The mTOR signaling pathway as a treatment target for intracranial neoplasms

European Association of Neuro-Oncology guideline on molecular testing of meningiomas for targeted therapy selection

Meningiomas are the most common primary intracranial tumors of adults. For meningiomas that progress or recur despite surgical resection and radiotherapy, additional treatment options are limited due to a lack of proven efficacy. Meningiomas show recurring molecular aberrations, which may serve as predictive markers for systemic pharmacotherapies with targeted drugs or immunotherapy, radiotherapy, or radioligand therapy. Here, we review the evidence for a predictive role of a wide range of molecular alterations and markers including NF2, AKT1, SMO, SMARCE1, PIK3CA, CDKN2A/B, CDK4/6, TERT, TRAF7, BAP1, KLF4,ARID1/2, SUFU, PD-L1, SSTR2A, PR/ER, mTOR, VEGF(R), PDGFR, as well as homologous recombination deficiency, genomic copy number variations, DNA methylation classes, and combined gene expression profiles. In our assessment based on the established ESMO ESCAT (European Society for Medical Oncology Scale for Clinical Actionability of molecular Targets) evidence-level criteria, no molecular target reached ESCAT I ("ready for clinical use") classification, and only mTOR pathway activation and NF2 alterations reached ESCAT II ("investigational") classification, respectively. Our evaluations may guide targeted therapy selection in clinical practice and clinical trial efforts and highlight areas for which additional research is warranted.

Meningioma: Novel Diagnostic and Therapeutic Approaches

Background/Objectives: Meningiomas are the most common intracranial tumors. Surgery and radiation therapy are the cornerstones of treatment and no standard of care therapy exists for refractory meningiomas. This manuscript aims to provide a comprehensive review of novel diagnostic and therapeutic approaches against these tumors. Methods: A search for the existing literature on systemic therapies for meningiomas was performed on PubMed and a search for presently accruing clinical trials was performed on ClinicalTrials.gov. Results: Systemic treatments, including chemotherapy, somatostatin analogs, anti-hormone therapy, and anti-angiogenic therapy, have been extensively studied with marginal success. Targeted therapies are actively being studied for the treatment of meningiomas, including focal adhesion kinase (FAK), sonic hedgehog signaling pathway, phosphoinositide-3-kinase (PI3K), and cyclin-dependent kinases (CDK) inhibitors. These driver mutations are present only in a subset of meningiomas. In stark contrast, somatostatin receptor 2 (SSTR2) is ubiquitously expressed in meningiomas and was formerly targeted with somatostatin analogs with modest success. Theranostic SSTR2-targeting via [68Ga]DOTATATE for PET imaging and β-emitting [177Lu]DOTATATE for the treatment of meningiomas are currently under active investigation. Conclusions: A nuanced approach is needed for the treatment of refractory meningiomas. Targeted therapies show promise.

Extra-temporal pediatric low-grade gliomas and epilepsy

Low-grade gliomas, especially glioneuronal tumors, are a common cause of epilepsy in children. Seizures associated with low-grade pediatric tumors are medically refractory and present a significant burden to patients. Often, morbidity and patients´ quality of life are determined rather by the control of seizures than the oncological process itself and the resolution of epilepsy represents an important part in the treatment of LGGs. The pathogenesis of tumor-related seizures in focal LGG tumors is multifactorial, and mechanisms differ probably among patients and tumor types. Pediatric low-grade tumors associated with epilepsy include a series of neoplasms that have a pure astrocytic or glioneuronal lineage. They are usually benign tumors with a neocortical localization typically in the temporal lobes, but also in other supratentorial locations. Gangliogliomas and dysembryoplastic neuroepithelial tumors (DNET) are the most common entities together with astrocytic gliomas (pilocytic astrocytomas and pleomorphic xanthoastrocytoma) and angiocentric gliomas, and dual pathology is found in up to 40% of glioneuronal tumors. The treatment of low-grade gliomas and associated epilepsy is based mainly on resection and the extent of surgery is the main predictor of postoperative seizure control in patients with a LGG. Long-term epilepsy-associated tumors (LEATs) tend to be well-circumscribed, and therefore, the chances for a complete resection and epilepsy control with a safe approach are very high. New treatments have emerged as alternatives to open microsurgical approaches, including laser thermal ablation or the use of BRAF inhibitors. Future advances in identifying seizure-related biomarkers and molecular tumor pathways will facilitate targeted treatment strategies that will have a deep impact both in oncologic and epilepsy outcomes.

Intramedullary pediatric low-grade glioma of the spine

PURPOSE

Pediatric intramedullary spinal cord low-grade gliomas (pLGGs) are rare diagnoses among central nervous system (CNS) tumors in the pediatric population. The classic presentation of the patients includes some degree of neurologic deficit, although many times the symptoms are vague which leads to delayed diagnosis.

MATERIAL AND METHODS

The first step in the diagnosis includes special parameters in spinal imaging, particularly magnetic resonance imaging (MRI), and surgical resection remains the cornerstone for both diagnosis and treatment. Yet, recent years advancement in molecular and genetic understanding of CNS tumors allows for better adjustment of the treatment and follow-up regimens. Based on postoperative status, adjuvant therapy may provide additional therapeutic advantage for some types of tumors.

CONCLUSION

Ultimately, patients have a very promising prognosis when treated appropriately in most of the cases of pediatric spinal cord LGG with continued advances arising. This manuscript summarizes the most contemporary evidence regarding clinical and treatment features of intramedullary pLGGs.

Novel Advances in Treatment of Meningiomas: Prognostic and Therapeutic Implications

Meningiomas are the most frequent histotypes of tumors of the central nervous system. Their incidence is approximately 35% of all primary brain tumors. Although they have the status of benign lesions, meningiomas are often associated with a decreased quality of life due to focal neurological deficits that may be related. The optimal treatment is total resection. Histological grading is the most important prognostic factor. Recently, molecular alterations have been identified that are specifically related to particular phenotypes and, probably, are also responsible for grading, site, and prognostic trend. Meningiomas recur in 10-25% of cases. In these cases, and in patients with atypical or anaplastic meningiomas, the methods of approach are relatively insufficient. To date, data on the molecular biology, genetics, and epigenetics of meningiomas are insufficient. To achieve an optimal treatment strategy, it is necessary to identify the mechanisms that regulate tumor formation and progression. Combination therapies affecting multiple molecular targets are currently opening up and have significant promise as adjuvant therapeutic options. We review the most recent literature to identify studies investigating recent therapeutic treatments recently used for meningiomas.

Unlocking the power of precision medicine for pediatric low-grade gliomas: molecular characterization for targeted therapies with enhanced safety and efficacy

In the past decade significant advancements have been made in the discovery of targetable lesions in pediatric low-grade gliomas (pLGGs). These tumors account for 30-50% of all pediatric brain tumors with generally a favorable prognosis. The latest 2021 WHO classification of pLGGs places a strong emphasis on molecular characterization for significant implications on prognosis, diagnosis, management, and the potential target treatment. With the technological advances and new applications in molecular diagnostics, the molecular characterization of pLGGs has revealed that tumors that appear similar under a microscope can have different genetic and molecular characteristics. Therefore, the new classification system divides pLGGs into several distinct subtypes based on these characteristics, enabling a more accurate strategy for diagnosis and personalized therapy based on the specific genetic and molecular abnormalities present in each tumor. This approach holds great promise for improving outcomes for patients with pLGGs, highlighting the importance of the recent breakthroughs in the discovery of targetable lesions.

Taste-immune associative learning amplifies immunopharmacological effects and attenuates disease progression in a rat glioblastoma model

Mechanistic target of rapamycin (mTOR)-signaling is one key driver of glioblastoma (GBM), facilitating tumor growth by promoting the shift to an anti-inflammatory, pro-cancerogenic microenvironment. Even though mTOR inhibitors such as rapamycin (RAPA) have been shown to interfere with GBM disease progression, frequently chaperoned toxic drug side effects urge the need for developing alternative or supportive treatment strategies. Importantly, previous work document that taste-immune associative learning with RAPA may be utilized to induce learned pharmacological placebo responses in the immune system. Against this background, the current study aimed at investigating the potential efficacy of a taste-immune associative learning protocol with RAPA in a syngeneic GBM rat model. Following repeated pairings of a novel gustatory stimulus with injections of RAPA, learned immune-pharmacological effects could be retrieved in GBM-bearing animals when re-exposed to the gustatory stimulus together with administering 10 % amount of the initial drug dose (0.5 mg/kg). These inhibitory effects on tumor growth were accompanied by an up-regulation of central and peripheral pro-inflammatory markers, suggesting that taste-immune associative learning with RAPA promoted the development of a pro-inflammatory anti-tumor microenvironment that attenuated GBM tumor growth to an almost identical outcome as obtained after 100 % (5 mg/kg) RAPA treatment. Together, our results confirm the applicability of taste-immune associative learning with RAPA in animal disease models where mTOR overactivation is one key driver. This proof-of-concept study may also be taken as a role model for implementing learning protocols as alternative or supportive treatment strategy in clinical settings, allowing the reduction of required drug doses and side effects without losing treatment efficacy.

Medical Treatment of Pediatric Low-Grade Glioma

Low-grade glioma (LGG) is the most common brain tumor in children and has excellent long-term survival. With an excellent survival rate, the choice of treatment involves careful consideration of minimizing late toxicity from surgery, radiation, and chemotherapy. Surgery, radiation therapy, and chemotherapy can be used as monotherapy or in combination, providing different therapeutic ratios and complications. As a result, establishing the selection of ideal therapies has been a controversial area, presenting challenges. Recent advances in understanding molecular characteristics of pediatric LGG affect classification and treatment approaches. This review aims to overview recent developments in medical treatment in pediatric LGG.

Co-Targeting MAP Kinase and Pi3K-Akt-mTOR Pathways in Meningioma: Preclinical Study of Alpelisib and Trametinib

Simple Summary

Multi recurrent or high-grade meningiomas remain an unmet medical need in neuro-oncology. Several studies have highlighted the potential therapeutic efficacy of mTor inhibitors to control tumoral growth of meningiomas. However, a positive feedback on AKT oncogenic pathway from these drugs may explain the modest success. Our aim was to target Pi3kinase upstream mTor, and MAP kinase pathway, overactivated in meningiomas, alone or in combined targeting in comparison to mTor targeting. Our in vitro results obtained on three meningioma cell lines and on a large series of fresh human meningiomas, including 35 WHO grade 1, 23 grade 2, and five grade 3, showed that co-targeting Pi3kinase and MAP kinase seemed promising, opening new therapeutic strategies in these tumors.

Abstract

Recurrent or high-grade meningiomas are an unmet medical need. Recently, we demonstrated that targeting mTOR by everolimus was relevant both in vitro and in humans. However, everolimus induces an AKT activation that may impact the anti-proliferative effect of the drug. Moreover, the MAP kinase pathway was shown to be involved in meningioma tumorigenesis. We therefore targeted both the Pi3k-AKT-mTOR and MAP kinase pathways by using combinations of the Pi3k inhibitor alpelisib and the MEK inhibitor trametinib. Our study was performed in vitro on the human meningioma cell lines and on a large series of primary cultures providing from 63 freshly operated meningiomas including 35 WHO grade 1, 23 grade 2, and five grade 3, half of which presented a NF2 genomic alteration. Alpelisib induced a higher inhibitory effect on cell viability and proliferation than everolimus in all cell lines and 32 randomly selected tumors no matter the genomic status, the histological subtype or grade. Trametinib also strongly inhibited cell proliferation and induced AKT activation. Combined treatment with alpelisib plus trametinib reversed the AKT activation induced by trametinib and induced an additive inhibitory effect irrespective of the cell lines or tumor features. Co-targeting pathways seems promising and may be considered particularly for aggressive meningioma.

mTOR Signaling and Potential Therapeutic Targeting in Meningioma

Meningiomas are the most frequent primary tumors arising in the central nervous system. They typically follow a benign course, with an excellent prognosis for grade I lesions through surgical intervention. Although radiotherapy is a good option for recurrent, progressive, or inoperable tumors, alternative treatments are very limited. mTOR is a protein complex with increasing therapeutical potential as a target in cancer. The current understanding of the mTOR pathway heavily involves it in the development of meningioma. Its activation is strongly dependent on PI3K/Akt signaling and the merlin protein. Both factors are commonly defective in meningioma cells, which indicates their likely function in tumor growth. Furthermore, regarding molecular tumorigenesis, the kinase activity of the mTORC1 complex inhibits many components of the autophagosome, such as the ULK1 or Beclin complexes. mTOR contributes to redox homeostasis, a vital component of neoplasia. Recent clinical trials have investigated novel chemotherapeutic agents for mTOR inhibition, showing promising results in resistant or recurrent meningiomas.

SF3B1 inhibition disrupts malignancy and prolongs survival in glioblastoma patients through BCL2L1 splicing and mTOR/ß-catenin pathways imbalances

BACKGROUND

Glioblastoma is one of the most devastating cancer worldwide based on its locally aggressive behavior and because it cannot be cured by current therapies. Defects in alternative splicing process are frequent in cancer. Recently, we demonstrated that dysregulation of the spliceosome is directly associated with glioma development, progression, and aggressiveness.

METHODS

Different human cohorts and a dataset from different glioma mouse models were analyzed to determine the mutation frequency as well as the gene and protein expression levels between tumor and control samples of the splicing-factor-3B-subunit-1 (SF3B1), an essential and druggable spliceosome component. SF3B1 expression was also explored at the single-cell level across all cell subpopulations and transcriptomic programs. The association of SF3B1 expression with relevant clinical data (e.g., overall survival) in different human cohorts was also analyzed. Different functional (proliferation/migration/tumorspheres and colonies formation/VEGF secretion/apoptosis) and mechanistic (gene expression/signaling pathways) assays were performed in three different glioblastomas cell models (human primary cultures and cell lines) in response to SF3B1 blockade (using pladienolide B treatment). Moreover, tumor progression and formation were monitored in response to SF3B1 blockade in two preclinical xenograft glioblastoma mouse models.

RESULTS

Our data provide novel evidence demonstrating that the splicing-factor-3B-subunit-1 (SF3B1, an essential and druggable spliceosome component) is low-frequency mutated in human gliomas (~ 1 %) but widely overexpressed in glioblastoma compared with control samples from the different human cohorts and mouse models included in the present study, wherein SF3B1 levels are associated with key molecular and clinical features (e.g., overall survival, poor prognosis and/or drug resistance). Remarkably, in vitro and in vivo blockade of SF3B1 activity with pladienolide B drastically altered multiple glioblastoma pathophysiological processes (i.e., reduction in proliferation, migration, tumorspheres formation, VEGF secretion, tumor initiation and increased apoptosis) likely by suppressing AKT/mTOR/ß-catenin pathways, and an imbalance of BCL2L1 splicing.

CONCLUSIONS

Together, we highlight SF3B1 as a potential diagnostic and prognostic biomarker and an efficient pharmacological target in glioblastoma, offering a clinically relevant opportunity worth to be explored in humans.

Comprehensive overview of extracellular vesicle proteomics in meningioma: future strategy

Background

Meningioma arising from meninges is one among the various types of brain tumors. Others are, astrocytomas originating from astrocyte, oligodendrogliomas originating from oligodendrocyte, Ependymomas originating from ependymal cells and medulloblastomas originating from neurons. Current knowledge of molecular biology, genetics and epigenetics of meningioma is not sufficient. Therefore, In depth understanding of the mechanism of meningioma formation and progression is needed for its treatment and management. Grade I Grade I meningiomas are majorly classified as grade I, grade II and grade III. Meningioma can be indolent, slow growing or can be invasive and metastatic which can recurre. Grade I meningioma can be removed by surgery in comparison to invasive meningioma which may recurre with high propensity. This property of recurrence is responsible for high morbidity and mortality. Meningioma are majorly classified into three classes namely grade I, grade II, grade III. Protein biomarkers are considered as promising candidates for the diagnosis of meningioma.

Study

Various studies done on differential expression of proteins have shown increased expression of EGFR, NEK9, EPS812, CKAP4, SET and STAT2, in all the three grades of meningioma. Additionally, some proteins like HK2 are overexpressed in grade II and grade III meningioma than in grade I meningioma. Protein Markers, found on extracellular vesicles of different grades of meningioma can serve the same purpose. A test done on a sample of any kind of body fluid like blood, tear, saliva, urine etc. for recognizing the circulating cancer cells or DNA and extracellular vesicles released from them to help detecting the early stage of cancer is known as liquid biopsy. Solid biopsy has several limitations as compared to liquid biopsy. This is because the samples can be easily collected and studied in case of liquid biopsy. Exosomes are related with liquid biopsy and hence provide platform for better diagnosis, prognosis and treatment of any type of cancer including meningioma. Exosomal tetraspanin are important example of exosomal biomarkers. The tetraspanin network is a molecular scaffold which connects various proteins for signal transduction.

Conclusion

This study tells about the utility of proper knowledge of extracellular vesicle proteins and their profiles in different grades, which can help in better understanding of pathogenesis, diagnosis, prognosis and treatment of meningioma. In Addition to use of these proteins as biomarkers, role of exosomes in currently available therapeutic approaches has been discussed.

Genomic Biomarkers of Meningioma: A Focused Review

Meningiomas represent a phenotypically and genetically diverse group of tumors which often behave in ways that are not simply explained by their pathologic grade. The genetic landscape of meningiomas has become a target of investigation as tumor genomics have been found to impact tumor location, recurrence risk, and malignant potential. Additionally, targeted therapies are being developed that in the future may provide patients with personalized chemotherapy based on the genetic aberrations within their tumor. This review focuses on the most common genetic mutations found in meningiomas of all grades, with an emphasis on the impact on tumor location and clinically relevant tumor characteristics. NF-2 and the non-NF-2 family of genetic mutations are summarized in the context of low-grade and high-grade tumors, followed by a comprehensive discussion regarding the genetic and embryologic basis for meningioma location and phenotypic heterogeneity. Finally, targeted therapies based on tumor genomics currently in use and under investigation are reviewed and future avenues for research are suggested. The field of meningioma genomics has broad implications on the way meningiomas will be treated in the future, and is gradually shifting the way clinicians approach this diverse group of tumors.

CKS2 (CDC28 protein kinase regulatory subunit 2) is a prognostic biomarker in lower grade glioma: a study based on bioinformatic analysis and immunohistochemistry

Gliomas account for the highest cases of primary brain malignancies. Whereas previous studies have demonstrated the roles of CDC28 Protein Kinase Regulatory Subunit 2 (CKS2) in various cancer types, its functions in lower grade gliomas (LGGs) remain elusive. This study aimed to profile the expression and functions of CKS2 in LGG. Multiple online databases such as The Cancer Genome Atlas (TCGA), the Chinese Glioma Genome Atlas (CGGA), Gene Expression Profiling Interactive Analysis 2nd edition (GEPIA2), Tumor Immune Estimation Resource 2nd edition (TIMER2.0) as well as Gene Expression Omnibus (GEO) were used in this study. Immunohistochemistry (IHC) was performed to evaluate CKS2 protein expression. Our data demonstrated upregulation of CKS2 in LGG tissues at both mRNA and protein level, especially in grade III gliomas. Similarly, there was increased expression of CKS2 in isocitrate dehydrogenase 1 (IDH1) wildtype gliomas. In addition, increased DNA copy number and DNA hypomethylation might be associated with the upregulation of the CKS2 in LGG. Using the Kaplan–Meier survival analysis and the Cox regression analysis, CKS2 was shown to be independently associated with poor prognosis of LGG patients. Receiver operating characteristic (ROC) analysis revealed that CKS2 could effectively predict the 1-, 3- and 5-year survival rates of LGG patients. Enrichment analyses revealed that CKS2 was mainly involved in the regulation of the cell cycle in LGG. Taken together, our study demonstrated that CKS2 might be a candidate prognostic biomarker for LGG and could predict the survival rates of LGG patients.

Abbreviations: LGG: lower grade glioma; CKS2: CDC28 protein kinase regulatory subunit 2; TCGA: The Cancer Genome Atlas; CGGA: the Chinese Glioma Genome Atlas; GEO: Gene Expression Omnibus; GEPIA: Gene Expression Profiling Interactive Analysis; TIMER: Tumor Immune Estimation Resource; IHC: immunohistochemistry; qRT-PCR: quantitative real-time polymerase chain reaction; PBS: phosphate buffered saline; DAB: diaminobenzidine tetrachloride; OS: overall survival; CAN: copy number alteration; IDH: Isocitrate dehydrogenase; GSEA: Gene Set Enrichment Analysis; DEG: differentially expressed gene; KEGG: Kyoto encyclopedia of genes and genomes; GO: Gene ontology; BP: biological process; CC: cellular component; MF: molecular function; NES: normalized enrichment score; NOM: nominal; FDR: false discovery rate

Review of PP2A Tumor Biology and Antitumor Effects of PP2A Inhibitor LB100 in the Nervous System

Simple Summary

Central and peripheral nervous system tumors represent a heterogenous group of neoplasms which often demonstrate resistance to treatment. Given that these tumors are often refractory to conventional therapy, novel pharmaceutical regimens are needed for successfully treating this pathology. One such therapeutic is the serine/threonine phosphatase inhibitor, LB100. LB100 is a water-soluble competitive protein phosphtase inhibitor that has demonstrated antitumor effects in preclinical and clinical trials. In this review, we aim to summarize current evidence demonstrating the efficacy of LB100 as an inhibitor of nervous system tumors. Furthermore, we review the involvement of the well-studied phosphatase, protein phosphatase 2A, in oncogenic cell signaling pathways, neurophysiology, and neurodevelopment.

Abstract

Protein phosphatase 2A (PP2A) is a ubiquitous serine/threonine phosphatase implicated in a wide variety of regulatory cellular functions. PP2A is abundant in the mammalian nervous system, and dysregulation of its cellular functions is associated with myriad neurodegenerative disorders. Additionally, PP2A has oncologic implications, recently garnering attention and emerging as a therapeutic target because of the antitumor effects of a potent PP2A inhibitor, LB100. LB100 abrogation of PP2A is believed to exert its inhibitory effects on tumor progression through cellular chemo- and radiosensitization to adjuvant agents. An updated and unifying review of PP2A biology and inhibition with LB100 as a therapeutic strategy for targeting cancers of the nervous system is needed, as other reviews have mainly covered broader applications of LB100. In this review, we discuss the role of PP2A in normal cells and tumor cells of the nervous system. Furthermore, we summarize current evidence regarding the therapeutic potential of LB100 for treating solid tumors of the nervous system.

High IER5 Gene Expression Is Associated With Poor Prognosis in Glioma Patients

Objective

Immediate early response 5 (IER5) plays a core role in cell cycle and response to irradiation. However, its role in glioma remains unclear. We aimed to evaluate its prognostic significance in glioma based on The Cancer Genome Atlas data resource.

Methods

The Kruskal–Wallis test, Wilcoxon signed-rank test, and logistic regression were employed to explore the relationship between IER5 expression and clinicopathological features. Kaplan–Meier and Cox regression analyses were implemented to investigate the relationship of IER5 with prognosis. A nomogram to estimate the impact of IER5 on prognosis was created based on the Cox multivariate data. We performed gene set enrichment analysis (GSEA) to determine the key signaling cascades associated with IER5. Immunohistochemistry was performed to examine IER5 expression in a tissue microarray (TMA) of glioma samples.

Results

Immediate early response 5 gene expression was elevated in glioma patients. The level of IER5 was significantly correlated with WHO grade [OR = 6.71 (4.34–10.68) for G4 vs. G2 and G3], IDH (isocitrate dehydrogenase enzyme) status [OR = 13.35 (8.92–20.46) for wild-type (WT) vs. mutated (Mut)], epidermal growth factor receptor status [OR = 8.42 (4.32–18.43) for Mut vs. WT], age [OR = 0.27 (0.18–0.41) for ≤ 60 years vs. >60 years], and histological type [OR = 7.13 (4.63–11.31] for glioblastoma vs. astrocytoma, oligoastrocytoma, and oligodendroglioma). Univariate analyses revealed that high IER5 expression was linked to short overall survival (OS) [hazard ratio (HR): 3.747; 95% confidence interval (CI): 2.847–4.933; and P < 0.001]. High IER5 expression was linked to poor OS in multivariate analyses (HR: 2.474; 95% CI: 1.552–3.943; and P < 0.001). TMA results showed that high IER5 protein levels were related to short OS (HR: 1.84; 95% CI: 1.10–3.07; and P = 0.021) and poor disease-specific survival (HR: 1.82; 95% CI: 1.09–3.04; and P = 0.023). GSEA showed that many tumor related pathways were enriched differentially in the IER5-high expression group. The C-index and calibration plots of the nomogram showed an effective estimation performance in glioma patients.

Conclusion

Herein, we established that IER5 plays a critical role in glioma progression and prognosis, which might be an important biomarker for the prognosis of glioma patients.

Upfront treatment with mTOR inhibitor everolimus in pediatric low-grade gliomas: A single-center experience

Pediatric low-grade gliomas (pLGGs) are the most frequent brain tumor in children. Adjuvant treatment, consisting in chemotherapy and radiotherapy, is often necessary if a complete surgical resection cannot be obtained. Traditional treatment approaches result in a significant long-term morbidity, with a detrimental impact on quality of life. Dysregulation of the mitogen-activated protein kinase (MAPK) pathway is the molecular hallmark of pLGGs and hyperactivation of the downstream mammalian target of rapamycin (mTOR) pathway is frequently observed. We report clinical and radiological results of front-line treatment with everolimus in 10 consecutive patients diagnosed with m-TOR positive pLGGs at the Bambino Gesù Children's Hospital in Rome, Italy. Median duration of treatment was 19 months (range from 13-60). Brain magnetic resonance imaging showed stable disease in 7 patients, partial response in 1 and disease progression in 2. Therapy-related adverse events were always reversible after dose reduction or temporary treatment interruption. To the best of our knowledge, this is the first report of everolimus treatment for chemo- and radiotherapy-naïve children with pLGG. Our results provide preliminary support, despite low sample size, for the use of everolimus as target therapy in pLGG showing lack of progression with a manageable toxicity profile.

Autophagy mediated lipid catabolism facilitates glioma progression to overcome bioenergetic crisis

BACKGROUND

Activation of mTORC1 plays a significant role in cancer development and progression. However, the metabolic mechanisms to sustain mTORC1 activation of cancer cells within stressed environments are still under-appreciated. We recently revealed high autophagy activity in tumour cells with mTORC1 hyper-activation. Nevertheless, the functions and mechanisms of autophagy in regulating mTORC1 in glioma are not studied.

METHODS

Using glioma patient database and human glioma cells, we assessed the mechanisms and function of selective autophagy to sustain mTORC1 hyper-activation in glioma.

RESULTS

We revealed a strong association of altered mRNA levels in mTORC1 upstream and downstream genes with prognosis of glioma patients. Our results indicated that autophagy-mediated lipid catabolism was essential to sustain mTORC1 activity in glioma cells under energy stresses. We found that autophagy inhibitors or fatty acid oxidation (FAO) inhibitors in combination with 2-Deoxy-D-glucose (2DG) decreased energy production and survival of glioma cells in vitro. Consistently, inhibition of autophagy or FAO inhibitors with 2DG effectively suppressed the progression of xenografted glioma with hyper-activated mTORC1.

CONCLUSIONS

This study established an autophagy/lipid degradation/FAO/ATP generation pathway, which might be used in brain cancer cells under energy stresses to maintain high mTORC1 signalling for tumour progression.

A POETIC Phase II study of continuous oral everolimus in recurrent, radiographically progressive pediatric low-grade glioma

BACKGROUND

To evaluate efficacy, pharmacokinetics (PK) and pharmacodynamics of single-agent everolimus in pediatric patients with radiographically progressive low-grade glioma (LGG).

METHODS

Everolimus was administered at 5 mg/m² once daily as a tablet or liquid for a planned 48-week duration or until unacceptable toxicity or disease progression. Patients with neurofibromatosis type 1 were excluded. PK and pharmacodynamic endpoints were assessed in consenting patients.

RESULTS

Twenty-three eligible patients (median age 9.2 years) were enrolled. All patients received prior chemotherapy (median number of prior regimens two) and/or radiotherapy (two patients). By week 48, two patients had a partial response, 10 stable disease, and 11 clinical or radiographic progression; two discontinued study prior to 1 year (toxicity: 1, physician determination: 1). With a median follow up of 1.8 years (range 0.2-6.7 years), the 2-, 3-, and 5-year progression-free survivals (PFS) were 39 ± 11%, 26 ± 11%, and 26 ± 11%, respectively; two patients died of disease. The 2-, 3-, and 5-year overall survival (OS) were all 93 ± 6%. Grade 1 and 2 toxicities predominated; two definitively related grade 3 toxicities (mucositis and neutropenia) occurred. Grade 4 elevation of liver enzymes was possibly related in one patient. Predose blood levels showed substantial variability between patients with 45.5% below and 18.2% above the target range of 5-15 ng/mL. Pharmacodynamic analysis demonstrated significant inhibition in phospho-S6, 4E-BP1, and modulation of c-Myc expression.

CONCLUSION

Daily oral everolimus provides a well-tolerated, alternative treatment for multiple recurrent, radiographically progressive pediatric LGG. Based on these results, everolimus is being investigated further for this patient population.

The glutamine antagonist prodrug JHU-083 slows malignant glioma growth and disrupts mTOR signaling

Background

Metabolic reprogramming is a common feature in cancer, and it is critical to facilitate cancer cell growth. Isocitrate Dehydrogenase 1/2 (IDH1 and IDH2) mutations (IDHmut) are the most common genetic alteration in glioma grade II and III and secondary glioblastoma and these mutations increase reliance on glutamine metabolism, suggesting a potential vulnerability. In this study, we tested the hypothesis that the brain penetrant glutamine antagonist prodrug JHU-083 reduces glioma cell growth.

Material and Methods

We performed cell growth, cell cycle, and protein expression in glutamine deprived or Glutaminase (GLS) gene silenced glioma cells. We tested the effect of JHU-083 on cell proliferation, metabolism, and mTOR signaling in cancer cell lines. An orthotopic IDH1R132H glioma model was used to test the efficacy of JHU-083 in vivo.

Results

Glutamine deprivation and GLS gene silencing reduced glioma cell proliferation in vitro in glioma cells. JHU-083 reduced glioma cell growth in vitro, modulated cell metabolism, and disrupted mTOR signaling and downregulated Cyclin D1 protein expression, through a mechanism independent of TSC2 modulation and glutaminolysis. IDH1R132H isogenic cells preferentially reduced cell growth and mTOR signaling downregulation. In addition, guanine supplementation partially rescued IDHmut glioma cell growth, mTOR signaling, and Cyclin D1 protein expression in vitro. Finally, JHU-083 extended survival in an intracranial IDH1 mut glioma model and reduced intracranial pS6 protein expression.

Conclusion

Targeting glutamine metabolism with JHU-083 showed efficacy in preclinical models of IDHmut glioma and measurably decreased mTOR signaling.

Molecular Mechanism and Approach in Progression of Meningioma

Meningioma is the most common tumor of the central nervous system, most of which is benign. Even after complete resection, a high rate of recurrence of meningioma is observed. From in-depth study of its pathogenesis, it has been found that a number of chromosomal variations and abnormal molecular signals are closely related to the occurrence and development of malignancy in meningioma, which may provide the theoretical basis and potential direction for accurate and targeted treatment. We have reviewed advances in chromosomal variations and molecular mechanisms involved in the progression of meningioma, and have highlighted the association with malignant biological behavior including cell proliferation, angiogenesis, increased invasiveness, and inhibition of apoptosis. In addition, the chemotherapy of meningioma is summarized and discussed.

Autophagy as a Potential Therapy for Malignant Glioma

Glioma is the most frequent and aggressive type of brain neoplasm, being anaplastic astrocytoma (AA) and glioblastoma multiforme (GBM), its most malignant forms. The survival rate in patients with these neoplasms is 15 months after diagnosis, despite a diversity of treatments, including surgery, radiation, chemotherapy, and immunotherapy. The resistance of GBM to various therapies is due to a highly mutated genome; these genetic changes induce a de-regulation of several signaling pathways and result in higher cell proliferation rates, angiogenesis, invasion, and a marked resistance to apoptosis; this latter trait is a hallmark of highly invasive tumor cells, such as glioma cells. Due to a defective apoptosis in gliomas, induced autophagic death can be an alternative to remove tumor cells. Paradoxically, however, autophagy in cancer can promote either a cell death or survival. Modulating the autophagic pathway as a death mechanism for cancer cells has prompted the use of both inhibitors and autophagy inducers. The autophagic process, either as a cancer suppressing or inducing mechanism in high-grade gliomas is discussed in this review, along with therapeutic approaches to inhibit or induce autophagy in pre-clinical and clinical studies, aiming to increase the efficiency of conventional treatments to remove glioma neoplastic cells.

Novel JAG1 Deletion Variant in Patient with Atypical Alagille Syndrome

Alagille syndrome (AGS) is an autosomal-dominant disorder characterized by various degrees of abnormalities in the liver, heart, eyes, vertebrae, kidneys, face, vasculature, skeleton, and pancreas. This case report describes a newborn child exhibiting a congenital neural tube defect and peculiar craniofacial appearance characterized by a prominent forehead, deep-set eyes, bulbous nasal tip, and subtle upper lip. Just a few hours after birth, congenital heart disease was suspected for cyanosis and confirmed by heart evaluation. In particular, echocardiography indicated pulmonary atresia with ventricular septal defect with severe hypoplasia of the pulmonary branches (1.5 mm), large patent ductus arteriosus and several major aortopulmonary collateral arteries. Due to the association of peculiar craniofacial appearance and congenital heart disease, a form of Alagille syndrome was suspected. In addition, on the fifth day after birth, the patient developed jaundice, had acholic stools, and high levels of conjugated bilirubin and gamma-glutamyltransferase (GGT) were detected in the blood. Genetic testing revealed the novel variant c.802del in a single copy of the JAG1 gene. No variants in the NOTCH2 gene were detected. To the best of our knowledge, this is the first clinical description of a congenital neural tube defect in a molecularly confirmed Alagille patient. This work demonstrates a novel pathogenic heterozygous JAG1 mutation is associated with an atypical form of Alagille syndrome, suggesting an increased risk for neural tube defects compared to other Alagille patients.

Radiosensitizers in the temozolomide era for newly diagnosed glioblastoma

Glioblastoma (GBM) is a challenging diagnosis with almost universally poor prognosis. Though the survival advantage of postoperative radiation (RT) is well established, around 90% of patients will fail in the RT field. The high likelihood of local failure suggests the efficacy of RT needs to be improved to improve clinical outcomes. Radiosensitizers are an established method of enhancing RT cell killing through the addition of a pharmaceutical agent. Though the majority of trials using radiosensitizers have historically been unsuccessful, there continues to be interest with a variety of approaches having been employed. Epidermal growth factor receptor inhibitors, histone deacetylase inhibitors, antiangiogenic agents, and a number of other molecularly targeted agents have all been investigated as potential methods of radiosensitization in the temozolomide era. Outcomes have varied both in terms of toxicity and survival, but some agents such as valproic acid and bortezomib have demonstrated promising results. However, reporting of results in phase 2 trials in newly diagnosed GBM have been inconsistent, with no standard in reporting progression-free survival and toxicity. There is a pressing need for investigation of new agents; however, nearly all phase 3 trials of GBM patients of the past 25 years have demonstrated no improvement in outcomes. One proposed explanation for this is the selection of agents lacking sufficient preclinical data and/or based on poorly designed phase 2 trials. Radiosensitization may represent a viable strategy for improving GBM outcomes in newly diagnosed patients, and further investigation using agents with promising phase 2 data is warranted.

The clinical characteristics and molecular mechanism of pituitary adenoma associated with meningioma

BACKGROUND

Pituitary adenoma and meningioma are the most common benign tumors in the central nervous system. Pituitary adenoma associated with meningioma (PAM) is a rare disease and the clinical features and mechanisms of PAM are unclear.

METHODS

We summarized the clinical data of 57 PAM patients and compared with sporadic pituitary adenoma (SPA) and sporadic meningioma (SM). 5 pituitary adenomas of PAM and 5 SPAs were performed ceRNA microarray. qRT-PCR, Western Blot, siMEN1 and rapamycin inhibition experiment were validated for ceRNA microarray.

RESULTS

Clinical variable analyses revealed that significant correlations between PAM and female sex as well as older age when compared with SPA and significant correlations between PAM and transitional meningioma as well as older age when compared with SM. Additionally, the characteristics of PAM were significantly different for MEN1 patients. Functional experiments showed lower expression of MEN1 can upregulate mTOR signaling, in accordance with the result of ceRNA microarray. Rapamycin treatment promotes apoptosis in primary pituitary adenoma and meningioma cells of PAM.

CONCLUSIONS

MEN1 plays an important role in PAM by upregulating mTOR signaling pathway. Rapamycin represents a potential therapeutic strategy for PAM in the future.

The Autophagy Status of Cancer Stem Cells in Gliobastoma Multiforme: From Cancer Promotion to Therapeutic Strategies

Glioblastoma multiforme (GBM) is the most common and aggressive primary brain tumor featuring rapid cell proliferation, treatment resistance, and tumor relapse. This is largely due to the coexistence of heterogeneous tumor cell populations with different grades of differentiation, and in particular, to a small subset of tumor cells displaying stem cell-like properties. This is the case of glioma stem cells (GSCs), which possess a powerful self-renewal capacity, low differentiation, along with radio- and chemo-resistance. Molecular pathways that contribute to GBM stemness of GSCs include mTOR, Notch, Hedgehog, and Wnt/β-catenin. Remarkably, among the common biochemical effects that arise from alterations in these pathways, autophagy suppression may be key in promoting GSCs self-renewal, proliferation, and pluripotency maintenance. In fact, besides being a well-known downstream event of mTOR hyper-activation, autophagy downregulation is also bound to the effects of aberrantly activated Notch, Hedgehog, and Wnt/β-catenin pathways in GBM. As a major orchestrator of protein degradation and turnover, autophagy modulates proliferation and differentiation of normal neuronal stem cells (NSCs) as well as NSCs niche maintenance, while its failure may contribute to GSCs expansion and maintenance. Thus, in the present review we discuss the role of autophagy in GSCs metabolism and phenotype in relationship with dysregulations of a variety of NSCs controlling pathways, which may provide novel insights into GBM neurobiology.

Management of pediatric low-grade glioma

PURPOSE OF REVIEW

Pediatric low-grade gliomas (pLGGs) have been treated with similar therapies for the last 30 years. Recent biological insights have allowed a new generation of targeted therapies to be developed for these diverse tumors. At the same time, technological advances may redefine the late toxicities associated with radiation therapy. Understanding recent developments in pLGG therapy is essential to the management of these common pediatric tumors.

RECENT FINDINGS

It is now well understood that aberrations of the mitogen-activated protein kinase pathway are key to oncogenesis in low-grade gliomas. This understanding, along with the development of available targeted agents, have heralded a new era of understanding and treatment for these patients. Promising, sustained responses are now being seen in early phase trials among patients with multiply recurrent/progressive disease. Also, newer and highly conformal radiation approaches such as proton beam radiotherapy maintain efficacy of radiation but limit radiation-associated toxicities.

SUMMARY

Novel therapies offer the potential for tumor control with greatly reduced toxicities. However, late effects of these therapies are just now being explored. Improved radiation approaches and targeted agents have the potential to redefine traditional therapy for pLGG.

A randomized phase II study of everolimus in combination with chemoradiation in newly diagnosed glioblastoma: results of NRG Oncology RTOG 0913

Background

This phase II study was designed to determine the efficacy of the mammalian target of rapamycin (mTOR) inhibitor everolimus administered daily with conventional radiation therapy and chemotherapy in patients with newly diagnosed glioblastoma.

Methods

Patients were randomized to radiation therapy with concurrent and adjuvant temozolomide with or without daily everolimus (10 mg). The primary endpoint was progression-free survival (PFS) and the secondary endpoints were overall survival (OS) and treatment-related toxicities.

Results

A total of 171 patients were randomized and deemed eligible for this study. Patients randomized to receive everolimus experienced a significant increase in both grade 4 toxicities, including lymphopenia and thrombocytopenia, and treatment-related deaths. There was no significant difference in PFS between patients randomized to everolimus compared with control (median PFS time: 8.2 vs 10.2 mo, respectively; P = 0.79). OS for patients randomized to receive everolimus was inferior to that for control patients (median survival time: 16.5 vs 21.2 mo, respectively; P = 0.008). A similar trend was observed in both O6-methylguanine-DNA-methyltransferase promoter hypermethylated and unmethylated tumors.

Conclusion

Combining everolimus with conventional chemoradiation leads to increased treatment-related toxicities and does not improve PFS in patients with newly diagnosed glioblastoma. Although the median survival time in patients receiving everolimus was comparable to contemporary studies, it was inferior to the control in this randomized study.

Diffuse Low-Grade Glioma-Related Epilepsy

The World Health Organization classifies diffuse low-grade gliomas (DLGGs) are highly epileptogenic primary brain tumors; epileptic seizures occur in more than 90% of cases. Epileptic seizures and drug resistance progress during the course of DLGGs. The glioma-related epileptogenic mechanisms are multifactorial; epileptogenic foci lie within the infiltrated peritumoral neocortex. A short seizure duration before surgery and a large extent of resection are the main predictors of postoperative seizure control in DLGGs. A supratotal resection of a DLGG can improve postoperative seizure control. Epileptic seizure at diagnosis positively affects DLGGs malignant transformation and overall survival.

Histologically defined intratumoral sequencing uncovers evolutionary cues into conserved molecular events driving gliomagenesis

Background

Glioblastoma represents an archetypal example of a heterogeneous malignancy. To understand the diverse molecular consequences of this complex tumor ecology, we analyzed RNA-seq data generated from commonly identified intratumoral structures in glioblastoma enriched using laser capture microdissection.

Methods

Raw gene-level values of fragments per kilobase of transcript per million reads mapped and the associated clinical data were acquired from the publicly available Ivy Glioblastoma Atlas Project database and analyzed using MetaboAnalyst (v3.0). The database includes gene expression data generated from multiple structural features commonly identified in glioblastoma enriched by laser capture microdissection.

Results

We uncovered a relationship between subtype heterogeneity in glioblastoma and its unique tumor microenvironment, with infiltrating cells harboring a proneural signature while the mesenchymal subtype was enriched in perinecrotic regions. When evaluating the tumors' transcriptional profiles in the context of their derived structural regions, there was a relatively small amount of intertumoral heterogeneity in glioblastoma, with individual regions from different tumors clustering tightly together. Analyzing the transcriptional profiles in the context of evolutionary progression identified unique cellular programs associated with specific phases of gliomagenesis. Mediators of cell signaling and cell cycle progression appear to be critical events driving proliferation in the tumor core, while in addition to a multiplex strategy for promoting angiogenesis and/or an immune-tolerant environment, transformation to perinecrotic zones involved global metabolic alterations.

Conclusion

These findings suggest that intratumoral heterogeneity in glioblastoma is a conserved, predictable consequence to its complex microenvironment, and combinatorial approaches designed to target these unequivocally present tumor biomes may lead to therapeutic gains.

Targeting of glioblastoma cell lines and glioma stem cells by combined PIM kinase and PI3K-p110α inhibition

The PIM family of proteins encodes serine/threonine kinases with important roles in protein synthesis and cancer cell metabolism. In glioblastoma (GBM) cell lines, siRNA-mediated knockdown of PIM kinases or pharmacological inhibition of PIM kinases by SGI-1776 or AZD-1208 results in reduced phosphorylation of classic PIM effectors and also elements of the PI3K/mTOR pathway, suggesting interplay between PIM and mTOR signals in GBM cells. Combination of PIM kinase inhibitors with BYL-719, an inhibitor specific for the PI3K catalytic isoform p110α, results in enhanced antineoplastic effects in GBM cells. Additionally, pharmacologic inhibition of PIM kinases impairs growth of patient-derived glioma sphere cells, suggesting an important role for PIM kinases in cancer stem cell (CSC) function and survival. Such effects are further enhanced by concomitant inhibition of PIM kinase and p110α activities. Altogether these findings suggest that pharmacological PIM targeting in combination with PI3K inhibition may provide a unique therapeutic approach for the treatment of heterogeneous tumors containing populations of therapy-resistant CSCs in GBM.

mTOR-Dependent Cell Proliferation in the Brain

The mammalian Target of Rapamycin (mTOR) is a molecular complex equipped with kinase activity which controls cell viability being key in the PI3K/PTEN/Akt pathway. mTOR acts by integrating a number of environmental stimuli to regulate cell growth, proliferation, autophagy, and protein synthesis. These effects are based on the modulation of different metabolic pathways. Upregulation of mTOR associates with various pathological conditions, such as obesity, neurodegeneration, and brain tumors. This is the case of high-grade gliomas with a high propensity to proliferation and tissue invasion. Glioblastoma Multiforme (GBM) is a WHO grade IV malignant, aggressive, and lethal glioma. To date, a few treatments are available although the outcome of GBM patients remains poor. Experimental and pathological findings suggest that mTOR upregulation plays a major role in determining an aggressive phenotype, thus determining relapse and chemoresistance. Among several activities, mTOR-induced autophagy suppression is key in GBM malignancy. In this article, we discuss recent evidence about mTOR signaling and its role in normal brain development and pathological conditions, with a special emphasis on its role in GBM.

Inhibiting 4EBP1 in Glioblastoma

Glioblastoma is the most common and aggressive adult brain cancer. Tumors show frequent dysregulation of the PI3K-mTOR pathway. Although a number of small molecules target the PI3K-AKT-mTOR axis, their preclinical and clinical efficacy has been limited. Reasons for treatment failure include poor penetration of agents into the brain and observations that blockade of PI3K or AKT minimally affects downstream mTOR activity in glioma. Clinical trials using allosteric mTOR inhibitors (rapamycin and rapalogs) to treat patients with glioblastoma have also been unsuccessful or uncertain, in part, because rapamycin inefficiently blocks the mTORC1 target 4EBP1 and feeds back to activate PI3K-AKT signaling. Inhibitors of the mTOR kinase (TORKi) such as TAK-228/MLN0128 interact orthosterically with the ATP- and substrate-binding pocket of mTOR kinase, efficiently block 4EBP1 in vitro, and are currently being investigated in the clinical trials. Preclinical studies suggest that TORKi have poor residence times of mTOR kinase, and our data suggest that this poor pharmacology translates into disappointing efficacy in glioblastoma xenografts. RapaLink-1, a TORKi linked to rapamycin, represents a drug with improved pharmacology against 4EBP1. In this review, we clarify the importance of 4EBP1 as a biomarker for the efficacy of PI3K-AKT-mTOR inhibitors in glioblastoma. We also review mechanistic data by which RapaLink-1 blocks p-4EBP1 and discuss future clinical strategies for 4EBP1 inhibition in glioblastoma. Clin Cancer Res; 24(1); 14-21. ©2017 AACR.

[Hereditary tumor syndromes in neuropathology]

Neoplasms in the central (CNS) and peripheral nervous system (PNS) in hereditary tumor syndromes play an important role in the neuropathological diagnostics. The benign and malignant PNS and CNS tumors that occur in the frequent neurofibromatosis type 1 (NF1) and type 2 (NF2) often represent essential factors for the course of the disease in those affected. Furthermore, certain clinical constellations (e.g. bilateral schwannomas of the auditory nerve, schwannomas at a young age and multiple meningiomas) can be important indications for a previously undiagnosed hereditary tumor disease. Other tumors occur practically regularly in association with certain germline defects, e.g. subependymal giant cell astrocytoma (SEGA) in tuberous sclerosis and dysplastic gangliocytoma of the cerebellum in Cowden's syndrome and can be indications in the diagnostics for an extended genetic counselling. This is not only important because many germline defects are based on new mutations, but also for the now established targeted therapy of certain tumors, e.g. inhibition of the mammalian target of rapamycin (mTOR) signaling pathway using temsirolimus for SEGA. Furthermore, knowledge about the possible constellations of genetic mosaics in hereditary tumor syndromes with the resulting (incomplete) syndrome manifestations is useful. This review article summarizes the most important hereditary tumor syndromes with involvement of the PNS and CNS.

Targeting SOX2 as a Therapeutic Strategy in Glioblastoma

Glioblastoma is the most common and malignant brain cancer in adults. Current therapy consisting of surgery followed by radiation and temozolomide has a moderate success rate and the tumor reappears. Among the features that a cancer cell must have to survive the therapeutic treatment and reconstitute the tumor is the ability of self-renewal. Therefore, it is vital to identify the molecular mechanisms that regulate this activity. Sex-determining region Y (SRY)-box 2 (SOX2) is a transcription factor whose activity has been associated with the maintenance of the undifferentiated state of cancer stem cells in several tissues, including the brain. Several groups have detected increased SOX2 levels in biopsies of glioblastoma patients, with the highest levels associated with poor outcome. Therefore, SOX2 silencing might be a novel therapeutic approach to combat cancer and particularly brain tumors. In this review, we will summarize the current knowledge about SOX2 in glioblastoma and recapitulate several strategies that have recently been described targeting SOX2 in this malignancy.

mTOR inhibition decreases SOX2-SOX9 mediated glioma stem cell activity and temozolomide resistance

Background: SOX2 and SOX9 are commonly overexpressed in glioblastoma, and regulate the activity of glioma stem cells (GSCs). Their specific and overlapping roles in GSCs and glioma treatment remain unclear.

Methods: SOX2 and SOX9 levels were examined in human biopsies. Gain and loss of function determined the impact of altering SOX2 and SOX9 on cell proliferation, senescence, stem cell activity, tumorigenesis and chemoresistance.

Results: SOX2 and SOX9 expression correlates positively in glioma cells and glioblastoma biopsies. High levels of SOX2 bypass cellular senescence and promote resistance to temozolomide. Mechanistic investigations revealed that SOX2 acts upstream of SOX9. mTOR genetic and pharmacologic (rapamycin) inhibition decreased SOX2 and SOX9 expression, and reversed chemoresistance.

Conclusions: Our findings reveal SOX2-SOX9 as an oncogenic axis that regulates stem cell properties and chemoresistance. We identify that rapamycin abrogate SOX protein expression and provide evidence that a combination of rapamycin and temozolomide inhibits tumor growth in cells with high SOX2/SOX9.

The mTOR signalling cascade: paving new roads to cure neurological disease

Defining the multiple roles of the mechanistic (formerly 'mammalian') target of rapamycin (mTOR) signalling pathway in neurological diseases has been an exciting and rapidly evolving story of bench-to-bedside translational research that has spanned gene mutation discovery, functional experimental validation of mutations, pharmacological pathway manipulation, and clinical trials. Alterations in the dual contributions of mTOR - regulation of cell growth and proliferation, as well as autophagy and cell death - have been found in developmental brain malformations, epilepsy, autism and intellectual disability, hypoxic-ischaemic and traumatic brain injuries, brain tumours, and neurodegenerative disorders. mTOR integrates a variety of cues, such as growth factor levels, oxygen levels, and nutrient and energy availability, to regulate protein synthesis and cell growth. In line with the positioning of mTOR as a pivotal cell signalling node, altered mTOR activation has been associated with a group of phenotypically diverse neurological disorders. To understand how altered mTOR signalling leads to such divergent phenotypes, we need insight into the differential effects of enhanced or diminished mTOR activation, the developmental context of these changes, and the cell type affected by altered signalling. A particularly exciting feature of the tale of mTOR discovery is that pharmacological mTOR inhibitors have shown clinical benefits in some neurological disorders, such as tuberous sclerosis complex, and are being considered for clinical trials in epilepsy, autism, dementia, traumatic brain injury, and stroke.

Temozolomide promotes genomic and phenotypic changes in glioblastoma cells

BACKGROUND

Temozolomide (TMZ) is a first-line drug for the treatment of glioblastoma. Long-term TMZ-treated tumour cells acquire TMZ resistance by profound reprogramming of the transcriptome, proteome, kinome, metabolism, and demonstrate versatile and opposite changes in proliferation, invasion, in vivo growth, and drug cross-resistance. We hypothesized that chromosomal instability (CIN) may be implicated in the generation of TMZ-driven molecular and phenotype diversity. CIN refers to the rate (cell-to-cell variability) with which whole chromosomes or portions of chromosomes are gained or lost.

METHODS

The long-term TMZ-treated cell lines were established in vitro (U251TMZ1, U251TMZ2, T98GTMZ and C6TMZ) and in vivo (C6R2TMZ). A glioma model was achieved by the intracerebral stereotactic implantation of C6 cells into the striatum region of rats. Genomic and phenotypic changes were analyzed by conventional cytogenetics, array CGH, trypan blue exclusion assay, soft agar colony formation assay, scratch wound healing assay, transwell invasion assay, quantitative polymerase chain reaction, and Western blotting.

RESULTS

Long-term TMZ treatment increased CIN-mediated genomic diversity in U251TMZ1, U251TMZ2 and T98GTMZ cells but reduced it in C6TMZ and C6R2TMZ cells. U251TMZ1 and U251TMZ2 cell lines, established in parallel with a similar treatment procedure with the only difference in the duration of treatment, underwent individual phenotypic changes. U251TMZ1 had a reduced proliferation and invasion but increased migration, whereas U251TMZ2 had an enhanced proliferation and invasion but no changes in migration. U251TMZ1 and U251TMZ2 cells demonstrated individual patterns in expression/activation of signal transduction proteins (e.g., MDM2, p53, ERK, AKT, and ASK). C6TMZ and C6R2TMZ cells had lower proliferation, colony formation efficiency and migration, whereas T98GTMZ cells had increased colony formation efficiency without any changes in proliferation, migration, and invasion. TMZ-treated lines demonstrated a differential response to a reduction in glucose concentration and an increased resistance to TMZ re-challenge but not temsirolimus (mTOR inhibitor) or U0126 (MEK1/2 inhibitor) treatment.

CONCLUSION

Long-term TMZ treatment selected resistant genotype-phenotype variants or generated novel versatile phenotypes by increasing CIN. An increase of resistance to TMZ re-challenge seems to be the only predictable trait intrinsic to all long-term TMZ-treated tumour cells. Changes in genomic diversity may be responsible for heterogeneous phenotypes of TMZ-treated cell lines.

mTOR inhibitor temsirolimus and MEK1/2 inhibitor U0126 promote chromosomal instability and cell type-dependent phenotype changes of glioblastoma cells

The phosphatidylinositol 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) and the RAF/mitogen-activated and extracellular signal-regulated kinase kinase (MEK)/extracellular signal-regulated kinase (ERK) signaling pathways are frequently deregulated in cancer. Temsirolimus (TEM) and its primary active metabolite rapamycin allosterically block mTOR complex 1 substrate recruitment. The context-/experimental setup-dependent opposite effects of rapamycin on the multiple centrosome formation, aneuploidy, DNA damage/repair, proliferation, and invasion were reported. Similarly, the context-dependent either tumor-promoting or suppressing effects of RAF-MEK-ERK pathway and its inhibitors were demonstrated. Drug treatment-mediated stress may promote chromosomal instability (CIN), accelerating changes in the genomic landscape and phenotype diversity. Here, we characterized the genomic and phenotypic changes of U251 and T98G glioblastoma cell lines long-term treated with TEM or U0126, an inhibitor of MEK1/2. TEM significantly increased clonal and non-clonal chromosome aberrations. Both TEM and U0126 affected copy number alterations (CNAs) pattern. A proliferation rate of U251TEM and U251U0126 cells was lower and higher, respectively, than control cells. Colony formation efficiency of U251TEM significantly decreased, whereas U251U0126 did not change. U251TEM and U251U0126 cells decreased migration. In contrast, T98GTEM and T98GU0126 cells did not change proliferation, colony formation efficiency, and migration. Changes in the sensitivity of inhibitor-treated cells to the reduction of the glucose concentration were observed. Our results suggest that CIN and adaptive reprogramming of signal transduction pathways may be responsible for the cell type-dependent phenotype changes of long-term TEM- or U0126-treated tumor cells.

Complications from pharmacotherapy

The pharmacotherapy management of cancers of the nervous system has significant overlap with systemic solid cancers that may utilize similar drugs or agents. There is however a unique aspect related to central nervous system (CNS) cancers where therapies directed against a malignant process may have enhanced toxicities or toxicities unique to the CNS. In addition, many agents used to treat CNS malignancies have unique CNS toxicities that may require a specific intervention. This chapter attempts to review conventional and biologic therapies utilized for CNS malignancies and characterize expected and, if known, unique toxicities.

Treating recurrent glioblastoma: an update

Glioblastoma, the most aggressive of the gliomas, has a high recurrence and mortality rate. The nature of this poor prognosis resides in the molecular heterogeneity and phenotypic features of this tumor. Despite research advances in understanding the molecular biology, it has been difficult to translate this knowledge into effective treatment. Nearly all will have tumor recurrence, yet to date very few therapies have established efficacy as salvage regimens. This challenge is further complicated by imaging confounders and to an even greater degree by the ever increasing molecular heterogeneity that is thought to be both sporadic and treatment-induced. The development of novel clinical trial designs to support the development and testing of novel treatment regimens and drug delivery strategies underscore the need for more precise techniques in imaging and better surrogate markers to help determine treatment response. This review summarizes recent approaches to treat patients with recurrent glioblastoma and considers future perspectives.

MicroRNA-199a-3p suppresses glioma cell proliferation by regulating the AKT/mTOR signaling pathway

Glioma has been investigated for decades, but the prognosis remains poor because of rapid proliferation, its aggressive potential, and its resistance to chemotherapy or radiotherapy. The mammalian target of rapamycin (mTOR) is highly expressed and regulates cellular proliferation and cell growth. MicroRNAs (miRNAs) are small non-coding RNAs that regulate gene transcription and translation via up-regulating or down-regulating the levels of miRNAs. This study was conducted to explore the molecular functions of miR-199a-3p in glioma. We detected the expression of miR-199a-3p in glioma samples by quantitative PCR (qPCR). Then, we transfected the U87 and U251 cell lines with miR-199a-3p. Cellular proliferation, invasion, and apoptosis were assessed to explain the function of miR-199a-3p. PCR confirmed that the expression of miR-199a-3p was lower in glioma samples combined with normal brain tissues. The over-expression of miR-199a-3p might target mTOR and restrained cellular growth and proliferation but not invasive and apoptosis capability. Results indicated that cellular proliferation was inhibited to regulate the AKT/mTOR signaling pathway by elevating levels of miR-199a-3p. MiR-199a-3p in glioma cell lines has effects similar to the tumor suppressor gene on cellular proliferation via the AKT/mTOR signaling pathway.