Signaling pathways and mesenchymal transition in pediatric high-grade glioma

Diffuse midline glioma invasion and metastasis rely on cell-autonomous signaling

BACKGROUND

Diffuse midline gliomas (DMG) are pediatric tumors with negligible 2-year survival after diagnosis characterized by their ability to infiltrate the central nervous system. In the hope of controlling the local growth and slowing the disease, all patients receive radiotherapy. However, distant progression occurs frequently in DMG patients. Current clues as to what causes tumor infiltration circle mainly around the tumor microenvironment, but there are currently no known determinants to predict the degree of invasiveness.

METHODS

In this study, we use patient-derived glioma stem cells (GSCs) to create patient-specific 3D avatars to model interindividual invasion and elucidate the cellular supporting mechanisms.

RESULTS

We show that GSC models in 3D mirror the invasive behavior of the parental tumors, thus proving the ability of DMG to infiltrate as an autonomous characteristic of tumor cells. Furthermore, we distinguished 2 modes of migration, mesenchymal and ameboid-like, and associated the ameboid-like modality with GSCs derived from the most invasive tumors. Using transcriptomics of both organoids and primary tumors, we further characterized the invasive ameboid-like tumors as oligodendrocyte progenitor-like, with highly contractile cytoskeleton and reduced adhesion ability driven by crucial over-expression of bone morphogenetic pathway 7 (BMP7). Finally, we deciphered MEK, ERK, and Rho/ROCK kinases activated downstream of the BMP7 stimulation as actionable targets controlling tumor cell motility.

CONCLUSIONS

Our findings identify 2 new therapeutic avenues. First, patient-derived GSCs represent a predictive tool for patient stratification in order to adapt irradiation strategies. Second, autocrine and short-range BMP7-related signaling becomes a druggable target to prevent DMG spread and metastasis.

Ferroptosis and EMT: key targets for combating cancer progression and therapy resistance

Iron-dependent lipid peroxidation causes ferroptosis, a form of regulated cell death. Crucial steps in the formation of ferroptosis include the accumulation of ferrous ions (Fe2+) and lipid peroxidation, of which are controlled by glutathione peroxidase 4 (GPX4). Its crucial role in stopping the spread of cancer has been shown by numerous studies undertaken in the last ten years. Epithelial-mesenchymal transition (EMT) is the process by which epithelial cells acquire mesenchymal characteristics. EMT is connected to carcinogenesis, invasiveness, metastasis, and therapeutic resistance in cancer. It is controlled by a range of internal and external signals and changes the phenotype from epithelial to mesenchymal like. Studies have shown that mesenchymal cancer cells tend to be more ferroptotic than their epithelial counterparts. Drug-resistant cancer cells are more easily killed by inducers of ferroptosis when they undergo EMT. Therefore, understanding the interaction between ferroptosis and EMT will help identify novel cancer treatment targets. In-depth discussion is given to the regulation of ferroptosis, the potential application of EMT in the treatment of cancer, and the relationships between ferroptosis, EMT, and signaling pathways associated with tumors. Invasion, metastasis, and inflammation in cancer all include ferroptosis and EMT. The goal of this review is to provide suggestions for future research and practical guidance for applying ferroptosis and EMT in clinical practice.

Radiotherapy and radio-sensitization in H3K27M -mutated diffuse midline gliomas

BACKGROUND

H3^K27M mutated diffuse midline gliomas (DMGs) are extremely aggressive and the leading cause of cancer-related deaths in pediatric brain tumors with 5-year survival <1%. Radiotherapy is the only established adjuvant treatment of H3^K27M DMGs; however, the radio-resistance is commonly observed.

METHODS

We summarized current understandings of the molecular responses of H3^K27M DMGs to radiotherapy and provide crucial insights into current advances in radiosensitivity enhancement.

RESULTS

Ionizing radiation (IR) can mainly inhibit tumor cell growth by inducing DNA damage regulated by the cell cycle checkpoints and DNA damage repair (DDR) system. In H3K27M DMGs, the aberrant genetic and epigenetic changes, stemness genotype, and epithelial-mesenchymal transition (EMT) disrupt the cell cycle checkpoints and DDR system by altering the associated regulatory signaling pathways, which leads to the development of radio-resistance.

CONCLUSIONS

The advances in mechanisms of radio-resistance in H3^K27M  DMGs promote the potential targets to enhance the sensitivity to radiotherapy.

Cyclin-dependent kinase subunit2 (CKS2) promotes malignant phenotypes and epithelial-mesenchymal transition-like process in glioma by activating TGFβ/SMAD signaling

BACKGROUND

Gliomas are a group of primary intracranial tumors with high morbidity and mortality. The previous researches indicated a crucial role of CKS2 (cyclin-dependent kinases regulatory subunit 2) in hepatocellular carcinoma and breast cancer; however, little is known about the molecular mechanism of CKS2 in the tumorigenesis and epithelial-mesenchymal transition-like (EMT) process in glioma.

METHODS

Datasets for bioinformatics analysis were obtained from the GEO, TCGA and CGGA databases. qRT-PCR, western blotting (WB), and immunohistochemistry (IHC) assays were used to investigate the expression patterns of CKS2 among glioma and brain tissues. Glioma cells were transfected with small interfering RNA/overexpression plasmid against CKS2, then clone formation assay, CCK-8, wound healing, Transwell assay, and flow cytometry were performed to detect changes in cell viability, invasiveness, and the apoptosis rate. Markers of cell invasion, apoptosis, EMT and TGFβ/SMAD signaling were evaluated by WB and immunofluorescence (IF) assays.

RESULTS

We found that CKS2 overexpression correlates with poor prognosis in human glioma and knockdown of CKS2 could inhibit cell proliferation, migration, invasion, and induced apoptosis in glioma cells. Besides, we also found that knockdown of CKS2 could reverse the EMT process via modulating EMT-related molecules. Glioma cells with overexpression of CKS2 were constructed to confirmed the fact that CKS2 induced nucleocytoplasmic translocation of SMAD2/3 and activated TGFβ/SMAD pathway, then upregulated its downstream targets expression, while inhibition of TGFβ/SMAD (by TGFβ inhibitor LY2157299 or SMAD4 siRNA) could reverse the tumor-promoting effects and malignant phenotype caused by CKS2 overexpression.

CONCLUSIONS

We identified CKS2 as a critical contributor to the gliomagenesis, which might provide a novel therapeutic target for inhibiting the spread and infiltration of glioma.

Single-Cell Analysis of Unidirectional Migration of Glioblastoma Cells Using a Fiber-Based Scaffold

Glioblastoma (GBM) is a malignant incurable brain tumor in which immature neoplastic cells infiltrate brain tissue by spreading along nerve fibers. The aim of the study was to compare the migration abilities of glioma cells with those of other cancer cells and elucidate the migratory profiles underlying the differential migration of glioma cells using a fiber-based quantitative migration assay. Here, wound healing and transwell assays were used to assess cell mobility in four cell lines: U87-MG glioblastoma cells, MDA-MB-231 breast cancer cells, HCT116 colorectal cancer cells, and MKN45 gastric cancer cells. We also assessed cell mobility using a fiber model that mimics nerve fibers. Time-lapse video microscopy was used to observe cell migration and morphology. The cytoskeleton arrangement was assessed in the fiber model and compared with that in the conventional cell culture model. The conventional evaluation of cell migration ability revealed that the migration ability of breast cancer and glioblastoma cell lines was higher than that of colon cancer and gastric cancer cell lines. The fiber model confirmed that the glioblastoma cell line had a significantly higher migration ability than other cell lines. Tubulin levels were significantly higher in the glioblastoma cells than in other cell lines. In conclusion, the developed fiber-based culture model revealed the specific migratory profile of GBM cells during invasion.

Global research trends and hotspots on glioma stem cells

Background

Glioma stem cells (GSCs) are a sub-population of cancer stem cells with capacity of self-renewal and differentiation. Accumulated evidence has revealed that GSCs were shown to contribute to gliomagenesis, distant metastasis as well as the resistance to radiotherapy and chemotherapy. As a result, GSCs were regarded as a promising therapeutic target in human glioma. The purpose of our study is to identify current state and hotspots of GSCs research by analyzing scientific publications through bibliometric methods.

Methods

All relevant publications on GSCs during 2003-2021 were extracted from the Science Citation Index Expanded of Web of Science Core Collection (WoSCC), and related information was collected and analyzed using Microsoft Excel 2016, GraphPad Prism 8 and VOSviewer software.

Results

A total of 4990 papers were included. The United States accounted for the largest number of publications (1852), the second average citations per item (ACI) value (67.54) as well as the highest H-index (157). Cancer Research was the most influential journal in this field. The most contributive institution was League of European Research Universities. RICH JN was the author with the most publications (109) and the highest H-index (59). All studies were clustered into 3 groups: “glioma stem cell properties”, “cell biological properties” and “oncology therapy”. The keywords “identification”, “CD133” and “side population” appeared earlier with the smaller average appearing years (AAY), and the keywords”radiotherapy” and “chemotherapy” had the latest AAY. The analysis of top cited articles showed that “temozolomide”, “epithelial-mesenchymal transition”, and “immunotherapy” emerged as new focused issues.

Conclusion

There has been a growing number of researches on GSCs. The United States has always been a leading player in this domain. In general, the research focus has gradually shifted from basic cellular biology to the solutions of clinical concerns. “Temozolomide resistance”, “epithelial-mesenchymal transition”, and “immunotherapy” should be given more attention in the future.

Diffuse Intrinsic Pontine Glioma: Molecular Landscape, Evolving Treatment Strategies and Emerging Clinical Trials

Diffuse intrinsic pontine glioma (DIPG) is a type of intrinsic brainstem glial tumor that occurs primarily in the pediatric population. DIPG is initially diagnosed based on clinical symptoms and the characteristic location on imaging. Histologically, these tumors are characterized by a heterogenous population of cells with multiple genetic mutations and high infiltrative capacity. The most common mutation seen in this group is a lysine to methionine point mutation seen at position 27 (K27M) within histone 3 (H3). Tumors with the H3 K27M mutation, are considered grade 4 and are now categorized within the H3 K27-altered diffuse midline glioma category by World Health Organization classification. Due to its critical location and aggressive nature, DIPG is resistant to the most eradicative treatment and is universally fatal; however, modern advances in the surgical techniques resulting in safe biopsy of the lesion have significantly improved our understanding of this disease at the molecular level. Genomic analysis has shown several mutations that play a role in the pathophysiology of the disease and can be targeted therapeutically. In this review, we will elaborate on DIPG from general aspects and the evolving molecular landscape. We will also review innovative therapeutic options that have been trialed along with new promising treatments on the horizon.

TMCO1 expression promotes cell proliferation and induces epithelial-mesenchymal transformation in human gliomas

Transmembrane and coiled-coil domains 1 (TMCO1) is a recently discovered transmembrane protein of endoplasmic reticulum (ER), which plays a critical role in maintaining calcium homeostasis. TMCO1 dysfunction has been proved to be closely related to a variety of human diseases, including glaucoma, deformities, mental retardation and tumorigenesis. However, the role of TMCO1 in gliomas remains unclear. The purpose of this study was to detect the role of TMCO1 in the pathogenesis and progression of gliomas. This study demonstrated that TMCO1 was upregulated in gliomas and its overexpression predicted poor prognosis. We also revealed that the expression of TMCO1 was associated with the World Health Organization (WHO) grade of gliomas. Knockdown of TMCO1 inhibited the proliferation and induced apoptosis of U87 and U251 cells. In addition, TMCO1 induced GBM cell migration and invasion by promoting epithelial-mesenchymal transition (EMT). These date collectively proved the crucial role of TMCO1 as a novel prognostic factor and underlying therapeutic target for glioma patients.

AURKA and PLK1 inhibition selectively and synergistically block cell cycle progression in diffuse midline glioma

Diffuse midline gliomas (DMG) are highly malignant incurable pediatric brain tumors. In this study, we show that Aurora kinase A (AURKA) is overexpressed in DMG and can be used as a therapeutic target. Additionally, AURKA inhibition combined with CRISPR/Cas9 screening in DMG cells, revealed polo-like kinase 1 (PLK1) as a synergistic target with AURKA. Using a panel of patient-derived DMG culture models, we demonstrate that treatment with volasertib, a clinically relevant and selective PLK1 inhibitor, synergizes with different AURKA inhibitors, supporting the CRISPR screen results. Mechanistically, our results show that combined loss of PLK1 and AURKA causes a G2/M cell cycle arrest which blocks vital parts of DNA-damage repair and induces apoptosis, solely in DMG cells. Altogether, our findings highlight the importance of AURKA and PLK1 for DMG propagation and demonstrate the potential of concurrently targeting these proteins as a therapeutic strategy for these devastating pediatric brain tumors.

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Kinome-wide CRISPR/Cas9 screening in primary DMG tumoroids

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CRISPR screening identifies AURKA as therapeutic target in DMG

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AURKA inhibition sensitizes DMG to PLK1 knockout

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Combined AURKA and PLK1 inhibition selectively impairs DMG cell division

Deploying Kinase Inhibitors to Study Pediatric Gliomas

Pediatric midline gliomas are a uniformly fatal disease for which there is no cure. The location of these tumors makes surgical resection impossible, and so novel therapies are urgently needed to improve outcomes. The biology of these tumors is increasingly understood, with the histone H3K27M mutation playing a critical role in the pathogenesis of these tumors. Efforts to inhibit the growth of these tumors have also focused on inhibiting the Aurora kinase and Janus-associated kinase (JAK)/signal transducer and activator of transcription (STAT) pathway in order to disrupt tumor proliferation. A number of small molecule inhibitors of these kinases have shown promise in early studies. Screening and preclinical assessment of such inhibitors requires a functional assay to assess the degree of kinase inhibition. We detail here a luciferase-based reporter assay for STAT3 transcriptional activity that we have employed frequently in order to assess the efficacy of kinase inhibitors in pediatric gliomas. The assay we describe is specific to STAT3, but the overall methodology is generalizable to other downstream targets of the kinase of interest.

Therapeutic Targets in Diffuse Midline Gliomas-An Emerging Landscape

Simple Summary

Diffuse midline gliomas (DMGs) remain one of the most devastating childhood brain tumour types, for which there is currently no known cure. In this review we provide a summary of the existing knowledge of the molecular mechanisms underlying the pathogenesis of this disease, highlighting current analyses and novel treatment propositions. Together, the accumulation of these data will aid in the understanding and development of more effective therapeutic options for the treatment of DMGs.

Abstract

Diffuse midline gliomas (DMGs) are invariably fatal pediatric brain tumours that are inherently resistant to conventional therapy. In recent years our understanding of the underlying molecular mechanisms of DMG tumorigenicity has resulted in the identification of novel targets and the development of a range of potential therapies, with multiple agents now being progressed to clinical translation to test their therapeutic efficacy. Here, we provide an overview of the current therapies aimed at epigenetic and mutational drivers, cellular pathway aberrations and tumor microenvironment mechanisms in DMGs in order to aid therapy development and facilitate a holistic approach to patient treatment.

Development of a Prognostic Model Based on the Identification of EMT-Related lncRNAs in Triple-Negative Breast Cancer

Background

Triple-negative breast cancer (TNBC) remains the most incurable subtype of breast cancer owing to high heterogeneity, aggressive nature, and lack of treatment options. It is generally acknowledged that epithelial-mesenchymal transition (EMT) is the key step in tumor metastasis.

Methods

With the application of TCGA and GEO databases, we identified EMT-related lncRNAs by the Cox univariate regression analysis. Optimum risk scores were calculated and used to divide TNBC patients into high-/low-risk subgroups by the median value using the Lasso regression analysis. The Kaplan–Meier and ROC curve analyses were applied for model validation. Then, we assessed the risk model from multi-omic aspects including immune infiltration, drug sensitivity, mutability spectrum, signaling pathways, and clinical indicators. We also analyzed the expression pattern of lncRNAs involved in the model using qRT-PCR in TNBC cell lines and constructed the ceRNA network.

Results

The risk model was composed of EMT-related long noncoding RNAs (lncRNAs), which seemed to be valuable in the prognostic prediction of TNBC patients. The model could act as an independent prognostic factor of TNBC and showed a robust prognostic ability in the stratification analysis. Further investigation demonstrated that the expression of lncRNAs was different between high aggressive and low aggressive TNBC cell lines, as well as TNBC patients.

Conclusions

Together, our study successfully established a risk model with great accuracy and efficacy in the prognostic prediction of TNBC patients.

Knockdown of ER-α36 expression inhibits glioma proliferation, invasion and epithelial-to-mesenchymal transition

Estrogen receptor-α36 (ER-α36), a subtype of the estrogen receptor, is reported to play roles in tumorigenesis and tamoxifen resistance in several tumors, especially breast cancer. However, the role of ER-α36 in glioma proliferation and invasion remains unknown. Here, we explored the function of ER-α36 in glioma cells, using U87 and U251 cell lines. We found that ER-α36 was upregulated in glioma tissues compared to adjacent nontumor tissues. In U87 and U251 glioma cell lines, inhibition of ER-α36 expression by shRNA suppressed cell proliferation and invasion. In addition, the expression of an epithelial marker, ZO-1, was upregulated while that of one mesenchymal marker, N-cadherin, was downregulated with ER-α36 knockdown. We also found that inhibition of ER-α36 inactivated both PI3K/AKT and MEK/ERK signals. Taken together, these data indicated that overexpression of ER-α36 is associated with glioma proliferation and progression but that inhibition of ER-α36 leads to suppressed invasion and the epithelial-to-mesenchymal transition via PI3K/AKT and MEK/ERK pathway inactivation in glioma cells.

Blocking hsa_circ_0006168 suppresses cell proliferation and motility of human glioblastoma cells by regulating hsa_circ_0006168/miR-628-5p/IGF1R ceRNA axis

BACKGROUND

hsa_circ_0006168 is an oncogenic circular RNA in esophageal cancer. However, its role remains unclarified in tumor progression of gliomas, especially in glioblastoma (GBM).

METHODS

Cell counting kit-8 assay, transwell assays, western blotting, and xenograft experiment, as well as colony formation assay and flow cytometry were performed to measure cell proliferation and motility. Expression of hsa_circ_0006168, microRNA (miR)-628-3p, insulin‑like growth factor 1 receptor (IGF1R), and Ras/extracellular signal regulated kinases (Erk)-related proteins were determined by quantitative real-time polymerase chain reaction and western blotting. The physical interaction was confirmed by dual-luciferase reporter assay and RNA pull-down assay.

RESULTS

hsa_circ_0006168 and IGF1R were upregulated, and miR-628-5p was downregulated in human GBM tissues and cells. Functionally, blocking hsa_circ_0006168 and overexpressing miR-628-5p suppressed cell proliferation, migration, invasion, and expression of Vimentin and Snail (mesenchymal markers) in A172 and LN229 cells, accompanied with increased E-cadherin (epithelial marker), decreased colony formation, and promoted apoptosis rate. Silencing miR-628-5p counteracted the suppression of hsa_circ_0006168 deficiency on these behaviors, and restoring IGF1R blocked miR-628-5p-mediated inhibition as well. More importantly, hsa_circ_0006168 knockdown could delay xenograft tumor growth in vivo and lower Ras and phosphorylated Erk1/2 expression in vitro and in vivo. Mechanically, hsa_circ_0006168 targeted and sponged miR-628-5p, and IFG1R was a novel target for miR-628-5p. Inhibiting miR-628-5p could abrogate in vitro role of hsa_circ_0006168 knockdown, and similarly IGF1R upregulation counteracted miR-628-5p role.

CONCLUSION

Silencing hsa_circ_0006168 might suppress GBM proliferation and motility via serving as competitive endogenous RNA for miR-628-5p and regulating IGF1R/Ras/Erk pathway.

Development and pre-clinical testing of a novel hypoxia-activated KDAC inhibitor

Tumor hypoxia is associated with therapy resistance and poor patient prognosis. Hypoxia-activated prodrugs, designed to selectively target hypoxic cells while sparing normal tissue, represent a promising treatment strategy. We report the pre-clinical efficacy of 1-methyl-2-nitroimidazole panobinostat (NI-Pano, CH-03), a novel bioreductive version of the clinically used lysine deacetylase inhibitor, panobinostat. NI-Pano was stable in normoxic (21% O₂) conditions and underwent NADPH-CYP-mediated enzymatic bioreduction to release panobinostat in hypoxia (<0.1% O₂). Treatment of cells grown in both 2D and 3D with NI-Pano increased acetylation of histone H3 at lysine 9, induced apoptosis, and decreased clonogenic survival. Importantly, NI-Pano exhibited growth delay effects as a single agent in tumor xenografts. Pharmacokinetic analysis confirmed the presence of sub-micromolar concentrations of panobinostat in hypoxic mouse xenografts, but not in circulating plasma or kidneys. Together, our pre-clinical results provide a strong mechanistic rationale for the clinical development of NI-Pano for selective targeting of hypoxic tumors.

Overexpression of FBXO17 Promotes the Proliferation, Migration and Invasion of Glioma Cells Through the Akt/GSK-3β/Snail Pathway

FBXO17 is a newly studied F-box protein associated with high-grade glioma. However, its exact role in glioma remains unclear. In the present study, we aimed to investigate the role of FBXO17 in glioma both in vitro and in vivo and explore the underlying mechanism. Our results showed that FBXO17 mRNA and protein levels were upregulated in glioma cells including U87, U251, SHG44, and U-118-MG cells as compared to the HA1800 cells. Downregulation of FBXO17 significantly suppressed the cellular behaviors of glioma cells including cell proliferation, migration, and invasion. In addition, FBXO17 knockdown induced E-cadherin expression and inhibited N-cadherin and vimentin expression at mRNA and protein levels in glioma cells. In contrast, overexpression of FBXO17 promoted cell proliferation, migration, invasion and EMT process. Furthermore, FBXO17 regulated the Akt/GSK-3β/snail signaling pathway in glioma cells with significant changes in the expression levels of p-Akt, p-GSK-3β and snail. Additionally, inhibition of Akt by LY294002 reversed the effects of FBXO17 overexpression on cellular behaviors of glioma cells. Finally, in vivo mouse xenograft assay proved that downregulation of FBXO17 suppresses the tumorigenesis of glioma. In conclusion, these findings demonstrated that FBXO17 acted as a promotor of glioma development via modulating Akt/GSK-3β/snail signaling pathway.

Radiosensitization in Pediatric High-Grade Glioma: Targets, Resistance and Developments

Pediatric high-grade gliomas (pHGG) are the leading cause of cancer-related death in children. These epigenetically dysregulated tumors often harbor mutations in genes encoding histone 3, which contributes to a stem cell-like, therapy-resistant phenotype. Furthermore, pHGG are characterized by a diffuse growth pattern, which, together with their delicate location, makes complete surgical resection often impossible. Radiation therapy (RT) is part of the standard therapy against pHGG and generally the only modality, apart from surgery, to provide symptom relief and a delay in tumor progression. However, as a single treatment modality, RT still offers no chance for a cure. As with most therapeutic approaches, irradiated cancer cells often acquire resistance mechanisms that permit survival or stimulate regrowth after treatment, thereby limiting the efficacy of RT. Various preclinical studies have investigated radiosensitizers in pHGG models, without leading to an improved clinical outcome for these patients. However, our recently improved molecular understanding of pHGG generates new opportunities to (re-)evaluate radiosensitizers in these malignancies. Furthermore, the use of radio-enhancing agents has several benefits in pHGG compared to other cancers, which will be discussed here. This review provides an overview and a critical evaluation of the radiosensitization strategies that have been studied to date in pHGG, thereby providing a framework for improving radiosensitivity of these rapidly fatal brain tumors.

A pilot radiogenomic study of DIPG reveals distinct subgroups with unique clinical trajectories and therapeutic targets

An adequate understanding of the relationships between radiographic and genomic features in diffuse intrinsic pontine glioma (DIPG) is essential, especially in the absence of universal biopsy, to further characterize the molecular heterogeneity of this disease and determine which patients are most likely to respond to biologically-driven therapies. Here, a radiogenomics analytic approach was applied to a cohort of 28 patients with DIPG. Tumor size and imaging characteristics from all available serial MRIs were evaluated by a neuro-radiologist, and patients were divided into three radiographic response groups (partial response [PR], stable disease [SD], progressive disease [PD]) based on MRI within 2 months of radiotherapy (RT) completion. Whole genome and RNA sequencing were performed on autopsy tumor specimens. We report several key, therapeutically-relevant findings: (1) Certain radiologic features on first and subsequent post-RT MRIs are associated with worse overall survival, including PD following irradiation as well as present, new, and/or increasing peripheral ring enhancement, necrosis, and diffusion restriction. (2) Upregulation of EMT-related genes and distant tumor spread at autopsy are observed in a subset of DIPG patients who exhibit poorer radiographic response to irradiation and/or higher likelihood of harboring H3F3A mutations, suggesting possible benefit of upfront craniospinal irradiation. (3) Additional genetic aberrations were identified, including DYNC1LI1 mutations in a subgroup of patients with PR on post-RT MRI; further investigation into potential roles in DIPG tumorigenesis and/or treatment sensitivity is necessary. (4) Whereas most DIPG tumors have an immunologically “cold” microenvironment, there appears to be a subset which harbor a more inflammatory genomic profile and/or higher mutational burden, with a trend toward improved overall survival and more favorable radiographic response to irradiation, in whom immunotherapy should be considered. This study has begun elucidating relationships between post-RT radiographic response with DIPG molecular profiles, revealing radiogenomically distinct subgroups with unique clinical trajectories and therapeutic targets.

Integrated Proteogenomic Characterization across Major Histological Types of Pediatric Brain Cancer

We report a comprehensive proteogenomics analysis, including whole-genome sequencing, RNA sequencing, and proteomics and phosphoproteomics profiling, of 218 tumors across 7 histological types of childhood brain cancer: low-grade glioma (n = 93), ependymoma (32), high-grade glioma (25), medulloblastoma (22), ganglioglioma (18), craniopharyngioma (16), and atypical teratoid rhabdoid tumor (12). Proteomics data identify common biological themes that span histological boundaries, suggesting that treatments used for one histological type may be applied effectively to other tumors sharing similar proteomics features. Immune landscape characterization reveals diverse tumor microenvironments across and within diagnoses. Proteomics data further reveal functional effects of somatic mutations and copy number variations (CNVs) not evident in transcriptomics data. Kinase-substrate association and co-expression network analysis identify important biological mechanisms of tumorigenesis. This is the first large-scale proteogenomics analysis across traditional histological boundaries to uncover foundational pediatric brain tumor biology and inform rational treatment selection.

MiR-4310 induced by SP1 targets PTEN to promote glioma progression

Background

miRNAs have been reported to be involved in multiple biological processes of gliomas. Here, we aimed to analyze miR-4310 and its correlation genes involved in the progression of human glioma.

Methods

miR-4310 expression levels were examined in glioma and non-tumor brain (NB) tissues. The molecular mechanisms of miR-4310 expression and its effects on cell proliferation, migration, and invasion were explored using 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide, Transwell chamber, Boyden chamber, and western blot analyses, as well as its effect on tumorigenesis was explored in vivo in nude mice. The relationships between miR-4310, SP1, phosphatase, and tensin homolog (PTEN) were explored using chromatin immunoprecipitation, agarose gel electrophoresis, electrophoresis mobility shift, and dual-luciferase reporter gene assays.

Results

miR-4310 expression was upregulated in glioma tissues compared to that in NB tissues. Overexpressed miR-4310 promoted glioma cell proliferation, migration, and invasion in vitro, as well as tumorigenesis in vivo. The inhibition of miR-4310 expression was sufficient to reverse these results. Mechanistic analyses revealed that miR-4310 promoted glioma progression through the PI3K/AKT pathway by targeting PTEN. Additionally, SP1 induced the expression of miR-4310 by binding to its promoter region.

Conclusion

miR-4310 promotes the progression of glioma by targeting PTEN and activating the PI3K/AKT pathway; meanwhile, the expression of miR-4310 was induced by SP1.

Identification of a differentiation stall in epithelial mesenchymal transition in histone H3-mutant diffuse midline glioma

BACKGROUND

Diffuse midline gliomas with histone H3 K27M (H3K27M) mutations occur in early childhood and are marked by an invasive phenotype and global decrease in H3K27me3, an epigenetic mark that regulates differentiation and development. H3K27M mutation timing and effect on early embryonic brain development are not fully characterized.

RESULTS

We analyzed multiple publicly available RNA sequencing datasets to identify differentially expressed genes between H3K27M and non-K27M pediatric gliomas. We found that genes involved in the epithelial-mesenchymal transition (EMT) were significantly overrepresented among differentially expressed genes. Overall, the expression of pre-EMT genes was increased in the H3K27M tumors as compared to non-K27M tumors, while the expression of post-EMT genes was decreased. We hypothesized that H3K27M may contribute to gliomagenesis by stalling an EMT required for early brain development, and evaluated this hypothesis by using another publicly available dataset of single-cell and bulk RNA sequencing data from developing cerebral organoids. This analysis revealed similarities between H3K27M tumors and pre-EMT normal brain cells. Finally, a previously published single-cell RNA sequencing dataset of H3K27M and non-K27M gliomas revealed subgroups of cells at different stages of EMT. In particular, H3.1K27M tumors resemble a later EMT stage compared to H3.3K27M tumors.

CONCLUSIONS

Our data analyses indicate that this mutation may be associated with a differentiation stall evident from the failure to proceed through the EMT-like developmental processes, and that H3K27M cells preferentially exist in a pre-EMT cell phenotype. This study demonstrates how novel biological insights could be derived from combined analysis of several previously published datasets, highlighting the importance of making genomic data available to the community in a timely manner.

Mesenchymal Transformation: The Rosetta Stone of Glioblastoma Pathogenesis and Therapy Resistance

Despite decades of research, glioblastoma (GBM) remains invariably fatal among all forms of cancers. The high level of inter- and intratumoral heterogeneity along with its biological location, the brain, are major barriers against effective treatment. Molecular and single cell analysis identifies different molecular subtypes with varying prognosis, while multiple subtypes can reside in the same tumor. Cellular plasticity among different subtypes in response to therapies or during recurrence adds another hurdle in the treatment of GBM. This phenotypic shift is induced and sustained by activation of several pathways within the tumor itself, or microenvironmental factors. In this review, the dynamic nature of cellular shifts in GBM and how the tumor (immune) microenvironment shapes this process leading to therapeutic resistance, while highlighting emerging tools and approaches to study this dynamic double-edged sword are discussed.

EEF1D Promotes Glioma Proliferation, Migration, and Invasion through EMT and PI3K/Akt Pathway

Eukaryotic translation elongation factor 1δ (EEF1D), a subunit of the elongation factor 1 complex of proteins, mediates the elongation process of protein synthesis. Besides this canonical role, EEF1D was found overexpressed in many tumors, like hepatocarcinomas and medulloblastomas. In the present study, we demonstrated for the first time that EEF1D may interact with other putative proteins to regulate cell proliferation, migration, and invasion through PI3K/Akt and EMT pathways in glioma. Furthermore, knockdown of EEF1D could reduce cell proliferation and impaired epithelial-mesenchymal transition (EMT) phenotypes, including cell invasion. Taken together, these results indicate that EEF1D and its partner proteins might play a critical role in glioma and serve as a potential therapeutic target of glioma.

Knockdown of circ0082374 inhibits cell viability, migration, invasion and glycolysis in glioma cells by miR-326/SIRT1

Circular RNAs (circRNAs) play important roles in the development and treatment of glioma. However, the role and mechanism of circRNA carboxypeptidase A4 (circ0082374) in glioma are largely unknown. Forty-two glioma patients and 28 normal patients were recruited. Glioma cell lines A172 and U251 were used for functional assays. The expression levels of circ0082374, microRNA-326 (miR-326) and sirtuin 1 (SIRT1) were examined via quantitative real-time polymerase chain reaction or western blot. Cell viability, migration, invasion and glycolysis were measured via cell counting kit-8, trans-well, oxygen consumption rate and western blot, respectively. The target correlation of circ0082374/miR-326 or miR-326/SIRT1 was explored via dual-luciferase reporter, RNA immunoprecipitation and pull-down assays. The role of circ0082374 in vivo was investigated via xenograft model. We found circ0082374 expression was elevated in glioma tissues and cells. Knockdown of circ0082374 suppressed the viability, migration, invasion and glycolysis in glioma cells. miR-326 was a target of circ0082374 and miR-326 knockdown attenuated the inhibitive role of circ0082374 silence in glioma progression. SIRT1 was a target of miR-326 and circ0082374 could promote SIRT1 expression by sponging miR-326. Silence of SIRT1 reversed the promoting effect of circ0082374 on glioma progression. Knockdown of circ0082374 reduced xenograft tumor growth by miR-326/SIRT1 in vivo. Collectively, silence of circ0082374 repressed the viability, migration, invasion and glycolysis in glioma cells by regulating miR-326 and SIRT1 in a ceRNA mechanism, providing a new mechanism for the pathogenesis of glioma.

Aberrant ASPM expression mediated by transcriptional regulation of FoxM1 promotes the progression of gliomas

Gliomas are the most common form of malignant tumour in the central nervous system. However, the molecular mechanism of the tumorigenesis and progression of gliomas remains unclear. In this study, we used the GEO database to identify genes differentially expressed in gliomas and predict the prognosis of glioma. We observed that ASPM mRNA was increased obviously in glioma tissue, and higher ASPM mRNA expression predicted worse disease prognosis. ASPM was highly expressed in glioma cell lines U87‐MG and U251, and knockdown of ASPM expression in these cells significantly repressed the proliferation, migration and invasion ability and induced G0/G1 phase arrest. In addition, down‐regulation of ASPM suppressed the growth of glioma in nude mice. Five potential binding sites for transcription factor FoxM1 were predicted in the ASPM promoter. FoxM1 overexpression significantly increased the expression of ASPM and promoted the proliferation and migration of glioma cells, which was abolished by ASPM ablation. ChIP and dual‐luciferase reporter analysis confirmed that FoxM1 bound to the ASPM promoter at −236 to ‐230 bp and −1354 to ‐1348 bp and activated the transcription of ASPM directly. Collectively, our results demonstrated for the first time that aberrant ASPM expression mediated by transcriptional regulation of FoxM1 promotes the malignant properties of glioma cells.

Pediatric high-grade glioma: aberrant epigenetics and kinase signaling define emerging therapeutic opportunities

INTRODUCTION

Supratentorial pediatric high-grade gliomas (pHGGs) are aggressive malignancies that lack effective treatment options. Deep genomic sequencing by multiple groups has revealed that the primary alterations unique to pHGGs occur in epigenetic and kinase genes. These mutations, fusions, and deletions present a therapeutic opportunity by use of small molecules targeting epigenetic modifiers and kinases that contribute to pHGG growth.

METHODS

Using a targeted search of the pre-clinical literature and clinicaltrials.gov for kinase and epigenetic pathways in pHGG, we collectively describe how these mechanisms are being targeted in pre-clinical animal models and in current clinical trials, as well as propose unexplored therapeutic possibilities for future investigations.

RESULTS

Relevant pHGG kinases are targetable by several FDA-approved or clinical-stage kinase inhibitors, including altered BRAF/MET/NTRK/ALK and wild-type PI3K/EGFR/PDGFR/VEGF/AXL. Epigenetic proteins implicated in pHGG are also clinically targetable and include histone erasers, writers and readers such as HDACs, demethylases LSD1/JMJD3, methyltransferase EZH2, chromatin reader bromodomains, and chromatin remodeler subunit BMI-1. Crosstalk between these pathways can occur involving kinases such as EGFR and AMPK interacting with epigenetic modifiers such as HDACs or EZH2. Single agent trial results of kinase inhibitors or epigenetic targets alone are underwhelming and hampered by poor pharmacokinetics, adaptive resistance, and broad inclusion criteria.

CONCLUSIONS

The genetic and phenotypic diversity of pHGGs is now well characterized after large-scale sequencing studies on patient tissue. However, clinical treatment paradigms have not yet shifted in response to this information. Combination therapies targeting multiple kinases or epigenetic targets may hold more promise, especially if attempted in selected patient populations with hemispheric pHGG tumors and relevant targeted therapeutic biomarkers.

STAT3 is a key molecule in the oncogenic behavior of diffuse intrinsic pontine glioma

Diffuse intrinsic pontine glioma (DIPG) is one of the most lethal childhood brain tumors. This tumor is unique because it is detected exclusively in the ventral pons of patients aged between 6 and 7 years, which suggests a developmental nature of its formation. Signal transducer and activator of transcription 3 (STAT3) is a critical molecule for the differentiation of neural stem cells into astrocytes during neurodevelopment. Additionally, STAT3 is associated with oncogenesis and the epithelial-mesenchymal transition (EMT) in various types of tumor. In recent years, several studies have demonstrated the oncogenic role of STAT3 in high-grade gliomas. However, the role of STAT3 in DIPG at the cellular level remains unknown. To assess the possible association between gliogenesis and DIPG, the expression levels of various molecules participating in the differentiation of neural stem cells were compared between normal brain control tissues and DIPG tissues using open public data. All of the screened genes exhibited significantly increased expression in DIPG tissues compared with normal tissues. As STAT3 expression was the most increased, the effect of STAT3 inhibition in a DIPG cell line was assessed via STAT3 short hairpin (sh)RNA transfection and treatment with AG490, a STAT3 inhibitor. Changes in viability, apoptosis, EMT and radiation therapy efficiency were also evaluated. Downregulation of STAT3 resulted in decreased cyclin D1 expression and cell viability, migration and invasion. Additionally, treatment with STAT3 shRNA or AG490 suppressed the EMT phenotype. Finally, when radiation was administered in combination with STAT3 inhibition, the therapeutic efficiency, assessed by cell viability and DNA damage repair, was increased. The present results suggest that STAT3 is a potential therapeutic target in DIPG, especially when combined with radiation therapy.

Elevation of CXCL1 indicates poor prognosis and radioresistance by inducing mesenchymal transition in glioblastoma

INTRODUCTION

Glioblastoma (GBM) is identified as a lethal malignant tumor derived from the nervous system. Despite the standard clinical strategy including maximum surgical resection, temozolomide (TMZ) chemotherapy, and radiotherapy, the median survival of GBM patients remains <15 months. Accumulating evidence indicates that rapid-acquired radioresistance is one of the most common reasons for GBM recurrence. Therefore, developing novel therapeutic targets for radioresistant GBM could yield long-term cures.

AIMS

To investigate the functional role of CXCL1 in the acquired radioresistance and identify the molecular pathway correlated to CXCL1.

RESULTS

In this study, we identified that CXCL1 is highly expressed in GBM and the elevation of CXCL1 is involved in radioresistance and poor prognosis in GBM patients. Additionally, silencing CXCL1 attenuated the proliferation and radioresistance of GBM cells. Furthermore, we demonstrated that CXCL1-overexpression induced radioresistance through mesenchymal transition of GBM via the activation of nuclear factor-kappa B (NF-κB) signaling.

CONCLUSION

CXCL1 was highly enriched in GBM and positively correlated with poor prognosis in GBM patients. Additionally, elevated CXCL1 induced radioresistance in GBM through regulation of NF-κB signaling by promoting mesenchymal transition in GBM.

Combined Therapy of AXL and HDAC Inhibition Reverses Mesenchymal Transition in Diffuse Intrinsic Pontine Glioma

PURPOSE

Diffuse intrinsic pontine glioma (DIPG) is an incurable type of pediatric brain cancer, which in the majority of cases is driven by mutations in genes encoding histone 3 (H3K27M). We here determined the preclinical therapeutic potential of combined AXL and HDAC inhibition in these tumors to reverse their mesenchymal, therapy-resistant, phenotype.

EXPERIMENTAL DESIGN

We used public databases and patient-derived DIPG cells to identify putative drivers of the mesenchymal transition in these tumors. Patient-derived neurospheres, xenografts, and allografts were used to determine the therapeutic potential of combined AXL/HDAC inhibition for the treatment of DIPG.

RESULTS

We identified AXL as a therapeutic target and regulator of the mesenchymal transition in DIPG. Combined AXL and HDAC inhibition had a synergistic and selective antitumor effect on H3K27M DIPG cells. Treatment of DIPG cells with the AXL inhibitor BGB324 and the HDAC inhibitor panobinostat resulted in a decreased expression of mesenchymal and stem cell genes. Moreover, this combination treatment decreased expression of DNA damage repair genes in DIPG cells, strongly sensitizing them to radiation. Pharmacokinetic studies showed that BGB324, like panobinostat, crosses the blood-brain barrier. Consequently, treatment of patient-derived DIPG xenograft and murine DIPG allograft-bearing mice with BGB324 and panobinostat resulted in a synergistic antitumor effect and prolonged survival.

CONCLUSIONS

Combined inhibition of AXL and HDACs in DIPG cells results in a synergistic antitumor effect by reversing their mesenchymal, stem cell-like, therapy-resistant phenotype. As such, this treatment combination may serve as part of a future multimodal therapeutic strategy for DIPG.

Genomics and Prognosis Analysis of Epithelial-Mesenchymal Transition in Glioma

Background: Epithelial-mesenchymal transition (EMT) is regulated by induction factors, transcription factor families and an array of signaling pathways genes, and has been implicated in the invasion and progression of gliomas.

Methods: We obtained the Clinicopathological data sets from Chinese Glioma Genome Atlas (CGGA). The “limma” package was used to analyze the expression of EMT-related genes in gliomas with different pathological characteristics. We used the “ConsensusClusterPlus” package to divide gliomas into two groups to study their correlation with glioma malignancy. The least absolute shrinkage and selection operator (LASSO) Cox regression was applied to select seven prognosis-associated genes to build the risk signature, and the coefficients obtained from the LASSO algorithm were used to calculate the risk score which we applied to determine the prognostic value of the risk signature. Univariate and multivariate Cox regression analyses were used to determine whether the risk signature is an independent prognostic indicator.

Results: We analyzed the differentially expressed 22 common epithelial-mesenchymal transition-associated genes in 508 gliomas graded by different clinicopathological features. Two glioma subgroups (EM1/2) were identified by consistent clustering of the proteins, of which the EM1 subgroup had a better prognosis than the EM2 subgroup, and the EM2 group was associated with cancer migration and proliferation. Significant enrichment analysis revealed that EMT-related transcriptional regulators and signaling pathways genes were highly related to glioma malignancies. Seven EMT-related genes were used to derive risk scores, which served as independent prognostic markers and prediction factors for the clinicopathological features of glioma. And we found the overall survival (OS) was significantly different between the low- and high-risk groups, the ROC curve indicated that the risk score can predict survival rates for glioma patients.

Conclusion: EMT-related induction factors, transcriptional regulators and signaling pathways genes are important players in the malignant progression of glioma and may help in decision making regarding the choice of prognosis assessment and provide us clues to understand EMT epigenetic modification in glioma.

Invaders Exposed: Understanding and Targeting Tumor Cell Invasion in Diffuse Intrinsic Pontine Glioma

Diffuse Intrinsic Pontine Glioma (DIPG) is a rare, highly aggressive pediatric brain tumor that originates in the pons. DIPG is untreatable and universally fatal, with a median life expectancy of less than a year. Resection is not an option, due to the anatomical location of the tumor, radiotherapy has limited effect and no chemotherapeutic or targeted treatment approach has proven to be successful. This poor prognosis is partly attributed to the tumor's highly infiltrative diffuse and invasive spread. Thus, targeting the invasive behavior of DIPG has the potential to be of therapeutic value. In order to target DIPG invasion successfully, detailed mechanistic knowledge on the underlying drivers is required. Here, we review both DIPG tumor cell's intrinsic molecular processes and extrinsic environmental factors contributing to DIPG invasion. Importantly, DIPG represents a heterogenous disease and through advances in whole-genome sequencing, different subtypes of disease based on underlying driver mutations are now being recognized. Recent evidence also demonstrates intra-tumor heterogeneity in terms of invasiveness and implies that highly infiltrative tumor subclones can enhance the migratory behavior of neighboring cells. This might partially be mediated by “tumor microtubes,” long membranous extensions through which tumor cells connect and communicate, as well as through the secretion of extracellular vesicles. Some of the described processes involved in invasion are already being targeted in clinical trials. However, more research into the mechanisms of DIPG invasion is urgently needed and might result in the development of an effective therapy for children suffering from this devastating disease. We discuss the implications of newly discovered invasive mechanisms for therapeutic targeting and the challenges therapy development face in light of disease in the developing brain.

PATZ1 Is Overexpressed in Pediatric Glial Tumors and Correlates with Worse Event-Free Survival in High-grade Gliomas

Glial tumors are the leading cause of cancer-related death and morbidity in children. Their diagnosis, mainly based on clinical and histopathological factors, is particularly challenging because of their high molecular heterogeneity. Thus, tumors with identical histotypes could result in variable biological behaviors and prognoses. The PATZ1 gene has been recently shown to be expressed in adult gliomas, including glioblastomas, where it correlates with the proneural subtype and with a better prognosis. Here, we analyzed the expression of PATZ1 in pediatric gliomas, first at mRNA level in a public database, and then at protein level, by immunohistochemistry, in a cohort of 52 glial brain tumors from young patients aged from 6 months to 16 years. As for adult tumors, we show that PATZ1 is enriched in glial tumors compared to the normal brain, where it correlates positively and negatively with a proneural and mesenchymal signature, respectively. Moreover, we show that PATZ1 is expressed at variable levels in our cohort of tumors. Higher expression was detected in high-grade than low-grade gliomas, suggesting a correlation with the malignancy. Among high-grade gliomas, higher levels of PATZ1 have consistently been found to correlate with worse event-free survival. Therefore, our study may imply new diagnostic opportunities for pediatric gliomas.

Antitumor activity of novel pyrazole-based small molecular inhibitors of the STAT3 pathway in patient derived high grade glioma cells

Abnormal activation of signal transducer and activator of transcription 3 (STAT3) transcription factor has been observed in many human cancers with roles in tumor initiation, progression, drug resistance, angiogenesis and immunosuppression. STAT3 is constitutively activated in a variety of cancers including adult high grade gliomas (aHGGs) such as glioblastoma (GBM), and pediatric high grade gliomas (pHGG). Inhibiting STAT3 is a promising target-specific chemotherapeutic strategy for tumors with aberrant STAT3 signaling. Here we investigated the antitumor effects of novel pyrazole-based STAT3 pathway inhibitors named MNS1 (Mayo Neurosurgery 1) in both pediatric and adult HGG tumor cells. MNS1 compounds selectively decreased cell viability and proliferation in patient-derived HGG cells with minimal toxicity on normal human astrocytes. These inhibitors selectively blocked IL-6-induced STAT3 phosphorylation and nuclear localization of pSTAT3 without affecting other signaling molecules including Akt, STAT1, JAK2 or ERK1/2 phosphorylation. Functional analysis showed that MNS1 compounds induced apoptosis and decrease tumor migration. The anti-tumor effects extended into a murine pHGG (diffuse intrinsic pontine glioma) patient derived xenograft, and systemic toxicity was not evident during dose escalation in mice. These results support further development of STAT3 inhibitors for both pediatric and adult HGG.

Preclinical therapeutic targets in diffuse midline glioma

Diffuse midline gliomas (DMG) are rapidly fatal tumors of the midbrain in children, characterized by a diffuse growing pattern and high levels of intrinsic resistance to therapy. The location of these tumors, residing behind the blood-brain barrier (BBB), and the limited knowledge about the biology of these tumors, has hindered the development of effective treatment strategies. However, the introduction of diagnostic biopsies and the implementation of autopsy protocols in several large centers world-wide has allowed for a detailed characterization of these rare tumors. This has resulted in the identification of novel therapeutic targets, as well as major advances in understanding the biology of DMG in relation to therapy resistance. We here provide an overview of the cellular pathways and tumor-specific aberrations that have been targeted in preclinical DMG research, and discuss the advantages and limitations of these therapeutic strategies in relation to therapy resistance and BBB-penetration. Therewith, we aim to provide researchers with a framework for successful preclinical therapy development.

Paediatric gliomas: diagnosis, molecular biology and management

Paediatric gliomas represent the most common brain tumour in children. Early diagnosis and treatment greatly improve survival. Histological grade is the most significant classification system affecting treatment planning and prognosis. Paediatric gliomas depend on pathways and genes responsible for mitotic activity and cell proliferation as well as angiogenesis (MAPK, VEGF, EFGR pathways). Symptoms such as focal neurologic deficit or seizures can facilitate diagnosis, but they are not always present and therefore diagnosis is occasionally delayed. Imaging has adequate diagnostic accuracy (surpassing 90%), and novel imaging techniques such as MR spectroscopy and PET increase only slightly this percentage. Low grade gliomas (LGG) can be approached conservatively but most authors suggest surgical excision. High grade gliomas (HGG) are always operated with exception of specific contradictions including butterfly or extensive dominant hemisphere gliomas. Surgical excision is universally followed by radiotherapy and chemotherapy, which slightly increase survival. Inoperable cases can be managed with or without radiosurgery depending on location and size, with adjunctive use of radiotherapy and chemotherapy. Surgical excision must be aggressive and gross total resection (GTR) should be attempted, if possible, since it can triple survival. Radiosurgery is effective on smaller tumours of <2 cm2. Surgical excision is always the treatment of choice, but glioma recurrences, and residual tumours in non-critical locations are candidates for radiosurgery especially if tumour volume is low. Management of recurrences includes surgery, radiosurgery and chemoradiotherapy and it should be individualized according to location and size. In combination with molecular targeted therapeutic schemes, glioma management will be immensely improved in the next years.