Expression of integrin alpha6beta1 enhances tumorigenesis in glioma cells

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.

Engineered organoids in oral and maxillofacial regeneration

Oral and maxillofacial organoids, as three-dimensional study models of organs, have attracted increasing attention in tissue regeneration and disease modeling. However, traditional strategies for organoid construction still fail to precisely recapitulate the key characteristics of real organs, due to the difficulty in controlling the self-organization of cells in vitro. This review aims to summarize the recent progress of novel approaches to engineering oral and maxillofacial organoids. First, we introduced the necessary components and their roles in forming oral and maxillofacial organoids. Besides, we discussed cutting-edge technology in advancing the architecture and function of organoids, especially focusing on oral and maxillofacial tissue regeneration via novel strategy with designed cell-signal scaffold compounds. Finally, current limitations and future prospects of oral and maxillofacial organoids were represented to provide guidance for further disciplinary progression and clinical application to achieve organ regeneration.

Inhibitory effect of phenolic extract from squirting cucumber (Ecballium elaterium (L.) A. Rich) seed oil on integrin-mediated cell adhesion, migration and angiogenesis

Integrin targeted therapies by natural bioactive compounds have attracted attention in the field of oncology and cancer treatment. This study evaluates the potential of phenolic extract from the medicinal herb Ecballium elaterium L. seed oil (PEO) to inhibit the adhesion and migration of the highly invasive human fibrosarcoma cell line HT1080. At safe concentrations (up to 40 μg mL-1), results show that PEO dose-dependently inhibits adhesion and migration of HT1080 to fibronectin (IC50 = 18 μg mL-1) and fibrinogen (IC50 = 12.86 μg mL-1). These observations were associated with the reduction of cell motility and migration velocity as revealed in the Boyden chamber and random motility using two-dimensional assays, respectively. Additional experiments using integrin blocking antibodies showed that PEO at the highest safe concentration (40 μg mL-1) competitively inhibited the attachment of HT1080 cell to anti-αvβ3 (>98%), anti-α5β1 (>86%), and to a lesser extent anti-α2 (>50%) immobilized antibodies, suggesting that αvβ3 and α5β1 integrins were selectively targeted by PEO. Moreover, PEO specifically targeted these integrins in human microvascular endothelial cells (HMEC-1) and dose-dependently blocked the in vitro tubulogenesis. In the CAM model, PEO inhibited the VEGF-induced neoangiogenesis confirming its anti-angiogenic effect. Collectively, these results indicate that PEO holds promise for the development of natural integrin-targeted therapies against fibrosarcoma.

Anoikis resistance in diffuse glioma: The potential therapeutic targets in the future

Glioma is the most common malignant intracranial tumor and exhibits diffuse metastasis and a high recurrence rate. The invasive property of glioma results from cell detachment. Anoikis is a special form of apoptosis that is activated upon cell detachment. Resistance to anoikis has proven to be a protumor factor. Therefore, it is suggested that anoikis resistance commonly occurs in glioma and promotes diffuse invasion. Several factors, such as integrin, E-cadherin, EGFR, IGFR, Trk, TGF-β, the Hippo pathway, NF-κB, eEF-2 kinase, MOB2, hypoxia, acidosis, ROS, Hsp and protective autophagy, have been shown to induce anoikis resistance in glioma. In our present review, we aim to summarize the underlying mechanism of resistance and the therapeutic potential of these molecules.

Alpha2beta1 Integrin Polymorphism in Diffuse Astrocytoma Patients

Integrins are heterodimeric transmembrane glycoproteins resulting from the non-covalent association of an α and β chain. The major integrin receptor for collagen/laminin, α2β1 is expressed on a wide variety of cell types and plays an essential role in the adhesion of normal and tumor cells to the extracellular matrix. Integrin-triggered signaling pathways promote the invasion and survival of glioma cells by modifying the brain microenvironment. In this study, we investigated the association of a specific genetic polymorphism of integrin α2β1 with the incidence of diffusely infiltrating astrocytoma and the progression of these tumors. Single-nucleotide polymorphism in intron 7 of the integrin ITGA2 gene was examined in 158 patients and 162 controls using polymerase chain reaction and restriction enzyme analysis. The ITGA2 genotype +/+ (with a BglII restriction site in both alleles) exhibited higher frequency in grade II astrocytoma compared to control (P = 0.02) whereas the genotype -/- (lacking the BglII site) correlated with the poorest survival rate (P = 0.04). In addition, in silico analyses of ITGA2 expression from low-grade gliomas (LGG, n = 515) and glioblastomas (GBM, n = 159) indicated that the higher expression of ITGA2 in LGG was associated with poor overall survival (P < 0.0001). However, the distribution of integrin ITGA2 BglII genotypes (+/+, +/-, -/-) was not significantly different between astrocytoma subgroups III and IV (P = 0.65, 0.24 and 0.33; 0.29, 0.48, 0.25, respectively) compared to control. These results suggest a narrow association between the presence of this SNP and indicate that further studies with larger samples are warranted to analyze the relation between tumor grade and overall survival, highlighting the importance of determining these polymorphisms for prognosis of astrocytomas.

Integrin-αvβ3 as a Therapeutic Target in Glioblastoma: Back to the Future?

Glioblastoma (GBM), the most common primary malignant brain tumor, is associated with a dismal prognosis. Standard therapies including maximal surgical resection, radiotherapy, and temozolomide chemotherapy remain poorly efficient. Improving GBM treatment modalities is, therefore, a paramount challenge for researchers and clinicians. GBMs exhibit the hallmark feature of aggressive invasion into the surrounding tissue. Among cell surface receptors involved in this process, members of the integrin family are known to be key actors of GBM invasion. Upregulation of integrins was reported in both tumor and stromal cells, making them a suitable target for innovative therapies targeting integrins in GBM patients, as their impairment disrupts tumor cell proliferation and invasive capacities. Among them, integrin-αvβ3 expression correlates with high-grade GBM. Driven by a plethora of preclinical biological studies, antagonists of αvβ3 rapidly became attractive therapeutic candidates to impair GBM tumorigenesis. In this perspective, the advent of nuclear medicine is currently one of the greatest components of the theranostic concept in both preclinical and clinical research fields. In this review, we provided an overview of αvβ3 expression in GBM to emphasize the therapeutic agents developed. Advanced current and future developments in the theranostic field targeting αvβ3 are finally discussed.

Type-I Collagen/Collagenase Modulates the 3D Structure and Behavior of Glioblastoma Spheroid Models

Multicellular tumor spheroids have emerged as well-structured, three-dimensional culture models that resemble and mimic the complexity of the dense and hypoxic cancer microenvironment. However, in brain tumor studies, a variety of glioblastoma multiforme (GBM) cell lines only self-assemble into loose cellular aggregates, lacking the properties of actual glioma tumors in humans. In this study, we used type-I collagen as an extracellular matrix component to promote the compaction of GBM aggregates forming tight spheroids to understand how collagen influences the properties of tumors, such as their growth, proliferation, and invasion, and collagenase to promote collagen degradation. The GBM cell lines U87MG, T98G, and A172, as well as the medulloblastoma cell line UW473, were used as standard cell lines that do not spontaneously self-assemble into spheroids, and GBM U251 was used as a self-assembling cell line. According to the findings, all cell lines formed tight spheroids at collagen concentrations higher than 15.0 μg mL^-1. Collagen was distributed along the spheroid, similarly to that observed in invasive GBM tumors, and decreased cell migration with no effect on the cellular uptake of small active molecules, as demonstrated by uptake studies using the photosensitizer verteporfin. The enzymatic cleavage of collagen affected spheroid morphology and increased cell migration while maintaining cell viability. Such behaviors are relevant to the physiological models of GBM tumors and are useful for better understanding cell migration and the in vivo infiltration path, drug screening, and kinetics of progression of GBM tumors.

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.

Integrin α10-Antibodies Reduce Glioblastoma Tumor Growth and Cell Migration

Simple Summary

Glioblastoma (GB) is the most common and most deadly form of brain tumor in adults which currently lacks effective treatments. Thus, there is a high need to identify new and effective ways to target the aggressive GB cells and treat the GB patients. In this study, we investigated the treatment effect of two antibodies that have been developed to target the protein integrin α10β1, which is present on the surface of GB cells. Our results show that the growth of GB tumor cells is reduced in the presence of the α10β1 antibodies. The treatment effect is demonstrated both in cell experiments and in an animal model. In addition, we found that the antibodies reduce the migration of the GB cells. We suggest that function-blocking antibodies targeting the integrin α10β1 is a promising new approach to treat glioblastoma patients.

Abstract

Glioblastoma (GB) is the most common and the most aggressive form of brain tumor in adults, which currently lacks efficient treatment strategies. In this study, we investigated the therapeutic effect of function-blocking antibodies targeting integrin α10β1 on patient-derived-GB cell lines in vitro and in vivo. The in vitro studies demonstrated significant inhibiting effects of the integrin α10 antibodies on the adhesion, migration, proliferation, and sphere formation of GB cells. In a xenograft mouse model, the effect of the antibodies on tumor growth was investigated in luciferase-labeled and subcutaneously implanted GB cells. As demonstrated by in vivo imaging analysis and caliper measurements, the integrin α10-antibodies significantly suppressed GB tumor growth compared to control antibodies. Immunohistochemical analysis of the GB tumors showed lower expression of the proliferation marker Ki67 and an increased expression of cleaved caspase-3 after treatment with integrin α10 antibodies, further supporting a therapeutic effect. Our results suggest that function-blocking antibody targeting integrin α10β1 is a promising therapeutic strategy for the treatment of glioblastoma.

Nanotheranostics through Mitochondria-targeted Delivery with Fluorescent Peptidomimetic Nanohybrids for Apoptosis Induction of Brain Cancer Cells

Overview: Malignant brain tumors remain one of the greatest challenges faced by health professionals and scientists among the utmost lethal forms of cancer. Nanotheranostics can play a pivotal role in developing revolutionary nanoarchitectures with multifunctional and multimodal capabilities to fight cancer. Mitochondria are vital organelles to eukaryotic cells, which have been recognized as a significant target in cancer therapy where, by damaging the mitochondria, it will cause irreparable cell death or apoptosis. Methods: We designed and produced novel hybrid nanostructures comprising a fluorescent semiconductor core (AgInS2, AIS) and cysteine-modified carboxymethylcellulose (termed thiomer, CMC_Cys) conjugated with mitochondria-targeting peptides (KLA) forming a macromolecular shell for combining bioimaging and for inducing brain cancer cell (U-87 MG) death. Results: The optical and physicochemical properties of the nanoconjugates demonstrated suitability as photoluminescent nanostructures for cell bioimaging and intracellular tracking. Additionally, the results proved a remarkable killing activity towards glioblastoma cells of cysteine-bearing CMC conjugates coupled with KLA peptides through the half-maximal effective concentration values, approximately 70-fold higher compared to the conjugate analogs without Cys residues. Moreover, these thiomer-based pro-apoptotic drug nanoconjugates displayed higher lethality against U-87 MG cancer cells than doxorubicin, a model drug in chemotherapy, although extremely toxic. Remarkably, these peptidomimetic nanohybrids demonstrated a relative "protective effect" regarding healthy cells while maintaining high killing activity towards malignant brain cells. Conclusion: These findings pave the way for developing hybrid nanoarchitectures applied as targeted multifunctional platforms for simultaneous imaging and therapy against cancer while minimizing the high systemic toxicity and side-effects of conventional drugs in anticancer chemotherapy.

The Role of Hypoxia and SRC Tyrosine Kinase in Glioblastoma Invasiveness and Radioresistance

Advances in functional imaging are supporting neurosurgery and radiotherapy for glioblastoma, which still remains the most aggressive brain tumor with poor prognosis. The typical infiltration pattern of glioblastoma, which impedes a complete surgical resection, is coupled with a high rate of invasiveness and radioresistance, thus further limiting efficient therapy, leading to inevitable and fatal recurrences. Hypoxia is of crucial importance in gliomagenesis and, besides reducing radiotherapy efficacy, also induces cellular and molecular mediators that foster proliferation and invasion. In this review, we aimed at analyzing the biological mechanism of glioblastoma invasiveness and radioresistance in hypoxic niches of glioblastoma. We also discussed the link between hypoxia and radiation-induced radioresistance with activation of SRC proto-oncogene non-receptor tyrosine kinase, prospecting potential strategies to overcome the current limitation in glioblastoma treatment.

Quantitative and qualitative analysis of integrin subtype expression in melanocytes and melanoma cells

Objectives: Changes in the integrin expression pattern have been associated with the malignant transformation of melanocytes suggesting that integrins may be potential biomarkers as well as molecular targets for individualized therapy. Since there is a lack of comprehensive qualitative and quantitative expression data, we characterized the integrin expression profile in normal and malignant human cells of the melanocytic lineage.Methods: Seven melanoma cell lines as well as normal human melanocytes were investigated in western blots including recombinant integrin subunits for quantification.Results: Expression patterns were heterogeneous. In melanoma, overexpression of α4, α6, αL, β5, and β6 was found. Integrins α7, α9, and β4 were overexpressed in a subset of the melanoma cell lines. Overexpression was defined as a lack of expression in melanocytes but expression in more than half (4) of the melanoma lines. 1.9 to 6.7 × 10⁶ integrin molecules (about 0.3% of total cellular protein) were estimated to be expressed per cell. Expression of integrin αE at the protein level was found in melanoma and melanocytes, to the best of our knowledge, for the first time. Integrins αM and β2 were not detected.Conclusion: Integrins α4, α6, αL, β5, and β6 appear to be overexpressed in melanoma cells. These subunits may serve as biomarkers and/or therapeutic targets.

Extracellular vesicles originating from glioblastoma cells increase metalloproteinase release by astrocytes: the role of CD147 (EMMPRIN) and ionizing radiation

BACKGROUND

Glioblastoma multiforme is an aggressive primary brain tumor that is characterized by local invasive growth and resistance to therapy. The role of the microenvironment in glioblastoma invasiveness remains unclear. While carcinomas release CD147, a protein that signals for increased matrix metalloproteinase (MMP) release by fibroblasts, glioblastoma does not have a significant fibroblast component. We hypothesized that astrocytes release MMPs in response to CD147 contained in glioblastoma-derived extracellular vesicles (EVs) and that ionizing radiation, part of the standard treatment for glioblastoma, enhances this release.

METHODS

Astrocytes were incubated with EVs released by irradiated or non-irradiated human glioblastoma cells wild-type, knockdown, or knockout for CD147. Levels of CD147 in glioblastoma EVs and MMPs secreted by astrocytes were quantified. Levels of proteins in the mitogen activated protein kinase (MAPK) pathway, which can be regulated by CD147, were measured in astrocytes incubated with EVs from glioblastoma cells wild-type or knockdown for CD147. Immunofluorescence was performed on the glioblastoma cells to identify changes in CD147 localization in response to irradiation, and to confirm uptake of the EVs by astrocytes.

RESULTS

Immunoblotting and mass spectrometry analyses showed that CD147 levels in EVs were transiently increased when the EVs were from glioblastoma cells that were irradiated with γ rays. Specifically, the highly-glycosylated 45 kDa form of CD147 was preferentially present in the EVs relative to the cells themselves. Immunofluorescence demonstrated that astrocytes incorporate glioblastoma EVs and subsequently increase their secretion of active MMP9. The increase was greater if the EVs were from irradiated glioblastoma cells. Testing MAPK pathway activation, which also regulates MMP expression, showed that JNK signaling, but not ERK1/2 or p38, was increased in astrocytes incubated with EVs from irradiated compared to non-irradiated glioblastoma cells. Knockout of CD147 in glioblastoma cells blocked the increased JNK signaling and the rise in secreted active MMP9 levels.

CONCLUSIONS

The results support a tumor microenvironment-mediated role of CD147 in glioblastoma invasiveness, and reveal a prominent role for ionizing radiation in enhancing the effect. They provide an improved understanding of glioblastoma intercellular signaling in the context of radiotherapy, and identify pathways that can be targeted to reduce tumor invasiveness. Video abstract.

Isolation of an Anti-Tumour Disintegrin: Dabmaurin-1, a Peptide Lebein-1-Like, from Daboia mauritanica Venom

In the soft treatment of cancer tumours, consequent downregulation of the malignant tissue angiogenesis constitutes an efficient way to stifle tumour development and metastasis spreading. As angiogenesis requires integrin–promoting endothelial cell adhesion, migration, and vessel tube formation, integrins represent potential targets of new therapeutic anti–angiogenic agents. Our work is a contribution to the research of such therapeutic disintegrins in animal venoms. We report isolation of one peptide, named Dabmaurin–1, from the hemotoxic venom of snake Daboia mauritanica, and we evaluate its potential anti–tumour activity through in vitro inhibition of the human vascular endothelial cell HMECs functions involved in tumour angiogenesis. Dabmaurin–1 altered, in a dose–dependent manner, without any significant cytotoxicity, HMEC proliferation, adhesion, and their mesenchymal migration onto various extracellular matrix proteins, as well as formation of capillary–tube mimics on Matrigel^TM. Via experiments involving HMEC or specific cancers cells integrins, we demonstrated that the above Dabmaurin–1 effects are possibly due to some anti–integrin properties. Dabmaurin–1 was demonstrated to recognize a broad panel of prooncogenic integrins (αvβ6, αvβ3 or αvβ5) and/or particularly involved in control of angiogenesis (α5β1, α6β4, αvβ3 or αvβ5). Furthermore, mass spectrometry and partial N–terminal sequencing of this peptide revealed, it is close to Lebein–1, a known anti–β1 disintegrin from Macrovipera lebetina venom. Therefore, our results show that if Dabmaurin–1 exhibits in vitro apparent anti–angiogenic effects at concentrations lower than 30 nM, it is likely because it acts as an anti–tumour disintegrin.

Integrin Signaling in Glioma Pathogenesis: From Biology to Therapy

Integrins are a large family of transmembrane adhesion receptors, which play a key role in interactions of a cell with the surrounding stroma. Integrins are comprised of non-covalently linked α and β chains, which form heterodimeric receptor complexes. The signals from integrin receptors are combined with those originating from growth factor receptors and participate in orchestrating morphological changes of cells, organization of the cytoskeleton, stimulation of cell proliferation and rescuing cells from programmed cell death induced by extracellular matrix (ECM) detachment. Upon binding to specific ligands or ECM components, integrin dimers activate downstream signaling pathways, including focal adhesion kinase, phosphoinositide-3-kinase (PI3K) and AKT kinases, which regulate migration, invasion, proliferation and survival. Expression of specific integrins is upregulated in both tumor cells and stromal cells in a tumor microenvironment. Therefore, integrins became an attractive therapeutic target for many cancers, including the most common primary brain tumors-gliomas. In this review we provide an overview of the involvement of integrin signaling in glioma pathogenesis, formation of the tumor niche and brain tissue infiltration. We will summarize up-to-date therapeutic strategies for gliomas focused on interference with integrin ligand-receptor signaling.

Signaling Determinants of Glioma Cell Invasion

Tumor cell invasiveness is a critical challenge in the clinical management of glioma patients. In addition, there is accumulating evidence that current therapeutic modalities, including anti-angiogenic therapy and radiotherapy, can enhance glioma invasiveness. Glioma cell invasion is stimulated by both autocrine and paracrine factors that act on a large array of cell surface-bound receptors. Key signaling elements that mediate receptor-initiated signaling in the regulation of glioblastoma invasion are Rho family GTPases, including Rac, RhoA and Cdc42. These GTPases regulate cell morphology and actin dynamics and stimulate cell squeezing through the narrow extracellular spaces that are typical of the brain parenchyma. Transient attachment of cells to the extracellular matrix is also necessary for glioblastoma cell invasion. Interactions with extracellular matrix components are mediated by integrins that initiate diverse intracellular signalling pathways. Key signaling elements stimulated by integrins include PI3K, Akt, mTOR and MAP kinases. In order to detach from the tumor mass, glioma cells secrete proteolytic enzymes that cleave cell surface adhesion molecules, including CD44 and L1. Key proteases produced by glioma cells include uPA, ADAMs and MMPs. Increased understanding of the molecular mechanisms that control glioma cell invasion has led to the identification of molecular targets for therapeutic intervention in this devastating disease.

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.

Heat processing effect of luteolin on anti-metastasis activity of human glioblastoma cells U87

Among the flavonoïds, luteolin is a flavone that has been identified in many plants. It is known for its apoptotic potential with damage to DNA and cell cycle blockage. Many studies have shown that luteolin has anti-oxidant, anti-inflammatory, and anti-cancer activities. However, it is known that heat treatment (boiling, cooking, and treating with microwaves …) can influence the structure of flavonoïds, which often leads to changes in their activities. The present study was conducted to study the effect of heated luteolin on anti-tumor activity of glioblastoma cells U87. Glioblastoma cell viability was evaluated by MTT assay. Adhesion assay was performed on different protein matrices (collagen type 1, vitronectin, fibronectin, and poly-L-lysine); migration assay was determined by modified Boyden chambers and videomicroscopy, and finally, angiogenesis was tested in vitro by capillary network formation on Matrigel™. The results obtained show that the thermal treatment significantly reduces its cytotoxic activity and ability to inhibit cell adhesion to different protein matrices. It was also found that the heat processed significantly reduced the ability of luteolin to inhibit cell migration, cell invasion, and endothelial cell angiogenesis (HMEC-1). This suggests that heat treated luteolin has a lower anti-tumor potential than native luteolin. Graphical abstract ᅟ.

Quantification of glioblastoma progression in zebrafish xenografts: Adhesion to laminin alpha 5 promotes glioblastoma microtumor formation and inhibits cell invasion

Glioblastoma (GBM) is a deadly disease due to its ability to quickly invade and destroy brain tissue. Slowing or stopping GBM cell progression is crucial to help those inflicted with the disease. Our lab created an embryo-larval zebrafish xenograft model as a tool to study human GBM progression in an observable brain environment. The zebrafish brain is a dynamic and complex environment providing an optimal setting for studying GBM cell progression. Here we demonstrate the ability of our model to quantitate GBM proliferation, dispersal, blood vessel association, microtumor formation, and individual cell invasion by evaluating the importance of an extracellular matrix protein, laminin alpha 5 (lama5), on U251MG cell progression. Lama5 has been implicated in cancer cell survival, proliferation and invasion and is a known adhesion site for GBM cells. While lama5 is highly expressed in endothelial cells in the brain, it is unknown how lama5 affects GBM behavior. Using a lama5 morpholino, we discovered that lama5 decreased U251MG dispersal by 23% and doubles the formation of blood vessel dependent microtumors. Despite lama5 being a known attachment site for GBM, lama5 expression had no effect on U251MG association with blood vessels. Analysis of individual U251MG cells revealed lama5 significantly lowered invasion as mobile U251MG cells traveled 32.5  μm less, invaded 5.0 μm/hr slower and initiated invasion 60% few times per cell.

RND1 regulates migration of human glioblastoma stem-like cells according to their anatomical localization and defines a prognostic signature in glioblastoma

Despite post-operative radio-chemotherapy, glioblastoma systematically locally recurs. Tumors contacting the periventricular zone (PVZ) show earlier and more distant relapses than tumors not contacting the PVZ. Since glioblastoma stem-like cells (GSCs) have been proposed to play a major role in glioblastoma recurrence, we decided to test whether GSC migration properties could be different according to their anatomical location (PVZ+/PVZ–). For that purpose, we established paired cultures of GSCs from the cortical area (CT) and the PVZ of glioblastoma patient tumors. We demonstrated that PVZ GSCs possess higher migration and invasion capacities than CT GSCs. We highlighted specific transcriptomic profiles in PVZ versus CT populations and identified a down-regulation of the RhoGTPase, RND1 in PVZ GSCs compared to CT GSCs. Overexpression of RND1, dramatically inhibited PVZ GSC migration and conversely, downregulation of RND1 increased CT GSC migration. Additionally, transcriptomic analyses also revealed a down-regulation of RND1 in glioblastoma compared to normal brain. Using the glioblastoma TCGA database, low levels of RND1 were also shown to correlate with a decreased overall survival of patients. Finally, based on signaling pathways activated in patients with low levels of RND1, we identified an RND1^low signature of six genes (MET, LAMC1, ITGA5, COL5A1, COL3A1, COL1A2) that is an independent prognostic factor in glioblastoma. These findings contribute to explain the shorter time to progression of patients with PVZ involvement and, point out genes that establish the RND1^low signature as key targets genes to impede tumor relapse after treatment.

Adaptive adhesion systems mediate glioma cell invasion in complex environments

Diffuse brain invasion by glioma cells prevents effective surgical or molecular-targeted therapy and underlies a detrimental outcome. Migrating glioma cells are guided by complex anatomical brain structures but the exact mechanisms remain poorly defined. To identify adhesion receptor systems and matrix structures supporting glioma cell invasion into brain-like environments we used 2D and 3D organotypic invasion assays in combination with antibody-, peptide- and RNA-based interference. Combined interference with β1 and αV integrins abolished the migration of U-251 and E-98 glioma cells on reconstituted basement membrane; however, invasion into primary brain slices or 3D astrocyte-based scaffolds and migration on astrocyte-deposited matrix was only partly inhibited. Any residual invasion was supported by vascular structures, as well as laminin 511, a central constituent of basement membrane of brain blood vessels. Multi-targeted interference against β1, αV and α6 integrins expressed by U-251 and E-98 cells proved insufficient to achieve complete migration arrest. These data suggest that mechanocoupling by integrins is relatively resistant to antibody- or peptide-based targeting, and cooperates with additional, as yet unidentified adhesion systems in mediating glioma cell invasion in complex brain stroma.

Engineering innervated secretory epithelial organoids by magnetic three-dimensional bioprinting for stimulating epithelial growth in salivary glands

Current saliva-based stimulation therapies for radiotherapy-induced xerostomia are not fully effective due to the presence of damaged secretory epithelia and nerves in the salivary gland (SG). Hence, three-dimensional bio-engineered organoids are essential to regenerate the damaged SG. Herein, a recently validated three-dimensional (3D) biofabrication system, the magnetic 3D bioprinting (M3DB), is tested to generate innervated secretory epithelial organoids from a neural crest-derived mesenchymal stem cell, the human dental pulp stem cell (hDPSC). Cells are tagged with magnetic nanoparticles (MNP) and spatially arranged with magnet dots to generate 3D spheroids. Next, a SG epithelial differentiation stage was completed with fibroblast growth factor 10 (4-400 ng/ml) to recapitulate SG epithelial morphogenesis and neurogenesis. The SG organoids were then transplanted into ex vivo model to evaluate their epithelial growth and innervation. M3DB-formed spheroids exhibited both high cell viability rate (>90%) and stable ATP intracellular activity compared to MNP-free spheroids. After differentiation, spheroids expressed SG epithelial compartments including secretory epithelial, ductal, myoepithelial, and neuronal. Fabricated organoids also produced salivary α-amylase upon FGF10 stimulation, and intracellular calcium mobilization and trans-epithelial resistance was elicited upon neurostimulation with different neurotransmitters. After transplantation, the SG-like organoids significantly stimulated epithelial and neuronal growth in damaged SG. It is the first time bio-functional innervated SG-like organoids are bioprinted. Thus, this is an important step towards SG regeneration and the treatment of radiotherapy-induced xerostomia.

Interest of integrins targeting in glioblastoma according to tumor heterogeneity and cancer stem cell paradigm: an update

Glioblastomas are malignant brain tumors with dismal prognosis despite standard treatment with surgery and radio/chemotherapy. These tumors are defined by an important cellular heterogeneity and notably contain a particular subpopulation of Glioblastoma-initiating cells, which recapitulate the heterogeneity of the original Glioblastoma. In order to classify these heterogeneous tumors, genomic profiling has also been undertaken to classify these heterogeneous tumors into several subtypes. Current research focuses on developing therapies, which could take into account this cellular and genomic heterogeneity. Among these targets, integrins are the subject of numerous studies since these extracellular matrix transmembrane receptors notably controls tumor invasion and progression. Moreover, some of these integrins are considered as membrane markers for the Glioblastoma-initiating cells subpopulation. We reviewed here integrin expression according to glioblastoma molecular subtypes and cell heterogeneity. We discussed their roles in glioblastoma invasion, angiogenesis, therapeutic resistance, stemness and microenvironment modulations, and provide an overview of clinical trials investigating integrins in glioblastomas. This review highlights that specific integrins could be identified as selective glioblastoma cells markers and that their targeting represents new diagnostic and/or therapeutic strategies.

Glioblastoma stem cells exploit the αvβ8 integrin-TGFβ1 signaling axis to drive tumor initiation and progression

Glioblastoma (GBM) is a primary brain cancer that contains populations of stem-like cancer cells (GSCs) that home to specialized perivascular niches. GSC interactions with their niche influence self-renewal, differentiation and drug resistance, although the pathways underlying these events remain largely unknown. Here, we report that the integrin αvβ8 and its latent transforming growth factor β1 (TGFβ1) protein ligand have central roles in promoting niche co-option and GBM initiation. αvβ8 integrin is highly expressed in GSCs and is essential for self-renewal and lineage commitment in vitro. Fractionation of β8^high cells from freshly resected human GBM samples also reveals a requirement for this integrin in tumorigenesis in vivo. Whole-transcriptome sequencing reveals that αvβ8 integrin regulates tumor development, in part, by driving TGFβ1-induced DNA replication and mitotic checkpoint progression. Collectively, these data identify the αvβ8 integrin-TGFβ1 signaling axis as crucial for exploitation of the perivascular niche and identify potential therapeutic targets for inhibiting tumor growth and progression in patients with GBM.

Rutin inhibits proliferation, attenuates superoxide production and decreases adhesion and migration of human cancerous cells

Lung and colorectal cancer are the principal causes of death in the world. Rutin, an active flavonoid compound, is known for possessing a wide range of biological activities. In this study, we examined the effect of rutin on the viability, superoxide anion production, adhesion and migration of human lung (A549) and colon (HT29 and Caco-2) cancer cell lines. In order to control the harmlessness of the tested concentrations of rutin, the viability of cancer cell lines was assessed using a 3-(4,5-dimethylthiazol- 2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) assay. ROS generation was measured by lucigenin chemiluminescence detecting superoxide ions. To investigate the effect of rutin on the behavior of human lung and colon cancer cell lines, we performed adhesion assays, using various purified extracellular matrix (ECM) proteins. Finally, in vitro cell migration assays were explored using modified Boyden chambers. The viability of cancerous cells was inhibited by rutin. It also significantly attenuated the superoxide production in HT29 cells. In addition, rutin affected adhesion and migration of A549 and HT29 cell. These findings indicate that rutin, a natural molecule, might have potential as anticancer agent against lung and colorectal carcinogenesis.

Targetting αvβ3 and α5β1 integrins with Ecballium elaterium (L.) A. Rich. seed oil

In the present study, the effect of Ecbalium elaterium seed oil on adhesion, migration and proliferation of human brain cancer cell line (U87) was determined. Treatment of U87 cell line with the seed oil resulted in strong inhibition of their adhesion to fibrinogen (Fg), fibronectin (Fn). It also reduced their migration and proliferation in a dose-dependent manner without being cytotoxic. Concomitantly, by using Matrigel™ assays, the oil significantly inhibited angiogenesis. The anti- tumor effect of the oil is specifically mediated by αvβ3 and α5β1 integrins. The presence of integrin antagonists in seed oil from E. elaterium could be used for the development of anticancer drugs with targeted "multi-modal" therapies combining anti-adhesif, antiproliferative, antimetastasic and anti-angiogenic, approaches.

β-eudesmol, a sesquiterpene from Teucrium ramosissimum, inhibits superoxide production, proliferation, adhesion and migration of human tumor cell

Reactive oxygen species are well-known mediators of various biological responses. Recently, new homologues of the catalytic subunit of NADPH oxidase have been discovered in non phagocytic cells. These new homologues (Nox1-Nox5) produce low levels of superoxides compared to the phagocytic homologue Nox2/gp91phox. In this study we examined the effect of β-eudesmol, a sesquiterpenoid alcohol isolated from Teucrium ramosissimum leaves, on proliferation, superoxide anion production, adhesion and migration of human lung (A549) and colon (HT29 and Caco-2) cancer cell lines. Proliferation of tumor cells was inhibited by β-eudesmol. It also significantly inhibited superoxide production in A549 cells. Furthermore, β-eudesmol inhibited adhesion and migration of A549 and HT29 cell. These results demonstrate that β-eudesmol may be a novel anticancer agent for the treatment of lung and colon cancer by different ways: by inhibition of superoxide production or by blocking proliferation, adhesion and migration.

Haploinsufficiency of the ESCRT Component HD-PTP Predisposes to Cancer

Endosomal sorting complexes required for transport (ESCRT) drive cell surface receptor degradation resulting in attenuation of oncogenic signaling and pointing to a tumor suppressor function. Here, we show that loss of function of an ESCRT protein (HD-PTP encoded by the PTPN23 gene, located on the tumor suppressor gene cluster 3p21.3) drives tumorigenesis in vivo. Indeed, Ptpn23(+/-) loss predisposes mice to sporadic lung adenoma, B cell lymphoma, and promotes Myc-driven lymphoma onset, dissemination, and aggressiveness. Ptpn23(+/-)-derived tumors exhibit an unaltered remaining allele and maintain 50% of HD-PTP expression. Consistent with the role of HD-PTP in attenuation of integrin recycling, cell migration, and invasion, hemizygous Ptpn23(+/-) loss increases integrin β1-dependent B cell lymphoma survival and dissemination. Finally, we reveal frequent PTPN23 deletion and downregulation in human tumors that correlates with poor survival. Altogether, we establish HD-PTP/PTPN23 as a prominent haploinsufficient tumor suppressor gene preventing tumor progression through control of integrin trafficking.

Mechanical confinement triggers glioma linear migration dependent on formin FHOD3

Glioblastomas are extremely aggressive brain tumors with highly invasive properties. Brain linear tracks such as blood vessel walls constitute their main invasive routes. Here we analyze rat C6 and patient-derived glioma cell motility in vitro using micropatterned linear tracks to mimic blood vessels. On laminin-coated tracks (3-10 μm), these cells used an efficient saltatory mode of migration similar to their in vivo migration. This saltatory migration was also observed on larger tracks (50-400 μm in width) at high cell densities. In these cases, the mechanical constraints imposed by neighboring cells triggered this efficient mode of migration, resulting in the formation of remarkable antiparallel streams of cells along the tracks. This motility involved microtubule-dependent polarization, contractile actin bundles and dynamic paxillin-containing adhesions in the leading process and in the tail. Glioma linear migration was dramatically reduced by inhibiting formins but, surprisingly, accelerated by inhibiting Arp2/3. Protein expression and phenotypic analysis indicated that the formin FHOD3 played a role in this motility but not mDia1 or mDia2. We propose that glioma migration under confinement on laminin relies on formins, including FHOD3, but not Arp2/3 and that the low level of adhesion allows rapid antiparallel migration.

Esculin and its oligomer fractions inhibit adhesion and migration of U87 glioblastoma cells and in vitro angiogenesis

Cancer metastasis is the major cause of cancer-related death. Chemoprevention is defined as the use of natural or synthetic substances to prevent cancer formation or cancer progress. In the present study, we investigate the antitumor activity of esculin and its oligomer fractions in U87 glioblastoma cells. We showed that esculin and its oligomers reduced U87 cell growth in a dose dependent manner. They also inhibited cell adhesion to collagen IV and vitronectin by interfering with the function of their respective receptors α2β1 and αvβ5 integrins. Furthermore, the tested samples were able to reduce migration of U87 cells towards another extracellular matrix fibronectin. Moreover, esculin and its oligomer fractions inhibited in vitro angiogenesis of endothelial cells (HMEC-1). In summary, our data provide the first evidence that esculin and its oligomer fractions are able to reduce adhesion, migration of glioblastoma cells and in vitro angiogenesis. Esculin and its oligomers may thus exert multi-target functions against cancer cells.

Tapered microtract array platform for antimigratory drug screening of human glioblastoma multiforme

Understanding the effects of topographic characteristics on tumor cell migration is important for the development of new anti-migratory therapies. However, simplified in vitro culture systems often lead to inaccurate results regarding the efficacy of drugs. Histopathologically, glioblastoma multiform (GBM) cells migrate along the orientation of thin, elongated anatomical structures, such as white-matter tracts. Here, a tapered microtract array platform which mimics the anatomical features of brain tissue is introduced. This platform enables optimization of design for platform fabrication depending on topographic effects. By monitoring the migration of GBM cells on a simple tapered microtract, a saltatory migration resembling the migratory phenotype of human GBM cells in vivo is observed. The platform effectively induces the native characteristics and behavior of cells by topographic cues, allowing to observe the critical point for crawling to saltatory transition. Furthermore, this platform can be applied to efficiently screen anti-cancer drug by inhibiting associated signaling pathways on GBM cells. In conclusion, the microtract array platform reported here may provide a better understanding of the effects of topographic characteristics on cell migration, and may also be useful to determine the efficacy of antimigratory drugs for glioblastoma cells with cellular and molecular research and high-throughput screening.

Tie2-dependent deletion of α6 integrin subunit in mice reduces tumor growth and angiogenesis

The α6 integrin subunit (α6) has been implicated in cancer cell migration and in the progression of several malignancies, but its role in tumor angiogenesis is unclear. In mice, anti-α6 blocking antibodies reduce tumor angiogenesis, whereas Tie1-dependent α6 gene deletion enhances neovessel formation in melanoma and lung carcinoma. To clarify the discrepancy in these results we used the cre-lox system to generate a mouse line, α6fl/fl‑Tie2Cre(+), with α6 gene deletion specifically in Tie2-lineage cells: endothelial cells, pericytes, subsets of hematopoietic stem cells, and Tie2-expressing monocytes/macrophages (TEMs), known for their proangiogenic properties. Loss of α6 expression in α6fl/fl‑Tie2Cre(+) mice reduced tumor growth in a murine B16F10 melanoma model. Immunohistological analysis of the tumors showed that Tie2-dependent α6 gene deletion was associated with reduced tumor vascularization and with reduced infiltration of proangiogenic Tie2-expressing macrophages. These findings demonstrate that α6 integrin subunit plays a major role in tumor angiogenesis and TEM infiltration. Targeting α6 could be used as a strategy to reduce tumor growth.

PIVL, a snake venom Kunitz-type serine protease inhibitor, inhibits in vitro and in vivo angiogenesis

Development and homeostasis of the vascular system requires integrin-promoting endothelial cell adhesion, migration and survival. Nowadays, integrins represent potential targets for pharmacological agents and open new avenues for the control of metastatic spread in the treatment of tumor malignancies. We have already reported that PIVL, a serine protease inhibitor isolated from Macrovipera lebetina venom, displays an anti-tumor effect through interference with integrin receptor function. Here, we report that PIVL inhibits human vascular endothelial cell adhesion and migration onto fibrinogen and fibronectin in a dose-dependent manner without any cytotoxicity. Furthermore, we show that PIVL increases microtubule dynamic instability in HMEC-1 transfected with EGFP-tagged α-tubulin. Using Matrigel™ and chick chorioallantoic membrane assays, we demonstrate that PIVL exhibits a strong anti-angiogenic effect both in vitro and in vivo. Interestingly, results herein reveal that the potent anti-angiogenic properties of PIVL are mediated by its RGD-like motif ((41)RGN(43)).

Laminins 411 and 421 differentially promote tumor cell migration via α6β1 integrin and MCAM (CD146)

α4-laminins, such as laminins 411 and 421, are mesenchymal laminins expressed by blood and lymphatic vessels and some tumor cells. Laminin-411 promotes migration of leukocytes and endothelial cells, but the effect of this laminin and laminin-421 on tumor cells is poorly understood. In the present study, we demonstrate that laminin-411 and, to a greater extent, laminin-421 significantly promote migration of tumor cells originated from melanomas, gliomas and different carcinomas via α6β1 integrin. In solid-phase binding assays, both laminins similarly bound α6β1 integrin but only laminin-421, among several laminin isoforms, readily bound MCAM (CD146), a cell-surface adhesion molecule strongly associated with tumor progression. Accordingly, a function-blocking mAb to MCAM inhibited tumor cell migration on laminin-421 but not on laminins 411 or 521. In tumor tissues, melanoma cells co-expressed MCAM, laminin α4, β1, β2 and γ1 chains, and integrin α6 and β1 chains. The present data highlight the novel role of α4-laminins in tumor cell migration and identify laminin-421 as a primary ligand for MCAM and a putative mediator of tumor invasion and metastasis.

Signaling determinants of glioma cell invasion

Tumor cell invasiveness is a critical challenge in the clinical management of glioma patients. In addition, there is accumulating evidence that current therapeutic modalities, including anti-angiogenic therapy and radiotherapy, can enhance glioma invasiveness. Glioma cell invasion is stimulated by both autocrine and paracrine factors that act on a large array of cell surface-bound receptors. Key signaling elements that mediate receptor-initiated signaling in the regulation of glioblastoma invasion are Rho family GTPases, including Rac, RhoA and Cdc42. These GTPases regulate cell morphology and actin dynamics and stimulate cell squeezing through the narrow extracellular spaces that are typical of the brain parenchyma. Transient attachment of cells to the extracellular matrix is also necessary for glioblastoma cell invasion. Interactions with extracellular matrix components are mediated by integrins that initiate diverse intracellular signalling pathways. Key signaling elements stimulated by integrins include PI3K, Akt, mTOR and MAP kinases. In order to detach from the tumor mass, glioma cells secrete proteolytic enzymes that cleave cell surface adhesion molecules, including CD44 and L1. Key proteases produced by glioma cells include uPA, ADAMs and MMPs. Increased understanding of the molecular mechanisms that control glioma cell invasion has led to the identification of molecular targets for therapeutic intervention in this devastating disease.

Deregulated microRNAs identified in isolated glioblastoma stem cells: an overview

Glioblastoma multiforme (GBM), the most common and aggressive primary brain tumor, is extremely resistant to current treatment paradigms and has a high rate of tumor recurrence. Recent progress in the field of tumor-initiating cells suggests that GBM stem cells (GBMSCs) may be responsible for tumor progression, resistance to treatment, and tumor relapse. Therefore, understanding the biologically significant pathways involved in modulating GBMSC-specific characteristics offers great promise for development of novel therapeutics, which may improve therapeutic efficacy and overcome present drug resistance. In addition, targeting deregulated microRNA (miRNA) has arisen as a new therapeutic strategy in treating malignant gliomas. In GBMSCs, miRNAs regulate a wide variety of tumorigenic processes including cellular proliferation, stemness maintenance, migration/invasion, apoptosis, and tumorigenicity. Nevertheless, the latest progress with GBMSCs and subsequent miRNA profiling is limited by the identification and isolation of GBMSCs. In this review, we thus summarize current markers and known features for isolation as well as the aberrant miRNAs that have been identified in GBM and GBMSCs.

Integrins and p53 pathways in glioblastoma resistance to temozolomide

Glioblastoma is the most common malignant primary brain tumor. Surgical resection, postoperative radiotherapy plus concomitant and adjuvant chemotherapy with temozolomide (TMZ) is the standard of care for newly diagnosed glioblastoma. In the past decade, efforts have been made to decipher genomic and core pathway alterations to identify clinically relevant glioblastoma subtypes. Based on these studies and more academic explorations, new potential therapeutic targets were found and several targeting agents were developed. Such molecules should hopefully overcome the resistance of glioblastoma to the current therapy. One of the hallmarks of glioblastoma subtypes was the enrichment of extracellular matrix/invasion-related genes. Integrins, which are cell adhesion molecules important in glioma cell migration/invasion and angiogenesis were one of those genes. Integrins seem to be pertinent therapeutic targets and antagonists recently reached the clinic. Although the p53 pathway appears often altered in glioblastoma, conflicting results can be found in the literature about the clinically relevant impact of the p53 status in the resistance to TMZ. Here, we will summarize the current knowledge on (1) integrin expression, (2) p53 status, and (3) relationship between integrins and p53 to discuss their potential impact on the resistance of glioblastoma to temozolomide.

Human U87 astrocytoma cell invasion induced by interaction of βig-h3 with integrin α5β1 involves calpain-2

It is known that βig-h3 is involved in the invasive process of many types of tumors, but its mechanism in glioma cells has not been fully clarified. Using immunofluorescent double-staining and confocal imaging analysis, and co-immunoprecipitation assays, we found that βig-h3 co-localized with integrin α5β1 in U87 cells. We sought to elucidate the function of this interaction by performing cell invasion assays and gelatin zymography experiments. We found that siRNA knockdowns of βig-h3 and calpain-2 impaired cell invasion and MMP secretion. Moreover, βig-h3, integrins and calpain-2 are known to be regulated by Ca²⁺, and they are also involved in tumor cell invasion. Therefore, we further investigated if calpain-2 was relevant to βig-h3-integrin α5β1 interaction to affect U87 cell invasion. Our data showed that βig-h3 co-localized with integrin α5β1 to enhance the invasion of U87 cells, and that calpain-2, is involved in this process, acting as a downstream molecule.

Endothelial expression of TNF receptor-1 generates a proapoptotic signal inhibited by integrin α6β1 in glioblastoma

Activation of TNF receptor 1 (TNF-R1) can generate signals that promote either apoptosis or survival. In this study, we show that these signals can be determined by the character of the extracellular matrix in the tumor microenvironment. Specifically, through studies of glioblastoma, we showed that TNFα stimulation induced apoptosis of primary brain endothelial cells (EC) attached to collagen or fibronectin (which engage integrins α2β1/α3β1 and α5β1, respectively), but did not induce apoptosis of ECs attached to laminin (which engages integrins α6β1 and α3β1). TNF-R1 expression was significantly higher in ECs in glioblastoma (GBM) tumors compared with ECs in normal brain specimens. TNFα was also expressed in GBM tumor-associated ECs, which was associated with longer patient survival. ECs plated on anti-integrin α2 or α3 antibody were susceptible to TNFα-induced apoptosis, whereas those plated on anti-integrin α6 antibody were not. Moreover, the ECs plated on laminin, but not collagen, expressed cellular FLICE inhibitory protein (cFLIP) and TNFα stimulation of laminin-attached cells in which cFLIP had been downregulated resulted in the induction of apoptosis. In contrast, attachment to laminin did not induce cFLIP expression in GBM tumor stem cells. Together, our findings indicate that the laminin receptor integrin α6β1 promotes the survival of brain ECs by inhibiting prodeath signaling by TNF-R1, in part by inducing cFLIP expression.

Proper cerebellar development requires expression of β1-integrin in Bergmann glia, but not in granule neurons

β1-class integrins play essential roles both in developmental biology as well as in cancer. Particularly, a Nestin-driven deletion of β1-integrin receptors results in severe abnormalities of brain development including a laminar disorganization of cerebellar granule neurons. However, since Nestin is expressed in all kinds of neural precursors, these data do not allow conclusions to be drawn about the role of β1-integrins in distinct neuronal and glial cell types. By generating conditional knockout mice using granule cell-specific Math1-promoter sequences, we show here that the expression of β1-integrins in granule neurons is dispensable for the development of the cerebellum. Also, deletion of β1-integrin from tumors that arise in a mouse model of granule cell precursor-derived medulloblastoma did not result in a significant survival benefit. Last, expression levels of β1-integrin in human medulloblastoma samples did not predict patient's outcome. However, a β1-integrin knockout using hGFAP-promoter sequences led to cerebellar hypoplasia, inappropriate positioning of Bergmann glia cells in the molecular layer, undirected outgrowth of radial glia fibers, and granule cell ectopia. We therefore conclude that β1-integrin expression in cerebellar granule neurons is not essential during normal development or medulloblastoma formation. In fact, it is the expression of β1-integrin in glia that is crucial for the proper development of the cerebellar cortex.

Extracellular matrix protein CCN1 limits oncolytic efficacy in glioma

Oncolytic viral therapy has been explored widely as an option for glioma treatment but its effectiveness has remained limited. Cysteine rich 61 (CCN1) is an extracellular matrix (ECM) protein elevated in cancer cells that modulates their adhesion and migration by binding cell surface receptors. In this study, we examined a hypothesized role for CCN1 in limiting the efficacy of oncolytic viral therapy for glioma, based on evidence of CCN1 induction that occurs in this setting. Strikingly, we found that exogenous CCN1 in glioma ECM orchestrated a cellular antiviral response that reduced viral replication and limited cytolytic efficacy. Gene expression profiling and real-time PCR analysis revealed a significant induction of type-I interferon responsive genes in response to CCN1 exposure. This induction was accompanied by activation of the Jak/Stat signaling pathway, consistent with induction of an innate antiviral cellular response. Both effects were mediated by the binding of CCN1 to the cell surface integrin α6β1, activating its signaling and leading to rapid secretion of interferon-α, which was essential for the innate antiviral effect. Together, our findings reveal how an integrin signaling pathway mediates activation of a type-I antiviral interferon response that can limit the efficacy of oncolytic viral therapy. Furthermore, they suggest therapeutic interventions to inhibit CCN1-integrin α6 interactions to sensitize gliomas to viral oncolysis.

IDH1 R132H decreases proliferation of glioma cell lines in vitro and in vivo

OBJECTIVE

A high percentage of grade II and III gliomas have mutations in the gene encoding isocitrate dehydrogenase (IDH1). This mutation is always a heterozygous point mutation that affects the amino acid arginine at position 132 and results in loss of its native enzymatic activity and gain of alternative enzymatic activity (producing D-2-hydroxyglutarate). The objective of this study was to investigate the cellular effects of R132H mutations in IDH1.

METHODS

Functional consequences of IDH1(R132H) mutations were examined among others using fluorescence-activated cell sorting, kinome and expression arrays, biochemical assays, and intracranial injections on 3 different (glioma) cell lines with stable overexpression of IDH1(R132H) .

RESULTS

IDH1(R132H) overexpression in established glioma cell lines in vitro resulted in a marked decrease in proliferation, decreased Akt phosphorylation, altered morphology, and a more contact-dependent cell migration. The reduced proliferation is related to accumulation of D-2-hydroxyglutarate that is produced by IDH1(R132H) . Mice injected with IDH1(R132H) U87 cells have prolonged survival compared to mice injected with IDH1(wt) or green fluorescent protein-expressing U87 cells.

INTERPRETATION

Our results demonstrate that IDH1(R132H) dominantly reduces aggressiveness of established glioma cell lines in vitro and in vivo. In addition, the IDH1(R132H) -IDH1(wt) heterodimer has higher enzymatic activity than the IDH1(R132H) -IDH1(R132H) homodimer. Our observations in model systems of glioma might lead to a better understanding of the biology of IDH1 mutant gliomas, which are typically low grade and often slow growing.

Purification, synthesis and characterization of AaCtx, the first chlorotoxin-like peptide from Androctonus australis scorpion venom

AaCtx is the first chlorotoxin-like peptide isolated from Androctonus australis scorpion venom. Its amino acid sequence shares 70% similarity with chlorotoxin from Leiurus quinquestriatus scorpion venom, from which it differs by twelve amino acids. Due to its very low concentration in venom (0.05%), AaCtx was chemically synthesized. Both native and synthetic AaCtx were active on invasion and migration of human glioma cells. However, their activity was found to be lower than that of chlorotoxin. The molecular model of AaCtx shows that most of amino acids differing between AaCtx and chlorotoxin are localized on the N-terminal loop and the α-helix. Based on known compounds that block chloride channels, we suggest that the absence of negative charged amino acids on AaCtx structure may be responsible for its weak activity on glioma cells migration and invasion. This finding serves as a starting point for structure-function relationship studies leading to design high specific anti-glioma drugs.

Involvement of β1-integrin via PIP complex and FAK/paxillin in dexamethasone-induced human mesenchymal stem cells migration

Although glucocorticoids strongly affect numerous biological processes including cell growth, development, and homeostasis, their effects on migration of human mesenchymal stem cells (hMSCs) are unclear. Therefore, we investigated the role of dexamethasone (DEX) and its related signaling pathways on migration of hMSCs. We found that DEX, at 10(-8) to 10(-6) M, significantly increased migration after a 24 h incubation, and DEX (10(-6) M) increased migration at >12 h. Moreover, DEX (10(-6) M) increased the level of glucocorticoid receptor (GR)-α mRNA and protein expression, but not GR-β mRNA. The increases in DEX-induced migration were inhibited by the GR antagonist mifepristone (10(-7) M). In addition, DEX increased integrin-linked kinase (ILK) and α-parvin expression but did not change PINCH-1/2 expression in lysate. DEX also increased formations of complex with ILK and α-parvin, and ILK and PINCH-1/2 as shown by immunoprecipitation, which were all inhibited by mifepristone. DEX-induced migration was blocked by ILK and α-parvin small interfering(si)RNAs. In addition, DEX increased focal adhesion kinase (FAK) and paxillin expression, which were attenuated by ILK and α-parvin siRNAs. DEX-induced cell migration was inhibited by FAK/paxillin siRNAs. DEX also increased β1-integrin expression, which was blocked by FAK/paxillin siRNAs. In addition, DEX-induced cell migration was inhibited by β1-integrin siRNA. Downregulation of ILK, α-parvin, FAK/paxillin and β1-integrin expression by siRNAs decreased DEX-induced filamentous(F)-actin organization and migration of hMSCs. In conclusion, DEX partially stimulates hMSC migration by the expression of β1-integrin through formation of a PINCH-1/2/ILK/α-parvin complex (PIP complex), and FAK and paxillin expression.