Knockdown of FRAT1 expression by RNA interference inhibits human glioblastoma cell growth, migration and invasion

Significant Genes Associated with Mortality and Disease Progression in Grade II and III Glioma

BACKGROUND

The Wnt/β-catenin pathway plays a critical role in the tumorigenesis and maintenance of glioma stem cells. This study aimed to evaluate significant genes associated with the Wnt/β-catenin pathway involved in mortality and disease progression in patients with grade II and III glioma, using the Cancer Genome Atlas (TCGA) database.

METHODS

We obtained clinicopathological information and mRNA expression data from 515 patients with grade II and III gliomas from the TCGA database. We performed a multivariate Cox regression analysis to identify genes independently associated with glioma prognosis.

RESULTS

The analysis of 34 genes involved in Wnt/β-catenin signaling demonstrated that four genes (CER1, FRAT1, FSTL1, and RPSA) related to the Wnt/β-catenin pathway were significantly associated with mortality and disease progression in patients with grade II and III glioma. We also identified additional genes related to the four significant genes of the Wnt/β-catenin pathway mentioned above. The higher expression of BMP2, RPL18A, RPL19, and RPS12 is associated with better outcomes in patients with glioma.

CONCLUSIONS

Using a large-scale open database, we identified significant genes related to the Wnt/β-catenin signaling pathway associated with mortality and disease progression in patients with grade II and III gliomas.

A new approach based on CXCR4-targeted combination liposomes for the treatment of liver fibrosis

Liver fibrosis results from excessive extracellular matrix accumulation due to injury and leads to cirrhosis, cancer, and death. Herein, we propose a chemokine receptor 4 (CXCR4)-targeted combination (CTC) liposomal therapy to treat carbon tetrachloride (CCl₄)-induced liver fibrosis in a mouse model. This study aims to combine small molecules such as pirfenidone and AMD3100 in a single nanoplatform to investigate their synergistic antifibrotic effects in a setting of CCl₄-induced liver fibrosis. CTC liposomes (CTC lipo) were prepared using the thin-film hydration method. CTC lipo exhibited a spherical shape, and the particle size was recorded at the nanoscale which confirms its appropriateness for in vitro and in vivo applications. CTC lipo had good storage and serum stability. The entrapped drugs in CTC lipo showed reduced toxicity at higher concentrations. CTC lipo displayed CXCR4 mediated cell uptake and were internalized by caveolae-mediated endocytosis. CTC lipo showed CXCR4 targeting and stromal cell-derived factor 1α (SDF1-α)/CXCR4 axis blocking activity. CTC lipo reduced the elevated serum aspartate aminotransferase (AST), alanine transaminase (ALT), and hydroxyproline (HYP) levels. The histological studies showed improved liver architecture and reduced collagen deposition after treatment. Transforming growth factor β (TGFβ), alpha-smooth muscle actin (α-SMA), and collagen I were elevated by CCl₄ in comparison with the Sham. Upon CTC liposomal treatment, the quantitative score for the elevated fibrotic proteins such as TGFβ, α-SMA, and collagen I was normalized. CTC lipo displayed significant downregulation of the upregulated TGFβ, α-SMA, collagen I, and P-p38 expressions at the molecular level. The CXCR4 targeted liposomes showed prolonged biodistribution at 24 h. Our findings indicated that CTC lipo might be an alternative antifibrotic therapy that may offer new access to research and development. In a nutshell, the present study suggests that systemic administration of CTC lipo has efficient antifibrotic potential and deserves to be investigated for further clinical applications.

FRAT1 promotes the angiogenic properties of human glioblastoma cells via VEGFA

Glioblastoma is a common central nervous system tumor and despite considerable advancements in treatment patient prognosis remains poor. Angiogenesis is a significant prognostic factor in glioblastoma, anti‑angiogenic treatments represent a promising therapeutic approach. Vascular endothelial growth factor A (VEGFA) is a predominant regulator of angiogenesis and mounting evidence suggests that the Wnt signaling pathway serves a significant role in tumor angiogenesis. As a positive regulator of the Wnt/β‑catenin signaling pathway, frequently rearranged in advanced T‑cell lymphomas‑1 (FRAT1) is highly expressed in human glioblastoma and is significantly associated with glioblastoma growth, invasion and migration, as well as poor patient prognosis. Bioinformatics analysis demonstrated that both VEGFA and FRAT1 were highly expressed in most tumor tissues and associated with prognosis. However, whether and how FRAT1 is involved in angiogenesis remains to be elucidated. In the present study, the relationship between FRAT1 and VEGFA in angiogenesis was investigated using the human glioblastoma U251 cell line. Small interfering RNAs (siRNAs) were used to silence FRAT1 expression in U251 cells, and the mRNA and protein expression levels of VEGFA, as well as the concentration of VEGFA in U251 cell supernatants, were determined using reverse transcription‑quantitative PCR, western blotting and ELISA. A tube formation assay was conducted to assess angiogenesis. The results demonstrated that siRNA knockdown significantly decreased the protein expression levels of FRAT1 in U251 cells and markedly decreased the mRNA and protein expression levels of VEGFA. Furthermore, the concentration of VEGFA in the cell supernatant was significantly reduced and angiogenesis was suppressed. These results suggested that FRAT1 may promote VEGFA secretion and angiogenesis in human glioblastoma cells via the Wnt/β‑catenin signaling pathway, supporting the potential use of FRAT1 as a promising therapeutic target in human glioblastoma.

STAT1 is a modulator of the expression of frequently rearranged in advanced T-cell lymphomas 1 expression in U251 cells

Aberrant expression of frequently rearranged in advanced T-cell lymphomas 1 (FRAT1) contributes to poor prognosis in a number of carcinomas. However, its role in glioma remains controversial. In the present study, gene expression profiling was performed using Kyoto Encyclopedia of Genes and Genomes (KEGG), Gene Ontology (GO) functional enrichment and ingenuity pathway analysis (IPA) to evaluate the differential expression of genes and proteins in FRAT1 knockdown U251 glioma cells in comparison with the control. Western blot analysis was conducted to assess the expression levels of FRAT1 and STAT1. A total of 895 downregulated genes were identified in FRAT1-silenced U251 cells. The most enriched processes determined by GO and KEGG analysis of the 895 differentially expressed genes were associated with proliferation, migration and invasion. According to IPA, significant canonical pathways, including the interferon, hepatic fibrosis and Wnt/β-catenin signaling pathways, were identified to be the major enriched pathways. The elevated expression of STAT1 in U251 cells was validated. These results highlighted the regulatory role of FRAT1 in glioma cells with upregulated STAT1 expression.

Long non-coding RNA DANCR promotes cervical cancer growth via activation of the Wnt/β-catenin signaling pathway

Background

Long non-coding RNAs (lncRNAs) are implicated in many pathophysiological processes, including cancers. In particular, lncRNA DANCR is regarded as a cancer-associated lncRNA exerting various regulatory mechanisms. However, the expressions, functions, and mechanisms of action of DANCR in cervical cancer are still unclear.

Methods

The expressions of DANCR in cervical cancer tissues and cell lines were evaluated using qRT-PCR. Correlations between DANCR expression and clinicopathological features and prognosis were analyzed. The roles of DANCR in cervical cancer growth were evaluated by in vitro CCK-8 and EdU assay, and in vivo xenograft assay. The regulatory effects of DANCR on Wnt/β-catenin signaling pathway were evaluated using nuclear proteins extraction, western blot, and qRT-PCR.

Results

DANCR is increased in cervical cancer tissues and cell lines. Increased expression of DANCR is associated with large tumor size, advanced FIGO stage, and poor overall survival of cervical cancer patients. Functional experiments showed that enhanced expression of DANCR promotes cervical cancer cell proliferation in vitro and xenograft growth in vivo. Conversely, DANCR knockdown inhibits cervical cancer cell proliferation in vitro and xenograft growth in vivo. Mechanistic investigation demonstrated that DANCR upregulates the expressions of FRAT1 and FRAT2 and activates the Wnt/β-catenin signaling pathway. Blocking the Wnt/β-catenin signaling pathway abolishes the pro-proliferative roles of DANCR overexpression and anti-proliferative roles of DANCR knockdown.

Conclusions

Our findings suggest DANCR as an oncogenic lncRNA in cervical cancer through activating the Wnt/β-catenin signaling pathway, and imply that DANCR may be a promising prognostic biomarker and therapeutic target for cervical cancer.

FRAT1 Enhances the Proliferation and Tumorigenesis of CD133+Nestin+ Glioma Stem Cells In Vitro and In Vivo

Glioma stem cells (GSCs) are considered the source for development, recurrence, and poor prognosis of glioma, so treatment targeted GSCs is of great interest. The frequently rearranged in advanced T cell lymphomas-1 (FRAT1) gene is an important member of the Wnt/β-catenin signaling transduction pathway, and aberrantly activation of Wnt signaling has been identified to contribute to the tumorigenesis, proliferation, invasion of a variety kinds of cancer stem cells. However, correlations between FRAT1 and GSCs and the specific mechanisms remain unclear. In this study, we aimed to investigate the effect of FRAT1 on GSCs proliferation, colony formation, sphere formation and tumorigenesity in vitro and in vivo and its underlying mechanism. Lentiviral transfection was used to construct GSCs with low FRAT1 expression. The expression of FRAT1 on GSCs proliferation in vitro was assessed by cell counting kit-8(CCK-8). Colony formation and sphere formation assays were conducted to assess the colony and sphere formation ability of GSCs. Then, an intracranial glioma nude mouse model was built to measure the effect of low FRAT1 expression on GSCs proliferation and tumorigenesity in vivo. Real-time PCR, Western blot, and Immunohistochemistry were processed to detect the mRNA and protein expressions of FRAT1, β-catenin in the glioma tissue of xenograft mice to study their correlations. The functional assays verifed that low FRAT1 expression inhibited CD133⁺Nestin⁺ GSCs proliferation, colony formation, sphere formation ability in vitro. In vivo GSCs xenograft mice model showed that low FRAT1 expression suppressed the proliferation and tumorigenesity of CD133⁺Nestin⁺ GSCs and reduced β-catenin mRNA and protein expression. Furthermore, the expression of FRAT1 and β-catenin were positively correlated. Altogether, results indicate that FRAT1 enhances the proliferation, colony formation, sphere formation and tumorigenesity of CD133⁺Nestin⁺ glioma stem cells in vitro and in vivo as well as the expression of β-catenin. Therefore, inhibiting proliferation of GSCs and FRAT1 may be a molecular target to GSCs in treating human glioma in the future.

CXCR4-targeted liposomal mediated co-delivery of pirfenidone and AMD3100 for the treatment of TGFβ-induced HSC-T6 cells activation

Background: Liver fibrosis is a chronic liver disease associated with an excessive accumulation of extracellualr matrix (ECM) proteins which ultimately lead to cirrohosis and hepatocellular carcinoma.

Purpose: Liver fibrosis therapies that use combination approaches with the ability to affect multiple disease pathways have proven higher efficacies. This study aimed at optimizing and characterizing the co-encapsulation of pirfenidone (PF) and AMD3100 (AMD) into CXCR4-targeted combination liposomes (CTC liposome) for CXCR4 targeting, and the inhibition of major molecular culprits ie α-SMA, CXCR4, TGFβ, and P-p38 involved in liver fibrosis in-vitro.

Methods: The CTC liposomes were prepared using the thin-film hydration method. The concentration of encapsulated AMD and PF was measured by HPLC and UV spectrophotometry, respectively. Tramsmission electron microscopy (TEM) was used to determine the liposomal morphology. The CXCR4 targeting ability was determined by CXCR4 redistribution assay. Confocal microscopy and flowcytometry were used to determine the CXCR4 mediated cell uptake. The apoptosis inducing and protein downreguating ability of CTC liposomes were determined by apoptosis assay and western blot analysis, respectively. In-vivo biodistribution and Hoechst staining were used to confirm the feasibility of CTC liposome for the in-vivo applications and drug targeted accumulation, respectively.

Results: The TEM studies revealed that CTC liposomes were spherical in shape. The cumulative release of AMD and PF from CTC liposome was 67% and 84%, respectively, at 48 h. Compared to the free drug counterparts, encapsulated drugs displayed higher cell viability. The CXCR4 redistribution assay confirmed the CXCR4 targeting and antagonistic ability of CTC liposomes. The CTC liposomes were internalized more effectively via caveolae-mediated endocytic pathways. CTC liposomes displayed aggressive apoptosis (87.3%) in TGFβ-induced activated HSC-T6 cells suggesting a propensity to fibrosis regression. Also, CTC liposomes significantly reduced α-SMA (65%), CXCR4 (77%), TGFβ (89%), and P-p38 (66%) expressions, better than free drugs. CTC@IR780 liposomes (CTC liposomes incorporating IR780 dye) were more accumulated in fibrotic livers compared to free IR780, as judged by in-vivo imaging, biodistribution analysis, and Hoechst staining. These findings suggest that this simple and stable CTC liposomal system holds a great promise for the treatment and prevention of liver fibrosis.

MiR-34a-3p alters proliferation and apoptosis of meningioma cells in vitro and is directly targeting SMAD4, FRAT1 and BCL2

Micro (mi)RNAs are short, noncoding RNAs and deregulation of miRNAs and their targets are implicated in tumor generation and progression in many cancers. Meningiomas are mostly benign, slow growing tumors of the central nervous system with a small percentage showing a malignant phenotype.

Following in silico prediction of potential targets of miR-34a-3p, SMAD4, FRAT1, and BCL2 have been confirmed as targets by dual luciferase assays with co-expression of miR-34a-3p and reporter gene constructs containing the respective 3'UTRs. Disruption of the miR-34a-3p binding sites in the 3'UTRs resulted in loss of responsiveness to miR-34a-3p overexpression. In meningioma cells, overexpression of miR-34a-3p resulted in decreased protein levels of SMAD4, FRAT1 and BCL2, while inhibition of miR-34a-3p led to increased levels of these proteins as confirmed by Western blotting. Furthermore, deregulation of miR-34a-3p altered cell proliferation and apoptosis of meningioma cells in vitro.

We show that SMAD4, FRAT1 and BCL2 are direct targets of miR-34a-3p and that deregulation of miR-34a-3p alters proliferation and apoptosis of meningioma cells in vitro. As part of their respective signaling pathways, which are known to play a role in meningioma genesis and progression, deregulation of SMAD4, FRAT1 and BCL2 might contribute to the aberrant activation of these signaling pathways leading to increased proliferation and inhibition of apoptosis in meningiomas.

Neighbours of cancer-related proteins have key influence on pathogenesis and could increase the drug target space for anticancer therapies

Even targeted chemotherapies against solid cancers show a moderate success increasing the need to novel targeting strategies. To address this problem, we designed a systems-level approach investigating the neighbourhood of mutated or differentially expressed cancer-related proteins in four major solid cancers (colon, breast, liver and lung). Using signalling and protein–protein interaction network resources integrated with mutational and expression datasets, we analysed the properties of the direct and indirect interactors (first and second neighbours) of cancer-related proteins, not found previously related to the given cancer type. We found that first neighbours have at least as high degree, betweenness centrality and clustering coefficient as cancer-related proteins themselves, indicating a previously unknown central network position. We identified a complementary strategy for mutated and differentially expressed proteins, where the affect of differentially expressed proteins having smaller network centrality is compensated with high centrality first neighbours. These first neighbours can be considered as key, so far hidden, components in cancer rewiring, with similar importance as mutated proteins. These observations strikingly suggest targeting first neighbours as a novel strategy for disrupting cancer-specific networks. Remarkably, our survey revealed 223 marketed drugs already targeting first neighbour proteins but applied mostly outside oncology, providing a potential list for drug repurposing against solid cancers. For the very central first neighbours, whose direct targeting would cause several side effects, we suggest a cancer-mimicking strategy by targeting their interactors (second neighbours of cancer-related proteins, having a central protein affecting position, similarly to the cancer-related proteins). Hence, we propose to include first neighbours to network medicine based approaches for (but not limited to) anticancer therapies.

Cancer is considered a systems disease in which the interactors of cancer-related proteins have a key role, also as targets to fight cancer. New therapeutic approaches are needed to improve success rates and to identify suitable proteins as novel, alternative drug targets. We designed a computational approach, combining mutation and differential expression data with network information, to analyse the interactions of cancer-related proteins in colon, breast, liver and lung cancer. We found that first (direct) neighbours, not linked previously to the given cancer type, are similarly important as mutated proteins known to be involved in cancer development. We found 223 drugs already in the clinic targeting these proteins but not yet used against cancer as their oncology relevance was hidden so far. Our observations open up new strategies for target selection and anti-cancer drug discovery.

FRAT1 expression regulates proliferation in colon cancer cells

Colorectal cancer is one of the most common gastric malignancies worldwide. However, the underlying mechanism of colon cancer development and valuable indicators of the disease remain unclear. In this study, the expression of frequently rearranged in advanced T-cell lymphomas 1 (FRAT1) in colon cancer was investigated and the association between FRAT1 expression and biological properties of tumors was analyzed. A total of 147 colon cancer tissue samples and adjacent normal tissues were collected between January 2013 and June 2014. The FRAT1 gene and protein expression levels were analyzed in tissues with different TNM and pathological stages. Small hairpin RNAs (shRNAs) containing the human FRAT1 gene were constructed and transfected into colon cancer HT-29 cells. The proliferation and migration of the cells was also analyzed in relation to a reduction in FRAT1 expression. In colon cancer tissues, the expression of FRAT1 was significantly higher when compared with adjacent tissues. In addition, FRAT1 expression was found to positively correlate with the degree of tumor malignancy, and this difference was determined to be statistically significant (P<0.05). Following shRNA transfection in HT-29 cells to decrease the expression of FRAT1, the proliferation and migration of the HT-29 cells decreased (due to conversion of the shRNA into small interfering RNA). These results indicate that in colon cancer, FRAT1 may present a novel tool for analyzing the tumor progression and may be a novel therapeutic target for the treatment of colon cancer.

Knockdown of FRAT1 inhibits hypoxia-induced epithelial-to-mesenchymal transition via suppression of the Wnt/β-catenin pathway in hepatocellular carcinoma cells

Hypoxia-induced epithelial-to-mesenchymal transition (EMT) in hepatocellular carcinoma (HCC) was investigated. Frequently rearranged in advanced T-cell lymphomas-1 (FRAT1) is a positive regulator of the Wnt/β-catenin signaling pathway and is overexpressed in many human tumors. However, the expression and role of FRAT1 in HCC has not been elucidated. In this study, we investigated the effect of FRAT1 on EMT process in HCC cells induced by hypoxia. Our results showed that FRAT1 is highly expressed in HCC tissues and cell lines. Hypoxia significantly induced FRAT1 expression in HCC cells. FRAT1 knockdown inhibited hypoxia-induced cell migration/invasion, downregulation of epithelial markers and upregulation of mesenchymal markers. Moreover, FRAT1 knockdown suppressed the expression levels of β-catenin, cyclin D1 and c-myc in HCC cells under the same hypoxic condition. Our results revealed that FRAT1 is a hypoxia factor that is critical for the induction of EMT in HCC cells. These data suggest a potential role for targeting FRAT1 in the prevention of hypoxia-induced HCC cancer progression and metastasis mediated by EMT.

Frequently rearranged in advanced T‑cell lymphomas‑1 demonstrates oncogenic properties in prostate cancer

Prostate cancer is the fifth most common cause of cancer-associated mortality for males worldwide. Although dysregulation of the β-catenin/T-cell factor (TCF) pathway has been previously reported in prostate cancer, the mechanisms underlying this process remain unknown. Frequently rearranged in advanced T-cell lymphomas-1 (FRAT1) functions as a positive regulator of the β-catenin/TCF signaling pathway. However, to the best of our knowledge, the molecular association between FRAT1 and the β-catenin/TCF pathway in prostate cancer has not been investigated. In the present study, FRAT1 expression was analyzed in normal prostate tissues and prostate adenocarcinoma samples using publicly available databases, a commercial tissue microarray and immunohistochemistry techniques. In addition, FRAT1 expression levels were altered by overexpression or RNA interference-mediated depletion in prostate cancer cells. The effects of FRAT1 expression on tumor growth were determined using cell growth curves in vitro and xenografts in nude mice in vivo. The effects of FRAT1 on β-catenin/TCF activity were measured using the TOPFLASH reporter assay. FRAT1 was expressed exclusively in the nuclei of normal prostate basal cells, and nuclear FRAT1 was detected in 68% (40/59) of prostate adenocarcinoma samples. In addition, FRAT1 activated the TCF luciferase reporter gene promoter in prostate cancer cells, and was observed to promote the growth of prostate cancer cells in vitro. Furthermore, FRAT1 expression was sufficient to transform NIH3T3 mouse embryonic fibroblast cells and lead to tumor formation in vivo. These results suggest that FRAT1 demonstrates oncogenic properties in prostate cancer, potentially by suppressing the inhibitory effect of nuclear glycogen synthase 3β against β-catenin/TCF activity, thus activating the Wnt/β-catenin signaling pathway and promoting cell growth.

Radioresistance of Brain Tumors

Radiation therapy (RT) is frequently used as part of the standard of care treatment of the majority of brain tumors. The efficacy of RT is limited by radioresistance and by normal tissue radiation tolerance. This is highlighted in pediatric brain tumors where the use of radiation is limited by the excessive toxicity to the developing brain. For these reasons, radiosensitization of tumor cells would be beneficial. In this review, we focus on radioresistance mechanisms intrinsic to tumor cells. We also evaluate existing approaches to induce radiosensitization and explore future avenues of investigation.

Silencing of FRAT1 by siRNA inhibits the proliferation of SGC7901 human gastric adenocarcinoma cells

Frequently rearranged in advanced T cell lymphomas-1 (FRAT1) positively regulates the Wnt/β-catenin signaling pathway by inhibiting glycogen synthase kinase-3 mediated phosphorylation of β-catenin. FRAT1 is a proto-oncogene, implicated in tumorigenesis. The present study aimed to investigate the effects of FRAT1 silencing on the proliferation and apoptosis of SGC7901 cells. FRAT1 in SGC7901 cells was silenced by RNA interference. Reverse transcription-quantitative polymerase chain reaction was used for the analysis of FRAT1 mRNA and western blotting was used to evaluate FRAT1 and β-catenin protein levels. Cell proliferation was analyzed by the MTT assay. Cell cycle distribution and apoptosis were analyzed by flow cytometry. The expression of FRAT1 mRNA, FRAT1 and β-catenin protein in FRAT1-silenced SGC7901 cells were reduced significantly compared to untreated cells. The proliferation of FRAT1 silenced SGC7901 cells decreased significantly The FRAT1 silenced SGC7901 cells were arrested at G0/G1 stage to a greater degree, and apoptosis was increased. In summary, silencing of FRAT1 inhibits SGC7901 cell proliferation and induces apoptosis, possible through a reduction in β-catenin expression. FRAT1 may serve as a prognostic biomarker and therapeutic target for gastric cancer.

The clinical significance of FRAT1 and ABCG2 expression in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is a highly malignant tumor with intrinsic resistance to cytotoxic agents. The molecular mechanisms associated with high malignancy and resistance to chemotherapy and radiotherapy have not been fully elucidated. This study investigated the clinicopathological significances of frequently rearranged in advanced T-cell lymphomas-1 (FRAT1) and ATP-binding cassette subfamily G member 2 (ABCG2) expression in PDAC. FRAT1 and ABCG2 protein expression in 106 PDAC, 35 peritumoral tissues, 55 benign pancreatic tissues, and 13 normal pancreatic tissues was measured by immunohistochemistry. FRAT1 and ABCG2 protein was overexpressed in PDAC tumors compared to peritumoral tissues, benign pancreatic tissues, and normal pancreatic tissues (P < 0.01). The percentage of cases with positive FRAT1 and ABCG2 overexpression was significantly higher in PDAC patients with poor differentiation, lymph node metastasis, invasion, and TNM stage III/IV disease than in patients with well-differentiated tumor, no lymph node metastasis and invasion, and TNM stage I/II disease (P < 0.05 or P < 0.01). In pancreatic tissues with benign lesions, tissues with positive FRAT1 and ABCG2 protein expression exhibited dysplasia or intraepithelial neoplasia. Kaplan-Meier survival analysis showed that PDAC patients with positive FRAT1 and ABCG2 expression survived significantly shorter than patients with negative FRAT1 and ABCG2 expression (P < 0.05 or P < 0.001). Cox multivariate analysis revealed that positive FRAT1 and ABCG2 expression was an independent poor prognosis factor in PDAC patients. FRAT1 and ABCG2 overexpression is associated with carcinogenesis, progression, and poor prognosis in patients with PDAC.

Laboratory models for central nervous system tumor stem cell research

Central nervous system (CNS) tumors are complex organ systems comprising of a neoplastic component with associated vasculature, inflammatory cells, and reactive cellular and extracellular components. Research has identified a subset of cells in CNS tumors that portray defining properties of neural stem cells, namely, that of self-renewal and multi-potency. Growing evidence suggests that these tumor stem cells (TSC) play an important role in the maintenance and growth of the tumor. Furthermore, these cells have also been shown to be refractory to conventional therapy and may be crucial for tumor recurrence and metastasis. Current investigations are focusing on isolating these TSC from CNS tumors to investigate their unique biological processes. This understanding will help identify and develop more effective and comprehensive treatment strategies. This chapter provides an overview of some of the most commonly used laboratory models for CNSTSC research.

Mechanisms regulating glioma invasion

Glioblastoma (GBM) is the most aggressive, deadliest, and most common brain malignancy in adults. Despite the advances made in surgical techniques, radiotherapy and chemotherapy, the median survival for GBM patients has remained at a mere 14 months. GBM poses several unique challenges to currently available treatments for the disease. For example, GBM cells have the propensity to aggressively infiltrate/invade into the normal brain tissues and along the vascular tracks, which prevents complete resection of all malignant cells and limits the effect of localized radiotherapy while sparing normal tissue. Although anti-angiogenic treatment exerts anti-edematic effect in GBM, unfortunately, tumors progress with acquired increased invasiveness. Therefore, it is an important task to gain a deeper understanding of the intrinsic and post-treatment invasive phenotypes of GBM in hopes that the gained knowledge would lead to novel GBM treatments that are more effective and less toxic. This review will give an overview of some of the signaling pathways that have been shown to positively and negatively regulate GBM invasion, including, the PI3K/Akt, Wnt, sonic hedgehog-GLI1, and microRNAs. The review will also discuss several approaches to cancer therapies potentially altering GBM invasiveness.

The role of FoxJ2 in the migration of human glioma cells

Previous studies have demonstrated that FoxJ2 (forkhead box J2) is a member of Forkhead Box transcription factors and acts as an important prognostic indicator in human breast cancer. Our study aimed to assess the expression and function in human glioma. Western blot analysis and immunohistochemistry were performed in human glioma tissues. Low FoxJ2 expression was observed in 80 samples and its level was correlated with the grade of malignancy. A strongly positive correlation was observed between FoxJ2 and E-cadherin. Overexpression of FoxJ2 increased E-cadherin expression and decreased vimentin expression. The wound healing and transwell assays showed that overexpression of FoxJ2 significantly inhibited their migration in U87 cells. Consistent with this, knockdown of FoxJ2 promoted cellular motility. In a word, FoxJ2 suppressed cell migration and invasion in glioma, which might be a potential novel molecular targeted therapy for surgery and immune treatment.

Current Understanding on EGFR and Wnt/β-Catenin Signaling in Glioma and Their Possible Crosstalk

Glioblastoma multiformes (GBMs) are extensively heterogeneous at both cellular and molecular levels. Current therapeutic strategies include targeting of key signaling molecules using pharmacological inhibitors in combination with genotoxic agents such as temozolomide. In spite of all efforts, the prognosis of glioma patients remains dismal. Therefore, a proper understanding of individual molecular pathways responsible for the progression of GBM is necessary. The epidermal growth factor receptor (EGFR) pathway is probably the most significant signaling pathway clinically implicated in glioma. Not surprisingly, anti-EGFR therapies mostly prevail for therapeutic purposes. The Wnt/β-catenin pathway is well implicated in multiple tumors; however, its role in glioma has only recently started to emerge. We give a concise account of the current understanding of the role of both these pathways in glioma. Last, taking evidences from a limited literature, we outline a number of points where these pathways intersect each other and put forward the possibility of combinatorially targeting them for treatment of glioma.

The metastasis suppressor NDRG1 modulates the phosphorylation and nuclear translocation of β-catenin through mechanisms involving FRAT1 and PAK4

N-myc downstream-regulated gene 1 (NDRG1) is a potent metastasis suppressor that has been demonstrated to inhibit the transforming growth factor β (TGF-β)-induced epithelial-to-mesenchymal transition (EMT) by maintaining the cell-membrane localization of E-cadherin and β-catenin in prostate and colon cancer cells. However, the precise molecular mechanism remains unclear. In this investigation, we demonstrate that NDRG1 inhibits the phosphorylation of β-catenin at Ser33/37 and Thr41 and increases the levels of non-phosphorylated β-catenin at the plasma membrane in DU145 prostate cancer cells and HT29 colon cancer cells. The mechanism of inhibiting β-catenin phosphorylation involves the NDRG1-mediated upregulation of the GSK3β-binding protein FRAT1, which prevents the association of GSK3β with the Axin1-APC-CK1 destruction complex and the subsequent phosphorylation of β-catenin. Additionally, NDRG1 is shown to modulate the WNT-β-catenin pathway by inhibiting the nuclear translocation of β-catenin. This is mediated through an NDRG1-dependent reduction in the nuclear localization of p21-activated kinase 4 (PAK4), which is known to act as a transporter for β-catenin nuclear translocation. The current study is the first to elucidate a unique molecular mechanism involved in the NDRG1-dependent regulation of β-catenin phosphorylation and distribution.

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.

The effect and mechanism of CXCR4 silencing on metastasis suppression of human glioma U87 cell line

Tumor metastasis is the major cause of treatment failure and poor prognosis of glioma. Inhibiting metastasis has become an important therapeutic strategy for glioma treatment. CXCR4 has been proved to play an important role in the occurrence and development of tumors. In order to illustrate the effect of CXCR4 on glioma metastasis, we investigated the role of CXCR4 in U87 cells metastasis based on the CXCR4 silencing tumor cells. In this study, we found that CXCR4 silencing could suppress U87 cells invasion and adhesion potential, production of TGF-β1, IL-6, and IL-8, and blocked the G0/G1 phase of the cell cycle. We also found that CXCR4 silencing could up-regulate the mRNA and protein expression of p53, p21, and E-cadherin, and down-regulate the mRNA and protein expression of CD44 and MMP-2/-9. Meanwhile, CXCR4 silencing could decrease the phosphorylation of p-AKT and transcription activity of NF-κB promoter, and increased the phosphorylation of PTEN. The results provided a new research basis for the further study of CXCR4 gene, the screening of human glioma, as well as the target treatment for glioma and its prognosis.