Lost in disruption: Role of proteases in glioma invasion and progression

Collagen and derivatives-based materials as substrates for the establishment of glioblastoma organoids

Glioblastoma (GBM) is a common primary brain malignancy known for its ability to invade the brain, resistance to chemotherapy and radiotherapy, tendency to recur frequently, and unfavorable prognosis. Attempts have been undertaken to create 2D and 3D models, such as glioblastoma organoids (GBOs), to recapitulate the glioma microenvironment, explore tumor biology, and develop efficient therapies. However, these models have limitations and are unable to fully recapitulate the complex networks formed by the glioma microenvironment that promote tumor cell growth, invasion, treatment resistance, and immune escape. Therefore, it is necessary to develop advanced experimental models that could better simulate clinical physiology. Here, we review recent advances in natural biomaterials (mainly focus on collagen and its derivatives)-based GBO models, as in vitro experimental platforms to simulate GBM tumor biology and response to tested drugs. Special attention will be given to 3D models that use collagen, gelatin, further modified derivatives, and composite biomaterials (e.g., with other natural or synthetic polymers) as substrates. Application of these collagen/derivatives-constructed GBOs incorporate the physical as well as chemical characteristics of the GBM microenvironment. A perspective on future research is given in terms of current issues. Generally, natural materials based on collagen/derivatives (monomers or composites) are expected to enrich the toolbox of GBO modeling substrates and potentially help to overcome the limitations of existing models.

ADAMTS1 as potential prognostic biomarker promotes malignant invasion of glioma

BACKGROUND

Glioma is the most common intracranial malignancy in adults with a high degree of malignancy and poor prognosis, which is largely attributed to the existence of glioma stem cells (GSCs). Previous evidence indicated that the matrix metalloproteinase ADAMTS1 was implicated in the process of tumor invasion, but the involvement of ADAMTS1 in glioma malignant invasion remains poorly understood.

METHODS

The expression and prognosis values of ADAMTS1 were investigated in patients with glioma based on ONCOMINE and GEPIA databases. ADAMTS1 expression of different malignancy grade tissues was determined by immunohistochemistry. The effects of ADAMTS1 on cell proliferation and invasion were determined by clone formation assay and Transwell migration assay. The animal experiment was performed in an intracranial orthotopic xenograft model by knockout of ADAMTS1. Stemness properties and Notch1-SOX2 pathway were examined in stable ADAMTS1 knockdown GSCs.

RESULTS

The expression levels of ADAMTS1 were significantly higher in glioma tissues and significantly correlated with the grade of malignancy and prognosis of glioma. Elevated ADAMTS1 expression was associated with SOX2, N-cadherin and the resistance of chemoradiotherapy of glioma patients. ADAMTS1 knockout suppressed the intracranial orthotopic xenograft growth and prolonged the survival of xenograft mice in vivo. Mechanistically, we found a blockade of the migration and invasiveness of GSCs and the expression levels of Notch1 and SOX2 in absence of ADAMTS1.

CONCLUSION

As a biomarker for prediction of prognosis, ADAMTS1 may affect the invasive phenotype of GSCs by regulating Notch1-SOX2 signaling pathway, thereby promoting the invasive growth of glioma.

A Disintegrin and Metalloproteinase (ADAM) Family-Novel Biomarkers of Selected Gastrointestinal (GI) Malignancies?

The global burden of gastrointestinal (GI) cancers is expected to increase. Therefore, it is vital that novel biomarkers useful for the early diagnosis of these malignancies are established. A growing body of data has linked secretion of proteolytic enzymes, such as metalloproteinases (MMPs), which destroy the extracellular matrix, to pathogenesis of GI tumours. A disintegrin and metalloproteinase (ADAM) proteins belong to the MMP family but have been proven to be unique due to both proteolytic and adhesive properties. Recent investigations have demonstrated that the expression of several ADAMs is upregulated in GI cancer cells. Thus, the objective of this review is to present current findings concerning the role of ADAMs in the pathogenesis of GI cancers, particularly their involvement in the development and progression of colorectal, pancreatic and gastric cancer. Furthermore, the prognostic significance of selected ADAMs in patients with GI tumours is also presented. It has been proven that ADAM8, 9, 10, 12, 15, 17 and 28 might stimulate the proliferation and invasion of GI malignancies and may be associated with unfavourable survival. In conclusion, this review confirms the role of selected ADAMs in the pathogenesis of the most common GI cancers and indicates their promising significance as potential prognostic biomarkers as well as therapeutic targets for GI malignancies. However, due to their non-specific nature, future research on ADAM biology should be performed to elucidate new strategies for the diagnosis of these common and deadly malignancies and treatment of patients with these diseases.

Hemodynamic molecular imaging of tumor-associated enzyme activity in the living brain

Molecular imaging could have great utility for detecting, classifying, and guiding treatment of brain disorders, but existing probes offer limited capability for assessing relevant physiological parameters. Here, we describe a potent approach for noninvasive mapping of cancer-associated enzyme activity using a molecular sensor that acts on the vasculature, providing a diagnostic readout via local changes in hemodynamic image contrast. The sensor is targeted at the fibroblast activation protein (FAP), an extracellular dipeptidase and clinically relevant biomarker of brain tumor biology. Optimal FAP sensor variants were identified by screening a series of prototypes for responsiveness in a cell-based bioassay. The best variant was then applied for quantitative neuroimaging of FAP activity in rats, where it reveals nanomolar-scale FAP expression by xenografted cells. The activated probe also induces robust hemodynamic contrast in nonhuman primate brain. This work thus demonstrates a potentially translatable strategy for ultrasensitive functional imaging of molecular targets in neuromedicine.

A Disintegrin and Metalloproteinase (ADAM) Family: Their Significance in Malignant Tumors of the Central Nervous System (CNS)

Despite the considerable advances in diagnostic methods in medicine, central nervous system (CNS) tumors, particularly the most common ones-gliomas-remain incurable, with similar incidence rates and mortality. A growing body of literature has revealed that degradation of the extracellular matrix by matrix metalloproteinases (MMPs) might be involved in the pathogenesis of CNS tumors. However, the subfamily of MMPs, known as disintegrin and metalloproteinase (ADAM) proteins are unique due to both adhesive and proteolytic activities. The objective of our review is to present the role of ADAMs in CNS tumors, particularly their involvement in the development of malignant gliomas. Moreover, we focus on the diagnostic and prognostic significance of selected ADAMs in patients with these neoplasms. It has been proven that ADAM12, ADAMTS4 and 5 are implicated in the proliferation and invasion of glioma cells. In addition, ADAM8 and ADAM19 are correlated with the invasive activity of glioma cells and unfavorable survival, while ADAM9, -10 and -17 are associated with tumor grade and histological type of gliomas and can be used as prognostic factors. In conclusion, several ADAMs might serve as potential diagnostic and prognostic biomarkers as well as therapeutic targets for malignant CNS tumors. However, future research on ADAMs biology should be performed to elucidate new strategies for tumor diagnosis and treatment of patients with these malignancies.

Melatonin improves cognitive behavior, oxidative stress, and metabolism in tumor-prone lethal giant larvae mutant of Drosophila melanogaster

Mutant lethal giant larvae (lgl) flies (Drosophila melanogaster) are known to develop epithelial tumors with invasive characteristics. The present study has been conducted to investigate the influence of melatonin (0.025 mM) on behavioral responses of lgl mutant flies as well as on biochemical indices (redox homeostasis, carbohydrate and lipid metabolism, transaminases, and minerals) in hemolymph, and head and intestinal tissues. Behavioral abnormalities were quantitatively observed in lgl flies but were found normalized among melatonin-treated lgl flies. Significantly decreased levels of lipid peroxidation products and antioxidants involved in redox homeostasis were observed in hemolymph and tissues of lgl flies, but had restored close to normalcy in melatonin-treated flies. Carbohydrates including glucose, trehalose, and glycogen were decreased and increased in the hemolymph and tissues of lgl and melatonin-treated lgl flies, respectively. Key enzymes of carbohydrate metabolism showed a significant increment in their levels in lgl mutants but had restored close to wild-type baseline levels in melatonin-treated flies. Variables of lipid metabolism showed significantly inverse levels in hemolymph and tissues of lgl flies, while normalization of most of these variables was observed in melatonin-treated mutants. Lipase, chitinase, transaminases, and alkaline phosphatase showed an increment in their activities and minerals exhibited decrement in lgl flies; reversal of changes was observed under melatonin treatment. The impairment of cognition, disturbance of redox homeostasis and metabolic reprogramming in lgl flies, and restoration of normalcy in all these cellular and behavioral processes indicate that melatonin could act as oncostatic and cytoprotective agents in Drosophila.

Effect of hnRNPA2/B1 on the proliferation and apoptosis of glioma U251 cells via the regulation of AKT and STAT3 pathways

Glioma is the most common malignant tumor in the human central nervous system. Although heterogeneous nuclear ribonucleoprotein A2/B1 (hnRNPA2/B1) was previously presumed to be a tumor-promoting gene, the relationship between hnRNPA2/B1 and glioma is unclear. Targeting hnRNPA2/B1 interference in glioma cells can significantly inhibit proliferation and increase apoptosis of human glioma cells in vitro. In a tumor xenograft model, knockdown of hnRNPA2/B1 suppressed tumor growth in glioma cells in vivo. In terms of a mechanism, the knockdown of hnRNPA2/B1 led to inactivation of the AKT and STAT3 signaling pathways, which ultimately reduced the expression of B-cell lymphoma-2 (Bcl-2), CyclinD1 and proliferating cell nuclear antigen (PCNA). Collectively, these data suggest that the inhibition of hnRNPA2/B1 can reduce the growth of gliomas through STAT3 and AKT signaling pathways, and this inhibition is expected to be a therapeutic target for gliomas.

Rap2B promotes the proliferation and migration of human glioma cells via activation of the ERK pathway

Glioma is one of the most common primary brain tumors and has a poor prognosis. Rap2B, a member of the Ras family of oncogenes, is highly expressed and promotes the progression of several tumors, including glioma. However, the mechanism underlying the role of Rap2B in glioma is not fully understood. In the present study, after transfection, Rap2B expression was detected by reverse transcription PCR and western blot analysis. Cell proliferation and cell migration assays were performed to determine the effects of Rap2B on the malignant biological behaviors of glioma cells. The changes of ERK pathway-associated proteins were examined by western blot analysis. Enzyme-linked immunosorbent assay (ELISA) and western blot analysis were utilized to detect the protein levels of matrix metalloproteinase (MMP)2 and MMP9. Then, The Cancer Genome Atlas database was used to determine the association between Rap2B expression and clinical parameters in patients with glioblastoma multiforme and low-grade glioma (LGG). Results revealed that Rap2B was highly expressed in human glioma compared with that in adjacent normal tissues and normal human astrocytes, and that silenced Rap2B led to a reduction of cell proliferation and migration ability in glioma cells. Conversely, overexpressed Rap2B in both U87 and U251 cells significantly enhanced these malignant activities. In addition, ELISA assay and western blotting showed that Rap2B increased MMP2 and MMP9 expression. The western blot assay revealed that Rap2B induced the phosphorylation of ERK in glioma cells. Furthermore, silencing the ERK pathway by SCH772984 led to the inhibition of Rap2B-mediated proliferation, migration and the reduction of MMP2 and MMP9 expression. Kaplan-Meier analysis revealed that increased Rap2B expression was associated with poorer survival of patients with LGG. These results demonstrated that Rap2B may participate in the processes of glioma cell proliferation and migration through enhancing MMP2 and MMP9 expression via the ERK pathway. Thus, Rap2B could potentially be used as a promising therapeutic target and prognostic biomarker in glioma.

Organoid Models of Glioblastoma and Their Role in Drug Discovery

Glioblastoma (GBM) is a devastating adult brain cancer with high rates of recurrence and treatment resistance. Cellular heterogeneity and extensive invasion of surrounding brain tissues are characteristic features of GBM that contribute to its intractability. Current GBM model systems do not recapitulate some of the complex features of GBM and have not produced sufficiently-effective treatments. This has cast doubt on the effectiveness of current GBM models and drug discovery paradigms. In search of alternative pre-clinical GBM models, various 3D organoid-based GBM model systems have been developed using human cells. The scalability of these systems and potential to more accurately model characteristic features of GBM, provide promising new avenues for pre-clinical GBM research and drug discovery efforts. Here, we review the current suite of organoid-GBM models, their individual strengths and weaknesses, and discuss their future applications with an emphasis on compound screening.

miRNA-182 regulated MTSS1 inhibits proliferation and invasion in Glioma Cells

Human glioma is the most common malignant and fatal primary tumor in the central nervous system. Currently, the high incidence and low cure rate of glioma make it a considerable threat to human health. Thus, elucidating the molecular mechanisms of glioma development and progression has become a major focus to identify new and effective biomarkers and improve the comprehensive neurosurgical treatment of glioma from the basic research and clinical perspectives. In our present study, we aimed to investigate the expression pattern and biological function of Metastasis suppressor protein 1(MTSS1) in glioma and to further explore whether miRNAs were involved in the deregulation of MTSS1. By overexpressing MTSS1 in highly malignant human glioma cells, we discovered a role for MTSS1 in suppressing the proliferation and invasion of glioma cells, and we showed that MTSS1 participated in transforming growth factor-beta 1 (TGF-β1) -induced epithelial-mesenchymal transition (EMT) in glioma cells. Biochemical analyses suggested that miR-182 may target MTSS1 and that miR-182 expression is negatively correlated with MTSS1 expression in glioma tissues. This finding was further confirmed by luciferase reporter experiments. Furthermore, a miR-182 inhibitor induced glioma cell proliferation and invasion by increasing MTSS1 expression. In conclusion, we believed that miR-182 modulates glioma cell migration and invasion by targeting the MTSS1 and suggested that miR-182 was a potential therapeutic target for gliomas.

Anti-Migration and Invasion Effects of Astaxanthin against A172 Human Glioblastoma Cell Line

Objectives:

The study was to investigate anti-migration and invasion effects of astaxanthin (ATX), a natural carotenoid derivative distributed in marine environments, against A172 human glioblastoma cells.

Materials and Methods:

Cell viability after ATX treatment was measured by MTT assays. Tumor cell migration and invasion were observed by scratch and Boyden chamber assays, respectively. Expression of MMP-2 and activity of MMP-9 were observed by immunoblotting and gelatin zymography, respectively.

Results:

ATX up to 150 µM was not toxic to A172 cells at 48 h post-treatment. In contrast, ATX at 50 and 100 µM significantly decreased migration and invasion of A172 cells at 24 and 48 h post-treatment. Metastatic-reducing effect of ATX is associated with the reduction of MMP-2 and MMP-9 expressions in a dose-dependent manner. Conclusion: This finding indicated that ATX has anti-migration and invasion effects against human glioblastoma cells and might be applicable for the protection against metastasis of glioblastoma.

CCR5-Mediated Signaling Is Involved in Invasion of Glioblastoma Cells in Its Microenvironment

The chemokine CCL5/RANTES is a versatile inflammatory mediator, which interacts with the receptor CCR5, promoting cancer cell interactions within the tumor microenvironment. Glioblastoma is a highly invasive tumor, in which CCL5 expression correlates with shorter patient survival. Using immunohistochemistry, we identified CCL5 and CCR5 in a series of glioblastoma samples and cells, including glioblastoma stem cells. CCL5 and CCR5 gene expression were significantly higher in a cohort of 38 glioblastoma samples, compared to low-grade glioma and non-cancerous tissues. The in vitro invasion of patients-derived primary glioblastoma cells and glioblastoma stem cells was dependent on CCL5-induced CCR5 signaling and is strongly inhibited by the small molecule CCR5 antagonist maraviroc. Invasion of these cells, which was enhanced when co-cultured with mesenchymal stem cells (MSCs), was inhibited by maraviroc, suggesting that MSCs release CCR5 ligands. In support of this model, we detected CCL5 and CCR5 in MSC monocultures and glioblastoma-associated MSC in tissue sections. We also found CCR5 expressing macrophages were in close proximity to glioblastoma cells. In conclusion, autocrine and paracrine cross-talk in glioblastoma and, in particular, glioblastoma stem cells with its stromal microenvironment, involves CCR5 and CCL5, contributing to glioblastoma invasion, suggesting the CCL5/CCR5 axis as a potential therapeutic target that can be targeted with repositioned drug maraviroc.

Methods for in vitro modeling of glioma invasion: Choosing tools to meet the need

Widespread tumor cell invasion is a fundamental property of diffuse gliomas and is ultimately responsible for their poor prognosis. A greater understanding of basic mechanisms underlying glioma invasion is needed to provide insights into therapies that could potentially counteract them. While none of the currently available in vitro models can fully recapitulate the complex interactions of glioma cells within the brain tumor microenvironment, if chosen and developed appropriately, these models can provide controlled experimental settings to study molecular and cellular phenomena that are challenging or impossible to model in vivo. Therefore, selecting the most appropriate in vitro model, together with its inherent advantages and limitations, for specific hypotheses and experimental questions achieves primary significance. In this review, we describe and discuss commonly used methods for modeling and studying glioma invasion in vitro, including platforms, matrices, cell culture, and visualization techniques, so that choices for experimental approach are informed and optimal.

Loss of SPINT2 expression frequently occurs in glioma, leading to increased growth and invasion via MMP2

PURPOSE

High-grade gliomas (HGG) remain one of the most aggressive tumors, which is primarily due to its diffuse infiltrative nature. Serine proteases and metalloproteases are known to play key roles in cellular migration and invasion mechanisms. SPINT2, also known as HAI-2, is an important serine protease inhibitor that can affect MET signaling. SPINT2 has been found to be frequently downregulated in various tumors, whereby hypermethylation of its promoter appears to serve as a common mechanism. Here, we assessed the clinical relevance of SPINT2 expression and promoter hypermethylation in pediatric and adult HGG and explored its functional role.

METHODS

A series of 371 adult and 77 pediatric primary HGG samples was assessed for SPINT2 protein expression (immunohistochemistry) and promoter methylation (methylation-specific PCR) patterns. After SPINT2 knockdown and knock-in in adult and pediatric HGG cell lines, a variety of in vitro assays was carried out to determine the role of SPINT2 in glioma cell viability and invasion, as well as their mechanistic associations with metalloprotease activities.

RESULTS

We found that SPINT2 protein expression was frequently absent in adult (85.3%) and pediatric (100%) HGG samples. The SPINT2 gene promoter was found to be hypermethylated in approximately half of both adult and pediatric gliomas. Through functional assays we revealed a suppressor activity of SPINT2 in glioma cell proliferation and viability, as well as in their migration and invasion. These functions appear to be mediated in part by MMP2 expression and activity.

CONCLUSIONS

We conclude that dysregulation of SPINT2 is a common event in both pediatric and adult HGG, in which SPINT2 may act as a tumor suppressor.

The unique invasiveness of glioblastoma and possible drug targets on extracellular matrix

Glioblastoma, or glioblastoma multiforme (GBM), is described as one of the most invasive cancer types. Although GBM is a rare disease, with a global incidence of <10 per 100,000 people, its prognosis is extremely poor. Patient survival without treatment is ~6 months, which can be extended to around 15 months with the standard treatment protocol. Given the propensity of GBM cells to show widespread local invasion, beyond the margins seen through the best current imaging techniques, tumor margins cannot be clearly defined. Recurrence is inevitable, as the highly invasive nature of GBM means complete surgical resection of the tumor is near impossible without extensive damage to healthy surrounding brain tissue. Here, we outline GBM cell invasion in the unique environment of the brain extracellular matrix (ECM), as well as a deeper exploration of the specific mechanisms upregulated in GBMs to promote the characteristic highly invasive phenotype. Among these is the secretion of proteolytic enzymes for the destruction of the ECM, as well as discussion of a novel theory of amoeboid invasion, termed the “hydrodynamic mode of invasion”. The vast heterogeneity of GBM means that there are significant redundancies in invasive pathways, which pose challenges to the development of new treatments. In the past few decades, only one major advancement has been made in GBM treatment, namely the discovery of temozolomide. Future research should look to elucidate novel strategies for the specific targeting of the invasive cells of the tumor, to reduce recurrence rates and improve patient overall survival.

Inhibition of Radiation and Temozolomide-Induced Invadopodia Activity in Glioma Cells Using FDA-Approved Drugs

The most common primary central nervous system tumor in adults is the glioblastoma multiforme (GBM). The highly invasive nature of GBM cells is a significant factor resulting in the inevitable tumor recurrence and poor patient prognosis. Tumor cells utilize structures known as invadopodia to faciliate their invasive phenotype. In this study, utilizing an array of techniques, including gelatin matrix degradation assays, we show that GBM cell lines can form functional gelatin matrix degrading invadopodia and secrete matrix metalloproteinase 2 (MMP-2), a known invadopodia-associated matrix-degrading enzyme. Furthermore, these cellular activities were augmented in cells that survived radiotherapy and temozolomide treatment, indicating that surviving cells may possess a more invasive phenotype posttherapy. We performed a screen of FDA-approved agents not previously used for treating GBM patients with the aim of investigating their "anti-invadopodia" and cytotoxic effects in GBM cell lines and identified a number that reduced cell viability, as well as agents which also reduced invadopodia activity. Importantly, two of these, pacilitaxel and vinorelbine tartrate, reduced radiation/temozolomide-induced invadopodia activity. Our data demonstrate the value of testing previously approved drugs (repurposing) as potential adjuvant agents for the treatment of GBM patients to reduce invadopodia activity, inhibit GBM cell invasion, and potentially improve patient outcome.

Perineuronal nets decrease membrane capacitance of peritumoral fast spiking interneurons in a model of epilepsy

Brain tumor patients commonly present with epileptic seizures. We show that tumor-associated seizures are the consequence of impaired GABAergic inhibition due to an overall loss of peritumoral fast spiking interneurons (FSNs) concomitant with a significantly reduced firing rate of those that remain. The reduced firing is due to the degradation of perineuronal nets (PNNs) that surround FSNs. We show that PNNs decrease specific membrane capacitance of FSNs permitting them to fire action potentials at supra-physiological frequencies. Tumor-released proteolytic enzymes degrade PNNs, resulting in increased membrane capacitance, reduced firing, and hence decreased GABA release. These studies uncovered a hitherto unknown role of PNNs as an electrostatic insulator that reduces specific membrane capacitance, functionally akin to myelin sheaths around axons, thereby permitting FSNs to exceed physiological firing rates. Disruption of PNNs may similarly account for excitation-inhibition imbalances in other forms of epilepsy and PNN protection through proteolytic inhibition may provide therapeutic benefits.

Localization patterns of cathepsins K and X and their predictive value in glioblastoma

Background

Glioblastoma is a highly aggressive central nervous system neoplasm characterized by extensive infiltration of malignant cells into brain parenchyma, thus preventing complete tumor eradication. Cysteine cathepsins B, S, L and K are involved in cancer progression and are overexpressed in glioblastoma. We report here for the first time that cathepsin X mRNA and protein are also abundantly present in malignant glioma.

Materials and methods

Gene expression of cathepsins K and X was analyzed using publically-available tran-scriptomic datasets and correlated with glioma grade and glioblastoma subtype. Kaplan-Maier survival analysis was performed to evaluate the predictive value of cathepsin K and X mRNA expression. Cathepsin protein expression was localized and semi-quantified in tumor tissues by immunohistochemistry.

Results

Highest gene expression of cathepsins K and X was found in glioblastoma, in particular in the mesenchymal subtype. Overall, high mRNA expression of cathepsin X, but not that of cathepsin K, correlated with poor patients’ survival. Cathepsin K and X proteins were abundantly and heterogeneously expressed in glioblastoma tissue. Immuno-labeling of cathepsins K and X was observed in areas of CD133-positive glioblastoma stem cells, localized around arterioles in their niches that also expressed SDF-1α and CD68. mRNA levels of both cathepsins K and X correlated with mRNA levels of markers of glioblastoma stem cells and their niches.

Conclusions

The presence of both cathepsins in glioblastoma stem cell niche regions indicates their possible role in regulation of glioblastoma stem cell homing in their niches. The clinical relevance of this data needs to be elaborated in further prospective studies.

Role of extracellular matrix and microenvironment in regulation of tumor growth and LAR-mediated invasion in glioblastoma

The cellular dispersion and therapeutic control of glioblastoma, the most aggressive type of primary brain cancer, depends critically on the migration patterns after surgery and intracellular responses of the individual cancer cells in response to external biochemical cues in the microenvironment. Recent studies have shown that miR-451 regulates downstream molecules including AMPK/CAB39/MARK and mTOR to determine the balance between rapid proliferation and invasion in response to metabolic stress in the harsh tumor microenvironment. Surgical removal of the main tumor is inevitably followed by recurrence of the tumor due to inaccessibility of dispersed tumor cells in normal brain tissue. In order to address this complex process of cell proliferation and invasion and its response to conventional treatment, we propose a mathematical model that analyzes the intracellular dynamics of the miR-451-AMPK- mTOR-cell cycle signaling pathway within a cell. The model identifies a key mechanism underlying the molecular switches between proliferative phase and migratory phase in response to metabolic stress in response to fluctuating glucose levels. We show how up- or down-regulation of components in these pathways affects the key cellular decision to infiltrate or proliferate in a complex microenvironment in the absence and presence of time delays and stochastic noise. Glycosylated chondroitin sulfate proteoglycans (CSPGs), a major component of the extracellular matrix (ECM) in the brain, contribute to the physical structure of the local brain microenvironment but also induce or inhibit glioma invasion by regulating the dynamics of the CSPG receptor LAR as well as the spatiotemporal activation status of resident astrocytes and tumor-associated microglia. Using a multi-scale mathematical model, we investigate a CSPG-induced switch between invasive and non-invasive tumors through the coordination of ECM-cell adhesion and dynamic changes in stromal cells. We show that the CSPG-rich microenvironment is associated with non-invasive tumor lesions through LAR-CSGAG binding while the absence of glycosylated CSPGs induce the critical glioma invasion. We illustrate how high molecular weight CSPGs can regulate the exodus of local reactive astrocytes from the main tumor lesion, leading to encapsulation of non-invasive tumor and inhibition of tumor invasion. These different CSPG conditions also change the spatial profiles of ramified and activated microglia. The complex distribution of CSPGs in the tumor microenvironment can determine the nonlinear invasion behaviors of glioma cells, which suggests the need for careful therapeutic strategies.

Cysteine cathepsins B, X and K expression in peri-arteriolar glioblastoma stem cell niches

Glioblastoma (GBM) is the most lethal brain tumor also due to malignant and therapy-resistant GBM stem cells (GSCs) that are localized in protecting hypoxic GSC niches. Some members of the cysteine cathepsin family of proteases have been found to be upregulated in GBM. Cathepsin K gene expression is highly elevated in GBM tissue versus normal brain and it has been suggested to regulate GSC migration out of the niches. Here, we investigated the cellular distribution of cathepsins B, X and K in GBM tissue and whether these cathepsins are co-localized in GSC niches. Therefore, we determined expression of these cathepsins in serial paraffin sections of 14 human GBM samples and serial cryostat sections of two samples using immunohistochemistry and metabolic mapping of cathepsin activity using selective fluorogenic substrates. We detected cathepsins B, X and K in peri-arteriolar GSC niches in 9 out of 16 GBM samples, which were defined by co-expression of the GSC marker CD133, the niche marker stromal-derived factor-1α (SDF-1α) and smooth muscle actin as a marker for arterioles. The expression of cathepsin B and X was detected in stromal cells and cancer cells throughout the GBM sections, whereas cathepsin K expression was more restricted to arteriole-rich regions in the GBM sections. Metabolic mapping showed that cathepsin B, but not cathepsin K is active in GSC niches. On the basis of these findings, it is concluded that cathepsins B, X and K have distinct functions in GBM and that cathepsin K is the most likely GSC niche-related cathepsin of the three cathepsins investigated.

Could a plant derived protein potentiate the anticancer effects of a stem cell in brain cancer?

Glioblastoma is the most aggressive brain tumor with poor overall survival bellow 2 years. The natural compounds with anti-cancer properties, are thus gaining attention for possible adjuvant GBM treatment. In various cancer models Enterolobium contortisiliquum Trypsin Inhibitor (EcTI) proved to have anti-cancer effects. Here, we investigated the EcTI effects on GBM U87 cells and on mesenchymal stem cells (MSC) compared to their direct coculture (MSC/U87). MSC are present in tumor stroma, modulating GBM cells phenotype, and also represent potential drug delivery vehicle due to their tumor tropism. We showed that in p53-wild type U87 cells, metabolic activity was less affected by EcTI as in MSC monocuture, but the metabolic rate of mixed coculture was significantly reduced at lower EcTI concentration. Under coculture condition, EcTI potentiated MSC induced cell cycle arrest, possible due to highly increased p53, p21 and lower D1 expression, but there was no effect on apoptosis. Accordingly, in the coculture EcTI also enhanced Ca²⁺ signalling mediated via bradykinin receptor 2, being associated with nitric oxide release that highly impaired proliferation and invasion. The mechanism did not seem to involve changes in cell adhesion but rather it down-regulated the β₁ integrin signaling with associated p-FAK in U87 cells, both supporting inhibition of invasion. Finally, some cytokines were down-regulated, indicating that EcTI inhibition of signalling might be mediated by cytokines. In conclusion, these results indicate that in cocultured MSC/U87 cells EcTI impairs the metabolic activity, proliferation, and reduced invasion, possibly associated with observed cytokines secretion. In this context, we confirmed that the plant derived protein potentiated the anticancer effects, induced by MSC, as represented by GBM U87 cell line.

Mesenchymal stem cells differentially affect the invasion of distinct glioblastoma cell lines

Glioblastoma multiforme are an aggressive form of brain tumors that are characterized by distinct invasion of single glioblastoma cells, which infiltrate the brain parenchyma. This appears to be stimulated by the communication between cancer and stromal cells. Mesenchymal stem cells (MSCs) are part of the glioblastoma microenvironment, and their ‘cross-talk’ with glioblastoma cells is still poorly understood. Here, we examined the effects of bone marrow-derived MSCs on two different established glioblastoma cell lines U87 and U373. We focused on mutual effects of direct MSC/glioblastoma contact on cellular invasion in three-dimensional invasion assays in vitro and in a zebrafish embryo model in vivo. This is the first demonstration of glioblastoma cell-type-specific responses to MSCs in direct glioblastoma co-cultures, where MSCs inhibited the invasion of U87 cells and enhanced the invasion of U373. Inversely, direct cross-talk between MSCs and both of glioblastoma cell lines enhanced MSC motility. MSC-enhanced invasion of U373 cells was assisted by overexpression of proteases cathepsin B, calpain1, uPA/uPAR, MMP-2, -9 and -14, and increased activities of some of these proteases, as determined by the effects of their selective inhibitors on invasion. In contrast, these proteases had no effect on U87 cell invasion under MSC co-culturing. Finally, we identified differentially expressed genes, in U87 and U373 cells that could explain different response of these cell lines to MSCs. In conclusion, we demonstrated that MSC/glioblastoma cross-talk is different in the two glioblastoma cell phenotypes, which contributes to tumor heterogeneity.

IL‑33 enhances glioma cell migration and invasion by upregulation of MMP2 and MMP9 via the ST2-NF-κB pathway

As an important member of the interleukin (IL)-1 family, IL‑33 plays a significant role in tumor progression. To explore this, we previously analyzed the association between IL‑33 expression and the prognosis of patients with glioma. However, the function of the IL‑33/ST2 axis in glioma remained unclear. In the present study, immunofluorescent staining results revealed that the expression levels of IL‑33 and ST2 receptor in glioma tissues were higher than those in normal brain tissues. Invasion and migration assays demonstrated that IL‑33 significantly increased glioma cell invasion and migration in vitro. Furthermore, knockdown of ST2 by siRNA attenuated the IL‑33-induced increase in invasion and migration. In addition, ELISA results revealed that IL‑33 upregulated the expression of matrix metalloproteinase (MMP)2 and MMP9. Western blot analysis results indicated that IL‑33 stimulation increased the phosphorylation of nuclear factor-κB (NF-κB) in a time- and dose-dependent manner. Moreover, silencing of the NF-κB pathway by BAY 11‑7082 resulted in the inhibition of IL‑33-induced invasion and migration, as well as the downregulation of MMP2 and MMP9 production. These findings indicate that IL‑33 may be involved in the process of glioma cell invasion and migration by upregulating MMP2 and MMP9 via the ST2-NF-κB signaling pathway. Thus, IL‑33 may be a novel therapeutic target for glioma.

The Combined Influence of Hydrogel Stiffness and Matrix-Bound Hyaluronic Acid Content on Glioblastoma Invasion

Glioblastoma (GBM) is the most common and lethal form of brain cancer. Its high mortality is associated with its aggressive invasion throughout the brain. The heterogeneity of stiffness and hyaluronic acid (HA) content within the brain makes it difficult to study invasion in vivo. A dextran-bead assay is employed to quantify GBM invasion within HA-functionalized gelatin hydrogels. Using a library of stiffness-matched hydrogels with variable levels of matrix-bound HA, it is reported that U251 GBM invasion is enhanced in softer hydrogels but reduced in the presence of matrix-bound HA. Inhibiting HA-CD44 interactions reduces invasion, even in hydrogels lacking matrix-bound HA. Analysis of HA biosynthesis suggests that GBM cells compensate for a lack of matrix-bound HA by producing soluble HA to stimulate invasion. Together, a robust method is showed to quantify GBM invasion over long culture times to reveal the coordinated effect of matrix stiffness, immobilized HA, and compensatory HA production on GBM invasion.

RUNX1 Regulates Migration, Invasion, and Angiogenesis via p38 MAPK Pathway in Human Glioblastoma

Runt-related transcription factor 1 (RUNX1) is essential for the establishment of fetal and adult hematopoiesis and neuronal development. Aberrant expression of RUNX1 led to proliferation and metastasis of several cancers. The aim of the present study was to investigate the role of RUNX1 in migration, invasion, and angiogenesis of human glioblastoma using IL-1β-treated U-87 MG human glioblastoma cells as a model. IL-1β at 10 ng/ml stimulated translocation of RUNX1 into the nucleus with increased expressions of RUNX1, MMP-1, MMP-2, MMP-9, MMP-19, and VEGFA in U-87 MG cells. In addition, silencing of RUNX1 gene significantly suppressed U-87 MG cell migration and invasion abilities. Moreover, knockdown of RUNX1 mRNA in U-87 MG cells reduced the tube formation of human umbilical vein endothelial cells. Further investigation revealed that IL-1β-induced RUNX1 expression might be mediated via the p38 mitogen-activated protein kinase (MAPK) signaling molecule for the expression of these invasion- and angiogenic-related molecules. Together with an inhibitor of p38 MAPK (SB203580) could decrease RUNX1 mRNA expression. Thus, RUNX1 may be one of the putative molecular targeted therapies against glioma metastasis and angiogenesis through the activation of p38 MAPK signaling pathway.

ADAM9 Expression Is Associate with Glioma Tumor Grade and Histological Type, and Acts as a Prognostic Factor in Lower-Grade Gliomas

The A disintegrin and metalloproteinase 9 (ADAM9) protein has been suggested to promote carcinoma invasion and appears to be overexpressed in various human cancers. However, its role has rarely been investigated in gliomas and, thus, in the current study we have evaluated ADAM9 expression in gliomas and examined the relevance of its expression in the prognosis of glioma patients. Clinical characteristics, RNA sequence data, and the case follow-ups were reviewed for 303 patients who had histological, confirmed gliomas. The ADAM9 expression between lower-grade glioma (LGG) and glioblastoma (GBM) patients was compared and its association with progression-free survival (PFS) and overall survival (OS) was assessed to evaluate its prognostic value. Our data suggested that GBM patients had significantly higher expression of ADAM9 in comparison to LGG patients (p < 0.001, t-test). In addition, among the LGG patients, aggressive astrocytic tumors displayed significantly higher ADAM9 expression than oligodendroglial tumors (p < 0.001, t-test). Moreover, high ADAM9 expression also correlated with poor clinical outcome (p < 0.001 and p < 0.001, log-rank test, for PFS and OS, respectively) in LGG patients. Further, multivariate analysis suggested ADAM9 expression to be an independent marker of poor survival (p = 0.002 and p = 0.003, for PFS and OS, respectively). These results suggest that ADAM9 mRNA expression is associated with tumor grade and histological type in gliomas and can serve as an independent prognostic factor, specifically in LGG patients.

Role of tenascins in the ECM of gliomas

Tenascins are a family of extracellular matrix molecules that are mainly expressed in embryonic development and down-regulated in adulthood. A re-expression in the adult occurs under pathological conditions such as inflammation, regeneration or neoplasia. As the most prominent member of the tenascin family, TN-C, is highly expressed in glioma tissue and rising evidence suggests that TN-C plays a crucial role in cell migration or invasion - the most fatal characteristics of glioma - also the other members of this protein family have been investigated with regard to their impact on glioma biology. For all tenascins correlations between the expression levels of the different family members and the degree of malignancy and invasiveness of glial tumors could be detected. Overall, the former and recent results in the research on glioma and tenascins point at distinct roles of each of the molecules in glioma biology and the devastating properties of these tumors.

ADAM-9 is a novel mediator of tenascin-C-stimulated invasiveness of brain tumor-initiating cells

BACKGROUND

Tenascin-C (TNC), an extracellular matrix protein overexpressed in malignant gliomas, stimulates invasion of conventional glioma cell lines (U251, U87). However, there is a dearth of such information on glioma stemlike cells. Here, we have addressed whether and how TNC may regulate the invasiveness of brain tumor-initiating cells (BTICs) that give rise to glioma progenies.

METHODS

Transwell inserts coated with extracellular matrix proteins were used to determine the role of TNC in BTIC invasion. Microarray analysis, lentiviral constructs, RNA interference-mediated knockdown, and activity assay ascertained the role of proteases in TNC-stimulated BTIC invasion in culture. Involvement of proteases was validated using orthotopic brain xenografts in mice.

RESULTS

TNC stimulated BTIC invasiveness in a metalloproteinase-dependent manner. A global gene expression screen identified the metalloproteinase ADAM-9 as a potential regulator of TNC-stimulated BTIC invasiveness, and this was corroborated by an increase of ADAM-9 protein in 4 glioma patient-derived BTIC lines. Notably, RNA interference to ADAM-9, as well as inhibition of mitogen-activated protein kinase 8 (c-Jun NH2-terminal kinase), attenuated TNC-stimulated ADAM-9 expression, proteolytic activity, and BTIC invasiveness. The relevance of ADAM-9 to tumor invasiveness was validated using resected human glioblastoma specimens and orthotopic xenografts where elevation of ADAM-9 and TNC expression was prominent at the invasive front of the tumor.

CONCLUSIONS

This study has identified TNC as a promoter of the invasiveness of BTICs through a mechanism involving ADAM-9 proteolysis via the c-Jun NH2-terminal kinase pathway.

Glioma biology and molecular markers

The tumors classified as gliomas include a wide variety of histologies including the more common (astrocytoma, glioblastoma), as well as the less common histologies (oligodendroglioma, mixed oligoastrocytoma, pilocytic astrocytoma). Recent efforts at comprehensive genetic characterization of various primary brain tumor types have identified a number of common alterations and pathways common to multiple tumor types. Common pathways in glioma biology include growth factor receptor tyrosine kinases and their downstream signaling via the MAP kinase cascade or PI3K signaling, loss of apoptosis through p53, cell cycle regulation, angiogenesis via VEGF signaling, and invasion. However, in addition to these common general pathway alterations, a number of specific alterations have been identified in particular tumor types, and a number of these have direct therapeutic implications. These include mutations or fusions in the BRAF gene seen in pilocytic astrocytomas (and gangliogliomas). In oligodendrogliomas, mutations in IDH1 and codeletion of chromosomes 1p and 19q are associated with improved survival with upfront use of combined chemotherapy and radiation, and these tumors also have unique mutations of CIC and FUBP1 genes. Low grade gliomas are increasingly seen to be divided into two groups based on IDH mutation status, with astrocytomas developing through IDH mutation followed by p53 mutation, while poor prognosis low grade gliomas and primary glioblastomas (GBMs) are characterized by EGFR amplification, loss of PTEN, and loss of cyclin-dependent kinase inhibitors. GBMs can be further characterized based on gene expression and gene methylation patterns into three or four distinct subgroups. Prognostic markers in diffuse gliomas include IDH mutation, 1p/19q codeletion, and MGMT methylation, and MGMT is also a predictive marker in elderly patients with glioblastoma treated with temozolomide monotherapy.

Expression analysis of all protease genes reveals cathepsin K to be overexpressed in glioblastoma

Background

Cancer genome and transcriptome analyses advanced our understanding of cancer biology. We performed transcriptome analysis of all known genes of peptidases also called proteases and their endogenous inhibitors in glioblastoma multiforme (GBM), which is one of the most aggressive and deadly types of brain cancers, where unbalanced proteolysis is associated with tumor progression.

Methods

Comparisons were performed between the transcriptomics of primary GBM tumors and unmatched non-malignant brain tissue, and between GBM cell lines (U87-MG and U373) and a control human astrocyte cell line (NHA). Publicly-available data sets and our own datasets were integrated and normalized using bioinformatics tools to reveal protease and protease inhibitor genes with deregulated expression in both malignant versus non-malignant tissues and cells.

Results

Of the 311 protease genes identified to be differentially expressed in both GBM tissues and cells, 5 genes were highly overexpressed, 2 genes coding for non-peptidase homologues transferrin receptor (TFRC) and G protein-coupled receptor 56 (GPR56), as well as 3 genes coding for the proteases endoplasmic reticulum aminopeptidase 2 (ERAP2), glutamine-fructose-6-phosphate transaminase 2 (GFPT2) and cathepsin K (CTSK), whereas one gene, that of the serine protease carboxypeptidase E (CPE) was strongly reduced in expression. Seventy five protease inhibitor genes were differentially expressed, of which 3 genes were highly overexpressed, the genes coding for stefin B (CSTB), peptidase inhibitor 3 (PI3 also named elafin) and CD74. Seven out of 8 genes (except CSTB) were validated using RT-qPCR in GBM cell lines. CTSK overexpression was validated using RT-qPCR in GBM tissues as well. Cathepsin K immunohistochemical staining and western blotting showed that only proteolytically inactive proforms of cathepsin K were overexpressed in GBM tissues and cells.

Conclusions

The presence of high levels of inactive proforms of cathepsin K in GBM tissues and cells indicate that in GBM the proteolytic/collagenolytic role is not its primary function but it plays rather a different yet unknown role.

A neurocentric perspective on glioma invasion

Malignant gliomas are devastating tumours that frequently kill patients within 1 year of diagnosis. The major obstacle to a cure is diffuse invasion, which enables tumours to escape complete surgical resection and chemo- and radiation therapy. Gliomas use the same tortuous extracellular routes of migration that are travelled by immature neurons and stem cells, frequently using blood vessels as guides. They repurpose ion channels to dynamically adjust their cell volume to accommodate to narrow spaces and breach the blood-brain barrier through disruption of astrocytic endfeet, which envelop blood vessels. The unique biology of glioma invasion provides hitherto unexplored brain-specific therapeutic targets for this devastating disease.

The role of AEG-1/MTDH/LYRIC in the pathogenesis of central nervous system disease

Astrocyte-elevated gene-1 (AEG-1/MTDH/LYRIC) is a potent oncogene that regulates key cellular processes underlying disease of the central nervous system (CNS). From its involvement in human immunodeficiency virus (HIV)-1 infection to its role in neurodegenerative disease and malignant brain tumors, AEG-1/MTDH/LYRIC facilitates cellular survival and proliferation through the control of a multitude of molecular signaling cascades. AEG-1/MTDH/LYRIC induction by HIV-1 and TNF highlights its importance in viral infection, and its incorporation into viral vesicles supports its potential role in active viral replication. Overexpression of AEG-1/MTDH/LYRIC in the brains of Huntington's disease patients suggests its function in neurodegenerative disease, and its association with genetic polymorphisms in large genome-wide association studies of migraine patients suggests a possible role in the pathogenesis of migraine headaches. In the field of cancer, AEG-1/MTDH/LYRIC promotes angiogenesis, migration, invasion, and enhanced tumor metabolism through key oncogenic signaling cascades. In response to external stress cues and cellular mechanisms to inhibit further growth, AEG-1/MTDH/LYRIC activates pathways that bypass cell checkpoints and potentiates signals to enhance survival and tumorigenesis. As an oncogene that promotes aberrant cellular processes within the CNS, AEG-1/MTDH/LYRIC represents an important therapeutic target for the treatment of neurological disease.

ProBDNF and its receptors are upregulated in glioma and inhibit the growth of glioma cells in vitro

BACKGROUND

High-grade glioma is incurable, with a short survival time and poor prognosis. The increased expression of p75 neurotrophin receptor (NTR) is a characteristic of high-grade glioma, but the potential significance of increased p75NTR in this tumor is not fully understood. Since p75NTR is the receptor for the precursor of brain-derived neurotrophic factor (proBDNF), it is suggested that proBDNF may have an impact on glioma.

METHODS

In this study we investigated the expression of proBDNF and its receptors p75NTR and sortilin in 52 cases of human glioma and 13 cases of controls by immunochemistry, quantitative real-time PCR, and Western blot methods. Using C6 glioma cells as a model, we investigated the roles of proBDNF on C6 glioma cell differentiation, growth, apoptosis, and migration in vitro.

RESULTS

We found that the expression levels of proBDNF, p75NTR, and sortilin were significantly increased in high-grade glioma and were positively correlated with the malignancy of the tumor. We also observed that tumors expressed proBDNF, p75NTR, and sortilin in the same cells with different subcellular distributions, suggesting an autocrine or paracrine loop. The ratio of proBDNF to mature BDNF was decreased in high-grade glioma tissues and was negatively correlated with tumor grade. Using C6 glioma cells as a model, we found that proBDNF increased apoptosis and differentiation and decreased cell growth and migration in vitro via p75NTR.

CONCLUSIONS

Our data indicate that proBDNF and its receptors are upregulated in high-grade glioma and might play an inhibitory effect on glioma.