Emerging targeted therapies for glioma

Mechanistic Modeling of Intrathecal Chemotherapy Pharmacokinetics in the Human Central Nervous System

PURPOSE

The pharmacokinetics of intrathecally administered antibody or small-molecule drugs in the human central nervous system (CNS) remains poorly understood. This study aimed to provide mechanistic and quantitative perspectives on the CNS pharmacokinetics of intrathecal chemotherapy, by using a physiologically based pharmacokinetic (PBPK) modeling approach.

EXPERIMENTAL DESIGN

A novel CNS PBPK model platform was developed and verified, which accounted for the human CNS general anatomy and physiologic processes governing drug distribution and disposition. The model was used to predict CNS pharmacokinetics of antibody (trastuzumab) and small-molecule drugs (methotrexate, abemaciclib, tucatinib) following intraventricular injection or intraventricular 24-hour infusion, and to assess the key determinants of drug penetration into the deep brain parenchyma.

RESULTS

Intraventricularly administered antibody and small-molecule drugs exhibited distinct temporal and spatial distribution and disposition in human CNS. Both antibody and small-molecule drugs achieved supratherapeutic or therapeutic concentrations in the cerebrospinal fluid (CSF) compartments and adjacent brain tissue. While intrathecal small-molecule drugs penetrated the deep brain parenchyma to a negligible extent, intrathecal antibodies may achieve therapeutic concentrations in the deep brain parenchyma. Intraventricular 24-hour infusion enabled prolonged CNS exposure to therapeutically relevant concentrations while avoiding excessively high and potentially neurotoxic drug concentrations.

CONCLUSIONS

CNS PBPK modeling, in line with available clinical efficacy data, confirms the therapeutic value of intrathecal chemotherapy with antibody or small-molecule drugs for treating neoplastic meningitis and warrants further clinical investigation of intrathecal antibody drugs to treat brain parenchyma tumors. Compared with intraventricular injection, intraventricular 24-hour infusion may mitigate neurotoxicity while retaining potential efficacy.

MTHFD2 suppresses glioblastoma progression via the inhibition of ERK1/2 phosphorylation

Glioblastoma (GBM) is a WHO grade 4 tumor and is the most malignant form of glioma. Methylenetetrahydrofolate dehydrogenase 2 (MTHFD2), a mitochondrial enzyme involved in folate metabolism, has been reported to be highly expressed in several human tumors. However, little is known about the role of MTHFD2 in GBM. In this study, we aimed to explore the biological functions of MTHFD2 in GBM and identify the associated mechanisms. We performed experiments such as immunohistochemistry, Western blot, and transwell assays and found that MTHFD2 expression was lower in high-grade glioma than in low-grade glioma. Furthermore, a high expression of MTHFD2 was associated with a favorable prognosis, and MTHFD2 levels showed good prognostic accuracy for glioma patients. The overexpression of MTHFD2 could inhibit the migration, invasion, and proliferation of GBM cells, whereas its knockdown induced the opposite effect. Mechanistically, our findings revealed that MTHFD2 suppressed GBM progression independent of its enzymatic activity, likely by inducing cytoskeletal remodeling through the regulation of extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation, thereby influencing GBM malignance. Collectively, these findings uncover a potential tumor-suppressor role of MTHFD2 in GBM cells. MTHFD2 may act as a promising diagnostic and therapeutic target for GBM treatment.

Targeting long non-coding RNA PVT1/TGF-β/Smad by p53 prevents glioma progression

Glioma is a primary intracranial malignant tumor with poor prognosis, and its pathogenesis is unclear. This study discussed the impact of p53/lncRNA plasmacytoma variant translocation 1 (lncRNA PVT1)/transforming growth factor beta (TGF-β)/Smad axis on the biological characteristics of glioma. Glioma and normal tissues were collected, in which relative lncRNA PVT1 and p53 expression was assessed. Pearson’s analysis was adopted for the correlation analysis between lncRNA PVT1 and p53. Short interfering RNA (siRNA) against lncRNA PVT1 (siRNA-PVT1), siRNA-p53 or both was transfected into the glioma cells to evaluate effects of lncRNA PVT1 and p53 on cell proliferation, migration, invasion, and apoptosis. Mouse xenograft model of glioma was established to verify function of lncRNA PVT1 and p53 in vivo. Relationship among p53, lncRNA PVT1 and TGF-β/Smad was predicted and confirmed. Glioma tissues and cells showed downregulated p53 expression and increased lncRNA PVT1 expression. An adverse relationship was noted between p53 expression and lncRNA PVT1 expression. p53 was shown to be enriched in the lncRNA PVT1 promoter region and resulted in its suppression. p53 inhibited glioma cell proliferation, migration, and invasion, and induced apoptosis as well as arrested tumor growth by downregulating lncRNA PVT1. LncRNA PVT1was found to bind to TGF-β and activate TGF-β/Smad pathway, promoting progression of glioma. Consequently, p53 exerts anti-oncogenic function on glioma development by suppressing lncRNA PVT1 and subsequently inactivating TGF-β/Smad pathway.

MD2 Is a Potential Biomarker Associated with Immune Cell Infiltration in Gliomas

BACKGROUND

Glioma is the most common primary malignant tumor in the central nervous system. Myeloid differentiation protein 2 (MD2) acts as a coreceptor of toll-like receptor 4 (TLR4) to mediate innate immune response. However, the actual roles of MD2 in the regulation of progression and immune cell infiltration in gliomas remain largely unclear. This study aims to explore whether MD2 could be an independent prognostic factor through the mediation of immune cell infiltration in gliomas.

METHODS

The mRNA expression and DNA methylation differential analyses of MD2 were performed using CGGA, TCGA and Rembrandt databases and survival analyses were performed using Kaplan-Meier plotter. Univariate and multivariate Cox regression was applied to analyze the prognostic value of MD2 and nomograms were constructed to evaluate the clinical value of MD2. Then, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) were utilized to analyze MD2-related signal pathways. Furthermore, correlations between MD2 and immune cell infiltration were calculated by TIMER and CIBERSOPT. The correlation between MD2 expression and the infiltrations of macrophages and neutrophils was experimentally verified by the knockdown of MD2 expression using small interfering RNA (siRNA) in glioma cells.

RESULTS

We found that MD2 was overexpressed and associated with a poor prognosis in gliomas. Meanwhile, higher expression of MD2 could be a result of lower DNA methylation of MD2 gene in gliomas. In addition, univariate and multivariate Cox regression analysis indicated that MD2 could be an independent prognostic factor for gliomas. Further functional enrichment analysis revealed that the functions of MD2 were closely related to immune responses. Moreover, the expression level of MD2 was strongly correlated with the infiltration and polarization of pro-tumor phenotype of tumor-associated macrophages and tumor-associated neutrophils in gliomas.

CONCLUSIONS

These findings have provided strong evidence that MD2 could be served as a valuable immune-related biomarker to diagnose and predict the progression of gliomas.

MD2 Is a Potential Biomarker Associated with Immune Cell Infiltration in Gliomas

Background

Glioma is the most common primary malignant tumor in the central nervous system. Myeloid differentiation protein 2 (MD2) acts as a coreceptor of toll-like receptor 4 (TLR4) to mediate innate immune response. However, the actual roles of MD2 in the regulation of progression and immune cell infiltration in gliomas remain largely unclear. This study aims to explore whether MD2 could be an independent prognostic factor through the mediation of immune cell infiltration in gliomas.

Methods

The mRNA expression and DNA methylation differential analyses of MD2 were performed using CGGA, TCGA and Rembrandt databases and survival analyses were performed using Kaplan-Meier plotter. Univariate and multivariate Cox regression was applied to analyze the prognostic value of MD2 and nomograms were constructed to evaluate the clinical value of MD2. Then, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) were utilized to analyze MD2-related signal pathways. Furthermore, correlations between MD2 and immune cell infiltration were calculated by TIMER and CIBERSOPT. The correlation between MD2 expression and the infiltrations of macrophages and neutrophils was experimentally verified by the knockdown of MD2 expression using small interfering RNA (siRNA) in glioma cells.

Results

We found that MD2 was overexpressed and associated with a poor prognosis in gliomas. Meanwhile, higher expression of MD2 could be a result of lower DNA methylation of MD2 gene in gliomas. In addition, univariate and multivariate Cox regression analysis indicated that MD2 could be an independent prognostic factor for gliomas. Further functional enrichment analysis revealed that the functions of MD2 were closely related to immune responses. Moreover, the expression level of MD2 was strongly correlated with the infiltration and polarization of pro-tumor phenotype of tumor-associated macrophages and tumor-associated neutrophils in gliomas.

Conclusions

These findings have provided strong evidence that MD2 could be served as a valuable immune-related biomarker to diagnose and predict the progression of gliomas.

miR-381-3p Involves in Glioma Progression by Suppressing Tumor-Promoter Factor ANTXR1

Accumulating studies revealed association between development of glioma and miRNA dysregulation. A case in point is miR-381-3p, but its mechanism in glioma is unclear yet. In this work, we confirmed that overexpressed miR-381-3p repressed biological functions of glioma cells. Additionally, we also discovered that upregulated anthrax toxin receptor 1 (ANTXR1) was negatively mediated by miR-381-3p. We further proved that miR-381-3p-targeted ANTXR1 was able to counteract the suppression of miR-381-3p on biological functions of glioma. We concluded that miR-381-3p and ANTXR1 were both important factors in modulating glioma progression. miR-381-3p/ANTXR1 axis is expected to be a molecular target for glioma.

PODNL1 Methylation Serves as a Prognostic Biomarker and Associates with Immune Cell Infiltration and Immune Checkpoint Blockade Response in Lower-Grade Glioma

Lower-grade glioma (LGG) is a diffuse infiltrative tumor of the central nervous system, which lacks targeted therapy. We investigated the role of Podocan-like 1 (PODNL1) methylation in LGG clinical outcomes using the TCGA-LGG transcriptomics dataset. We identified four PODNL1 CpG sites, cg07425555, cg26969888, cg18547299, and cg24354933, which were associated with unfavorable overall survival (OS) and disease-free survival (DFS) in univariate and multivariate analysis after adjusting for age, gender, tumor-grade, and IDH1-mutation. In multivariate analysis, the OS and DFS hazard ratios ranged from 0.44 to 0.58 (p < 0.001) and 0.62 to 0.72 (p < 0.001), respectively, for the four PODNL1 CpGs. Enrichment analysis of differential gene and protein expression and analysis of 24 infiltrating immune cell types showed significantly increased infiltration in LGGs and its histological subtypes with low-methylation levels of the PODNL1 CpGs. High PODNL1 expression and low-methylation subgroups of the PODNL1 CpG sites were associated with significantly increased PD-L1, PD-1, and CTLA4 expressions. PODNL1 methylation may thus be a potential indicator of immune checkpoint blockade response, and serve as a biomarker for determining prognosis and immune subtypes in LGG.

Tyrosine Kinase Inhibitors in Adult Glioblastoma: An (Un)Closed Chapter?

Glioblastoma (GBM) is the most common and lethal form of malignant brain tumor. GBM patients normally undergo surgery plus adjuvant radiotherapy followed by chemotherapy. Numerous studies into the molecular events driving GBM highlight the central role played by the Epidermal Growth Factor Receptor (EGFR), as well as the Platelet-derived Growth Factor Receptors PDGFRA and PDGFRB in tumor initiation and progression. Despite strong preclinical evidence for the therapeutic potential of tyrosine kinase inhibitors (TKIs) that target EGFR, PDGFRs, and other tyrosine kinases, clinical trials performed during the last 20 years have not led to the desired therapeutic breakthrough for GBM patients. While clinical trials are still ongoing, in the medical community there is the perception of TKIs as a lost opportunity in the fight against GBM. In this article, we review the scientific rationale for the use of TKIs targeting glioma drivers. We critically analyze the potential causes for the failure of TKIs in the treatment of GBM, and we propose alternative approaches to the clinical evaluation of TKIs in GBM patients.

TP53 Mutation Is a Prognostic Factor in Lower Grade Glioma and May Influence Chemotherapy Efficacy

BACKGROUND

Identification of prognostic biomarkers in cancers is a crucial step to improve overall survival (OS). Although mutations in tumour protein 53 (TP53) is prevalent in astrocytoma, the prognostic effects of TP53 mutation are unclear.

METHODS

In this retrospective study, we sequenced TP53 exons 1 to 10 in a cohort of 102 lower-grade glioma (LGG) subtypes and determined the prognostic effects of TP53 mutation in astrocytoma and oligodendroglioma. Publicly available datasets were analysed to confirm the findings.

RESULTS

In astrocytoma, mutations in TP53 codon 273 were associated with a significantly increased OS compared to the TP53 wild-type (HR (95% CI): 0.169 (0.036-0.766), p = 0.021). Public datasets confirmed these findings. TP53 codon 273 mutant astrocytomas were significantly more chemosensitive than TP53 wild-type astrocytomas (HR (95% CI): 0.344 (0.13-0.88), p = 0.0148). Post-chemotherapy, a significant correlation between TP53 and YAP1 mRNA was found (p = 0.01). In O (6)-methylguanine methyltransferase (MGMT) unmethylated chemotherapy-treated astrocytoma, both TP53 codon 273 and YAP1 mRNA were significant prognostic markers. In oligodendroglioma, TP53 mutations were associated with significantly decreased OS.

CONCLUSIONS

Based on these findings, we propose that certain TP53 mutant astrocytomas are chemosensitive through the involvement of YAP1, and we outline a potential mechanism. Thus, TP53 mutations may be key drivers of astrocytoma therapeutic efficacy and influence survival outcomes.

Transmembrane protein 45A regulates the proliferation, migration, and invasion of glioma cells through nuclear factor kappa-B

Gliomas are the most common and aggressive type of primary brain cancer in adults. The expression of transmembrane protein 45A (TMEM45A) in glioma patients and glioma cell lines was analyzed by quantitative real-time PCR. The influence of TMEM45A on the survival of glioma patients was also explored in this study. To verify the interaction between TMEM45A and key genes, correlation analysis of expression levels and the siRNA knock down method were performed. TMEM45A was upregulated in glioma tissues, and its overexpression was strongly correlated with the poor survival of glioma patients. Experiments using the overexpression and knock down of TMEM45A were carried out to demonstrate its correlation with enhanced proliferation, migration, and invasion in glioma cells. Nuclear factor kappa-B (NFκB) expression was shown to be a downstream factor of TMEM45A in glioma cells. In conclusion, TMEM45A is an oncogenic gene in glioma. The proliferation, migration, and invasion of gliomas could be effectively impeded by inhibition of TMEM45A, and the cancer-promoting effect of TMEM45A on gliomas was involved with the NFκB pathway.

Silencing of lncRNA LBX2-AS1 suppresses glioma cell proliferation and metastasis through the Akt/GSK3β pathway in vitro

Long non-coding RNAs (lncRNAs) have been proposed to play pivotal roles in the tumorigenesis of various malignant tumors. Previous studies have found that lncRNA LBX2-AS1 is involved in the progression of various tumors. However, currently, the expression and exact mechanism of LBX2-AS1 in glioma remain unclear. In this study, using online-available datasets combined with clinical glioma tissues collected, we found that LBX2-AS1 was significantly increased and negatively correlated with prognosis in glioma. In vitro functional assays such as CCK-8, Annexin V, transwell assay, and western blot analysis showed that silencing of LBX2-AS1 suppressed the proliferation, migration, and invasion of glioma cells and increased apoptosis. RNA sequencing and western blot analysis confirmed that LBX2-AS1 regulates the Akt/GSK3β pathway. In conclusion, this study showed that lncRNA LBX2-AS1 depletion inhibits the proliferation, migration, and invasion of glioma cells and increases apoptosis through the Akt/GSK3β pathway. lncRNA LBX2-AS1 is expected to become a new target for glioma therapy.

Long noncoding RNA H19 contributes to the proliferation and autophagy of glioma cells through mTOR/ULK1 pathway

Long noncoding RNA (LncRNA) H19 has been proven to be involved in many kinds of cancers including glioma, and a previous study has shown an autophagy regulation of H19. The mammalian target of rapamycin (mTOR) signaling pathway plays a key role in autophagy and Unc-51 like autophagy activating kinase 1 (ULK1) is also thought to be involved in autophagy signaling. In our study, we investigated the role of mTOR/ULK1 autophagy signaling in the H19-mediated promotion of glioma proliferation. Human glioma cells U87 and U251 and normal human astrocytes HA1800 were used in the study. First, the expression of H19 was determined in U87, U251, and HA1800 cells. Then, the cell proliferation and migration of glioma cells were detected, while the protein levels of main molecules of the mTOR/ULK1 pathway and autophagy-related proteins were also examined. Rapamycin, an inhibitor of mTOR, was used to further study the role of H19 in autophagy. We observed that overexpressed H19 promoted the proliferation and migration in glioma cells. The autophagy of U87 cells was suppressed when H19 was overexpressed and enhanced when H19 was silenced. H19 overexpression inhibited mTOR phosphorylation and promoted ULK1 phosphorylation. H19 promoted proliferation, migration, and autophagy by regulating mTOR signaling. In conclusion, we validate that H19 contributes to the proliferation and autophagy of glioma cells through the mTOR/ULK1 pathway.

Lactoferrin/phenylboronic acid-functionalized hyaluronic acid nanogels loading doxorubicin hydrochloride for targeting glioma

Herein, lactoferrin (Lf)/phenylboronic acid (PBA)-functionalized hyaluronic acid nanogels crosslinked with disulfide-bond crosslinker was developed as a reduction-sensitive dual-targeting glioma therapeutic platform for doxorubicin hydrochloride (DOX) delivery (Lf-DOX/PBNG). Spherical Lf-DOX/PBNG with optimized physicochemical properties was obtained, and it could rapidly release the encapsulated DOX under high glutathione concentration. Moreover, enhanced cytotoxicity, superior cellular uptake efficiency, and significantly improved brain permeability of Lf-DOX/PBNG were observed in cytological studies compared with those of DOX solution, DOX-loaded PBA functionalized nanogels (DOX/PBNG), and Lf modified DOX-loaded nanogels (Lf-DOX/NG). The pharmacokinetic study exhibited that the area under the curve of DOX/PBNG, Lf-DOX/NG, and Lf-DOX/PBNG increased by 8.12, 4.20 and 4.32 times compared with that of DOX solution, respectively. The brain accumulation of Lf-DOX/PBNG was verified in biodistribution study to be 12.37 and 4.67 times of DOX solution and DOX/PBNG, respectively. These findings suggest that Lf-DOX/PBNG is an excellent candidate for achieving effective glioma targeting.

miR-4530 inhibits the malignant biological behaviors of human glioma cells by directly targeting RTEL1

Human glioma is the most common primary brain tumor and is associated with high morbidity and mortality. Aberrant expressions of microRNAs (miRNAs) are involved in glioma progression. In the present study, we aimed to elucidate the roles of miR-4530 in the pathogenesis of gliomas. miR-4530 expression was examined in human glioma clinical tissues and cell lines including U251 and T98G. The target gene of miR-4530, RTEL1, was predicted with online tools and validated by luciferase reporter assay. Lentivirus infection, transfection of plasmids, and miRNA mimics were used to manipulate gene expression. Cell proliferation was determined using the CCK-8 method, and migration and invasion assays were determined with transwell experiments. Colony formation was measured by crystal violet staining, while apoptosis was determined by Annexin V/PI staining. The anti-tumor effects of miR-4530 were evaluated in nude mice xenografted using U251 cells. Our results showed that miR-4530 was significantly down-regulated in human glioma tissues and cell lines. miR-4530 over-expression inhibited the malignant behaviors of U251 and T98G cells, including reduced proliferation, diminished colony formation, migration and invasion, and increased apoptosis. Further mechanistic investigations revealed that RTEL1 is a direct functional target of miR-4530 in gliomas, and its over-expression remarkably reverses the effects of miR-4530 mimics on inhibiting these malignant behaviors. In addition, miR-4530 over-expression inhibited the growth of xenografted U251 glioma in nude mice. Therefore, miR-4530 acts as a tumor-suppressor gene and inhibits the malignant biological behaviors of human glioma cells, which is associated with directly targeting RTEL1. The miR-4530/RTEL1 axis is a potential therapeutic target for gliomas.

Interrogation of kinase genetic interactions provides a global view of PAK1-mediated signal transduction pathways

Kinases are critical components of intracellular signaling pathways and have been extensively investigated with regard to their roles in cancer. p21-activated kinase-1 (PAK1) is a serine/threonine kinase that has been previously implicated in numerous biological processes, such as cell migration, cell cycle progression, cell motility, invasion, and angiogenesis, in glioma and other cancers. However, the signaling network linked to PAK1 is not fully defined. We previously reported a large-scale yeast genetic interaction screen using toxicity as a readout to identify candidate PAK1 genetic interactions. En masse transformation of the PAK1 gene into 4,653 homozygous diploid Saccharomyces cerevisiae yeast deletion mutants identified ∼400 candidates that suppressed yeast toxicity. Here we selected 19 candidate PAK1 genetic interactions that had human orthologs and were expressed in glioma for further examination in mammalian cells, brain slice cultures, and orthotopic glioma models. RNAi and pharmacological inhibition of potential PAK1 interactors confirmed that DPP4, KIF11, mTOR, PKM2, SGPP1, TTK, and YWHAE regulate PAK1-induced cell migration and revealed the importance of genes related to the mitotic spindle, proteolysis, autophagy, and metabolism in PAK1-mediated glioma cell migration, drug resistance, and proliferation. AKT1 was further identified as a downstream mediator of the PAK1-TTK genetic interaction. Taken together, these data provide a global view of PAK1-mediated signal transduction pathways and point to potential new drug targets for glioma therapy.

Physiologically Based Pharmacokinetic Modeling of Central Nervous System Pharmacokinetics of CDK4/6 Inhibitors to Guide Selection of Drug and Dosing Regimen for Brain Cancer Treatment

A better understanding of the human central nervous system (CNS) pharmacokinetics is critical to the selection of the right drug and refinement of dosing regimen for more effective treatment of primary and metastatic brain cancer. Using the physiologically‐based pharmacokinetic (PBPK) modeling approach, we systematically compared the CNS pharmacokinetics of three cyclin D‐cyclin dependent kinase 4 and 6 (CDK4/6) inhibitors (ribociclib, palbociclib, and abemaciclib) in patients with cancer. A PBPK model platform was developed and verified for predicting plasma and CNS pharmacokinetics. Target engagement ratio (TER), defined as the ratio of the average steady‐state unbound drug brain concentration to the in vitro half‐maximal inhibitory concentration (IC₅₀) for CDK4/6 inhibition, was used as a crude predictor of efficacy. As compared with ribociclib and palbociclib, abemaciclib penetrated into the human brain to a larger extent, but at a slower rate, and was retained in the brain longer. Following the standard dosing regimens, the predicted CDK4/6 TERs were 26/5.2 for abemaciclib, 2.4/0.62 for ribociclib, and 0.36/0.27 for palbociclib. Simulations suggested that abemaciclib achieved comparable TERs following twice daily or daily dosing; ribociclib may sufficiently inhibit both CDK4 and CDK6 at the maximum tolerated dose; whereas, palbociclib achieved TERs < 0.5 even at a dose 50% higher than the standard dose. In conclusion, the PBPK modeling, supported by available preclinical and clinical evidence, suggests that abemaciclib is the best CDK4/6 inhibitor for brain cancer treatment, whereas palbociclib is not recommended. The model refined dosing regimen is 300 mg daily on a 4‐weeks‐on schedule for abemaciclib, and 900 mg daily on a 3‐weeks‐on/1‐week‐off schedule for ribociclib.

Plasma microRNA-720 may predict prognosis and diagnosis in glioma patients

We enrolled 122 patients with glioma who received surgery treatment in our hospital from June 2010 to May 2012, and 60 healthy individuals. We found that the plasma miR-720 in the glioma group was significantly higher than that in the healthy control group (3.19 ± 1.26 vs 0.98 ± 0.65, P<0.001). The sensitivity and specificity were 71.3% (95%CI: 62.4-79.1%) and 83.3% (71.5-91.7%), respectively. The results indicated that the plasma miR-720 level was associated with tumor grade (t = 104.418, P<0.001). The advanced tumor tended to have higher miR-720 expression level. No significant association was found between miR-720 and age, sex, tumor size, KPS and tumor position (P=0.438, 0.514, 0.518, 0.058, 0.226). The multivariate cox analysis indicated that the high expression of miR-720 (HR = 1.48, 95%CI: 1.12-2.97, P=0.023) was independently predictors of adverse prognosis in patients with glioma. The high expression of miR-720 was also associated with recurrence or development in patients with glioma (HR = 1.47, 95%CI: 1.18-3.14, P=0.012). Plasma miR-720 has a moderate diagnostic ability in early diagnostic of glioma and may be a potential tumor biomarker. The high plasma miR-720 was related to adverse prognosis in patients with glioma and could be a prognosis predictor of glioma patients.

Borneol promotes apoptosis of Human Glioma Cells through regulating HIF-1a expression via mTORC1/eIF4E pathway

The main reason for the failure of malignant glioma treatment is local tumor recurrence. Tumor cells in hypoxic microenvironment activate HIF-1 α transcription, and thus promoting tumor invasion and metastasis is one of the important reasons. In our previous study, we clearly established that borneol opens the blood-brain tumor barrier and its related mechanism. However, the effects of borneol itself on glioma proliferation have not yet been elucidated. Therefore, in this study, we evaluated the effect of borneol on glioma by constructing in vivo SD rat brain glioma model and in vitro human primary cultured glioma cell model. We found that borneol could suppress the proliferation of primary glioma cells and the tumor volume of SD rat brain glioma. Further, we measured the apoptosis effect induced by borneol in human primary cultured glioma cells. The results showed that the higher the concentration of borneol, the higher the apoptosis rate of human primary cultured glioma cells, but the effect was reversed after transfection of HIF-1 overexpression plasmid; In addition, borneol could downregulate the expression of Bcl-2 and upregulation the expression of Bax and caspase-3, similarly, the effect was also reversed after transfection of HIF-1 overexpression plasmid, suggesting that the apoptosis effect induced by borneol in human primary cultured glioma cells is mediated via HIF-1α. Moreover, the bioinformatics analysis of correlation between HIF-1α and apoptosis-related factors based on CGGA database showed that there was a positive correlation between the expression of eIF4E and HIF-1 α (P < 0.05), and in patients with high expression of eIF4E and HIF-1α had poor survival and prognosis (P<0.001). It was further discovered that in the human primary cultured glioma cells borneol regulated HIF-1a expression via mTORC1/eIF4E pathway. In conclusion, the findings of the present study suggest that HIF-1α may be a key factor in borneol induced apoptosis of glioma cells, and mTORC1 / eIF4E pathway is involved in the HIF-1α regulation by borneol in malignant glioma. Our results not only reveal the target and molecular mechanism and action of borneol leading to promote apoptosis in glioma cells, but also provide experimental basis and theoretical support for the clinical application of borneol.

Activation of BDNF-AS/ADAR/p53 Positive Feedback Loop Inhibits Glioblastoma Cell Proliferation

Despite progress in conventional treatment for glioblastoma (GBM), the prognosis remains poor due to high tumor recurrence. Therefore, identification of new molecular mechanisms is a pressing need for betterment of GBM patient outcomes. qRT-PCR was used to determine BDNF-AS expression in GBM cells. CCK-8, EdU incorporation, and caspase-3 activity assays were employed to analyze biological functions of BDNF-AS. RIP and RNA pull-down were conducted to detect the interactions among BDNF-AS, ADAR, and p53. Actinomycin D was utilized to examine the stability of p53 mRNA. ChIP and luciferase reporter assays were performed to detect transcriptional activation of BDNF-AS by p53. We found that BDNF-AS was significantly downregulated in GBM cell lines, and its overexpression inhibited GBM cell growth, and promoted apoptosis. Importantly, we illustrated that BDNF-AS coupled with ADAR protein to potentiate stability of p53 mRNA and thus upregulate p53. Interestingly, we further identified p53 as a transcription factor of BDNF-AS, activating transcription of BNDF-AS. This study firstly demonstrated that BDNF-AS acted as a tumor suppressor in GBM and the positive feedback circuit of BDNF-AS/ADAR/p53 served an important mechanism to control GBM proliferation. Targeting this auto-regulatory loop may provide a potential therapeutic strategy for GBM patients.

Repurposing Potential of Riluzole as an ITAF Inhibitor in mTOR Therapy Resistant Glioblastoma

Internal ribosome entry site (IRES)-mediated protein synthesis has been demonstrated to play an important role in resistance to mechanistic target of rapamycin (mTOR) targeted therapies. Previously, we have demonstrated that the IRES trans-acting factor (ITAF), hnRNP A1 is required to promote IRES activity and small molecule inhibitors which bind specifically to this ITAF and curtail IRES activity, leading to mTOR inhibitor sensitivity. Here we report the identification of riluzole (Rilutek^®), an FDA-approved drug for amyotrophic lateral sclerosis (ALS), via an in silico docking analysis of FDA-approved compounds, as an inhibitor of hnRNP A1. In a riluzole-bead coupled binding assay and in surface plasmon resonance imaging analyses, riluzole was found to directly bind to hnRNP A1 and inhibited IRES activity via effects on ITAF/RNA-binding. Riluzole also demonstrated synergistic anti-glioblastoma (GBM) affects with mTOR inhibitors in vitro and in GBM xenografts in mice. These data suggest that repurposing riluzole, used in conjunction with mTOR inhibitors, may serve as an effective therapeutic option in glioblastoma.

HOTAIR-EZH2 inhibitor AC1Q3QWB upregulates CWF19L1 and enhances cell cycle inhibition of CDK4/6 inhibitor palbociclib in glioma

BACKGROUND

Glioblastoma (GBM) is the most common primary tumor in the brain, and the median survival time for GBM patients is only about 14 months; therefore, there is an urgent need for new and more effective strategies. Since cell cycle disorder is a key factor in tumor progression and immortalization, there is great potential for controlling cell cycle disorders in tumor cells in GBM patients. We began to study a novel combination of AQB and palbociclib to evaluate its potential as a new therapeutic target.

METHODS

Protein mass spectrometry was used to identify the tumor suppressor genes up-regulated by AQB.The effects of HOTAIR - EZH2 inhibitor AQB and CDK4/6 inhibitor Palbociclib on glioma cells lines were examined in vitro and in vivo experiments.

RESULTS

The combination of AQB and palbociclib inhibitors has a more pronounced suppression effect on the cell cycle, especially gliomas with high expression of HOTAIR and EZH2 and low expression of CWF19L1. We performed protein mass spectrometry to identify AQB upregulated tumor suppressor genes and confirmed that CWF19L1 is regulated by H3K27ac through chromatin immunoprecipitation-quantitative PCR results. Univariate and multivariate Cox regression analysis and database analysis were performed to suggest CWF19L1 is a good prognostic factor. Our experimental results suggested that CWF19L1 can be significantly upregulated by AQB and lead to degradation of CDK4/6, resulting in G1 arrest. The combination of AQB and CDK4/6 inhibitor palbociclib is more effective in inhibiting the growth of glioma than in the single drug, both in vivo and in vitro. Similarly, we found that both AQB and palbociclib can inhibit Wnt/β-catenin signaling, and the combined use of the two inhibitors has a stronger inhibitory effect on tumor metastasis.

CONCLUSIONS

The combination of AQB and CDK4/6 inhibitor palbociclib has been found to have significant antitumor effects, which is likely to become a new strategy for glioma treatment.

Assessment of brain delivery of a model ABCB1/ABCG2 substrate in patients with non-contrast-enhancing brain tumors with positron emission tomography

BACKGROUND

P-glycoprotein (ABCB1) and breast cancer resistance protein (ABCG2) are two efflux transporters expressed at the blood-brain barrier which effectively restrict the brain distribution of the majority of currently known anticancer drugs. High-grade brain tumors often possess a disrupted blood-brain tumor barrier (BBTB) leading to enhanced accumulation of magnetic resonance imaging contrast agents, and possibly anticancer drugs, as compared to normal brain. In contrast to high-grade brain tumors, considerably less information is available with respect to BBTB integrity in lower grade brain tumors.

MATERIALS AND METHODS

We performed positron emission tomography imaging with the radiolabeled ABCB1 inhibitor [¹¹C]tariquidar, a prototypical ABCB1/ABCG2 substrate, in seven patients with non-contrast -enhancing brain tumors (WHO grades I-III). In addition, ABCB1 and ABCG2 levels were determined in surgically resected tumor tissue of four patients using quantitative targeted absolute proteomics.

RESULTS

Brain distribution of [¹¹C]tariquidar was found to be very low across the whole brain and not significantly different between tumor and tumor-free brain tissue. Only one patient showed a small area of enhanced [¹¹C]tariquidar uptake within the brain tumor. ABCG2/ABCB1 ratios in surgically resected tumor tissue (1.4 ± 0.2) were comparable to previously reported ABCG2/ABCB1 ratios in isolated human micro-vessels (1.3), which suggested that no overexpression of ABCB1 or ABCG2 occurred in the investigated tumors.

CONCLUSIONS

Our data suggest that the investigated brain tumors had an intact BBTB, which is impermeable to anticancer drugs, which are dual ABCB1/ABCG2 substrates. Therefore, effective drugs for antitumor treatment should have high passive permeability and lack ABCB1/ABCG2 substrate affinity.

TRIAL REGISTRATION

European Union Drug Regulating Authorities Clinical Trials Database (EUDRACT), 2011-004189-13. Registered on 23 February 2012, https://www.clinicaltrialsregister.eu/ctr-search/search?query=2011-004189-13.

Recurrent or Refractory High-Grade Gliomas Treated by Convection-Enhanced Delivery of a TGFβ2-Targeting RNA Therapeutic: A Post-Hoc Analysis with Long-Term Follow-Up

Background. OT101 is a first-in-class RNA therapeutic designed to abrogate the immunosuppressive actions of transforming growth factor beta 2 (TGFβ2). Here, we report our post-hoc analysis of the single-agent activity of OT101 in adult patients with recurrent and/or refractory (R/R) high-grade gliomas. Methods. In a Phase 2 clinical trial (ClinicalTrials.gov, NCT00431561), OT101 was administered to 89 R/R high-grade glioma (HGG) (anaplastic astrocytoma/AA: 27; glioblastoma multiforme/GBM: 62) patients with an intratumoral catheter using a convection enhanced delivery (CED) system. Seventy-seven patients (efficacy population; GBM: 51; AA: 26) received at least the intended minimum number of four OT101 treatment cycles. Response determinations were based on central review of magnetic resonance imaging (MRI) scans according to the McDonald criteria. Standard statistical methods were applied for the analysis of data. Findings. Nineteen patients had a complete response (CR) or partial response (PR) following a slow but robust size reduction of their target lesions (median time for 90% reduction of the baseline tumor volume = 11.7 months, range: 4.9-57.7 months). The mean log reduction of the tumor volume was 2.2 ± 0.4 (median = 1.4: range: 0.4-4.5) logs. In addition, seven patients had a stable disease (SD) lasting ≥6 months. For the combined group of 26 AA/GBM patients with favorable responses, the median progression-free survival (PFS) of 1109 days and overall survival (OS) of 1280 days were significantly better than the median PFS (p < 0.00001) and OS (p < 0.00001) of the non-responders among the 89 patients or the 77-patient efficacy population. Conclusion. Intratumorally administered OT101 exhibits clinically meaningful single-agent activity and induces durable CR/PR/SD in R/R HGG patients.

IFITM3/STAT3 axis promotes glioma cells invasion and is modulated by TGF-β

Glioma is the most aggressive primary brain tumor. We have previously provided evidence that IFITM3 promoted glioma cells migration. However, the mechanism of how IFITM3 regulates glioma cells invasion and whether IFITM3 participates in TGF-β-mediated glioma invasion are still unknown. In this paper, we proved that IFITM3 was notably up-regulated in glioma tissues. Knockdown of IFITM3 suppressed STAT3 phosphorylation in vitro, and a specific STAT3 inhibitor AG490 reversed IFITM3-induced invasion of glioma cells. Furthermore, IFITM3 expression was induced by TGF-β in glioma and IFITM3 knockdown abolished TGF-β-mediated glioma cells invasion. Collectively, the results indicate that IFITM3/STAT3 axis may promote TGF-β-induced glioma cells invasion. This study provided some suggestions for the clinical treatment of the brain tumor.

Novel sphingomyelin biomarkers for brain glioma and associated regulation research on the PI3K/Akt signaling pathway

Glioma is one of the most common malignant tumor types of the central nervous system. It is necessary to identify biomarkers and novel therapeutic targets for glioma. The purpose of the present study was to distinguish lipid biomarkers with differential expression patterns in glioma tissues and normal brain tissues by matrix assisted laser desorption/ionization (MALDI)-imaging and MALDI-time of flight (TOF)-mass spectrometry (MS). Additionally, identification of lipid biomarkers was performed to describe novel therapeutic targets for glioma treatment. A total of six tissues from three patients with glioma and three control patients with traumatic brain injury were analyzed using UltrafleXtreme MALDI-TOF/TOF. The expression levels of 15 lipid peaks were higher in the TBT samples compared with in the GBT samples. The expression levels of another 16 lipid peaks were higher in the GBT samples compared with in the TBT samples. 14 peaks were identified as sphingomyelins using MS/MS. Additional results were also obtained from experiments using the glioma cell line U373-MG. These results indicated that treatment with the drug desipramine (Desi) inhibited the accumulation of ceramide on the cell membranes of glioma U373-MG cells. Treatment with Desi inhibited the activation of insulin-like growth factor-1 receptor and inhibited the activation of proteins in the PI3K/Akt signaling pathway.

Development and characterization of sorafenib-loaded lipid nanocapsules for the treatment of glioblastoma

Anticancer agents that target both tumor cells and angiogenesis are of potential interest for glioblastoma (GB) therapy. One such agent is sorafenib (SFN), a tyrosine kinase inhibitor. However, poor aqueous solubility and undesirable side effects limit its clinical application, including local treatment. We encapsulated SFN in lipid nanocapsules (LNCs) to overcome these drawbacks. LNCs are nanocarriers formulated according to a solvent-free process, using only components that have received regulatory approval. SFN-LNCs had a diameter of 54 ± 1 nm, high encapsulation efficiency (>90%), and a drug payload of 2.11 ± 0.03 mg/g of LNC dispersion. They inhibited in vitro angiogenesis and decreased human U87MG GB cell viability similarly to free SFN. In vivo studies showed that the intratumoral administration of SFN-LNCs or free SFN in nude mice bearing an orthotopic U87MG human GB xenograft decreased the proportion of proliferating cells in the tumor relative to control groups. SFN-LNCs were more effective than free SFN for inducing early tumor vascular normalization, characterized by increases in tumor blood flow and decreases in tumor vessel area. These results highlight the potential of LNCs as delivery systems for SFN. The vascular normalization induced by SFN-LNCs could be used to improve the efficacy of chemotherapy or radiotherapy for treating GB.

Roles of Extracellular Vesicles in High-Grade Gliomas: Tiny Particles with Outsized Influence

High-grade gliomas, particularly glioblastomas (grade IV), are devastating diseases with dismal prognoses; afflicted patients seldom live longer than 15 months, and their quality of life suffers immensely. Our current standard-of-care therapy has remained essentially unchanged for almost 15 years, with little new therapeutic progress. We desperately need a better biologic understanding of these complicated tumors in a complicated organ. One area of rejuvenated study relates to extracellular vesicles (EVs)-membrane-enclosed nano- or microsized particles that originate from the endosomal system or are shed from the plasma membrane. EVs contribute to tumor heterogeneity (including the maintenance of glioma stem cells or their differentiation), the impacts of hypoxia (angiogenesis and coagulopathies), interactions amid the tumor microenvironment (concerning the survival of astrocytes, neurons, endothelial cells, blood vessels, the blood-brain barrier, and the ensuing inflammation), and influences on the immune system (both stimulatory and suppressive). This article reviews glioma EVs and the ways that EVs manifest themselves as autocrine, paracrine, and endocrine factors in proximal and distal intra- and intercellular communications. The reader should note that there is much controversy, and indeed confusion, in the field over the exact roles for EVs in many biological processes, and we will engage some of these difficulties herein.

Oligonucleotide Therapeutics as a New Class of Drugs for Malignant Brain Tumors: Targeting mRNAs, Regulatory RNAs, Mutations, Combinations, and Beyond

Malignant brain tumors are rapidly progressive and often fatal owing to resistance to therapies and based on their complex biology, heterogeneity, and isolation from systemic circulation. Glioblastoma is the most common and most aggressive primary brain tumor, has high mortality, and affects both children and adults. Despite significant advances in understanding the pathology, multiple clinical trials employing various treatment strategies have failed. With much expanded knowledge of the GBM genome, epigenome, and transcriptome, the field of neuro-oncology is getting closer to achieve breakthrough-targeted molecular therapies. Current developments of oligonucleotide chemistries for CNS applications make this new class of drugs very attractive for targeting molecular pathways dysregulated in brain tumors and are anticipated to vastly expand the spectrum of currently targetable molecules. In this chapter, we will overview the molecular landscape of malignant gliomas and explore the most prominent molecular targets (mRNAs, miRNAs, lncRNAs, and genomic mutations) that provide opportunities for the development of oligonucleotide therapeutics for this class of neurologic diseases. Because malignant brain tumors focally disrupt the blood-brain barrier, this class of diseases might be also more susceptible to systemic treatments with oligonucleotides than other neurologic disorders and, thus, present an entry point for the oligonucleotide therapeutics to the CNS. Nevertheless, delivery of oligonucleotides remains a crucial part of the treatment strategy. Finally, synthetic gRNAs guiding CRISPR-Cas9 editing technologies have a tremendous potential to further expand the applications of oligonucleotide therapeutics and take them beyond RNA targeting.

Sinomenine Induces G1-Phase Cell Cycle Arrest and Apoptosis in Malignant Glioma Cells Via Downregulation of Sirtuin 1 and Induction of p53 Acetylation

Sinomenine, a bioactive alkaloid isolated from the traditional Chinese herb Sinomenium acutum, possesses antiinflammatory, antinociceptive, antifibrotic, and antitumorigenic properties. In this work, we sought to explore the biological effects of sinomenine on glioma cells. It was found that sinomenine caused a concentration-dependent inhibition of viability in both U87 and U251 glioma cells. Sinomenine at 16 μmol/L caused 55% to 60% reduction in the proliferation of U87 and U251 cells. Moreover, sinomenine treatment induced a G0/G1 cell cycle arrest and apoptosis. Mechanistically, sinomenine promoted p53 expression and acetylation and reduced the expression of sirtuin 1. Ectopic expression of sirtuin 1 significantly prevented sinomenine-induced p53 acetylation and growth suppression in glioma cells. Moreover, sinomenine inhibited the growth of U87 xenograft tumors in vivo and raised the p53 protein expression. Collectively, sinomenine shows antiproliferative effects against glioma cells which is mediated through downregulation of sirtuin 1 and induction of p53 activity.

The effect of the mTOR inhibitor rapamycin on glucoCEST signal in a preclinical model of glioblastoma

PURPOSE

The mammalian target of rapamycin is an enzyme that regulates cell metabolism and proliferation. It is up-regulated in aggressive tumors, such as glioblastoma, leading to increased glucose uptake and consumption. It has been suggested that glucose CEST signals reflect the delivery and tumor uptake of glucose. The inhibitor rapamycin (sirolimus) has been applied as a glucose deprivation treatment; thus, glucose CEST MRI could potentially be useful for monitoring the tumor responses to inhibitor treatment.

METHODS

A human U87-EGFRvIII xenograft model in mice was studied. The mice were treated with a mammalian target of Rapamycin inhibitor, rapamycin. The effect of the treatment was evaluated in vivo with dynamic glucose CEST MRI.

RESULTS

Rapamycin treatment led to significant increases (P < 0.001) in dynamic glucose-enhanced signal in both the tumor and contralateral brain as compared to the no-treatment group, namely a maximum enhancement of 3.7% ± 2.3% (tumor, treatment) versus 1.9% ± 0.4% (tumor, no-treatment), 1.7% ± 1.1% (contralateral, treatment), and 1.0% ± 0.4% (contralateral, no treatment). Dynamic glucose-enhanced contrast remained consistently higher in treatment versus no-treatment groups for the duration of the experiment (17 min). This was confirmed with area-under-curve analysis.

CONCLUSION

Increased glucose CEST signal was found after mammalian target of Rapamycin inhibition treatment, indicating potential for dynamic glucose-enhanced MRI to study tumor response to glucose deprivation treatment.

Circular RNAs: Functions and Prospects in Glioma

Improving the survival rate of patients with glioma, a malignant tumor of the human brain has become increasingly important. In recent years, the function of circular RNAs (circRNAs) in different diseases and the pathophysiological mechanisms involved have been elucidated. In the pathophysiological mechanism, the primary function of circRNAs is to act as microRNA sponges. An increasing number of studies have found that circRNAs are differentially expressed in gliomas and regulate the occurrence, proliferation, and invasion of glioma and thus may be potential markers for the diagnosis of gliomas. Additionally, some circRNAs have been associated with glioma staging and may be useful in determining prognosis. Based on the stability and high conservation of circRNAs, we believe that circRNAs may have molecular targets that are useful for the treatment of glioma. In this review, we summarize the current research regarding the role of circRNAs in gliomas, discuss the potential value and role of circRNAs in gliomas, and provide new perspectives for future research.

Dual functions of ARP101 in targeting membrane type-1 matrix metalloproteinase: Impact on U87 glioblastoma cell invasion and autophagy signaling

Membrane type-1 matrix metalloproteinase (MT1-MMP) possesses both extracellular proteolytic and intracellular signal-transducing functions in tumorigenesis. An imbalance in MT1-MMP expression and/or function triggers a metastatic, invasive, and therapy resistance phenotype. MT1-MMP is involved in extracellular matrix (ECM) proteolysis, activation of latent MMPs, as well as in autophagy signaling in human hepatoma and glioblastoma cells. A low autophagy index in tumorigenesis has been inferred by recent studies where autophagic capacity was decreased during tumor progression. Here, we establish ARP101 as a dual-function small-molecule inhibitor against MT1-MMP ECM hydrolysis and autophagy signal-transducing functions in a model of grade IV glioblastoma cells. ARP101 inhibited concanavalin-A-mediated proMMP-2 activation into MMP-2, as well as MT1-MMP auto-proteolytic processing. When overexpressing recombinant Wt MT1-MMP, ARP101 inhibited proMMP-2 activation and triggered the formation of MT1-MMP oligomers that required trafficking to the plasma membrane. ARP101 further induced cell autophagy as reflected by increased formation of acidic vacuole organelles, LC3 puncta, and autophagy-related protein ATG9 transcription. These were all significantly reversed upon siRNA-mediated gene silencing of MT1-MMP. ARP101 can thus concomitantly inhibit MT1-MMP extracellular catalytic function and exploit its intracellular transducing signal function to trigger autophagy-mediated cell death in U87 glioblastoma cancer cells.

Emerging Gene Fusion Drivers in Primary and Metastatic Central Nervous System Malignancies: A Review of Available Evidence for Systemic Targeted Therapies

Primary and metastatic tumors of the central nervous system present a difficult clinical challenge, and they are a common cause of disease progression and death. For most patients, treatment consists primarily of surgery and/or radiotherapy. In recent years, systemic therapies have become available or are under investigation for patients whose tumors are driven by specific genetic alterations, and some of these targeted treatments have been associated with dramatic improvements in extracranial and intracranial disease control and survival. However, the success of other systemic therapies has been hindered by inadequate penetration of the drug into the brain parenchyma. Advances in molecular characterization of oncogenic drivers have led to the identification of new gene fusions driving oncogenesis in some of the most common sources of intracranial tumors. Systemic therapies targeting many of these alterations have been approved recently or are in clinical development, and the ability to penetrate the blood-brain barrier is now widely recognized as an important property of such drugs. We review this rapidly advancing field with a focus on recently uncovered gene fusions and brain-penetrant systemic therapies targeting them.

IMPLICATIONS FOR PRACTICE

Driver gene fusions involving receptor tyrosine kinases have been identified across a wide range of tumor types, including primary central nervous system (CNS) tumors and extracranial solid tumors that are associated with high rates of metastasis to the CNS (e.g., lung, breast, melanoma). This review discusses the systemic therapies that target emerging gene fusions, with a focus on brain-penetrant agents that will target the intracranial disease and, where present, also extracranial disease.

Multidimensional communication in the microenvirons of glioblastoma

Glioblastomas are heterogeneous and invariably lethal tumours. They are characterized by genetic and epigenetic variations among tumour cells, which makes the development of therapies that eradicate all tumour cells challenging and currently impossible. An important component of glioblastoma growth is communication with and manipulation of other cells in the brain environs, which supports tumour progression and resistance to therapy. Glioblastoma cells recruit innate immune cells and change their phenotype to support tumour growth. Tumour cells also suppress adaptive immune responses, and our increasing understanding of how T cells access the brain and how the tumour thwarts the immune response offers new strategies for mobilizing an antitumour response. Tumours also subvert normal brain cells - including endothelial cells, neurons and astrocytes - to create a microenviron that favours tumour success. Overall, after glioblastoma-induced phenotypic modifications, normal cells cooperate with tumour cells to promote tumour proliferation, invasion of the brain, immune suppression and angiogenesis. This glioblastoma takeover of the brain involves multiple modes of communication, including soluble factors such as chemokines and cytokines, direct cell-cell contact, extracellular vesicles (including exosomes and microvesicles) and connecting nanotubes and microtubes. Understanding these multidimensional communications between the tumour and the cells in its environs could open new avenues for therapy.

Age-Dependent Cellular and Behavioral Deficits Induced by Molecularly Targeted Drugs Are Reversible

Newly developed targeted anticancer drugs inhibit signaling pathways commonly altered in adult and pediatric cancers. However, as these pathways are also essential for normal brain development, concerns have emerged of neurologic sequelae resulting specifically from their application in pediatric cancers. The neural substrates and age dependency of these drug-induced effects in vivo are unknown, and their long-term behavioral consequences have not been characterized. This study defines the age-dependent cellular and behavioral effects of these drugs on normally developing brains and determines their reversibility with post-drug intervention. Mice at different postnatal ages received short courses of molecularly targeted drugs in regimens analagous to clinical treatment. Analysis of rapidly developing brain structures important for sensorimotor and cognitive function showed that, while adult administration was without effect, earlier neonatal administration of targeted therapies attenuated white matter oligodendroglia and hippocampal neuronal development more profoundly than later administration, leading to long-lasting behavioral deficits. This functional impairment was reversed by rehabilitation with physical and cognitive enrichment. Our findings demonstrate age-dependent, reversible effects of these drugs on brain development, which are important considerations as treatment options expand for pediatric cancers.Significance: Targeted therapeutics elicit age-dependent long-term consequences on the developing brain that can be ameliorated with environmental enrichment. Cancer Res; 78(8); 2081-95. ©2018 AACR.

Up-regulation of MSH6 is associated with temozolomide resistance in human glioblastoma

The impact of DNA mismatch repair (MMR) on resistance to temozolomide (TMZ) therapy in patients with glioblastoma (GBM) is recently reported but the mechanisms are not understood. We aim to analyze the correlation between MMR function and the acquired TMZ resistance in GBM using both relevant clinical samples and TMZ resistant cells. First we found increased expression of MSH6, one of key components of MMR, in recurrent GBM patients' samples who underwent TMZ chemotherapy, comparing with those matched samples collected at the time of diagnosis. Using the cellular models of acquired resistance to TMZ, we further confirmed the up-regulation of MSH6 in TMZ resistant cells. Moreover, a TCGA dataset contains a large cohort of GBM clinical samples with or without TMZ treatment reinforced the increased expression of MSH6 and other MMR genes after long-term TMZ chemotherapy, which may resulted in MMR dysfunction and acquired TMZ resistance. Our results suggest that increased expression of MSH6, or other MMR, may be a new mechanism contributing to the acquired resistance during TMZ therapy; and may serve as an indicator to the resistance in GBM.

Therapeutic Potential of Thymoquinone in Glioblastoma Treatment: Targeting Major Gliomagenesis Signaling Pathways

Glioblastoma multiforme (GBM) is one of the most devastating brain tumors with median survival of one year and presents unique challenges to therapy because of its aggressive behavior. Current treatment strategy involves surgery, radiotherapy, immunotherapy, and adjuvant chemotherapy even though optimal management requires a multidisciplinary approach and knowledge of potential complications from both the disease and its treatment. Thymoquinone (TQ), the main bioactive component of Nigella sativa L., has exhibited anticancer effects in numerous preclinical studies. Due to its multitargeting nature, TQ interferes in a wide range of tumorigenic processes and counteract carcinogenesis, malignant growth, invasion, migration, and angiogenesis. TQ can specifically sensitize tumor cells towards conventional cancer treatments and minimize therapy-associated toxic effects in normal cells. Its potential to enter brain via nasal pathway due to volatile nature of TQ adds another advantage in overcoming blood-brain barrier. In this review, we summarized the potential role of TQ in different signaling pathways in GBM that have undergone treatment with standard therapeutic modalities or with TQ. Altogether, we suggest further comprehensive evaluation of TQ in preclinical and clinical level to delineate its implied utility as novel therapeutics to combat the challenges for the treatment of GBM.

LBH589 Inhibits Glioblastoma Growth and Angiogenesis Through Suppression of HIF-1α Expression

Glioblastoma (GBM) is an angiogenic malignancy with a highly unfavorable prognosis. Angiogenesis in GBM represents an adaptation to a hypoxic microenvironment and is correlated with tumor growth, invasion, clinical recurrence, and lethality. LBH589 (also called panobinostat) is a histone deacetylase (HDAC) inhibitor with potent antitumor activity. In the current study, we investigated the mechanism and effects of LBH589 on GBM growth and hypoxia-induced angiogenesis in vitro and in vivo. To determine the antitumor and angiogenesis activity and mechanism of LBH589, we used cell proliferations in vitro and GBM xenografts in vivo. To clarify mechanisms of LBH589 on angiogenesis, HDAC assay, RT-PCR, Western blot, and co-immunoprecipitation assays were performed. We found LBH589 displayed significant antitumor effects on GBM as demonstrated by inhibited cell proliferation, slower tumor growth, and decreased microvessel density of subcutaneous xenografts. These actions of LBH589 resulted from the disruption of heat shock protein 90/HDAC6 complex, increased HIF-1α instability and degradation, and decreased VEGF expression. Our results indicate the potential antiangiogenic activity of LBH589 in human GBM and provide some preclinical data to warrant further exploration of HDAC inhibitors for the treatment of advanced glioma. Moreover, our study supports the role of HDAC inhibitors as a therapeutic strategy to target tumor angiogenesis.

Response Assessment in Neuro-Oncology Clinical Trials

Development of novel therapies for CNS tumors requires reliable assessment of response and progression. This requirement has been particularly challenging in neuro-oncology for which contrast enhancement serves as an imperfect surrogate for tumor volume and is influenced by agents that affect vascular permeability, such as antiangiogenic therapies. In addition, most tumors have a nonenhancing component that can be difficult to accurately quantify. To improve the response assessment in neuro-oncology and to standardize the criteria that are used for different CNS tumors, the Response Assessment in Neuro-Oncology (RANO) working group was established. This multidisciplinary international working group consists of neuro-oncologists, medical oncologists, neuroradiologists, neurosurgeons, radiation oncologists, neuropsychologists, and experts in clinical outcomes assessments, working in collaboration with government and industry to enhance the interpretation of clinical trials. The RANO working group was originally created to update response criteria for high- and low-grade gliomas and to address such issues as pseudoresponse and nonenhancing tumor progression from antiangiogenic therapies, and pseudoprogression from radiochemotherapy. RANO has expanded to include working groups that are focused on other tumors, including brain metastases, leptomeningeal metastases, spine tumors, pediatric brain tumors, and meningiomas, as well as other clinical trial end points, such as clinical outcomes assessments, seizures, corticosteroid use, and positron emission tomography imaging. In an effort to standardize the measurement of neurologic function for clinical assessment, the Neurologic Assessment in Neuro-Oncology scale was drafted. Born out of a workshop conducted by the Jumpstarting Brain Tumor Drug Development Coalition and the US Food and Drug Administration, a standardized brain tumor imaging protocol now exists to reduce variability and improve reliability. Efforts by RANO have been widely accepted and are increasingly being used in neuro-oncology trials, although additional refinements will be needed.

Rapamycin (mTORC1 inhibitor) reduces the production of lactate and 2-hydroxyglutarate oncometabolites in IDH1 mutant fibrosarcoma cells

BACKGROUND

Multiple studies concluded that oncometabolites (e.g. D-2-hydroxyglutarate (2-HG) related to mutant isocitrate dehydrogenase 1/2 (IDH1/2) and lactate) have tumour promoting potential. Regulatory mechanisms implicated in the maintenance of oncometabolite production have great interest. mTOR (mammalian target of rapamycin) orchestrates different pathways, influences cellular growth and metabolism. Considering hyperactivation of mTOR in several malignancies, the question has been addressed whether mTOR operates through controlling of oncometabolite accumulation in metabolic reprogramming.

METHODS

HT-1080 cells - carrying originally endogenous IDH1 mutation - were used in vitro and in vivo. Anti-tumour effects of rapamycin were studied using different assays. The main sources and productions of the oncometabolites (2-HG and lactate) were analysed by ¹³C-labeled substrates. Alterations at protein and metabolite levels were followed by Western blot, flow cytometry, immunohistochemistry and liquid chromatography mass spectrometry using rapamycin, PP242 and different glutaminase inhibitors, as well.

RESULTS

Rapamycin (mTORC1 inhibitor) inhibited proliferation, migration and altered the metabolic activity of IDH1 mutant HT-1080 cells. Rapamycin reduced the level of 2-HG sourced mainly from glutamine and glucose derived lactate which correlated to the decreased incorporation of ¹³C atoms from ¹³C-substrates. Additionally, decreased expressions of lactate dehydrogenase A and glutaminase were also observed both in vitro and in vivo.

CONCLUSIONS

Considering the role of lactate and 2-HG in regulatory network and in metabolic symbiosis it could be assumed that mTOR inhibitors have additional effects besides their anti-proliferative effects in tumours with glycolytic phenotype, especially in case of IDH1 mutation (e.g. acute myeloid leukemias, gliomas, chondrosarcomas). Based on our new results, we suggest targeting mTOR activity depending on the metabolic and besides molecular genetic phenotype of tumours to increase the success of therapies.