Protein disulfide isomerase expression is related to the invasive properties of malignant glioma

Proteomics of gliomas: initial biomarker discovery and evolution of technology

Gliomas are a group of aggressive brain tumors that diffusely infiltrate adjacent brain tissues, rendering them largely incurable, even with multiple treatment modalities and agents. Mostly asymptomatic at early stages, they present in several subtypes with astrocytic or oligodendrocytic features and invariably progress to malignant forms. Gliomas are difficult to classify precisely because of interobserver variability during histopathologic grading. Identifying biological signatures of each glioma subtype through protein biomarker profiling of tumor or tumor-proximal fluids is therefore of high priority. Such profiling not only may provide clues regarding tumor classification but may identify clinical biomarkers and pathologic targets for the development of personalized treatments. In the past decade, differential proteomic profiling techniques have utilized tumor, cerebrospinal fluid, and plasma from glioma patients to identify the first candidate diagnostic, prognostic, predictive, and therapeutic response markers, highlighting the potential for glioma biomarker discovery. The number of markers identified, however, has been limited, their reproducibility between studies is unclear, and none have been validated for clinical use. Recent technological advancements in methodologies for high-throughput profiling, which provide easy access, rapid screening, low sample consumption, and accurate protein identification, are anticipated to accelerate brain tumor biomarker discovery. Reliable tools for biomarker verification forecast translation of the biomarkers into clinical diagnostics in the foreseeable future. Herein we update the reader on the recent trends and directions in glioma proteomics, including key findings and established and emerging technologies for analysis, together with challenges we are still facing in identifying and verifying potential glioma biomarkers.

The phosphoinositide 3-kinase inhibitor LY294002, decreases aminoacyl-tRNA synthetases, chaperones and glycolytic enzymes in human HT-29 colorectal cancer cells

The proposed anticancer drug LY294002, inhibits phosphoinositide-3 kinase (PI3K) that initiates a signalling pathway often activated in colorectal cancer (CRC). The effects of LY294002 (10 μM, 48 h) on the cytosolic, mitochondrial and nuclear proteomes of human HT-29 CRC cells have been determined using iTRAQ (isobaric tag for relative and absolute quantitation) and tandem mass spectrometry (MS/MS). Analysis of cells treated with LY294002 identified 26 differentially abundant proteins that indicate several mechanisms of action. The majority of protein changes were directly or indirectly associated with Myc and TNF-α, previously implicated in CRC progression. LY294002 decreased the levels of 6 aminoacyl-tRNA synthetases (average 0.39-fold) required for protein translation, 5 glycolytic enzymes (average 0.37-fold) required for ATP synthesis, and 3 chaperones required for protein folding. There was a 3.2-fold increase in lysozyme C involved in protein-glycoside hydrolysis. LY294002 increased cytosolic p53 with a concomitant decrease in nuclear p53, suggesting transfer of p53 to the cytosol where apoptosis might be initiated via the intrinsic mitochondrial pathway. Protein changes described here suggest that the anti-angiogenic effects of LY294002 may be related to p53; the mutational status of p53 in CRC may be an important determinant of the efficacy of PI3K inhibitors for treatment.

Identification of two portal vein tumor thrombosis associated proteins in hepatocellular carcinoma: protein disulfide-isomerase A6 and apolipoprotein A-I

BACKGROUND AND AIM

Portal vein tumor thrombus (PVTT) is one of the factors that can affect prognosis and survival of hepatocellular carcinoma (HCC). In the present study, we aimed to find out some biomarkers associated with vascular invasion features of HCC with the method of comparative proteomic analysis.

METHODS

The proteins were extracted from a pair of HCC tissues with PVTT and without PVTT, and then separated by two-dimensional polyacrylamide gel electrophoresis. Differentially expressed protein spots were identified by matrix assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS). Further analysis of two proteins were completed using real-time fluorescence quantitative polymerase chain reaction and western-blot in 40 HCC tissues with PVTT (n = 20) and without PVTT (n = 20).

RESULTS

Among 465 protein spots displayed on the gels, 33 unique proteins (> twofold change, P < 0.01) were identified, including 24 upregulated in HCC tissue without PVTT and nine upregulated in HCC tissue with PVTT. The real-time fluorescence quantitative PCR showed no statistically significant difference between HCC tissues with PVTT and without PVTT for mRNA expressions of protein disulfide-isomerase, A6 (PDI A6) (P = 0.137) and apolipoprotein A-I (Apo A-I) (P = 0.718). However, compared with HCC tissues without PVTT, protein expression of PDI A6 was higher in HCC tissues with PVTT (P < 0.001), while protein expression of Apo A-I was lower in HCC tissues with PVTT (P = 0.012).

CONCLUSIONS

PDI A6 and Apo A-I are closely related to vascular invasion feature of HCC.

Novel animal glioma models that separately exhibit two different invasive and angiogenic phenotypes of human glioblastomas

OBJECTIVE

Invasive behaviors of malignant gliomas are fundamental traits and major reasons for treatment failure. Delineation of invasive growth is important in establishing treatment for gliomas and experimental neuro-oncology could benefit from an invasive glioma model. In this study, we established two new cell line-based animal models of invasive glioma.

METHODS

Two cell lines, J3T-1 and J3T-2, were derived from the same parental canine glioma cell line, J3T. These cells were inoculated to establish brain tumors in athymic mice and rats. Pathologic samples of these animal gliomas were examined to analyze invasive patterns in relation to angiogenesis, and were compared with human glioblastoma samples. The molecular profiles of these cell lines were also shown.

RESULTS

Histologically, J3T-1 and J3T-2 tumors exhibited different invasive patterns. J3T-1 cells clustered around newly developed vessels at tumor borders, whereas J3T-2 cells showed diffuse single cell infiltration into surrounding healthy parenchyma. In human malignant glioma samples, both types of invasion were observed concomitantly. Molecular profiles of these cell lines were analyzed by immunocytochemistry and with quantitative reverse transcription polymerase chain reaction. Vascular endothelial growth factor, matrix metalloproteinase-9, hypoxia-inducible factor-1, and platelet-derived growth factor were overexpressed in J3T-1 cells rather than in J3T-2 cells, whereas integrin αvβ3, matrix metalloproteinase-2, nestin, and secreted protein acidic and rich in cysteine were overexpressed in J3T-2 cells rather than in J3T-1 cells.

CONCLUSIONS

These animal models histologically recapitulated two invasive and angiogenic phenotypes, namely angiogenesis-dependent and angiogenesis-independent invasion, also observed in human glioblastoma. These cell lines provided a reproducible in vitro and in vivo system to analyze the mechanisms of invasion and angiogenesis in glioma progression.

Proteomics and bioinformatics analysis of lovastatin-induced differentiation in ARO cells

Lovastatin (lova), a 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor, can induce differentiation in cancer cells at low concentration, thus having potential to be used as an auxiliary agent in cancer therapy. However, biological networks associated with the differentiation effect of lova have not been elucidated. To investigate molecular mechanisms of lova, the present study was aimed at proteomics and bioinformatics analyses on anaplastic thyroid cancer cell line ARO differentiated with low concentration of lova. Thyroid differentiation was induced by treating ARO cells with 25 μM of lova and confirmed by checking upregulation of some thyroid differentiation markers. Gel-based proteomics analysis was then performed to identify proteins differentially expressed between undifferentiated and lova-differentiated ARO cells. Bioinformatics analysis was finally performed to estimate biological networks regulated by lova. Our results showed that lova impacted on proteins involved in protein folding, biomolecule metabolism, signal transduction, protein expression and protein degradation. Specifically, transfecting ARO cells with plasmid DNA encoding flotillin 1 (FLOT1) up-regulated the thyroid differentiation markers, indicating that FLOT1 might at least partially mediate the lova-induced thyroid differentiation. These data may shed light on the mechanism underlying lova-induced re-differentiation of thyroid cancer, and give a rationale for clinical use of lova as an auxiliary agent in cancer therapy.

Characterization of the estradiol-binding site structure of human protein disulfide isomerase (PDI)

Background

Earlier studies showed that 17β-estradiol (E₂), an endogenous female sex hormone, can bind to human protein disulfide isomerase (PDI), a protein folding catalyst for disulfide bond formation and rearrangement. This binding interaction can modulate the intracellular levels of E₂ and its biological actions. However, the structure of PDI's E₂-binding site is still unclear at present, which is the focus of this study.

Methodology/Principal Findings

The E₂-binding site structure of human PDI was studied by using various biochemical approaches coupled with radiometric receptor-binding assays, site-directed mutagenesis, and molecular computational modeling. Analysis of various PDI protein fragments showed that the [³H]E₂-binding activity is not associated with the single b or b' domain but is associated with the b-b' domain combination. Computational docking analyses predicted that the E₂-binding site is located in a hydrophobic pocket composed mainly of the b' domain and partially of the b domain. A hydrogen bond, formed between the 3-hydroxyl group of E₂ and His256 of PDI is critical for the binding interaction. This binding model was jointly confirmed by a series of detailed experiments, including site-directed mutagenesis of the His256 residue coupled with selective modifications of the ligand structures to alter the binding interaction.

Conclusions/Significance

The results of this study elucidated the structural basis for the PDI–E₂ binding interaction and the reservoir role of PDI in modulating the intracellular E₂ levels. The identified PDI E₂-binding site is quite different from its known peptide binding sites. Given that PDI is a potential therapeutic target for cancer chemotherapy and HIV prevention and that E₂ can inhibit PDI activity in vitro, the E₂-binding site structure of human PDI determined here offers structural insights which may aid in the rational design of novel PDI inhibitors.

AGR2 is a novel surface antigen that promotes the dissemination of pancreatic cancer cells through regulation of cathepsins B and D

Pancreatic ductal adenocarcinoma (PDAC) remains one of the most lethal cancers largely due to disseminated disease at the time of presentation. Here, we investigated the role and mechanism of action of the metastasis-associated protein anterior gradient 2 (AGR2) in the pathogenesis of pancreatic cancer. AGR2 was induced in all sporadic and familial pancreatic intraepithelial precursor lesions (PanIN), PDACs, circulating tumor cells, and metastases studied. Confocal microscopy and flow cytometric analyses indicated that AGR2 localized to the endoplasmic reticulum (ER) and the external surface of tumor cells. Furthermore, induction of AGR2 in tumor cells regulated the expression of several ER chaperones (PDI, CALU, RCN1), proteins of the ubiquitin-proteasome degradation pathway (HIP2, PSMB2, PSMA3, PSMC3, and PSMB4), and lysosomal proteases [cathepsin B (CTSB) and cathepsin D (CTSD)], in addition to promoting the secretion of the precursor form pro-CTSD. Importantly, the invasiveness of pancreatic cancer cells was proportional to the level of AGR2 expression. Functional downstream targets of the proinvasive activity of AGR2 included CTSB and CTSD in vitro, and AGR2, CTSB, and CTSD were essential for the dissemination of pancreatic cancer cells in vivo. Taken together, the results suggest that AGR2 promotes dissemination of pancreatic cancer and that its cell surface targeting may permit new strategies for early detection as well as therapeutic management.

An novel role of sphingosine kinase-1 (SPHK1) in the invasion and metastasis of esophageal carcinoma

Background

Treatment failure for esophageal carcinoma is frequently due to lymph node metastasis and invasion to neighboring organs. The aim of the present study was to investigate invasion- and metastasis-related genes in esophageal carcinoma cells in vitro and in vivo.

Methods

A metastasis model using a Matrigel invasion clonal selection approach was employed to establish a highly invasive subline EC9706-P4 from the esophageal carcinoma cell (ESCC) line EC9706. The differentially expressed genes of the subline and the parental cells determined by gene microarrays were further analyzed by RT-PCR and Western blotting.

Results

We identified sphingosine kinase 1 (SPHK1) as an invasion and metastasis-related gene of esophageal cancer. SPHK1 was overexpressed in the EC9706-P4 subline with high invasive capacity. Among six ESCC lines tested, KYSE2 and KYSE30 cells showed the highest SPHK1 mRNA and protein expressions as well as the most invasive phenotype. By Western blotting, in 7/12 cases (58%), SPHK1 expression was higher in esophageal carcinomas than in the companion normal tissue. In 23/30 cases (76%), SPHK1 protein expression was upregulated in the tumors compared to matched normal tissue by immunohistochemistry (IHC). Esophageal carcinoma tissue microarray analysis indicated that SPHK1 expression correlated with the depth of tumor invasion (P < 0.0001) and lymph node metastasis (P = 0.016). By Kaplan-Meier analysis, strong SPHK1 expression was significantly associated with clinical failure (P < 0.01), suggesting the involvement of SPHK1 in aggressiveness of human esophageal carcinoma. SPHK1 overexpression significantly increased the invasiveness of EC9706 cells in vitro and also increased EC9706 cell growth and spontaneous metastasis in vivo, promoting significant increases in tumor growth, tumor burden and spontaneous lung metastasis in nude mice. SPHK1 expression significantly correlated with the expression of many EGFR pathway genes associated with invasion of cancer cells. SPHK1 protein expression also significantly correlated with the phosphorylation of EGFR.

Conclusion

In summary, our data implicate SPHK1 in the metastasis of esophageal cancer. Our study also identified downstream mediators of SPHK1 in esophageal cancer cells that may mediate enhanced malignant behavior, and several of these mediators may be useful as therapeutic targets.

Galectin-9 binding to cell surface protein disulfide isomerase regulates the redox environment to enhance T-cell migration and HIV entry

Interaction of cell surface glycoproteins with endogenous lectins on the cell surface regulates formation and maintenance of plasma membrane domains, clusters signaling complexes, and controls the residency time of glycoproteins on the plasma membrane. Galectin-9 is a soluble, secreted lectin that binds to glycoprotein receptors to form galectin-glycoprotein lattices on the cell surface. Whereas galectin-9 binding to specific glycoprotein receptors induces death of CD4 Th1 cells, CD4 Th2 cells are resistant to galectin-9 death due to alternative glycosylation. On Th2 cells, galectin-9 binds cell surface protein disulfide isomerase (PDI), increasing retention of PDI on the cell surface and altering the redox status at the plasma membrane. Cell surface PDI regulates integrin function on platelets and also enhances susceptibility of T cells to infection with HIV. We find that galectin-9 binding to PDI on Th2 cells results in increased cell migration through extracellular matrix via β3 integrins, identifying a unique mechanism to regulate T-cell migration. In addition, galectin-9 binding to PDI on T cells potentiates infection with HIV. We identify a mechanism for regulating cell surface redox status via a galectin-glycoprotein lattice, to regulate distinct T-cell functions.

Proteomic patterns of cervical cancer cell lines, a network perspective

Background

Cervical cancer is a major mortality factor in the female population. This neoplastic is an excellent model for studying the mechanisms involved in cancer maintenance, because the Human Papilloma Virus (HPV) is the etiology factor in most cases. With the purpose of characterizing the effects of malignant transformation in cellular activity, proteomic studies constitute a reliable way to monitor the biological alterations induced by this disease. In this contextual scheme, a systemic description that enables the identification of the common events between cell lines of different origins, is required to distinguish the essence of carcinogenesis.

Results

With this study, we sought to achieve a systemic perspective of the common proteomic profile of six cervical cancer cell lines, both positive and negative for HPV, and which differ from the profile corresponding to the non-tumourgenic cell line, HaCaT. Our objectives were to identify common cellular events participating in cancer maintenance, as well as the establishment of a pipeline to work with proteomic-derived results. We analyzed by means of 2D SDS-PAGE and MALDI-TOF mass spectrometry the protein extracts of six cervical cancer cell lines, from which we identified a consensus of 66 proteins. We call this group of proteins, the "central core of cervical cancer". Starting from this core set of proteins, we acquired a PPI network that pointed, through topological analysis, to some proteins that may well be playing a central role in the neoplastic process, such as 14-3-3ζ. In silico overrepresentation analysis of transcription factors pointed to the overexpression of c-Myc, Max and E2F1 as key transcription factors involved in orchestrating the neoplastic phenotype.

Conclusions

Our findings show that there is a "central core of cervical cancer" protein expression pattern, and suggest that 14-3-3ζ is key to determine if the cell proliferates or dies. In addition, our bioinformatics analysis suggests that the neoplastic phenotype is governed by a non-canonical regulatory pathway.

LyGDI, a novel SHIP-interacting protein, is a negative regulator of FcγR-mediated phagocytosis

SHIP and SHIP-2 are inositol phosphatases that regulate FcγR-mediated phagocytosis through catalytic as well as non-catalytic mechanisms. In this study we have used two-dimensional fluorescence difference gel electrophoresis (DIGE) analysis to identify downstream signaling proteins that uniquely associate with SHIP or SHIP-2 upon FcγR clustering in human monocytes. We identified LyGDI as a binding partner of SHIP, associating inducibly with the SHIP/Grb2/Shc complex. Immunodepletion and competition experiments with recombinant SHIP domains revealed that Grb2 and the proline-rich domain of SHIP were necessary for SHIP-LyGDI association. Functional studies in primary human monocytes showed that LyGDI sequesters Rac in the cytosol, preventing it from localizing to the membrane. Consistent with this, suppression of LyGDI expression resulted in significantly enhanced FcγR-mediated phagocytosis.

Bacitracin inhibits the reductive activity of protein disulfide isomerase by disulfide bond formation with free cysteines in the substrate-binding domain

The peptide antibiotic bacitracin is widely used as an inhibitor of protein disulfide isomerase (PDI) to demonstrate the role of the protein-folding catalyst in a variety of molecular pathways. Commercial bacitracin is a mixture of at least 22 structurally related peptides. The inhibitory activity of individual bacitracin analogs on PDI is unknown. For the present study, we purified the major bacitracin analogs, A, B, H, and F, and tested their ability to inhibit the reductive activity of PDI by use of an insulin aggregation assay. All analogs inhibited PDI, but the activity (IC(50) ) ranged from 20 μm for bacitracin F to 1050 μm for bacitracin B. The mechanism of PDI inhibition by bacitracin is unknown. Here, we show, by MALDI-TOF/TOF MS, a direct interaction of bacitracin with PDI, involving disulfide bond formation between an open thiol form of the bacitracin thiazoline ring and cysteines in the substrate-binding domain of PDI.

A novel brain metastases model developed in immunodeficient rats closely mimics the growth of metastatic brain tumours in patients

AIMS

brain metastasis is a common cause of mortality in cancer patients, and associated with poor prognosis. Our objective was to develop a clinically relevant animal model by transplanting human biopsy spheroids derived from metastatic lesions into brains of immunodeficient rats.

METHODS

nine different patient brain metastases from four different primary cancers were implanted into brains of immunodeficient rats. The xenografts were compared with patient tumours by magnetic resonance imaging, histochemistry, immunohistochemistry and DNA copy number analysis.

RESULTS

after transplantation, tumour growth was achieved in seven out of nine human brain metastases. Spheroids derived from four of the metastases initiated in the rat brains were further serially transplanted into new animals and a 100% tumour take was observed during second passage. Three of the biopsies were implanted subcutaneously, where no tumour take was observed. The animal brain metastases exhibited similar radiological features as observed clinically. Histological comparisons between the primary tumours from the patients, the patient brain metastases and the derived xenografts showed striking similarities in histology and growth patterns. Also, immunohistochemistry showed a strong marker expression similarity between the patient tumours and the corresponding xenografts. DNA copy number analysis between the brain metastases, and the corresponding xenografts revealed strong similarities in gains and losses of chromosomal content.

CONCLUSION

we have developed a representative in vivo model for studying the growth of human metastatic brain cancers. The model described represents an important tool to assess responses to new treatment modalities and for studying mechanisms behind metastatic growth in the central nervous system.

Regulatory functions of glutathione S-transferase P1-1 unrelated to detoxification

Glutathione S-transferase P1-1 (GSTP) is one member of the family of GSTs and is ubiquitously expressed in human tissues. The literature is replete with reports of high levels of GSTP linked either with cancer incidence or drug resistance, and yet no entirely cogent explanation for these correlations exists. The catalytic detoxification properties of the GST isozyme family have been a primary research focus for the last four decades. However, it has become apparent that they have undergone structural and functional convergence where evolutionary selective pressures have favored the emergence of noncatalytic properties of GSTP that has imbued this isozyme with expanded biological importance. For example, GSTP has now been linked with two cell-signaling functions that are critical to survival. Through protein:protein interactions, GSTP can sequester c-jun N-terminal kinase (JNK) and act as a negative regulator of this stress kinase. Pharmacologically, this activity has been linked with the activity of GSTP inhibitors in stimulating myeloproliferation. In addition, GSTP is linked with the forward S-glutathionylation reaction, a post-translational modification that impacts the function/activity of a number of proteins. Catalytic reversal of S-glutathionylation is well characterized, but the role of GSTP in catalyzing the forward reaction contributes to the "glutathionylation cycle." Moreover, GSTP is itself susceptible to S-glutathionylation, providing an autoregulatory loop for the cycle. Because oxidative stress regulates both S-glutathionylation and JNK-signaling pathways, such links may help to explain the aberrant patterns of GSTP expression in the cancer phenotype. As such, there is an ongoing preclinical and clinical platform of drug discovery and development around GSTP.

Proteomic comparison of spherical aggregates and adherent cells of cardiac stem cells

BACKGROUND

Previously published papers showed that cardiac stem cells (CSCs) form (cardio)sphere. However, recent studies questioned the significance of the sphere-formation as one of the characteristics of CSCs. We isolated c-kit-positive cardiac stem cells, cultured as bulk (CSC-BC) and characterized them previously. Among them, CSC-BC21 formed an extraordinary number of spheres. Using a clone derived from this bulk culture, we investigated the effect of sphere-formation on differentiation and performed proteomics analysis comparing two statuses, cardiosphere and dish substrate attachment.

METHODS

We performed sphere-forming assay to compare the sphere-forming ability among CSC-BCs. The cloned cells from CSC-BC21, which had distinct sphere-forming ability, were cultured in a differentiation medium (DM) to induce cardiac myocyte differentiation. We performed RT-PCR analysis to investigate if cardiosphere-formation affects cardiac myocyte gene expression level. Furthermore, proteome analysis was performed to compare floating cardiosphere (flCS) and dish-attached cardiosphere-derived cells (daCS).

RESULTS

One of the cloned cells, CSC-21E expressed higher troponin I message than CSC-BC21. Moreover, the message level of troponin I was enhanced when they had experienced cardiosphere prior to the treatment of myocyte differentiation medium. The change from flCS to daCS accompanied up-regulation of chaperones and down regulation of glycolytic and other metabolic enzymes. Calreticulin and Hsp 90 were among the up-regulated chaperons. Calreticulin is known to be an essential component of cardiogenesis.

CONCLUSION

These results suggest that the switch from aggregated sphere to the cell attachment, is important for advancing the cardiac cell differentiation.

αB-crystallin is elevated in highly infiltrative apoptosis-resistant glioblastoma cells

We have previously established two distinct glioma phenotypes by serial xenotransplantation of human glioblastoma (GBM) biopsies in nude rats. These tumors undergo a gradual transition from a highly invasive nonangiogenic to a less-invasive angiogenic phenotype. In a protein screen to identify molecular markers associated with the infiltrative phenotype, we identified α-basic-crystallin (αBc), a small heat-shock protein with cytoprotective properties. Its increased expression in the infiltrative phenotype was validated by immunohistochemistry and Western blots, confirming its identity to be tumor-derived and not from the host. Stereotactic human GBM biopsies taken from MRI-defined areas verified stronger αBc expression in the infiltrative edge compared to the tumor core. Cell migration assays and immunofluorescence staining showed αBc to be expressed by migrating cells in vitro. To determine αBc function, we altered its expression levels. αBc siRNA depletion caused a loss of migrating tumor cells from biopsy spheroids and delayed monolayer wound closure. In contrast, glioma cell migration in a Boyden chamber assay was unaffected by either αBc knockdown or overexpression, indicating that αBc is not functionally linked to the cell migration machinery. However, after siRNA αBc depletion, a significant sensitization of cells to various apoptotic inducers was observed (actinomycin, tumor necrosis factor α, and TNF-related apoptosis-inducing ligand [TRAIL]). In conclusion, αBc is overexpressed by highly migratory glioma cells where it plays a functional role in apoptosis resistance.

Anterior gradient-2 plays a critical role in breast cancer cell growth and survival by modulating cyclin D1, estrogen receptor-alpha and survivin

Introduction

Anterior-gradient 2 (AGR2) is an estrogen-responsive secreted protein. Its upregulation has been well documented in a number of cancers, particularly breast cancer, for which mixed data exist on the prognostic implications of AGR2 expression. Although emerging evidence indicates that AGR2 is associated with poor prognosis, its function and impact on cancer-relevant pathways have not been elucidated in breast cancer.

Methods

To investigate the biologic role of AGR2 in breast cancer, AGR2 was transiently knocked down, by using siRNA, in T47 D and ZR-75-1 (estrogen receptor-α (ER)-positive) and MDA-MB-231 and SK-BR-3 (ER-negative) human breast cancer cell lines. The impact of silencing AGR2 was evaluated in both anchorage-dependent and anchorage-independent growth (soft agar, spheroid) assays. Cell-cycle profiles in ER-positive cell lines were determined with BrdU incorporation, and cell death was measured with Annexin V, JC-1, and F7-26 staining. After transiently silencing AGR2 or stimulating with recombinant AGR2, modulation of key regulators of growth and survival pathways was assessed with Western blot. Combination studies of AGR2 knockdown with the antiestrogens tamoxifen and fulvestrant were carried out and assessed at the level of anchorage-dependent growth inhibition and target modulation (cyclin D1, ER).

Results

AGR2 knockdown inhibited growth in anchorage-dependent and anchorage-independent assays, with a more-pronounced effect in ER-positive cell lines. Cyclin D1 levels and BrdU incorporation were reduced with AGR2 knockdown. Conversely, cyclin D1 was induced with recombinant AGR2. AGR2 knockdown induced cell death in ZR-75-1 and T47 D cells, and also downregulated survivin and c-Myc. Evidence of AGR2-ER crosstalk was demonstrated by a reduction of ER at the protein level after transiently silencing AGR2. AGR2 knockdown in combination with fulvestrant or tamoxifen did not preclude the efficacy of the antiestrogens, but enhanced it. In addition, p-Src, implicated in tamoxifen resistance, was downregulated with AGR2 knockdown.

Conclusions

Transiently silencing AGR2 in ER-positive breast cancer cell lines inhibited cell growth and cell-cycle progression and induced cell death. Breast cancer drivers (ER and cyclin D1) as well as cancer-signaling nodes (pSrc, c-Myc, and survivin) were demonstrated to be downstream of AGR2. Collectively, the data presented support the utility of anti-AGR2 therapy in ER-positive breast cancers because of its impact on cancer-relevant pathways.

Bacitracin is not a specific inhibitor of protein disulfide isomerase

To successfully dissect molecular pathways in vivo, there is often a need to use specific inhibitors. Bacitracin is very widely used as an inhibitor of protein disulfide isomerase (PDI) in vivo. However, the specificity of action of an inhibitor for a protein-folding catalyst cannot be determined in vivo. Furthermore, in vitro evidence for the specificity of bacitracin for PDI is scarce, and the mechanism of inhibition is unknown. Here, we present in vitro data showing that 1 mM bacitracin has no significant effect on the ability of PDI to introduce or isomerize disulfide bonds in a folding protein or on its ability to act as a chaperone. Where bacitracin has an effect on PDI activity, the effect is relatively minor and appears to be via competition of substrate binding. Whereas 1 mM bacitracin has minimal effects on PDI, it has significant effects on both noncatalyzed protein folding and on other molecular chaperones. These results suggest that the use of bacitracin as a specific inhibitor of PDI in cellular systems requires urgent re-evaluation.

Multiple changes induced by fibroblasts on breast cancer cells

It is now widely recognized that the cross-talk between cancer and stromal cells may play a crucial role in cancer progression. However, little is known about the complex underlying molecular mechanisms that occur within the tumor microenvironment. Fibroblasts are the major stromal cells with multiple roles, especially toward both the extracellular matrix and the neighboring cell population, including neoplastic cells. Consequently, proteomic analyses would provide a wider resource for a better understanding of the potential modulating effects exerted by fibroblasts on cancer cells. In this article we describe the effects of fibroblast stimulation on the breast cancer cell line (8701-BC) proteomics, using a trans-well coculture system. Our results clearly indicate that fibroblasts induce considerable proteomic modulations on 8701-BC, mainly in the cytoskeleton proteins and glycolytic enzymes. Additionally, fibroblast-conditioned medium increased neoplastic cell proliferation and invasion with a concurrent upregulation of the c-Myc oncogene. Collectively these results suggest that fibroblast stimulation may enhance the malignant potential of breast cancer cells in vitro.

Glioma proteomics: status and perspectives

High grade gliomas are the most common brain tumors in adults and their malignant nature makes them the fourth biggest cause of cancer death. Major efforts in neuro-oncology research are needed to reach similar progress in treatment efficacy as that achieved for other cancers in recent years. In addition to the urgent need to identify novel effective drug targets against malignant gliomas, the search for glioma biomarkers and grade specific protein signatures will provide a much needed contribution to diagnosis, prognosis, treatment decision and assessment of treatment response. Over the past years glioma proteomics has been attempted at different levels, including proteome analysis of patient biopsies and bodily fluids, of glioma cell lines and animal models. Here we provide an extensive review of the outcome of these studies in terms of protein identifications (protein numbers and regulated proteins), with an emphasis on the methods used and the limitations of the studies with regard to biomarker discovery. This is followed by a perspective on novel technologies and on the potential future contribution of proteomics in a broad sense to understanding glioma biology.

Immunohistochemical analysis of oxidative stress and DNA repair proteins in normal mammary and breast cancer tissues

BACKGROUND

During the course of normal cellular metabolism, oxygen is consumed and reactive oxygen species (ROS) are produced. If not effectively dissipated, ROS can accumulate and damage resident proteins, lipids, and DNA. Enzymes involved in redox regulation and DNA repair dissipate ROS and repair the resulting damage in order to preserve a functional cellular environment. Because increased ROS accumulation and/or unrepaired DNA damage can lead to initiation and progression of cancer and we had identified a number of oxidative stress and DNA repair proteins that influence estrogen responsiveness of MCF-7 breast cancer cells, it seemed possible that these proteins might be differentially expressed in normal mammary tissue, benign hyperplasia (BH), ductal carcinoma in situ (DCIS) and invasive breast cancer (IBC).

METHODS

Immunohistochemistry was used to examine the expression of a number of oxidative stress proteins, DNA repair proteins, and damage markers in 60 human mammary tissues which were classified as BH, DCIS or IBC. The relative mean intensity was determined for each tissue section and ANOVA was used to detect statistical differences in the relative expression of BH, DCIS and IBC compared to normal mammary tissue.

RESULTS

We found that a number of these proteins were overexpressed and that the cellular localization was altered in human breast cancer tissue.

CONCLUSIONS

Our studies suggest that oxidative stress and DNA repair proteins not only protect normal cells from the damaging effects of ROS, but may also promote survival of mammary tumor cells.

A reproducible brain tumour model established from human glioblastoma biopsies

Background

Establishing clinically relevant animal models of glioblastoma multiforme (GBM) remains a challenge, and many commonly used cell line-based models do not recapitulate the invasive growth patterns of patient GBMs. Previously, we have reported the formation of highly invasive tumour xenografts in nude rats from human GBMs. However, implementing tumour models based on primary tissue requires that these models can be sufficiently standardised with consistently high take rates.

Methods

In this work, we collected data on growth kinetics from a material of 29 biopsies xenografted in nude rats, and characterised this model with an emphasis on neuropathological and radiological features.

Results

The tumour take rate for xenografted GBM biopsies were 96% and remained close to 100% at subsequent passages in vivo, whereas only one of four lower grade tumours engrafted. Average time from transplantation to the onset of symptoms was 125 days ± 11.5 SEM. Histologically, the primary xenografts recapitulated the invasive features of the parent tumours while endothelial cell proliferations and necrosis were mostly absent. After 4-5 in vivo passages, the tumours became more vascular with necrotic areas, but also appeared more circumscribed. MRI typically revealed changes related to tumour growth, several months prior to the onset of symptoms.

Conclusions

In vivo passaging of patient GBM biopsies produced tumours representative of the patient tumours, with high take rates and a reproducible disease course. The model provides combinations of angiogenic and invasive phenotypes and represents a good alternative to in vitro propagated cell lines for dissecting mechanisms of brain tumour progression.

Glycoproteomics of paclitaxel resistance in human epithelial ovarian cancer cell lines: towards the identification of putative biomarkers

Glycosylation, one of the most common post translational modifications (PTMs) of proteins, is often associated with carcinogenesis and tumor malignancy. Ovarian cancer is the sixth cause of cancer-related death in Western countries. Currently, it is treated by debulking surgery followed by chemotherapy based on paclitaxel, alone or in combination with other drugs. However, chemoresistance represents a major obstacle to positive clinical outcome. We used two approaches, Multiplexed Proteomics (MP) technology and Multilectin Affinity Chromatography (MAC) to characterize the glycoproteome of the human ovarian cancer cell line A2780 and its paclitaxel resistant counterpart A2780TC1. Furthermore proteins were separated by traditional 2DE or DIGE and identified by MS (MALDI TOF or LC MS/MS). Seventy glycoproteins were successfully identified in ovarian cancer cells and 10 were found to be differentially expressed between sensitive and resistant cell lines. We focused on four glycoproteins (tumor rejection antigen (gp96) 1, triose phosphate isomerase, palmitoyl-protein thioesterase 1 precursor and ER-associated DNAJ) which were remarkably upregulated in A2780TC1 compared to A2780 cell line and which may represent biomarkers for paclitaxel resistance in ovarian cancer.

Redox-directed cancer therapeutics: molecular mechanisms and opportunities

Redox dysregulation originating from metabolic alterations and dependence on mitogenic and survival signaling through reactive oxygen species represents a specific vulnerability of malignant cells that can be selectively targeted by redox chemotherapeutics. This review will present an update on drug discovery, target identification, and mechanisms of action of experimental redox chemotherapeutics with a focus on pro- and antioxidant redox modulators now in advanced phases of preclinal and clinical development. Recent research indicates that numerous oncogenes and tumor suppressor genes exert their functions in part through redox mechanisms amenable to pharmacological intervention by redox chemotherapeutics. The pleiotropic action of many redox chemotherapeutics that involves simultaneous modulation of multiple redox sensitive targets can overcome cancer cell drug resistance originating from redundancy of oncogenic signaling and rapid mutation.Moreover, some redox chemotherapeutics may function according to the concept of synthetic lethality (i.e., drug cytotoxicity is confined to cancer cells that display loss of function mutations in tumor suppressor genes or upregulation of oncogene expression). The impressive number of ongoing clinical trials that examine therapeutic performance of novel redox drugs in cancer patients demonstrates that redox chemotherapy has made the crucial transition from bench to bedside.

Stress as an intercellular signal: the emergence of stress-associated molecular patterns (SAMP)

Abstrct Cells are continuously exposed to stressful situations that generally entail generation of reactive oxygen species and other redox alterations. Low levels of stress are physiological and can transmit essential survival or adaptive signals. At higher levels, however, the responses become maladaptive and cause damage. Frequently, stressful events occurring in a few cells propagate, resulting in tissue or even systemic response. Here we review recent evidence suggesting that stressed cells signal their state by expressing on their surface and secreting suitable molecular clues, which we propose to term Stress-Associated Molecular Patterns (SAMP). A unifying mechanism seems to involve the release of oxidoreductases and redox modifiers into the intercellular space, with structural and functional alterations in key signaling molecules. These observations open the way to novel therapeutic strategies.

Comparative proteomic analysis of paclitaxel sensitive A2780 epithelial ovarian cancer cell line and its resistant counterpart A2780TC1 by 2D-DIGE: the role of ERp57

Epithelial ovarian cancer is the leading cause of gynecological cancer mortality. Despite good response to surgery and initial chemotherapy, chemoresistance occurrence represents a major obstacle to a successful therapy. To better understand biological mechanisms at the basis of paclitaxel resistance, a comparative proteomic approach based on DIGE coupled with mass spectrometry (MALDI-TOF and LC-MS/MS) was applied to the human epithelial ovarian cancer cell lines A2780 and its paclitaxel resistant counterpart A2780TC1. Most of the differentially expressed proteins between the two cell lines belong to the class of stress response (29%), metabolism (21%), and cell cycle and apoptosis (17%). We focused on proteins which were most strongly modulated by paclitaxel resistance and in particular on the disulphide isomerase ERp57, which may represent a chemoresistance biomarker. ERp57 was found to interact with class III beta-tubulin (TUBB3), involved in paclitaxel resistance in ovarian and other cancers. Moreover, we demonstrated a novel localization of this protein in cytoskeleton and described that ERp57/TUBB3 interaction occurs also in the nuclear compartment and in association with a multimeric complex formed by nucleolin, nucleophosmin, hnRNPK, and mortalin. Our data suggest that ERp57 plays an important role in chemoresistance mechanisms in ovarian cancer by modulating the attachment of microtubules to chromosomes following paclitaxel treatment through its interaction with TUBB3.

Nitrosative stress-induced s-glutathionylation of protein disulfide isomerase leads to activation of the unfolded protein response

The rapid proliferation of cancer cells mandates a high protein turnover. The endoplasmic reticulum (ER) is intimately involved in protein processing. An accumulation of unfolded or misfolded proteins in the ER leads to a cascade of transcriptional and translational events collectively called the unfolded protein response (UPR). Protein disulfide isomerase (PDI) is one of the most abundant ER proteins and maintains a sentinel function in organizing accurate protein folding. Treatment of cells with O(2)-[2,4-dinitro-5-(N-methyl-N-4-carboxyphenylamino)phenyl]1-(N,N-dimethylamino)diazen-1-ium-1,2-diolate (PABA/NO) resulted in a dose-dependent increase in intracellular nitric oxide that caused S-glutathionylation of various proteins. Within 4 h, PABA/NO activated the UPR and led to translational attenuation as measured by the phosphorylation and activation of the ER transmembrane kinase, pancreatic ER kinase, and its downstream effector eukaryotic initiation factor 2 in human leukemia (HL60) and ovarian cancer cells (SKOV3). Cleavage of the transcription factor X-box protein 1 and transcriptional activation of the ER resident proteins BiP, PDI, GRP94, and ERO1 (5- to 10-fold induction) also occurred. Immunoprecipitation of PDI showed that whereas nitrosylation was undetectable, PABA/NO treatment caused S-glutathionylation of PDI. Mass spectroscopy analysis showed that single cysteine residues within each of the catalytic sites of PDI had a mass increase [+305.3 Da] consistent with S-glutathionylation. Circular dichroism confirmed that S-glutathionylation of PDI results in alterations in the alpha-helix content of PDI and is concurrent with inhibition of its isomerase activity. Thus, it appears that S-glutathionylation of PDI is an upstream signaling event in the UPR and may be linked with the cytotoxic potential of PABA/NO.

iTRAQ-based proteomics profiling reveals increased metabolic activity and cellular cross-talk in angiogenic compared with invasive glioblastoma phenotype

Malignant gliomas (glioblastoma multiforme) have a poor prognosis with an average patient survival under current treatment regimens ranging between 12 and 14 months. The tumors are characterized by rapid cell growth, extensive neovascularization, and diffuse cellular infiltration of normal brain structures. We have developed a human glioblastoma xenograft model in nude rats that is characterized by a highly infiltrative non-angiogenic phenotype. Upon serial transplantation this phenotype will develop into a highly angiogenic tumor. Thus, we have developed an animal model where we are able to establish two characteristic tumor phenotypes that define human glioblastoma (i.e. diffuse infiltration and high neovascularization). Here we aimed at identifying potential biomarkers expressed by the non-angiogenic and the angiogenic phenotypes and elucidating the molecular pathways involved in the switch from invasive to angiogenic growth. Focusing on membrane-associated proteins, we profiled protein expression during the progression from an invasive to an angiogenic phenotype by analyzing serially transplanted glioma xenografts in rats. Applying isobaric peptide tagging chemistry (iTRAQ) combined with two-dimensional LC and MALDI-TOF/TOF mass spectrometry, we were able to identify several thousand proteins in membrane-enriched fractions of which 1460 were extracted as quantifiable proteins (isoform- and species-specific and present in more than one sample). Known and novel candidate proteins were identified that characterize the switch from a non-angiogenic to a highly angiogenic phenotype. The robustness of the data was corroborated by extensive bioinformatics analysis and by validation of selected proteins on tissue microarrays from xenograft and clinical gliomas. The data point to enhanced intercellular cross-talk and metabolic activity adopted by tumor cells in the angiogenic compared with the non-angiogenic phenotype. In conclusion, we describe molecular profiles that reflect the change from an invasive to an angiogenic brain tumor phenotype. The identified proteins could be further exploited as biomarkers or therapeutic targets for malignant gliomas.

Protein disulfide isomerase increases in myocardial endothelial cells in mice exposed to chronic hypoxia: a stimulatory role in angiogenesis

Previous studies have shown that exposure to chronic hypoxia protects against myocardial infarction, but little is known about the cellular and molecular mechanisms involved. Here we observed that chronic hypoxia for 3 wk resulted in improved survival of mice (from 64% to 83%), reduced infarction size (from 45 +/- 4% to 32 +/- 4%, P < 0.05), increased cardiac ejection fraction (from 19 +/- 4% to 35 +/- 5%, P < 0.05), coronary flow velocity under adenosine-induced hyperemia (from 58 +/- 2 to 75 +/- 5 cm/s, P < 0.05), myocardial capillary density (from 3,772 +/- 162 to 4,760 +/- 197 capillaries/mm(2), P < 0.01), and arteriolar density (from 8.04 +/- 0.76 to 10.34 +/- 0.69 arterioles/mm(2), P < 0.05) 3 wk after myocardial infarction. With two-dimensional gel electrophoresis, we identified that protein disulfide isomerase (PDI) was highly upregulated in hypoxic myocardial capillary endothelial cells. The loss of PDI function in endothelial cells by small interfering RNA significantly increased the number of apoptotic cells (by 3.4-fold at hypoxia, P < 0.01) and reduced migration (by 52% at hypoxia, P < 0.001) and adhesion to collagen I (by 42% at hypoxia, P < 0.01). In addition, the specific inhibition of PDI by PDI small interfering RNA (by 46%, P < 0.01) and bacitracin (by 72%, P < 0.001) reduced the formation of tubular structures by endothelial cells. Our data indicate that chronic hypoxic exposure improves coronary blood flow and protects the myocardium against infarction. These beneficial effects may be partly explained by the increased endothelial expression of PDI, which protects cells against apoptosis and increases cellular migration, adhesion, and tubular formation. The increased PDI expression in endothelial cells may be a novel mechanism to protect the myocardium against myocardial ischemic diseases.

Autophagy suppresses tumorigenesis through elimination of p62

Allelic loss of the essential autophagy gene beclin1 occurs in human cancers and renders mice tumor-prone suggesting that autophagy is a tumor-suppression mechanism. While tumor cells utilize autophagy to survive metabolic stress, autophagy also mitigates the resulting cellular damage that may limit tumorigenesis. In response to stress, autophagy-defective tumor cells preferentially accumulated p62/SQSTM1 (p62), endoplasmic reticulum (ER) chaperones, damaged mitochondria, reactive oxygen species (ROS), and genome damage. Moreover, suppressing ROS or p62 accumulation prevented damage resulting from autophagy defects indicating that failure to regulate p62 caused oxidative stress. Importantly, sustained p62 expression resulting from autophagy defects was sufficient to alter NF-kappaB regulation and gene expression and to promote tumorigenesis. Thus, defective autophagy is a mechanism for p62 upregulation commonly observed in human tumors that contributes directly to tumorigenesis likely by perturbing the signal transduction adaptor function of p62-controlling pathways critical for oncogenesis.

ROCKs are expressed in brain tumors and are required for glioma-cell migration on myelinated axons

The interactions between migrating glioma cells and myelinated fiber tracts are poorly understood. We identified that C6 glioma cells can migrate along myelinated chicken retinal axons in a novel coculture, thereby expressing small GTPases of the Rho family and serine/threonine Rho-associated kinases (ROCKs). We found that the ROCK1 isoform is also highly expressed in native human high-grade gliomas. Glioma cells migrated faster in vitro along myelinated axons than on laminin-1, with the former but not the latter being specifically and reversibly blocked by the ROCK inhibitor Y27632. These data suggest that the mechanisms underlying the migration of glioma cells on myelinated axons differ from those underlying the migration on extracellular matrix molecules such as laminin-1.

Proteomics Reveals Protein Profile Changes in Cyclooxygenase-2 Inhibitor-Treated Endometrial Cancer Cells

Objective:

To examine effects of an inhibitor of cyclooxygenase (COX)-2, NS-398, on the proliferation, apoptosis and invasion characteristics of endometrial cancer cell RL95-2.

Methods:

(1) Western blotting was carried out to determine COX-2 protein expression in RL95-2 cells and normal endometrium specimens. (2) The effect of NS-398 treatment on the cell proliferation, apoptosis, and invasion was assessed by methyl thiazolyl tetrazolium assay, flow cytometry, and matrigel invasion assay, respectively. (3) Finally, the proteomic analysis was used to find out proteins that are differentially expressed because of NS-398 treatment.

Results:

(1) COX-2 protein in RL95-2 cell line was significantly higher than that in normal endometrium. (2) NS-398 had significant growth inhibition effects on RL95-2 cells in a dose- and time-dependent manner. (3) NS-398 increased the proportion of cells in G1 and decreased the proportion of cells in the G2 phase in RL95-2 cells. (4) NS-398 could restrain endometrial cancer cells invasion. (5) The proteomic analysis revealed several proteins that are differentially expressed because of NS-398 treatment; the down-regulated proteins identified are hnRNP K, α enolase, Hsp70, tropomyosin, and protein disulfide isomerase, the up-regulated protein is phosphatidylethanolamine binding protein.

Conclusions:

The expression of COX-2 plays an important role in tumorigenesis of endometrial cancer. NS-398 can inhibit the ability of RL95-2 cell proliferation, viability, and invasion. In this study, the well-resolved reproducible 2-DE maps of NS-398 treated and control RL95-2 cells were established, and the significantly different expressed proteins are preliminary identified.

ERdj5 sensitizes neuroblastoma cells to endoplasmic reticulum stress-induced apoptosis

Down-regulation of the unfolded protein response (UPR) can be therapeutically valuable in cancer treatment, and endoplasmic reticulum (ER)-resident chaperone proteins may thus be targets for developing novel chemotherapeutic strategies. ERdj5 is a novel ER chaperone that regulates the ER-associated degradation of misfolded proteins through its associations with EDEM and the ER stress sensor BiP. To investigate whether ERdj5 can regulate ER stress signaling pathways, we exposed neuroblastoma cells overexpressing ERdj5 to ER stress inducers. ERdj5 promoted apoptosis in tunicamycin, thapsigargin, and bortezomib-treated cells. To provide further evidence that ERdj5 induces ER stress-regulated apoptosis, we targeted Bcl-2 to ER of ERdj5-overexpressing cells. Targeting the Bcl-2 to ER prevented the apoptosis induced by ER stress inducers but not by non-ER stress apoptotic stimuli, suggesting induction of ER stress-regulated apoptosis by ERdj5. ERdj5 enhanced apoptosis by abolishing the ER stress-induced phosphorylation of eukaryotic translation initiation factor 2alpha (eIF2alpha) and the subsequent translational repression. ERdj5 was found to inhibit the eIF2alpha phosphorylation under ER stress through inactivating the pancreatic endoplasmic reticulum kinase. The compromised integrated stress response observed in ERdj5-overexpressing ER-stressed cells due to repressed eIF2alpha phosphorylation correlated with impaired neuroblastoma cell resistance under ER stress. These results demonstrate that ERdj5 decreases neuroblastoma cell survival by down-regulating the UPR, raising the possibility that this protein could be a target for anti-tumor approaches.

Protein disulfide isomerases are antibody targets during immune-mediated tumor destruction

The identification of cancer antigens that contribute to transformation and are linked with immune-mediated tumor destruction is an important goal for immunotherapy. Toward this end, we screened a murine renal cell carcinoma cDNA expression library with sera from mice vaccinated with irradiated tumor cells engineered to secrete granulocyte macrophage colony-stimulating factor (GM-CSF). Multiple nonmutated, overexpressed proteins that function in tumor cell migration, protein/nucleic acid homeostasis, metabolism, and stress responses were detected. Among these, the most frequently recognized clone was protein disulfide isomerase (PDI). High titer antibodies to human PDI were similarly induced in an acute myeloid leukemia patient who achieved a complete response after vaccination with irradiated, autologous GM-CSF-secreting tumor cells in the setting of nonmyeloablative allogeneic bone marrow transplantation. Moreover, ERp5, a closely related disulfide isomerase involved in major histocompatibility complex (MHC) class I chain-related protein A (MICA) shedding, also evoked potent humoral reactions in diverse solid and hematologic malignancy patients who responded to GM-CSF-secreting tumor cell vaccines or antibody blockade of cytotoxic T lymphocyte-associated antigen 4 (CTLA-4). Together, these findings reveal the unexpected immunogenicity of PDIs and raise the possibility that these gene products might serve as targets for therapeutic monoclonal antibodies.

Two distinct tumor phenotypes isolated from glioblastomas show different MRS characteristics

We have developed a human brain tumor model in immunodeficient rats that gradually changes its phenotype by serial passages in vivo, from a highly infiltrative, non-angiogenic one with numerous stem cell markers [low-generation (LG) tumor] to a more typical glioblastoma one with extensive angiogenesis and necrosis [high-generation (HG) tumor]. In this study we determined the metabolic properties of these two phenotypes, using (1)H MRS. The LG tumors showed an intact blood-brain barrier and normal vascular morphology, as shown by MRI and Hoechst staining. In contrast, the HG tumors exhibited vascular leakage and necrosis. The animals with HG tumor had raised concentrations of choline and myo-inositol, and decreased concentrations of glutamate and N-acetylaspartate. In the LG tumor group, similar changes in metabolic concentrations were detected, although the alterations were more pronounced. The LG tumors also had higher concentrations of choline, taurine, and lactate. Subdividing the LG and HG tumors into large and small tumors revealed a significant increase in choline and decrease in glutamate as the LG tumors increased in size. Our results show that metabolic profiles produced by (1)H MRS can be used to distinguish between two distinct glioblastoma phenotypes. More pronounced anaerobic metabolism was present in the LG stem-cell-like tumors, suggesting a more malignant phenotype.

Pharmacology of a mimetic of glutathione disulfide, NOV-002

NOV-002 is a novel therapeutic agent in development for oncology indications used in combination with chemotherapy. Clinical trials in Russia and the USA have demonstrated clinical activity and the present focus is on non-small cell lung cancer (NSCLC) patients. The active component of the drug is oxidized glutathione (GSSG) and this imparts multiple effects upon redox pathways both at the cell surface and inside the cell. The drug induces S-glutathionylation of some proteins and impacts kinase/phosphatase regulated signaling pathways. Induction of myeloproliferation is believed to contribute to the clinical advantages provided by NOV-002 that include improved tolerance of chemotherapy and increased survival.

NOV-002, a mimetic of glutathione disulfide

BACKGROUND

Oxidative signaling to modulate redox-sensitive cell functions is a heretofore unexploited approach to developing new drugs for poorly treated oncology indications, where current therapies are often only palliative and accompanied by severe toxicities.

OBJECTIVE

Clinical and non-clinical findings with NOV-002 (a mimetic of glutathione disulfide that represents such an approach) are reviewed and evaluated.

METHODS

Published data on NOV-002 along with unpublished information from the drug's sponsor were reviewed. Literature analysis also focused on protein S-glutathionylation as a regulatory mechanism, particularly in relation to cell signaling, proliferation and cytoskeletal architecture.

RESULTS/CONCLUSION

NOV-002 is a mechanistically novel agent with potential for ameliorating hematologic toxicity and enhancing efficacy when used in combination with standard chemotherapy to treat cancer patients.

Increasing melanoma cell death using inhibitors of protein disulfide isomerases to abrogate survival responses to endoplasmic reticulum stress

Exploiting vulnerabilities in the intracellular signaling pathways of tumor cells is a key strategy for the development of new drugs. The activation of cellular stress responses mediated by the endoplasmic reticulum (ER) allows cancer cells to survive outside their normal environment. Many proteins that protect cells against ER stress are active as protein disulfide isomerases (PDI) and the aim of this study was to test the hypothesis that apoptosis in response to ER stress can be increased by inhibiting PDI activity. We show that the novel chemotherapeutic drugs fenretinide and velcade induce ER stress-mediated apoptosis in melanoma cells. Both stress response and apoptosis were enhanced by the PDI inhibitor bacitracin. Overexpression of the main cellular PDI, procollagen-proline, 2-oxoglutarate-4-dioxygenase beta subunit (P4HB), resulted in increased PDI activity and abrogated the apoptosis-enhancing effect of bacitracin. In contrast, overexpression of a mutant P4HB lacking PDI activity did not increase cellular PDI activity or block the effects of bacitracin. These results show that inhibition of PDI activity increases apoptosis in response to agents which induce ER stress and suggest that the development of potent, small-molecule PDI inhibitors has significant potential as a powerful tool for enhancing the efficacy of chemotherapy in melanoma.

NOV-002, a glutathione disulfide mimetic, as a modulator of cellular redox balance

NOV-002 is a novel glutathione disulfide mimetic that when administered in combination with standard chemotherapeutic regimens has resulted in increased efficacy (survival, tumor response) and improved tolerance to chemotherapy (e.g., hematologic recovery) in advanced non-small cell lung cancer patients. We show that NOV-002, which is not cytotoxic as a single agent, generated time- and concentration-dependent oxidative signals at the cell surface (reduction in protein thiols) and intracellularly [altered oxidized glutathione (GSSG) and reduced glutathione levels and ratio; increased reactive oxygen species] in the premyeloid HL-60 cell line and that this was associated with an increase in S-glutathionylation of cell proteins, particularly actin. Commensurate with these effects, NOV-002 activated p38, c-Jun-NH(2)-kinase, and extracellular signal-regulated kinase and caused a dose-dependent increase in phosphorylation of three proteins that have previously been linked with hematopoiesis, AKT, JAK2, and STAT5. The effect of NOV-002 on enzymes involved in glutathione metabolism was evaluated. Relative to oxidized glutathione, NOV-002 was an equivalent substrate for glutathione reductase and was an inhibitor of protein disulfide isomerase, one of the components of the redox-sensitive unfolded protein response pathway. These redox-stimulated cell signaling actions occurred in the context of increased HL-60 cell proliferation after treatment with NOV-002. Overall, the pleiotropic pharmacologic effects of NOV-002 can be attributed to the GSSG component of the drug, and modulation of cellular redox balance is a feature central to the mechanism of action of NOV-002. Such modulation may underlie its clinical actions, including hematologic recovery and immunostimulation in the face of chemosuppression.

Oncolytic herpes simplex virus type-1 therapy in a highly infiltrative animal model of human glioblastoma

We have examined the spread and antitumor efficacy of an oncolytic herpes simplex virus-1-based vector (G207) in glioblastoma biopsy spheroids in vitro and in vivo after local delivery to corresponding intracranial xenografts. Spheroids from three patients were infected with increasing doses of G207 and transgene expression was quantified. Other infected spheroids were followed for 10 days to assess cytotoxic effects. For the in vivo study, spheroids were grafted intracerebrally into Rowett nude rats. The resulting highly infiltrative xenografts were injected with 3.4 x 10(6) plaque-forming units (penetration study) or 6.8 x 10(6) plaque-forming units (therapeutic study) of G207 using microprocessor-controlled stereotaxic delivery. Vector spread was tracked by histochemical staining. In the therapeutic study, tumor volumes were monitored weekly by magnetic resonance imaging, and survival data were collected. In vitro, lacZ expression was seen at the spheroid surfaces 24 h postinfection, whereas the spheroid cores were transgene positive after 96 h. Cytotoxic susceptibility varied between the patients, showing a 36% to 95% lysis 10 days postinfection. Local delivery of G207 into intracranial xenografts resulted in extensive vector spread throughout the lesions. In the therapeutic study, G207 application reduced tumor volumes compared with controls, but did not significantly improve survival of the animals. Histologic analysis revealed infection of host structures such as the ventricular and choroid plexus ependyma. In conclusion, G207 replicates in patient-derived glioblastoma multiforme xenografts and tumor volumes are reduced after intratumoral delivery; however, the survival data suggest that the therapeutic effect could be improved by repeated vector application or through combination with other treatment modalities.

Proteomic analysis of differential proteins in pancreatic carcinomas: Effects of MBD1 knock-down by stable RNA interference

Background

Methyl-CpG binding domain protein 1 (MBD1), a suppressor of gene transcription, may be involved in inactivation of tumor suppressor genes during tumorigenesis. Over-expression of MBD1 has been reported in human pancreatic carcinomas.

Methods

In this study, we established a MBD1-knock-down pancreatic cancer cell line (BxPC-3) using stable RNA interference, to compare the proteomic changes between control and MBD1-knock-down cells using two-dimensional gel electrophoresis and mass spectrometry.

Results

We identified five proteins that were up-regulated and nine proteins that were down-regulated. Most of the identified proteins are involved in tumorigenesis, some are prognostic biomarkers for human malignant tumors.

Conclusion

Our data suggest that these differential proteins may be associated with the function of MBD1, and provide some insight into the functional mechanism of MBD1 in the development of pancreatic cancer.

CD133 negative glioma cells form tumors in nude rats and give rise to CD133 positive cells

CD133 is a cell surface marker expressed on progenitors of haematopoietic and endothelial cell lineages. Moreover, several studies have identified CD133 as a marker of brain tumor-initiating cells. In this study, human glioblastoma multiforme biopsies were engrafted intracerebrally into nude rats. The resulting tumors were serially passaged in vivo, and monitored by magnetic resonance imaging. CD133 expression was analyzed at various passages. Tumors initiated directly from the biopsies expressed little or no CD133, and showed no contrast enhancement suggesting an intact blood-brain barrier. During passaging, the tumors gradually displayed more contrast enhancement, increased angiogenesis and a shorter survival. Real-time qPCR and immunoblots showed that this was accompanied by increased CD133 expression. Primary biopsy spheroids and xenograft tumors were subsequently dissociated and flow sorted into CD133 negative and CD133 positive cell populations. Both populations incorporated BrdU in cell culture, and expressed the neural precursor marker nestin. Notably, CD133 negative cells derived from 6 different patients were tumorgenic when implanted into the rat brains. For 3 of these patients, analysis showed that the resulting tumors contained CD133 positive cells. In conclusion, we show that CD133 negative glioma cells are tumorgenic in nude rats, and that CD133 positive cells can be obtained from these tumors. Upon passaging of the tumors in vivo, CD133 expression is upregulated, coinciding with the onset of angiogenesis and a shorter survival. Thus, our findings do not suggest that CD133 expression is required for brain tumor initiation, but that it may be involved during brain tumor progression.

Prognostic markers of astrocytoma: how to predict the unpredictable?

Astrocytomas are the most frequent tumors originating in the human nervous system. They carry a dismal prognosis as high-grade astroctyoma patients (World Health Organization [WHO] grade III and IV) rarely live beyond 5 years. At present, these tumors are mainly diagnosed through the difficult task of histologic examination of tissue obtained through stereotactic biopsy or tumor resection. In addition to determining the malignancy grade through histologic studies, the only other prognostic factors used in clinical setting are patient age and performance status. To overcome current limitations, research is underway to develop molecular approaches for glioma classification. These include identification, characterization and expansion of clinical (patient characteristics and imaging variables), histologic (WHO classification criteria) and molecular (genetic and proteomic) factors with prognostic potential. In this review the established classification characteristics, along with recent advances that may lead to the addition of new parameters and thus improve patient management and survival, are discussed.

Differential expression of mimecan and thioredoxin domain-containing protein 5 in colorectal adenoma and cancer: a proteomic study

Adenoma is the major precursor lesion of colorectal cancer, one of the most common cancers worldwide. The elucidation of the molecular mechanism underlying adenoma is essential for early detection, prevention, and intervention of colorectal cancer. Using a combination of two-dimensional gel electrophoresis and mass spectrometry, we identified 27 differentially expressed proteins in adenoma, compared with matched normal mucosa and cancer tissue. Seventeen proteins were upregulated and six downregulated in adenoma when compared with the same proteins in individual-matched normal mucosa. Four were downregulated, but none upregulated in adenoma when compared with the same proteins in matched cancer tissue. Two novel proteins, mimecan and thioredoxin domain-containing protein 5 (TXNDC5), were further validated by Western blot in 8 colorectal adenomas and 19 cancers that were matched with normal mucosa. All adenoma and cancer tissues did not express mimecan, but all normal mucosa did (P < 0.01). In contrast, TXNDC5 was significantly upregulated in colorectal adenoma and cancer tissues as compared with that in normal mucosa (P < 0.05). This study clearly demonstrated that absence of mimecan and upregulation of TXNDC5 are involved in the early development of colorectal cancer. Thus, the differentially expressed proteins might serve as potential biomarkers for colorectal cancer detection and intervention.

Generating disulfides with the Quiescin-sulfhydryl oxidases

The Quiescin-sulfhydryl oxidase (QSOX) family of flavoenzymes catalyzes the direct and facile insertion of disulfide bonds into unfolded reduced proteins with concomitant reduction of oxygen to hydrogen peroxide. This review discusses the chemical mechanism of these enzymes and the involvement of thioredoxin and flavin-binding domains in catalysis. The variability of CxxC motifs in the QSOX family is highlighted and attention is drawn to the steric factors that may promote efficient thiol/disulfide exchange during oxidative protein folding. The varied cellular location of these multi-domain sulfhydryl oxidases is reviewed and potential intracellular and extracellular roles are summarized. Finally, this review identifies important unresolved questions concerning this ancient family of sulfhydryl oxidases.