Neural stem/progenitors and glioma stem-like cells have differential sensitivity to chemotherapy

Early region-specific impact of adjuvant radiation therapy on cognition and quality of life in adult patients with primary brain tumors

PURPOSE

While treatments for primary brain tumors increase survival, they have cognitive sequelae. Neurocognition's anatomical distribution makes it susceptible to brain damage. This study aims to evaluate the contribution of radiotherapy on short-term cognitive impairment.

METHODS/PATIENTS

Using a prospective database of cognitive rehabilitation in adults operated on for primary brain tumors, a retrospective sub-analysis of the contribution of radiotherapy was performed. Thirty-four subdivisions of 12 neurocognitive regions were delineated in 48 irradiated patients and 30 non-irradiated patients. In the first group, the correlation between radiation dose and deterioration was evaluated. In all patients, the impact of tumor and surgical changes on dysfunction was calculated and compared with dose-dependent response.

RESULTS

The correlation between cognitive status and radiation dose is especially strong and significant in the left hemisphere and in specific subdivisions such as the posterior hippocampus or the dorsolateral prefrontal cortex, with the left prevailing over posterior dominance. Memory is the most affected domain 1 month after radiotherapy, as attention is three months later. The hippocampus is involved in various cognitive domains in addition to memory. The prefrontal subregions and the genu of the corpus callosum are more affected by the relationship with disease and surgical changes than by radiation exposure. Patients ongoing a course of radiotherapy do not benefit from concurrent cognitive rehabilitation.

CONCLUSIONS

There is a correlation between the dose of radiation received by several encephalic regions and degree of short-term domain-specific cognition decline, considering other factors of risk and cognitive rehabilitation.

Dual targeting of the mitochondrial Lon peptidase 1 and the chymotrypsin-like proteasome activity as a potential therapeutic strategy in malignant astrocytoma models

Malignant astrocytomas are aggressive primary brain tumors characterized by extensive hypoxia-induced, mitochondria-dependent changes such as altered respiration, increased chymotrypsin-like (CT-L) proteasome activity, decreased apoptosis, drug resistance, stemness, and increased invasiveness. Mitochondrial Lon Peptidase 1 (LonP1) overexpression and increased CT-L proteasome activity are biomarkers of an aggressive high-grade phenotype and found to be associated with recurrence and poor patient survival. In preclinical models, small molecule agents targeting either LonP1 or the proteasome CT-L activity have anti-astrocytoma activity. Here, we present evidence that the dual inhibition of LonP1 and CT-L proteasome activity effectively induces ROS production, leading to apoptosis in malignant astrocytoma established cell lines and patient-derived glioma stem cell-like cultures. We also evaluated a novel small molecule, BT317, derived from the coumarinic compound 4 (CC4) using structure-activity modeling, which we found to inhibit both LonP1 and CT-L proteasome activity. Using gain- and loss-of-function genetic models, we discovered that LonP1 is both necessary and sufficient to drive BT317 drug sensitivity in established and patient-derived glioma stem-like cells by generating ROS and inducing apoptosis. In vitro, BT317 had activity as a single agent but, more importantly, enhanced synergy with the standard of care commonly used chemotherapeutic temozolomide (TMZ). In an orthotopic xenograft astrocytoma model, BT317 crossed the blood-brain barrier, showed selective activity at the tumor site, and demonstrated therapeutic efficacy as a single agent and combined with TMZ. BT317 defines an emerging class of LonP1 and CT-L inhibitors that exhibited promising anti-tumor activity and could be a potential candidate for malignant astrocytoma therapeutics. SIMPLE SUMMARY: Malignant astrocytoma patients have poor clinical outcomes, and novel treatments are needed to limit tumor recurrence and improve their overall survival. These tumors have a malignant phenotype mediated by altered mitochondrial metabolism, abnormal protein processing, and adaptation to hypoxia. We have previously published that astrocytomas are especially vulnerable to proteasome inhibitors as well as to inhibitors of the mitochondrial Lon Peptidase 1 (LonP1), but the effect of combining the two strategies has not been reported. Here, we present evidence that the dual inhibition of LonP1 and Chymotrypsin-like (CT-L) proteasome activity effectively induces cellular reactive oxygen species (ROS) production, leading to apoptosis in malignant astrocytoma established cell lines and patient-derived glioma stem cell-like cultures. We developed BT317, a small molecule dual inhibitor, which crosses the blood-brain barrier and shows strong synergy with the standard of care, temozolomide (TMZ), in the astrocytoma cell lines independent of their isocitrate dehydrogenase (IDH) profile and in an orthotopic glioma murine model. This preclinical study demonstrated the potential of dual LonP1 and CT-L proteasome inhibition as a novel therapeutic strategy for malignant astrocytoma and provides insight for future clinical translational studies alone or in combination with other chemotherapies.

Hyperbaric oxygen promotes both the proliferation and chemosensitization of glioblastoma cells by inhibiting HIF1α/HIF2α-ABCG2

Introduction

Hyperbaric oxygen enhances glioma chemosensitivity, but the mechanism remains unclear. Hypoxia is common in gliomas, and as the main effector molecules of hypoxia, HIF1α and HIF2α promote the malignant progression by inhibiting cell apoptosis and maintaining stemness. ABCG2 is a marker protein of tumor stem cells and drug efflux transporter protein. This study aims to reveal the detailed mechanism of hyperbaric oxygen promote both proliferation and chemosensitization.

Methods

Under hyperbaric oxygen and hypoxic conditions, we investigated the differences in cell cycle, proliferation, apoptosis, LDH release, and the expression of proteins and mRNA. We also conducted studies on transcriptional regulation and performed in vivo experiments.

Results

It revealed that under hypoxic conditions, HIF1α, HIF2α, and ABCG2 are highly expressed, and both HIF1α and HIF2α promote ABCG2 expression. After hyperbaric oxygen treatment, the expression of HIF1α, HIF2α, and ABCG2 decreased, both cell proliferation and chemosensitivity increased. After knocking out HIF1α and HIF2α, cell proliferation and chemosensitivity increased, but the expression of stem cell marker proteins decreased. ChIP-qPCR revealed that HIF1α and HIF2α target the ABCG2 promoter. Gain-and loss-of-function experiments suggested that ABCG2 can promote the expression of stem cell marker proteins, inhibit cell apoptosis, and promote tumor progression.

Conclusion

This study confirmed that hyperbaric oxygen can inhibit ABCG2 expression through HIF1α and HIF2α, thereby promoting the proliferation and chemosensitization of gliomas.

The influence of homologous recombination repair on temozolomide chemosensitivity in gliomas

Gliomas represent a prevalent form of primary brain tumors, with temozolomide (TMZ) serving as the established first-line therapeutic option. Nevertheless, the effectiveness of TMZ is hindered by the development of chemoresistance. Recent investigations have underscored the correlation of homologous recombination repair (HRR), a pivotal mechanism responsible for mending DNA double-strand breaks, with TMZ resistance in glioma treatment. This review centers on elucidating the significance of HRR in the management of gliomas, with a particular emphasis on pivotal molecules implicated in the HRR process, including RAD51, ATM, ATR, and newly identified small molecules that impact HRR. Modulating the expression of these genes can effectively restrain pathways such as ATM/CHK2, ATR/CHK1, and PI3K/AKT, subsequently augmenting the sensitivity of gliomas to TMZ. Noteworthy efforts have been directed towards exploring inhibitors of these pathways in recent research endeavors, culminating in encouraging outcomes. In conclusion, the involvement of HRR in glioma resistance unveils novel therapeutic avenues, with targeting crucial molecules in the HRR pathway, holding promise for enhancing the effectiveness of TMZ therapy.

Real-time viscoelastic deformability cytometry: High-throughput mechanical phenotyping of liquid and solid biopsies

In principle, the measurement of mechanical property differences between cancer cells and their benign counterparts enables the detection, diagnosis, and classification of diseases. Despite the existence of various mechanophenotyping methods, the ability to perform high-throughput single-cell deformability measurements on liquid and/or solid tissue biopsies remains an unmet challenge within clinical settings. To address this issue, we present an ultrahigh-throughput viscoelastic microfluidic platform able to measure the mechanical properties of single cells at rates of up to 100,000 cells per second (and up to 10,000 cells per second in real time). To showcase the utility of the presented platform in clinical scenarios, we perform single-cell phenotyping of both liquid and solid tumor biopsies, cytoskeletal drug analysis, and identification of malignant lymphocytes in peripheral blood samples. Our viscoelastic microfluidic methodology offers opportunities for high-throughput, label-free single-cell analysis, with diverse applications in clinical diagnostics and personalized medicine.

Ruta graveolens, but Not Rutin, Inhibits Survival, Migration, Invasion, and Vasculogenic Mimicry of Glioblastoma Cells

Glioblastoma (GBM) is the most aggressive type of brain tumor, characterized by poor outcome and limited therapeutic options. During tumor progression, GBM may undergo the process of vasculogenic mimicry (VM), consisting of the formation of vascular-like structures which further promote tumor aggressiveness and malignancy. The resulting resistance to anti-angiogenetic therapies urges the identification of new compounds targeting VM. Extracts of natural plants may represent potential therapeutic tools. Among these, components of Ruta graveolens water extract (RGWE) display a wide range of biological activities. To test the effect of RGWE on human GBM and rat glioma cell line VM, tube formation on a gelled matrix was monitored. Quantitative assessment of VM formation shows the clear-cut inhibitory activity of RGWE. Unlike rutin, one of the most abundant extract components, the whole RGWE strongly reduced the migration and invasion of GBM tumor cells. Moreover, RGWE induced cell death of GBM patient-derived cancer stem cells and impaired VM at sub-lethal doses. Overall, our data reveal a marked RGWE-dependent inhibition of GBM cell survival, migration, invasion, and VM formation. Thus, the clear-cut ability of RGWE to counteract GBM malignancy deserves attention, holding the promise to bring natural products to clinical use, thus uncovering new therapeutic opportunities.

WITHDRAWN: Dual targeting of mitochondrial Lon peptidase 1 and chymotrypsin-like protease by small molecule BT317, as potential therapeutics in malignant astrocytomas

The authors have withdrawn their manuscript owing to massive revision and data validation. Therefore, the authors do not wish this work to be cited as reference for the project. If you have any questions, please contact the corresponding author.

More than a small adult brain: Lessons from chemotherapy-induced cognitive impairment for modelling paediatric brain disorders

Childhood is recognised as a period of immense physical and emotional development, and this, in part, is driven by underlying neurophysiological transformations. These neurodevelopmental processes are unique to the paediatric brain and are facilitated by augmented rates of neuroplasticity and expanded neural stem cell populations within neurogenic niches. However, given the immaturity of the developing central nervous system, innate protective mechanisms such as neuroimmune and antioxidant responses are functionally naïve which results in periods of heightened sensitivity to neurotoxic insult. This is highly relevant in the context of paediatric cancer, and in particular, the neurocognitive symptoms associated with treatment, such as surgery, radio- and chemotherapy. The vulnerability of the developing brain may increase susceptibility to damage and persistent symptomology, aligning with reports of more severe neurocognitive dysfunction in children compared to adults. It is therefore surprising, given this intensified neurocognitive burden, that most of the pre-clinical, mechanistic research focuses exclusively on adult populations and extrapolates findings to paediatric cohorts. Given this dearth of age-specific research, throughout this review we will draw comparisons with neurodevelopmental disorders which share comparable pathways to cancer treatment related side-effects. Furthermore, we will examine the unique nuances of the paediatric brain along with the somatic systems which influence neurological function. In doing so, we will highlight the importance of developing in vitro and in vivo paediatric disease models to produce age-specific discovery and clinically translatable research.

Targeting Glioblastoma Stem Cells to Overcome Chemoresistance: An Overview of Current Therapeutic Strategies

Glioblastoma (GBM) is the most malignant primary brain tumor. The current standard approach in GBM is surgery, followed by treatment with radiation and temozolomide (TMZ); however, GBM is highly resistant to current therapies, and the standard of care has not been revised over the last two decades, indicating an unmet need for new therapies. GBM stem cells (GSCs) are a major cause of chemoresistance due to their ability to confer heterogeneity and tumorigenic capacity. To improve patient outcomes and survival, it is necessary to understand the properties and mechanisms underlying GSC chemoresistance. In this review, we describe the current knowledge on various resistance mechanisms of GBM to therapeutic agents, with a special focus on TMZ, and summarize the recent findings on the intrinsic and extrinsic mechanisms of chemoresistance in GSCs. We also discuss novel therapeutic strategies, including molecular targeting, autophagy inhibition, oncolytic viral therapy, drug repositioning, and targeting of GSC niches, to eliminate GSCs, from basic research findings to ongoing clinical trials. Although the development of effective therapies for GBM is still challenging, this review provides a better understanding of GSCs and offers future directions for successful GBM therapy.

Inhibition of Carbonic Anhydrase 2 Overcomes Temozolomide Resistance in Glioblastoma Cells

About 95% of Glioblastoma (GBM) patients experience tumor relapse as a consequence of resistance to the first-line standard chemotherapy using temozolomide (TMZ). Recent studies reported consistently elevated expression levels of carbonic anhydrase CA2 in recurrent glioblastoma and temozolomide-resistant glioblastoma stem-like cells (GSCs). Here we show that CA2 is preferentially expressed in GSCs and upregulated by TMZ treatment. When expressed in GBM cell lines, CA2 exerts significant metabolic changes reflected by enhanced oxygen consumption and increased extracellular acidification causing higher rates of cell invasion. Notably, GBM cells expressing CA2 respond to combined treatment with TMZ and brinzolamide (BRZ), a non-toxic and potent CA2 inhibitor. Interestingly, brinzolamide was more effective than the pan-CA inhibitor Acetazolamide (ACZ) to sensitize naïve GSCs and TMZ-resistant GSCs to TMZ induced cell death. Mechanistically, we demonstrated that the combined treatment of GBM stem cells with TMZ and BRZ caused autophagy of GBM cell lines and GSCs, reflected by enhanced LC3 cleavage (LC3-II) and p62 reduction. Our findings illustrate the potential of CA2 as a chemo-sensitizing drug target in recurrent GBM and propose a combined treatment of TMZ with CA2 inhibitor to tackle GBM chemoresistance and recurrence.

Pineal parenchymal tumor of intermediate differentiation: a systematic review and contemporary management of 389 cases reported during the last two decades

Pineal parenchymal tumor of intermediate differentiation (PPTID) is a WHO grade II and III tumor arising from pineal parenchymal cells. PPTID is a rare tumor accounting for less than 1% of all primary central nervous system neoplasms. Therefore, reports describing the clinical characteristics and biological features of PPTID are lacking. Moreover, the therapeutic strategy remains controversial. The current study aimed to evaluate treatment results and problems of contemporary therapeutic modalities of PPTID based on its features compared with other pineal parenchymal tumors. A comprehensive systematic literature review of 69 articles was performed, including articles on PPTID (389 patients) and similar tumors. Patient demographics, disease presentation, imaging characteristics, biological features, and current therapeutic options and their results were reviewed. We found that histopathological findings based on current WHO classification are well associated with survival; however, identifying and treating aggressive PPTID cases with uncommon features could be problematic. A molecular and genetic approach may help improve diagnostic accuracy. Therapeutic strategy, especially for grade III and aforementioned uncommon and aggressive tumors, remains controversial. A combination therapy involving maximum tumor resection, chemotherapy, and radiotherapy could be the first line of treatment. However, although challenging, a large prospective study would be required to identify ways to improve the clinical results of PPTID treatment.

Nicotinamide Mononucleotide Prevents Cisplatin-Induced Cognitive Impairments

Chemotherapy-induced cognitive impairment (CICI) is often reported as a neurotoxic side effect of chemotherapy. Although CICI has emerged as a significant medical problem, meaningful treatments are not currently available due to a lack of mechanistic understanding underlying CICI pathophysiology. Using the platinum-based chemotherapy cisplatin as a model for CICI, we show here that cisplatin suppresses nicotinamide adenine dinucleotide (NAD+) levels in the adult female mouse brain in vivo and in human cortical neurons derived from induced pluripotent stem cells in vitro. Increasing NAD+ levels through nicotinamide mononucleotide (NMN) administration prevented cisplatin-induced abnormalities in neural progenitor proliferation, neuronal morphogenesis, and cognitive function without affecting tumor growth and antitumor efficacy of cisplatin. Mechanistically, cisplatin inhibited expression of the NAD+ biosynthesis rate-limiting enzyme nicotinamide phosphoribosyl transferase (Nampt). Selective restoration of Nampt expression in adult-born neurons was sufficient to prevent cisplatin-induced defects in dendrite morphogenesis and memory function. Taken together, our findings suggest that aberrant Nampt-mediated NAD+ metabolic pathways may be a key contributor in cisplatin-induced neurogenic impairments, thus causally leading to memory dysfunction. Therefore, increasing NAD+ levels could represent a promising and safe therapeutic strategy for cisplatin-related neurotoxicity. SIGNIFICANCE: Increasing NAD+ through NMN supplementation offers a potential therapeutic strategy to safely prevent cisplatin-induced cognitive impairments, thus providing hope for improved quality of life in cancer survivors. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/81/13/3727/F1.large.jpg.

Cognitive complications of cancer and cancer-related treatments - Novel paradigms

As advances in diagnostics and therapeutic strategies in oncology have increased the number of cancer survivors, the investigation of the mechanisms associated with long-term cognitive complications of cancer treatment has become an important topic of interest. The neurotoxic effects of chemotherapeutic agents have been described in pre-clinical and clinical research. In vitro and rodent studies have identified some underlying mechanisms contributing to chemotherapy-induced neurotoxicity and cognitive impairment for various chemotherapy drugs and other cancer treatments. However, investigation of the direct biological effects of cancer and other potential contributing factors in the pathogenesis of cancer-related cognitive impairment (CRCI) has only recently come into focus. This review will highlight evidence from pre-clinical tumor-bearing rodent models suggesting that cancer influences the cognitive and behavioral changes reported in human cancer populations through direct or indirect pathways that alter the normal neuroinflammatory responses, induce structural brain deficits, and decrease neurogenesis. We reflect on human clinical cancer research indicating that cognitive and behavioral changes precede cancer treatment in some malignancies. We also highlight implications for future areas of CRCI research based on novel findings on the interplay between cancer, chemotherapy, inflammation, tau pathology, and dysregulation of the microbiota-gut-brain axis.

TRPV2: A Cancer Biomarker and Potential Therapeutic Target

The Transient Receptor Potential Vanilloid type-2 (TRPV2) channel exhibits oncogenicity in different types of cancers. TRPV2 is implicated in signaling pathways that mediate cell survival, proliferation, and metastasis. In leukemia and bladder cancer, the oncogenic activity of TRPV2 was linked to alteration of its expression profile. In multiple myeloma patients, TRPV2 overexpression correlated with bone tissue damage and poor prognosis. In prostate cancer, TRPV2 overexpression was associated with the castration-resistant phenotype and metastasis. Loss or inactivation of TRPV2 promoted glioblastoma cell proliferation and increased resistance to CD95-induced apoptotic cell death. TRPV2 overexpression was associated with high relapse-free survival in triple-negative breast cancer, whereas the opposite was found in patients with esophageal squamous cell carcinoma or gastric cancer. Another link was found between TRPV2 expression and either drug-induced cytotoxicity or stemness of liver cancer. Overall, these findings validate TRPV2 as a prime candidate for cancer biomarker and future therapeutic target.

Temozolomide-Induced RNA Interactome Uncovers Novel LncRNA Regulatory Loops in Glioblastoma

Simple Summary

Glioblastoma (GBM) is the most aggressive brain tumor and most resistant to therapy. The identification of novel predictive biomarkers or targets to counteract chemoresistance, requires a better understanding of the GBM primary response to therapy. The aim of our study was to assess the molecular response of GBM to the standard of care chemotherapy by temozolomide (TMZ). We established a comprehensive map of gene expression changes after treatment and discovered that GBM cells elicit a coordinated gene expression program after chemotherapy that differs between sensitive and resistant cells. We found that a novel class of genes expressed as long non-coding RNAs (lncRNAs) is involved in gene regulatory circuits in GBM and could represent novel markers of GBM patient prognosis. By shedding light on the involvement of the non-coding genome in GBM, our results may provide new mechanistic insight on lncRNAs and their importance in chemoresistance.

Abstract

Resistance to chemotherapy by temozolomide (TMZ) is a major cause of glioblastoma (GBM) recurrence. So far, attempts to characterize factors that contribute to TMZ sensitivity have largely focused on protein-coding genes, and failed to provide effective therapeutic targets. Long noncoding RNAs (lncRNAs) are essential regulators of epigenetic-driven cell diversification, yet, their contribution to the transcriptional response to drugs is less understood. Here, we performed RNA-seq and small RNA-seq to provide a comprehensive map of transcriptome regulation upon TMZ in patient-derived GBM stem-like cells displaying different drug sensitivity. In a search for regulatory mechanisms, we integrated thousands of molecular associations stored in public databases to generate a background “RNA interactome”. Our systems-level analysis uncovered a coordinated program of TMZ response reflected by regulatory circuits that involve transcription factors, mRNAs, miRNAs, and lncRNAs. We discovered 22 lncRNAs involved in regulatory loops and/or with functional relevance in drug response and prognostic value in gliomas. Thus, the investigation of TMZ-induced gene networks highlights novel RNA-based predictors of chemosensitivity in GBM. The computational modeling used to identify regulatory circuits underlying drug response and prioritizing gene candidates for functional validation is applicable to other datasets.

Proteasome inhibition for the treatment of glioblastoma

INTRODUCTION

Glioblastoma is a primary brain tumor with a poor prognosis despite multimodal therapy including surgery, radiotherapy and alkylating chemotherapy. Novel therapeutic options are therefore urgently needed; however, there have been various drug failures in late-stage clinical development. The proteasome represents a key target for anti-cancer therapy as successfully shown in multiple myeloma and other hematologic malignancies.

AREAS COVERED

This review article summarizes the preclinical and clinical development of proteasome inhibitors in the context of glioblastoma.

EXPERT OPINION

Early clinical trials with bortezomib ended with disappointing results, possibly because this agent does not cross the blood-brain barrier. In contrast to bortezomib and other proteasome inhibitors, marizomib is a novel drug that displays strong inhibitory properties on all enzymatic subunits of the proteasome and, most importantly, crosses the blood-brain barrier, making it a potentially very active novel agent against intrinsic brain tumors. While preclinical studies have demonstrated significant anti-glioma activity, its clinical benefit has yet to be proven. Exploiting the biological effects of proteasome inhibitors in combination with other therapeutic strategies may represent a key next step in their clinical development.

The Prognostic Value of MRI Subventricular Zone Involvement and Tumor Genetics in Lower Grade Gliomas

BACKGROUND AND PURPOSE

Glioblastomas (GBMs) that involve the subventricular zone (SVZ) have a poor prognosis, possibly due to recruitment of neural stem cells. The purpose of this study was to evaluate whether SVZ involvement by lower grade gliomas (LGG), WHO grade II and III, similarly predicts poorer outcomes. We further assessed whether tumor genetics and cellularity are associated with SVZ involvement and outcomes.

METHODS

Forty-five consecutive LGG patients with preoperative imaging and next generation sequencing were included in this study. Regional SVZ involvement and whole tumor apparent diffusion coefficient (ADC) values, as a measure of cellularity, were assessed on magnetic resonance imaging. Progression was determined by RANO criteria. Kaplan-Meier curves and Cox regression analyses were used to determine the hazard ratios (HR) for progression and survival.

RESULTS

Frontal, parietal, temporal, and overall SVZ involvement and ADC values were not associated with progression or survival (P ≥ .05). However, occipital SVZ involvement, seen in two patients, was associated with a higher risk of tumor progression (HR = 6.6, P = .016) and death (HR = 31.5, P = .015), CDKN2A/B mutations (P = .03), and lower ADC histogram values at the 5th (P = .026) and 10th percentiles (P = .046). Isocitrate dehydrogenase, phosphatase and tensin homolog, epidermal growth factor receptor, and cyclin-dependent kinase 4 mutations were also prognostic (P ≤ .05).

CONCLUSIONS

Unlike in GBM, overall SVZ involvement was not found to strongly predict poor prognosis in LGGs. However, occipital SVZ involvement, though uncommon, was prognostic and found to be associated with CDKN2A/B mutations and tumor hypercellularity. Further investigation into these molecular mechanisms underlying occipital SVZ involvement in larger cohorts is warranted.

The necessity for standardization of glioma stem cell culture: a systematic review

BACKGROUND

The cancer stem cell hypothesis is an old idea which has been revived in recent years for many cancers, including gliomas. However, this concept has become controversial due to a series of studies with conflicting results.

METHODS

A systematic literature search was conducted in PubMed and the Web of Science database to analyze studies using serum-free medium and its components in glioma stem cells, glioma stem-like cells, glioma-initiating cells, or glioma neurosphere cultures. All the studies reviewed were published between 1970 and 2019. We found that no standardized culture method was used, and the data were incomparable due to differing culture conditions and the use of media with different components.

CONCLUSIONS

Here, we review the most commonly used serum-free media and added components for glioma stem cell culture while highlighting the function of each component used in the media. We emphasize the necessity for standardization of glioma stem cell culture and propose a standard culture medium to prevent bias in glioma stem cell research.

Mitochondrial-associated impairments of temozolomide on neural stem/progenitor cells and hippocampal neurons

Primary brain tumor patients often experience neurological, cognitive, and depressive symptoms that profoundly affect quality of life. The DNA alkylating agent, temozolomide (TMZ), along with radiation therapy forms the standard of care for glioblastoma (GBM) - the most common and aggressive of all brain cancers. Numerous studies have reported that TMZ disrupts hippocampal neurogenesis and causes spatial learning deficits in rodents; however, the effect of TMZ on mature hippocampal neurons has not been addressed. In this study, we examined the mitochondrial-mediated mechanisms involving TMZ-induced neural damage in primary rat neural stem/progenitor cells (NSC) and hippocampal neurons. TMZ inhibited mtDNA replication and transcription of mitochondrial genes (ND1 and Cyt b) in NSC by 24 h, whereas the effect of TMZ on neuronal mtDNA transcription was less pronounced. Transmission electron microscopy imaging revealed mitochondrial degradation in TMZ-treated NSC. Acute TMZ exposure (4 h) caused a rapid reduction in dendritic branching and loss of postsynaptic density-95 (PSD95) puncta on dendrites. Longer TMZ exposure impaired mitochondrial respiratory activity, increased oxidative stress, and induced apoptosis in hippocampal neurons. The presented findings suggest that NSC may be more vulnerable to TMZ than hippocampal neurons upon acute exposure; however long-term TMZ exposure results in neuronal mitochondrial respiratory dysfunction and dendritic damage, which may be associated with delayed cognitive impairments.

Influence of wide opening of the lateral ventricle on survival for supratentorial glioblastoma patients with radiotherapy and concomitant temozolomide-based chemotherapy

The prognosis for glioblastoma (GBM) varies among patients. Ventricular opening during surgery has been reported as a prognostic factor for GBM patients, but the influence of ventricular opening itself on patient prognosis remains controversial. We presumed that the degree of ventricular opening would correlate with the degree of subventricular zone (SVZ) resection and with prognosis in GBM patients. This study therefore investigated whether the degree of ventricular opening correlates with prognosis in GBM patients treated with the standard protocol of chemo-radiotherapy. Participants comprised 111 patients with newly diagnosed GBM who underwent surgery and received postoperative radiotherapy and temozolomide-based chemotherapy from 2005 to 2018. We classified 111 patients into "No ventricular opening (NVO)", "Ventricular opening, small (VOS; distance < 23.2 mm)", and "Ventricular opening, wide (VOW; distance ≥ 23.2 mm)" groups. We evaluated the relationship between degree of ventricular opening and prognosis using survival analyses that included other clinicopathological factors. Log-rank testing revealed age, Karnofsky performance status (KPS), extent of resection, O6-methylguanine-DNA methyltransferase (MGMT) status, isocitrate dehydrogenase (IDH)1 mutation, and degree of ventricular opening correlated significantly with overall survival. Multivariate analysis identified the degree of ventricular opening (small vs. wide) as the most significant prognostic factor (hazard ratio = 3.674; p < 0.0001). We demonstrated that wide opening of the lateral ventricle (LV) contributes to longer survival compared with small opening among GBM patients. Our results indicate that wide opening of the LV may correlate with the removal of a larger proportion of tumor stem cells from the SVZ.

DHFR/TYMS are positive regulators of glioma cell growth and modulate chemo-sensitivity to temozolomide

Glioma is one of the most lethal malignancies and molecular regulators driving gliomagenesis are incompletely understood. Although temozolomide (TMZ) has been applied for malignant gliomas as a canonical chemotherapy, the treatment of glioma still remains limited due to frequently developed resistance to TMZ. Therefore, promising strategies that sensitize glioma cells to temozolomide are overwhelming to develop. Here we found that the expression of dihydrofolate reductase (DHFR) and thymidylate synthetase (TYMS), which played an essential role in folate metabolism and several types of tumors, were up-regulated in both human glioma tissues and cell lines, and overexpression of DHFR/TYMS promoted the proliferation of glioma cells. Notably, inhibition of DHFR/TYMS by pemetrexed exhibited synergistic anti-glioma activity with TMZ in both cell lines and U251 xenografts, which suggested potential combined chemotherapy for glioma. Mechanistically, the synergistic effect of inhibition of DHFR/TYMS with TMZ was due to activated AMPK and subsequently suppressed mTOR signaling pathway. Taken together, these findings identify an uncharacterized role of DHFR/TYMS in glioma growth and TMZ sensitivity mediated by AMPK-mTOR signal pathway, and provide a prospective approach for improving the anti-tumor activity of TMZ in glioma.

Advancing towards Effective Glioma Therapy: MicroRNA Derived from Umbilical Cord Mesenchymal Stem Cells' Extracellular Vesicles

A glioma, especially a grade IV glioblastoma, is a malignant tumour with a poor prognosis despite growing medical advancements. Researchers have been looking for better and more effective treatments targeting the molecular pathways of gliomas due to glioblastomas’ ability to develop resistance to chemotherapies. Moreover, glioma stem cells (GSC) contribute to maintaining the glioma population, which benefits from its ability to self-renew and differentiate. Recent research has reported that through the introduction of umbilical cord mesenchymal stem cells (UCMSC) into glioma cells, the growth and development of the glioma cells can be downregulated. It has more currently been found out that UCMSC release extracellular vesicles (EVs) containing miRNA that are responsible for this phenomenon. Therefore, this review analyses literature to discuss all possible miRNAs contained within the UCMSC’s EVs and to elaborate on their molecular mechanisms in halting gliomas and GSC growth. This review will also include the challenges and limitations, to account for which more in vivo research is suggested. In conclusion, this review highlights how miRNAs contained within UCMSC’s EVs are able to downregulate multiple prominent pathways in the survival of gliomas.

QKI deficiency maintains glioma stem cell stemness by activating the SHH/GLI1 signaling pathway

PURPOSE

Glioblastoma (GBM) stem cells (GSCs) have been found to be the main cause of malignant GBM progression. It has also been found that Quaking homolog (QKI) plays a predominant role in driving GBM development. Here, we aimed to asses the role of QKI in maintaining GSC stemness and inducing the invasiveness of GBM cells.

METHODS

Public databases were used to assess the expression of QKI and its correlation with stemness markers in primary GBMs. The CRISPR-Cas9 technology was used to generate QKI knockout GBM cells, and RNA immunoprecipitation was used to assess QKI-GLI1 protein-mRNA interactions. In addition, in vitro and in vivo GBM cell proliferation, migration, xenografting and neurosphere formation assays were performed.

RESULTS

Using public GBM databases, QKI was identified as a potential GSC regulator. We found that QKI could inhibit stem-like cell (SLC) stemness and prolong the survival of xenografted mice. Mechanistically, we found that QKI knockout increased the GLI Family Zinc Finger 1 (GLI1) mRNA level, which is essential for maintaining the self-renewal ability of GSCs. In addition, we found that QKI knockout activated the Hedgehog signaling pathway via Tra-2 and GLI response element (TGE)-specific GLI1 mRNA disruption.

CONCLUSION

Our data indicate that upregulation of GLI1 induced by QKI deficiency maintains GSC stemness and enhances the invasiveness of GBM cells, thereby hinting at new options for the treatment of GBM.

Neurocognitive evaluation in older adult patients affected by glioma

BACKGROUND

Glioblastoma (GBM) has an increasing incidence and dismal prognosis in older adults. This study evaluated neurocognitive status of an older adult population with GBM and its correlation with clinical and demographical variables.

METHODS

Each patient underwent an extended neuropsychological evaluation by means of a battery of standardized tests describing eight cognitive domains: global function; verbal learning; short- and long-term memory (LTM); executive functions (EFs); abstract reasoning (AR); attention; and visuo-constructional abilities (CA).

RESULTS

We assessed 79 patients with GBM (median age: 74 years). Out of this initial sample, a subgroup of seventeen patients with six-month median time underwent a follow-up test session. 46 out of the 79 patients (58.2%) presented multi-domain cognitive impairment, 24 patients (30.3%) showed single-domain cognitive impairment and only seven (9%) showed no cognitive impairment. Kaplan Meier estimator showed that patients with AR deficit had a poorer prognosis in terms of progression-free survival and overall survival (p < .001). At the multivariate analysis AR (deficit vs non; hazard ratio (HR) = 5.07, 95%; confidence interval (CI): 1.91-13.46; p < .001) was correlated with disease progression and overall survival, AR (deficit vs non; HR = 7.24, 95% CI: 2.58-20.32; p < .001). Eight out of seventeen patients who underwent follow-up test session showed cognitive improvement, five resulted in further deterioration, and four patients remained stable. LTM, EF, and CA were the most affected functions at follow-up, while verbal learning was the most improved one in patients with cognitive improvement.

CONCLUSIONS

Cognitive functioning evaluation should be included among the standard clinical endpoints in the treatment of older adult neuro-oncology patients.

Therapeutic strategy for pineal parenchymal tumor of intermediate differentiation (PPTID): case report of PPTID with malignant transformation to pineocytoma with leptomeningeal dissemination 6 years after surgery

Pineal parenchymal tumor of intermediate differentiation (PPTID) is rare. The WHO first classified PPTID in 2000 as a pineal parenchymal tumor (PPT) with an intermediate prognosis between pineocytoma (PC) and pineoblastoma (PB). It is considered an intermediate-grade tumor and divided into WHO grade II or III.The number of available reports about PPTID is presently limited, and the appropriate management for this tumor has not yet been determined.The authors report a rare case of PC in a 63-year-old woman who presented with lower-extremity weakness and gait disturbance. A pineal mass lesion was detected on MRI. A diagnosis of PC was established after microsurgical gross-total tumor resection, and the patient received no adjuvant therapy after surgery. Two years after surgery, a partial recurrence was recognized and Gamma Knife radiosurgery was performed. Fours years later, the patient developed diffuse leptomeningeal dissemination. She was successfully treated with craniospinal irradiation. Leptomeningeal dissemination may develop 6 years after the initial diagnosis of PC. A histopathological study of the recurrent tumor revealed a malignant change from PC to PPTID.The present case shows the importance of long-term follow-up of patients with PPTs following resection and the efficacy of craniospinal irradiation in the treatment of leptomeningeal dissemination.

Histone Deacetylase Inhibitors Impair Vasculogenic Mimicry from Glioblastoma Cells

Glioblastoma (GBM), a high-grade glioma (WHO grade IV), is the most aggressive form of brain cancer. Available treatment options for GBM involve a combination of surgery, radiation and chemotherapy but result in a poor survival outcome. GBM is a high-vascularized tumor and antiangiogenic drugs are widely used in GBM therapy as adjuvants to control abnormal vasculature. Vasculogenic mimicry occurs in GBM as an alternative vascularization mechanism, providing a means whereby GBM can escape anti-angiogenic therapies. Here, using an in vitro tube formation assay on Matrigel^®, we evaluated the ability of different histone deacetylase inhibitors (HDACis) to interfere with vasculogenic mimicry. We found that vorinostat (SAHA) and MC1568 inhibit tube formation by rat glioma C6 cells. Moreover, at sublethal doses for GBM cells, SAHA, trichostatin A (TSA), entinostat (MS275), and MC1568 significantly decrease tube formation by U87MG and by patient-derived human GBM cancer stem cells (CSCs). The reduced migration and invasion of HDACis-treated U87 cells, at least in part, may account for the inhibition of tube formation. In conclusion, our results indicate that HDACis are promising candidates for blocking vascular mimicry in GBM.

The Transient Receptor Potential Vanilloid Type-2(TRPV2) Ion Channels in Neurogenesis andGliomagenesis: Cross-Talk between TranscriptionFactors and Signaling Molecules

Recently, the finding of cancer stem cells in brain tumors has increased the possibilities for advancing new therapeutic approaches with the aim to overcome the limits of current available treatments. In addition, a role for ion channels, particularly of TRP channels, in developing neurons as well as in brain cancer development and progression have been demonstrated. Herein, we focus on the latest advancements in understanding the role of TRPV2, a Ca²⁺ permeable channel belonging to the TRPV subfamily in neurogenesis and gliomagenesis. TRPV2 has been found to be expressed in both neural progenitor cells and glioblastoma stem/progenitor-like cells (GSCs). In developing neurons, post-translational modifications of TRPV2 (e.g., phosphorylation by ERK2) are required to stimulate Ca²⁺ signaling and nerve growth factor-mediated neurite outgrowth. TRPV2 overexpression also promotes GSC differentiation and reduces gliomagenesis in vitro and in vivo. In glioblastoma, TRPV2 inhibits survival and proliferation, and induces Fas/CD95-dependent apoptosis. Furthermore, by proteomic analysis, the identification of a TRPV2 interactome-based signature and its relation to glioblastoma progression/recurrence, high or low overall survival and drug resistance strongly suggest an important role of the TRPV2 channel as a potential biomarker in glioblastoma prognosis and therapy.

Mitochondrial transfer from mesenchymal stem cells to neural stem cells protects against the neurotoxic effects of cisplatin

Mesenchymal stem cells (MSCs) transfer healthy mitochondria to damaged acceptor cells via actin-based intercellular structures. In this study, we tested the hypothesis that MSCs transfer mitochondria to neural stem cells (NSCs) to protect NSCs against the neurotoxic effects of cisplatin treatment. Our results show that MSCs donate mitochondria to NSCs damaged in vitro by cisplatin. Transfer of healthy MSC-derived mitochondria decreases cisplatin-induced NSC death. Moreover, mitochondrial transfer from MSCs to NSCs reverses the cisplatin-induced decrease in mitochondrial membrane potential. Blocking the formation of actin-based intercellular structures inhibited the transfer of mitochondria to NSCs and abrogated the positive effects of MSCs on NSC survival. Conversely, overexpression of the mitochondrial motor protein Rho-GTPase 1 (Miro1) in MSCs increased mitochondrial transfer and further improved survival of cisplatin-treated NSCs.

In vivo, MSC administration prevented the loss of DCX+ neural progenitor cells in the subventricular zone and hippocampal dentate gyrus which occurs as a result of cisplatin treatment. We propose mitochondrial transfer as one of the mechanisms via which MSCs exert their therapeutic regenerative effects after cisplatin treatment.

ABCG2 downregulation in glioma stem cells enhances the therapeutic efficacy of demethoxycurcumin

We analyzed the role of ABCG2, a drug transporter, in determining the sensitivity of glioma stem cells (GSCs) to demethoxycurcumin (DMC). We first demonstrated that ABCG2 is more highly expressed in GSCs than primary astrocytes. Modulation of ABCG2 levels in GSCs by transfection of ABCG2 shRNA or a lentiviral vector encoding ABCG2 revealed an inverse relation between ABCG2 levels and DMC-induced GSC growth inhibition. Suppressing ABCG2 increased DMC-induced apoptosis and G0/G1 cell cycle arrest in GSCs. It also increased levels reactive oxygen species (ROS) in GSCs treated with DMC, resulting in increased cytochrome C and caspase-3 activity. When GSCs transfected with ABCG2 shRNA or overexpressing ABCG2 were xenografted and the tumor-bearing, immunodeficient mice were treated with DMC, ABCG2 expression suppressed the tumor proliferation rate (T/C %). These findings demonstrate that ABCG2 expression is critical for DMC resistance in GSCs and is a potential therapeutic target for GBM.

Fasudil increases temozolomide sensitivity and suppresses temozolomide-resistant glioma growth via inhibiting ROCK2/ABCG2

Resistance to temozolomide (TMZ) is a major clinical challenge in glioma treatment, but the mechanisms of TMZ resistance are poorly understood. Here, we provided evidence that ROCK2 acted redundantly to maintain resistance of TMZ in TMZ-resistant gliomas, and as a ROCK2 phosphorylation inhibitor, fasudil significantly suppressed proliferation of TMZ-resistant gliomas in vivo and vitro via enhancing the chemosensitivity of TMZ. Additionally, the membrane translocation of ABCG2 was decreased with fasudil by ROCK2/moesin pathway. We also showed that fasudil suppressed the expression of ABCG2 via ROCK2/moesin/β-catenin pathway. Our results reveal an indispensable role for ROCK2 and provide strong evidence for the therapeutic use of fasudil in the clinical setting for TMZ-resistant gliomas.

Therapeutic targeting of chemoresistant and recurrent glioblastoma stem cells with a proapoptotic variant of oncolytic herpes simplex virus

Temozolomide (TMZ) chemotherapy, in combination with maximal safe resection and radiotherapy, is the current standard of care for patients with glioblastoma (GBM). Despite this multimodal approach, GBM inevitably relapses primarily due to resistance to chemo-radiotherapy, and effective treatment is not available for recurrent disease. In this study we identified TMZ resistant patient-derived primary and previously treated recurrent GBM stem cells (GSC), and investigated the therapeutic activity of a pro-apoptotic variant of oHSV (oHSV-TRAIL) in vitro and in vivo. We show that oHSV-TRAIL modulates cell survival and MAP Kinase proliferation signaling pathways as well as DNA damage response pathways in both primary and recurrent TMZ-resistant GSC. Utilizing real time in vivo imaging and correlative immunohistochemistry, we show that oHSV-TRAIL potently inhibits tumor growth and extends survival of mice bearing TMZ-insensitive recurrent intracerebral GSC tumors via robust and selective induction of apoptosis-mediated death in tumor cells, resulting in cures in 40% of the treated mice. In comparison, the anti-tumor effects in a primary chemoresistant GSC GBM model exhibiting a highly invasive phenotype were significant but less prominent. This work thus demonstrates the ability of oHSV-TRAIL to overcome the therapeutic resistance and recurrence of GBM, and provides a basis for its testing in a GBM clinical trial.

Mutations in Cockayne Syndrome-Associated Genes (Csa and Csb) Predispose to Cisplatin-Induced Hearing Loss in Mice

Cisplatin is a common and effective chemotherapeutic agent, yet it often causes permanent hearing loss as a result of sensory hair cell death. The causes of sensitivity to DNA-damaging agents in nondividing cell populations, such as cochlear hair and supporting cells, are poorly understood, as are the specific DNA repair pathways that protect these cells. Nucleotide excision repair (NER) is a conserved and versatile DNA repair pathway for many DNA-distorting lesions, including cisplatin-DNA adducts. Progressive sensorineural hearing loss is observed in a subset of NER-associated DNA repair disorders including Cockayne syndrome and some forms of xeroderma pigmentosum. We investigated whether either of the two overlapping branches that encompass NER, transcription-coupled repair or global genome repair, which are implicated in Cockayne syndrome and xeroderma pigmentosum group C, respectively, modulates cisplatin-induced hearing loss and cell death in the organ of Corti, the auditory sensory epithelium of mammals. We report that cochlear hair cells and supporting cells in transcription-coupled repair-deficient Cockayne syndrome group A (Csa(-/-)) and group B (Csb(-/-)) mice are hypersensitive to cisplatin, in contrast to global genome repair-deficient Xpc(-/-) mice, both in vitro and in vivo We show that sensory hair cells in Csa(-/-) and Csb(-/-) mice fail to remove cisplatin-DNA adducts efficiently in vitro; and unlike Xpc(-/-) mice, Csa(-/-) and Csb(-/-) mice lose hearing and manifest outer hair cell degeneration after systemic cisplatin treatment. Our results demonstrate that Csa and Csb deficiencies predispose to cisplatin-induced hearing loss and hair/supporting cell damage in the mammalian organ of Corti, and emphasize the importance of transcription-coupled DNA repair in the protection against cisplatin ototoxicity.

SIGNIFICANCE STATEMENT

The utility of cisplatin in chemotherapy remains limited due to serious side effects, including sensorineural hearing loss. We show that mouse models of Cockayne syndrome, a progeroid disorder resulting from a defect in the transcription-coupled DNA repair (TCR) branch of nucleotide excision repair, are hypersensitive to cisplatin-induced hearing loss and sensory hair cell death in the organ of Corti, the mammalian auditory sensory epithelium. Our work indicates that Csa and Csb, two genes involved in TCR, are preferentially required to protect against cisplatin ototoxicity, relative to global genome repair-specific elements of nucleotide excision repair, and suggests that TCR is a major force maintaining DNA integrity in the cochlea. The Cockayne syndrome mice thus represent a model for testing the contribution of DNA repair mechanisms to cisplatin ototoxicity.

Pediatric low-grade gliomas: implications of the biologic era

For the past decade, it has been recognized that pediatric low-grade gliomas (LGGs) and glial-neuronal tumors carry distinct molecular alterations with resultant aberrant intracellular signaling in the Ras-mitogen-activated protein kinase pathway. The conclusions and recommendations of a consensus conference of how best to integrate the growing body of molecular genetic information into tumor classifications and, more importantly, for future treatment of pediatric LGGs are summarized here. There is uniform agreement that molecular characterization must be incorporated into classification and is increasingly critical for appropriate management. Molecular-targeted therapies should be integrated expeditiously, but also carefully into the management of these tumors and success measured not only by radiographic responses or stability, but also by functional outcomes. These trials need to be carried out with the caveat that the long-term impact of molecularly targeted therapy on the developing nervous system, especially with long duration treatment, is essentially unknown.

Targeting Cancer Stem Cells-A Renewed Therapeutic Paradigm

Metastasis is often accompanied by radio- and chemotherapeutic resistance to anticancer treatments and is the major cause of death in cancer patients. Better understanding of how cancer cells circumvent therapeutic insults and how disseminated cancer clones generate life-threatening metastases would therefore be paramount to the development of effective therapeutic approaches for clinical management of malignant disease. Mounting reports over the past two decades have provided evidence for the existence of a minor population of highly malignant cells within liquid and solid tumors, which are capable of self-renewing and of regenerating secondary growths with the heterogeneity of the primary tumors from which they derive. These cells, called tumor-initiating cells or cancer stem cells (CSCs) exhibit increased resistance to standard radio- and chemotherapies and appear to have mechanisms that enable them to evade immune surveillance. CSCs are therefore considered to be responsible for systemic residual disease after cancer therapy, as well as for disease relapse. How CSCs develop, the nature of the interactions they establish with their microenvironment, their phenotypic and functional characteristics, as well as their molecular dependencies have all taken center stage in cancer therapy. Indeed, improved understanding of CSC biology is critical to the development of important CSC-based anti-neoplastic approaches that have the potential to radically improve cancer management. Here, we summarize some of the most pertinent elements regarding CSC development and properties, and highlight some of the clinical modalities in current development as anti-CSC therapeutics.

Subventricular zones: new key targets for glioblastoma treatment

Background

We aimed to identify subventricular zone (SVZ)-related prognostic factors of survival and patterns of recurrence among patients with glioblastoma.

Methods

Forty-three patients with primary diagnosed glioblastoma treated in our Cancer Center between 2006 and 2010 were identified. All patients received surgical resection, followed by temozolomide-based chemoradiation. Ipsilateral (iSVZ), contralateral (cSVZ) and bilateral (bSVZ) SVZs were retrospectively segmented and radiation dose-volume histograms were generated. Multivariate analysis using the Cox proportional hazards model was assessed to examine the relationship between prognostic factors and time to progression (TTP) or overall survival (OS).

Results

Median age was 59 years (range: 25–85). Median follow-up, OS and TTP were 22.7 months (range 7.5–69.7 months), 22.7 months (95% CI 14.5–26.2 months) and 6.4 months (95% CI 4.4–9.3 months), respectively. On univariate analysis, initial contact to SVZ was a poor prognostic factor for OS (18.7 vs 41.7 months, p = 0.014) and TTP (4.6 vs 12.9 months, p = 0.002). Patients whose bSVZ volume receiving at least 20 Gy (V20Gy) was greater than 84% had a significantly improved TTP (17.7 months vs 5.2 months, p = 0.017). This radiation dose coverage was compatible with an hippocampal sparing. On multivariate analysis, initial contact to SVZ and V20 Gy to bSVZ lesser than 84% remained poor prognostic factors for TTP (HR = 3.07, p = 0.012 and HR = 2.67, p = 0.047, respectively).

Conclusion

Our results suggest that contact to SVZ, as well as insufficient bSVZ radiation dose coverage (V20Gy <84%), might be independent poor prognostic factors for TTP. Therefore, targeting SVZ could be of crucial interest for optimizing glioblastoma treatment.

Intratumoral delivery of bortezomib: impact on survival in an intracranial glioma tumor model

OBJECTIVE Glioblastoma (GBM) is the most prevalent and the most aggressive of primary brain tumors. There is currently no effective treatment for this tumor. The proteasome inhibitor bortezomib is effective for a variety of tumors, but not for GBM. The authors' goal was to demonstrate that bortezomib can be effective in the orthotopic GBM murine model if the appropriate method of drug delivery is used. In this study the Alzet mini-osmotic pump was used to bring the drug directly to the tumor in the brain, circumventing the blood-brain barrier; thus making bortezomib an effective treatment for GBM. METHODS The 2 human glioma cell lines, U87 and U251, were labeled with luciferase and used in the subcutaneous and intracranial in vivo tumor models. Glioma cells were implanted subcutaneously into the right flank, or intracranially into the frontal cortex of athymic nude mice. Mice bearing intracranial glioma tumors were implanted with an Alzet mini-osmotic pump containing different doses of bortezomib. The Alzet pumps were introduced directly into the tumor bed in the brain. Survival was documented for mice with intracranial tumors. RESULTS Glioma cells were sensitive to bortezomib at nanomolar quantities in vitro. In the subcutaneous in vivo xenograft tumor model, bortezomib given intravenously was effective in reducing tumor progression. However, in the intracranial glioma model, bortezomib given systemically did not affect survival. By sharp contrast, animals treated with bortezomib intracranially at the tumor site exhibited significantly increased survival. CONCLUSIONS Bypassing the blood-brain barrier by using the osmotic pump resulted in an increase in the efficacy of bortezomib for the treatment of intracranial tumors. Thus, the intratumoral administration of bortezomib into the cranial cavity is an effective approach for glioma therapy.

Cisplatin-induced mitochondrial dysfunction is associated with impaired cognitive function in rats

PURPOSE

Chemotherapy-related cognitive impairment (CRCI) is commonly reported following the administration of chemotherapeutic agents and comprises a wide variety of neurological problems. No effective treatments for CRCI are currently available. Here we examined the mechanisms involving cisplatin-induced hippocampal damage following cisplatin administration in a rat model and in cultured rat hippocampal neurons and neural stem/progenitor cells (NSCs). We also assessed the protective effects of the antioxidant, N-acetylcysteine in mitigating these damages.

EXPERIMENTAL DESIGN

Adult male rats received 6mg/kg cisplatin in the acute studies. In chronic studies, rats received 5mg/kg cisplatin or saline injections once per week for 4 weeks. N-acetylcysteine (250mg/kg/day) or saline was administered for five consecutive days during cisplatin treatment. Cognitive testing was performed 5 weeks after treatment cessation. Cisplatin-treated cultured hippocampal neurons and NSCs were examined for changes in mitochondrial function, oxidative stress production, caspase-9 activation, and neuronal dendritic spine density.

RESULTS

Acute cisplatin treatment reduced dendritic branching and spine density, and induced mitochondrial degradation. Rats receiving the chronic cisplatin regimen showed impaired performance in contextual fear conditioning, context object discrimination, and novel object recognition tasks compared to controls. Cisplatin induced mitochondrial DNA damage, impaired respiratory activity, increased oxidative stress, and activated caspase-9 in cultured hippocampal neurons and NSCs. N-acetylcysteine treatment prevented free radical production, ameliorated apoptotic cellular death and dendritic spine loss, and partially reversed the cisplatin-induced cognitive impairments.

CONCLUSIONS

Our results suggest that mitochondrial dysfunction and increased oxidative stress are involved in cisplatin-induced cognitive impairments. Therapeutic agents, such as N-acetylcysteine, may be effective in mitigating the deleterious effects of cisplatin.

3D bioprinted glioma stem cells for brain tumor model and applications of drug susceptibility

Glioma is still difficult to treat because of its high malignancy, high recurrence rate, and high resistance to anticancer drugs. An alternative method for research of gliomagenesis and drug resistance is to use in vitro tumor model that closely mimics the in vivo tumor microenvironment. In this study, we established a 3D bioprinted glioma stem cell model, using modified porous gelatin/alginate/fibrinogen hydrogel that mimics the extracellular matrix. Glioma stem cells achieved a survival rate of 86.92%, and proliferated with high cellular activity immediately following bioprinting. During the in vitro culture period, the printed glioma stem cells not only maintained their inherent characteristics of cancer stem cells (Nestin), but also showed differentiation potential (glial fibrillary acidic protein and β-tubulin III). In order to verify the vascularization potential of glioma stem cells, tumor angiogenesis biomarker, vascular endothelial growth factor was detected by immunohistochemistry, and its expression increased from week one to three during the culture period. Drug-sensitivity results showed that 3D printed tumor model was more resistant to temozolomide than 2D monolayer model at TMZ concentrations of 400-1600 μg ml^-1. In summary, 3D bioprinted glioma model provides a novel alternative tool for studying gliomagenesis, glioma stem cell biology, drug resistance, and anticancer drug susceptibility in vitro.

Phase I trial of dose-escalating metronomic temozolomide plus bevacizumab and bortezomib for patients with recurrent glioblastoma

The average survival time for patients with recurrent glioblastoma is between 5 and 9 months. Phase I and II trials have shown a modest survival benefit with combination temozolomide and other chemotherapeutics. We conducted a phase I trial of dose-escalating temozolomide with bevacizumab and the proteasome inhibitor bortezomib for patients with recurrent disease. Three groups of three patients were scheduled to receive daily doses of temozolomide at 25, 50, and 75 mg/m². Fixed doses of bortezomib and bevacizumab were given at standard intervals. Patients were monitored for dose-limiting toxicities (DLT) to determine the maximum-tolerated dose (MTD) of temozolomide with this regimen. No DLT were seen in the first two groups (25 and 50 mg/m² temozolomide). One patient in the 75 mg/m² group experienced a grade 4 elevation of ALT and three more patients were accrued for a total of six patients at that dose level. No other DLT occurred, thus making 75 mg/m² the MTD. Progression-free survival was 3.27 months for all patients and mean overall survival was 20.75 months. The MTD of temozolomide was 75 mg/m² in combination with bevacizumab and bortezomib for recurrent glioblastoma. Only one patient experienced a severe (Grade 4) elevation of ALT. This study will provide the framework for further studies to elicit effectiveness and better determine a safety profile for this drug combination.

Do Increased Doses to Stem-Cell Niches during Radiation Therapy Improve Glioblastoma Survival?

Background and Purpose. The reasons for the inevitable glioblastoma recurrence are yet understood. However, recent data suggest that tumor cancer stem cells (CSCs) in the stem-cell niches, with self-renewing capacities, might be responsible for tumor initiation, propagation, and recurrence. We aimed to analyze the effect of higher radiation doses to the stem-cell niches on progression-free survival (PFS) and overall survival (OS) in glioblastoma patients. Materials and Methods. Sixty-five patients with primary glioblastoma treated with radiation therapy were included in this retrospective analysis. The SVZ and DG were segmented on treatment planning magnetic resonance imaging, and the dose distributions to the structures were calculated. The relationship of dosimetry data and survival was evaluated using the Cox regression analysis. Results. Conventionally fractionated patients (n = 54) who received higher doses (D_mean ≥ 40 Gy) to the IL SVZ showed improved PFS (8.5 versus 5.2 months; p = 0.013). Furthermore, higher doses (D_mean ≥ 30 Gy) to the CL SVZ were associated with increased PFS (10.1 versus 6.9 months; p = 0.025). Conclusion. Moderate higher IL SVZ doses (≥40 Gy) and CL SVZ doses (≥30 Gy) are associated with improved PFS. Higher doses to the DG, the second stem-cell niche, did not influence the survival. Targeting the potential cancer stem cells in the SVZ might be a promising treatment approach for glioblastoma and should be addressed in a prospective randomized trial.

Marizomib activity as a single agent in malignant gliomas: ability to cross the blood-brain barrier

BACKGROUND

The proteasome plays a vital role in the physiology of glioblastoma (GBM), and proteasome inhibition can be used as a strategy for treating GBM. Marizomib is a second-generation, irreversible proteasome inhibitor with a more lipophilic structure that suggests the potential for penetrating the blood-brain barrier. While bortezomib and carfilzomib, the 2 proteasome inhibitors approved for treatment of multiple myeloma, have little activity against malignant gliomas in vivo, marizomib could be a novel therapeutic strategy for primary brain tumors.

METHODS

The in-vitro antitumor activity of marizomib was studied in glioma cell lines U-251 and D-54. The ability of marizomib to cross the blood-brain barrier and regulate proteasome activities was evaluated in cynomolgus monkeys and rats. The antitumor effect of marizomib in vivo was tested in an orthotopic xenograft model of human GBM.

RESULTS

Marizomib inhibited the proteasome activity, proliferation, and invasion of glioma cells. Meanwhile, free radical production and apoptosis induced by marizomib could be blocked by antioxidant N-acetyl cysteine. In animal studies, marizomib distributed into the brain at 30% of blood levels in rats and significantly inhibited (>30%) baseline chymotrypsin-like proteasome activity in brain tissue of monkeys. Encouragingly, the immunocompromised mice, intracranially implanted with glioma xenografts, survived significantly longer than the control animals (P < .05) when treated with marizomib.

CONCLUSIONS

These preclinical studies demonstrated that marizomib can cross the blood-brain barrier and inhibit proteasome activity in rodent and nonhuman primate brain and elicit a significant antitumor effect in a rodent intracranial model of malignant glioma.

Are we over treating Pineal Parenchymal tumour with intermediate differentiation? Assessing the role of localised radiation therapy and literature review

Pineal Parenchymal tumour with intermediate differentiation (PPTID) is a rare disorder, first classified by World Health Organisation in 2000. There are very few published data available and optimal management is yet to be determined. Management has varied from surgery alone to craniospinal radiotherapy with or without chemotherapy. We present our experience of PPTID treated with radiotherapy alone. We conducted a retrospective review of patients who were diagnosed with PPTID and treated with radiation therapy at our institute from 2010 onwards. Between January 2010 to January 2013, 5 patients of PPTID were treated at our institute. Median age is 44 (range 24-62). All patients had preoperative MRI scan of brain and spine. Imaging did not identify any spinal dissemination. None of the patients underwent a gross total resection, due to the tumour location and technical difficulties. All patients were treated with external beam radiation therapy to primary lesion only with a dose of 54 Gy in 30 fractions after surgery. 4 patients had good partial response and the remaining 1 has stable disease. After 21.4 months of median follow up no disease recurrence was reported. So far there is no evidence of cerebral white matter abnormalities on MRI scan or neurocognitive disorders. Our experience indicated that localised radiation therapy could be an effective treatment strategy for PPTID, considering the long natural course of the disease and the late adverse effects of intensive treatment.

[Attention system functions and their relationship with self-reported health in patients with brain damage due to tumor]

AIM

To compare parameters of attention in healthy people and patients with neoplasms in different regions of the cerebral cortex and to evaluate quality of life (QoL) indices with regard to impairment of different attention systems.

MATERIAL AND METHODS

Twenty patients with oncological lesions of the brain (mean age 56.5±8.8 years) who did not undergo surgery were studied. Tumor localization was confirmed using contrast-enhanced computed tomography, the tumor type was histologically verified. A control group included 18 healthy people matched for age, sex and education level. To determine attention system functions, we developed a computed version of the Attention Network Test. Error rate and reaction time for correct responses to the target stimulus, displayed along with neutral, congruent and incongruent signals, were the indicators of the efficacy of selective processes. QoL indices were assessed using SF-36 health survey questionnaire.

RESULTS AND CONCLUSION

The readiness to respond to incoming stimuli was mostly impaired in patients with brain tumors. Efficacy of executive attention, assessed as the increase in the number of errors in selection of visual stimuli, was decreased while temporary parameters of the functions of this system were not changed in patients compared to controls. The SF-36 total score was stable in patients with marked reduction in scores on the Role and Emotional Functioning scales. The most severe health impairment measured on the SF-36 scales of role/social emotional functioning and viability was recorded in patients with the lesions of frontal cortical areas compared to temporal/parietal areas. The relationship between SF-36 Health self-rating and attention systems was found. This finding puts the question of the importance of attention characteristics and QoL for survival prognosis of patients with brain tumors.

MEK2 is a prognostic marker and potential chemo-sensitizing target for glioma patients undergoing temozolomide treatment

Although temozolomide (TMZ) is the first-line chemotherapeutic agent for glioblastoma, it is often non-curative due to drug resistance. To overcome the resistance of glioblastoma cells to TMZ, it is imperative to identify prognostic markers for outcome prediction and to develop chemo-sensitizing agents. Here, the gene expression profiles of TMZ-resistant and TMZ-sensitive samples were compared by microarray analysis, and mitogen-activated protein kinase kinase 2 (MEK2) was upregulated specifically in resistant glioma cells but not in sensitive tumor cells or non-tumor tissues. Moreover, a comprehensive analysis of patient data revealed that the increased level of MEK2 expression correlated well with the advancement of glioma grade and worse prognosis in response to TMZ treatment. Furthermore, reducing the level of MEK2 in U251 glioma cell lines or xenografted glioma models through shRNA-mediated gene knockdown inhibited cell proliferation and enhanced the sensitivity of cells toward TMZ treatment. Further analysis of tumor samples from glioma patients by real-time PCR indicated that an increased MEK2 expression level was closely associated with the activation of many drug resistance genes. Finally, these resistance genes were downregulated after MEK2 was silenced in vitro, suggesting that the mechanism of MEK2-induced chemo-resistance could be mediated by the transcriptional activation of these resistance genes. Collectively, our data indicated that the expression level of MEK2 could serve as a prognostic marker for glioma chemotherapy and that MEK2 antagonists can be used as chemo-sensitizers to enhance the treatment efficacy of TMZ.

Stem cell niche irradiation in glioblastoma: providing a ray of hope?

Glioblastomas are organized hierarchically with a small number of glioblastoma stem cells that have unique self-renewal capacity and multilineage potency. The subventricular zone (SVZ) constitutes the largest neural stem cell niche in the adult human brain; it may also act as a reservoir of glioblastoma stem cells that can initiate, promote or repopulate a tumor. Incidental irradiation of SVZ has been shown to potentially influence outcomes suggesting that aggressively targeting the stem cell niche may offer a ray of hope in glioblastoma. The following review provides a summary of the experimental evidence supporting the origin and location of the putative glioblastoma stem cell in the SVZ, and offers a critical appraisal of the growing body of clinical evidence correlating SVZ dosimetry with outcomes in glioblastoma.