Isolation of tumor spheres and mesenchymal stem-like cells from a single primitive neuroectodermal tumor specimen

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 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.

Crosstalk between GBM cells and mesenchymal stemlike cells promotes the invasiveness of GBM through the C5a/p38/ZEB1 axis

BACKGROUND

Mesenchymal stemlike cells (MSLCs) have been detected in many types of cancer including brain tumors and have received attention as stromal cells in the tumor microenvironment. However, the cellular mechanisms underlying their participation in cancer progression remain largely unexplored. The aim of this study was to determine whether MSLCs have a tumorigenic role in brain tumors.

METHODS

To figure out molecular and cellular mechanisms in glioma invasion, we have cultured glioma with MSLCs in a co-culture system.

RESULTS

Here, we show that MSLCs in human glioblastoma (GBM) secrete complement component C5a, which is known for its role as a complement factor. MSLC-secreted C5a increases expression of zinc finger E-box-binding homeobox 1 (ZEB1) via activation of p38 mitogen-activated protein kinase (MAPK) in GBM cells, thereby enhancing the invasion of GBM cells into parenchymal brain tissue.

CONCLUSION

Our results reveal a mechanism by which MSLCs undergo crosstalk with GBM cells through the C5a/p38 MAPK/ZEB1 signaling loop and act as a booster in GBM progression.

KEY POINTS

1. MSLCs activate p38 MAPK-ZEB1 signaling in GBM cells through C5a in a paracrine manner, thereby boosting the invasiveness of GBM cells in the tumor microenvironment.2. Neutralizing of C5a could be a potential therapeutic target for GBM by inhibition of mesenchymal phenotype.

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.

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.

Force-mediated proinvasive matrix remodeling driven by tumor-associated mesenchymal stem-like cells in glioblastoma

In carcinoma, cancer-associated fibroblasts participate in force-mediated extracellular matrix (ECM) remodeling, consequently leading to invasion of cancer cells. Likewise, the ECM remodeling actively occurs in glioblastoma (GBM) and the consequent microenvironmental stiffness is strongly linked to migration behavior of GBM cells. However, in GBM the stromal cells responsible for force-mediated ECM remodeling remain unidentified. We show that tumor-associated mesenchymal stem-like cells (tMSLCs) provide a proinvasive matrix condition in GBM by force-mediated ECM remodeling. Importantly, CCL2-mediated Janus kinase 1 (JAK1) activation increased phosphorylation of myosin light chain 2 in tMSLCs and led to collagen assembly and actomyosin contractility. Collectively, our findings implicate tMSLCs as stromal cells providing force-mediated proinvasive ECM remodeling in the GBM microenvironment, and reminiscent of fibroblasts in carcinoma.

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.

Tumor Mesenchymal Stem-Like Cell as a Prognostic Marker in Primary Glioblastoma

The isolation from brain tumors of tumor mesenchymal stem-like cells (tMSLCs) suggests that these cells play a role in creating a microenvironment for tumor initiation and progression. The clinical characteristics of patients with primary glioblastoma (pGBM) positive for tMSLCs have not been determined. This study analyzed samples from 82 patients with pGBM who had undergone tumor removal, pathological diagnosis, and isolation of tMSLC from April 2009 to October 2014. Survival, extent of resection, molecular markers, and tMSLC culture results were statistically evaluated. Median overall survival was 18.6 months, 15.0 months in tMSLC-positive patients and 29.5 months in tMSLC-negative patients (P = 0.014). Multivariate cox regression model showed isolation of tMSLC (OR = 2.5, 95% CI = 1.1~5.6, P = 0.021) showed poor outcome while larger extent of resection (OR = 0.5, 95% CI = 0.2~0.8, P = 0.011) has association with better outcome. The presence of tMSLCs isolated from the specimen of pGBM is associated with the survival of patient.

Potential use of glioblastoma tumorsphere: clinical credentialing

A decade ago, cancer stem cells (CSCs) were introduced as target cells for an innovative cancer treatment. Particularly, there have been a lot of biological researches on glioblastoma (GBM) CSCs. However, as there is a comprehensive change in the concept of CSCs, it is required to review how the different CSCs for patients can be clinically used, or clinical credentialing, and summarize the possibilities of clinical credentialing. In this regard, this review aims to introduce the tumorsphere obtained from GBM specimen and summarize the clinical dilemma and clinically applicable areas.

Prognostic value of glioma cancer stem cell isolation in survival of primary glioblastoma patients

Cancer stem cells (CSCs) have been reported to be critical in the initiation, maintenance, and progression of cancers. The expression of stem cell markers, such as podoplanin (PDPN), CD133, and nestin, may have been correlated with malignant progression. However, the effects of CSCs and stem cell markers on clinical outcomes in cancer patients remain unclear. In this study, we assessed the prognostic roles of glioma CSCs (gCSCs) isolation and stem cell markers in patients with primary glioblastoma (pGBM). A cohort of 39 patients with pGBM was separated into two groups, those positive or negative for gCSCs, and the correlation between gCSC and patient survival was evaluated. We observed significantly different cumulative survival (P = 0.045) when comparing patients positive for gCSCs patients and negative for gCSC. Among the patients positive for gCSCs, we observed no significant differences in survival between those whose gCSCs were each positive or negative for PDPN, CD133, or nestin. This study strongly supports the prognostic value of gCSCs isolation on the survival of patients with pGBM.