Potential use of glioblastoma tumorsphere: clinical credentialing

Comparison of Glioblastoma Cell Culture Platforms Based on Transcriptional Similarity with Paired Tissue

No standardized in vitro cell culture models for glioblastoma (GBM) have yet been established, excluding the traditional two-dimensional culture. GBM tumorspheres (TSs) have been highlighted as a good model platform for testing drug effects and characterizing specific features of GBM, but a detailed evaluation of their suitability and comparative performance is lacking. Here, we isolated GBM TSs and extracellular matrices (ECM) from tissues obtained from newly diagnosed IDH1 wild-type GBM patients and cultured GBM TSs on five different culture platforms: (1) ordinary TS culture liquid media (LM), (2) collagen-based three-dimensional (3D) matrix, (3) patient typical ECM-based 3D matrix, (4) patient tumor ECM-based 3D matrix, and (5) mouse brain. For evaluation, we obtained transcriptome data from all cultured GBM TSs using microarrays. The LM platform exhibited the most similar transcriptional program to paired tissues based on GBM genes, stemness- and invasiveness-related genes, transcription factor activity, and canonical signaling pathways. GBM TSs can be cultured via an easy-to-handle and cost- and time-efficient LM platform while preserving the transcriptional program of the originating tissues without supplementing the ECM or embedding it into the mouse brain. In addition to applications in basic cancer research, GBM TSs cultured in LM may also serve as patient avatars in drug screening and pre-clinical evaluation of targeted therapy and as standardized and clinically relevant models for precision medicine.

Classification of IDH wild-type glioblastoma tumorspheres into low- and high-invasion groups based on their transcriptional program

BACKGROUND

Glioblastoma (GBM), one of the most lethal tumors, exhibits a highly infiltrative phenotype. Here, we identified transcription factors (TFs) that collectively modulate invasion-related genes in GBM.

METHODS

The invasiveness of tumorspheres (TSs) were quantified using collagen-based 3D invasion assays. TF activities were quantified by enrichment analysis using GBM transcriptome, and confirmed by cell-magnified analysis of proteome imaging. Invasion-associated TFs were knocked down using siRNA or shRNA, and TSs were orthotopically implanted into mice.

RESULTS

After classifying 23 patient-derived GBM TSs into low- and high-invasion groups, we identified active TFs in each group-PCBP1 for low invasion, and STAT3 and SRF for high invasion. Knockdown of these TFs reversed the phenotype and invasion-associated-marker expression of GBM TSs. Notably, MRI revealed consistent patterns of invasiveness between TSs and the originating tumors, with an association between high invasiveness and poor prognosis. Compared to controls, mice implanted with STAT3- or SRF-downregulated GBM TSs showed reduced normal tissue infiltration and tumor growth, and prolonged survival, indicating a therapeutic response.

CONCLUSIONS

Our integrative transcriptome analysis revealed three invasion-associated TFs in GBM. Based on the relationship among the transcriptional program, invasive phenotype, and prognosis, we suggest these TFs as potential targets for GBM therapy.

Mesenchymal Stem-Like Cells Derived from the Ventricle More Effectively Enhance Invasiveness of Glioblastoma Than Those Derived from the Tumor

PURPOSE

Glioblastoma (GBM) is one of the most lethal human tumors with a highly infiltrative phenotype. Our previous studies showed that GBM originates in the subventricular zone, and that tumor-derived mesenchymal stem-like cells (tMSLCs) promote the invasiveness of GBM tumorspheres (TSs). Here, we extend these studies in terms of ventricles using several types of GBM patient-derived cells.

MATERIALS AND METHODS

The invasiveness of GBM TSs and ventricle spheres (VSs) were quantified via collagen-based 3D invasion assays. Gene expression profiles were obtained from microarray data. A mouse orthotopic xenograft model was used for in vivo experiments.

RESULTS

After molecular and functional characterization of ventricle-derived mesenchymal stem-like cells (vMSLCs), we investigated the effects of these cells on the invasiveness of GBM TSs. We found that vMSLC-conditioned media (CM) significantly accelerated the invasiveness of GBM TSs and VSs, compared to the control and even tMSLC-CM. Transcriptome analyses revealed that vMSLC secreted significantly higher levels of several invasiveness-associated cytokines. Moreover, differentially expressed genes between vMSLCs and tMSLCs were enriched for migration, adhesion, and chemotaxis-related gene sets, providing a mechanistic basis for vMSLC-induced invasion of GBM TSs. In vivo experiments using a mouse orthotopic xenograft model confirmed vMSLC-induced increases in the invasiveness of GBM TSs.

CONCLUSION

Although vMSLCs are non-tumorigenic, this study adds to our understanding of how GBM cells acquire infiltrative features by vMSLCs, which are present in the region where GBM genesis originates.

Dual inhibition of CPT1A and G6PD suppresses glioblastoma tumorspheres

PURPOSE

Limited treatment options are currently available for glioblastoma (GBM), an extremely lethal type of brain cancer. For a variety of tumor types, bioenergetic deprivation through inhibition of cancer-specific metabolic pathways has proven to be an effective therapeutic strategy. Here, we evaluated the therapeutic effects and underlying mechanisms of dual inhibition of carnitine palmitoyltransferase 1A (CPT1A) and glucose-6-phosphate dehydrogenase (G6PD) critical for fatty acid oxidation (FAO) and the pentose phosphate pathway (PPP), respectively, against GBM tumorspheres (TSs).

METHODS

Therapeutic efficacy against GBM TSs was determined by assessing cell viability, neurosphere formation, and 3D invasion. Liquid chromatography-mass spectrometry (LC-MS) and RNA sequencing were employed for metabolite and gene expression profiling, respectively. Anticancer efficacy in vivo was examined using an orthotopic xenograft model.

RESULTS

CPT1A and G6PD were highly expressed in GBM tumor tissues. Notably, siRNA-mediated knockdown of both genes led to reduced viability, ATP levels, and expression of genes associated with stemness and invasiveness. Similar results were obtained upon combined treatment with etomoxir and dehydroepiandrosterone (DHEA). Transcriptome analyses further confirmed these results. Data from LC-MS analysis showed that this treatment regimen induced a considerable reduction in the levels of metabolites associated with the TCA cycle and PPP. Additionally, the combination of etomoxir and DHEA inhibited tumor growth and extended survival in orthotopic xenograft model mice.

CONCLUSION

Our collective findings support the utility of dual suppression of CPT1A and G6PD with selective inhibitors, etomoxir and DHEA, as an efficacious therapeutic approach for GBM.

A lignan from Alnus japonica inhibits glioblastoma tumorspheres by suppression of FOXM1

Forkhead Box M1 (FOXM1) is known to regulate cell proliferation, apoptosis and tumorigenesis. The lignan, (-)-(2R,3R)-1,4-O-diferuloylsecoisolariciresinol (DFS), from Alnus japonica has shown anti-cancer effects against colon cancer cells by suppressing FOXM1. The present study hypothesized that DFS can have anti-cancer effects against glioblastoma (GBM) tumorspheres (TSs). Immunoprecipitation and luciferase reporter assays were performed to evaluate the ability of DFS to suppress nuclear translocation of β-catenin through β-catenin/FOXM1 binding. DFS-pretreated GBM TSs were evaluated to assess the ability of DFS to inhibit GBM TSs and their transcriptional profiles. The in vivo efficacy was examined in orthotopic xenograft models of GBM. Expression of FOXM1 was higher in GBM than in normal tissues. DFS-induced FOXM1 protein degradation blocked β-catenin translocation into the nucleus and consequently suppressed downstream target genes of FOXM1 pathways. DFS inhibited cell viability and ATP levels, while increasing apoptosis, and it reduced tumorsphere formation and the invasiveness of GBM TSs. And DFS reduced the activities of transcription factors related to tumorigenesis, stemness, and invasiveness. DFS significantly inhibited tumor growth and prolonged the survival rate of mice in orthotopic xenograft models of GBM. It suggests that DFS inhibits the proliferation of GBM TSs by suppressing FOXM1. DFS may be a potential therapeutic agent to treat GBM.

A novel biguanide (IM1761065) inhibits bioenergetics of glioblastoma tumorspheres

PURPOSE

Glioblastoma (GBM) is a rapidly growing tumor in the central nervous system with altered metabolism. Depleting the bioenergetics of tumors with biguanides have been suggested as an effective therapeutic approach for treating GBMs. The purpose of this study was to determine the effects of IM1761065, a novel biguanide with improved pharmacokinetics, on GBM-tumorspheres (TSs).

METHODS

The biological activities of IM1761065 on GBM-TSs, including their effects on viability, ATP levels, cell cycle, stemness, invasive properties, and transcriptomes were examined. The in vivo efficacy of IM1761065 was tested in a mouse orthotopic xenograft model.

RESULTS

IM1761065 decreased the viability and ATP levels of GBM-TSs in a dose-dependent manner, and reduced basal and spare respiratory capacity in patient-derived GBM-TS, as measured by the oxygen consumption rate. Sphere formation, expression of stemness-related proteins, and invasive capacity of GBM-TSs were also significantly suppressed by IM1761065. A gene-ontology comparison of IM1761065-treated groups showed that the expression levels of stemness-related, epithelial mesenchymal transition-related, and mitochondrial complex I genes were also significantly downregulated by IM1761065. An orthotopic xenograft mouse model showed decreased bioluminescence in IM1761065-treated cell-injected mice at 5 weeks. IM1761065-treated group showed longer survival than the control group (P = 0.0289, log-rank test).

CONCLUSION

IM1761065 is a potent inhibitor of oxidative phosphorylation. The inhibitory effect of IM1761065 on the bioenergetics of GBM-TS suggests that this novel compound could be used as a new drug for the treatment of GBM.

Influence of the Amount of Fresh Specimen on the Isolation of Tumor Mesenchymal Stem-Like Cells from High-Grade Glioma

PURPOSE

A critical indicator of the overall survival of patients with high-grade glioma is the successful isolation of tumor mesenchymal stem-like cells (tMSLCs), which play important roles in glioma progression. However, attempts to isolate tMSLCs from surgical specimens have not always been successful, and the reasons for this remain unclear. Considering that the amount of surgical high-grade glioma specimens varies, we hypothesized that larger surgical specimens would be better for tMSLC isolation.

MATERIALS AND METHODS

We assessed 51 fresh, high-grade glioma specimens and divided them into two groups according to the success or failure of tMSLC isolation. The success of tMSLC isolation was confirmed by plastic adherence, presenting antigens, tri-lineage differentiation, and non-tumorigenicity. Differences in characteristics between the two groups were tested using independent two sample t-tests, chi-square tests, or Kaplan-Meier survival analysis.

RESULTS

The mean specimen weights of the groups differed from each other (tMSLC-negative group: 469.9±341.9 mg, tMSLC positive group: 546.7±618.9 mg), but the difference was not statistically significant. The optimal cut-off value of specimen weight was 180 mg, and the area under the curve value was 0.599.

CONCLUSION

Our results suggested a minimum criterion for specimen collection, and found that the specimen amount was not deeply related to tMSLC detection. Collectively, our findings imply that the ability to isolate tMSLCs is determined by factors other than the specimen amount.

Co-expression of cancer driver genes: IDH-wildtype glioblastoma-derived tumorspheres

BACKGROUND

Driver genes of GBM may be crucial for the onset of isocitrate dehydrogenase (IDH)-wildtype (WT) glioblastoma (GBM). However, it is still unknown whether the genes are expressed in the identical cluster of cells. Here, we have examined the gene expression patterns of GBM tissues and patient-derived tumorspheres (TSs) and aimed to find a progression-related gene.

METHODS

We retrospectively collected primary IDH-WT GBM tissue samples (n = 58) and tumor-free cortical tissue samples (control, n = 20). TSs are isolated from the IDH-WT GBM tissue with B27 neurobasal medium. Associations among the driver genes were explored in the bulk tissue, bulk cell, and a single cell RNAsequencing techniques (scRNAseq) considering the alteration status of TP53, PTEN, EGFR, and TERT promoter as well as MGMT promoter methylation. Transcriptomic perturbation by temozolomide (TMZ) was examined in the two TSs.

RESULTS

We comprehensively compared the gene expression of the known driver genes as well as MGMT, PTPRZ1, or IDH1. Bulk RNAseq databases of the primary GBM tissue revealed a significant association between TERT and TP53 (p < 0.001, R = 0.28) and its association increased in the recurrent tumor (p  < 0.001, R = 0.86). TSs reflected the tissue-level patterns of association between the two genes (p < 0.01, R = 0.59, n = 20). A scRNAseq data of a TS revealed the TERT and TP53 expressing cells are in a same single cell cluster. The driver-enriched cluster dominantly expressed the glioma-associated long noncoding RNAs. Most of the driver-associated genes were downregulated after TMZ except IGFBP5.

CONCLUSIONS

GBM tissue level expression patterns of EGFR, TERT, PTEN, IDH1, PTPRZ1, and MGMT are observed in the GBM TSs. The driver gene-associated cluster of the GBM single cells were enriched with the glioma-associated long noncoding RNAs.

Combined effects of niclosamide and temozolomide against human glioblastoma tumorspheres

PURPOSE

Glioblastoma (GBM) is the most aggressive type of brain tumor and has poor survival outcomes, even after a combination of surgery, radiotherapy, and chemotherapy. Temozolomide is the only agent that has been shown to be effective against GBM, suggesting that combination of temozolomide with other agents may be more effective. Niclosamide, an FDA approved anthelmintic agent, has shown anti-cancer effects against human colon, breast, prostate cancers as well as GBM. However, the efficacy of the combination of niclosamide with temozolomide against GBM tumorspheres (TSs) has not been determined. We hypothesized that the combined treatment could effectively suppress GBM TSs.

METHODS

GBM TSs (TS15-88, GSC11) were treated with niclosamide and/or temozolomide. Combined effects of two drugs were evaluated by measuring viability, neurosphere formation, and 3D-invasion in collagen matrix. Transcriptional profiles of GBM TS were analyzed using RNA sequencing. In vivo anticancer efficacy of combined drugs was tested in a mouse orthotopic xenograft model.

RESULTS

Combination treatment of niclosamide and temozolomide significantly inhibited the cell viability, stemness, and invasive properties of GBM TSs. This combined treatment significantly down-regulated the expression of epithelial mesenchymal transition-related markers, Zeb1, N-cadherin, and β-catenin. The combined treatment also significantly decreased tumor growth in orthotopic xenograft models.

CONCLUSION

The combination of niclosamide and temozolomide effectively decreased the stemness and invasive properties of GBM TSs, suggesting that this regimen may be therapeutically effective in treating patients with GBM.

Regulation of bioenergetics through dual inhibition of aldehyde dehydrogenase and mitochondrial complex I suppresses glioblastoma tumorspheres

Background

Targeted approaches for treating glioblastoma (GBM) attempted to date have consistently failed, highlighting the imperative for treatment strategies that operate on different mechanistic principles. Bioenergetics deprivation has emerged as an effective therapeutic approach for various tumors. We have previously found that cancer cells preferentially utilize cytosolic NADH supplied by aldehyde dehydrogenase (ALDH) for ATP production through oxidative phosphorylation (OxPhos). This study is aimed at examining therapeutic responses and underlying mechanisms of dual inhibition of ALDH and OxPhos against GBM.

Methods

For inhibition of ALDH and OxPhos, the corresponding inhibitors, gossypol and phenformin were used. Biological functions, including ATP levels, stemness, invasiveness, and viability, were evaluated in GBM tumorspheres (TSs). Gene expression profiles were analyzed using microarray data. In vivo anticancer efficacy was examined in a mouse orthotopic xenograft model.

Results

Combined treatment of GBM TSs with gossypol and phenformin significantly reduced ATP levels, stemness, invasiveness, and cell viability. Consistently, this therapy substantially decreased expression of genes associated with stemness, mesenchymal transition, and invasion in GBM TSs. Supplementation of ATP using malate abrogated these effects, whereas knockdown of ALDH1L1 mimicked them, suggesting that disruption of ALDH-mediated ATP production is a key mechanism of this therapeutic combination. In vivo efficacy confirmed remarkable therapeutic responses to combined treatment with gossypol and phenformin.

Conclusion

Our findings suggest that dual inhibition of tumor bioenergetics is a novel and effective strategy for the treatment of GBM.

Glioblastoma Cellular Origin and the Firework Pattern of Cancer Genesis from the Subventricular Zone

Glioblastoma (GBM) is a disease without any definite cure. Numerous approaches have been tested in efforts to conquer this brain disease, but patients invariably experience recurrence or develop resistance to treatment. New surgical tools, carefully chosen samples, and experimental methods are enabling discoveries at single-cell resolution. The present article reviews the cell-of-origin of isocitrate dehydrogenase (IDH)-wildtype GBM, beginning with the historical background for focusing on cellular origin and introducing the cancer genesis patterned on firework. The authors also review mutations associated with the senescence process in cells of the subventricular zone (SVZ), and biological validation of somatic mutations in a mouse SVZ model. Understanding GBM would facilitate research on the origin of other cancers and may catalyze the development of new management approaches or treatments against IDH-wildtype GBM.

Inhibition of TFEB oligomerization by co-treatment of melatonin with vorinostat promotes the therapeutic sensitivity in glioblastoma and glioma stem cells

Glioblastoma (GBM) is the most aggressive malignant glioma and most lethal form of human brain cancer (Clin J Oncol Nurs. 2016;20:S2). GBM is also one of the most expensive and difficult cancers to treat by the surgical resection, local radiotherapy, and temozolomide (TMZ) and still remains an incurable disease. Oncomine platform analysis and Gene Expression Profiling Interactive Analysis (GEPIA) show that the expression of transcription factor EB (TFEB) was significantly increased in GBMs and in GBM patients above stage IV. TFEB requires the oligomerization and localization to regulate transcription in the nucleus. Also, the expression and oligomerization of TFEB proteins contribute to the resistance of GBM cells to conventional chemotherapeutic agents such as TMZ. Thus, we investigated whether the combination of vorinostat and melatonin could overcome the effects of TFEB and induce apoptosis in GBM cells and glioma cancer stem cells (GSCs). The downregulation of TFEB and oligomerization by vorinostat and melatonin increased the expression of apoptosis-related genes and activated the apoptotic cell death process. Significantly, the inhibition of TFEB expression dramatically decreased GSC tumor-sphere formation and size. The inhibitory effect of co-treatment resulted in decreased proliferation of GSCs and induced the expression of cleaved PARP and p-γH2AX. Taken together, our results definitely demonstrate that TFEB expression contributes to enhanced resistance of GBMs to chemotherapy and that vorinostat- and melatonin-activated apoptosis signaling in GBM cells by inhibiting TFEB expression and oligomerization, suggesting that co-treatment of vorinostat and melatonin may be an effective therapeutic strategy for human brain cancers.

Combined treatment with 2'-hydroxycinnamaldehyde and temozolomide suppresses glioblastoma tumorspheres by decreasing stemness and invasiveness

INTRODUCTION

Glioblastoma (GBM) is the most common and aggressive human primary brain malignancy. The key properties of GBM, stemness and invasiveness, are known to be associated with a highly unfavorable prognosis. Notably, the process of epithelial-mesenchymal transition (EMT) is closely related to the progression of GBM. On the basis of reports that 2'-hydroxycinnamaldehyde (HCA) and its derivative, 2'-benzoyloxycinnamaldehyde (BCA), suppresses EMT in several human cancer cells, we sought to evaluate the therapeutic efficacy of HCA and BCA, alone and in combination with temozolomide (TMZ), on GBM tumorspheres (TSs).

METHODS

Two human GBM TSs were treated with HCA, BCA, or TMZ. Therapeutic effects were evaluated by measuring ATP levels, neurosphere formation, 3D-invasion in collagen matrix, and viability. Protein expression profiles after drug treatment were evaluated by western blotting. In vivo anticancer efficacy of drugs was examined in a mouse orthotopic xenograft model.

RESULTS

Combined treatment of GBM TSs with HCA or BCA and TMZ significantly reduced cell viability, stemness, and invasiveness. Expression levels of stemness-, invasiveness-, and mesenchymal transition-associated markers, Zeb1, N-cadherin, and β-catenin, were also substantially decreased by the combined treatment. The combined treatment also reduced tumor growth in a mouse orthotopic xenograft model.

CONCLUSION

Our findings suggest that HCA and BCA, combined with TMZ, are potential therapeutic agents in the treatment of GBM.

Glioblastoma Treatments: An Account of Recent Industrial Developments

The different drugs and medical devices, which are commercialized or under industrial development for glioblastoma treatment, are reviewed. Their different modes of action are analyzed with a distinction being made between the effects of radiation, the targeting of specific parts of glioma cells, and immunotherapy. Most of them are still at a too early stage of development to firmly conclude about their efficacy. Optune, which triggers antitumor activity by blocking the mitosis of glioma cells under the application of an alternating electric field, seems to be the only recently developed therapy with some efficacy reported on a large number of GBM patients. The need for early GBM diagnosis is emphasized since it could enable the treatment of GBM tumors of small sizes, possibly easier to eradicate than larger tumors. Ways to improve clinical protocols by strengthening preclinical studies using of a broader range of different animal and tumor models are also underlined. Issues related with efficient drug delivery and crossing of blood brain barrier are discussed. Finally societal and economic aspects are described with a presentation of the orphan drug status that can accelerate the development of GBM therapies, patents protecting various GBM treatments, the different actors tackling GBM disease, the cost of GBM treatments, GBM market figures, and a financial analysis of the different companies involved in the development of GBM therapies.

NAMPT Is a Potent Oncogene in Colon Cancer Progression that Modulates Cancer Stem Cell Properties and Resistance to Therapy through Sirt1 and PARP

Purpose: Colorectal cancer is the second most common cancer in women and the third most common in men worldwide. However, despite current progress, many patients with advanced and metastatic tumors still die from the malignancy. Refractory disease often relies on nicotinamide adenine dinucleotide (NAD)-dependent mechanisms. NAD metabolism and a stable NAD regeneration circuit are required to maintain tissue homeostasis and metabolism. However, high levels of NAD confer therapy resistance to tumors.Experimental Design: Ectopic overexpression of nicotinamide phosphoribosil transferase (NAMPT) and shRNAs in colorectal cancer cell lines, tumorigenic and stemness properties and transcription measurement in culture and in vivo Transcriptional analysis in public databases. Therapeutic approaches.Results: NAMPT, the rate-limiting enzyme responsible for the highest source of physiologic NAD biosynthesis, increases tumorigenic properties and induces cancer stem cell-like properties through pathways that control stem cell signaling, thus enriching the cancer-initiating cell (CIC) population. Furthermore, NAMPT expression correlated with high levels of CIC-like cells in colon tumors directly extracted from patients, and transcription meta-analysis revealed that NAMPT is also a key factor that induces cancer stem pathways in colorectal cancer tumors. This effect is mediated by PARP and SIRT1. In addition, we report a novel NAMPT-driven signature that stratifies prognosis from high to low expression groups. The NAMPT signature contained SIRT1 and PARP1 levels as well as other cancer stem cell-related genes. Finally, NAMPT inhibition increased the sensitivity to apoptosis in both NAMPT-expressing cells and tumorspheres.Conclusions: NAMPT represents a novel therapeutic target in colon cancer progression and relapse, particularly the CIC subset of human colon cancers. Clin Cancer Res; 24(5); 1202-15. ©2017 AACR.

NAMPT overexpression induces cancer stemness and defines a novel tumor signature for glioma prognosis

Gliomas are the most prevalent primary malignant brain tumors associated with poor prognosis. NAMPT, a rate-limiting enzyme that boosts the nicotinamide adenine dinucleotide (NAD) regeneration in the salvage pathway, is commonly expressed in these tumors. NAD metabolism is required to maintain tissue homeostasis. To maintain metabolism, cancer cells require a stable NAD regeneration circuit. However, high levels of NAD confer resistance to therapy to these tumors, usually treated with Temozolomide (TMZ). We report that NAMPT overexpression in glioma cell lines increases tumorigenic properties controlling stem cell pathways and enriching the cancer-initiating cell (CIC) population. Furthermore, NAMPT expression correlated with high levels of Nanog, CD133 and CIC-like cells in glioblastoma directly extracted from patients. Meta-analysis reveals that NAMPT is also a key factor inducing cancer stem pathways in glioma cells. Furthermore, we report a novel NAMPT-driven signature which stratify prognosis within tumor staging. NAMPT signature also correlates directly with EGFR positive and IDH negative tumors. Finally, NAMPT inhibition increases sensitivity to apoptosis in both NAMPT-expressing cells and tumorspheres. Therefore, NAMPT represents a novel therapeutic target in Glioma progression and relapse.

Inhibition of glioblastoma tumorspheres by combined treatment with 2-deoxyglucose and metformin

Background

Deprivation of tumor bioenergetics by inhibition of multiple energy pathways has been suggested as an effective therapeutic approach for various human tumors. However, this idea has not been evaluated in glioblastoma (GBM). We hypothesized that dual inhibition of glycolysis and oxidative phosphorylation could effectively suppress GBM tumorspheres (TS).

Methods

Effects of 2-deoxyglucose (2DG) and metformin, alone and in combination, on GBM-TS were evaluated. Viability, cellular energy metabolism status, stemness, invasive properties, and GBM-TS transcriptomes were examined. In vivo efficacy was tested in a mouse orthotopic xenograft model.

Results

GBM-TS viability was decreased by the combination of 2DG and metformin. ATP assay and PET showed that cellular energy metabolism was also decreased by this combination. Sphere formation, expression of stemness-related proteins, and invasive capacity of GBM-TS were also significantly suppressed by combined treatment with 2DG and metformin. A transcriptome analysis showed that the expression levels of stemness- and epithelial mesenchymal transition-related genes were also significantly downregulated by combination of 2DG and metformin. Combination treatment also prolonged survival of tumor-bearing mice and decreased invasiveness of GBM-TS.

Conclusion

The combination of 2DG and metformin effectively decreased the stemness and invasive properties of GBM-TS and showed a potential survival benefit in a mouse orthotopic xenograft model. Our findings suggest that targeting TS-forming cells by this dual inhibition of cellular bioenergetics warrants expedited clinical evaluation for the treatment of GBM.

Inhibiting stemness and invasive properties of glioblastoma tumorsphere by combined treatment with temozolomide and a newly designed biguanide (HL156A)

Studies have investigated biguanide-derived agents for the treatment of cancers and have reported their effects against tumorspheres (TSs). The purpose of this study was determining the effects of HL156A, a newly designed biguanide with improved pharmacokinetics, on glioblastoma TSs (GMB TSs) and assess the feasibility of this drug as a new line of therapy against glioblastoma, alone or combined with a conventional therapeutic agent, temozolomide(TMZ). The effects of HL156A, alone and combined with TMZ, on the stemness and invasive properties of GBM TSs and survival of orthotopic xenograft animals were assessed. HL156A, combined with TMZ, inhibited the stemness of GBM TSs, proven by neurosphere formation assay and marker expression. Three-dimensional collagen matrix invasion assays provided evidence that combined treatment inhibited invasive properties, compared with control and TMZ-alone treatment groups. TMZ alone and combined treatment repressed the expression of epithelial-mesenchymal transition-related genes. A gene ontology comparison of TMZ and combination-treatment groups revealed altered expression of genes encoding proteins involved in cellular adhesion and migration. Combined treatment with HL156A and TMZ showed survival benefits in an orthotopic xenograft mouse model. The inhibitory effect of combination treatment on the stemness and invasive properties of GBM TSs suggest the potential usage of this regimen as a novel strategy for the treatment of GBM.

Success of tumorsphere isolation from WHO grade IV gliomas does not correlate with the weight of fresh tumor specimens: an immunohistochemical characterization of tumorsphere differentiation

BACKGROUND

A trend of stage-by-stage increase in tumorsphere (TS) formation from glioma samples has been reported. Despite this trend, not all surgical specimens give rise to TSs, even World Health Organization (WHO) grade IV gliomas. Furthermore, it has been reported that differences in overall survival of primary glioblastoma patients depends on the propensity of their tumors to form TSs. However, the weights of fresh specimens vary from one surgical isolate to the next.

METHODS

Accordingly, we evaluated the relationship between the weights of surgical specimens in WHO grade IV gliomas with the capacity to isolate TSs. Thirty-five fresh WHO grade IV glioma specimens were separated into two groups, based on whether they were positive or negative for TS isolation, and the relationship between TS isolation and weight of surgical specimens was assessed.

RESULTS

We observed no significant difference in the weights of surgical samples in the two groups, and found that the optimal weight of specimens for TSs isolation was 500 mg.

CONCLUSION

Thus, contrary to our expectations, the ability to isolate TSs from WHO grade IV glioma specimens was not related to the weight of fresh specimens.

Failure of a patient-derived xenograft for brain tumor model prepared by implantation of tissue fragments

Background

With the continuing development of new anti-cancer drugs comes a need for preclinical experimental models capable of predicting the clinical activity of these novel agents in cancer patients. However existing models have a limited ability to recapitulate the clinical characteristics and associated drug sensitivity of tumors. Among the more promising approaches for improving preclinical models is direct implantation of patient-derived tumor tissue into immunocompromised mice, such as athymic nude or non-obese diabetic/severe combined immunodeficient (NOD/SCID) mice. In the current study, we attempted to develop patient-derived xenograft (PDX) models using tissue fragments from surgical samples of brain tumors.

Methods

In this approach, tiny tissue fragments of tumors were biopsied from eight brain tumor patients—seven glioblastoma patients and one primitive neuroectodermal tumor patient. Two administration methods—a cut-down syringe and a pipette—were used to implant tissue fragments from each patient into the brains of athymic nude mice.

Results

In contrast to previous reports, and contrary to our expectations, we found that none of these fragments from brain tumor biopsies resulted in the successful establishment of xenograft tumors.

Conclusions

These results suggest that fragments of surgical specimens from brain tumor patients are unsuitable for implementation of brain tumor PDX models, and instead recommend other in vivo testing platforms for brain tumors, such as cell-based brain tumor models.

Electronic supplementary material

The online version of this article (doi:10.1186/s12935-016-0319-0) contains supplementary material, which is available to authorized users.

Isolation and characterization of tumorspheres from a recurrent pineoblastoma patient: Feasibility of a patient-derived xenograft

The existence of tumorspheres (TSs) might confer treatment resistance to pineoblastoma (PB). The existence of PB TSs with cellular immortalization potential has not yet been reported. We developed a procedure for isolating TSs from recurrent PB (rPB) and tested whether their properties made them suitable for use as a patient-derived xenograft (PDX). Immunocytochemical staining, RT-PCR and quantitative real-time PCR showed that, among stemness proteins, CD133, musashi and podoplanin were expressed at elevated levels in rPB TSs, but nestin was not. rPB TSs cultured under neuro-glial differentiation conditions expressed TUBB3, but not GFAP, MBP or NeuN. Unlike glioblastoma TSs, rPB TSs showed no clear evidence of invasion in 3D invasion assay or increased expression of genes associated with epithelial-mesenchymal transition. An orthotopic xenograft showed that tumor xenografts replicated the histopathological features of the patient tumor and expressed similar genome profiles, as determined by short tandem repeat genotyping. These data demonstrate the isolation and the characterization of rPB TSs for the first time. Using an orthotopic xenograft, we showed that rPB TSs could replicate the patient tumor, demonstrating their potential as a PDX for precision medicine.