Therapeutic Targets in Diffuse Midline Gliomas-An Emerging Landscape

Hypofractionated radiotherapy combined with bevacizumab plus low-dose ifosfamide, carboplatin, and etoposide as second-line chemoradiotherapy for progressing spinal diffuse midline glioma, H3K27-altered: illustrative case

BACKGROUND

Spinal cord diffuse midline glioma (DMG) is a relatively rare disease with a poor prognosis and no effective treatment.

OBSERVATIONS

A 45-year-old man presented with rapidly progressive paraplegia in both lower extremities, along with bladder and bowel disturbance. Spinal magnetic resonance imaging (MRI) showed a heterogeneously contrast-enhanced mass at the T1-4 levels. A biopsy via T1-4 decompressive laminectomy with expansive duraplasty was performed. The histopathological diagnosis was DMG, H3K27-altered, World Health Organization grade 4. Radiation plus concomitant temozolomide was started; however, follow-up MRI showed tumor progression. Additional hypofractionated radiotherapy (HFRT; 24 Gy/5 fractions) was performed, with bevacizumab (BEV) plus low-dose ifosfamide-carboplatin-etoposide (ICE) as second-line treatment. One month later, MRI showed tumor regression with significant improvement in the peritumoral edema. The chemotherapy regimen was repeated every 4-6 weeks, and the patient remained stable. After 13 courses of chemotherapy, the size of the spinal DMG increased markedly, with dissemination to the temporal lobe. The patient died approximately 21 months after the initial diagnosis.

LESSONS

Spinal DMG is a malignant tumor with a poor prognosis. However, treatment with additional HFRT combined with BEV plus low-dose ICE may inhibit tumor progression to prolong the progression-free period and survival. https://thejns.org/doi/10.3171/CASE2464.

Insights of immune cell heterogeneity, tumor-initiated subtype transformation, drug resistance, treatment and detecting technologies in glioma microenvironment

BACKGROUND

With the gradual understanding of glioma development and the immune microenvironment, many immune cells have been discovered. Despite the growing comprehension of immune cell functions and the clinical application of immunotherapy, the precise roles and characteristics of immune cell subtypes, how glioma induces subtype transformation of immune cells and its impact on glioma progression have yet to be understood.

AIM OF THE REVIEW

In this review, we comprehensively center on the four major immune cells within the glioma microenvironment, particularly neutrophils, macrophages, lymphocytes, myeloid-derived suppressor cells (MDSCs), and other significant immune cells. We discuss (1) immune cell subtype markers, (2) glioma-induced immune cell subtype transformation, (3) the mechanisms of each subtype influencing chemotherapy resistance, (4) therapies targeting immune cells, and (5) immune cell-associated single-cell sequencing. Eventually, we identified the characteristics of immune cell subtypes in glioma, comprehensively summarized the exact mechanism of glioma-induced immune cell subtype transformation, and concluded the progress of single-cell sequencing in exploring immune cell subtypes in glioma.

KEY SCIENTIFIC CONCEPTS OF REVIEW

In conclusion, we have analyzed the mechanism of chemotherapy resistance detailly, and have discovered prospective immunotherapy targets, excavating the potential of novel immunotherapies approach that synergistically combines radiotherapy, chemotherapy, and surgery, thereby paving the way for improved immunotherapeutic strategies against glioma and enhanced patient outcomes.

Dual targeting of histone deacetylases and MYC as potential treatment strategy for H3-K27M pediatric gliomas

Diffuse midline gliomas (DMGs) are aggressive and fatal pediatric tumors of the central nervous system that are highly resistant to treatments. Lysine to methionine substitution of residue 27 on histone H3 (H3-K27M) is a driver mutation in DMGs, reshaping the epigenetic landscape of these cells to promote tumorigenesis. H3-K27M gliomas are characterized by deregulation of histone acetylation and methylation pathways, as well as the oncogenic MYC pathway. In search of effective treatment, we examined the therapeutic potential of dual targeting of histone deacetylases (HDACs) and MYC in these tumors. Treatment of H3-K27M patient-derived cells with Sulfopin, an inhibitor shown to block MYC-driven tumors in vivo, in combination with the HDAC inhibitor Vorinostat, resulted in substantial decrease in cell viability. Moreover, transcriptome and epigenome profiling revealed synergistic effect of this drug combination in downregulation of prominent oncogenic pathways such as mTOR. Finally, in vivo studies of patient-derived orthotopic xenograft models showed significant tumor growth reduction in mice treated with the drug combination. These results highlight the combined treatment with PIN1 and HDAC inhibitors as a promising therapeutic approach for these aggressive tumors.

National trends in the treatment of adult diffuse midline gliomas: a rare clinical scenario

PURPOSE

Diffuse midline gliomas (DMG) include all midline gliomas with a point mutation to the histone H3 gene resulting in the substitution of a lysine with a methionine (K27M). These tumors are classified as World Health Organization grade 4 with a mean survival between 9- and 19-months following diagnosis. There is currently no standard of care for DMG, and palliative radiation therapy has been proven to only extend survival by months. Our current study aims to report current treatment trends and predictors of the overall survival of DMG.

METHODS

We searched the National Cancer Database for adult patients treated for DMG from 2016 to 2020. Patients were required to have been treated with primary radiation directed at the brain with or without concurrent chemotherapy. Univariable and multivariable Cox regressions were used to determine predictors of overall survival.

RESULTS

Of the 131 patients meeting the inclusion criteria, 113 (86%) received radiation and chemotherapy. Based on multivariable Cox regression, significant predictors of survival were Charlson-Deyo comorbidity index and race. Patients with a Charlson-Deyo score of 1 had 2.72 times higher odds of mortality than those with a score of 0. Patients not identifying as White or Black had 2.67 times higher odds of mortality than those identifying as White. The median survival for all patients was 19 months.

CONCLUSIONS

Despite being considered ineffective, chemotherapy is still administered in most adult patients diagnosed with DMG. Significant predictors of survival were Charlson-Deyo comorbidity index and race.

H3K27M mutant glioma: Disease definition and biological underpinnings

High-grade glioma (HGG) is the most common cause of cancer death in children and the most common primary central nervous system tumor in adults. While pediatric HGG was once thought to be biologically similar to the adult form of disease, research has shown these malignancies to be significantly molecularly distinct, necessitating distinct approaches to their clinical management. However, emerging data have shown shared molecular events in pediatric and adult HGG including the histone H3K27M mutation. This somatic missense mutation occurs in genes encoding one of two isoforms of the Histone H3 protein, H3F3A (H3.3), or HIST1H3B (H3.1), and is detected in up to 80% of pediatric diffuse midline gliomas and in up to 60% of adult diffuse gliomas. Importantly, the H3K27M mutation is associated with poorer overall survival and response to therapy compared to patients with H3 wild-type tumors. Here, we review the clinical features and biological underpinnings of pediatric and adult H3K27M mutant glioma, offering a groundwork for understanding current research and clinical approaches for the care of patients suffering with this challenging disease.

Fimepinostat Impairs NF-κB and PI3K/AKT Signaling and Enhances Gemcitabine Efficacy in H3.3K27M-Diffuse Intrinsic Pontine Glioma

Diffuse intrinsic pontine glioma (DIPG) is the most aggressive pediatric brain tumor, and the oncohistone H3.3K27M mutation is associated with significantly worse clinical outcomes. Despite extensive research efforts, effective approaches for treating DIPG are lacking. Through drug screening, we identified the combination of gemcitabine and fimepinostat as a potent therapeutic intervention for H3.3K27M DIPG. H3.3K27M facilitated gemcitabine-induced apoptosis in DIPG, and gemcitabine stabilized and activated p53, including increasing chromatin accessibility for p53 at apoptosis-related loci. Gemcitabine simultaneously induced a prosurvival program in DIPG through activation of RELB-mediated NF-κB signaling. Specifically, gemcitabine induced the transcription of long terminal repeat elements, activated cGAS-STING signaling, and stimulated noncanonical NF-κB signaling. A drug screen in gemcitabine-treated DIPG cells revealed that fimepinostat, a dual inhibitor of HDAC and PI3K, effectively suppressed the gemcitabine-induced NF-κB signaling in addition to blocking PI3K/AKT activation. Combination therapy comprising gemcitabine and fimepinostat elicited synergistic antitumor effects in vitro and in orthotopic H3.3K27M DIPG xenograft models. Collectively, p53 activation using gemcitabine and suppression of RELB-mediated NF-κB activation and PI3K/AKT signaling using fimepinostat is a potential therapeutic strategy for treating H3.3K27M DIPG.

SIGNIFICANCE

Gemcitabine activates p53 and induces apoptosis to elicit antitumor effects in H3.3K27M DIPG, which can be enhanced by blocking NF-κB and PI3K/AKT signaling with fimepinostat, providing a synergistic combination therapy for DIPG.

Early prognostication of overall survival for pediatric diffuse midline gliomas using MRI radiomics and machine learning: a two-center study

Background

Diffuse midline gliomas (DMG) are aggressive pediatric brain tumors that are diagnosed and monitored through MRI. We developed an automatic pipeline to segment subregions of DMG and select radiomic features that predict patient overall survival (OS).

Methods

We acquired diagnostic and post-radiation therapy (RT) multisequence MRI (T1, T1ce, T2, T2 FLAIR) and manual segmentations from two centers of 53 (internal cohort) and 16 (external cohort) DMG patients. We pretrained a deep learning model on a public adult brain tumor dataset, and finetuned it to automatically segment tumor core (TC) and whole tumor (WT) volumes. PyRadiomics and sequential feature selection were used for feature extraction and selection based on the segmented volumes. Two machine learning models were trained on our internal cohort to predict patient 1-year survival from diagnosis. One model used only diagnostic tumor features and the other used both diagnostic and post-RT features.

Results

For segmentation, Dice score (mean [median]±SD) was 0.91 (0.94)±0.12 and 0.74 (0.83)±0.32 for TC, and 0.88 (0.91)±0.07 and 0.86 (0.89)±0.06 for WT for internal and external cohorts, respectively. For OS prediction, accuracy was 77% and 81% at time of diagnosis, and 85% and 78% post-RT for internal and external cohorts, respectively. Homogeneous WT intensity in baseline T2 FLAIR and larger post-RT TC/WT volume ratio indicate shorter OS.

Conclusions

Machine learning analysis of MRI radiomics has potential to accurately and non-invasively predict which pediatric patients with DMG will survive less than one year from the time of diagnosis to provide patient stratification and guide therapy.

Early prognostication of overall survival for pediatric diffuse midline gliomas using MRI radiomics and machine learning: A two-center study

Background

Diffuse midline gliomas (DMG) are aggressive pediatric brain tumors that are diagnosed and monitored through MRI. We developed an automatic pipeline to segment subregions of DMG and select radiomic features that predict patient overall survival (OS).

Methods

We acquired diagnostic and post-radiation therapy (RT) multisequence MRI (T1, T1ce, T2, and T2 FLAIR) and manual segmentations from 2 centers: 53 from 1 center formed the internal cohort and 16 from the other center formed the external cohort. We pretrained a deep learning model on a public adult brain tumor data set (BraTS 2021), and finetuned it to automatically segment tumor core (TC) and whole tumor (WT) volumes. PyRadiomics and sequential feature selection were used for feature extraction and selection based on the segmented volumes. Two machine learning models were trained on our internal cohort to predict patient 12-month survival from diagnosis. One model used only data obtained at diagnosis prior to any therapy (baseline study) and the other used data at both diagnosis and post-RT (post-RT study).

Results

Overall survival prediction accuracy was 77% and 81% for the baseline study, and 85% and 78% for the post-RT study, for internal and external cohorts, respectively. Homogeneous WT intensity in baseline T2 FLAIR and larger post-RT TC/WT volume ratio indicate shorter OS.

Conclusions

Machine learning analysis of MRI radiomics has potential to accurately and noninvasively predict which pediatric patients with DMG will survive less than 12 months from the time of diagnosis to provide patient stratification and guide therapy.

Decoding Diffuse Midline Gliomas: A Comprehensive Review of Pathogenesis, Diagnosis and Treatment

Diffuse midline gliomas (DMGs) are a group of aggressive CNS tumors, primarily affecting children and young adults, which have historically been associated with dismal outcomes. As the name implies, they arise in midline structures in the CNS, primarily in the thalamus, brainstem, and spinal cord. In more recent years, significant advances have been made in our understanding of DMGs, including molecular features, with the identification of potential therapeutic targets. We aim to provide an overview of the most recent updates in the field of DMGs, including classification, molecular subtypes, diagnostic techniques, and emerging therapeutic strategies including a review of the ongoing clinical trials, thus providing the treating multidisciplinary team with a comprehensive understanding of the current landscape and potential therapeutic strategies for this devastating group of tumors.

Epidemiology, Diagnostic Strategies, and Therapeutic Advances in Diffuse Midline Glioma

Object: Diffuse midline glioma (DMG) is a highly aggressive and lethal brain tumor predominantly affecting children and young adults. Previously known as diffuse intrinsic pontine glioma (DIPG) or grade IV brain stem glioma, DMG has recently been reclassified as "diffuse midline glioma" according to the WHO CNS5 nomenclature, expanding the DMG demographic. Limited therapeutic options result in a poor prognosis, despite advances in diagnosis and treatment. Radiotherapy has historically been the primary treatment modality to improve patient survival. Methods: This systematic literature review aims to comprehensively compile information on the diagnosis and treatment of DMG from 1 January 2012 to 31 July 2023. The review followed the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) statement and utilized databases such as PubMed, Cochrane Library, and SciELO. Results: Currently, molecular classification of DMG plays an increasingly vital role in determining prognosis and treatment options. Emerging therapeutic avenues, including immunomodulatory agents, anti-GD2 CAR T-cell and anti-GD2 CAR-NK therapies, techniques to increase blood-brain barrier permeability, isocitrate dehydrogenase inhibitors, oncolytic and peptide vaccines, are being explored based on the tumor's molecular composition. However, more clinical trials are required to establish solid guidelines for toxicity, dosage, and efficacy. Conclusions: The identification of the H3K27 genetic mutation has led to the reclassification of certain midline tumors, expanding the DMG demographic. The field of DMG research continues to evolve, with encouraging findings that underscore the importance of highly specific and tailored therapeutic strategies to achieve therapeutic success.

Potential Molecular Targets in the Treatment of Patients with CNS Tumors

The challenges in identifying effective therapies for CNS tumors continue to be daunting [...].

Epigenetic and Metabolic Changes in Diffuse Intrinsic Pontine Glioma

Diffuse midline glioma (DMG), hitherto known as diffuse intrinsic pontine glioma (DIPG), is a rare and aggressive form of brain cancer that primarily affects children. Although the exact cause of DMG/DIPG is not known, a large proportion of DMG/DIPG tumors harbor mutations in the gene encoding the histone H3 protein, specifically the H3K27M mutation. This mutation decreases the level of H3K27me3, a histone modification that plays a vital role in regulating gene expression through epigenetic regulation. The mutation also alters the function of polycomb repressive complex 2 (PRC2), thereby preventing the repression of genes associated with cancer development. The decrease in H3K27me3 caused by the histone H3 mutation is accompanied by an increase in the level of H3K27ac, a post-translational modification related to active transcription. Dysregulation of histone modification markedly affects gene expression, contributing to cancer development and progression by promoting uncontrolled cell proliferation, tumor growth, and metabolism. DMG/DIPG alters the metabolism of methionine and the tricarboxylic acid cycle, as well as glucose and glutamine uptake. The role of epigenetic and metabolic changes in the development of DMG/DIPG has been studied extensively, and understanding these changes is critical to developing therapies targeting these pathways. Studies are currently underway to identify new therapeutic targets for DMG/DIPG, which may lead to the development of effective treatments for this devastating disease.

Gene Therapy for High Grade Glioma: The Clinical Experience

INTRODUCTION

High-grade gliomas (HGG) are the most common malignant primary brain tumors in adults, with a median survival of ~18 months. The standard of care (SOC) is maximal safe surgical resection, and radiation therapy with concurrent and adjuvant temozolomide. This protocol remains unchanged since 2005, even though HGG median survival has marginally improved.

AREAS COVERED

Gene therapy was developed as a promising approach to treat HGG. Here, we review completed and ongoing clinical trials employing viral and non-viral vectors for adult and pediatric HGG, as well as the key supporting preclinical data.

EXPERT OPINION

These therapies have proven safe, and pre- and post-treatment tissue analyses demonstrated tumor cell lysis, increased immune cell infiltration, and increased systemic immune function. Although viral therapy in clinical trials has not yet significantly extended the survival of HGG, promising strategies are being tested. Oncolytic HSV vectors have shown promising results for both adult and pediatric HGG. A recently published study demonstrated that HG47Δ improved survival in recurrent HGG. Likewise, PVSRIPO has shown survival improvement compared to historical controls. It is likely that further analysis of these trials will stimulate the development of new administration protocols, and new therapeutic combinations that will improve HGG prognosis.

Overcoming translational barriers in H3K27-altered diffuse midline glioma: Increasing the drug-tumor residence time

Background

H3K27-altered diffuse midline glioma (DMG) is the deadliest pediatric brain tumor; despite intensive research efforts, every clinical trial to date has failed. Is this because we are choosing the wrong drugs? Or are drug delivery and other pharmacokinetic variables at play? We hypothesize that the answer is likely a combination, where optimization may result in a much needed novel therapeutic approach.

Methods

We used in vitro drug screening, patient samples, and shRNA knockdown models to identify an upregulated target in DMG. A single small molecule protein kinase inhibitor with translational potential was selected for systemic and direct, loco-regional delivery to patient-derived xenografts (PDX) and genetically engineered mouse models (GEMM). Pharmacokinetic studies were conducted in non-tumor bearing rats.

Results

Aurora kinase (AK) inhibitors demonstrated strong antitumor effects in DMG drug screens. Additional in vitro studies corroborated the importance of AK to DMG survival. Systemic delivery of alisertib showed promise in subcutaneous PDX but not intracranial GEMM and PDX models. Repeated loco-regional drug administration into the tumor through convection-enhanced delivery (CED) was equally inefficacious, and pharmacokinetic studies revealed rapid clearance of alisertib from the brain. In an effort to increase the drug to tumor residence time, continuous CED over 7 days improved drug retention in the rodent brainstem and significantly extended survival in both orthotopic PDXs and GEMMs.

Conclusions

These studies provide evidence for increasing drug-tumor residence time of promising targeted therapies via extended CED as a valuable treatment strategy for DMG.

Pediatric Diffuse Midline Gliomas: An Unfinished Puzzle

Diffuse midline glioma (DMG) is a heterogeneous group of aggressive pediatric brain tumors with a fatal prognosis. The biological hallmark in the major part of the cases is H3K27 alteration. Prognosis remains poor, with median survival ranging from 9 to 12 months from diagnosis. Clinical and radiological prognostic factors only partially change the progression-free survival but they do not improve the overall survival. Despite efforts, there is currently no curative therapy for DMG. Radiotherapy remains the standard treatment with only transitory benefits. No chemotherapeutic regimens were found to significantly improve the prognosis. In the new era of a deeper integration between histological and molecular findings, potential new approaches are currently under investigation. The entire international scientific community is trying to target DMG on different aspects. The therapeutic strategies involve targeting epigenetic alterations, such as methylation and acetylation status, as well as identifying new molecular pathways that regulate oncogenic proliferation; immunotherapy approaches too are an interesting point of research in the oncology field, and the possibility of driving the immune system against tumor cells has currently been evaluated in several clinical trials, with promising preliminary results. Moreover, thanks to nanotechnology amelioration, the development of innovative delivery approaches to overcross a hostile tumor microenvironment and an almost intact blood-brain barrier could potentially change tumor responses to different treatments. In this review, we provide a comprehensive overview of available and potential new treatments that are worldwide under investigation, with the intent that patient- and tumor-specific treatment could change the biological inauspicious history of this disease.