMCs were isolated from OAC patients and expanded ex vivo for 5 days using anti-CD3/28 + IL-2 T cell activation protocol and then further cultured under conditions of nutrient deprivation or hypoxia for 48 h and T cell phenotypes were then assessed by flow cytometry. Key findings: (A) TIGIT, CTLA-4 and PD-L2 were upregulated on CD45+ immune cells and CTLA-4 expression on CD45+ cells correlated with a subsequent decreased response to neoadjuvant regimen. (B) Following a 48 h co-culture with OE33 cells, T cells upregulated LAG-3 and decreased CD27 co-stimulatory marker. (C) Nutrient deprivation and hypoxia upregulated a range of ICs on T cells and decreased IFN-γ production by T cells. Nivolumab decreased IL-10 production by T cells under nutrient deprivation-hypoxic conditions.

Glycosylation defects, offset by PEPCK-M, drive entosis in breast carcinoma cells

On glucose restriction, epithelial cells can undergo entosis, a cell-in-cell cannibalistic process, to allow considerable withstanding to this metabolic stress. Thus, we hypothesized that reduced protein glycosylation might participate in the activation of this cell survival pathway. Glucose deprivation promoted entosis in an MCF7 breast carcinoma model, as evaluated by direct inspection under the microscope, or revealed by a shift to apoptosis + necrosis in cells undergoing entosis treated with a Rho-GTPase kinase inhibitor (ROCKi). In this context, curbing protein glycosylation defects with N-acetyl-glucosamine partially rescued entosis, whereas limiting glycosylation in the presence of glucose with tunicamycin or NGI-1, but not with other unrelated ER-stress inducers such as thapsigargin or amino-acid limitation, stimulated entosis. Mitochondrial phosphoenolpyruvate carboxykinase (PEPCK-M; PCK2) is upregulated by glucose deprivation, thereby enhancing cell survival. Therefore, we presumed that PEPCK-M could play a role in this process by offsetting key metabolites into glycosyl moieties using alternative substrates. PEPCK-M inhibition using iPEPCK-2 promoted entosis in the absence of glucose, whereas its overexpression inhibited entosis. PEPCK-M inhibition had a direct role on total protein glycosylation as determined by Concanavalin A binding, and the specific ratio of fully glycosylated LAMP1 or E-cadherin. The content of metabolites, and the fluxes from ¹³C-glutamine label into glycolytic intermediates up to glucose-6-phosphate, and ribose- and ribulose-5-phosphate, was dependent on PEPCK-M content as measured by GC/MS. All in all, we demonstrate for the first time that protein glycosylation defects precede and initiate the entosis process and implicates PEPCK-M in this survival program to dampen the consequences of glucose deprivation. These results have broad implications to our understanding of tumor metabolism and treatment strategies.

Spautin-1 inhibits mitochondrial complex I and leads to suppression of the unfolded protein response and cell survival during glucose starvation

The unfolded protein response (UPR) is an adaptive stress response pathway that is essential for cancer cell survival under endoplasmic reticulum stress such as during glucose starvation. In this study, we identified spautin-1, an autophagy inhibitor that suppresses ubiquitin-specific peptidase 10 (USP10) and USP13, as a novel UPR inhibitor under glucose starvation conditions. Spautin-1 prevented the induction of UPR-associated proteins, including glucose-regulated protein 78, activating transcription factor 4, and a splicing variant of x-box-binding protein-1, and showed preferential cytotoxicity in glucose-starved cancer cells. However, USP10 and USP13 silencing and treatment with other autophagy inhibitors failed to result in UPR inhibition and preferential cytotoxicity during glucose starvation. Using transcriptome and chemosensitivity-based COMPARE analyses, we identified a similarity between spautin-1 and mitochondrial complex I inhibitors and found that spautin-1 suppressed the activity of complex I extracted from isolated mitochondria. Our results indicated that spautin-1 may represent an attractive mitochondria-targeted seed compound that inhibits the UPR and cancer cell survival during glucose starvation.

GRP78 in lung cancer

Glucose-regulating protein 78 (GRP78) is a molecular chaperone in the endoplasmic reticulum (ER) that promotes folding and assembly of proteins, controls the quality of proteins, and regulates ER stress signaling through Ca²⁺ binding to the ER. In tumors, GRP78 is often upregulated, acting as a central stress sensor that senses and adapts to changes in the tumor microenvironment, mediating ER stress of cancer cells under various stimulations of the microenvironment to trigger the folding protein response. Increasing evidence has shown that GRP78 is closely associated with the progression and poor prognosis of lung cancer, and plays an important role in the treatment of lung cancer. Herein, we reviewed for the first time the functions and mechanisms of GRP78 in the pathological processes of lung cancer, including tumorigenesis, apoptosis, autophagy, progression, and drug resistance, giving a comprehensive understanding of the function of GRP78 in lung cancer. In addition, we also discussed the potential role of GRP78 as a prognostic biomarker and therapeutic target for lung cancer, which is conducive to improving the assessment of lung cancer and the development of new therapeutic interventions.

Development of antitumor biguanides targeting energy metabolism and stress responses in the tumor microenvironment

To develop antitumor drugs capable of targeting energy metabolism in the tumor microenvironment, we produced a series of potent new biguanide derivatives via structural modification of the arylbiguanide scaffold. We then conducted biological screening using hypoxia inducible factor (HIF)-1- and unfolded protein response (UPR)-dependent reporter assays and selective cytotoxicity assay under low glucose conditions. Homologation studies of aryl-(CH2)n-biguanides (n = 0-6) yielded highly potent derivatives with an appropriate alkylene linker length (n = 5, 6). The o-chlorophenyl derivative 7l (n = 5) indicated the most potent inhibitory effects on HIF-1- and UPR-mediated transcriptional activation (IC50; 1.0 ± 0.1 μM, 7.5 ± 0.1 μM, respectively) and exhibited selective cytotoxicity toward HT29 cells under low glucose condition (IC50; 1.9 ± 0.1 μM). Additionally, the protein expression of HIF-1α induced by hypoxia and of GRP78 and GRP94 induced by glucose starvation was markedly suppressed by the biguanides, thereby inhibiting angiogenesis. Metabolic flux and fluorescence-activated cell sorting analyses of tumor cells revealed that the biguanides strongly inhibited oxidative phosphorylation and activated compensative glycolysis in the presence of glucose, whereas both were strongly suppressed in the absence of glucose, resulting in cellular energy depletion and apoptosis. These findings suggest that the pleiotropic effects of these biguanides may contribute to more selective and effective killing of cancer cells due to the suppression of various stress adaptation systems in the tumor microenvironment.

Dunaimycin C3, a new GRP78 downregulator from Streptomyces sp. RAN389

A new member of the dunaimycin family, dunaimycin C3 (2), was isolated from a fermented broth of Streptomyces sp. RAN389. The molecular formula of 2 was established as C₄₂H₇₀O₁₀ by high-resolution FAB-MS, and the structure was elucidated by NMR spectroscopic analyses. Dunaimycin C3 inhibited the expression of the molecular chaperone GRP78 in HT1080 G-L cells in the presence of 10 mM of 2-deoxyglucose with an IC₅₀ of 8.4 nM.

Neocurromycin A, a new GRP78 downregulator from Streptomyces sp. RAI364

A new curromycin-related compound, neocurromycin A (2), was isolated from the fermented broth of Streptomyces sp. RAI364. The molecular formula of 2 was established as C₃₅H₄₄N₄O₇ by ESI-MS and the structure was elucidated by NMR spectroscopic analyses. Neocurromycin A showed selective cytotoxicity against MKN45 human gastric cancer cells in a nutrient-deprived medium with an IC₅₀ of 380 nM and inhibited the expression of the molecular chaperone GRP78 in HT1080 G-L cells in the presence of 10 mM of 2-deoxyglucose with an IC₅₀ of 1.7 µM.

Pancastatin A and B Have Selective Cytotoxicity on Glucose-Deprived PANC-1 Human Pancreatic Cancer Cells

Glucose deprivation and hypoxia frequently occur in solid tumor cells, including pancreatic cancer cells. Glucose deprivation activates the unfolded protein response (UPR) and causes the upregulation of glucose-regulated protein 78 (GRP78). Induction of GRP78 has been shown to protect cancer cells. Therefore, shutting down of GRP78 expression may be a novel strategy in anticancer drug development. Based on this understanding, a screening system established for anticancer agents that exhibit selective cytotoxicity on pancreatic cancer cells under glucose-deprived conditions. To test this hypothesis, the new compounds isolated, pancastatin A (PST-A) and B (PSTB), from Ponciri Fructus. PST-A and B were identified as glabretal triterpenoid moieties by electrospray ionization mass spectrometry and nuclear magnetic resonance spectroscopic methods. PST-A and B suppressed the accumulation of the UPR hallmark gene, GRP78, during glucose deprivation. Furthermore, PST-A and B showed selective cytotoxicity on PANC-1 pancreatic cancer cells under glucose deprivation. Interestingly, PST-A and B had no effect on these cells under normal growth conditions. Our results suggest that PST-A and B act as novel therapeutic agents to induce selective cell death in glucose-deprived pancreatic cancer cells.

Kuanoniamine C stimulates bortezomib-induced cell death via suppression of glucose-regulated protein 78 in osteosarcoma

Osteosarcoma is the most frequent and intractable malignancy of the bone in children and young adults. Surgical operation requires extensive excision of the cancer tissue and neighboring normal tissues. In addition, anticancer drugs and radiation therapy are thought to be almost ineffective. Glucose-regulated protein 78 (GRP78), a cell-protective endoplasmic reticulum (ER) chaperone protein, is one of the most promising anticancer targets for osteosarcoma. Here, by analyzing the molecular mechanisms of kuanoniamine C, we report that kuanoniamine C suppresses GRP78 expression via GRP78 mRNA degradation in an ER stress response-independent manner. Interestingly, kuanoniamine C-induced cell death and downregulation of GRP78 expression was regulated by p53 signaling. Moreover, co-treatment with bortezomib, which is a newly identified anticancer drug for osteosarcoma, and kuanoniamine C suppressed GRP78 protein expression, which is essential for the stimulation of bortezomib-induced cell death. These results suggest that co-treatment with bortezomib and kuanoniamine C is a novel therapeutic strategy for the treatment of osteosarcoma that enhances bortezomib-dependent cell death by the downregulation of GRP78, and this combination selectively targets the major cell population of osteosarcoma, which expresses wild-type p53.

The oxazolomycin family: a review of current knowledge

Oxazolomycin A and neooxazolomycin were firstly isolated in 1985 by the group of Uemura et al. from the Streptomyces sp. bacteria.

microRNAs in Cardiovascular Disease: Small Molecules but Big Roles

microRNAs (miRNAs) are an evolutionarily conserved class of small single-stranded noncoding RNAs. The aberrant expression of specific miRNAs has been implicated in the development and progression of diverse cardiovascular diseases. For many decades, miRNA therapeutics has flourished, taking advantage of the fact that miRNAs can modulate gene expression and control cellular phenotypes at the posttranscriptional level. Genetic replacement or knockdown of target miRNAs by chemical molecules, referred to as miRNA mimics or inhibitors, has been used to reverse their abnormal expression as well as their adverse biological effects in vitro and in vivo in an effort to fully implement the therapeutic potential of miRNA-targeting treatment. However, the limitations of the chemical structure and delivery systems are hindering progress towards clinical translation. Here, we focus on the regulatory mechanisms and therapeutic trials of several representative miRNAs in the context of specific cardiovascular diseases; from this basic perspective, we evaluate chemical modifications and delivery vectors of miRNA-based chemical molecules and consider the underlying challenges of miRNA therapeutics as well as the clinical perspectives on their applications.

Parallel Signaling through IRE1α and PERK Regulates Pancreatic Neuroendocrine Tumor Growth and Survival

Master regulators of the unfolded protein response (UPR), IRE1α and PERK, promote adaptation or apoptosis depending on the level of endoplasmic reticulum (ER) stress. Although the UPR is activated in many cancers, its effects on tumor growth remain unclear. Derived from endocrine cells, pancreatic neuroendocrine tumors (PanNET) universally hypersecrete one or more peptide hormones, likely sensitizing these cells to high ER protein-folding stress. To assess whether targeting the UPR is a viable therapeutic strategy, we analyzed human PanNET samples and found evidence of elevated ER stress and UPR activation. Genetic and pharmacologic modulation of IRE1α and PERK in cultured cells, xenograft, and spontaneous genetic (RIP-Tag2) mouse models of PanNETs revealed that UPR signaling was optimized for adaptation and that inhibiting either IRE1α or PERK led to hyperactivation and apoptotic signaling through the reciprocal arm, thereby halting tumor growth and survival. These results provide a strong rationale for therapeutically targeting the UPR in PanNETs and other cancers with elevated ER stress. SIGNIFICANCE: The UPR is upregulated in pancreatic neuroendocrine tumors and its inhibition significantly reduces tumor growth in preclinical models, providing strong rationale for targeting the UPR in these cancers.

Leucinostatin Y: A Peptaibiotic Produced by the Entomoparasitic Fungus Purpureocillium lilacinum 40-H-28

Leucinostatin Y, a new peptaibiotic, was isolated from the culture broth of the entomoparasitic fungus Purpureocillium lilacinum 40-H-28. The planar structure was elucidated by detailed analysis of its NMR and MS/MS data. The absolute configurations of the amino acids were partially determined by an advanced Marfey's method. The biological activities of leucinostatin Y were assessed using human pancreatic cancer cells, revealing the importance of the C-terminus of leucinostatins for preferential cytotoxicity to cancer cells under glucose-deprived conditions and inhibition of mitochondrial function.

Targeting Proteotoxic Stress in Cancer: A Review of the Role that Protein Quality Control Pathways Play in Oncogenesis

Despite significant advances in cancer diagnostics and therapeutics the majority of cancer unfortunately remains incurable, which has led to continued research to better understand its exceptionally diverse biology. As a result of genomic instability, cancer cells typically have elevated proteotoxic stress. Recent appreciation of this functional link between the two secondary hallmarks of cancer: aneuploidy (oxidative stress) and proteotoxic stress, has therefore led to the development of new anticancer therapies targeting this emerging “Achilles heel” of malignancy. This review highlights the importance of managing proteotoxic stress for cancer cell survival and provides an overview of the integral role proteostasis pathways play in the maintenance of protein homeostasis. We further review the efforts undertaken to exploit proteotoxic stress in multiple myeloma (as an example of a hematologic malignancy) and triple negative breast cancer (as an example of a solid tumor), and give examples of: (1) FDA-approved therapies in routine clinical use; and (2) promising therapies currently in clinical trials. Finally, we provide new insights gleaned from the use of emerging technologies to disrupt the protein secretory pathway and repurpose E3 ligases to achieve targeted protein degradation.

Unfolded Protein Response as a Therapeutic Target in Cardiovascular Disease

Cardiovascular disease is the leading cause of death worldwide. Despite overwhelming socioeconomic impact and mounting clinical needs, our understanding of the underlying pathophysiology remains incomplete. Multiple forms of cardiovascular disease involve an acute or chronic disturbance in cardiac myocytes, which may lead to potent activation of the Unfolded Protein Response (UPR), a cellular adaptive reaction to accommodate protein-folding stress. Accumulation of unfolded or misfolded proteins in the Endoplasmic Reticulum (ER) elicits three signaling branches of the UPR, which otherwise remain quiescent. This ER stress response then transiently suppresses global protein translation, augments production of protein-folding chaperones, and enhances ER-associated protein degradation, with an aim to restore cellular homeostasis. Ample evidence has established that the UPR is strongly induced in heart disease. Recently, the mechanisms of action and multiple pharmacological means to favorably modulate the UPR are emerging to curb the initiation and progression of cardiovascular disease. Here, we review the current understanding of the UPR in cardiovascular disease and discuss existing therapeutic explorations and future directions.

Reprogramming of the antimycin NRPS-PKS assembly lines inspired by gene evolution

Reprogramming of the NRPS/PKS assembly line is an attractive method for the production of new bioactive molecules. However, it is usually hampered by the loss of intimate domain/module interactions required for the precise control of chain transfer and elongation reactions. In this study, we first establish heterologous expression systems of the unique antimycin-type cyclic depsipeptides: JBIR-06 (tri-lactone) and neoantimycin (tetra-lactone), and engineer their biosyntheses by taking advantage of bioinformatic analyses and evolutionary insights. As a result, we successfully accomplish three manipulations: (i) ring contraction of neoantimycin (from tetra-lactone to tri-lactone), (ii) ring expansion of JBIR-06 (from tri-lactone to tetra-lactone), and (iii) alkyl chain diversification of JBIR-06 by the incorporation of various alkylmalonyl-CoA extender units, to generate a set of unnatural derivatives in practical yields. This study presents a useful strategy for engineering NRPS-PKS module enzymes, based on nature’s diversification of the domain and module organizations.

Modifying the non-ribosomal peptide synthase (NRPS)/polyketide synthase (PKS) pathway to generate novel non-ribosomal peptides often results in a loss of productivity. Here the authors use evolutionary alignments of NRPS/PKS gene clusters to guide rational design of complexes that can produce novel lactones.

Chloroform fraction of Serratulae chinensis S. Moore suppresses proliferation and induces apoptosis via the phosphatidylinositide 3-kinase/Akt pathway in human gastric cancer cells

The chloroform fraction of the folk Chinese medicine, Serratulae chinensis S. Moore (CSC) and its anti-inflammatory activity is well recognized. However, the molecular mechanisms underlying the beneficial anticancer effects of CSC remain largely unknown. The aim of the present study was to examine the effects of CSC on the regulation of cell proliferation and apoptosis in SGC-7901 gastric cancer cells, as well as to investigate the underlying molecular mechanisms involved. The results from the present study demonstrated that CSC treatment inhibited SGC-7901 cell viability and survival in a dose- and/or time-dependent manner. CSC treatment further induced the apoptosis of SGC-7901 cells, characterized by distinct chromatin condensation and fragmented nuclear morphology. In addition, CSC treatment suppressed protein kinase-B (Akt) phosphorylation and phosphatidylinositide 3-kinase (PI3K) expression in SGC-7901 cells, which in turn promoted cancer cell apoptosis and inhibited cell proliferation. Furthermore, CSC treatment altered the expression pattern of several key target genes of the PI3K/Akt signaling pathway through the downregulation of Cyclin D1, cyclin-dependent kinase-4 and B-cell lymphoma-2 and the upregulation of Bcl-2-associated X protein. Therefore, the results from the present study demonstrated that CSC suppressed cell survival and induced apoptosis in human gastric cancer cells, via targeting the PI3K/Akt pathway.

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.

Anti-cancer agents and reactive oxygen species modulators that target cancer cell metabolism

Traditionally the perspective on reactive oxygen species (ROS) has centered on the role they play as carcinogenic or cancer-causing radicals. Over the years, characterization and functional studies have revealed the complexity of ROS as signaling molecules that regulate various physiological cellular responses or whose levels are altered in various diseases. Cancer cells often maintain high basal level of ROS and are vulnerable to any further increase in ROS levels beyond a certain protective threshold. Consequently, ROS-modulation has emerged as an anticancer strategy with synthesis of various ROS-inducing or responsive agents that target cancer cells. Of note, an increased carbohydrate uptake and/or induction of death receptors of cancer cells was exploited to develop glycoconjugates that potentially induce cellular stress, ROS and apoptosis. This mini review highlights the development of compounds that target cancer cells by taking advantage of redox or metabolic alteration in cancer cells.

Questiomycin A stimulates sorafenib-induced cell death via suppression of glucose-regulated protein 78

Hepatocellular carcinoma (HCC) is one of the most difficult cancers to treat owing to the lack of effective chemotherapeutic methods. Sorafenib, the first-line and only available treatment for HCC, extends patient overall survival by several months, with a response rate below 10%. Thus, the identification of an agent that enhances the anticancer effect of sorafenib is critical for the development of therapeutic options for HCC. Endoplasmic reticulum (ER) stress response is one of the methods of sorafenib-induced cell death. Here we report that questiomycin A suppresses expression of GRP78, a cell-protective ER chaperone protein. Analysis of the molecular mechanisms of questiomycin A revealed that this compound stimulated GRP78 protein degradation in an ER stress response-independent manner. Cotreatment with sorafenib and questiomycin A suppressed GRP78 protein expression, which is essential for the stimulation of sorafenib-induced cell death. Moreover, our in vivo study demonstrated that the coadministration of sorafenib and questiomycin A suppressed tumor formation in HCC-induced xenograft models. These results suggest that cotreatment with sorafenib and questiomycin A is a novel therapeutic strategy for HCC by enhancing sorafenib-dependent ER stress-induced cell death, and downregulation of GRP78 is a new target for the stimulation of the therapeutic effects of sorafenib in HCC.

Tissue cell stress response to obesity and its interaction with late gestation diet

Intrauterine growth restriction in late pregnancy can contribute to adverse long-term metabolic health in the offspring. In the present study we used an animal (sheep) model of maternal dietary manipulation in late pregnancy, combined with exposure of the offspring to a low-activity, obesogenic environment after weaning, to characterise the effects on glucose homeostasis. Dizygotic twin-pregnant sheep were either fed to 60% of requirements (nutrient restriction (R)) or fed ad libitum (~140% of requirements (A)) from 110 days gestation until term (~147 days). After weaning (~3 months of age), the offspring were kept in either a standard (in order to remain lean) or low-activity, obesogenic environment. R mothers gained less weight and produced smaller offspring. As adults, obese offspring were heavier and fatter with reduced glucose tolerance, regardless of maternal diet. Molecular markers of stress and autophagy in liver and adipose tissue were increased with obesity, with gene expression of hepatic glucose-related protein 78 (Grp78) and omental activation transcription factor 6 (Atf6), Grp78 and ER stress degradation enhancer molecule 1 (Edem1) only being increased in R offspring. In conclusion, the adverse effect of juvenile-onset obesity on insulin-responsive tissues can be amplified by previous exposure to a suboptimal nutritional environment in utero, thereby contributing to earlier onset of insulin resistance.

Noninvasive and Highly Selective Monitoring of Intracellular Glucose via a Two-Step Recognition-Based Nanokit

Accurate determination of intracellular glucose is very important for exploring its chemical and biological functions in metabolism events of living cells. In this paper, we developed a new noninvasive and highly selective nanokit for intracellular glucose monitoring via two-step recognition. The liposome-based nanokit coencapsulated the aptamer-functionalized gold nanoparticles (AuNPs) and the Shinkai's receptor together. When the proposed nanokit was transfected into living cells, the Shinkai's receptor could recognize glucose first and then changed its conformation to endow aptamers with binding and sensing properties which were not readily accessible otherwise. Then, the binary complexes formed by the intracellular glucose and the Shinkai's receptor can in situ displace the complementary oligonucleotide of the aptamer on the surface of AuNPs. The fluorophore-labeled aptamer was away from the AuNPs, and the fluorescent state switched from "off" to "on". Through the secondary identification of aptamer, the selectivity of the Shinkai's receptor could be greatly improved while the intracellular glucose level was assessed by fluorescence signal recovery of aptamer. In the follow-up application, the approach exhibits excellent selectivity and is noninvasive for intracellular glucose monitoring under normoxia and hypoxia. To the best of our knowledge, this is the first time that the advantages of organic receptors and nucleic acids have been combined and highly selective monitoring of intracellular glucose has been realized via two-step recognition. We expect it to open up new possibilities to integrate devices for diagnosis of various metabolic diseases and insulin delivery.

Inhibition of Sp1 prevents ER homeostasis and causes cell death by lysosomal membrane permeabilization in pancreatic cancer

Endoplasmic reticulum (ER) stress initiates an important mechanism for cell adaptation and survival, named the unfolded protein response (UPR). Severe or chronic/prolonged UPR can breach the threshold for survival and lead to cell death. There is a fundamental gap in knowledge on the molecular mechanism of how chronic ER stress is stimulated and leads to cell death in pancreatic ductal adenocarcinoma (PDAC). Our study shows that downregulating specificity protein 1 (Sp1), a transcription factor that is overexpressed in pancreatic cancer, activates UPR and results in chronic ER stress. In addition, downregulation of Sp1 results in its decreased binding to the ER stress response element present in the promoter region of Grp78, the master regulator of ER stress, thereby preventing homeostasis. We further show that inhibition of Sp1, as well as induction of ER stress, leads to lysosomal membrane permeabilization (LMP), a sustained accumulation of cytosolic calcium, and eventually cell death in pancreatic cancer.

New frontiers in the treatment of colorectal cancer: Autophagy and the unfolded protein response as promising targets

Colorectal cancer (CRC), despite numerous therapeutic and screening attempts, still remains a major life-threatening malignancy. CRC etiology entails both genetic and environmental factors. Macroautophagy/autophagy and the unfolded protein response (UPR) are fundamental mechanisms involved in the regulation of cellular responses to environmental and genetic stresses. Both pathways are interconnected and regulate cellular responses to apoptotic stimuli. In this review, we address the epidemiology and risk factors of CRC, including genetic mutations leading to the occurrence of the disease. Next, we discuss mutations of genes related to autophagy and the UPR in CRC. Then, we discuss how autophagy and the UPR are involved in the regulation of CRC and how they associate with obesity and inflammatory responses in CRC. Finally, we provide perspectives for the modulation of autophagy and the UPR as new therapeutic options for CRC treatment.

Endoplasmic reticulum-mediated unfolded protein response and mitochondrial apoptosis in cancer

Abrogation of endoplasmic reticulum (ER) protein folding triggered by exogenous or endogenous factors, stimulates a cellular stress response, termed ER stress. ER stress re-establishes ER homeostasis through integrated signaling termed the ER-unfolded protein response (UPR^ER). In the presence of severe toxic or prolonged ER stress, the pro-survival function of UPR^ER is transformed into a lethal signal transmitted to and executed through mitochondria. Mitochondria are key for both apoptotic and autophagic cell death. Thus ER is vital in sensing and coordinating stress pathways to maintain overall physiological homeostasis. However, this function is deregulated in cancer, resulting in resistance to apoptosis induction in response to various stressors including therapeutic agents. Here we review the connections between ER stress and mitochondrial apoptosis, describing potential cancer therapeutic targets.

Immunomodulation by MYB is associated with tumor relapse in patients with early stage colorectal cancer

The presence of tumor immune infiltrating cells (TILs), particularly CD8⁺ T-cells, is a robust predictor of outcome in patients with colorectal cancer (CRC). We revisited TIL abundance specifically in patients with microsatellite stable (MSS) CRC without evidence of lymph node or metastatic spread. Examination of the density of CD8⁺ T-cells in primary tumors in the context of other pro-oncogenic markers was performed to investigate potential regulators of TILs. Two independent cohorts of patients with MSS T2-4N0M0 CRC, enriched for cases with atypical relapse, were investigated. We quantified CD8⁺ and CD45RO⁺ -TILs, inflammatory markers, NFkBp65, pStat3, Cyclo-oxygenase-2 (COX2) and GRP78 as well as transcription factors (TF), β-catenin and MYB. High CD8⁺ TILs correlated with a better relapse-free survival in both cohorts (p = 0.002) with MYB and its target gene, GRP78 being higher in the relapse group (p = 0.001); no difference in pSTAT3 and p65 was observed. A mouse CRC (CT26) model was employed to evaluate the effect of MYB on GRP78 expression as well as T-cell infiltration. MYB over-expressing in CT26 cells increased GRP78 expression and the analysis of tumor-draining lymph nodes adjacent to tumors showed reduced T-cell activation. Furthermore, MYB over-expression reduced the efficacy of anti-PD-1 to modulate CT26 tumor growth. This high MYB and GRP78 show a reciprocal relationship with CD8⁺ TILs which may be useful refining the prediction of patient outcome. These data reveal a new immunomodulatory function for MYB suggesting a basis for further development of anti-GRP78 and/or anti-MYB therapies.

Melanoma and the Unfolded Protein Response

The UPR (unfolded protein response) has been identified as a key factor in the progression and metastasis of cancers, notably melanoma. Several mediators of the UPR are upregulated in cancers, e.g., high levels of GRP78 (glucose-regulator protein 78 kDa) correlate with progression and poor outcome in melanoma patients. The proliferative burden of cancer induces stress and activates several cellular stress responses. The UPR is a tightly orchestrated stress response that is activated upon the accumulation of unfolded proteins within the ER (endoplasmic reticulum). The UPR is designed to mediate two conflicting outcomtes, recovery and apoptosis. As a result, the UPR initiates a widespread signaling cascade to return the cell to homeostasis and failing to achieve cellular recovery, initiates UPR-induced apoptosis. There is evidence that ER stress and subsequently the UPR promote tumourigenesis and metastasis. The complete role of the UPR has yet to be defined. Understanding how the UPR allows for adaption to stress and thereby assists in cancer progression is important in defining an archetype of melanoma pathology. In addition, elucidation of the mechanisms of the UPR may lead to development of effective treatments of metastatic melanoma.

Effect of nutrient starvation on proliferation and cytokine secretion of peripheral blood lymphocytes

Proliferating cancer cells are exposed to nutrient deprivation. Numerous previous studies have demonstrated how nutrient deprivation affects cancer cells; however, immune cells exposed to the identical conditions have not been completely examined. Furthermore, T-helper 2 lymphocyte predominance in certain neoplastic diseases has been reported; however, the mechanism remains unclear. The present study aimed to confirm whether nutrient deprivation affected proliferation and cytokine secretion of peripheral blood lymphocytes (PBLs). The proliferation of PBLs from healthy donors, cultured in a medium containing various glucose levels, was assessed by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium, inner salt (MTS) assay. The expression levels of interleukin (IL)-4 and interferon (IFN)-γ among CD4(+) T cells, cultured with or without glucose and activated with phorbol 12-myristate 13-acetate and ionomycin, were examined using an intracellular cytokine staining method. The proliferation of PBLs cultured in a medium containing <100 mg/dl glucose of the standard blood sugar (BS) level was significantly reduced compared with the proliferation observed in a medium containing a standard BS level or higher. PBLs cultured in a glucose-free medium contained a significantly higher percentage of IL-4-positive and a lower percentage of IFN-γ-positive CD4(+) T cells compared with those cultured in a high-glucose medium. Nutrient deprivation suppressed the proliferation of PBLs, fostered the secretion of IL-4 and reduced secretion of IFN-γ. It is therefore possible that glucose-deficient microenvironments in local cancer tissues cause a partial immunodeficiency, which is advantageous to cancer growth.

High TXNDC5 expression predicts poor prognosis in renal cell carcinoma

Clear cell renal cell carcinoma (ccRCC) is the most common primary kidney cancer in adults, and the identification of biomarkers involved in the pathogenesis and prognosis of ccRCC is crucial for early diagnosis and anticancer treatment. In this study, we demonstrate that thioredoxin domain-containing protein 5 (TXNDC5) expression is markedly upregulated in ccRCC tissues in comparison with adjacent non-cancerous tissues through quantitative RT-PCR, Western blotting, and immunohistochemical analyses. Importantly, TXNDC5 expression is negatively correlated with the overall survival of patients. Knockdown of TXNDC5 by siRNAs inhibits the cell growth, migration, and invasion of ccRCC cells as well as sensitizes ccRCC cells to chemotherapeutic drugs, such as Camptothecin and 5-Fluorouracil. Moreover, we used complementary DNA (cDNA) microarray analyses to explore the underlying molecular mechanisms of TXNDC5 in the pathogenesis of ccRCC. We demonstrate that knockdown of TXNDC5 affects the messenger RNA (mRNA) and protein levels of numerous important genes associated with tumorigenesis. In summary, our findings indicate that TXNDC5 performs an essential function in ccRCC pathogenesis and can serve as a novel prognostic marker of ccRCC.

Cancer Microenvironment and Endoplasmic Reticulum Stress Response

Different stressful conditions such as hypoxia, nutrient deprivation, pH changes, or reduced vascularization, potentially able to act as growth-limiting factors for tumor cells, activate the unfolded protein response (UPR). UPR is therefore involved in tumor growth and adaptation to severe environments and is generally cytoprotective in cancer. The present review describes the molecular mechanisms underlying UPR and able to promote survival and proliferation in cancer. The critical role of UPR activation in tumor growth promotion is discussed in detail for a few paradigmatic tumors such as prostate cancer and melanoma.

Protein Folding and Mechanisms of Proteostasis

Highly sophisticated mechanisms that modulate protein structure and function, which involve synthesis and degradation, have evolved to maintain cellular homeostasis. Perturbations in these mechanisms can lead to protein dysfunction as well as deleterious cell processes. Therefore in recent years the etiology of a great number of diseases has been attributed to failures in mechanisms that modulate protein structure. Interconnections among metabolic and cell signaling pathways are critical for homeostasis to converge on mechanisms associated with protein folding as well as for the preservation of the native structure of proteins. For instance, imbalances in secretory protein synthesis pathways lead to a condition known as endoplasmic reticulum (ER) stress which elicits the adaptive unfolded protein response (UPR). Therefore, taking this into consideration, a key part of this paper is developed around the protein folding phenomenon, and cellular mechanisms which support this pivotal condition. We provide an overview of chaperone protein function, UPR via, spatial compartmentalization of protein folding, proteasome role, autophagy, as well as the intertwining between these processes. Several diseases are known to have a molecular etiology in the malfunction of mechanisms responsible for protein folding and in the shielding of native structure, phenomena which ultimately lead to misfolded protein accumulation. This review centers on our current knowledge about pathways that modulate protein folding, and cell responses involved in protein homeostasis.

Ethanolic extract of Tulipa edulis Bak induces apoptosis in SGC-7901 human gastric carcinoma cells via the mitochondrial signaling pathway

Tulipa edulis Bak (TEB) is an active ingredient in various traditional Chinese medicine compounds and is commonly used to treat swelling and redness, remove toxicity and eliminate stagnation, as well as to prevent and treat certain cancer types. However, the underlying molecular mechanism of the anticancer activity of TEB remains unclear. The aim of the current study was to investigate the effect and underlying mechanism of the ethanolic extract of TEB (EETEB) on SGC-7901 human gastric carcinoma cells. An MTT assay was performed to analyze cell viability. In addition, transmission electron microscopy, an Annexin V/fluorescein isothiocyanate assay, a JC-1 assay and laser scanning confocal microscopy with DAPI staining were used to determine the rate of apoptosis. Furthermore, reverse transcription-polymerase chain reaction and western blot analysis were used to detect the expression levels of the apoptosis gene and protein. EETEB was identified to inhibit the growth of SGC-7901 cells in a dose-dependent manner and induce changes in cell morphology. At the molecular level, EETEB induced SGC-7901 cell DNA fragmentation, loss of plasma membrane and asymmetrical collapse of the mitochondrial membrane potential, while it increased the expression of pro-apoptotic B-cell lymphoma-2 (Bcl-2)-associated X protein and reduced expression of anti-apoptotic Bcl-2. Thus, the results of the current study revealed that the application of EETEB may inhibit the growth of the SGC-7901 cells due to mitochondria-mediated apoptosis.

Metabolic stress induces a Wnt-dependent cancer stem cell-like state transition

Reciprocal interactions between cancer cells and the tumor microenvironment drive multiple clinically significant behaviors including dormancy, invasion, and metastasis as well as therapy resistance. These microenvironment-dependent phenotypes share typical characteristics with cancer stem cells (CSC). However, it is poorly understood how metabolic stress in the confined tumor microenvironment contributes to the emergence and maintenance of CSC-like phenotypes. Here, we demonstrate that chronic metabolic stress (CMS) in a long-term nutrient deprivation induces a Wnt-dependent phenoconversion of non-stem cancer cells toward stem-like state and this is reflected in the transcriptome analysis. Addition of Wnt3a as well as transfection of dominant-negative Tcf4 establishes an obligatory role for the Wnt pathway in the acquisition of CSC-like characteristics in response to metabolic stress. Furthermore, systematic characterization for multiple single cell-derived clones and negative enrichment of CD44+/ESA+ stem-like cancer cells, all of which recapitulate stem-like cancer characteristics, suggest stochastic adaptation rather than selection of pre-existing subclones. Finally, CMS in the tumor microenvironment can drive a CSC-like phenoconversion of non-stem cancer cells through stochastic state transition dependent on the Wnt pathway. These findings contribute to an understanding of the metabolic stress-driven dynamic transition of non-stem cancer cells to a stem-like state in the tumor metabolic microenvironment.

Down-regulation of the autophagy gene, ATG7, protects bone marrow-derived mesenchymal stem cells from stressful conditions

Background

Mesenchymal stem cells (MSCs) are valuable for cell-based therapy. However, their application is limited owing to their low survival rate when exposed to stressful conditions. Autophagy, the process by which cells recycle the cytoplasm and dispose of defective organelles, is activated by stress stimuli to adapt, tolerate adverse conditions, or trigger the apoptotic machinery. This study aimed to determine whether regulation of autophagy would affect the survival of MSCs under stress conditions.

Methods

Autophagy was induced in bone marrow-derived MSCs (BM-MSCs) by rapamycin, and was inhibited via shRNA-mediated knockdown of the autophagy specific gene, ATG7. ATG7 expression in BM-MSCs was evaluated by reverse transcription polymerase chain reaction (RT-PCR), western blot, and quantitative PCR (qPCR). Cells were then exposed to harsh microenvironments, and a water-soluble tetrazolium salt (WST)-1 assay was performed to determine the cytotoxic effects of the stressful conditions on cells.

Results

Of 4 specific ATG7-inhibitor clones analyzed, only shRNA clone 3 decreased ATG7 expression. Under normal conditions, the induction of autophagy slightly increased the viability of MSCs while autophagy inhibition decreased their viability. However, under stressful conditions such as hypoxia, serum deprivation, and oxidative stress, the induction of autophagy resulted in cell death, while its inhibition potentiated MSCs to withstand the stress conditions. The viability of autophagy-suppressed MSCs was significantly higher than that of relevant controls (P<0.05, P<0.01 and P<0.001).

Conclusion

Autophagy modulation in MSCs can be proposed as a new strategy to improve their survival rate in stressful microenvironments.

Small-Animal PET Imaging of Pancreatic Cancer Xenografts Using a 64Cu-Labeled Monoclonal Antibody, MAb159

Overexpression of the GRP78 receptor on cell surfaces has been linked with tumor growth, metastasis, and resistance to therapy. We developed a (64)Cu-labeled probe for PET imaging of tumor GRP78 expression based on a novel anti-GRP78 monoclonal antibody, MAb159.

METHODS

MAb159 was conjugated with the (64)Cu-chelator DOTA through lysines on the antibody. DOTA-human IgG was also prepared as a control that did not bind to GRP78. The resulting PET probes were evaluated in BXPC3 pancreatic cancer xenografts in athymic nude mice.

RESULTS

The radiotracer was synthesized with a specific activity of 0.8 MBq/μg of antibody. In BXPC3 xenografts, (64)Cu-DOTA-MAb159 demonstrated prominent tumor accumulation (4.3 ± 1.2, 15.4 ± 2.6, and 18.3 ± 1.0 percentage injected dose per gram at 1, 17, and 48 after injection, respectively). In contrast, (64)Cu-DOTA-human IgG had low BXPC3 tumor accumulation (4.8 ± 0.5, 7.5 ± 0.7, and 4.6 ± 0.8 percentage injected dose per gram at 1, 17, and 48 h after injection, respectively).

CONCLUSION

We demonstrated that GRP78 can serve as a valid target for pancreatic cancer imaging. The success of this approach will be valuable for evaluating disease course and therapeutic efficacy at the earliest stages of anti-GRP78 treatment. Moreover, these newly developed probes may have important applications in other types of cancer overexpressing GRP78.

Stress responses from the endoplasmic reticulum in cancer

The endoplasmic reticulum (ER) is a dynamic organelle that is essential for multiple cellular functions. During cellular stress conditions, including nutrient deprivation and dysregulation of protein synthesis, unfolded/misfolded proteins accumulate in the ER lumen, resulting in activation of the unfolded protein response (UPR). The UPR also contributes to the regulation of various intracellular signaling pathways such as calcium signaling and lipid signaling. More recently, the mitochondria-associated ER membrane (MAM), which is a site of close contact between the ER and mitochondria, has been shown to function as a platform for various intracellular stress responses including apoptotic signaling, inflammatory signaling, the autophagic response, and the UPR. Interestingly, in cancer, these signaling pathways from the ER are often dysregulated, contributing to cancer cell metabolism. Thus, the signaling pathway from the ER may be a novel therapeutic target for various cancers. In this review, we discuss recent research on the roles of stress responses from the ER, including the MAM.

Spirotetronate polyketides as leads in drug discovery

The discovery of chlorothricin (1) defined a new family of microbial metabolites with potent antitumor antibiotic properties collectively referred to as spirotetronate polyketides. These microbial metabolites are structurally distinguished by the presence of a spirotetronate motif embedded within a macrocyclic core. Glycosylation at the periphery of this core contributes to the structural complexity and bioactivity of this motif. The spirotetronate family displays impressive chemical structures, potent bioactivities, and significant pharmacological potential. This review groups the family members based on structural and biosynthetic considerations and summarizes synthetic and biological studies that aim to elucidate their mode of action and explore their pharmacological potential.

Expression and significance of glucose-regulated protein 78 in human osteosarcoma

The present study aimed to investigate the expression of glucose-regulated protein 78 (GRP78) in osteosarcoma cells, and analyze the differences in expression between tumor and normal tissues, pre- and post-chemotherapy patients and metastatic and non-metastatic tumors. According to these results, the associations between the expression of GRP78 and tumor growth, metastasis and chemotherapeutics could be determined. Between 2007 and 2012, 60 patients who had been diagnosed with osteosarcoma were selected for the present study. Of these patients, 20 presented with non-metastatic tumors and 40 with metastatic tumors, and 20 had been treated without chemotherapy and 40 with chemotherapy. In addition, 60 specimens obtained from adjacent normal tissues were collected for the control groups. Immunofluorescence staining was used to examine the expression of GRP78 in the different tissues. The total RNA and protein were extracted from crushed tissues and used in the reverse transcription polymerase chain reaction and western blot analysis. GRP78 was primarily located in the intracavity of the endoplasmic reticulum. The expression level of GRP78 in the tumor tissue was higher than that in the normal tissue surrounding the tumor (P<0.01). In addition, the level was higher in the metastatic tumors compared with the non-metastatic tumors (P<0.05), and in the non-chemotherapy-treated patients compared with the chemotherapy-treated patients (P<0.01). The expression level of GRP78 mRNA in the tumor tissue was higher than that in the normal tissue (P<0.01). Furthermore, the level was higher in the metastasis group than in the non-metastasis group (P<0.05), and in the non-chemotherapy group than in the chemotherapy group (P<0.01). The expression level of GRP78 protein was higher in the tumor tissue compared with the normal tissue (P<0.01), in the metastasis group compared with the non-metastasis group (P<0.05), and in the non-chemotherapy group compared with the chemotherapy group (P<0.01). In conclusion, the present study detected the expression of GRP78 in patients with osteosarcoma and revealed a higher expression level in the tumor tissues compared with the normal tissues around the tumor, in the metastasis group compared with the non-metastasis group and in the non-chemotherapy-treated group compared with the chemotherapy-treated group.

Disruption of the unfolded protein response (UPR) by lead compound selectively suppresses cancer cell growth

Identifying chemotherapy candidates with high selectivity against cancer cells is a major challenge in cancer treatment. Tumor microenvironments cause chronic endoplasmic reticulum (ER) stress and activate the unfolded protein response (UPR) as an adaptive response. Here, one novel small-molecule compound, 17#, was discovered as a potent pan-UPR inhibitor. It exhibited good selection for growth inhibition when cancer cells were cultured in 2-deoxy-D-glucose (2DG), mimicking an in vitro glucose-deprived status. Additionally, 17# alone could mildly suppress the growth of HeLa tumor xenografts, and a synergistic anti-cancer effect was observed when 17# was combined with 2DG. A mechanistic study showed that 17#-induced selective anti-cancer effects were highly dependent on UPR inhibition, and overexpressing GRP78 or XBP1s reversed the 17#-induced growth inhibition and cell cycle arrest, partially by delaying the downregulation of the cell cycle regulator cyclin B1. Furthermore, 17# improved the sensitivity of anti-cancer drugs such as doxorubicin or etoposide. Our study presents evidence that disrupting the UPR has selective therapeutic potential and may enhance drug sensitivity.

Screening of trace elements in hair of the female population with different types of cancers in Wielkopolska region of Poland

Background. Cancer constitutes a major health problem worldwide. Thus, search for reliable and practical markers of the disease process remains the key issue of the diagnostic process. Objectives. The study aims at linking the trace element status of an organism, assessed by hair analysis, with the occurrence of cancer diseases. Material and Methods. Hair samples were collected from 299 patients with cancer diseases confirmed by a histopathological test and from 100 controls. Cancer patients were divided into three groups, depending on cancer type: hormone-dependent cancer, cancer of the alimentary tract, and cancer with high glycolytic activity. Mineral element analysis of hair was performed using an atomic emission spectrophotometer with inductively coupled plasma (ICP-OES) and inductively coupled plasma mass spectrometry (ICP-MS). Results. Statistically significantly lower concentrations of selenium, zinc, copper, germanium and boron, iron, and magnesium were observed in the three groups of cancer patients. Disturbance in the axis glucose-insulin and changes in concentrations of heavy metals and toxic elements were also noted. Conclusions. It seems safe to conclude that our results confirmed usefulness of hair element analysis in screening tests for the assessment of the biomarker of various cancer diseases in a female population.