Correlation of N-cadherin expression in high grade gliomas with tissue invasion

Platycodin D inhibits glioblastoma cell proliferation, migration, and invasion by regulating DEPDC1B-mediated epithelial-to-mesenchymal transition

BACKGROUND

Platycodin D (PD) is a potent bioactive constituent in the medicinal herb Platycodon grandiflorum. It has shown anticancer properties, particularly against glioblastoma (GB) and other human malignancies. DEPDC1B (DEP domain-containing protein 1B) is an oncogene associated with epithelial-mesenchymal transition (EMT). It is highly expressed in GB and correlated with tumor grade and patient prognosis. In this study, we investigated whether the antiglioma effect of PD was associated with downregulation of DEPDC1B.

METHODS

Gene expression and clinical data were obtained from the China Glioma Genome Atlas and The Cancer Genome Atlas databases for glioma samples. In vitro experiments were conducted using Cell Counting Kit-8 and Transwell assays to assess the impact of PD on the proliferation, migration, and invasion of GB cells. mRNA and protein expression was evaluated using real-time polymerase chain reaction and western blotting, respectively.

RESULTS

PD exerted inhibitory effects on the proliferation and motility of GB cells. PD downregulated DEPDC1B protein as well as several markers associated with EMT, namely N-cadherin, vimentin, and Snail. The suppressive effects of PD were enhanced when DEPDC1B was knocked down in GB cells, while overexpression of DEPDC1B in cells reversed the inhibitory effects of PD.

CONCLUSION

PD exerts an antiglioma effect by regulating DEPDC1B-mediated EMT.

Molecular mechanisms of microRNAs in glioblastoma pathogenesis

Glioblastoma (GBM) is human's most prevalent and severe brain cancer. Epigenetic regulators, micro(mi)RNAs, significantly impact cellular health and disease because of their wide range of targets and functions. The "epigenetic symphony" in which miRNAs perform is responsible for orchestrating the transcription of genetic information. The discovery of regulatory miRNA activities in GBM biology has shown that various miRNAs play a vital role in disease onset and development. Here, we summarize our current understanding of the current state-of-the-art and latest findings regarding the interactions between miRNAs and molecular mechanisms commonly associated with GBM pathogenesis. Moreover, by literature review and reconstruction of the GBM gene regulatory network, we uncovered the connection between miRNAs and critical signaling pathways such as cell proliferation, invasion, and cell death, which provides promising hints for identifying potential therapeutic targets for the treatment of GBM. In addition, the role of miRNAs in GBM patient survival was investigated. The present review, which contains new analyses of the previous literature, may lead to new avenues to explore in the future for the development of multitargeted miRNA-based therapies for GBM.

Use of phage display biopanning as a tool to design CAR-T cells against glioma stem cells

Background

Glioblastoma (GBM) is both the most common and aggressive type of primary brain tumor, associated with high mortality rates and resistance to conventional therapy. Despite recent advancements in knowledge and molecular profiling, recurrence of GBM is nearly inevitable. This recurrence has been attributed to the presence of glioma stem cells (GSCs), a small fraction of cells resistant to standard-of-care treatments and capable of self-renewal and tumor initiation. Therefore, targeting these cancer stem cells will allow for the development of more effective therapeutic strategies against GBM. We have previously identified several 7-amino acid length peptides which specifically target GSCs through in vitro and in vivo phage display biopanning.

Methods and results

We have combined two of these peptides to create a dual peptide construct (EV), and demonstrated its ability to bind GSCs in vitro and target intracranial GBM in mouse models. A peptide pull-down performed with peptide EV followed by mass spectrometry determined N-cadherin as the binding partner of the peptide, which was validated by enzyme-linked immunosorbent assay and surface plasmon resonance. To develop cytotoxic cellular products aimed at specifically targeting GSCs, chimeric antigen receptors (CARs) were engineered containing the peptide EV in place of the single-chain variable fragment (scFv) as the antigen-binding domain. EV CAR-transduced T cells demonstrated specific reactivity towards GSCs by production of interferon-gamma when exposed to GSCs, in addition to the induction of GSC-specific apoptosis as illustrated by Annexin-V staining.

Conclusion

These results exemplify the use of phage display biopanning for the isolation of GSC-targeting peptides, and their potential application in the development of novel cytotoxic therapies for GBM.

Substrate stiffness effect on molecular crosstalk of epithelial-mesenchymal transition mediators of human glioblastoma cells

The complexity of the microenvironment effects on cell response, show accumulating evidence that glioblastoma (GBM) migration and invasiveness are influenced by the mechanical rigidity of their surroundings. The epithelial–mesenchymal transition (EMT) is a well-recognized driving force of the invasive behavior of cancer. However, the primary mechanisms of EMT initiation and progression remain unclear. We have previously showed that certain substrate stiffness can selectively stimulate human GBM U251-MG and GL15 glioblastoma cell lines motility. The present study unifies several known EMT mediators to uncover the reason of the regulation and response to these stiffnesses. Our results revealed that changing the rigidity of the mechanical environment tuned the response of both cell lines through change in morphological features, epithelial-mesenchymal markers (E-, N-Cadherin), EGFR and ROS expressions in an interrelated manner. Specifically, a stiffer microenvironment induced a mesenchymal cell shape, a more fragmented morphology, higher intracellular cytosolic ROS expression and lower mitochondrial ROS. Finally, we observed that cells more motile showed a more depolarized mitochondrial membrane potential. Unravelling the process that regulates GBM cells’ infiltrative behavior could provide new opportunities for identification of new targets and less invasive approaches for treatment.

Nascent Proteome and Glycoproteome Reveal the Inhibition Role of ALG1 in Hepatocellular Carcinoma Cell Migration

Asparagine-linked glycosylation protein 1 homolog (ALG1) participates in the initial stage of protein N-glycosylation and N-glycosylation has been implicated in the process of hepatocellular carcinoma (HCC) progression. However, whether ALG1 plays a role in human HCC remains unknown. In this study, the expression profile of ALG1 in tumorous and corresponding adjacent non-tumor tissues was analyzed. The relationship of ALG1 expression with clinical features and prognosis of HCC patients was also evaluated using immuno-histochemical method. Here we found ALG1 decreased in HCC tissues compared with adjacent normal liver tissues, which predicted an unfavorable prognosis. Combined with RNA interference, nascent proteome and glycoproteome were determined systematically in Huh7 cell line. Bioinformatics analysis indicated that the differentially expressed proteins participating in the response of ALG1 knockdown were most significantly associated with cell-cell adhesion. Functional studies confirmed that knockdown of ALG1 reduced cell adhesion capacity, and promoted cell migration. Furthermore, down-regulation of H8N2 (on N-glycosite N651) and H5N4S2F1 (on N-glycosite N692) from N-cadherin was identified as a feature of ALG1 knockdown. Our findings revealed that ALG1 controlled the expression of glycosylated N-cadherin and played a role in HCC migration, with implications for prognosis.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s43657-022-00050-5.

ZEB1 induces N-cadherin expression in human glioblastoma and may alter patient survival

The present study investigated the expression of epithelial-mesenchymal transition (EMT)-related factors zinc finger E-box-binding homeobox 1 (ZEB1), cadherin-1 (CDH1), cadherin-2 (CDH2) and the cell cycle modulating kinase cyclin-dependent kinase 1 (CDK1) in human glioblastoma (GBM) compared to normal brain tissue, as well as whether the levels of expression were associated with the overall and progression-free survival of the GBM patients. In 44 GBM and five normal brain tissue specimens, the expression levels of ZEB1, CDH1, CDH2 and CDK1 were evaluated by real-time PCR and immunostaining, and the results were correlated with clinical data. The expression levels of all investigated genes as detected by immunostaining were significantly higher in the GBM when compared to the normal brain tissues. There was no influence on survival. A linear correlation between ZEB1 and CDH2 and CDK1 expression was observed in GBM. Moreover, ZEB1 was involved in EMT (e.g., signaling in human GBM) and high ZEB1 levels were linked to an aberrant cell cycle processing, marked by CDK1 overexpression.

Mechanical Properties of the Extracellular Environment of Human Brain Cells Drive the Effectiveness of Drugs in Fighting Central Nervous System Cancers

The evaluation of nanomechanical properties of tissues in health and disease is of increasing interest to scientists. It has been confirmed that these properties, determined in part by the composition of the extracellular matrix, significantly affect tissue physiology and the biological behavior of cells, mainly in terms of their adhesion, mobility, or ability to mutate. Importantly, pathophysiological changes that determine disease development within the tissue usually result in significant changes in tissue mechanics that might potentially affect the drug efficacy, which is important from the perspective of development of new therapeutics, since most of the currently used in vitro experimental models for drug testing do not account for these properties. Here, we provide a summary of the current understanding of how the mechanical properties of brain tissue change in pathological conditions, and how the activity of the therapeutic agents is linked to this mechanical state.

Crosstalk between PI3K/AKT/mTOR and WNT/β-Catenin signaling in GBM - Could combination therapy checkmate the collusion?

Glioblastoma multiforme is one of the calamitous primary glial brain tumors with extensive heterogeneity at cellular and molecular levels. While maximal surgical resection trailed by radio and chemotherapy employing temozolomide remains the gold-standard treatment for malignant glioma patients, the overall prognosis remains dismal and there exists an unmet need for effective therapeutic strategies. In this context, we hypothesize that proper understanding of signaling pathways responsible for glioblastoma multiforme proliferation would be the first trump card while searching for novel targeted therapies. Among the pathways aberrantly activated, PI3K/AKT/mTOR is the most significant pathway, that is clinically implicated in malignancies such as high-grade glioma. Further, the WNT/β-Catenin cascade is well-implicated in several malignancies, while its role in regulating glioma pathogenesis has only emerged recently. Nevertheless, oncogenic activation of both these pathways is a frequent event in malignant glioma that facilitates tumor proliferation, stemness and chemo-resistance. Recently, it has been reported that the cross-talk of PI3K/AKT/mTOR pathway with multiple signaling pathways could promote glioma progression and reduce the sensitivity of glioma cells to the standard therapy. However, very few studies had focused on the relationship between PI3K/AKT/mTOR and WNT/β-Catenin pathways in glioblastoma multiforme. Interestingly, in homeostatic and pathologic circumstances, both these pathways depict fine modulation and are connected at multiple levels by upstream and downstream effectors. Thus, gaining deep insights on the collusion between these pathways would help in discovering unique therapeutic targets for glioblastoma multiforme management. Hence, the current review aims to address, "the importance of inter-play between PI3K/AKT/mTOR and WNT/β-Catenin pathways", and put forward, "the possibility of combinatorially targeting them", for glioblastoma multiforme treatment enhancement.

Glioblastoma Microenvironment and Cellular Interactions

Simple Summary

This paper summarizes the crosstalk between tumor/non-tumor cells and other elements of the glioblastoma (GB) microenvironment. In tumor pathology, glial cells result in the highest number of cancers, and GB is considered the most lethal tumor of the central nervous system (CNS). The tumor microenvironment (TME) is a complex peritumoral hallo composed of tumor cells and several non-tumor cells (e.g., nervous cells, stem cells, fibroblasts, vascular and immune cells), which might be a key factor for the ineffective treatment since the microenvironment modulates the biologic status of the tumor with the increase in its evasion capacity. A deeper understanding of cell–cell interactions in the TME and with the tumor cells could be the basis for a more efficient therapy.

Abstract

The central nervous system (CNS) represents a complex network of different cells, such as neurons, glial cells, and blood vessels. In tumor pathology, glial cells result in the highest number of cancers, and glioblastoma (GB) is considered the most lethal tumor in this region. The development of GB leads to the infiltration of healthy tissue through the interaction between all the elements of the brain network. This results in a GB microenvironment, a complex peritumoral hallo composed of tumor cells and several non-tumor cells (e.g., nervous cells, stem cells, fibroblasts, vascular and immune cells), which might be the principal factor for the ineffective treatment due to the fact that the microenvironment modulates the biologic status of the tumor with the increase in its evasion capacity. Crosstalk between glioma cells and the brain microenvironment finally inhibits the beneficial action of molecular pathways, favoring the development and invasion of the tumor and its increasing resistance to treatment. A deeper understanding of cell–cell interactions in the tumor microenvironment (TME) and with the tumor cells could be the basis for a more efficient therapy.

The Role of Autophagy in Childhood Central Nervous System Tumors

OPINION STATEMENT

Autophagy is a physiological process that occurs in normal tissues. Under external environmental pressure or internal environmental changes, cells can digest part of their contents through autophagy in order to reduce metabolic pressure or remove damaged organelles. In cancer, autophagy plays a paradoxical role, acting as a tumor suppressor-by removing damaged organelles and inhibiting inflammation or by promoting genome stability and the tumor-adaptive responses-as a pro-survival mechanism to protect cells from stress. In this article, we review the autophagy-dependent mechanisms driving childhood central nervous system tumor cell death, malignancy invasion, chemosensitivity, and radiosensitivity. Autophagy inhibitors and inducers have been developed, and encouraging results have been achieved in autophagy modulation, suggesting that these might be potential therapeutic agents for the treatment of pediatric central nervous system (CNS) tumors.

Cadherin‐3 is a novel oncogenic biomarker with prognostic value in glioblastoma

Glioblastoma (GBM) is the most common and malignant primary brain tumor in adults. The prognosis of patients is very poor, with a median overall survival of ~ 15 months after diagnosis. Cadherin‐3 (also known as P‐cadherin), a cell–cell adhesion molecule encoded by the CDH3 gene, is deregulated in several cancer types, but its relevance in GBM is unknown. In this study, we investigated the functional roles, the associated molecular signatures, and the prognostic value of CDH3/P‐cadherin in this highly malignant brain tumor. CDH3/P‐cadherin mRNA and protein levels were evaluated in human glioma samples. Knockdown and overexpression models of P‐cadherin in GBM were used to evaluate its functional role in vitro and in vivo. CDH3‐associated gene signatures were identified by enrichment analyses and correlations. The impact of CDH3 in the survival of GBM patients was assessed in independent cohorts using both univariable and multivariable models. We found that P‐cadherin protein is expressed in a subset of gliomas, with an increased percentage of positive samples in grade IV tumors. Concordantly, CDH3 mRNA levels in glioma samples from The Cancer Genome Atlas (TCGA) database are increased in high‐grade gliomas. P‐cadherin displays oncogenic functions in multiple knockdown and overexpression GBM cell models by affecting cell viability, cell cycle, cell invasion, migration, and neurosphere formation capacity. Genes that were positively correlated with CDH3 are enriched for oncogenic pathways commonly activated in GBM. In vivo, GBM cells expressing high levels of P‐cadherin generate larger subcutaneous tumors and cause shorter survival of mice in an orthotopic intracranial model. Concomitantly, high CDH3 expression is predictive of shorter overall survival of GBM patients in independent cohorts. Together, our results show that CDH3/P‐cadherin expression is associated with aggressiveness features of GBM and poor patient prognosis, suggesting that it may be a novel therapeutic target for this deadly brain tumor.

Cadherin Expression and EMT: A Focus on Gliomas

Cadherins are calcium-binding proteins with a pivotal role in cell adhesion and tissue homeostasis. The cadherin-dependent mechanisms of cell adhesion and migration are exploited by cancer cells, contributing to tumor invasiveness and dissemination. In particular, cadherin switch is a hallmark of epithelial to mesenchymal transition, a complex development process vastly described in the progression of most epithelial cancers. This is characterized by drastic changes in cell polarity, adhesion, and motility, which lead from an E-cadherin positive differentiated epithelial state into a dedifferentiated mesenchymal-like state, prone to metastization and defined by N-cadherin expression. Although vastly explored in epithelial cancers, how these mechanisms contribute to the pathogenesis of other non-epithelial tumor types is poorly understood. Herein, the current knowledge on cadherin expression in normal development in parallel to tumor pathogenesis is reviewed, focusing on epithelial to mesenchymal transition. Emphasis is taken in the unascertained cadherin expression in CNS tumors, particularly in gliomas, where the potential contribution of an epithelial-to-mesenchymal-like process to glioma genesis and how this may be associated with changes in cadherin expression is discussed.

Therapeutic targeting of membrane-associated proteins in central nervous system tumors

The activity of the most complex system, the central nervous system (CNS) is profoundly regulated by a huge number of membrane-associated proteins (MAP). A minor change stimulates immense chemical changes and the elicited response is organized by MAP, which acts as a receptor of that chemical or channel enabling the flow of ions. Slight changes in the activity or expression of these MAPs lead to severe consequences such as cognitive disorders, memory loss, or cancer. CNS tumors are heterogeneous in nature and hard-to-treat due to random mutations in MAPs; like as overexpression of EGFRvIII/TGFβR/VEGFR, change in adhesion molecules α5β3 integrin/SEMA3A, imbalance in ion channel proteins, etc. Extensive research is under process for developing new therapeutic approaches using these proteins such as targeted cytotoxic radiotherapy, drug-delivery, and prodrug activation, blocking of receptors like GluA1, developing viral vector against cell surface receptor. The combinatorial approach of these strategies along with the conventional one might be more potential. Henceforth, our review focuses on in-depth analysis regarding MAPs aiming for a better understanding for developing an efficient therapeutic approach for targeting CNS tumors.

Glycation of benign meningioma cells leads to increased invasion

Meningiomas are the most common non-malignant intracranial tumors. Like most tumors, meningiomas prefer anaerobic glycolysis for energy production (Warburg effect). This leads to an increased synthesis of the metabolite methylglyoxal (MGO). This metabolite is known to react with amino groups of proteins. This reaction is called glycation, thereby building advanced glycation endproducts (AGEs). In this study, we investigated the influence of glycation on two meningioma cell lines, representing the WHO grade I (BEN-MEN-1) and the WHO grade III (IOMM-Lee). Increasing MGO concentrations led to the formation of AGEs and decreased growth in both cell lines. When analyzing the influence of glycation on adhesion, chemotaxis and invasion, we could show that the glycation of meningioma cells resulted in increased invasive potential of the benign meningioma cell line, whereas the invasive potential of the malignant cell line was reduced. In addition, glycation increased the E-cadherin- and decreased the N-cadherin-expression in BEN-MEN-1 cells, but did not affect the cadherin-expression in IOMM-Lee cells.

N-cadherin upregulation mediates adaptive radioresistance in glioblastoma

Glioblastoma (GBM) is composed of heterogeneous tumor cell populations, including those with stem cell properties, termed glioma stem cells (GSCs). GSCs are innately less radiation sensitive than the tumor bulk and are believed to drive GBM formation and recurrence after repeated irradiation. However, it is unclear how GSCs adapt to escape the toxicity of repeated irradiation used in clinical practice. To identify important mediators of adaptive radioresistance in GBM, we generated radioresistant human and mouse GSCs by exposing them to repeat cycles of irradiation. Surviving subpopulations acquired strong radioresistance in vivo, which was accompanied by a reduction in cell proliferation and an increase in cell-cell adhesion and N-cadherin expression. Increasing N-cadherin expression rendered parental GSCs radioresistant, reduced their proliferation, and increased their stemness and intercellular adhesive properties. Conversely, radioresistant GSCs lost their acquired phenotypes upon CRISPR/Cas9-mediated knockout of N-cadherin. Mechanistically, elevated N-cadherin expression resulted in the accumulation of β-catenin at the cell surface, which suppressed Wnt/β-catenin proliferative signaling, reduced neural differentiation, and protected against apoptosis through Clusterin secretion. N-cadherin upregulation was induced by radiation-induced IGF1 secretion, and the radiation resistance phenotype could be reverted with picropodophyllin, a clinically applicable blood-brain-barrier permeable IGF1 receptor inhibitor, supporting clinical translation.

The Strange Case of Jekyll and Hyde: Parallels Between Neural Stem Cells and Glioblastoma-Initiating Cells

During embryonic development, radial glial precursor cells give rise to neural lineages, and a small proportion persist in the adult mammalian brain to contribute to long-term neuroplasticity. Neural stem cells (NSCs) reside in two neurogenic niches of the adult brain, the hippocampus and the subventricular zone (SVZ). NSCs in the SVZ are endowed with the defining stem cell properties of self-renewal and multipotent differentiation, which are maintained by intrinsic cellular programs, and extrinsic cellular and niche-specific interactions. In glioblastoma, the most aggressive primary malignant brain cancer, a subpopulation of cells termed glioblastoma stem cells (GSCs) exhibit similar stem-like properties. While there is an extensive overlap between NSCs and GSCs in function, distinct genetic profiles, transcriptional programs, and external environmental cues influence their divergent behavior. This review highlights the similarities and differences between GSCs and SVZ NSCs in terms of their gene expression, regulatory molecular pathways, niche organization, metabolic programs, and current therapies designed to exploit these differences.

Human giant larvae-1 promotes migration and invasion of malignant glioma cells by regulating N-cadherin

Human giant larvae-1 (Hugl-1) is a human homologue of Drosophila tumor suppressor lethal (2)-giant larvae and has been reported to be involved in the development of human malignancies. Previous studies performed by our group demonstrated that Hugl-1 inhibits glioma cell proliferation in an intracranial model of nude mice. However, the exact molecular mechanisms underlying the participation of Hugl-1 in glioma invasion and migration, and in the depolarizing process remain largely unknown. Utilizing the U251-MG cells with stable expression of Hugl-1, the present study used wound healing, Transwell invasion and western blot assays to explore the role and specific mechanism of Hugl-1 in glioma invasion and migration. The results of the present study demonstrated that overexpression of Hugl-1 decreased cell-cell adhesion and increased cell-cell extracellular matrix adhesion. In addition, overexpression of Hugl-1 promoted pseudopodia formation, glioma cell migration and invasion. The molecular mechanism of action involved the negative regulation of N-cadherin protein levels by Hugl-1. Overexpression or knockdown of N-cadherin partially suppressed or enhanced the effects of Hugl-1 on glioma cell migration and invasion, respectively. Furthermore, Hugl-1 inhibited cell proliferation, while promoting cell migration, which suggests that it may serve a two-sided biological role in cellular processes. Taken together, these results suggest that Hugl-1 promotes the migration and invasion of malignant glioma cells by decreasing N-cadherin expression. Thus, Hugl-1 may be applied in the development of targeted and personalized treatment.

The impact of autophagy during the development and survival of glioblastoma

Glioblastoma is the most common and aggressive adult brain tumour, with poor median survival and limited treatment options. Following surgical resection and chemotherapy, recurrence of the disease is inevitable. Genomic studies have identified key drivers of glioblastoma development, including amplifications of receptor tyrosine kinases, which drive tumour growth. To improve treatment, it is crucial to understand survival response processes in glioblastoma that fuel cell proliferation and promote resistance to treatment. One such process is autophagy, a catabolic pathway that delivers cellular components sequestered into vesicles for lysosomal degradation. Autophagy plays an important role in maintaining cellular homeostasis and is upregulated during stress conditions, such as limited nutrient and oxygen availability, and in response to anti-cancer therapy. Autophagy can also regulate pro-growth signalling and metabolic rewiring of cancer cells in order to support tumour growth. In this review, we will discuss our current understanding of how autophagy is implicated in glioblastoma development and survival. When appropriate, we will refer to findings derived from the role of autophagy in other cancer models and predict the outcome of manipulating autophagy during glioblastoma treatment.

Dual-specificity phosphatase (DUSP6) in human glioblastoma: epithelial-to-mesenchymal transition (EMT) involvement

Objective

Glioblastoma (GBM) is the most aggressive and common form of primary brain cancer. Survival is poor and improved treatment options are urgently needed. Dual specificity phosphatase-6 (DUSP6) is actively involved in oncogenesis showing unexpected tumor-promoting properties in human glioblastoma, contributing to the development and expression of the full malignant and invasive phenotype. The purpose of this study was to assess if DUSP6 activates epithelial-to-mesenchymal transition (EMT) in glioblastoma and its connection with the invasive capacity.

Results

We found high levels of transcripts mRNA by qPCR analysis in a panel of primary GBM compared to adult or fetal normal tissues. At translational levels, these data correlate with high protein expression and long half-life values by cycloheximide-chase assay in immunoblot experiments. Next, we demonstrate that DUSP6 gene is involved in epithelial-to-mesenchymal transition (EMT) in GBM by immunoblot characterization of the mesenchymal and epithelial markers. Vimentin, N-Cadherin, E-Cadherin and fibronectin were measured with and without DUSP6 over-expression, and in response to several stimuli such as chemotherapy treatment. In particular, the high levels of vimentin were blunted at increasing doses of cisplatin in condition of DUSP6 over-expression while N-Cadherin contextually increased. Finally, DUSP6 per se increased invasion capacity of GBM. Overall, our data unveil the DUSP6 involvement in invasive mesenchymal-like properties in GBM.

Tumor Cell Invasion in Glioblastoma

Glioblastoma (GBM) is a particularly devastating tumor with a median survival of about 16 months. Recent research has revealed novel insights into the outstanding heterogeneity of this type of brain cancer. However, all GBM subtypes share the hallmark feature of aggressive invasion into the surrounding tissue. Invasive glioblastoma cells escape surgery and focal therapies and thus represent a major obstacle for curative therapy. This review aims to provide a comprehensive understanding of glioma invasion mechanisms with respect to tumor-cell-intrinsic properties as well as cues provided by the microenvironment. We discuss genetic programs that may influence the dissemination and plasticity of GBM cells as well as their different invasion patterns. We also review how tumor cells shape their microenvironment and how, vice versa, components of the extracellular matrix and factors from non-neoplastic cells influence tumor cell motility. We further discuss different research platforms for modeling invasion. Finally, we highlight the importance of accounting for the complex interplay between tumor cell invasion and treatment resistance in glioblastoma when considering new therapeutic approaches.

The Role of BEHAB/Brevican in the Tumor Microenvironment: Mediating Glioma Cell Invasion and Motility

Malignant gliomas are the most common tumors in the central nervous system (CNS) and, unfortunately, are also the most deadly. The lethal nature of malignant gliomas is due in large part to their unique and distinctive ability to invade the surrounding neural tissue. The invasive and dispersive nature of these tumors makes them particularly challenging to treat, and currently there are no effective therapies for malignant gliomas. The brain tumor microenvironment plays a particularly important role in mediating the invasiveness of gliomas, and, therefore, understanding its function is key to developing novel therapies to treat these deadly tumors. A defining aspect of the tumor microenvironment of gliomas is the unique composition of the extracellular matrix that enables tumors to overcome the typically inhibitory environment found in the CNS. One conspicuous component of the glioma tumor microenvironment is the neural-specific ECM molecule, brain-enriched hyaluronan binding (BEHAB)/brevican (B/b). B/b is highly overexpressed in gliomas, and its expression in these tumors contributes importantly to the tumor invasiveness and aggressiveness. However, B/b is a complicated protein with multiple splice variants, cleavage products, and glycoforms that contribute to its complex functions in these tumors and provide unique targets for tumor therapy. Here we review the role of B/b in glioma tumor microenvironment and explore targeting of this protein for glioma therapy.

Upregulation of Epithelial-To-Mesenchymal Transition Markers and P2X7 Receptors Is Associated to Increased Invasiveness Caused by P2X7 Receptor Stimulation in Human Glioblastoma Stem Cells

Glioblastoma (GBM) stem cells (GSCs), which contribute to GBM unfavorable prognosis, show high expression levels of ATP/P2X7 receptors (P2X7R). Here, we reported that cells exposure to 2’(3’)-O-(4-benzoylbenzoyl)-ATP (BzATP), a P2X7R agonist, up-regulated the expression of markers associated to epithelial-to-mesenchymal transition (EMT), a process likely contributing to GSC malignancy, and increased GSC migration/invasiveness like the known EMT inducer, Transforming Growth Factor β1 (TGFβ1). These effects were coupled to phosphorylation of SMAD2, a downstream effector in the TGFβ pathway, suggesting its involvement in P2X7R-mediated activity in GSCs. All BzATP effects, including a decrease in the caspase 3/7 activity in GSC medium, were mostly counteracted by the P2X7R antagonist A438079. Finally, BzATP increased the subunit expression of two main human P2X7R splice variants, the full-length P2X7A and the truncated P2X7B, lacking the carboxylic tail, which have different functional properties depending on their arrangement. Since up-regulation of A/B subunits might favor their assembly into a heterotrimeric P2X7R with great sensitivity towards agonists and cell energy support, this is in line with increased EMT markers expression, cell migration/invasion and GSC survival observed following P2X7R stimulation. As in GBM microenvironment extracellular ATP levels may activate P2X7R, our data suggest a P2X7R role in GBM recurrence/invasiveness.

Native and iron-saturated bovine lactoferrin differently hinder migration in a model of human glioblastoma by reverting epithelial-to-mesenchymal transition-like process and inhibiting interleukin-6/STAT3 axis

Glioblastoma, the most lethal form of brain cancer, is characterized by fast growth, migration and invasion of the surrounding parenchyma, with epithelial-to-mesenchymal transition (EMT)-like process being mostly responsible for tumour spreading and dissemination. A number of actors, including cadherins, vimentin, transcriptional factors such as SNAIL, play critical roles in the EMT process. The interleukin (IL)-6/STAT3 axis has been related to enhanced glioblastoma's migration and invasion abilities as well. Here, we present data on the differential effects of native and iron-saturated bovine lactoferrin (bLf), an iron-chelating glycoprotein of the innate immune response, in inhibiting migration in a human glioblastoma cell line. Through a wound healing assay, we found that bLf was able to partially or completely hinder cell migration, depending on its iron saturation rate. At a molecular level, bLf down-regulated both SNAIL and vimentin expression, while inducing a notable increase in cadherins' levels and inhibiting IL-6/STAT3 axis. Again, these effects positively correlated to bLf iron-saturation state, with the Holo-form resulting more efficient than the native one. Overall, our data suggest that bLf could represent a novel and efficient adjuvant treatment for glioblastoma's standard therapeutic approaches.

De Novo Pathogenic Variants in N-cadherin Cause a Syndromic Neurodevelopmental Disorder with Corpus Collosum, Axon, Cardiac, Ocular, and Genital Defects

Cadherins constitute a family of transmembrane proteins that mediate calcium-dependent cell-cell adhesion. The extracellular domain of cadherins consists of extracellular cadherin (EC) domains, separated by calcium binding sites. The EC interacts with other cadherin molecules in cis and in trans to mechanically hold apposing cell surfaces together. CDH2 encodes N-cadherin, whose essential roles in neural development include neuronal migration and axon pathfinding. However, CDH2 has not yet been linked to a Mendelian neurodevelopmental disorder. Here, we report de novo heterozygous pathogenic variants (seven missense, two frameshift) in CDH2 in nine individuals with a syndromic neurodevelopmental disorder characterized by global developmental delay and/or intellectual disability, variable axon pathfinding defects (corpus callosum agenesis or hypoplasia, mirror movements, Duane anomaly), and ocular, cardiac, and genital anomalies. All seven missense variants (c.1057G>A [p.Asp353Asn]; c.1789G>A [p.Asp597Asn]; c.1789G>T [p.Asp597Tyr]; c.1802A>C [p.Asn601Thr]; c.1839C>G [p.Cys613Trp]; c.1880A>G [p.Asp627Gly]; c.2027A>G [p.Tyr676Cys]) result in substitution of highly conserved residues, and six of seven cluster within EC domains 4 and 5. Four of the substitutions affect the calcium-binding site in the EC4-EC5 interdomain. We show that cells expressing these variants in the EC4-EC5 domains have a defect in cell-cell adhesion; this defect includes impaired binding in trans with N-cadherin-WT expressed on apposing cells. The two frameshift variants (c.2563_2564delCT [p.Leu855Valfs^∗4]; c.2564_2567dupTGTT [p.Leu856Phefs^∗5]) are predicted to lead to a truncated cytoplasmic domain. Our study demonstrates that de novo heterozygous variants in CDH2 impair the adhesive activity of N-cadherin, resulting in a multisystemic developmental disorder, that could be named ACOG syndrome (agenesis of corpus callosum, axon pathfinding, cardiac, ocular, and genital defects).

Molecular and Clinical Insights into the Invasive Capacity of Glioblastoma Cells

The invasive capacity of GBM is one of the key tumoral features associated with treatment resistance, recurrence, and poor overall survival. The molecular machinery underlying GBM invasiveness comprises an intricate network of signaling pathways and interactions with the extracellular matrix and host cells. Among them, PI3k/Akt, Wnt, Hedgehog, and NFkB play a crucial role in the cellular processes related to invasion. A better understanding of these pathways could potentially help in developing new therapeutic approaches with better outcomes. Nevertheless, despite significant advances made over the last decade on these molecular and cellular mechanisms, they have not been translated into the clinical practice. Moreover, targeting the infiltrative tumor and its significance regarding outcome is still a major clinical challenge. For instance, the pre- and intraoperative methods used to identify the infiltrative tumor are limited when trying to accurately define the tumor boundaries and the burden of tumor cells in the infiltrated parenchyma. Besides, the impact of treating the infiltrative tumor remains unclear. Here we aim to highlight the molecular and clinical hallmarks of invasion in GBM.

Alternative splicing-derived intersectin1-L and intersectin1-S exert opposite function in glioma progression

Intersectin1 (ITSN1) contains two isoforms: ITSN1-S and ITSN1-L, which is highly regulated by alternative splicing. However, the alteration of alternative splicing and its importance in cancer is still unknown. In this study, our transcriptome analysis by using a large glioma cohort indicated the two isoforms exerted opposite function in glioma progression. Our previous results had shown ITSN1-S could promote glioma development; however, the function of ITSN1-L remained unknown. In this study, we first confirmed that ITSN1-L exerted an inhibitory role in glioma progression both in vivo and in vitro, which was contrary to the function of ITSN1-S. In additional, we also elucidated the mechanisms of ITSN1-L in inhibiting tumor progression. First, we revealed ITSN1-L could interact with α-tubulin to promote HDAC6-dependent deacetylation of ac-tubulin leading to decreased cell motility. Second, ITSN1-L could attenuate cell-substrate adhesion through FAK/integrin β3 pathway. Third, ITSN1-L was able to strengthen cell-cell adhesion by upregulating N-cadherin expression and its re-localization to membrane by ANXA2 and TUBB3/TUBB4. In conclusion, we found for the first time that two isoforms produced by alternative splicing exerted opposite functions in glioma development. Therefore, upregulation of ITSN1-L expression as well as downregulation of ITSN1-S expression probably was a better strategy in glioma treatment. Our present study laid a foundation for the importance of alternative splicing in glioma progression and raised the possibility of controlling glioma development completely at an alternative splicing level to be a more effective strategy.

Increased DKC1 expression in glioma and its significance in tumor cell proliferation, migration and invasion

The dyskeratosis congenita 1 (DKC1) gene is located on the X chromosome at Xq28. Dyskerin encoded by the DKC1 gene is associated with the formation of certain small RNAs and the telomerase activity. Inherited mutations in DKC1 inactivate the dyskerin and causes dyskeratosis congenital, which is characterized by skin defects, hematopoiesis failure, and increased susceptibility to cancer. DKC1 reportedly up-regulates in several human cancers, including renal cell carcinoma and prostate cancer. Dyskerin is deregulated in B-chronic lymphocytic leukemia and breast carcinomas, but its expression and function in glioma have hardly been investigated. Hence, we were prompted to collect tissue samples and implement cell experiments. Our study reveals that DKC1 expression is significantly increased in the pathological tissues of glioma compared with that in normal tissues. The increased staining of DKC1 is related to the World Health Organization stages of tumors. DKC1 knockdown also significantly inhibits glioma cell growth by altering the expression of cell cycle-relative molecules to arrest at the G1 phase. In the transwell chamber, DKC1 knockdown glioma cells exhibit low motility. Consistent with classic oncogenic pathways, N-cadherin, HIF-1α, and MMP2 expression levels are lower compared with those of the control group. Therefore, DKC1 up-regulation in gliomas is common and necessary for extensive tumor growth. The phenotype of glioma cell lines after DKC1 down-regulation suggests its use as a valuable clinical treatment strategy.

EMT Regulation by Autophagy: A New Perspective in Glioblastoma Biology

Epithelial-to-mesenchymal transition (EMT) and its reverse process MET naturally occur during development and in tissue repair in vertebrates. EMT is also recognized as the crucial event by which cancer cells acquire an invasive phenotype through the activation of specific transcription factors and signalling pathways. Even though glial cells have a mesenchymal phenotype, an EMT-like process tends to exacerbate it during gliomagenesis and progression to more aggressive stages of the disease. Autophagy is an evolutionary conserved degradative process that cells use in order to maintain a proper homeostasis, and defects in autophagy have been associated to several pathologies including cancer. Besides modulating cell resistance or sensitivity to therapy, autophagy also affects the migration and invasion capabilities of tumor cells. Despite this evidence, few papers are present in literature about the involvement of autophagy in EMT-like processes in glioblastoma (GBM) so far. This review summarizes the current understanding of the interplay between autophagy and EMT in cancer, with special regard to GBM model. As the invasive behaviour is a hallmark of GBM aggressiveness, defining a new link between autophagy and EMT can open a novel scenario for targeting these processes in future therapeutical approaches.

The Opposing Contribution of SMS1 and SMS2 to Glioma Progression and Their Value in the Therapeutic Response to 2OHOA

Background: 2-Hydroxyoleic acid (2OHOA) is particularly active against glioblastoma multiforme (GBM) and successfully finished a phase I/IIA trial in patients with glioma and other advanced solid tumors. However, its mechanism of action is not fully known. Methods: The relationship between SMS1 and SMS2 expressions (mRNA) and overall survival in 329 glioma patients was investigated, and so was the correlation between SMS expression and 2OHOA's efficacy. The opposing role of SMS isoforms in 2OHOA's mechanism of action and in GBM cell growth, differentiation and death, was studied overexpressing or silencing them in human GBM cells. Results: Patients with high-SMS1 plus low-SMS2 expression had a 5-year survival ~10-fold higher than patients with low-SMS1 plus high-SMS2 expression. SMS1 and SMS2 also had opposing effect on GBM cell survival and 2OHOA's IC₅₀ correlated with basal SMS1 levels and treatment induced changes in SMS1/SMS2 ratio. SMSs expression disparately affected 2OHOA's cancer cell proliferation, differentiation, ER-stress and autophagy. Conclusions: SMS1 and SMS2 showed opposite associations with glioma patient survival, glioma cell growth and response to 2OHOA treatment. SMSs signature could constitute a valuable prognostic biomarker, with high SMS1 and low SMS2 being a better disease prognosis. Additionally, low basal SMS1 mRNA levels predict positive response to 2OHOA.

EMT-like process in glioblastomas and reactive astrocytes

The concept of the epithelial-to-mesenchymal transition (EMT) in epithelial cells has accelerated our understanding about cancer spreading. Fortunately, much of this information has been able to be extrapolated to non-epithelial cancers, such as glioblastoma (GBM). Interestingly, reactive astrocytes, which are present in the tumor edge in association with glioma cells, might also undergo EMT-like under stimuli of GBM cells. As result, the positive feedback of reactive astrocytes and glioma cells, could act to promote cancer progression making use of the dynamism of the mesenchymal phenotype. Nonetheless, the interpretation of data regarding EMT-like in GBM and astrocytes requires prudence, mainly because the program of EMT in epithelial tumors may not necessarily be the same as those in gliomas and astrocytes.

Integrating in vitro experiments with in silico approaches for Glioblastoma invasion: the role of cell-to-cell adhesion heterogeneity

Glioblastoma cells adopt migration strategies to invade into the brain parenchyma ranging from individual to collective mechanisms, whose role and dynamics are not yet fully understood. In this work, we explore Glioblastoma heterogeneity and recapitulate its invasive patterns both in vitro, by utilizing primary cells along with the U87MG cell line, and in silico, by adopting discrete, individual cell-based mathematics. Glioblastoma cells are cultured three-dimensionally in an ECM-like substrate. The primary Glioblastoma spheroids adopt a novel cohesive pattern, mimicking perivascular invasion in the brain, while the U87MG adopt a typical, starburst invasive pattern under the same experimental setup. Mathematically, we focus on the role of the intrinsic heterogeneity with respect to cell-to-cell adhesion. Our proposed mathematical approach mimics the invasive morphologies observed in vitro and predicts the dynamics of tumour expansion. The role of the proliferation and migration is also explored showing that their effect on tumour morphology is different per cell type. The proposed model suggests that allowing cell-to-cell adhesive heterogeneity within the tumour population is sufficient for variable invasive morphologies to emerge which remain originally undetectable by conventional imaging, indicating that exploration in pathological samples is needed to improve our understanding and reveal potential patient-specific therapeutic targets.

Autophagy induction impairs Wnt/β-catenin signalling through β-catenin relocalisation in glioblastoma cells

Autophagy is an evolutionary conserved process mediating lysosomal degradation of cytoplasmic material. Its involvement in cancer progression is highly controversial, due to its dual role in both limiting tumoural transformation and in protecting established tumoral cells from unfavorable conditions. Little is known about the cross-talk between autophagy and intracellular signalling pathways, as well as about autophagy impact on signalling molecules turnover. An aberrantly activated Wnt/β-catenin signalling is responsible for tumour proliferation, invasion, and stemness maintenance. Here we show that autophagy negatively regulates Wnt/β-catenin signalling in glioblastoma multiforme (GBM) cells, through Dishevelled degradation. We also provide the first evidence that autophagy promotes β-catenin relocalisation within the cell, by inducing a decrease of the nuclear protein fraction. In particular, upon autophagy induction, β-catenin appears mainly localized in sub-membrane areas where it associates with N-cadherin to form epithelial-like cell-cell adhesion structures. Our data indicate, for the first time, that autophagy induction results in Wnt signalling attenuation and in β-catenin relocalisation within the GBM cell. These findings further support the idea that autophagy modulation could represent a potential therapeutical strategy to contrast GBM progression.

Precursor N-cadherin mediates glial cell line-derived neurotrophic factor-promoted human malignant glioma

As the most prevalent primary brain tumor, gliomas are highly metastatic, invasive and are characteristic of high levels of glial cell-line derived neurotrophic factor (GDNF). GDNF is an important factor for invasive glioma cell growth; however, the underlying mechanism involved is unclear. In this study, we affirm a significantly higher expression of the precursor of N-cadherin (proN-cadherin) in most gliomas compared with normal brain tissues. Our findings reveal that GDNF interacts with the extracellular domain of proN-cadherin, which suggests that proN-cadherin mediates GDNF-induced glioma cell migration and invasion. We hypothesize that proN-cadherin might cause homotypic adhesion loss within neighboring cells and at the same time promote heterotypic adhesion within the extracellular matrix (ECM) through a certain mechanism. This study also demonstrates that the interaction between GDNF and proN-cadherin activates specific intracellular signaling pathways; furthermore, GDNF promoted the secretion of matrix metalloproteinase-9 (MMP-9), which degrades the ECM via proN-cadherin. To reach the future goal of developing novel therapies of glioma, this study, reveals a unique mechanism of glioma cell migration and invasion.

Increased expression of EphA2 and E-N cadherin switch in primary hepatocellular carcinoma

Aim

To investigate the expression and clinical significance of ephrin type-A receptor 2 and epithelial-mesenchymal transition-related proteins in primary hepatocellular carcinoma.

Methods

Tissues from 52 primary hepatocellular carcinomas and 12 human normal liver tissues were detected for expression of ephrin type-A receptor 2, E-cadherin, and N-cadherin by immunochemistry. Cinicopathological features of hepatocellular carcinoma and tumor recurrence after operation were studied for the association with these molecular expressions and E-N cadherin switch.

Results

Increased expressions of ephrin type-A receptor 2 and N-cadherin and reduced expression of E-cadherin were significantly detected in hepatocellular carcinoma compared with normal liver tissues. Univariate analysis showed that there were close associations between unfavorable clinicopathological features and expressions of ephrin type-A receptor 2, E-cadherin, N-cadherin, and E-N cadherin switch. Ephrin type-A receptor 2 and E-cadherin expressions were confirmed as independent prognostic factors when corrected with age, gender, AFP, HBsAg, liver cirrhosis, tumor size, nodules, capsule, portal vein invasion, cell differentiation, and TNM stage.

Conclusions

The overexpression of ephrin type-A receptor 2 protein is correlated with the number of tumors, capsular integrity, portal vein cancer thrombus and clinical stages. Epithelial-mesenchymal transition regulated by ephrin type-A receptor 2 is involved in the aggressive clinicopathological features and prognosis, suggesting that the receptor may play an important role in the progression and metastasis of hepatocellular carcinoma.

Homeobox B3 promotes tumor cell proliferation and invasion in glioblastoma

Glioblastoma (GBM) is the most aggressive brain tumor in adults with the highest mortality rate. Despite advances achieved in treatment and research, the median survival for patients with GBM remains <1.5 years. This figure prompted the present study to identify novel genes associated with GBM development and progression to ultimately improve GBM treatment. The current study sought to determine the role of homeobox B3 (HOXB3) in GBM cell invasion and proliferation. HOXB3 was highly expressed in GBM tissues and glioma cell lines. To establish in vitro cell models for investigation, U87-MG and U251-MG, two typical GBM cells, were selected to generate corresponding cells lines that constitutively silenced HOXB3 expression using a lentivirus-mediated RNA interference approach. The results of the knockdown revealed that glioma cells stably expressing HOXB3 short hairpin RNA exhibited significantly decreased proliferation levels when compared with untransfected cells. The effect of HOXB3 on glioma cell invasion was also examined. Silencing of HOXB3 resulted in a marked reduction in invasiveness. Furthermore, HOXB3 silencing led to the upregulation of E-cadherin and downregulation of mesenchymal markers, N-cadherin and vimentin. Taken together, the findings of the present study indicate that HOXB3 promotes cell proliferation and invasion.

Inhibition of glioblastoma dispersal by the MEK inhibitor PD0325901

Background

Dispersal of glioblastoma (GBM) cells leads to recurrence and poor prognosis. Accordingly, molecular pathways involved in dispersal are potential therapeutic targets. The mitogen activated protein kinase/extracellular signal regulated kinase (MAPK/ERK) pathway is commonly dysregulated in GBM, and targeting this pathway with MEK inhibitors has proven effective in controlling tumor growth. Since this pathway also regulates ECM remodeling and actin organization − processes crucial to cell adhesion, substrate attachment, and cell motility – the aim of this study was to determine whether inhibiting this pathway could also impede dispersal.

Methods

A variety of methods were used to quantify the effects of the MEK inhibitor, PD0325901, on potential regulators of dispersal. Cohesion, stiffness and viscosity were quantified using a method based on ellipsoid relaxation after removal of a deforming external force. Attachment strength, cell motility, spheroid dispersal velocity, and 3D growth rate were quantified using previously described methods.

Results

We show that PD0325901 significantly increases aggregate cohesion, stiffness, and viscosity but only when tumor cells have access to high concentrations of fibronectin. Treatment also results in reorganization of actin from cortical into stress fibers, in both 2D and 3D culture. Moreover, drug treatment localized pFAK at sites of cell-substratum adhesion. Collectively, these changes resulted in increased strength of substrate attachment and decreased motility, a decrease in aggregate dispersal velocity, and in a marked decrease in growth rate of both 2D and 3D cultures.

Conclusions

Inhibition of the MAPK/ERK pathway by PD0325901 may be an effective therapy for reducing dispersal and growth of GBM cells.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-017-3107-x) contains supplementary material, which is available to authorized users.

Forkhead box P3 regulates ARHGAP15 expression and affects migration of glioma cells through the Rac1 signaling pathway

Forkhead box P3 (FOXP3) plays a crucial role in the development and function of regulatory T cells and was recently identified as a tumor suppressor in different cancer types. Forkhead box P3 is expressed in normal brain tissues, but is strongly downregulated or absent in glioblastomas. In order to understand the FOXP3 adjustment mechanisms in glioma cells, we performed a DNA microarray in U87 cells overexpressing FOXP3 and validated the differences using quantitative real‐time PCR, Western blot analysis, and immunohistochemistry in vitro and in vivo. We found that FOXP3 can regulate the expression of ARHGAP15. Expression of FOXP3 was also correlated with ARHGAP15 in glioma samples. Overexpression of FOXP3 inhibited glioma cell migration through ARHGAP15 upregulation and Rac1 inactivation. Silencing of FOXP3 promoted migration through ARHGAP15 downregulation and Rac1 activation. ARHGAP15, a GTPase‐activating protein for Rac1, inhibits small GTPase signaling in a dual negative manner. We found that there is a correlation between expression of ARHGAP15 and glioma level. The small GTPase Rac1 plays an important role in cell migration. In addition, we found that FOXP3 regulates expression of epithelial–mesenchymal transition markers E‐cadherin and N‐cadherin, which is important given that epithelial–mesenchymal transition is critically involved in tumor spreading and dissemination. Thus, FOXP3 or ARHGAP15 may serve as a new molecular target for antimetastatic therapies in treating glioma.

Analysis of cellular and molecular antitumor effects upon inhibition of SATB1 in glioblastoma cells

Background

The Special AT-rich Sequence Binding Protein 1 (SATB1) regulates the expression of many genes by acting as a global chromatin organizer. While in many tumor entities SATB1 overexpression has been observed and connected to pro-tumorigenic processes, somewhat contradictory evidence exists in brain tumors with regard to SATB1 overexpression in glioblastoma and its association with poorer prognosis and tumor progression. On the functional side, initial data indicate that SATB1 may be involved in several tumor cell-relevant processes.

Methods

For the detailed analysis of the functional relevance and possible therapeutic potential of SATB1 inhibition, we employ transient siRNA-mediated knockdown and comprehensively analyze the cellular and molecular role of SATB1 in glioblastoma.

Results

In various cell lines with different SATB1 expression levels, a SATB1 gene dose-dependent inhibition of anchorage-dependent and –independent proliferation is observed. This is due to cell cycle-inhibitory and pro-apoptotic effects of SATB1 knockdown. Molecular analyses reveal SATB1 knockdown effects on multiple important (proto-) oncogenes, including Myc, Bcl-2, Pim-1, EGFR, β-catenin and Survivin. Molecules involved in cell cycle, EMT and cell adhesion are affected as well. The putative therapeutic relevance of SATB1 inhibition is further supported in an in vivo tumor xenograft mouse model, where the treatment with polymeric nanoparticles containing SATB1-specific siRNAs exerts antitumor effects.

Conclusion

Our results demonstrate that SATB1 may represent a promising target molecule in glioblastoma therapy whose inhibition or knockdown affects multiple crucial pathways.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-016-3006-6) contains supplementary material, which is available to authorized users.

Adhering towards tumorigenicity: altered adhesion mechanisms in glioblastoma cancer stem cells

Glioblastoma (GBM) is the most aggressive malignant primary brain tumor in adults with a high recurrence and mortality rate. GBM tumors contain a high degree of cellular heterogeneity, with cells exhibiting stem-like properties (cancer stem cells; CSCs) that are highly efficient at tumor initiation and are resistant to conventional therapies. CSCs interact with their tumor microenvironment by a large group of diverse cell adhesion molecules (CAMs) that participate in intercellular, intracellular and cell-extracellular matrix interactions. Despite the initial description of CAMs as tumor suppressors, recent work has highlighted specific CAMs that are essential for CSC maintenance and tumor progression. This review will highlight recent findings that provide support for a context-specific role of CAMs in CSC function and GBM progression.

KITENIN promotes glioma invasiveness and progression, associated with the induction of EMT and stemness markers

KITENIN (KAI1 COOH-terminal interacting tetraspanin) promotes tumor invasion and metastasis in various cancers. This study assessed the association between KITENIN expression and advanced glioma grade in patients. In vitro assays revealed that KITENIN knockdown inhibited the invasion and migration of glioma cells, whereas KITENIN overexpression promoted their invasion and migration. In orthotopic mouse tumor models, mice transplanted with KITENIN-transfected glioma cells had significantly shorter survival than mice transplanted with mock-transfected cells. Patients with low KITENIN expression showed a significantly longer progression-free survival than patients with high KITENIN expression. KITENIN induced the expression of the epithelial-mesenchymal transition (EMT) markers (N-cadherin, ZEB1, ZEB2, SNAIL and SLUG) as well as the glioma stemness markers (CD133, ALDH1 and EPH-B1). Taken together, these findings showed that high levels of KITENIN increased glioma invasiveness and progression, associated with the up-regulation of EMT and stemness markers.

Life is three dimensional-as in vitro cancer cultures should be

For many decades, fundamental cancer research has relied on two-dimensional in vitro cell culture models. However, these provide a poor representation of the complex three-dimensional (3D) architecture of living tissues. The more recent 3D culture systems, which range from ridged scaffolds to semiliquid gels, resemble their natural counterparts more closely. The arrangement of the cells in 3D systems allows better cell-cell interaction and facilitates extracellular matrix secretion, with concomitant effects on gene and protein expression and cellular behavior. Many studies have reported differences between 3D and 2D systems as regards responses to therapeutic agents and pivotal cellular processes such as cell differentiation, morphology, and signaling pathways, demonstrating the importance of 3D culturing for various cancer cell lines.

The ZEB1 pathway links glioblastoma initiation, invasion and chemoresistance

Glioblastoma remains one of the most lethal types of cancer, and is the most common brain tumour in adults. In particular, tumour recurrence after surgical resection and radiation invariably occurs regardless of aggressive chemotherapy. Here, we provide evidence that the transcription factor ZEB1 (zinc finger E-box binding homeobox 1) exerts simultaneous influence over invasion, chemoresistance and tumourigenesis in glioblastoma. ZEB1 is preferentially expressed in invasive glioblastoma cells, where the ZEB1-miR-200 feedback loop interconnects these processes through the downstream effectors ROBO1, c-MYB and MGMT. Moreover, ZEB1 expression in glioblastoma patients is predictive of shorter survival and poor Temozolomide response. Our findings indicate that this regulator of epithelial-mesenchymal transition orchestrates key features of cancer stem cells in malignant glioma and identify ROBO1, OLIG2, CD133 and MGMT as novel targets of the ZEB1 pathway. Thus, ZEB1 is an important candidate molecule for glioblastoma recurrence, a marker of invasive tumour cells and a potential therapeutic target, along with its downstream effectors.

Cadmium induces N-cadherin cleavage via ERK-mediated γ-secretase activation in C6 astroglia cells

N-cadherin has known to be involved in tumor progression and metastasis. However, it is still obscure about the signaling pathway involving in the processing of N-cadherin. Thus, we examined which signaling pathway plays a major role in the processing of N-cadherin in C6 glioma cells following treatment of cadmium (Cd), a highly ubiquitous heavy metal. A cleavage product of N-cadherin, N-cad/CTF2 was observed by the treatment of Cd to C6 cells in a time and concentration-dependent manner. The production of N-cad/CTF2 was inhibited by pretreatment of γ-secretase inhibitors or siRNA transfection of nicastrin, indicating that γ-secretase is involved in the cleavage. Interestingly, Cd could activate both ERK and JNK signaling pathways in C6 cells; however, γ-secretase-mediated N-cad/CTF2 production by Cd was completely blocked by MEK1/2 inhibitors PD184352 and U0126, but not by a JNK inhibitor SP600125, demonstrating that the ERK signaling pathway plays a major role in the cleavage. In addition, pretreatment of an antioxidant or Ca²⁺ blocker blocked the production of N-cad/CTF2 by Cd together with the inhibition of ERK1/2 phosphorylation. Collectively, these results suggest that Cd increases intracellular Ca²⁺ or ROS, which induces γ-secretase-dependent N-cad/CTF2 production via the activation of the ERK signaling pathway in C6 glial cells.