Understanding Ependymoma Oncogenesis: an Update on Recent Molecular Advances and Current Perspectives

Molecular subgrouping of ependymoma across three anatomic sites and their prognostic implications

The 2021 WHO classification stratifies ependymoma (EPN) into nine molecular subgroups according to the anatomic locations which outperforms histological grading. We aimed at molecularly reclassifying 200 EPN using immunohistochemistry (IHC) and sequencing for ZFTA fusions in supratentorial (ST) EPN. Further, we assessed the utility of L1CAM, cyclinD1, and p65 markers in identifying ZFTA fusion. Demographic profiles, histologic features, molecular subgroups and clinical outcome were retrospectively analyzed. IHC for L1CAM, cyclinD1, p65, H3K27me3, and H3K27M and sequencing for ZFTA fusion were performed. ZFTA fusions were identified in 44.8% ST EPN. p65 displayed the highest specificity (93.8%), while L1CAM had the highest sensitivity (92.3%) in detecting ZFTA fusions. The negative predictive value approached 96.6% and sensitivity improved to 96.2% with combinatorial IHC (L1CAM, cyclinD1, p65). H3K27me3 loss (PF-A) was noted in 65% PF EPN. Our results provide evidence that a combination of two of three (L1CAM, p65, and cyclinD1) can be used as surrogate markers for predicting fusion. ZFTA fusion, and its surrogate markers in ST, and H3K27me3 and younger age (< 5 years) in PF showed significant correlation with PFS and OS on univariate and Kaplan-Meier analysis. On multivariate analysis, H3K27me3 loss and younger age group are associated with poor clinical outcome.

Cellular type of hemangioblastoma. Case report and literature review

The authors report a patient with spinomedullary tumor who underwent resection with subsequent histological examination. However, the authors encountered difficulties in determining the exact histological type of neoplasm. Microscopic and immunohistochemical examination of spinomedullary neoplasm revealed two types of tumor: ependymoma and hemangioblastoma. However, analysis of literature data indicated that the identified tumor could be attributed to a certain cellular type of hemangioblastoma.

Molecular Classification and Therapeutic Targets in Ependymoma

Ependymoma is a biologically diverse tumor wherein molecular classification has superseded traditional histological grading based on its superior ability to characterize behavior, prognosis, and possible targeted therapies. The current, updated molecular classification of ependymoma consists of ten distinct subgroups spread evenly among the spinal, infratentorial, and supratentorial compartments, each with its own distinct clinical and molecular characteristics. In this review, the history, histopathology, standard of care, prognosis, oncogenic drivers, and hypothesized molecular targets for all subgroups of ependymoma are explored. This review emphasizes that despite the varied behavior of the ependymoma subgroups, it remains clear that research must be performed to further elucidate molecular targets for these tumors. Although not all ependymoma subgroups are oncologically aggressive, development of targeted therapies is essential, particularly for cases where surgical resection is not an option without causing significant morbidity. The development of molecular therapies must rely on building upon our current understanding of ependymoma oncogenesis, as well as cultivating transfer of knowledge based on malignancies with similar genomic alterations.

An Insight into Pathophysiological Features and Therapeutic Advances on Ependymoma

Simple Summary

Although biological information and the molecular classification of ependymoma have been studied, the treatment systems for ependymoma are still insufficient. In addition, because the disease occurs infrequently, it is difficult to obtain sufficient data to conduct large-scale or randomized clinical trials. Therefore, this study is intended to emphasize the importance of understanding its pathological characteristics and prognosis as well as developing treatments for ependymoma through multilateral studies.

Abstract

Glial cells comprise the non-sensory parts of the central nervous system as well as the peripheral nervous system. Glial cells, also known as neuroglia, constitute a significant portion of the mammalian nervous system and can be viewed simply as a matrix of neural cells. Despite being the “Nervenkitt” or “glue of the nerves”, they aptly serve multiple roles, including neuron repair, myelin sheath formation, and cerebrospinal fluid circulation. Ependymal cells are one of four kinds of glial cells that exert distinct functions. Tumorigenesis of a glial cell is termed a glioma, and in the case of an ependymal cell, it is called an ependymoma. Among the various gliomas, an ependymoma in children is one of the more challenging brain tumors to cure. Children are afflicted more severely by ependymal tumors than adults. It has appeared from several surveys that ependymoma comprises approximately six to ten percent of all tumors in children. Presently, the surgical removal of the tumor is considered a standard treatment for ependymomas. It has been conspicuously evident that a combination of irradiation therapy and surgery is much more efficacious in treating ependymomas. The main purpose of this review is to present the importance of both a deep understanding and ongoing research into histopathological features and prognoses of ependymomas to ensure that effective diagnostic methods and treatments can be developed.

Brain Tumor-Derived Extracellular Vesicles as Carriers of Disease Markers: Molecular Chaperones and MicroRNAs

Primary and metastatic brain tumors are usually serious conditions with poor prognosis, which reveal the urgent need of developing rapid diagnostic tools and efficacious treatments. To achieve these objectives, progress must be made in the understanding of brain tumor biology, for example, how they resist natural defenses and therapeutic intervention. One resistance mechanism involves extracellular vesicles that are released by tumors to meet target cells nearby or distant via circulation and reprogram them by introducing their cargo. This consists of different molecules among which are microRNAs (miRNAs) and molecular chaperones, the focus of this article. miRNAs modify target cells in the immune system to avoid antitumor reaction and chaperones are key survival molecules for the tumor cell. Extracellular vesicles cargo reflects the composition and metabolism of the original tumor cell; therefore, it is a source of markers, including the miRNAs and chaperones discussed in this article, with potential diagnostic and prognostic value. This and their relatively easy availability by minimally invasive procedures (e.g., drawing venous blood) illustrate the potential of extracellular vesicles as useful materials to manage brain tumor patients. Furthermore, understanding extracellular vesicles circulation and interaction with target cells will provide the basis for using this vesicle for delivering therapeutic compounds to selected tumor cells.

Intracranial ependymomas: molecular insights and translation to treatment

Ependymomas are primary central nervous system tumors (CNS), arising within the posterior fossa and supratentorial regions of the brain, and in the spine. Over the last decade, research has resulted in substantial insights into the molecular characteristics of ependymomas, and significant advances have been made in the establishment of a molecular classification system. Ependymomas both within and between the three CNS regions in which they arise, have been shown to contain distinct genetic, epigenetic and cytogenic aberrations, with at least three molecularly distinct subgroups identified within each region. However, these advances in molecular characterization have yet to be translated into clinical practice, with the standard treatment for ependymoma patients largely unchanged. This review summarizes the advances made in the molecular characterization of intracranial ependymomas, outlines the progress made in establishing preclinical models and proposes strategies for moving toward subgroup-specific preclinical investigations and treatment.

Tumor-infiltrating immune cell subpopulations and programmed death ligand 1 (PD-L1) expression associated with clinicopathological and prognostic parameters in ependymoma

Ependymomas are biologically and clinically heterogeneous tumors of the central nervous system that have variable clinical outcomes. The status of the tumor immune microenvironment in ependymoma remains unclear. Immune cell subsets and programmed death ligand 1 (PD-L1) expression were measured in 178 classical ependymoma cases by immunohistochemistry using monoclonal antibodies that recognized tumor-infiltrating lymphocyte subsets (TILs; CD3, CD4, CD8, FOXP3, and CD20), tumor-associated macrophages (TAMs; CD68, CD163, AIF1), indoleamine 2,3-dioxygenase (IDO)+ cells and PD-L1-expressing tumor cells. Increases in CD3+ and CD8+ cell numbers were associated with a prolonged PFS. In contrast, increased numbers of FOXP3+ and CD68+ cells and a ratio of CD163/AIF1+ cells were significantly associated with a shorter PFS. An increase in the IDO+ cell number was associated with a significantly longer PFS. To consider the quantities of TILs, TAMs, and IDO+ cells together, the cases were clustered into 2 immune cell subgroups using a k-means clustering analysis. Immune cell subgroup A, which was defined by high CD3+, low CD68+ and high IDO+ cell counts, predicted a favorable PFS compared to subgroup B by univariate and multivariate analyses. We found six ependymoma cases expressing PD-L1. All these cases were supratentorial ependymoma, RELA fusion-positive (ST-RELA). PD-L1 expression showed no prognostic significance. This study showed that the analysis of tumor-infiltrating immune cells could aid in predicting the prognosis of ependymoma patients and in determining therapeutic strategies to target the tumor microenvironment. PD-L1 expression in the ST-RELA subgroup suggests that this marker has a potential added value for future immunotherapy treatments.

Prognostic Implications of Histological Clear Cells in High-Grade Intracranial Ependymal Tumors: A Retrospective Analysis from a Tertiary Care Hospital in Pakistan

Background:

Clear cell variant in ependymal tumors is rare. We aimed to compare the features and outcome of the World Health Organization (WHO) Grade 3 ependymal tumors with clear cells to the WHO Grade 3 classic anaplastic ependymoma (AE).

Materials and Methods:

A retrospective cohort study conducted at the Department of Neurosurgery, Aga Khan University, Pakistan, from 2003 to 2013. The medical records and radiology of patients with proven histopathology were reviewed. The analysis was done on SPSS 20.

Results:

Nine cases of clear cell variant and 23 cases of classic AE were found, both of which combined equated to 4% of the total tumor burden in 11 years. The median age of clear cell ependymoma (CCE) and AE were 49 and 37 years, respectively. Presenting symptoms included headache in 66% of CCE and 63% in AE, raised intracranial pressure accounting for 33% of CCE and 54% of AE, dizziness in 22% CCE and 39% AE, while seizures presented equally in both. Supratentorial location was observed in 77% CCE and 48% AE. Both showed hypointense signals on T1-weighted images of magnetic resonance imaging (MRI) while T2-weighted images showed hyperintensity in all cases of CCE but only 80% of AE. MRI characteristics such as the presence of cystic component were found in 89% of CCE and 68% of AE, necrosis in 33% CCE, and 22% AE, hemorrhagic in 22% CCE and 9% AE, and equivalent contrast enhancement. Gross total resection was achieved in 5 (55%) patients of CCE, compared to 6 (26%) patients in AE. Subtotal resection was done in 4 (44%) patients of CCE and 15 (65%) patients of AE. Radiotherapy was given to 5 (55%) patients of CCE and 12 (52%) patients of AE. Recurrence was observed in 77% cases of CCE and 70% of AE, with metastasis in 29% of AE and in only one patient of CCE. Repeat surgery was done in 3 (33%) cases of CCE and 8 (35%) cases of AE. Median progression-free survival and overall survival were 9 and 13 months, respectively, in CCE while 14 and 18 months, respectively, for AE.

Conclusion:

Clear cells in the WHO Grade 3 ependymal tumors are found mainly in a comparatively older adult population with a predilection for supratentorial location and are more aggressive in behavior with poorer outcome than AE.