Targeting Epigenetic Pathways in the Treatment of Pediatric Diffuse (High Grade) Gliomas

The role of adjuvant chemotherapy in patients with H3K27 altered diffuse midline gliomas: a multicentric retrospective study

PURPOSE

Adult Diffuse midline glioma (DMG) is a very rare disease. DMGs are currently treated with radiotherapy and chemotherapy even if only a few retrospective studies assessed the impact on overall survival (OS) of these approaches.

METHODS

We carried out an Italian multicentric retrospective study of adult patients with H3K27-altered DMG to assess the effective role of systemic therapy in the treatment landscape of this rare tumor type.

RESULTS

We evaluated 49 patients from 6 Institutions. The median age was 37.3 years (range 20.1-68.3). Most patients received biopsy as primary approach (n = 30, 61.2%) and radiation therapy after surgery (n = 39, 79.6%). 25 (51.0%) of patients received concurrent chemotherapy and 26 (53.1%) patients received adjuvant temozolomide. In univariate analysis, concurrent chemotherapy did not result in OS improvement while adjuvant temozolomide was associated with longer OS (21.2 vs. 9.0 months, HR 0.14, 0.05-0.41, p < 0.001). Multivariate analysis confirmed the role of adjuvant chemotherapy (HR 0.1, 95%CI: 0.03-0.34, p = 0.003). In patients who progressed after radiation and/or chemotherapy the administration of a second-line systemic treatment had a significantly favorable impact on survival (8.0 vs. 3.2 months, HR 0.2, 95%CI 0.1-0.65, p = 0.004).

CONCLUSION

In our series, adjuvant treatment after radiotherapy can be useful in improving OS of patients with H3K27-altered DMG. When feasible another systemic treatment after treatment progression could be proposed.

Midline Gliomas: A Retrospective Study from a Cancer Center in the Middle East

Midline gliomas are tumors that occur in midline structures and can be circumscribed or diffuse. Classical midline structures include the thalamus, brainstem, and spinal cord. Other midline structures include the corpus callosum, basal ganglia, ventricles, paraventricular structures, and cerebellum. Diffuse midline glioma (DMG) is a diffuse glioma that occurs in the classical midline structures, characterized by a specific genetic alteration, and associated with grim outcome. This study was conducted at King Hussein Cancer Center and reviewed the medical records of 104 patients with circumscribed and diffuse gliomas involving midline structures that underwent biopsy between 2005 and 2022. We included a final cohort of 104 patients characterized by a median age of 23 years and a male-to-female ratio of 1.59-to-1. Diffuse high-grade glioma (DHGG) was the most common pathological variant (41.4%), followed by DMG (28.9%). GFAP was positive in most cases (71.2%). Common positive mutations/alterations detected by surrogate immunostains included H3 K27me3 (28.9%), p53 (25.0%), and H3 K27M (20.2%). Age group, type of treatment, and immunohistochemistry were significantly associated with both the location of the tumor and tumor variant (all; p < 0.05). DMGs were predominantly found in the thalamus, whereas circumscribed gliomas were most commonly observed in the spinal cord. None of the diffuse gliomas outside the classical location, or circumscribed gliomas harbored the defining DMG mutations. The median overall survival (OS) for the entire cohort was 10.6 months. Only the tumor variant (i.e., circumscribed gliomas) and radiotherapy were independent prognosticators on multivariate analysis.

How I treat recurrent pediatric high-grade glioma (pHGG): a Europe-wide survey study

PURPOSE

As there is no standard of care treatment for recurrent/progressing pediatric high-grade gliomas (pHGG), we aimed to gain an overview of different treatment strategies.

METHODS

In a web-based questionnaire, members of the SIOPE-BTG and the GPOH were surveyed on therapeutic options in four case scenarios (children/adolescents with recurrent/progressing HGG).

RESULTS

139 clinicians with experience in pediatric neuro-oncology from 22 European countries participated in the survey. Most respondents preferred further oncological treatment in three out of four cases and chose palliative care in one case with marked symptoms. Depending on the case, 8-92% would initiate a re-resection (preferably hemispheric pHGG), combined with molecular diagnostics. Throughout all case scenarios, 55-77% recommended (re-)irradiation, preferably local radiotherapy > 20 Gy. Most respondents would participate in clinical trials and use targeted therapy (79-99%), depending on molecular genetic findings (BRAF alterations: BRAF/MEK inhibitor, 64-88%; EGFR overexpression: anti-EGFR treatment, 46%; CDKN2A deletion: CDK inhibitor, 18%; SMARCB1 deletion: EZH2 inhibitor, 12%). 31-72% would administer chemotherapy (CCNU, 17%; PCV, 8%; temozolomide, 19%; oral etoposide/trofosfamide, 8%), and 20-69% proposed immunotherapy (checkpoint inhibitors, 30%; tumor vaccines, 16%). Depending on the individual case, respondents would also include bevacizumab (6-18%), HDAC inhibitors (4-15%), tumor-treating fields (1-26%), and intraventricular chemotherapy (4-24%).

CONCLUSION

In each case, experts would combine conventional multimodal treatment concepts, including re-irradiation, with targeted therapy based on molecular genetic findings. International cooperative trials combining a (chemo-)therapy backbone with targeted therapy approaches for defined subgroups may help to gain valid clinical data and improve treatment in pediatric patients with recurrent/progressing HGG.

Sinomenine ester derivative inhibits glioblastoma by inducing mitochondria-dependent apoptosis and autophagy by PI3K/AKT/mTOR and AMPK/mTOR pathway

Glioblastoma multiforme (GBM) in the central nervous system is the most lethal advanced glioma and currently there is no effective treatment for it. Studies of sinomenine, an alkaloid from the Chinese medicinal plant, Sinomenium acutum, showed that it had inhibitory effects on several kinds of cancer. Here, we synthesized a sinomenine derivative, sino-wcj-33 (SW33), tested it for antitumor activity on GBM and explored the underlying mechanism. SW33 significantly inhibited proliferation and colony formation of GBM and reduced migration and invasion of U87 and U251 cells. It also arrested the cell cycle at G2/M phase and induced mitochondria-dependent apoptosis. Differential gene enrichment analysis and pathway validation showed that SW33 exerted anti-GBM effects by regulating PI3K/AKT and AMPK signaling pathways and significantly suppressed tumorigenicity with no obvious adverse effects on the body. SW33 also induced autophagy through the PI3K/AKT/mTOR and AMPK/mTOR pathways. Thus, SW33 appears to be a promising drug for treating GBM effectively and safely.

New Developments in the Pathogenesis, Therapeutic Targeting, and Treatment of H3K27M-Mutant Diffuse Midline Glioma

H3K27M-mutant diffuse midline gliomas (DMGs) are rare childhood central nervous system tumors that carry a dismal prognosis. Thus, innovative treatment approaches are greatly needed to improve clinical outcomes for these patients. Here, we discuss current trends in research of H3K27M-mutant diffuse midline glioma. This review highlights new developments of molecular pathophysiology for these tumors, as they relate to epigenetics and therapeutic targeting. We focus our discussion on combinatorial therapies addressing the inherent complexity of treating H3K27M-mutant diffuse midline gliomas and incorporating recent advances in immunotherapy, molecular biology, genetics, radiation, and stereotaxic surgical diagnostics.

Genetic Alterations in Gliomas Remodel the Tumor Immune Microenvironment and Impact Immune-Mediated Therapies

High grade gliomas are malignant brain tumors that arise in the central nervous system, in patients of all ages. Currently, the standard of care, entailing surgery and chemo radiation, exhibits a survival rate of 14-17 months. Thus, there is an urgent need to develop new therapeutic strategies for these malignant brain tumors. Currently, immunotherapies represent an appealing approach to treat malignant gliomas, as the pre-clinical data has been encouraging. However, the translation of the discoveries from the bench to the bedside has not been as successful as with other types of cancer, and no long-lasting clinical benefits have been observed for glioma patients treated with immune-mediated therapies so far. This review aims to discuss our current knowledge about gliomas, their molecular particularities and the impact on the tumor immune microenvironment. Also, we discuss several murine models used to study these therapies pre-clinically and how the model selection can impact the outcomes of the approaches to be tested. Finally, we present different immunotherapy strategies being employed in clinical trials for glioma and the newest developments intended to harness the immune system against these incurable brain tumors.

World Cancer Day 2021 - Perspectives in Pediatric and Adult Neuro-Oncology

Significant advances in our understanding of the molecular genetics of pediatric and adult brain tumors and the resulting rapid expansion of clinical molecular neuropathology have led to improvements in diagnostic accuracy and identified new targets for therapy. Moreover, there have been major improvements in all facets of clinical care, including imaging, surgery, radiation and supportive care. In selected cohorts of patients, targeted and immunotherapies have resulted in improved patient outcomes. Furthermore, adaptations to clinical trial design have facilitated our study of new agents and other therapeutic innovations. However, considerable work remains to be done towards extending survival for all patients with primary brain tumors, especially children and adults with diffuse midline gliomas harboring Histone H3 K27 mutations and adults with isocitrate dehydrogenase (IDH) wild-type, O6 guanine DNA-methyltransferase gene (MGMT) promoter unmethylated high grade gliomas. In addition to improvements in therapy and care, access to the advances in technology, such as particle radiation or biologic therapy, neuroimaging and molecular diagnostics in both developing and developed countries is needed to improve the outcome of patients with brain tumors.

Characteristics of diffuse hemispheric gliomas, H3 G34-mutant in adults

Background

Diffuse hemispheric gliomas, H3 G34-mutant (DHG H3G34-mutant) constitute a distinct type of aggressive brain tumors. Although initially described in children, they can also affect adults. The aims of this study were to describe the characteristics of DHG H3G34-mutant in adults and to compare them to those of established types of adult WHO grade IV gliomas.

Methods

The characteristics of 17 adult DHG H3G34-mutant, 32 H3.3 K27M-mutant diffuse midline gliomas (DMG), 100 IDH-wildtype, and 36 IDH-mutant glioblastomas were retrospectively analyzed.

Results

Median age at diagnosis in adult DHG H3G34-mutant was 25 years (range: 19–33). All tumors were hemispheric. For 9 patients (56%), absent or faint contrast enhancement initially suggested another diagnosis than a high-grade glioma, and diffusion-weighted imaging seemed retrospectively more helpful to suspect an aggressive tumor than MR-spectroscopy and perfusion MRI. All cases were IDH-wildtype. Most cases were immunonegative for ATRX (93%) and Olig2 (100%) and exhibited MGMT promoter methylation (82%). The clinical and radiological presentations of adult DHG H3G34-mutant were different from those of established types of adult grade IV gliomas. Median overall survival of adult DHG H3G34-mutant was 12.4 months compared to 19.6 months (P = .56), 11.7 months (P = .45), and 50.5 months (P = .006) in H3.3 K27M-mutant DMG, IDH-wildtype, and IDH-mutant glioblastomas, respectively.

Conclusions

Adult DHG H3G34-mutant are associated with distinct characteristics compared to those of established types of adult WHO grade IV gliomas. This study supports considering these tumors as a new type of WHO grade IV glioma in future classifications.

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.

Genetic signature and treatment of pediatric high-grade glioma

Pediatric high-grade glioma (HGG) is a type of malignancy that carries a poor prognosis. The genetic analysis of HGGs has previously identified useful mutations, the targeting of which has improved prognosis. Thus, further research into the more common mutations, such as H3 histone variants (HIST1H3B and H3F3A) and BRAF V600E, may be useful in identifying tumors with different prognoses, as the mutations are considered to drive two distinct oncogenic programs. The present study performed a retrospective analysis of pediatric HGGs. In total, 42 cases of HGG, including 32 cases (76.1%) of anaplastic astrocytoma and 10 cases (23.8%) of glioblastoma multiforme (GBM), were assessed. The median age of the patients was 7 years (range, 0-32 years). Mutations on histone H3, in particular the K27M and G34R mutations in the distinct variants HIST1H3B and H3F3A, in addition to the presence of the BRAF V600E mutation, were analyzed in 24 patients. The H3F3A K27M mutation was identified in 7 patients (29.1%), while the HIST1H3B K27M mutation was only observed in 1 patient with GBM. In addition, 5 patients harbored a BRAF V600E mutation (21%), while the H3F3A G34R mutation was not recorded in any of the patients. The overall survival of the wild-type patients at 20 months was 68% [confidence interval (CI): 38-85%] compared with 28% (CI: 0.4-60%) in patients with the H3F3A K27M mutation. These results suggested that patients with the H3F3A K27M mutation had a worse prognosis compared with wild-type patients (P=0.0045). Moreover, 3/5 patients with the BRAF V600E mutation had HGGs that were derived from a previous low-grade glioma (LGG; P=0.001). In conclusion, these results suggested that histone H3 mutations may help predict the outcome in patients with HGG. In addition, the BRAF V600E mutation was found to be associated with an increased risk of anaplastic progression. The novel data of the present study may help better define the clinical and radiological characteristics of glioma.

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.

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.

NTRK Fusions in Central Nervous System Tumors: A Rare, but Worthy Target

The neurotrophic tropomyosin receptor kinase (NTRK) genes (NTRK1, NTRK2, and NTRK3) code for three transmembrane high-affinity tyrosine-kinase receptors for nerve growth factors (TRK-A, TRK-B, and TRK-C) which are mainly involved in nervous system development. Loss of function alterations in these genes can lead to nervous system development problems; conversely, activating alterations harbor oncogenic potential, promoting cell proliferation/survival and tumorigenesis. Chromosomal rearrangements are the most clinically relevant alterations of pathological NTRK activation, leading to constitutionally active chimeric receptors. NTRK fusions have been detected with extremely variable frequencies in many pediatric and adult cancer types, including central nervous system (CNS) tumors. These alterations can be detected by different laboratory assays (e.g., immunohistochemistry, FISH, sequencing), but each of these approaches has specific advantages and limitations which must be taken into account for an appropriate use in diagnostics or research. Moreover, therapeutic targeting of this molecular marker recently showed extreme efficacy. Considering the overall lack of effective treatments for brain neoplasms, it is expected that detection of NTRK fusions will soon become a mainstay in the diagnostic assessment of CNS tumors, and thus in-depth knowledge regarding this topic is warranted.

Plasma and cerebrospinal fluid pharmacokinetics of the DNA methyltransferase inhibitor, 5-azacytidine, alone and with inulin, in nonhuman primate models

BACKGROUND

Epigenetic modifiers are being investigated for a number of CNS malignancies as tumor-associated mutations such as isocitrate dehydrogenase mutations (IDH1/IDH2) and H3K27M mutations, which result in aberrant signaling, are identified. We evaluated the CNS exposure of the DNA methyltransferase inhibitor, 5-azacytidine (5-AZA), in preclinical nonhuman primate (NHP) models to inform its clinical development for CNS tumors.

METHODS

5-AZA and 5-AZA+Inulin pharmacokinetics (PK) were evaluated in NHPs (n = 10) following systemic (intravenous [IV]) and intrathecal (intraventricular [IT-V], intralumbar [IT-L], and cisternal [IT-C]) administration. Plasma, cerebrospinal fluid (CSF), cortical extracellular fluid (ECF), and tissues were collected. 5-AZA levels were quantified via ultra-high-performance liquid chromatography with tandem mass spectrometric detection assay and inulin via ELISA. PK parameters were calculated using noncompartmental methods.

RESULTS

After IV administration, minimal plasma exposure (area under the curve [AUC] range: 2.4-3.2 h*µM) and negligible CSF exposure were noted. CSF exposure was notably higher after IT-V administration (AUCINF 1234.6-5368.4 h*µM) compared to IT-L administration (AUCINF 7.5-19.3 h*µM). CSF clearance after IT administration exceeded the mean inulin CSF flow rate of 0.018 ± 0.003 ml/min as determined by inulin IT-V administration. 5-AZA IT-V administration with inulin increased the 5-AZA CSF duration of exposure by 2.2-fold. IT-C administration yielded no quantifiable 5-AZA ECF concentrations but resulted in quantifiable tissue levels.

CONCLUSIONS

IT administration of 5-AZA is necessary to achieve adequate CNS exposure. IT administration results in pronounced and prolonged 5-AZA CSF exposure above the reported IC50 range for IDH-mutated glioma cell lines. Inulin administered with 5-AZA increased the duration of exposure for 5-AZA.

Challenging the indiscriminate use of temozolomide in pediatric high-grade gliomas: A review of past, current, and emerging therapies

Pediatric high-grade gliomas (pHGG) constitute 8% to 12% of primary brain tumors in childhood. The most widely utilized treatment encompasses surgical resection followed by focal radiotherapy and temozolomide. However, experiences over past decades have not demonstrated improved outcomes. pHGG have been classified into different molecular subgroups defined by mutations in histone 3, IDH gene, MAPK pathway, and others, thereby providing a rationale for various targeted therapies. Additionally, immunotherapy and drug repurposing have also become attractive adjunctive treatments. This review focuses on past, present, and emerging treatments for pHGG integrating molecular research with the mainstream pediatric drug development in Europe and the United States to sketch a way forward in the development of novel therapeutic approaches. The implementation of randomized clinical trials with adaptive designs, underpinned by a robust biological rationale, and harnessing collaboration between the pharmaceutical industry, academia, regulators and patients/parents organizations will be essential to improve the outcomes for these children.

Genetic and Epigenetic Features of Rapidly Progressing IDH-Mutant Astrocytomas

IDH-mutant astrocytomas are significantly less aggressive than their IDH-wildtype counterparts. We analyzed The Cancer Genome Atlas dataset (TCGA) and identified a small group of IDH-mutant, WHO grade II-III astrocytomas (n = 14) with an unexpectedly poor prognosis characterized by a rapid progression to glioblastoma and death within 3 years of the initial diagnosis. Compared with IDH-mutant tumors with the typical, extended progression-free survival in a control group of age-similar patients, the tumors in the rapidly progressing group were characterized by a markedly increased level of overall copy number alterations ([CNA]; p = 0.006). In contrast, the mutation load was similar, as was the methylation pattern, being consistent with IDH-mutant astrocytoma. Two of the gliomas (14%) in the rapidly progressing, IDH-mutant group but none of the other grade II-III gliomas in the TCGA (n = 283) had pathogenic mutations in genes (FANCB and APC) associated with maintaining chromosomal stability. These results suggest that chromosomal instability can negate the beneficial effect of IDH mutations in WHO II-III astrocytomas. The mechanism of the increased CNA is unknown but in some cases appears to be due to mutations in genes with a role in chromosomal stability. Increased CNA could serve as a biomarker for tumors at risk for rapid progression.

Postoperative resveratrol administration improves prognosis of rat orthotopic glioblastomas

Background

Although our previous study revealed lumbar punctured resveratrol could remarkably prolong the survival of rats bearing orthotopic glioblastomas, it also suggested the administration did not completely suppress rapid tumour growth. These evidences led us to consider that the prognosis of tumour-bearing rats may be further improved if this treatment is used in combination with neurosurgery. Therefore, we investigated the effectiveness of the combined treatment on rat orthotopic glioblastomas.

Methods

Rat RG2 glioblastoma cells were inoculated into the brains of 36 rats. The rats were subjected to partial tumour removal after they showed symptoms of intracranial hypertension. There were 28 rats that survived the surgery, and these animals were randomly and equally divided into the control group without postoperative treatment and the LP group treated with 100 μl of 300 μM resveratrol via the LP route. Resveratrol was administered 24 h after tumour resection in 3-day intervals, and the animals received 7 treatments. The intracranial tumour sizes, average life span, cell apoptosis and STAT3 signalling were evaluated by multiple experimental approaches in the tumour tissues harvested from both groups.

Results

The results showed that 5 of the 14 (35.7%) rats in the LP group remained alive over 60 days without any sign of recurrence. The remaining nine animals had a longer mean postoperative survival time (11.0 ± 2.9 days) than that of the (7.3 + 1.3 days; p < 0.05) control group. The resveratrol-treated tumour tissues showed less Ki67 labelling, widely distributed apoptotic regions, upregulated PIAS3 expression and reduced p-STAT3 nuclear translocation.

Conclusions

This study demonstrates that postoperative resveratrol administration efficiently improves the prognosis of rat advanced orthotopic glioblastoma via inhibition of growth, induction of apoptosis and inactivation of STAT3 signalling. Therefore, this therapeutic approach could be of potential practical value in the management of glioblastomas.

Epigenetic Regulation of Telomere Maintenance for Therapeutic Interventions in Gliomas

High-grade astrocytoma of WHO grade 4 termed glioblastoma multiforme (GBM) is a common human brain tumor with poor patient outcome. Astrocytoma demonstrates two known telomere maintenance mechanisms (TMMs) based on telomerase activity (TA) and on alternative lengthening of telomeres (ALT). ALT is associated with lower tumor grades and better outcome. In contrast to ALT, regulation of TA in tumors by direct mutation and epigenetic activation of the hTERT promoter is well established. Here, we summarize the genetic background of TMMs in non-malignant cells and in cancer, in addition to clinical and pathological features of gliomas. Furthermore, we present new evidence for epigenetic mechanisms (EMs) involved in regulation of ALT and TA with special emphasis on human diffuse gliomas as potential therapeutic drug targets. We discuss the role of TMM associated telomeric chromatin factors such as DNA and histone modifying enzymes and non-coding RNAs including microRNAs and long telomeric TERRA transcripts.