Ezrin-dependent promotion of glioma cell clonogenicity, motility, and invasion mediated by BCL-2 and transforming growth factor-beta2

Huntingtin-Interacting Protein 1-Related (HIP1R) Regulates Rheumatoid Arthritis Synovial Fibroblast Invasiveness

Huntingtin-interacting protein 1-related (HIP1R) shares some function similarities with HIP1, and HIP1 regulates arthritis and RA fibroblast-like synoviocytes (FLS) invasiveness. Therefore, we hypothesized that HIP1R might be involved in the regulation of FLS phenotypes and molecular processes relevant to RA. siRNA was used to knockdown HIP1R, HIP1 or control in RA FLS, followed by cell studies for invasion in Matrigel, migration, proliferation, and adhesion. RNA was sequenced and analyzed. HIP1R knockdown significantly reduced RA FLS invasiveness and migration (p < 0.05). The DEGs in siRNA HIP1R had an enrichment for GO processes "astrocyte and glial cell projection", "small GTPase signaling", and "PDGFR signaling". The most significantly DEGs had decreased expression in siRNA HIP1R and included AKT1S1, GABBR2, GPR56, and TXNDC12. siRNA HIP1 RA FLS had an enrichment for the "Rap1 signaling pathway" and "Growth factor receptor binding". The most significantly DEGs in HIP1 siRNA included FGF2, PGF, and SLC39A8. HIP1R and HIP1 DEG lists had a greater than expected number of similar genes (p = 0.0015), suggesting that, despite the major differences detected, both have partially overlapping functions in RA FLS. The most significantly DEGs in both HIP1R and HIP1 analyses are involved in cancer cell behaviors and outcomes. HIP1R is a new gene implicated in RA FLS invasiveness and migration, and regulates unique pathways and cell processes relevant to both RA as well as cancer biology. Our study provides new insight into processes implicated in FLS invasiveness, which is relevant for joint damage in RA, and identify new potential gene targets for FLS-specific treatments.

Ezrin gone rogue in cancer progression and metastasis: An enticing therapeutic target

Cancer metastasis is the primary cause of morbidity and mortality in cancer as it remains the most complicated, devastating, and enigmatic aspect of cancer. Several decades of extensive research have identified several key players closely associated with metastasis. Among these players, cytoskeletal linker Ezrin (the founding member of the ERM (Ezrin-Radixin-Moesin) family) was identified as a critical promoter of metastasis in pediatric cancers in the early 21st century. Ezrin was discovered 40 years ago as a aminor component of intestinal epithelial microvillus core protein, which is enriched in actin-containing cell surface structures. It controls gastric acid secretion and plays diverse physiological roles including maintaining cell polarity, regulating cell adhesion, cell motility and morphogenesis. Extensive research for more than two decades evinces that Ezrin is frequently dysregulated in several human cancers. Overexpression, altered subcellular localization and/or aberrant activation of Ezrin are closely associated with higher metastatic incidence and patient mortality, thereby justifying Ezrin as a valuable prognostic biomarker in cancer. Ezrin plays multifaceted role in multiple aspects of cancer, with its significant contribution in the complex metastatic cascade, through reorganizing the cytoskeleton and deregulating various cellular signaling pathways. Current preclinical studies using genetic and/or pharmacological approaches reveal that inactivation of Ezrin results in significant inhibition of Ezrin-mediated tumor growth and metastasis as well as increase in the sensitivity of cancer cells to various chemotherapeutic drugs. In this review, we discuss the recent advances illuminating the molecular mechanisms responsible for Ezrin dysregulation in cancer and its pleiotropic role in cancer progression and metastasis. We also highlight its potential as a prognostic biomarker and therapeutic target in various cancers. More importantly, we put forward some potential questions, which we strongly believe, will stimulate both basic and translational research to better understand Ezrin-mediated malignancy, ultimately leading to the development of Ezrin-targeted cancer therapy for the betterment of human life.

CircGLIS3 Promotes High-Grade Glioma Invasion via Modulating Ezrin Phosphorylation

High-grade glioma is highly invasive and malignant, resistant to combined therapies, and easy to relapse. A better understanding of circular RNA (circRNA) biological function in high-grade glioma might contribute to the therapeutic efficacy. Here, a circRNA merely upregulated in high-grade glioma, circGLIS3 (hsa_circ_0002874, originating from exon 2 of GLIS3), was validated by microarray and Real-time quantitative reverse transcription PCR (qRT-PCR). The role of circGLIS3 in glioma was assessed by functional experiments both in vitro and in vivo. Fluorescence in situ hybridization (FISH), RNA pull-down, RNA immunoprecipitation (RIP), and immunohistochemical staining were performed for mechanistic study. Cocultured brain endothelial cells with glioma explored the role of exosome-derived circGLIS3 in the glioma microenvironment. We found that upregulation of circGLIS3 promoted glioma cell migration and invasion and showed aggressive characteristics in tumor-bearing mice. Mechanistically, we found that circGLIS3 could promote the Ezrin T567 phosphorylation level. Moreover, circGLIS3 could be excreted by glioma through exosomes and induced endothelial cell angiogenesis. Our findings indicate that circGLIS3 is upregulated in high-grade glioma and contributes to the invasion and angiogenesis of glioma via modulating Ezrin T567 phosphorylation.

Knockdown of Ezrin inhibited migration and invasion of cervical cancer cells in vitro

Cervical cancer is the fourth most common malignancy in women. The aim of this study was to investigate the functions of Ezrin in cervical cancer cells. Two cervical cancer cell lines, SiHa and CaSki, were cultured in vitro. Following the knockdown of Ezrin using siRNA, real-time reverse transcription-polymerase chain reaction (RT-PCR) and Western blot analysis were applied to analyze Ezrin expression at the messenger RNA (mRNA) and protein levels. Subsequently, wound healing assay, transwell assay, and sulforhodamine B (SRB) assay were used to detect the migration, invasion, and viability of cervical cancer cells, respectively. Results revealed that Ezrin siRNA can notably inhibit the migration and invasion of SiHa and CaSki cells (P < 0.05). However, knockdown of Ezrin shows no effects on the viability of SiHa and CaSki cells (P < 0.05). It is indicated that Ezrin plays a possible role in promoting the migration and invasion of cervical cancer cells and may be a therapeutic target to prevent metastasis of cervical cancer.

Nuclear factor IX promotes glioblastoma development through transcriptional activation of Ezrin

Enhanced migration is pivotal for the malignant development of glioblastoma (GBM), but the underlying molecular mechanism that modulates the migration of the GBM cells remains obscure. Here we show that nuclear factor IX (NFIX) is significantly upregulated in human GBM lesions compared with normal or low-grade gliomas. NFIX deficiency impairs the migration of GBM cells and inhibits the tumor growth in the hippocampus of immunodeficient nude mice. Mechanistically, NFIX silencing suppresses the expression of Ezrin, a protein that crosslinks actin cytoskeleton and plasma membrane, which is also positively correlated with GBM malignancy. NFIX depletion induced migration inhibition of GBM cells can be rescued by the replenishment of Ezrin. Furthermore, we identify a NFIX response element (RE) between −840 and −825 bp in the promoter region of the Ezrin gene. Altogether, our findings show, for the first time that NFIX can transcriptionally upregulate the expression of Ezrin and contribute to the enhanced migration of GBM cells, suggesting that NFIX is a potential target for GBM therapy.

Perspectives for Ezrin and Radixin in Astrocytes: Kinases, Functions and Pathology

Astrocytes are increasingly perceived as active partners in physiological brain function and behaviour. The structural correlations of the glia–synaptic interaction are the peripheral astrocyte processes (PAPs), where ezrin and radixin, the two astrocytic members of the ezrin-radixin-moesin (ERM) family of proteins are preferentially localised. While the molecular mechanisms of ERM (in)activation appear universal, at least in mammalian cells, and have been studied in great detail, the actual ezrin and radixin kinases, phosphatases and binding partners appear cell type specific and may be multiplexed within a cell. In astrocytes, ezrin is involved in process motility, which can be stimulated by the neurotransmitter glutamate, through activation of the glial metabotropic glutamate receptors (mGluRs) 3 or 5. However, it has remained open how this mGluR stimulus is transduced to ezrin activation. Knowing upstream signals of ezrin activation, ezrin kinase(s), and membrane-bound binding partners of ezrin in astrocytes might open new approaches to the glial role in brain function. Ezrin has also been implicated in invasive behaviour of astrocytomas, and glial activation. Here, we review data pertaining to potential molecular interaction partners of ezrin in astrocytes, with a focus on PKC and GRK2, and in gliomas and other diseases, to stimulate further research on their potential roles in glia-synaptic physiology and pathology.

Regulation of human glioma cell migration, tumor growth, and stemness gene expression using a Lck targeted inhibitor

Migration of human glioma cells (hGCs) within the brain parenchyma makes glioblastoma one of the most aggressive and lethal tumors. Studies of the cellular and molecular mechanisms underlying hGC migration are hindered by the limitations of existing glioma models. Here we developed a dorsal root ganglion axon-oligodendrocyte-hGC co-culture to study in real time the migration and interaction of hGCs with their microenvironment. hGCs interact with myelinated and non-myelinated axons through the formation of pseudopodia. Isolation of pseudopodia-localized polysome-bound RNA reveals transcripts of Lck, Paxillin, Crk-II, and Rac1 that undergo local translation. Inhibition of Lck phosphorylation using a small-molecule inhibitor (Lck-I), blocks the phosphorylation of Paxillin and Crk-II, the formation of pseudopodia and the migration of hGCs. In vivo intraventricular administration of the Lck-I using an orthotopic xenograft glioma model, results in statistically significant inhibition of tumor size and significant down-regulation of Nanog-targeted genes, which are associated with glioblastoma patient survival. Moreover, treatment of human glioma stem cells (hGSCs) with Lck-I, results in significant inhibition of self-renewal and tumor-sphere formation. The involvement of Lck in different levels of glioma malignant progression, such as migration, tumor growth, and regulation of cancer stemness, makes Lck a potentially important therapeutic target for human glioblastomas.

Mesenchymal stem cells enhance tumorigenic properties of human glioblastoma through independent cell-cell communication mechanisms

Mesenchymal stem cells (MSC) display tumor tropism and have been addressed as vehicles for delivery of anti-cancer agents. As cellular components of the tumor microenvironment, MSC also influence tumor progression. However, the contribution of MSC in brain cancer is not well understood since either oncogenic or tumor suppressor effects have been reported for these cells. Here, MSC were found capable of stimulating human Glioblastoma (GBM) cell proliferation through a paracrine effect mediated by TGFB1. Moreover, when in direct cell-cell contact with GBM cells, MSC elicited an increased proliferative and invasive tumor cell behavior under 3D conditions, as well as accelerated tumor development in nude mice, independently of paracrine TGFB1. A secretome profiling of MSC-GBM co-cultures identified 126 differentially expressed proteins and 10 proteins exclusively detected under direct cell-cell contact conditions. Most of these proteins are exosome cargos and are involved in cell motility and tissue development. These results indicate a dynamic interaction between MSC and GBM cells, favoring aggressive tumor cell traits through alternative and independent mechanisms. Overall, these findings indicate that MSC may exert pro-tumorigenic effects when in close contact with tumor cells, which must be carefully considered when employing MSC in targeted cell therapy protocols against cancer.

Sulforaphane-cysteine induces apoptosis by sustained activation of ERK1/2 and caspase 3 in human glioblastoma U373MG and U87MG cells

We previously demonstrated that sulforaphane (SFN) inhibited invasion via sustained activation of ERK1/2 in human glioblastoma cells. However, sulforaphane-cysteine (SFN-Cys), an analog of SFN, enriched in plasma with longer half-life, had more potentiality to induce apoptosis. Here we investigated the molecular mechanisms of SFN-Cys-induced apoptosis in human glioblastoma U373MG and U87MG cells. Cell viability assay showed that SFN-Cys inhibited cell viability in a dose-dependent manner. Cell morphology observation also showed SFN-Cys increased the phenotype of cell death in a dose-dependent manner. Furthermore, flow cytometry assay showed that SFN-Cys induced apoptosis significantly in a dose-dependent manner in both cell lines. Furthermore, western blot analysis demonstrated that SFN-Cys induced activation of ERK1/2 in a sustained manner and the activation contributed to upregulation of Bax/Bcl-2 ratio and cleaved caspase 3, and these results can be reversed by the ERK1/2 blocker PD98059. Our results showed that SFN-Cys induced cell apoptosis via sustained activation of ERK1/2 and the ERK1/2 mediated signaling pathways such as activation of caspase 3 and apoptosis-related proteins, thus indicating that SFN-Cys might be a more promising therapeutic agent versus SFN to resist glioblastoma cells, especially in Taxol-resistant cancer cells.

RETRACTED: Downregulation of miR-204 expression correlates with poor clinical outcome of glioma patients

Glioma is the most common type of malignant neoplasm in the central nervous system, with high incidence and mortality rate. MicroRNAs, as a class of small noncoding RNAs, play an important role in carcinogenesis and correlate with glioma diagnosis and prognosis. In this study, we investigated the microRNA-204 (miR-204) concentration in glioma tissues and its relation to the expression of ezrin and bcl-2 mRNA, as well as its potential predictive and prognostic values in glioma. The concentrations of miR-204 were significantly lower in glioma tissues than in nontumor brain tissues and also were lower in high-grade than in low-grade gliomas (World Health Organization grades III and IV versus grades I and II). The miR-204 concentration was inversely correlated with the ezrin and bcl-2 concentrations. The miR-204 concentration was classified as high or low according to the median value, and low miR-204 correlated with higher World Health Organization grade, larger tumor, and worse Karnofsky performance score. Kaplan-Meier survival analysis demonstrated that patients with low miR-204 expression had shorter progression-free survival and overall survival than patients with high miR-204 expression. In addition, univariate and multivariate analyses showed that miR-204 expression was an independent prognostic feature of overall survival and progression-free survival. In conclusion, our study indicates that miR-204 is downregulated in glioma and may be a biomarker of poor prognosis in patients with this cancer.

Effects of Ezrin and Heat Shock Protein 70 on Apoptosis and Proliferation of Human Osteosarcoma Cells

OBJECTIVE

To investigate the influence of knocking down ezrin expression in combination with heat shock protein (HSP)-induced immune killing on the apoptosis and proliferation of mouse osteosarcoma cells.

METHODS

The HSP70 and ezrin-shRNA DNA fragments cloned into the expression vector pGFP-V-RS and the expression vectors pGFP-V-RS-shRNA and pGFP-V-RS-shRNA-HSP70 constructed and transfected into MG63 cell line, where their status was observed by fluorescent microscopy. Expression of ezrin and HSP70 was determined by RT-PCR and western blot. Changes in cell apoptosis and proliferation were assessed by flow cytometry and MTS and changes in expression of apoptosis and cell cycle-related proteins by western blot. Specific cytotoxic T lymphocytes (CTLs) were induced by HSP70 and its lethal effect on target MG63 tumor cells analyzed by MTS assay.

RESULTS

The specific vector simultaneously downregulated ezrin and upregulated HSP70. Compared with ezrin knockdown alone, simultaneous HSP70 overexpression partially recovered the promoted cellular apoptosis and proliferation suppression by induced by ezrin knockdown; however, the apoptosis rate of MG63 cells was significantly greater than that of a negative control. In addition, ezrin-shRNA and ezrin-shRNA/HSP70 promoted expression of Bax. However, expression of these agents reduces Bcl-2 and Cyclin D1. The cytotoxic effects of CTLs on target MG63 tumor cells were significantly greater in the CTL + IL-2 + HSP70 group than the CTL + IL-2 group.

CONCLUSIONS

Simultaneously knocking down ezrin and overexpressing HSP70 promotes apoptosis and inhibits proliferation of osteosarcoma cells and HSP70 induces CTL, enhancing the lethal effect on tumor cells.

HOXA10 promotes cell invasion and MMP-3 expression via TGFβ2-mediated activation of the p38 MAPK pathway in pancreatic cancer cells

BACKGROUND

HOXA10 is closely related to tumor progression in many human cancers. However, the role of HOXA10 in pancreatic cancer remains unclear. The aim of this study was to determine the involvement of HOXA10 in pancreatic cancer cell invasion and migration.

METHODS

The effect of HOXA10 on the invasion and migration of pancreatic cancer cells was assessed by invasion and migration assays. The protein of transforming growth factor beta-2 (TGFβ2) was neutralized by TGFβ2 blocking antibody. The activation of p38 was inhibited by SB239063.

RESULTS

HOXA10 could promote the invasion and migration of pancreatic cancer cells. Knockdown of HOXA10 decreased the expressions of TGFβ2 and matrix metallopeptidase-3 (MMP-3) and suppressed the activation of p38. Conversely, overexpression of HOXA10 increased the levels of TGFβ2 and MMP-3. Further experiments identified that TGFβ2 contributed to the HOXA10-promoted invasion and migration and regulated MMP-3 expression and p38 activation. Additionally, inhibition of p38 suppressed cell invasion and MMP-3 expression in pancreatic cancer cells.

CONCLUSIONS

HOXA10 promotes cell invasion and MMP-3 expression of pancreatic cancer cells via TGFβ2-p38 MAPK pathway. Thus, HOXA10 could be a useful target for the treatment of pancreatic cancer.

Systematic review of protein biomarkers of invasive behavior in glioblastoma

Glioblastoma (GBM) is an aggressive and incurable brain tumor with a grave prognosis. Recurrence is inevitable even with maximal surgical resection, in large part because GBM is a highly invasive tumor. Invasiveness also contributes to the failure of multiple cornerstones of GBM therapy, including radiotherapy, temozolomide chemotherapy, and vascular endothelial growth factor blockade. In recent years there has been significant progress in the identification of protein biomarkers of invasive phenotype in GBM. In this article, we comprehensively review the literature and survey a broad spectrum of biomarkers, including proteolytic enzymes, extracellular matrix proteins, cell adhesion molecules, neurodevelopmental factors, cell signaling and transcription factors, angiogenic effectors, metabolic proteins, membrane channels, and cytokines and chemokines. In light of the marked variation seen in outcomes in GBM patients, the systematic use of these biomarkers could be used to form a framework for better prediction, prognostication, and treatment selection, as well as the identification of molecular targets for further laboratory investigation and development of nascent, directed therapies.

Lactate-modulated induction of THBS-1 activates transforming growth factor (TGF)-beta2 and migration of glioma cells in vitro

Background

An important phenomenon observed in glioma metabolism is increased aerobic glycolysis in tumor cells, which is generally referred to as the Warburg effect. Transforming growth factor (TGF)-beta2, which we previously showed to be induced by lactic acid, is a key pathophysiological factor in glioblastoma, leading to increased invasion and severe local immunosuppression after proteolytic cleavage from its latency associated peptide. In this study we tested the hypothesis, that lactate regulates TGF-beta2 expression and glioma cell migration via induction of Thrombospondin-1 (THBS-1), a TGF-beta activating protein.

Methods

Lactate levels were reduced by knockdown of LDH-A using specific small interfering RNA (siRNA) and competitive inhibition of LDH-A by sodium oxamate. Knockdown of THBS-1 was performed using specific siRNA. Western Blot, qRT-PCR, and ELISA were used to investigate expression levels of LDH-A, LDH-B, TGF-beta2 and THBS-1. Migration of cells was examined by Spheroid, Scratch and Boyden Chamber assays.

Results

Knockdown of LDH-A with subsequent decrease of lactate concentration leads to reduced levels of THBS-1 and TGF-beta2 in glioma cells. Lactate addition increases THBS-1 protein, leading to increased activation of TGF-beta2. Inhibition of THBS-1 reduces TGF-beta2 protein and migration of glioma cells. Addition of synthetic THBS-1 can rescue reduced TGF-beta2 protein levels and glioma cell migration in siLDH-A treated cells.

Conclusion

We define a regulatory cascade between lactate, THBS-1 and TGF-beta2, leading to enhanced migration of glioma cells. Our results demonstrate a specific interaction between tumor metabolism and migration and provide a better understanding of the mechanisms underlying glioma cell invasion.

Sphingolipid regulation of ezrin, radixin, and moesin proteins family: implications for cell dynamics

A key but poorly studied domain of sphingolipid functions encompasses endocytosis, exocytosis, cellular trafficking, and cell movement. Recently, the ezrin, radixin and moesin (ERM) family of proteins emerged as novel potent targets regulated by sphingolipids. ERMs are structural proteins linking the actin cytoskeleton to the plasma membrane, also forming a scaffold for signaling pathways that are used for cell proliferation, migration and invasion, and cell division. Opposing functions of the bioactive sphingolipid ceramide and sphingosine-1-phosphate (S1P), contribute to ERM regulation. S1P robustly activates whereas ceramide potently deactivates ERM via phosphorylation/dephosphorylation, respectively. This recent dimension of cytoskeletal regulation by sphingolipids opens up new avenues to target cell dynamics, and provides further understanding of some of the unexplained biological effects mediated by sphingolipids. In addition, these studies are providing novel inroads into defining basic mechanisms of regulation and action of bioactive sphingolipids. This review describes the current understanding of sphingolipid regulation of the cytoskeleton, it also describes the biologies in which ERM proteins have been involved, and finally how these two large fields have started to converge. This article is part of a Special Issue entitled New Frontiers in Sphingolipid Biology.

Knockdown of Ezrin by RNA interference reverses malignant behavior of human pancreatic cancer cells in vitro

BACKGROUND

Pancreatic cancer is one of the most aggressive tumors with a dismal prognosis. The membrane cytoskeletal crosslinker Ezrin participates in several functions including cell proliferation, adhesion, motility and survival. There is increasing evidence that Ezrin is overexpressed in vast majority of malignant tumors and regulates tumor progression. However, its roles in pancreatic cancer remain elusive.

METHODS

Three pairs of specific Ezrin siRNAs were designed and synthetized and screened to determine the most efficient one for construction of a hairpin RNA plasmid targeting Ezrin. After transfection into the Panc-1 pancreatic cancer cell line, real-time quantitative PCR and Western blotting were performed to examine the expression of mRNA and protein. The MTT method was applied to examine the proliferation and the drug sensibility to Gemcitabine. Flow cytometry was used to assess the cycle and apoptosis, while capacity for invasion was determined with transwell chambers. Furthermore, we detected phosphorylated-Erk1/2 protein and phosphorylated-Akt protein by Western blotting.

RESULTS

Real-time quantitative PCR and Western blotting revealed that Ezrin expression was notably down-regulated at both mRNA and protein levels by RNA interference (P< 0.01). Proliferation was inhibited and drug resistance to gemcitabine was improved (P< 0.05). Flow cytometry showed that the proportion of cells in the G1/G0 phase increased (P< 0.01), and in G2/M and S phases decreased (P< 0.05), with no apparent differences in apoptosis (P> 0.05). The capacity for invasion was markedly reduced (P< 0.01). In addition, down-regulating Ezrin expression had no effect on phosphorylated-Akt protein (P>0.05), but could decrease the level of phosphorylated-Erk1/2 protein (P< 0.05).

CONCLUSIONS

RNA interference of Ezrin could inhibit its expression in the pancreatic cancer cells line Panc-1, leading to a potent suppression of malignant behavior in vitro. Assessment of potential as a target for pancreatic cancer treatment is clearly warranted.

Mechanisms underlying cancer progression caused by ezrin overexpression in tongue squamous cell carcinoma

BACKGROUND

Ezrin is a member of the ezrin, radixin, and moesin family that provides a functional link between the plasma membrane and the cortical actin cytoskeleton. A correlation between ezrin overexpression and aggressive cancer behavior has been recently reported in various tumor types. However, its roles in the mechanisms underlying progression of tongue squamous cell carcinoma (SCC) are unclear.

METHOD

We used human tongue SCC and noncancerous tissue microarrays to immunohistochemically analyze the ezrin expression level and its relationship with proliferative activity. The human tongue SCC cell line HSC-3 was used to determine the effects of ezrin RNA interference (RNAi) on cancer cells during MTT; wound healing and invasion assays; immunofluorescence of the actin cytoskeleton; and western blotting of E-cadherin, N-cadherin, β-catenin, and the active and total RhoA/Rac1/cdc42.

RESULTS

Ezrin was overexpressed in 46.4% of the tumors examined in human tongue SCC tissue microarrays. Ezrin expression was correlated with the Ki-67 index. Ezrin depletion by RNAi in the HSC-3 cells significantly reduced cell proliferation, migration, and invasiveness and disturbed actin reorganization during podia formation. Its effects on RhoA/Rac1/cdc42 expression were not significant, whereas it enhanced E-cadherin and β-catenin expression and decreased N-cadherin expression.

CONCLUSIONS

Ezrin is often overexpressed in primary tongue SCCs and may have an important role in their growth, migration, and invasiveness possibly via its relationship with the E-cadherin/β-catenin complex and the cadherin switch. Thus, ezrin could be a therapeutic target in tongue SCC.

Astrocytes enhance the invasion potential of glioblastoma stem-like cells

Glioblastomas (GBMs) are characterized as highly invasive; the contribution of GBM stem-like cells (GSCs) to the invasive phenotype, however, has not been completely defined. Towards this end, we have defined the invasion potential of CD133+ GSCs and their differentiated CD133− counterparts grown under standard in vitro conditions and in co-culture with astrocytes. Using a trans-well assay, astrocytes or astrocyte conditioned media in the bottom chamber significantly increased the invasion of GSCs yet had no effect on CD133− cells. In addition, a monolayer invasion assay showed that the GSCs invaded farther into an astrocyte monolayer than their differentiated progeny. Gene expression profiles were generated from two GSC lines grown in trans-well culture with astrocytes in the bottom chamber or directly in contact with astrocyte monolayers. In each co-culture model, genes whose expression was commonly increased in both GSC lines involved cell movement and included a number of genes that have been previously associated with tumor cell invasion. Similar gene expression modifications were not detected in CD133− cells co-cultured under the same conditions with astrocytes. Finally, evaluation of the secretome of astrocytes grown in monolayer identified a number of chemokines and cytokines associated with tumor cell invasion. These data suggest that astrocytes enhance the invasion of CD133+ GSCs and provide additional support for a critical role of brain microenvironment in the regulation of GBM biology.

Rosiglitazone suppresses glioma cell growth and cell cycle by blocking the transforming growth factor-beta mediated pathway

Glioma is one of the most malignant tumors in the central nervous system. As a peroxisome proliferator-activated receptor γ (PPAR-γ) activator, the thiazolidinediones (TZDs) induce growth arrest and cell death in a broad spectrum of tumor cells. In this study, we investigated the role of rosiglitazone in glioma cells. We found that rosiglitazone, a member of TZDs, suppresses growth of human glioma cell lines U87 and U251. Rosiglitazone also induces cell cycle arrest and apoptosis, which may be the mechanism of its anti-proliferation effect. Next, we found that rosiglitazone suppresses the expression of TGF-beta and its receptor TGF-betaR2, and suppresses phosphorylation of Smad3. Rosiglitazone also inhibits formation of the Smad3/Smad4 complex. Furthermore, Rosiglitazone affects the expression of Smad3/Smad4 associated regulators of gene expression, including p21 and c-Myc. These results suggest that rosiglitazone suppresses growth and cell cycle of human glioma cells by blocking the TGF-beta mediated pathway.

MicroRNA-21 inhibitor sensitizes human glioblastoma U251 stem cells to chemotherapeutic drug temozolomide

MicroRNAs (miRNAs) are small noncoding RNA molecules that regulate protein expression by cleaving or repressing the translation of target mRNAs. In mammals, their function mainly represses the target mRNA transcripts via imperfect complementary sequences in the 3'UTR of target mRNAs. Several miRNAs have been recently reported to be involved in modulation of glioma development, especially some upregulated miRNAs, such as microRNA-21 (miR-21), which has been found to function as an oncogene in cultured glioblastoma multiforme cells. Temozolomide (TMZ), an alkylating agent, is a promising chemotherapeutic agent for treating glioblastoma. Although chemotherapy with temozolomide may contain tumor growth for some months, invariable tumor recurrence suggests that cancer stem cells maintaining these tumors persist. Previous research showed that TMZ could inhibit the proliferation of human glioblastoma stem cells (GSC), but not induced apoptosis, which could supply the chance for glioblastoma recurrence. Accumulating evidence indicated that downregulation of miR-21 in glioblastoma cells caused repression of growth and increased apoptosis, all of which could theoretically enhance the chemotherapeutic effects of cancer therapy. In this study, we aimed to explore whether miR-21 downregulation could enhance the chemotherapeutic effects of TMZ and induce apoptosis on GSC. Interestingly, the results demonstrated that either miR-21 inhibitor or TMZ could not induce apoptosis on GSC. However, miR-21 inhibitor combined with TMZ significantly enhanced GSC apoptosis. Taken together, a combination of miR-21 inhibitor and TMZ could be an effective therapeutic strategy for GSC apoptosis to prevent potential glioblastoma recurrence.

Atypical ezrin localization as a marker of locally advanced breast cancer

Locally advanced breast cancer (LABC) was initially characterized as a large primary tumor (≥5 cm), associated with or without skin or chest-wall involvement, fixed axillary lymph nodes, or disease spread to the ipsilateral internal mammary or supraclavicular nodes. Since 2002, LABC has been reclassified to include smaller stage IIB tumors (2 to <5 cm) with lymph node involvement, or stages IIIA-IIIB (≥5 cm) with or without nodal involvement. Despite the rather common presentation of LABC, it remains a poorly understood and highly variable clinical presentation of breast cancer that is a challenge to treatment. Here, we characterized a panel of breast tumors of known stage, grade, and key clinical-pathological parameters for the expression of the protein ezrin, which is involved in promoting signaling of the PI3K-Akt-mTOR pathway in response to extracellular and tumor micro-environmental signals, and is involved in breast cancer invasion and metastasis. We show that ezrin, which resides primarily in the apical membrane in normal breast epithelium, relocalizes primarily to the cytoplasm in >80 % of traditional (T3) invasive ductal LABC tumors (≥5 cm). Cytoplasmic ezrin is very strongly associated with a single characteristic in breast cancer-large tumor size. In contrast, in large non-malignant fibroadenomas, ezrin staining was similar to that of normal breast epithelium. Small (T1, 1 cm) invasive ductal carcinomas displayed largely apical membrane and perinuclear ezrin localization with weak cytoplasmic staining. Cytoplasmic ezrin localization was also associated with positive lymph node status, but no other clinical-pathological features, including hormone receptor status, histological or nuclear grade of tumor cell. The cytoplasmic relocalization of ezrin may therefore represent a novel marker for large malignant tumor size, reflecting the unique biology of LABC.

Is there a world beyond bevacizumab in targeting angiogenesis in glioblastoma?

INTRODUCTION

Antiangiogenic approaches are currently the dominating experimental therapeutic strategy in glioblastoma. First enthusiasm was provoked by promising radiological response rates and an apparent clinical benefit with some of these agents. Major limitations include the modest number of durable responses, the lack of cytotoxic antitumor activity, of synergy when combined with chemotherapy and of an overall survival benefit.

AREAS COVERED

We review the rationale as well as preclinical and clinical evidence for the future development of antiangiogenic agents in glioblastoma. The most prominent approach targets VEGF and includes agents such as the VEGF antibody bevacizumab, the VEGF receptor fusion protein aflibercept or the tyrosine kinase inhibitors cediranib and XL-184. Inhibition of angiogenic pathways by small molecules, for example, enzastaurin, or anti-integrin-based approaches, for example, cilengitide, represent alternative strategies.

EXPERT OPINION

Enzastaurin and cediranib failed in randomized Phase III trials in recurrent glioblastoma, aflibercept in Phase II. By contrast, bevacizumab was conditionally approved in many countries. Recently completed Phase III trials for bevacizumab and cilengitide in the first-line setting will define the future role of these agents. This intense clinical trial activity reflects the hope that antiangiogenic agents will become part of the limited therapeutic options for glioblastoma.

Testing the promiscuity of commercial kinase inhibitors against the AGC kinase group using a split-luciferase screen

Using a newly developed competitive binding assay dependent upon the reassembly of a split reporter protein, we have tested the promiscuity of a panel of reported kinase inhibitors against the AGC group. Many non-AGC targeted kinase inhibitors target multiple members of the AGC group. In general, structurally similar inhibitors consistently exhibited activity toward the same target as well as toward closely related kinases. The inhibition data was analyzed to test the predictive value of either using identity scores derived from residues within 6 Å of the active site or identity scores derived from the entire kinase domain. The results suggest that the active site identity in certain cases may be a stronger predictor of inhibitor promiscuity. The overall results provide general guidelines for establishing inhibitor selectivity as well as for the future design of inhibitors that either target or avoid AGC kinases.

Costimulatory protein 4IgB7H3 drives the malignant phenotype of glioblastoma by mediating immune escape and invasiveness

PURPOSE

Recent work points out a role of B7H3, a member of the B7-family of costimulatory proteins, in conveying immunosuppression and enforced invasiveness in a variety of tumor entities. Glioblastoma is armed with effective immunosuppressive properties resulting in an impaired recognition and ineffective attack of tumor cells by the immune system. In addition, extensive and diffuse invasion of tumor cells into the surrounding brain tissue limits the efficacy of local therapies. Here, 4IgB7H3 is assessed as diagnostic and therapeutic target for glioblastoma.

EXPERIMENTAL DESIGN

To characterize B7H3 in glioblastoma, we conduct analyses not only in glioma cell lines and glioma-initiating cells but also in human glioma tissue specimens.

RESULTS

B7H3 expression by tumor and endothelial cells correlates with the grade of malignancy in gliomas and with poor survival. Both soluble 4IgB7H3 in the supernatant of glioma cells and cell-bound 4IgB7H3 are functional and suppress natural killer cell-mediated tumor cell lysis. Gene silencing showed that membrane and soluble 4IgB7H3 convey a proinvasive phenotype in glioma cells and glioma-initiating cells in vitro. These proinvasive and immunosuppressive properties were confirmed in vivo by xenografted 4IgB7H3 gene silenced glioma-initiating cells, which invaded significantly less into the surrounding brain tissue in an orthotopic model and by subcutaneously injected LN-229 cells, which were more susceptible to natural killer cell-mediated cytotoxicity than unsilenced control cells.

CONCLUSIONS

Because of its immunosuppressive and proinvasive function, 4IgB7H3 may serve as a therapeutic target in the treatment of glioblastoma.

Gadofluorine M enhanced MRI in experimental glioma: superior and persistent intracellular tumor enhancement compared with conventional MRI

PURPOSE

To compare conventional magnetic resonance imaging (MRI) techniques (T2-w and Gadolinium-DTPA-enhanced T1-w images) and Gadofluorine-M (GfM), a novel contrast agent in MRI, in murine gliomas.

MATERIALS AND METHODS

Growth monitoring of murine gliomas (induced in mice) was performed on a 2.3 Tesla Bruker Biospec MRI unit. First all animals were investigated with conventional MRI techniques. In group I GfM was applied at an early stage of disease, in group II at a later stage. After injection of GfM follow-up MRI was performed without further injection of contrast agent. On MR images tumor size and signal intensities were assessed. Animals were killed for histological evaluation.

RESULTS

In both groups GfM delineated tumor extents larger and more precisely than conventional MRI techniques. The difference between GfM and conventional MRI techniques reached level of significance at both tumor stages. Follow-up MRI after singular injection of GfM showed persistence of GfM in tumor tissue. On tissue sections GfM-enhancing areas corresponded closely to vital tumor tissue. GfM showed a mainly intracellular accumulation.

CONCLUSION

Application of GfM resulted in superior delineation of experimental glioma compared with conventional MRI techniques. Thus, GfM bears a high potential in clinical application.

Trimodal glioblastoma treatment consisting of concurrent radiotherapy, temozolomide, and the novel TGF-β receptor I kinase inhibitor LY2109761

Here we investigate the effects of the novel transforming growth factor-β receptor I (TGF-βRI) serine/threonine kinase inhibitor LY2109761 on glioblastoma when combined with the present clinical standard combination regimen radiotherapy and temozolomide (TMZ). Human GBM U87 (methylated MGMT promoter), T98 (unmethylated MGMT promoter), and endothelial cells (HUVECs) were treated with combinations of LY2109761, TMZ, and radiation. We found that LY2109761 reduced clonogenic survival of U87 and T98 cells and further enhanced the radiation-induced anticlonogenicity. In addition, LY2109761 had antimigratory and antiangiogenic effects in Matrigel migration and tube formation assays. In vivo, in human xenograft tumors growing subcutaneously on BALB/c nu/nu mice, LY2109761 delayed tumor growth alone and in combination with fractionated radiation and TMZ. Interestingly, as expected, the methylated U87 model was more sensitive to TMZ than the unmethylated T98 model in all experiments, whereas the opposite was found for LY2109761. Moreover, with respect to tumor angiogenesis, while LY2109761 decreased the glioblastoma proliferation index (Ki-67) and the microvessel density (CD31 count), the relative pericyte coverage (α-SMA/CD31 ratio) increased in particular after triple therapy, suggesting a vascular normalization effect induced by LY2109761. This normalization could be attributed in part to a decrease in the Ang-2/Ang-1 messenger RNA ratio. LY2109761 also reduced tumor blood perfusion as quantified by noninvasive dynamic contrast-enhanced magnetic resonance imaging. Together, the data indicate that the addition of a TGF-βRI kinase inhibitor to the present clinical standard (radiation plus TMZ) has the potential to improve clinical outcome in human glioblastoma, especially in patients with unmethylated MGMT promoter status.

Inhibitors of Glioma Growth that Reveal the Tumour to the Immune System

Treated glioblastoma patients survive from 6 to 14 months. In the first part of this review, we describe glioma origins, cancer stem cells and the genomic alterations that generate dysregulated cell division, with enhanced proliferation and diverse response to radiation and chemotherapy. We review the pathways that mediate tumour cell proliferation, neo-angiogenesis, tumor cell invasion, as well as necrotic and apoptotic cell death. Then, we examine the ability of gliomas to evade and suppress the host immune system, exhibited at the levels of antigen recognition and immune activation, limiting the effective signaling between glioma and host immune cells.The second part of the review presents current therapies and their drawbacks. This is followed by a summary of the work of our laboratory during the past 20 years, on oligosaccharide and glycosphingolipid inhibitors of astroblast and astrocytoma division. Neurostatins, the O-acetylated forms of gangliosides GD1b and GT1b naturally present in mammalian brain, are cytostatic for normal astroblasts, but cytotoxic for rat C6 glioma cells and human astrocytoma grades III and IV, with ID50 values ranging from 200 to 450 nM. The inhibitors do not affect neurons or fibroblasts up to concentrations of 4 μM or higher.At least four different neurostatin-activated, cell-mediated antitumoral processes, lead to tumor destruction: (i) inhibition of tumor neovascularization; (ii) activation of microglia; (iii) activation of natural killer (NK) cells; (iv) activation of cytotoxic lymphocytes (CTL). The enhanced antigenicity of neurostatin-treated glioma cells, could be related to their increased expression of connexin 43. Because neurostatins and their analogues show specific activity and no toxicity for normal cells, a clinical trial would be the logical next step.

PPAR Gamma Activators: Off-Target Against Glioma Cell Migration and Brain Invasion

Today, there is increasing evidence that PPARγ agonists, including thiazolidinediones (TDZs) and nonthiazolidinediones, block the motility and invasiveness of glioma cells and other highly migratory tumor entities. However, the mechanism(s) by which PPARγ activators mediate their antimigratory and anti-invasive properties remains elusive. This letter gives a short review on the debate and adds to the current knowledge by applying a PPARγ inactive derivative of the TDZ troglitazone (Rezulin) which potently counteracts experimental glioma progression in a PPARγ independent manner.

Dexamethasone differentially regulates functional membrane properties in glioma cell lines and primary astrocytes in vitro

Similar to astrocytes, glioma cells form a well-coupled syncytium via gap junctions. This can be influenced, for example, by activated microglia, the main inflammatory cell population within the central nervous system (CNS). Under pathological conditions such as neoplastic cell growth, microglia number and activation state are enhanced. The aim of the present study is to analyze the influence of dexamethasone (DEX) on cellular and molecular properties in glial coculture models consisting of astroglia and microglia and human and rat glioma cell lines. Primary rat glial cocultures of astrocytes containing 5% (M5, representing "physiological" conditions) or 30% (M30, representing "pathological" conditions) microglia as well as rat and human glioma cell lines (F98, C6, U87) were incubated with DEX for 24 h. DEX-treated M30 cocultures showed significant increased gap junctional intercellular communication (GJIC). DEX treatment of glioma cells resulted in depolarization of the membrane resting potential (MRP) and a significant reduction of GJIC. Furthermore, DEX reduced the amount of activated microglia in M30 cocultures. DEX had no significant effects on the tested variables in the M5 coculture. DEX differentially regulates functional membrane properties of glioma cells and astrocytes in primary glial cocultures, which might resemble steroid effects in glioma cells and adjacent glial components in vivo.

MiR-21 protected human glioblastoma U87MG cells from chemotherapeutic drug temozolomide induced apoptosis by decreasing Bax/Bcl-2 ratio and caspase-3 activity

MicroRNAs (miRNAs) are small noncoding RNA molecules that regulate protein expression by cleaving or repressing the translation of target mRNAs. In mammal animals, their function mainly represses the target mRNAs transcripts via imperfectly complementary to the 3'UTR of target mRNAs. Several miRNAs have been recently reported to be involved in modulation of glioma development, especially some up-regulated miRNAs, such as microRNA-21 (miR-21), which has been found to function as an oncogene in cultured glioblastoma multiforme cells. Temozolomide (TMZ), an alkylating agent, is a promising chemotherapeutic agent for treating glioblastoma. However, resistance develops quickly and with high frequency. To explore the mechanism of resistance, we found that miR-21 could protect human glioblastoma U87MG cells from TMZ induced apoptosis. Our studies showed that TMZ markedly enhanced apoptosis in U87MG cells compared with untreated cells (P<0.05). However, over-express miR-21 in U87MG cells could significantly reduce TMZ-induced apoptosis (P<0.05). Pro-apoptotic Bax and anti-apoptotic Bcl-2 proteins are known to regulate the apoptosis of glioma cells. Bcl-2, resistance to induction of apoptosis, constitutes one major obstacle to chemotherapy in many cancer cells. Bax is shown to correlate with an increased survival of glioblastoma multiforme patients. Further research demonstrated that the mechanism was associated with a shift in Bax/Bcl-2 ratio and change in caspase-3 activity. Compared to control cells, cells treated with TMZ showed a significant increase in the Bax/Bcl-2 ratio and caspase-3 activity (P<0.01). However, such effect was partly prevented by treatment of cells with miR-21 overexpression before, which appeared to downregulate the Bax expression, upregulate the Bcl-2 expression and decrease caspase-3 activity. Taken together, these results suggested that over-express miR-21 could inhibit TMZ-induced apoptosis in U87MG cells, at least in part, by decreasing Bax/Bcl-2 ratio and caspase-3 activity, which highlighted the possibility of miR-21 overexpression in the clinical resistance to chemotherapeutic therapy of TMZ.

Ezrin promotes invasion and metastasis of pancreatic cancer cells

BACKGROUND

Pancreatic cancer has a high mortality rate because it is usually diagnosed when metastasis have already occurred (microscopic and gross disease). Ezrin plays important roles in cell motility, invasion and tumor progression, and it is especially crucial for metastasis. However, its function in pancreatic cancer remains elusive.

METHODS AND RESULTS

We found that ezrin overexpression promoted cell protrusion, microvillus formation, anchorage-independent growth, motility and invasion in a pancreatic cancer cell line, MiaPaCa-2, whereas ezrin silencing resulted in the opposite effects. Ezrin overexpression also increased the number of metastatic foci (6/8 vs. 1/8) in a spontaneous metastasis nude mouse model. Furthermore, ezrin overexpression activated Erk1/2 in MiaPaCa-2 cells, which might be partially related to the alteration of cell morphology and invasion. Immunohistochemical analysis showed that ezrin was overexpressed in pancreatic ductal adenocarcinoma (PDAC) (91.4%) and precancerous lesions, i.e. the tubular complexes in chronic pancreatitis (CP) and pancreatic intraepithelial neoplasm (PanIN) (85.7% and 97.1%, respectively), compared to normal pancreatic tissues (0%). Ezrin was also expressed in intercalated ducts adjacent to the adenocarcinoma, which has been considered to be the origin of ducts and acini, as well as the starting point of pancreatic ductal carcinoma development.

CONCLUSIONS

We propose that ezrin might play functional roles in modulating morphology, growth, motility and invasion of pancreatic cancer cells, and that the Erk1/2 pathway may be involved in these roles. Moreover, ezrin may participate in the early events of PDAC development and may promote its progression to the advanced stage.

mTOR regulates the invasive properties of synovial fibroblasts in rheumatoid arthritis

The invasive properties of fibroblast-like synoviocytes (FLS) correlate with radiographic and histologic damage in rheumatoid arthritis (RA) and pristane-induced arthritis (PIA). We previously determined that highly invasive FLS obtained from PIA-susceptible DA (blood type D, Agouti) rats have increased expression of genes associated with invasive cancers, including Villin-2/ezrin. Villin-2/ezrin mediates invasion via mTOR. In the present study we used the mTOR inhibitor rapamycin to assess the role of the ezrin-mTOR pathway on the invasive properties of FLS. FLS were isolated from synovial tissues from arthritic DA rats, and from RA patients. FLS were treated with rapamycin or dimethyl sulfoxide (DMSO) for 24 h and then studied in a Matrigel-invasion assay. Supernatants were assayed for matrix metalloproteinase (MMP) activity, and cell lysates were used for quantification of mTOR, p70S6K1, 4EBP1 and FAK, as well as their respective phosphorylated subsets. Actin filament and FAK localization were determined by immunofluorescence. Rapamycin decreased FLS invasion in DA and RA tissues by 93% and 82%, respectively. Rapamycin treatment reduced the phosphorylation of mTOR and its substrates, p70S6K1 and 4EBP1, confirming mTOR inhibition. In conclusion, rapamycin prevented actin reorganization in both DA and RA FLS, and inhibited the directional formation of lamellipodia. Phosphorylation of the lamellipodia marker FAK was also reduced by rapamycin. MMPs were not significantly affected by rapamycin. Rapamycin significantly reduced RA and DA rat FLS invasion via the suppression of the mTOR signaling pathway. This discovery suggests that rapamycin could have a role in RA therapy aimed at reducing the articular damage and erosive changes mediated by FLS.

The role of the membrane cytoskeleton cross-linker ezrin in medulloblastoma cells

Medulloblastoma is a highly malignant brain tumor that occurs predominantly in children. The molecular pathogenesis of medulloblastoma is under investigation. Previously, we used complementary DNA microarray analysis to compare patterns of gene expression in medulloblastoma samples versus normal cerebellum. The cytoskeletal protein ezrin was found to be overexpressed in medulloblastoma compared with normal cerebellum, an observation that was further validated by immunohistochemistry and real-time PCR analysis. To assess the role of ezrin in medulloblastoma, we studied ezrin's role in medulloblastoma migration, invasion, and adhesion. Western blotting and immunofluorescence showed high expression of ezrin in four medulloblastoma cell lines, and ezrin was primarily localized to filopodia. Ezrin-specific small interfering RNA suppressed the formation of filopodia and in vitro migration, invasion, and adhesion. We also used a stably transfected medulloblastoma cell line to study the effect of ezrin overexpression. We showed that high expression of ezrin promotes filopodia formation and in vitro invasion. Finally, athymic mice implanted with ezrin-overexpressing DAOY medullo-blastoma cell clones in the cerebellum showed shortened survival compared with controls. These findings suggest that, in addition to other cytoskeletal proteins, ezrin plays an important role in medulloblastoma adhesion, migration, and invasion.

Lactate promotes glioma migration by TGF-beta2-dependent regulation of matrix metalloproteinase-2

Lactate dehydrogenase type A (LDH-A) is a key metabolic enzyme catalyzing pyruvate into lactate and is excessively expressed by tumor cells. Transforming growth factor-beta2 (TGF-beta2) is a key regulator of invasion in high-grade gliomas, partially by inducing a mesenchymal phenotype and by remodeling the extracellular matrix. In this study, we tested the hypothesis that lactate metabolism regulates TGF-beta2-mediated migration of glioma cells. Small interfering RNA directed against LDH-A (siLDH-A) suppresses, and lactate induces, TGF-beta2 expression, suggesting that lactate metabolism is strongly associated with TGF-beta2 in glioma cells. Here we demonstrate that TGF-beta2 enhances expression, secretion, and activation of matrix metalloproteinase-2 (MMP-2) and induces the cell surface expression of integrin alpha(v)beta(3) receptors. In spheroid and Boyden chamber migration assays, inhibition of MMP-2 activity using a specific MMP-2 inhibitor and blocking of integrin alpha(v)beta(3) abrogated glioma cell migration stimulated by TGF-beta2. Furthermore, siLDH-A inhibited MMP2 activity, leading to inhibition of glioma migration. Taken together, we define an LDH-A-induced and TGF-beta2-coordinated regulatory cascade of transcriptional regulation of MMP-2 and integrin alpha(v)beta(3). This novel interaction between lactate metabolism and TGF-beta2 might constitute a crucial mechanism for glioma migration.

Prognostic value of tumor microinvasion and metalloproteinases expression in intracranial pediatric ependymomas

Ependymomas are common pediatric intracranial neoplasms that often appear well circumscribed on imaging but may recur when they are treated by surgical resection alone. The current World Health Organization histological grading system does not accurately predict clinical behavior. The aim of this study was to identify histological and immunohistochemical features that correlate with clinical course in patients with ependymomas treated by gross total resection. We analyzed 41 pediatric ependymomas for microinvasion and correlated immunostaining for the metalloproteinase (MMP)-2 and MMP14 and for ezrin and bcl-2 with clinical outcome. Gross total resection had a significantly positive effect on overall survival and progression-free survival. In 28 patients who underwent gross total resection, microinvasion correlated with poor overall survival (p = 0.003) and progression-free survival (p = 0.03). Gross totally resected tumors with high expression of MMP2 and MMP14 had significantly shorter overall survival. Ezrin staining identified tumor cells invading the adjacent white matter that were not identified by routine stains, but Ezrin staining and bcl-2 staining did not provide strong prognostic correlations. The data indicate that tumor microinvasion into adjacent brain and tumor expression of MMP2 and MMP14 predict both overall and progression-free survival in pediatric ependymomas, and these are useful prognostic markers that may help stratify patients for adjuvant therapies.

Characterization of the Ca2+ -regulated ezrin-S100P interaction and its role in tumor cell migration

Ezrin is a multidomain protein providing regulated membrane-cytoskeleton contacts that play a role in cell differentiation, adhesion, and migration. Within the cytosol of resting cells ezrin resides in an autoinhibited conformation in which the N- and C-terminal ezrin/radixin/moesin (ERM) association domains (ERMADs) interact with one another. Activation of the ezrin membrane-cytoskeleton linker function requires an opening of this interdomain association that can result from phosphatidylinositol 4,5-bisphosphate binding to the N-ERMAD and threonine 567 phosphorylation in the C-ERMAD. We have shown that ezrin can also be activated by Ca(2+)-dependent binding of the EF-hand protein S100P. We now provide a quantitative analysis of this interaction and map the respective binding sites to the F2 lobe in the ezrin N-ERMAD and a stretch of hydrophobic residues in the C-terminal extension of S100P. Phospholipid binding assays reveal that S100P and phosphatidylinositol 4,5-bisphosphate compete to some extent for at least partially overlapping binding sites in N-ERMAD. Using interaction-competent as well as interaction-incompetent S100P derivatives and permanently active ezrin mutants, we also show that the protein interaction and a resulting activation of ezrin promote the transendothelial migration of tumor cells. Thus, a prometastatic role of ezrin and S100P that had been proposed based on their overexpression in highly metastatic cancers is probably due to a direct interaction between the two proteins and the S100P-mediated activation of ezrin.

Intense cytoplasmic ezrin immunoreactivity predicts poor survival in colorectal cancer

Ezrin is a membrane-cytoskeleton anchor, which, in experimental models, regulates tumor cell invasion and metastatic ability. We carried out immunohistochemical analysis of ezrin in 74 advanced colorectal cancer patients and correlated it to clinicopathologic variables and disease outcome. In contrast to the predominantly membraneous immunoreactivity of normal colorectal epithelium, ezrin expression in the colorectal cells was typically cytoplasmic. Altogether, 16.2% (12/74) of the tumors showed negative/weak ezrin staining, 35.1% (26/74) had moderate staining, and 48.6% (36/74) had intense staining. The expression was more intense in colon than in rectal carcinomas (P = .003). Increased ezrin expression was associated with adverse outcome, that is, shorter disease-specific survival; 48.3 months and 36.6 months for negative-weak versus intense expression (P = .041) as well as shorter survival with metastases at 36 months (P = .030); the metastases(36) rates in ezrin(neg/weak), ezrin(moderate), ezrin(intense) are 58.3%, 25.0%, and 18.4%, respectively. In univariate survival analysis, dichotomized (negative/weak versus moderate/strong) ezrin expression significantly predicted both the 5-year disease specific survival (P = .035) and 5-year metastases (P = .018) but lost this predictive power in multivariate (Cox) analysis. High ezrin expression was also related to high E-cadherin (cytoplasmic) expression, DNA aneuploidy, and high thymidylate synthase expression (P = .046, P = .042, P = .046, respectively). These results suggest that ezrin may play a role in colorectal cancer progression and that ezrin expression might provide clinically valuable information in predicting the biological behavior of colorectal cancer.

Transforming growth factor-beta (TGF-beta) and brain tumours

Since its discovery in the late 1970s considerable research has linked transforming growth factor-beta (TGF-beta) to several human diseases such as fibrosis, auto-immunity and cancer. TGF-beta acts initially as a growth inhibitory factor in early stages of tumour development. In contrast, as tumours evolve, they develop mechanisms to evade the growth-regulatory effects of TGF-beta, resulting in greater tumour invasiveness, increased metastatic potential and inhibition of surrounding immune responses. However, although extensively studied, the molecular mechanisms that trigger tumour cells to "switch" from TGF-beta-inhibited to TGF-beta-promoted are still not fully understood. Contradictory studies that demonstrate opposite cellular effects mediated by TGF-beta are abundant throughout the literature. This review summarizes the current molecular mechanisms involved in the tumour suppressive and tumour progressive characteristics of TGF-beta in brain tumours. Potential therapeutic agents that target TGF-beta and related proteins being evaluated against brain tumours is also discussed.

Malignant astrocytic glioma: genetics, biology, and paths to treatment

Malignant astrocytic gliomas such as glioblastoma are the most common and lethal intracranial tumors. These cancers exhibit a relentless malignant progression characterized by widespread invasion throughout the brain, resistance to traditional and newer targeted therapeutic approaches, destruction of normal brain tissue, and certain death. The recent confluence of advances in stem cell biology, cell signaling, genome and computational science and genetic model systems have revolutionized our understanding of the mechanisms underlying the genetics, biology and clinical behavior of glioblastoma. This progress is fueling new opportunities for understanding the fundamental basis for development of this devastating disease and also novel therapies that, for the first time, portend meaningful clinical responses.

HGF increases cisplatin resistance via down-regulation of AIF in lung cancer cells

Our previous study had shown that advanced stages of lung adenocarcinomas (ADC) was frequently associated with overexpression of hepatocyte growth factor (HGF), which has multipotent and anti-apoptotic activities. In this study, we examined the effect of HGF on gene expression of apoptosis-inducing factor (AIF) and cisplatin sensitivity in lung ADC cells. Expression of AIF was determined by immunocytochemistry and confocal immunofluorescence microscopy. Our data show that addition of HGF suppressed AIF expression and increased cisplatin resistance. The effect could be through HGF receptor and its downstream effector, focal adhesion kinase (FAK). Interestingly, knockout of FAK gene increased AIF expression and drug sensitivity. Re-introduction of FAK gene, on the other hand, restored drug resistance. These results suggested that HGF might induce cisplatin resistance via c-Met to activate FAK and down-regulate AIF expression.

The peroxisome proliferator-activated receptor-gamma agonist troglitazone inhibits transforming growth factor-beta-mediated glioma cell migration and brain invasion

Gliomas are the most common primary tumors of the central nervous system, with glioblastomas as the most malignant entity. Rapid proliferation and diffuse brain invasion of these tumors are likely to determine the unfavorable prognosis. Considering its promigratory properties, the transforming growth factor-beta (TGF-beta) signaling pathway has become a major therapeutic target. Analyses of resected glioma tissues revealed an intriguing correlation between tumor grade and the expression of TGF-beta(1-3) as well as their receptors I and II. Here, we analyzed the effects of peroxisome proliferator-activated receptor gamma (PPAR-gamma) agonists on glioma proliferation, migration, and brain invasion. Using an organotypic glioma invasion model, we show that micromolar doses of the PPAR-gamma activator troglitazone blocked glioma progression without neurotoxic damage to the organotypic neuronal environment observed. This intriguing antiglioma property of troglitazone seems to be only partially based on its moderate cytostatic effects. We identified troglitazone as a potent inhibitor of glioma cell migration and brain invasion, which occurred in a PPAR-gamma-independent manner. The antimigratory property of troglitazone was in concordance with the transcriptional repression of TGF-beta(1-3) and their receptors I and II and associated with reduced TGF-beta release. Due to its capacity to counteract TGF-beta release and glioma cell motility and invasiveness already at low micromolar doses, troglitazone represents a promising drug for adjuvant therapy of glioma and other highly migratory tumor entities.

Inhibiting TGF-beta signaling restores immune surveillance in the SMA-560 glioma model

Transforming growth factor-beta (TGF-beta) is a proinvasive and immunosuppressive cytokine that plays a major role in the malignant phenotype of gliomas. One novel strategy of disabling TGF-beta activity in gliomas is to disrupt the signaling cascade at the level of the TGF-beta receptor I (TGF-betaRI) kinase, thus abrogating TGF-beta-mediated invasiveness and immune suppression. SX-007, an orally active, small-molecule TGF-betaRI kinase inhibitor, was evaluated for its therapeutic potential in cell culture and in an in vivo glioma model. The syngeneic, orthotopic glioma model SMA-560 was used to evaluate the efficacy of SX-007. Cells were implanted into the striatum of VM/Dk mice. Dosing began three days after implantation and continued until the end of the study. Efficacy was established by assessing survival benefit. SX-007 dosed at 20 mg/kg p.o. once daily (q.d.) modulated TGF-beta signaling in the tumor and improved the median survival. Strikingly, approximately 25% of the treated animals were disease-free at the end of the study. Increasing the dose to 40 mg/kg q.d. or 20 mg/kg twice daily did not further improve efficacy. The data suggest that SX-007 can exert a therapeutic effect by reducing TGF-beta-mediated invasion and reversing immune suppression. SX-007 modulates the TGF-beta signaling pathway and is associated with improved survival in this glioma model. Survival benefit is due to reduced tumor invasion and reversal of TGF-beta-mediated immune suppression, allowing for rejection of the tumor. Together, these results suggest that treatment with a TGF-betaRI inhibitor may be useful in the treatment of glioblastoma.

The expression of ezrin in NPC and its interaction with NGX6, a novel candidate suppressor

Ezrin, the linker between membrane protein and cytoskeleton, plays an important role in the cellular morphology, cytoskeleton reorganization, adhesion, invasion and metastasis. In this study, ezrin was found to express in high levels either in nasopharyngeal carcinoma tissues or in nasopharyngeal carcinoma 5-8F cells and the knockdown of ezrin expression in the 5-8F cells by RNA interferance could reduce invasive ability, suggesting that ezrin is involved in the progression and invasion of nasopharyngeal carcinoma. Nasopharyngeal carcinoma-associated gene 6 is a novel candidate suppressor gene of tumor metastasis, which was originally cloned in nasopharyngeal carcinoma high-frequency heterozygosity loss region 9p21-22 and is down-regulated in nasopharyngeal carcinoma. In the present study, we hypothesize that nasopharyngeal carcinoma-associated gene 6 plays an inhibitory role in the migration and invasion of nasopharyngeal carcinoma cells via modulating the function of ezrin. Firstly, different mutants of NGX6 were constructed and transfected into nasopharyngeal carcinoma 5-8F cells. The invasion and migration of 5-8F cells overexpressing nasopharyngeal carcinoma-associated gene 6 or mutants were measured. The results showed that enhanced expression of nasopharyngeal carcinoma-associated gene 6 could reduce invasive and migratory abilities of 5-8F cells, and the cytoplasmic domain was essential for nasopharyngeal carcinoma-associated gene 6 to modulate cell migration and invasion. Further experiment results showed that nasopharyngeal carcinoma-associated gene 6 protein was associated with ezrin by its cytoplasm region, and it could down-regulate the expression level of ezrin. These results demonstrated that nasopharyngeal carcinoma-associated gene 6 was probably involved in the modulation of invasive and adhesive ability of nasopharyngeal carcinoma cells by down-regulating the expression level of ezrin.

EFFECT OF THE ANGIOGENESIS INHIBITOR CILENGITIDE (EMD 121974) ON GLIOBLASTOMA GROWTH IN NUDE MICE

OBJECTIVE

To determine the effect of the angiogenesis inhibitor Cilengitide (EMD 121974) on glioblastoma growth and associated angiogenesis in the brains of nude mice.

METHODS

Human glioblastoma cells (10 U87MG cells) in 1 mul of medium were stereotactically injected during a 20-minute period into the caudate/putamen of nude mice. The mice were intraperitoneally treated daily with Cilengitide or solvent (control) beginning 5 days after tumor injection. The mice were sacrificed from 1 hour to 63 days after tumor implantation and examined for tumor size, vascularity, apoptosis, and cell replication.

RESULTS

This injection technique resulted in a highly reproducible, localized, spherical tumor cell placement in the parenchyma without reflux into the subarachnoid space or penetration into the ventricle. Serial brain sections showed the tumor size remained unchanged at 1 to 2 mm for approximately 30 to 40 days. Thereafter, the control tumors showed exponential growth to a volume of 120 mm, with death of the mice at approximately 8 to 9 weeks. Serial staining for Ki-67, a marker for cell replication, and CD31, an indicator for angiogenesis, demonstrated an increase in proportion to the growth of the tumor. In contrast, the tumor volume in Cilengitide-treated mice stayed unchanged at 1 to 2 mm during the entire length of the experiment, with staining for Ki-67 and CD31 remaining low.

CONCLUSION

This standardized brain tumor model is highly reproducible and useful for testing new treatment regimens. Cilengitide is highly effective in suppressing blood vessel growth, thereby controlling orthotopic growth of this glioblastoma cell line.

Ezrin mediates growth and survival in Ewing’s sarcoma through the AKT/mTOR, but not the MAPK, signaling pathway

Recent reports on the role of the membrane-cytoskeleton linker protein ezrin in sarcomas showed an effect on the formation of metastases, dependent on the level of ezrin expression. In this study, we explore the role of ezrin in Ewing's sarcoma, a frequently fatal mesenchymal neoplasm of children and young adults. Through both immunohistochemistry and Western immunoblot studies we find ubiquitous, high-level expression of ezrin in Ewing's sarcoma. In contrast to the observations in osteosarcoma and rhabdomyosarcoma, we demonstrate that inhibition of ezrin-mediated signal transduction, through the expression of a non-phosphorylatable T567A mutant, slows primary growth of Ewing's sarcoma cells in vitro. This reduction in growth is a result of increased apoptosis in the mutant expressing cells. We further show that expression of this mutant reduces the ability of Ewing's sarcoma cells to form experimental metastases in vivo. Molecular examination reveals that the action of ezrin in Ewing's sarcoma is dependent on the AKT/mTOR signal transduction cascade, but not MAP Kinase. These results, therefore, demonstrate that, in Ewing's sarcoma, the biology of ezrin is distinct from that described in other sarcomas. This study further validates ezrin as a potential therapeutic target.

Neurodevelopmental disorders as a cause of seizures: neuropathologic, genetic, and mechanistic considerations

This review will consider patterns of developmental neuropathologic abnormalities-malformations of cortical development (MCD)--encountered in infants (often with infantile spasms), children, and adults with intractable epilepsy. Treatment of epilepsy associated with some MCD, such as focal cortical dysplasia and tubers of tuberous sclerosis, may include cortical resection performed to remove the "dysplastic" region of cortex. In extreme situations (eg, hemimegalencephaly), hemispherectomy may be carried out on selected patients. Neuropathologic (including immunohistochemical) findings within these lesions will be considered. Other conditions that cause intractable epilepsy and often mental retardation, yet are not necessarily amenable to surgical treatment (eg, lissencephaly, periventricular nodular heterotopia, double cortex syndrome) will be discussed. Over the past 10 years there has been an explosion of information on the genetics of MCD. The genes responsible for many MCD (eg, TSC1, TSC2, LIS-1, DCX, FLN1) have been cloned and permit important mechanistic studies to be carried out with the purpose of understanding how mutations within these genes result in abnormal cortical cytoarchitecture and anomalous neuroglial differentiation. Finally, novel techniques allowing for analysis of patterns of gene expression within single cells, including neurons, is likely to provide answers to the most vexing and important question about these lesions: Why are they epileptogenic?