Invasion Of Glioma Cell Lines Research Articles

Abstract A47: Interstitial flow increases patient-derived glioma stem cell invasion via CXCR4, CXCL12, and CD44-mediated mechanisms in distinctive cell populations

Abstract Background: Glioblastoma (GBM) is the most common and aggressive brain tumor with an average survival of 15 months. Standard of care treatment strategies, which include surgical resection, radiotherapy, and chemotherapy, do not result in long-term survival(1). Much of this poor response is due to the invasiveness of GBM cells. We have shown that interstitial fluid flow (IFF) can increase invasion of glioma cell lines in vitro through both activation of the CXCR4 receptor and formation of autologous pericellular gradients of CXCL12(2). In other studies, mechanotransduction via the CD44 receptor has been implicated in IFF-mediated invasion(3). We hypothesize that these mechanisms are interrelated and vary depending on populations of receptor positive glioma cells. Therefore, we examined both CD44 and CXCR4-CXCL12 mechanisms in multiple primary patient-derived glioma stem cells (GSCs), which show increased heterogeneity compared to traditional cell lines, to identify both the clinical relevance and potential mechanisms of IFF-induced invasion. Methods: Four patient-derived GSC lines were used for our experiments (G2, G34, G62, and G528) from four individual patients and were derived/maintained as described (4). GSCs were seeded at 1E6 cells/mL into hyaluronan-collagen gels atop 8μm-pore tissue culture inserts(2). A pressure head was applied to yield a superficial velocity of 1 μm/s through the cell/gel compartment for flow, or media held level for static conditions. After 18h, gels were removed and inserts analyzed for transmigrated cells. Blocking antibodies for CD44, CXCL12, or CXCR4 were applied in media. For generation of irradiated cells, gamma-irradiation (0.3, 1 and 2 Gy) was applied 7 days before flow experiments. Flow cytometry for CXCR4, CD44, and CXCL12 was conducted to identify positive populations. We inoculated 15,000 GSCs (n=6 per GSC) into the cortices of male NOD-SCID mice. Prior to euthanasia, intravenous Evans blue was delivered to identify high/low flow regions. Tissue was processed and GSCs identified by human nuclear antigen to quantify invasion. Results: Characterization of our four patient-derived GSC lines for baseline migratory potential and expression of CXCR4, CXCL12, and CD44 showed separate populations of CXCR4+, CXCL12+, CD44+, CXCR4/CXCL12+ and CXCR4/CD44+ cells which varied by GSC, though baseline migration was relatively similar across GSCs. Using our 3D in vitro assay we demonstrated that IFF increased invasion in three of four cell lines. This flow-mediated invasion was reduced by blockade of CXCR4, CXCL12, CD44, or all, revealing that GSCs are migrating via both mechanisms, and that this varies depending on the GSC. Radiation increased flow-mediated invasion in G62, while eliminated it in G34. In vivo we see increased invasion in high flow regions compared to low flow that correspond to our in vitro results. Conclusion: Together, these data indicate heterogeneous flow response across patient-derived GSCs and contribute to mechanisms of invasion in vitro and in vivo. These results indicate, for the first time, that within a single patient, there are subpopulations of GSCs that respond to flow via both CD44-CXCR4 and CXCR4-CXCL12 mechanisms and these responses are affected by standard of care radiotherapy.

Paxillin functions as an oncogene in human gliomas by promoting cell migration and invasion.

BackgroundPaxillin is implicated in tumorigenesis, progression and aggressive phenotypes of various malignancies, highlighting its functions in cellular adhesion, migration and survival. However, the roles of paxillin in human gliomas remain unclear. The aim of this study was to evaluate the clinical implication of paxillin expression in patients with gliomas and its biological function in glioma cells.Patients and methodsExpression levels of paxillin gene and protein, respectively, were detected by quantitative real-time reverse transcription polymerase chain reaction, Western blot and immunohistochemistry analyses in 120 pairs of glioma and matched nontumorous brain tissues. The associations between paxillin expression and various histopathological features of glioma patients were also statistically evaluated. Then, the functions of paxillin in cell migration and invasion of glioma cell lines were determined by transwell assays in vitro.ResultsThe expression levels of both paxillin gene and protein in glioma tissues were markedly higher than those in matched nontumorous brain tissues. Notably, paxillin overexpression was significantly associated with the grade of malignancy (P<0.05). Moreover, the enforced expression of paxillin promoted the migration and invasion of glioma cells, while the loss of paxillin expression efficiently suppressed cell migration and invasion of glioma cell lines.ConclusionOur data suggest that paxillin may function as an oncogene and its overexpression may be closely correlated with tumor progression of human gliomas by modulating tumor cell motility, implying the potential of paxillin as a new therapeutic target for glioma intervention.

Let-7b inhibits the malignant behavior of glioma cells and glioma stem-like cells via downregulation of E2F2.

Glioblastoma multiforme (GBM), the most common and lethal primary brain tumor in adults characterized by high proliferative ability and mortality rate, contains a small subpopulation of cancer stem-like cells (CSCs), which is responsible for GBM progression and therapeutic resistance. Numerous microRNAs are strongly implicated in the malignancy of glioma. However, their specific functions and roles have yet to be fully demonstrated. In the present study, we revealed that the upregulation of Let-7b, a member of the Let-7 microRNA family, inhibited proliferation, migration, and invasion in glioma cell lines. Using bioinformatics, expression analysis, and luciferase assay, E2F2 was confirmed as a candidate target of Let-7b. Moreover, we also observed that elevated levels of Let-7b resulted in a reduction of tumor sphere growth and stemness of glioma stem-like cells. Furthermore, we found that knockdown of E2F2 expression could reduce the proliferation of glioma and GSCs, while overexpression of E2F2 partially abrogated the inhibitory effect of Let-7b on the proliferation of glioma and GSCs. In conclusion, we suggest that Let-7b could be developed into a promising anticancer target in glioma.

Abstract 2519: A novel role for brachyury as a key regulator of sonic hedgehog signaling (Shh) and maintenance of stemness in gliomas

Abstract Glioblastomas are the most common and aggressive form of adult primary brain tumors and are associated with a dismal prognosis. Accumulating evidences suggest that a subset of therapy-resistant cancer stem cells are responsible for recurrence in tumors targeting which may help in gliomas. We identified a significant overexpression of Brachyury (T-box transcription factor) in correlation with glioma histological grade when compared to non-tumor brain controls, with the highest expression being in grade IV gliomas. We also observed increased expression of Brachyury in several glioma cell lines and stem cells (GSCs) when compared to normal human astrocytes. Serum-induced differentiation of GSCs resulted in loss of Brachyury expression along with decreased stem-cell marker levels in these cells, which prompted us to study the potential role of Brachyury in glioma stemness and to delineate the underlying signaling mechanisms. Specific shRNA-mediated knockdown of Brachyury significantly decreased proliferation, migration and invasion in glioma cell lines. Brachyury suppression led to inhibition of sphere formation of GSCs and decreased stem cells marker expression including CD133, nestin and Nanog. Brachyury knockdown also inhibited the activation of sonic hedgehog (Shh) signaling and decreased Gli1 levels in these cells. On the other hand, stable overexpression of Brachyury resulted in the activation of Shh pathway and elevated stem cell marker expression in GSCs. Based on these in vitro findings, our future studies will be focused on determining the role of Brachyury in orthotopic tumor growth in vivo. In summary, our data reveals a novel role for Brachyury in the regulation of tumor invasiveness and stemness, and indicates a potential for therapeutic targeting of Brachyury in patients with gliomas. Citation Format: Divya Kesanakurti, Alessandro Canella, Jihong Xu, Vinay K. Puduvalli. A novel role for brachyury as a key regulator of sonic hedgehog signaling (Shh) and maintenance of stemness in gliomas. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2519.

SHP-2-upregulated ZEB1 is important for PDGFRα-driven glioma epithelial-mesenchymal transition and invasion in mice and humans.

Gliomas are highly malignant brain tumors that are highly invasive and resistant to conventional therapy. Receptor tyrosine kinases (RTKs) such as PDGFRα (platelet-derived growth factor receptor-α), which show frequent aberrant activation in gliomas, are associated with a process of epithelial–mesenchymal transition (EMT), a cellular alteration that confers a more invasive and drug-resistant phenotype. Although this phenomenon is well documented in human cancers, the processes by which RTKs including PDGFRα mediate EMT are largely unknown. Here, we report that SHP-2 (encoded by PTPN11) upregulates an EMT inducer, ZEB1, to mediate PDGFRα-driven glioma EMT, invasion and growth in glioma cell lines and patient-derived glioma stem cells (GSCs) using cell culture and orthotopic xenograft models. ZEB1 and activated PDGFRα were coexpressed in invasive regions of mouse glioma xenografts and clinical glioma specimens. Glioma patients with high levels of both phospho-PDGFRα (p-PDGFRα) and ZEB1 had significantly shorter overall survival compared with those with low expression of p-PDGFRα and ZEB1. Knockdown of ZEB1 inhibited PDGFA/PDGFRα-stimulated glioma EMT, tumor growth and invasion in glioma cell lines and patient-derived GSCs. PDGFRα mutant deficient of SHP2 binding (PDGFRα-F720) or phosphoinositide 3-kinase (PI3K) binding (PDGFRα-F731/42), knockdown of SHP2 or treatments of pharmacological inhibitor for PDGFRα-signaling effectors attenuated PDGFA/PDGFRα-stimulated ZEB1 expression, cell migration and GSC proliferation. Importantly, SHP-2 acts together with PI3K/AKT to regulate a ZEB1-miR-200 feedback loop in PDGFRα-driven gliomas. Taken together, our findings uncover a new pathway in which ZEB1 functions as a key regulator for PDGFRα-driven glioma EMT, invasiveness and growth, suggesting that ZEB1 is a promising therapeutic target for treating gliomas with high PDGFRα activation.

CSIG-09NOVEL PAK4 REGULATION OF PPARγ-MEDIATED EPITHELIAL-MESENCHYMAL TRANSITION IN GLIOBLASTOMA

Tumor recurrence is inevitable despite using the post-surgical chemo- and radiotherapies for Glioblastomas (GB), the most aggressive of primary brain tumors associated with poor prognosis. Epithelial-mesenchymal transition (EMT) is the dynamic transdifferentiation process which potentially leads to acquisition of invasiveness, stemness and therapy resistance in tumors. Recent studies focused to develop the novel targets against EMT and stemness in tumors; however, key factors which regulate EMT signaling and radioresistance in GBs still remains to be identified. Our studies indicated p21-activated kinase 4 (PAK4) deregulation in positive correlation with glioma pathological grades, and showed its role in proliferation and invasion in glioma cell lines. Here, we aimed to study whether PAK4-regulated invasiveness is associated with EMT of glioma cells and to delineate the essential signaling events that govern EMT and maintenance of stemness in GBs. PAK4 overexpression increased EMT in glioma cells by elevating N-cadherin and vimentin levels. Conversely, specific shRNA-mediated PAK4 downregulation led to loss of mesenchymal phenotype in these cells. Further, irradiation (IR, 8 Gy) treatment significantly increased PAK4 nuclear localization in correlation with increased EMT in IR-treated cells. Transcription factor (TF) interaction arrays with immunoprecipitated PAK4 as a bait revealed the novel nuclear-PAK4 association with TFs, including PPARγ. Moreover, ChIP and EMSA assays showed IR-induced PAK4 binding with PPARγ-DNA binding complex and recruitment on PPREs of Nox-1 promoter. PAK4-knockdown suppressed the IR-induced Nox1 levels and EMT in glioma cells. In line with these in vitro results, mouse orthotopic intracranial xenograft experiments showed decreased tumor growth in PAK4-shRNA tumors when compared with controls. These results strongly support a novel PAK4 regulation of IR-induced EMT via PPARγ/Nox1 signaling and provide a rationale for PAK4 as a new therapeutic target against radioresistance in glioblastoma.

MicroRNA response element‑regulated TIKI2 expression suppresses the tumorigencity of malignant gliomas.

Glioma is the most common brain malignancy and has a very poor prognosis. The current treatment options have a minimal benefit on prolonging patient survival time. Accumulating data have shown that the WNT signaling pathway has a critical function in the progression and invasion of glioma. Thus, targeting WNT signaling appears to be an effective anti‑glioma strategy. TIKI2 was recently found to suppress the activation of the WNT signaling pathway by post‑translationally modifying secreted WNT proteins. The implication of TIKI2 aberrance in cancers and its potential therapeutic effect, however, has not been studied. In the present study, a glioma‑specific adenoviral vector was constructed, which was regulated by response elements of miR‑124, to express TIKI2 in glioma cells (Ad‑TIKI2‑124). Ad‑TIKI2‑124 was found to potently suppress the activation of WNT signaling in glioma cells. This inhibitory effect on the WNT signaling pathway lead to the reduction in proliferation, colony formation ability and invasion of glioma cell lines. In addition, animal experiments confirmed that the expression of the Ad‑TIKI2‑124 construct could compromise the tumorigenicity of glioma cells in vivo. Furthermore, this glioma‑selective TIKI2 expression protected normal cells from toxicity. In conclusion, the present study demonstrated that adenovirus‑mediated TIKI2 therapy may be used for glioma treatment and therefore warrants further clinical studies.

An axis involving SNAI1, microRNA-128 and SP1 modulates glioma progression.

BackgroundGlioblastoma is an extraordinarily aggressive disease that requires more effective therapeutic options. Snail family zinc finger 1, dysregulated in many neoplasms, has been reported to be involved in gliomas. However, the biological mechanisms underlying SNAI1 function in gliomas need further investigation.MethodsQuantitative real-time PCR was used to measure microRNA-128 (miR-128) expression level and western blot was performed to detect protein expression in U87 and U251 cells and human brain tissues. Cell cycle, CCK-8, transwell and wound-healing assays were performed. Dual-luciferase reporter assay was used for identifying the mechanism of SNAI1 and miR-128b regulation. The mechanism of miR-128 targeting SP1 was also tested by luciferase reporter assay. Immunohistochemistry and in situ hybridisation staining were used for quantifying SNAI1, SP1 and miR-128 expression levels in human glioma samples.ResultsThe Chinese Glioma Genome Atlas (CGGA) data revealed that SNAI1 was up-regulated in glioma and we confirmed the findings in normal and glioma tissues. SNAI1 depletion by shRNA retarded the cell cycle and suppressed proliferation and invasion in glioma cell lines. The CGGA data showed that the Pearson correlation index between SNAI1 and miR-128 was negatively correlated. SNAI1 suppressed miR-128b expression by binding to the miR-128b specific promoter motif, and miR-128 targeted SP1 via binding to the 3′-untranslated region of SP1. Moreover, introduction of miR-128 anti-sense oligonucleotide alleviated the cell cycle retardation, proliferation and invasion inhibition induced by SNAI1 shRNA. Immunohistochemistry and in situ hybridisation analysis of SNAI1, SP1 and miR-128 unraveled their expression levels and correlations in glioma samples.ConclusionsWe propose that the SNAI1/miR-128/SP1 axis, which plays a vital role in glioma progression, may come to be a clinically relevant therapeutic target.

Anti-miRNA-23a Oligonucleotide Suppresses Glioma Cells Growth by Targeting Apoptotic Protease Activating Factor-1

Abnormal expression of microRNAs (miRNAs) is closely related to glioma, which is one of the most common malignant brain tumors. The current study is to identify the key miRNAs involved in the pathogenesis of glioma and to discover novel therapeutic targets for this disease. Total RNA was extracted from glioma tissues of 100 patients. The microRNA microarray and the northern blot were used to detect the changes of miRNAs expression in 7 pairs of glioma specimens. Relative expressions of miR-23a were validated by real-time reverse transcription polymerase chain reaction (RT-PCR) with specific Taqman probes. In order to evaluate the role of miR-23a, the miR-23a mimics and anti-miR-23a oligonucleotides were transfected to glioma cell lines; the cell proliferation, apoptosis, cell cycle percentage, cell migration and invasion abilities were evaluated in vitro. The target genes of miR-23a were also investigated using the bioinformatics tools. The expression of the apoptotic protease activating factor-1 (APAF1), which might be one of the direct targets of miR-23a, was also analyzed using the luciferase reporter assay and western blot analysis in 293T cells and glioma cell line, respectively. The microRNA microarray and the northern blot results showed that the expressions of miR-23a in glioma tissues were significantly upregulated. The miR-23a expression levels identified using real time RT-PCR in tumor tissues of 79 samples were higher than in the matched adjacent tissues. By transfection of anti-miR-23a oligonucleotide, the results showed that the proliferation, migration, and invasion of glioma cell lines were significantly suppressed. The bioinformatics searching results showed that APAF1 might be a direct target gene of miR-23a, and it was supported by the luciferase reporter gene assay and western blot analysis results. Finally, experiments showed that overexpression of APAF1 suppressed glioma cell growth and promoted cell apoptosis. Our findings characterized the expression properties of miR-23a, contributed to the function and molecular mechanism of miR-23a in glioma and implied that miR-23a might be employed as novel prognostic markers and therapeutic targets of glioma.

Abstract 3797: Regulation and function of the mucin-like glycoprotein podoplanin in glioma.

Abstract Podoplanin (PDPN) is a mucin like type-1 transmembrane protein consisting of 162 amino acids, which comprises a highly glycosylated extracellular domain and a nine amino acid intracellular domain. The specific expression of PDPN on lymphatic but not on blood vascular endothelial cells has established application as a histological marker for lymphangiogenesis and lymphatic vessels in different species. PDPN is highly expressed in tumors of different origin, including squamous cell cancers, germinal neoplasia and tumors of the central nervous system. Recently, we found strong overexpression of PDPN in human astrocytic brain tumors, specifically in primary glioblastoma multiforme (GB). Regulation of PDPN expression involves increased PI3 kinase activation, subsequent activation of protein kinaseB/Akt and the downstream transcription factor AP-1. Activation of this pathway is mediated by loss of PTEN function, consistently, mice lacking Pten exhibit elevated Pdpn protein levels in the subventricular zone of the brain tissue. Additionally, PDPN expression is subject to negative transcriptional regulation by promoter methylation in human GB and in glioma cell lines. In patients high expression of PDPN is associated with poor prognosis. Silencing of PDPN results in a decrease in proliferation, migration and invasion of glioma cell lines in vitro and slows down the migration in orthotopic brain slices. Consistently, tumor formation after injection of PDPN knock-down cells into SCID mice is significantly reduced compared to tumors after injection of parental cells. These data highlight a functional role of PDPN in glioma progression and suggest targeting of PDPN expression as a promising strategy for the treatment of patients with primary GB. Citation Format: Heike Peterziel, Julia Müller, Danner Andreas, Sebastian Barbus, Haikun Liu, Philipp Pfenning, Patrick N. Harter, Michel Mittelbronn, Wolfgang Wick, Günther Schuetz, Bernhard Radlwimmer, Peter Lichter, Jochen Hess, Peter Angel. Regulation and function of the mucin-like glycoprotein podoplanin in glioma. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3797. doi:10.1158/1538-7445.AM2013-3797

Overexpression of RKIP Inhibits Cell Invasion in Glioma Cell Lines through Upregulation of miR-98

Raf-1 kinase inhibitor protein (RKIP) is a tumor and metastasis suppressor in cancer cells. MicroRNAs (miRNAs) have been suggested to play a vital role in tumor initiation and progression by negatively regulating oncogenes and tumor suppressors. Quite recently, studies have identified some miRNAs operating to promote or suppress tumor invasion or metastasis via regulating metastasis-related genes, providing potential therapeutic targets on antimetastasis strategy. In this study, we found that the expression of RKIP and miR-98 in glioma tissues were significantly lower than that in normal brain tissues. Overexpression of RKIP upregulated miR-98 expression and inhibited glioma cell invasion and miR-98 target gene HMGA2 but had no effect in glioma cell proliferation. Moreover, forced expression of miR-98 accelerated the inhibition of glioma cell invasion and the expression of HMGA2 also had no effect in glioma cell proliferation. Our findings newly described RKIP/miR-98 to HMGA2 link and provided a potential mechanism for glioma cell invasion. RKIP and miR-98 may illustrate the potential therapeutic utility of signaling pathway signatures.

Epidermal growth factor induces matrix metalloproteinase-1 (MMP-1) expression and invasion in glioma cell lines via the MAPK pathway

Glioblastoma multiforme (GBM) is an aggressive cancer with a poor survival rate. A key component that contributes to the poor prognosis is the capacity of glioma cells to invade local brain tissue in a diffuse manner. Among various proteases that aid in the process of invasion, matrix metalloproteinase-1 (MMP-1) has been identified as an important contributory factor in various cancers. Apart from its traditional role in cleaving its primary extracellular matrix (ECM) substrates, and like other members of the matrix metalloproteinase family, MMP-1 can activate latent forms of bio-active molecules initiating downstream pro-invasive and pro-oncogenic signaling mechanisms. MMP-1 expression is regulated by several growth factors including epidermal growth factor (EGF). Due to the fact that the epidermal growth factor receptor (EGFR) is aberrantly overexpressed in GBM, we wanted to examine in greater detail the signaling mechanisms by which MMP-1 expression and invasion is driven by EGF in GBM cells. T98G cells treated with EGF resulted in an induction of MMP-1 expression following EGFR activation. Inhibition of EGFR by both pharmacologic and genetic approaches abrogated this induction. Repression of the mitogen activated protein kinase (MAPK) signaling led to the inhibition of EGF-induced MMP-1 whereas the PI3-kinase/AKT signaling was not associated with EGFR-mediated MMP-1 induction. Inhibition of EGFR signaling also led to a decrease in T98G invasion. These data suggest that EGFR mediated MMP-1 regulation is mainly via the MAPK pathway in T98G cells and inhibition of EGFR and MMP-1 results in a decrease in T98G cell invasion.

The Dexamethasone-induced Inhibition of Proliferation, Migration, and Invasion in Glioma Cell Lines Is Antagonized by Macrophage Migration Inhibitory Factor (MIF) and Can Be Enhanced by Specific MIF Inhibitors

Glioblastomas (GBMs) are the most frequent and malignant brain tumors in adults. Glucocorticoids (GCs) are routinely used in the treatment of GBMs for their capacity to reduce the tumor-associated edema. Few in vitro studies have suggested that GCs inhibit the migration and invasion of GBM cells through the induction of MAPK phosphatase 1 (MKP-1). Macrophage migration inhibitory factor (MIF), an endogenous GC antagonist is up-regulated in GBMs. Recently, MIF has been involved in tumor growth and migration/invasion and specific MIF inhibitors have been developed on their capacity to block its enzymatic tautomerase activity site. In this study, we characterized several glioma cell lines for their MIF production. U373 MG cells were selected for their very low endogenous levels of MIF. We showed that dexamethasone inhibits the migration and invasion of U373 MG cells, through a glucocorticoid receptor (GR)- dependent inhibition of the ERK1/2 MAPK pathway. Oppositely, we found that exogenous MIF increases U373 MG migration and invasion through the stimulation of the ERK1/2 MAP kinase pathway and that this activation is CD74 independent. Finally, we used the Hs 683 glioma cells that are resistant to GCs and produce high levels of endogenous MIF, and showed that the specific MIF inhibitor ISO-1 could restore dexamethasone sensitivity in these cells. Collectively, our results indicate an intricate pathway between MIF expression and GC resistance. They suggest that MIF inhibitors could increase the response of GBMs to corticotherapy.

Upregulation of LRIG1 suppresses malignant glioma cell growth by attenuating EGFR activity

Activated epidermal growth factor receptor (EGFR) has emerged as an important therapeutic target for a variety of solid tumors, particularly malignant gliomas. A recently discovered transmembrane glycoprotein, LRIG1, antagonizes the activity of epidermal growth factor receptor family receptor tyrosine kinases and acts as a negative feedback loop of EGFR and proposed tumor suppressors. The aim of this study was to investigate the impact of LRIG1 on the biological features of glioma cells and the possible mechanisms of enhanced apoptosis induced by upregulation of LRIG1. We observed that the expression of LRIG1 was decreased, while the expression of EGFR was increased in the majority of astrocytomas, and the ratio of EGFR/LRIG1 was increased by sixfold in tumors versus corresponding non-neoplastic tissue. Upregulation of LRIG1, followed by a decrease of EGFR on the cytomembrane of the cells, induced cell apoptosis and cell growth inhibition, and further reversed invasion in glioma cell lines and primary glioma cells. Our study now clearly indicates that LRIG1 indeed affects cell fate and biology behaviors of the cells in vitro by inhibiting phosphorylation of downstream MAPK and AKT signaling pathway, and the elevated release level of caspase-8 might contribute to the enhanced apoptosis in LRIG1 transfected glioma cells. Taken together, these findings provide us with an insight into LRIG1 function, and we conclude that LRIG1 evolved in gliomas as a rare feedback negative attenuator of EGFR and could offer a novel therapeutic target to treat patients with malignant gliomas.

Increased expression of pituitary tumor-transforming gene (PTTG)-1 is correlated with poor prognosis in glioma patients

Pituitary tumor-transforming gene (PTTG), which is homologous to a mammalian securin, plays a pivotal role in cell transformation and is overexpressed in numerous cancer cell lines and tissues. PTTG functions in the control of mitosis, cell transformation, DNA repair and gene regulation. In the present study, we investigated whether the expression of PTTG1 is correlated with tumorigenicity and prognosis in glioma patients. Expression of PTTG1 was confirmed in three glioma cell lines at the mRNA and protein levels using RT-PCR analysis and Western blotting, respectively. Furthermore, PTTG1 protein was detected in 44 glioma tissue samples using immunohistochemical techniques, markedly increased in high-grade gliomas compared to low-grade gliomas and associated with an unfavorable patient outcome. Moreover, siRNA against the PTTG1 gene inhibited cell proliferation and invasion in glioma cell lines. These data suggest that increased expression of PTTG1 contributes to the tumorigenicity of glioma cells and may be useful as a prognostic marker for glioma patients.