Partial biological characterization of cancer stem-like cell line (WJ(2)) of human glioblastoma multiforme

Glioblastoma Stem Cell-Derived Exosomes Enhance Stemness and Tumorigenicity of Glioma Cells by Transferring Notch1 Protein

Exosomes contain plenty of bioactive information, playing an important role in intercellular communication by transfer their bioactive molecular contents to recipient cells. Glioblastoma stem cells (GSCs) and non-GSC glioma cells coexist in GBM microenvironment; GSC-released exosomes contain intracellular signaling molecules, which may affect the biological phenotypes of recipient cells. However, whether GSC exosomes could affect the biological phenotype of non-GSC glioma cells has not yet been defined. To explore whether GSC exosomes could reprogramme non-GSC glioma cells into GSCs and its possible mechanism involved, non-GSC glioma cells were treated with GSCs released exosomes; the potential mechanisms of action were studied with RNA interference, Notch inhibitors and Western blot analysis. The proliferation, neurosphere formation, invasive capacities, and tumorigenicity of non-GSC glioma cells were increased significantly after GSC exosome treatment; Notch1 signaling pathway was activated in GSCs; Notch1 protein was highly enriched in GSC exosomes; Notch1 signaling pathway and stemness-related protein expressions were increased in GSC exosome treated non-GSC glioma cells and these cell generated tumor tissues; Notch1 protein expression in GSCs and their exosomes, and the neurosphere formation of GSCs were decreased by Notch1 RNA interference; Notch1 signaling pathway protein and stemness protein expressions were decreased in GSC exosome treated non-GSC glioma cells by Notch1 RNA interference and Notch inhibitors. The findings in this study indicated that GSC exosomes act as information carriers, mediated non-GSC glioma cell dedifferentiation into GSCs by delivering Notch1 protein through Notch1 signaling activation, and enhanced stemness and tumorigenicity of non-GSC glioma cells.

Establishment and Biological Characterization of a Panel of Glioblastoma Multiforme (GBM) and GBM Variant Oncosphere Cell Lines

Objective

Human tumor cell lines form the basis of the majority of present day laboratory cancer research. These models are vital to studying the molecular biology of tumors and preclinical testing of new therapies. When compared to traditional adherent cell lines, suspension cell lines recapitulate the genetic profiles and histologic features of glioblastoma multiforme (GBM) with higher fidelity. Using a modified neural stem cell culture technique, here we report the characterization of GBM cell lines including GBM variants.

Methods

Tumor tissue samples were obtained intra-operatively and cultured in neural stem cell conditions containing growth factors. Tumor lines were characterized in vitro using differentiation assays followed by immunostaining for lineage-specific markers. In vivo tumor formation was assayed by orthotopic injection in nude mice. Genetic uniqueness was confirmed via short tandem repeat (STR) DNA profiling.

Results

Thirteen oncosphere lines derived from GBM and GBM variants, including a GBM with PNET features and a GBM with oligodendroglioma component, were established. All unique lines showed distinct genetic profiles by STR profiling. The lines assayed demonstrated a range of in vitro growth rates. Multipotency was confirmed using in vitro differentiation. Tumor formation demonstrated histologic features consistent with high grade gliomas, including invasion, necrosis, abnormal vascularization, and high mitotic rate. Xenografts derived from the GBM variants maintained histopathological features of the primary tumors.

Conclusions

We have generated and characterized GBM suspension lines derived from patients with GBMs and GBM variants. These oncosphere cell lines will expand the resources available for preclinical study.

Polycomb group gene BMI1 controls invasion of medulloblastoma cells and inhibits BMP-regulated cell adhesion

Background

Medulloblastoma is the most common intracranial childhood malignancy and a genetically heterogeneous disease. Despite recent advances, current therapeutic approaches are still associated with high morbidity and mortality. Recent molecular profiling has suggested the stratification of medulloblastoma from one single disease into four distinct subgroups namely: WNT Group (best prognosis), SHH Group (intermediate prognosis), Group 3 (worst prognosis) and Group 4 (intermediate prognosis). BMI1 is a Polycomb group repressor complex gene overexpressed across medulloblastoma subgroups but most significantly in Group 4 tumours. Bone morphogenetic proteins are morphogens belonging to TGF-β superfamily of growth factors, known to inhibit medulloblastoma cell proliferation and induce apoptosis.

Results

Here we demonstrate that human medulloblastoma of Group 4 characterised by the greatest overexpression of BMI1, also display deregulation of cell adhesion molecules. We show that BMI1 controls intraparenchymal invasion in a novel xenograft model of human MB of Group 4, while in vitro assays highlight that cell adhesion and motility are controlled by BMI1 in a BMP dependent manner.

Conclusions

BMI1 controls MB cell migration and invasion through repression of the BMP pathway, raising the possibility that BMI1 could be used as a biomarker to identify groups of patients who may benefit from a treatment with BMP agonists.

Glioblastoma stem-like cells-biology and therapeutic implications

The cancer stem-cell hypothesis proposes that malignant tumors are likely to encompass a cellular hierarchy that parallels normal tissue and may be responsible for the maintenance and recurrence of glioblastoma multiforme (GBM) in patients. The purpose of this manuscript is to review methods for optimizing the derivation and culturing of stem-like cells also known as tumor stem cells (TSCs) from patient-derived GBM tissue samples. The hallmarks of TSCs are that they must be able to self-renew and retain tumorigenicity. The isolation, optimization and derivation of TSCs as outlined in this review, will be important in understanding biology and therapeutic applications related to these cells.

Progress in research of markers for cancer stem cells in esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is one of the most common malignant tumors in China, with high morbidity or mortality. In recent years, there has been a growing amount of evidence supporting the existence of a rare proportion of tumor cells termed cancer stem cells (CSCs) in diverse solid malignancies including ESCC. CSCs are closely related to the poor biological behaviors and drug resistance of ESCC. Markers for CSCs play an important role in the separation of CSCs, and the research on CSC markers can help clarify the mechanisms behind tumor development and guide tumor treatment.

TRAIL and paclitaxel synergize to kill U87 cells and U87-derived stem-like cells in vitro

U87-derived stem-like cells (U87-SLCs) were cultured using serum-free stem cell media and identified by both biological behaviors and markers. Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) and paclitaxel (PX), in combination or alone, was used to treat U87-MG human glioma cells (U87 cells) or U87-SLCs. The results showed that TRAIL/PX cannot only synergistically inhibit U87 cells but also U87-SLCs. We observed a significantly higher apoptotic rate in U87 cells simultaneously treated with TRAIL/PX for 24 h compared to cells treated with either drug alone. Furthermore, there was a remarkably higher apoptosis rate in U87-SLCs induced by the TRAIL/PX combination compared with either drug alone. Unlike the simultaneous treatment in U87 cells, U87-SLCs were pretreated for 24 h with 1 μmol/L of PX followed by 1000 ng/mL of TRAIL. Protein assays revealed that TRAIL/PX synergy was related to DR4, cleaved caspase-8 and cleaved caspase-3 upregulation, whereas the mitochondrial pathway was not involved in TRAIL-induced apoptosis. The present study indicates that PX can sensitize U87 cells and U87-SLCs to TRAIL treatment through an extrinsic pathway of cell apoptosis. The combined treatment of TRAIL and PX may be a promising glioma chemotherapy because of its successful inhibition of U87-SLCs, which are hypothesized to influence chemotherapeutic outcomes of gliomas.

β-Catenin Signalling in Glioblastoma Multiforme and Glioma-Initiating Cells

Glioblastoma multiforme (GBM) is a commonly occurring brain tumor with a poor prognosis. GBM can develop both "de novo" or evolve from a previous astrocytoma and is characterized by high proliferation and infiltration into the surrounding tissue. Following treatment (surgery, radiotherapy, and chemotherapy), tumors often reappear. Glioma-initiating cells (GICs) have been identified in GBM and are thought to be responsible for tumors initiation, their continued growth, and recurrence. β-catenin, a component of the cell-cell adhesion complex and of the canonical Wnt pathway, regulates proliferation, adhesion, and migration in different cell types. β-catenin and components of the Wnt canonical pathway are commonly overexpressed in GBM. Here, we review previous work on the role of Wnt/β-catenin signalling in glioma initiation, proliferation, and invasion. Understanding the molecular mechanisms regulating GIC biology and glioma progression may help in identifying novel therapeutic targets for GBM treatment.

Progress on potential strategies to target brain tumor stem cells

The identification of brain tumor stem cells (BTSCs) leads to promising progress on brain tumor treatment. For some brain tumors, BTSCs are the driving force of tumor growth and the culprits that make tumor revive and resistant to radiotherapy and chemotherapy. Therefore, it is specifically significant to eliminate BTSCs for treatment of brain tumors. There are considerable similarities between BTSCs and normal neural stem cells (NSCs), and diverse aspects of BTSCs have been studied to find potential targets that can be manipulated to specifically eradicate BTSCs without damaging normal NSCs, including their surface makers, surrounding niche, and aberrant signaling pathways. Many strategies have been designed to kill BTSCs, and some of them have reached, or are approaching, effective therapeutic results. Here, we will focus on advantages in the issue of BTSCs and emphasize on potential therapeutic strategies targeting BTSCs.