CD271+ Cells Are Diagnostic and Prognostic and Exhibit Elevated MAPK Activity in SHH Medulloblastoma

A group 3 medulloblastoma stem cell program is maintained by OTX2-mediated alternative splicing

OTX2 is a transcription factor and known driver in medulloblastoma (MB), where it is amplified in a subset of tumours and overexpressed in most cases of group 3 and group 4 MB. Here we demonstrate a noncanonical role for OTX2 in group 3 MB alternative splicing. OTX2 associates with the large assembly of splicing regulators complex through protein-protein interactions and regulates a stem cell splicing program. OTX2 can directly or indirectly bind RNA and this may be partially independent of its DNA regulatory functions. OTX2 controls a pro-tumorigenic splicing program that is mirrored in human cerebellar rhombic lip origins. Among the OTX2-regulated differentially spliced genes, PPHLN1 is expressed in the most primitive rhombic lip stem cells, and targeting PPHLN1 splicing reduces tumour growth and enhances survival in vivo. These findings identify OTX2-mediated alternative splicing as a major determinant of cell fate decisions that drive group 3 MB progression.

Differential Signaling Pathways in Medulloblastoma: Nano-biomedicine Targeting Non-coding Epigenetics to Improve Current and Future Therapeutics

BACKGROUND

Medulloblastomas (MDB) are malignant, aggressive brain tumors that primarily affect children. The survival rate for children under 14 is approximately 72%, while for ages 15 to 39, it is around 78%. A growing body of evidence suggests that dysregulation of signaling mechanisms and noncoding RNA epigenetics play a pivotal role in this disease.

METHODOLOGY

This study conducted an electronic search of articles on websites like PubMed and Google. The current review also used an in silico databases search and bioinformatics analysis and an extensive comprehensive literature search for original research articles and review articles as well as retrieval of current and future medications in clinical trials.

RESULTS

This study indicates that several signaling pathways, such as sonic hedgehog, WNT/β-catenin, unfolded protein response mediated ER stress, notch, neurotrophins and TGF-β and ERK, MAPK, and ERK play a crucial role in the pathogenesis of MDB. Gene and ncRNA/protein are also involved as an axis long ncRNA to sponge micro-RNAs that affect downstream signal proteins expression and translation affection disease pathophysiology, prognosis and present potential target hit for drug repurposing. Current treatment options include surgery, radiation, and chemotherapy; unfortunately, the disease often relapses, and the survival rate is less than 5%. Therefore, there is a need to develop more effective treatments to combat recurrence and improve survival rates.

CONCLUSION

This review describes various MDB disease hallmarks, including the signaling mechanisms involved in pathophysiology, related-causal genes, epigenetics, downstream genes/epigenes, and possibly the causal disease genes/non-protein coding (nc)RNA/protein axis. Additionally, the challenges associated with MDB treatment are discussed, along with how they are being addressed using nano-technology and nano-biomedicine, with a listing of possible treatment options and future potential treatment modalities.

Cross-species analysis of SHH medulloblastoma models reveals significant inhibitory effects of trametinib on tumor progression

Sonic Hedgehog (SHH) medulloblastomas (MBs) exhibit an intermediate prognosis and extensive intertumoral heterogeneity. While SHH pathway antagonists are effective in post-pubertal patients, younger patients exhibit significant side effects, and tumors that harbor mutations in downstream SHH pathway genes will be drug resistant. Thus, novel targeted therapies are needed. Here, we performed preclinical testing of the potent MEK inhibitor (MEKi) trametinib on tumor properties across 2 human and 3 mouse SHH MB models in vitro and in 3 orthotopic MB xenograft models in vivo. Trametinib significantly reduces tumorsphere size, stem/progenitor cell proliferation, viability, and migration. RNA-sequencing on human and mouse trametinib treated cells corroborated these findings with decreased expression of cell cycle, stem cell pathways and SHH-pathway related genes concomitant with increases in genes associated with cell death and ciliopathies. Importantly, trametinib also decreases tumor growth and increases survival in vivo. Cell cycle related E2F target gene sets are significantly enriched for genes that are commonly downregulated in both trametinib treated tumorspheres and primary xenografts. However, IL6/JAK STAT3 and TNFα/NFκB signaling gene sets are specifically upregulated following trametinib treatment in vivo indicative of compensatory molecular changes following long-term MEK inhibition. Our study reveals a novel role for trametinib in effectively attenuating SHH MB tumor progression and warrants further investigation of this potent MEK1/2 inhibitor either alone or in combination with other targeted therapies for the treatment of SHH MB exhibiting elevated MAPK pathway activity.

PP2A-based triple-strike therapy overcomes mitochondrial apoptosis resistance in brain cancer cells

Mitochondrial glycolysis and hyperactivity of the phosphatidylinositol 3-kinase-protein kinase B (AKT) pathway are hallmarks of malignant brain tumors. However, kinase inhibitors targeting AKT (AKTi) or the glycolysis master regulator pyruvate dehydrogenase kinase (PDKi) have failed to provide clinical benefits for brain tumor patients. Here, we demonstrate that heterogeneous glioblastoma (GB) and medulloblastoma (MB) cell lines display only cytostatic responses to combined AKT and PDK targeting. Biochemically, the combined AKT and PDK inhibition resulted in the shutdown of both target pathways and priming to mitochondrial apoptosis but failed to induce apoptosis. In contrast, all tested brain tumor cell models were sensitive to a triplet therapy, in which AKT and PDK inhibition was combined with the pharmacological reactivation of protein phosphatase 2A (PP2A) by NZ-8-061 (also known as DT-061), DBK-1154, and DBK-1160. We also provide proof-of-principle evidence for in vivo efficacy in the intracranial GB and MB models by the brain-penetrant triplet therapy (AKTi + PDKi + PP2A reactivator). Mechanistically, PP2A reactivation converted the cytostatic AKTi + PDKi response to cytotoxic apoptosis, through PP2A-elicited shutdown of compensatory mitochondrial oxidative phosphorylation and by increased proton leakage. These results encourage the development of triple-strike strategies targeting mitochondrial metabolism to overcome therapy tolerance in brain tumors.

Transcriptomic analysis of the cerebral hippocampal tissue in spontaneously hypertensive rats exposed to acute hypobaric hypoxia: associations with inflammation and energy metabolism

We evaluated the effect of acute hypobaric hypoxia (AHH) on the hippocampal region of the brain in early-stage spontaneously hypertensive male rats. The rats were classified into a control (ground level; ~ 400 m altitude) group and an AHH experimental group placed in an animal hypobaric chamber at a simulated altitude of 5500 m for 24 h. RNA-Seq analysis of the brains and hippocampi showed that differentially expressed genes (DEGs) were primarily associated with ossification, fibrillar collagen trimer, and platelet-derived growth factor binding. The DEGs were classified into functional categories including general function prediction, translation, ribosomal structure and biogenesis, replication, recombination, and repair. Pathway enrichment analysis revealed that the DEGs were primarily associated with relaxin signaling, PI3K-Akt signaling, and amoebiasis pathways. Protein-protein interaction network analysis indicated that 48 DEGs were involved in both inflammation and energy metabolism. Further, we performed validation experiments to show that nine DEGs were closely associated with inflammation and energy metabolism, of which two (Vegfa and Angpt2) and seven (Acta2, Nfkbia, Col1a1, Edn1, Itga1, Ngfr, and Sgk1) genes showed up and downregulated expression, respectively. Collectively, these results indicated that inflammation and energy metabolism-associated gene expression in the hippocampus was altered in early-stage hypertension upon AHH exposure.

Combination of BMI1 and MAPK/ERK inhibitors is effective in medulloblastoma

BACKGROUND

Epigenetic changes play a key role in the pathogenesis of medulloblastoma (MB), the most common malignant pediatric brain tumor.

METHODS

We explore the therapeutic potential of BMI1 and MAPK/ERK inhibition in BMI1High;CHD7Low MB cells and in a preclinical xenograft model.

RESULTS

We identify a synergistic vulnerability of BMI1High;CHD7Low MB cells to a combination treatment with BMI1 and MAPK/ERK inhibitors. Mechanistically, CHD7-dependent binding of BMI1 to MAPK-regulated genes underpins the CHD7-BMI1-MAPK regulatory axis responsible of the antitumour effect of the inhibitors in vitro and in a preclinical mouse model. Increased ERK1 and ERK2 phosphorylation activity is found in BMI1High;CHD7Low G4 MB patients, raising the possibility that they could be amenable to a similar therapy.

CONCLUSIONS

The molecular dissection of the CHD7-BMI1-MAPK regulatory axis in BMI1High;CHD7Low MB identifies this signature as a proxy to predict MAPK functional activation, which can be effectively drugged in preclinical models, and paves the way for further exploration of combined BMI1 and MAPK targeting in G4 MB patients.

Combined MEK and JAK/STAT3 pathway inhibition effectively decreases SHH medulloblastoma tumor progression

Medulloblastoma (MB) is the most common primary malignant pediatric brain cancer. We recently identified novel roles for the MEK/MAPK pathway in regulating human Sonic Hedgehog (SHH) MB tumorigenesis. The MEK inhibitor, selumetinib, decreased SHH MB growth while extending survival in mouse models. However, the treated mice ultimately succumbed to disease progression. Here, we perform RNA sequencing on selumetinib-treated orthotopic xenografts to identify molecular pathways that compensate for MEK inhibition specifically in vivo. Notably, the JAK/STAT3 pathway exhibits increased activation in selumetinib-treated tumors. The combination of selumetinib and the JAK/STAT3 pathway inhibitor, pacritinib, further reduces growth in two xenograft models and also enhances survival. Multiplex spatial profiling of proteins in drug-treated xenografts reveals shifted molecular dependencies and compensatory changes following combination drug treatment. Our study warrants further investigation into MEK and JAK/STAT3 inhibition as a novel combinatory therapeutic strategy for SHH MB.

RNA sequencing of MEK inhibitor (selumetinib)-treated tumors reveals an upregulation of the JAK/STAT3 pathway, with combinatorial therapeutic strategies of JAK/STAT3 inhibitors and selumetinib investigated for the SHH subgroup of medulloblastoma.

Cell Surface Proteins for Enrichment and In Vitro Characterization of Human Pluripotent Stem Cell-Derived Myogenic Progenitors

Human myogenic progenitors can be derived from pluripotent stem cells (PSCs) for use in modeling natural and pathological myogenesis, as well as treating muscle diseases. Transgene-free methods of deriving myogenic progenitors from different PSC lines often produce mixed populations that are heterogeneous in myogenic differentiation potential, yet detailed and accurate characterization of human PSC-derived myogenic progenitors remains elusive in the field. The isolation and purification of human PSC-derived myogenic progenitors is thus an important methodological consideration when we investigate the properties and behaviors of these cells in culture. We previously reported a transgene-free, serum-free floating sphere culture method for the derivation of myogenic progenitors from human PSCs. In this study, we first performed comprehensive cell surface protein profiling of the sphere culture cells through the screening of 255 antibodies. Next, we used magnetic activated cell sorting and enriched the cells according to the expression of specific surface markers. The ability of muscle differentiation in the resulting cells was characterized by immunofluorescent labeling and quantification of positively stained cells. Our results revealed that myotube-forming cells resided in the differentiated cultures of CD29+, CD56+, CD271+, and CD15– fractions, while thick and multinucleated myotubes were identified in the differentiated cultures from CD9+ and CD146+ fractions. We found that PAX7 localization to the nucleus correlates with myotube-forming ability in these sorted populations. We also demonstrated that cells in unsorted, CD271+, and CD15– fractions responded differently to cryopreservation and prolonged culture expansion. Lastly, we showed that CD271 expression is essential for terminal differentiation of human PSC-derived myogenic progenitors. Taken together, these cell surface proteins are not only useful markers to identify unique cellular populations in human PSC-derived myogenic progenitors but also functionally important molecules that can provide valuable insight into human myogenesis.

Upregulation of CD271 transcriptome in breast cancer promotes cell survival via NFκB pathway

BACKGROUND

Biological treatment of many cancers currently targets membrane bound receptors located on a cell surface. We are in a great to need identify novel membrane proteins associated with migration and metastasis of breast cancer cells. CD271, a single transmembrane protein belongs to tumor necrosis factor receptor family acts and play its role in proliferation of cancer cell. The purpose of this study is to investigate the role of CD271 in breast cancer.

METHODS AND RESULTS

In this study we analyzed the mRNA expression of CD271 in breast tumor tissue, breast cancer cell line MCF7 and isolated cancer stem cells (MCF7-CSCs) by RT-qPCR. We also measured the protein levels through western blotting in MCF-7 cell line. CD271 was upregulated in breast cancer patients among all age groups. Within the promoter region of CD271, there is a binding site for NF-κB1 which overlaps a putative quadraplex forming sequence. While CD271 also activates NF-κB pathway, down regulation of CD271 through quadraplex targeting resulted in inhibition of NF-κB and its downstream targets Nanog and Sox2.

CONCLUSION

In conclusion, our data shows that CD271 and NF-κB are regulated in interdependent manner. Upon CD271 inhibition, the NF-κB expression also reduces which in turn affects the cell proliferation and migration. These results suggest that CD271 is playing a crucial rule in cancer progression by regulating NF-κB and is a good candidate for the therapeutic targeting.

Integrated computational analyses reveal novel insights into the stromal microenvironment of SHH-subtype medulloblastoma

Medulloblastoma is the most common malignant brain tumour of childhood. While our understanding of this disease has progressed substantially in recent years, the role of tumour microenvironment remains unclear. Given the increasing role of microenvironment-targeted therapeutics in other cancers, this study was aimed at further exploring its role in medulloblastoma. Multiple computational techniques were used to analyze open-source bulk and single cell RNA seq data from primary samples derived from all subgroups of medulloblastoma. Gene expression is used to infer stromal subpopulations, and network-based approaches are used to identify potential therapeutic targets. Bulk data was obtained from 763 medulloblastoma samples and single cell data from an additional 7241 cells from 23 tumours. Independent bulk (285 tumours) and single cell (32,868 cells from 29 tumours) validation cohorts were used to verify results. The SHH subgroup was found to be enriched in stromal activity, including the epithelial-to-mesenchymal transition, while group 3 is comparatively stroma-suppressed. Several receptor and ligand candidates underlying this difference are identified which we find to correlate with metastatic potential of SHH medulloblastoma. Additionally, a biologically active gradient is detected within SHH medulloblastoma, from "stroma-active" to "stroma-suppressed" cells which may have relevance to targeted therapy. This study serves to further elucidate the role of the stromal microenvironment in SHH-subgroup medulloblastoma and identify novel treatment possibilities for this challenging disease.

The role of human endogenous retroviruses in gliomas: from etiological perspectives and therapeutic implications

Accounting for approximately 8% of the human genome, Human Endogenous Retroviruses (HERVs) have been implicated in a variety of cancers including gliomas. In normal cells, tight epigenetic regulation of HERVs prevent aberrant expression; however, in cancer cells, HERVs expression remains pervasive, suggesting a role of HERVs in oncogenic transformation. HERVs may contribute to oncogenesis in several ways including insertional mutagenesis, chromosomal rearrangements, proto-oncogene formation, and maintenance of stemness. On the other hand, recent data has suggested that reversing epigenetic silencing of HERVs may induce robust anti-tumor immune responses, suggesting HERVs' potential therapeutic utility in gliomas. By reversing epigenetic modifications that silence HERVs, DNA methyltransferase and histone deacetylase inhibitors may stimulate a viral-mimicry cascade via HERV-derived dsRNA formation that induce interferon-mediated apoptosis. Leveraging this anti-tumor autoimmune response may be a unique avenue to target certain subsets of epigenetically-dysregulated gliomas. Nevertheless, the role of HERVs in gliomas as either arbitrators of oncogenesis or forerunners of the innate anti-tumor immune response remains unclear. Here, we review the role of HERVs in gliomas, their potential dichotomous function in propagating oncogenesis and stimulating the anti-tumor immune response and identify future directions for research.

From sorting to sequencing in the molecular era: the evolution of the cancer stem cell model in medulloblastoma

The cancer stem cell (CSC) model posits that tumors contain subpopulations that display defining features of normal stem cells including self-renewal capacity and differentiation. Tumor cells exhibiting these features are now considered to be responsible for tumor propagation and drug resistance in a wide variety of cancers. Therefore, the identification of robust CSC markers and characterization of CSC-specific molecular signatures may lead to the identification of novel therapeutics that selectively abolish this clinically relevant cell population while preserving normal tissue. Brain tumor researchers have been at the forefront of the CSC field. From initial in vitro cell sorting experiments to the sophisticated bioinformatic technologies that now exquisitely resolve primary brain tumors at a single-cell level, recent glioma and medulloblastoma (MB) studies have integrated developmental state with genomic and transcriptome data to identify the spectrum of cell types that may drive tumor progression. This review will examine the last two decades of CSC studies in the field. Seminal discoveries, emerging controversies, and outstanding questions will be covered with a particular focus on MB, the most common malignant primary brain tumor in children.

Cancer-Associated Fibroblasts Suppress Cancer Development: The Other Side of the Coin

Cancer-associated fibroblasts (CAFs) are the main stromal components of cancer, representing a group of heterogeneous cells. Many studies indicate that CAFs promote tumor development. Besides, evidence of the tumor suppression effects of CAFs keeps on merging. In the tumor microenvironment, multiple stimuli can activate fibroblasts. Notably, this does not necessarily mean the activated CAFs become strong tumor promoters immediately. The varying degree of CAFs activation makes quiescent CAFs, tumor-restraining CAFs, and tumor-promoting CAFs. Quiescent CAFs and tumor-restraining CAFs are more present in early-stage cancer, while comparatively, more tumor-promoting CAFs present in advanced-stage cancer. The underlying mechanism that balances tumor promotion or tumor inhibition effects of CAFs is mostly unknown. This review focus on the inhibitory effects of CAFs on cancer development. We describe the heterogeneous origin, markers, and metabolism in the CAFs population. Transgenetic mouse models that deplete CAFs or deplete CAFs activation signaling in the tumor stroma present direct evidence of CAFs protective effects against cancer. Moreover, we outline CAFs subpopulation and CAFs derived soluble factors that act as a tumor suppressor. Single-cell RNA-sequencing on CAFs population provides us new insight to classify CAFs subsets. Understanding the full picture of CAFs will help translate CAFs biology from bench to bedside and develop new strategies to improve precision cancer therapy.

Early-Life Multiple Sevoflurane Exposures Alleviate Long-term Anxiety-Like Behaviors in Mice via the proBDNF/ERK Pathway

Early-life multiple anesthetics exposure causes neurotoxicity and hence cognitive dysfunction on developing brain. However, the effects of early-life multiple sevoflurane exposures on emotional changes, especially upon stress, are far beyond understood. In young male C57BL6/J mice, the present study showed that 3% sevoflurane inhalation for 2 h in three consecutive days did not influence anxiety-like behaviors as measured by open field test, light dark transition, and elevated plus maze test. In addition, foot shocks stress induced both the short- and long-term anxiety-like behaviors. However, triple sevoflurane exposures ameliorated the long-term anxiety-like behaviors induced by the foot shocks. In parallel, foot shocks stress upregulated the expression of phosphorylated extracellular signal-regulated kinase (p-ERK) and brain-derived neurotrophic factor precursor (proBDNF) in the anterior cingulate cortex (ACC), which were significantly inhibited by triple sevoflurane exposures. Immunofluorescence further indicated that the increased p-ERK was mainly expressed in the proBDNF-positive staining cells. Intra-ACC injection of recombinant proBDNF protein upregulated the p-ERK expression and blocked the anxiolytic effect of sevoflurane exposure on long-term anxiety-like behaviors. Therefore, our study demonstrated that multiple sevoflurane exposures alleviate long-term anxiety-like behaviors upon acute stress in young mice by inhibiting proBDNF-ERK signaling in the ACC.

Real-time sensing of MAPK signaling in medulloblastoma cells reveals cellular evasion mechanism counteracting dasatinib blockade of ERK activation during invasion

Aberrantly activated kinase signaling pathways drive invasion and dissemination in medulloblastoma (MB). A majority of tumor-promoting kinase signaling pathways feed into the mitogen-activated protein kinase (MAPK) extracellular regulated kinase (ERK1/2) pathway. The activation status of ERK1/2 during invasion of MB cells is not known and its implication in invasion control unclear. We established a synthetic kinase activation relocation sensor (SKARS) for the MAPK ERK1/2 pathway in MB cells for real-time measuring of drug response. We used 3D invasion assays and organotypic cerebellum slice culture to test drug effects in a physiologically relevant tissue environment. We found that hepatocyte growth factor (HGF), epidermal growth factor (EGF), or basic fibroblast growth factor (bFGF) caused rapid nuclear ERK1/2 activation in MB cells, which persisted for several hours. Concomitant treatment with the BCR/ABL kinase inhibitor dasatinib completely repressed nuclear ERK1/2 activity induced by HGF and EGF but not by bFGF. Increased nuclear ERK1/2 activity correlated positively with speed of invasion. Dasatinib blocked ERK-associated invasion in the majority of cells, but we also observed fast-invading cells with low ERK1/2 activity. These ERK1/2-low, fast-moving cells displayed a rounded morphology, while ERK-high fast-moving cells displayed a mesenchymal morphology. Dasatinib effectively blocked EGF-induced proliferation while it only moderately repressed tissue invasion, indicating that a subset of cells may evade invasion repression by dasatinib through non-mesenchymal motility. Thus, growth factor-induced nuclear activation of ERK1/2 is associated with mesenchymal motility and proliferation in MB cells and can be blocked with the BCR/ABL kinase inhibitor dasatinib.

Neurotrophin Signaling in Medulloblastoma

Neurotrophins are a family of secreted proteins that act by binding to tropomyosin receptor kinase (Trk) or p75NTR receptors to regulate nervous system development and plasticity. Increasing evidence indicates that neurotrophins and their receptors in cancer cells play a role in tumor growth and resistance to treatment. In this review, we summarize evidence indicating that neurotrophin signaling influences medulloblastoma (MB), the most common type of malignant brain cancer afflicting children. We discuss the potential of neurotrophin receptors as new therapeutic targets for the treatment of MB. Overall, activation of TrkA and TrkC types of receptors seem to promote cell death, whereas TrkB might stimulate MB growth, and TrkB inhibition displays antitumor effects. Importantly, we show analyses of the gene expression profile of neurotrophins and their receptors in MB primary tumors, which indicate, among other findings, that higher levels of NTRK1 or NTRK2 are associated with reduced overall survival (OS) of patients with SHH MB tumors.

An OTX2-PAX3 signaling axis regulates Group 3 medulloblastoma cell fate

OTX2 is a potent oncogene that promotes tumor growth in Group 3 medulloblastoma. However, the mechanisms by which OTX2 represses neural differentiation are not well characterized. Here, we perform extensive multiomic analyses to identify an OTX2 regulatory network that controls Group 3 medulloblastoma cell fate. OTX2 silencing modulates the repressive chromatin landscape, decreases levels of PRC2 complex genes and increases the expression of neurodevelopmental transcription factors including PAX3 and PAX6. Expression of PAX3 and PAX6 is significantly lower in Group 3 medulloblastoma patients and is correlated with reduced survival, yet only PAX3 inhibits self-renewal in vitro and increases survival in vivo. Single cell RNA sequencing of Group 3 medulloblastoma tumorspheres demonstrates expression of an undifferentiated progenitor program observed in primary tumors and characterized by translation/elongation factor genes. Identification of mTORC1 signaling as a downstream effector of OTX2-PAX3 reveals roles for protein synthesis pathways in regulating Group 3 medulloblastoma pathogenesis.

OTX2 promotes tumour growth in Group 3 medulloblastoma. Here, the authors show that OTX2 regulates PAX3 to induce neural de-differentiation and promote tumourigenesis in Group 3 medulloblastoma.

Methylation Profiling of Medulloblastoma in a Clinical Setting Permits Sub-classification and Reveals New Outcome Predictions

Medulloblastoma (MB) is the most common childhood malignant brain tumor and is a leading cause of cancer-related death in children. DNA methylation profiling has rapidly advanced our understanding of MB pathogenesis at the molecular level, but assessments in Saudi Arabian (SA)-MB cases are sparse. MBs can be sub-grouped according to methylation patterns from FPPE samples into Wingless (WNT-MB), Sonic Hedgehog (SHH-MB), Group 3 (G3), and Group 4 (G4) tumors. The WNT-MB and SHH-MB subgroups are characterized by gain-of function mutations that activate oncogenic cell signaling, whilst G3/G4 tumors show recurrent chromosomal alterations. Given that each subgroup has distinct clinical outcomes, the ability to subgroup SA-FPPE samples holds significant prognostic and therapeutic value. Here, we performed the first assessment of MB-DNA methylation patterns in an SA cohort using archival biopsy material (FPPE n = 49). Of the 41 materials available for methylation assessments, 39 could be classified into the major DNA methylation subgroups (SHH, WNT, G3, and G4). Furthermore, methylation analysis was able to reclassify tumors that could not be sub-grouped through next-generation sequencing, highlighting its superior accuracy for MB molecular classifications. Independent assessments demonstrated known clinical relationships of the subgroups, exemplified by the high survival rates observed for WNT tumors. Surprisingly, the G4 subgroup did not conform to previously identified phenotypes, with a high prevalence in females, high metastatic rates, and a large number of tumor-associated deaths. Taking our results together, we demonstrate that DNA methylation profiling enables the robust sub-classification of four disease sub-groups in archival FFPE biopsy material from SA-MB patients. Moreover, we show that the incorporation of DNA methylation biomarkers can significantly improve current disease-risk stratification schemes, particularly concerning the identification of aggressive G4 tumors. These findings have important implications for future clinical disease management in MB cases across the Arab world.

Cytometric analysis of cell suspension generated by cavitron ultrasonic surgical aspirator in pediatric brain tumors

PURPOSE

The aim of this study was to test the possibility of using specimens obtained by a cavitron ultrasonic surgical aspirator (CUSA) in flow and mass cytometry investigations of pediatric brain tumors.

METHODS

CUSA specimens obtained from 19 pediatric patients with brain tumors were investigated. Flow and mass cytometry methods were applied to analyze the composition of material collected using the CUSA. Cell suspensions were prepared from CUSA aspirates. Then sample viability was assessed by conventional flow cytometry and subsequently stained with a panel of 31 metal-labeled antibodies.

RESULTS

Viability assessment was performed using conventional flow cytometry. Viability of cells in the acquired samples was below 50% in 16 of 19 cases. A mass cytometry investigation and subsequent analysis enabled us to discriminate brain tumor cells from contaminating leukocytes, whose proportions varied across the specimens. The addition of the viability marker cisplatin directly into the mass cytometry panel gave the means to selecting viable cells only for subsequent analyses. The proportion of non-viable cells was higher among tumor cells compared leukocytes.

CONCLUSIONS

When the analysis of the tumor cell immunophenotype is performed with markers for determining viability, the expression of the investigated markers can be evaluated. Suitable markers can be selected by high-throughput methods, such as mass cytometry, and those that are diagnostically relevant can be investigated using flow cytometry, which is more flexible in terms of time.

Genetic Abnormalities, Clonal Evolution, and Cancer Stem Cells of Brain Tumors

Brain tumors are highly heterogeneous and have been classified by the World Health Organization in various histological and molecular subtypes. Gliomas have been classified as ranging from low-grade astrocytomas and oligodendrogliomas to high-grade astrocytomas or glioblastomas. These tumors are characterized by a peculiar pattern of genetic alterations. Pediatric high-grade gliomas are histologically indistinguishable from adult glioblastomas, but they are considered distinct from adult glioblastomas because they possess a different spectrum of driver mutations (genes encoding histones H3.3 and H3.1). Medulloblastomas, the most frequent pediatric brain tumors, are considered to be of embryonic derivation and are currently subdivided into distinct subgroups depending on histological features and genetic profiling. There is emerging evidence that brain tumors are maintained by a special neural or glial stem cell-like population that self-renews and gives rise to differentiated progeny. In many instances, the prognosis of the majority of brain tumors remains negative and there is hope that the new acquisition of information on the molecular and cellular bases of these tumors will be translated in the development of new, more active treatments.