Immunohistochemical investigation of collagen subtypes in human glioblastomas

Acquired Temozolomide Resistance Instructs Patterns of Glioblastoma Behavior in Gelatin Hydrogels

Acquired drug resistance in glioblastoma (GBM) presents a major clinical challenge and is a key factor contributing to abysmal prognosis, with less than 15 months median overall survival. Aggressive chemotherapy with the frontline therapeutic, temozolomide (TMZ), ultimately fails to kill residual highly invasive tumor cells after surgical resection and radiotherapy. Here, a 3D engineered model of acquired TMZ resistance is reported using two isogenically matched sets of GBM cell lines encapsulated in gelatin methacrylol hydrogels. Response of TMZ-resistant versus TMZ-sensitive GBM cell lines within the gelatin-based extracellular matrix platform is benchmarked and drug response at physiologically relevant TMZ concentrations is further validated. The changes in drug sensitivity, cell invasion, and matrix-remodeling cytokine production are shown as the result of acquired TMZ resistance. This platform lays the foundation for future investigations targeting key elements of the GBM tumor microenvironment to combat GBM's devastating impact by advancing the understanding of GBM progression and treatment response to guide the development of novel treatment strategies.

Acquired temozolomide resistance instructs patterns of glioblastoma behavior in gelatin hydrogels

Acquired drug resistance in glioblastoma (GBM) presents a major clinical challenge and is a key factor contributing to abysmal prognosis, with less than 15 months median overall survival. Aggressive chemotherapy with the frontline therapeutic, temozolomide (TMZ), ultimately fails to kill residual highly invasive tumor cells after surgical resection and radiotherapy. Here, we report a three-dimensional (3D) engineered model of acquired TMZ resistance using two isogenically-matched sets of GBM cell lines encapsulated in gelatin methacrylol hydrogels. We benchmark response of TMZ-resistant vs. TMZ-sensitive GBM cell lines within the gelatin-based extracellular matrix platform and further validate drug response at physiologically relevant TMZ concentrations. We show changes in drug sensitivity, cell invasion, and matrix-remodeling cytokine production as the result of acquired TMZ resistance. This platform lays the foundation for future investigations targeting key elements of the GBM tumor microenvironment to combat GBM's devastating impact by advancing our understanding of GBM progression and treatment response to guide the development of novel treatment strategies.

Teaser

A hydrogel model to investigate the impact of acquired drug resistance on functional response in glioblastoma.

Collagen VI sustains cell stemness and chemotherapy resistance in glioblastoma

Microenvironmental factors are known fundamental regulators of the phenotype and aggressiveness of glioblastoma (GBM), the most lethal brain tumor, characterized by fast progression and marked resistance to treatments. In this context, the extracellular matrix (ECM) is known to heavily influence the behavior of cancer cells from several origins, contributing to stem cell niches, influencing tumor invasiveness and response to chemotherapy, mediating survival signaling cascades, and modulating inflammatory cell recruitment. Here, we show that collagen VI (COL6), an ECM protein widely expressed in both normal and pathological tissues, has a distinctive distribution within the GBM mass, strongly correlated with the most aggressive and phenotypically immature cells. Our data demonstrate that COL6 sustains the stem-like properties of GBM cells and supports the maintenance of an aggressive transcriptional program promoting cancer cell proliferation and survival. In particular, we identified a specific subset of COL6-transcriptionally co-regulated genes, required for the response of cells to replicative stress and DNA damage, supporting the concept that COL6 is an essential stimulus for the activation of GBM cell response and resistance to chemotherapy, through the ATM/ATR axis. Altogether, these findings indicate that COL6 plays a pivotal role in GBM tumor biology, exerting a pleiotropic action across different GBM hallmarks, including phenotypic identity and gene transcription, as well as response to treatments, thus providing valuable information for the understanding of the complex microenvironmental cues underlying GBM malignancy.

Perivascular Stromal Cells Instruct Glioblastoma Invasion, Proliferation, and Therapeutic Response within an Engineered Brain Perivascular Niche Model

Glioblastoma (GBM) tumor cells are found in the perivascular niche microenvironment and are believed to associate closely with the brain microvasculature. However, it is largely unknown how the resident cells of the perivascular niche, such as endothelial cells, pericytes, and astrocytes, influence GBM tumor cell behavior and disease progression. A 3D in vitro model of the brain perivascular niche developed by encapsulating brain-derived endothelial cells, pericytes, and astrocytes in a gelatin hydrogel is described. It is shown that brain perivascular stromal cells, namely pericytes and astrocytes, contribute to vascular architecture and maturation. Cocultures of patient-derived GBM tumor cells with brain microvascular cells are used to identify a role for pericytes and astrocytes in establishing a perivascular niche environment that modulates GBM cell invasion, proliferation, and therapeutic response. Engineered models provide unique insight regarding the spatial patterning of GBM cell phenotypes in response to a multicellular model of the perivascular niche. Critically, it is shown that engineered perivascular models provide an important resource to evaluate mechanisms by which intercellular interactions modulate GBM tumor cell behavior, drug response, and provide a framework to consider patient-specific disease phenotypes.

Protocol to assess human glioma propagating cell migration on linear micropatterns mimicking brain invasion tracks

Glioblastoma (GBM) cells invade the brain by following linear structures like blood vessel walls and white matter tracts by using specific motility modes. In this protocol, we describe two micropatterning techniques allowing recapitulation of these linear tracks in vitro: micro-contact printing and deep UV photolithography. We also detail how to maintain, transfect, and prepare human glioma propagating cells (hGPCs) for migration assays on linear tracks, followed by image acquisition and analysis, to measure key parameters of their motility.

For complete details on the use and execution of this protocol, please refer to Monzo et al. (2016) and Monzo et al. (2021a).

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Micropatterning of linear tracks on imaging dishes

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Maintenance and preparation of human glioma propagating cells (hGPC) for transfection

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Transfection of hGPC by electroporation and preparation for imaging

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Imaging of hGPC migration on linear tracks, cell tracking, and analysis

Tumor Cell Infiltration into the Brain in Glioblastoma: From Mechanisms to Clinical Perspectives

Glioblastoma is the most common and malignant primary brain tumor, defined by its highly aggressive nature. Despite the advances in diagnostic and surgical techniques, and the development of novel therapies in the last decade, the prognosis for glioblastoma is still extremely poor. One major factor for the failure of existing therapeutic approaches is the highly invasive nature of glioblastomas. The extreme infiltrating capacity of tumor cells into the brain parenchyma makes complete surgical removal difficult; glioblastomas almost inevitably recur in a more therapy-resistant state, sometimes at distant sites in the brain. Therefore, there are major efforts to understand the molecular mechanisms underpinning glioblastoma invasion; however, there is no approved therapy directed against the invasive phenotype as of now. Here, we review the major molecular mechanisms of glioblastoma cell invasion, including the routes followed by glioblastoma cells, the interaction of tumor cells within the brain environment and the extracellular matrix components, and the roles of tumor cell adhesion and extracellular matrix remodeling. We also include a perspective of high-throughput approaches utilized to discover novel players for invasion and clinical targeting of invasive glioblastoma cells.

Manipulation of immune‒vascular crosstalk: new strategies towards cancer treatment

Tumor vasculature is characterized by aberrant structure and function, resulting in immune suppressive profiles of tumor microenvironment through limiting immune cell infiltration into tumors, endogenous immune surveillance and immune cell function. Vascular normalization as a novel therapeutic strategy tends to prune some of the immature blood vessels and fortify the structure and function of the remaining vessels, thus improving immune stimulation and the efficacy of immunotherapy. Interestingly, the presence of "immune‒vascular crosstalk" enables the formation of a positive feedback loop between vascular normalization and immune reprogramming, providing the possibility to develop new cancer therapeutic strategies. The applications of nanomedicine in vascular-targeting therapy in cancer have gained increasing attention due to its specific physical and chemical properties. Here, we reviewed the recent advances of effective routes, especially nanomedicine, for normalizing tumor vasculature. We also summarized the development of enhancing nanoparticle-based anticancer drug delivery via the employment of transcytosis and mimicking immune cell extravasation. This review explores the potential to optimize nanomedicine-based therapeutic strategies as an alternative option for cancer treatment.

Hyaluronic acid induces ROCK-dependent amoeboid migration in glioblastoma cells

Glioblastoma (GBM) is the most aggressive and deadly adult brain tumor, primarily because of its high infiltrative capacity and development of resistance to therapy. Although GBM cells are typically believed to migrate via mesenchymal (e.g., fibroblast-like) migration modes, amoeboid (e.g., leucocyte-like) migration modes have been identified and may constitute a salvage pathway. However, the mesenchymal to amoeboid transition (MAT) process in GB is not well characterized, most likely because most culture models induce MAT via pharmacological or genetic inhibition conditions that are far from physiological. In this study, we examined the ability of hyaluronic acid (HA) content in three-dimensional collagen (Col) hydrogels to induce MAT in U87 GBM cells. HA and Col are naturally-occurring components of the brain extracellular matrix (ECM). In pure Col gels, U87 cells displayed primarily mesenchymal behaviors, including elongated cell morphology, clustered actin and integrin expression, and crawling migration behaviors. Whereas an increasing population of cells displaying amoeboid behaviors, including rounded morphology, cortical actin expression, low/no integrin expression, and squeezing or gliding motility, were observed with increasing HA content (0.1-0.2 wt% in Col). Consistent with amoeboid migration, these behaviors were abrogated by ROCK inhibition with the non-specific small molecule inhibitor Y27632. Toward identification of histological MAT classification criteria, we also examined the correlation between cell and nuclear aspect ratio (AR) in Col and Col-HA gels, finding that nuclear AR has a small variance and is not correlated to cell AR in HA-rich gels. These results suggest that HA may regulate GBM cell motility in a ROCK-dependent manner.

Procollagen-lysine 2-oxoglutarate 5-dioxygenase 2 promotes hypoxia-induced glioma migration and invasion

Poor prognosis of glioblastoma multiforme is strongly associated with the ability of tumor cells to invade the brain parenchyma, which is believed to be the major factor responsible for glioblastoma recurrence. Therefore, identifying the molecular mechanisms driving invasion may lead to the development of improved therapies for glioblastoma patients. Here, we investigated the role of procollagen-lysine 2-oxoglutarate 5-dioxygenase 2 (PLOD2), an enzyme catalyzing collagen cross-linking, in the biology of glioblastoma invasion. PLOD2 mRNA was significantly overexpressed in glioblastoma compared to low-grade tumors based on the Oncomine datasets and REMBRANDT database for human gliomas. Kaplan-Meier estimates based on the TCGA dataset demonstrated that high PLOD2 expression was associated with poor prognosis. In vitro, hypoxia upregulated PLOD2 protein in U87 and U251 human glioma cell lines. siRNA knockdown of endogenous HIF-1α or treatment of cells with the HIF-1α inhibitor PX-478 largely abolished the hypoxia-mediated PLOD2 upregulation. Knockdown of PLOD2 in glioma cell lines led to decreases in migration and invasion under normoxia and hypoxia. In addition, levels of phosphorylated FAK (Tyr 397), an important kinase mediating cell adhesion, were reduced in U87-shPLOD2 and U251-shPLOD2 cells, particularly under hypoxic conditions. Finally, orthotopic U251-shPLOD2 xenografts were circumscribed rather than locally invasive. In conclusion, the results indicated that PLOD2 was a gene of clinical relevance with implications in glioblastoma invasion and treatment strategies.

Association of collagen architecture with glioblastoma patient survival

OBJECTIVE Glioblastoma (GBM) is the most malignant primary brain tumor. Collagen is present in low amounts in normal brain, but in GBMs, collagen gene expression is reportedly upregulated. However, to the authors' knowledge, direct visualization of collagen architecture has not been reported. The authors sought to perform the first direct visualization of GBM collagen architecture, identify clinically relevant collagen signatures, and link them to differential patient survival. METHODS Second-harmonic generation microscopy was used to detect collagen in a GBM patient tissue microarray. Focal and invasive GBM mouse xenografts were stained with Picrosirius red. Quantitation of collagen fibers was performed using custom software. Multivariate survival analysis was done to determine if collagen is a survival marker for patients. RESULTS In focal xenografts, collagen was observed at tumor brain boundaries. For invasive xenografts, collagen was intercalated with tumor cells. Quantitative analysis showed significant differences in collagen fibers for focal and invasive xenografts. The authors also found that GBM patients with more organized collagen had a longer median survival than those with less organized collagen. CONCLUSIONS Collagen architecture can be directly visualized and is different in focal versus invasive GBMs. The authors also demonstrate that collagen signature is associated with patient survival. These findings suggest that there are collagen differences in focal versus invasive GBMs and that collagen is a survival marker for GBM.

Accessibilome of human glioblastoma: collagen-VI-alpha-1 is a new target and a marker of poor outcome

Functional targeted therapy has unfortunately failed to improve the outcome of glioblastoma patients. Success stories evidenced by the use of antibody-drug conjugates in other tumor types are encouraging, but targets specific to glioblastoma and accessible through the bloodstream remain scarce. In the current work, we have identified and characterized novel and accessible proteins using an innovative proteomic approach on six human glioblastomas; the corresponding data have been deposited in the PRIDE database identifier PXD001398. Among several clusters of uniquely expressed proteins, we highlight collagen-VI-alpha-1 (COL6A1) as a highly expressed tumor biomarker with low levels in most normal tissues. Immunohistochemical analysis of glioma samples from 61 patients demonstrated that COL6A1 is a significant and consistent feature of high-grade glioma. Deposits of COL6A1 were evidenced in the perivascular regions of the tumor-associated vasculature and in glioma cells found in pseudopalisade structures. Retrospective analysis of public gene-expression data sets from over 300 glioma patients demonstrated a significant correlation of poor patient outcome and high COL6A1 expression. In a proof-of-concept study, we use chicken chorioallantoic membrane in vivo model to show that COL6A1 is a reachable target for IV-injected antibodies. The present data warrant further development of human COL6A1 antibodies for assessing the quantitative biodistribution in the preclinical tumor models.

Intracranial gliofibroma: a case report and review of the literature

Gliofibroma is a rare tumor with biphasic morphology, commonly occurring in the first two decades of life. Currently, the tumor is not listed as a distinct entity in the current World Health Organization (WHO) classification of central nervous system tumors. As its biological behavior, histogenesis, and prognostic factors are still debated, the aim of this paper was to describe a case of a gliofibroma and to update the data about these lesions. Hence, we present here clinical symptoms, pathological findings, and evolution observed in a child with gliofibroma. A 10-year-old girl with seizures was referred for study. Neuroimaging showed a hemispheric hyperdense tumor with little peritumoral edema and no mass effect. The tumor was totally removed. Histologically, the tumor consisted of a mixture of glial cells and collagen-rich stroma. Immunohistochemical examination revealed positive staining for GFAP, CD 99, S100, and vimentin. EMA staining showed a paranuclear dot pattern in only few cells in isolated areas. These findings of a glial component with collagenous stroma were consistent with a desmoplastic glioma. Because of the rarity of this entity, we believe it is important to report every case in order to adequately analyze and categorize the tumor in the next WHO classification.

Aligned chitosan-polycaprolactone polyblend nanofibers promote the migration of glioblastoma cells

In vitro models that accurately mimic the microenvironment of invading glioblastoma multiform (GBM) cells will provide a high-throughput system for testing potential anti-invasion therapies. Here, the ability of chitosan-polycaprolactone polyblend nanofibers to promote a migratory phenotype in human GBM cells by altering the nanotopography of the nanofiber membranes is investigated. Fibers are prepared with diameters of 200 nm, 400 nm, and 1.1 μm, and are either randomly oriented or aligned to produce six distinct nanotopographies. Human U-87 MG GBM cells, a model cell line commonly used for invasion assays, are cultured on the various nanofibrous substrates. Cells show elongation and alignment along the orientation of aligned fibers as early as 24 h and up to 120 h of culture. After 24 h of culture, human GBM cells cultured on aligned 200 nm and 400 nm fibers show marked upregulation of invasion-related genes including β-catenin, Snail, STAT3, TGF-β, and Twist, suggesting a mesenchymal change in these migrating cells. Additionally, cells cultured on 400 nm aligned fibers show similar migration profiles as those reported in vivo, and thus these nanofibers should provide a unique high-throughput in vitro culture substrate for developing anti-migration therapies for the treatment of GBM.

Invasion as target for therapy of glioblastoma multiforme

The survival of cancer patients suffering from glioblastoma multiforme is limited to just a few months even after treatment with the most advanced techniques. The indefinable borders of glioblastoma cell infiltration into the surrounding healthy tissue prevent complete surgical removal. In addition, genetic mutations, epigenetic modifications and microenvironmental heterogeneity cause resistance to radio- and chemotherapy altogether resulting in a hardly to overcome therapeutic scenario. Therefore, the development of efficient therapeutic strategies to combat these tumors requires a better knowledge of genetic and proteomic alterations as well as the infiltrative behavior of glioblastoma cells and how this can be targeted. Among many cell surface receptors, members of the integrin family are known to regulate glioblastoma cell invasion in concert with extracellular matrix degrading proteases. While preclinical and early clinical trials suggested specific integrin targeting as a promising therapeutic approach, clinical trials failed to deliver improved cure rates up to now. Little is known about glioblastoma cell motility, but switches in invasion modes and adaption to specific microenvironmental cues as a consequence of treatment may maintain tumor cell resistance to therapy. Thus, understanding the molecular basis of integrin and protease function for glioblastoma cell invasion in the context of radiochemotherapy is a pressing issue and may be beneficial for the design of efficient therapeutic approaches. This review article summarizes the latest findings on integrins and extracellular matrix in glioblastoma and adds some perspective thoughts on how this knowledge might be exploited for optimized multimodal therapy approaches.

Collagen VI in cancer and its biological mechanisms

Collagen VI is a widely distributed extracellular matrix protein highly expressed in a variety of cancers that favors tumor growth and progression. A growing number of studies indicate that collagen VI directly affects malignant cells by acting on the Akt-GSK-3β-β-catenin-TCF/LEF axis, enhancing the production of protumorigenic factors and inducing epithelial-mesenchymal transition. Moreover, it affects the tumor microenvironment by increasing the recruitment of macrophages and endothelial cells, thus promoting tumor inflammation and angiogenesis. Furthermore, collagen VI promotes chemotherapy resistance and can be regarded as a potential biomarker for cancer diagnosis. Collectively, these findings strongly support a role for collagen VI as an important regulator in tumors and provide new targets for cancer therapies.

Pericytes on the tumor vasculature: jekyll or hyde?

The induction of tumor vasculature, known as the 'angiogenic switch', is a rate-limiting step in tumor progression. Normal blood vessels are composed of two distinct cell types: endothelial cells which form the channel through which blood flows, and mural cells, the pericytes and smooth muscle cells which serve to support and stabilize the endothelium. Most functional studies have focused on the responses of endothelial cells to pro-angiogenic stimuli; however, there is mounting evidence that the supporting mural cells, particularly pericytes, may play key regulatory roles in both promoting vessel growth as well as terminating vessel growth to generate a mature, quiescent vasculature. Tumor vessels are characterized by numerous structural and functional abnormalities, including altered association between endothelial cells and pericytes. These dysfunctional, unstable vessels contribute to hypoxia, interstitial fluid pressure, and enhanced susceptibility to metastatic invasion. Increasing evidence points to the pericyte as a critical regulator of endothelial activation and subsequent vessel development, stability, and function. Here we discuss both the stimulatory and inhibitory effects of pericytes on the vasculature and the possible utilization of vessel normalization as a therapeutic strategy to combat cancer.

Inhibition of collagen XVI expression reduces glioma cell invasiveness

Glioblastomas are characterized by an intense local invasiveness that limits surgical resection. One mechanism by which glioma cells enforce their migration into brain tissue is reorganization of tumour associated extracellular matrix (ECM). Collagen XVI is a minor component of connective tissues. However, in glioblastoma tissue it is dramatically upregulated compared to the ECM of normal cortex. The aim of this study is to delineate tumour cell invasion and underlying mechanisms involving collagen XVI by using a siRNA mediated collagen XVI knockdown model in U87MG human glioblastoma cells. Knockdown of collagen XVI resulted in decreased invasiveness in Boyden chamber assays, and in a reduction of focal adhesion contact numbers per cell. Gene expression was upregulated for protocadherin 18 and downregulated for kindlin-1 and -2. Proliferation was not affected while flow cytometric analysis demonstrated reduced β1-integrin activation in collagen XVI knockdown cells. We suggest that in glioblastoma tissue collagen XVI may impair the cell-cell interaction in favour of enhancement of invasion. The modification of the β1-integrin activation pattern through collagen XVI might be a molecular mechanism to further augment the invasive phenotype of glioma cells. Elucidating the underlying mechanisms of glioma cell invasion promoted by collagen XVI may provide novel cancer therapeutic approaches in neurooncology.

Quantitative analysis of complex glioma cell migration on electrospun polycaprolactone using time-lapse microscopy

Malignant gliomas are the most common tumors originating within the central nervous system and account for over 15,000 deaths annually in the United States. The median survival for glioblastoma, the most common and aggressive of these tumors, is only 14 months. Therapeutic strategies targeting glioma cells migrating away from the tumor core are currently hampered by the difficulty of reproducing migration in the neural parenchyma in vitro. We utilized a tissue engineering approach to develop a physiologically relevant model of glioma cell migration. This revealed that glioma cells display dramatic differences in migration when challenged by random versus aligned electrospun poly-epsilon-caprolactone nanofibers. Cells on aligned fibers migrated at an effective velocity of 4.2 +/- 0.39 microm/h compared to 0.8 +/- 0.08 microm/h on random fibers, closely matching in vivo models and prior observations of glioma spread in white versus gray matter. Cells on random fibers exhibited extension along multiple fiber axes that prevented net motion; aligned fibers promoted a fusiform morphology better suited to infiltration. Time-lapse microscopy revealed that the motion of individual cells was complex and was influenced by cell cycle and local topography. Glioma stem cell-containing neurospheres seeded on random fibers did not show cell detachment and retained their original shape; on aligned fibers, cells detached and migrated in the fiber direction over a distance sixfold greater than the perpendicular direction. This chemically and physically flexible model allows time-lapse analysis of glioma cell migration while recapitulating in vivo cell morphology, potentially allowing identification of physiological mediators and pharmacological inhibitors of invasion.

Suberoylanilide hydroxamic acid limits migration and invasion of glioma cells in two and three dimensional culture

High grade gliomas are aggressive cancers that are not well addressed by current chemotherapies, in large measure because these drugs do not curtail the diffuse invasion of glioma cells into brain tissue surrounding the tumor. Here, we investigate the effects of suberoylanilide hydroxamic acid (SAHA) on glioma cells in 2D and 3D in vitro assays, as SAHA has previously been shown to significantly increase apoptosis, decrease proliferation, and interfere with migration in other cell lines. We find that SAHA has significant independent effects on proliferation, migration, and invasion. These effects are seen in both 2D and 3D culture. In 3D culture, with glioma spheroids embedded in collagen I matrices, SAHA independently limits both glioma invasion and the reorganization of the tumor surroundings that usually proceeds such invasion. The decreased matrix reorganization and invasion is not accompanied by decreased production or activity of matrix-metalloproteases but instead may be related to increased cell-cell adhesion.

Reduction of protein kinase C delta attenuates tenascin-C stimulated glioma invasion in three-dimensional matrix

The invasiveness of glioma cells, a major cause of mortality in malignant brain tumors, is mediated in part by the cellular microenvironment. We have reported that in a three-dimensional matrix of type 1 collagen (3D-CL) gel, the extracellular matrix protein tenascin-C (TN) increased the invasiveness of glioma cells through the downstream production of matrix metalloproteinase (MMP)-12. In the present study, we have investigated the signaling mechanisms involved in the TN-stimulated glioma invasiveness. We found that the pan protein kinase C (PKC) inhibitor, bisindolylmaleimide I, decreased TN-enhanced glioma invasion in 3D-CL. Calphostin C, an inhibitor of conventional and novel PKC isozymes, and the relatively selective PKCdelta inhibitor rottlerin decreased TN-stimulated glioma invasiveness in a concentration- and time-dependent manner. These findings of the possible involvement of PKCdelta was supported by its translocation from the cytosol to membrane fraction in 3D-CL gel supplemented with TN as detected by western blot assays and immunofluorescence microscopy and by elevation of PKCdelta enzyme activity. Moreover, pharmacological blockade of PKCdelta decreased MMP-12 levels and glioma invasiveness. Finally, small interfering RNA to PKCdelta reduced TN-stimulated glioma invasiveness concurrent with decreased MMP-12 production. Our results implicate PKCdelta as a therapeutic target to reduce MMP-12 expression and glioma invasiveness when tumor cells are stimulated by the TN-enriched glioma microenvironment.

Inflammatory cytokine modulation of matrix metalloproteinase expression and invasiveness of glioma cells in a 3-dimensional collagen matrix

Glioma invasiveness is accomplished in part by matrix metalloproteinases (MMPs) which remodel the constraints of the three dimensional (3D) matrix of the brain parenchyma. Tissue culture studies have advanced knowledge of glioma invasiveness but the majority of studies have used a two dimensional (2D) monolayer culture system which does not reproduce the spatial constraints of invasiveness in vivo. Here, we have used a 3D matrix of type I collagen (CL) gel to address glioma invasiveness in vitro. We show that in 3D CL matrix, interleukin-1 beta (IL-1beta) and tumor necrosis factor-alpha (TNF-alpha), cytokines which are elevated in gliomas in vivo, increased glioma cell invasiveness with correspondent elevation of MMP-2 and MMP-9. Cytokine-stimulated glioma invasiveness was blocked by three pharmacological metalloproteinase inhibitors and by small interfering RNAs to MMP-2. Thus, in 3D matrix of CL, MMP-2 expression is modulated by inflammatory cytokines with the concomitant increase in glioma invasiveness.

Tenascin-C stimulates glioma cell invasion through matrix metalloproteinase-12

The capacity of glioma cells to invade extensively within the central nervous system is a major cause of the high morbidity rate of primary malignant brain tumors. Glioma cell invasion involves the attachment of tumor cells to extracellular matrix (ECM), degradation of ECM components, and subsequent penetration into adjacent brain structures. These processes are accomplished in part by matrix metalloproteinases (MMP) within a three-dimensional milieu of the brain parenchyma. As the majority of studies have used a two-dimensional monolayer culture system, we have used a three-dimensional matrix of collagen type I gel to address glioma-secreted proteases, ECM, and invasiveness of glioma cells. We show that in a three-dimensional collagen type I matrix, the presence of tenascin-C, commonly elevated in high-grade gliomas, increased the invasiveness of glioma cells. The tenascin-C-mediated invasiveness was blocked by metalloproteinase inhibitors, but this did not involve the gelatinases (MMP-2 and MMP-9) commonly implicated in two-dimensional glioma growth. A thorough analysis of 21 MMPs and six members of a disintegrin and metalloproteinase domain showed that MMP-12 was increased in gliomas by tenascin-C in three-dimensional matrix. Furthermore, examinations of resected specimens revealed high MMP-12 levels in the high-grade glioblastoma multiforme tumors. Finally, a function-blocking antibody as well as small interfering RNA to MMP-12 attenuated the tenascin-C-stimulated glioma invasion. These results identify a new factor, MMP-12, in regulating glioma invasiveness through interaction with tenascin-C.

Mechanisms of glioma cell invasion

Invasive growth is one of the characteristics of gliomas--local infiltration into the surrounding nerve tissue decisively restricts all treatment strategies. Particularly the merit of all local treatment modalities is queried. The question whether a glioma represents a diffuse disease of the CNS or a local disturbance with unrestrained expansion tendency is still at issue. Understanding of the invasion mechanisms is of importance inasmuch as biologically reasonable and effective strategies of limiting and suppressing glioma invasion can only hence be derived. The affinity of glioma cells towards certain structures of the extracellular matrix as well as taking advantage of tumour vascularisation with regard to extension play a decisive role. Still not fully understood are tumour host interactions. Future thinking will have to take into account these interactions as well as evidence to be derived from development neurobiology and regeneration capacity of the CNS. The present review is meant to give a short overview and disclose many questions.

Angiogenesis and invasion in gliomas

Angiogenesis and tumor cell invasion are pathophysiological processes playing a pivotal role in glioma development and growth since the earliest phase. Angiogenesis and tumor invasion both can be considered as an invasive process in which cells are activated, and move away from their initial location, by modyfing the adhesiveness with the extracellular matrix, expressing new adhesion molecules, and degrading the extracellular matrix components by the active secretion of proteases. This process requires a complex cross-talking between endothelial and tumor cells, extracellular matrix components, and cellular elements of the host microenviroment. Both processes are under the tight regulation of a balance between stimulating and inhibiting factors. The existence of common mechanisms of regulation and the presence of naturally occurring factors that inihibit angiogenesis and invasion, makes the inhibition of both processes possible. Tumor cells may develop adapting mechanims that can allow the tumor to partially escape to the treatment, particularly when only one mechanism or one process is inhibited. The ideal treatment should simultaneously affect both angiogenesis and invasion, by the isolation or development of novel therapeutics capable of influencing both processes. As their efficacy seems also be dependent on the mode of delivery, additional studies are also needed to improve these modalities, in order to ultimately improve the extent and the duration of the therapeutic response. The most widely used in vitro and in vivo models to study angiogenesis and invasion are also discussed.

Extracellular matrix glycoproteins and diffusion barriers in human astrocytic tumours

The extracellular matrix (ECM) and changes in the size and geometry of the extracellular space (ECS) in tumour tissue are thought to be of critical importance in influencing the migratory abilities of tumour cells as well as the delivery of therapeutic agents into the tumour. In 21 astrocytic neoplasms, the ECM composition was investigated in situ by the immunohistochemical detection of ECM glycoproteins (tenascin, laminin, vitronectin, fibronectin, collagen types I-VI). To explain the changes in ECS size and to detect barriers to diffusion in the tumour tissue, the ECM composition, the cellularity, the density of glial fibrillary acidic protein (GFAP)-positive tumour cell processes and the proliferative activity of the tumours were compared with the size and geometry of the ECS. The ECS volume fraction and the complex of hindrances to diffusion in the ECS (i.e. the tortuosity) were revealed by the real-time iontophoretic tetramethylammonium method. Increased proliferative activity of the tumours correlated with increased ECS volume fraction and tortuosity. The tortuosity of the tumour tissue was not significantly influenced by tumour cell density. Higher tortuosity was found in low-grade astrocytomas associated with the presence of a dense net of GFAP-positive fibrillary processes of the tumour cells. The increase in tortuosity in high-grade tumours correlated with an increased accumulation of ECM molecules, particularly of tenascin. We conclude that the increased malignancy of astrocytic tumours correlates with increases in both ECS volume and ECM deposition.

Abnormalities of basement membrane on blood vessels and endothelial sprouts in tumors

Often described as incomplete or absent, the basement membrane of blood vessels in tumors has attracted renewed attention as a source of angiogenic and anti-angiogenic molecules, site of growth factor binding, participant in angiogenesis, and potential target in cancer therapy. This study evaluated the composition, extent, and structural integrity of the basement membrane on blood vessels in three mouse tumor models: spontaneous RIP-Tag2 pancreatic islet tumors, MCa-IV mammary carcinomas, and Lewis lung carcinomas. Tumor vessels were identified by immunohistochemical staining for the endothelial cell markers CD31, endoglin (CD105), vascular endothelial growth factor receptor-2, and integrin alpha5 (CD49e). Confocal microscopic studies revealed that basement membrane identified by type IV collagen immunoreactivity covered >99.9% of the surface of blood vessels in the three tumors, just as in normal pancreatic islets. Laminin, entactin/nidogen, and fibronectin immunoreactivities were similarly ubiquitous on tumor vessels. Holes in the basement membrane, found by analyzing 1- micro m confocal optical sections, were <2.5 micro m in diameter and involved only 0.03% of the vessel surface. Despite the extensive vessel coverage, the basement membrane had conspicuous structural abnormalities, including a loose association with endothelial cells and pericytes, broad extensions away from the vessel wall, and multiple layers visible by electron microscopy. Type IV collagen-immunoreactive sleeves were also present on endothelial sprouts, supporting the idea that basement membrane is present where sprouts grow and regress. These findings indicate that basement membrane covers most tumor vessels but has profound structural abnormalities, consistent with the dynamic nature of endothelial cells and pericytes in tumors.

Cost of migration: invasion of malignant gliomas and implications for treatment

Tumors of glial origin consist of a core mass and a penumbra of invasive, single cells, decreasing in numbers towards the periphery and still detectable several centimeters away from the core lesion. Several decades ago, the diffuse nature of malignant gliomas was recognized by neurosurgeons when super-radical resections using hemispherectomies failed to eradicate these tumors. Local invasiveness eventually leads to regrowth of a recurrent tumor predominantly adjacent to the resection cavity, which is not significantly altered by radiation or chemotherapy. This raises the question of whether invasive glioma cells activate cellular programs that render these cells resistant to conventional treatments. Clinical and experimental data demonstrate that glioma invasion is determined by several independent mechanisms that facilitate the spread of these tumors along different anatomic and molecular structures. A common denominator of this cellular behavior may be cell motility. Gene-expression profiling showed upregulation of genes related to motility, and functional studies demonstrated that cell motility contributes to the invasive phenotype of malignant gliomas. There is accumulating evidence that invasive glioma cells show a decreased proliferation rate and a relative resistance to apoptosis, which may contribute to chemotherapy and radiation resistance. Interestingly, interference with cell motility by different strategies results in increased susceptibility to apoptosis, indicating that this dynamic relationship can potentially be exploited as an anti-invasive treatment paradigm. In this review, we discuss mechanisms of glioma invasion, characteristics of the invasive cell, and consequences of this cellular phenotype for surgical resection, oncologic treatments, and future perspectives for anti-invasive strategies.

Mixed conventional and desmoplastic infantile ganglioglioma: an autopsied case with 6-year follow-up

We describe a case of desmoplastic infantile ganglioglioma (DIG) arising in the ventral diencephalon of a 3-1/2-month-old boy. On biopsy, the tumor featured a desmoplastic, S-100 protein and GFAP immunoreactive stromal element, as well as a variable spectrum of ganglion cells. Electron microscopy demonstrated astrocytes, and morphologically fibroblasts, as well as neurons containing 120-nm dense core granules. In addition, tubular structures composed of tightly apposed cells with features of astrocytes and of Schwann-like cells were also noted. Devoid of fibroblasts, the tubular structures were surrounded by a single basal lamina. At autopsy 6 years later, the multinodular, cystic mass had replaced the diencephalon, extended into both temporal lobes as well as the optic nerves, and showed marked leptomeningeal involvement. Microscopically, superficial portions of the tumor consisted of typical DIG, whereas deep, nondesmoplastic portions exhibited pattern variation ranging from pilocytic astrocytoma to ganglioglioma and gangliocytoma. There was also a minor element of small, 'primitive-appearing' neuroepithelial cells. Dysplastic ganglion cells variously reactive for neurofilament protein and synaptophysin were present throughout the tumor. Our study not only confirms DIG as a variant of ganglioglioma, one capable of slow growth, infiltration, and fatal progression but suggests that its differentiating potential includes elements of both the central and peripheral nervous systems. If so, their derivation may be from multipotential cells of the neural plate.

ECM-mediated glioma cell invasion

Cell adhesion receptors of the integrin superfamily, CD44, and adhesion receptors of the immunoglobulin superfamily are expressed by high-grade astrocytic tumors of the central nervous system. These receptors are critical for the invasion of these tumors in the nervous system. Glioma cells utilize these receptors to adhere to and migrate along the components of the extracellular matrix, which is uniquely distributed and regulated within the brain and the spinal cord. For this reason, glioma cell invasion into the adjacent brain tissue is dependent on the interaction of glioma cells with the extracellular matrix. The receptor-ECM component interaction is discussed, focusing on the role of cell adhesion molecules of the integrin family and CD44 in glioma cell adhesion and invasion.

Effects of growth factors and basement membrane proteins on the phenotype of U-373 MG glioblastoma cells as determined by the expression of intermediate filament proteins

Various growth factors and basement membrane proteins have been implicated in the pathobiology of astrocytomas. The goal of this study was to determine the relative contribution of these two factors in modulating the phenotype of U-373 MG glioblastoma cells as determined by the expression of the intermediate filament proteins glial fibrillary acidic protein, vimentin, and nestin. For these determinations, cells plated in serum-free medium were treated either with growth factors binding to tyrosine kinase receptors including transforming growth factor-alpha, epidermal growth factor, platelet-derived growth factor-AA, basic fibroblast growth factor, and insulin-like growth factor-1 or with basement membrane proteins including collagen IV, laminin, and fibronectin. The changes in the expression levels of intermediate filament proteins in response to these treatments were analyzed by quantitation of immunoblots. The results demonstrate that collagen IV and growth factors binding to tyrosine kinase receptors decrease the glial fibrillary acidic protein content of U-373 MG cells. Growth factors binding to tyrosine kinase receptors also decrease the vimentin content of these cells but do not affect their nestin content. On the other hand, basement membrane proteins decrease the nestin content of U-373 MG cells but do not affect their vimentin content. The significance of these results with respect to the role played by different factors in modulating the phenotype of neoplastic astrocytes during tumor progression is discussed.

A central segment of the NG2 proteoglycan is critical for the ability of glioma cells to bind and migrate toward type VI collagen

Previous studies have established that the NG2 proteoglycan binds directly to type VI collagen. To further our understanding of the biochemical and functional significance of this interaction we have used NG2 cDNA to construct a series of NG2 mutants with deletions spaced throughout the entire length of the 260-kDa NG2 core protein. Following transfection of these mutant cDNAs into B28 glioma cells, we determined the ability of mutant NG2 molecules to anchor type VI collagen on the cell surface. Eight of 11 transfectant populations were able to anchor type VI collagen. The three NG2 variants incapable of anchoring type VI collagen have deletions clustered within the central one-third of the NG2 ectodomain. These deletions identify a 469-amino-acid domain of NG2 responsible for binding of type VI collagen. Functional consequences of the NG2-type VI collagen interaction were explored by testing the relative ability of NG2-transfected and untransfected glioma cells to migrate toward type VI collagen. NG2-expressing cells exhibited a greater migratory response toward type VI collagen than their NG2-negative counterparts. This enhanced migration could be specifically inhibited with NG2 antibodies. Furthermore, glioma cells expressing NG2 in which the collagen-binding domain was deleted failed to exhibit this enhanced migration, whereas NG2 mutants in which non-collagen-binding regions were deleted continued to exhibit increased chemotaxis toward the type VI collagen. These comparisons confirm the importance of the central collagen-binding domain in mediating functionally important interactions between NG2 and type VI collagen.

Local spread of malignant neuroepithelial tumors

A short review of invasiveness of primary malignant neoplasms in the nervous system is given. Invasiveness implies progressive spread and destruction locally, which eventually leads to a fatal outcome in the patient. In particular, the malignant cells are able to rapidly migrate over large parts of the brain. This process includes the capacity to adhere to a substratum, usually constituted by the various components of the extracellular matrix, followed by detachment and migration. Anatomical structures and local regulatory factors in the brain influence the direction and extent of this migration. Several model systems are now available for monitoring the aggressiveness of such tumours both in vivo and in vitro, and different phenotypic properties characteristic of invasive cells have been elucidated. Although still in its infancy, and currently as an experimental approach, anti-invasive therapy may in the future be an interesting alternative to conventional chemotherapy of brain tumours.

Role of extracellular matrix proteins in regulation of human glioma cell invasion in vitro

Primary brain tumors lack the metastatic behavior that is in part believed to be promoted by the extracellular matrix (ECM) components of the basement membrane. This study was intended to examine the influence of the ECM components present in the basement membrane that may act as natural barriers to tumor cell invasion. We examined the effect of type I and type IV collagens, fibronectin, laminin, and hyaluronic acid on the migration and invasion of four established glioblastoma cell lines, SNB19, U251, UWR1, and UWR2. Lower concentrations of all the ECM components induced the migration and invasion of all the cell lines. However, in the case of SNB19, laminin inhibited both migration and invasion in a concentration-dependent manner. We have also examined the influence of individual ECM components on the migration of cells from a spheroid to a monolayer on ECM component-coated coverslips. Consistent with the invasion studies using the modified Boyden chamber assays, lower concentrations of ECM components induced the migration of cells from spheroids to monolayer. Again, laminin inhibited the migration of cells from SNB19 spheroids. These results indicate that ECM components induce the invasion of glioma cells, apart from components like laminin, which may act as natural inhibitors.

Glioma invasion in the central nervous system

Invading glioma cells seem to follow distinct anatomic structures within the central nervous system. Tumor cell dissemination may occur along structures, such as the basement membranes of blood vessels or the glial limitans externa, that contain extracellular matrix (ECM) proteins. Frequently, invasive glioma cells are also found to migrate along myelinated fiber tracts of white matter. This behavior is most likely a consequence of using constitutive extracellular ligands expressed along the pathways of preferred dissemination. The extracellular space in anatomic structures, such as blood vessel basement membranes or between myelinated axons, is profoundly different, thus suggesting that glioma cells may be able to use a multiplicity of matrix ligands, possibly activating separate mechanisms for invasion. In addition, enzymatic modification of the extracellular space or deposition of ECM by the tumor cells may also create a more permissive environment for tumor spread into the adjacent brain. Tumor cell invasion is defined as translocation of neoplastic cells through host cellular and ECM barriers. This process has been studied in other cancers, in which a cascade of events has been described that involves receptor-mediated matrix adhesion, degradation of matrix by tumor-secreted metalloproteinases, and, subsequently, active cell locomotion into the newly created space. Although some of these mechanisms may play an important role in glioma invasion, there are some significant differences that are mainly the result of the profoundly different composition of the extracellular environment within the brain. This review focuses on the composition of central nervous system ECM and the recent evidence for the use by glioma cells of multiple invasion mechanisms in response to this unique environment.

The effect of type III collagen on migration and invasion of human glioblastoma cell lines in vitro

The effect of type III collagen, an extracellular matrix protein, on the in vitro migration and invasion of glioblastoma cells was assayed by chemotaxis using four cell lines. Migration and invasion of gliomablastoma cells was observed in the presence of varying concentrations of type III collagen. In contrast to control experiments in which the protein was not added, type III collagen significantly increased migration and invasion of glioblastoma cells in a dose dependent manner up to 10 micrograms/ml; however, higher concentrations of the protein eliminated this affect on migration and invasion as did the presence of a monoclonal type III collagen antibody. Type III collagen was also shown to stimulate the migration of glioblastoma cells from spheroids to monolayers. The results of this study indicate that type III collagen does influence the migration and invasion of human glioblastoma cells in vitro.

Clinicopathologic features of primary and postirradiation cerebral gliosarcoma

BACKGROUND

Gliosarcoma is an uncommon malignant brain tumor with mixed glial and mesenchymal elements. Experience is limited to case series, and pathologic data are disparate, leading to uncertainty about clinical features, management, and histogenesis.

METHODS

A clinicopathologic review of 32 patients with survival analysis and immunohistochemical studies was performed including glial fibrillary acidic protein analysis, alpha-1-antitrypsin (alpha-1-AT) analysis, and smooth muscle actin (SMA) analysis.

RESULTS

Twenty-five patients had primary gliosarcoma, whereas 7 developed gliosarcoma after irradiation for glioblastoma multiforme (GBM). Clinical features were similar to those of GBM. Most tumors were intraaxial and diffusely infiltrating by radiologic studies and at surgery. Median survival for primary gliosarcoma was 25 weeks overall, with patients who received irradiation surviving longer (46 vs. 13 weeks, P < 0.025). Gliosarcoma occurring after irradiation appeared hyperdense by computed tomography in five of seven cases, and median survival was 53 weeks. Primary gliosarcoma was a dimorphic tumor with malignant glial elements and features of malignant fibrous histiocytoma (MFH) or fibrosarcoma and one osteosarcoma. Smooth muscle actin labeled tumor vessels heavily, but in 15/25 primary cases, it extended to the surrounding spindle cells. The remaining cases appeared morphologically like MFH and tended to be positive for alpha-1-AT. Postirradiation gliosarcoma was fibrosarcomatous with positive SMA in 75% of the cases examined.

CONCLUSIONS

Gliosarcoma behaves clinically like GBM, and survival may be improved by cranial irradiation of selected patients. Smooth muscle actin reactivity in sarcomatous areas suggests histogenesis in some tumors from the smooth muscle within GBM, whereas others may arise via different mechanisms including differentiation from a pluripotential precursor. Transformation of the smooth muscle within GBM may have therapeutic implications for antiangiogenesis agents.

Report of a case of congenital glioblastoma multiforme: an immunohistochemical study

We report a rare case of congenital glioblastoma multiforme in a 13-day-old male neonate born at term who died from cardiocirculatory failure. The cerebral tumor was diagnosed in vivo by magnetic resonance imaging and confirmed histologically after autopsy. The histological and immunohistochemical features of this case were similar to those reported in the adult.

Adhesion of human glioma cell lines to fibronectin, laminin, vitronectin and collagen I is modulated by gangliosides in vitro

Adhesion of eight cell lines, derived from human gliomas of different histological types, to fibronectin, collagen I, vitronectin, and laminin was investigated in vitro. The glioma cell lines were found to attach to these substrates to different extents. Interestingly, all cell lines strongly attached to laminin. In addition, glioma cell adhesion was found to be dose dependent. Moreover, adhesion of three cell lines to fibronectin and collagen I was partially inhibited and to vitronectin completely prevented by GRGDTP peptide, indicating the involvement of integrin receptors in glioma cell adhesion. We have demonstrated, recently, that gangliosides play an important role in promoting glioma cell invasion of the reconstituted basement membrane, Matrigel, in vitro. In order to study the mechanism of action of gangliosides in this process, the role of six gangliosides (GM1, GM3, GD3, GD1a, GD1b, and GT1b) in cell adhesion to the four proteins was investigated in three cell lines. Although all gangliosides, with the exception of GM3, were found to enhance cell adhesion to these proteins to different extents, GD3 proved to be the most effective adhesion-promoting ganglioside in all three cell lines. GM3 was found to inhibit cell adhesion to the four proteins in one cell line but enhanced cell adhesion in two other cell lines. The three cell lines were found to express both GD3 and gangliosides recognised by the A2B5 antibody. Furthermore, adhesion of the three cell lines to fibronectin, vitronectin, laminin, and collagen I was inhibited by incubation with A2B5, demonstrating the involvement of intrinsic cell membrane gangliosides in adhesion of glioma cells to these proteins. Taken together with the observation that gangliosides modulate integrin receptor function, these data suggest that gangliosides may play a central role in the control of the adhesive and invasive properties of human glioma cells.

Extracellular matrix proteins inhibit proliferation, upregulate migration and induce morphological changes in human glioma cell lines

The influence of an artificial basement membrane (BM), Matrigel, and four individual extracellular matrix proteins, fibronectin, laminin, collagen I and vitronectin, on cell proliferation, morphology and migration was assessed in four glioma cell lines. Matrigel and individual BM proteins differentially inhibited cell proliferation of all cell lines studied. In addition, Matrigel was found to induce extensive morphological changes in glioma cells. Polycarbonate filters, of 8-microns porosity in modified Boyden chambers, were used to assess the chemoattraction activity of Matrigel and the individual proteins on glioma cells. All these components were found to stimulate cell migration, albeit to different extents but laminin proved to be the most effective chemoattractant for glioma cells in vitro. These data suggest that basement membrane proteins may inhibit proliferation and stimulate migration in order to facilitate invasion.

Collagens, integrins and the mesenchymal drift in glioblastomas: a comparison of biopsy specimens, spheroid and early monolayer cultures

To analyze the process of mesenchymal differentiation in vitro, we examined 5 human glioblastomas as biopsy specimens, monolayer cultures and 3-dimensional fragment spheroid cultures for the immunohistochemical expression of extracellular matrix (ECM) components (collagen types I, III-VI, laminin) and integrin receptors (beta 1, beta 2, beta 3 and beta 4 chains). mRNA for type-I and type-IV collagen alpha I chains was quantified using reverse transcription-polymerase chain reaction. In situ, glioma cells expressed beta 1, the common beta chain of most integrin ECM receptors, while ECM components were restricted to vascular elements. Early monolayer cultures showed a marked increase in ECM components (interstitial collagens more than basement membrane components), and coexpression of ECM components and glial fibrillary acidic protein (GFAP) by most cells. beta 2 and beta 3 integrins were upregulated in the primary cultures. In the fifth passages, GFAP-positive cells were decreased and collagen-expressing cells increased. The spheroids exhibited preserved GFAP staining, neoexpression of beta 4 integrin in some tumors, and variable ECM expression by glioma cells which was lower than that in monolayer cultures. ECM deposition usually commenced in central spheroid areas where the Ki-67 proliferation index was low. We conclude that different culture systems are characterized by distinct expression patterns for ECM components and receptors, and that mesenchymal features in cultured gliomas arise due to transdifferentiation of glioma cells.

Basement membrane invasion of glioma cells mediated by integrin receptors

Basement membrane invasion precedes meningeal dissemination and systemic metastasis of glioma cells. In order to investigate the invasive ability of glioblastomas and the functional role of extracellular matrix receptors, the authors performed in vitro invasion assays where the number of cells was determined from freshly resected tumors (primary cultures and fifth passages) and from cell lines (U-138 MG, U-373 MG, and GaMg) that had migrated through a filter coated with a reconstituted basement membrane (Matrigel). The involvement of integrin adhesion molecules was examined by preincubation of glioma cells with blocking antibodies to specific integrin chains. Cells from all of the glioblastomas had migrated through the Matrigel after 4 to 24 hours; the number of invasive cells was highest in the cell lines. Invasion of U-138 MG cells was reduced with antibodies to alpha 7, alpha v, beta 1, and beta 3 integrin chains and markedly increased by anti-alpha 5, while invasion of U-373 MG cells was reduced by antibodies to alpha 3, alpha v, beta 1, and beta 3 and increased by anti-alpha 6. It is concluded that: 1) glioma cells are able to penetrate Matrigel, indicating that the basement membrane is not a resistant barrier for infiltrating cells; and 2) basement membrane invasion is mediated by integrins in a complex manner. Some integrins promote while others inhibit basement membrane invasion. Furthermore, the integrins involved may differ between various glioma cells.

Desmoplastic cerebral astrocytoma of infancy. A case report with immunohistochemical, ultrastructural and proliferation studies

We present a case of desmoplastic cerebral astrocytoma of infancy (DCAI) in a 7 1/2-month-old girl and include immunohistochemical, ultrastructural and proliferative activity studies. The dural-based cystic tumor showed a biphasic pattern consisting of glial fibrillary acidic protein (GFAP)-positive astrocytes embedded in a desmoplastic stroma. The astrocytic processes were lined with basal lamina at their surface contacting the collagen. Scattered islands of undifferentiated small cells were seen acquiring GFAP positivity at their peripheral zone facing the collagen. Studies with silver nucleolar organizer region and proliferating cell nuclear antigen disclosed a high proliferative activity. Flow cytometric study showed an elevated S phase and 15% hypertetraploid cell population. These findings contrast the favorable prognosis of the tumor at 26 months follow-up. Probably, extracellular-matrix-induced maturation of the undifferentiated cells with the formation of basal lamina may account for this unique disparity.

Cellular components of microvascular proliferation in human glial and metastatic brain neoplasms. A light microscopic and immunohistochemical study of formalin-fixed, routinely processed material

Since the origin of cells contributing to microvascular proliferation (MVP) in glial neoplasms is unsettled, a light microscopic and immunohistochemical study for vascular smooth muscle cells and endothelial cells was performed in formalin-fixed, routinely processed brain tumor biopsy material. MVP in glial neoplasms was compared with that in intracerebral metastatic carcinomas and in intracranial granulation tissue. On the basis of the degree of hyperplasia of hypertrophic cells in the microvascular wall, MVP was subjectively divided into mild, moderate, and glomeruloid (marked) proliferation. The relative contribution of vascular smooth muscle cells and endothelial cells to different degrees of MVP was estimated immunohistochemically using antibodies against alpha-smooth muscle actin and von Willebrand factor, respectively. Glomeruloid MVP occurred in 50% of the malignant glial neoplasms. Moderate MVP was found in most malignant gliomas and in some pilocytic astrocytomas. Glomeruloid MVP was present in peritumoral glial tissue in 4 out of 15 intracerebral metastatic carcinomas, while only mild to moderate MVP was found within these tumors. In granulation tissue MVP was mild. In glomeruloid and moderate MVP vascular smooth muscle cells were more hypertrophic and more numerous than endothelial cells. The contribution of hypertrophic vascular smooth muscle cells to mild MVP was variable. MVP in glial neoplasms was generally not accompanied by a matrix of fibrous stroma but was directly embedded in glial tissue. The architecture of this MVP suggested "in situ" proliferation of microvascular cells without migration of these cells into the surrounding tissue.

Gliofibromas (including malignant forms), and gliosarcomas: a comparative study and review of the literature

The presence of connective tissue elements in gliomas necessitates in every case a thorough analysis of the character and derivation of such elements to allow the formulation of an appropriate diagnosis. Four cases are presented in this paper. In cases 1 and 2 (anaplastic astrocytomas in two children, 9 and 4 years old, respectively) all the neoplastic elements were astrocytes and their ability to produce or indirectly promote the production of reticulin and collagen fibers accounted for the presence of such elements in close association with the tumor cells. The term "gliofibroma" has been coined for such tumors, but "desmoplastic astrocytoma", (low grade or anaplastic) or in highly malignant cases "desmoplastic glioblastoma", as the case may be, also seem to be appropriate terms for such neoplasms. In contrast, cases 3 and 4 represented composite tumors in adults (66 and 58 years old, respectively) and the neoplasms of these patients consisted of glioblastoma and sarcoma, the latter component demonstrably being of vascular origin. This is the type of tumor usually referred to as gliosarcoma or "Feigin tumor". Although some apparent similarities between the two groups may exist at times, the histogenesis of the latter group's sarcomatous or sarcoma-like portions is different from that of the first group and, therefore, warrants separate diagnostic terms and placement in brain tumor classification.

Desmoplastic supratentorial neuroepithelial tumours of infancy

The clinicopathological features of two infants with desmoplastic supratentorial neuroepithelial tumours are described. The cases were similar to the 26 cases reported previously as desmoplastic infantile ganglioglioma and superficial cerebral astrocytoma attached to dura. Neuronal differentiation was absent on routine stains, but was immunohistochemically established. We review the literature and suggest classifying this clinicopathological entity by using a general designation such as desmoplastic supratentorial neuroepithelial tumours of infancy, a term which indicates the variability in the amount and lines of differentiation.

Primary leptomeningeal glioma: ultrastructural and laminin immunohistochemical studies

We studied a case of primary leptomeningeal glioma (PLG) on the left parietal lobe of a 74-year-old woman and compared the tissue with heterotopic glial tissue from another case. The PLG tumor consisted of spindle-shaped cells with marked nuclear atypism, which tended to be arranged in a fascicular pattern, and the majority of its cells were positive for glial fibrillary acidic protein. Ultrastructural examination demonstrated that most of the tumor cells contained intermediate filaments and often junctional complexes were present on their plasma membranes. Frequently, basal lamina-like structures surrounding the tumor cell surfaces were observed. Laminin immunohistochemistry clearly demonstrated a fine network of linear positive staining around the cytoplasm and processes of the tumor cells. The ultrastructure of the heterotopic glial tissue consisted of many astrocytes partially surrounded by basal lamina. These findings strongly suggest that PLG is a distinct tumor, which arises from the heterotopic astrocytes within the subarachnoid space.