Gliomagenesis and the use of neural stem cells in brain tumor treatment

Stationary-to-migratory transition in glioblastoma stem-like cells driven by a fatty acid-binding protein 7-RXRα neurogenic pathway

BACKGROUND

Glioblastoma (GBM) stem-like cells (GSCs) are crucial drivers of treatment resistance and tumor recurrence. While the concept of "migrating" cancer stem cells was proposed a decade ago, the roles and underlying mechanisms of the heterogeneous populations of GSCs remain poorly defined.

METHODS

Cell migration using GBM cell lines and patient-derived GSCs was examined using Transwell inserts and the scratch assay. Single-cell RNA sequencing data analysis were used to map GSC drivers to specific GBM cell populations. Xenografted mice were used to model the role of brain-type fatty acid-binding protein 7 (FABP7) in GBM infiltration and expansion. The mechanism by which FABP7 and its fatty acid ligands promote GSC migration was examined by gel shift and luciferase gene reporter assays.

RESULTS

A subpopulation of FABP7-expressing migratory GSCs was identified, with FABP7 upregulating SOX2, a key modulator for GBM stemness and plasticity, and ZEB1, a prominent factor in GBM epithelial-mesenchymal transition and invasiveness. Our data indicate that GSC migration is driven by nuclear FABP7 through activation of RXRα, a nuclear receptor activated by polyunsaturated fatty acids (PUFAs).

CONCLUSION

Infiltrative progression in GBM is driven by migratory GSCs through activation of a PUFA-FABP7-RXRα neurogenic pathway.

Imaging Spectrum of the Developing Glioblastoma: A Cross-Sectional Observation Study

Glioblastoma (GBM) has the typical radiological appearance (TRA) of a centrally necrotic, peripherally enhancing tumor with surrounding edema. The objective of this study was to determine whether the developing GBM displays a spectrum of imaging changes detectable on routine clinical imaging prior to TRA GBM. Patients with pre-operative imaging diagnosed with GBM (1 January 2014-31 March 2022) were identified from a neuroscience center. The imaging was reviewed by an experienced neuroradiologist. Imaging patterns preceding TRA GBM were analyzed. A total of 76 out of 555 (14%) patients had imaging preceding TRA GBM, 57 had solitary lesions, and 19 had multiple lesions (total = 84 lesions). Here, 83% of the lesions had cortical or cortical/subcortical locations. The earliest imaging features for 84 lesions were T2 hyperintensity/CT low density (n = 18), CT hyperdensity (n = 51), and T2 iso-intensity (n = 15). Lesions initially showing T2 hyperintensity/CT low density later showed T2 iso-intensity. When CT and MRI were available, all CT hyperdense lesions showed T2 iso-intensity, reduced diffusivity, and the following enhancement patterns: nodular 35%, solid 29%, none 26%, and patchy peripheral 10%. The mean time to develop TRA GBM from T2 hyperintensity was 140 days and from CT hyperdensity was 69 days. This research suggests that the developing GBM shows a spectrum of imaging features, progressing through T2 hyperintensity to CT hyperdensity, T2 iso-intensity, reduced diffusivity, and variable enhancement to TRA GBM. Red flags for non-TRA GBM lesions are cortical/subcortical CT hyperdense/T2 iso-intense/low ADC. Future research correlating this imaging spectrum with pathophysiology may provide insight into GBM growth patterns.

Research Progress on the Regulation Mechanism of Key Signal Pathways Affecting the Prognosis of Glioma

As is known to all, glioma, a global difficult problem, has a high malignant degree, high recurrence rate and poor prognosis. We analyzed and summarized signal pathway of the Hippo/YAP, PI3K/AKT/mTOR, miRNA, WNT/β-catenin, Notch, Hedgehog, TGF-β, TCS/mTORC1 signal pathway, JAK/STAT signal pathway, MAPK signaling pathway, the relationship between BBB and signal pathways and the mechanism of key enzymes in glioma. It is concluded that Yap1 inhibitor may become an effective target for the treatment of glioma in the near future through efforts of generation after generation. Inhibiting PI3K/Akt/mTOR, Shh, Wnt/β-Catenin, and HIF-1α can reduce the migration ability and drug resistance of tumor cells to improve the prognosis of glioma. The analysis shows that Notch1 and Sox2 have a positive feedback regulation mechanism, and Notch4 predicts the malignant degree of glioma. In this way, notch cannot only be treated for glioma stem cells in clinic, but also be used as an evaluation index to evaluate the prognosis, and provide an exploratory attempt for the direction of glioma treatment. MiRNA plays an important role in diagnosis, and in the treatment of glioma, VPS25, KCNQ1OT1, KB-1460A1.5, and CKAP4 are promising prognostic indicators and a potential therapeutic targets for glioma, meanwhile, Rheb is also a potent activator of Signaling cross-talk etc. It is believed that these studies will help us to have a deeper understanding of glioma, so that we will find new and better treatment schemes to gradually conquer the problem of glioma.

Research Progress on the Regulation Mechanism of Key Signal Pathways Affecting the Prognosis of Glioma

As is known to all, glioma, a global difficult problem, has a high malignant degree, high recurrence rate and poor prognosis. We analyzed and summarized signal pathway of the Hippo/YAP, PI3K/AKT/mTOR, miRNA, WNT/β-catenin, Notch, Hedgehog, TGF-β, TCS/mTORC1 signal pathway, JAK/STAT signal pathway, MAPK signaling pathway, the relationship between BBB and signal pathways and the mechanism of key enzymes in glioma. It is concluded that Yap1 inhibitor may become an effective target for the treatment of glioma in the near future through efforts of generation after generation. Inhibiting PI3K/Akt/mTOR, Shh, Wnt/β-Catenin, and HIF-1α can reduce the migration ability and drug resistance of tumor cells to improve the prognosis of glioma. The analysis shows that Notch1 and Sox2 have a positive feedback regulation mechanism, and Notch4 predicts the malignant degree of glioma. In this way, notch cannot only be treated for glioma stem cells in clinic, but also be used as an evaluation index to evaluate the prognosis, and provide an exploratory attempt for the direction of glioma treatment. MiRNA plays an important role in diagnosis, and in the treatment of glioma, VPS25, KCNQ1OT1, KB-1460A1.5, and CKAP4 are promising prognostic indicators and a potential therapeutic targets for glioma, meanwhile, Rheb is also a potent activator of Signaling cross-talk etc. It is believed that these studies will help us to have a deeper understanding of glioma, so that we will find new and better treatment schemes to gradually conquer the problem of glioma.

Impaired generation of mature neurons due to extended expression of Tlx by repressing Sox2 transcriptional activity

As a master regulator of the dynamic process of adult neurogenesis, timely expression and regulation of the orphan nuclear receptor Tailless (Tlx) is essential. However, there is no study yet to directly investigate the essential role of precise spatiotemporal expressed Tlx. Here, we generated a conditional gain of Tlx expression transgenic mouse model, which allowed the extended Tlx expression in neural stem cells (NSCs) and their progeny by mating with a TlxCreER^T2 mouse line. We demonstrate that extended expression of Tlx induced the impaired generation of mature neurons in adult subventricular zone and subgranular zone. Furthermore, we elucidated for the first time that this mutation decreased the endogenous expression of Sox2 by directly binding to its promoter. Restoration experiments further confirmed that Sox2 partially rescued these neuron maturation defects. Together, these findings not only highlight the importance of shutting-off Tlx on time in controlling NSC behavior, but also provide insights for further understanding adult neurogenesis and developing treatment strategies for neurological disorders.

Stem cell-based therapy treating glioblastoma multiforme

Glioblastoma (GB) is one of the most malignant types of central nervous system tumours, classified as grade IV by the World Health Organization. Despite the therapeutic advances, the prognosis is ominous, with a median survival of about 12-15 months post diagnosis. Although therapeutic options available can increase the survival, they are ineffective in treating patients with GB. Impairing factors such as the blood-brain barrier, cancer stem cells, and infiltration into brain parenchyma lead to failure of current therapies. Therefore, clinicians need novel/alternative effective strategies to treat GB. Due to their ability to preserve healthy tissues and to provide an effective and long-lasting response, stem cells (SCs) with tropism for tumour cells have attracted considerable attention in the scientific community. As is the case here, SCs can be used to target brain tumour cancer cells, especially high-grade malignant gliomas like GB, by overcoming the resistance and exerting benefits for patients affected with such lethal disease. Herein, we will discuss the research knowledge regarding SC-based therapy for the treatment of GB, focalising our attention on SCs and SC-released extracellular vesicles modified to express/load different antitumour payloads, as well as on SCs exploited as a diagnostic tool. Advantages and unresolved issues of anticancer SC-based therapy will also be considered.

STAT3 is a key molecule in the oncogenic behavior of diffuse intrinsic pontine glioma

Diffuse intrinsic pontine glioma (DIPG) is one of the most lethal childhood brain tumors. This tumor is unique because it is detected exclusively in the ventral pons of patients aged between 6 and 7 years, which suggests a developmental nature of its formation. Signal transducer and activator of transcription 3 (STAT3) is a critical molecule for the differentiation of neural stem cells into astrocytes during neurodevelopment. Additionally, STAT3 is associated with oncogenesis and the epithelial-mesenchymal transition (EMT) in various types of tumor. In recent years, several studies have demonstrated the oncogenic role of STAT3 in high-grade gliomas. However, the role of STAT3 in DIPG at the cellular level remains unknown. To assess the possible association between gliogenesis and DIPG, the expression levels of various molecules participating in the differentiation of neural stem cells were compared between normal brain control tissues and DIPG tissues using open public data. All of the screened genes exhibited significantly increased expression in DIPG tissues compared with normal tissues. As STAT3 expression was the most increased, the effect of STAT3 inhibition in a DIPG cell line was assessed via STAT3 short hairpin (sh)RNA transfection and treatment with AG490, a STAT3 inhibitor. Changes in viability, apoptosis, EMT and radiation therapy efficiency were also evaluated. Downregulation of STAT3 resulted in decreased cyclin D1 expression and cell viability, migration and invasion. Additionally, treatment with STAT3 shRNA or AG490 suppressed the EMT phenotype. Finally, when radiation was administered in combination with STAT3 inhibition, the therapeutic efficiency, assessed by cell viability and DNA damage repair, was increased. The present results suggest that STAT3 is a potential therapeutic target in DIPG, especially when combined with radiation therapy.

Differentiation of Human Mesenchymal Stem Cells towards Neuronal Lineage: Clinical Trials in Nervous System Disorders

Mesenchymal stem cells (MSCs) have been proposed as an alternative therapy to be applied into several pathologies of the nervous system. These cells can be obtained from adipose tissue, umbilical cord blood and bone marrow, among other tissues, and have remarkable therapeutic properties. MSCs can be isolated with high yield, which adds to their ability to differentiate into non-mesodermal cell types including neuronal lineage both in vivo and in vitro. They are able to restore damaged neural tissue, thus being suitable for the treatment of neural injuries, and possess immunosuppressive activity, which may be useful for the treatment of neurological disorders of inflammatory etiology. Although the long-term safety of MSC-based therapies remains unclear, a large amount of both pre-clinical and clinical trials have shown functional improvements in animal models of nervous system diseases following transplantation of MSCs. In fact, there are several ongoing clinical trials evaluating the possible benefits this cell-based therapy could provide to patients with neurological damage, as well as their clinical limitations. In this review we focus on the potential of MSCs as a therapeutic tool to treat neurological disorders, summarizing the state of the art of this topic and the most recent clinical studies.

Differences between primary central nervous system lymphoma and glioblastoma: topographic analysis using voxel-based morphometry

AIM

To evaluate the diagnostic feasibility of probabilistic analysis using voxel-based morphometry (VBM) in differentiating primary central nervous system lymphoma (PCNSL) from glioblastoma (GBM).

MATERIALS AND METHODS

In total, 118 patients with GBM (57 males, 61 females; mean [± standard deviation] age, 56.9±19.3 years; median, 61 years) and 52 patients with PCNSL (37 males, 15 females; mean age, 62±13.3 years, median, 66 years) were studied retrospectively. Each patient underwent preoperative contrast-enhanced T1-weighted imaging (CE-T1WI) using a 1.5 or 3 T magnetic resonance imaging (MRI) system. To assess preferential occurrence sites, images from CE-T1WI were co-registered and spatially normalised using the MNI152 T1 template. Subsequently, a region of interest (ROI) was placed in the centre of the enhancing tumour in normalised images with 1-mm isotropic resolution. The same ROI between normalised and T1 template images was set up using an ROI manager function in ImageJ software. A spherical volume of interest (VOI) with a radius of 10 mm was determined. A probability map was created by overlaying each image with the VOI. Each VOI was removed from T1 template images for VBM analysis. VBM analysis was performed using statistical parametric mapping (SPM) 12 software under default settings.

RESULTS

VBM analysis showed significantly higher frequency in the splenium of the corpus callosum among PCNSL patients than among GBM patients (p<0.05; family-wise error correction).

CONCLUSION

Topographic analysis using VBM provides useful information for differentiating PCNSL from GBM.

The inhibiting effect of neural stem cells on proliferation and invasion of glioma cells

The invasive and infiltrative nature of tumor cells leads to the poor prognosis of glioma. Currently, novel therapeutic means to eliminate the tumor cells without damaging the normal brain tissue are still strongly demanded. Significant attentions had been paid to stem cell-based therapy and neural stem cell (NSC) had been considered as one of the efficient delivery vehicles for targeting therapeutic genes. However, whether the NSCs could directly affect glioma cells remains to be seen. In this study, both rat and human glioma cells (C6 and U251) were co-cultured with normal rat embryonic NSCs directly or in-directly. We found the survival, proliferation, invasion and migration of glioma cells were significantly inhibited, while the differentiation was not affected in the in vitro co-culture system. In nude mice, although no significant difference was observed in the tumor growth, survival status and time of tumor-bearing mice were significantly promoted when U251 cells were subcutaneously injected with NSCs. In coincidence with the suppression of glioma cell growth in vitro, expression of mutant p53 and phosphorylation of AKT, ERK1/2 decreased while the level of caspase-3 increased significantly. Our results suggested that normal NSCs could possess direct anti-glioma properties via inhibiting the glioma cell viability, proliferation, invasion and migration. It could be a very promising candidate for glioma treatment.

Human Neural Stem Cell Biodistribution and Predicted Tumor Coverage by a Diffusible Therapeutic in a Mouse Glioma Model

Engineered neural stem cells (NSCs) intrinsically migrating to brain tumors offer a promising mechanism for local therapeutic delivery. However, difficulties in quantitative assessments of NSC migration and in estimates of tumor coverage by diffusible therapeutics have impeded development and refinement of NSC-based therapies. To address this need, we developed techniques by which conventional serial-sectioned formalin-fixed paraffin-embedded (FFPE) brains can be analyzed in their entirety across multiple test animals. We considered a conventional human glioblastoma model: U251 glioma cells orthotopically engrafted in immunodeficient mice receiving intracerebral (i.c.) or intravenous (i.v.) administrations of NSCs expressing a diffusible enzyme to locally catalyze chemotherapeutic formation. NSC migration to tumor sites was dose-dependent, reaching 50%-60% of total administered NSCs for the i.c route and 1.5% for the i.v. route. Curiously, the most efficient NSC homing was seen with smaller NSC doses, implying existence of rate-limiting process active during administration and/or migration. Predicted tumor exposure to a diffusing therapeutic (assuming a 50 µm radius of action) could reach greater than 50% of the entire tumor volume for i.c. and 25% for i.v. administration. Within individual sections, coverage of tumor area could be as high as 100% for i.c. and 70% for i.v. routes. Greater estimated therapeutic coverage was observed for larger tumors and for larger tumor regions in individual sections. Overall, we have demonstrated a framework within which investigators may rationally evaluate NSC migration to, and integration into, brain tumors, and therefore enhance understanding of mechanisms that both promote and limit this therapeutic modality. Stem Cells Translational Medicine 2017;6:1522-1532.

Early-Stage Glioblastomas: MR Imaging-Based Classification and Imaging Evidence of Progressive Growth

BACKGROUND AND PURPOSE

The serial imaging changes describing the growth of glioblastomas from small to large tumors are seldom reported. Our aim was to classify the imaging patterns of early-stage glioblastomas and to define the order of appearance of different imaging patterns that occur during the growth of small glioblastomas.

MATERIALS AND METHODS

Medical records and preoperative MR imaging studies of patients diagnosed with glioblastoma between 2006 and 2013 were reviewed. Patients were included if their MR imaging studies showed early-stage glioblastomas, defined as small MR imaging lesions detected early in the course of the disease, demonstrating abnormal signal intensity but the absence of classic imaging findings of glioblastoma. Each lesion was reviewed by 2 neuroradiologists independently for location, signal intensity, involvement of GM and/or WM, and contrast-enhancement pattern on MR imaging.

RESULTS

Twenty-six patients with 31 preoperative MR imaging studies met the inclusion criteria. Early-stage glioblastomas were classified into 3 types and were all hyperintense on FLAIR/T2-weighted images. Type I lesions predominantly involved cortical GM (n = 3). Type II (n = 12) and III (n = 16) lesions involved both cortical GM and subcortical WM. Focal contrast enhancement was present only in type III lesions at the gray-white junction. Interobserver agreement was excellent (κ = 0.95; P < .001) for lesion-type classification. Transformations of lesions from type I to type II and type II to type III were observed on follow-up MR imaging studies. The early-stage glioblastomas of 16 patients were pathologically confirmed after imaging progression to classic glioblastoma.

CONCLUSIONS

Cortical lesions may be the earliest MR imaging-detectable abnormality in some human glioblastomas. These cortical tumors may progress to involve WM.

Icariin promotes cell proliferation and regulates gene expression in human neural stem cells in vitro

Icariin (ICA), which is an essential bioactive component extracted from the herb Epimedium, possesses neuroprotective properties. The aim of the present study was to investigate the regulatory roles of ICA in cell proliferation and gene expression in human neural stem cells (NSCs) in vitro. Single cells were isolated from the corpus striatum of 16‑20‑week human fetuses obtained following spontaneous abortion. The cells were cultured in Dulbecco's modified Eagle's medium/F12 complete medium and were characterized by immunostaining and cell differentiation assay. NSCs were treated with ICA, and cell proliferation was assessed using the Cell Counting kit‑8 cell proliferation assay kit. In addition, neurosphere formation was comparatively studied between the ICA‑treated and control cells. cDNA microarray analysis was performed to examine the effects of ICA on gene expression. Altered expression of genes important for regulating NSC proliferation was further analyzed by quantitative polymerase chain reaction (qPCR). The results demonstrated that typical neurospheres appeared after 7‑10 days of culturing of individual cells isolated from the corpus striatum. These cells expressed nestin, an important NSC marker, and in the presence of differentiation medium they expressed β‑III‑tubulin, a specific neuronal marker, and glial fibrillary acidic protein, an astrocyte marker. Treatment with ICA enhanced NSC proliferation and the formation of neurospheres. Microarray data and pathway analysis revealed that the genes regulated by ICA were involved in several signaling pathways, including the Wnt and basic fibroblast growth factor (bFGF) pathways, which are important for the regulation of NSC function. Upregulation of frizzled class receptor 7 and dishevelled segment polarity protein 3, which are key players in the Wnt pathway, and fibroblast growth factor receptor 1, which is the receptor for bFGF, and downregulation of glycogen synthase kinase‑3β, which is a Wnt pathway inhibitor, was further validated by qPCR. In conclusion, ICA promoted proliferation and regulated gene expression in human NSCs, thus suggesting that ICA may exert its neuroprotective effects by regulating NSC activity.

The human orphan nuclear receptor tailless (TLX, NR2E1) is druggable

Nuclear receptors (NRs) are an important group of ligand-dependent transcriptional factors. Presently, no natural or synthetic ligand has been identified for a large group of orphan NRs. Small molecules to target these orphan NRs will provide unique resources for uncovering regulatory systems that impact human health and to modulate these pathways with drugs. The orphan NR tailless (TLX, NR2E1), a transcriptional repressor, is a major player in neurogenesis and Neural Stem Cell (NSC) derived brain tumors. No chemical probes that modulate TLX activity are available, and it is not clear whether TLX is druggable. To assess TLX ligand binding capacity, we created homology models of the TLX ligand binding domain (LBD). Results suggest that TLX belongs to an emerging class of NRs that lack LBD helices α1 and α2 and that it has potential to form a large open ligand binding pocket (LBP). Using a medium throughput screening strategy, we investigated direct binding of 20,000 compounds to purified human TLX protein and verified interactions with a secondary (orthogonal) assay. We then assessed effects of verified binders on TLX activity using luciferase assays. As a result, we report identification of three compounds (ccrp1, ccrp2 and ccrp3) that bind to recombinant TLX protein with affinities in the high nanomolar to low micromolar range and enhance TLX transcriptional repressive activity. We conclude that TLX is druggable and propose that our lead compounds could serve as scaffolds to derive more potent ligands. While our ligands potentiate TLX repressive activity, the question of whether it is possible to develop ligands to de-repress TLX activity remains open.

Identification of aberrant microRNA expression pattern in pediatric gliomas by microarray

Background

Brain tumor remains the leading cause of disease-related death in children. Many studies have focused on the complex biological process involved in pediatric brain tumors but little is know about the possible role of microRNAs in the genesis of these tumors.

Methods

In this study, we used a microRNA microarray assay to study the expression pattern of microRNAs in pediatric gliomas and matched normal tissues.

Results

We found 40 differentially expressed microRNAs, among which miR-1321, miR-513b, miR-769-3p were found be related to cancer genesis for the first time. The expression of selected microRNAs were then confirmed by qRT-PCR. Furthermore, GO and pathway analysis showed that the target genes of the 40 differentially expressed microRNAs were significantly enriched in nervous system-related and tumor-related biological processes and signaling pathways. Additionally, an apoptosis-related network of microRNA–mRNA interaction, representing the critical microRNAs and their targets, was constructed based on microRNA status.

Conclusions

In the present study we identified the changed expression pattern of microRNAs in pediatric gliamas. Our study also provides a better understanding of pediatric brain tumor biology and may assist in the development of less toxic therapies and in the search for better markers for disease stratification.

Virtual slides

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1323049861105720

Subventricular zone localized irradiation affects the generation of proliferating neural precursor cells and the migration of neuroblasts

Radiation therapy is a part of the standard treatment for brain tumor patients, often resulting in irreversible neuropsychological deficits. These deficits may be due to permanent damage to the neural stem cell (NSC) niche, damage to local neural progenitors, or neurotoxicity. Using a computed tomography-guided localized radiation technique, we studied the effects of radiation on NSC proliferation and neuroblast migration in the mouse brain. Localized irradiation of the subventricular zone (SVZ) eliminated the proliferating neural precursor cells and migrating neuroblasts. After irradiation, type B cells in the SVZ lacked the ability to generate migrating neuroblasts. Neuroblasts from the unirradiated posterior SVZ did not follow their normal migratory path through the irradiated anterior SVZ. Our results indicate that the migrating neuroblasts were not replenished, despite the presence of type B cells in the SVZ post-irradiation. This study provides novel insights into the effects of localized SVZ radiation on neurogenesis and cell migration that may potentially lead to the development of new radiotherapy strategies to minimize damage to NSCs and neuroblast migration.

Contact and encirclement of glioma cells in vitro is an intrinsic behavior of a clonal human neural stem cell line

Pathotropic neural stem and/or progenitor cells (NSCs) can potentially deliver therapeutic agents to otherwise inaccessible cancers. In glioma, NSCs are found in close contact with tumor cells, raising the possibility that specificity of NSC contact with glioma targets originates in the tumor cells themselves. Alternatively, target preferences may originate, at least in part, in the tumor microenvironment. To better understand mechanisms underlying NSC interactions with glioma cells, we examined NSC-target cell contacts in a highly simplified 3-dimensional peptide hydrogel (Puramatrix) in which cell behaviors can be studied in the relative absence of external cues. HB1.F3 is an immortalized clonal human NSC line extensively characterized in preclinical investigations. To study contact formation between HB1.F3 NSCs and glioma cells, we first examined co-cultures of eGFP-expressing HB1.F3 (HB1.F3.eGFP) NSCs and dsRed-expressing U251 glioma (U251.dsRed) cells. Using confocal microscopy, HB1.F3.eGFP cells were observed contacting or encircling U251.dsRed glioma cells, but never the reverse. Next, examining specificity of these contacts, no significant quantitative differences in either percentages of HB1.F3 NSCs contacting targets, or in the extent of target cell encirclement, were observed when HB1.F3.eGFP cells were presented with various potential target cells (human glioma and breast cancer cell lines, patient-derived brain tumor lines, non-tumor fibroblasts, primary mouse and human astroglial cells, and primary adult and newborn human dermal fibroblasts) except that interactions between HB1.F3 cells did not progress beyond establishing contacts. Finally cytoskeletal mechanisms employed by HB1.F3.eGFP cells varied with the substrate. When migrating in Puramatrix, HB1.F3 NSCs exhibited intermittent process extension followed by soma translocation, while during encirclement their movements were more amoeboid. We conclude that formation of contacts and subsequent encirclement of target cells by HB1.F3 NSCs is an intrinsic property of these NSCs, and that preferential contact formation with tumor cells in vivo must therefore be highly dependent on microenvironmental cues.

Cancer-initiating enriched cell lines from human glioblastoma: preparing for drug discovery assays

Glioblastoma multiforme (GBM) is the most lethal type of brain tumour in the adult humans. The cancer-initiating cell (CIC) hypothesis supports the notion that failures in current approaches to GBM treatment might be attributed to the survival of the CIC subpopulation. Recent evidence shows the idea that using CIC-enriched cell lines derived from human GBM as new targets for drug discovery programs, may improve the chance of successfully translating the basic research findings into clinical trials. Although this approach appears promising, many important biological and technical issues (characterization of functional CIC markers, inter- and intra-tumoral CIC heterogeneity, and isolation and maintenance inconsistency) need to be resolved.

Neurotransplantation: lux et veritas, fiction or reality?

Neurotransplantation remains a much-debated frontier in contemporary neurosurgery and neuroscience, with roots dating to the late 19th century. Contemporary applications are far-reaching, and ongoing laboratory research and clinical trials seek to define the mechanisms at play in neurotransplant engraftment and growth, while advancing the field forward into the 21st century. Neural transplantation therapy remains an attractive idea for treating central nervous system (CNS) and peripheral nervous system (PNS) pathologies. Phase I and phase II clinical trials assessing safety and efficacy are currently underway for various disorders. The remainder of this review will focus on ongoing clinical trials and more recent research advances involving neural transplantation therapy for neuronal death, axonal injury, peripheral nerve lesions, and cancer. The field of neural transplantation, while promising, is not without ethical and scientific dilemmas; this review will conclude with a discussion of the challenges researchers and clinicians face as the field of neural transplantation moves forward.

The role of stem cells in tumor targeting and growth suppression of gliomas

Glioma remains the most challenging solid organ tumor to treat successfully. Based on the capacity of stem cells to migrate extensively and target invading glioma cells, the transplantation of stem cells as a cell-based delivery system may provide additional tools for the treatment of gliomas. In addition to the use of modified stem cells for the delivery of therapeutic agents, unmodified stem cells have been shown to have growth-suppressing effects on tumors in vitro and in vivo. This review outlines the probable factors involved in tumor tropism and tumor growth suppression, with a specific focus on the use of unmodified stem cells in the treatment of gliomas. Based on these and further future data, clinical trials may be justified.